Mt Eden Enabling Works Flocculent Treatment Management Plan
CRL-MTE-RME-LKA-PLN-800026
Revision: 000 Date: November 2019
Flocculent Treatment Management Plan
Mt Eden Enabling Works Flocculent Treatment Management Plan CRL-MTE-RME-LKA-PLN-800026
This document is uncontrolled when printed. This document should be printed in colour
Revision Status Revision
Date
Version details
Prepared By
Approved By
Rev A00
27/9/2019
Draft for Community Liaison Group and Mana Whenua
Mike McConnell
Peter Roan
Rev A01
20/11/2019
Draft for Auckland Council Review
Mike McConnell
Peter Roan
Rev 000
02/12/2019
Final for Submission
Mike McConnell
Peter Roan
Approval Status Name/Title
Signature
Date
Prepared by:
Mike McConnell Erosion and Sediment Control Advisor
2 December 2019
Approved by:
Peter Roan Consents Lead – Link Alliance
2 December 2019
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Table of contents 1. Introduction ............................................................................................. 5 1.1
Overview of CRL works in Mt Eden ................................................................................ 5
1.2
Purpose of the Flocculent Treatment Management Plan (FTMP)..................................... 6
1.3
Associated management plans ...................................................................................... 7
1.4
Stage Specific Erosion and Sediment Control Plans ......................................................... 7
1.4.1.
Settlement tanks ............................................................................................................. 7
1.5
FTMP audience.............................................................................................................. 7
1.6
Relevant conditions....................................................................................................... 8
1.7
Sustainability .............................................................................................................. 13
1.8
FTMP review and updates ........................................................................................... 13
2. Project description ................................................................................. 14 2.1
Construction methodology .......................................................................................... 14
3. Use of flocculants and coagulants .......................................................... 15 3.1
Soil testing .................................................................................................................. 15
3.2
Test procedure ............................................................................................................ 15
3.3
Potential flocculants and coagulants ............................................................................ 16
4. Dosing options ....................................................................................... 17 4.1
Introduction ................................................................................................................ 17
4.2
Rainfall activated dosing.............................................................................................. 17
4.2.1.
Introduction .................................................................................................................. 17
4.2.2.
Rainfall catchment tray ................................................................................................. 18
4.2.3.
Header tank................................................................................................................... 18
4.2.4.
Displacement tank ........................................................................................................ 18
4.2.5.
Flocculent reservoir ...................................................................................................... 18
4.3
Flow activated dosing .................................................................................................. 19
4.3.1.
Introduction .................................................................................................................. 19
4.3.2.
Site Water Treatment Plant(s) ...................................................................................... 19
4.3.3.
Site Water Treatment Plant operation ......................................................................... 19
4.4
Batch dosing ............................................................................................................... 20
4.4.1.
Introduction .................................................................................................................. 20
4.4.2.
Dosing trigger level ....................................................................................................... 20
4.4.3.
Batch dosing methodology ........................................................................................... 20
5. Storage and handling of chemicals ......................................................... 22 Page 3
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6. Emergency Spill Response Plan .............................................................. 23 7. Responsibilities for operation and maintenance .................................... 24 8. Monitoring and maintenance................................................................. 25 8.1
Monitoring.................................................................................................................. 25
8.2
Maintenance ............................................................................................................... 25
8.3
Transportation of flocculation chemicals...................................................................... 26
9. Water Quality Discharge Monitoring Programme (WQDMP).................. 27 9.1
Sampling locations ...................................................................................................... 27
9.2
Monitoring parameters ............................................................................................... 27
9.2.1.
Daily............................................................................................................................... 27
9.2.2.
Weekly .......................................................................................................................... 27
9.3
Monitoring methods ................................................................................................... 27
9.3.1.
Daily............................................................................................................................... 27
9.3.2.
Weekly .......................................................................................................................... 28
9.4
Trigger levels ............................................................................................................... 28
9.4.1.
Daily parameters ........................................................................................................... 28
9.4.2.
Weekly parameters ....................................................................................................... 28
9.5
Monitoring reports ...................................................................................................... 29
9.5.1.
Initial monitoring report ............................................................................................... 29
9.5.2.
Non-conforming result report....................................................................................... 29
9.5.3.
Annual monitoring reports ........................................................................................... 29
Appendix A: ISCA Requirements .................................................................. 31 Appendix B: Record of CLG and Auckland Council Comments ...................... 32 B1. CLG Comments ................................................................................................................ 32 B2. Auckland Council Comments ............................................................................................ 32
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1.
Introduction
The City Rail Link (CRL) project comprises the construction, operation and maintenance of a 3.4 km underground passenger railway, running between Britomart Station and the North Auckland Rail Line (NAL) in the vicinity of Mt Eden Station. The CRL involves the construction of two new underground stations at Aotea and Karangahape, and a redeveloped station at Mt Eden (refer to Figure 1-1). The design and construction of the CRL infrastructure between the Aotea and Mt Eden Stations is being delivered by the Link Alliance. This Flocculent Treatment Management Plan (FTMP) has been prepared in relation to the Mt Eden Enabling Works (“the Project”), particularly for the works undertaken within Mt Eden Construction Support Area (CSA).
Figure 1-1: CRL Route and Location
1.1 Overview of CRL works in Mt Eden The CRL works in the Mt Eden area involve the construction of the southern section of the tunnel structures and the tie-in to the existing NAL, including the construction of the redeveloped Mt Eden Station. The Mt Eden Active Construction Zone (ACZ) and Construction Support Area (CSA4) is generally located between Nikau Street to the north, State Highway 1 (SH1) to the east, Dominion Road to the west and the existing NAL to the south. The works in this area include: • • • •
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Construction of an underground grade separation structure near Mt Eden Station; A new Mt Eden Station building incorporating passenger linkages; Modifications to the existing Mt Eden Station platforms; Road over rail bridges at Mt Eden Road, Normanby Road and Ruru Street with sections of road realignment;
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Flocculent Treatment Management Plan • • •
Grade separation structures for the existing and new rail lines to pass-over and connect with each other; Pedestrian and cyclist bridge structures at Fenton Street and Porters Avenue; and New road linkages within the reinstated area post-construction.
