2023 City of Tyler Wastewater Treatment Plants Master Plan by cityoftyler

Master Plan Report

City of Tyler Wastewater Treatment Plants Master Plan City of Tyler, Texas

Prepared by:

100 E Ferguson Street Suite 814 Tyler, TX 75702 August 2023 Garver Project No. 21W05170

Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Engineer’s Certification I hereby certify that this Master Plan Report, associated with the Tyler Wastewater Treatment Plants Master Plan, was prepared by Garver under my direct supervision for the City of Tyler.

Justin A. Rackley, PE State of TX PE License #102342

Digitally signed 08/29/2023

Russell D. Tate, PE State of TX PE License #132233 Digitally Signed 09/05/2023

Garver Project No. 21W05170

Page 1

Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Table of Contents Executive Summary ...................................................................................................................................... 7 1.0

Introduction...................................................................................................................................... 12

2.0

Basis of Planning ............................................................................................................................ 14

2.1

Flow Projections .......................................................................................................................... 14

2.2

Loadings Projections ................................................................................................................... 16

2.3

Regulatory Projections ................................................................................................................ 16

2.4

Cost Estimating Criteria .............................................................................................................. 18

2.5

Additional Information ................................................................................................................. 19

3.0

Westside WWTP Improvements ..................................................................................................... 20

3.1

Condition Assessment ................................................................................................................ 21

3.2

Modeling ...................................................................................................................................... 22

3.2.1

Baseline Process Model.......................................................................................................... 22

3.2.2

Hydraulic Model....................................................................................................................... 24

3.3

Gap Analysis ............................................................................................................................... 26

3.4

Recommended Improvements .................................................................................................... 27

3.5

Westside WWTP Improvements CIP .......................................................................................... 31

3.6

Additional Information ................................................................................................................. 32

4.0

Southside WWTP Improvements .................................................................................................... 33

4.1

Condition Assessment ................................................................................................................ 34

4.2

Expansion Feasibility Evaluation................................................................................................. 35

4.3

Modeling ...................................................................................................................................... 36

4.3.1

Baseline Process Model.......................................................................................................... 36

4.3.2

Hydraulic Model....................................................................................................................... 38

4.4

Gap Analysis ............................................................................................................................... 41

4.5

Recommended Improvements .................................................................................................... 42

4.6

Southside WWTP Improvements CIP ......................................................................................... 45

4.7

Additional Information ................................................................................................................. 46

5.0 5.1

Conclusion....................................................................................................................................... 46 Additional Information ................................................................................................................. 47

Garver Project No. 21W05170

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

List of Figures Figure ES-1: Overview of Master Plan Tasks for the City of Tyler WWTPs ................................................. 7 Figure ES-2: Site Layout of Westside WWTP Holistic Alternative……………………………………………...9 Figure ES-3: Site Layout of Southside WWTP Holistic Alternative……………………………………………11 Figure 1-1: Location of Westside and Southside WWTP in relation to the City of Tyler, Texas................. 12 Figure 1-2: Overview of Master Plan Tasks for the City of Tyler WWTPs .................................................. 13 Figure 2-1: Population Projections for the City of Tyler, Texas .................................................................. 14 Figure 2-2: Pipeline Analysis Map Showing Westside and Southside Basins and 2040 Growth Areas .... 15 Figure 3-1: PFD of Existing Westside WWTP............................................................................................. 20 Figure 3-2: Core Risk Map of the Westside WWTP Facilities .................................................................... 21 Figure 3-3: Schematic PFD of the Westside WWTP Developed in GPS-X ................................................ 23 Figure 3-4: Westside WWTP Site Layout Identifying Hydraulic Segments ................................................ 25 Figure 3-5: PFD of Westside WWTP Holistic Alternative ........................................................................... 29 Figure 3-6: Site Layout of Westside WWTP Holistic Alternative................................................................. 30 Figure 4-1: PFD of Existing Southside WWTP ........................................................................................... 33 Figure 4-2: Core Risk Map of the Southside WWTP Facilities ................................................................... 34 Figure 4-3: Schematic PFD of the Southside WWTP Developed in GPS-X............................................... 37 Figure 4-4: Southside WWTP Site Layout Identifying Hydraulic Segments ............................................... 39 Figure 4-5: PFD of Southside WWTP Holistic Alternative .......................................................................... 44 Figure 4-6: Site Layout of Southside WWTP Holistic Alternative ............................................................... 45

List of Tables Table ES-1: Summary of Current and Future Flows at Tyler WWTPs ......................................................... 8 Table ES-2: Summary of CIP Projects for the Westside WWTP .................................................................. 8 Table ES-3: Summary of CIP Projects for the Southside WWTP ............................................................... 10 Table 2-1: Flow Projections for Westside and Southside WWTPs ............................................................. 15 Table 2-2: Projected Future Constituent Loadings to the Westside WWTP ............................................... 16 Table 2-3: Projected Future Constituent Loadings to the Southside WWTP.............................................. 16 Table 2-4: TPDES Permit Requirements for Westside WWTP .................................................................. 17 Table 2-5: TPDES Permit Requirements for Southside WWTP ................................................................. 17 Table 2-6: Cost Estimate Contingency and Contractor Margins................................................................. 18

Garver Project No. 21W05170

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Table 2-7: Additional Information for the Basis of Planning ........................................................................ 19 Table 3-1: Summary of Condition Assessment for the Existing Westside WWTP ..................................... 22 Table 3-2: Summary of Hydraulic Capacity of Segments at the Westside WWTP..................................... 26 Table 3-3: Summary of Gap Analysis for Westside WWTP........................................................................ 27 Table 3-4: Summary of Recommended Improvements for Westside WWTP ............................................ 28 Table 3-5: Additional Information for the Westside WWTP Improvements ................................................ 32 Table 4-1: Summary of Condition Assessment for the Existing Southside WWTP .................................... 35 Table 4-2: Conveyance Alternatives for the Southside WWTP .................................................................. 36 Table 4-3: Summary of Hydraulic Capacity of Segments at the Southside WWTP ................................... 40 Table 4-4: Summary of Gap Analysis for Southside WWTP ...................................................................... 41 Table 4-5: Summary of Recommended Improvements for Southside WWTP ........................................... 43 Table 4-6: Additional Information for the Southside WWTP Improvements ............................................... 47 Table 5-1: Summary of Cost Estimates for Tyler WWTPs Improvements .................................................. 48 Table 5-2: Summary of Technical Memoranda in Tyler Master Plan ......................................................... 48

Garver Project No. 21W05170

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

List of Acronyms Acronym 4,4’ - DDT ADF BFP BOD cBOD CCB CIP COD COF DO GBT hr lb/d LOF MGD mg/L ml N/A NH3-N OPCC P2HF PFAS PFB PFD RAS SHT TCEQ TKN TM TP TPDES TRC TSS TWU VSS WAS WRF WWTP

Garver Project No. 21W05170

Definition Dichlorodiphenyltrichloroethane Average Daily Flow Belt Filter Press Biochemical Oxygen Demand Carbonaceous Biochemical Oxygen Demand Chlorine Contact Basin Capital Improvement Plan Chemical Oxygen Demand Consequence of Failure Dissolved Oxygen Gravity Belt Thickener Hour Pounds per Day Likelihood of Failure Million Gallons per Day Milligrams per Liter Milliliters Not Applicable Ammonia-Nitrogen Opinion of Probable Construction Cost Peak Two-Hour Flow Per- and polyfluoroalkyl substances Peak Flow Basin Process Flow Diagram Return Activated Sludge Sludge Holding Tank Texas Commission on Environmental Quality Total Kjeldahl Nitrogen Technical Memorandum Total Phosphorous Texas Pollutant Discharge Elimination System Total Residual Chlorine Total Suspended Solids Tyler Water Utility Volatile Suspended Solids Waste Activated Sludge Water Research Federation Wastewater Treatment Plant

Page 5

Tyler Wastewater Treatment Plants Master Plan Master Plan Report

List of Appendices Appendix A: Historical Data Review TM Appendix B: Planning Criteria TM Appendix C: Baseline Analysis TM Appendix D: Holistic Alternatives TM Appendix E: Southside Conveyance Alternative Memorandum

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Executive Summary The Master Plan for the City of Tyler Wastewater Treatment Plants (WWTPs) was developed by Garver over the course of 2021-2023, with the purpose of identifying the near-term needs of the city’s two WWTPs, Westside and Southside, and planning for the needs of the facilities over the next 30 years. The service populations of both the Westside and Southside WWTP are expected to increase significantly over the master plan period; therefore, along with current condition concerns, capacity improvements were evaluated as a part of the Master Plan. In order to determine what improvements would be needed over the master plan period, Garver performed eleven individual tasks. The tasks included a project kickoff focused on establishing goals for the master plan, a review of the historical data and existing plant condition, establishment of planning criteria, a needs assessment, and a holistic site improvements evaluation. The tasks are listed in Figure ES-1.

Figure ES-1: Overview of Master Plan Tasks for the City of Tyler WWTPs Historical data collected at the Westside and Southside WWTPs from January 2016 to August 2021 was used to analyze the flow and loadings entering and leaving the plants. Flow averages over this time period were used to determine current flowrates. Multiple flow projection methods were evaluated and presented to the Tyler Water Utilities (TWU) staff. The selected method was used to predict future annual average daily flows for the Westside and Southside WWTPs. Peaking factors calculated in the Historical Data Review TM were utilized to calculate future maximum month flows in the Planning Criteria TM. The existing and projected flows to each plant used for future planning are shown in Table ES-1.

Garver Project No. 21W05170

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Table ES-1: Summary of Current and Future Flows at Tyler WWTPs

Westside WWTP

Current Average Daily Flow

Current Permitted Average Day Flows

Future Average Daily Flow

Future Peak 2hour Flow

9.5 MGD

13.0 MGD

14.0 MGD

47.2 MGD1

Southside WWTP 6.7 MGD 9.0 MGD 10.0 MGD 39.5 MGD2 Notes: 1. Peak flow downstream of headworks facility is reduced to 36.0 MGD with PFB in use 2. Peak flow downstream of headworks facility is reduced to 22.5 MGD with PFB in use Additionally, a review of the existing conditions at both plants is included in the Historical Data Review TM. Baseline models of the Westside and Southside WWTPs were developed to analyze the existing processes and aid in the development of improvement recommendations. A hydraulic model was used to determine the current hydraulic capacities and identify critical hydraulic control points throughout the processes of both plants. These models are documented in the Baseline Analysis TM along with a gap analysis identifying required additional capacity and the available alternatives to address facility needs. The Holistic Alternatives TM presents a whole plant improvement approach for each plant that addresses the individual facility needs while also considering consequences of improvements in relation to one another. Capital Improvement Plans (CIPs) were then developed for each plant to recommend a prioritization of implementation of the improvements based on the needs previously identified throughout the master plan project. The CIPs also account for changes to operation during construction of the improvements. A summary of the CIP projects designed for the Westside WWTP is given in Table ES-2. A site layout of the recommended plant-wide improvements for the Westside WWTP is shown in Figure ES-2. Table ES-2: Summary of CIP Projects for the Westside WWTP Project

Total Project Cost

Annual O&M Cost $376,000 $65,000-$55,000

New Headworks Facility

$34,076,000 $2,572,000$11,643,000 $11,927,000

New Influent Pump Station

$13,054,000

$167,000

New Odor Control Facility

$4,810,000

$8,000

Sludge Lagoon Rehabilitation

$3,490,000

$24,000

Secondary Clarifier Rehabilitation

$9,283,000

$14,000

Chlorine Contact Basin Improvements

$3,106,000

$26,000

New Primary Clarifiers

$17,107,000

$14,000

Primary Clarifier Conversion to EQ

$621,000

N/A

New RAS/WAS Pump Station

$6,874,000

$76,000

$10,896,000 $117,816,000 $126,887,000

$191,000 $993,000 – 1,003,000

New Aeration Basins Anaerobic Digester Improvements

Dewatering Facility Improvements Total Costs

Garver Project No. 21W05170

$42,000

Page 8

NOTES: 1-WS-AB: New Aeration Basins and Blower Facility 2-WS-AD: Anaerobic Digester Improvements 3-WS-HW: New Headworks Facility 4-WS-IPS: New Influent Pump Station 5-WS-OC: New Odor Control Facility 6-WS-SL: Sludge Lagoon Rehabilitation 7-WS-SC: Secondary Clarifier Rehabilitation 8-WS-CCB: Chlorine Contact Basin Improvements 9-WS-PC: New Primary Clarifiers 10-WS-EQB: Primary Clarifier Conversion to EQ Basins 11-WS-RWPS: New RAS/WAS Pump Station 12-WS-DF: Dewatering Facility Expansion

39 390 2

HEADWORKS

© 2023 GARVER, LLC THIS DOCUMENT, ALONG WITH THE IDEAS AND DESIGNS CONVEYED HEREIN, SHALL BE CONSIDERED INSTRUMENTS OF PROFESSIONAL SERVICE AND ARE PROPERTY OF GARVER, LLC. ANY USE, REPRODUCTION, OR DISTRIBUTION OF THIS DOCUMENT, ALONG WITH THE IDEAS AND DESIGN CONTAINED HEREIN, IS PROHIBITED UNLESS AUTHORIZED IN WRITING BY GARVER, LLC OR EXPLICITLY ALLOWED IN THE GOVERNING PROFESSIONAL SERVICES AGREEMENT FOR THIS WORK.

PRIMARY CLARIFIER NO.1

ANAEROBIC DIGESTER 392

39 2

2-WS-AD

3-WS-HW FIRST-STAGE TRICKLING FILTER NO.1 5-WS-OC

CONTROL BUILDING PUMP PIT

ANAEROBIC DIGESTER

10-WS-EQB

338 846

4-WS-IPS PRIMARY CLARIFIER NO.2

X 386

392 38

FIRST-STAGE TRICKLING FILTER NO.2

SLUDGE DEWATERING FACILITY

12-WS-DF

9-WS-PC

SECOND-STAGE TRICKLING FILTER NO.1

CHLORINATION BUILDING FINAL CLARIFIER NO.1

DATE

SULPHUR DIOXIDE BUILDING

REV

7-WS-SC

CHLORINE

SECOND STAGE TRICKLING FILTER NO.2

8-WS-CCB CONTACT

CHAMBER

RETURN PUMP STATION

4 39

400 404

1-WS-AB

406

11-WS-RWPS 390

CAUSTIC TANK

WESTSIDE E WWTP CIP

388

TYLER, TX

392

390 39 0 39 2

TYLER WWTP

FINAL CLARIFIER NO.2

39 4

TYLER WWTP MASTER PLAN

392

2 39

NITRIFICATION BASINS 392

2 40

6-WS-SL SLUDGE LAGOON

406

404

40 2

JOB NO.: 21W05170 DATE: AUG 2023 DESIGNED BY: KBD DRAWN BY: KBD

400

406

CHECKED BY: --404

BAR IS ONE INCH ON ORIGINAL DRAWING 1" 0 IF NOT ONE INCH ON THIS SHEET, ADJUST SCALES ACCORDINGLY.

40 2 400 398

396 396

File: L:\2021\21W05170 - Tyler WWTPs Master Plan\Drawings\EXHIBITS\TWWTPMP-Exhibit Westside WWTP.dwg Last Save: 1/24/2023 4:13 PM Last saved by: EXCastro Last plotted by: Castro, Emily X. Plot Style: AECmono.ctb Plot Scale: 1:2.5849 Plot Date: 1/24/2023 4:15 PM Plotter used: None

392

DESCRIPTION

396

398

402

404

406

390

X 400

39 4 394 394

DRAWING NUMBER

394 0

392

30'

60'

120' (IN FEET)

180'

FIGURE ES-2 SHEET NUMBER

Tyler Wastewater Treatment Plants Master Plan Master Plan Report

The CIP projects developed for the Southside WWTP are provided in Table ES-3. Table ES-3: Summary of CIP Projects for the Southside WWTP Project

Total Project Cost

Annual O&M Cost

Site Stormwater Improvements

$1,970,000

$3,000

Primary Clarifier Odor Control

$1,700,000

$8,000

Headworks Facility Expansion

$7,645,000

$10,000

Influent Pump Station Expansion

$5,929,000

$33,000

Peak Flow Basin and Pump Station

$4,616,000

$18,000

New Sludge Holding Tank

$4,895,000

$30,000

GBT Building Expansion

$5,515,000

$86,000

New Aeration Basins

$25,432,000

$244,000

New RAS/WAS Pump Station

$6,923,000

$71,000

Secondary Clarifier Reconstruction

$21,692,000

$17,000

Dewatering Facility Expansion

$4,392,000

$136,000

$90,709,000

$656,000

Total Costs

A site layout of the recommended plant-wide improvements for the Southside WWTP is displayed in Figure ES-3.

Garver Project No. 21W05170

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504

504 4

504

0 46

X 434

43443 3 444

X PRIMARY CLARIFIER NO.2

428

F 426F P P

2-SS-PCOC

PRIMARY SLUDGE PUMP STATION

442

440

RAS/WAS PUMP STATION

7-SS-GBTB

9-SS-RWPS

DIGESTED SLUDGE PUMP STATION 8

436 438

428

44558 8

6 42 426

426 4426 26

FINAL CLARIFIER NO.3

454

FINAL CLARIFIER NO.2 45

424

DEWATERING BUILDING

4424 24 4

446

10-SS-SC

4 42 24 4

CHLORINE CONTACT CHAMBER

I I

448

GRAVITY BELT THICKENER BUILDING

442

42 4 424

424

42 4266

422

CHECKED BY: ---

I I

42 2 42 0

I I

DRAWING NUMBER

X 0

25'

BAR IS ONE INCH ON ORIGINAL DRAWING 1" 0 IF NOT ONE INCH ON THIS SHEET, ADJUST SCALES ACCORDINGLY.

4402 41822 416 41 4

424

JOB NO.: 21W05170 DATE: AUG 2023 DESIGNED BY: KBD DRAWN BY: KBD

418 16 4 414

420

4244 42 42 4

I I

CHLORINATION / DECHLORINATION BUILDING

414416

418

I I

8 41

41 8 418

SOUTHSIDE WWTP CIP

420

I I

SLUDGE DRYING BEDS

43 8

I I

41 8

TYLER WWTP

1-SS-SWI

445544454 454

456

X FINAL CLARIFIER NO.1

RETURN SLUDGE PUMP STATION NO.2

438 6 43434 I I432 430 428 426 424

422

50'

100'

File: L:\2021\21W05170 - Tyler WWTPs Master Plan\Drawings\EXHIBITS\TWWTPMP-Exhibit.dwg Last Save: 1/20/2023 11:24 AM Last saved by: MAWalker Last plotted by: Walker, Mark A. Plot Style: AECmono.ctb Plot Scale: 1:2.5849 Plot Date: 1/23/2023 12:14 PM Plotter used: None

434 43 2 430

PLANT LIFT STATION

11-SS-DF

464

ANAEROBIC DIGESTERS

4 42

46 4644

8 43 436

424

0 44

462

6-SS-SHT

LAB / OFFICE BUILDING

440

DIGESTER HEATER ROOM

AERATION BASIN NO.3 42 4266 426

FINAL CLARIFIER NO.1 SLUDGE HOLDING TANK

TYLER WWTP MASTER PLAN

68 444234343 80234

AERATION BASIN NO.2

AERATION BASIN NO.1

452 50 4

TYLER, TX

4 44

P FP

460 458 56 4 454

CONTROL BUILDING

5-SS-PFB F

AERATION BASIN INFLUENT SPLITTER BOX

466 46 4

8-SS-AB

FP FP

FP P F

FP FP

6 44

43 0

FP FP

448

432

HEADWORKS

STATION

4-SS-IPS SEPTAGE DUMP FP FP

PRIMARY CLARIFIER NO.1

3-SS-HW

45 0

DESCRIPTION

452

PRIMARY CLARIFIER SPLITTER BOX

DATE

4344 43

INFLUENT SCREW PUMP STATION

REV

4554 44

448

456

458

2 46

NOTES: 504 502 500 1-SS-SWI: Stormwater Improvements - Site Levy, Detention Pond, and 498 496 Return Pump Station 4 49 2-SS-PCOC: Primary Clarifier Odor Control 492 3-SS-HW: New Headworks Facility 490 4-SS-IPS: New Influent Pump Station 488 5-SS-PFB: New Peak Flow Basin and Peak Flow Pump Station 486 6-SS-SHT: New Sludge Holding Tank 484 7-SS-GBTB: GBT Building Expansion 482 480 8-SS-AB: New Aeration Basins and Blower Facility 478 9-SS-RWPS: New RAS/WAS Pump Station 47 6 47 10-SS-SC: Secondary Clarifier Reconstruction 4 472 11-SS-DF: Dewatering Facility Expansion 47

(IN FEET)

150'

FIGURE ES-3 SHEET NUMBER

Tyler Wastewater Treatment Plants Master Plan Master Plan Report

1.0

Introduction

This master plan was developed for the Westside and Southside wastewater treatment plants (WWTPs), which provide wastewater treatment for the City of Tyler, Texas. The purpose was to review and evaluate the existing plants and provide recommended improvements over a 30-year planning period (2022-2052). A collection of technical memoranda (TMs) was developed to assess current treatment capabilities and propose facility improvements. The Westside WWTP is located in the northwest corner of the City of Tyler, and the Southside WWTP is located south of the city. Generally, the north half of the city is serviced by the Westside WWTP and the south half is serviced by the Southside WWTP. A site map displaying the locations of the two WWTPs is shown below in Figure 1-1.

Figure 1-1: Location of Westside and Southside WWTP in relation to the City of Tyler, Texas

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

The City of Tyler has grown significantly in recent years and is projected to continue growing in the future decades. The capacity of the WWTPs in the city will need to be increased to keep up with this growth. Additionally, the condition of the WWTPs needs to be addressed. The age and condition of many of the facilities at both the Westside and Southside WWTP have led to interruptions of plant operations. In recent years, the Westside WWTP has encountered difficulties resultant from the insufficient performance of their headworks; regular grit and trash buildup within the clarifiers, anaerobic digesters, and aeration basins has led to inadequate treatment on multiple occasions.

DRIVERS

NEEDS

CHALLENGES

Increased Criticalinfluent to plantflow and loadings as a result operation of population growth

Increased hydraulic Address corrosion capacity and treatment concerns for exterior substation capabilities

Aging equipment Transformer mayand fail duefacility to unplanned poor condition

transformers in Pump Station 6A

outage and capacity of plant could be compromised

This master plan identifies and addresses the necessary upgrades and improvements at the WWTPs based on existing plant conditions, treatment capabilities, projected capacity, and permit requirements. A summary of the tasks included in this master plan project is presented in Figure 1-2.

Figure 1-2: Overview of Master Plan Tasks for the City of Tyler WWTPs

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

2.0

Basis of Planning

The Historical Data Review TM findings were utilized in the Planning Criteria TM development to establish the basis of planning for this master plan project. Projected average daily flows for the Westside and Southside WWTPs were determined to account for anticipated population growth in the City of Tyler. Historical influent characteristics were then applied to these predicted flows to calculate future constituent loadings. 2.1

Flow Projections

Flow projections were determined over a 30-year planning horizon (2022-2052). Two different methods were used for average daily flow (ADF) projections: Method 1 – linear flow projection based on census data and Method 2 – flow projection based on projected growth areas. With Method 1, a linear trend found in the last 3 decades was extended to project the population in the year 2052. The flow per capita from 2020 (156 gallons per capita per day) was used to calculate an estimate of the future ADF. The results of this method are presented in Figure 2-1.

2052 projected population: 140,000

Figure 2-1: Population Projections for the City of Tyler, Texas Method 2 utilized the acreage of growth areas in the City of Tyler, identified in the 2020 City-Wide Hydraulic Model Capacity Assessment and Remedial Measures Plan, to project population growth, and subsequently the additional flow sent to the Tyler WWTPs. The growth areas depicted in Figure 2-2 demonstrate there is anticipated growth in both the regions that send flow to the Westside and Southside WWTPs.

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Figure 2-2: Pipeline Analysis Map Showing Westside and Southside Basins and 2040 Growth Areas The results of both flow projection strategies were presented to the Tyler Water Utility (TWU) staff, and it was determined Method 1 was more conservative and therefore more appropriate for master planning purposes. This prediction was increased by an additional 10% to account for future growth from anticipated commercial building expansions in the city. The projected ADFs were multiplied by the flow peaking factors for the Westside and Southside WWTPs to determine the future maximum month flow. Additional peaking factors were utilized to calculate the future peak 2-hour (P2HF) flows. A summary of the flow projections for the Westside and Southside WWTPs is presented in Table 2-1. Table 2-1: Flow Projections for Westside and Southside WWTPs WWTP Westside WWTP

Average Daily Flow 14.0 MGD

Max Month Flow 20.4 MGD

Peak 2-hour Flow 47.2 MGD2

Southside WWTP 10.0 MGD 12.8 MGD1 39.5 MGD3 Notes: 1. Max Month flows are based on peaking factors for each WWTP that were identified in the Historical Data Review TM (1.46 for Westside WWTP, 1.28 for Southside WWTP) 2. Based on the 3.37 peak-2-hour to average daily flow factor 3. Based on the 3.95 peak-2-hour to average daily flow factor

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

2.2

Loadings Projections

Historical influent wastewater flows and characteristics entering the Westside and Southside WWTPs were the basis for predicting influent loadings in future conditions. Future loadings were calculated with existing influent concentrations at projected flowrates, constituent peaking factors used to determine maximum monthly loading rates. A summary of the projected constituent loadings at the Westside WWTP is shown in Table 2-2. Table 2-2: Projected Future Constituent Loadings to the Westside WWTP

Parameter BOD TSS NH3-N TP

Average Daily Conc. Loading (mg/L) (lb/d) 162 18,920 180 21,020 23 2,670 6.5 760

Maximum Monthly Loading Peaking (lb/d) Factor 24,210 1.28 29,420 1.40 3,950 1.47 990 -

A summary of the projected constituent loadings at the Southside WWTP is given in Table 2-3. Table 2-3: Projected Future Constituent Loadings to the Southside WWTP

Parameter BOD TSS NH3-N TP 2.3

Average Daily Conc. Loading (mg/L) (lb/d) 146 12,180 259 21,600 20 1,670 4.3 360

Maximum Monthly Loading Peaking (lb/d) Factor 15,340 1.26 31,320 1.45 2,150 1.29 470 -

Regulatory Projections

The Westside and Southside WWTPs are required to meet requirements issued by the Texas Commission on Environmental Quality (TCEQ). In evaluating past treatment efficiency, historical effluent concentrations were compared to these limits to identify instances of extreme exceedances or extended periods of permit violations. The Westside WWTP has operated under Texas Pollutants Discharge Elimination System (TPDES) permit number WQ0010653001 since February 21, 2020. The details of the permit limits are presented in Table 2-4.

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Table 2-4: TPDES Permit Requirements for Westside WWTP Concentration (mg/L) Daily 7-day Daily Average Average Max

Parameter

Mass (lb/d)1

cBOD (Mar-Nov)

1,084

cBOD (Dec-Feb)

2,168

TSS (Mar-Nov)

1,626

TSS (Dec-Feb)

Sample Type

Single Grab

Frequency

One/day

2,168

One/day

NH3-N (Mar-Nov)

325

One/day

NH3-N (Dec-Feb)

1,084

One/day

4,4’ – DDT

7 x 10-6

6.48x10-7

N/A

1.37x10-6

1.9x10-6

Two/Week

E. coli (cfu/100ml) TRC (before dechlorination) TRC (after dechlorination)

126

N/A

399

N/A

Five/week

24-hr composite 24-hr composite 24-hr composite 24-hr composite 24-hr composite 24-hr composite 24-hr composite Grab

≥ 1.0

One/day

Grab

≤ 0.1

One/day

Grab

Five/week

Grab

Min: 6.0 Max: 9.0 6.0 5.0

DO (Mar-Nov) One/day Grab DO (Dec-Feb) One/day Grab Notes: 1. Mass Loadings are determined based on the current permitted annual average flow of 13 MGD. The facility also has a permitted 2-hour peak flow of 32.5 MGD. Since September 17, 2021, Southside WWTP has operated under TPDES permit number WQ0010653002. The permit limits for the Southside WWTP effluent are displayed in Table 2-5. Table 2-5: TPDES Permit Requirements for Southside WWTP

Parameter

Mass (lb/d)1

cBOD (5-day)

Concentration (mg/L) Daily Average

7-day Average

Daily Max

Single Grab

Frequency

751

Five/week

TSS

1,126

Five/week

NH3-N (Mar-Oct)

225

Five/week

NH3-N (Nov-Feb)

300

Five/week

E. coli2 (cfu/100ml)

126

N/A

399

N/A

Three/week

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Sample Type 24-hr composite 24-hr composite 24-hr composite 24-hr composite Grab

Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Parameter TRC (before dechlorination) TRC (after dechlorination) pH

Concentration (mg/L)

Mass (lb/d)1

Daily Average

7-day Average

Daily Max

Single Grab

Frequency

Sample Type

≥ 1.0

One/day

Grab

≤ 0.1

One/day

Grab

Five/Week

Grab

Min: 6.0 Max: 9.0 5.0 4.0

DO (Mar-Nov) Five/Week Grab DO (Dec-Feb) Five/Week Grab Notes: 1. Mass Loadings are determined based on the current permitted annual average flow of 9 MGD. Peak 2hour flow capacity of the Southside facility is 22.5 MGD. One additional consideration that is not currently regulated by environmental agencies, but could potentially become regulated in the future, is the level of per- and polyfluoroalkyl substances/ perfluorooctanoic acid (PFAS/PFOA) in the waste biosolids. This potential future regulation was not considered as a part of this master plan, however if it is implemented within the 30-year planning horizon, it could impact the findings of the master plan regarding the CIP projects presented that involve solids handling and disposal. Currently, the three most commonly studied biosolids management options for mitigating PFAS/PFOA compounds are thermal hydrolysis, pyrolysis/gasification, and incineration. Each of these options includes treating sludge at high temperatures with varying pressures and residence time. 2.4

Cost Estimating Criteria

The capital improvement plan (CIP) for each plant and its assets includes a Class 5 opinion of probable construction cost (OPCC) for each investigated alternative in 2023 U.S. dollars. Cost estimates consist of excavation, backfill, concrete, and electrical costs for each facility. Contingency, contractor margin, and engineering and design fee assumptions were also assumed to calculate a total estimated project cost of each CIP project. The assumptions for these additional project costs used throughout the master plan project are given in Table 2-6. Table 2-6: Cost Estimate Contingency and Contractor Margins Consideration Contingency Mobilization Contractor Overhead and Profit

Assumption 35% 5% 18%

In addition to a total estimated project cost of each CIP project, an estimated annual operations and maintenance (O&M) cost is also presented. The O&M costs include electrical costs associated with average day operating electrical consumption of each of the proposed improvements, an estimation of yearly costs for replacement items for large equipment such as pumps, mixers, etc., and labor costs associated with maintaining the equipment included in the CIP projects.

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2.5

Additional Information

The full evaluations used to develop the basis of planning for the master plan project are summarized in Table 2-7. Table 2-7: Additional Information for the Basis of Planning Appendix

Document

Appendix A

Historical Data Review TM

Appendix B

Planning Criteria TM

Garver Project No. 21W05170

Information Existing flow and loading data Projected loading and flow data and future regulatory limits

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3.0

Westside WWTP Improvements

A process flow diagram (PFD) of the existing Westside WWTP treatment plant is illustrated in Figure 3-1.

Figure 3-1: PFD of Existing Westside WWTP The current condition and treatment capacities of the Westside WWTP were assessed with the following evaluations to identify areas for improvement:

A condition assessment was performed to develop an understanding of the criticality of the existing facilities. Then a process model and hydraulic model of the plant were developed to determine current treatment capabilities and hydraulic limitations. A gap analysis was then used to compare the existing capacities to the future required flow and loadings. The results of the evaluations were then used to recommend improvements for the plant.

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3.1

Condition Assessment

The condition assessment was performed as a part of the Historical Data Review TM. The findings of this assessment aided in prioritizing facility improvements. Garver performed a site visit to review the plant and document staff input on maintenance issues and current operations at the Westside WWTP. This evaluation was developed by multiple engineers to analyze the plant from a process, structural, and electrical perspective. The Water Research Federation (WRF) SIMPLE framework was utilized to quantify the findings of the site visit in terms of each facility’s Likelihood of Failure (LOF) and Consequence of Failure (COF). A core risk map was developed, with the LOF score of each facility represented by the y-axis and the COF score represented by the x-axis. The core risk map for the existing facilities at the Westside WWTP is displayed in Figure 3-2.

Figure 3-2: Core Risk Map of the Westside WWTP Facilities The WRF SIMPLE framework was used to determine the overall criticality of each facility based on the combined LOF and COF ratings, with low criticality indicating good condition and/or low impact of failure and a critical rating indicating poor condition and/or catastrophic consequences in the case of failure. The facility ratings are summarized in Table 3-1.

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Table 3-1: Summary of Condition Assessment for the Existing Westside WWTP Facility No.

Asset ID

Facility

Criticality

WS-WWTP-MS

Mechanical Screen

Critical

WS-WWTP-GR

Grit Removal

Critical

WS-WWTP-FPS

Filter Pump Station

Critical

WS-WWTP-NB

Nitrification Basin

Critical

WS-WWTP-CB

Chlorine Building

Critical

WS-WWTP-AD

Anaerobic Digesters

Critical

WS-WWTP-RWPS

Raw Water Pump Station

High

WS-WWTP-FSTF

First Stage Trickling Filters

High

WS-WWTP-SC

Secondary Clarifiers

High

WS-WWTP-RASPS

RAS Pump Station

High

WS-WWTP-CCB

Chlorine Contact Basin

High

WS-WWTP-OPS

Operations Building/Lab

High

WS-WWTP-PC

Primary Clarifiers

Medium

WS-WWTP-SSTF

Second Stage Trickling Filters

Medium

WS-WWTP-LSPS

Light Sludge Pump Station

Low

WS-WWTP-CHEM

Chemical Feed Facility

Low

WS-WWTP-PSPS

Primary Sludge Pump Station

Low

WS-WWTP-BFPPS

BFP Pump Station

Low

WS-WWTP-DF

Dewatering Facility

Low

The criticality of each facility was used to prioritize the recommended facility improvements for the Westside WWTP. 3.2

Modeling

To evaluate the treatment capacity of the Westside WWTP, hydraulic and process models were developed and included in the Baseline Analysis TM. Designed and calibrated with current conditions and historical flow characteristics, the baseline process model was created to simulate the existing treatment capabilities. The hydraulic model allowed for the determination of maximum hydraulic capacity through the process flow segments and identification of limits throughout the plant. 3.2.1

Baseline Process Model

A baseline process model of the Westside WWTP was created to illustrate the current performance of the plant with GPS-X software (Hydromantis, v.8.1). It was constructed with the existing facilities and designed to reflect historical wastewater characteristics. The details of process model development are

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given in the process model section of the Baseline Analysis TM. A schematic of the overall process model developed for the Westside WWTP is displayed in Figure 3-3.

Figure 3-3: Schematic PFD of the Westside WWTP Developed in GPS-X The model was calibrated with special sampling results to allow for adjustment from the default parameters in GPS-X to ones specific to the Westside WWTP. This allowed for the model to be aligned with historical constituent concentrations at multiple points in the process to accurately demonstrate the plant’s treatment capabilities. Special sampling was completed in the following key areas with data from October 11 to October 22, 2021: • • • •

Raw Influent Primary Clarifier Effluent Secondary Clarifier Effluent Final Effluent

Model predictions were compared to historical data on the Westside WWTP wastewater characteristics from 2019 to 2021 to validate the process model. Observations in evaluating the model’s accuracy were as follows: • •

The raw influent featured a ratio of BOD : COD that is lower than is typically observed at the WWTP. Addition of metal salts at the Influent Pump Station could have contributed to low PO4-P concentrations in raw influent and primary effluent samples.

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• • • •

•

Recycle of first-stage trickling filter effluent in model calibrated for sBOD removal in the primary effluent. Final effluent constituents were calibrated to have acceptable to excellent agreement with special sampling results. Solid stream concentrations calibrated to have good agreement with historical facility measurements. The calibrated model predicted all of the historical influent and effluent constituent concentrations (Ave Jan 2019 to Aug 2021) with excellent accuracy, except for NH3-N, which was slightly underestimated by an acceptable error. The calibrated model predicted the TSS and VSS concentrations of the historical operating MLSS and the solids production rate with good accuracy.

The validated baseline process model for the Westside WWTP was determined to be an accurate representation of the plant’s current operations. The process model could then be used to accomplish the following to aid in future planning efforts: • • • 3.2.2

Simulate the existing liquid treatment and solids handling processes, including recycle streams Predict future process capacities at projected flows and loadings Identify gaps in treatment capacity and recommend improvements Hydraulic Model

A hydraulic model of the Westside WWTP was built with GarverFlow, an in-house Microsoft Excel spreadsheet tool, to identify hydraulic bottlenecks throughout the plant and evaluate the hydraulic capacity of the current facilities. The treatment process was broken into different hydraulic segments based on hydraulic control points, like weirs and free outfalls where the upstream water surface elevation (WSE) is independent of the downstream WSE. A site layout of the existing Westside WWTP divided into segments is given in Figure 3-4.

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Figure 3-4: Westside WWTP Site Layout Identifying Hydraulic Segments The capacity of each segment was determined by finding the maximum flow that did not violate hydraulic criteria. The methodology, assumptions, and evaluation criteria utilized in the modeling process are detailed in the hydraulic model section of the Baseline Analysis TM. Hydraulic criteria were determined by combining TCEQ regulations and Garver’s engineering experience and judgment. The current ADF is 9.5 MGD and the projected ADF and P2HF for this plant were established as 14.0 MGD and 47.2 MGD, respectively. To capture hydraulic capabilities at current and future flows, the range of flows 5.0 MGD to 50.0 MGD were used in modeling efforts. This analysis determined critical hydraulic inadequacies to be used in future planning development. The existing capacity and hydraulic limitations of each segment of the Westside WWTP are displayed in Table 3-2.

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Table 3-2: Summary of Hydraulic Capacity of Segments at the Westside WWTP Segment No. Segment 1 Segment 2 Segment 3 Segment 4 Segment 5 Segment 6 Segment 7 Segment 8 Segment 9 Segment 10 Segment 11

Segment Identifier Chlorine Contact Basin to Plant Outfall Secondary Clarifier to Chlorine Contact Basin Tower Splitter Box to Secondary Clarifier 1 Nitrification Basin to Tower Splitter Box Filter Pump Station to Nitrification Basin Primary Clarifier 1 to SecondStage Trickling Filter 1 First-Stage Trickling Filter 1 to Filter Pump Station Primary Clarifier 1 to FirstStage Trickling Filter 1 Raw Water Pump Station to Primary Clarifier 1 Grit Effluent Weirs to Influent Parshall Flume Screen Channel to Grit Effluent Weir

Hydraulic Capacity N/A1 16.0 MGD (50% of plant flow) 16.3 MGD (50% of plant flow + 50% of RAS) 47.0 MGD (total plant flow + RAS) > 50.0 MGD (total plant flow) 13.0 MGD (50% of total plant flow) 42.0 MGD (total plant flow) 16.0 MGD (50% of total plant flow) 36.0 MGD (total plant flow) 20.0 MGD > 50.0 MGD

Hydraulic Limitation Floodway elevation is flooding CCB structure Secondary Clarifier weir is flooded Tower Splitter Box weir is flooded Nitrification Basin effluent weir is flooded Pipe velocity in segment is > 9 ft/s Primary clarifier effluent weirs are flooded Pipe velocity in segment is > 9 ft/s Primary clarifier effluent weirs are flooded Pipe velocity in segment is > 9 ft/s Grit effluent weir is flooded Pipe velocity in segment is > 9 ft/s

Notes: 1. When the receiving water body is at normal flood stage, the CCB has a capacity greater than 45 MGD. The main hydraulic constraints identified through the modeling effort include: • Chlorine Contact Basin is flooded at the 100-year flood condition • Due to the size and elevation of the influent Parshall flume and the yard piping in Segment 10, the grit effluent weirs are submerged at flows higher than 20 MGD. Submergence of these weirs can lead to inefficiencies within the grit removal system. • All modeled segments, except for segment 4, 5, and 11 have a hydraulic capacity lower than the projected future peak flow of 47.2MGD. 3.3

Gap Analysis

Along with hydraulic and process models, the Baseline Analysis TM also included a gap analysis for the Westside WWTP to identify facilities requiring additional capacity to treat projected flow and loadings. The future flow and loadings were determined in the Planning Criteria TM. The following industry-accepted design and operating standards were utilized to calculate the existing and future capacities: • • • •

Planning criteria (flow and loadings) developed for each facility. TCEQ requirements for wastewater treatment facilities Design of Water Resource Recovery Facilities Manual of Practice (Water Environment Federation, MOP 8) Wastewater Engineering: Treatment and Resource Recovery, Metcalf and Eddy (M&E)

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To reduce the peak flow requirements of the treatment plant processes, the utilization of a Peak Flow Basin (PFB) was recommended. A hydrograph of the peak storm event at the plant was used to find the capacity required to reduce the peak flow from 47.2 MGD to 36.0 MGD . A PFB with a storage capacity of 1.4 MG would reduce the required peak flow through processes downstream of the raw water pump station. It was proposed to construct new primary clarifiers and convert the existing structures into PFBs, which meet storage requirements. This alternative was discussed with the City of Tyler and was concluded to be cost effective, as it lessens the required improvements and is conservative for future peak flow projections. The gap analysis assumed the PFB was in use and reduced the peak flow accordingly. A summary of each facility’s current capacity and required additional capacity are presented in Table 3-3. Table 3-3: Summary of Gap Analysis for Westside WWTP

32.5 MGD 20.0 MGD

Future Required Capacity 47.2 MGD 47.2 MGD

32.0 MGD

47.2 MGD

None

15.2 MGD

42.4 MGD 4,500 lb BOD/day 46 MGD 27.1 MGD

36.0 MGD 14,500 lb BOD/day 36.0 MGD 36.0 MGD

None 5,000 lb BOD/day None 5.4 MGD

None 10,000 lb BOD/day None 8.9 MGD

6,720 lb/day

1,800 lb/day

None

1,920 lb/day

450 lb/day

None

29.7 MGD

36.0 MGD

2.8 MGD

6.3 MGD

960 lb O2/day 3.2 MG

1,500 lb O2/day 0.57 MG

395 lb O2/day None

540 lb O2/day None

3,200 lb/hr

5,670 lb/hr

627 lb/hr

2,470 lb/hr

Existing Capacity

Facility Mechanical Screens Grit Removal Raw Water Pump Station Primary Clarifiers Biological Treatment Train Filter Pump Station Secondary Clarifiers Chlorine Facility – Chlorine Gas Chlorine Facility – Sulfur Dioxide Chlorine Contact Basin Oxygenation Anaerobic Digesters Sludge Dewatering Facility

Existing Gap

Future Gap

None 12.5 MGD

14.7 MGD 27.2 MGD

An analysis of different improvement alternatives to address the needs of each facility is provided in the available alternatives section of the Baseline Analysis TM. The selected upgrades will be detailed in the following section. 3.4

Recommended Improvements

The design improvements discussed in the Baseline Analysis TM address facility needs individually. The whole plant improvement approach for the Westside WWTP was developed in the Holistic Alternatives TM, combining the individual facility recommendations. This holistic alternative considers the consequences of the design recommendations in relation to other upgrades, creating a cohesive schedule of improvements.

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The selected upgrades for each facility address the conditions of the existing facilities, along with the gaps in hydraulic and treatment capacity identified in the preceding evaluations. The CIP for the Westside WWTP was developed with cost estimates for each facility. A summary of the recommended improvements for each facility is provided in Table 3-4. Table 3-4: Summary of Recommended Improvements for Westside WWTP Facility

Mechanical Screening

Grit Removal Influent Pump Station New Odor Control Facility Primary Clarifiers

Aeration Basins Secondary Clarifiers RAS/WAS Pump Station Chlorine Contact Basin

Sludge Digesters Sludge Dewatering Sludge Lagoon Rehabilitation

Improvements • • • • • • • • • • • • • •

Project Cost

• • • • •

Demolish existing headworks facility Relocate existing septage receiving station Build new headworks structure 3 new 18 MGD mechanical screens 1 new manual bar screen 3 new vortex grit removal units Grit pumps and grit classifiers Decommission existing Raw Water Pump Station Construct new influent pump station 4 new 12 MGD influent pumps 2 new 12 MGD peak flow pumps Control biotrickling filter for odor control Install screen/grit channel covers Convert existing primary clarifiers into peak flow storage basins 2 new 100-ft diameter primary clarifiers Decommission existing nitrification basin channels Construct 3 new aeration basin channels utilizing diffused aeration Construct a new blower facility 4 new blowers Rehabilitate the existing 150-ft secondary clarifiers with double sided weir mechanisms Decommission existing RAS pump station Construct a new RAS/WAS pump station 4 new RAS pumps 2 new WAS pumps Raise the outer walls of the existing chlorine contact basin Replace the existing surface aerators Construct a new Parshall flume channel Remove existing basin covers, repair existing basins and fill in the conical floors Install a diffused aeration system Construct a new blower facility 3 new blowers Construct additional dewatering facility area Install 2 additional 2-m Belt Filter Presses (BFPs)

•

Replace the sludge lagoon liner and install mixers

• • • • • • • • • • • • • •

$11,927,000

$13,054,000

$4,810,000 $17,107,000 + $621,000

$34,076,000

$9,283,000

$6,874,000

$3,106,000

$2,572,000$11,643,000

$10,896,000 $3,490,000

A PFD of the Westside WWTP operating with the selected alternatives from the holistic alternative evaluation is depicted in Figure 3-5.

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Figure 3-5: PFD of Westside WWTP Holistic Alternative

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A potential site layout of the Westside WWTP implementing the holistic alternative is displayed in Figure 3-6.

Figure 3-6: Site Layout of Westside WWTP Holistic Alternative

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3.5

Westside WWTP Improvements CIP

Project Description: Improvements are needed at the Westside WWTP to address condition and capacity concerns to ensure that the plant will be capable of treating current and future flows adequately. These improvements include the construction of multiple new facilities, including: a new headworks facility, a new influent pump station, new primary clarifiers, new aeration basins, and a new RAS/WAS pump station. Additionally, many of the existing facilities require rehabilitation or expansion, including: the secondary clarifiers, the chlorine contact basin, the anaerobic digesters (two available alternatives including conversion to aerated sludge holding tanks and rehabilitation of the existing digesters), the sludge lagoon, and the dewatering facility. The existing primary clarifiers will also be converted into flow equalization basins. The overall estimated total project cost of the recommended improvements is between $118 Million and $127 Million, depending on which anaerobic digester improvements project is chosen for construction. Justification: As documented in the condition assessment, many of the facilities at the Westside WWTP are in critical condition and in need of nearterm rehabilitation or reconstruction. As a result, the facility has been struggling to maintain permit compliance in recent years due to condition based treatment deficiencies. The recommended improvements included in this CIP aim to address the critical concerns as well as less critical items that will increase performance, efficiency, and resiliency of the plant as a whole. Special Considerations: Construction phasing will be evaluated to ensure that the most critical improvements needed at the plant are addressed first. Some construction sequencing will also be needed to ensure that clarification capacity is maintained during the primary clarifier conversion and the secondary clarifier rehabilitation.

Garver Project No. 21W05170

Project Identification WS-CIP Drivers Primary

Rehabilitation

Secondary

Capacity

Projects Included (in order of priority ranking)

Total Project Cost

New Aeration Basins

$34,076,000

Anaerobic Digester Improvements

$2,572,000$11,643,000

New Headworks Facility

$11,927,000

New Influent Pump Station

$13,054,000

New Odor Control Facility

$4,810,000

Sludge Lagoon Rehabilitation

$3,490,000

Secondary Clarifier Rehabilitation

$9,283,000

Chlorine Contact Basin Improvements

$3,106,000

New Primary Clarifiers

$17,107,000

Primary Clarifier Conversion to EQ

$621,000

New RAS/WAS Pump Station

$6,874,000

Dewatering Facility Improvements $10,896,000 Implementation Duration

Months

Engineering Design

Bid Phase

Construction

Start-up

Total Duration

Estimated Costs in August 2023 USD Total Project Cost

$117,816,000 $126,887,000

Annual O&M Cost

$993,000 – 1,003,000

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3.6

Additional Information

The evaluation of the existing Westside WWTP and recommended improvements were developed with the combined findings of the documents given in Table 3-5. Table 3-5: Additional Information for the Westside WWTP Improvements Appendix

Document

Appendix A

Historical Data Review TM

Existing facilities condition assessment

Appendix C (section 2.0) Appendix C (section 3.0) Appendix C (section 4.0) Appendix C (section 5.0)

Baseline Analysis TM: Process Model Baseline Analysis TM: Hydraulic Model Baseline Analysis TM: Gap Analysis Baseline Analysis TM: Available Alternatives

Development of process model for treatment capacities Development of hydraulic model for hydraulic limit identification Evaluation of additional required capacities for each facility Comparison of design alternatives for each facility

Appendix D

Holistic Alternatives TM

Development of whole plant improvement plan

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Information

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4.0

Southside WWTP Improvements

A PFD of the existing treatment process is displayed in Figure 4-1.

Figure 4-1: PFD of Existing Southside WWTP The current condition and treatment capacities of the Southside WWTP were assessed with the following evaluations to identify areas for improvement:

A condition assessment was developed to review the criticality of existing facilities. A process and hydraulic model were created to determine current treatment capabilities and hydraulic limitations. The

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future required flow and loadings were used to calculate the additional required capacity for each facility in a gap analysis. The findings of these evaluations were used to recommend improvements for the plant. 4.1

Condition Assessment

As a part of the Historical Data Review of the Southside WWTP, a condition assessment was developed to review the existing facilities and their equipment. The criticality of each facility was determined to help prioritize areas of improvement. Garver conducted a site visit where staff input on plant operations was recorded and each facility was reviewed from a process, structural, and electrical perspective. The findings were input into the WRF SIMPLE framework to determine the Likelihood of Failure (LOF) and Consequences of Failure (COF) for each asset. A core risk map summarizing the facility ratings was developed, with the LOF represented on the y-axis and the COF represented on the x-axis. The resulting core risk map for the facilities at the Southside WWTP is shown in Figure 4-2.

Figure 4-2: Core Risk Map of the Southside WWTP Facilities The combined LOF and COF ratings were then used to determine the overall criticality of each facility, with low criticality indicating good condition and/or low impact of failure and a critical rating indicating poor condition and/or catastrophic consequences in the case of failure. The criticality ratings of each facility are provided in Table 4-1.

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Table 4-1: Summary of Condition Assessment for the Existing Southside WWTP Facility No.

Asset ID

SS-WWTP-AB1&2

SS-WWTP-CB

Facility

Criticality

Aeration Basins 1 & 2

Critical

Chlorine Building

Critical

SS-WWTP-RWPS

RAS/WAS Pump Station

Critical

SS-WWTP-AB3

Aeration Basin 3

High

SS-WWTP-FC1&2

Final Clarifiers 1 & 2

High

SS-WWTP-FC3

Final Clarifier 3

High

SS-WWTP-CCB

Chlorine Contact Basin

High

SS-WWTP-SSPS

Secondary Sludge Pump Station

High

SS-WWTP-STPS

Sludge Transfer Pump Station

High

SS-WWTP-SHT

Sludge Holding Tank

SS-WWTP-GR

Grit Removal

Medium

SS-WWTP-PLS

Plant Lift Station

Medium

SS-WWTP-GBT

GBT Facility

Medium

SS-WWTP-AD

Anaerobic Digesters

Medium

SS-WWTP-CHEM

Chemical Feed Facility

Low

SS-WWTP-ISP

Influent Screw Pumps

Low

SS-WWTP-MS

Mechanical Screens

Low

SS-WWTP-PC

Primary Clarifier

Low

SS-WWTP-PSPS

Primary Sludge Pump Station

Low

SS-WWTP-DF

Dewatering Facility

Low

WWTP-PC2-001

Plant 480V MDC

Low

High

The criticality ratings of each facility enabled the prioritization of the recommended upgrades for the Southside WWTP. 4.2

Expansion Feasibility Evaluation

The City of Tyler expressed interest in the construction of a new greenfield WWTP to treat the additional flows sent to the Southside WWTP or replace the Southside WWTP altogether. The existing Southside WWTP is located in an area of growth and development and there were concerns about the lack of adequate odor control. During the Baseline Analysis Workshop on October 17, 2022, three different approaches to address needs at the Southside WWTP were proposed with an OPCC for each, summarized in Table 4-2.

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Table 4-2: Conveyance Alternatives for the Southside WWTP Design Alternative Alternative 1 Alternative 2 Alternative 3

Description Expand the Southside WWTP (no greenfield WWTP) Upgrade the Southside WWTP and construct new greenfield WWTP to treat additional flow and loadings Decommission the Southside WWTP and divert all flow to new greenfield WWTP

Total Cost Estimate $202 Million $286 Million $406 Million

After conceptual cost estimates were reviewed, alternative 1 was ultimately determined to be the most cost-effective strategy, as the construction of greenfield WWTP in any capacity was significantly more expensive than upgrading and expanding the Southside WWTP. Full details of this analysis are in the Southside Conveyance Alternatives Memo, provided in Appendix E. The following evaluation of the Southside WWTP assumes alternative 1 will be implemented. 4.3

Modeling

A process and hydraulic model of the Southside WWTP were developed as a part of the Baseline Analysis to review the current treatment and hydraulic capacities of the facilities and study their performance at projected flow and loadings. This allowed for needs to be identified and design alternatives to be compared. 4.3.1

Baseline Process Model

A baseline process model of the Southside WWTP was created with GPS-X software (Hydromantis, v.8.1) to simulate existing treatment capabilities and enable the analysis of design alternatives. A schematic of the overall process model developed for the Southside WWTP is given in Figure 4-3.

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Figure 4-3: Schematic PFD of the Southside WWTP Developed in GPS-X Special samples collected between October and November 2021 were used to calibrate the model from several points throughout the treatment process. This allowed for the model’s default influent fractionation parameters to be changed to values custom to the Southside WWTP. The special samples were taken from the following key areas: 1) 2) 3) 4) 5)

Raw Influent Primary Clarifier Effluent Secondary Clarifier Effluent Final Effluent Belt Filter Press Filtrate

Raw influent samples were collected between October 5 and October 18, 2021, and the remaining special samples were obtained from November 2 to November 15, 2021. The model was validated by comparing model predictions to historical data from January 2019 to August 2021. In reviewing the process model’s performance, the following observations were made:

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• • • • • • • •

The raw influent featured lower than typical ratio of BOD : COD and low fractions of sCOD : COD and sBOD : sCOD. Addition of metal salts at influent pump station could explain low PO4-P values in the raw influent samples and provide rationale for PO4-P removal during primary treatment. Primary effluent calibration produced model results that were predicted with good to excellent accuracy for most constituents. Unsatisfactory errors for modeled BOD and sBOD concentrations in primary effluent could have been due to unrepresentative parameter measurements during the special sampling campaign. Final effluent calibrated to have acceptable to excellent agreement with special sampling results MLSS, TSS, and VSS concentrations calibrated to have good to excellent agreement with operational measurements. Calibration of solids handling procedures provided acceptable depiction of recycled NH3-N load to the head of the treatment train. The calibrated model represented the historical performance of the facility with high accuracy, evidenced by good to excellent error values for nearly all influent, effluent, and solid stream concentrations. The exceptions were the facility’s effluent NH3-N concentration and solids production rate, which had acceptable agreement with special sampling averages.

The process model for the Southside WWTP was concluded to be an accurate simulation of the existing facilities. The process model could then be used to accomplish the following to aid in future planning efforts: • • • 4.3.2

A hydraulic model of the Southside WWTP was developed as a part of the Baseline Analysis TM to determine the hydraulic capacity of existing facilities and identify hydraulic limits throughout the plant. This model was created with GarverFlow, an in-house Microsoft Excel spreadsheet tool. The plant was studied in segments based on hydraulic control points. A site layout of the Southside WWTP with the process divided into segments is shown in Figure 4-4.

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Figure 4-4: Southside WWTP Site Layout Identifying Hydraulic Segments The capacity of each segment was calculated as the maximum flow that did not violate hydraulic criteria. The methodology and hydraulic criteria used in model development are detailed in the hydraulic model section of the Baseline Analysis TM. The current ADF is 6.7 MGD and the projected ADF and P2HF were determined to be 10.0 MGD and 39.5 MGD, respectively. The range of flows from 5.0 MGD to 45.0 MGD were used in the hydraulic model to capture any hydraulic capacity issues at existing and future conditions. The resulting hydraulic limitations of the plant were used in developing improvement recommendations. The findings of the hydraulic model are presented in Table 4-3.

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Table 4-3: Summary of Hydraulic Capacity of Segments at the Southside WWTP

Segment Identifier

Hydraulic Capacity at 100-Year Flood

Hydraulic Capacity at Normal Flood Levels1

Segment 1

Chlorine Contact Basin Effluent to Plant Outfall

N/A

45.0 MGD

Segment 2

Secondary Clarifier 2 to Chlorine Contact Basin

N/A

7.2 MGD (28% of plant flow)

Segment 3

Secondary Clarifier 3 to Chlorine Contact Basin

N/A

10.3 MGD (44% of plant flow)

Segment 4

Aeration Basin 2 to Secondary Clarifier 2

Segment 5

Aeration Basin 3 to Secondary Clarifier 3

Segment 6

Aeration Basin Splitter Box to Aeration Basin 2

Segment 7

Aeration Basin Splitter Box to Aeration Basin 3

Segment No.

Segment 8 Segment 9 Segment 10 Segment 11 Segment 12

Primary Clarifier 1 to Aeration Basin Splitter Box Primary Clarifier Splitter Box to Primary Clarifier 1 Grit Effluent Weirs to Primary Clarifier Splitter Box Influent Parshall Flume to Grit Effluent Weirs Influent Screw Pumps to Influent Parshall Flume

2.0 MGD (28% of plant flow + RAS) < 2.90 MGD (44% of plant flow + RAS) 8.70 MGD (28% of plant flow) 13.20 MGD (44% of plant flow)

Hydraulic Limitation Floodway elevation is flooding CCB Effluent Weir Floodway Elevation is flooding secondary clarifier weirs Floodway Elevation is flooding secondary clarifier weirs

11.2 MGD (28% of plant flow + 28% of RAS) 17.0 MGD (44% of plant flow + 44% of RAS)

Aeration Basin 2 weir is flooded Aeration Basin 3 weir is flooded

11.5 MGD (28% of plant flow)

Aeration Basin Splitter Box weir is flooded

17.5 MGD (44% of plant flow)

Aeration Basin Splitter Box weir is flooded

15.0 MGD (50% of plant flow)

Primary clarifier weir is flooded

19.0 MGD (50% of plant flow)

Primary Clarifier Splitter Box is flooded

34.0 MGD (total plant flow)

Grit effluent weir is flooded

21.0 MGD (50% of plant flow) 10.0 MGD (total plant flow)

Parshall flume is submerged Walls of headworks structure are flooded

Notes: 1. Segments were also analyzed based on a starting WSE within the river of 419.50 ft to determine the “nonflooded” hydraulic capacity, independent of the 100-year flood elevation. The main hydraulic constraints identified through the modeling effort include: • The weirs of the chlorine contact basin and secondary clarifiers are flooded at the 100-year flood condition • Due to the size and elevation of the influent Parshall flume, there is little room within the headworks facility for variations in the level of blinding of the mechanical screes. The water surface elevation inside of the headworks facility violates wall freeboard criteria at flows higher than 10 MGD when the screens are 50% blinded.

