February 13, 2019 CAC packet

Citizen Advisory Committee 7:00 PM, Wednesday, February 13, 2019 – Capitol Region Watershed District 595 Aldine Street, Saint Paul, MN 55104 Agenda 7:00

I)

Welcome, Announcements, Updates, and Introductions

7:05

II)

Public Comment for Issues Not on the Agenda (3 minutes per person)

7:08

III)

Approval of the Agenda

7:09

IV)

Approval of Minutes A) Approval of the January 9, 2019 Minutes

7:10

V)

District Initiatives for Review, Comment and Recommendations A) B)

McCarrons Sediment Coring Report (Houle) 2018 Lakes Summary (Wein)

8:10

VI)

CAC Initiatives A) Service Learning Student Update (Lilly)

8:40

VII)

Project and Program Updates A) B)

Materials Enclosed

Master Water Stewards (Schwantes) 2018 Watershed Awards (Bromelkamp)

8:45

VIII) CAC Observer Update

8:50

IX)

Discussion A) New & Old Issues B) CAC Observer for February 27, 2019 and March 6, 2019 Board of Managers Meetings

9:00

X)

Adjourn

Our mission is to protect, manage and improve the water resources of Capitol Region Watershed District.

Citizen Advisory Committee Meeting Wednesday, January 9, 2019– 7:00 p.m.

CAC Members Present: Steve Duerre Gwen Willems Bob Simonet David Arbeit Cheryl Braun Pat Cavanaugh Mary Lilly Mike MacDonald Kathryn Swanson Richard Weil Tom Elko Carol Zierman

Others Present: Mark Doneux, CRWD Belinda Gardner, CRWD Jessica Bromelkamp, CRWD Rick Sanders, Board of Managers Jenny Berry, Hamline University

Members absent: William Barton, w/notice Michelle Ulrich, w/notice Nicole Soderholm, w/notice I. Welcome, Announcements, and Updates Ms. Willems opened the meeting at 7:00 p.m. Ms. Willems asked for any announcements or updates and introductions.

II. Approval of Agenda CAC 18-034 Motion: To approve the CAC January 9, 2019 agenda.

MacDonald/Cavanaugh Unanimously approved III. Approval of Minutes A) December 12, 2018 CAC Meeting Minutes CAC 18-035 Motion: To approve the December 12, 2018 minutes as amended.

Simonet/Swanson Unanimously approved 1

IV. District Initiatives for Review, Comment, and Recommendations A) 2018 Adopt a Drain Report (Bromelkamp) Ms. Berry of Hamline University reviewed the 2018 Adopt a Drain program. 1,100 St. Paul residents participated in the program.

Ms. Cavanaugh asked about the overall goal of the program. Mr. Arbeit asked about the red labeled drains on the map and inquired about the availability to adopt. Mr. MacDonald confirmed that the red labeled drains are open for adoption. Ms. Willems asked about Falcon Heights recruitment. Ms. Berry confirmed that Adopt a Drain program will open in March for Falcon Heights. Mr. Simonet asked about maintaining enthusiasm for the program. Ms. Berry mentioned that they are still working on encouraging current and new participants. Ms. Lilly asked about the strategy for rental properties. Ms. Berry replied that Hamline Midway discussed having tools available to borrow for residents who might live in apartments. Ms. Braun asked about an event for her area. Mr. Weil asked about signage near the drain. Mr. Duerre asked about the spring sediment comment on the brochure. Ms. Berry replied and there was much discussion.

B) Community Event Calendar Ms. Bromelkamp shared the CRWD Community and Cultural Events List.

C) Building Update Administrator Doneux mentioned that the punch list is smaller but there are some items that are still be worked through. Administrator Doneux mentioned that there will be an Open House on January 31, 2019.

V. CAC Initiatives A) Watershed Steward Awards Program Update (Bromelkamp) Ms. Bromelkamp provided an update on the Awards Program and asked for volunteers to assist with the event.

B)

Service-Learning Student Update (Lilly)

Ms. Lilly provided an update from her conversation with her main contact at the U of MN about the opportunity for Service-Learning Student. The next step is to collect applications of those who might be interested from the position description posted on job board.

VI. Project and Program Updates Mr. Duerre asked about the soccer stadium. Administrator Doneux replied that the district will be working with the site.

Mr. Arbeit asked about permits for an area on the north side of Selby between Victoria and Dale.