Given the nature and scale of CRL works in Mt Eden, construction will be undertaken in a staged manner. This FTMP relates to the first stage of these works (the Mt Eden Enabling Works), as described in Section 2 below. Following completion of the Project, works in this area will involve: •
•
Main construction works – these works will include: Tunnel Boring Machine (TBM) operations, structure construction and waterproofing/tanking for cut and cover tunnels, utilities installation, retaining wall for Ruru street extension, construction of the rail line tieins including junctions and grade separation structures, realignment of the existing Western Line including platform reconstruction, grade separation of Normanby Road, pedestrian / cyclist bridges at Fenton and Porters, construction of the new station buildings. The Main Works will be undertaken from Mid 2020 through to 2024. Public realm reinstatement – these works will involve establishing the final finishings and features that will comprise the completed Mt Eden Station and surrounds and will likely to be undertaken from 2021 to first quarter-2024.
1.2 Purpose of the Flocculent Treatment Management Plan (FTMP) This FTMP has been prepared to identify measures that will be implemented to enhance the effectiveness of the erosion and sediment control measures utilised on site to mitigate and manage the potential adverse effects on water quality during the Mt Eden Enabling Works. This FTMP also includes the Water Quality Discharge Monitoring Programme (WQDMP). The objective of the FTMP is: • •
To manage all bulk earthworks to minimise any discharge of debris, soil, sediment or sediment-laden water beyond the site to either land and/or stormwater drainage systems. To detail how the discharges of water from the site will be monitored to ensure compliance with the above.
This FTMP addresses the requirements of the Aotea to North Auckland Line (A2N) resource consent and will be implemented throughout the construction period. It is to be noted that the Mt Eden Enabling Works are to be undertaken within areas of varying degrees of contamination. As such the ability to discharge runoff generated by the works is also primarily regulated by compliance with the Contamination Delivery Work Plan (C DWP). This FTMP has been prepared by McConnell Consultancy Ltd on behalf of the Link Alliance and forms part of the Construction Environmental Management Plan (CEMP) for the Project. It has been prepared in accordance with condition 59 of the A2N resource consent, in consultation with the Mt Eden Community and Business Liaison Group (CLG) prior to submission to Auckland Council (as per condition 19 of the A2N resource consent). Page 6
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Flocculent Treatment Management Plan No construction activities will commence until certification of this FTMP has been received from Auckland Council (as per condition 60 of the A2N resource consent).
1.3 Associated management plans The CEMP outlines the environmental management framework for the Project and details the relationship between the CEMP, environmental management plans, design certification requirements and the resource consent conditions. It also provides an overview of the management plans required by the conditions (their purpose and content etc.) and other environmental mitigation measures to be implemented during construction. The CEMP also includes details of stakeholder management, training and roles and responsibilities. Associated management plans that are particularly relevant to the implementation of this FTMP include: • •
C DWP Erosion and Sediment Control Plan (ESCP)
1.4 Stage Specific Erosion and Sediment Control Plans The ESCP is the overarching document which details the minimum standards and management practices to be used during the Mt Eden Enabling Works. The ESCP is supported by the Stage Specific Erosion and Sediment Control Plans (SSESCPs) that detail the control measures to be implemented for specific phases of the Enabling Works, including decanting earth bunds (DEBs), sediment retention ponds (SEPs) and containerised sediment control devices. Specific designs of the flocculation systems will be included in Stage Specific Erosion and Sediment Control Plans (SSESCPs).
1.4.1. Settlement tanks Condition 168 of the A2N consent requires that settlement tanks are utilised to control runoff from the grout plant and segment storage yard. These activities do not fall within the scope of this Enabling Works ESCP. Condition 168 of the A2N consent also requires that two settlement tanks are installed in all ACZ, with the sizing of the tanks to be based on 2% of the contributing catchment. It is considered that the control measures, specifically DEBs, SRPs and containerised sediment control devices as detailed in the SSESCPs, achieve the outcomes sought by condition 168 and the requirement for settlement tanks can be appropriately modified as provided for by condition 169 of the A2N consent.
1.5 FTMP audience The primary audience of this FTMP is the management staff of the project, including Environmental Advisors and Site Engineers. This FTMP also provides details of the flocculation management practices to be utilised on the project to stakeholders including Auckland Council and the general community. The details of the measures required for specific stages are set out in the SSESCPs. It is these documents that provide the on-site staff with the information needed to ensure that the approved flocculation management practices are implemented on site. Page 7
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Flocculent Treatment Management Plan This separation of information and tailoring the included information to the intended audience is critical to ensuring that the flocculation management practices are correctly designed, understood, implemented, maintained and improved.
1.6 Relevant conditions Table 1.1 identifies the resource consent conditions relevant to this FTMP and where they are addressed in the document. Table 1-1: FTMP conditions and location in Plan
Condition No.
Condition
Relevant section of DWP
Land Use Consent R/LUC/2016/1890 Flocculent Treatment Management Plan 59
At least 20 working days prior to the commencement of construction, the Consent Holder shall submit to Council (Team Leader Central Monitoring) for certification an FTMP which confirms the measures that will be taken to ensure that the construction of the Project or Project Stage will be generally consistent with the Water Quality Assessment and the Industrial and Trade Activities Assessment prepared by Golder Associates (NZ) Limited, both dated December 2014.
Section 1.2
60
The Consent Holder shall request the Council's (Team Leader Central Monitoring) written determination as to whether the FTMP can be certified, in writing, within 10 working days of receipt of the FTMP.