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

4.4

Gap Analysis

A gap analysis of each facility at the Southside WWTP was included in the Baseline Analysis TM. It utilized the existing capacities found with the hydraulic and process models. The future required capacities were determined with the criteria established in the Planning Criteria TM. The following industry-accepted design and operating standards were utilized for this analysis: • • • •

Similar to the Westside WWTP, a PFB was recommended to reduce the peak flow requirements. The peak day hydrograph for the Southside WWTP was used to calculate the storage volume needed to reduce the peak flow from the projected 39.5 MGD to the plant’s current peak flow of 22.5 MGD. It was determined that a 1 MG PFB would reduce the peak flow through processes downstream of the headworks facility. Assuming the PFB was being implemented, a summary of the gap analysis is given in Table 4-4. Table 4-4: Summary of Gap Analysis for Southside WWTP Facility Influent Pump Station Mechanical Screens Grit Removal Primary Clarifiers Primary Sludge Pump Station Aeration Basins Secondary Clarifiers Chlorine Contact Basin Chlorine Facility – Chlorine Gas Chlorine Facility – Sulfur Dioxide RAS/WAS Pump Station Gravity Belt Thickener Sludge Holding Tank Sludge Dewatering Facility

Existing Capacity 21.7 MGD 13 MGD 31 MGD 18.1 MGD 250 gpm 13,800 lb BOD/day 30.3 MGD 34.7 MGD 3,360 lb/day 1,440 lb/day 1.0 MGD 167 gpm 0.70 MG 3,200 lb/h

Future Required Capacity 39.5 MGD 39.5 MGD 39.5 MGD 22.5 MGD 250 gpm 10,800 lb BOD/day 22.5 MGD 22.5 MGD 2,000 lb/day 500 lb/day 5.6 MGD 124 gpm 0.36 MG 4,400 lb/h

Existing Gap 0.8 MGD 9.5 MGD None 4.4 MGD None

Future Gap 17.8 MGD 26.5 MGD 8.5 MGD 4.4 MGD None

None

None None None None 4.0 MGD None None None

None None None None 4.6 MGD None None 1,200 lb/h

Different improvement alternatives to address the identified gaps were compared in the available alternatives section of the Baseline Analysis TM. The recommended upgrades are detailed in the following section.

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4.5

Recommended Improvements

Design alternatives for individual facilities of the Southside WWTP were analyzed in the Baseline Analysis TM. These upgrades addressed the existing conditions and additional hydraulic and treatment capacities required to treat projected flow and loadings. The recommended improvements were used to develop a whole plant improvement plan that accounted for the consequences of upgrades with a cohesive schedule for the project phases. The overall plant improvements are described in the Holistic Alternatives TM, with individual facility OPCCs in the CIP for the Southside WWTP. A summary of the recommended improvements with cost estimates for each facility is presented in Table 4-5.

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Table 4-5: Summary of Recommended Improvements for Southside WWTP Facility

Improvements •

Project Cost

• •

Construct a 12-ft wide levy around the southern portion of the site. Construct a 55,000cf detention pond 2 new stormwater return pumps that send collected stormwater to the head of the plant Maintain existing screw pump station Construct a new submersible influent pump station 4 new peak flow pumps Maintain existing mechanical screens Construct a new headworks structure adjacent to the existing facility 1 new mechanical screen 1 new manual screen Maintain existing grit removal system 1 new vortex grit removal unit New grit pumps and grit classifiers Construct a new 120-ft diameter peak flow storage basin Relocate existing electrical equipment between the anaerobic digester basins Maintain existing primary clarifiers Install odor control Decommission and demolish existing aeration basins Construct 3 new aeration basin channels utilizing diffused aeration Construct a new blower facility 4 blowers

•

Rebuild the three existing secondary clarifiers

Sludge Thickening

• • • • • • • •

Sludge Dewatering

• •

Demolish existing RAS pump station Construct a new RAS/WAS pump station 4 new RAS pumps 2 new WAS pumps Maintain existing sludge storage tank Construct a second 100-ft diameter sludge storage tank Replace the existing GBT Construct additional GBT Building space to house a second GBT Construct additional dewatering facility area Install 1 additional 2-m BFP

Site Stormwater Improvements

Influent Pump Station

Mechanical Screening

Grit Removal Peak Flow Storage Primary Clarifiers

• • • • • • • • • • • • • • • • • •

Aeration Basins

Secondary Clarifiers RAS/WAS Pump Station Sludge Holding Tank

Garver Project No. 21W05170

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$1,970,000

$5,929,000

$7,645,000

$4,616,000 $1,700,000

$25,432,000

$21,692,000

$6,923,000

$4,895,000 $5,515,000 $4,392,000

Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Figure 4-5

Figure 4-5: PFD of Southside WWTP Holistic Alternative

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

A potential site layout of the Southside WWTP with the recommended improvements is provided in Figure 4-6.

Figure 4-6: Site Layout of Southside WWTP Holistic Alternative

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

4.6

Southside WWTP Improvements CIP

Project Description: Upgrades are needed at the Southside WWTP to address concerns regarding facility conditions, lack of redundancy and capacity required to treat future flows. These improvements include construction of the following new facilities: a stormwater levy and detention pond, a peak flow basin and pump station, new aeration basins, a new RAS/WAS pump station, and a new sludge holding tank. Multiple existing facilities need rehabilitation or expansion, including: the influent pump station, the headworks facility, secondary clarifiers, the GBT building, and the dewatering facility. Additionally, odor control will be installed for each facility upstream of the biological treatment train. The overall estimated total project cost of the recommended improvements is $91 Million. Justification: As demonstrated in the condition assessment, many of the existing facilities do not have the capacity or redundancy necessary to treat future peak flows. Additionally, there are multiple facilities in critical condition, which require rehabilitation or new facility construction. The construction of the proposed new facilities will also reduce the risk of on-site flooding. The recommended improvements in this CIP target critical concerns and overall plant performance. Special Considerations: Improvements will be implemented in phases to ensure the most critical needs of the plant are addressed first. Additionally, construction sequencing will be necessary to maintain functionality during the construction of the new aeration basins and the secondary clarifier reconstruction.

Project Identification SS-CIP Drivers Primary

Capacity

Secondary

Rehabilitation

Projects Included (in order of Total Project priority ranking) Cost Stormwater Levy, Detention Pond, $1,970,000 and Return Pump Station Primary Clarifier Odor Control

$1,700,000

Headworks Facility Expansion

$7,645,000

Influent Pump Station Expansion

$5,929,000

Peak Flow Basin and Pump Station

$4,616,000

New Sludge Holding Tank

$4,895,000

GBT Building Expansion

$5,515,000

New Aeration Basins

$25,432,000

New RAS/WAS Pump Station

$6,923,000

Secondary Clarifier Reconstruction

$21,692,000

Dewatering Facility Expansion

$4,392,000

Implementation Duration

Months

Engineering Design

Bid Phase

Construction

Start-up

Total Duration

Estimated Costs in August 2023 USD

Garver Project No. 21W05170

Total Project Cost

$90,709,000

Annual O&M Cost

$656,000

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

4.7

Additional Information

The existing Southside WWTP operations were assessed, and an improvement plan was developed with the documents provided in Table 4-6. Table 4-6: Additional Information for the Southside WWTP Improvements

5.0

Appendix

Document

Information

Appendix A Appendix C (section 2.0) Appendix C (section 3.0) Appendix C (section 4.0) Appendix C (section 5.0)

Historical Data Review TM Baseline Analysis TM: Process Model Baseline Analysis TM: Hydraulic Model Baseline Analysis TM: Gap Analysis Baseline Analysis TM: Available Alternatives

Appendix D

Holistic Alternatives TM

Appendix E

Southside WWTP Conveyance Alternatives Memo

Existing facilities condition assessment Development of process model for treatment capacities Development of hydraulic model for hydraulic limit identification Evaluation of additional required capacities for each facility Comparison of design alternatives for each facility Development of whole plant improvement plan Feasibility and cost analysis of expansion options available for the Southside basin

Conclusion

The Master Plan for the City of Tyler WWTPs evaluated the existing operations of both the Westside and Southside plants and projected future influent flows and loadings extending to 2052 (30-year planning period) to identify and address near-term needs. The population of the City of Tyler is expected to increase, requiring additional treatment capacity at both plants. The conditions of the treatment processes at both plants were assessed to determine the criticality of individual facilities. A baseline process model of each plant was designed to simulate existing conditions and predict performance at future conditions. A hydraulic model of the Westside and Southside WWTP was developed to determine the hydraulic capacity of each facility and identify critical hydraulic control points throughout the process. The existing capacities and treatment capabilities were compared to projected flows and loadings and future permit requirements to identify the needs of each plant. To address the needs for expansion and rehabilitation, a holistic improvement plan was developed for the Westside and Southside WWTPs with upgrade details provided for each facility. Nearly every facility requires equipment upgrades/replacement or complete restoration. The Westside WWTP and Southside WWTP projects will be implemented in phases to ensure the most critical needs are addressed first, each project duration projected to be 54 months total. The total cost estimates for the Westside and Southside WWTP improvement projects are given in Table 5-1.

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Tyler Wastewater Treatment Plants Master Plan Master Plan Report

Table 5-1: Summary of Cost Estimates for Tyler WWTPs Improvements Total Project Cost $118,000,000$127,000,000 $91,000,000

Westside WWTP1

Annual O&M Cost Impact $993,000-$1,003,000

Southside WWTP $656,000 Notes: 1. Westside cost range includes two alternatives for the existing anaerobic digester improvements 5.1

Additional Information

This report provides an overview of the evaluations conducted as a part of the Tyler WWTPs Master Plan. The details of the existing operation assessments and improvement analyses can be found in the TMs included in this master plan project. A summary of the TMs and the information provided in each is presented in Table 5-2. Table 5-2: Summary of Technical Memoranda in Tyler Master Plan Appendix

Document

Appendix A

Historical Data Review TM

Appendix B

Planning Criteria TM

Appendix C Appendix C Appendix C Appendix C

Baseline Analysis TM: Process Model Baseline Analysis TM: Hydraulic Model Baseline Analysis TM: Gap Analysis Baseline Analysis TM: Available Alternatives

Appendix D

Holistic Alternatives TM

Appendix E

Southside WWTP Conveyance Alternatives Memo

Garver Project No. 21W05170

Information Existing flow and loading data; existing facilities condition assessment Projected loading and flow data and future regulatory limits Development of process model for treatment capacities Development of hydraulic model for hydraulic limit identification Evaluation of additional required capacities for each facility Comparison of design alternatives for each facility Development of whole plant improvement plans Feasibility and cost analysis of expansion options available for the Southside basin

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Appendix A Historical Data Review TM

Garver Project No. 21W05170

Appendix A

Technical Memorandum Historical Data Review City of Tyler Wastewater Treatment Plants Master Plan City of Tyler, Texas

Prepared by:

3010 Gaylord Parkway Suite 190 Frisco, TX 75034 April 2022 Garver Project No. 21W05170

Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

Engineer’s Certification I hereby certify that this Historical Data Review Technical Memorandum, associated with the Tyler Wastewater Treatment Plants Master Plan, was prepared by Garver under my direct supervision for the City of Tyler.

Lance P. Klement, PE State of TX PE License #113630

Digitally Signed 04/27/2022

Russell D. Tate, PE State of TX PE License #132233 Digitally Signed 04/27/2022

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

Table of Contents 1.0

Introduction...................................................................................................................................... 11

2.0

Background ..................................................................................................................................... 11

2.1

Planned Projects ......................................................................................................................... 11

2.2

Data Analysis .............................................................................................................................. 12 Westside Wastewater Treatment Plant – Historical Data ............................................................... 13

3.0 3.1

Historical Influent and Effluent Flows – Westside WWTP .......................................................... 13

3.2

Historical Influent Quality - Westside WWTP .............................................................................. 16

3.2.1

Historical BOD Loading ........................................................................................................... 16

3.2.2

Historical TSS Loading ............................................................................................................ 17

3.2.3

Historical Ammonia-N Loading ................................................................................................ 18

3.2.4

Summary of Historical Flow and Loading ............................................................................... 19

3.2.5

Historical Influent Data Review Summary ............................................................................... 19 Historical Effluent Quality – Westside WWTP ............................................................................. 20

3.3 3.3.1

Effluent Discharge Limitations and Monitoring Requirements ................................................ 20

3.3.2

Historical Effluent Quality ........................................................................................................ 21

3.3.3

Historical Effluent Data Review Summary .............................................................................. 28

Southside Wastewater Treatment Plant – Historical Data .............................................................. 29

4.0 4.1

Historical Influent and Effluent Flows – Southside WWTP ......................................................... 29

4.2

Historical Influent Quality – Southside WWTP ............................................................................ 32

4.2.1

Historical BOD Loading ........................................................................................................... 32

4.2.2

Historical TSS Loading ............................................................................................................ 33

4.2.3

Historical Ammonia-N Loading ................................................................................................ 34

4.2.4

Summary of Historical Flow and Loading ............................................................................... 35

4.2.5

Historical Influent Data Review Summary ............................................................................... 35 Historical Effluent Quality – Southside WWTP ........................................................................... 36

4.3 4.3.1

Effluent Discharge Limitations and Monitoring ........................................................................ 36

4.3.2

Historical Effluent Quality ........................................................................................................ 36

4.3.3

Historical Effluent Data Review Summary .............................................................................. 43

5.0

Summary of Historical Data Review................................................................................................ 44

6.0

Condition Assessment .................................................................................................................... 45

6.1

Westside Wastewater Treatment Plant ....................................................................................... 45

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6.1.1

Mechanical Screen .................................................................................................................. 47

6.1.2

Grit Removal ........................................................................................................................... 48

6.1.3

Chemical Feed Facility ............................................................................................................ 50

6.1.4

Raw Water Pump Station ........................................................................................................ 52

6.1.5

Primary Clarifiers ..................................................................................................................... 54

6.1.6

Light Sludge Pump Station ...................................................................................................... 56

6.1.7

First Stage Trickling Filters ...................................................................................................... 57

6.1.8

Filter Pump Station .................................................................................................................. 58

6.1.9

Nitrification Basin..................................................................................................................... 59

6.1.10 Second Stage Trickling Filters ................................................................................................ 61 6.1.11 Secondary Clarifiers ................................................................................................................ 62 6.1.12 RAS Pump Station .................................................................................................................. 63 6.1.13 Chlorine Building ..................................................................................................................... 64 6.1.14 Chlorine Contact Basin and Oxygenation ............................................................................... 65 6.1.15 Anaerobic Digesters ................................................................................................................ 67 6.1.16 Primary Sludge Pump Station ................................................................................................. 68 6.1.17 Belt Filter Press Pump Station ................................................................................................ 69 6.1.18 Dewatering Facility .................................................................................................................. 70 6.1.19 Operations Building ................................................................................................................. 71 6.1.20 Westside WWTP Condition Assessment Summary ................................................................ 71 6.2

Southside Wastewater Treatment Plant ..................................................................................... 74

6.2.1

Chemical Feed Facility ............................................................................................................ 76

6.2.2

Influent Screw Pumps ............................................................................................................. 78

6.2.3

Mechanical Screens ................................................................................................................ 79

6.2.4

Grit Removal ........................................................................................................................... 81

6.2.5

Primary Clarifiers ..................................................................................................................... 83

6.2.6

Primary Sludge Pump Station ................................................................................................. 85

6.2.7

Aeration Basins 1 & 2 .............................................................................................................. 86

6.2.8

Aeration Basin 3 ...................................................................................................................... 88

6.2.9

Final Clarifiers 1 & 2 ................................................................................................................ 89

6.2.10 Final Clarifier 3 ........................................................................................................................ 90 6.2.11 Plant Lift Station ...................................................................................................................... 91 6.2.12 Chlorine Contact Basin ........................................................................................................... 92

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6.2.13 Chemical Storage Facility ....................................................................................................... 94 6.2.14 RAS/WAS Pump Station ......................................................................................................... 95 6.2.15 Secondary Sludge Pump Station ............................................................................................ 97 6.2.16 Sludge Transfer Pump Station ................................................................................................ 98 6.2.17 Gravity Belt Thickener ............................................................................................................. 98 6.2.18 Anaerobic Digesters .............................................................................................................. 100 6.2.19 Sludge Holding Tank ............................................................................................................. 100 6.2.20 Sludge Dewatering Facility .................................................................................................... 102 6.2.21 Southside WWTP Condition Assessment Summary ............................................................ 103 7.0

Findings and Recommendations................................................................................................... 106

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List of Figures Figure 3-1: Historical Influent Flow at the Westside WWTP ....................................................................... 13 Figure 3-2: Historical Total Effluent Flow .................................................................................................... 14 Figure 3-3: Influent and Effluent Flows ....................................................................................................... 15 Figure 3-4: Historical Influent BOD Loading ............................................................................................... 16 Figure 3-5: Historical Influent TSS Loading ................................................................................................ 17 Figure 3-6: Historical Influent Ammonia-N Loading .................................................................................... 18 Figure 3-7: Historical Effluent cBOD Concentration ................................................................................... 22 Figure 3-8: Historical Effluent TSS Concentration ...................................................................................... 23 Figure 3-9: Historical Effluent NH3-N Concentration ................................................................................... 24 Figure 3-10: Historical Effluent E. Coli ........................................................................................................ 25 Figure 3-11: Historical Effluent pH .............................................................................................................. 26 Figure 3-12: Historical Effluent DO Data ..................................................................................................... 27 Figure 4-1: Historical Influent Flow at the Southside WWTP ...................................................................... 29 Figure 4-2: Historical Total Effluent Flow .................................................................................................... 30 Figure 4-3: Influent and Effluent Flows ....................................................................................................... 31 Figure 4-4: Historical Influent BOD Loading ............................................................................................... 32 Figure 4-5: Historical Influent TSS Loading ................................................................................................ 33 Figure 4-6: Historical Influent Ammonia-N Loading .................................................................................... 34 Figure 4-7: Historical Effluent cBOD Concentration ................................................................................... 37 Figure 4-8: Historical Effluent TSS Concentration ...................................................................................... 38 Figure 4-9: Historical Effluent Ammonia-N Concentration .......................................................................... 39 Figure 4-10: Historical Effluent E. Coli ........................................................................................................ 40 Figure 4-11: Historical Effluent pH .............................................................................................................. 41 Figure 4-12: Historical Effluent DO ............................................................................................................. 42 Figure 4-13: Historical Effluent Alkalinity .................................................................................................... 43 Figure 6-1: PFD of Westside WWTP .......................................................................................................... 46 Figure 6-2: Photo of the Mechanical Fine Screen and Discharge Chute ................................................... 48 Figure 6-3: Photo of the Grit Detritor Basins ............................................................................................... 49 Figure 6-4: Photo of the Basin Isolation Gates Exhibiting Corrosion .......................................................... 50 Figure 6-5: Photo of the Mg(OH)2 Storage and Feed Equipment ............................................................... 52 Figure 6-6: Photo of the Parshall Flume ..................................................................................................... 54

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

Figure 6-7: Photo of the Raw Water Pump Station ..................................................................................... 54 Figure 6-8: Photo of Primary Clarifier 1 ..................................................................................................... 55 Figure 6-9: Photo of a Clarifier Bridge Exhibiting Corrosion ....................................................................... 56 Figure 6-10: Photo of the Light Sludge Pumps ........................................................................................... 57 Figure 6-11: Photo of the First Stage Trickling Filter Exhibiting Dried-Out Media ...................................... 58 Figure 6-12: Photo of the Filter Pumps ....................................................................................................... 59 Figure 6-13: Photo of the Nitrification Basin ............................................................................................... 60 Figure 6-14: Photo of the Second Stage Trickling Filter ............................................................................. 61 Figure 6-15: Photo of One of the Secondary Clarifiers ............................................................................... 62 Figure 6-16: Photo of the RAS Pumps ........................................................................................................ 63 Figure 6-17: Photo of the Chlorine Storage and Dosing Area .................................................................... 64 Figure 6-18: Photo of the Out of Service Aerator ....................................................................................... 66 Figure 6-19: Photo of the CCB Effluent Weir .............................................................................................. 66 Figure 6-20: Photo of the Damaged Anaerobic Digester Roof ................................................................... 67 Figure 6-21: Photo of the Primary Sludge Pump Station ............................................................................ 68 Figure 6-22: Photo of the BFP Pumps ........................................................................................................ 69 Figure 6-23: Photo of the BFPs in the Dewatering Facility ......................................................................... 71 Figure 6-24: Core Risk Map of the Westside WWTP Facilities .................................................................. 73 Figure 6-25: PFD of the Southside WWTP ................................................................................................. 75 Figure 6-26: Photo of the Chemical Storage Tanks - FeSO4 (left) and Mg(OH)2 (middle, right) ................ 77 Figure 6-27: Photo of the Mg(OH)2 Metering Equipment ............................................................................ 77 Figure 6-28: Photo of the Existing Influent Lift Station ................................................................................ 79 Figure 6-29: Photo of Existing Mechanical Screens and Screen Conveyance Equipment ........................ 81 Figure 6-30: Photo of the Existing Screen Conveyor and Dumpster .......................................................... 81 Figure 6-31: Photo of the Existing Detritor Grit Removal Basins ................................................................ 83 Figure 6-32: Photo of the Decommissioned Grit Cyclone/Classifier Unit ................................................... 83 Figure 6-33: Photo of the Existing Primary Clarifiers .................................................................................. 84 Figure 6-34: Photo of the Existing Primary Sludge Pumps ......................................................................... 85 Figure 6-35: Photo of the Existing Aeration Basin Exhibiting Dark MLSS Color ........................................ 87 Figure 6-36: Photo of the Existing RAS/WAS Distribution Piping ............................................................... 87 Figure 6-37: Photo of the Existing Aeration Basin 3 ................................................................................... 88 Figure 6-38: Photo of Secondary Clarifier 1 Skimmer Arm ......................................................................... 90

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Figure 6-39: Photo of Secondary Clarifier 3 ................................................................................................ 91 Figure 6-40: Photo of the Plant Lift Station Access Hatch .......................................................................... 92 Figure 6-41: Photo of the Existing CCB Exhibiting Solids Buildup and Corrosion...................................... 94 Figure 6-42: Photo of the Chemical Storage Facility Showing Structural Damage .................................... 95 Figure 6-43: Photo of the Existing RAS/WAS Pump Station Showing Empty Pump Well ......................... 96 Figure 6-44: Photo of the Secondary Sludge Pump Station ....................................................................... 97 Figure 6-45: Photo of the Existing Gravity Belt Thickener Facility .............................................................. 99 Figure 6-46: Photo of the Existing Anaerobic Digester Basins ................................................................. 100 Figure 6-47: Photo of the Existing Sludge Storage Basin ......................................................................... 101 Figure 6-48: Photo of the BFPs in the Dewatering Facility ....................................................................... 103 Figure 6-49: Core Risk Map of the Southside WWTP Facilities ............................................................... 105

List of Tables Table 2-1: CIP of Tyler Wastewater Treatment Plants ............................................................................... 11 Table 3-1: Summary of Current Annual Average Daily Flow and Max Month Flow ................................... 15 Table 3-2: Flow and Constituent Peaking Factors ...................................................................................... 19 Table 3-3:Average Flow and Influent Constituent Loadings Based on Time Period .................................. 19 Table 3-4: Average Daily Concentration, Loading and Peaking Factors for Design Criteria ...................... 20 Table 3-5: TPDES Permit Requirements for Westside WWTP .................................................................. 20 Table 3-6: Effluent Quality Summary from January 2016 to August 2021 ................................................. 28 Table 4-1: Summary of Current Annual Average Daily Flow and Max Month Flow ................................... 31 Table 4-2: Flow and Constituent Peaking Factors ...................................................................................... 35 Table 4-3: Influent Constituent Loadings Based on Time Period ............................................................... 35 Table 4-4: Average Daily Concentration and Peaking Factors for Design Criteria..................................... 35 Table 4-5: TPDES Permit Requirements for Southside WWTP ................................................................. 36 Table 4-6: Effluent Quality Summary from January 2019 to August 2021 ................................................. 43 Table 5-1: Peaking Factors Identified at the Westside and Southside WWTPs ......................................... 44 Table 6-1: Design Details of the Existing Screening Facility ...................................................................... 47 Table 6-2: Design Details of the Existing Grit Removal Facility .................................................................. 49 Table 6-3: Design Details of the Existing Chemical Feed Facility .............................................................. 51 Table 6-4: Design Details of the Existing Raw Water Pump Station .......................................................... 53 Table 6-5: Design Details of the Existing Primary Clarifiers ....................................................................... 55

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

Table 6-6: Design Details of the Existing Light Sludge Pump Station ........................................................ 56 Table 6-7: Design Details of the Existing First Stage Trickling Filters ........................................................ 57 Table 6-8: Design Details of the Existing Filter Pumps ............................................................................... 59 Table 6-9: Design Details of the Existing Nitrification Basin ....................................................................... 60 Table 6-10: Design Details of the Existing Second Stage Trickling Filters ................................................. 61 Table 6-11: Design Details of the Existing Secondary Clarifiers ................................................................ 62 Table 6-12: Design Details of the Existing RAS Pump Station ................................................................... 63 Table 6-13: Design Details of the Chlorine Building ................................................................................... 64 Table 6-14: Design Details of the Existing CCB ......................................................................................... 65 Table 6-15: Design Details of the Existing Anaerobic Digesters ................................................................ 67 Table 6-16: Design Details of the Existing Primary Sludge Pump Station ................................................. 68 Table 6-17: Design Details of the Existing BFP Pump Station ................................................................... 69 Table 6-18: Design Details of the Existing Dewatering Facility .................................................................. 70 Table 6-19: Criticality Ranking of the Administration Building .................................................................... 71 Table 6-20: Condition Assessment Summaryfor the Westside WWTP ...................................................... 72 Table 6-21: Details of Existing Chemical Feed Facility ............................................................................... 76 Table 6-22: Details of Existing Influent Lift Station ..................................................................................... 78 Table 6-23: Design Details of Existing Mechanical Screening Equipment ................................................. 80 Table 6-24: Design Details of Existing Grit Removal System ..................................................................... 82 Table 6-25: Design Details of the Existing Primary Clarifiers ..................................................................... 84 Table 6-26: Design Details of Existing Primary Sludge Pumps .................................................................. 85 Table 6-27: Design Details of the Existing Aeration Basins 1 & 2 .............................................................. 86 Table 6-28: Design Details of Aeration Basin 3 .......................................................................................... 88 Table 6-29: Design Details of the Final Clarifiers 1 and 2 .......................................................................... 89 Table 6-30: Design Details of Final Clarifier 3 ............................................................................................ 90 Table 6-31: Design Details of the Plant Lift Station .................................................................................... 91 Table 6-32: Design Details of the Chlorine Contact Basin .......................................................................... 93 Table 6-33: Design Details of the Chemical Storage Facility ...................................................................... 94 Table 6-34: Design Details of the RAS/WAS Pump Station ....................................................................... 95 Table 6-35: Design Details of the Secondary Sludge Pump Station .......................................................... 97 Table 6-36: Design Details of the Sludge Transfer Pumps ......................................................................... 98 Table 6-37: Design Details of the Gravity Belt Thickener Facility ............................................................... 99

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Table 6-38: Design Details of the Anaerobic Digesters ............................................................................ 100 Table 6-39: Design Details of the Sludge Holding Tank ........................................................................... 101 Table 6-40: Design Details of the Existing Dewatering Facility ................................................................ 102 Table 6-41: Summary of the Condition Assessment for the Southside WWTP ........................................ 104 Table 7-1: Peaking Factors Identified at the Westside and Southside WWTPs ....................................... 106 Table 7-2: Condition Assessment Summary for the Westside WWTP ..................................................... 107 Table 7-3: Summary of the Condition Assessment for the Southside WWTP .......................................... 108

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

List of Acronyms Acronym AADF

Definition Average Annual Daily Flow

BNR

Biological Nutrient Removal

BOD

Biochemical Oxygen Demand

cBOD

Carbonaceous Biochemical Oxygen Demand

cfu

Colony-Forming Units

CIP

Capital Improvements Plan

COD

Chemical Oxygen Demand

ºF

Degree Fahrenheit

ºC

Degree Centigrade

Dissolved Oxygen

Detention Time

gpcd

Gallons per Capita per Day

FCB

Fecal Coliform Bacteria

Linear Feet

Million Gallons

MGD

Million Gallons per Day

MLSS

Mixed Liquor Suspended Solids

N/A

Not Applicable

Ammonia-N

Ammonia-Nitrogen

NH3-N

Ammonia-Nitrogen

NPDES

National Pollutant Discharge Elimination System

PFD

Process Flow Diagram

ppd

Pounds per Day

RAS

Return Activated Sludge

s.u.

Standard Unit

TCEQ

Texas Commission on Environmental Quality

TKN

Total Kjeldahl Nitrogen

Technical Memorandum

Total Phosphorous

TPDES

Texas Pollutant Discharge Elimination System

TRC

Total Residual Chlorine

TSS

Total Suspended Solids

WWTP

Wastewater Treatment Plant

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

1.0

Introduction

The purpose of this Technical Memorandum (TM) is to review and summarize the historical influent wastewater characteristics entering the two Tyler Wastewater Treatment Plants (WWTPs): the Southside WWTP and the Westside WWTP. In addition to the influent wastewater, the historical effluent quality discharged from the WWTPs was also reviewed. Historical data was provided by the City of Tyler staff for the period from January 2016 to August 2021 for Garver’s review and analysis. Wastewater characteristics reviewed by Garver include carbonaceous biochemical oxygen demand (cBOD), ammonia nitrogen (NH3N), total suspended solids (TSS), E. coli bacteria, dissolved oxygen (DO) and total residual chlorine (TRC). The Southside and Westside WWTPs are currently providing treatment for the wastewater collected in the City of Tyler, Texas. Constituent and flow peaking factors are established herein to be used for future design criteria based on historical influent data trends identified during the data analysis. Furthermore, findings of condition assessment walk-through visits at both Southside and Westside facilities are summarized in this TM.

2.0

Background

The following section provides a summary of the previously planned projects at the WWTPs. In addition, the methodology used in this TM to analyze the historical data is presented. 2.1 Planned Projects The previously planned projects at the Southside and Westside WWTPs include a replacement of their chlorine and sulfur dioxide feed systems in early 2022. In addition, at the Southside WWTP, the chemical feed system will be enclosed, and a chemical scrubber system will be installed. A summary of the Tyler WWTPs’ capital improvements plan (CIP), as provided by City of Tyler staff for the period from 2021 to 2030 is provided in Table 2-1. The findings of the master plan that is being developed by Garver may impact some of the planned projects listed in this table. Table 2-1: CIP of Tyler Wastewater Treatment Plants Facility/Element Fiscal Year Grande Lift Station and Sewer Line 2028 WWTP/Lift Station – Pump, Motor, Gear Box Replacement Annual

Total Budget $1,602,235 $1,500,000

Southside WWTP Primary Clarifier Rehabilitation Chlorination/Dechlorination System Improvements ROW Procurement Final Clarifier Rehabilitation Aeration Improvements

2021-2022 2021-2022 2021, 2023-2028 2024-2025 2027

$5,016,800 $1,400,000 $1,855,000 $1,800,000 $500,000

New Office and Lab Trickling Filter Improvements Aeration Basin/Filter Pump Electrical Feed Replacement Fine Screen Replacement

2022 2027 2027 2028

$650,000 $1,000,000 $1,200,000 $950,000

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Westside WWTP

Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

2.2 Data Analysis Influent and effluent water quality characteristics were measured routinely from January 2016 to August 2021 by both WWTPs staff and records were provided to Garver for evaluation. Influent and effluent flow measurements were taken as daily average flows throughout the focused period. Influent and effluent water quality parameters were typically measured once per day or once per weekday, except for influent NH3-N, which was sampled as a weekly average. Extreme data points are not presented in the provided graphics to increase resolution of the rolling averages for each parameter, as this information is more indicative of plant influent loadings. Data obtained from Westside and Southside WWTPs were used to calculate the rolling averages and peaking factors. Rolling averages were taken on a 30-day (monthly) and a 365-day (annual) basis for the influent data and a 7-day (weekly) and 30-day basis for the effluent data. Rolling averages presented in this analysis were calculated by including the preceding daily data with the day associated with the average value. Influent rolling averages were calculated on these bases, in part, to calculate the maximum month peaking factor for plant flows and influent constituent loadings. Peaking factors for a given date and parameter are calculated according to the following equation: 𝐏𝐞𝐚𝐤𝐢𝐧𝐠 𝐅𝐚𝐜𝐭𝐨𝐫(𝐃𝐚𝐭𝐞, 𝐏𝐚𝐫𝐚𝐦𝐞𝐭𝐞𝐫 𝐗) =

𝟑𝟎 𝐃𝐚𝐲 𝐀𝐯𝐞𝐫𝐚𝐠𝐞 𝐋𝐨𝐚𝐝𝐢𝐧𝐠 (𝐃𝐚𝐭𝐞, 𝐏𝐚𝐫𝐚𝐦𝐞𝐭𝐞𝐫 𝐗) 𝟑𝟔𝟓 𝐃𝐚𝐲 𝐀𝐯𝐞𝐫𝐚𝐠𝐞 𝐋𝐨𝐚𝐝𝐢𝐧𝐠 (𝐃𝐚𝐭𝐞, 𝐏𝐚𝐫𝐚𝐦𝐞𝐭𝐞𝐫 𝐗)

In addition to the graphical peaking factors described above, Garver implemented a second method of peaking factor calculation by using the 92nd percentile of the data values within a yearly range for a given parameter. The more stringent permit limits of the WWTPs are considered on a monthly basis and the 92 nd percentile method effectively considers the collective month of data with the highest values within a year (1 month contains approximately 8.3% of the year’s data). The ratio of the 92nd percentile and the yearly average can provide a peaking factor for a given year that considers all peaking events as a collective value. In this TM, both graphical and 92nd percentile peaking factors are considered to determine the most applicable design factor. Effluent rolling averages were taken on a 7-day and a 30-day basis for easy comparison to the WWTP’s Texas Pollutant Discharge Elimination System (TPDES) permits, which provides regulatory limits on a weekly and monthly basis. However, weekly and monthly averages are not calculated on a calendar basis in this TM as these measurements can miss brief mid-week and mid-month peaks of effluent parameters including nutrients, E. coli, and TRC. Therefore, any averages that appear to exceed permitted limits may not have resulted in a permit violation.

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.0

Westside Wastewater Treatment Plant – Historical Data

This section presents historical data collected at the Westside WWTP. 3.1

Historical Influent and Effluent Flows – Westside WWTP

This section will discuss the historical influent flow measurements to the Westside WWTP as well as the measured effluent flows from January 2016 to August 2021. Figure 3-1 presents average influent monthly flows over the sampling period. Influent flows have increased from approximately 9.6 MGD (2016-2018 annual average) to 11.7 MGD (2019-2021 annual average). The annual average influent daily flow for the past 6 years (January 2016 to August 2021) is 10.5 MGD.

Figure 3-1: Historical Influent Flow at the Westside WWTP

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

Figure 3-2 presents the historical effluent wastewater flow discharged from the Westside WWTP. The 30day average flows range from 7.3 to 14.3 MGD. The annual average effluent flows range from 8.7 to 11.0 MGD. The annual average effluent daily flow for the past 6 years (January 2016 to August 2021) is 9.4 MGD.

Figure 3-2: Historical Total Effluent Flow

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

It has been observed that the measured influent and effluent flow values at the WWTP have significant differences from each other over the past 3 years. Figure 3-3 demonstrates the measured annual average influent and effluent flows from January 2016 to August 2021, as well as the discrepancy between the historical influent and effluent flows.

Figure 3-3: Influent and Effluent Flows As shown, the divergence of influent and effluent flow values began in early 2019 and has grown steadily since that point. The difference between the historical influent flow values and the effluent values ranges from 0.02 to 3.70 MGD. In discussion with WWTP staff, the effluent flow measurement weir reads more accurately as compared to the influent Parshall flume, and therefore the effluent flow measurements will be used to determine peaking factors for future flow design criteria as well as for current and projected loadings in this TM. The annual average daily effluent flow from January 2016 to August 2021 will be used as the Average Dry Weather flow value. The graphical peaking factor of 1.46 (identified in the early-2019 data) will be used to determine the current max month flow for design criteria. This data is summarized in Table 3-1. Table 3-1: Summary of Current Annual Average Daily Flow and Max Month Flow Annual Average Daily Flow (MGD)

Peaking Factor

Max Month Flow (MGD)

9.5

1.46

13.9

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.2 Historical Influent Quality - Westside WWTP In this section, influent wastewater quality parameters (BOD, TSS, and NH3-N) are discussed in terms of contaminant loadings. For each parameter, loading is calculated using the equation below and influent flow values from Section 3.1: 𝐋𝐨𝐚𝐝 ( 3.2.1

𝐥𝐛 𝐝𝐚𝐲

) = 𝐅𝐥𝐨𝐰 (𝐦𝐠𝐝) × 𝐂𝐨𝐧𝐜𝐞𝐧𝐭𝐫𝐚𝐭𝐢𝐨𝐧 (

𝐦𝐠 𝐋

) × 𝟖. 𝟑𝟒

Historical BOD Loading

Figure 3-4 presents the historical influent BOD loading entering the Westside WWTP. Occasional daily BOD loadings up to approximately 66,600 lb/day were observed from 2016 to the present time. As shown, the monthly average BOD loading ranges from 8,900 to 19,000 lb/day. Annual average BOD loading ranges from 11,000 to 15,200 lb/day. Additionally, the annual average BOD loading to the WWTP has decreased by approximately 8% during the study period from approximately 13,900-lb/day to 12,800-lb/day. Graphical peaking factors for several events are also presented in Figure 3-4. A maximum graphical peaking factor of 1.28 was observed during January 2019. The 92nd percentile peaking factors range from 1.43 to 1.60 from January 2016 to August 2021.

Figure 3-4: Historical Influent BOD Loading

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.2.2

Historical TSS Loading

The historical TSS loading to Westside WWTP is illustrated in Figure 3-5. As shown, monthly average TSS ranges from 10,100 to 22,200 lb/day and annual average TSS ranges from approximately 12,500 to 16,300 lb/day. The annual average TSS loading to the WWTP has remained fairly stable, increasing only by approximately 0.50% during the study period from 14,100-lb/day to 14,200-lb/day. A maximum graphical peaking factor of 1.40 is observed for TSS loading during January 2019. Peaking factors in the 92nd percentile range from 1.45 to 1.79 from January 2016 to August 2021.

Figure 3-5: Historical Influent TSS Loading

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.2.3

Historical Ammonia-N Loading

The historical NH3-N loading is depicted in Figure 3-6. NH3-N loadings as high as approximately 4,500 lb/day were observed during the study period. As shown, monthly average NH3-N ranges from 1,000 to 2,500 lb/day and the annual average ranges from approximately 1,500 to 1,900 lb/day. Additionally, the annual average NH3-N loading to the WWTP has increased during the study period by 8% from approximately 1,700 lb/day to 1,800 lb/day. A maximum graphical peaking factor of 1.47 is observed for NH3-N loading during August 2019. Peaking factors in the 92nd percentile for the past 6 years have steadily increased, with an average peaking factor of 1.35 over the study period and a maximum peaking factor of 1.55 in 2021.

Figure 3-6: Historical Influent Ammonia-N Loading

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.2.4

Summary of Historical Flow and Loading

The highest graphical peaking factors for all measured constituents are as follows: Flow (1.46), BOD (1.28), TSS (1.40), NH3-N (1.47). Table 3-2 summarizes the calculated peaking factors using both the graphical method and the 92nd percentile method. The maximum graphical peaking factors were used for flow and all evaluated constituents. Table 3-2: Flow and Constituent Peaking Factors

Parameter

92nd Percentile Peaking Factor 6-year 6-year Average Max

Graphical Peaking Factor

Selected Peaking Factor

1st

2nd

Influent Flow

1.46

1.32

1.30

1.38

1.46

BOD

1.28

1.27

1.50

1.60

1.28

TSS

1.40

1.30

1.62

1.79

1.40

NH3-N

1.47

1.43

1.35

1.55

1.47

3.2.5

Historical Influent Data Review Summary

This TM has determined that, due to a greater conservatism in effluent flow measurements, max month flow design criteria may be based on the chosen graphical peaking factor for effluent flow in this study, identified as 1.46. Constituent loadings for the parameters have varied over the sampling period, with annual average shifts of approximately -8.0% to 8.0%. Table 3-3 compares the average constituent loadings for January 2016 – December 2018 with the average values from the more recent period within the study (January 2019 – August 2021). Table 3-3:Average Flow and Influent Constituent Loadings Based on Time Period Flow

BOD

TSS

NH3-N

MGD

lb/day

Jan 2016 – Dec 2018

9.5

14,000

14,100

1,700

Jan 2019 – Aug 2021

9.5

12,800

14,200

1,800

Time Period

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

As shown in Table 3-4, the more recent annual average day flow and loadings are used to calculate the concentrations to be utilized as the basis of design. Table 3-4: Average Daily Concentration, Loading and Peaking Factors for Design Criteria Concentration1

Loading2

Peaking Factor3

mg/L

lb/day

BOD

162

12,800

1.28

TSS

180

14,200

1.40

NH3-N

1,800

1.47

Parameter

Concentration is calculated using the average loads reported in this table and the average influent flow for the study period (9.5 MGD). 2 Loads based on existing data set. Loads will increase when concentrations are applied to design flows. 3 Peaking factors are for loads not concentrations.

Historical Effluent Quality – Westside WWTP

3.3

In this section, historical effluent quality parameters at the Westside WWTP for the period of January 2016 through August 2021 are reviewed. 3.3.1

Effluent Discharge Limitations and Monitoring Requirements

The Westside WWTP operates under TPDES permit number WQ0010653001 originally issued by Texas Commission on Environmental Quality (TCEQ) on February 21, 2020. The permit limits for the Westside WWTP effluents are listed in Table 3-5 excluding those parameters not considered in this report (4-4’ DDT, Diazinon, and Oxodiazinon). Table 3-5: TPDES Permit Requirements for Westside WWTP

Parameter

Mass (lb/day)1

Concentration (mg/L) Daily Average

7-day Average

Daily Max

Single Grab

Frequency

1,084

One/day

2,168

One/day

TSS (Mar-Nov)

1,626

One/day

TSS (Dec-Feb)

2,168

One/day

325

One/day

1,084

One/day

cBOD (MarNov) cBOD (DecFeb)

NH3-N (MarNov) NH3-N (DecFeb)

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Sample Type 24-hr composite 24-hr composite 24-hr composite 24-hr composite 24-hr composite 24-hr composite

Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

Parameter

Mass (lb/day)1

Concentration (mg/L) Daily Average

7-day Average

Daily Max

Single Grab

Frequency

Sample Type

E. coli (cfu/100ml)

126

N/A

399

N/A

Five/week

Grab

TRC (before dechlorination)

≥ 1.0

One/day

Grab

TRC (after dechlorination)

≤ 0.1

One/day

Grab

Min: 6.0 Max: 9.0

Five/week

Grab

DO (Mar-Nov)

6.0

One/day

Grab

DO (Dec-Feb)

5.0

One/day

Grab

Notes: (1) Mass Loadings are determined based on the permitted annual average flow of 13 MGD. The facility also has a permitted 2-hour peak flow of 32.5 MGD. 3.3.2

Historical Effluent Quality

This section covers historical effluent quality parameters for the Westside WWTP during the study period. For each effluent characteristic pertaining to permitting, daily values are presented along with rolling 7-day average concentrations and rolling 30-day average concentrations. Weekly and monthly permit limits are presented as applicable. With respect to some parameters including TSS and NH 3-N, some exceedances were observed. However, these measurements may not have occurred within one calendar week, or a single calendar month therefore may not necessarily constitute a permit violation.

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.3.2.1 Historical Effluent cBOD Figure 3-7 illustrates the historical effluent cBOD concentration. Weekly average cBOD concentration ranges from 1.2 to 12 mg/L. Monthly average cBOD concentration ranges from 1.54 to 6.04 mg/L. As shown, during the study period, there were no observations of weekly or monthly average cBOD discharge exceeding permitted limits.

Figure 3-7: Historical Effluent cBOD Concentration

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.3.2.2 Historical Effluent TSS Historical effluent TSS concentration is given in Figure 3-8. Daily values as well as weekly and monthly average values are presented. Weekly average TSS concentration ranges from 1.5 to 54 mg/L. Monthly average TSS concentration ranges from 1.90 to 18.1 mg/L. There have been multiple occasions of weekly and monthly average TSS concentrations exceeding the permit limits, however as previously stated, this may not constitute a failure to meet permit requirements.

Figure 3-8: Historical Effluent TSS Concentration

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.3.2.3 Historical Effluent Ammonia-N Figure 3-9 presents the historical NH3-N concentration of the Westside WWTP effluent. The weekly average effluent NH3-N concentration ranges from 0.06 to 15.80 mg/L. The monthly average effluent NH3-N concentration ranges from 0.13 to 10.21 mg/L, with an average of 1.5 mg/L. There are multiple instances of weekly and monthly average effluent NH3-N levels exceeding permit limits in 2016, early 2017, and 2020; however, this may not constitute a permit violation.

Figure 3-9: Historical Effluent NH3-N Concentration

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.3.2.4 Historical Effluent E. Coli Historical Effluent E. coli data are shown in Figure 3-10. Average weekly and monthly values of daily data points are presented, although E. coli measurements were only taken Monday-Friday. Although some measurements appear to exceed permitted levels of E. coli (July and August of 2015, July of 2018, and July of 2019), these measurements were from single day events and may not be considered a weekly average violation of the permit.

Figure 3-10: Historical Effluent E. Coli

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.3.2.5 Historical Effluent pH Historical effluent pH data are shown in Figure 3-11. Average 30-day and 365-day values of daily data points are presented. Annual average pH values range from approximately 6.7 to 7.0.

Figure 3-11: Historical Effluent pH

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.3.2.6 Historical Effluent DO Historical effluent DO data are shown in Figure 3-12. Average 30-day and 365-day values of daily data points are presented along with the monthly permit limits. Annual average DO values range from approximately 7.7 to 8.1; however, monthly average values vary drastically based on climate conditions; in warmer months (March-November), monthly average DO levels typically range from 7-8 mg/L and in colder months (December-February) typically range from 8-9 mg/L.

Figure 3-12: Historical Effluent DO Data 3.3.2.7 Historical Effluent Total Chlorine Residual Total Chlorine Residual (TRC) was measured on a daily basis during the study period. Based on the review of the data provided to Garver, there were no single day measurements of TRC concentrations that exceeded the permitted limit of 0.1 mg/L.

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

3.3.3

Historical Effluent Data Review Summary

This review of historical effluent data suggests a few instances where constituent exceedances may have occurred. The exceedances included elevated concentrations of TSS and NH3-N. Table 3-6 summarizes the historical effluent quality review results, which are averaged over the study period. Table 3-6: Effluent Quality Summary from January 2016 to August 2021 Parameter

Unit

Average

cBOD Concentration

mg/L

2.9

TSS Concentration

mg/L

5.8

Ammonia-N Concentration

mg/L

1.5

E. coli

Colonies/100 mL

16.1

mg/L

7.9

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

4.0

Southside Wastewater Treatment Plant – Historical Data

This section presents the historical data collected at the Southside WWTP. 4.1 Historical Influent and Effluent Flows – Southside WWTP This section will discuss the historical influent flow measurements to the Southside WWTP as well as the measured effluent flows from January 2016 to August 2021. Figure 4-1 presents average influent monthly flows from January 2016 to August 2021. Influent flows have increased from approximately 6.5 MGD (20162018 annual average) to 7.0 MGD (2019-2021 annual average). The annual average influent daily flow for the past 6 years (January 2016 to August 2021) is 6.7 MGD.

Figure 4-1: Historical Influent Flow at the Southside WWTP

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

Figure 4-2 presents the historical effluent wastewater flow leaving the Southside WWTP. The 30-day average flows range from 4.9 to 8.87 MGD. The annual average effluent flows range from 5.5 to 6.9 MGD. The annual average effluent daily flow for the past 6 years (January 2016 to August 2021) is 6.1 MGD.

Figure 4-2: Historical Total Effluent Flow

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

It has been observed that the measured influent flow values at the WWTP have been consistently higher than the measured effluent flow values. Figure 4-3 demonstrates the measured annual average influent and effluent flows from January 2016 to August 2021, as well as the discrepancy between the historical influent and effluent flows.

Figure 4-3: Influent and Effluent Flows The difference between the historical effluent flow values over the influent values ranges from 0.39 to 0.75 MGD with an average difference of 0.60 MGD. The influent flow measurements are higher in magnitude, and therefore provide a more conservative option for future projections. The influent flow measurements will be used to determine peaking factors for future flow design criteria as well as for current and projected loadings in this TM. The annual average daily influent flow from January 2016 to August 2021 and the peaking factor of 1.28 will be used to determine the current max month for design criteria. This data is summarized in Table 4-1. Table 4-1: Summary of Current Annual Average Daily Flow and Max Month Flow Annual Average Daily Flow (MGD)

Peaking Factor

Max Month Flow (MGD)

6.7

1.28

8.6

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

4.2 Historical Influent Quality – Southside WWTP In this section, influent wastewater quality parameters (BOD, TSS, and NH3-N) are discussed in terms of contaminant loadings. 4.2.1

Historical BOD Loading

Figure 4-4 presents the historical influent BOD loading entering the Southside WWTP. Occasional daily BOD loadings up to approximately 19,900 lb/day were observed from 2016 to the present time. As shown, the monthly average BOD loading ranges from 6,700 to 11,500 lb/day. Annual average BOD loading ranges from 8,000 to 10,130 lb/day. Additionally, the annual average BOD loading to the WWTP has decreased by approximately 11% during the study period from approximately 9,600-lb/day to 8,500-lb/day. Graphical peaking factors for several events are also presented in Figure 4-4 maximum graphical peaking factor of 1.26 was observed during December 2019. The 92nd percentile peaking factors are fairly consistent over the past 6 years and provide an average peaking factor of 1.25 from January 2016 to August 2021.

Figure 4-4: Historical Influent BOD Loading

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

4.2.2

Historical TSS Loading

The historical TSS loading to Southside WWTP is illustrated in Figure 4-5. Single-day loadings of TSS were observed to be as high as approximately 32,000 lb/day for the study period. As shown, monthly average TSS ranges from 9,000 to 20,500 lb/day and annual average TSS ranges from approximately 12,000 to 16,700 lb/day. TSS values have varied over the study period; the annual average TSS loading to the WWTP has increased by approximately 16.6% during the study period from approximately 13,000-lb/day to 15,100lb/day. A maximum graphical peaking factor of 1.45 is observed for TSS loading during October 2019. Peaking factors in the 92nd percentile for the past 6 years have ranged from 1.32 to 1.44, with an average peaking factor of 1.36.

Figure 4-5: Historical Influent TSS Loading

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Tyler Wastewater Treatment Plants Master Plan Historical Data Review Technical Memorandum

4.2.3

Historical Ammonia-N Loading

The historical NH3-N loading is depicted in Figure 4-6. NH3-N loadings as high as approximately 2,300 lb/day were observed during the study period. As shown, monthly average NH3-N ranges from 840 to 1,500 lb/day and the annual average ranges from approximately 1,070 to 1,200 lb/day. Additionally, the annual average NH3-N loading to the WWTP has increased by 3.6% during the study period from approximately 1120-lb/day to 1,160-lb/day. A maximum graphical peaking factor of 1.29 is observed for NH3-N loading during March 2019. Peaking factors in the 92nd percentile for the past 6 years have ranged from 1.08 to 1.24 with an average of 1.17.

Figure 4-6: Historical Influent Ammonia-N Loading

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4.2.4

Summary of Historical Flow and Loading

The highest graphical peaking factors for all measured constituents are as follows: Flow (1.28), BOD (1.26), TSS (1.45), NH3-N (1.29). Table 4-2 summarizes the calculated peaking factors using both the graphical method and the 92nd percentile method. The flow peaking factor of 1.28 was determined in Section 4.1 through the graphical peaking factor method. Maximum graphical peaking factors were also used for the following constituents: BOD, TSS, and NH3-N. Table 4-2: Flow and Constituent Peaking Factors Graphical Peaking Factor

Parameter

92nd Percentile Peaking Factor 6-year Average 6-year Max

Selected Peaking Factor

1st

2nd

Influent Flow

1.28

1.26

1.19

1.25

1.28

BOD

1.26

1.21

1.25

1.31

1.26

TSS

1.45

1.31

1.36

1.44

1.45

NH3-N

1.29

1.26

1.17

1.24

1.29

4.2.5

Historical Influent Data Review Summary

Constituent loadings for each parameter have remained fairly consistent over the course of the study except for BOD, which demonstrated a gradual decrease in magnitude (See Figure 4-4). Table 4-3 compares the average constituent loadings for January 2016 – December 2018 with the average values from the most recent period within the study (January 2019 – August 2021). Table 4-3: Influent Constituent Loadings Based on Time Period

Jan 2016 – Dec 2018

Flow MGD 6.5

BOD lb/day 9,550

TSS lb/day 13,000

NH3-N lb/day 1,100

Jan 2019 – Aug 2021

7.0

8,500

15,100

1,150

Time Period

As shown in Table 4-4, the most recent annual average day flow and loadings are used to calculate the concentrations to be utilized as the basis of design. Table 4-4: Average Daily Concentration and Peaking Factors for Design Criteria Concentration1

Loading2

Peaking Factor3

mg/L

lb/day

BOD

146

8,500

1.26

TSS

259

15,100

1.45

NH3-N

1,150

1.29

Parameter

Concentration is calculated using the loads reported in this table and the average influent flow for the period of January 2019 to August 2021 (7.0 MGD). 2 Loads based on existing data set. Loads will increase when concentrations are applied to design flows. 3 Peaking factors are for loads not concentrations.

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4.3 Historical Effluent Quality – Southside WWTP 4.3.1

Effluent Discharge Limitations and Monitoring

The Southside WWTP operates under TPDES permit number WQ0010653002 originally issued by TCEQ on September 17, 2021. The permit limits for the Southside WWTP effluents are listed in Table 4-5 excluding those parameters not considered in this report: Total Dissolved Solids (TDS) and Sulfate. Table 4-5: TPDES Permit Requirements for Southside WWTP

Parameter

Mass (lb/day)1

cBOD (5-day) TSS

Concentration (mg/L)

Sample Type

Daily Average

7-day Average

Daily Max

Single Grab

Frequency

751

Five/week

1,126

Five/week

225

Five/week

300

Five/week

126

N/A

399

N/A

Three/week

Grab

TRC (before dechlorination)

≥ 1.0

One/day

Grab

TRC (after dechlorination)

≤ 0.1

One/day

Grab

Min: 6.0 Max: 9.0

Five/Week

Grab

DO (Mar-Nov)

5.0

Five/Week

Grab

DO (Dec-Feb)

4.0

Five/Week

Grab

Ammonia-N (Mar-Oct) Ammonia-N (Nov-Feb) E. coli2 (cfu/100ml)

24-hr composite 24-hr composite 24-hr composite 24-hr composite

Notes: 1. Mass Loadings are determined based on the permitted annual average flow of 9 MGD. Peak 2hour flow capacity of the Southside facility is 22.5 MGD. 4.3.2

Historical Effluent Quality

This section covers historical effluent quality parameters for the Southside WWTP during the study period. For each effluent characteristic pertaining to permitting, daily values are presented along with rolling 7-day average concentrations and rolling 30-day average concentrations. Weekly and monthly permit limits are presented as applicable. With respect to some parameters including cBOD, TSS, and NH3-N, some exceedances were observed. However, these measurements may not have occurred within one calendar week, or a single calendar month therefore may not constitute permit violation.

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4.3.2.1 Historical Effluent cBOD Figure 4-7 illustrates the historical effluent cBOD concentration. In general, cBOD concentrations exhibited more variability during the period from 2019 to 2021. Weekly average cBOD concentration ranges from 1.31 to 17.1 mg/L. Monthly average cBOD concentration ranges from 1.62 to 9.88 mg/L. As shown, during the study period, there was only one occasion of weekly average cBOD levels exceeding permitted levels; this was in April of 2021.

Figure 4-7: Historical Effluent cBOD Concentration

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4.3.2.2 Historical Effluent TSS Historical effluent TSS concentration is given in Figure 4-8. Daily values as well as monthly and annual average values are presented. Weekly average TSS concentration ranges from 3.88 to 160 mg/L. Monthly average TSS concentration ranges from 4.68 to 47.7 mg/L. There have been multiple instances of weekly and monthly average TSS levels exceeding the permitted levels, however this may not have resulted in failure to meet permit.

Figure 4-8: Historical Effluent TSS Concentration

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4.3.2.3 Historical Effluent Ammonia-N Figure 4-9 presents the historical NH3-N concentration of the Southside WWTP effluent. The weekly average effluent NH3-N concentration ranges from 0.04 to 10.3 mg/L. The monthly average effluent NH3-N concentration ranges from 0.08 to 5.57 mg/L, with an average of 1.4 mg/L. Several instances of weekly and monthly permit exceedances were observed throughout the sampling period, most notably between January and March of 2019, 2020, and 2021. These clusters of elevated single-day NH3-N effluent concentrations may have yielded weekly/monthly average permit exceedances.

Figure 4-9: Historical Effluent Ammonia-N Concentration

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4.3.2.4 Historical Effluent E. Coli Historical Effluent E. coli data are shown in Figure 4-10. Average 7-day and 30-day values of daily data points are presented, although E. coli measurements were only taken Monday-Friday. The measurements in this 6-year time frame are consistently below permitted levels of E. coli.

Figure 4-10: Historical Effluent E. Coli

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4.3.2.5 Historical Effluent pH Historical effluent pH data are shown in Figure 4-11. Average 30-day and 365-day values of daily data points are presented. Annual average pH values range from approximately 6.6 to 7.2. It is noticed that pH has slightly reduced over the study period.

Figure 4-11: Historical Effluent pH

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4.3.2.6 Historical Effluent Dissolved Oxygen Historical effluent DO data are shown in Figure 4-12. Average 30-day and 365-day values of daily data points are presented along with the monthly permit limits. Annual average DO values range from approximately 6.3 to 6.6; however, monthly average values vary drastically based on climate conditions; DO values in warmer months (March-October), monthly average DO levels typically range from 5.7-6.5 mg/L and in colder months (November-February) typically range from 6.5-7.4 mg/L.

Figure 4-12: Historical Effluent DO 4.3.2.7 Historical Effluent Total Chlorine Residual Total Chlorine Residual (TRC) was measured daily during the study period. There were no single day measurements of TRC concentrations that exceeded the permitted limit of 0.1 mg/L.

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4.3.2.8 Historical Effluent Alkalinity Figure 4-13 demonstrates the historical effluent alkalinity concentrations. Monthly average values range from 56 to 110 mg/L. However, it is notable that the effluent alkalinity values have remained fairly constant from January 2016 to August 2021.