Administrator Doneux mentioned that the site is challenging, but they will need to meet the rules, they don’t have the green space so they might use collection tanks in structured parking.

VII. CAC Observer Update VIII. Discussion a. New & Old Issues b. CAC observer for January 16, 2019 and February 6, 2019 Board of Managers Meeting “Our mission is to protect, manage, and improve the water resources of the Capitol Region Watershed District.”

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c. 2018 Agenda Plan A) New & Old issues None B) CAC Observer for the Board of Managers Meetings January 16, 2019 and January 2, 2019 Ms. Cavanaugh reported on January 2 meeting. The Board approved permit for redevelopment site on Larpenteur. Summarized discussion on Ford Site Redevelopment and Area C. Mr. Sanders mentioned the Board is looking forward to workshops in 2019.

C) 2019 Agenda Plan The following is a list of District Initiatives for 2019 CAC Meetings: Permit Program Partner Grant Program Monitoring Program Board Workshops Watershed Management Plan BMP tools, etc.

IX. Adjourn CAC 18-033 Motion: To adjourn the January 9, 2019, CAC Meeting.

Arbeit/MacDonald Unanimously approved The meeting was adjourned at 8:30 PM. Respectfully submitted, Belinda Gardner W:\05 Citizen Advisory Committee\Minutes\2018\January 9, 2018 Draft Minutes.doc

“Our mission is to protect, manage, and improve the water resources of the Capitol Region Watershed District.�

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February 13, 2019 CAC Meeting V. A) District Initiatives for Review- Lake McCarrons Sediment Core Analysis Report (Houle)

DATE: TO: FROM: RE:

February 7, 2019 CRWD Citizen Advisory Committee Mark Houle, Water Resource Technician Lake McCarrons Sediment Core Analysis Report

Background In October 2004, an alum treatment was applied to Lake McCarrons to minimize algal blooms and maintain water quality. In 2015 Wenck Associates took six sediment cores to determine the phosphorus release rates in Lake McCarrons and evaluate the effectiveness of the alum treatment. This report expands upon that analysis with additional coring taken in February 2017 and evaluates sediment characteristics and alum distributions.

Issues As expected, hypolimnetic (lake bottom) phosphorus levels have increased since 2004 and are approaching pre-treatment levels. The 2015 Wenck report indicates a weakening of the alum treatment.

Sediment deposition since the time of the treatment may have reduced the efficacy of the alum layer by preventing it from interacting with dissolved phosphorus in the hypolimnion. CRWD partnered with the National Lacustrine Core Repository (LacCore) at the University of Minnesota to extract 23 cores from Lake McCarrons to assess the distribution and thickness of alum and the characteristics of the overlying sediment. This report analyzes the results of those cores to understand the effectiveness of the alum treatment and identify potential sources of the sediment deposited on the lake bottom since 2004 to guide future management efforts.

Action Requested None Enc.

Lake McCarrons Sediment Core Analysis Report (Electronic Only)

W:\07 Programs\Monitoring & Data Acquisition\0 Projects\2017 Lake McCarrons_LacCore-Amy Myrbo\BoardMemo_McCarrons Coring Report_2-7 -19.docx

Our mission is to protect, manage and improve the water resources of Capitol Region Watershed District.

Lake McCarrons Sediment Core Analysis February 2019

PREPARED BY: Capitol Region Watershed District

DATE: 02/13/2019

CAPITOL REGION WATERSHED DISTRICT

Introduction Lake McCarrons is a 75-acre deep lake located in Roseville, MN with a maximum depth of 57 ft. and 36% littoral zone area. It is located within the 1,070-acre Lake McCarrons subwatershed of the Capitol Region Watershed District (Figure 1, Table 1). The subwatershed contains residential and commercial properties, public parks, highway, and wetland areas. The primary input to Lake McCarrons is stormwater from the surrounding areas. Lake McCarrons outlets through a pipe on the southeast corner and flows into the Trout Brook – West Branch storm sewer. It then discharges into the Trout Brook Storm Sewer Interceptor and, eventually, into the Mississippi River.

Figure 1: Lake McCarrons subwatershed map.

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Table 1: Lake McCarrons Morphometric Data Surface Area (acres)

Maximum Depth (ft)

Littoral Area

Volume (acre-ft)

Watershed Area (acres)

Watershed: Lake Area (ratio)

74.7

57.0

34%

1,892

1,070

14.3

The primary management concern in the Lake McCarrons subwatershed is phosphorus. Currently, Lake McCarrons is neither impaired for nutrients nor listed on the MPCA 303(d) list of impaired waters, so maintaining phosphorus concentrations is an important management goal.