Section 1.2
No construction activity shall commence until certification from Council is provided. 61
The FTMP shall include, but not be limited to, the following matters:
Section 1.4
• Specific design details of the flocculent treatment system based on a batch dosing methodology for the site's settlement tanks, including the potential for use of non - flocculants (e.g. chitin based flocculants); • Monitoring, maintenance (including post-storm) and contingency programme (including a record sheet); • Details of optimum dosage (including assumptions); • Results of initial flocculent treatment trial; • A spill contingency plan; and • Details of the person or bodies who will hold responsibility for the long-term operation and maintenance of the flocculent treatment system and the organisational structure which will support this system.
Section 3.0
62
Any change to an FTMP shall be submitted to the Council (Team Leader Central Monitoring) for certification.
Section 1.8
63
The Consent Holder shall request the Council's (Team Leader Central Monitoring) written determination as to whether the proposed change can be certified, to be provided within 10 working days of submission of the change. No activity reliant upon a change to the FTMP can be undertaken until the change has been certified.
Section 1.8
64
The Consent Holder shall comply with the ESCP for the duration of the earthworks associated with the Project.
Section 1.4
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Section 4.0 Section 5.0 Section 6.0 Section 7.0
Flocculent Treatment Management Plan As Built Certification 65
66
Prior to the commencement of bulk earthworks, a certificate signed by a Senior Qualified Person shall be submitted to the Council (Team Leader Central Monitoring) to certify that the erosion and sediment controls (including diversion bunds, silt fences and sumps) have been constructed in accordance with the certified ESCP(s) as required by Condition 53 of this consent.
Section 1.3
The certification from the Senior Qualified Person for these measures shall be supplied to the Council (Team Leader Central Monitoring) immediately upon completion of construction of those measures. Information supplied, if applicable, shall include:
Section 1.3
Section 8.1
Section 8.1
• The contributing catchment area; • The shape of structure (dimensions of structure); • The position of inlets/outlets; and • The stabilisation of the structure. General Performance Standards 68
70
The operational effectiveness and efficiency of all erosion and sediment control measures specifically required as a condition of resource consent, including the certified ESCP referred to in Condition 53, shall be maintained throughout the duration of earthworks, or until the Project site is permanently stabilised against erosion.
Section 8.0
The Consent Holder shall ensure that the erosion and sediment control measures are constructed and maintained in accordance with TP90, except where a higher standard is detailed in an ESCP/FTMP, in which case the higher standard shall apply.
Section 8.0
Section 9.0
Section 9.0
Specific conditions – discharge permit (contaminated land) R/REG/2016/1895 and land use consent R/LUC/2016/1890 (Contaminated Land and Resource Management (National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health) Regulations 2011) Contaminated Soils Management Plan 139
The Consent Holder shall manage all soil disturbance works to minimise any discharge of debris, soil, silt, sediment or sediment-laden water from the subject site to either land, stormwater systems or the receiving marine environment. The implementation of erosion and sediment controls shall be in accordance with the ESCP required by Condition 53.
Section 1.3 Section 8.0 Section 9.0
Advice Note: Measures such as covering the excavations overnight and during heavy rainfall, diverting overland flow around the works area, and appropriate treatment of any water collected in an excavation prior to the disposal may be required to comply with this condition. 144
The Consent Holder shall implement the procedures for the management, treatment, temporary containment, testing, and disposal of groundwater and surface run-off water via the stormwater system in accordance with the report titled Auckland City Rail Link: Resource Consent Package 2: Aotea Station to North Auckland Line Construction and CRL Operation: Draft Erosion & Sediment Control Management Plan, dated 13 May 2016, prepared by Aurecon New Zealand Limited, and provided with the application.
Section 1.3 Section 8.0 Section 9.0
Specific conditions – discharge permit (other) R/REG/2016/1896 and discharge permit (ITA) R/REG/2016/1898 (CONSTRUCTION) Structural Controls Page 9
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Flocculent Treatment Management Plan 166
167
The Industrial Trade and Activity area for each of the Construction Support Areas shall not exceed the following: CSA
Exposed Area not to exceed (m2)
1
25,000
2
9,000
3
9,000
4
36,000
5
6,500
In the event that any CSA requires an increase in area, the following information shall be provided to the Team Leader – Central Monitoring whose certification shall be requested prior to implementation:
Section 2.0
Section 1.8
a. Plans and drawings outlining the details of the modifications; and b. Supporting information that confirms how the proposal does not affect the capacity or performance of the existing structural and procedural controls. 168
The Consent Holder shall ensure that the following structural controls are constructed for the following catchment areas and design standards and they are completed prior to discharges commencing from the site: Works / Controls
Device catchment area
Design requirements
2 x Settlement Tanks located on CSA 4
Activity area of grout plant (400m2), and segment storage yard (2660m2) on CSA 4 On all catch pits within CSA areas
Settlement Tanks sizing to be based on 2% of the contributing catchment Design in accordance with Auckland Council Best Management Practice: Catch pit Protection Area (AC 2011). Settlement Tank sizing to be based on 2% of the contributing catchment
Inlet protection measures
169
2 x Settlement Tanks located in CSA 1, CSA 2, CSA 3, CSA 4 and CSA 5
All Active Construction Zone (ACZ)
Bunding of Environmentally Hazardous Substances
As required
110% largest container
In the event that any minor modifications to the structural system are required, the following information shall be provided to the Team Leader – Central Monitoring whose certification shall be requested prior to implementation: a. Plans and drawings outlining the details of the modifications; and
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Section 1.4.1
Section 1.4.1 Section 1.8
Flocculent Treatment Management Plan b. Supporting information that confirms how the proposal does not affect the capacity or performance of the existing structural and procedural controls. 170
Within 30 days of implementation, As-Built certification and plans of the stormwater management works, certified (signed) by a suitably qualified registered surveyor or a Chartered Professional Engineer as a true record of the stormwater management system, shall be provided to the Team Leader – Central Monitoring.