Figure 4-13: Historical Effluent Alkalinity 4.3.3

Historical Effluent Data Review Summary

This review of historical effluent data suggests a few instances where constituent exceedances may have occurred, although permit violation records have not been consulted. The exceedances included elevated concentrations of cBOD, TSS and NH3-N. Table 4-6 summarizes the historical effluent quality review results, which are averaged over the study period. Table 4-6: Effluent Quality Summary from January 2019 to August 2021 Parameter

Unit

Average

cBOD Concentration

mg/L

3.5

TSS Concentration

mg/L

11.3

Ammonia-N Concentration

mg/L

1.4

E. coli

no. colonies/100 mL

10.87

mg/L

6.4

Alkalinity

mg/L

77.3

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5.0

Summary of Historical Data Review

A summary of the average historical flow and concentrations together with peaking factors identified in this TM are shown below in Table 5-1. Constituent peaking factors for BOD, TSS, and NH3-N were determined as further bases of design for future technical evaluations. Table 5-1: Peaking Factors Identified at the Westside and Southside WWTPs

Flow

Westside WWTP Average Peaking Value Factor 1 9.5 MGD 1.46

Southside WWTP Average Peaking Value Factor 1 7.0 MGD 1.29

BOD

162 mg/L

1.28

146 mg/L

1.26

TSS

180 mg/L

1.40

259 mg/L

1.45

Parameter

NH3-N 23 mg/L 1.47 20 mg/L Notes: 1. Future average day flows for each facility will be developed in the forthcoming Planning Criteria TM.

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6.0

Condition Assessment

This section of the TM includes a condition assessment of Westside and Southside WWTPs. Site visits were performed by Garver on November 1st and 2nd of 2021 to review the existing facilities and document staff input regarding performance and maintenance issues of all equipment at the WWTPs. The engineers present during the site visit, together with their disciplines, were: • • • •

Lance Klement, Project Manager/Operations Kam Sardari, Process Kipp Martin, Structural Hunter Wick, Electrical

The findings of the site visit were consolidated and summarized, and the WERF SIMPLE tool was used to score the major facilities based on their condition, capacity, reliability, availability, and maintainability from a process, structural and electrical standpoint. The likelihood of failure and consequence of failure were then calculated and used to determine the overall criticality of the facilities. The overall criticality was presented as one of the following ratings: • • • •

Low: The facility is in good condition and/or a failure would not impact plant operations Medium: The facility is in fair condition and/or failure of the facility would have a minor impact on plant operations High: The facility is in poor condition and/or failure of the facility would have a major impact on plant operations Critical: The facility is in poor condition and/or failure of the facility would be catastrophic (i.e., wastewater cannot be conveyed through the plant and/or effluent permit limits would be exceeded.)

The following sections will present the overall condition and determined criticality of each facility at the Westside and Southside WWTPs. 6.1

Westside Wastewater Treatment Plant

The Westside WWTP is located at 14939 County Rd 46 in Smith County, Texas and is currently permitted for a design flow of 13 MGD. A process flow diagram (PFD) of the Westside WWTP can be seen in Figure 6-1. The current treatment facility consists of a headworks facility housing a mechanical screen and grit removal. The flow then enters the raw sewage pump station and is pumped to the primary clarifiers. Following primary clarification, the flow enters the first stage trickling filters. The flow is then split and sent to either nitrification basins or second stage trickling filters. Consequently, the flow from nitrification basin and second stage trickling filters is combined and sent to the final clarifiers where sludge is removed and sent to a RAS/WAS pump station. RAS is pumped back to a flow control structure upstream of the nitrification basins/second stage trickling filters and is mixed with the process flow. Flow is then sent to a chlorine contact basin where it is disinfected prior to being discharged to Black Fork Creek. The flow is oxygenated via mechanical surface aerators within the chlorine contact chambers. The WAS and primary sludge removed from the clarifiers is sent to an anaerobic digester. The digested sludge is then sent to the dewatering building where is it dewatered by belt filter presses (BFPs) before being disposed of.

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Figure 6-1: PFD of Westside WWTP

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6.1.1

Mechanical Screen

The first facility at the Westside WWTP is the headworks facility which consists of a mechanical screen and grit removal. The mechanical screen is a perforated plate fine screen, manufactured by JWC Environmental. The screen was installed in 2006 but was rehabilitated in 2017; the rehabilitation included a motor replacement together with restoration of other ancillary items that were corroded. The screenings that are removed enter a compactor that discharges into a dumpster. A summary of the design details of the existing screening facility is seen in Table 6-1. Table 6-1: Design Details of the Existing Screening Facility Design Detail

Value

Unit

Mechanical Perforated Plate 1

JWC Environmental 2006 Fair Screening Conveyor Shaftless Screw Conveyor 1

Screens Type Quantity Manufacturer Year Installed Overall Condition Type Quantity Manufacturer Year Installed Overall Condition

JWC Environmental 2006 Fair Overall Criticality of the Facility

Likelihood of Failure Consequence of Failure

6.5 6.8

Overall Criticality

Critical

The screening facility is in fair condition and undergoes routine maintenance. According to WWTP staff, the screen requires service by the manufacturer every two (2) years to maintain operation. The screens are currently operated on a timer, as the level sensor that was originally controlling screen operation is no longer in service. The consequence of failure score is 6.8 for the screening facility due to the lack of bypass screening. A bypass pipe allows operators to divert influent flow directly to the grit removal units if necessary, however, the bypass flow path does not have a manual bar screen to remove screenings and therefore negatively impacts the downstream processes. The criticality of the screening facility was determined to be critical because of the impact a failure would have on the downstream processes. A photo of the existing screen and screw conveyor can be seen in Figure 6-2.

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Figure 6-2: Photo of the Mechanical Fine Screen and Discharge Chute 6.1.2

Grit Removal

After screening, the flow enters the grit removal units which consist of two detritor basins where grit settles out of the process flow and two grit augers that carry grit from the basin floors up to a dumpster where they are disposed of. The facility was originally constructed in 1968, however, the equipment within the basins (detritor scrapers, paddles, and screw conveyor) was replaced in 2006. The design details of the existing grit removal facility can be seen in Table 6-2.

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Table 6-2: Design Details of the Existing Grit Removal Facility Design Detail

Value

Unit

Grit Removal Basins Type Quantity Manufacturer Year Installed Overall Condition Type Quantity Manufacturer Year Installed Overall Condition

Detritor 2 Walker Process 2006 Poor Grit Conveyor

Shaftless Screw Conveyor 2 Walker Process 2006 Poor Overall Criticality of the Facility

Likelihood of Failure Consequence of Failure Overall Criticality

9.1 6.8 Critical

During the site visit, it was observed that the grit removal facility exhibits significant corrosion damage and equipment failure resulting in inadequate grit removal performance. The detritor paddles and scraper mechanisms are in poor condition, as well as the basin isolation gates and weirs. Similar to the mechanical screen facility, a failure of the grit basins would negatively impact downstream processes and can contribute to the buildup of sand within the existing treatment basins. The criticality of the grit removal facility was therefore determined to be critical. A photo of the grit detritor basins is shown in Figure 6-3 and a photo exhibiting some of the severe corrosion observed during the site visit is shown in Figure 6-4.

Figure 6-3: Photo of the Grit Detritor Basins

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Figure 6-4: Photo of the Basin Isolation Gates Exhibiting Corrosion 6.1.3

Chemical Feed Facility

The chemical feed facility at the Westside WWTP consists of a magnesium hydroxide (Mg(OH) 2) storage tank and metering system that were installed in 2010. The operators manually dose Mg(OH) 2 to achieve odor control via pH alteration at the Parshall flume downstream of the headworks facilities. The metering pump and tank mixer have recently been rehabilitated. Table 6-3 summarizes the design details of the chemical feed facility.

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Table 6-3: Design Details of the Existing Chemical Feed Facility Design Detail Quantity Manufacturer Size Year Installed Overall Condition Quantity Manufacturer Size Year Installed Overall Condition

Value Mg(OH)2 Storage Tank 1 Premier Chemical 5,000 2010 Good Mg(OH)2 Metering Pump 1 Bredel

Unit gal -

0.75 2010 Fair Overall Criticality of the Facility Likelihood of Failure Consequence of Failure

hp 3.0 3.0

Overall Criticality

Low

The facility is in good condition overall. There are signs of previous chemical spill on the piping and inside the containment area. The WWTP staff noted that the chemical metering pump requires frequent maintenance. WWTP staff also mentioned that the cost of the chemical is too high for the facility to maintain odor control throughout the year. It was observed during the site visit that the control panel door is in poor condition and the seal has worn off. It was also noted that there is no safety eyewash station in proximity of the tank. Furthermore, the chemical piping associated with the tank and metering pump extends outside the containment curb which poses a safety hazard. The criticality of the chemical feed facility is low. A photo of the existing chemical storage tank and metering equipment can be seen in Figure 6-5.

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Figure 6-5: Photo of the Mg(OH)2 Storage and Feed Equipment 6.1.4

Raw Water Pump Station

From the grit removal facility, the flow enters a Parshall flume that was constructed in 1968 for flow measurement. The flume discharges into a wet well where three 200-hp vertical dry-pit pumps lift the flow and send it to the primary clarifiers. The pumps housed in the raw water pump station are manufactured by Flowserve and were installed in 1968, however they were upgraded in 2006. A 5-ton crane is located within the pump station for pump removal/maintenance. Two of the pumps are on VFDs, and the third pump is controlled by a three-way switch. A summary of the design details of the raw water pump station is listed in Table 6-4.

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Table 6-4: Design Details of the Existing Raw Water Pump Station Design Detail Type Quantity Manufacturer Size Year Installed Overall Condition Quantity Year Installed Overall Condition

Value

Unit

Raw Water Pumps Vertical Dry-Pit Centrifugal 3

Flowserve 200 2006 Fair Pump VFDs 2

2006, 2021 Fair, Good Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

hp 5.7 7.3 High

The Parshall flume exhibited some corrosion on the handrailing, presenting a safety hazard. In addition, chemical scaling was observed on the flume wall near the point of Mg(OH)2 dosing. The influent flume level sensor was replaced in 2020 and is in good condition. WWTP staff noted that the Parshall flume measures approximately 2 to 3 MGD higher than the effluent flow meter on average. The pumps are in fair condition and can pump up to 17.5 MGD. However, WWTP staff noted that during rain events the electrical junction boxes get wet; this has caused the inlet valve actuators to become inoperable due to water damage to the electrical panels. The criticality of the raw water pump station was determined to be high. Photos of the existing flume and raw water pumps can be seen in Figure 6-6 and Figure 6-7.

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Figure 6-6: Photo of the Parshall Flume

Figure 6-7: Photo of the Raw Water Pump Station 6.1.5

Primary Clarifiers

The Westside WWTP has two 150-ft diameter primary clarifiers that were constructed in 1968 and rehabilitated in 2006 when the mechanisms were replaced. The primary clarifiers co-settle WAS with primary sludge. The motors and gearboxes on clarifier number 1 were replaced recently and on clarifier no. 2 are scheduled for replacement in late 2021/early 2022. The clarifiers have double-sided weirs, and

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each clarifier has a scum pump that pumps the scum removed from the clarifier surface to the anaerobic digesters. A summary of the design details of the primary clarifiers can be seen in Table 6-5. Table 6-5: Design Details of the Existing Primary Clarifiers Design Detail Quantity Manufacturer Diameter

Value

Unit

2 Walker-Process 150 1968 Original Construction 2006 Mechanisms Replaced Fair Overall Criticality of the Facility

Year Installed Overall Condition Likelihood of Failure

ft 4.6

Consequence of Failure Overall Criticality

5.0 Medium

The mechanisms in both clarifiers are in fair condition. The skimmer arm in primary clarifier 2 is broken and is currently undergoing maintenance, and some of the surface sprayers on both clarifiers are inoperable. In addition, the gates in both clarifiers do not work. The WWTP staff indicated that the clarifiers have flooded in the past during high flow events. It was noted during the site visit that when the raw water pumps are operating at a high capacity, the primary clarifiers become flooded, suggesting that they may be undersized for peak flow events. Structurally, the clarifier bridges and railings exhibited significant wear and need to be repainted or replaced. The criticality of the primary clarifiers was determined to be medium. A photo of one of the existing primary clarifiers can be seen in Figure 6-8 and a photo of the corroded clarifier bridge can be seen in Figure 6-9.

Figure 6-8: Photo of Primary Clarifier 1

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Figure 6-9: Photo of a Clarifier Bridge Exhibiting Corrosion 6.1.6

Light Sludge Pump Station

The light sludge pump station pumps WAS and decant from the anaerobic digesters back to the primary clarifiers. The pump station houses two 3-hp Gorman Rupp self-priming centrifugal pumps. The pump station was built in 1968, however one of the pumps was replaced in 2010, and the other replaced in 2015 with new units. A summary of the design details of the pumps is seen in Table 6-6. Table 6-6: Design Details of the Existing Light Sludge Pump Station Design Detail

Value

Unit

Self-Priming Centrifugal

2 Gorman Rupp 3 2010, 2015 Good Overall Criticality of the Facility

hp -

Type Quantity Manufacturer Size Year Installed Overall Condition

Likelihood of Failure Consequence of Failure Overall Criticality

3.2 3.7 Low

The pumps are in good condition overall, however the valves have never been replaced and are not operating properly. In addition, it was noted during the site visit that the pump shafts are exposed, which poses a safety hazard to operators. The criticality of the facility was determined to be low.

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A photo of the existing light sludge pumps can be seen in Figure 6-10.

Figure 6-10: Photo of the Light Sludge Pumps 6.1.7

First Stage Trickling Filters

The first stage trickling filters (TFs) receive flow from the primary clarifiers for nutrient removal, however some of the primary effluent is diverted straight to the filter pump station. The TFs contain rock media and are 150-ft in diameter. These trickling filters were a part of the original construction of the plant in 1968. The connection between primary clarifiers and TFs is designed in a way that primary clarifier 1 sends flow to trickling filter no.1 and primary clarifier no. 2 sends flow to trickling filter no. 2; hence, if a primary clarifier is not in service, the associated trickling filter will not be in service either. A summary of the design details of the trickling filters is shown in Table 6-7. Table 6-7: Design Details of the Existing First Stage Trickling Filters Design Detail Quantity Diameter Year Installed Overall Condition

Value

Unit

2 150 1968

ft -

Poor Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

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The trickling filter mechanism on both trickling filters are poor condition. TF no. 1’s mechanism no longer rotates due to issues with the bearings. The filter mechanism on TF 2 does not discharge in some areas. These deficiencies have led to portions of the filter media drying out, which decreases the BOD removal capacity of the TFs. Therefore, the filter arms will need recuring maintenance to provide adequate treatment. The criticality of the first stage TFs is high. A photo of one of the first stage TFs exhibiting the dried-out media is shown in Figure 6-11.

Figure 6-11: Photo of the First Stage Trickling Filter Exhibiting Dried-Out Media 6.1.8

Filter Pump Station

The filter pump station houses three 200-hp vertical turbine pumps manufactured by Flowserve. These pumps transfer the first-stage TF effluent and a portion of the primary clarifier effluent to a splitter box. The pump station was originally installed in 1968, however, the pumps have been upgraded since. The pumps are located on a slab between the two secondary clarifiers. A summary of the design details of the filter pumps is shown in Table 6-8.

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Table 6-8: Design Details of the Existing Filter Pumps Design Detail Quantity Type Manufacturer Size Year Installed Overall Condition

Value

Unit

3 Vertical Turbine

Flowserve 200 1968 (Original Construction) 1988 (First upgrade) Pump 3 rebuilt in 2015 Pump 2 rebuilt 2017 Fair

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

6.0 9.1 Critical

Filter pumps 2 and 3 were rebuilt by Odessa in 2017 and 2015, respectively. Filter pump 1 is not currently in service and needs to be refurbished to be operational. The power supply to pump 1 is tied to the supply to pump 3, and the two pumps cannot be operated simultaneously. The criticality of this facility is rated as critical, as it is required to transfer the plant flow from the first treatment stage to the second and cannot be bypassed. In addition, currently there is no redundancy within this facility. The VFDs for these pumps were replaced approximately 10 years ago. A photo of the filter pumps can be seen in Figure 6-12.

Figure 6-12: Photo of the Filter Pumps 6.1.9

Nitrification Basin

From the splitter box, a portion of the plant flow (approximately 80%) is mixed with RAS and sent to the nitrification basin which was constructed in 1988. Aeration is achieved in the basin by five 120-hp surface aerators manufactured by Flender. The aerators are controlled via two-speed soft starts. Effluent from the

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nitrification basin is then sent to the secondary clarifiers. A summary of the design details of the nitrification basin can be seen in Table 6-9. Table 6-9: Design Details of the Existing Nitrification Basin Design Detail

Value

Unit

Aerators Surface Aerators 5

Type Quantity Manufacturer Size Year Installed Overall Condition

Flender 125 1988 Poor

hp -

Overall Criticality of the Facility Likelihood of Failure

6.7 7.7 Critical

Consequence of Failure Overall Criticality

The condition of the nitrification basin is poor due to the age of the equipment and a line break that, per WWTP staff, caused the basin to fill partially with sand. One of the aerators has been out of service for about 15 years and needs to be replaced. The WWTP staff noted that they have not had any major maintenance issues with the aerator motors or gearboxes. The operators indicated that the nitrification basin is operated with a higher-than-average mixed liquor suspended solids (MLSS) concentration of about 6,000 mg/L. All gates in the facility are in poor condition and cannot be operated to take the basin offline for any maintenance or cleaning. In addition, the floating weirs appear to be non-functional. The criticality of the nitrification basin was determined to be critical due to the poor condition of much of the equipment and the lack of bypass capability or redundancy. A photo of the nitrification basin can be seen in Figure 6-13.

Figure 6-13: Photo of the Nitrification Basin

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6.1.10 Second Stage Trickling Filters The remaining portion of the first stage TF effluent (approximately 20%) is sent to two 150-ft diameter second stage TFs. The second stage TFs were built in 1968 and contain rock media, similar to the first stage TFs, however the rotating arms are configured differently. A common influent center column splits the flow between the trickling filter arms. At low flows, the flow is split between two of the filter arms and at high flows, the water elevation in the center column reaches a weir that allows the flow to be dispersed between all four arms. A summary of the design details of the second stage TFs can be seen in Table 6-10. Table 6-10: Design Details of the Existing Second Stage Trickling Filters Design Detail Quantity Diameter Year Installed Overall Condition

Value

Unit

2 150 1968 Fair

ft -

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

5.6 4.3 Medium

The WWTP staff mentioned that groundwater intrusion has been an issue at the site near the second stage TFs and nitrification basin. Overall, the second stage TFs are in fair condition and were determined to have a medium criticality. A photo of one of the existing second stage TFs can be seen in Figure 6-14.

Figure 6-14: Photo of the Second Stage Trickling Filter

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6.1.11 Secondary Clarifiers The second stage TF effluent and nitrification basin effluent are combined and sent to two 150-ft diameter secondary clarifiers. Secondary clarifiers 1 and 2 were built in 1968 and the mechanisms of both units were replaced in 1988. A summary of the design details of the existing secondary clarifiers can be seen in Table 6-11. Table 6-11: Design Details of the Existing Secondary Clarifiers Design Detail Quantity Manufacturer Diameter Year Installed Overall Condition

Value

Unit

2 Eimco (motor and gearbox) 150

1968 Original Construction 1988 Mechanisms Replaced Fair

Overall Criticality of the Facility 5.7 5.0 High

Likelihood of Failure Consequence of Failure Overall Criticality

The WWTP staff noted that the secondary clarifiers have relatively few issues, with the exception of frequent clogging in the secondary clarifier 2 scum box. In addition, the staff indicated that the secondary clarifier 1 receives higher flows during wet weather and high influent flow conditions. It was also observed that the clarifier mechanisms and metal walkways exhibit surface corrosion. Sludge is wasted through a gravity discharge line at each clarifier, conveying WAS to the light sludge pump station by gravity. Further, the WWTP staff indicated that they maintain a sludge blanket depth of approximately 8 ft in the clarifiers as they believe this depth enables better operation of the RAS pumps. The criticality of the secondary clarifiers is high. A photo of one of the secondary clarifiers is shown in Figure 6-15.

Figure 6-15: Photo of One of the Secondary Clarifiers

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6.1.12 RAS Pump Station The RAS pump station receives sludge from the secondary clarifiers and pumps it to the tower splitter box to be mixed with the nitrification basin influent. The pump station houses three Flygt centrifugal pumps that are all connected to VFDs; however, the pumps are operated manually. A 2-ton crane is also housed within the pump station for pump removal and maintenance. A summary of the pump design details can be seen in Table 6-12. Table 6-12: Design Details of the Existing RAS Pump Station Design Detail Type Quantity Manufacturer Size Year Installed Overall Condition

Value

Unit

Horizontal Centrifugal

3 Flygt 60 1988 (Original Construction) 2016 (Pump No. 3 Replaced) Fair

hp -

Overall Criticality of the Facility 3.5 7.4

Likelihood of Failure Consequence of Failure Overall Criticality

High

The RAS pumps are in fair condition overall. The RAS flow rate is manually controlled by operators who monitor a RAS flow meter. The RAS flow meter was observed to be in poor condition and in need of replacement. It was also noted during the site visit that the check valve on pump 2 is no longer capable of fully opening. The VFDs for the pumps were replaced approximately 10 years ago. The criticality of the facility is high due to the high consequence of failure. A photo of the RAS pump station is shown in Figure 6-16.

Figure 6-16: Photo of the RAS Pumps

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6.1.13 Chlorine Building The chlorine gas used for disinfection as well as the sulfur dioxide (SO 2) used for dechlorination at the WWTP is stored under a canopy at the chlorine building. The chlorine building has space to house 12 1ton Cl2 cylinders, with two cylinders on scales to measure the amount of gas remaining, and eight cylinders connected to a chlorinator manifold. The facility also has a dedicated space for 12 1-ton SO2 cylinders, with two cylinders on scales and four cylinders connected to a manifold. A summary of the design details of the facility can be seen in Table 6-13. Table 6-13: Design Details of the Chlorine Building Design Detail

Value

Unit

Chlorine Storage and Feed System 12 Quantity of Storage Cylinders 1 Size 8 Quantity of Manifold Connections

ton -

Sulfur Dioxide Storage Cylinders 12 Quantity 1 Size 4 Quantity of Manifold Connections Overall Criticality of the Facility Likelihood of Failure

ton 7.2 7.6 Critical

Consequence of Failure Overall Criticality

The criticality of the chlorine building was determined to be critical. The facility is currently in the design phase of an improvements project being performed by another City consultant. A photo of the chlorine storage and dosing area is shown in Figure 6-17.

Figure 6-17: Photo of the Chlorine Storage and Dosing Area

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6.1.14 Chlorine Contact Basin and Oxygenation The chlorine contact basin (CCB) was constructed in 1968 and has two channels where a chlorine solution is added to disinfect the secondary effluent. At the effluent end of the channels, surface aerators, installed in 1988, mix the effluent to increase the DO level before the effluent is discharged into the creek. SO2 is also added after disinfection to dechlorinate the water. Some of the disinfected effluent is diverted by nonpotable water (NPW) pumps and sent throughout the plant to be used as wash water and to supply yard hydrants. Table 6-14 summarizes the design details of the facility. Table 6-14: Design Details of the Existing CCB Design Detail Quantity Length Width (each)

Value

Chlorine Contact Basin Channels 2 75 50

Depth Year Constructed Overall Condition

11 1968 Poor

Unit ft ft ft -

Type Quantity (per basin, total) Manufacturer Size Year Installed Overall Condition

Aerator Mixers Surface Aerators 2, 4 Tornado 5 1988 Fair

hp -

Type Quantity Size Year Installed Overall Condition

NPW Pumps Vertical Turbine 2 20 2015 Fair

hp -

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

5.4 6.0 High

The CCB facility is in poor condition. The channel isolation gates are rusted and no longer work. The aerators were rebuilt in 2011 and are in fair condition except for one aerator which is currently out of service. The criticality of the CCB is high, as it is imperative for the facility to achieve proper disinfection to meet permit. A photo of the CCB aerators is shown in Figure 6-18, and a photo of the CCB effluent weir is shown in Figure 6-19.

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Figure 6-18: Photo of the Out of Service Aerator

Figure 6-19: Photo of the CCB Effluent Weir

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6.1.15 Anaerobic Digesters There are two 100-ft diameter anaerobic digester basins located north of the primary clarifiers where cosettled WAS and primary sludge are sent for digestion. The basins were constructed in 1968; the primary clarifier pump station and BFP pump station are housed between the two tanks inside a pump room. A summary of the design details of the existing anaerobic digesters is shown in Table 6-15. Table 6-15: Design Details of the Existing Anaerobic Digesters Design Detail

Value

Unit

Quantity Diameter Year Installed

2 95 1968

ft -

Overall Condition

Poor

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

9.3 7.0 Critical

The digesters are in poor condition and the dome cover of both basins have collapsed. Digester basin no. 2 is the only basin currently being used by the plant to store sludge before it is sent to the dewatering facility. However, this dome of this basin is submerged under a thick matt of sludge and per WWTP staff, it is gradually sinking. The criticality of this facility is rated as critical due to its poor/inoperable condition and the need for operational reliability. A photo of the collapsed anaerobic digester basin can be seen in Figure 6-20.

Figure 6-20: Photo of the Damaged Anaerobic Digester Roof

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6.1.16 Primary Sludge Pump Station The primary sludge pumps are housed between the two anaerobic digesters and are used to transfer primary sludge from the primary clarifiers to the anaerobic digesters. Four double-disk pumps, manufactured by Penn Valley are used for primary sludge transfer. The pumps are located below grade within the pump station. A summary of the pump design details can be seen in Table 6-16. Table 6-16: Design Details of the Existing Primary Sludge Pump Station Design Detail Type Quantity Manufacturer Size Year Installed Overall Condition

Value

Unit

Double disk 4 Penn Valley

5 1988 Replaced in 2011 Fair

hp -

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

4.1 4.4 Low

The pumps are in fair condition, however the electrical MCCs located in the pump station are in poor condition and need to be replaced and relocated. The pump room has experienced flooding in the past however is cleaned occasionally to reduce the negative effect of dirt buildup on the equipment. The criticality of this facility was determined to be low. A photo of the primary sludge pump station is shown in Figure 6-21.

Figure 6-21: Photo of the Primary Sludge Pump Station

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6.1.17 Belt Filter Press Pump Station The BFP pumps housed in the same room as the primary sludge pumps and are used to pump digested sludge to the dewatering building. Two double disk pumps, manufactured by Penn Valley, were installed in the pump station in 2015. A summary of the BFP pump design details can be seen in Table 6-17. Table 6-17: Design Details of the Existing BFP Pump Station Design Detail Type Quantity Manufacturer Size Year Installed Overall Condition

Value

Unit

Double disk 2 Penn Valley 20 2015 Good

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

hp 3.3 4.1 Low

The condition of the BFP pumps is good and they were determined to have low criticality. A photo of the BFP pumps is shown in Figure 6-22.

Figure 6-22: Photo of the BFP Pumps

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6.1.18 Dewatering Facility The dewatering facility is a two-story building that was built in 2015 and houses two 2-m BFPs, manufactured by Alfa Laval, for dewatering purposes. The BFPs typically achieve 20-26% solids concentration and discharge into a common hopper on the second floor. The solids are loaded into a semitruck which hauls the solids away for disposal (3 times per day on average per staff). Two polymer storage and injection system, a grinder, and two booster pumps are also housed within the building. A summary of the design details of the equipment in the dewatering facility can be seen in Table 6-18. Table 6-18: Design Details of the Existing Dewatering Facility Design Detail

Value

Unit

Overall Condition

Dewatering Unit Belt Filter Press 2 Alfa Lava 2 2015 Good

m -

Quantity Manufacturer Year Installed Overall Condition

Polymer Feed Units 2 UGSI Chemical Feed, Inc 2015 Good

Booster Pump Vertical Turbine 2 Timex 7.5 2015 Good

hp -

Type Quantity Manufacturer Belt Width (each) Year Installed

Type Quantity Manufacturer Size Year Installed Overall Condition

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

3.1 3.1 Low

The equipment in the dewatering facility is in good condition; the BFPs have been maintained well and the polymer units and grinder were repaired in 2021. It was noted during the site visit that the polymer flow meter in the control room of the facility may not be reporting correctly. The criticality of the dewatering facility is low. A photo of the BFPs in the facility can be seen in Figure 6-23.

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Figure 6-23: Photo of the BFPs in the Dewatering Facility 6.1.19 Operations Building The operations building is located adjacent to the raw water pump station and houses a laboratory room used for sample analysis and testing at the Westside WWTP. Due to its proximity to the headworks and raw water pump station facilities, the building has been exposed to excess amounts of Hydrogen Sulfide (H2S), which has caused significant corrosion outside and inside of the building. In addition, it was observed during the site visit that some of the windows in the facility are broken. The building was determined to have a high criticality. A table listing the criticality ranking of the operations building is shown in Table 6-19. Table 6-19: Criticality Ranking of the Administration Building Overall Criticality of the Facility Likelihood of Failure Consequence of Failure

9.0 5.0

Overall Criticality

High

6.1.20 Westside WWTP Condition Assessment Summary Table 6-20 lists the facilities defined in the WERF SIMPLE tool for the Westside WWTP. An Asset ID has been designated to each facility. In addition, the WERF SIMPLE took core risk map exhibiting the criticality of each facility is shown in Figure 6-24. The facilities determined to have a critical criticality include: the mechanical screen, the grit basins, the filter pump station, the nitrification basin, the chlorine building, and the anaerobic digesters.

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Table 6-20: Condition Assessment Summaryfor the Westside WWTP Facility No.

Asset ID

WS-WWTP-MS

Mechanical Screen

WS-WWTP-GR

Grit Removal

WS-WWTP-CHEM

Chemical Feed Facility

WS-WWTP-RWPS

Raw Water Pump Station

WS-WWTP-PC

Primary Clarifiers

WS-WWTP-LSPS

Light Sludge Pump Station

WS-WWTP-FSTF

First Stage Trickling Filters

WS-WWTP-FPS

Filter Pump Station

WS-WWTP-NB

Nitrification Basin

WS-WWTP-SSTF

Second Stage Trickling Filters

WS-WWTP-SC

Secondary Clarifiers

WS-WWTP-RASPS

RAS Pump Station

WS-WWTP-CB

Chlorine Building

WS-WWTP-CCB

Chlorine Contact Basin

WS-WWTP-AD

Anaerobic Digesters

WS-WWTP-PSPS

Primary Sludge Pump Station

WS-WWTP-BFPPS

BFP Pump Station

WS-WWTP-DF

Dewatering Facility

WS-WWTP-OPS

Operations Building/Lab

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Figure 6-24: Core Risk Map of the Westside WWTP Facilities

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6.2

Southside Wastewater Treatment Plant

The Southside WWTP is located at 620 West Cumberland Rd. in Tyler, Texas and is currently permitted for a design flow of 9 MGD. The current treatment facility consists of an influent pump station connected to a headworks facility housing mechanical screens and grit removal units. The screened and degritted wastewater then flows to the primary clarifiers before entering the aeration basins. The flow is then sent to the secondary clarifiers where sludge is removed and either wasted or recycled. Then, the final effluent is disinfected in chlorine contact basins prior to being discharged into West Mud Creek. Solids that were removed at the clarifiers are thickened, stored and dewatered prior to disposal. A PFD of the Southside WWTP is shown in Figure 6-25.

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Figure 6-25: PFD of the Southside WWTP

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6.2.1

Chemical Feed Facility

An open-air chemical feed facility is located at the head of the plant storing Iron Sulfate (FeSO 4) and Magnesium Hydroxide (Mg(OH)2), which are both used for odor control at the headworks facility. The storage tanks and metering equipment are stored on a concrete pad located to the North of the headworks facility. The FeSO4 system is not owned by the Southside WWTP; the dosing equipment is owned by a third party and is controlled via the plant SCADA system. Therefore, the FeSO 4 dosing equipment are not included in the condition assessment. Table 6-21 lists the details of the existing chemical feed facility housing the Mg(OH)2 and FeSO4 storage and feed equipment. Table 6-21: Details of Existing Chemical Feed Facility Design Detail Quantity Manufacturer Size Year Installed Overall Condition Quantity Manufacturer Size Year Installed Overall Condition Quantity Manufacturer Size Year Installed Overall Condition

Value FeSO4 Storage Tank 1 Polyprocessing 6,000 2017 Good

gal -

Mg(OH)2 Storage Tank 2 Polyprocessing 2,500 (each)

gal

~ 2011, 2021 Poor, Good

Mg(OH)2 Metering Pump 2 Bredel, Graco ST 23 0.75, 0.25 ~ 2011, 2017 Poor, Good

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

Unit

hp 4.4 3.1 Low

Overall, the condition of the facility is good with the exception of one of the Mg(OH) 2 storage tanks and metering pumps. The storage tank and pump are >10 years old and are both reaching the end of their useful life; this equipment will need to be replaced in the near future. However, the overall criticality of the chemical feed facility at the Southside WWTP is low, due to the condition of the equipment and its function being primarily for odor control. A photo of the three existing storage tanks is shown in Figure 6-26. The Mg(OH)2 metering equipment can be seen in Figure 6-27.

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Figure 6-26: Photo of the Chemical Storage Tanks - FeSO4 (left) and Mg(OH)2 (middle, right)

Figure 6-27: Photo of the Mg(OH)2 Metering Equipment

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6.2.2

Influent Screw Pumps

The process flow is lifted to the headworks facility by four screw pumps. The screw pumps were all installed in 1979 but were rehabilitated in 2021 and are in good condition. They are manufactured by Landustrie and each have a 40 hp motor. An H2S sensor is located within the influent lift station to monitor odor; a signal from this sensor is sent to the plant SCADA system, which controls the dosing of FeSO 4 from the chemical feed facility to control odor. A summary of the design details of the existing screw pumps is shown in Table 6-22. Table 6-22: Details of Existing Influent Lift Station Design Detail Type Quantity Manufacturer Size Year Installed Overall Condition

Value Screw Pumps Enclosed Screw 4 Landustrie 7.24 2021 Good

Unit MGD -

Manufacturer Quantity

Pump Lubrication System Graco 2

Manufacturer Quantity

H2S Sensor Penn Co 1

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure

2.0 5.7

Overall Criticality

Low

The screw pumps and lubrication system are working well, and WWTP staff have been happy with their performance. The criticality of this facility is low, as the equipment is in good condition and not at risk of failure. A photo of the influent lift station facility can be seen in Figure 6-28.

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Figure 6-28: Photo of the Existing Influent Lift Station 6.2.3

Mechanical Screens

The influent screw pumps lift the raw sewage to two mechanical chain and rake screens where screenings are removed and conveyed to a dumpster adjacent to the facility. The screens and conveyor were manufactured by Vulcan and were installed in 2020. The screens and conveyor operate continuously and are modulated based on head conditions in the screening channels. A summary of the design details of the existing system is shown in Table 6-23.

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Table 6-23: Design Details of Existing Mechanical Screening Equipment Design Detail

Value

Unit

Mechanical Chain and Rake 2 Vulcan 1 2021

hp -

Good Screening Conveyor Shaftless Screw Conveyor 1 Vulcan 2021

Screens Type Quantity Manufacturer Size Year Installed Overall Condition Type Quantity Manufacturer Year Installed Overall Condition

Good Overall Criticality of the Facility

Likelihood of Failure Consequence of Failure Overall Criticality

2.3 3.0 Low

Similar to the influent screw pumps, the mechanical screens were installed recently are in good working condition due to their recent upgrades and therefore, have a low criticality. Photos of the existing screening equipment can be seen in Figure 6-29 and Figure 6-30.

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Figure 6-29: Photo of Existing Mechanical Screens and Screen Conveyance Equipment

Figure 6-30: Photo of the Existing Screen Conveyor and Dumpster 6.2.4

Grit Removal

After screening, the flow enters a Parshall flume for flow measurement and then enters the grit removal units. The existing grit removal mechanism at the Southside WWTP consists of two grit detritor basins, two

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grit pumps and two grit cyclones/classifiers all located at the headworks facility. The grit detritor basins were constructed and installed in 1979 as a part of the original headworks facility construction. The grit that settles in the detritor basins is pumped to the grit classifiers where it is dewatered and then conveyed to a dumpster for disposal. A summary of the design details of the existing system can be seen in Table 6-24. Table 6-24: Design Details of Existing Grit Removal System Design Detail Type Quantity Manufacturer Size Year Installed Overall Condition Type Quantity Manufacturer Size Year Installed Overall Condition Quantity Manufacturer Size Year Installed Overall Condition

Value

Unit

Grit Removal Units Detritor 2 Walker Process 0.75

1979 Fair

Grit Pumps Centrifugal 2 Wemco

15 2021 (rehab’d as a part of the headworks project) Poor

Grit Classifiers 2 Wemco 1 2008

hp -

Fair

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

5.4 4.0 Medium

Currently, only one of the grit classifiers is in operation; the classifier units require significant maintenance. In addition, the dumpster used for grit disposal must be emptied every 1-2 weeks). Overall, the grit removal equipment is in good condition, with the exception of the out of service grit cyclone. The WWTP staff mentioned that the pump seals leak. The grit chambers exhibit some corrosion; with visible deterioration of concrete and rebars being exposed in some areas. The criticality of the grit removal system was determined to be medium. Photos of the existing grit removal system can be seen in Figure 6-31 and Figure 6-32.

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Figure 6-31: Photo of the Existing Detritor Grit Removal Basins

Figure 6-32: Photo of the Decommissioned Grit Cyclone/Classifier Unit 6.2.5

Primary Clarifiers

The de-gritted flow then enters the primary clarifier bypass splitter box where the WWTP staff can either direct it to a primary clarifier splitter box or bypass the clarifiers and send flow to the aeration basin splitter

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box. From the primary clarifier splitter box, flow is split and sent to two 100-ft diameter primary clarifiers. The clarifier basins were built in the 1970s, however the clarifier mechanisms have recently been replaced. A control panel for the primary clarifiers is located inside of the primary sludge pump station room. A summary of the details of the existing primary clarifiers is shown in Table 6-25. Table 6-25: Design Details of the Existing Primary Clarifiers Design Detail Quantity Manufacturer Diameter Year Installed Overall Condition

Value

Unit

2 Walker-Process 100 2021 Good

ft -

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

2.4 5.0 Low

The primary clarifier mechanisms are in good condition due to their recent rehabilitation/replacement. In addition, the clarifier basins are in good structural condition. Therefore, the criticality of the primary clarifier facility is low. A photo of the existing primary clarifier can be seen in Figure 6-33.

Figure 6-33: Photo of the Existing Primary Clarifiers

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6.2.6

Primary Sludge Pump Station

The primary sludge pump station houses two 20-hp progressive cavity pumps that transfer primary sludge to the sludge holding tank and anaerobic digesters. The pumps were installed in 2020 and were manufactured by Seepex. The pumps are operated 1.5 minutes every 100 minutes to remove sludge from the primary clarifiers. The pump room also houses a 1-ton crane for pump removal and control panels for the primary sludge pumps and primary clarifiers. A summary of the design details of the existing primary sludge pumps is shown in Table 6-26. Table 6-26: Design Details of Existing Primary Sludge Pumps Design Detail Type Quantity Manufacturer Size Year Installed Overall Condition

Value

Unit

Progressive Cavity 4 Seepex

20 2021 Good

hp -

Overall Criticality of the Facility Likelihood of Failure

3.0

Consequence of Failure Overall Criticality

4.4 Low

The primary sludge pump station is in good condition, overall. WWTP staff noted their satisfaction with the Seepex pumps. The pump station has an Heating and Air Condition (HVAC) unit that is in working order. MCC-7 housed within the pump station is in fair condition and has been retrofitted many times. The criticality of the primary sludge pumps was determined to be low. A photo of the existing primary sludge pumps can be seen in Figure 6-34.

Figure 6-34: Photo of the Existing Primary Sludge Pumps

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6.2.7

Aeration Basins 1 & 2

An aeration basin splitter box splits the primary effluent between three aeration basins; basins 1 and 2 were built in 1978, and basin 3 was built in 1994. All the equipment within basins 1 and 2 is manufactured by Siemens. In addition to primary effluent, basins 1 and 2 receive RAS from the RAS/WAS pump station through a sludge distribution pipe that runs along the top of the channels. The sludge distribution pipe has valves that allow operators to control the flow of RAS to the channels individually. The three outer channels of the basins are aerated by 40- hp disk surface aerators, while the two channels in the center are not aerated and are used to achieve anaerobic digestion of WAS. The aerated process flow is then sent to the final clarifiers and the digested flow is sent to the sludge holding tank or the anaerobic digesters. Design details of aeration basins 1 and 2 can be seen in Table 6-27. Table 6-27: Design Details of the Existing Aeration Basins 1 & 2 Design Detail

Value

Unit

Aeration Basins 1 & 2: Surface Aerators Disk Surface Aerators Type 6, 5 Quantity (basin 1, basin 2) Siemens Manufacturer 40 Size (each) Year Installed Overall Condition

1978 Poor

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

hp 7.8 7.7 Critical

The aerators in aeration basins 1 and 2 are old and have required frequent maintenance over the years. The disks break frequently and must be replaced, as well as the gearboxes on the aerator motors. The aerator motors used to be operated based on DO measurements, however due to mechanical wear caused by the on/off control, the WWTP staff decided to operate the aerators continuously. In addition, it was noted during the site visit that the mixed liquor in the basins exhibits significant foaming. Also, the freeboard appears to be insufficient with water surface nearing the top of wall. RAS addition is controlled manually and is measured with a ruler in the RAS/WAS pump station’s Parshall flumes. The criticality of aeration basins 1 and 2 was determined to be critical due to their condition and the significant role that they play in reducing nutrient levels to meet permit limits. Photos of aeration basins 1 and 2 aerators and the sludge inlet piping can be seen in Figure 6-35 and Figure 6-36. As seen, multiple paddles on the mixers are broken.

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Figure 6-35: Photo of the Existing Aeration Basin Exhibiting Dark MLSS Color

Figure 6-36: Photo of the Existing RAS/WAS Distribution Piping

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6.2.8

Aeration Basin 3

Aeration basin 3 was built in 1994 and is configured differently than the first two basins. The third aeration basin has three 100-hp Siemens surface aerators. RAS is added into the basin near the influent and flow is routed through the basin to achieve maximum nutrient removal. A summary of the equipment design details can be seen in Table 6-28. Table 6-28: Design Details of Aeration Basin 3 Design Detail

Value

Unit

Aeration Basin 3: Surface Aerators Impeller Surface Aerators Type 3 Quantity Siemens Manufacturer 100 Size (each) 1994 Year Installed Fair Overall Condition

hp -

Overall Criticality of the Facility 6.0 7.7 High

Likelihood of Failure Consequence of Failure Overall Criticality

The aerators within aeration basin 3 are in fair condition. The aerator motors have been replaced and/or rebuilt many times since the facility’s construction. The aerators, DO sensors, and transmitters all appear to be worn, but overall, the staff indicated that the facility’s operation has been satisfactory. The criticality of aeration basin 3 is high. A photo of the existing basin can be seen in Figure 6-37.

Figure 6-37: Photo of the Existing Aeration Basin 3

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6.2.9

Final Clarifiers 1 & 2

The effluent from each aeration basin flows to a dedicated final clarifier where secondary sludge is settled and recycled to the aeration basins. Similar to the aeration basins, the first two final clarifiers were built in 1978 and the third was built in 1994. A summary of the design details of final clarifiers 1 & 2 can be seen in Table 6-29. Table 6-29: Design Details of the Final Clarifiers 1 and 2 Design Detail Quantity Manufacturer Size Year Installed Overall Condition

Value

Unit

100 1978 Poor

ft -

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

6.7 5.0 High

Final clarifiers 1 and 2 have required significant maintenance over the years; the motors have been replaced as well as one of the gearboxes. There are visible signs of corrosion on the mechanisms and railing and leakage on the motor gearboxes. In addition, the skimmer arm on secondary clarifier 2 is broken and the effluent valve for secondary clarifier 1 is inoperable. The WWTP staff noted that during high flow events, the weirs become flooded and the creek that the plant discharges to backs up into the plant. The criticality of the secondary clarifiers 1 and 2 was determined to be high. A photo of the skimmer arm on secondary clarifier 1 can be seen in Figure 6-38.

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Figure 6-38: Photo of Secondary Clarifier 1 Skimmer Arm 6.2.10 Final Clarifier 3 As previously stated, the third final clarifier was built in 1994, at the same time as aeration basin 3. The third final clarifier only treats the flow from aeration basin 3, with no interconnection to aeration basins 1 & 2. A summary of the design details of final clarifier 3 can be seen in Table 6-30. Table 6-30: Design Details of Final Clarifier 3 Design Detail Quantity Manufacturer Size Year Installed Overall Condition

Value

Unit

ft -

110 1994 Good

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

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4.6 4.0 Medium

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The third final clarifier has similar flooding issues during high flow events but is otherwise in better condition than the first two. The criticality of the secondary clarifier no. 3 was determined to be medium due to its fair condition. A photo of the existing secondary clarifiers can be seen in Figure 6-39.

Figure 6-39: Photo of Secondary Clarifier 3 6.2.11 Plant Lift Station The plant lift station was built in 1994 and houses two 7.4 hp submersible pumps. These pumps send scum from final clarifier 3, BFP filtrate, and wastewater from the onsite office buildings back to the primary clarifiers. The pumps were rehabilitated in 2021. A summary of the design details of the submersible lift station pumps is shown in Table 6-31. Table 6-31: Design Details of the Plant Lift Station Design Detail Type Quantity Manufacturer Size (each) Year Installed Overall Condition

Value

Unit

Submersible Centrifugal 2

Wilo, Pentair 7.5 1994 Good

hp -

Overall Criticality of the Facility 4.6

Likelihood of Failure Consequence of Failure Overall Criticality

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4.0 Medium

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The plant lift station is in good condition; the criticality of the facility is medium. A photo of the existing plant lift station pumps can be seen in Figure 6-40.

Figure 6-40: Photo of the Plant Lift Station Access Hatch 6.2.12 Chlorine Contact Basin Secondary effluent then flows to the CCB where it is dosed with a chlorine gas solution for disinfection. The CCB was built in 1978 and has two separate channels each housing a submersible flash mixer. The chlorine gas solution is injected into the process flow at the influent end of the basins and sulfur dioxide (SO2) is injected at the effluent end for dechlorination. After disinfection and dechlorination, the flow exits the basin over an effluent flow measurement weir and is discharged. Two nonpotable water pumps are located at the effluent end of the CCB which provide wash water to the dewatering equipment. Design details of the existing CCB are listed in Table 6-32.

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Table 6-32: Design Details of the Chlorine Contact Basin Design Detail

Value

Unit

Chlorine Contact Basin Channels 2 Quantity 98 Length 32 Width (each) 9.5 Depth 1978 Year Constructed Poor Overall Condition

ft ft ft -

NPW Pumps 2 Submersible Centrifugal 2015, 2020 Fair

Quantity Type Year Installed Overall Condition

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

6.5 6.0 High

The condition of the CCB disinfection facility is overall poor; the mixers are not in operational condition and according to WWTP staff, the basin has been flooded during high flow events. It was noted during the site visit that the basin received a higher-than-average volume of solids that build up in the channels and have to be removed every two weeks, required one of the channels to be taken offline and drained. In addition, the basins frequently have algae and scum build up on the water surface. Furthermore, the walkways show significant signs of corrosion. The criticality of the CCB facility is high due to its poor condition and the importance of the disinfection process to meeting permit limits. A photo of the existing CCB and the surface scum buildup can be seen in Figure 6-41.

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Figure 6-41: Photo of the Existing CCB Exhibiting Solids Buildup and Corrosion 6.2.13 Chemical Storage Facility The chemical storage facility located adjacent to the CCB houses the chlorine gas used for disinfection as well as the SO2 used for dechlorination. Up to ten 1-ton chlorine gas cylinders are stored outside of the facility underneath a canopy. Six cylinders at a time can be connected to vacuum valves that feed the chlorinators, however only two cylinders are stored on scales. Within the building, nine 1-ton SO2 cylinders are stored, two of which are connected to vacuum valves for dosing and stored on scales. A summary of the design details for the facility are shown in Table 6-33. Table 6-33: Design Details of the Chemical Storage Facility Design Detail

Value

Unit

Chlorine Storage and Feed System 9 Quantity of Storage Cylinders 1 Size 6 Quantity of Manifold Connections Fair Overall Condition

ton -

Sulfur Dioxide Storage Cylinders 9 Quantity 1 Size 2 Quantity of Manifold Connections Fair Overall Condition

ton -

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

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7.5 7.6 Critical

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The structural condition of the facility is poor. The outdoor storage of the gas cylinders poses a safety risk. In addition, the HVAC system in the facility appeared to be worn and may require maintenance. However, an improvements design for the facility is currently in progress by another consultant to fix the issues noted during the site visit. A photo of the structural damage at the existing chlorine storage facility can be seen in Figure 6-42.

Figure 6-42: Photo of the Chemical Storage Facility Showing Structural Damage 6.2.14 RAS/WAS Pump Station The RAS/WAS pump station is located between aeration basins 1 and 2 and houses three screw pumps that lift solids from secondary clarifiers 1 and 2 to aeration basins 1 and 2. The solids are pumped to either the outer three channels or the inner two channel, separating them into RAS and WAS. The pump station was built in 1978. A summary of the design details of the facility can be seen in Table 6-34. Table 6-34: Design Details of the RAS/WAS Pump Station Design Detail Type Quantity Manufacturer Year Installed Overall Condition

Value

Unit

Screw Pumps 3 Brenker 1978, 2020, 2010 Poor

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

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Two of the pump motors have been replaced since the original construction of the facility, one after 2010 and the other in 2020. The center pump is broken, and the WWTP staff have not been able to find a suitable replacement. One of the screws has been replaced. The criticality of this facility is critical. A photo of the RAS/WAS pump station pumps can be seen in Figure 6-43.

Figure 6-43: Photo of the Existing RAS/WAS Pump Station Showing Empty Pump Well

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6.2.15 Secondary Sludge Pump Station The secondary sludge pump station pumps RAS and WAS from secondary clarifier 3 to aeration basin 3 and to the gravity belt thickener. The pump station houses three 15-hp centrifugal pumps manufactured by Fairbanks-Morse. A 2-ton crane is also located in the pump station to aid in maintenance of the pumps. An electrical room housing the pump controls as well as control panels for final clarifier 3 and aeration basin 3. A summary of the design details of the facility can be seen in Table 6-35. Table 6-35: Design Details of the Secondary Sludge Pump Station Design Detail Type Quantity Manufacturer Size Year Installed Overall Condition

Value

Unit

Centrifugal 3 Fairbanks Morse 15 1994

hp -

Fair

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

6.1 7.4 High

One of the pumps in the secondary sludge pump station is currently being rebuilt and is therefore not in operation. It was observed during the site visit that the pump shafts are exposed, which poses a safety hazard to the operators. The criticality of the secondary sludge pump station was determined to be high. A photo of the secondary sludge pump station pumps can be seen in Figure 6-44.

Figure 6-44: Photo of the Secondary Sludge Pump Station

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6.2.16 Sludge Transfer Pump Station The digested sludge pump station is located west of aeration basins 1 and 2 and houses two screw pumps that were installed in 1978. The screw pumps were initially intended to pump WAS from the aeration basins to the gravity belt thickener, however they are no longer in use by the WWTP staff. A summary of the design details of the digested sludge pumps can be seen in Table 6-36. Table 6-36: Design Details of the Sludge Transfer Pumps Design Detail Type Quantity Year Installed Overall Condition

Value

Unit

Enclosed Screw Pumps

2 1978 Poor Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

5.5 6.1 High

The digested sludge pump station no longer serves its purpose at the WWTP and is in poor condition. The WAS that is digested in the aerobic digester channels of aeration basins 1 and 2 is sent directly to the gravity belt thickener (GBT) building instead. The criticality of this facility was determined to be high due to its poor condition and the need for increased operational flexibility of the GBT. 6.2.17 Gravity Belt Thickener All WAS at the plant (from aeration basins 1 and 2 as well as the secondary clarifiers) is sent to the GBT building for thickening. The facility was constructed in 1978 and houses a Roediger GBT. Roediger is no longer in business, however some manufacturers have stated that they can provide services and spare parts to repair the existing equipment if required. The WAS is sent to the GBT building where polymer is injected before it is sent through the GBT. Thickened sludge from GBT can be returned to aerobic digesters or sent directly to sludge holding tank. The thickened sludge pump and polymer pump are also located within the building. A summary of the design details of the gravity belt thickener facility can be seen in Table 6-37.

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Table 6-37: Design Details of the Gravity Belt Thickener Facility Design Detail Type Quantity Manufacturer Size Year Installed Overall Condition

Value Mechanical Thickener Gravity Belt 1 Roediger 1.2 1978 Fair

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

Unit m 6.9 3.7 Medium

The GBT building has poor drainage, which results in water pooling within the facility. The GBT has been able to consistently achieve 4-5% solids and has never needed major rehabilitation or replacement of the rollers. The criticality of the facility was determined to be medium due to the lack of redundancy and fair condition of the equipment. A photo of the existing thickener building can be seen in Figure 6-45.

Figure 6-45: Photo of the Existing Gravity Belt Thickener Facility

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6.2.18 Anaerobic Digesters The anaerobic digesters are located on the north side of the plant and were constructed before 1978 and are no longer in use by the WWTP staff. Design details of the anaerobic digesters is shown in Table 6-38. Table 6-38: Design Details of the Anaerobic Digesters Design Detail Quantity Manufacturer Size Year Installed Overall Condition

Value

Unit

50 Poor

ft -

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure Overall Criticality

6.0 2.9 Medium

The overall condition of the anaerobic digesters is poor. The WWTP staff noted during the site visit that the digesters are too small and were causing operational issues prior to their decommissioning. The criticality of the anaerobic digester facility is medium, as there are other methods of sludge holding/treatment prior to the dewatering facility and digestion is not required. A photo of the anaerobic digesters can be seen in Figure 6-46.

Figure 6-46: Photo of the Existing Anaerobic Digester Basins 6.2.19 Sludge Holding Tank The sludge holding tank was converted from an existing final clarifier in 1994 and can hold approximately 750,000 gallons of sludge. The basins are covered and connected to an odor control system, however the odor control system has not been operated in recent years. Within the tank, there are two recycle pumps that work to keep the tank fully mixed to prevent septic conditions from occurring. A grinder pump sends

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the stored solids to the belt filter press facility. A summary of the design details of the sludge holding tank is shown in Table 6-39. Table 6-39: Design Details of the Sludge Holding Tank Design Detail

Value

Unit

Sludge Holding Tank 1 Quantity 750,000 Size 1978, 1994 Year Constructed (original, retrofit) Overall Condition Type Quantity Size Year Installed Overall Condition

gal -

Fair

Recycle Pumps Submersible 2 750,000 1994

gal -

Fair

Overall Criticality of the Facility 5.4 6.7 High

Likelihood of Failure Consequence of Failure Overall Criticality

The sludge holding tank is in fair condition. The odor control system for the facility is no longer in use as it frequently required maintenance. The Mg(OH)2 system is now utilized for odor control and pH adjustment. The criticality of the sludge holding tank was determined to be high. A photo of the facility can be seen in Figure 6-47.

Figure 6-47: Photo of the Existing Sludge Storage Basin

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6.2.20 Sludge Dewatering Facility The sludge dewatering facility houses two 2-m BFPs which are used to dewater the stored sludge before disposal. The facility also houses two sludge pumps by Seepex, two polymer storage and feed units, and a 2-ton crane. The BFPs are both manufactured by Ashbrook. One of the BFPs was on site before the dewatering facility was constructed; the BFP was installed in 1978, then refurbished and moved to the new facility in 2016. The BFPs are typically operated 12-hr/day, Monday-Friday, and achieve 19-22% solids. After dewatering the solids are disposed of and hauled offsite. A summary of the design details of the equipment in the sludge dewatering facility is shown in Table 6-40. Table 6-40: Design Details of the Existing Dewatering Facility Design Detail

Value

Type Quantity Manufacturer Size (each) Year Installed Overall Condition

Dewatering Equipment Belt Filter Press 2 Ashbrook 2 1978, 2017 Good

Type Quantity Manufacturer Size (each) Year Installed

Sludge Feed Pumps Progressive Cavity Pumps 2 Seepex 20 2017

Overall Condition Quantity

Unit m -

Good Polymer Feed System 2

Overall Criticality of the Facility Likelihood of Failure Consequence of Failure

2.5 5.7

Overall Criticality

Low

The BFPs and associated equipment are in good condition. Both of the BFPs are currently operated approximately 12 hr/day on weekdays. WWTP staff noted that the lighting in the building needs to be updated to make operation easier. The criticality of the sludge dewatering facility is low. A photo of the BFPs in the dewatering facility can be seen in Figure 6-48.

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Figure 6-48: Photo of the BFPs in the Dewatering Facility 6.2.21 Southside WWTP Condition Assessment Summary Table 6-41 lists the facilities defined in the WERF SIMPLE tool for the Southside WWTP. An Asset ID has been designated to each facility. In addition, the WERF SIMPLE took core risk map exhibiting the criticality of each facility is shown in Figure 6-49. The facilities determined to have a critical criticality include: aeration basins 1&2, the chlorine building, and the RAS/WAS pump station.

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Table 6-41: Summary of the Condition Assessment for the Southside WWTP Facility No.

Asset ID

Facility

SS-WWTP-CHEM

Chemical Feed Facility

SS-WWTP-ISP

Influent Screw Pumps

SS-WWTP-MS

Mechanical Screens

SS-WWTP-GR

Grit Removal

SS-WWTP-PC

Primary Clarifier

SS-WWTP-PSPS

Primary Sludge Pump Station

SS-WWTP-AB1&2

Aeration Basins 1 & 2

SS-WWTP-AB3

Aeration Basin 3

SS-WWTP-FC1&2

Final Clarifiers 1 & 2

SS-WWTP-FC3

Final Clarifier 3

SS-WWTP-PLS

Plant Lift Station

SS-WWTP-CCB

Chlorine Contact Basin

SS-WWTP-CB

Chlorine Building

SS-WWTP-RWPS

RAS/WAS Pump Station

SS-WWTP-SSPS

Secondary Sludge Pump Station

SS-WWTP-STPS

Sludge Transfer Pump Station

SS-WWTP-GBT

GBT Facility

SS-WWTP-AD

Anaerobic Digesters

SS-WWTP-SHT

Sludge Holding Tank

SS-WWTP-DF

Dewatering Facility

WWTP-PC2-001

Plant 480V MDC

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Figure 6-49: Core Risk Map of the Southside WWTP Facilities

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7.0

Findings and Recommendations

In this TM, the historical quantity and quality of the Tyler WWTPs influent and effluent streams were reviewed. In addition to influent characteristics (BOD, TSS, NH 3-N, etc.), effluent quality data were compared to permit requirements, and projected flows were presented. At the Westside WWTP, BOD has decreased by 8% from 2016 to 2021 and NH3-N has increased by approximately 3%. Over the same time period, TSS and flow has remained fairly constant. The identification of these trends will aid in the development of the planning criteria for the master plan project. At the Southside WWTP, it was noted in the data review that some influent loadings have increased while others have decreased or remained fairly consistent. NH3-N has increased by less than 5% from 2016 to 2021 and TSS has increased by 16.6%. BOD influent loadings however have decreased by 11% over the same period. Influent flows increased by about 7%. The identification of these trends will aid in the development of the planning criteria for the master plan project or both Westside and Southside WWTPs. A summary of the peaking factors identified in this TM are shown below in Table 7-1. Constituent peaking factors for BOD, TSS, and NH3-N were determined as further bases of design for future technical evaluations. Table 7-1: Peaking Factors Identified at the Westside and Southside WWTPs Westside WWTP Parameter

Southside WWTP

Average Value

Peaking Factor

Average Value

Peaking Factor

Flow

9.5 MGD1

1.46

7.0 MGD1

1.29

BOD

162 mg/L

1.28

146 mg/L

1.26

TSS

180 mg/L

1.40

259 mg/L

1.45

NH3-N

23 mg/L

1.47

20 mg/L

1.29

Notes: 1. Future average day flows for each facility will be developed in the forthcoming Planning Criteria TM. In addition to the historical data review, findings of two site visits performed by the project team are documented in this TM. Site visits were performed by Garver on November 1st and 2nd of 2021 to review the existing facilities and document staff input regarding performance and maintenance issues of all equipment at the WWTPs. The following pages present a summary of criticality ratings for the facilities at the Westside and Southside treatment plants using the WERF SIMPLE tool.