The 2003 Lake McCarrons Management Plan set a goal of 33 Âľg/L of phosphorus to minimize algal blooms and maintain water quality. With the implementation of the Lake Management Plan, the District also approved an application of an alum treatment to target internal phosphorus loading. When applied to water, aluminum sulfate forms an aluminum hydroxide floc that precipitates to the lake bottom. As it settles, the aluminum hydroxide binds with phosphorus, removing it from the water column. Further, at the lake bottom, the alum precipitate forms a layer on the sediment surface that binds with phosphorus as it is released from anaerobic sediments.

To prepare for the alum treatment and to calculate dosage rates, seven sediment cores were taken at various depths in Lake McCarrons on September 5, 2003 (Pilgrim et al, 2003). A strong smell of sulfur was observed, suggesting severe anaerobic conditions. Further, phosphorus was determined to be mobile up to a depth of 6 cm. Thus, the alum dosage was calculated to target phosphorus in the top 6 cm of sediment.

Dose tests were performed on the cores, and a dose of 77 grams of alum per square meter (1408 gal of alum per lake acre) was determined to be necessary to reach the goals of immobilizing phosphorus in sediments of Lake McCarrons.

CRWD contracted Sweetwater Technology to apply 492.3 tons of alum to Lake McCarrons from October 21 through 24, 2004. The total cost of the project was $90,010.19. Alum was distributed across the entire surface area of Lake McCarrons, as shown in the GPS tracking map in Figure 2. The alum treatment was designed to achieve the summer phosphorus goal defined by the Lake Management Plan of 33 Âľg/L. The weather conditions around the time of the alum treatment are shown in Table 2. There were moderate south and northwest winds during the time of the application and some strong gusts up to 24 miles per hour. It rained on two of the four days when alum was being applied, and three days in the week following.

Precipitation and wind can contribute to lake mixing and potentially impact the settling of the alum floc.

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Figure 2: GPS record of alum application barge movements across Lake McCarrons.

Table 2: Climatic Conditions during the Alum Treatment (October 21-24, 2004) from NWS Twin Cities Station, October 2004

Parameter 10/21/2004 10/22/2004 10/23/2004 10/24/2004 10/25/2004 10/26/2004 10/27/2004 10/28/2004 10/29/2004 10/30/2004 10/31/2004 Wind Speed 11 14.1 15 7.6 8.6 12.4 9.8 10.9 9.2 14 6.4 Max Wind Speed 20 23 24 17 21 22 15 20 21 28 15 Wind Direction 150 (SSE) 150 (SSE) 290 (WNW) 170 (S) 320 (NW) 90 (E) 90 (E) 140 (SE) 220 (SW) 280 (W) 290 (WNW) Precip (in) T 0.06 0.17 0 0 0T 0.88 0.06 0.19 T High Temp 51 64 65 66 56 50 49 58 75 57 44 Low Temp 43 50 45 37 42 43 43 49 56 42 40

Effects from the alum treatment were immediately visible during the 2005 monitoring season. Figure 3 shows the average annual epilimnetic and hypolimnetic TP values for Lake McCarrons from 1988 – 2017.

The average hypolimnetic TP value decreased dramatically from 800 µg/L in 2004 to 41 µg/L in 2005.

Since 2004, the annual hypolimnetic TP concentrations have shown a gradual increase over time, suggesting a decrease in the effectiveness of the alum treatment.

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1200 Hypolimnetic Average TP Epilimnetic Average TP 1000

Total Phosphorus (Âľg/l)

800

600

400

200

0

Figure 3: Lake McCarrons hypolimnetic and epilimnetic average TP and deep lake standard, 1988 – 2018.

Ramsey County Public Works (RCPW) has conducted regular water quality monitoring of Lake McCarrons since 1988. RCPW data from the week prior to, and the week after the alum treatment is included below in Table 3 and shows a more immediate effect of the alum treatment on hypolimnetic TP and SRP. The temperature and dissolved oxygen data indicate that lake turnover did not occur between October 15 and October 26, which could have potentially interfered with the settling of the alum floc.