Section 8.1
171
The As-Built plans shall include, but not be limited to:
Section 8.1
a. The surveyed location (to the nearest 0.1m) of the discharge points, with co-ordinates expressed in terms of NZTM and LINZ datum; b. Location, dimensions and levels of any major overland flow paths including cross sections and long sections; c. Plans and cross sections of all stormwater management devices, including confirmation of the Water Quality Volume, storage volumes and levels of any outflow control structure d. Documentation of any discrepancies between the design plans and the As-Built plans.
Discharge Monitoring 173
Within 30 days of the installation of the water treatment systems, and prior to operation, the Consent Holder shall develop and submit to the Council (Team Leader Central Monitoring) for certification a discharge monitoring programme.
Section 9.0
174
The water quality monitoring programme shall include, but not be limited to:
Section 9.0
a. Sampling locations (to include the final discharge from the treatment system located in CSA 1, CSA 2, CSA 3, CSA 5 and CSA 4); b. Methods and procedures for discharge sampling; and c. Monitoring parameters for analysis, which shall include: Daily • Water clarity (black disc) cm • Turbidity (NTU) • pH Weekly (in addition to the above) • Total Suspended Solids g/m3 • Total recoverable copper g/m3 • Dissolved copper g/m3 • Total recoverable zinc g/m3 • Dissolved zinc g/m3 • Total petroleum hydrocarbons g/m3 • Ammoniacal nitrogen* g/m3 • Nitrate nitrogen* g/m3 *only in discharge from treatment systems in CSA 3 and CSA 4 d. identified trigger levels for each of the above parameters. These trigger levels shall be developed with reference to the ANZECC Guidelines for water quality where applicable; and Page 11
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Flocculent Treatment Management Plan e. the methods and procedures for investigating and reporting stormwater discharge monitoring results to the Council (Team Leader Central Monitoring). 175
The discharge monitoring programme shall be implemented upon completion of works set out in Condition 168.
Section 1.2 Section 9.0 Section 9.5
176
Within five working days of receipt of sample results showing contaminants exceeding the agreed trigger levels in Condition 174(d):
Section 9.5.2
a. An investigation shall be undertaken to determine why exceedances were detected and to identify any additional source controls or treatment required; and b. The results of the investigation shall be reported to the Council (Team Leader Central Monitoring). Discharge Reporting Requirements 177
Within eight weeks following the start of the monitoring required by Condition 173 a monitoring report shall be submitted to the Council (Team Leader Central Monitoring). The monitoring report shall include, but not be limited to, the following:
Section 9.5.1
a. a summary of the monitoring results to date; b. an interpretation of those results and suggestions for improvement to the site operations; c. a programme for ongoing monitoring including the reporting of results; and d. a programme for the ongoing maintenance of the discharge water management and treatment system. 178
For the duration of the construction stages of the Project, the Consent Holder shall forward a report annually from the date of granting of this consent to the Council (Team Leader Central Monitoring) evaluating the site’s environmental performance for the year to date.
Section 9.5.1
179
The Annual Report required by Condition 178 shall include but not be limited to:
Section 9.5.3
a. all aspects of the performance of the EMP relating to this consent; b. a summary of all revisions and revised sections of the EMP; c. details of all inspections and maintenance of the stormwater system for the preceding 12 months; d. details of and changes to the person(s) or body responsible for the maintenance of site and the organisational structure supporting this process; e. results and analysis of the preceding 12 months of stormwater monitoring, along with an interpretation of those results and suggestions for improvement to the site operations; and f. records of any spills or incidents which occurred within the previous 12 months and the response which was undertaken.
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1.7 Sustainability The Link Alliance is seeking an Infrastructure Sustainability Council of Australia (ISCA) Infrastructure Sustainability (IS) Rating. Further details can be found in the Project CEMP and Sustainability Rating Management Plan. Project sustainability requirements that relate directly to this FTMP are included in Appendix A. These requirements are imbedded within this ESCP to ensure that sustainability is a key focus and ‘the way we do things’. In some cases, the IS requirements and sustainability goals enhance the designation and consent requirements.
1.8 FTMP review and updates This FTMP is a live document that will be reviewed at least annually, or as a result of a material change to the Project, or to address unforeseen erosion and sediment runoff effects arising from construction, or unresolved complaints. The ability to make changes to the FTMP is vital to maintain its effectiveness and relevance. Modification may also be required to accommodate additional consents as detailed design and construction methods are finalised. Revisions to the FTMP will be made: • • • •
As the Link Alliance considers necessary Promptly on any material change (including named personnel changes) If requested by Auckland Council As and when reasonably required by the City Rail Link Limited.
Any material changes to this FTMP must be certified by Auckland Council prior to any on-site activity reliant upon the change commencing (as per conditions 62 and 63 of the A2N resource consent). Refer to the CEMP for further detail on the review and updating process.
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2.
Project description
In order to launch the TBM and commence construction of the CRL tie-ins to the NAL, a range of ‘enabling’ works are proposed, which are the subject of this ESCP. These enabling works are described in detail in the CEMP. In summary, the Mt Eden Enabling Works involve: • • •
•
• • • •
Continuation of the demolition and clearance of the Mt Eden CSA (commenced under the Mt Eden Demolitions Outline Plan) Set up of a temporary site office, which is anticipated to be a 2-3 storey modular building (likely made up of containers) located in the western extent of the CSA. Piling and excavation associated with the preparation of the portal. This will involve the demolition of the redundant stormwater shaft located in the portal area; the installation of bored piles and associated works (ground anchors and shotcrete) to support the excavation face; and removal of spoil. Bulk excavation to form what will become the rail trenches/cut and cover tunnels, which will also provide a ramp for the TBM to be manoeuvred into position. The excavation will encounter basalt, which is to be blasted in order to expedite the works and minimise the amount of rock-breaking required. In places, softer ground conditions are anticipated to be encountered, which may require the use of sheet piles. Local mined tunnelling to facilitate the TBM launch. Construction of the additional Mt Eden Road bridge (north of the existing bridge), including temporary diversion of shallow utilities in this location. Construction of the Ruru Street bridge, including diversion of the Huia 2 watermain in this location. Temporary and permanent utility diversions (such as water, wastewater, stormwater, Vector overhead cables and ducting, gas and communications) along Fenton Street, Porters Avenue, Haultain Street and Wynyard Street to provide adequate clearance between the Huia 2 watermain and NAL, associated retaining walls, and the proposed Fenton Street pedestrian bridge.