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A summary of the observed condition along with the determined criticality of each facility at the Westside WWTP is shown below in Table 7-2. The facilities determined to have a critical criticality include: the mechanical screen, the grit removal basins, the filter pump station, the nitrification basin, the chlorine building and the anaerobic digesters. Table 7-2: Condition Assessment Summary for the Westside WWTP Facility No.

Asset ID

WS-WWTP-MS

Mechanical Screen

Critical

WS-WWTP-GR

Grit Removal

Critical

WS-WWTP-FPS

Filter Pump Station

Critical

WS-WWTP-NB

Nitrification Basin

Critical

WS-WWTP-CB

Chlorine Building

Critical

WS-WWTP-AD

Anaerobic Digesters

Critical

WS-WWTP-RWPS

Raw Water Pump Station

High

WS-WWTP-FSTF

First Stage Trickling Filters

High

WS-WWTP-SC

Secondary Clarifiers

High

WS-WWTP-RASPS

RAS Pump Station

High

WS-WWTP-CCB

Chlorine Contact Basin

High

WS-WWTP-OPS

Operations Building/Lab

High

WS-WWTP-PC

Primary Clarifiers

Medium

WS-WWTP-SSTF

Second Stage Trickling Filters

Medium

WS-WWTP-LSPS

Light Sludge Pump Station

Low

WS-WWTP-CHEM

Chemical Feed Facility

Low

WS-WWTP-PSPS

Primary Sludge Pump Station

Low

WS-WWTP-BFPPS

BFP Pump Station

Low

WS-WWTP-DF

Dewatering Facility

Low

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A summary of the observed condition along with the determined criticality of each facility at the Southside WWTP is shown below in Table 7-3. The facilities determined to have a high criticality include aeration basins 1 & 2, the chlorine building, and the RAS/WAS pump station. Table 7-3: Summary of the Condition Assessment for the Southside WWTP Facility No.

Asset ID

SS-WWTP-AB1&2

SS-WWTP-CB

Facility

Criticality

Aeration Basins 1 & 2

Critical

Chlorine Building

Critical

SS-WWTP-RWPS

RAS/WAS Pump Station

Critical

SS-WWTP-AB3

Aeration Basin 3

High

SS-WWTP-FC1&2

Final Clarifiers 1 & 2

High

SS-WWTP-FC3

Final Clarifier 3

High

SS-WWTP-CCB

Chlorine Contact Basin

High

SS-WWTP-SSPS

Secondary Sludge Pump Station

High

SS-WWTP-STPS

Sludge Transfer Pump Station

High

SS-WWTP-SHT

Sludge Holding Tank

High

SS-WWTP-GR

Grit Removal

Medium

SS-WWTP-PLS

Plant Lift Station

Medium

SS-WWTP-GBT

GBT Facility

Medium

SS-WWTP-AD

Anaerobic Digesters

Medium

SS-WWTP-CHEM

Chemical Feed Facility

Low

SS-WWTP-ISP

Influent Screw Pumps

Low

SS-WWTP-MS

Mechanical Screens

Low

SS-WWTP-PC

Primary Clarifier

Low

SS-WWTP-PSPS

Primary Sludge Pump Station

Low

SS-WWTP-DF

Dewatering Facility

Low

WWTP-PC2-001

Plant 480V MDC

Low

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Appendix B Planning Criteria TM

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Appendix B

Technical Memorandum Planning Criteria (Reissued) City of Tyler Wastewater Treatment Plants Master Plan City of Tyler, Texas

Prepared by:

3010 Gaylord Parkway Suite 190 Frisco, TX 75034 November 2022 Garver Project No. 21W05170

Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

Engineer’s Certification I hereby certify that this Planning Criteria Technical Memorandum, associated with the Tyler Wastewater Treatment Plants Master Plan, was prepared by Garver under my direct supervision for the City of Tyler.

Justin A. Rackley, PE State of TX PE License #102342

Digitally signed 11/15/2022

Russell D. Tate, PE State of TX PE License #132233 Digitally Signed 11/21/2022

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

Table of Contents 1.0

Introduction........................................................................................................................................ 5

2.0

Existing Flow and Loadings .............................................................................................................. 5

3.0

Flow Projections ................................................................................................................................ 6

3.1

Method 1 - Linear Flow Projection based on Census Data .......................................................... 6

3.2

Method 2 - Flow Projection based on Projected Growth Areas .................................................... 7

3.3

Peak 2-Hour Flow Projections....................................................................................................... 9

3.3.1

Westside WWTP ....................................................................................................................... 9

3.3.2

Southside WWTP .................................................................................................................... 10

3.4

Potential Addition of a Future WWTP ......................................................................................... 11

3.5

Recommended Flow Projection .................................................................................................. 11

4.0

Loading Projections ......................................................................................................................... 12

4.1

Westside WWTP ......................................................................................................................... 12

4.2

Southside WWTP ........................................................................................................................ 13

5.0

Future Regulatory Limits ................................................................................................................. 13

5.1

Westside WWTP ......................................................................................................................... 13

5.2

Southside WWTP ........................................................................................................................ 14

5.3

Potential Permit Updates Over the Planning Horizon ................................................................. 15

6.0

Cost Estimating Criteria .................................................................................................................. 15

7.0

Conclusion....................................................................................................................................... 15

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List of Figures Figure 3-1: Population Projections for the City of Tyler, Texas .................................................................... 6 Figure 3-2: Pipeline Analysis Map Showing Westside and Southside Basins and 2040 Growth Areas ...... 8 Figure 3-3: Westside WWTP Peak 2-Hour Flow Factors ........................................................................... 10 Figure 3-4: Southside WWTP Peak 2-Hour Flow Factors .......................................................................... 10

List of Tables Table 2-1: Existing Influent Flow and Loadings at Westside and Southside WWTPs .................................. 5 Table 3-1: 2052 Projected Flow Calculation ................................................................................................. 7 Table 3-2: 2052 Linear Flow Projection and Flow Distribution (Method 1) ................................................... 7 Table 3-3: Tyler, Texas Growth Area Delineation and Area ......................................................................... 8 Table 3-4: Future Flow Projection using Projected Growth Areas (Method 2) ............................................. 9 Table 3-5: Flow Distribution Comparison .................................................................................................... 11 Table 3-6: Recommended 2052 Flow Projections ...................................................................................... 12 Table 4-1: Projected Future Constituent Loadings to the Westside WWTP ............................................... 12 Table 4-2: Projected Future Constituent Loadings to the Southside WWTP.............................................. 13 Table 5-1: TPDES Permit Requirements for Westside WWTP .................................................................. 13 Table 5-2: TPDES Permit Requirements for Southside WWTP ................................................................. 14 Table 6-1: Preliminary Cost Estimate Contingency and Contractor Margins ............................................. 15

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

List of Acronyms Acronym

Definition

ADF

Average Daily Flow

BOD

Biochemical Oxygen Demand

cBOD

Carbonaceous Biochemical Oxygen Demand

CCN

Certificate of Convenience and Necessity

cfu

Colony-Forming Units

CIP

Capital Improvement Plan

Dissolved Oxygen

gpcd

Gallons per Capita per Day

Hour

lb/d

Pounds per Day

MGD

Million Gallons per Day

mg/L

Milligrams per Liter

Milliliters

N/A

Not Applicable

NH3-N

Ammonia-Nitrogen

OPCC

Opinion of Probable Construction Cost

P2HF

Peak Two-Hour Flow

TCEQ

Texas Commission on Environmental Quality

Technical Memorandum

Total Phosphorous

TPDES

Texas Pollutant Discharge Elimination System

TRC

Total Residual Chlorine

TSS

Total Suspended Solids

WWTP

Wastewater Treatment Plant

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

1.0

Introduction

The purpose of this Technical Memorandum (TM) is to document and establish the basis of planning criteria for the two (2) Tyler Wastewater Treatment Plants (WWTPs), Southside WWTP and Westside WWTP, as a part of the WWTPs Master Plan project. The following items have been reviewed by the project team to establish the planning criteria that will be used to establish baseline conditions, assess future needs, and Capital Improvement Plan (CIP) development: • • • •

Population projections, Flow projections, Loading projections, Regulatory and effluent quality requirements,

In addition to the flow and loading projections and effluent quality requirements, the basis for cost estimating to be used in upcoming master planning tasks (i.e. technical evaluations) were established.

2.0

Existing Flow and Loadings

The Westside and Southside WWTPs jointly service the City of Tyler, Texas. The City of Tyler has a total average daily flow (ADF) of approximately 16.5 million gallons per day (MGD) and a current flow split between the Westside and Southside WWTPs of 9.5 MGD and 7.0 MGD, respectively. This data was documented in the Historical Data Review TM, dated April 2022. The flow and loadings entering the WWTPs from 2016 to 2021 were reviewed and summarized in the Historical Data Review TM. Table 2-1 shows a summary of the historical influent characteristics for the Westside and Southside WWTPs. These values are used in this TM to develop the future flow and loading projections. Influent biochemical oxygen demand (BOD), total suspended solids (TSS), and ammonia-nitrogen (NH3N) concentrations are routinely measured routinely at the WWTPs and historical data was provided for these constituents to determine the average concentrations, as well as maximum month peaking factors. However, influent total phosphorous (TP) is not among the routine measurements at the Westside and Southside WWTPs. Hence, average TP data from the conducted special sampling campaign was used to determine the average daily TP concentrations for planning. Further, an industry-recommended peaking factor of 1.30 is used for TP. Table 2-1: Existing Influent Flow and Loadings at Westside and Southside WWTPs Westside WWTP Parameter Flow BOD TSS NH3-N TP

Garver Project No. 21W05170

Average Value 9.5 MGD 162 mg/L 180 mg/L 23 mg/L 6.5 mg/L

Peaking Factor 1.46 1.28 1.40 1.47 1.30

Southside WWTP Average Value 7.0 MGD 146 mg/L 259 mg/L 20 mg/L 4.3 mg/L

Page 5

Peaking Factor 1.29 1.26 1.45 1.29 1.30

Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

3.0

Flow Projections

This section presents two (2) methods of flow projection, as well as the recommended flow projections. The linear projection method consists of projecting the future population of the city based on a linear extrapolation of the city’s population growth trend based on census data. The growth area projection method takes into account the population growth regions throughout the city and allocates them to either the Westside WWTP or the Southside WWTP based on the 2020 City-Wide Hydraulic Model Capacity Assessment and Remedial Measures Plan. Per discussion with the City staff, no water conservation plans are considered for the planning horizon. 3.1

Method 1 - Linear Flow Projection based on Census Data

In this method, the census population data for the City of Tyler is reviewed and extrapolated to determine the projected population for the 30-year planning horizon. As seen in Figure 3-1, the population of the city has increased linearly for the past 3 decades; following this linear trend results in a projected population of approximately 140,000 in the year 2052. 160,000

Tyler, TX Population

140,000 120,000 100,000

2052 projected population: 140,000

80,000 60,000 40,000 1980

1990

2000

2010

2020

Year

2030

2040

2050

2060

Figure 3-1: Population Projections for the City of Tyler, Texas The flow associated with this future population was calculated based on the per capita wastewater production for the year 2020. The flow per capita was determined by dividing the average measured influent flow to the WWTPs in 2020 based on the historical data influent flow by the city’s population in 2020, determined during the 2020 census. The resulting flow per capita is approximately 156 gallons per capita per day (gpcd). During further evaluations, this value will be reviewed and discussed for use as planning criteria. Table 3-1 shows the projected average daily wastewater flow for the City of Tyler in the year 2052 of 21.8 MGD.

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Table 3-1: 2052 Projected Flow Calculation 2020 Average Influent Flow

2020 Average Flowrate per Capita

2052 Projected Population

2052 Projected Average Daily Influent Flow

16.5 MGD

156 gpcd

140,000

21.8 MGD

For this method, the distribution of the flow to the Westside and Southside WWTPs will be based on the current distribution. The current total average daily flow is 16.5 MGD; 9.5 MGD is sent to the Westside WWTP (approximately 58%) and 7.0 MGD is sent to the Southside WWTP (approximately 42%). Therefore, the future flow projections based on this method to the WWTPs are 12.6 MGD to the Westside WWTP and 9.2 MGD to Southside WWTP. A summary of the linear flow projection for the 2052 master plan horizon is shown in Table 3-2. Table 3-2: 2052 Linear Flow Projection and Flow Distribution (Method 1)

3.2

Total Average Daily Influent Flow

Westside WWTP

Southside WWTP

21.8 MGD

12.6 MGD

9.2 MGD

Method 2 - Flow Projection based on Projected Growth Areas

As a part of the 2020 City-Wide Hydraulic Model Capacity Assessment and Remedial Measures Plan, the future flows being carried through the city’s wastewater collection system were analyzed. A map of the City of Tyler, Texas displaying the current area that is serviced by the Westside and Southside WWTPs, as well as the 2040 projected areas of growth in the city was developed and is shown in Figure 3-2.

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

Figure 3-2: Pipeline Analysis Map Showing Westside and Southside Basins and 2040 Growth Areas The details of the projected growth areas provided by the City of Tyler are shown in Table 3-3. Table 3-3: Tyler, Texas Growth Area Delineation and Area Growth Area ID

Area (acres)

WWTP Assignment

2,123

Southside

1,645

Southside

1,212

Southside

4-W

583

Westside

4-S

463

Southside

964

Westside

879

Westside

723

Westside

433

Westside

1,712

Westside

269

Westside

636

Southside

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

To project the future flows, the acreage of the growth areas was used to determine an additional flow amount added to the current flow determined in the Historical Data Review TM. The assumptions established in the City-Wide Hydraulic Model Capacity Assessment and Remedial Measures Plan for people per acre (i.e., 1.73 persons per acre) and flow per capita (i.e.,173 gpcd) were used to determine the future flow of the growth areas. The calculated future flow for each WWTP was then added to the existing flows; the existing and future projected flows can be seen in Table 3-4. Table 3-4: Future Flow Projection using Projected Growth Areas (Method 2) Existing Flow

Added Population

Westside WWTP

9.5 MGD

9,624

Expected Additional Flow 1.7 MGD

Southside WWTP

7.0 MGD

10,517

1.8 MGD

8.8 MGD

16.5 MGD

20,141

3.5 MGD

20.0 MGD

WWTP

Total 3.3

Future Flow 11.2 MGD

Peak 2-Hour Flow Projections

Two-hour flow data collected by the Westside and Southside WWTP operators was analyzed and used to determine a peak 2-hour flow (P2HF) factor for the future planning criteria. The recorded daily 2-hour flows were divided by the rolling 365-day average daily flow values to determine daily P2HF factors. The maximum P2HF factor determined for each day was graphed, shown in the following sections, and compared to the current P2HF factor used in the WWTP permits (2.5). These P2HF factors will be multiplied by the projected ADFs for the two plants to determine the future P2HF to be used for master planning purposes. 3.3.1

Westside WWTP

Daily P2HF data from the Westside WWTP was provided from December 2020 to June 2022, however the P2HF factors were determined only up to January 2022 due to availability of average daily flow data. As shown in Figure 3-3, the maximum P2HF factor identified for the Westside WWTP was 3.37 in December of 2021. This factor will be used to determine the future P2HF flow for the Westside WWTP.

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

4.00

3.37

Peak 2-Hour Flow Factor

3.50 3.00

Existing P2HF Factor, 2.5 2.50 2.00 1.50 1.00

0.50 0.00 11/15/20

1/4/21

2/23/21

4/14/21

6/3/21

7/23/21

9/11/21

10/31/21 12/20/21

2/8/22

Figure 3-3: Westside WWTP Peak 2-Hour Flow Factors 3.3.2

Southside WWTP

Daily P2HF data from the Southside WWTP was provided from January 2019 to April 2022, however the P2HF factors were determined only up to October 2021 due to availability of average daily flow data. As shown in Figure 3-4, the second highest P2HF factor identified for the Southside WWTP was 3.95 in September of 2020. This factor will be used to determine the future P2HF for the Southside WWTP. 6.00

5.88

Peak 2-Hour Flow Factor

5.00

3.95

4.00

3.00

Existing P2HF Factor, 2.5 2.00

1.00

0.00 12/16/18

7/4/19

1/20/20

8/7/20

2/23/21

Figure 3-4: Southside WWTP Peak 2-Hour Flow Factors

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

The maximum P2HF factor identified (5.88, also from September 2020) was ruled out of the P2HF analysis due to a storm event on the day of that measurement. TCEQ requires that the P2HF be based on the 2year, 24-hour storm event (TAC 217.34(1)(C)). This storm was determined to be greater than the 2-year 24-hour storm and therefore was ruled out of the analysis. 3.4

Potential Addition of a Future WWTP

In conversation with the City of Tyler staff, it was noted that a potential green field site has been located for the construction of a future WWTP. The necessity of a future plant will be discussed in further TMs based on the treatment capacity of the existing facilities. It was determined that if capacity gaps are identified at the Southside WWTP, the additional capacity is to be provided via the third (future) WWTP. In addition, the City of Tyler has been discussing with a nearby Certificate of Convenience and Necessity (CCN), Liberty Utilities, about taking on their flow if a new plant is constructed. The ADF from the CCN that would need to be treated is 1.1 MGD based on the Liberty Utilities’ discharge permit. This flow will be added to the overall capacity needed at the future WWTP. 3.5

Recommended Flow Projection

The two flow projection methods resulted in future overall average daily flow ranging from 20.0 MGD to 21.8 MGD. In addition to this difference, the projected flow distribution between Westside and Southside WWTPs varied for the two methods, due to the growth area projection within the Southside basin being slightly higher than that of the Westside basin. A comparison of the flow distribution determined by each method is shown in Table 3-5. Table 3-5: Flow Distribution Comparison WWTP

Flow Distribution: Method 1

Flow Distribution: Method 2

Percentage

Flow (MGD)

Percentage

Flow (MGD)

Westside WWTP

58%

12.6

56%

11.2

Southside WWTP

42%

9.2

44%

8.8

The findings of the two flow projection methods were presented to the City of Tyler staff during a progress workshop in March 2022, and it was determined that the Method 1 (linear flow projection) would be more applicable and preferred for future planning. In addition, a flow split concurrent with the existing distribution (Method 1) will be considered. In a subsequent meeting, the city staff requested that the projected ADF for both WWTPs be increased by approximately 10% to account for additional future growth to accommodate the anticipated commercial building expansions in the city. This increased the projected ADFs from 12.6 MGD to 14 MGD for the Westside WWTP and 9.2 MGD to 10 MGD for the Southside WWTP. A summary of the determined flow projections for the Westside and Southside WWTPs is shown in Table 3-6. Maximum month flows are determined via the established peaking factors discussed in Section 2.0. As detailed in Section 3.3, the P2HF factors used for Westside and Southside WWTPs were 2.88 and 3.33, respectively.

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

Table 3-6: Recommended 2052 Flow Projections WWTP

Average Daily Flow

Max Month Flow

Peak 2-hour Flow

Westside WWTP

14 MGD

20.4 MGD1

47.2 MGD2

Southside WWTP

10 MGD

12.8 MGD1

39.5 MGD3

Potential Flow from Liberty Utilities4

1.1 MGD

1.5 MGD5

3.2 MGD

Total 25.1 MGD 34.7 MGD 89.9 MGD Notes: 1. Max Month flows are based on peaking factors for each WWTP that were identified in the Historical Data Review TM (1.46 for Westside WWTP, 1.28 for Southside WWTP) 2. Based on the 3.37 peak-2-hour to average daily flow factor. 3. Based on the 3.95 peak-2-hour to average daily flow factor. 4. ADF and P2HF is from Liberty Utilities effluent permits. Flow from Liberty Utilities will only be considered in the flow projections if a new greenfield facility is constructed. 5. Maximum month peaking factor of 1.4 considered for Liberty Utilities.

4.0

Loading Projections

The Historical Data Review TM provided a summary of the historical influent wastewater flows and characteristics entering the Tyler WWTPs. Findings of the Historical Data Review TM were used as a baseline for establishing anticipated influent loadings for master planning purposes and were discussed with the City staff. The loading projections for both the Westside and Southside WWTPs are presented in the following section. 4.1

Westside WWTP

Table 4-1 shows a summary of the established influent loadings for planning, modeling, and sizing of the future Westside WWTP. The existing constituent concentrations presented in Table 2-1 (Existing Influent Flows and Loadings, based on the data from 2016 to 2021) were used to calculate the future loadings. Table 4-1: Projected Future Constituent Loadings to the Westside WWTP

Average Day Max Month1 Peak 2Hour Flow

Flow (MGD)

BOD (mg/L)

BOD (lb/d)

TSS (mg/L)

TSS (lb/d)

NH3-N (mg/L)

NH3-N (lb/d)

TP (mg/L)

TP (lb/d)

162

18,920

180

21,020

2,670

6.5

760

20.4

24,210

29,420

3,950

990

47.2

Notes: 1. Constituent max month loadings are based on peaking factors shown in Table 2-1 applied to the average daily loadings.

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

4.2

Southside WWTP

Table 4-2 shows the established flow and loadings for planning, modeling, and sizing of the future Southside WWTP. Table 4-2: Projected Future Constituent Loadings to the Southside WWTP Flow (MGD)

BOD (mg/L)

BOD (lb/d)

TSS (mg/L)

TSS (lb/d)

NH3-N (mg/L)

NH3-N (lb/d)

TP (mg/L)

TP (lb/d)

Average 10 146 12,180 259 21,600 20 1,670 4.3 360 Day Max 12.8 15,340 31,320 2,150 470 Month1 Peak 2Hour 39.5 Flow 1. Constituent max month loadings are based on peaking factors shown in Table 2-1 applied to the average daily loadings.

5.0

Future Regulatory Limits

The regulatory limits used for the future effluent planning criteria of the two WWTPs will be presented in the following section. 5.1

Westside WWTP

The Westside WWTP operates under Texas Pollutant Discharge Elimination System (TPDES) permit number WQ0010653001 originally issued by Texas Commission on Environmental Quality (TCEQ) on February 24, 2015. The permit limits for the Westside WWTP effluents are listed in Table 5-1. Table 5-1: TPDES Permit Requirements for Westside WWTP

Parameter

Mass (lb/d)1

cBOD (Mar-Nov)

Concentration (mg/L) Frequency

Daily Average

7-day Average

Daily Max

Single Grab

1,084

One/day

cBOD (Dec-Feb)

2,168

One/day

TSS (Mar-Nov)

1,626

One/day

TSS (Dec-Feb)

2,168

One/day

NH3-N (Mar-Nov)

325

One/day

NH3-N (Dec-Feb)

1,084

One/day

4,4’ - DDT

7 x 10-6

6.48x10-7

N/A

1.37x10-6

1.9x10-6

Two/Week

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Sample Type 24-hr composite 24-hr composite 24-hr composite 24-hr composite 24-hr composite 24-hr composite 24-hr composite

Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

Parameter

Mass (lb/d)1

Concentration (mg/L) 7-day Average N/A

Daily Max 399

Single Grab N/A

Frequency

Sample Type

Five/week

Grab

E. coli (cfu/100ml) TRC (before dechlorination) TRC (after dechlorination)

Daily Average 126

≥ 1.0

One/day

Grab

≤ 0.1

One/day

Grab

Five/week

Grab

DO (Mar-Nov)

One/day

Grab

Min: 6.0 Max: 9.0 6.0

DO (Dec-Feb) 5.0 One/day Grab Notes: 1. Mass Loadings are determined based on the current permitted annual average flow of 13 MGD. The facility also has a permitted 2-hour peak flow of 32.5 MGD. 5.2

Southside WWTP

The Southside WWTP operates under TPDES permit number WQ0010653002 originally issued by TCEQ on October 7, 2016. The permit limits for the Southside WWTP effluents are listed in Table 5-2. Table 5-2: TPDES Permit Requirements for Southside WWTP

Parameter

Mass (lb/d)1

cBOD (5-day)

Concentration (mg/L)

Sample Type

Daily Average

7-day Average

Daily Max

Single Grab

Frequency

751

Five/week

TSS

1,126

Five/week

NH3-N (Mar-Oct)

225

Five/week

NH3-N (Nov-Feb)

300

Five/week

126

N/A

399

N/A

Three/week

Grab

≥ 1.0

One/day

Grab

≤ 0.1

One/day

Grab

Five/Week

Grab

DO (Mar-Nov)

Min: 6.0 Max: 9.0 5.0

Five/Week

Grab

DO (Dec-Feb)

4.0

Five/Week

Grab

24-hr composite 24-hr composite 24-hr composite 24-hr composite

E. coli (cfu/100ml) TRC (before dechlorination) TRC (after dechlorination)

1. Mass Loadings are determined based on the current permitted annual average flow of 9 MGD. Peak 2-hour flow capacity of the Southside facility is 22.5 MGD.

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Tyler Wastewater Treatment Plants Master Plan Planning Criteria Technical Memorandum (Reissued)

5.3

Potential Permit Updates Over the Planning Horizon

Currently, there are no TP effluent discharge limits included in either of these permits; however, TCEQ can add parameters and reduce allowable concentrations in the future. Hence, it is recommended that the City of Tyler include potential projects and processes to their facilities in case changes to the permits are made. In this planning horizon, TCEQ could enforce TP limits on both existing WWTPs and lower the permitted NH3-N concentration. For TP parameter limits, the WWTPs master plan will allow for space if a phosphorus removal facility is required in the future. A minimum solids retention time of 7-day will be considered for design and planning purposes of the biological treatment train at the WWTPs to confirm full nitrification and maintain the effluent NH3-N below 2.0 mg/L.

6.0

Cost Estimating Criteria

As a part of the WWTPs master plan, various process alternatives will be evaluated in the forthcoming tasks to provide the required treatment capacity over the 30-year planning horizon (i.e., 2022-2052). The estimated opinion of probable construction cost (OPCC) for each investigated alternative will be provided in 2022 U.S. dollars. Excavation, backfill, concrete, and electrical costs will be assigned to each individual facility as necessary. The following items will also be used as a baseline for preparation of the OPCCs: • • • •

Actual cost estimates, Proposals provided by equipment manufacturers and suppliers, Previous cost estimates prepared by Garver, and Contractor bid tabulations from recent project deliveries.

Table 6-1 lists the contingency, mobilization costs, and contractor overhead and profit percentages that will be considered in the development of the estimated OPCCs. Table 6-1: Preliminary Cost Estimate Contingency and Contractor Margins Consideration

7.0

Assumption

Contingency

35%

Mobilization

Contractor Overhead and Profit

18%

Conclusion

In this TM, the basis of planning criteria for the City of Tyler master plan project were established and documented. Findings of the previous Historical Data Review TM were summarized and used to develop the basis of planning criteria. The findings of this TM will be used as a baseline for the upcoming planning, modeling, and technical evaluations of the Westside and Southside WWTPs. The potential for the construction of a future greenfield WWTP was also discussed and will be further evaluated in future TMs. Furthermore, cost estimate contingency and contractor margins were established to be used as a basis for cost estimates associated with the forthcoming technical evaluation tasks.

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Appendix C Baseline Analysis TM

Garver Project No. 21W05170

Appendix C

Technical Memorandum Baseline Analysis City of Tyler Wastewater Treatment Plants Master Plan City of Tyler, Texas

Prepared by:

3010 Gaylord Parkway Suite 190 Frisco, TX 75034 April 2023 Garver Project No. 21W05170

Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Engineer’s Certification I hereby certify that this Baseline Analysis Technical Memorandum, associated with the Tyler Wastewater Treatment Plants Master Plan, was prepared by Garver under my direct supervision for the City of Tyler.

Justin A. Rackley, PE State of TX PE License #102342

Digitally signed 04/17/2023

Russell D. Tate, PE State of TX PE License #132233 Digitally Signed 04/18/2023

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Table of Contents Engineer’s Certification ............................................................................................................................ 1 Table of Contents .................................................................................................................................... 2 List of Figures .......................................................................................................................................... 5 List of Tables ........................................................................................................................................... 8 List of Acronyms .................................................................................................................................... 12 Executive Summary............................................................................................................................... 13 1.

Introduction ................................................................................................................................ 16

Process Model Evaluation .......................................................................................................... 16

2.1.

Model Development ................................................................................................................... 16

2.1.1. Data Collection and Reconciliation ............................................................................................. 17 2.1.2. Plant Model Representations ..................................................................................................... 17 2.1.3. Model Calibration and Validation ................................................................................................ 17 2.1.4. Qualification of Results for Model Calibration and Validation....................................................... 18 2.2.

Westside WWTP Baseline Process Model.................................................................................. 20

2.2.1. Westside WWTP Sampling Data ................................................................................................ 20 2.2.2. Westside WWTP Model Representation ..................................................................................... 20 2.2.3. Westside WWTP Calibration Results .......................................................................................... 23 2.2.4. Westside WWTP Validation Results ........................................................................................... 26 2.2.5. Westside WWTP Process Model Summary ................................................................................ 28 2.3.

Southside WWTP Baseline Process Model ................................................................................ 28

2.3.1. Southside WWTP Sampling Data ............................................................................................... 28 2.3.2. Southside WWTP Model Representation .................................................................................... 30 2.3.3. Southside WWTP Calibration Results......................................................................................... 32 2.3.4. Southside WWTP Validation Results .......................................................................................... 37 2.3.5. Southside WWTP Process Model Summary ............................................................................... 38 3.

Hydraulic Model Evaluation ........................................................................................................ 38

3.1.

Methodology of Hydraulic Models ............................................................................................... 38

3.2.

Evaluation Criteria ...................................................................................................................... 39

3.3.

Westside WWTP ........................................................................................................................ 40

3.3.1. Model Assumptions .................................................................................................................... 40

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3.3.2. Model Results – Hydraulic Segments ......................................................................................... 42 3.4.

Southside WWTP....................................................................................................................... 60

3.4.1. Model Assumptions .................................................................................................................... 61 3.4.2. Model Results – Hydraulic Sections ........................................................................................... 63 4.

Gap Analysis.............................................................................................................................. 86

4.1.

Westside WWTP ........................................................................................................................ 87

4.1.1

Mechanical Screen..................................................................................................................... 88

4.1.2

Grit Removal .............................................................................................................................. 88

4.1.3

Raw Water Pump Station ........................................................................................................... 89

4.1.4

Primary Clarifiers ....................................................................................................................... 89

4.1.5

Biological Treatment Train.......................................................................................................... 90

4.1.6

Filter Pump Station..................................................................................................................... 91

4.1.7

Secondary Clarifiers ................................................................................................................... 91

4.1.8

RAS Pump Station ..................................................................................................................... 92

4.1.9

Chlorine Building ........................................................................................................................ 92

4.1.10 Chlorine Contact Basin............................................................................................................... 93 4.1.11 Oxygenation............................................................................................................................... 93 4.1.12 Anaerobic Digesters ................................................................................................................... 93 4.1.13 Primary Sludge and Belt Filter Press Pump Station .................................................................... 94 4.1.14 Sludge Dewatering Facility ......................................................................................................... 94 4.1.15. Westside WWTP Gap Analysis Summary................................................................................... 95 4.2.

Southside WWTP....................................................................................................................... 95

4.2.1

Influent Screw Pumps ................................................................................................................ 96

4.2.2

Mechanical Screens ................................................................................................................... 97

4.2.3

Grit Removal .............................................................................................................................. 97

4.2.4

Primary Clarifiers ....................................................................................................................... 98

4.2.5

Primary Sludge Pump Station..................................................................................................... 99

4.2.6

Aeration Basins .......................................................................................................................... 99

4.2.7

Secondary Clarifiers ................................................................................................................. 100

4.2.8

Chlorine Contact Basin............................................................................................................. 100

4.2.9

Chlorine Facility ....................................................................................................................... 101

4.2.10 RAS/WAS Pump Station .......................................................................................................... 101 4.2.11 Gravity Belt Thickener .............................................................................................................. 102

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4.2.12 Sludge Holding Tank ................................................................................................................ 103 4.2.13 Sludge Dewatering Facility ....................................................................................................... 103 4.2.14. Southside WWTP Gap Analysis Summary ............................................................................... 104 5.

Available Alternatives ............................................................................................................... 104

5.1.

Westside WWTP ...................................................................................................................... 104

5.1.1. Sludge Lagoon Rehabilitation ................................................................................................... 106 5.1.2. Headworks ............................................................................................................................... 108 5.1.3. Peak Flow Basin ...................................................................................................................... 110 5.1.4. Raw Water Pump Station ......................................................................................................... 114 5.1.5. Primary Clarifiers ..................................................................................................................... 116 5.1.6. Biological Treatment Train........................................................................................................ 119 5.1.7. Filter Pump Station................................................................................................................... 124 5.1.8. Secondary Clarifiers ................................................................................................................. 127 5.1.9. RAS/WAS Pump Station .......................................................................................................... 129 5.1.10. Chlorine Contact Basin............................................................................................................. 131 5.1.11. Oxygenation............................................................................................................................. 132 5.1.12. Anaerobic Digesters ................................................................................................................. 133 5.1.13. Sludge Dewatering Facility ....................................................................................................... 138 5.1.14. Summary of Available Alternatives at Westside WWTP ............................................................ 140 5.2.

Southside WWTP..................................................................................................................... 140

5.2.1. Influent Pump Station ............................................................................................................... 142 5.2.2. Headworks ............................................................................................................................... 144 5.2.3. Peak Flow Basin ...................................................................................................................... 146 5.2.4. Primary Clarifiers ..................................................................................................................... 148 5.2.5. Aeration Basins ........................................................................................................................ 148 5.2.6. Secondary Clarifiers ................................................................................................................. 154 5.2.7. Chlorine Contact Basin............................................................................................................. 156 5.2.8. RAW/WAS Pump Station ......................................................................................................... 156 5.2.9. Gravity Belt Thickener .............................................................................................................. 159 5.2.10. Sludge Holding Tank ................................................................................................................ 161 5.2.11. Dewatering Facility ................................................................................................................... 163 5.2.12. Summary of Available Alternatives at the Southside WWTP ..................................................... 165 6.

Conclusion ............................................................................................................................... 165

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List of Figures Figure 2-1: Calibration and Validation Flow Chart .................................................................................. 18 Figure 2-2: Example of a Box and Whisker Diagram .............................................................................. 19 Figure 2-3: Schematic PFD of the Westside WWTP Developed in GPS-X .............................................. 21 Figure 2-4: Westside WWTP Raw Influent Calibration Check ................................................................. 24 Figure 2-5: Schematic PFD of the Southside WWTP Developed in GPS-X............................................. 30 Figure 2-6: Southside WWTP Raw Influent Calibration Check ................................................................ 34 Figure 3-1: FEMA Flood Map of the Black Fork Creek Near the Westside WWTP .................................. 41 Figure 3-2: Westside WWTP Site Layout Identifying Hydraulic Segments .............................................. 43 Figure 3-3: Site Layout Highlighting Segment 1...................................................................................... 44 Figure 3-4: Site Layout Highlighting Segment 2...................................................................................... 45 Figure 3-5: WSE Downstream of Secondary Clarifier 1 Weir as a Function of Flow ................................ 46 Figure 3-6: Site Layout Highlighting Segment 3...................................................................................... 46 Figure 3-7: WSE Downstream of the Tower Splitter Box Weirs as a Function of Flowrate ....................... 47 Figure 3-8: Site Layout Highlighting Segment 4...................................................................................... 48 Figure 3-9: WSE Downstream of the Nitrification Basin Effluent Weirs as a Function of Flowrate ........... 49 Figure 3-10: Site Layout Highlighting Segment 5.................................................................................... 49 Figure 3-11: Maximum Pipe Velocity in Segment 5 as a Function of Flowrate ........................................ 50 Figure 3-12: Site Layout Highlighting Segment 6.................................................................................... 51 Figure 3-13: WSE Downstream of Primary Clarifier 1 Weir as a Function of Flow ................................... 52 Figure 3-14: Site Layout Highlighting Segment 7.................................................................................... 52 Figure 3-15: Maximum Pipe Velocity in Segment 7 as a Function of Flowrate ........................................ 53 Figure 3-16: Site Layout Highlighting Segment 8.................................................................................... 54 Figure 3-17: WSE Downstream of Primary Clarifier 1 Weir as a Function of Flowrate ............................. 55 Figure 3-18: Site Layout Highlighting Segment 9.................................................................................... 55 Figure 3-19: Maximum Pipe Velocity in Segment 9 as a Function of Flowrate ........................................ 56 Figure 3-20: Site Layout Highlighting Segment 10 .................................................................................. 57 Figure 3-21: WSE Downstream of Grit Removal Unit Effluent Weirs as a Function of Flowrate ............... 58 Figure 3-22: Site Layout Highlighting Segment 11 .................................................................................. 58 Figure 3-23: Pipe Velocity in Segment 11 as a Function of Flowrate ...................................................... 59 Figure 3-24: FEMA Flood Map of the West Mud Creek Near the Westside WWTP ................................. 61 Figure 3-25: Southside WWTP Site Layout Identifying Hydraulic Segments ........................................... 64

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Figure 3-26: Site Layout Highlighting Segment 1.................................................................................... 65 Figure 3-27: Site Layout Highlighting Segment 2.................................................................................... 66 Figure 3-28: Site Layout Highlighting Segment 3.................................................................................... 67 Figure 3-29: Site Layout Highlighting Segment 4.................................................................................... 68 Figure 3-30: WSE Downstream of Aeration Basin 2 Weir as a Function of Flowrate ............................... 69 Figure 3-31: Site Layout Highlighting Segment 5.................................................................................... 70 Figure 3-32: WSE Downstream of Aeration Basin 3 Effluent Weir as a Function of Flowrate .................. 71 Figure 3-33: Site Layout Highlighting Segment 6.................................................................................... 72 Figure 3-34: WSE Downstream of Aeration Basin Splitter Box as a Function of Flowrate ....................... 73 Figure 3-35: Site Layout Highlighting Segment 7.................................................................................... 73 Figure 3-36: WSE Downstream of Aeration Basin Splitter Box as a Function of Flowrate ....................... 74 Figure 3-37: Site Layout Highlighting Segment 8.................................................................................... 75 Figure 3-38: WSE Downstream of Primary Clarifier 1 Weir as a Function of Flowrate ............................. 76 Figure 3-39: Site Layout Highlighting Segment 9.................................................................................... 77 Figure 3-40: WSE Downstream of Primary Clarifier Splitter Box as a Function of Flowrate ..................... 78 Figure 3-41: Site Layout Highlighting Segment 10 .................................................................................. 79 Figure 3-42: WSE Downstream of the Grit Effluent Weirs as a Function of Flowrate ............................... 80 Figure 3-43: Site Layout Highlighting Segment 11 .................................................................................. 81 Figure 3-44: WSE Downstream of the Influent Parshall Flume as a Function of Flowrate ....................... 82 Figure 3-45: Site Layout Highlighting Segment 12 .................................................................................. 83 Figure 3-46: WSE Downstream of Influent Screw Pumps as a Function of Flowrate ............................... 84 Figure 4-1: Peak Day Hydrograph for Westside WWTP ......................................................................... 87 Figure 4-2: Southside WWTP Peak Flow Hydrograph ............................................................................ 96 Figure 5-1: PFD of the Sludge Lagoon Rehabilitation ........................................................................... 106 Figure 5-2: Site Layout of the Sludge Lagoon Rehabilitation ................................................................ 107 Figure 5-3: PFD of Proposed Headworks Improvements ...................................................................... 108 Figure 5-4: Site Layout of Proposed Headworks Facility....................................................................... 109 Figure 5-5: PFD of PFB Alternative 1 ................................................................................................... 111 Figure 5-6: Site Layout Showing Proposed Location of PFB Alternative 1 ............................................ 111 Figure 5-7: PFD of PFB Alternative 2 ................................................................................................... 113 Figure 5-8: Site Layout of Peak Flow Basin Alternative 2 ..................................................................... 113 Figure 5-9: PFD of Raw Water Pump Station Alternative 2 ................................................................... 115

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Figure 5-10: Site Layout of Alternative 2 Influent Pump Station ............................................................ 115 Figure 5-11: PFD of Primary Clarifier Alternative 1 ............................................................................... 117 Figure 5-12: PFD of Primary Clarifier Alternative 2 ............................................................................... 118 Figure 5-13: Site Layout of Primary Clarifier Alternative 2..................................................................... 118 Figure 5-14: PFD of Biological Treatment Train Alternative 1 ............................................................... 120 Figure 5-15: Site Layout of Biological Treatment Train Alternative 1 ..................................................... 121 Figure 5-16: PFD of Biological Treatment Train Alternative 2 ............................................................... 123 Figure 5-17: Site Layout of Biological Treatment Train Improvements Alternative 2 .............................. 123 Figure 5-18: PFD of New Filter Pump Station....................................................................................... 125 Figure 5-19: Site Layout Showing the Location of the New Filter Pump Station .................................... 126 Figure 5-20: PFD of Secondary Clarifier Rehabilitation......................................................................... 127 Figure 5-21: Site Layout of Secondary Clarifier Improvements ............................................................. 128 Figure 5-22: PFD of Proposed RAS/WAS Pump Station ...................................................................... 129 Figure 5-23: Site Layout of Proposed RAS/WAS Pump Station ............................................................ 130 Figure 5-24: PFD of Chlorine Contact Basin Improvements.................................................................. 131 Figure 5-25: PFD of Anaerobic Digester Basin Conversion Alternative 1 .............................................. 134 Figure 5-26: Site Layout of Digester Basin Conversion Alternative 1 .................................................... 135 Figure 5-27: PFD of Anaerobic Digester Basin Conversion Alternative 2 .............................................. 136 Figure 5-28: Site Layout of Anaerobic Digester Conversion Alternative 2 ............................................. 137 Figure 5-29: PFD of Proposed Dewatering Facility Improvements ........................................................ 138 Figure 5-30: Site Layout of the Proposed Dewatering Facility Improvements ........................................ 139 Figure 5-31: PFD of the Proposed Influent Pump Station Improvements .............................................. 142 Figure 5-32: Site Layout of Proposed Influent Pump Station Improvements .......................................... 143 Figure 5-33: PFD of Proposed Headworks Improvements .................................................................... 144 Figure 5-34: Potential Site Layout of the Proposed Headworks Improvements ..................................... 145 Figure 5-35: PFD of the Proposed Peak Flow Basin and Peak Flow Pumps ......................................... 146 Figure 5-36: Potential Site Layout of the Proposed Peak Flow Basin and Peak Flow Pumps ................ 147 Figure 5-37: PFD of Aeration Basin Alternative 1 ................................................................................. 149 Figure 5-38: Site Layout of Aeration Basin Alternative 1 ....................................................................... 150 Figure 5-39: PFD of the Proposed Aeration Basins .............................................................................. 152 Figure 5-40: Potential Site Layout of the Proposed Aeration Basins ..................................................... 153 Figure 5-41: PFD of the Proposed Secondary Clarifiers ....................................................................... 154

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Figure 5-42: Site Layout of the Proposed Secondary Clarifier Improvements........................................ 155 Figure 5-43: PFD of the RAS/WAS Pump Station Improvements.......................................................... 157 Figure 5-44: Site Layout of the Proposed RAS/WAS Pump Station ...................................................... 158 Figure 5-45: PFD of the Proposed GBT Improvements ........................................................................ 159 Figure 5-46: Site Layout of Proposed GBT Building Addition ................................................................ 160 Figure 5-47: PFD of the Proposed Sludge Holding Tank ...................................................................... 161 Figure 5-48: Potential Site Layout of the Proposed Sludge Holding Tank ............................................. 162 Figure 5-49: PFD of the Proposed Dewatering Building Expansion ...................................................... 163 Figure 5-50: Site Layout of the Dewatering Facility Expansion ............................................................. 164

List of Tables Table ES-1: Summary of Westside WWTP Gap Analysis and Needs Assessment……………………….. 14 Table ES-2: Summary of Southside WWTP Gap Analysis and Needs Assessment………………… ….. 15 Table 2-1: Qualification of Calibration and Validation Results ................................................................. 19 Table 2-2: Westside WWTP Special Sampling Results Summary........................................................... 20 Table 2-3: Westside WWTP Influent Fractionation Values ...................................................................... 23 Table 2-4: Westside WWTP Primary Effluent Calibration Check ............................................................. 24 Table 2-5: Westside WWTP Final Effluent Calibration Check ................................................................. 25 Table 2-6: Westside WWTP MLSS Concentration and Solid Handling Calibration Check ....................... 26 Table 2-7: Historical Flows and Concentrations for Westside WWTP ..................................................... 27 Table 2-8: Validation Results of Constituent Concentrations .................................................................. 27 Table 2-9: Validation Results of MLSS Concentrations and Solid Production Rate ................................. 27 Table 2-10: Southside WWTP Special Sampling Results Summary ....................................................... 29 Table 2-11: Southside WWTP Influent Fractionation Values ................................................................... 33 Table 2-12: Southside WWTP Primary Effluent Calibration Check .......................................................... 35 Table 2-13: Southside WWTP Final Effluent Calibration Check .............................................................. 35 Table 2-14: Southside WWTP MLSS Concentration, Solid Handling, and Recycle Flow Calibration Check .............................................................................................................................................................. 36 Table 2-15: Historical Flows and Concentrations for Southside WWTP .................................................. 37 Table 2-16: Validation Results of Constituent Concentrations................................................................. 37 Table 2-17: Validation Results of MLSS Concentrations and Solid Production Rate ............................... 37 Table 3-1: Comparison of Record Drawings and Survey Information at Westside WWTP ....................... 42

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Table 3-2: Summary of Hydraulic Capacity of Segments at the Westside WWTP ................................... 60 Table 3-3: Comparison of Record Drawing and Survey Information at Southside WWTP ....................... 62 Table 3-4: Summary of Hydraulic Capacity of Segments at the Southside WWTP .................................. 85 Table 4-1: Projected Future Flow and Loadings to the Westside and Southside WWTPs ....................... 86 Table 4-2: Westside WWTP Mechanical Screen Gap Analysis ............................................................... 88 Table 4-3: Westside WWTP Grit Removal Gap Analysis ........................................................................ 88 Table 4-4: Westside WWTP Raw Water Pump Station Gap Analysis ..................................................... 89 Table 4-5: Westside WWTP Primary Clarifiers Gap Analysis .................................................................. 90 Table 4-6: Westside WWTP Biological Treatment Train Gap Analysis .................................................... 91 Table 4-7: Westside WWTP Filter Pump Station Gap Analysis ............................................................... 91 Table 4-8: Westside WWTP Secondary Clarifiers Gap Analysis ............................................................. 92 Table 4-9: Westside WWTP Chlorine Building Gap Analysis .................................................................. 92 Table 4-10: Westside WWTP Existing CCB Gap Analysis ...................................................................... 93 Table 4-11: Westside WWTP Oxygenation Gap Analysis ....................................................................... 93 Table 4-12: Westside WWTP Anaerobic Digesters Gap Analysis ........................................................... 94 Table 4-13: Westside WWTP Dewatering Facility Gap Analysis ............................................................. 94 Table 4-14: Westside WWTP Gap Analysis Summary............................................................................ 95 Table 4-15: Southside WWTP Influent Screw Pumps Gap Analysis ....................................................... 97 Table 4-16: Southside WWTP Mechanical Screens Gap Analysis .......................................................... 97 Table 4-17: Southside WWTP Grit Removal Gap Analysis ..................................................................... 98 Table 4-18: Southside WWTP Primary Clarifiers Gap Analysis ............................................................... 98 Table 4-19: Southside WWTP Primary Sludge Pump Station Gap Analysis............................................ 99 Table 4-20: Southside WWTP Aeration Basins Gap Analysis ................................................................. 99 Table 4-21: Southside WWTP Secondary Clarifiers Gap Analysis ........................................................ 100 Table 4-22: Southside WWTP Chlorine Contact Basin Gap Analysis .................................................... 100 Table 4-23: Southside WWTP Chlorine Facility Gap Analysis............................................................... 101 Table 4-24: Southside WWTP RAS/WAS Pump Station Gap Analysis ................................................. 102 Table 4-25: Southside WWTP Gravity Belt Thickener Gap Analysis ..................................................... 102 Table 4-26: Southside WWTP Sludge Holding Tank Gap Analysis ....................................................... 103 Table 4-27: Southside WWTP Sludge Dewatering Facility Gap Analysis .............................................. 103 Table 4-28: Southside WWTP Gap Analysis Summary ........................................................................ 104 Table 5-1: Summary of Westside WWTP Gap Analysis, Condition, and Proposed Expansion Needs ... 105

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Table 5-2: Design Details of the Sludge Lagoon Rehabilitation............................................................. 106 Table 5-3: Estimated Total Project Cost of the Sludge Lagoon Rehabilitation ....................................... 107 Table 5-4: Design Details of the Proposed Headworks Improvements .................................................. 108 Table 5-5: Estimated Total Project Cost of the Headworks Improvements Project ................................ 109 Table 5-6: Design Details of PFB Alternative 1..................................................................................... 110 Table 5-7: Estimated Total Project Cost of PFB Alternative 1 ............................................................... 112 Table 5-8: Design Details of First-Stage Trickling Filters ...................................................................... 112 Table 5-9: Estimated Total Project Cost of PFB Alternative 2 ............................................................... 114 Table 5-10: Design Details of Influent Pump Station............................................................................. 114 Table 5-11: Estimated Total Project Cost of New Influent Pump Station ............................................... 116 Table 5-12: Estimated Total Project Cost of Primary Clarifier Alternative 1 ........................................... 117 Table 5-13: Estimated Total Project Cost of Primary Clarifier Alternative 2 ........................................... 119 Table 5-14: Design Details of Biological Treatment Train Alternative 1 ................................................. 120 Table 5-15: Total Estimated Project Cost of Alternative 1 ..................................................................... 122 Table 5-16: Design Details of Biological Treatment Train Alternative 2 ................................................. 122 Table 5-17: OPCC of the Biological Treatment Train Improvements Alternative 2................................. 124 Table 5-18: Design Details of Filter Pump Station Improvements ......................................................... 124 Table 5-19: Estimated Total Project Cost of Filter Pump Station Improvements .................................... 126 Table 5-20: Design Details of the Secondary Clarifier Improvements.................................................... 127 Table 5-21: Estimated Total Project Cost of Secondary Clarifier Rehabilitation ..................................... 128 Table 5-22: Design Details of RAS/WAS Pump Station ........................................................................ 129 Table 5-23: Estimated Total Project Cost of the Proposed RAS/WAS Pump Station ............................. 130 Table 5-24: Design Details of the Chlorine Contact Basin Improvements.............................................. 131 Table 5-25: Estimated Total Project Cost of CCB Improvements .......................................................... 132 Table 5-26: Design Details of the Surface Aerator Replacement .......................................................... 132 Table 5-27: Estimated Total Project Cost of the Surface Aerator Replacement ..................................... 133 Table 5-28: Design Details of Anaerobic Digester Basin Conversion Alternative 1 ................................ 133 Table 5-29: Estimated Total Project Cost for the Digester Basin Conversion Alternative 1 .................... 135 Table 5-30: Design Details of Anaerobic Digester Basin Conversion Alternative 2 ................................ 136 Table 5-31: Estimated Total Project Cost of the Anaerobic Digester Conversion Alternative 2 .............. 137 Table 5-32: Design Details of Sludge Dewatering Equipment Improvements ........................................ 138 Table 5-33: Estimated Total Project Cost of the Dewatering Facility Improvements .............................. 139

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Table 5-34: Summary of the Estimated Costs of the Recommended Improvements ............................. 140 Table 5-35: Summary of the Southside WWTP Gap Analysis, Facility Criticality, and Recommended Expansion Needs ................................................................................................................................ 141 Table 5-36: Design Details of the Proposed Influent Pump Station ....................................................... 142 Table 5-37: Estimated Total Project Cost of the Proposed Influent Pump Station Improvements .......... 143 Table 5-38: Design Details of the Proposed Headworks Improvements ................................................ 144 Table 5-39: Estimated Total Project Cost of the Proposed Headworks Improvements .......................... 145 Table 5-40: Design Details of the Proposed Peak Flow Basin and Peak Flow Pumps........................... 146 Table 5-41: Estimated Total Project Cost for Peak Flow Basin and Peak Flow Pumps.......................... 147 Table 5-42: Estimated Total Project Cost of Primary Clarifier Odor Control System .............................. 148 Table 5-43: Design Details of the Proposed Aeration Basins ................................................................ 148 Table 5-44: Estimated Total Project Cost of Aeration Basin Alternative 1 ............................................. 150 Table 5-45: Design Details of Aeration Basin Alternative 2 ................................................................... 151 Table 5-46: Estimated Total Project Cost of the Proposed Aeration Basins .......................................... 153 Table 5-47: Design Details of the Proposed Secondary Clarifiers ......................................................... 154 Table 5-48: Estimated Total Project Cost of the Proposed Secondary Clarifiers ................................... 155 Table 5-49: Estimated Total Project Cost of CCB Improvments ............................................................ 156 Table 5-50: Design Details of the Proposed RAS/WAS Pump Station .................................................. 156 Table 5-51: Estimated Total Project Cost of the Proposed RAS/WAS Pump Station ............................. 158 Table 5-52: Design Detail of the GBT Building Improvements .............................................................. 159 Table 5-53: Estimated Total Project Cost of the GBT Building Expansion ............................................. 160 Table 5-54: Design Details of the Proposed Sludge Holding Tan .......................................................... 161 Table 5-55: Estimated Total Project Cost of the Proposed Sludge Holding Tank .................................. 162 Table 5-56: Design Details of the Proposed New BFP.......................................................................... 163 Table 5-57: Estimated Total Project Cost of the Dewatering Facility Expansion .................................... 164 Table 5-58: Estimated Total Project Costs of Recommended Improvements ........................................ 165

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

List of Acronyms Acronym

Definition

AB ADF BOD cBOD CCB cfu CMU COD DO EL FEMA gpcd gpd gpm HGL hr lb/d MGD mg/L mL N/A NH3-N OPCC P2HF

Aeration Basin Average Daily Flow Biochemical Oxygen Demand Carbonaceous Biochemical Oxygen Demand Chlorine Contact Basin Colony-Forming Units Concrete Masonry Unit Chemical Oxygen Demand Dissolved Oxygen Elevation Federal Emergency Management Agency Gallons per Capita per Day Gallons per Day Gallons per Minute Hydraulic Grade Line Hour Pounds per Day Million Gallons per Day Milligrams per Liter Milliliters Not Applicable Ammonia-Nitrogen Opinion of Probable Construction Cost Peak 2-Hour Flow

pCOD RAS TCEQ TM TP TPDES TRC TSS TP WWTP

Particulate Chemical Oxygen Demand Return Activated Sludge Texas Commission on Environmental Quality Technical Memorandum Total Phosphorous Texas Pollutant Discharge Elimination System Total Residual Chlorine Total Suspended Solids Total Phosphorous Wastewater Treatment Plant

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Executive Summary The Baseline Analysis Technical Memorandum (TM) documents the findings of Master Plan Project Task 6 and Task 7. This includes methodology and results of the process model evaluation, the hydraulic model evaluation, and the gap analysis and needs assessment for the two Tyler Wastewater Treatment Plants (WWTPs). The process model evaluation consists of constructing GPS-X process models of the liquid and solids handing processes at the Westside and Southside WWTPs. The models were calibrated and validated by comparing the inputs and resulting outputs with historical and special sampling data collected by the plant staff. The models were then used to project the future process capacities at the predicted future influent flow and loading conditions. The hydraulic model evaluations consist of a full plant hydraulic profile for both Westside WWTP and Southside WWTP to account for the hydraulic grade line through the plants. The models were used to determine the hydraulic capacity of the treatment facilities and identify the critical hydraulic control points throughout the main process flow paths. The main hydraulic constraints identified through the modeling effort at the Westside WWTP include: • The Chlorine Contact Basin is flooded at the 100-year flood condition. • Due to the size and elevation of the influent Parshall flume and the yard piping in Segment 10, the grit effluent weirs are submerged at flows higher than 20 MGD. Submergence of these weirs can lead to inefficiencies within the grit removal system. • All modeled segments, except for segment 4 and segment 5, have a hydraulic capacity lower than the projected future peak flow of 47.2 MGD. The main hydraulic constraints identified through the modeling effort at the Southside WWTP include: • The weirs of the chlorine contact basin and secondary clarifiers are flooded at the 100-year flood condition. • Due to the size and elevation of the influent Parshall flume, there is little room within the headworks facility to allow for variations in the level of blinding of the mechanical screens. The water surface elevation inside of the headworks facility exceeds the minimum wall freeboard criteria required by TCEQ at flows higher than 10 MGD when the screens are 50% blinded. The gap analysis was developed by comparing the existing capacity of each facility to the future required capacity. The capacities of the mechanical components of each facility were determined, based on the size of the equipment as well as the condition concerns identified in the Historical Data Review TM. These capacities along with the capacities identified by the process model and hydraulic model were used to determine the gaps. The gap analysis results were used to develop the needs assessment. Alternatives available to the City of Tyler were presented along with design details, process flow diagrams (PFDs), potential site layouts, and estimated project costs. A summary of the results of the gap analysis and needs assessment for the Westside and Southside WWTPs are shown in Table ES-1 and Table ES-2, respectively. For each of the WWTPs, a peak flow basin (PFB) is recommended to be constructed to shave the peak flow requirements of the plant processes downstream of the headworks facility and reduce the costs of the facilities that are sized based on the peak 2-hour flow.

