Download - 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
Google Earth