2.1 Construction methodology The Project will be divided into stages as described in the CEMP.
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3.
Use of flocculants and coagulants
The use of flocculants and coagulants (commonly referred to as flocculation) can decrease the settlement time within sediment retention devices and therefore increase the sediment removal efficiency of these devices. In order to maximise the efficiency of sediment retention devices utilised on site, and therefore minimise the adverse environmental effects associated with the discharge of sediment the use of flocculants and coagulants is to be investigated for all sediment retention devices on site. Typically, flocculation for a sediment retention device will be provided unless: • •
Bench testing of soils in the contributing catchment confirms there is no benefit from flocculation, or Where the duration of the earthworks is very short.
Flocculation will be undertaken in accordance with Section F2.0 Coagulant and Flocculant Treatment of Auckland Council Guideline Document 2016/005 “Erosion and Sediment Control Guide for Land Disturbing Activities in the Auckland Region” (GD05). The details of the specific erosion and sediment control measures to be utilised, including the design of the flocculation management practices is detailed within the SSESCP prepared for each stage of work. The initial design of the flocculation management practices will be based on previous information of soil types until the soil testing (Section 3.1) can be undertaken. The implementation and as-builts of any flocculation device will be in accordance with the inspection and as-built procedures contained within the ESCP.
3.1 Soil testing As part of the initial earthworks associated with areas where flocculation is to be considered, soil samples will be taken and will be bench tested to confirm flocculation options for those soils, including flocculants or coagulants to be used, optimum dosage rates and dosage methodology. This bench testing will also identify any soils where the existing pH is outside of the baseline range of 5.0 – 9.0. This assessment of the additive to be used will also determine the most efficient method of dosing (refer Section 4). In accordance with the monitoring and maintenance detailed in Section 8, as the soil types in each area changes due to deeper cuts and/or altering fill sources, the optimum flocculation option may also change. Any changes to the flocculation for a device will be recorded as part of the monitoring records for that device.
3.2 Test procedure Testing is undertaken by mixing a representative sample of soil from the site with water to produce a weak slurry, representative of sediment laden runoff from the site. Page 15
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Flocculent Treatment Management Plan Four samples of this are then taken and placed in clear jars along with a fifth reference sample. Potential chemical additives are then added at varying concentrations (where appropriate). At regular intervals (10 minutes, 30 minutes and 60 minutes), the depth of clarity is measured in each sample to determine which dosage of chemical provides the greatest level of settlement. The pH of each sample is also measured after 60 minutes to ensure that this remains within the required limits of 5.0 – 9.0. The appropriate dosage rate is then used to calculate the sizes of the various components of the rainfall activated treatment devices.
3.3 Potential flocculants and coagulants A number of potential flocculants and coagulants are available, however experience with the typical soils in the area indicate that the greatest increases in efficiency will be provided by: • • •
Polyaluminium Chloride (PAC) PolyDADMAC EC20 (80% PAC / 20% PolyDADMAC)
When initial testing is undertaken, an assessment will also be made to determine if the use of biobased flocculants provide suitable increases in efficiency. As industry experience changes during the course of the project, other additives or blends of additives will be considered as appropriate. Each of the above additives can be used in a rainfall activated or a batch dosing method. The use of chemicals in addition to PAC or PolyDADMAC products will be included in a revision to this FTMP. The revisions to address this will identify the chemicals, the dosing procedures and testing and sampling proposed to ensure that residual chemicals are monitored and within acceptable limits.
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4.
Dosing options 4.1 Introduction
There are three main forms of dosing: Rainfall Activated; Flow Activated; and Batch Dosing. In the rainfall activated process during rainfall the dosing system is automatically activated by rainfall to provide the appropriate volume of additive to the sediment laden surface runoff. In the flow activated process the dosing system is automatically activated by flow (typically pumped) to provide the appropriate volume of additive to the sediment laden inflows. The batch dosing process is typically undertaken to treat an impounded volume of sediment laden water, typically as the result of pumping. This is a manual process where the volume of impounded water is determined and from this the appropriate volume of additive determined, added and mixed. The sampling and testing of soils detailed in Section 3 of this FTMP will be utilised to determine the appropriate chemical and dose rate.
4.2 Rainfall activated dosing 4.2.1. Introduction Rainfall activated dosing will be utilised where the sediment retention devices receive runoff as a gravity surface flow. This system will typically be used in the early stages of the works with a transition to flow activated dosing as the excavation progresses and gravity surface flow decreases. The flocculation systems to be used will be designed in accordance with GD05. The basic design will be a rainfall activated system (typically) using Polyaluminium Chloride (PAC) to dose the Sediment Retention Pond (SRP). The layout of a typical PAC Rainfall Activated System is shown in Figure 4-1 below.
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Figure 4-2: Typical PAC Rainfall Activated System Layout
4.2.2. Rainfall catchment tray The rainfall catchment tray will be sized to provide treatment at the design dose rate for 100% of the runoff from exposed earthwork areas and for 60% of the runoff from any stabilised areas within the catchment. A 50mm storm event will be used for calculating the size of the tray.
4.2.3. Header tank The header tank design provides for 12mm of rainfall before dosing commences. At this point a low rate outlet hose with a 3mm orifice is installed. The high rate outlet hose with a 10mm orifice is installed at the level reached by a further 12mm of rain above the low flow outlet. The header tank has a minimum freeboard of 50mm above the high rate outlet. The header tank typically has a diameter of 580mm (a recycled PAC drum).
4.2.4. Displacement tank The displacement tank will be a neat fit inside the flocculent reservoir tank. The minimum displacement tank capacity will be the equivalent of a 100mm rainfall event.
