TMDL Critique: MCWD Lakes TMDL – Lake Nokomis, Parley Lake, Lake Virginia, Wassermann Lake

1. TMDL Critique:MCWD Lakes TMDL– Lake Nokomis, Parley Lake, Lake Virginia, Wassermann Lake Blake Wageman and Lu Zhang BBE 4535

2. Lake and Watershed Description Parley Nokomis Virginia Wassermann

3. Lake and Watershed DescriptionLake Nokomis • Location: Eastern MCWD, in Minneapolis • Land use: • single family residential dominated; projected 16% growth • high concentration of commercial/industrial land use • Lake use: primarily recreational • Watershed history:  • 1891, flow control to ensure the water flow over Minnehaha Falls • 1892, lake would be secured as a reservoir •  1907-1930s, surrounding wetlands were dredged and filled for recreational uses • 1973: first study of lake water quality- storm water runoff •  1998: swimmable, fishable, aesthetically pleasing, and should support diverse populations of plants and wildlife

4. Lake and Watershed DescriptionLake Parley • Location: Along Six Mile Creek, Western MCWD • Land use: • primarily agricultural, undeveloped, and parkland; • projected 2020 land use increase in single family residential • Lake use: • DNR public access ramp • Primarily boating and fishing

5. Lake and Watershed DescriptionLake Wassermann • Location: Along Six Mile Creek, Western MCWD • Land use: • primarily agricultural, undeveloped, and parkland; • projected 2020 land use increase in single family residential • Lake use: • DNR public access ramp • Primarily boating and fishing, and water sports • Watershed management: Victoria’s Shoreland District would include a 1,000-ft buffer around Wassermann Lake

6. Lake and Watershed DescriptionLake Virginia • Location: South Central MCWD, within the cities of Victoria, Chanhassen, Chaska, and Shorewood • Land use: predominantly single family residential; projected 2020 land use increase in single family residential •  Lake use: • DNR public access • private lakeshore properties • aquatic recreation • Watershed management:   • control exotic species • improve water quality • restore and preserve shoreland habitat • provide for compatible recreational uses

7. 303 (d) Listing • 5B: Impaired by multiple pollutants and at least one TMDL study plan is approved by EPA • 5C: Impaired by one pollutant and no TMDL study plan is approved by EPA • Impaired Use: Aquatic recreation • Pollutant or Stressor: Nutrient/eutrophication biological indicators

8. Pollution Sources

9. Pollution Sources

10. Phosphorus Sources • Regulated stormwater runoff • Non-regulated stormwater runoff • Point sources • Internal loading • Atmospheric deposition • Groundwater discharge • Agricultural runoff • Failing septics http://ci.billings.mt.us/images/pages/N571//stormwater_problem_large.jpg

11. Water Quality Standard • Class 2B: aquatic life and recreation • Class 3C: industrial consumption • Class 4A: agriculture and wildlife • Class 5: aesthetic enjoyment and navigation • Class 6: other uses and protection of border water

12. Lake Nokomis Mean TP

13. Lake Nokomis TP Distribution

14. TMDL Approach Pollutant sources: • Stormwater runoff:  • Internal loading and atmospheric deposition: In-lake models were developed using Bathtub.

15. Calculation TMDL=WLA+LA

16. Margin of Safety • MOS implicitly included in modeling assumptions for the TMDL equation. • Accounts for both the inability to precisely describe current WQ conditions and the unknowns in the relationship between the LA and the in-lake WQ • Basis of reasoning for implicit MOS from the MCWD TMDL:

17. Lake Nokomis TMDL

18. Seasonal Variation and Critical Conditions • Critical conditions in summer months • TP concentrations peak • Clarity is at its worst • Lakes respond to long term load changes, i.e. not sensitive to short term changes • Accounted for by use of annual loads in the lake WQ model used • Accounts for summer period where frequency and severity of nuisance algal growth is the greatest • Follows MPCA nutrient standards for growing season concentration average (June – September) • Setting TMDL to summer (critical) period ensures WQ standards are met for all other seasons

19. Implementation • Incorporates load reduction strategies from the MCWD Capital Improvement Plan • Use adaptive management (ongoing assessment process) to evaluate impact of implementation activities • Carver County Lakes (Wassermann, Parley, and Virginia) • Focus: new development and rural BMP’s • Hennepin County (Lake Nokomis) • Focus: redevelopment and retrofits • Implementation Strategies fully developed in the MCWD Lakes TMDL Implementation Plan, a work in progress • CWLA TMDL total cost approximation (preliminary)

20. Implementation • Watershed wide activities • MCWD Rule N (50% minimum removal) • P-free fertilizer laws (est. Minneapolis 2001, MN State 2004) • Carver County Lakes (Wassermann, Parley, and Virginia) • Internal load management projects, Aquatic vegetation management • Tributary wetland restoration (Parley) • Lake Virginia watershed regional infiltration projects as identified by MCWD (4) • Ag BMPs, wetland/lake shore restoration, stream restoration • Lake Nokomis • Lake Nokomis Internal Load Management project (2007) • Small and Large scale retrofits, rain gardens, other BMPs

21. Monitoring • Parley, Wassermann, Virginia • MCWD annual monitoring program • DO, Temp, pH, Specific Conductivity, 1m depth increments • Secchi transparency • Surface: TP, SRP, TN, CHL-A • Thermocline/bottom: TP, SRP • Bi-weekly from ice-out to fall mixing • Stream sampling weekly (TN, Cl/ mo.) • DNR fish surveys every 6 years • Lake Nokomis • MRPB’s annual in-lake program • DO, Temp, pH, Conductivity Secchi transparency, Surface TP, SRP, TN, CHL-A Phyto/Zoo Plankton • Bi-weekly from May-September • Once per winter Oct.-March/April • Macrophyte survey Aug. 2005

22. Critique • Great job communicating with stakeholders, public participation, education (9) • Reasonable Assurances/Level of Confidence • Site Specific Standard for Lake Nokomis • Implicit MOS may be underrepresented since analysis was done with insufficient WQ data • No Load Duration Curves; related to monitoring data • Why didn’t they use historical data • WLA outflow parameters lumped to 150 μg/L

23. Critique: Pollution Sources • Regulated stormwater runoff • Non-regulated stormwater runoff • Point sources • Internal loading • Atmospheric deposition • Groundwater discharge • Agricultural runoff • Failing septics ‘unidentified loads’? http://ci.billings.mt.us/images/pages/N571//stormwater_problem_large.jpg

24. Critique: Pollution Sources • TSI relationships for Powderhorn Lake, not for any of the lakes in this TMDL

25. Critique • Considering this, why lump these 4 lakes into 1 TMDL? • Perspectives: • Lake Classification for modeling (polymictic) • Implementation Programs/Monitoring • Land use and Pollution sources • Differences in Reserve Capacity

27. References Emmons & Olivier Resources, Inc. MCWD Lakes TMDL- Lake Nokomis, Parley Lake, Lake Virginia, Wassermann Lake. 2011. MPCA TMDL Projects. MN Rules Chapter 7050.0140 https://www.revisor.mn.gov/rules/?id=7050.0140 http://ci.billings.mt.us/images/pages/N571//stormwater_problem_large.jpg Google Earth