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Table ES-1: Summary of Westside WWTP Gap Analysis and Needs Assessment

Sludge Lagoon

Existing Capacity N/A

Existing Gap N/A

Future Gap (with PFB) N/A

Facility Criticality N/A

Peak Flow Basin

N/A

Alternative 1: Construct a new PFB Alternative 2: Convert the First-Stage TFs into PFBs

Screening Grit Removal Raw Water Pump Station

32.5 MGD 20 MGD

None 12.5 MGD

14.7 MGD 27.2 MGD

Critical

Construct new headworks facility

$10,309,000

32 MGD

None

15.2 MGD

High

Construct a new pump station

$12,805,000

Primary Clarifiers

42.4 MGD

None

Medium

$7,547,000 $12,124,000

Biological Treatment Train

4,500 lb BOD/day1

5,000 lb BOD/day

10,000 lb BOD/day

Critical

Filter Pump Station

46 MGD

None

Critical

Alternative 1: Replace mechanisms Alternative 2: Construct two new PCs Alternative 1: Rehabilitate existing nitrification basin and build additional volume Alternative 2: Construct new aeration basins including a new blower facility Construct a duplicate pump station

Secondary Clarifiers

27.1 MGD

5.4 MGD

8.9 MGD

High

Replace mechanisms in existing clarifiers

$9,078,000

N/A

High

$5,111,000

29.7 MGD

2.8 MGD

6.3 MGD

High

Construct new RAS/WAS Pump Station Raise outer walls of the CCB and construct a new Parshall flume effluent channel

None

Critical

None – Facility is currently under design for improvements

None

Critical

None – Facility is currently under design for improvements

395 lb O2/day

540 lb O2/day

High

Replace surface aerators

Facility

RAS Pumps Chlorine Contact Basin Chlorine Facility – Chlorine Gas Chlorine Facility – Sulfur Dioxide Oxygenation

Anaerobic Digester Sludge Dewatering Facility

6,720 lb/day 1,920 lb/day 960 lb O2/day 3.2 MG

3,200 lb/hr

Garver Project No. 21W05170

None

627 lb/hr

None

2,470 lb/hr

Critical

Low

Expansion Needs Replace Lagoon Liner and Install Mixers

Alternative 1: Convert into aerated sludge storage tanks with diffused aeration. Alternative 2: Convert into aerated sludge storage tanks with surface aeration. Expand dewatering facility to house two additional BFPs

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Total Estimated Project Cost $3,262,000 $552,000 $279,000

$21,918,000 $29,138,000 $7,608,000

$1,646,000

$398,000 $5,010,000 $2,990,000 $9,647,000

Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Table ES-2: Summary of Southside WWTP Gap Analysis and Needs Assessment Current Capacity

Existing Gap

Future Gap (with PFB)

Facility Criticality

N/A

Influent Pump Station

21.7 MGD

0.8 MGD

17.8 MGD

Low

Mechanical Screens

13.0 MGD

9.5 MGD

26.5 MGD

Low

Grit Removal

31.0 MGD

None

8.5 MGD

Medium

Primary Clarifiers Primary Sludge Pump Station

18.1 MGD2

4.4 MGD

250 gpm

None

Aeration Basins

13,800 lb BOD/day

Secondary Clarifiers Chlorine Contact Basin

Facility Peak Flow Basin

Expansion Needs Construct new PFB and peak flow pump station Construct new influent pump station to pump flows above 22.5 MGD

Estimated Total Project Cost $4,509,000 $5,441,000

Construct new headworks facility to treat flow above 22.5 MGD

$7,058,000

Low

Install odor control

$1,700,000

None

Low

No necessary improvements

None

Critical

30.3 MGD

None

High

34.7 MGD

None

High

3,360 lb/day

None

Critical

None – Facility is currently under design for improvements

1,440 lb/day

None

Critical

None – Facility is currently under design for improvements

1.0 MGD

4.0 MGD

4.6 MGD

Critical

N/A

High

Gravity Belt Thickener

167 gpm

None

Medium

Sludge Holding Tank

0.70 MG

None

High

Sludge Dewatering Facility

3,200 lb/h

None

1,200 lb/h

Low

Chlorine Facility – Chlorine Gas Chlorine Facility – Sulfur Dioxide RAS/WAS Pump Station Secondary Sludge Pump Station

Rehab basin 3 and build similar basin

$17,530,000

Construct all new diffused aeration basins

$20,254,000

Rebuild existing clarifiers Clean basins and replace walkways, railing, and gates

$16,079,000

Construct a new RAS/WAS pump station

Garver Project No. 21W05170

Expand building to house one additional GBT unit and replace existing unit Construct one additional sludge holding tank Expand building to house one additional BFP

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$661,000

$5,554,000

$5,071,000 $3,152,000 $4,039,000

Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

1. Introduction The purpose of this Technical Memorandum (TM) is to establish the treatment needs of the two WWTPs, Westside WWTP and Southside WWTP, for the Tyler, TX Master Plan project and to provide a path forward for the city to meet the projected future requirements. In this TM, the findings of the hydraulic and process models of the existing WWTPs are presented, and the gaps in the existing treatment capacity based on future flow and loading projections are determined. These findings, along with the findings of the previously performed condition assessment, presented in the Historical Data Review TM (April 2022) are used to develop design alternatives to address the treatment gaps. The design alternatives will be presented along with site layouts, process flow diagrams (PFDs), and estimated total project costs.

2. Process Model Evaluation The purpose of this section of the TM is to develop calibrated and validated process models for the City of Tyler’s Westside and Southside Wastewater Treatment Plants (WWTPs). Each model is developed using a fractionated influent derived from independent special sampling data collected at each plant. In this TM, we demonstrate the following tasks: -

Construct each model to simulate the existing conditions of the WWTPs Calibrate the models for baseline operation using datasets collected by the Tyler staff during October and November of 2021 Validate each model’s accuracy by inputting influent characteristics from 2019 to 2021 and comparing the results with how each facility performed during that time frame

This effort is being conducted as part of the Tyler WWTPs Master Plan to illustrate the current performance of the Westside and Southside facilities and, as part of the upcoming gap analysis and alternatives evaluation, to predict the future process capacities when both influent flows and loadings are increased. 2.1. Model Development GPS-X software (Hydromantis, v.8.1) is used to model the treatment performance of the existing treatment trains at the Westside and Southside WWTPs. The model for each WWTP is built to simulate the existing liquid treatment process and the solids handling processes, including recycle streams. The process modeling efforts are guided by a unified protocol recommended by Rieger et. al. (Guidelines for Using Activated Sludge Models, International Water Association, 2014). The five (5) steps of model development are defined as: 1. 2. 3. 4. 5.

Project Definition (Scope of Plant Treatment Goals) Data Collection and Reconciliation (Verification of Inputs) Plant Model Setup (Physical and Hydraulic Plant Dimensions) Calibration and Validation (Measurement of Wastewater Characteristics at Treatment Stages) Simulation and Results Interpretation (Summary of Baseline Performance)

GPS-X is a dynamic wastewater plant model that can help to predict outcomes of process control schemes and plant capacity evaluations. It also provides an analytical rationale that aids in investigating many possible design scenarios, which enables the overall design planning for a facility. The project goal for this modeling effort is to develop calibrated and validated process models for the Westside and Southside WWTPs including their respective influent wastewater fractionation.

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

The following sections discuss the general methods by which each model has been built and calibrated, and how they are validated to properly represent the two WWTPs. 2.1.1.

Data Collection and Reconciliation

A process model uses a collection of on-site data measurements to evaluate the performance of the facility. The collected data requires a high degree of accuracy to effectively predict the potential outcomes and overall facility operation. Accurate field measurements aid in the proper calibration of a process model, while erroneous data can compromise its predictive power to the point where the process model loses its validity. To properly perform data reconciliation, a given dataset must be scrutinized for errors and inconsistencies that defy scientific logic so that they may be removed. Thorough preparation of a dataset provides a comprehensive understanding of the facility’s performance and improves the quality of the input parameters that the process model is built upon and, in turn, the model’s predictive performance. 2.1.2.

Plant Model Representations

The baseline process model for each facility is assembled to replicate the physical treatment scheme at the Westside and Southside Tyler WWTPs. Therefore, the process model sections for each facility contain a process flow diagram (PFD) of the existing liquid and solids treatment trains developed in GPS-X. The process units are grouped together to represent the existing process schemes. Actual dimensions of the unit process (e.g. dimensions of the aerobic volumes of the process trains, secondary clarifiers, etc.) as well as actual equipment types (e.g. mechanical aeration) are used in the process models. 2.1.3.

Model Calibration and Validation

A process model is calibrated by adjusting its algorithmic parameters so that when a set of measured influent data is applied, it produces results that match those that were observed on-site. General adjustments to the process model are made to parameters pertaining to facility operation, and to the biological kinetic coefficients included in secondary treatment. However, the most significant impact to model performance is the correct raw influent characterization. Proper fractionation of influent wastewater is crucial to process modeling because the performance of the model relies heavily on the accuracy of influent inputs. Influent fractionation and characteristics determine the soluble and particulate portions of a wastewater stream, and as such, influence the performance of both liquid and solids treatment processes. The GPS-X modeling and simulation software contains default fractionation values that have been derived from typical wastewater characterizations across many municipalities. The purpose of calibrating the model with the special sampling results from the two Tyler WWTPs is to customize influent fractionation values within GPS-X from default values to those specific to each facility. Figure 2-1 depicts an overall flow chart of the calibration and validation process as described by the unified protocol described above.

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Figure 2-1: Calibration and Validation Flow Chart The following sections detail the calibration and validation efforts carried out by the project team for the two Tyler WWTPs. 2.1.4.

Qualification of Results for Model Calibration and Validation

The special sampling results for the raw influent are plotted in box-and-whisker diagrams. An example of these diagrams is shown in Figure 2-2.

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Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

Figure 2-2: Example of a Box and Whisker Diagram As shown, the top and bottom sides of the box represent the upper and lower quartiles, respectively. In addition, the median is marked by a horizontal line inside the box, and the whiskers are the two lines above and below the box that demonstrate the highest and lowest values. The portion of the box located above the median contains 25% of the data points with higher values than median, and the lower portion of the box contains 25% of the data points with lower values than the median. Cross marks represent the modeled result that is acquired when using the plant process model developed and calibrated by the GPS-X software. Parameters with higher measurement values (ie, COD, BOD, TSS) are shown in the primary vertical axis and parameters with lower values (ie NH3-N, TP, pH) are shown in the secondary vertical axis. For the other sampling locations at the WWTPs (ie, secondary effluent and final effluent), calibration results are compared to measured results in terms of milligrams per liter (mg/L). This is due to the small magnitude of the measured constituents (< 10 mg/L) at these stages. Differences of 0.5 mg/L and less are determined to be “excellent,” measurements that differ by 1.0 mg/L or less are considered “good,” those between 1.0 and 2.0 mg/L are considered “acceptable,” and those above the 2.0 mg/L threshold are “unsatisfactory” and will require some explanation. For measured parameters greater than 10 mg/L, percent differences of 5% or less are considered “excellent,” those between 5%-10% are considered “good,” those between 10%20% termed “acceptable,” and those over 20% deemed “unsatisfactory.” Finally, “excellent” results are highlighted in dark green, “good” results in light green, “acceptable” in orange, and “unsatisfactory” in red. A visual display of these error definitions is shown in Table 2-1. Table 2-1: Qualification of Calibration and Validation Results Percentage Error for Constituents with Concentration above 10 mg/L < 5% 5% - 10% 10% - 20% > 20%

Garver Project No. 21W05170

Difference Error for Constituents with Concentration below 10 mg/L < 0.5 mg/L 0.5 mg/L - 1.0 mg/L 1.0 mg/L - 2.0 mg/L > 2.0 mg/L

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Error Qualification Excellent Good Acceptable Unsatisfactory

Tyler Wastewater Treatment Plants Master Plan Baseline Analysis Technical Memorandum

The process of calibration can improve the measured-projected agreement for some parameters while decreasing agreement in others, the overall agreement of a set of parameters is favored even if one or two parameters have an unsatisfactory agreement. 2.2. Westside WWTP Baseline Process Model 2.2.1.

Westside WWTP Sampling Data

This section presents the special sampling data collected at the Westside WWTP from October 11 to October 22, 2021. Samples were taken at the following locations: 1) 2) 3) 4)

Raw Influent Primary Clarifier Effluent Secondary Clarifier Effluent Final Effluent

Field measurements at the Westside WWTP were analyzed and reconciled to aid in model calibration and to represent the facility’s current treatment performance with an acceptable degree of accuracy. Table 2-2 shows a summary of the results from the special sampling campaign which is utilized as the basis for model calibration. Table 2-2: Westside WWTP Special Sampling Results Summary Raw Influent

COD

sCOD

BOD

sBOD

TSS

VSS

NH3-N

TKN

NO3-N

PO4-P

Flow

Average

466.8

164.4

171.6

97.7

161.6

133.3

28.2

42.8

2.7

6.5

7.1

8.6

Min

290.0

103.0

88.0

58.0

50.5

20.4

26.6

1.1

4.3

6.8

7.3

Max

688.0

206.0

237.0

125.0

288.0

225.0

46.7

65.7

3.7

8.7

7.3

10.0

144.6

81.7

68.4

65.9

61.5

22.1

38.5

2.3

4.1

7.1

Primary Clarifier Effluent Average

281.8

Min

174.0

77.1

67.0

50.0

39.8

49.8

16.0

21.6

0.9

2.3

7.0

Max

366.0

186.0

92.0

90.0

94.3

70.5

29.8

62.3

3.4

5.8

7.2

1.7

1.9

7.1

Secondary Clarifier Effluent Average

36.3

27.4

3.5

1.2

1.7

0.0

0.5

Min

20.0

2.2

0.9

0.6

0.0

0.1

2.5

0.6

0.7

6.8

Max

72.8

36.7

5.4

1.7

4.4

0.0

1.1

10.0

2.5

7.2

Final Effluent Average

36.4

29.4

0.9

1.1

0.5

8.1

2.0

2.2

7.3

Min

22.9

20.0

0.0

0.6

0.2

0.1

5.7

1.4

1.6

7.1

Max

48.2

45.5

1.7

1.5

1.8

1.1

9.8

2.6

2.7

7.5

The units used are mg/L, except for pH (s.u.) and Q (MGD)

2.2.2.

Westside WWTP Model Representation

Figure 2-3 demonstrates a model representation of the existing process layout of the Westside WWTP developed in GPS-X. The specific treatment modules will be discussed in detail in the following sections. In addition to the special sampling data collections mentioned above, the Tyler Water Utility staff have

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provided plant data for the period of January 2019 through August 2021 to define the influent flows and loadings that were used as inputs for validation of the process model.

Figure 2-3: Schematic PFD of the Westside WWTP Developed in GPS-X 2.2.2.1 Preliminary Chemical Treatment Magnesium hydroxide (Mg(OH)2) is dosed to the screened and de-gritted influent flow for odor control. This chemical can react with orthophosphate (PO4-P) and form particulate magnesium-phosphate complexes. This reaction converts a fraction of the soluble phosphorous to particulate TP. Therefore, metal salt injection is considered within the model. 2.2.2.2 Primary Clarifiers After passing through a grit removal system, the de-gritted wastewater flows through two 150-ft diameter primary clarifiers. Waste activated sludge (WAS) from the secondary clarifiers is conveyed by the light sludge pump station to the primary clarifiers. WAS and a portion of the influent’s particulate matter co-settle in the primary clarifiers. The module empirically removes 67% of TSS. which is representative of typical performance in co-settling scenarios (55%-80% TSS removal; Metcalf & Eddy, et al., Wastewater Engineering Treatment and Resource Recovery, 5th edition).

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2.2.2.3 First-Stage Trickling Filters Primary clarifier effluent is directed to two 140-ft rock-media trickling filters. However, flow may also be diverted around them. Primary effluent undergoes the first step of the biological treatment at the trickling filters. A portion of the flow that exits the trickling filters is recycled to the head of the primary treatment process to maintain wetted conditions within the first-stage trickling filters during low flow conditions. Flow that is not recycled enters the Filter Pump Station, which directs the flow to a splitter box that divides flow in an approximate 80%:20% ratio between the nitrification basin and the second-stage trickling filters, which are discussed below. 2.2.2.4 Second-Stage Trickling Filters Two second-stage 140-ft rock-media trickling filters receive 20% of the first-stage trickling filter effluent from the splitter box. Effluent from the second-stage trickling filters is combined with the remaining 80% of the first-stage trickling filter effluent within the Filter Pump Station and directed to the splitter box mentioned above.

2.2.2.5 Nitrification Basins A mixture of flow from the filter pump station and RAS enters two nitrification basins that provide a total volume of 2.31 MG and are mechanically aerated. The nitrification basins have been modeled to operate under an aeration regime that best symbolizes the location of the mechanical aerators and where flow enters and exits the basins. A recycle flow stream has been included with the plug-flow reactor (PFR) module to simulate the recirculation of flow that occurs in the continuous channels of the nitrification basins. It was inferred from special sampling data that denitrification may occur as part of the biological process due to low-oxygen “dead spots” within the basin. This information was used in calibration by establishing a modeled dissolved oxygen (DO) profile within the nitrification basins. 2.2.2.6 Secondary Clarifiers The mixed liquor from the nitrification basins is conveyed to two 150-ft diameter secondary clarifiers, which physically separate activated sludge from the treated effluent. While the RAS stream is recycled to the nitrification basins, WAS is transferred by gravity to a light sludge pump station that carries the flow to the primary clarifiers to be co-settled with solids from the screened and de-gritted influent flow. 2.2.2.7 Anaerobic Digester Co-settled sludge (primary sludge and WAS) from the primary clarifiers is conveyed to a 100-ft diameter anaerobic digester with a volume of 1.5 MG. The digester is no longer used for digestion but does serve as a sludge holding tank (SHT). The SHT is considered in the developed model to simulate the biological

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reactions that may occur during sludge storage. A belt filter press (BFP) pump station conveys stored sludge to the dewatering building. 2.2.2.8 Belt Filter Presses Transferred sludge from the anaerobic digester is dewatered by two 2-meter BFPs. The BFP was modeled to achieve 95% solids capture rate and to produce a 21% dewatered cake, based on the average solids concentrations of disposed sludge during October 2021. The filtrate is recycled back to the head of the plant and this flow is also represented within the process model. 2.2.3.

Westside WWTP Calibration Results

In this subsection, two weeks of special sampling influent data from October 2021 is used to fractionate the constituents of the influent that arrives at the Westside WWTP. Then, operational constraints are applied to the model, such as constituent removal at primary clarifiers, RAS flow rates, and recycle flow rates generated from solids handling. The model is calibrated for treatment at facility locations where special sampling occurred. Finally, the results that are predicted by the model are checked against the treatment results that were observed in the facility to quantify the model’s analytical performance over the special sampling period. 2.2.3.1. Influent Fractionation Influent fractionation is performed by using influent data from the special sampling campaign over the period of October 11 to October 22, 2021. Table 2-3 gives a summary of the measured, modeled, and GPS-X default influent fractionation values. Table 2-3: Westside WWTP Influent Fractionation Values Fractionation

Special Sampling Average

Modeled Result

Model Default

VSS : TSS

0.82

0.75

sCOD : COD

0.37

0.36

0.34

BOD : COD

0.36

0.35

0.58

sBOD : sCOD

0.59

0.61

pCOD : VSS

2.4

2.0

1.80

Nitrogen Content of Inert Particulate Material

0.06

0.05

The model default values for VSS : TSS, and BOD : COD have been changed to match or closely match the ratios that were measured in the special sampling. Meanwhile, the modeled sCOD : COD and sBOD : sCOD ratios are similar to their respective special sampling averages and the model default values. The GPS-X default value for the ratio of particulate COD (pCOD) to VSS (1.80) is increased to 2.0, which is in between the default value and the calculated value of 2.4. The pCOD value is assumed to be the difference between measurements of total and soluble COD measurements in the special sampling data. Lastly, the percentage of inert particulate content due to nitrogen has been slightly increased from 5% to 6% to most

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accurately fractionate the influent constituents. This modification decreases the quantity of soluble nitrogen within the modeled raw influent that would be available for transformation within the biological process. 2.2.3.2. Calibration Results for Raw Influent Using the influent fractionation values that are discussed above, the raw influent has been simulated in GPS-X. Figure 2-4 represents the parameters measured from field samples of the raw influent plotted in a box and whisker diagram.

700

10 9

600 500

400

5 300

4 3

200

Concentration (mg/L)

2 100

0 COD sCOD BOD sBOD TSS

VSS

NH3

TKN

PO4

Figure 2-4: Westside WWTP Raw Influent Calibration Check As shown in Figure 2-4, all the modeled influent constituents display excellent agreement with special sampling measurements, except for TSS (19%) and VSS (20%), which are modeled with acceptable accuracy. 2.2.3.3. Calibration Results for Primary Effluent Table 2-4 illustrates the calibration results for constituents measured in the primary effluent. Table 2-4: Westside WWTP Primary Effluent Calibration Check Constituent

Sampling Results (mg/L)

Modeling Results (mg/L)

Error

281.8 144.6 81.7

232.7 139.0 96.9

17% 4% 19%

COD sCOD BOD

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Constituent

Sampling Results (mg/L)

Modeling Results (mg/L)

Error

68.4 65.9 61.5 22.1 38.5 2.3 4.1 7.1

78.7 65.4 52.0 27.3 34.4 2.2 3.9 7.0

15% 2% 15% 23% 11% 0.1 mg/L 0.2 mg/L 1%

sBOD TSS VSS NH3-N TKN PO4-P TP pH

COD and sCOD in the primary effluent have acceptable and excellent error values, respectively. BOD and sBOD are predicted with acceptable accuracy and modeled TSS results had excellent agreement, while VSS had acceptable error. The primary clarifiers accept raw influent flow and WAS from the secondary clarifiers. Westside WWTP staff informed Garver that an undetermined quantity of flow from the first-stage trickling filters is recycled to the head of primary treatment, which increases the flow entering and leaving the primary clarifiers. By configuring the model to recycle approximately half of the effluent from the first-stage trickling filters back through the primary treatment process, greater soluble organic removal (sBOD and sCOD) is simulated to occur within the first-stage tricking filters. During the special sampling campaign, the concentration of ammonia was observed to decrease by more than 20% from its raw influent measurement (28.2 mg/L) to its primary effluent measurement (22.1 mg/L). Soluble ammonia is not physically separated by primary clarification, so other biological and operational factors are likely to have affected this differential in influent and effluent concentrations. However, the TKN value modeled in the primary effluent has acceptable agreement with special sampling measurements. PO4-P and TP modeled parameters were found to have excellent agreement with special sampling measurements. The removal of PO4-P by the primary clarifiers that was observed during the special sampling campaign is modeled through the use of metal salt injection upstream of the facility. It is assumed that the precipitated phosphate was removed as primary sludge. 2.2.3.4. Calibration Results for Final Effluent Table 2-5 illustrates the final effluent calibration results for the Westside WWTP. As opposed to primary effluent, TKN was not measured at this location. Table 2-5: Westside WWTP Final Effluent Calibration Check Constituent

Sampling Results (mg/L)

Modeling Results (mg/L)

Error

36.3 27.4 3.5 1.2

36.5 31.7 2.2 1.7

1% 16% 1.3 mg/L 0.5 mg/L

COD sCOD BOD sBOD

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Constituent

Sampling Results (mg/L)

Modeling Results (mg/L)

Error

1.7 1.3 0.5 7.2 1.7 1.9 7.1

3.7 2.9 0.3 8.3 2.2 2.6 7.0

2.0 mg/L 1.6 mg/L 0.2 mg/L 1.1 mg/L 0.5 mg/L 0.7mg/L 1%

TSS VSS NH3-N NO3-N PO4-P TP pH

COD, sBOD, NH3-N, and PO4-P are predicted with excellent accuracy, while TP is modeled with good agreement to special sampling measurements and sCOD, BOD, TSS, and VSS are modeled to have acceptable agreement with measured values. Nitrate (NO3-N) modeled in the final effluent has acceptable agreement with special sampling measurements. The quantity of NO3-N measured in the final effluent (7.2 mg/L) during the special sampling campaign is significantly less than the quantity of NH3-N found in the raw influent (28.2 mg/L). This implies an imbalance between the nitrogen entering and leaving the facility and suggests that a large percentage of organic nitrogen is removed by denitrification within the treatment train. It was inferred from special sampling data that denitrification may occur as part of the biological process due to non-aerated “dead spots” within the nitrification basin. Therefore, the model is calibrated to promote denitrification by lowering the aeration supplied to the nitrification basins. The secondary process was calibrated by establishing a wasting rate of 0.031 MGD and setting the final clarification performance to remove 99.9% of mixed liquor suspended solids. 2.2.3.5. Calibration Results for MLSS Solids Concentrations The calibration results for the TSS and VSS solid concentrations of the MLSS determined by the GPS-X model are shown in Table 2-6. The TSS and VSS concentrations of the MLSS both have good agreement (8-9% error) with their special sampling averages. Solids production at the Westside WWTP is not used in the calibration of the model but is validated in the following section. Table 2-6: Westside WWTP MLSS Concentration and Solid Handling Calibration Check Constituent

Sampling Results (mg/L)

Modeling Results (mg/L)

Error

MLSS

5,990

5,530

MLVSS

3,940

4,290

2.2.4.

Westside WWTP Validation Results

The calibrated model has been tested to determine its predictive ability by using historical plant data collected by the Tyler Water Utility staff over the period of January 2019 through August 2021 to define the influent flows and loadings that were used as inputs for validation of the process model. The measured influent constituents for this date range are illustrated in Table 2-7.

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Table 2-7: Historical Flows and Concentrations for Westside WWTP Historical Value (Jan 2019 – Aug 2021)

Parameter Flow (MGD)

9.5

BOD (mg/L)

163.6

NH3-N (mg/L)

22.4

TP (mg/L) 1

6.5

: Parameter was averaged from special sampling data (October 2021)

The results of the model validation for raw influent and final effluent are depicted in Table 2-8. Table 2-8: Validation Results of Constituent Concentrations Raw Influent

Final Effluent

Measured Results (mg/L)

Modeled Results (mg/L)

Error

Measured Results (mg/L)

Modeled Results (mg/L)

Error

BOD

163.6

2.8

2.6

0.2 mg/L

TSS

190.8

187.1

5.8

0.0 mg/L

NH3-N

22.4

1.5

0.3

1.2 mg/L

Constituent

Modeled values of BOD and NH3-N in the raw influent are both predicted with high accuracy (i.e. 0% error) and TSS is also modeled with excellent results compared to the historical average values. The final effluent validation demonstrated excellent accuracy in terms of BOD and TSS (< 0.5 mg/L), and acceptable error in the prediction of NH3-N (1.2 mg/L). The calibrated model successfully predicts the mixed liquor concentrations and the solid production rate at the Westside WWTP for the month of October 2021, which are shown in Table 2-9. Table 2-9: Validation Results of MLSS Concentrations and Solid Production Rate MLSS Constituent

Historical Data

Modeling Results

Error

6,420 mg/L 4,230 mg/L 13,890 lb/d

5,840 mg/L 4,530 mg/L 12,790 lb/d

9% 7% 8%

TSS VSS Solid Production Rate1 1

: Historical Data from October 2021

The solid concentrations of the MLSS within the aeration basins are well-predicted with error values of 9% and 7% for TSS and VSS, respectively. The modeled concentrations indicate that the model produces a mixed liquor with a higher fraction of soluble suspended solids (78% VSS/TSS) than at the facility (66%

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VSS/TSS). The modeled solid production rate has good agreement with the average solids production observed during October 2021. 2.2.5.

Westside WWTP Process Model Summary

A process model for the Westside WWTP has been built to simulate the physical dimensions of the facility, has been calibrated, and showed predictive ability by accurately depicting the liquid treatment and solids handling performance of the facility from January 2019 to August 2021. Modeling the Westside WWTP has resulted in the following observations: • • • • • •

•

The raw influent features a ratio of BOD : COD that is lower than is typically observed at WWTP. Addition of metal salts at the Influent Pump Station may contribute to low PO4-P concentrations in raw influent and primary effluent samples. Recycle of first-stage trickling filter effluent in model calibrates for sBOD removal in the primary effluent. Final effluent constituents are calibrated to have acceptable to excellent agreement with special sampling results. Solid stream concentrations are calibrated to have good agreement with historical facility measurements. The calibrated model predicts all of the historical influent and effluent constituent concentrations (Ave Jan 2019 to Aug 2021) with excellent accuracy, except for NH3-N, which is slightly underestimated by an acceptable error. The calibrated model predicts the TSS and VSS concentrations of the historical operating MLSS and the solids production rate with good accuracy.

This calibrated and validated model can now be used to determine the process capacity of the Westside WWTP and to identify areas of improvement as flows and loadings increase and/or additional permit regulations are identified for compliance. 2.3. Southside WWTP Baseline Process Model 2.3.1.

Southside WWTP Sampling Data

This section presents special sampling data collected at the Southside WWTP. Samples were taken at the following locations: 1) 2) 3) 4) 5)

Raw Influent Primary Clarifier Effluent Secondary Clarifier Effluent Final Effluent Belt Filter Press Filtrate

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Raw influent samples were collected from October 5 through October 18, 2021, and the remaining locations were sampled from November 2 to November 15, 2021. Field measurements at the Southside WWTP have been analyzed and reconciled to aid in model calibration and to represent the facility’s current treatment performance with an acceptable degree of accuracy. Table 2-10 shows a summary of the special sampling results which are utilized as the basis for model calibration. Table 2-10: Southside WWTP Special Sampling Results Summary Raw Influent

COD

sCOD

BOD

sBOD

TSS

VSS

NH3-N

TKN

NO3-N

PO4-P

Average

480.8

115.2

131.4

234.0

25.4

35.4

0.7

4.2

5.8

Min

383.0

88.5

103.0

170.0

25.1

32.6

0.3

3.7

5.5

Max

645.0

151.0

188.0

280.0

25.4

38.2

1.0

5.4

6.1

Primary Clarifier Effluent Average

340.7

133.7

162.7

97.1

131.8

111.6

23.4

33.9

0.7

2.8

7.0

Min

305.0

86.2

145.0

72.0

110.0

93.5

20.4

29.3

0.3

2.3

6.8

Max

418.0

215.0

175.0

174.0

154.0

129.4

25.9

40.2

1.0

3.5

7.2

Secondary Clarifier Effluent Average

34.2

28.4

4.4

0.8

9.9

6.9

0.1

11.9

0.2

0.3

7.2

Min

25.3

23.0

3.6

0.4

6.5

4.9

0.0

9.1

0.2

0.3

6.9

Max

41.0

32.4

6.7

1.1

12.3

8.5

0.2

13.4

0.2

0.3

7.4

Average

33.1

31.6

5.6

0.9

11.5

7.9

0.2

12.0

0.2

0.3

7.1

Min

24.5

4.8

0.7

6.0

5.5

0.1

8.7

0.2

0.3

6.9

Max

41.7

38.1

7.6

1.3

19.6

11.3

0.3

14.5

0.2

0.3

7.2

Final Effluent

Belt Filter Press Recycle Average

145.3

Min

117.0

Max

180.0

The units used are mg/L except for pH (s.u.) and Q (MGD).

The special sampling measurements above indicate a significantly lower level of dissolved phosphorous (i.e. ortho-phosphate, PO4-P) in the raw influent (0.7 mg/L) than is typically observed in untreated wastewater (3.2 - 6.3 mg/L in medium to high strength wastewater: Metcalf and Eddy, 5th ed.). However, based on discussions with plant staff during three site visits, it was determined that raw influent data were collected at the influent pump station, which is downstream of where metal salts are introduced to the raw influent to manage odor control. The dosing of Mg(OH)2 and ferric sulfate (Fe2(SO4)3) results in dissolved magnesium and iron which can bind with phosphate and convert soluble PO4-P to insoluble metalphosphate salts. This may indicate that chemical removal of phosphate may have occurred, leading to decreased PO4-P measurements in the composite samples taken from the raw influent and primary effluent locations.

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2.3.2.

Southside WWTP Model Representation

Figure 2-5 shows a model representation of the existing process layout of the Southside WWTP developed in GPS-X.

Figure 2-5: Schematic PFD of the Southside WWTP Developed in GPS-X 2.3.2.1 Preliminary Chemical Treatment Mg(OH)2 and Fe2(SO4)3 are dosed to the raw influent flow for odor control prior to the influent pump station. As mentioned in the Westside WWTP analysis, these coagulating chemicals can react with ortho-phosphate loads that are brought to the head of the treatment train from solid handling recycle streams and convert a fraction of soluble phosphorous to particulate material, allowing for its physical removal. While magnesium ion (Mg2+) can bind with PO4-P to some extent, the ferric iron ion (Fe3+) has a greater capacity for complexation and is commonly used for chemically enhanced primary treatment (CEPT) towards the removal of soluble phosphorous.

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2.3.2.2 Primary Clarifiers After passing through a grit removal system, the influent wastewater flows through two 100-ft diameter primary clarifiers. Special sampling data provided information about the solid separation performance of the primary clarifier and indicated that TSS was removed at a rate of approximately 44%. The sludge generated by the primary clarifiers is directed by a primary sludge pump station to a sludge holding tank for storage. The historical operation of the primary sludge pumps was considered in modeling the solids concentration of the primary sludge. In this process model, the primary treatment is represented with a TSS removal rate of 45%. 2.3.2.3 Aeration Basins The primary effluent is routed through an aeration basin splitter box towards three aeration basins. Aeration Basins 1 and 2 each have an Orbal oxidation ditch configuration and an aerobic volume of 1.0 MG. Aeration Basin 3 has a folded cylinder configuration with a volume of 0.95 MG. The aeration basins have been modeled to operate under an aeration regime that best symbolizes the location of the mechanical aerators and where flow enters and exits the basins. The aeration basins have been represented as PFRs with recycle streams to reproduce the recirculated flow within the basin channels. The model is set to provide a flow split of 28%, 28%, and 44% for Aeration Basins 1, 2, and 3, respectively. The flow split was determined by a hydraulic analysis that is described in Sections 2.4.2.4. through 2.4.2.7. of the Hydraulic Modeling section of this TM. 2.3.2.4 Secondary Clarifiers Effluent from the aeration basins is transferred to three secondary clarifiers. Two of the clarifiers have 100-ft diameters and 10.2-ft side wall depths (SWDs) and the third clarifier has a diameter of 110-ft and a 14-ft SWD. The RAS/WAS Pump Station delivers RAS from Secondary Clarifiers 1 and 2 to Aeration Basins 1 and 2. The Secondary Sludge Pump Station delivers RAS from Secondary Clarifier 3 to Aeration Basin 3. To reduce excessive model complexity, all secondary clarifiers are modeled as one unit with the combined hydraulic and performance capacity of the secondary clarifier facility. 2.3.2.5 Aerobic Digesters WAS from the secondary clarifiers undergoes aerobic digestion in open-air carousel raceways at the center of Aeration Basins 1 and 2. Each aeration basin contains 0.46 MG of volume dedicated to aerobic digestion. Mechanical aeration is provided by disk surface aerators. The aerobic digesters are modeled as a single aeration basin that accepts all produced solids from the secondary treatment. The digested WAS from the aerobic digesters is transferred to the sludge thickening facility.

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2.3.2.6 Gravity Belt Thickener The sludge thickening facility accepts digested WAS from the aerobic digesters. A thickening module is used in the developed plant model to simulate the existing gravity belt thickener (GBT) at the Southside WWTP. The GBT is modeled to achieve 95% solids capture rate and produce a sludge flow with a 4.5% solids concentration, based upon historical data collection. The filtrate that results from the sludge thickening process is recycled back to the head of the plant and is represented within the plant model. 2.3.2.7 Sludge Holding Tank Thickened WAS and primary sludge are combined and stored within a 100-ft diameter sludge holding tank (Volume: 0.59 MG) that contains two internal recycle pumps. The sludge flow can be further managed by plant staff by diverting solids back to the aerobic digestion channels. The sludge storage tank located upstream of the dewatering facility is considered in the developed model to simulate the potential biological reactions that may occur during sludge storage period. A grinder pump conveys the stored sludge to the dewatering building. 2.3.2.8 Belt Filter Presses Transferred sludge from the sludge storage tank is dewatered by two 2-meter BFPs. The BFP was modeled to achieve 95% solids capture rate and to produce a 21% dewatered cake, based on solids production data from November 2021. The filtrate is combined with that from the GBT and the total filtrate flow is recycled back to the head of the plant. This flow is represented within the treatment model. 2.3.3.

Southside WWTP Calibration Results

In this subsection, special sampling influent data from October and November 2021 is used to fractionate the constituents of the influent for the Southside WWTP. As with the Westside WWTP, the designed process model was calibrated to simulate existing operational processes at the facility and modeled results of treatment were compared to the results of the special sampling campaign. 2.3.3.1. Influent Fractionation Influent fractionation is performed using influent data from the special sampling campaign during November 2 through November 15, 2021. Two influent constituents (sBOD and VSS) were measured during the October 5 through October 18, 2021 campaign, which included BOD and TSS measurements. These measurements provide VSS : TSS and sBOD : BOD ratios that are assumed to also apply to the targeted special sampling period that began only 2 weeks later. Further, two characterization parameters (BOD and TSS) use values that are averaged measurements from daily operational samples taken during the November 2021 special sampling period. Table 2-11 gives a summary of the measured, modeled and GPS-X default influent fractionation values.

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Table 2-11: Southside WWTP Influent Fractionation Values Special Sampling Average

Modele d Result

Model Default

VSS : TSS

0.921

0.83

0.75

sCOD : COD

0.24

0.28

0.34

BOD : COD

0.292

0.29

0.58

sBOD : sCOD

0.443

0.55

0.61

PO4-P : TP

0.18

0.80

Nitrogen Content of Inert Particulate Material

0.025

0.05

Phosphorous Content of Inert Particulate Material

0.001

0.01

Fractionation

: The VSS : TSS ratio was derived using measurements from a previous sampling dataset (October 5 through October 18, 2021). 2 : The BOD : COD ratio was derived using BOD measurements from daily operations at the facility during the special sampling period. 3 : The sBOD : sCOD ratio was calculated using sBOD values that were derived using an sBOD : BOD ratio (0.37) determined from a previous and recent sampling dataset (October 5 through October 18, 2021).

The modeled VSS : TSS ratio of approximately 0.83 is between the model’s default value of 0.75 and the measured average of 0.92, which provides good overall characterization of the influent constituents. The other influent fractions of sCOD : COD, BOD : COD, and sBOD : sCOD are likewise modeled to be either similar to special sampling measurements or in between those measurements and the model default values. The dissolved phosphorous loading in the raw influent has been changed from the measured special sampling values due to the assumption that sampling occurred at a location after the addition of metal salts used during preliminary treatment. Therefore, the measured ratio of PO4-P : TP is increased from 0.18 to 0.80, which provides a more realistic expectation of phosphate loading and matches the model’s default value. Finally, the ratios of inert particulate content due to nitrogen (0.025) and phosphorous (0.001) have been decreased from model default values. These modifications allowed for the best compromise in fractionation for all the considered constituents within raw influent at the Southside WWTP. As is observed at the Westside WWTP, the BOD : COD ratio at the Southside WWTP is notably lower than is measured in standard raw influent. 2.3.3.2. Calibration Results for Raw Influent Using the influent fractionation values mentioned above, the composition of the raw influent for the Southside WWTP is simulated in GPS-X. Figure 2-6 represents the parameters measured from field samples of the raw influent plotted in a box and whisker diagram.

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Figure 2-6: Southside WWTP Raw Influent Calibration Check As shown, all modeled influent parameters have excellent agreement with special sampling data parameters, except for sCOD which is predicted with 7% error. Measurements for sBOD, VSS, and NO3N were not collected for the raw influent during the November 2021 special sampling campaign. The low values of PO4-P that were observed in the raw influent during the special sampling campaign are assumed to be the result of metal salt dosing upstream of the sampling location. The odor control chemicals are injected at the influent pump station before raw influent samples were collected. As discussed in the Westside WWTP analysis, the metal salts could convert soluble PO4-P to insoluble phosphorous. It is assumed that the PO4-P loads within the raw influent and the recycled solid stream flows form insoluble precipitates and are removed at the primary clarifier facility. 2.3.3.3. Calibration Results for Primary Effluent Table 2-12 illustrates the calibration results for the primary effluent. All modeled constituents are predicted with good to excellent accuracy, except for COD, which has acceptable error, and BOD and sBOD, which each have significantly underpredicted values in comparison to their special sampling averages and resulted in unsatisfactory errors.

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Table 2-12: Southside WWTP Primary Effluent Calibration Check Sampling Results (mg/L)

Modeling Results (mg/L)

Error

COD

340.7

302.8

11%

sCOD

133.7

122.9

BOD

162.7

100.1

38%1

sBOD

97.1

68.0

30%2

TSS

131.8

129.2

VSS

111.6

101.0

10%

NH3-N

23.4

25.7

10%

TKN

33.9

32.5

PO4-P

0.7

0.8

0.1 mg/L

2.8

2.9

0.1mg/L

7.0

Constituent

: Special Sampling Primary Effluent BOD measurements were higher than historical raw influent average (Jan 2019 – Aug 2021: 147.8 mg/L) and special sampling raw influent average (131.4 mg/L). 2 : sBOD error is correlated to BOD error due to the sBOD : BOD ratio discussed in the influent fractionation section.

As discussed above, the removal of phosphate by the primary clarifiers that was observed during the special sampling campaign has been modeled through the use of a ferric sulfate injection upstream of the facility. It is assumed that the phosphate precipitate was removed as a component of the primary sludge. 2.3.3.4. Calibration Results for Final Effluent Table 2-13 illustrates the calibration results for the final effluent. Table 2-13: Southside WWTP Final Effluent Calibration Check Final Effluent Sampling Results (mg/L)

Final Effluent Modeling Results (mg/L)

Error

COD

35.0

38.0

sCOD

30.5

31.9

BOD

4.6

3.1

1.5mg/L

sBOD

3.4

2.7

0.7 mg/L

TSS

6.8

4.9

1.9 mg/L

VSS

5.3

3.6

1.7 mg/L

Constituent

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Final Effluent Sampling Results (mg/L)

Final Effluent Modeling Results (mg/L)

Error

NH3-N

0.1

0.2

0.1 mg/L

NO3

12.2

10.9

11%

PO4-P

0.2

0.5

0.3 mg/L

0.3

0.8

0.6 mg/L

7.1

7.0

Constituent

Most of the measured constituents have good to excellent agreement with the modeled results. The exceptions were BOD, TSS VSS and NO3-N, which were predicted with acceptable accuracy. The secondary process was calibrated by establishing a wasting rate of 0.039 MGD and setting the final clarification performance to remove 99.9% of mixed liquor solids. 2.3.3.5. Calibration Results for MLSS Solids Concentration and Recycle Loads The Southside WWTP model is calibrated in regard to the measured concentrations of MLSS for the combined aeration basins, and the recycled NH3-N load from the BFP returning to the facility headworks. The calibration results are shown in Table 2-14. Table 2-14: Southside WWTP MLSS Concentration, Solid Handling, and Recycle Flow Calibration Check Constituent

Sampling Results

Modeling Results

Error

MLSS (mg/L)

5,790

5,410-

MLVSS (mg/L)

4,100

3,980

BFP NH3-N Recycle (mg/L)

145

121

17%

The TSS and VSS concentrations of the MLSS averaged from Aeration Basins 1, 2, and 3 are found to have good to excellent agreement with the special sampling averages, differing by 7% and 3%, respectively. As with the Westside WWTP, the solid production of the Southside WWTP is not used in calibrating the model. However, the November 2021 solids production data is used to validate the model, which is discussed in the following section. Further, the recycled ammonia load modeled to return to the head of the plant also has acceptable error in relation to the special sampling dataset. The volume of the sludge holding tank was increased in the model to provide a longer residence time for the bacteria within the thickened solids to break down under anaerobic conditions and release soluble ammonia. The ammonia load is then recycled to the head of the facility after it is separated from the solids during the dewatering process.

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2.3.4.

Southside WWTP Validation Results

The calibrated model has been tested for its predictive ability by using historical data from January 2019 through August 2021 as model inputs. The measured influent constituents for this date range are illustrated in Table 2-15. Table 2-15: Historical Flows and Concentrations for Southside WWTP Historical Value (Jan 2019 – Aug 2021)

Parameter Flow (MGD)

7.0

BOD (mg/L)

147.8

NH3-N (mg/L)

21.8

TP1 (mg/L)

4.2

: Parameter was averaged from special sampling data (November 2021)

The results of the model validation for raw influent and final effluent are depicted in Table 2-16. Modeled values for all parameters observed in raw influent and the final effluent are predicted with good to excellent accuracy, except for NH3-N, which is underreported in the effluent by 1.4 mg/L. The high historical value of NH3-N observed at the Southside WWTP may be due to recent primary clarifier improvements in 2020, which may have influenced the organic loading to the aeration basins and resulted in higher than desired NH3-N discharges at the facility. Table 2-16: Validation Results of Constituent Concentrations Raw Influent Constituent

Final Effluent

Historical Data (mg/L)

Modeled Results (mg/L)

Error

Historical Data (mg/L)

Modeled Results (mg/L)

Error

BOD

147.8

153.0

4.1

4.0

0.1 mg/L

TSS

278.0

274.3

12.6

13.2

0.6 mg/L

NH3

21.8

1.7

0.3

1.4 mg/L

The calibrated model successfully predicts the solid quantities at the Southside WWTP when compared to those averaged over the course of January 2019 to August 2021. The results of the solid modeling are shown in Table 2-17 and demonstrate that both the predicted TSS and VSS values are within 6% of those measured at the facility. The modeled solid production rate has acceptable agreement with the average solids production observed during November 2021. Table 2-17: Validation Results of MLSS Concentrations and Solid Production Rate MLSS Constituent

Historical Data

Modeling Results

Error

TSS VSS Solid Production Rate1

7,430 mg/L 5,050 mg/L 10,940 lb/d

6,950 mg/L 5,220 mg/L 12,690 lb/d

6% 3% 16%

: Historical Data from November 2021

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2.3.5.

Southside WWTP Process Model Summary

A process model for the Southside Tyler WWTP has been built to simulate the physical dimensions of the facility, has been calibrated, and shows predictive ability by accurately depicting the liquid treatment and solids handling performance of the facility from January 2019 to August 2021. The results of the Southside WWTP modeling effort are summarized with the following details: • • • • • • • •

The raw influent features lower than typical ratio of BOD : COD and low fractions of sCOD : COD and sBOD : sCOD. Addition of metal salts at influent pump station may explain low PO4-P values in the raw influent samples and provide rationale for PO4-P removal during primary treatment. Primary effluent calibration produced model results that were predicted with good to excellent accuracy for most constituents. Unsatisfactory errors for modeled BOD and sBOD concentrations in primary effluent may be due to unrepresentative parameter measurements during the special sampling campaign. Final effluent calibrated to have acceptable to excellent agreement with special sampling results MLSS TSS and VSS concentrations calibrated to have good to excellent agreement with operational measurements. Calibration of solids handling procedures provided acceptable depiction of recycled NH3-N load to the head of the treatment train. The calibrated model represents the historical performance of the facility with high accuracy, evidenced by good to excellent error values for nearly all influent, effluent, and solid stream concentrations. The exceptions were the facility’s effluent NH3-N concentration and solids production rate, which had acceptable agreement with special sampling averages.

This model can now be used to determine the process capacity of the Southside WWTP and to identify areas of improvement as flows and loadings increase and/or additional permit regulations are identified for compliance.

3. Hydraulic Model Evaluation Two full plant hydraulic models were developed for the Westside and Southside WWTPs. The hydraulic profiles account for the hydraulic grade line (HGL) through the plant. These models were then used to determine the hydraulic capacity of the treatment facilities and identify critical hydraulic control points throughout the main process flow paths. This section of the TM documents the assumptions, methodology, and findings of the hydraulic models, and establishes the capacity of the treatment facilities at the two plants. 3.1. Methodology of Hydraulic Models Garver has built the hydraulic models using an in-house Microsoft Excel spreadsheet tool that calculates friction and minor losses as well as the HGL at hydraulic control points. The main objective of the model is to identify hydraulic bottlenecks and document the hydraulic capacity of the existing treatment facilities. The information presented in this TM follows the process flow for both WWTPs from the effluent discharge point of the plant to the influent intake structure.

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The following methodology and assumptions were used for the hydraulic models: 1. Available record drawings, site survey results, Federal Emergency Management Agency (FEMA) flood map data, and field observations were used to build the hydraulic models and establish baseline assumptions. 2. Dimensions of structures were assumed to be consistent with record drawings and elevations are assumed to be as reported in the most recent survey, commissioned by Garver. This is discussed in more detail in Section 3.3.1. 3. The Return Activated Sludge (RAS) recycle flow rate was assumed to be 100% of average daily flow (ADF), which is equal to 30% of the peak flow at the Westside WWTP and 25% of the peak flow at the Southside WWTP 4. Headloss (the drop in HGL caused by fluid flow) was calculated in a spreadsheet model to determine the HGL profile through the plant. 5. Headloss in open channels was estimated using the Manning’s friction loss method, assuming a Manning’s roughness coefficient “n” of 0.013, typical for regular, concrete channels. 6. Headloss in pipes was estimated using the Hazen-Williams equation, using nominal pipe diameter as the estimated internal diameter, and using a Hazen-Williams coefficient “C” value of 100, typical of wastewater piping that experiences normal levels of solids deposition and/or biofilm growth. 7. The change in HGL over weirs and through submerged orifices was calculated using standard equations. Hydraulic segments were delineated based on hydraulic controls points such as weirs and free outfalls where the upstream water surface elevation (WSE) is independent of the downstream WSE. The capacity of a segment is determined by increasing the plant flow through the modeled profile until the criteria listed in Section 1 is violated; the maximum plant flow that does not result in a violation of the criteria is the hydraulic capacity. 3.2. Evaluation Criteria In this hydraulic model analysis, tank wall and weir freeboard, as well as pipe velocity criteria, are used to determine the capacity of the hydraulic segments by defining a benchmark that the hydraulic models will be compared to. These criteria are based on a combination of Texas Commission on Environmental Quality (TCEQ) regulations and Garver’s engineering experience and judgement. The criteria are contained within the following list: • • • •

Aeration basin (AB) wall freeboard shall be 18 inches (1.5 feet) or greater at peak flows to prevent overflows due to foaming or surface turbulence. (TCEQ 217.153, b. (1)) Wall freeboard within clarifiers shall be 12 inches (1.0 foot) or greater at peak flows to prevent any splashing over the walls. (TCEQ 217.153, b. (2)) Wall freeboard within other structures shall be 12 inches (1.0 foot) or greater to prevent splashing over the walls. During peak flow events, weir freeboard shall be 3 inches (0.25 feet) or greater at the weirs used to maintain even flow split to ensure proper weir function. At the Westside and Southside plants, the following weirs are included in this criterion: o Westside ▪ Grit effluent weirs ▪ Primary clarifier weirs ▪ Tower splitter box weirs ▪ Nitrification basin rotary weirs

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▪ Secondary clarifier weirs Southside ▪ Grit effluent weirs ▪ Primary clarifier splitter box weirs ▪ Primary clarifier weirs ▪ Aeration basin splitter box weirs ▪ Aeration basin effluent weirs ▪ Secondary clarifier weirs During bypass operations, weir freeboard may be less than 3 inches, and in some cases weirs may become submerged. In these scenarios, wall freeboard was considered the governing factor for hydraulic capacity. Pipe flow velocities shall be no greater than 9 ft/s. o

•

3.3. Westside WWTP The assumptions and results of the hydraulic analysis for the Westside WWTP are presented in this section. 3.3.1.

Model Assumptions

The FEMA flood map for the Westside WWTP outfall was reviewed to determine the starting WSE of the profile in the receiving water body, Black Fork Creek. The flood map can be seen in Figure 3-1; as shown in the flood map, the starting WSE of the profile should be between 395.00 ft and 396.00 ft. Also observed from the flood map is the projected 100-year flood delineation. The floodway, representing the 100-year flood area for Black Fork Creek, extends into the majority of the Westside WWTP site. It should be noted that construction on land located within the floodway can be difficult and requires additional permitting and work to ensure that the construction will not alter the floodway stage. The implications of the floodway delineation were discussed with the City of Tyler during coordination meetings. It was determined that a new flood study to confirm the validity of the current floodway map might be beneficial to ensure that improvements to the existing site can be made. This will be discussed further in future TMs.

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Figure 3-1: FEMA Flood Map of the Black Fork Creek Near the Westside WWTP As stated previously, the record drawings as well as survey data were used to develop the hydraulic profiles. The record drawings from the 1988, 1991, 2003, and 2014 plant improvements were reviewed to identify the design elevations and dimensions of the structures at the plant. In general, the survey results for the existing structures elevations differed from the elevations reported on the record drawings; survey data was used as the basis of the hydraulic analysis. The results of the survey and the methods used to incorporate those elevation differences into the hydraulic profile are included in Table 3-1. The table lists the record drawing elevations and dimensions along with the surveyed elevations of the different structures at the Westside WWTP along with the values used in the hydraulic analysis.

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Table 3-1: Comparison of Record Drawings and Survey Information at Westside WWTP Structure Outfall CCB Secondary Clarifiers

Tower Splitter Box

Nitrification Basin Second-Stage Trickling Filters Control Box First-Stage Trickling Filter Effluent Box First-Stage Trickling Filters Primary Clarifiers Influent Parshall Flume Box Headworks

Record Drawing Value (ft) 379.00 393.00 389.00 10.0 404.00 398.48 402.25 411.00 407.00

Survey Elevation (ft) 378.71 392.55 388.68 N/A1 403.59 N/A1 401.88 410.83 406.82

Difference (ft) N/A 0.45 N/A N/A 0.41 N/A 0.37 0.17 0.18

Value Used (ft) 378.71 392.55 388.68 10 403.59 398.48 401.88 410.83 406.82

403.50

403.25

0.25

403.25

403.00 408.00 405.71

402.98 407.58 405.56

0.02 0.42 0.15

402.98 407.58 405.56

394.00

393.53

0.47

393.53

Top of Wall EL Top of Wall EL Opening 2 Invert EL Opening 1 Invert EL Top of Wall EL

400.00 393.00 N/A1 N/A1

399.45 392.64 382.59 382.64

0.55 0.36 N/A N/A

399.45 392.64 382.59 382.64

394.00

393.55

0.45

393.55

Top of Wall EL Weir EL Box 2 Top of Wall EL Top of Wall EL Parshall Flume EL

400.00 398.50 400.00 393.00

399.59 398.00 399.58 392.61

0.41 0.5 0.42 0.39

399.59 398.00 399.58 392.61

381.00

380.72

0.28

380.72

Top of Wall EL Grit Effluent Weir EL

393.00 383.50

392.60 383.03

0.4 0.47

392.60 383.03

Point Location Effluent Pipe Invert EL Outer Walls EL Effluent Weir EL Effluent Weir Width Top of Wall EL Top of Wall Notch EL Weir EL Top of Upper Wall EL Top of Lower Wall EL Secondary Clarifier Splitter Chamber Weir EL Parshall Flume EL Top of Outer Wall EL Weir EL Top of Wall EL

Notes: 1. As-built information was not available in the provided record drawings. 3.3.2.

Model Results – Hydraulic Segments

In the Planning Criteria TM, dated June 2022, a future ADF and peak 2-hour flow (P2HF) for the Westside WTP were established as 14.0 MGD and 47.2 MGD, respectively. The range of flows used in the hydraulic segment modeling range from 5.0 MGD to 50.0 MGD to capture any hydraulic capacity issues at current and future projected flows. In order to get an accurate idea of the capacity of the plant segments as a whole, the results of each hydraulic segment were used as the starting WSE of each subsequent segment. The following sections discuss the hydraulic capacity of each segment and identify the limiting factors and bottlenecks of the existing plant.

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Figure 3-2 shows a layout of the existing Westside WWTP with the facilities and hydraulic segments labelled.

Figure 3-2: Westside WWTP Site Layout Identifying Hydraulic Segments

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3.3.2.1. Segment 1: Chlorine Contact Basin to Plant Outfall The plant discharges from the chlorine contact basin (CCB) to the Black Fork Creek through a 48” diameter pipe. Prior to the discharge pipe, an effluent measurement weir is located in the outlet box of the CCB. As previously stated, the FEMA flood map was used to establish the downstream control WSE in the receiving water body, Black Fork Creek. The WSE estimated from the FEMA map was 395.50 ft; this elevation was used as the starting elevation of the hydraulic profile. It should be noted that this elevation is higher than the wall elevation of the existing chlorine contact basin, 392.55 ft. Therefore, it was assumed that at the 100-year flood stage condition, the existing chlorine contact basin will experience flooding of the overall structure and effluent weir. Segment 1 is shown below in Figure 2-3.

Figure 3-3: Site Layout Highlighting Segment 1 3.3.2.2. Segment 2: Secondary Clarifier 1 to Chlorine Contact Basin Segment 2 includes the flow path upstream of the CCB effluent weirs and extends to the Secondary Clarifier 1 effluent launder trough. Effluent from the secondary clarifiers enters the clarifier effluent box, and is then piped to the CCB. The flow from both clarifiers combines within the piping segment. Segment 2 is shown below in Figure 3-4.

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Figure 3-4: Site Layout Highlighting Segment 2 Due to the flooded condition of the CCB at the 100-year flood event, creating an accurate model of the CCB is challenging. An assumption was made that there would be negligible losses accrued within the chlorine contact basin structure due to flooding of the walls. Losses through the secondary effluent piping and in the secondary clarifier effluent box were accounted for to calculate the WSE downstream of the secondary clarifier weirs. Segment 2 includes the following elements: • • •

48” piping between the chlorine contact basins and secondary clarifiers Secondary clarifier 1 outlet box Secondary clarifier 1 effluent launder trough

The flow split between the two secondary clarifiers was assumed to be equal for the purposes of this hydraulic analysis. Therefore, the flow through the majority of Segment 2 is half of the total plant flow. To reflect this, the hydraulic analysis for Segment 2 ranges from 2.5 MGD to 25.0 MGD. Figure 2-5 shows the change in WSE downstream of the secondary clarifier weirs at different flow conditions. Also shown is the WSE that would violate the freeboard criteria for the secondary clarifier weirs, as detailed in Section 3.3.1. The maximum allowable WSE downstream of the secondary clarifiers to meet the weir freeboard criterion is 401.63 ft. As shown, the estimated hydraulic capacity of Segment 2 is roughly 16.0 MGD. It should also be noted that the secondary clarifiers have notches in the outlet box walls at an elevation of 397.15 ft; the notches have been raised to 398.48 ft by the addition of Concrete Masonry Unit (CMU) blocks.

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When the WSE in the outlet box rises, leaking is observed above the original notch elevation and between the CMU blocks. The WSE within the outlet box encroaches on freeboard of the original notch when flow through the segment is higher than 16 MGD.

WSE at Secondary Clarifier Weirs (ft)

402.20 402.00 401.80

Maximum WSE = 401.63 ft

401.60 401.40 401.20 401.00

400.80 400.60 0.00

5.00

10.00

15.00

20.00

25.00

30.00

Flow (MGD) Figure 3-5: WSE Downstream of Secondary Clarifier 1 Weir as a Function of Flow 3.3.2.3. Segment 3: Tower Splitter Box to Secondary Clarifier 1 Segment 3 includes the flow path between Secondary Clarifier 1 and the Tower Splitter Box. Within the Tower Splitter box, the Nitrification Basin effluent is split evenly between the two secondary clarifiers. Segment 3 is shown below in Figure 3-6.

Figure 3-6: Site Layout Highlighting Segment 3

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Segment 3 at the Westside WWTP includes the following elements: • • •

Secondary Clarifier 1 effluent weir Secondary Clarifier 1 influent column 48” piping between Secondary Clarifier 1 and the Tower Splitter Box effluent weirs

The flow split between the two secondary clarifiers was assumed to be equal and the flow path modeled followed the longest pipe run (between the splitter box and Secondary Clarifier 1). The flows simulated through Segment 3 include half of the total plant flow as well as RAS, ranging from 2.5 MGD to 25.0 MGD.

WSE at Secondary Clarifier Splitter Box Weirs (ft)

Similar to Segment 2, the maximum allowable WSE is based on the weir freeboard criterion. The maximum allowable WSE downstream of the Tower Splitter Box weirs to meet the criterion is 403.00 ft. As shown in Figure 3-7, the freeboard criterion is violated in Segment 3 at a flow of approximately 16.3 MGD.

403.80 403.60 403.40 403.20

Maximum WSE = 403.00 ft

403.00 402.80

402.60 402.40 402.20 402.00

Flow (MGD) Figure 3-7: WSE Downstream of the Tower Splitter Box Weirs as a Function of Flowrate 3.3.2.4. Segment 4: Nitrification Basin to Tower Splitter Box Segment 4 includes the flow path between the nitrification basin effluent channel and the Tower Splitter Box. Segment 4 is shown below in Figure 3-8.