4.2.5. Flocculent reservoir The flocculent reservoir tank will have a minimum capacity to store sufficient flocculent to dose runoff from a 100mm rainfall event. Page 18
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Flocculent Treatment Management Plan
4.3 Flow activated dosing 4.3.1. Introduction Flow activated dosing will be utilised where the sediment retention devices receive runoff as a pumped flow. This system will typically be used in the mid to later stages of the works as the excavation progresses and gravity surface flow decreases. Flow activated dosing will be utilised as part of a Site Water Treatment Plant (SWTP). Subject to the activities taking place on site and the contaminants encountered, more than one SWTP may be utilised at any one time. The use of and specific design of each SWTP is detailed within the applicable SSESCP.
4.3.2. Site Water Treatment Plant(s) The SWTP will be a treatment device that allows for: • • •
•
•
Pumping sediment laden runoff captured within the site into a storage tank(s) (such as a 75m3 modified shipping container(s) or similar). The system will buffer flow volumes, allow for initial settlement of sediments and any chemical treatment (i.e. pH adjustment, flocculation). The discharge will be piped to the stormwater network, unless monitoring has shown that contaminant levels prevent discharges to stormwater. In this event discharges will be directed to the wastewater network in accordance with the Trade Waste Agreement (to be obtained). The SWTP will be manned during operation, ensuring that in the event of discharge standards being exceeded, the transfer pump will be stopped and the discharge will cease until the required water quality parameters can be met. The water can be recirculated from the settlement tank to the buffer tanks using submersible pumps if required. The SWTP will be located in a suitable location to provide connections to power and a connection to the stormwater and wastewater network.
4.3.3. Site Water Treatment Plant operation The SWTP will be operated in the following manner: •
Inflows from the site will be pumped to the buffer tanks, which are the primary storage tanks.
Typically flows will be pumped from the site to the buffer tanks as fast as possible so as to keep the site as dry as possible.
•
From the buffer tanks water will be pumped to the settlement tank as follows:
Inflow to the settlement tank will be measured by a flow meter, which in turn will trigger flocculent dosing and pH adjustment dosing as required (see below).
•
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In order to maximise the efficiency of the settlement tank, it is anticipated that flocculant dosing will be beneficial. The dosing will be undertaken as follows:
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Flocculent Treatment Management Plan
The specific flocculant to be used and dose rate will be determined by bench testing that will be undertaken during setup of the water treatment plant and prior to commencing operation.
As works progress additional testing will be undertaken as required by changing soil types.
The flocculant dosing will be undertaken by an automated pump, triggered by inflow rates which will add the flocculant at the required rate.
•
To comply with the WQDMP pH adjustment will also likely be required and undertaken as follows:
pH adjustment will be undertaken using citric acid or similar product, dosed using an automated pump triggered by inflow rates.
The dose rate to buffer the pH will be determined by a pH sensor, which will sample water within the settlement tank and will be adjusted by the SWTP operator as required.
• • •
•
From the settlement tank, compliant outflow will be discharged to the stormwater network. The SWTP operation and discharge quality will be monitored daily by the SWTP plant operator. Where this discharge quality is identified as non-compliant for stormwater discharge the discharge will be recirculated for additional treatment. If this is impractical and the flow is compliant for trade waste disposal the discharge will be directed to the wastewater network. Maintenance of the SWTP will include the following:
Regular cleaning of pH sensors; Top up of flocculant and pH buffer; and Regular removal of accumulated sediment within the buffer and settlement tanks (before the total storage volume of the tanks has been reduced by 20%).
4.4 Batch dosing 4.4.1. Introduction Batch dosing will be undertaken where runoff is impounded and may be the result of ineffective rainfall activated or flow activated dosing. It will also be utilised for minor flows
4.4.2. Dosing trigger level The trigger level for batch dosing will be 100mm clarity, i.e., when the clarity of impounded sediment laden runoff falls below 100mm batch dosing will be undertaken in accordance with the following batch dosing methodology.
4.4.3. Batch dosing methodology The outlet of any impounded runoff will be blocked. This may be done either with a pre-installed valve or a crimped (folded) section of lay flat hose connected to the outlet of the decant or other methods such as raising the decant. Page 20
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Flocculent Treatment Management Plan Following rainfall, the clarity will be checked and if less than 100mm, the required chemical will be added by spraying it on the surface of the SRP or by careful application using a bucket or other small container to evenly disperse the chemical over the surface of the SRP. The chemical will be added at the standard rate of dosing for the devices on site, this rate expressed as a litre of chemical per 10m3 of impounded runoff will be included within the specific FMTP details for that device. The impounded water will then be mixed with the chemical using one of the following methods: • • •
Mixing with a pole, paddle or oar; Mixing by circulating the impounded flows through a pump; or Mixing by dragging semi-submerged floats through the surface area of the impounded water.
Once settlement has occurred, typically within 2-3 hours the pH and clarity within the device will be checked. If the pH is between the range of 5.0 and 9.0 and the clarity is greater than 100mm the decant will be opened and the device drained. If the clarity is less than 100mm a further dose of chemical will be added at 50% of the original rate and a further settlement period of 2-3 hours allowed before retesting. If the pH levels fall outside the acceptable range of 5.0 to 9.0 the Environmental and Sustainability Manager will be contacted to determine appropriate actions which could include off site removal of impounded water or adding alternate chemicals, such as sodium carbonate or sodium bi-sulphate, to alter the pH. Subject to the weather conditions at the time and the level by which the range has been exceeded it may be appropriate to use the impounded water for dust control.
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5.
Storage and handling of chemicals
The water treatment chemicals (if assisted settlement is required) will be stored in the CSA in the vicinity of the SWTP. The chemicals will be stored within bunded enclosures in order to contain any spillage or failure of container vessels or pipe connections. The storage and monitoring of the chemicals will be undertaken by trained personnel in accordance with the requirements of the Industrial and Trade Activity Environmental Management Plan (ITA EMP). These personnel will be the same as those responsible for managing the chemical dosing of the influent water. Monitoring will ensure all chemicals used on site are accounted for, and the daily volumes used will be captured on the daily record sheets.