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Table 3: RCPW Monitoring Data for Lake McCarrons, October 2004 10/15/2004

10/26/2004

Secchi Secchi Sample Temperature- ChlorophylSample Temperature- ChlorophylDO-MG/L Depth TP-MG/L SRP-MG/L DO-MG/L Depth TP-MG/L SRP-MG/L Depth (m) DEGC A - MG/M3 Depth (m) DEGC A - MG/M3 (m) (m) 0 8.2 13.66 8.468064 2.1 0.038 <.01 0 9 10.64 0.72765 8.1 0.019 <.01 1 8.61 13.68 1 7.8 10.62 2 7.98 13.69 7.954848 0.022 <.01 2 7.7 10.61 1.0692 0.01 <.01 3 8.12 13.67 3 7.67 10.6 4 7.93 13.67 4 7.65 10.6 5 7.81 13.66 5 7.65 10.59 6 7.93 13.6 0.02 <.01 6 7.64 10.59 0.011 <.01 7 6.45 13.36 7 7.52 10.55 8 3.31 8.88 8 6.75 10.44 8.5 0.254 0.176 9 1.76 9.42 9 0.98 6.47 10 0.65 6.65 0.181 0.063 10 0.51 5.47 12 0.29 5.12 12 0.22 4.66 0.604 0.472 12.5 0.459 0.278 14 0.14 4.47 14 0.2 4.79 15.6 0.921 0.628 14.8 0.541 0.405 16 0.11 4.44 15.5 0.15 4.71 16.3 0.08 4.5

In 2016, six sediment cores were taken to determine the rates of phosphorus release and to evaluate the effectiveness and longevity of the alum treatment (Wenck, 2016). Anaerobic phosphorus release was calculated at the two deepest sites, one at a depth greater than 40 feet, and the other between 30 and 40 feet. The measured values were 2.2 and 4.0 mg/m2/day. This rate is average for mesotrophic lakes but relatively high for a lake recently treated with alum. It was also discovered in these cores that the alum layer was buried by varying thicknesses of sediment, potentially limiting its interactions with phosphorus.

This finding, along with the increasing hypolimnetic TP concentrations observed in Figure 3, suggests a weakening of the alum effectiveness in Lake McCarrons, prompting additional analysis to understand the alum’s efficacy.

The 2017 Lake McCarrons Sediment Core Analysis serves to understand the effectiveness and longevity of the 2004 Lake McCarrons alum treatment. This project aims to expand upon the findings in 2016 by extracting additional cores and analyzing them for grain size and sediment composition across the lake to address the following questions: • • •

Is alum detectable in lake sediments today?

How is the alum distributed across the lake bottom?

What are the characteristics of the sediment deposited on top of the alum layer, if present?

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Methods Data Collection CRWD staff used GIS to create a uniform grid structure for core sampling locations with the goal of identifying between 20 and 25 sample points evenly distributed across the non-littoral area of Lake McCarrons. A grid was selected based on its distribution of points across all bathymetric contours. The final core sampling grid is shown below in Figure 4 with the 23 identified sampling locations.

CRWD partnered with LacCore, the National Lacustrine Core Repository (LacCore) operated by the Limnological Research Center at the University of Minnesota. Twenty-three core samples were extracted from the bed sediments on February 7 and February 20, 2017 by LacCore personnel. CRWD assisted by marking the sampling locations using a GPS unit and flagging paint. LacCore personnel later visited the marked points and used an ice auger to drill two holes spaced a half meter apart. One hole was used to take water depth measurements and the other was used to take the sediment core samples. A Griffith drive rod piston corer was used to extract the sediment core samples, which uses a square drive rod to push the sampler into the sediments and a piston to provide suction needed for sample recovery. The sample was brought to the surface and sealed with Zorbitol (sodium polyacrylate) gel.

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Figure 4: Lake McCarrons Sediment Core Sample Location Map, 2017. *The grid was structured to accommodate four other sediment cores taken in 2016 within the 50 m bathymetric contour; these cores were later removed from the analysis due to discrepancies in methods, accuracy, and personnel.

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Twenty-one cores were recovered from the 23 identified sampling locations. Core 10 and Core 19 fell out upon retrieval; no material was recovered for further analysis. LacCore personnel noted Cores 10 and 19 being entirely composed of sand, and presumed alum to be absent at these locations.

Core Analysis Cores were split, cleaned, and imaged using standard LacCore lab techniques. High resolution images of cores containing a ruler were used to estimate alum presence and thickness. Images of the 21 cores can be seen in Appendix A. Alum was identified by the presence of a bright blue band (Figure 5). Sediment deposition since 2004 was measured as the thickness of sediment above the alum layer; this measurement was only possible at sites where alum was present.