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Figure 3-8: Site Layout Highlighting Segment 4 Segment 4 consists of the following elements: •

54” piping between the Nitrification Basin effluent channel and the Tower Splitter Box influent chamber.

The flows through Segment 4 include the full plant flow plus RAS flow. The maximum allowable WSE in the Nitrification Basin effluent channel to meet the weir freeboard criterion is 405.31 ft. As shown in Figure 3-9, the hydraulic capacity of Segment 4 is roughly 47.0 MGD. In addition to the weir freeboard, the wall freeboard criterion is violated at flows higher than 57.0 MGD. It was observed during the site visit that turbulence within the basin near the surface aerators may also contribute to wall freeboard violation.

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WSE at the Nitrification Basin Weirs (ft)

407.50 407.00 406.50

Wall Freeboard WSE = 406.08 ft

406.00

Weir Freeboard WSE = 405.31 ft

405.50 405.00 404.50 404.00 403.50 403.00 0.0

5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0

Flow (MGD) Figure 3-9: WSE Downstream of the Nitrification Basin Effluent Weirs as a Function of Flowrate 3.3.2.5. Segment 5: Filter Pump Station to Nitrification Basin Segment 5 includes the flow path between the Filter Pump Station and the Nitrification Basin. The flow is pumped from the Filter Pump Station up to the Tower Splitter Box and combined with RAS before being sent to the Nitrification Basin. Segment 5 is shown below in Figure 3-10.

Figure 3-10: Site Layout Highlighting Segment 5

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Segment 5 consists of the following elements: • • • •

48” piping between the Tower Splitter Box and the Nitrification Basin The influent gate at the Tower Splitter Box 42” piping between the Filter Pump Station and the Tower Splitter Box The valves and fittings downstream of the Filter Pumps

The criterion used to determine the capacity of Segment 5 is the maximum pipe velocity recommendation of 9.0 ft/s. The maximum pipe velocity within Segment 5 occurs in the 30” pump header piping downstream of the filter pumps. As shown in Figure 3-11, the maximum pipe velocity throughout the segment at the applicable range of flows never violates the 9.0 ft/s criterion; therefore, the capacity of Segment 5 is greater than 50 MGD.

WSE at the Nitrification Basin Weirs (ft)

10.0

Maximum Pipe Velocity = 9.0 ft/s

9.0 8.0 7.0 6.0 5.0 4.0

3.0 2.0 1.0 0.0 0

Flow (MGD)

Figure 3-11: Maximum Pipe Velocity in Segment 5 as a Function of Flowrate 3.3.2.6. Segment 6: Primary Clarifier 1 to Second-Stage Trickling Filter 1 Segment 6 includes the flow path that bypasses the first-stage trickling filters and routes primary effluent directly to the control box and then to the second-stage trickling filters. Segment 6 is shown below in Figure 3-12.

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Figure 3-12: Site Layout Highlighting Segment 6 Segment 6 consists of the following elements: • • • • • • •

36” piping between the Filter Pump Station and Second-Stage Trickling Filter 1 Influent column of Second-Stage Trickling Filter 1 36” piping between Second-Stage Trickling Filter 1 and the Control Box 42” piping between the Control Box and the primary effluent junction box Gate opening within the primary effluent junction box 42” piping between the primary effluent junction box and Primary Clarifier 1 Primary Clarifier 1 effluent channel and effluent launder

An equal flow split was assumed between the two primary clarifiers as well as between the two secondstage trickling filters and the flow path modeled follows the longest pipe run within the segment (including Primary Clarifier 1). The primary clarifier bypass flow path is often utilized by the plant operators and typically contains 40-50% of the total plant flow. Therefore, the flows simulated through Segment 6 range from 2.5 MGD to 25.0 MGD. The hydraulic capacity of this segment is limited by the WSE downstream of the primary clarifier effluent weirs. The weir freeboard criterion was applied to determine a maximum WSE of 397.75 ft downstream of the primary clarifier weirs. As shown in Figure 3-13, the flow through Segment 6 where this freeboard is violated is approximately 13.0 MGD.

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WSE at the Primary Clarifier Weirs

405.00 404.00 403.00 402.00 401.00 400.00

Wall Freeboard WSE = 398.59 ft

399.00

Weir Freeboard WSE = 397.75 ft

398.00 397.00 396.00 0.00

5.00

10.00

15.00

20.00

25.00

Flow (MGD) Figure 3-13: WSE Downstream of Primary Clarifier 1 Weir as a Function of Flow 3.3.2.7. Segment 7: First-Stage Trickling Filter 1 to Filter Pump Station Segment 7 includes the piping from First-Stage Trickling Filter 1 to the trickling filter junction box and the piping from the trickling filter junction box to the Filter Pump Station. Segment 7 is shown below in Figure 3-14.

Figure 3-14: Site Layout Highlighting Segment 7

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Segment 7 consists of the following elements: • • •

48” piping between the Filter Pump Station and the Trickling Filter Junction Box Gate opening within the Trickling Filter Junction Box 36” and 30” piping between the first stage trickling filters and the Trickling Filter Junction Box

The hydraulic capacity of this segment was determined based on the maximum pipe velocity within the segment. The maximum pipe velocity of the segment occurs in the first-stage trickling filter effluent pipe where the flow from both trickling filters is combined. As shown in Figure 3-15, the maximum capacity of Segment 7 is approximately 42.0 MGD.

Maximum Pipe Velocity in Segment (ft/s)

12.00 10.00

Maximum Pipe Velocity = 9.0 ft/s

8.00 6.00 4.00 2.00 0.00 0

Flow (MGD) Figure 3-15: Maximum Pipe Velocity in Segment 7 as a Function of Flowrate 3.3.2.8. Segment 8: Primary Clarifier 1 to First-Stage Trickling Filter 1 Segment 8 includes the flow path between Primary Clarifier 1 and First-Stage Trickling Filter 1. Each firststage trickling filter and primary clarifier are independently connected and have the same piping configuration, therefore only the flow path between Primary Clarifier 1 and First-Stage Trickling Filter 1 was chosen for modeling purposes. The layout of Segment 7 is shown below in Figure 3-16.

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Figure 3-16: Site Layout Highlighting Segment 8 Segment 8 consists of the following elements: • • • •

First-Stage Trickling Filter 1 influent column 30” piping between the First-Stage Trickling Filter 1 and Primary Clarifier 1 Primary Clarifier 1 effluent box Primary Clarifier 1 effluent channel and effluent launder

As previously stated, the primary clarifier bypass flow path to the second-stage trickling filters is utilized for 40-50% of the total plant flow. The remaining 50-60% of the total plant flow is sent from the primary clarifiers to the first-stage trickling filters; therefore, flows simulated through Segment 8 range from 2.5 MGD to 25.0 MGD. The maximum WSE allowed downstream of the primary clarifier weirs to meet the weir freeboard criterion is 397.75 ft. As shown in Figure 3-17, the hydraulic capacity of Segment 8 is approximately 16.0 MGD.

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WSE at the Primary Clarifier Weirs

398.50

398.00

Maximum WSE = 397.75 ft 397.50

397.00

396.50

396.00 0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

Flow (MGD) Figure 3-17: WSE Downstream of Primary Clarifier 1 Weir as a Function of Flowrate 3.3.2.9. Segment 9: Raw Water Pump Station to Primary Clarifier 1 Segment 9 includes the flow path between the Raw Water Pump Station wet well and Primary Clarifier 1. It was assumed for modeling purposes that the raw water pumps are capable of maintaining the wet well level at 379.00 ft, which will ensure that the Influent Parshall Flume is unsubmerged. Segment 9 is shown in Figure 3-18.

Figure 3-18: Site Layout Highlighting Segment 9

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Segment 9 consists of the following elements: • • • • •

Primary Clarifier 1 effluent weir Primary Clarifier 1 influent column and ports 36” and 42” Piping between the Raw Water Pump Station and the primary clarifiers Piping and valves on the raw water pump headers The raw water pumps

The hydraulic capacity of Segment 9 is determined based on maximum pipe velocity. The maximum pipe velocity in Segment 9 is observed in the 24” piping and valves downstream of the raw water pumps. As shown in Figure 3-19, the hydraulic capacity of Segment 9 is approximately 36.0 MGD.

Maximum Pipe Velocity in Segment (ft/s)

14.0 12.0 10.0

Maximum Pipe Velocity = 9.0 ft/s

8.0 6.0 4.0 2.0 0.0 0

Flow (MGD) Figure 3-19: Maximum Pipe Velocity in Segment 9 as a Function of Flowrate 3.3.2.10.

Segment 10: Grit Effluent Weirs to Influent Parshall Flume

Segment 10 includes the piping between the grit removal units and the Influent Parshall Flume. As stated in the previous section, it was assumed that the Influent Parshall Flume will be unsubmerged in every flow scenario due to adequate pumping capacity. Segment 10 is shown in Figure 3-20.

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Figure 3-20: Site Layout Highlighting Segment 10 Segment 10 consists of the following elements: • • • •

48” wide Influent Parshall Flume 48” piping between the Headworks facility and the Influent Parshall Flume Gates in grit removal effluent channels Channel losses downstream of the grit removal units

The majority of Segment 10 includes the full plant flow, therefore the flows modeled through the segment range from 5.0 MGD to 50.0 MGD. The maximum allowable WSE at the grit effluent weirs to meet the weir freeboard criterion is 382.78 ft. As shown in Figure 3-21, the hydraulic capacity of segment 10 is approximately 20 MGD.

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WSE at the Grit Efluent Weirs

385.50 385.00 384.50 384.00 383.50 383.00

Maximum WSE = 382.78 ft

382.50 382.00 381.50 381.00 0

Flow (MGD) Figure 3-21: WSE Downstream of Grit Removal Unit Effluent Weirs as a Function of Flowrate 3.3.2.11.

Segment 11: Screen Channel to Grit Effluent Weirs

Segment 11 consists of the headworks facility upstream of the grit effluent weirs, including the mechanical screen. The layout of this segment is shown in Figure 3-22.

Figure 3-22: Site Layout Highlighting Segment 11

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Segment 11 consists of the following elements: • • • •

Grit effluent weirs Grit detritor units 54” piping between the grit units and the screen channel Mechanical screen (assuming approximately 50% blinding)

The WSE within the headworks facility does not approach the top of the facility wall under the modeled flow conditions, therefore the pipe velocity within the 54” pipe between the screen channel and the grit channels was used to determine the hydraulic capacity of the segment. As shown in Figure 3-23, the pipe velocity doesn’t reach the maximum criterion of 9 ft/s within the flow conditions between 5.0 and 50.0 MGD, therefore the capacity of the segment is greater than 45 MGD. However, it should be noted that, due to the constraints of the downstream segment (Segment 10), the grit effluent weirs are submerged at flows above 20 MGD. 10.0

Maximum Pipe Velocity = 9.0 ft

Maximum Pipe Velocity in Segment (ft/s)

9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0

Flow (MGD) Figure 3-23: Pipe Velocity in Segment 11 as a Function of Flowrate

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3.3.2.12.

Westside Hydraulic Model Summary and Results

Table 3-2 shows a summary of the hydraulic capacity of the segments at the Westside WWTP; the segment capacities range from 13.0 MGD to greater than 50.0 MGD. Table 3-2: Summary of Hydraulic Capacity of Segments at the Westside WWTP Segment No. Segment 1 Segment 2 Segment 3 Segment 4 Segment 5 Segment 6 Segment 7 Segment 8 Segment 9 Segment 10 Segment 11

Notes: 1. When the receiving water body is at normal flood stage, the CCB has a capacity greater than 45 MGD. The main hydraulic constraints identified through the modeling effort include: • The Chlorine Contact Basin is flooded at the 100-year flood condition. • Due to the size and elevation of the influent Parshall flume and the yard piping in Segment 10, the grit effluent weirs are submerged at flows higher than 20 MGD. Submergence of these weirs can lead to inefficiencies within the grit removal system. • All modeled segments, except for segment 4 and segment 5, have a hydraulic capacity lower than the projected future peak flow of 47.2MGD. The plant requires improvements to alleviate these constraints at future flow conditions. 3.4. Southside WWTP The assumptions and results of the hydraulic analysis for the Southside WWTP are presented in this section.

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3.4.1.

Model Assumptions

The FEMA flood map of the Southside WWTP location was reviewed to determine the starting WSE in the receiving water body, West Mud Creek, during 100-year flood conditions. As shown in Figure 3-24, the starting WSE for the Southside WWTP hydraulic model is 424.00 ft. The majority of the Southside WWTP is located within the floodplain, which means that it is probable that the plant site will experience flooding during large rain events. However, unlike the Westside WWTP, the majority of the plant is not located within the floodway and planned construction will not require as extensive permitting and planning.

Figure 3-24: FEMA Flood Map of the West Mud Creek Near the Westside WWTP Record drawings as well as site survey data were used to develop the hydraulic model of the WWTP. Record drawings from the 1978, 1991, 1992, 2003, and 2020 plant improvements were reviewed to identify the design elevations and dimensions of the structures at the plant. In some cases, survey data was inconsistent with record drawing information. In such situations, survey data was used as the basis of the hydraulic analysis. The results of the survey and the methods used to incorporate those elevation differences into the hydraulic profile are included in Table 3-3. The table lists the record drawing elevations and dimensions along with the surveyed elevations of the different structures at the Southside WWTP along with the elevations and dimensions used in the hydraulic profile.

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Table 3-3: Comparison of Record Drawing and Survey Information at Southside WWTP Structure Outfall

CCB

Junction Box Junction Manhole Secondary Clarifier 2 Secondary Clarifier 3 Aeration Basin 2

Aeration Basin 3

Aeration Basin Splitter Box Primary Clarifiers Primary Clarifier Splitter Box

Headworks

Point Location Effluent Channel Invert EL Outer Walls EL Effluent Weir EL Effluent Weir Length Weir Wall EL Top of Wall EL Top of Concrete EL Top of Wall EL Weir EL Top of Wall EL Weir EL Top of Outer Wall EL Weir El Weir Length Top of Outer Wall EL Weir EL Weir Length Top of Wall EL AB 1&2 Weir EL AB 1&2 Weir Length AB 3 Weir EL AB 3 Weir Length Top of Wall EL Weir EL Top of Wall EL Weir EL Weir Length Top of Wall EL Grit Effluent Weir EL Grit Effluent Weir Length Parshall Flume EL

Record Drawing Value (ft)

Survey Elevation (ft)

Difference (ft)

Value Used in Profile (ft)

N/A

412.62

N/A

412.62

426.00 420.50

425.93 420.42

0.07 0.08

425.93 420.42

6.0

N/A

6.0

419.00 426.00

419.01 425.96

-0.01 0.04

419.01 425.96

N/A1

423.76

N/A

423.76

426.00 423.00 426.00 423.00

425.94 423.05 425.90 422.97

0.06 -0.05 0.1 0.03

425.94 423.05 425.9 422.97

426.00

426.08

-0.08

426.08

424.50 16.0

424.58 N/A

-0.08 N/A

424.58 16.0

427.00

426.83

0.17

426.83

424.50 30.0 434.00 427.00

424.46 N/A 433.94 427.60

0.04 N/A 0.06 -0.6

424.46 30.0 433.94 427.6

6.0

N/A

6.0

427.00 8.87 432.00 429.25 434.00 430.00 0.83 438.00

427.51 N/A 432.58 429.29 434.19 430.87 N/A 438.04

-0.51 N/A -0.58 -0.04 -0.19 -0.87 N/A -0.04

427.51 8.87 432.58 429.29 434.19 430.87 0.83 438.04

434.00

433.98

0.02

433.98

22.0

N/A

22.0

434.50

434.56

-0.06

434.56

Notes: 1. As-built information was not available in the provided record drawings.

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3.4.2.

Model Results – Hydraulic Sections

Figure 3-25 shows a layout of the existing Southside WWTP with the facilities and hydraulic segments labelled. The projected future ADF and P2HF for the Southside WWTP are 10.0 MGD and 39.5 MGD, respectively. The range of plant flows used in the hydraulic segment modeling range from 5.0 MGD to 45.0 MGD to capture any hydraulic capacity issues at current and future projected flows. The results of each hydraulic segment were used as the starting WSE of each subsequent segment in order to model the capacity of the plant segments collectively. The following sections discuss the hydraulic capacity of each segment and identify the limiting factors and bottlenecks of the existing plant.

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Figure 3-25: Southside WWTP Site Layout Identifying Hydraulic Segments Garver Project No. 21W05170

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3.4.2.1. Segment 1: Chlorine Contact Basin Effluent to Plant Outfall Treated effluent is discharged from the Southside WWTP to West Mud Creek through a 60-ft long effluent channel at the effluent of the Chlorine Contact Basin (CCB). As shown in Figure 3-24, the 100-year flood elevation at the plant discharge is 424.00 ft. This elevation was used as the starting WSE of the profile. The bottom of the chlorine contact basin effluent weir is set at 420.42 ft and therefore, at the 100-year flood stage condition, the existing chlorine contact basin will experience flooding of the effluent weir. Segment 1 is shown below in Figure 3-26.

Figure 3-26: Site Layout Highlighting Segment 1 3.4.2.2. Segment 2: Secondary Clarifier 2 to Chlorine Contact Basin Flow from the aeration basin splitter box is split into three independent trains, each containing an aeration basin and secondary clarifier. The two oldest trains, train 1 and 2, were constructed in 1978 and are identical, therefore it is assumed that they will have the same hydraulic capacity. Train 3 was constructed in 1992 and has a different configuration that that of train 1 and 2. The aeration basin splitter box was also constructed in 1992 and has different weir lengths designed to send approximately 44% of the total plant flow to train 3 and approximately 28% of the total plant flow to each of the aeration basins in train 1 and 2. Due to this flow split and the different configuration of the aeration basins, individual segments were modeled with the flow split assumptions to determine the hydraulic capacities of the different treatment trains. Train 1 & 2 were constructed identically, with the exception of yard piping. It was determined that the flow path of train 2 is a more conservative than that of train 1, therefore, the flow path through treatment train 2

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was used to analyze the hydraulic capacity of the trains. Segment 2 includes the chlorine contact basin and extends to the effluent launder of Secondary Clarifier 2. Segment 2 is shown in Figure 3-27.

Figure 3-27: Site Layout Highlighting Segment 2 Segment 2 consists of the following elements: • • • • •

The submerged chlorine contact basin effluent weir Channels and orifices within the CCB A junction box upstream of the CCB 48” and 36” piping between the CCB and Secondary Clarifier 2 The Secondary Clarifier 2 effluent launder channel

Flow through the majority of this segment includes 28% of the total plant flow. The hydraulic capacity of Segment 2 is determined by the weir freeboard requirements below the secondary clarifier weirs. However, similar to Segment 1, the 100-year flood elevation of the receiving water body, 424.00 ft, is higher than the elevation of the secondary clarifier weirs, 423.05 ft. Therefore, none of the flow scenarios modeled meet the criteria used in this analysis.

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3.4.2.3. Segment 3: Secondary Clarifier 3 to Chlorine Contact Basin Segment 3 includes the flow path within the chlorine contact basin and extends to the effluent launder channel of Secondary Clarifier 3. Segment 3 is shown in Figure 3-28.

Figure 3-28: Site Layout Highlighting Segment 3 The third hydraulic segment consists of the following elements: • • • •

The submerged chlorine contact basin effluent weir Channels and orifices within the chlorine contact basin 48” piping between the chlorine contact basin and Secondary Clarifier 3 The Secondary Clarifier 3 effluent launder channel

Flow through the majority of this segment includes 44% of the total plant flow. The effluent weirs of Secondary Clarifier 3 are set at 422.97 ft, which is lower than the 100-year flood elevation of the receiving water body. Therefore, similar to Segments 1 and 2, none of the flow scenarios meet the criteria used in this analysis.

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3.4.2.4. Segment 4: Aeration Basin 2 to Secondary Clarifier 2 Segment 4 includes Secondary Clarifier 2 and the piping between the clarifier and Aeration Basin 2. Segment 4 is shown in Figure 3-29.

Figure 3-29: Site Layout Highlighting Segment 4 Segment 4 consists of the following hydraulic elements: • • • •

Influent column and ports in Secondary Clarifier 2 30” piping between Aeration Basin 2 and Secondary Clarifier 2 Aeration Basin 2 effluent box 30” piping between Aeration Basin 2 effluent box and effluent weir

The flow through Segment 4 includes 28% of the total plant flow plus RAS; the flow analyzed through the segment ranges from 2.0 MGD to 17.0 MGD. The hydraulic constraint of Segment 4 is the aeration basin effluent weir. To determine the hydraulic capacity of this segment, the weir freeboard as well as TCEQ aeration basin wall freeboard criteria will be compared to the results of the hydraulic modeling effort. The maximum allowable WSE at the Aeration Basin 2 weir is 424.21 ft. As shown in Figure 3-30, every flow scenario above 2.0 MGD breaks this weir freeboard criterion. The hydraulic capacity of Segment 4 is therefore roughly 2.0 MGD; at flows higher than 2.0 MGD during the 100-year flood event, the weirs in Aeration Basin 2 will experience submergence and at flows higher than approximately 4.0 MGD, the WSE in Aeration Basin 2 will encroach upon wall freeboard of the structure.

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WSE at Aeration Basin 2 Weir (ft)

430.00 429.00 428.00

427.00 426.00 425.00

Wall Freeboard WSE = 424.58 ft Weir Freeboard WSE = 424.21 ft

424.00 423.00 0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

Flow (MGD) Figure 3-30: WSE Downstream of Aeration Basin 2 Weir as a Function of Flowrate

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3.4.2.5. Segment 5: Aeration Basin 3 to Secondary Clarifier 3 Segment 5 includes the flow path between Aeration Basin 3 and Secondary Clarifier 3. Segment 5 is shown in Figure 3-31.

Figure 3-31: Site Layout Highlighting Segment 5 Segment 5 consists of the following elements: • •

Final Clarifier 3 influent port and column 36” piping between Aeration Basin 3 and Final Clarifier 3

The flow through Segment 5 includes 44% of the total plant flow plus RAS; the total flow analyzed ranges from 2.9 MGD to 26.0 MGD. The flow velocity within the piping in the segment does not exceed the velocity criterion within the range of flows used for the hydraulic analysis. The hydraulic capacity of Segment 5 is determined based on the weir freeboard and TCEQ aeration basin wall freeboard criteria. Figure 3-32 shows the WSE downstream of the effluent weir in Aeration Basin 3 as a function of flowrate. The maximum WSE that meets weir freeboard criterion is 424.21 ft. As shown, the weir freeboard criterion is violated at the lowest flow scenario, 2.9 MGD. The hydraulic capacity of Segment 5 is therefore determined to be less than 2.9 MGD. During the 100-year flood event, the facility will experience submergence of the effluent weir and will experience flooding of the walls at a flow of 11.5 MGD.

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WSE at Aeration Basin 3 Weir (ft)

430.00 429.00 428.00 427.00 426.00

Wall Freeboard WSE = 425.33 ft 425.00

Weir Freeboard WSE = 424.21 ft 424.00 423.00

0.0

2.5

5.0

7.5

10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5

Flow (MGD) Figure 3-32: WSE Downstream of Aeration Basin 3 Effluent Weir as a Function of Flowrate 3.4.2.6. Segment 6: Aeration Basin Splitter Box to Aeration Basin 2 Segment 6 includes the flow path between the Aeration Basin Splitter Box and Aeration Basin 2. Segment 6 is shown in Figure 3-33.

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Figure 3-33: Site Layout Highlighting Segment 6 Segment 6 consists of the following hydraulic elements: • • •

Aeration Basin 2 Effluent Weir Aeration Basin 2 channels and openings 30” piping between the Aeration Basin Splitter Box and Aeration Basin 2

Flow through Segment 6 includes 28% of the total plant flow; the flows analyzed for the hydraulic analysis ranges from 1.50 MGD to 13.0 MGD. The flow velocity within the piping in the segment does not exceed the velocity criterion within the range of flows used for the hydraulic analysis. The hydraulic capacity of Segment 6 is determined based on the weir freeboard criterion. Figure 3-34 shows the WSE downstream of the effluent weir in the Aeration Basin Splitter Box as a function of flowrate. The maximum WSE that meets weir freeboard criterion is 427.35 ft. As shown, the weir freeboard criterion is violated at a flow of approximately 8.70 MGD; the flow capacity of this segment is therefore determined to be 8.70 MGD.

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WSE at Aeration Basin Splitter Box Weir (ft)

432.00 431.00 430.00

429.00 428.00

Maximum WSE = 427.35 ft

427.00 426.00

425.00 424.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

Flow (MGD) Figure 3-34: WSE Downstream of Aeration Basin Splitter Box as a Function of Flowrate 3.4.2.7. Segment 7: Aeration Basin Splitter Box to Aeration Basin 3 Segment 7 includes the flow path between the Aeration Basin Splitter Box and Aeration Basin 3. Segment 7 is shown in Figure 3-35.

Figure 3-35: Site Layout Highlighting Segment 7

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Segment 7 consists of the following hydraulic elements: • •

Aeration Basin 3 Effluent Weir 36” and 30” piping between the Aeration Basin Splitter Box and Aeration Basin 3

Flow through Segment 7 includes 44% of the total plant flow; the flows used in the hydraulic analysis of this segment range from 2.20 MGD to 19.80 MGD. The flow velocity within the piping in the segment does not exceed the velocity criterion within the range of flows used for the hydraulic analysis. The hydraulic capacity of Segment 7 is determined based on the weir freeboard criterion. Figure 3-36 shows the WSE downstream of the effluent weir in the Aeration Basin Splitter Box as a function of flowrate. The maximum WSE that meets weir freeboard criterion is 427.26 ft. As shown, the weir freeboard criterion is violated at a flow of approximately 13.20 MGD; the flow capacity of this segment is therefore determined to be 13.20 MGD.

WSE at Aeration Basin Splitter Box Weirs (ft)

432.00 431.00 430.00 429.00 428.00

Maximum WSE = 427.26 ft

427.00 426.00 425.00 424.00 423.00 422.00 0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

Flow (MGD) Figure 3-36: WSE Downstream of Aeration Basin Splitter Box as a Function of Flowrate

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3.4.2.8. Segment 8: Primary Clarifier 1 to Aeration Basin Splitter Box Segment 8 includes the flow path between Primary Clarifier 1 and the Aeration Basin Splitter Box. Segment 8 is shown in Figure 3-37.

Figure 3-37: Site Layout Highlighting Segment 8 Segment 8 consists of the following hydraulic elements: • • •

Aeration Basin Splitter Box weir Piping between the Aeration Basin Splitter Box and Primary Clarifier 1 Primary Clarifier 1 effluent launder trough

The main portion of Segment 8 includes half of the plant flow. The flows used for the analysis of Segment 8, therefore, range from 2.5 MGD to 22.5 MGD. The flow velocity within the piping in the segment does not exceed the velocity criterion within the range of flows used for the hydraulic analysis. The hydraulic capacity of Segment 8 is determined based on the weir freeboard criterion. Figure 3-38 shows the WSE downstream of the effluent weir in Primary Clarifier 1 as a function of flowrate. The maximum WSE that meets weir freeboard criterion is 429.04 ft. As shown, the weir freeboard criterion is violated at a flow of approximately 15.0 MGD; the flow capacity of this segment is therefore determined to be 15.0 MGD.

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432.50

WSE at the Primary Clarifier Weirs

432.00 431.50 431.00 430.50 430.00 429.50

Maximum WSE = 429.04 ft

429.00 428.50 428.00 427.50 0.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

Flow (MGD) Figure 3-38: WSE Downstream of Primary Clarifier 1 Weir as a Function of Flowrate

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3.4.2.9. Segment 9: Primary Clarifier Splitter Box to Primary Clarifier 1 Segment 9 includes the flow path between the Primary Clarifier Splitter Box and Primary Clarifier 1. Segment 9 is shown in Figure 3-39.

Figure 3-39: Site Layout Highlighting Segment 9 Segment 9 consists of the following hydraulic elements: • • •

Effluent weir in Primary Clarifier 1 Influent port and column in Primary Clarifier 1 42” pipe between Primary Clarifier 1 and the Primary Clarifier Splitter Box

Flow through Segment 9 is half of the total plant flow, therefore the flows used for the hydraulic analysis of the segment range from 2.5 MGD to 22.5 MGD. The flow velocity within the piping in the segment does not exceed the velocity criterion within the range of flows used for the hydraulic analysis. The hydraulic capacity of Segment 9 is determined based on the weir freeboard criterion. Figure 3-40 shows the WSE downstream of the effluent weir in the Primary Clarifier Splitter Box as a function of flowrate. The maximum WSE that meets weir freeboard criterion is 430.62 ft. As shown, the weir freeboard criterion is violated at a flow of approximately 19.0 MGD; the flow capacity of this segment is therefore determined to be 19.0 MGD.

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Maximum WSE in Primary Clarifier Splitter Box (ft)

433.50 433.00 432.50 432.00 431.50 431.00

Maximum WSE = 430.62 ft

430.50 430.00 429.50 429.00 0

2.5

7.5

12.5

17.5

22.5

Flow (MGD) Figure 3-40: WSE Downstream of Primary Clarifier Splitter Box as a Function of Flowrate

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3.4.2.10.

Segment 10: Grit Effluent Weirs to Primary Clarifier Splitter Box

Segment 10 includes the flow path between the grit effluent weirs and the primary clarifier splitter box. Segment 10 is shown in Figure 3-41.

Figure 3-41: Site Layout Highlighting Segment 10 Segment 10 consists of the following hydraulic elements: • • • • •

Effluent weir in the Primary Clarifier Splitter Box 42” piping between the Primary Clarifier Splitter Box and the Primary Clarifier Bypass Box Primary Clarifier Bypass Box 42” piping between the Primary Clarifier Bypass Box and the Headworks facility Grit effluent channel

Flow through the majority of the hydraulic segment includes the full plant flow, therefore, the flows used for hydraulic analysis of Segment 10 range from 5.0 MGD to 45.0 MGD. The pipe flow velocity throughout the segment does not violate the velocity criteria within the range of flows used for the hydraulic analysis. The

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determining factor for the hydraulic capacity of the segment is the weir freeboard below the grit effluent weirs. Figure 3-42 shows the WSE downstream of the grit effluent weirs as a function of flowrate. The maximum WSE that meets weir freeboard criterion is 466.73 ft. As shown, the weir freeboard criterion is violated at a flow of approximately 34.0 MGD; the flow capacity of this segment was therefore determined to be 34.0 MGD.

WSE at the Grit Effluent Weirs (ft)

438 437 436 435

Maximum WSE = 433.73 ft

434 433 432 431 430 0

Flow (MGD) Figure 3-42: WSE Downstream of the Grit Effluent Weirs as a Function of Flowrate

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3.4.2.11.

Segment 11: Influent Parshall Flume to Grit Effluent Weirs

Segment 11 includes the flow path between the Influent Parshall Flume and the grit effluent weirs. Segment 11 is shown in Figure 3-43.

Figure 3-43: Site Layout Highlighting Segment 11 Segment 11 consists of the following hydraulic elements: • •

Grit detritor unit (assumption of 0.5 ft of headloss through the system) Channel between the Influent Parshall Flume and the grit detritor unit

The flow through the majority of Segment 11 is half of the total plant flow, therefore the flow used for the hydraulic analysis ranges from 2.5 MGD to 22.5 MGD. The hydraulic capacity of Segment 11 is limited by the submergence level of the Influent Parshall Flume. The Parshall flume starts experiencing submergence at a downstream WSE of 436.50 ft. Figure 3-44 shows the WSE downstream of the Influent Parshall Flume as a function of flowrate. As shown, the maximum WSE to ensure proper function of the flume, 436.50 ft, is reached at a flowrate of approximately 21.0 MGD. Therefore, the hydraulic capacity of Segment 11 is 21.0 MGD.

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WSE Downstream of Parshall Flume (ft)

438.00 437.50

Wall Freeboard WSE = 436.50 ft 437.00

Weir Freeboard WSE = 436.50 ft

436.50 436.00 435.50

435.00 434.50 434.00 0

2.5

7.5

12.5

17.5

22.5

Flow (MGD) Figure 3-44: WSE Downstream of the Influent Parshall Flume as a Function of Flowrate

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3.4.2.12.

Segment 12: Influent Screw Pumps to Influent Parshall Flume

The final segment of the Southside WWTP is Segment 12 which includes the elements between the Influent Parshall Flume and the Influent Screw Pump effluent channel. Segment 12 is shown in Figure 3-45.

Figure 3-45: Site Layout Highlighting Segment 12 Segment 12 consists of the following hydraulic elements: • • • •

48” Parshall flume Channel between Parshall flume and screen channel Mechanical bar screen (assumed to be 50% blinded) Channel between screen channel and influent screw pump effluent channel

The flow through the majority of Segment 12 is the full plant flow, therefore the flows used for the hydraulic analysis range from 5.0 MGD to 45.0 MGD. The hydraulic capacity of Segment 12 is limited by the wall freeboard criterion. Figure 3-46 shows the WSE downstream of the influent screw pumps as a function of flowrate. As shown, the WSE within the channel reaches the maximum allowable elevation to meet the freeboard criterion, 437.04 ft, at a flow of 10.0 MGD. The capacity in this section is majorly affected by the size and elevation of the Influent Parshall Flume; the flume is 3-ft wide and the invert is set at 434.56 ft, which results in a high WSE downstream of the screen channels. In addition, the mechanical screens were assumed to be 50% blinded to provide a conservative idea of the WSE within the headworks facility.

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WSE Downstream of Influent Screw Pumps(ft)

441.50

441.00 440.50 440.00 439.50 439.00 438.50

T/Wall Elevation = 438.00 ft

438.00

437.50

WSE to maintain 1-ft of freeboard = 437.04 ft

437.00 436.50 436.00 0

Flow (MGD) Figure 3-46: WSE Downstream of Influent Screw Pumps as a Function of Flowrate

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3.4.2.13.

Southside Hydraulic Model Summary

Table 3-4 shows a summary of the hydraulic capacity of the segments at the Southside WWTP; the segment capacities range from 2.0 MGD to 34.0 MGD. Table 3-4: Summary of Hydraulic Capacity of Segments at the Southside WWTP Segment No. Segment 1 Segment 2 Segment 3 Segment 4 Segment 5 Segment 6 Segment 7 Segment 8 Segment 9 Segment 10 Segment 11 Segment 12

Segment Identifier Chlorine Contact Basin Effluent to Plant Outfall Secondary Clarifier 2 to Chlorine Contact Basin Secondary Clarifier 3 to Chlorine Contact Basin Aeration Basin 2 to Secondary Clarifier 2 Aeration Basin 3 to Secondary Clarifier 3 Aeration Basin Splitter Box to Aeration Basin 2 Aeration Basin Splitter Box to Aeration Basin 3 Primary Clarifier 1 to Aeration Basin Splitter Box Primary Clarifier Splitter Box to Primary Clarifier 1 Grit Effluent Weirs to Primary Clarifier Splitter Box Influent Parshall Flume to Grit Effluent Weirs Influent Screw Pumps to Influent Parshall Flume

Hydraulic Capacity at 100-Year Flood

Hydraulic Capacity at Normal Flood Levels1

N/A

45.0 MGD

N/A N/A 2.0 MGD (28% of plant flow + RAS) < 2.90 MGD (44% of plant flow + RAS) 8.70 MGD (28% of plant flow) 13.20 MGD (44% of plant flow)

7.2 MGD (28% of plant flow) 10.3 MGD (44% of plant flow) 11.2 MGD (28% of plant flow + 28% of RAS) 17.0 MGD (44% of plant flow + 44% of RAS) 11.5 MGD (28% of plant flow) 17.5 MGD (44% of plant flow)

Hydraulic Limitation Floodway elevation is flooding CCB Effluent Weir Floodway Elevation is flooding secondary clarifier weirs Floodway Elevation is flooding secondary clarifier weirs Aeration Basin 2 weir is flooded Aeration Basin 3 weir is flooded Aeration Basin Splitter Box weir is flooded Aeration Basin Splitter Box weir is flooded

15.0 MGD (50% of plant flow)

Primary clarifier weir is flooded

19.0 MGD (50% of plant flow)

Primary Clarifier Splitter Box is flooded

34.0 MGD (total plant flow)

Grit effluent weir is flooded

21.0 MGD (50% of plant flow)

Parshall flume is submerged

10.0 MGD (total plant flow)

Walls of headworks structure are flooded

Notes: 1. Segments were also analyzed based on a starting WSE within the river of 419.50 ft to determine the “non-flooded” hydraulic capacity, independent of the 100-year flood elevation.

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The main hydraulic constraints identified through the modeling effort include: • The weirs of the chlorine contact basin and secondary clarifiers are flooded at the 100-year flood condition • Due to the size and elevation of the influent Parshall flume, there is little room within the headworks facility to allow for variations in the level of blinding of the mechanical screens. The water surface elevation inside of the headworks facility violates wall freeboard criteria at flows higher than 10 MGD when the screens are 50% blinded. The plant requires improvements to alleviate these constraints at future flow conditions.

4. Gap Analysis The purpose of the gap analysis is to identify areas at the WWTPs that don’t have sufficient capacity to treat the projected future flow and loadings. The future flow and loadings presented in the planning criteria TM were used to determine future required capacity of each facility at the Westside and Southside WWTPs. When determining each facility’s capacity, the following industry-accepted design and operating standards were used: • • • •

Planning criteria (flow and loadings) developed for each facility, shown in Table 4-1. TCEQ requirements for wastewater treatment facilities Design of Water Resource Recovery Facilities Manual of Practice (Water Environment Federation, MOP 8) Wastewater Engineering: Treatment and Resource Recovery, Metcalf and Eddy (M&E) Table 4-1: Projected Future Flow and Loadings to the Westside and Southside WWTPs Flow (MGD)

BOD (mg/L)

BOD (lb/d)

TSS (mg/L)

TSS (lb/d)

NH3-N (mg/L)

NH3-N (lb/d)

TP (mg/L)

TP (lb/d)

Westside WWTP Average Day Max Month1 Peak 2Hour Flow

162

18,920

180

21,020

2,670

6.5

760

20.4

24,210

29,420

3,950

990

47.22

Southside WWTP Average 10 146 12,180 259 21,600 20 1,670 4.3 360 Day Max 12.8 15,340 31,320 2,150 470 Month1 Peak 239.52 Hour Flow Notes: 1. Constituent max month loadings are based on peaking factors shown in Table 2-1 applied to the average daily loadings. 2. The peak 2-hour flow through the processes downstream of the headworks and influent pump stations will be capped at 36 MGD for Westside and 22.5 MGD for Southside through the use of a Peak Flow Basin (PFB).

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The capacities of the mechanical components of each facility were determined, based on the size of the equipment as well as the condition concerns identified in the Historical Data Review TM. These capacities along with the capacities identified by the process model and hydraulic model were used to determine the gaps. 4.1. Westside WWTP This section discusses the capacity evaluation and gap analysis results for the Westside WWTP liquid and solid treatment facilities. The disparities between the capacity of the existing facilities and the capacity required to meet the treatment demand for the future planning horizon of 2052 are presented. One recommended improvement that will impact the gap analysis is the use of a Peak Flow Basin (PFB) to shave the peak flow requirements of the treatment plant processes. This recommendation was introduced in the Peak Flow Comparison TM and was discussed with the City in recent project workshops. Costs for plant upgrades including and excluding a PFB were estimated, and it was concluded that a PFB would be cost effective by reducing the required improvements and would ensure that the design is conservative for future peak flow projections. The first-stage TFs have an available storage volume of 1.4 million gallons (MG) and were proposed to be utilized as future PFBs. A hydrograph of the peak storm event at the plant was used to determine the peak flow through the plant (downstream of the headworks facility) if the first-stage TF basins are utilized for peak flow storage. As shown in Figure 4-1, this results in a peak flow through the main treatment processes of 36.0 MGD.

Figure 4-1: Peak Day Hydrograph for Westside WWTP Figure 4-1 depicts the influent flow over a 24-hour period entering the Westside WWTP. The area under the hydrograph curve and above the yellow line, called out as 36 MGD, is the volume of influent required to be stored to maintain a flow of 36 MGD through the plant. It was assumed during the gap analysis that a 1.4 MG PFB will be utilized in the future to reduce the required peak flow through the processes downstream of the raw water pump station from 47.2 MGD to 36 MGD. The gaps shown in the tables throughout this section reflect the use of this PFB. Design alternatives for the PFB will be reviewed in Section 5.

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4.1.1

Mechanical Screen

The headworks facility at the Westside WWTP contains one mechanical screen. A bypass pipe allows operators to divert influent flow directly to the grit removal units if necessary. However, this bypass does not have any screening capabilities and therefore, utilizing this flow path negatively impacts the downstream processes. The facility’s criticality ranking was determined to be critical. TCEQ requires that the facility must be able to catch screenings from the raw influent at predicted peak flows and have emergency overflow capacity to maintain screen removal operation in the event of a mechanical screen mechanism failure. The proposed PFB will be located downstream of the headworks facility to ensure that screenings and grit are removed prior to peak flow storage and therefore will not buffer the peak flow going to the facility. The gap analysis for the mechanical screens is shown in Table 4-2. Table 4-2: Westside WWTP Mechanical Screen Gap Analysis TCEQ Design Criteria Number of Process Units1

Screen Capacity

Existing Capacity

Future Required Capacity

Existing Gap

N/A

32.5 MGD 2

47.2 MGD

None

14.7 MGD

Overall Facility Gap

None

14.7 MGD

Future Gap

No redundancy

Notes: 1. Screen system must have overflow screening capacity capable of handling the peak flow, required by TAC 217.121(b) 2. Capacity shown does not include redundancy. In addition, the emergency overflow is not equipped with a manual screen. 4.1.2

Grit Removal

Screened flow enters the two detritor grit removal units. Each unit has a dedicated grit auger that lifts settled particles from the grit collection sump to a dumpster for disposal. The facility was determined to be in critical condition due to performance failure and the poor condition of equipment and concrete structure. At flows above 20 MGD, the weir freeboard criterion for the grit basins is violated, limiting the hydraulic capacity of the facility. The capacity evaluation of the grit removal facility is shown in Table 4-3. Table 4-3: Westside WWTP Grit Removal Gap Analysis Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

20 MGD

47.2 MGD

12.5 MGD

27.2 MGD

≥2

N/A

≤ 1.0 ft/s

72.4 MGD

47.2 MGD

None

Overall Facility Gap

12.5 MGD

27.2 MGD

TCEQ Design Criteria Hydraulic Capacity Number of Process Units1 Grit Chamber Velocity2

Notes: 1. Redundancy required by TAC 217.124 (c) 2. TAC 217.125(c)(1) requires velocity through mechanical grit chamber to be no greater than 1 ft/s; calculations assumed lowest allowed velocity

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4.1.3

Raw Water Pump Station

From the grit removal facility, the flow passes through a Parshall flume and is discharged into a wet well. Three 200-hp vertical dry-pit pumps lift the flow and send it to the primary clarifiers. The pumps are in fair condition. Each pump is rated for 17.5 MGD, providing a firm capacity of 35.0 MGD. An additional 12.2 MGD of pumping capacity is required to handle future peak flows with one standby pump. The existing wet well was also evaluated for hydraulic capacity. Due to the wet well’s dimensions and the pump configuration, the volume in the wet well that is available for storage is very low. In addition, the spacing within the wet well was compared to spacing recommendations provided by Hydraulic Institute and industry experts in wet well design and it was found to be smaller than recommended to ensure proper pump performance at peak flows above 32 MGD. The capacity evaluation of the raw water pump station is shown in Table 4-4. Table 4-4: Westside WWTP Raw Water Pump Station Gap Analysis TCEQ Design Criteria

Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

Number of Process Units1

N/A

Header Piping Capacity1

Peak Flow

36 MGD

47.2 MGD

None

11.2 MGD

Peak Flow

35 MGD

47.2 MGD

None

12.2 MGD

Peak Flow

32 MGD

47.2 MGD

0.5 MGD

15.2 MGD

Overall Facility Gap

0.5 MGD

15.2 MGD

Firm Pumping Capacity Wet Well Capacity

Notes: 1. Header piping capacity is based on velocity within the pipes. As presented in the hydraulic modeling section of the TM, if the pipe velocity reaches 9 ft/s or higher, the piping is considered undersized. 2. As required by TAC 217.61(c), pump capacity must be able to handle peak flows with one unit out of service 3. The wet well capacity was estimated based on the dimensions recommended by Hydraulic Institute and industry experts for proper pump performance. 4.1.4

Primary Clarifiers

Flow pumped by the Raw Water Pump Station arrives at two 150-ft diameter primary clarifiers that co-settle WAS with the raw influent. The clarifiers have double-sided weirs, and each clarifier has a scum pump that pumps the scum removed from the clarifier surface to the anaerobic digesters. The primary clarifiers were determined to have a medium criticality. TCEQ regulatory requirements were used to determine the capacity of the existing facility, including the following loading rates: • •

•

Weir loading rate (peak flow) ≤ 30,000 gpd/ft Surface loading rate (SLR) (peak flow) ≤ 1800 gpd/ft2 o A maximum SLR of 1200 gpd/ft2 at peak flows will be used in this gap analysis. A lower solids loading rate is more appropriate because the primary clarifiers are currently used to co-settle WAS and primary sludge. SLR (design flow) ≤ 1000 gpd/ft2 o A design SLR of 600 gpd/ft2 will be used because of the co-settling operation.

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The capacity evaluation of the primary clarifiers is presented in Table 4-5. If the proposed PFB is constructed, the primary clarifiers have sufficient weir length and surface area to treat future flows. However, it is recommended that the co-settling method be discontinued to increase the efficiency of the primary clarifiers. Table 4-5: Westside WWTP Primary Clarifiers Gap Analysis

Number of Process Units1

Future Required Capacity N/A

Weir Loading Rate2 (peak)

≤ 30,000 gpd/ft

53.2 MGD

36.0 MGD

None

Surface Loading Rate2,3 (peak)

≤ 1200 gpd/ft2

42.4 MGD

36.0 MGD

None

≤ 600 gpd/ft

21.2 MGD

14.0 MGD

None

Existing Capacity

TCEQ Design Criteria

2,3

Surface Loading Rate

(design)

Existing Gap

Future Gap (with PFB)

N/A

Overall Facility Gap None None Notes: 1. Redundancy required by TAC 217.153(c)(1) 2. Weir and surface loading rates required by TAC 217.129 3. The SLR criteria is based on industry standard design practices regarding co-settling primary clarifiers. The capacity of the facility based on solids loading rate would be 63 MGD (peak) and 35.3 MGD (design) if co-settling was no longer practiced. 4.1.5

Biological Treatment Train

Primary effluent is sent to the biological treatment train for Biochemical Oxygen Demand (BOD) and Ammonia (NH3) removal. The train consists of the first-stage trickling filters (TFs), the second-stage TFs, and the nitrification basin. The BOD removal capacity was calculated as a part of the biological modeling effort with assumptions to accurately represent the TFs capacity based on their current condition. The nitrification basin is suspected to have a sand buildup that takes up as much as half of the available basin volume. This was represented in the process model to capture the realistic organic loading capacity of the basin. The capacity of the basins after cleaning was also calculated for reference. In addition, the aeration capacity was calculated based on the TCEQ requirement of 2.2 lb O2/lb BOD. The capacity evaluation of the biological treatment train is shown in Table 4-6. The facilities in their current condition must be able to handle an additional 10,000 lb BOD/day at future MM conditions. If in the future the TFs are decommissioned due to age and condition, the rated BOD removal capacity will decrease.

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Table 4-6: Westside WWTP Biological Treatment Train Gap Analysis Design Criteria Organic Loading Capacity (assuming sand buildup) Organic Loading Capacity (assuming basins have been cleaned) Aeration ≥ 2.2 lb O2/lb Requirements2 (MM) BOD

Existing Capacity 4,500 lb BOD/day 10,800 lb BOD/day1 15,500 lb O2/day 3

Future Required Capacity 14,500 lb BOD/day

Existing Gap 5,000 lb BOD/day None

32,000 lb O2/day Overall Facility Gap

6,000 lb O2/day 5,000 lb BOD/day

Future Gap 10,000 lb BOD/day 3,700 lb BOD/day 16,500 lb O2/day 10,000 lb BOD/day

Notes: 1. TAC 217.154(b)(2),Table F-1 states that the loading rate should not exceed 35 lb BOD/1000 cf-day 2. Aeration requirements as specified in TAC 217.155(a)(3), Table F-3. 3. The existing aeration capacity was calculated based on the current state of the surface aerators; Two of the existing 120 HP surface aerators are currently out of service and need to be replaced. 4.1.6

Filter Pump Station

The filter pump station directs flow to the tower splitter box. The facility consists of three 200-hp pumps and is in critical condition due to lack of redundancy. Each pump has a capacity of 23 MGD, and assuming one pump is on standby, the firm capacity is 46 MGD. No additional pumping capacity is needed to handle peak flows, however there is no way to isolate the pumps for maintenance. The capacity evaluation for the filter pump station is presented in Table 4-7. Table 4-7: Westside WWTP Filter Pump Station Gap Analysis TCEQ Design Criteria Number of Process Units Firm Capacity

Existing Capacity 3 46 MGD1

Future Required Capacity N/A 36.0 MGD Overall Facility Gap

Existing Gap N/A None None

Future Gap (with PFB) N/A None None

Notes: 1. As required by TAC 217.61(c), firm capacity must be able to handle peak flows 4.1.7

Secondary Clarifiers

Effluent from the biological treatment train is sent to the secondary clarifiers. Sludge is wasted through a gravity discharge line at each clarifier and is conveyed to the light sludge pump station. TCEQ regulatory requirements were used to calculate the current capacity of the secondary clarifiers, including the following loading rates: • •

Weir loading rate (peak flow) ≤ 30,000 gpd/ft Surface loading rate (peak flow) ≤ 1,200 gpd/ft2

The hydraulic capacity is limited by the weir loading rate, leaving a gap of 8.9 MGD in the treatment capacity at future peak flows. The capacity evaluation of the secondary clarifiers is presented in Table 4-8.

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Table 4-8: Westside WWTP Secondary Clarifiers Gap Analysis

≥2 ≤ 30,000 gpd/ft

Existing Capacity 2 27.1 MGD

Future Required Capacity N/A 36.0 MGD

Existing Gap N/A 5.4 MGD

Future Gap (with PFB) N/A 8.9 MGD

≤ 1,200 gpd/ft2

42.4 MGD

36.0 MGD

None

5.4 MGD

8.9 MGD

TCEQ Design Criteria Number of Process Units1 Weir Loading Rate2 (peak) Surface Loading Rate3 (peak)

Overall Facility Gap Notes: 1. Redundancy required by TAC 217.153(c)(1) 2. Weir loading rate specified in TAC 217.152(d)(5) 3. Surface loading rate specified in TAC 217.154(c)(1), Table F-2 4.1.8

RAS Pump Station

The RAS pump station sends sludge from the secondary clarifiers to the tower splitter box to be mixed with nitrification basin influent. The facility consists of three 60-hp centrifugal pumps that are operated manually. The facility is in fair condition overall, however due to the high consequence of failure, the facility was assigned a high criticality. 4.1.9

Chlorine Building

The chlorine building houses the chlorine gas cylinders used for disinfection and the sulfur dioxide (SO2) cylinders used for dechlorination. A design improvements project is currently in progress to address the issues at the facility. The chlorine building houses 12 chlorine cylinders and 12 sulfur dioxide cylinders, 8 of each are connected to a chemical distribution manifold and are used to dose the chemicals at the plant. The remaining cylinders are used for additional storage capacity. As shown in Table 4-9, the facility does not have a gap in capacity. However, the facility was found to be in critical condition. Table 4-9: Westside WWTP Chlorine Building Gap Analysis TCEQ Design Criteria

Storage Required

15 days

Dosage (Peak Flow)

6 mg/L

Storage Required Dosage (Peak Flow)

15 days 1.5 mg/L

Existing Future Required Capacity Capacity Chlorine Gas 12 tons 5.3 tons1

Existing Gap

Future Gap

None

None None

6,720 lb/day 1,800 lb/day Sulfur Dioxide 12 tons 2 tons1 1,920 lb/day 450 lb/day2

Overall Facility Gap None None Notes: 1. Storage requirement was calculated based on average day flow conditions and a required chlorine dosage of 6 mg/L and a require sulfur dioxide dosage of 1.5 mg/L. 2. Peak flow dosage was calculated using the peak two hour flow of 36.0 MGD. The calculation also assumed a maximum dosage capacity of each chlorine cylinder of 560 lb/day and of each sulfur dioxide cylinder of 240 lb/day.

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4.1.10 Chlorine Contact Basin The chlorine contact basin (CCB) consists of two channels where secondary effluent is disinfected and dechlorinated. The current capacity of the facility was found using the TCEQ criterion for minimum contact time required to achieve proper disinfection at peak flows. A treatment gap of 6.3 MGD was identified. The capacity evaluation of the CCB facility is shown in Table 4-10. Table 4-10: Westside WWTP Existing CCB Gap Analysis TCEQ Design Criteria Minimum Contact Time1

20 min

Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

29.7 MGD

36.0 MGD

2.8 MGD

6.3 MGD

2.8 MGD

6.3 MGD

Overall Facility Gap Notes: 1. Minimum contact time required by TAC 217.281(b)(1) 4.1.11 Oxygenation

Post-aeration is provided within the CCB; a total of four 5-hp surface aerators increase the dissolved oxygen (DO) level in the effluent before it is discharged to Black Fork Creek. The surface aerators are in fair condition, however, one of the units is currently out of service. A gap was calculated for both the existing design conditions and future design conditions based on the permitted effluent DO requirement. The results of the gap analysis are shown in Table 4-11. Table 4-11: Westside WWTP Oxygenation Gap Analysis Design Criteria Aeration Requirement

Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

960 lb O2/day1

1,500 lb O2/day 2

395 lb O2/day

540 lb O2/day

Overall Facility Gap

395 lb O2/day

540 lb O2/day

Notes: 1. Existing surface aerators can provide 2.0 lb O2 per HP and have a combined power of 20 HP. 2. Future required capacity is based on a peak flow of 36 MGD. 4.1.12 Anaerobic Digesters The 100-ft diameter anaerobic digesters receive co-settled WAS and primary sludge from the primary clarifiers. The digesters are in poor condition; digester basin 1 is currently not in use due to the digester cover sinking into the basin. Digester basin 2 is currently used for sludge storage prior to dewatering. The facility has been determined to be in critical condition due to its poor condition and the need for operational reliability. The current capacity includes both anaerobic digesters. The future required capacity is based on the minimum solids retention time (SRT) required and predicted solids production at MM conditions, which was calculated in the whole-plant mass balance. No storage gap was identified. The capacity evaluation of the anaerobic digesters is presented in Table 4-12.

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Table 4-12: Westside WWTP Anaerobic Digesters Gap Analysis Design Criteria Number of Process Units Storage Capacity

Existing Capacity 2 3.2

Future Required Capacity N/A 0.57 MG1 Overall Facility Gap

Existing Gap N/A None None

Future Gap N/A None None

Notes: 1. Minimum SRT of 4 days 4.1.13 Primary Sludge and Belt Filter Press Pump Station The primary sludge pumps and belt filter press (BFP) pumps are housed in the same facility. The primary sludge pumps transfer primary sludge from the primary clarifiers to the anaerobic digesters and the BFP pumps send digested sludge to the dewatering building. The facility consists of four 5-hp double-disk primary sludge pumps and two 20-hp double disk BFP pumps that are located below grade in a pump station. 4.1.14 Sludge Dewatering Facility The dewatering facility consists of two 2-m BFPs, two polymer feed units, a grinder, and two 7.5-hp booster pumps. The facility is overall in good condition. Industry standards were used to calculate the current sludge dewatering capacity, including the following loading rates: • •

Hydraulic loading rate ≤ 100 gpm/m Solids Loading rate ≤ 800 lb/h-m

The gap analysis assumes that the BFPs will be operated 8 hrs/day, 5 days/wk with the projected BFP solids and hydraulic loading rates at future AADF conditions. The capacity evaluation for the dewatering facility is shown in Table 4-13. An additional 2,470 lb/h of dewatering capacity is required. Table 4-13: Westside WWTP Dewatering Facility Gap Analysis Design Criteria Number of Process Units1 Hydraulic Loading Rate2 Solids Loading Rate2

≥2 100 gpm/m 800 lb/h-m

Existing Capacity 2 400 gpm 3,200 lb/h

Future Required Capacity N/A 419 gpm 3 5,670 lb/h 3

Existing Gap N/A None 627 lb/hr

Future Gap N/A 19 gpm 2,470 lb/h

Overall Facility Gap

627 lb/hr

2,470 lb/h

Notes: 1. Redundancy required by TAC 217.250(c)(3) 2. BFP capacity criteria is based on industry standards 3. Required capacity was found in the whole-plant mass balance, assuming 5 days/wk, 8 h/day operation at future MM conditions.

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4.1.15. Westside WWTP Gap Analysis Summary Table 4-14 summarizes the capacity gaps identified at the Westside WWTP. As shown, the gaps range from no gap up to a gap of 27.2 MGD. These gaps along with the identified condition of the facilities and mechanical components will be used in Section 5 to develop design recommendations. Table 4-14: Westside WWTP Gap Analysis Summary Facility Mechanical Screens Grit Removal Raw Water Pump Station Primary Clarifiers Biological Treatment Train Filter Pump Station Secondary Clarifiers Chlorine Facility – Chlorine Gas Chlorine Facility – Sulfur Dioxide Chlorine Contact Basin Oxygenation Anaerobic Digesters Sludge Dewatering Facility

Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

32.5 MGD 20.0 MGD 32.0 MGD 42.4 MGD 4,500 lb BOD/day 46 MGD 27.1 MGD 6,720 lb/day 1,920 lb/day 29.7 MGD 960 lb O2/day 3.2 MG 3,200 lb/hr

47.2 MGD 47.2 MGD 47.2 MGD 36.0 MGD 14,500 lb BOD/day 36.0 MGD 36.0 MGD 1,800 lb/day 450 lb/day 36.0 MGD 1,500 lb O2/day 0.57 MG 5,670 lb/hr

None 12.5 MGD None None 5,000 lb BOD/day None 5.4 MGD None None 2.8 MGD 395 lb O2/day None 627 lb/hr

14.7 MGD 27.2 MGD 15.2 MGD None 10,000 lb BOD/day None 8.9 MGD None None 6.3 MGD 540 lb O2/day None 2,470 lb/hr

4.2. Southside WWTP This section discusses the capacity evaluation and gap analysis results for the Southside WWTP liquid and solid treatment facilities. The disparities between the capacity of the existing facilities and the capacity required to meet the treatment demand for the future planning horizon of 2052 are presented.

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Similar to the Westside WWTP, a Peak Flow Basin (PFB) is recommended for the Southside WWTP as well to reduce the hydraulic improvements for the processes downstream of the headworks facility. The peak day hydrograph for the Southside WWTP was utilized to determine the required volume of storage to reduce the peak flow through the plant processes from 39.5 MGD to the plant’s current peak flow of 22.5 MGD. Figure 4-2 shows the peak hydrograph exhibiting the influent flow to the Southside Plant over a 24hour period. A 1 MG PFB is proposed to limit the peak flow through the treatment processes to 22.5 MGD.