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6.
Emergency Spill Response Plan
Should chemical treatment be required during the Project, the chemical substances to be used will be in liquid form. A Project Emergency Spill Response Plan (ESRP) has been developed to set out the project spill management procedures. The ESRP is Appendix C to the ITA EMP.
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7.
Responsibilities for operation and maintenance
The Environmental and Sustainability Manager and Mt Eden Station Construction Manager will be responsible for the implementation of the FTMP, including the operation and maintenance of the treatment system, as outlined in the following Table. Responsibilities for implementation of the FTMP are contained in Table 7-1 below. Table 7-1: Responsibilities for FTMP implementation
Party
Construction Manager
Environmental and Sustainability Manager
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Responsibility
• Implements environmental protection measures in accordance with the contract, CEMP and sub-plans including FTMP. • Inspection of works to assess compliance with the FTMP and sub-plans – including operation and maintenance of the Chemical Treatment System and daily monitoring. • Develops, implements and reviews environmental management systems including the FTMP • On-site compliance with designation and resource consent conditions and other requirements, and tracking compliance information. • Undertakes regular site inspections and audits to ensure compliance with the CEMP and sub-plans, including the FTMP and consent conditions • Manages maintenance and monitoring of the effectiveness of the Chemical Treatment System.
Flocculent Treatment Management Plan
8.
Monitoring and maintenance
In addition to the Water Quality Discharge Monitoring Programme (WQDMP) (Section 9 of this FTMP), the following monitoring and maintenance specific to the flocculation management practices is required.
8.1 Monitoring Monitoring will include: • • • •
Certification of all ESC devices; Inspection after rainfall event; Weekly audits; and Pre and post rain event audits, including significant weather events.
The specific monitoring of the flocculation system will be undertaken by the Site Foremen and Site Engineers with regular checks of this monitoring made by the Environmental and Sustainability Manager. This monitoring will be undertaken weekly and following heavy rain events of the following items: • • • • • • • •
Rainfall in previous 24 hours; Depth of water in displacement tank; Volume of flocculent used (added); pH of the pond; Initial header tank level; Any changes in degree of stabilisation of the site; Appearance of pond (relative turbidity); and Estimated level of accumulated sediment within pond.
The frequency of this testing may be increased during extended periods of heavy rainfall or reduced during dry periods. Additionally, prior to any forecast heavy rain or if the site is to be unattended for more than 48 hours the flocculent reservoir tank will be filled to ensure that chemical treatment will occur through the following (or potential) 50mm of rainfall. The results of pH sampling will be used to determine if any modifications are required to the dosage rate. The acceptable limits for the pH is between 5.0 and 9.0. If the pH levels fall outside these ranges the Environmental and Sustainability Manager will determine appropriate actions which could include decommissioning the flocculation unit or adding alternate chemicals, such as sodium carbonate or sodium bi-sulphate, to alter the pH. Monitoring of pH will be a key indicator of the potential for residual aluminium discharges. Specifically, overdosing of PAC may cause a reduction in pH, raising the potential for aluminium within the PAC to react, forming toxic aluminium compounds that are bioavailable to fresh and marine water organisms.
8.2 Maintenance The Site Foreman will have responsibility for the maintenance of the chemical treatment devices on their site.
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Flocculent Treatment Management Plan The maintenance of the chemically treated sediment retention devices will be similar to that of nonchemically treated devices. The exception will be that the devices will require removal of the accumulated sediment more frequently. This accumulated sediment will be removed, dried and placed in fill areas of the site when this volume exceeds 20% of the pond storage volume or otherwise decreases the efficiency of the pond. For a rainfall activated system the maintenance will include checking that the catchment tray is kept clear of leaves etc., and that the outlet point of the delivery hose is encouraging adequate mixing of the flocculant with inflows. All hoses, connections etc. will be checked to ensure they are sound and that there is no leakage. Flocculant levels etc. will be topped up and the displacement tank emptied at this time. The daily maintenance of the system will also include the setting of the header tank level. This level allows a degree of rainfall to take place prior to dosing occurring. This initial level will be set to the following parameters: • •
When the site is dry, the header tank will be left empty so that 12mm of rain will fall prior to discharge of flocculent During extended periods of rainfall or if the site is already saturated (i.e., runoff will occur as soon as rain begins) the header tank will be filled to the level of the low rate outlet.
As the area of the contributing catchment and the degree of stabilisation within the contributing catchment alters the area of the catchment tray will be altered to account for these changes. The catchment tray area will also be used as a method of controlling the pH and dissolved aluminium levels. The results of the daily and weekly inspections and sampling will be retained for inspection as requested.
8.3 Transportation of flocculation chemicals The transportation of flocculation chemicals (including chemicals for pH balance) to and from the Project will be undertaken in accordance with the required Hazardous Goods, Traffic and Transport regulations. On site the chemicals will be transported in sealed containers, securely retained within the site vehicle. These containers will be small enough to be easily handled and only the expected required volume will be transported. The use of these chemicals will be in accordance with the Construction Health and Safety Management Plan.
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9.
Water Quality Discharge Monitoring Programme (WQDMP)
Condition 174 of the A2N resource consent details the requirements of the WQDMP. These are addressed as follows.
9.1 Sampling locations The sampling locations within the CSA are identified in the SSESCPs for the Mt Eden Enabling Works. Typically, the daily sampling will be undertaken at the outfall of each sediment retention device (SRP, Decanting Earth Bund or containerised device). The weekly sampling will be undertaken at the lowest stormwater manhole within or immediately below the CSA.