Figure 5: Core 7 high resolution image showing alum layer, 0 – 30 cm.

The cores were split into 3 sections for composition analysis. A buffer of 0.2 – 0.5 cm was maintained on the top of the core to act as a barrier between the sediment and the Zorbitol sealant. For cores with alum present, the area above the alum was split into two 1.5 cm thick samples and one 1.5 cm thick sample directly below the alum. This was done to estimate the pre- and post-alum treatment sediment conditions.

For cores with no apparent alum present, the upper 3 cm was split into two samples of 1.5 cm each, and a third 1.5 cm thick sample 2 cm below the base of the upper two samples. All composition data was taken from the topmost section of the sediment core, as this represents the most recent deposits.

The subsamples were homogenized and split, and analyzed for mean grain size and organic, inorganic, and carbonate composition. Organic composition includes all matter derived from the biological productivity including: algae, aquatic plants, aquatic animals, microbes, and the organic portion of soil washed into the lake. Carbonate composition consists of shells of mollusks, ostracods, and inorganically precipitated calcite formed throughout the lake. Inorganic composition is the remainder of the sediment after organic matter and carbonate have been removed. Inorganic portions of the sediments consist primarily of “siliciclastic” material, i.e., sand, silt, and clay washed into the lake.

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Sediment composition was calculated using weight-loss techniques. Sediment was first dried and combusted to remove organic matter, then combusted at a higher temperature to remove carbonate matter.

The remaining matter represents the inorganic material. By comparing the weights lost throughout the process to the original dry weight, a relative percentage for the three composition types was generated.

Therefore, percent organic, percent carbonate, and percent inorganic are relative values, and an increase in one will be reflected by a proportional decrease in the others.

GIS Activities CRWD staff used ArcGIS 10.4.1 to analyze data from the Lake McCarrons sediment cores using the Geostatistical Analyst extension package. Staff created interpolated surfaces between the 21 sampling points based on the following measured variables: 1. Thickness of alum layer present 2. Depth of sediment deposited since the 2004 alum treatment 3. Sediment Composition o Percent organic sediments in topmost layer of sediment sampled o Percent carbonate sediments in topmost layer of sediment sampled o Percent inorganic sediments in topmost layer of sediment sampled 4. Grain size and sediment type of sediments in the topmost layer of sediment sampled Isoline surfaces were created using the Radial Basis Function (RBF) interpolation technique. The RBF interpolator creates a smooth surface that upholds measured data points in the modeled surface. A RBF is a function that changes with distance from the origin location. With N number of points, this creates N number of equations to solve, creating a network of various curves that intersect to create a smooth, exact surface. The RBF models were adjusted with the goal of achieving an average error closest to zero and the smallest possible root mean square prediction error. Once adjusted, the models were classified with five breaks along geometric intervals.

Results Results from the core analysis are shown in Table 4. Core numbers correspond to the core sampling location grid in Figure 4.

1. Alum Presence & Thickness Figure 6 indicates the presence of alum in Lake McCarrons. Alum was found to be present at 10 out of 23 sampling locations, all of which occurred in the nonlittoral zone. All the cores with alum were taken from depths of 9 meters or greater, towards the center of the lake. Alum is estimated to be absent in 59% of the total area of Lake McCarrons, mostly in shallow areas less than 9 meters deep and around the periphery of the lake near the littoral/limnetic transition zone.

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Figure 7, below, shows the expected alum thickness in Lake McCarrons based on the coring results. The average thickness of the alum layer found was 2.2 cm. The thickest layer of alum (3.6 cm) was found in the deep center of the lake, with thickness decreasing as depth decreases.

Table 4: Lake McCarrons Sediment Core Data Summary Table, 2017.