Figure 4-2: Southside WWTP Peak Flow Hydrograph Figure 4-2 depicts the influent flow over a 24-hour period entering the Southside WWTP. The area under the hydrograph curve and above the yellow line, called out as 22.5 MGD, is the volume of influent required to be stored to maintain a flow of 22.5 MGD through the plant. It was assumed during the gap analysis that the PFB will be constructed in the future to reduce the required peak flow through the processes downstream of the headworks facility from 39.5 MGD to 22.5 MGD. The gaps shown in the tables throughout this section reflect the use of this PFB. Design alternatives for the PFB will be reviewed in Section 5. 4.2.1

Influent Screw Pumps

The influent flow is lifted to the headworks facility by four screw pumps. The pumps were rehabilitated in 2021 and remain in good condition. Each pump is rated for 7.24 MGD. With one standby pump, the firm capacity is 21.7 MGD. Future peak flows require an additional 17.8 MGD of pumping capacity. A summary of the gap analysis for the influent screw pumps is presented in Table 4-15.

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Table 4-15: Southside WWTP Influent Screw Pumps Gap Analysis Design Criteria Number of Process Units1 Firm Capacity1

>1 Peak Flow

Existing Capacity 4 21.7 MGD

Future Required Capacity N/A 39.5 MGD Overall Facility Gap

Existing Gap N/A 0.8 MGD 0.8 MGD

Future Gap N/A 17.8 MGD 17.8 MGD

Notes: 1. Redundancy required by TAC 217.61(c), firm capacity must be able to handle peak flows 4.2.2

Mechanical Screens

The influent screw pumps lift raw sewage to the two mechanical chain and rake screens. Screenings are removed and conveyed to a dumpster adjacent to the facility. The screens were installed recently and are in good working condition. The current capacity of each screen is 13.0 MGD, and since the facility is lacking overflow screening capacity, this makes the facility’s firm capacity 13.0 MGD as well. Therefore, a gap of 26.5 MGD was identified. The gap analysis of the mechanical screen is shown in Table 4-16. Table 4-16: Southside WWTP Mechanical Screens Gap Analysis Existing Capacity

Design Criteria Number of Process Units1 Firm Capacity

>1 ≥ 12 in

2 13.0 MGD

Future Required Capacity

Existing Gap

Future Gap

N/A

39.5 MGD

9.5 MGD

26.5 MGD

Overall Facility Gap

9.5 MGD

26.5 MGD

Notes: 1. Screen system must have overflow screening capacity capable of handling the peak flow, required by TAC 217.121(b) 2. Calculation assumes one screen unit out of service. 4.2.3

Grit Removal

After screening, the flow enters a Parshall flume for flow measurement and is then split between two grit removal units. Each unit consists of a grit detritor basin, grit pump, and grit cyclone/classifier. Classified grit is disposed of in a dumpster. Overall, the facility is in decent condition except for one of the grit classifiers being out of service.

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The current capacity was determined with TCEQ criteria for horizontal velocity within the detritor basins. A summary of the gap analysis for the grit removal facility is provided in Table 4-17. Table 4-17: Southside WWTP Grit Removal Gap Analysis Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

≥2

N/A

≤ 1.0 ft/s

31 MGD

39.5 MGD

None

8.5 MGD

Overall Facility Gap

None

8.5 MGD

Design Criteria Number of Process Units1 Grit Chamber Velocity2

Notes: 1. Redundancy required by TAC 217.124(c) 2. TAC 217.125(c)(1) requires velocity through mechanical grit chamber to be no greater than 1.0 ft/s; calculations assumed lowest allowed velocity 4.2.4

Primary Clarifiers

De-gritted flow enters the primary clarifier bypass splitter box where it can be directed to the primary clarifier splitter box or bypass the clarifiers and flow to the aeration basin splitter box. The capacity evaluation assumes that a PFB will be constructed to limit the peak flow sent to the primary clarifiers. The primary clarifier mechanisms were recently replaced and remain in good condition. TCEQ regulatory requirements were used to determine the capacity of the existing facility, including the following loading rates: • • •

Weir loading rate (peak flow) ≤ 30,000 gpd/ft Surface loading rate (peak flow) ≤ 1,800 gpd/ft2 Surface loading rate (design flow) ≤ 1,000 gpd/ft2

The future required capacities are based on the projected ADF and P2HF (buffered by a PFB). The current capacity is sufficient at average flows, but not at peak flows. The gap predicted is 4.4 MGD, which was determined with the weir loading rate criterion at peak flows. A summary of the gap analysis is provided Table 4-18. Table 4-18: Southside WWTP Primary Clarifiers Gap Analysis TCEQ Design Criteria Number of Process Units1

≥2

Existing Capacity

Future Required Capacity

Existing/Future Gap (with PFB)

N/A

≤ 30,000 gpd/ft

18.1 MGD

22.5 MGD

4.4 MGD

≤ 1,800 gpd/ft

28.3 MGD

22.5 MGD

None

≤ 1,000 gpd/ft

15.7 MGD

10.0 MGD

None

Weir Loading rate (peak) Surface Loading Rate (peak) Surface Loading Rate (design)

Overall Facility Gap 4.4 MGD Notes: 1. Redundancy required by TAC 217.153 2. Weir and surface loading rates required by TAC 217.129(c)(5) and TAC 217.129(d)(3)(A)(i),(ii)

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4.2.5

Primary Sludge Pump Station

The primary sludge pump station houses two 20-hp progressive cavity pumps that send primary sludge to the sludge holding tank and anaerobic digesters. The pumps were recently installed and are in good condition. Each primary sludge pump is rated for 125 gpm. The future operational capacity requires no additional pumping capacity. The capacity evaluation of the primary sludge pump station is presented in Table 4-19. Table 4-19: Southside WWTP Primary Sludge Pump Station Gap Analysis Design Criteria Number of Process Units Firm Capacity

Existing Capacity 4 250 gpm

Future Required Capacity N/A 250 gpm Overall Facility Gap

Existing/Future Gap (with PFB) N/A None None

Notes: 1. TAC 217.244(b) requires firm capacity provided with largest unit out of service 4.2.6

Aeration Basins

The aeration basin splitter box divides primary effluent between the three aeration basins. Aeration Basins 1 and 2 are identical. The three outer channels are aerated by 40-hp brush surface aerators and the two center channels are used for anaerobic digestion of WAS. Aeration Basins 1 and 2 were determined to be in critical condition due to frequent operational issues and age. Aeration Basin 3 was constructed later and is configured differently, containing three 100-hp surface aerators. The aerators and other mechanisms are in fair condition.TCEQ regulatory requirements were used to determine the combined current capacity of the aeration basins, including the following: • •

Organic loading rate (MM flow) ≤ 35 lb BOD/1000 cf-day Aeration requirements (MM flow) ≥ 2.2 lb O2/lb BOD

The combined gap analysis for the aeration basins is presented in Table 4-20. No treatment gap was identified. Table 4-20: Southside WWTP Aeration Basins Gap Analysis Design Criteria Number of Process Units1 Organic Loading Rate2 (MM) Aeration Requirements3 (MM)

≥2 ≤ 35 lb BOD/1000 cf-day ≥ 2.2 lb O2/lb BOD

Existing Capacity 3 13,800 lb BOD/day 35,500 lb/day O24

Future Required Capacity N/A 10,800 lb BOD/day

Existing Gap N/A

Future Gap N/A

None

12,300 lb/day O2

None

Overall Facility Gap None None Notes: 1. Redundancy required by TAC 217.153(c)(1) 2. Maximum organic loading rate as specified in TAC 217.154(b)(2),Table F-1 3. Oxygen requirements as specified in TAC 217.155(a)(3), Table F-3 4. Existing surface aerators can provide 2.0 lb O2 per HP and have a combined power of 740 HP.

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4.2.7

Secondary Clarifiers

The effluent of each aeration basin flows to the corresponding secondary clarifier, where solids are further removed via settling and recycled to the aeration basin. TCEQ regulatory requirements were used to calculate the combined current capacity of the secondary clarifiers, including the following loading rates: • •

Weir loading rate (peak flow) ≤ 30,000 gpd/ft Surface loading rate (peak flow) ≤ 1,200 gpd/ft2

A summary of the gap analysis for the secondary clarifiers is provided in Table 4-21. Table 4-21: Southside WWTP Secondary Clarifiers Gap Analysis Design Criteria Number of Process Units1 Weir Loading Rate2 (peak) Surface Loading Rate3 (peak)

≥2 ≤ 30,000 gpd/ft ≤ 1,200 gpd/ft2

Existing Capacity

Future Required Capacity

Existing/Future Gap (with PFB)

N/A

35.0 MGD

22.5 MGD

None

30.3 MGD

22.5 MGD

None

Overall Facility Gap

None

Notes: 1. Redundancy required by TAC 217.153(c)(1) 2. Weir loading rate specified in TAC 217.152(d)(5) 3. Surface loading rate specified in TAC 217.154(c)(1), Table F-2 4.2.8

Chlorine Contact Basin

Secondary effluent flows to the chlorine contact basin for disinfection. The facility has two separate channels, each housing a submersible flash mixer. The chlorine gas solution is injected into the process flow at the influent end of the basins and sulfur dioxide (SO2) is injected at the effluent end for dechlorination. Due to operational issues, poor condition, and importance of disinfection in meeting permit limits, the state of the CCB was determined to be critical. The current treatment capacity of this facility was calculated using the minimum chlorine contact time regulated by TCEQ. The facility must be able to meet treatment criteria at future peak flows. The gap analysis for the chlorine contact basin is presented in Table 4-22. Table 4-22: Southside WWTP Chlorine Contact Basin Gap Analysis Existing Capacity

Design Criteria Minimum Contact Time1

20 min

Future Required Capacity

Existing/Future Gap (with PFB)

22.5 MGD

None

Overall Facility Gap

None

34.7 MGD

Notes: 1. Minimum contact time required by TAC 217.281(b)(1)

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4.2.9

Chlorine Facility

The chlorine facility houses the chlorine gas cylinders used for disinfection and the SO2 cylinders used for dechlorination. A design improvements project is currently in progress to address the issues at the facility; however, the treatment gap was determined for the facility to provide contextual consistency. The chlorine building houses 9 chlorine cylinders and 9 SO2 cylinders, 6 of each are connected to a chemical distribution manifold and are used to dose the chemicals at the plant. The remaining cylinders are used for additional storage capacity. As shown in Table 4-23, the facility does not have a gap in capacity. However, the facility was found to be in critical condition during the condition assessment. Table 4-23: Southside WWTP Chlorine Facility Gap Analysis TCEQ Design Criteria

Existing Capacity

Future Required Capacity

Existing/Future Gap (with PFB)

Chlorine Gas Storage Required

15 days

Dosage (Peak Flow)

6 mg/L

Storage Required

15 days

3.7 tons1

9 tons 3,360 lb/day

None

1,100 lb/day

None

Sulfur Dioxide Dosage (Peak Flow)

1.5 mg/L

9 tons 1,440 lb/day

1 tons1 300 lb/day

None 2

Overall Facility Gap

None None

Notes: 1. Storage requirement was calculated based on average day flow conditions and a required chlorine dosage of 6 mg/L and a require sulfur dioxide dosage of 1.5 mg/L. 2. Peak flow dosage was calculated using the peak two hour flow of 22.5 MGD. The calculation also assumed a maximum dosage capacity of each chlorine cylinder of 560 lb/day and of each sulfur dioxide cylinder of 240 lb/day. 4.2.10 RAS/WAS Pump Station The RAS/WAS pump station sends solids from Secondary Clarifiers 1 and 2 to Aeration Basins 1 and 2. This facility houses three sludge return pumps that lift the sludge to the aeration basins as well as the anaerobic digesters. This facility is in critical condition due to the center pump being out of service currently. Each pump has a 1.0 MGD rating, and due to one of the pumps being out of service, the current firm pumping capacity is 1.0 MGD. It is assumed the rate of RAS/WAS pumping from Secondary Clarifiers 1, 2, and 3 follows the same flow split ratio as the different process trains (28%-28%-44%, respectively). A total RAS flow equal to the future ADF of the plant was used to determine the future required capacity. An additional 4.6 MGD of pumping capacity is required.

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The gap analysis of the RAS/WAS pump station is presented in Table 4-24. Table 4-24: Southside WWTP RAS/WAS Pump Station Gap Analysis Design Criteria Number of Process Units RAS + WAS Flow

Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

N/A

1.0 MGD1

5.6 MGD

4.0 MGD

4.6 MGD

Overall Facility Gap

4.0 MGD

4.6 MGD

Notes: 1. TAC 217.244(b) requires firm capacity be provided with the largest unit out of service 2. Future required capacity is based on the future ADF of 10 MGD, and the total percent of flow going to process trains 1 & 2 of 56%. 4.2.11 Gravity Belt Thickener WAS from Aeration Basins 1 and 2 and Secondary Clarifiers 1, 2, and 3 is sent to the GBT building for thickening. Polymer is injected before WAS is sent through the GBT. The facility consists of one GBT unit with a 1-m belt width. The GBT has consistent performance but lacks redundancy. TCEQ regulations state that the GBT design must meet either a maximum hydraulic loading rate or a maximum solids loading rate: • •

Hydraulic loading rate (MM flow) ≤ 250 gpm Or solids loading rate (MM flow) ≤ 1,250 lb/m-h

The future required capacity was based on future max month flows at 7 day/wk, 16 h/day operation, as calculated in the whole-plant mass balance. TCEQ requires that either a solids loading rate criterion or a hydraulic loading rate criterion be met; therefore, the two criteria were evaluated and compared to determine the gap. A summary of the GBT gap analysis is shown in Table 4-25. Table 4-25: Southside WWTP Gravity Belt Thickener Gap Analysis Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

≥2

N/A

No Redundancy

250 gpm/m

167 gpm 2

124 gpm 3

None

1,250 lb/m-h

2,000 lb/day 2

13,900 lb/day 3

None

Overall Facility Gap

None

TCEQ Design Criteria Number of Process Units Hydraulic Loading Rate1 (MM) Solids Loading Rate1 (MM)

Notes: 1. TAC 217.248(e)(2)(A),(B) requires that either the hydraulic loading rate or solids loading rate be met 2. Existing capacities were calculated assuming the GBT is being operated 7 day/wk, 16 h/day. 3. Future required capacities are based on the whole plant mass balance.

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4.2.12 Sludge Holding Tank The sludge holding tank receives thickened sludge from the GBT. The tank remains in good condition. The sludge holding tank currently has a storage capacity of 0.70 MG, which satisfies the future required capacity of 0.36 MG based on solids retention time (SRT) requirements and predicted solids production at MM conditions. The gap analysis of the sludge holding tank is shown in Table 4-26. Table 4-26: Southside WWTP Sludge Holding Tank Gap Analysis Design Criteria

Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

0.70 MG

0.36 MG1

None

Overall Facility Gap

None

Total Storage

Notes: 1. Future required capacity was calculated based on a minimum SRT of 4 days. 4.2.13 Sludge Dewatering Facility The sludge dewatering facility consists of two 2-m BFPs, two sludge pumps, two polymer storage and feed units, and a 2-ton crane. The BFPs are typically operated 8-hr/day, Monday-Friday, and consistently achieve 19-22% solids. Industry standards were used to calculate the current sludge dewatering capacity, including the following loading rates: • •

Hydraulic loading rate ≤ 100 gpm/m Solids Loading rate ≤ 800 lb/h-m

The future required capacity is based on predicted max month sludge flows. The gap analysis of the sludge dewatering facility is provided in Table 4-27. As shown, the current dewatering facility requires 1,200 lb/hr of additional capacity to meets the future requirements. Table 4-27: Southside WWTP Sludge Dewatering Facility Gap Analysis Design Criteria ≥2

Number of Process Units1 2

Hydraulic Loading Rate

100 gpm/m

Existing Capacity

Future Required Capacity

Existing Gap

Future Gap

N/A

None

400 gpm

3 3

260 gpm

4 4

Solids Loading Rate 800 lb/h-m 3,200 lb/h 4,400 lb/h None 1,200 lb/h Notes: 1. Redundancy required by TAC 217.250(c)(3)(A) 2. BFP capacity criteria is based on industry standards. 3. TAC 217.250(c)(3)(B) requires firm capacity with largest dewatering unit out of service 4. Required capacity was found assuming 5 days/wk, 8 h/day operation at future AADF in the wholeplant mass balance

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4.2.14. Southside WWTP Gap Analysis Summary Table 4-28 lists the gaps identified for each facility at the Southside WWTP. As shown, the gaps range from no gap up to a gap of 26.5 MGD. These gaps along with the identified condition of the facilities and mechanical components will be used in Section 5 to develop design recommendations. Table 4-28: Southside WWTP Gap Analysis Summary Facility Influent Pump Station Mechanical Screens Grit Removal Primary Clarifiers Primary Sludge Pump Station Aeration Basins Secondary Clarifiers Chlorine Contact Basin Chlorine Facility – Chlorine Gas Chlorine Facility – Sulfur Dioxide RAS/WAS Pump Station Gravity Belt Thickener Sludge Holding Tank Sludge Dewatering Facility

Existing Capacity 21.7 MGD 13 MGD 31 MGD 18.1 MGD 250 gpm 13,800 lb BOD/day 30.3 MGD 34.7 MGD 3,360 lb/day 1,440 lb/day 1.0 MGD 167 gpm 0.70 MG 3,200 lb/h

Future Required Capacity 39.5 MGD 39.5 MGD 39.5 MGD 39.5 MGD 250 gpm 10,800 lb BOD/day 39.5 MGD 39.5 MGD 2,000 lb/day 500 lb/day 5.6 MGD 124 gpm 0.36 MG 4,400 lb/h

Existing Gap 0.8 MGD 9.5 MGD None 4.4 MGD None

Future Gap 17.8 MGD 26.5 MGD 8.5 MGD 4.4 MGD None

None

None None None None 4.0 MGD None None None

None None None None 4.6 MGD None None 1,200 lb/h

5. Available Alternatives This section of the TM presents and evaluates the design alternatives available to the City of Tyler to address the previously established hydraulic, process, and regulatory capacity disparities at the WWTPs. These proposed design alternatives will include design details, Process Flow Diagrams (PFDs), potential site layouts, and estimated total project costs; however more detail will be added, and design decisions will be refined throughout the remaining master plan tasks. 5.1. Westside WWTP The Near-Term CIP Needs TM provided to the City of Tyler presented six projects to improve the headworks facility, filter pump station, nitrification basin, anaerobic digesters, secondary clarifiers, and the sludge storage lagoon. Within this section, these previously presented projects along with additional alternatives available to the city to address the current and future gaps will be proposed. As mentioned in Section 3, the feasibility of the proposed improvements is dependent on the finalization of a floodway study at the Westside WWTP.

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Table 5-1 summarizes the gap analysis and shows a comparison of the gaps in the treatment processes with and without a 1.4 MG PFB. As shown, the gaps of the facilities that are hydraulicly limited are lower, which will lead to fewer required expansion needs. The recommended expansion needs are also listed in the table; these will be expanded further in the subsequent sections of the TM. Table 5-1: Summary of Westside WWTP Gap Analysis, Condition, and Proposed Expansion Needs Existing Existing Future Gap Facility Facility Expansion Needs Capacity Gap (with PFB) Criticality Screening 32.5 MGD None 14.7 MGD Decommission existing headworks facility and construct Critical new headworks facility Grit Removal 20 MGD 12.5 MGD 27.2 MGD Construct a new IPS structure, including peak flow Raw Water Pump Station 32 MGD None 15.2 MGD High pumping Alternative 1: Replace mechanisms Primary Clarifiers 42.4 MGD None None Medium Alternative 2: Construct two new PC structures Alternative 1: Rehabilitate existing Nitrification Basin 4,500 lb 5,000 lb 10,000 lb Biological Treatment Train Critical Alternative 2: Decommission and demolish all facilities, 1 BOD/day BOD/day BOD/day build new aeration basins including a new blower facility Filter Pump Station 46 MGD None None Critical Construct a duplicate pump station Replace mechanisms in existing clarifiers with doubleSecondary Clarifiers 27.1 MGD 5.4 MGD 8.9 MGD High sided weir mechanisms RAS Pumps N/A N/A N/A High Construct a new RAS/WAS pump station Raise outer walls of the CCB and construct a new Parshall Chlorine Contact Basin 29.7 MGD 2.8 MGD 6.3 MGD High flume effluent measurement channel Chlorine Facility – Chlorine 6,720 lb/day None None Critical None – Facility is currently under design for improvements Gas Chlorine Facility – Sulfur 1,920 lb/day None None Critical None – Facility is currently under design for improvements Dioxide 395 lb 540 lb Oxygenation 960 lb O2/day High Replace surface aerators O2/day O2/day Alternative 1: Convert into aerated sludge storage tanks with diffused aeration. Anaerobic Digester 3.2 MG None None Critical Alternative 2: Convert into aerated sludge storage tanks with surface aeration. Sludge Dewatering Facility 1,600 lb/hr 627 lb/hr 2,470 lb/hr Low Build an additional dewatering facility to house new BFPs

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. 5.1.1.

Sludge Lagoon Rehabilitation

Rehabilitation of the sludge lagoon was included in the Near-Term CIP TM (June 2022). A new polyliner layer is considered to be installed in order to replace the existing deteriorated liner at the bottom of the lagoon. In addition, new floating surface mixers are to be installed at the lagoon to provide mixing for the stored solids. A new sludge recycle pump station is also proposed to be constructed to pump sludge from the lagoon back to the head of the plant. Design details of the sludge lagoon rehabilitation are shown in Table 5-2. Table 5-2: Design Details of the Sludge Lagoon Rehabilitation Parameter

Value Sludge Lagoon Rehabilitation Liner Type Polyliner Quantity of Floating Mixers 14 Quantity of Sludge Pumps 3

Unit -

A PFD of the proposed improvements is shown in Figure 5-1.

Figure 5-1: PFD of the Sludge Lagoon Rehabilitation A site layout exhibiting the sludge lagoon rehabilitation is shown in Figure 5-2. The sludge pump station is proposed to be located near the sludge lagoon.

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Figure 5-2: Site Layout of the Sludge Lagoon Rehabilitation The estimated total project cost of the sludge lagoon rehabilitation is $3,262,000. A breakdown of this cost is shown in Table 5-3; the cost includes a replacement of the lagoon liner, new floating mixers, a sludge pump station housing three sludge pumps, and allowances for site civil improvements, electrical improvements, contractor overhead and profit (OH&P) and engineering services. Table 5-3: Estimated Total Project Cost of the Sludge Lagoon Rehabilitation Facility

Sludge Lagoon Rehabilitation

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity 1 14 3 LS

Element Lagoon Polyliner Floating Mixers Sludge Pumps Sludge Pump Station Structure $1,128,000 $282,000 $226,000 $573,000 $111,000 $398,000 $544,000 $3,262,000

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5.1.2.

Headworks

The recommended improvements for the headworks facility at the Westside WWTP, as presented in the Near-Term CIP TM, are to demolish the existing facility and construct a new facility including mechanical screening and vortex grit removal. The condition of the mechanical and structural components of the facility are not conducive to rehabilitation and reuse of the existing facility. Therefore, in order to meet the future P2HF of 47.2 MGD, it is recommended that a new structure be built to house mechanical screening and grit removal equipment. Table 5-4 lists the design criteria and sizing of the proposed facility. Table 5-4: Design Details of the Proposed Headworks Improvements Parameter

Value

Unit

Screening Mechanical Screen Quantity Mechanical Screen Type Manual Screen Quantity Size (each)

3 Mechanical Bar Screen 1 16.0 Grit Removal Grit Removal Type Mechanical Vortex Quantity of Grit Removal Units 3 Size (each) 16.0

MGD MGD

The proposed facility will house three mechanical bar screens and will include one manual bar screen to provide screen removal if the mechanical screens are taken out of service for maintenance. Three vortex grit removal units are also proposed. A process flow diagram (PFD) of the proposed headworks improvements is shown in Figure 5-3. The improvements, in total, will treat the future peak flow of 47.2 MGD at full build out. Phasing options for the improvements will be discussed in the next tasks.

Figure 5-3: PFD of Proposed Headworks Improvements A site layout is provided in Figure 5-4 showing the proposed location of the headworks improvements. To allow for continued operation of the existing headworks facility during construction, the new headworks facility can be located South of the existing headworks facility and brought online for service before the demolition of the existing facility.

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Figure 5-4: Site Layout of Proposed Headworks Facility The estimated total project cost of the headworks improvements is shown in Table 5-5. The estimated project cost of the headworks facility is $10,309,000; this cost includes construction of a new headworks structure, three new mechanical screens with a screen conveyor and washer/compactor, three new grit units, a grit classifier, and associated yard piping as well as professional services. In addition, the project includes the demolition of the existing headworks facility and relocation of the septage receiving station. Table 5-5: Estimated Total Project Cost of the Headworks Improvements Project Facility

Headworks

Garver Project No. 21W05170

Quantity LS LS LS 1 3 1 3 1

Element Demo of Existing Structure Relocation of septage receiving station Yard Piping Concrete Structure Mechanical Screens Manual Bar Screen Vortex Grit Removal Units Screen Conveyor and Washer/Compactor

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Facility

Quantity

Element

Grit Classifier $3,568,000 $892,000 $714,000 $1,811,000

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost 5.1.3.

$349,000 $1,257,000 $1,718,000 $10,309,000

Peak Flow Basin

A peak flow basin (PFB) is recommended for the Westside WWTP to store peak flows and lower the peak hydraulic requirements of the plant. The peak flow through the plant impacts many aspects of plant design including pump sizing, pipe sizing, clarifier sizing, etc. Having a peak flow basin to store large spikes in influent flow would allow for the plant processes that are hydraulically governed to be sized to handle smaller flows, and therefore lower the overall cost of any necessary improvements. Two PFB design alternatives will be considered in this TM: 1. Construct a new PFB 2. Convert the first-stage trickling filter (TF) basins into PFBs As shown in , a hydrograph of the peak storm event at the plant was used to determine the peak flow through the plant if the available storage space in the TFs of 1.4 MG is utilized for peak flow storage. Flows above 36 MGD will be diverted to the PFB downstream of the headworks facility. The headworks processes will not be bypassed during peak flows to ensure that large solids and grit will not be sent to the PFB and allowed to settle out in the basin. The two alternatives considered will both be evaluated to provide 1.4 MG of storage and will be compared on a cost and construction feasibility basis. 5.1.3.1. Alternative 1: New PFB The first PFB alternative includes a newly constructed basin to store 1.4 MG of influent. A circular basin with a diameter of 130-ft will be constructed to store the influent at peak flow. A summary of the design details of PFB alternative 1 are shown in Table 5-6. Table 5-6: Design Details of PFB Alternative 1 Parameter Diameter Depth Available Peak Flow Storage Volume

Value 140 12 1.40

Unit ft ft MG

A PFD of PFB Alternative 1 is shown in Figure 5-5; peak flows above 36 MGD will be pumped by the Raw Water Pump Station to the new PFB. Once flows return to average levels, the water stored in the PFB will be returned to the pump station and subsequently sent to the primary clarifiers.

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Figure 5-5: PFD of PFB Alternative 1 The proposed site layout showing PFB Alternative 1 is shown in Figure 5-6. The proposed PFB location is on the area currently occupied by the first-stage TFs, which will be demolished if the new PFB is chosen for construction.

Figure 5-6: Site Layout Showing Proposed Location of PFB Alternative 1

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The estimated total project cost of PFB Alternative 1 is $3,884,000. A breakdown of the total project cost estimate is shown in Table 5-7. Table 5-7: Estimated Total Project Cost of PFB Alternative 1 Facility

Quantity LS

New PFB

LS Facility Subtotal Electrical and Instrumentation (10%) Site Civil (10%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Element 140-ft Pre-Fabricated Peak Flow Basin Demo of Existing Trickling Filter $1,622,000 $163,000 $163,000 $682,000 $132,000 $474,000 $648,000 $3,884,000

5.1.3.2. Alternative 2: Converted First-Stage TFs The second PFB alternative includes retrofitting the existing first-stage TF basins to be used for peak flow storage. The retrofit effort will consist of removing the TF rock media from the basins, removing the TF mechanisms, and repairing the concrete TF structures. The feasibility of this alternative depends on the condition of the TF structures once the rock media is removed. Design details of the first-stage trickling filters is shown in Table 5-8. Table 5-8: Design Details of First-Stage Trickling Filters Parameter

Value

Unit

Quantity Diameter Depth Available Peak Flow Storage Volume

2 150 6 1.40

ft ft MG

Similar to alternative 1, influent flows above 36 MGD will be sent to the converted trickling filter basins. Once the influent flow returns to average conditions, the stored influent will be routed back to the Raw Water Pump Station to be pumped to the primary clarifiers. A PFD of Alternative 2 is shown in Figure 5-7

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Figure 5-7: PFD of PFB Alternative 2 The site layout exhibiting the first-stage trickling filter conversion is shown in Figure 5-8.

Figure 5-8: Site Layout of Peak Flow Basin Alternative 2

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The estimated total project cost for PFB alternative 2 is $279,000. A breakdown of the cost is shown in Table 5-9; the cost includes estimates for removing the trickling filter equipment, cleaning the basins, and minor concrete repairs. The cost assumes that the condition of the trickling filter basins is sufficient for retrofitting with only minor improvements and repairs, however this should be investigated further to ensure that alternative 2 is feasible. Table 5-9: Estimated Total Project Cost of PFB Alternative 2 Facility

Quantity

First-Stage Trickling Filters Converted into PFBs

LS LS

Facility Subtotal Electrical and Instrumentation (10%) Site Civil (10%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost 5.1.4.

Element Remove Trickling Filter Arms and Media Basin Cleaning and Minor Repairs $115,000 $12,000 $12,000 $49,000 $10,000 $34,000 $47,000 $279,000

Raw Water Pump Station

The Raw Water Pump Station was determined to have a capacity gap of 35.2 MGD due to the size and dimensions of the existing wet well. In addition, the pumps were determined to have a high criticality rating due to the condition of both the pumps and the pump station. The existing pump station would require significant hydraulic improvements to be considered practical for use at the future flow conditions. Therefore, a new influent pump station is recommended to replace the existing Raw Water Pump Station to pump flows from the headworks to the primary clarifiers, and to pump peak flows above 36 MGD to the PFB. Table 5-10 lists the design criteria and details of the new influent pump station. Table 5-10: Design Details of Influent Pump Station Parameter

Value

Unit

Type Quantity Size (each)

Influent Pumps Wet-Pit Submersible 4 12.0 Peak Flow Pumps

MGD

Type Quantity Size (each)

Wet-Pit Submersible 2 12

MGD

The pump station will be designed to be capable of sending flow to the primary clarifiers, as well as the peak flow basin. The pump station will also include a split wet well design, housing two pumps within each

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wet well section. This design allows for isolation and draining of each wet well to make maintenance and operational adjustments easier. A PFD of this alternative is shown in Figure 5-9.

Figure 5-9: PFD of Raw Water Pump Station Alternative 2 The proposed location of the new influent pump station is near the existing Raw Water Pump Station. A potential site layout of the alternative is shown in Figure 5-10.

Figure 5-10: Site Layout of Alternative 2 Influent Pump Station An estimated total project cost of the new influent pump station is $12,805,000; a breakdown of the cost is shown in Table 5-11. The estimated cost includes a new pump station structure, four new influent pumps

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and associated piping and valves as well as allowances for electrical improvements, site civil improvements, contractor OH&P, and engineering services. Table 5-11: Estimated Total Project Cost of New Influent Pump Station Facility

Influent Pump Station

Quantity LS 4 2 6 6 LS

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost 5.1.5.

Element Pump Station Structure 12 MGD Influent Pumps 12 MGD Peak Flow Pumps 18-in Check Valves 18-in Plug Valves Associated Piping $4,432,000 $1,108,000 $886,000 $2,249,000 $434,000 $1,562,000 $2,134,000 $12,805,000

Primary Clarifiers

The primary clarifiers are located downstream of the proposed PFB, and therefore do not have a gap in capacity for the future flow and loading conditions. The clarifiers were given a medium criticality rating due to the age of the mechanisms and observed deterioration of metal components. The clarifiers mechanisms will require rehabilitation at some point in the master plan planning horizon to provide adequate treatment. In addition, it is recommended that the facility no longer be utilized for sludge co-settling, but for primary sludge settling only. This would increase the treatment capacity of the clarifiers and simplify plant operations. Two design alternatives have been developed to address the condition issues of the existing primary clarifiers. 5.1.5.1. Alternative 1: Replacement of Clarifier Mechanisms Alternative 1 includes the replacement of the two existing primary clarifier mechanisms within the existing clarifier structures. A PFD of alternative 1 is shown in Figure 5-11.

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Figure 5-11: PFD of Primary Clarifier Alternative 1 The estimated total project cost for alternative 1 is $7,613,000, a breakdown of the components is presented in Table 5-12. The costs include two new 150-ft double-sided weir primary clarifier mechanisms, two scum pumps, replacement of the metal walkways and stairs, and associated piping. The cost also includes allowances for site civil improvements, electrical improvements, contractor OH&P and engineering services. No major changes or improvements to the existing site are expected in alternative 1. Table 5-12: Estimated Total Project Cost of Primary Clarifier Alternative 1 Facility

Quantity

Element

Removal of Existing Mechanisms 150-ft Primary Clarifier Mechanisms Scum Pump Splitter Box Associated Metals Associated Piping $2,635,000 $659,000 $527,000 $1,337,000 $258,000 $928,000 $1,269,000

2 Primary Clarifiers

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

2 LS LS LS

$7,613,000

5.1.5.2. Alternative 2: New Primary Clarifiers Alternative 2 includes the demolition of the existing primary clarifiers and the construction of two new 120ft double sided weir primary clarifiers at a higher elevation than the existing basins. As a part of alternative

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2, the primary clarifier outer wall and weir elevations will be above the existing elevations. This elevation change will allow for the primary effluent to flow by gravity through the remainder of the plant and eliminate the need for intermediate pumping by the Filter Pumps. A PFD of this alternative is shown in Figure 5-12.

Figure 5-12: PFD of Primary Clarifier Alternative 2 The new primary clarifiers can be constructed in the same location as the existing basins. A site layout of alternative 2 is shown in Figure 5-13.

Figure 5-13: Site Layout of Primary Clarifier Alternative 2

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The estimated total project cost for primary clarifier alternative 2 is presented in Table 5-13. The costs include the same elements as alternative 1 along with the cost of two new primary clarifier structures. The cost also includes allowances for site civil improvements, electrical improvements, contractor OH&P and engineering services. The total estimated project cost of alternative 2 is $12,124,000. Table 5-13: Estimated Total Project Cost of Primary Clarifier Alternative 2 Facility

Primary Clarifiers

Quantity

Element

LS 2 2 2 LS LS LS

Demo of Existing Primary Clarifiers 120-ft Primary Clarifier Mechanisms 120-ft Primary Clarifier Structures Scum Pump Splitter Box Associated Metals Associated Piping $4,196,000 $1,049,000 $839,000 $2,129,000 $411,000 $1,478,000 $2,021,000 $12,124,000

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost 5.1.6.

Biological Treatment Train

The biological treatment train, including the First-Stage Trickling Filters (TFs), the Nitrification Basin, and the Second-Stage TFs, is sized based on the loading projections rather than hydraulic projections and therefore are not impacted by the PFB addition. The biological treatment train has a capacity gap of 7,000 lb/day BOD at current conditions and a capacity gap of 12,500 lb/day BOD at future conditions. The facilities were also ranked with high and critical criticality due to issues with the filter mechanisms, broken isolation gates, and a suspected sand buildup within the nitrification basin. Two alternatives for how to increase the biological treatment capacity were developed for the Westside WWTP. Alternative 1 includes rehabilitation of the existing nitrification basin and alternative 2 includes construction of a new basin featuring diffused aeration. 5.1.6.1. Alternative 1: Rehabilitate Existing Nitrification Basin The first alternative includes rehabilitation of the existing nitrification basin. This effort would require that the isolation gates on both basin channels be repaired so that each basin can be rehabilitated while the other remains in service. The rehabilitation effort will include draining the channels and removing any sand that has built up within the basin as well as replacing the existing surface aerators with new units. An additional basin volume of 840,000 gallons is also required to meet the future requirements.

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A new aeration basin channel shaped like an oval, similar to the existing nitrification basin channels, is proposed to provide the additional required volume. Surface aerators are also proposed to be installed within the new channel. Design details of alternative 1 are shown in Table 5-14. Table 5-14: Design Details of Biological Treatment Train Alternative 1 Parameter

Value Nitrification Basin Channel Quantity of New Channels 1 Length 180 Width 60 Side Water Depth 14 Aeration Equipment Surface Aerator Quantity 7 Aerator Size (each) 120

Unit ft ft ft HP

A PFD of alternative 1 is shown in Figure 5-14; as shown, the new nitrification basin channel will be constructed to share a common wall with the existing basin. A new splitter box will also be constructed to enable a proper flow split to be achieved between the three basin channels.

Figure 5-14: PFD of Biological Treatment Train Alternative 1

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A site layout of the first biological treatment train alternative is shown in Figure 5-15. The new nitrification basin channel is proposed to be located to the north of the existing basin channels. Also shown on the site layout are a new splitter box and a junction box.

Figure 5-15: Site Layout of Biological Treatment Train Alternative 1

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The total estimated project cost of the alternative 1, shown in Table 5-15, is $21,918,000. This cost includes the new nitrification basin channel, all new surface aerators, a new splitter box, demo of the existing secondstage trickling filters and allowances for site civil work, electrical improvements, contractor OH&P, and engineering services. Table 5-15: Total Estimated Project Cost of Alternative 1 Facility

Nitrification Basin

Quantity

Element

1 1 7 LS LS LS LS

New Nitrification Basin Channel New Splitter Box New Surface Aerators Demo of Existing Second-Stage TFs Demo and Removal of Existing Aerators Gates Associated Piping $7,585,000 $1,897,000 $1,517,000 $3,850,000 $743,000

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

$2,673,000 $3,653,000 $21,918,000

5.1.6.2. Alternative 2: Construct New Aeration Basins Alternative 2 for the biological treatment train improvements, as presented in the Near-Term CIP TM (June 2022), is to decommission the existing trickling filters and nitrification basin facility and construct a new aeration basin equipped with a diffused aeration system along with a new blower facility. Design details of the second alternative for biological treatment train improvements are shown in Table 5-16. Table 5-16: Design Details of Biological Treatment Train Alternative 2 Parameter Quantity Length Width (each) Side Water Depth Blower Quantity Blower Size (each) Diffuser Quantity

Value Aeration Basins 3 185 50 18 Aeration Equipment 3 300 7,400

Unit ft ft ft HP -

Three aeration basin are proposed to provide biological treatment capacity at the plant. Each basin will be equipped with diffusers to provide aeration and enable nutrient removal. A blower facility will be constructed

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adjacent to the aeration basins to house three 300 HP blowers. A PFD of biological treatment train alternative 2 is shown in Figure 5-16.

Figure 5-16: PFD of Biological Treatment Train Alternative 2 Figure 5-17 shows a potential site layout of alternative 2 including the proposed aeration basins and blower facility. The location of the new aeration basins will be in the current location of the Second-Stage TFs, which are recommended to be decommissioned and demolished.

Figure 5-17: Site Layout of Biological Treatment Train Improvements Alternative 2

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The OPCC of biological treatment train improvements alternative 2 is shown in Table 5-17. The estimated project cost is $29,138,000; this cost includes the demolition of the second-stage trickling filters, a new splitter box, the new nitrification basins, a diffused aeration system, a new blower facility housing three blowers with VFDs, as well as professional services. The cost calculated here is greater than the cost previously presented in the Near-Term CIP TM; the main cause of this cost increase is that the CIP cost included the improvements to meet the current influent flow and loadings, and the cost presented here is based on the full build out at future conditions. Table 5-17: OPCC of the Biological Treatment Train Improvements Alternative 2 Facility

Aeration Basins

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost 5.1.7.

Quantity

Element

LS 1 3 1 1 3 LS

Demolition of Second-Stage Trickling Filters New Splitter Box New Aeration Basin Channels Diffused Aeration System Blower Facility and Electrical Building Aeration Blowers and VFDs Rehabilitation of Existing Nitrification Basins $10,085,000 $2,521,000 $2,017,000 $5,118,000 $987,000 $3,554,000 $4,856,000 $29,138,000

Filter Pump Station

The existing filter pump station does not have a gap in capacity at the future flow conditions due to the proposed PFB, however, the facility does not have any redundant capacity or any means to isolate the wetwell for maintenance. The recommended improvements for this facility include a new, similarly sized pump station that can serve as a redundant facility to maintain intermediate pumping if the facility requires maintenance. The proposed filter pump station improvements were presented in the Near Term CIP TM, and includes three vertical turbine pumps, housed inside of a wetwell similar to the existing facility. The pumps will have variable frequency drives (VFDs) and will be sized to pump 18 MGD, each. Design details of the filter pump station improvements are shown in Table 5-18. Table 5-18: Design Details of Filter Pump Station Improvements Parameter Pump Quantity Pump Type Size (each)

Garver Project No. 21W05170

Value 3 Vertical Turbine 200

Unit HP

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A PFD of the Filter Pump Station Improvements is shown in Figure 5-18. The new pump station will be built to receive primary clarifier effluent in the case that the existing pump station is out of service for maintenance. Parallel piping will be constructed to allow for bypassing of the existing pump station to the new one.

Figure 5-18: PFD of New Filter Pump Station The site layout including the new filter pump station is shown in Figure 5-19. The new pump station is proposed to be located in the space between the two existing second-stage TFs.

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Figure 5-19: Site Layout Showing the Location of the New Filter Pump Station The estimated total project cost associated with the proposed new filter pump station is $7,608,000. A breakdown of this cost is shown in Table 5-19. The cost includes three new vertical turbine pumps, a new wetwell structure and associated piping and valves within the pump station. It also includes an allowance for electrical improvements, site civil improvements, contractor OH&P and engineering services. Table 5-19: Estimated Total Project Cost of Filter Pump Station Improvements Facility

Secondary Clarifiers Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

Vertical Turbine Pumps

LS LS

Associated Piping and Valves New Pump Station $2,633,000 $658,000 $527,000 $1,336,000 $258,000 $928,000 $1,268,000 $7,608,000

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5.1.8.

Secondary Clarifiers

The secondary clarifiers have a gap of 4.8 MGD based on the TCEQ weir loading rate criteria. In addition, the facility was given a high criticality ranking due to the condition of the clarifier mechanisms. It is recommended to replace the mechanisms within the existing basins with double-sided weir mechanisms to meet the weir loading rate criteria. A summary of the design criteria used to develop the proposed design is shown in Table 5-20. Table 5-20: Design Details of the Secondary Clarifier Improvements Parameter Total Secondary Clarifier Quantity Clarifier Type Diameter Side Water Depth

Value 2 Double-Sided Weir 150 15

Unit ft ft

The recommended improvements include replacement of the existing secondary clarifier mechanisms with 150-ft double-sided weir mechanisms. These improvements will provide the additional weir length needed to meet the future peak flow requirements. A PFD of the improvements is shown in Figure 5-20.

Figure 5-20: PFD of Secondary Clarifier Rehabilitation A site layout of the proposed improvements is shown in Figure 5-21.

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Figure 5-21: Site Layout of Secondary Clarifier Improvements An estimate of the total project cost of the proposed improvements is shown in Table 5-21. The costs include new clarifier mechanisms and associated metal component replacements. Allowances for electrical improvements, site civil improvements, contractor OH&P and engineering services are also included. The estimated total project cost is $9,078,000. Table 5-21: Estimated Total Project Cost of Secondary Clarifier Rehabilitation Facility

Quantity 2

Secondary Clarifiers

2 LS LS

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%)

Element 150-ft Double Sided Weir Secondary Clarifier Mechanisms Scum Pumps Walkway and Stairway Replacement Demolition of Existing Clarifier Mechanisms $3,142,000 $785,000 $628,000 $1,595,000 $308,000 $1,107,000

Professional Services (20%) Estimated Project Cost

$1,513,000 $9,078,000

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5.1.9.

RAS/WAS Pump Station

The existing return activated sludge (RAS) pumps at the plant have an unknown capacity but were determined to have a high criticality due to a high consequence of failure. In addition, there are no dedicated waste activated sludge (WAS) pumps at the facility; the WAS from the secondary clarifiers flows to the sludge return pumps and is pumped up to the primary clarifiers to co-settle with primary sludge. Garver recommends decommissioning the RAS pumps and constructing a new RAS/WAS pump station. The design criteria and sizing details for the proposed RAS and WAS pumps are shown in Table 5-22. Table 5-22: Design Details of RAS/WAS Pump Station Parameter Quantity Type Capacity (each) Quantity Type Capacity (each)

Value RAS Pumps 4 Submersible Centrifugal 7 WAS Pumps 2 Submersible Centrifugal 250

Unit MGD gpm

The new RAS/WAS Pump Station facility will house four new RAS pumps and two new WAS pumps. The facility will have a common wet well where sludge from the secondary clarifiers is combined and then pumped to either the nitrification basin or the sludge digesters. A PFD of the proposed facility is shown in Figure 5-22.

Figure 5-22: PFD of Proposed RAS/WAS Pump Station

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The proposed RAS/WAS pump station facility will be located nearby the existing RAS Pump Station. The existing RAS Pump Station and caustic storage tank, which is no longer in use, will be demolished. A site layout of the proposed improvements is shown in Figure 5-23.

Figure 5-23: Site Layout of Proposed RAS/WAS Pump Station An estimated total project cost of the new RAS/WAS pump station is shown below in Table 5-23. The cost includes four new RAS pumps and two new WAS pumps, a cost for the new pump station structure, and a cost for the demolition of the existing RAS pump station and caustic storage equipment. The cost also includes allowances for site civil improvements, electrical improvements, contractor OH&P and engineering services. The estimated project cost is $5,111,000. Table 5-23: Estimated Total Project Cost of the Proposed RAS/WAS Pump Station Facility

Quantity LS

RAS/WAS Pump Station

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

1 4 2 LS

Element Demolition of Existing RAS Pump Station Building and Caustic Storage New Pump Station Structure RAS Pumps WAS Pumps Piping and Valves $1,769,000 $442,000 $354,000 $898,000 $173,000 $623,000 $852,000 $5,111,000

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5.1.10. Chlorine Contact Basin The chlorine contact basin does not have a gap in capacity due to the utilization of the PFB, and the required improvements to the basin are minimal. As identified in Section 3, the elevation of the CCB walls is below the flood stage of the receiving creek, therefore it is recommended that the walls of the basin be raised to ensure that during high flood stage events, disinfection will still be achieved. In addition, a new Parshall flume is recommended to provide effluent flow measurement. Table 5-24 lists the design details of the CCB improvements. Table 5-24: Design Details of the Chlorine Contact Basin Improvements Parameter CCB Existing Wall Elevation CCB Future Wall Elevation Parshall Flume Size Length Parshall Flume Channel Length

Value 392.55 399.00 4 40

Unit ft ft ft ft

The existing CCB effluent box and weir will be demolished and a new effluent flow measurement channel will be constructed along the southern wall of the CCB with a 4-ft Parshall flume. In addition, a weir wall will be constructed within the CCB channels to reduce flow short circuiting within the basin at high flows and to create a common effluent channel. A PFD of the CCB channels is shown in Figure 5-24.

Figure 5-24: PFD of Chlorine Contact Basin Improvements

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An estimated total project cost of the CCB improvements is shown in Table 5-25. The costs shown include raising the CCB walls and constructing a new Parshall flume channel. The cost also includes allowances for site civil improvements, electrical improvements, contractor OH&P and engineering services. The estimated total project cost for the CCB improvements is $1,646,000. Table 5-25: Estimated Total Project Cost of CCB Improvements Facility

Chlorine Contact Basins

Quantity

Element

CCB Channel Wall Height Increase

LS LS 1 LS

CCB Weir Wall Effluent Flow Measurement Channel 4-ft Parshall Flume New Handrailing $570,000 $142,000 $114,000 $289,000 $56,000 $201,000 $274,000 $1,646,000

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost 5.1.11. Oxygenation

The oxygenation capacity of the facility also needs to be increased to meet the permitted DO requirement at future flow conditions. The existing surface aerators would need to be replaced with larger units to meet the future DO requirement. Four 10-hp surface aerators would be sufficient to provide the required future oxygen requirement of 1,501 lb O2/day. The design details of the surface aerators are shown in Table 5-26. Table 5-26: Design Details of the Surface Aerator Replacement Parameter Aeration Required Aerator Quantity Aerator Size (each)

Value 1,501 4 (2 per basin) 10

Unit lb O2/day HP

The surface aerators can be installed within the CCB basins, in a similar configuration to the existing surface aerators. However, a more thorough review of the oxygenation system should be performed during detailed design. The estimated total project cost of the surface aerator replacement is $398,000; a breakdown of the cost is shown in Table 5-27.

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Table 5-27: Estimated Total Project Cost of the Surface Aerator Replacement Facility Surface Aerators

Quantity 4

Element 10-HP Surface Aerator

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

$138,000 $34,000 $28,000 $70,000 $13,000 $49,000 $66,000 $398,000

5.1.12. Anaerobic Digesters Two alternatives were developed to address the critical condition of the anaerobic digester basin. The first alternative was presented in the Near-Term CIP TM and includes the cleaning and repairing of the concrete basin structures, filling in the conical floor, and installing diffused aeration. The second alternative includes cleaning and repairing the concrete basin structures and installing surface aerators. 5.1.12.1.

Alternative 1: Conversion with Diffused Aeration

Alternative 1 consists of converting the anaerobic digesters into aerated sludge storage tanks with structural improvements and the installation of diffusers. The existing basins have conical floors that are 44-ft deep at the deepest point and 25-ft deep at the shallowest point. To accommodate the aeration diffusers, the floor of the basins will need to be filled with sand or granular fill and covered with concrete to create a flat surface for the diffusers to be mounted. Three new blowers will be installed and connected to air piping to provide air to the stored solids and prevent septic conditions from occurring. Design details of the proposed improvements are shown in Table 5-28. Table 5-28: Design Details of Anaerobic Digester Basin Conversion Alternative 1 Parameter Value Aerobic Sludge Holding Tanks Sludge Design SRT 4 Type of Mixing Diffused Air Total Air Required 5,000 Blower Quantity 3 Blower Size 150 Side Water Depth 22

Unit days scfm ft HP ft

A PFD of alternative 1 is shown in Figure 5-25. WAS and primary sludge will be sent to the digesters for storage prior to dewatering. With the structural improvements, the sludge digester basins will be able to provide a solids retention time (SRT) of 4 days.

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Figure 5-25: PFD of Anaerobic Digester Basin Conversion Alternative 1 The proposed site layout for the anaerobic digester basin conversion alternative 1 is shown in Figure 5-26. The area to the north of the digester basins is proposed to be used for the blower facility.

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Figure 5-26: Site Layout of Digester Basin Conversion Alternative 1 The estimated total project cost of the digester basin improvements is $5,010,000. A breakdown of the cost elements that went into the total project cost is presented in Table 5-29.The cost includes cleaning and repairing the digester basins, filling in the basin floors with concrete, the aeration system and blowers, as well as allowances for electrical and site civil improvements, contractor OH&P and engineering services. Table 5-29: Estimated Total Project Cost for the Digester Basin Conversion Alternative 1 Facility

Digester Basin

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

LS LS LS 3 LS

Clean and Repair Existing Structures Concrete Fill of Conical Floors Diffused Aeration System Blowers with VFDs Blower Facility $2,388,000 $597,000 $478,000 $1,212,000 $234,000 $841,000 $1,150,000 $5,010,000

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5.1.12.2.

Alternative 2: Conversion with Surface Aeration

The second alternative for the anaerobic digester conversion consists of cleaning and repairing the basins structures and installing two 40-hp surface aerators in each basin. Four 40-hp surface aerators will be installed in the existing Nitrification basin to provide aeration while the new aeration basins are constructed. Once the aeration basins are in use, the aerators will be removed from the nitrification basin, the nitrification basin will be taken offline, and the aerators will be installed inside of the anaerobic digester basins. The design details of alternative 2 are shown in Table 5-30. Table 5-30: Design Details of Anaerobic Digester Basin Conversion Alternative 2 Parameter Value Aerated Sludge Storage Basins Design SRT 4 Type of Aeration/Mixing Surface Aerators Quantity of Surface Aerators (total, in each basin) 4, 2 Aerator Size 40 Side Water Depth 25

Unit days hp ft

A PFD of alternative 2 is shown in Figure 5-27. The surface aerators will be installed within the digester basins. The sludge will be stored and aerated/mixed by the surface aerators. A level control device will be installed to maintain a maximum depth within the basins to prevent septic conditions.

Figure 5-27: PFD of Anaerobic Digester Basin Conversion Alternative 2 A site layout showing the rehabilitated digester basins is shown in Figure 5-28.

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Figure 5-28: Site Layout of Anaerobic Digester Conversion Alternative 2 The estimated total project cost of the anaerobic digester basin conversion alternative 2 is shown in Table 5-31. The total estimated cost is $2,990,000; this cost includes the cleaning and repairing of the existing basins, new surface aerators, filling in the basin floors with concrete, level control devices, and allowances for site civil and electrical improvements, contractor OH&P, and engineering services. Table 5-31: Estimated Total Project Cost of the Anaerobic Digester Conversion Alternative 2 Facility

Anaerobic Digester Conversion

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

Clean and Repair Existing Structures

4 2 LS LS

40-HP Surface Aerators Level Control Devices Clean and Repair Existing Structures Concrete Fill of Conical Floors $1,687,000 $422,000 $338,000 $857,000 $166,000 $595,000 $813,000 $2,990,000

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5.1.13. Sludge Dewatering Facility The sludge dewatering facility has a future gap of 2,470 lb/hr; two additional 2-m BFPs will be required to meet this gap for future operation. The existing sludge dewatering facility does not have enough room to house additional BFPs, therefore an addition to the building is proposed to house the new BFPs. The design details of the proposed BFPs are shown in Table 5-32. Table 5-32: Design Details of Sludge Dewatering Equipment Improvements Parameter

Value Sludge Dewatering Quantity of Belt Filter Presses 2 BFP Size 2 BFP Hydraulic Loading Rate (each) 1,600

Unit m lb/hr

Sludge from the digester basins will be sent to the existing and new dewatering facilities and then discharged for disposal. A PFD of the proposed dewatering facility improvements is shown in Figure 5-29.

Figure 5-29: PFD of Proposed Dewatering Facility Improvements A potential site layout for the proposed dewatering facility improvements is shown in Figure 5-30. The area adjacent to the existing dewatering facility is suitable for the facility expansion. This location would also enable the utilization of the existing roadway for discharging the dewatered solids into a truck for disposal.

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Figure 5-30: Site Layout of the Proposed Dewatering Facility Improvements The estimated total project cost of the dewatering facility improvements is $9,647,000. A breakdown of the cost elements is shown in Table 5-33. The cost shown includes two new 2-m BFPs, a new sludge conveyor, the cost of expanding the dewatering building, associated piping, and allowances for electrical and site civil improvements, contractor OH&P and engineering services. Table 5-33: Estimated Total Project Cost of the Dewatering Facility Improvements Facility

Dewatering Facility Expansion

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

Belt Filter Press

1 LS LS

Sludge Conveyor Dewatering Facility Expansion Associated Piping $3,339,000 $835,000 $668,000 $1,694,000 $327,000 $1,176,000 $1,608,000 $9,647,000

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5.1.14. Summary of Available Alternatives at Westside WWTP A summary of the available alternatives and estimated costs for these improvements at the Westside WWTP is shown in Table 5-34. Table 5-34: Summary of the Estimated Costs of the Recommended Improvements Facility Sludge Lagoon Rehabilitation Peak Flow Basin Headworks Raw Water Pump Station Primary Clarifiers

Biological Treatment Train Filter Pump Station Secondary Clarifiers RAS/WAS Pump Station Chlorine Contact Basin Oxygenation Anaerobic Digesters

Sludge Dewatering Facility

Estimated Total Project Cost

Project Description Replace Sludge Lagoon Liner and Install Mixers Alternative 1: Construct a new PFB Alternative 2: Convert the First-Stage TFs into PFBs Construct new headworks facility Construct a new pump station Alternative 1: Replace mechanisms Alternative 2: Construct two new PC structures Alternative 1: Rehabilitate existing nitrification basin and construct additional volume Alternative 2: Construct new aeration basins including a new blower facility Construct a duplicate pump station Replace mechanisms in existing clarifiers Construct new RAS/WAS Pump Station Raise outer walls of the CCB and construct a new Parshall flume effluent measurement channel Replace surface aerators Alternative 1: Convert into aerated sludge storage tanks with diffused aeration Alternative 2: Convert into aerated sludge storage tanks with surface aeration Expand dewatering facility to house two additional BFPs

$3,262,000 $552,000 $279,000 $10,309,000 $12,805,000 $7,547,000 $12,124,000 $21,918,000 $29,138,000 $7,608,000 $9,078,000 $5,111,000 $1,646,000 $398,000 $5,010,000 $2,990,000 $9,647,000

5.2. Southside WWTP A summary of the gaps identified in Section 4.2 is shown in Table 5-35, along with an updated gap to reflect the additional capacity required for each facility after a PFB is constructed. Also included in the table is a summary of facility’s criticality assessment along with the recommended expansions needs. The expansion needs for each facility are based on both the identified capacity gaps and the criticality of the facility; these will be further detailed in the subsequent report sections.

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Table 5-35: Summary of the Southside WWTP Gap Analysis, Facility Criticality, and Recommended Expansion Needs Current Capacity

Existing Gap

Future Gap (with PFB)

Facility Criticality

Influent Screw Pump Station

21.7 MGD

0.8 MGD

17.8 MGD

Low

Construct new influent pump station

Mechanical Screens

13.0 MGD

9.5 MGD

26.5 MGD

Low

Grit Removal

31.0 MGD

None

8.5 MGD

Medium

Construct new headworks facility housing screening and grit removal equipment

Primary Clarifiers

18.1 MGD2

4.4 MGD

Low

Utilize existing infrastructure at a higher loading rate

Primary Sludge Pump Station

250 gpm

None

Low

No necessary improvements

Facility

Aeration Basins

13,800 lb BOD/day

None

Critical

Secondary Clarifiers

30.3 MGD

None

High

Chlorine Contact Basin

34.7 MGD

None

High

None

Critical

None

Critical

1.0 MGD

4.0 MGD

4.6 MGD

Critical

N/A

High

Gravity Belt Thickener

167 gpm

None

Medium

Sludge Holding Tank

0.70 MG

None

High

Sludge Dewatering Facility

3,200 lb/h

None

1,200 lb/h

Low

Chlorine Facility – Chlorine Gas Chlorine Facility – Sulfur Dioxide RAS/WAS Pump Station Secondary Sludge Pump Station

Garver Project No. 21W05170

3,360 lb/day 1,440 lb/day

Expansion Needs

Alternative 1: Construct a new aeration basin. Demolish Aeration Basins 1 & 2 and rehabilitate Aeration Basin 3. Alternative 2: Decommission and demolish basins 1, 2, & 3, and build new aeration basins Rebuild existing secondary clarifiers Clean basins and replace all walkways, railings and gates None – Facility is currently under design for improvements None – Facility is currently under design for improvements Decommission and demolish existing pump stations and build new pump station Construct additional building space to house a second GBT for redundancy Construct an additional sludge holding tank for redundancy Construct additional building space to house a third BFP

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5.2.1.

