tmdl critique: mcwd lakes tmdl – lake nokomis, parley lake, lake virginia, wassermann lake

TMDL Critique:

MCWD Lakes TMDL– Lake Nokomis, Parley Lake, Lake

Virginia, Wassermann Lake

Blake Wageman and Lu ZhangBBE 4535

Lake and Watershed Description

Parley

Wassermann

Virginia

Nokomis

Lake and Watershed DescriptionLake Nokomis

• Location: Eastern MCWD, in Minneapolis• Land use:

o single family residential dominated; projected 16% growtho high concentration of commercial/industrial land use

• Lake use: primarily recreational

• Watershed history: o 1891, flow control to ensure the water flow

over Minnehaha Fallso 1892, lake would be secured as a reservoiro  1907-1930s, surrounding wetlands were

dredged and filled for recreational useso 1973: first study of lake water quality-

storm water runoffo  1998: swimmable, fishable, aesthetically

pleasing, and should support diverse populations of plants and wildlife

Lake and Watershed DescriptionLake Parley

• Location: Along Six Mile Creek, Western MCWD

• Land use: o primarily agricultural,

undeveloped, and parkland; o projected 2020 land use

increase in single family residential

• Lake use: o DNR public access ramp o Primarily boating and fishing

Lake and Watershed DescriptionLake Wassermann

• Location: Along Six Mile Creek, Western MCWD

• Land use: o primarily agricultural, undeveloped,

and parkland; o projected 2020 land use increase in

single family residential• Lake use:

o DNR public access ramp o Primarily boating and fishing, and

water sports• Watershed management:

Victoria’s Shoreland District would include a 1,000-ft buffer around Wassermann Lake

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: o DNR public access o private lakeshore propertieso aquatic recreation

• Watershed management:  o control exotic species o improve water quality o restore and preserve shoreland habitato provide for compatible recreational uses

303 (d) Listing

Lake Name Lake ID Year Listed TargetStart/Completion

CALM Category

Nokomis 27-19 2002 2003/2008 5B

Parley 10-42 2002 2003/2008 5C

Virginia 10-15 2004 2003/2008 5B

Wassermann 10-48 2002 2003/2008 5B

• 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

Pollution Sources

Pollution Sources

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

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

Parameter Eutrophication Standard, General

Eutrophication Standard, Shallow Lakes

TP (ug/L) TP<40 TP<60

Chlorophyll-a (ug/L) Chl<14 Chl<20

Secchi depth (m) SD>1.4 SD>1.0

Lakes the standards apply to Nokomis, Virginia, Wassermann

Parley

Lake Nokomis Mean TP

Lake Nokomis TP Distribution

TMDL Approach

Pollutant sources:o Stormwater runoff: 

o Internal loading and atmospheric deposition: In-lake models were developed using Bathtub.

Calculation

TMDL=WLA+LA

Lake Name TMDL (lbs/yr)

WLA (lbs/yr) LA (lbs/yr)

Lake Nokomis State Eutrophication Standard 490 330 160

Requested Site-Specific Standard 742 463 279

Parley Lake State Eutrophication Standard 1,270 175 1,097

Lake Virginia State Eutrophication Standard 306 133 173

Wassermann State Eutrophication Standard 283 125 158

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:

Lake Nokomis TMDL

Seasonal Variation and Critical Conditions

 • Critical conditions in summer months

o TP concentrations peako 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 usedo 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

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)o Focus: new development and rural BMP’s

• Hennepin County (Lake Nokomis)o Focus: redevelopment and retrofits

• Implementation Strategies fully developed in the MCWD Lakes TMDL Implementation Plan, a work in progress

Lake Cost (millions)

Wassermann $2.2 - $2.6

Virginia $0.5 - $1.1

Parley $2.7 - $3.8

Nokomis $1.1 - $4.5

Total $6 - $12

CWLA TMDL total cost

approximation (preliminary)

Implementation

  • Watershed wide activitieso MCWD Rule N (50% minimum removal)o P-free fertilizer laws (est. Minneapolis 2001, MN State 2004)

• Carver County Lakes (Wassermann, Parley, and Virginia)o Internal load management projects, Aquatic vegetation

managemento Tributary wetland restoration (Parley)o Lake Virginia watershed regional infiltration projects as identified

by MCWD (4)o Ag BMPs, wetland/lake shore restoration, stream restoration

• Lake Nokomiso Lake Nokomis Internal Load Management project (2007)o Small and Large scale retrofits, rain gardens, other BMPs

Monitoring• Parley, Wassermann, Virginia• MCWD annual monitoring program

o DO, Temp, pH, Specific Conductivity, 1m depth increments

o Secchi transparencyo Surface: TP, SRP, TN, CHL-Ao Thermocline/bottom: TP, SRPo Bi-weekly from ice-out to fall mixingo Stream sampling weekly (TN, Cl/ mo.)o DNR fish surveys every 6 years

• Lake Nokomis• MRPB’s annual in-lake program

o DO, Temp, pH, Conductivity Secchi transparency, Surface TP, SRP, TN, CHL-A Phyto/Zoo Plankton

o Bi-weekly from May-Septembero Once per winter Oct.-March/Aprilo Macrophyte survey Aug. 2005

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

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

Critique: Pollution Sources

• TSI relationships for Powderhorn Lake, not for any of the lakes in this TMDL

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

References

Emmons & Olivier Resources, Inc. MCWD Lakes TMDL- Lake Nokomis, Parley Lake, Lake Virginia, Wassermann Lake. 2011. MPCA TMDL Projects.

MN Rules Chapter 7050.0140https://www.revisor.mn.gov/rules/?id=7050.0140

http://ci.billings.mt.us/images/pages/N571//stormwater_problem_large.jpg

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