Core Number

Water Depth (m)

Latitutde

Longitude

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

5.099 7.518 9.777 6.368 7.888 14.34 16.28 14.17 7.988 6.368 14.53 14.57 13.58 8.488 6.358 12.71 14.67 13.5 4.479 4.299 5.968 4.939 1.91

44.9960 44.9967 44.9973 44.9979 44.9992 44.9985 44.9976 44.9970 44.9963 44.9968 44.9976 44.9985 44.9992 44.9998 45.0005 44.9999 44.9992 44.9986 44.9979 44.9979 44.9986 44.9992 44.9998

-93.1096 -93.1096 -93.1096 -93.1096 -93.1114 -93.1114 -93.1114 -93.1114 -93.1114 -93.1132 -93.1132 -93.1132 -93.1132 -93.1132 -93.1150 -93.1150 -93.1150 -93.1150 -93.1150 -93.1168 -93.1166 -93.1168 -93.1168

Alum Thickness Post 2004 Organic Carbonate Inorganic (cm) Sediment (cm) Percent (%) Percent (%) Percent (%)

0 0 1.1 0 0 2.4 2.1 3.6 0

6.1

4.0 3.3 5.2

1.9 3.3 2.2 0 0 1.7 2.5 1.0

3.5 3.5 4.1

9.7 5.2 3.9

0 0 0 0

1.2 22.0 28.6 0.7 29.7 28.8 30.4 27.7 21.4 no core 29.6 37.1 28.5 24.1 20.3 30.7 28.4 28.1 no core 15.0 19.4 17.1 18.6

Grain Size (Âľm)

1.6 31.9 28.5 4.7 27.3 31.3 27.8 32.1 23.4

97.2 46.0 42.9 94.6 43.0 39.9 41.8 40.2 55.2

137.2 35.6 15.9 281.2 15.1 12.4 12.5 11.8 45.1

29.9 26.4 31.0 27.5 17.0 25.8 29.6 30.8

40.6 36.5 40.5 48.4 62.7 43.5 42.0 41.1

12.6 12.3 13.8 18.1 47.9 738.9 13.6 13.6

14.5 45.0 44.2 39.6

70.5 35.6 38.7 41.8

50.8 21.1 39.8 33.0

2. Sedimentation Thickness Figure 8 shows the sediment deposition on the lake bottom since the 2004 alum application. The area of this model is limited to the area where alum was present. The remaining 13 samples contained no indication of when the alum treatment occurred, and thus no calculation of sedimentation since 2004 could be made at those locations.

Alum is buried by a minimum of 3.3 cm of sediment in the deep part of the lake and a maximum of 9.7 cm of sediment towards the edges of the alum area. On average, 4.9 cm of sediment was deposited at the 10 sites where alum was present. The thickness of alum is roughly inversely proportional to the thickness of the deposited sediment, with the thickest sediment deposits existing on the peripheries of the alum area.

This is further demonstrated in the cross section of Lake McCarrons in Figure 9, extending from the 10

northwest corner to the southeast corner of the zone where alum was present. In areas where alum is covered by a thick layer of sediment, its ability to bind phosphorous is limited. In areas with the thinnest layer of deposited sediment, the alum may still be able to effectively bind phosphorus.

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Figure 6: Lake McCarrons presence/absence of alum, 2017.

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Figure 7: Lake McCarrons thickness of alum layer (cm), 2017.

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Figure 8: Lake McCarrons sediment deposition since 2004 alum treatment, 2017.

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Figure 9: Lake McCarrons sediment deposition in cross section, 2017.

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3. Sediment Composition Figures 10, 11, and 12 show the relative percent composition of organic, carbonate, and inorganic matter, respectively, in the topmost layer of deposited sediment. Organic material is found at its highest relative percent in the center, deep portion of the lake, where it is most equal to the relative percent of the other two composition types (Figure 10). Organic material in lake sediment is most likely the product of internal loading (Myrbo 2008). The relative percent of carbonate material is found at moderate values throughout the lake, with the highest concentration (up to 45% carbonate) near the outlet of the Villa Park Wetland System (Figure 11). Carbonate material is also likely derived from internal sources. Inorganic material is found in particularly high ratios (up to 97%) along the shoreline and in the littoral zone of Lake McCarrons (Figure 12), and this is likely from external sources from the surrounding subwatershed. The proportion of dominant sediment types for all cores is shown in Figure 14.

Table 5: Potential Sources of Dominant Sediment Types Sediment Type Potential Sources Figure Internal: decaying aquatic vegetation, Organic 10 aquatic organisms.

Carbonate Inorganic

Internal: shells of aquatic organisms, carbonate precipitate External: erosion from the surrounding landscape, road runoff

11 12

Figure 13 shows the mean sediment grain size in terms of sediment type. Seventy four percent of the lake exhibits silt-sized sediments. Areas with larger sands can be found along the southeastern shore bordering the public beach, which introduces larger sand sized particles from the largely destabilized shoreline.