Influent Pump Station

The influent pump station and headworks facilities are upstream of the proposed PFB; this will reduce the amount of solids going to the PFB during peak flow events and limit the amount of cleaning/maintenance needed due to screening and grit build up within the basin. The existing influent pump station is rated for roughly 21.7 MGD, therefore an additional pump station should be constructed to convey the remaining 18 MGD under future flow conditions. The new pump station is recommended to be constructed in a split wet well configuration, housing four submersible pumps. The design criteria of the new influent pump station is shown below in Table 5-36. Table 5-36: Design Details of the Proposed Influent Pump Station Parameter Quantity Type Capacity (each)

Value Influent Pumps 4 (3 duty, 1 standby) Submersible Centrifugal 6

Unit MGD

A Process Flow Diagram (PFD) of the proposed influent pump station improvements is shown in Figure 5-31. The four new influent pumps would be housed within a split wet well design (two wet wells connected by a gate) to allow for isolation of each wet well section for maintenance and cleaning. The pumps will send flow downstream to the proposed 18 MGD headworks improvements but will have piping connections to connect to the existing headworks facility, if necessary.

Figure 5-31: PFD of the Proposed Influent Pump Station Improvements A potential site layout of the proposed influent pump station is shown in Figure 5-32. The location of the influent pump station is recommended to be near the existing influent pump station, however this location is flexible and will be reviewed during the holistic alternatives evaluation.

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Figure 5-32: Site Layout of Proposed Influent Pump Station Improvements The total cost of the proposed influent pump station is $5,441,000. This cost includes the pump station structure, four new pumps, associated pipes and valves as well as the allowances for electrical improvements, site civil work, contractor overhead and profit (OH&P) and engineering services. A breakdown of the costs included is shown in Table 5-37. Table 5-37: Estimated Total Project Cost of the Proposed Influent Pump Station Improvements Facility

Influent Pump Station

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

Pump Station Structure

4 3 LS LS

6 MGD Influent Pumps Slide Gates Associated Piping Associated Valves $1,883,000 $471,000 $377,000 $956,000 $184,000 $663,000 $907,000 $5,441,000

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5.2.2.

Headworks

The existing headworks facility at the Southside WWTP has a gap in capacity as well as a gap due to the lack of redundancy for the mechanical screens. An additional 17 MGD of headworks capacity is required downstream of the new influent pump station. The proposed headworks improvements include one new 17 MGD mechanical screen and one manual bar screen for redundancy. The improvements also include a 17 MGD vortex grit removal unit. A summary of the proposed design details is shown in Table 5-38. Table 5-38: Design Details of the Proposed Headworks Improvements Parameter

Value Screening Mechanical Screen Quantity 1 Screen Capacity 17 Manual Screen Quantity 1 Grit Removal Grit Removal Type Mechanical Vortex Quantity of Grit Removal Units 1 Size (each) 17

Unit MGD MGD

A PFD of the proposed headworks improvements is shown in Figure 5-33. Flow from the new influent pump station and will be sent to the new headworks facility where screenings and grit will be removed before the flow is sent to the proposed peak flow basin.

Figure 5-33: PFD of Proposed Headworks Improvements The new headworks facility is proposed to be located adjacent to the existing headworks facility, similar to the influent pump station. A site layout with the proposed location is shown in Figure 5-34.

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Figure 5-34: Potential Site Layout of the Proposed Headworks Improvements An estimate of the total project cost of the headworks improvements is shown in Table 5-39. A new channel and manual bar screen as well as channel isolation gates and piping are included in the cost. The new vortex grit system along with a bypass channel and associated gates and piping are also included. In addition, the cost includes allowances for odor control, electrical improvements, site civil improvements, contractor OH&P and engineering services. Table 5-39: Estimated Total Project Cost of the Proposed Headworks Improvements Facility

Quantity

Element

LS 1 1 4 1 1 1 1 LS

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

New Screening Structure 17 MGD Mechanical Screen Manual Bar Screen Slide Gates Screen Conveyor 17 MGD Vortex Grit Unit Grit Pump Grit Washer Compactor Odor Control System $2,443,000 $611,000 $489,000 $1,240,000 $239,000 $861,000 $1,176,000 $7,058,000

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5.2.3.

Peak Flow Basin

As previously explained, a new 1 Million Gallon (MG) PFB is proposed to store flows higher than 22.5 MGD coming into the plant. In addition to the PFB, a peak flow pump station is proposed to pump the water stored in the PFB back up to the existing grit effluent box. The design details of the proposed peak flow basin are shown in Table 5-40. Table 5-40: Design Details of the Proposed Peak Flow Basin and Peak Flow Pumps Parameter Pump Quantity Pump Size (each) Basin Diameter Basin Depth

Value

Unit

Peak Flow Pumps 2 15 Peak Flow Basin 120 12

HP ft ft

A PFD of the proposed peak flow system is shown in Figure 5-35. The screened and degritted flow from the new headworks facility will be sent to the PFB and then pumped back to the existing grit effluent box.

Figure 5-35: PFD of the Proposed Peak Flow Basin and Peak Flow Pumps There are multiple alternatives for the location of the proposed PFB. One of the potential locations, shown in Figure 5-36, is in the area currently occupied by the anaerobic digesters.

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Figure 5-36: Potential Site Layout of the Proposed Peak Flow Basin and Peak Flow Pumps The estimated total project cost of the PFB and peak flow pumps is $4,509,000, the cost is broken down in Table 5-41Table 5-41 The cost includes the PFB, the peak flow pump station and pumps, and associated piping and valves. In addition, the cost includes allowances for electrical improvements, site civil improvements, contractor OH&P and engineering services. Table 5-41: Estimated Total Project Cost for Peak Flow Basin and Peak Flow Pumps Facility

Peak Flow Basin

Facility Subtotal Electrical and Instrumentation (10%) Site Civil (10%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

LS LS LS 2 LS LS

Prefabricated 120-ft Diameter PFB Odor Control System Peak Flow Pump Station Peak Flow Pumps Associated Piping Associated Valves $1,884,000 $189,000 $189,000 $792,000 $153,000 $550,000 $3,757,000 $4,509,000

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5.2.4.

Primary Clarifiers

After peak flow storage, the existing primary clarifiers only require 4.4 MGD of additional capacity to meet the future peak flow requirements. To meet this gap, the primary clarifiers may be operated at a higher weir loading rate during peak flows. The primary clarifiers were recently rehabilitated and are in good condition, however, a new odor control system is recommended to be installed at the facility. The estimated total project cost of the odor control system is $1,700,000. The estimated cost is shown in Table 5-42. Table 5-42: Estimated Total Project Cost of Primary Clarifier Odor Control System Facility Primary Clarifier Odor Control System Facility Subtotal Electrical and Instrumentation (10%) Site Civil (10%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost 5.2.5.

Quantity 1 LS 2

Element Biotrickling Filter Ductwork and Associated Supports Primary Clarifier Covers $711,000 $71,000 $71,000 $299,000 $58,000 $207,000 $283,000 $1,700,000

Aeration Basins

The aeration basins at the Southside WWTP are large enough to handle the future flow and loadings of the plant, however, the condition of Aeration Basins 1 and 2 is not conducive to continued use. Two design alternatives were developed for how to meet the future needs at the Southside WWTP. One design alternative includes rehabilitating existing Aeration Basin 3 and constructing a new similarly sized aeration basin to meet the additional volume and aeration requirements. The other design alternative include demolition of all three existing aeration basins and construction of three new basins with diffused aeration. 5.2.5.1. Alternative 1: Rehabilitate Aeration Basin 3 and Construct Additional Volume Alternative 1 includes rehabilitating existing Aeration Basin 3 by replacing the surface aerators and constructing a new aeration basin that is sized and designed similarly to Aeration Basin 3. Table 5-43: Design Details of the Proposed Aeration Basins Parameter Quantity of Channels Length Width (each) Side Water Depth Surface Aerator Quantity Aerator Size (each)

Garver Project No. 21W05170

Value New Aeration Basin 2 130 52 14 Aeration Equipment 2 (per basin) 100

Unit ft ft ft HP

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A PFD of aeration basin alternative 1 is shown in Figure 5-37. The flow will be split by the existing aeration basin splitter box and sent to Aeration Basin 3 as well as the two new aeration basin channels. The aeration basin effluent from all three aeration basin channels will then be combined in a new secondary clarifier splitter box.

Figure 5-37: PFD of Aeration Basin Alternative 1 A site layout showing a potential location of the new aeration basin channels is shown in Figure 5-38. The basins can be located in the area currently occupied by Aeration Basin 1.

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Figure 5-38: Site Layout of Aeration Basin Alternative 1 The estimated total project cost of aeration basin alternative 1 is $17,530,000. A breakdown of the costs is shown in Table 5-44; the cost includes the new aeration basin and surface aerators, replacement of the aerators in aeration basin 3, a secondary clarifier splitter box, isolation gates, and allowances for electrical improvements, site civil work, contractor OH&P, and engineering services. Table 5-44: Estimated Total Project Cost of Aeration Basin Alternative 1 Facility

Aeration Basins

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity LS 7 7 LS LS

Element Aeration Basin Structure Surface Aerators Slide Gates Secondary Clarifier Splitter Box Demo of Existing Aeration Basins 1 & 2 $6,067,000 $1,517,000 $1,213,000 $3,079,000 $594,000 $2,138,000 $2,922,000 $17,530,000

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5.2.5.2. Alternative 2: Demolish All Existing Basins and Construct New Basins with Diffused Aeration Alternative 2 consists of demolishing all three existing aeration basins and constructing three new aeration basins with a diffused aeration system. Design details of the proposed improvements are shown in Table 5-45. Table 5-45: Design Details of Aeration Basin Alternative 2 Parameter Quantity Length Width (each) Side Water Depth Blower Quantity Blower Size (each) Diffuser Quantity

Value Aeration Basins 3 160 35 18 Aeration Equipment 4 (3 duty, 1 standby) 200 5,100

Unit ft ft ft HP -

A PFD of aeration basin alternative 2 is shown in Figure 5-39. The flow would be split equally between the three basins and then recombined before being sent to the secondary clarifiers. A blower facility would be constructed to house the blowers to provide aeration. RAS will be mixed into the process flow in the aeration basin splitter box.

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Figure 5-39: PFD of the Proposed Aeration Basins A potential site layout of the proposed aeration basins is shown in Figure 5-40. Similar to alternative 1, the aeration basins can be constructed in the location currently occupied by aeration basin 1. The blower facility can be constructed adjacent to the proposed aeration basins.

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Figure 5-40: Potential Site Layout of the Proposed Aeration Basins The estimated total project cost of the aeration basins and blower facility is $20,254,000. A breakdown of the costs is shown in Table 5-46; the cost includes the aeration basin and blower facility structures, a new secondary clarifier splitter box, associated piping and valves, and allowances for electrical improvements, site civil work, contractor OH&P, and engineering services. Table 5-46: Estimated Total Project Cost of the Proposed Aeration Basins Facility

Aeration Basins

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

LS LS 4 LS LS LS LS LS

Aeration Basin Structure Diffused Aeration System Blowers Blower Facility Concrete Pad and Canopy Associated Piping Associated Valves Secondary Clarifier Splitter Box Demo of Existing Aeration Basins $7,010,000 $1,752,000 $1,402,000 $3,558,000 $686,000 $2,470,000 $3,376,000 $20,254,000

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5.2.6.

Secondary Clarifiers

The secondary clarifiers at the Southside WWTP are in fair structural condition, however the mechanisms are reaching the end of their useful life. The recommended path forward for these basins is to demolish the existing structure and mechanisms and construct new 100-ft clarifiers. The design details of the proposed secondary clarifiers are shown in Table 5-47. Table 5-47: Design Details of the Proposed Secondary Clarifiers Parameter Quantity Type Size (Diameter)

Value Secondary Clarifiers 3 Single-Sided Weir 100

Unit ft

A PFD of the proposed secondary clarifier improvements is shown in Figure 5-41. Aeration basin effluent will be split equally between the three secondary clarifiers and then sent to the chlorine contact basin. Sludge from the secondary clarifiers will be sent to the new RAS/WAS Pump Station (proposed in Section 5.2.7).

Figure 5-41: PFD of the Proposed Secondary Clarifiers A site layout of the proposed secondary clarifier improvements is shown in Figure 5-42. The clarifiers can be rebuilt in the current location of the existing secondary clarifiers. A secondary clarifier splitter box will be constructed in a central location near the clarifiers.

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Figure 5-42: Site Layout of the Proposed Secondary Clarifier Improvements The estimated total project cost of the secondary clarifier improvements is $16,079,000. A breakdown of the costs is shown in Table 5-48. The costs include three 100-ft secondary clarifier structures, clarifier mechanisms, a clarifier splitter box structure, along with allowances for electrical improvements, site civil improvements, contractor OH&P, and engineering services. Table 5-48: Estimated Total Project Cost of the Proposed Secondary Clarifiers Facility

Secondary Clarifiers

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

3 3 3 LS LS

100-ft Secondary Clarifier Mechanisms 100-ft Secondary Clarifier Basins Scum Pumps Associated Metals Associated Piping $5,565,000 $1,391,000 $1,113,000 $2,824,000 $545,000 $1,961,000 $2,680,000 $16,079,000

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5.2.7.

Chlorine Contact Basin

The chlorine contact basin (CCB) does not require any additional capacity, however, due to the condition of the walkways, railings, and gates, minor improvements and replacements should be made. In addition, a new level sensor is included to replace the existing. The estimated total project cost of the chlorine contact basins improvements, shown in Table 5-49, is $661,000. This cost includes replacement of the walkways, railings and gates, cleaning of the basins, and installation of a new level sensor. In addition, some allowances are included to account for electrical and site civil improvements, mobilization, contractor OH&P and engineering services. Table 5-49: Estimated Total Project Cost of CCB Improvements Facility

RAS/WAS Pump Station

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost 5.2.8.

Quantity

Element

Replacement of all metals

8 1 LS

Slide Gates Level Sensor Cleaning of Basins $229,000 $57,000 $46,000 $116,000 $22,000 $81,000 $110,000 $661,000

RAW/WAS Pump Station

The existing RAS/WAS pumps do not have capacity to meet the future solids pumping demand at the Southside WWTP and are in critical condition. A new RAS/WAS pump station is proposed to pump solids from the secondary clarifiers to the aeration basin splitter box and to the solids handling facilities. Design details of the proposed RAS/WAS pump station are shown in Table 5-50. Table 5-50: Design Details of the Proposed RAS/WAS Pump Station Parameter Quantity Type Capacity (each) Quantity Type Capacity (each)

Garver Project No. 21W05170

Value RAS Pumps 4 (3 duty, 1 standby) Submersible Centrifugal 6 WAS Pumps 2 (1 duty, 1 standby) Submersible Centrifugal 250

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Unit MGD gpm

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A PFD of the proposed RAS/WAS pump station improvements is shown in Figure 5-43. The proposed pump station features a split wet well design, similar to the proposed influent pump station. This design feature allows for the two wet well sections to be isolated and individually drained for cleaning and maintenance. The sludge from the secondary clarifiers will be pumped by the RAS pumps to the aeration basin splitter box and by the WAS pumps to the solids handling facilities.

Figure 5-43: PFD of the RAS/WAS Pump Station Improvements A site layout showing the proposed location of the RAS/WAS pump station is shown in Figure 5-44. The proposed location of the RAS/WAS pump station is between existing secondary clarifiers 1 and 2. Constructing the pump station in this location would necessitate the demolition of the existing, currently decommissioned, digested sludge pump station.

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Figure 5-44: Site Layout of the Proposed RAS/WAS Pump Station The estimated total project cost of the proposed RAS/WAS pump station is $5,554,000. A breakdown of the total estimated cost is shown in Table 5-51; the cost includes the new pumps, a new pump station, associated piping and valves, as well as allowances for electrical and site civil improvements, contractor OH&P, and engineering services. Table 5-51: Estimated Total Project Cost of the Proposed RAS/WAS Pump Station Facility

RAS/WAS Pump Station

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

Pump Station Structure

4 2

RAS Pumps WAS Pumps

3 LS LS

Slide Gates Associated Piping Associated Valves $1,922,000 $481,000 $384,000 $976,000 $188,000 $677,000 $926,000 $5,554,000

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5.2.9.

Gravity Belt Thickener

There is no capacity gap for the gravity belt thicker (GBT) at the Southside WWTP, however the city has requested that a second GBT be considered in the master plan to provide redundancy. In addition, the condition of the existing GBT is not adequate for use over the master planning horizon and will be considered to be replaced as a part of the GBT improvements. There is no space in the existing GBT facility to house a second GBT, so an addition to the building space is proposed. The design details of the GBT improvements are shown in Table 5-52. Table 5-52: Design Detail of the GBT Building Improvements Parameter

Value Sludge Dewatering Quantity of Belt Filter Presses 2 GBT Size 1 GBT Hydraulic Loading Rate (each) 1,250

Unit m lb/hr

A PFD of the GBT improvements is shown in Figure 5-45. The new GBT and replaced existing GBT will receive solids from the WAS pumps. The WAS will be mixed with polymer, thickened and then pumped by thickened sludge pumps to the sludge holding tank.

Figure 5-45: PFD of the Proposed GBT Improvements A site layout exhibiting the potential location of the GBT building expansion is shown in Figure 5-46.

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Figure 5-46: Site Layout of Proposed GBT Building Addition The estimated total project cost of the GBT building expansion is $5,071,000. A breakdown of the cost is shown in Table 5-53; the cost includes the two GBTs, a new polymer system, two new thickened sludge pumps, the building expansion, as well as allowances for electrical and site civil improvements, contractor OH&P and engineering services. Table 5-53: Estimated Total Project Cost of the GBT Building Expansion Facility

GBT Building Expansion

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%)

Quantity

Element

Gravity Belt Thickeners

2 1 LS LS

Thickened Sludge Pumps Polymer System GBT Building Expansion Associated Piping $1,755,000 $439,000 $351,000 $891,000

Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

$172,000 $618,000 $845,000 $5,071,000

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5.2.10. Sludge Holding Tank The existing sludge holding tank was determined to have a high criticality due to the age and condition of the mixing equipment. The recommended path forward is to construct a second sludge holding tank to provide redundancy. Design details of the proposed sludge holding tank is shown in Table 5-54. Table 5-54: Design Details of the Proposed Sludge Holding Tan Parameter Quantity Size (Diameter) Depth

Value Sludge Holding Tank 1 100 10

Unit ft ft

A PFD of the proposed sludge holding tank is shown in Figure 5-47. The proposed sludge holding tank, similar to the existing tank, will receive thickened solids from the GBTs. Solids from the holding tanks will then be sent to the dewatering system.

Figure 5-47: PFD of the Proposed Sludge Holding Tank A potential site layout of the proposed sludge holding tank is shown in Figure 5-48. The proposed sludge holding tank location could be next to the existing sludge holding tank, if aeration basin 3 is demolished. This location was chosen to increase the ease of operation and limit the required site piping improvements.

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Figure 5-48: Potential Site Layout of the Proposed Sludge Holding Tank The estimated total project cost of the proposed sludge holding tank is $3,152,000. A breakdown of the cost is shown in Table 5-55; this includes the cost of the tank, mixers, sludge transfer pumps, and associated piping, as well as allowances for electrical and site civil improvements, contractor overhead and profit (OH&P), and engineering services. Table 5-55: Estimated Total Project Cost of the Proposed Sludge Holding Tank Facility

Sludge Holding Tank

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%)

Quantity

Element

100-ft Sludge Holding Tank

3 2 LS

Mixers Sludge Transfer Pumps Associated Piping $1,091,000 $273,000 $218,000 $554,000 $107,000

Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

$384,000 $525,000 $3,152,000

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5.2.11. Dewatering Facility The existing dewatering facility has a future gap of 1,200 lb/hr. An additional BFP unit is required to meet this gap, however the existing dewatering facility does not have space to house a third BFP unit. Similar to the GBT building, a building expansion is proposed for the dewatering facility to house an additional BFP. Design details of the proposed BFP are shown in Table 5-56. Table 5-56: Design Details of the Proposed New BFP Parameter

Value Sludge Dewatering Quantity of Belt Filter Presses 1 BFP Size 2 BFP Hydraulic Loading Rate (each) 1,600

Unit m lb/hr

A PFD of the proposed dewatering building expansion is shown in Figure 5-49. The new BFP will receive solids from the sludge holding tank and discharge the dewatered solids to a truck for disposal.

Figure 5-49: PFD of the Proposed Dewatering Building Expansion A site layout exhibiting the location of the dewatering building expansion is shown in Figure 5-50. The area on site adjacent to the existing dewatering building is suitable for the building expansion.

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Figure 5-50: Site Layout of the Dewatering Facility Expansion The estimated total project cost of the dewatering facility expansion is $4,039,000. A breakdown of the estimated cost is shown in Table 5-57.The cost shown includes a new 2-m BFP, a new sludge conveyor, the cost of expanding the dewatering building, associated piping, and allowances for electrical and site civil improvements, contractor OH&P and engineering services. Table 5-57: Estimated Total Project Cost of the Dewatering Facility Expansion Facility

Dewatering Facility Expansion

Facility Subtotal Electrical and Instrumentation (25%) Site Civil (20%) Contingency (35%) Mobilization (5%) Contractor OH&P (18%) Professional Services (20%) Estimated Project Cost

Garver Project No. 21W05170

Quantity

Element

Belt Filter Press

1 LS LS

Sludge Conveyor Dewatering Facility Expansion Associated Piping $1,398,000 $349,000 $280,000 $709,000 $137,000 $493,000 $673,000 $4,039,000

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5.2.12. Summary of Available Alternatives at the Southside WWTP A summary of the available alternatives and estimated costs for these improvements at the Southside WWTP is shown in Table 5-58. Table 5-58: Estimated Total Project Costs of Recommended Improvements Facility Influent Pump Station Headworks Peak Flow Basin Primary Clarifiers Aeration Basins Secondary Clarifiers Chlorine Contact Basin RAS/WAS Pump Station GBT Building Sludge Holding Tank Sludge Dewatering Facility

Estimated Total Project Cost

Project Description Construct new influent pump station to pump flows above 22.5 MGD Construct new headworks facility to treat flow above 22.5 MGD Construct new PFB and peak flow pump station Install odor control Alternative 1: Rehabilitate Aeration Basin 3 and build new basin Alternative 2: Construct new diffused aeration basins Rebuild all three existing clarifiers Clean basins and replace all walkways, railings, and gates Construct a new RAS/WAS pump station Expand building to house one additional GBT unit and replace existing unit Construct one additional sludge holding tank Expand building to house one additional BFP

$5,441,000 $7,058,000 $4,509,000 $1,700,000 $17,530,000 $20,254,000 $16,079,000 $661,000 $5,554,000 $5,071,000 $3,152,000 $4,039,000

6. Conclusion Within this TM, findings of the process and hydraulic models created for the Westside and Southside WWTPs were presented. In addition, the capacities of each facility were determined and compared to future flow and loading projections to analyze the treatment gaps at both WWTPs. Design recommendations and alternatives were then developed to meet the identified gaps. For each proposed design, the details of the design were presented along with a process flow diagram, a site layout, and an estimated total project cost. In the next master plan task, the design recommendations and alternatives will be evaluated all together in the holistic alternatives analysis.

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Appendix D Holistic Alternatives TM

Garver Project No. 21W05170

Appendix D

Technical Memorandum Holistic Alternatives Evaluation City of Tyler Wastewater Treatment Plants Master Plan City of Tyler, Texas

Prepared by:

14160 Dallas Parkway Suite 850 Dallas, TX 75254 April 2023 Garver Project No. 21W05170

Tyler Wastewater Treatment Plants Master Plan Holistic Alternatives Evaluation Technical Memorandum

Engineer’s Certification I hereby certify that this Holistic Alternatives Evaluation Technical Memorandum, associated with the Tyler Wastewater Treatment Plants Master Plan, was prepared by Garver under my direct supervision for the City of Tyler.

Justin A. Rackley, PE State of TX PE License #102342

Digitally signed 04/19/2023

Russell D. Tate, PE State of TX PE License #132233 Digitally Signed 04/20/2023

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Table of Contents 1.0

Introduction .................................................................................................................................. 5

1.1

Design Impacts Overview ......................................................................................................... 5

1.2

Estimated Total Project Cost Assumptions ............................................................................... 6

2.0

Westside WWTP .......................................................................................................................... 6

2.1

Baseline Analysis Recommendations ....................................................................................... 6

2.2

Holistic Alternative .................................................................................................................... 7

3.0

Southside WWTP....................................................................................................................... 13

3.1

Baseline Analysis Recommendations ..................................................................................... 13

3.2

Holistic Alternative .................................................................................................................. 14

4.0

Conclusion ................................................................................................................................. 20

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List of Figures Figure 2-1: PFD of Westside WWTP Holistic Alternative .......................................................................... 9 Figure 2-2: Site Layout of Westside WWTP Holistic Alternative .............................................................. 10 Figure 2-3: Hydraulic Profile for Westside WWTP Holistic Alternative ..................................................... 11 Figure 2-4: Simplified Layout of Westside WWTP Process Model .......................................................... 11 Figure 3-1: PFD of the Southside WWTP Holistic Alternative ................................................................. 16 Figure 3-2: Site Layout of Southside WWTP Holistic Alternative ............................................................. 17 Figure 3-3: Hydraulic Profile for Southside WWTP Holistic Alternative.................................................... 18 Figure 3-4: Simplified Layout of Southside WWTP Process Model ......................................................... 18

List of Tables Table ES-1: Estimated Total Project Cost of the Holistic Improvements Alternatives………………………. 5 Table 1-1: Preliminary Cost Estimate Contingency and Contractor Margins.............................................. 6 Table 2-1: Holistic Improvements for the Westside WWTP ....................................................................... 7 Table 2-2: Westside WWTP Process Modeling Results .......................................................................... 12 Table 2-3: Estimated Total Project Cost for Westside WWTP Holistic Alternative ................................... 13 Table 3-1: Holistic Improvements for the Southside WWTP.................................................................... 14 Table 3-2: Southside WWTP Process Modeling Results ........................................................................ 19 Table 3-3: Estimated Total Project Cost for Southside WWTP Holistic Alternative .................................. 20

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List of Acronyms Acronym

Definition

ADF

Average Daily Flow

BFP

Belt Filter Press

BOD

Biochemical Oxygen Demand

CaCO3

Calcium Carbonate

cBOD

Carbonaceous Biochemical Oxygen Demand

CCB

Chlorine Contact Basin

COD

Chemical Oxygen Demand

Dissolved Oxygen

GBT

Gravity Belt Thickener

Hour

lb/d

Pounds per Day

MGD

Million Gallons per Day

mg/L

Milligrams per Liter

Milliliters

N/A

Not Applicable

NH3-N

Ammonia-Nitrogen

OPCC

Opinion of Probable Construction Cost

P2HF

Peak Two-Hour Flow

PFB

Peak Flow Basin

PFD

Process Flow Diagram

RAS

Return Activated Sludge

SHT

Sludge Holding Tank

TCEQ

Texas Commission on Environmental Quality

TKN

Total Kjeldahl Nitrogen

Technical Memorandum

Total Nitrogen

Total Phosphorous

TPDES

Texas Pollutant Discharge Elimination System

TSS

Total Suspended Solids

VSS

Volatile Suspended Solids

WAS

Waste Activated Sludge

WWTP

Wastewater Treatment Plant

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Tyler Wastewater Treatment Plants Master Plan Holistic Alternatives Evaluation Technical Memorandum

Executive Summary Within this technical memorandum (TM), holistic alternatives are presented for the improvements at the Westside Wastewater Treatment Plant (WWTP) and the Southside WWTP in Tyler, TX. The holistic alternatives presented are designed to address the condition concerns as well as the treatment gaps identified in the previous deliverables. Full plant hydraulic profiles and process models were created to confirm that the holistic alternatives are feasible and can achieve the effluent treatment requirements. Site layouts and process flow diagrams (PFDs) were also created and presented in the TM. Estimated total project costs for the two holistic alternatives were developed and are shown in Table ES-1. Table ES-1: Estimated Total Project Cost of the Holistic Improvements Alternatives WWTP

1.0

Estimated Total Project Cost

Westside WWTP

$112,940,000

Southside WWTP

$89,582,000

Introduction

The purpose of this TM is to combine the previously presented recommendations and design alternatives into whole-plant holistic designs. The previous design alternatives analysis, presented in the Baseline Analysis TM, considered the improvements independent of one another. However, the work presented in this TM aims to develop a whole plant improvement approach that combines the recommended improvements cohesively. Any consequences related to the recommended designs will be identified and mitigated in these alternatives. One holistic alternative will be presented for each of the Westside and Southside WWTPs that include whole-plant site layouts, PFDs, and total project cost estimates. During development of the Baseline Analysis TM, Garver’s design team created full plant hydraulic and biological process models for both of the existing Tyler WWTPs. The hydraulic model was used to identify hydraulic bottlenecks within the WWTPs and the biological process model was used to simulate the existing liquid and solids treatment processes and identify deficiencies. The existing infrastructure at the plants was also reviewed during the gap analysis to identify areas in the plant where either the size or condition of the existing processes was inadequate to meet the projected future requirements of the plants. Garver then performed a needs assessment, in which the needs of the two WWTPs were identified and design alternatives for how to meet these needs were developed. In the following sections, the design alternatives that were presented in the Baseline Analysis TM are reviewed and holistic alternatives are presented. 1.1

Design Impacts Overview

The design alternatives shown in the previous deliverables were developed independently of one another and further considerations must be made to ensure that each of the proposed improvements is feasible in relation to the other improvements. A list of the potential impacts includes: -

Change in the hydraulic grade line

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Improvements that render other facilities redundant Increase of the process capacity Increase of operational flexibility Site constraints

These impacts have been considered and mitigated as a part of the holistic alternatives evaluation. 1.2

Estimated Total Project Cost Assumptions

Estimated total project costs for each of the holistic alternatives in this TM are represented in 2023 U.S. dollars. The cost estimating criteria used throughout the master plan project was detailed in the Planning Criteria TM, dated July 2022. The contingency and contractor margin assumptions from that TM, shown in Table 1-1, will be utilized for the holistic alternatives cost estimates as well. Table 1-1: Preliminary Cost Estimate Contingency and Contractor Margins Consideration

Assumption

Contingency

35%

Mobilization

Contractor Overhead and Profit

18%

The unit cost assumptions for excavation, backfill, concrete, electrical and site civil work were increased from the previously presented baseline analysis to reflect market increases in 2023.

2.0

Westside WWTP

The Westside WWTP requires multiple improvements to ensure that the plant can treat the future flow and loadings. These improvements have been discussed in the previous master plan deliverables and will be combined in this section of the TM. The following sections include a summary of the previously discussed improvements and a holistic alternative for the Westside WWTP, including a PFD, site layout, updated hydraulic profile and process model, and an estimated total project cost. 2.1

Baseline Analysis Recommendations

The improvements recommended in the Baseline Analysis TM for the Westside WWTP are listed below. The alternatives shown in bold were selected by the design team and Tyler Water Utilities for the holistic alternative evaluation. • •

•

Headworks o Decommission existing facility and construct a new headworks facility Raw Water Pump Station o Decommission existing and construct a new IPS structure, including peak flow pumping Peak Flow Basin o Alternative 1: Build new peak flow basin (PFB) o Alternative 2: Utilize existing infrastructure for peak flow storage Primary Clarifiers o Alternative 1: Replace clarifier mechanisms

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•

• • •

•

2.2

o Alternative 2: Build new primary clarifiers at a higher elevation Biological Treatment Train o Alternative 1: Rehabilitate existing nitrification basin o Alternative 2: Build new aeration basins utilizing diffused aeration Filter Pump Station o Construct a duplicate filter pump station Secondary Clarifiers o Replace clarifier mechanisms with double sided weir mechanisms Chlorine Contact Basin o Raise walls of existing basin and construct a new effluent Parshall flume channel o Replace surface aerators with larger units RAS/WAS Pump Station o Decommission existing pump station and build a new RAS/WAS pump station Anaerobic Digesters o Clean basins, repair concrete, fill in conical floor, install floating surface aerators Dewatering Facility o Build additional dewatering facility space to house two additional belt filter presses (BFPs) Sludge Holding Lagoon o Replace lagoon liner and install mixers Holistic Alternative

The holistic alternative for the Westside WWTP considers primary clarifier alternative 2 from the Baseline Analysis TM. The improvements include a full reconstruction of the primary clarifier basins at a higher elevation. The resulting impact on the hydraulic profile of the plant would increase the required size of the influent pumps and eliminate the need for intermediate pumping. This alternative also impacts the available options for peak flow storage. A full list of the design details of the Westside WWTP holistic alternative are shown below in Table 2-1. Table 2-1: Holistic Improvements for the Westside WWTP Facility

Mechanical Screening

Grit Removal

Influent Pump Station

Primary Clarifiers Aeration Basins

Garver Project No. 21W05170

Improvements • • • • • • • • • • • • • •

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Tyler Wastewater Treatment Plants Master Plan Holistic Alternatives Evaluation Technical Memorandum

Facility

Improvements •

Filter Pump Station Secondary Clarifiers

RAS/WAS Pump Station

Chlorine Contact Basin

Sludge Digesters

Sludge Dewatering Sludge Lagoon Rehabilitation

• • • • •

Construct 3 new aeration basin channels utilizing diffused aeration Construct a new blower facility 4 new blowers Decommission existing filter pump station Rehabilitate the existing 150-ft secondary clarifiers with double sided weir mechanisms Decommission existing RAS pump station Construct a new RAS/WAS pump station 4 new RAS pumps 2 new WAS pumps Raise the outer walls of the existing chlorine contact basin Replace the existing surface aerators Construct a new Parshall flume channel Remove existing basin covers, repair existing basins and fill in the conical floors Install a diffused aeration system Construct a new blower facility 3 new blowers Construct additional dewatering facility area Install 2 additional 2-m Belt Filter Presses (BFPs)

•

Replace the sludge lagoon liner and install mixers

• • • • • • • • • • • •

2.2.1.1 Process Flow Diagram Figure 2-1 shows a PFD of the Westside holistic improvements. The holistic alternative improvements include a new headworks facility and a new influent pump station to replace the existing facilities. As these improvements include constructing new primary clarifiers at a higher elevation, the existing primary clarifiers, which are in good structural condition, can be reused as PFBs. New splitter boxes upstream of the primary clarifiers and the nitrification basin are included to ensure an even flow split between each unit. All new aeration basin channels are included along with a blower facility. The secondary clarifier mechanisms will be replaced along with the metal components of the basins. A new effluent Parshall flume will be constructed, and the walls of the chlorine contact basin will be raised. In addition, a whole new sludge pump station will be built, housing both RAS pumps and WAS pumps. The anaerobic digester basins will be converted into aerated SHTs via the addition of surface aerators, and the dewatering building will be expanded to house two new BFPs. The sludge lagoon will also be rehabilitated, and a new sludge pump station will be constructed.

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Figure 2-1: PFD of Westside WWTP Holistic Alternative

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2.2.1.2 Site Layout A potential site layout of the Westside WWTP holistic alternative is shown in Figure 2-2. Though many new structures are proposed, the footprint of the overall site will not change. As shown, to make room for new facilities, the first stage and second stage trickling filter basins will be decommissioned and demolished.

Figure 2-2: Site Layout of Westside WWTP Holistic Alternative

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2.2.1.3 Hydraulic Profile Figure 2-3 shows the hydraulic profile of the Westside WWTP holistic alternative. The effluent pipe will be increased from 48” to 54” and a new effluent Parshall flume will be constructed for flow measurement. The chlorine contact basin walls will be raised to accommodate the 100-year flood elevation. To eliminate the need for intermediate pumping via the filter pump station, the primary clarifiers and new splitter boxes proposed in this alternative will be built at a higher elevation than the existing nitrification basins. Site grading improvements will be required to enable construction at these elevations.

Figure 2-3: Hydraulic Profile for Westside WWTP Holistic Alternative 2.2.1.4 Process Model The Westside WWTP holistic alternative was modeled in GPS-X to confirm that the proposed design is sufficient to treat the wastewater. Figure 2-4 shows a simplified layout of the GPS-X process model.

Influent

Mg(OH)2 Injection

Primary Clarifier

Aeration Basin

Secondary Clarifier

Effluent

WAS Primary Sludge

RAS

Figure 2-4: Simplified Layout of Westside WWTP Process Model Table 2-2 illustrates the process modeling results for the Westside WWTP at average daily flow of 14.0 MGD and the maximum month flow of 20.4 MGD at a liquid temperature of 55oF. Concentrations of different parameters are shown for the main process streams. As shown, the secondary clarifier effluent parameters, such as TSS, cBOD, and ammonia, all achieve the specific TPDES permit requirements.

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Table 2-2: Westside WWTP Process Modeling Results Item

Unit

Influent

Primary Clarifier Effluent

Aeration Basin Effluent

Secondary Clarifier Effluent

Primary Sludge

RAS

WAS

TPDES Permit

Average Daily Flow: 14.0 MGD Flow

MGD

14.00

14.12

24.62

13.99

0.06

10.50

0.14

TSS

mg/L

180

119

4,454

14.3

42,960

10,293

cBOD

mg/L

162

131

1,044

6.5

15,823

2,408

COD

mg/L

441

344

5,658

58,500

12,990

NH3-N

mg/L

23.0

22.8

0.53

TKN

mg/L

323

2,349

742

Mar-Nov: 15 Dec-Fed: 20 Mar-Nov: 10 Dec-Fed: 20 Mar-Nov: 3 Dec-Fed: 10

Maximum Monthly Flow: 20.4 MGD Flow

MGD

20.40

20.54

30.74

20.38

0.08

10.20

0.16

TSS

mg/L

173

3,141

13.0

27,860

9,295

cBOD

mg/L

142

104

980

8.49

10,200

2,892

COD

mg/L

387

254

3,809

35,583

11,154

NH3-N

mg/L

22.8

0.95

TKN

mg/L

35.2

29.4

223

4.8

1,550

652

Note: *GPS-X model has calculated organic matter in MLSS as cBOD content in aeration basin effluent.

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Tyler Wastewater Treatment Plants Master Plan Holistic Alternatives Evaluation Technical Memorandum

2.2.1.5 Estimated Total Project Cost Estimated total project costs of the holistic improvements is shown in Table 2-3. This cost includes the opinion of probable construction cost (OPCC) of each of the improvements, along with assumptions for contractor overhead and profit (OH&P) and engineering design services. The estimated total cost of the improvements is $112,940,000. Table 2-3: Estimated Total Project Cost for Westside WWTP Holistic Alternative

3.0

Facility

Estimated Total Project Cost

Sludge Lagoon Rehabilitation Peak Flow Basin (Existing Primary Clarifiers) Headworks Raw Water Pump Station Primary Clarifiers Aeration Basins Secondary Clarifiers Chlorine Contact Basin and Effluent Parshall Flume RAS/WAS Pump Station Aerated Sludge Holding Tanks Dewatering Building Total

$3,490,000 $489,000 $12,218,000 $12,805,000 $16,925,000 $34,327,000 $9,283,000 $3,108,000 $6,822,000 $2,868,000 $10,896,000 $112,940,000

Southside WWTP

The improvements required at the Southside WWTP were previously discussed in the Baseline Analysis TM. The following section includes a summary of the previously discussed improvements and a holistic alternative for the Southside WWTP, including a PFD, site layout, updated hydraulic profile and process model, and an estimated total project cost. 3.1

Baseline Analysis Recommendations

The improvements recommended in the Baseline Analysis TM for the Southside WWTP are listed below. The alternatives shown in bold were selected by the design team and Tyler Water Utilities for the holistic alternative evaluation. • •

• • •

Influent Pump Station o Build new influent pump station to pump flows above 22.5 MGD Headworks o Build new headworks housing screening and grit removal equipment to treat flows above 22.5 MGD Peak Flow Basin o Construct new PFB to provide peak flow storage Primary Clarifiers o Install odor control Aeration Basins o Alternative 1: Demolish aeration basins 1 and 2. Rehabilitate aeration basin 3 and build additional aeration basin volume.

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•

• • •

• •

Alternative 2: Demolish all existing aeration basins and build new diffused-air aeration basins Secondary Clarifier o Demolish existing basins and construct three new 100-ft clarifiers with double sided weir mechanisms Chlorine Contact Basin o Replace metal components RAS/WAS Pump Station o Decommission existing pump station and construct a new RAS/WAS pump station Sludge Thickening Facility o Construct additional building space to house an additional gravity belt thickener (GBT) Sludge Holding Tank o Construct a new sludge holding tank Dewatering Facility o Construct additional building space to house an additional BFP

In addition to the baseline analysis improvements, a stormwater levee will also be included in the design to mitigate flooding at the site. Further analysis is needed during detailed design to determine if an effluent pump station would be required in addition to the stormwater levee. 3.2

Holistic Alternative

A full list of the design details of the Southside WWTP holistic improvements are shown below in Table 3-1. All of the recommended improvements from the baseline analysis are included in the holistic improvements design including all new aeration basins with diffused aeration. Table 3-1: Holistic Improvements for the Southside WWTP Facility Stormwater Levee Influent Pump Station

Improvements • • • • • •

Mechanical Screening

Grit Removal Peak Flow Storage Primary Clarifiers Aeration Basins

Garver Project No. 21W05170

• • • • • • • • •

Construct a 12-ft wide levee around the southern portion of the site. Maintain existing screw pump station Construct a new submersible influent pump station 4 new peak flow pumps Maintain existing mechanical screens Construct a new headworks structure adjacent to the existing facility 1 new mechanical screen 1 new manual screen Maintain existing grit removal system 1 new vortex grit removal unit New grit pumps and grit classifiers Construct a new 120-ft diameter peak flow storage basin Maintain existing primary clarifiers Install odor control Decommission and demolish existing aeration basins

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Tyler Wastewater Treatment Plants Master Plan Holistic Alternatives Evaluation Technical Memorandum

Facility

Improvements •

Sludge Holding Tank

• • • • • • • • • •

Sludge Thickening

• •

Secondary Clarifiers RAS/WAS Pump Station Chlorine Contact Basin (CCB)

Sludge Dewatering

• •

Construct 3 new aeration basin channels utilizing diffused aeration Construct a new blower facility 4 blowers Rebuild the three existing secondary clarifiers Demolish existing RAS pump station Construct a new RAS/WAS pump station 4 new RAS pumps 2 new WAS pumps Replace the metal components of the existing CCB Maintain existing sludge storage tank Construct a second 100-ft diameter sludge storage tank Replace the existing GBT Construct additional GBT Building space to house a second GBT Construct additional dewatering facility area Install 1 additional 2-m BFP

3.2.1.1 Process Flow Diagram Figure 3-1 shows the PFD of the Southside WWTP holistic alternative. The proposed holistic alternative improvements utilize the existing influent screw pump station and headworks facility to treat the influent flows up to 22.5 MGD. Flows above 22.5 MGD will be sent to a new influent pump station and headworks facility to remove screenings and grit and send the influent to a new PFB. Odor control will be installed for the influent pump station, headworks facilities, and primary clarifiers. New aeration basins will be constructed that utilize diffused aeration; the existing aeration basins will be demolished. The secondary clarifiers will be rebuilt with higher walls to accommodate hydraulic fluctuations at the plant. A new RAS/WAS pump station is also be included to send RAS to the aeration basin splitter box and WAS to the gravity belt thickener (GBT) facility. The GBT facility will be expanded to house an additional GBT and the existing GBT will be replaced. The dewatering building will also be expanded to house an additional BFP. A new sludge holding tank will be constructed to provide redundancy in the solids handling train.

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Figure 3-1: PFD of the Southside WWTP Holistic Alternative Garver Project No. 21W05170

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Tyler Wastewater Treatment Plants Master Plan Holistic Alternatives Evaluation Technical Memorandum

3.2.1.2 Site Layout A potential site layout of the Southside WWTP holistic alternative is shown in Figure 3-2. Though many new structures are proposed, the footprint of the overall site will not change. As shown, to make room for new facilities, all three existing aeration basins will be decommissioned and demolished along with the existing RAS/WAS pump station.

Figure 3-2: Site Layout of Southside WWTP Holistic Alternative 3.2.1.3 Hydraulic Profile Figure 3-3 shows the hydraulic profile of the Southside WWTP holistic alternative. The secondary clarifiers and new aeration basins will be constructed at elevations that prevent the structures from flooding at peak flows and during the 100-year storm event. Consequently, the weirs within the existing aeration basin splitter box will need to be raised slightly. No improvements will need to be made to the primary clarifiers or other upstream facilities to accommodate this change. The site levee will be constructed to limit flooding of the site. As previously mentioned, the impact of the levee on site hydraulics should be further evaluated to determine if the construction of an effluent pump station is necessary.

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Figure 3-3: Hydraulic Profile for Southside WWTP Holistic Alternative 3.2.1.4 Process Model The Southside WWTP holistic alternative was modeled in GPS-X to confirm that the proposed design is sufficient to treat the wastewater. Figure 3-4 shows a simplified layout of the GPS-X process model. Influent

Mg(OH)2 Injection

Primary Clarifier

Aeration Basin

Secondary Clarifier

Effluent

WAS Primary Sludge

RAS

Figure 3-4: Simplified Layout of Southside WWTP Process Model Table 3-2 illustrates process modeling results for Southside WWTP at average daily flow of 10.0 MGD and the maximum month flow of 12.8 MGD at a liquid temperature of 55oF. Concentrations of different parameters are shown for the main process streams. As shown, he secondary clarifier effluent parameters, such as TSS, cBOD, and ammonia, all achieve the specific TPDES permit requirements.

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Table 3-2: Southside WWTP Process Modeling Results Item

Unit

Influent

Primary Clarifier Effluent

Aeration Basin Secondary Effluent Clarifier Effluent Average Daily Flow: 10 MGD

Primary Sludge

RAS

WAS

Flow

MGD

10.00

10.12

17.62

9.99

0.04

7.50

0.13

TSS

mg/L

259

138

4,409

14.1

33,619

10,161

cBOD

mg/L

146

108

823

7.3

9,143

1,891

COD

mg/L

534

333

6,067

49,996

13,939

NH3-N

mg/L

19.8

0.94

TKN

mg/L

204

3.7

740

466

TPDES Permit

Mar-Nov: 15 Dec-Fed: 20 Mar-Nov: 10 Dec-Fed: 20 Mar-Nov: 3 Dec-Fed: 10

Maximum Monthly Flow: 12.8 MGD Flow

MGD

12.80

12.97

22.57

12.79

0.06

9.60

0.19

TSS

mg/L

293

139

4,264

11.3

36,344

9,819

cBOD

mg/L

144

103

855*

7.6

8,734

1,962

COD

mg/L

526

307

5,252

47,692

12,049

NH3-N

mg/L

1.56

TKN

mg/L

185**

4.1

741

422

Note: *GPS-X model has calculated organic matter in MLSS as cBOD content in aeration basin effluent.

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3.2.1.5 Estimate Total Project Cost Estimated total project costs of each of the holistic improvements for the Southside WWTP is shown in Table 3-3. This cost includes the OPCC of each of the improvements, along with assumptions for contractor OH&P and engineering design services. The total estimated cost of the improvements is $89,582,000. Table 3-3: Estimated Total Project Cost for Southside WWTP Holistic Alternative Facility

Estimated Total Project Cost

Stormwater Levee Influent Pump Station Headworks Peak Flow Basin Primary Clarifiers Aeration Basins Secondary Clarifiers Chlorine Contact Basin RAS/WAS Pump Station GBT Building Sludge Holding Tank Dewatering Building Total

4.0

$979,000 $5,929,000 $7,645,000 $4,616,000 $1,700,000 $25,432,000 $21,193,000 $780,000 $6,923,000 $5,515,000 $4,478,000 $4,392,000 $89,582,000

Conclusion

Two holistic alternatives, one for Westside WWTP and one for Southside WWTP, were presented in this TM. The holistic designs including a process flow diagram, site layout, hydraulic profile, process model, and estimated total project cost were all presented. The recommended design for the Westside WWTP had a total estimated project cost of $112,940,000, and for the Southside WWTP had a total project cost of $89,582,000.

Garver Project No. 21W05170

Page 20

Appendix E Southside Conveyance Alternatives Memorandum

Garver Project No. 21W05170

Appendix E

14160 N. Dallas Parkway Suite 850 Dallas, TX 75254 TEL 214.451.2950 www.GarverUSA.com

City of Tyler WWTPs Master Plan: Conveyance Alternatives Memorandum To: From:

Tyler Water Utilities Garver

Date:

01/31/2023

Introduction The City of Tyler has expressed interest in constructing a new greenfield Wastewater Treatment Plant (WWTP) in southern Smith County to minimize the capital investment necessary to expand Southside WWTP to meet future demands and has asked Garver to prepare high-level opinions of probable construction costs (OPCC) for various alternatives. The existing Southside WWTP is located in an area of growth and development in the City of Tyler and concerns have been raised citing the potential for odorous gases to impact the public in proximity to the WWTP. Because of this, the City of Tyler is looking to understand the cost implications of decommissioning the existing Southside WWTP in favor of constructing a new greenfield WWTP in southern Smith County, east of the City of Bullard. During the Baseline Analysis Workshop on October 17th, 2022, three OPCCs were presented to the City of Tyler for different alternatives for a potential greenfield WWTP. The purpose of this memorandum is to describe these alternatives and present the OPCCs associated with each alternative. Background and Assumptions The City of Tyler currently has two collection system basins. Wastewater from the north basin shaded in blue on Figure 1 is sent to Westside WWTP for treatment and the south basin shaded in pink is sent to the Southside WWTP for treatment. Figure 1 illustrates the delineation between the two collection system basins.

Figure 1: City of Tyler WWTP Collection Basin Delineation from the Previous Hydraulic Model Report (2020) The current and projected future flows from the Southside WWTP collection basin are shown in Table 1. The 2052 projected average daily flow (ADF) is 10 million gallons per day (MGD), and the 2052 projected peak 2-hour flow (P2HF) is 39.5 MGD. These flows were established for Southside WWTP in the Planning Criteria TM.

Table 1: Comparison of Existing and Future Flows from the Southside WWTP Collection Basin Southside WWTP Parameter Current Flows

Projected Future Flow

ADF

7.0 MGD

10 MGD

P2HF

22.5 MGD

39.5 MGD

Future growth of the City of Tyler is expected in both the Westside WWTP and Southside WWTP collection basins. Growth areas identified by Halff Associates, Inc. (Halff) as a part of the Water Master Plan for the City of Tyler, were used to determine the potential locations of future collection system piping and lift stations that will be required to route wastewater from new developments to either Southside WWTP or a new greenfield WWTP. A plot of land was purchased by the City of Tyler (approximately 9 miles south of the existing Southside WWTP, east of the City of Bullard) to be used for the location of the greenfield WWTP. This location was used in the alternatives analysis to estimate collection system improvements. It was assumed that lift stations would be required to pump wastewater from the growth areas to either Southside WWTP or the new greenfield WWTP. The lift stations were assumed to be located at the low points of the Southside WWTP collection basin. The quantity and size of the lift stations were estimated for each alternative, as well as the collection system and force main piping. Some other assumptions and allowances that were made when developing the OPCCs include: • • • • • •

AACE Class 5 representing 0% to 2% concept screening Standard Lift Station Cost: $650,000/million gallons of wastewater pumped Overall Contingency: 35% Mobilization Allowance: 5% Contractor OH&P: 18% Engineering Services: 12%

Evaluated Alternatives Three alternatives were evaluated by Garver for the City of Tyler future growth plan in the Southside WWTP collection basin. This alternatives evaluation aims to weigh the costs and benefits of varying levels of utilization of the existing Southside WWTP. The alternatives are described below: •

Alternative 1: Maintain and utilize the existing Southside WWTP for future growth o

•

Alternative 1 includes addressing the condition related issues at Southside WWTP, increasing the overall capacity of the plant to treat future flow and loadings from the Southside WWTP collection basin, and odor control improvements. This alternative also includes cost for collection system improvements to route flow from the new growth areas to Southside WWTP. No greenfield plant will be constructed in Alternative 1.

Alternative 2: Maintain the existing Southside WWTP at its current permitted treatment capacity and build a new greenfield WWTP to treat the additional projected future growth o

Alternative 2 includes addressing the condition related issues at Southside WWTP to maintain the current permitted treatment capacity, odor control improvements at Southside WWTP, and constructing a new greenfield WWTP in the location allocated for future construction to treat the additional future flow and loadings. This alternative includes collection system improvements to route flow from the new growth areas to the new greenfield WWTP.

•

Alternative 3: Decommission existing Southside WWTP and construct new greenfield WWTP to handle all future flow and loadings from the Southside WWTP collection basin. o

Alternative 3 includes a full decommissioning and demolition of Southside WWTP. A new greenfield is considered to treat the future projected flow and loading for the Southside WWTP collection basin. This alternative also includes costs for collection system improvements to route all flow from the collection basin to the new greenfield WWTP.

Comparison of Alternatives Alternative 1: Maintain and utilize the existing Southside WWTP for future growth Alternative 1 requires the full build out expansion and rehabilitation of Southside WWTP including odor control improvements. The overall estimated OPCC for improvements at Southside WWTP is $80 Million. The details of the OPCC associated with increasing the capacity of Southside WWTP to 39.5 MGD were presented in the Peak Flow Comparison memo, dated October 2022. The estimated OPC includes the improvements listed in the Peak Flow Comparison memo, as well as a new stormwater levee to mitigate flooding of the site. The collection system improvements for Alternative 1 include two new lift stations, shown in Figure 2, that will collect wastewater from the Southside WWTP collection basin growth areas and pump to Southside WWTP. A detailed analysis of the collection system will be required to determine the exact number, location, and capacity of the lift stations. The populations associated with growth areas together with the per capita flow rates were used to determine the flow to each lift station.

Figure 2: Southside Collection Basin Growth Areas and Lift Station Locations Figure 2 indicates the areas in the City of Tyler that are projected to experience growth within the next 25 years (shaded in green). For high level planning purposes, Southside WWTP basin growth areas were split into two segments, each with a dedicated lift station located at the low point within the segment (called out in blue).

OPCCs for the lift stations, collection system piping, and force main piping were estimated based on the assumptions and criteria listed in the previous section. The OPCC of the collection system was estimated to be $76 Million, and the OPCC of conveying the flow back to Southside WWTP was estimated to be $46 Million. The overall OPCC of alternative 1 was estimated to be $202 Million. A summary of the alternative 1 OPCC is shown in Table 2. Table 2: Estimated Total OPCC of Alternative 1 Design Element

Estimated OPCC

Collection System Improvements at Southside Basin’s Growth Areas Conveyance to Southside WWTP Southside WWTP Improvements

$76 Million

Total

$46 Million $80 Million $202 Million

Alternative 2: Maintain the existing Southside WWTP at its current permitted treatment capacity and build a new greenfield WWTP to treat the additional projected future growth Alternative 2 requires that Southside WWTP be rehabilitated to be able to continue to treat the permitted treatment capacity. The OPCC associated with this rehabilitation effort was estimated to be $54 Million. This OPCC includes minor improvements to the headworks facility to increase redundancy, odor control improvements, new aeration basins, new secondary clarifiers, a site stormwater levee, and improvements to the solids handling facilities. The greenfield WWTP will be required to treat the future flows that exceed the existing Southside WWTP permitted treatment capacity. The new greenfield WWTP was sized to handle the additional P2HF of 17 MGD and, based on the peaking factor of 3.95, an ADF of 4.3 MGD. The OPCC of the new greenfield WWTP was estimated to be $108 Million for both the liquid and solid treatment trains. This was based on the cost assumption of $25/gallon ADF treatment capacity. The OPCC of the collection system improvements in the Southside WWTP collection basin growth areas for Alternative 2 is similar to that of Alternative 1 (see Figure 2). The OPCC of the collection system improvements is $76 Million. The wastewater from the Southside WWTP collection basin growth areas then has to be conveyed down to the greenfield WWTP. The OPCC for the conveyance system to the greenfield facility was estimated to be $48 Million. The overall OPCC of alternative 2 was estimated to be $286 Million. A summary of the alternative 2 cost estimate is shown in Table 3. Table 3: Estimated Total OPCC of Alternative 2 Design Element

Estimated OPCC

Conveyance to Greenfield Facility Collection System Improvements at Southside Basin’s Growth Areas Greenfield WWTP Southside WWTP Improvements

$48 Million $76 Million

Total

$108 Million $54 Million $286 Million

Alternative 3: Decommission Southside WWTP and construct new greenfield WWTP to handle all future flow and loadings from the Southside WWTP collection basin Alternative 3 includes a full decommissioning and demolition of the Southside WWTP, which was estimated to cost $5 Million. The full projected Southside WWTP collection basin flow and loadings will be sent to the new greenfield WWTP. The future ADF and P2HF for the new greenfield WWTP, as shown in Table 1, are 10 MGD and 39.5 MGD, respectively. Therefore, based on the greenfield WWTP cost assumption of $25/gallon ADF, the OPCC of the greenfield WWTP in alternative 3 is $250 Million.

In addition to the greenfield WWTP construction, collection system and conveyance improvements must be constructed. The cost of the collection system improvements in the Southside WWTP collection basin growth areas for alternative 3 is similar to that of alternative 1 and 2 (see Figure 2). The OPCC for collection system improvements for alternative 3 is $76 Million. The conveyance costs, however, include conveyance of the new growth areas as well as conveyance of the flows that go to the existing Southside WWTP to the new greenfield WWTP. A conveyance pipeline from the existing Southside WWTP was estimated and is shown in Figure 3. The pipeline shown is representative of a potential pipeline following the West Mud Creek and extending approximately 9 miles south of the Southside WWTP and including a lift station. The OPCC of the conveyance line to the new greenfield WWTP is $75 Million.

Figure 3: New Interceptor Conveyance Pipeline from the Southside WWTP to the New Greenfield Plant Figure 3 shows the approximate location of the future greenfield WWTP and a representation of the potential conveyance pipeline between the Southside WWTP and the new greenfield WWTP.

A summary of the alternative 3 cost estimate is shown in Table 4. Table 4: Estimated Total OPCC of Alternative 3 Design Element

Estimated OPCC

Conveyance to Greenfield Facility

$75 Million

Collection System Improvements at Southside Basin’s Growth Areas

$76 Million

Greenfield WWTP

$250 Million

Southside WWTP Improvements

$5 Million (Demolition) Total

$406 Million

Recommendations The three alternatives presented in this memorandum provide a high-level conceptual comparison of the OPCCs associated with different options available to the City of Tyler regarding the construction of a new greenfield WWTP. A summary table comparing the OPCCs of the three alternatives is shown in Table 5. Alternative 1 has the lowest OPCC and leverages the existing Southside WWTP assets, therefore, alternative 1 is the recommended path forward. Table 5: Comparison of OPCCs for Southside and Greenfield WWTP Alternatives Alternative 1: Expand Southside (No Greenfield WWTP)

Alternative 2: Partial Flow Diversion to Greenfield WWTP

Alternative 3: Complete Flow Diversion to Greenfield WWTP

None

$48 Million

$75 Million

$76 Million

$46 Million

None

$108 Million

$250 Million

Southside WWTP Improvements

$80 Million

$54 Million

$5 Million (Demolition)

Total

$202 Million

$286 Million

$406 Million

Design Element Conveyance to Greenfield Facility Collection system Improvements at Southside Basin’s Growth Areas Conveyance to Southside WWTP Greenfield Treatment Plant

The details of the Southside WWTP expansion associated with alternative 1 are presented in the Baseline Analysis TM, dated November 2022. Alternative 1 will be used as the basis of the remaining Master Plan project tasks.