9.2 Monitoring parameters 9.2.1. Daily Daily sampling and measurement will be made of: • • •
Water clarity Turbidity pH
(cm) (NTU)
9.2.2. Weekly Weekly sampling and measurement will be made of: • • • • • • • •
Total Suspended Solids g/m3 Total recoverable copper g/m3 Dissolved copper g/m3 Total recoverable zinc g/m3 Dissolved zinc g/m3 Total petroleum hydrocarbons g/m3 Ammoniacal nitrogen g/m3 Nitrate nitrogen g/m3
9.3 Monitoring methods 9.3.1. Daily The method of daily monitoring will depend on the sediment retention device utilised. For the majority of devices this monitoring will be undertaken manually with a grab sample taken at the outlet. For the measurement of clarity this outflow will be collected in a 20L bucket, with the clarity then measured using a 100mm black disk. The turbidity will be measured utilising a handheld turbidity meter. The pH will also be measured using a handheld pH meter. This monitoring will be recorded on daily record sheets detailing the following information: Page 27
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Flocculent Treatment Management Plan •
• • • • •
Visual check of influent and effluent water clarity, pH, presence/absence visible TPH (e.g. conspicuous oil or grease film, sheen or odour), flocculant type and volume used, dosing system operation; Water clarity; Turbidity; pH; Record any notes for maintenance or additional information (e.g. ordering additional flocculant supplies); and Record of daily volume of chemicals used.
9.3.2. Weekly Weekly sampling will be undertaken by retrieving a sample(s) of outflows from the lowest stormwater manhole within or immediately below the CSA. This sample(s) will be forwarded to an accredited laboratory for testing of: • • • • • • • •
Total Suspended Solids g/m3 Total recoverable copper g/m3 Dissolved copper g/m3 Total recoverable zinc g/m3 Dissolved zinc g/m3 Total petroleum hydrocarbons g/m3 Ammoniacal nitrogen g/m3 Nitrate nitrogen g/m3
9.4 Trigger levels The initial trigger levels for discharges from the site are:
9.4.1. Daily parameters • • •
A minimum water clarity for all discharges of 10 cm or greater measured with a black disc pH between 5 and 9; and No visible total petroleum hydrocarbons (TPH) - sheen or odour.
The trigger for turbidity will be determined following the first month of sampling.
9.4.2. Weekly parameters The initial trigger values for the weekly parameters are taken from the Water Quality Assessment prepared by Golder Associates (NZ) Limited, dated December 2014. These initial trigger levels took into account dilution within the receiving environment, being Motions Creek. This consideration resulted in trigger levels being related to the flows within Motions Creek at the time of the discharge. Specifically, the Water Quality Assessment states that the trigger levels for discharges from the Mt Eden CSA are 25 x ANZECC 95% Freshwater during low flow (being 25 L/s) and 100 x ANZECC 95% Freshwater all other times The flow within Motions Creek at the time of discharge will be determined from the Auckland Council continuous flow recorder on Motions Creek (ARC site 8104). Page 28
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Flocculent Treatment Management Plan These initial trigger levels are set out in Table 9-1 below. Table 9-1: Initial Trigger Values
Total Recoverable Copper
Initial Trigger Value Low Flow (25L/s at Motions Creek) 50 mg/m3 for 95% of the time 35 mg/m3
Dissolved Copper
35 mg/m3
140 mg/m3
Total Recoverable Zinc
200 mg/m3
800 mg/m3
Dissolved Zinc
200 mg/m3
800 mg/m3
Total Petroleum Hydrocarbons Ammoniacal Nitrogen
15 mg/m3
15 mg/m3
>1.0 and ≤3.5 (mg/m3)
>1.0 and ≤3.5 (mg/m3)
Nitrate Nitrogen
>0.03 and ≤0.4 (mg/m3)
>0.03 and ≤0.4 (mg/m3)
Chemical / Parameter Total Suspended Solids
Flows > than low flow
Notes
50 mg/m3 for 95% of the time 140 mg/m3
Water Quality Assessment 25 & 100 x ANZECC 95% Freshwater 25 & 100 x ANZECC 95% Freshwater 25 & 100 x ANZECC 95% Freshwater 25 & 100 x ANZECC 95% Freshwater ARC TP10 MFE (2014), Attribute State B MFE (2014), Attribute State B
9.5 Monitoring reports The monitoring reports outlined in Sections 9.5.1-9.5.3 below will be prepared and forwarded to Auckland Council (Team Leader Central Monitoring).
9.5.1. Initial monitoring report Within eight weeks of monitoring commencing an initial report outlining: • • • •
A summary of the monitoring results to date; An interpretation of those results and suggestions for improvement to the site operations were required; A programme for ongoing monitoring including the reporting of results; and Water treatment plant maintenance programme.
9.5.2. Non-conforming result report Within five working days of receipt of sample results showing contaminants exceeding the trigger levels set out in Section 5.4 of the FTMP, an investigation will be undertaken to determine why exceedances were detected and to identify any additional source controls or treatment required. The results of this investigation will be sent in a report format to Auckland Council (Team Leader Central Monitoring).
9.5.3. Annual monitoring reports An annual report will be prepared and submitted detailing: • • Page 29
all aspects of the performance of the EMP relating to this consent; a summary of all revisions and revised sections of the EMP; | Mt Eden Enabling Works
Flocculent Treatment Management Plan • • • •
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details of all inspections and maintenance of the stormwater system for the preceding 12 months; details of and changes to the person(s) or body responsible for the maintenance of site and the organisational structure supporting this process; results and analysis of the preceding 12 months of stormwater monitoring, along with an interpretation of those results and suggestions for improvement to the site operations; and records of any spills or incidents which occurred within the previous 12 months and the response which was undertaken.
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Appendix A: ISCA Requirements To be completed
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Appendix B: Record of CLG and Auckland Council Comments B1. CLG Comments A Mt Eden CLG meeting was held on 8 October to discuss the enabling works and for the CLG to provide comments / feedback on the CEMP and sub-plans, including this FTMP. No comments were received from the CLG on this FTMP.
B2. Auckland Council Comments The FTMP was reviewed by the Timothy O’Grady. There were no comments received from Council on the FTMP.
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