Larger particles are also found in the northwest near the outlet of the Villa Park Wetland System. The wetland system has the potential to produce high velocity flows during storm events capable of entraining larger sized particles, which explains the deposition of larger particles a few hundred feet away from the inlet.

Representative categories of sediment composition can be used to classify clusters of cores. Cores 1, 4, and 20 exhibit the highest relative percent of inorganic sediments (Table 4, Figure 15). A relatively small amount of organic or carbonate matter is present in these areas. These cores were taken from the edges of the lake at shallower depths, particularly near the beach area on the southeast shore. The high proportion of inorganic material in these cores could be explained by the faster settling velocity of inorganic sediment.

If they are derived from external sources, their fast settling velocity could force them to settle soon after entering the lake, preventing them from reaching greater depths in high volumes.

The deep part of the lake exhibits the most equal distribution of organic, carbonate, and inorganic sediments (Figure 10, Figure 11, Figure 12). This area is best represented by Cores 6, 8, 11, and 12 (Table 4, Figure 15). While these cores have the highest relative percent of organic sediments, this area also has the thickest layers of alum.

Cores 21, 22, and 23 represent an area with the highest relative carbonate sediments (Table 4, Figure 15).

These cores are clustered near the outlet of the Villa Park Wetland System (Figure 11).

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Figure 10: Lake McCarrons relative percent organic matter in top layer of sediment, 2017. (Likely Autochthonous Sources)

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Figure 11: Lake McCarrons relative percent carbonate matter in top layer of sediment, 2017. (Likely Autochthonous Sources)

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Figure 12: Lake McCarrons relative percent inorganic matter in top layer of sediment, 2017. (Likely Allochthonous Sources)

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Figure 13: Lake McCarrons mean sediment grain size in top layer of sediment, 2017.

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Dominant Sediment Type

14.29% 4.76%

66.67%

Inorganic

Organic

Carbonate

Figure 14: Dominant Sediment Type Prevalence

High Relative Inorganic Matter

High Relative Carbonate Matter

Equal Composition

1% 5% 18%

29% 40%

38%

44%

94%

Organic

Carbonate

Inorganic

Organic

Carbonate

31%

Inorganic

Organic

Carbonate

Figure 15: Three representative compositions observed in the sediment core analysis

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Inorganic

Summary & Conclusions The 2004 Lake McCarrons alum treatment showed immediate results following application, reducing hypolimnetic TP by 95% from 2004 to 2005 (Figure 3). Thirteen years later, hypolimnetic TP gradually increased to 932% of the 2005 value, from 41.25 µg/l to 384.56 µg/l. Average epilimnetic TP continues to meet the deep lake standard of 40 µg/L, and only exceeded the CRWD goal of 33 µg/L in one year since the alum application.

While the alum barge demonstratively applied alum across the entire lake surface (Figure 2), the preferential deposition of alum in areas with depths greater than 30 ft. suggests that other factors prevented equal distribution (Figure 6). Wind direction and lake currents could have affected the settling of alum particles. Alum is susceptible to resuspension for days after being applied, and there are cases of alum settling downwind outside of the targeted area (Welch et al, 2017). During the alum application, and in the seven days following, there were moderate winds (7.6-15 miles per hour), including gusts up to 28 miles per hour, and five days with precipitation, including a significant rain event of 0.88” (Table 2). It is possible these conditions mixed the lake sufficiently to keep the alum floc in suspension, allowing it to disperse and settle in an unequal distribution. A lake’s bathymetry can also play a role in the settling of suspended particles, where the slope of a lake’s bottom may direct particles towards low lying areas (Huser et al, 2016). Fall turnover could also contribute to additional mixing that would disperse the alum if it were to coincide with the timing of the application. Monitoring data from October 2004 (Table 3), however, indicates that the fall turnover already occurred by the time of the alum application, because the water temperature and dissolved oxygen profiles remained consistent between October 15 and October 26.

Above all, CRWD should continue efforts to prevent further sedimentation and external phosphorus loading to the lake. An average of 4.9 cm of sediment has buried the alum in the last thirteen years (0.37 cm/year). Sediment will likely continue to accumulate on the bottom sediments, further decreasing the alum’s ability to bind mobile phosphorus. The sediment composition results from the 2017 cores allude to the potential sources of sediment being deposited into Lake McCarrons and will help CRWD target projects in the subwatershed accordingly. The sources by dominant sediment type are as follows: • • •

Organic-dominant: Likely internal, biogenic sources Inorganic-dominant: Likely external, anthropogenic sources Carbonate-dominant: Likely internal sources

By conducting this core analysis of 23 sample locations throughout the lake, CRWD better understands the distribution of alum across Lake McCarrons. However, additional expertise is needed to understand the relationship between sediment composition, internal loading, and buried alum efficacy. To continue this research, CRWD seeks answers to the following questions: • •

Why did most of the alum tend to settle at depths greater than 30 ft?

What is the settling velocity of an alum floc particle and how is it impacted by typical lake current and weather conditions?

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• • • • •

After how much sediment deposition does the effectiveness of alum decrease?

Is the sediment deposition rate of 0.37 cm/year typical of similar urban lakes?

Does the type of sediment covering alum impact its effectiveness?

Are the trends of sediment composition shown in Figure 10, 11, and 12 typical of urban mesotrophic lakes?

Is it still valid to assume phosphorus is mobile in the top six cm of sediment, as demonstrated by the pre-alum treatment cores? If the alum is buried by an average of 4.9 cm of sediment, then is the buried alum still effectively binding mobile phosphorus?

References E. B. Welch, H. L. Gibbons, S. K. Brattebo & H. A. Corson-Rikert (2017) Distribution of aluminum and phosphorus fractions following alum treatments in a large shallow lake, Lake and Reservoir Management, 33:2, 198204, DOI: 10.1080/10402381.2016.1276653 Huser, B. J., Egemose, S., Harper, H., Hupfer, M., Jensen, H., Pilgrim, K. M., . . . Futter, M. (2016). Longevity and effectiveness of aluminum addition to reduce sediment phosphorus release and restore lake water quality. Water Research,97, 122-132. doi:10.1016/j.watres.2015.06.051 Myrbo, A. (2008). Sedimentary and historical context of eutrophication and remediation in urban Lake McCarrons (Roseville, Minnesota). Lake and Reservoir Management,24(4), 349-360. doi:10.1080/07438140809354845 Osgood, D. (2003). Lake McCarrons Management Plan(Rep.). Roseville, MN: Capitol Region Watershed District Pilgrim, K., Wilson, G., Runke, H. (2003). Alum Treatment of Lake McCarrons-Results of Tasks 1 and 2. St. Paul, MN: Capitol Region Watershed District Smol, J. P. (2008). Pollution of Lakes and Rivers: A Paleoenvironmental Perspective (2nd ed.). Blackwell Publishing. (pp.

22-74).

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Appendix A

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February 13, 2019 CAC Meeting

DATE: TO: FROM: RE:

February 13, 2019 CRWD Citizen Advisory Committee Sarah Wein, Water Resource Technician 2018 Lakes Update

VII. Project and Program Updates E) 2018 Lakes Update (Wein)

Background There are five lakes within the boundaries of CRWD: Como Lake, Crosby Lake, Little Crosby Lake, and Loeb Lake in St. Paul, and Lake McCarrons in Roseville. Each lake is collaboratively monitored

by Ramsey County Public Works (RCPW), the Ramsey County Soil and Water Conservation Division, the Minnesota Department of Natural Resources (DNR), and CRWD to evaluate overall health, assess compliance with water quality standards, and determine if each lake supports its designated uses for swimming, fishing, and/or aesthetics. Data has been collected annually on each lake for varying periods of record, with the Como Lake dataset being the longest, dating back to 1984.

Issue In 2018, CRWD, in partnership with RCPW and the Ramsey County Soil and Water Conservation Division, collected chemical, physical, and biological data from all five District lakes. Data collected included: dissolved oxygen, total phosphorus, chlorophyll-a, temperature, Secchi depth, phytoplankton, zooplankton, macrophyte samples, biovolume surveys of vegetation, and continuous water level data.

All of the lakes data collected in 2018 have been analyzed and summarized. Historical lake data and summer average total phosphorus, chlorophyll-a, and Secchi depth calculations are also available online via the CRWD Water Data Portal. An update will be given on 2018 lake monitoring, 2018 lake quality in comparison to the historical data record, 2018 accomplishments, and 2019 initiatives.

Requested Action None W:\07 Programs\Monitoring & Data Acquisition\2018 Monitoring\2018 Lakes\CAC Meeting_02132019\CAC Memo_2018 Lakes_02-13-19.docx

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