Minnehaha Creek TMDL Project Update June 7, 2012 Minnehaha Creek Watershed District Office
Minnehaha Creek TMDL Discussion Overview Discussion Overview CIP Summary CIP Summary Li k Linkage Analysis A l i Quick “re-cap” Allocations Allocations Potential Options
Linkage Analysis Quick “Re-Cap” Cap” Quick “Re Bacteria Bacteria
Linkage Analysis Quick “Re-Cap” Cap” Quick “Re Total Phosphorus Total Phosphorus
Linkage Analysis Reduction Needs Reduction Needs 2001-2011 Parameter Target Reduction Average 301 1 E. coli (#/100mL) 126 58% 40 2 44% Total Phosphorus (µg/L) p (µg ) 70.9 50 3 3 29% 1 Average values reflect geometric mean, consistent with WQS. Notes: 2 Minnesota Rule 7050 2 Minnesota Rule 7050. 3 MCWD Lake Hiawatha water quality goal.
Linkage Analysis Assessment Points Assessment Points Grays Grays Bay McGinty West 34 th Lake Hiawatha 32 nd Ave Excelsior COL to Hiawatha Browndale BD to COL McGinty
Linkage Analysis Reduction Needs Reduction Needs Bacteria Bacteria Group High Moist Mid Dry Low --- Grays Bay --- --- --- --- --- A McGinty (Minnetonka) --- --- --- --- --- B W. 34th (Minnetonka, SLP, Hopkins) --- --- --- 25% 4% C Excelsior (SLP, Hopkins) 12% 35% 55% 76% 45% D Browndale --- --- --- --- --- ( (SLP, Edina) ) E BD to COL (Edina, Minneapolis) 19% 32% 16% 46% 47% F COL to Hiawatha (Minneapolis) 40% 54% 58% 73% 68%
Linkage Analysis Watershed Loading Watershed Loading
TMDL Development Regulatory Regulatory Framework Framework TMDL Report -- Required Elements TMDL Report Required Elements Applicable WQ Standards Loading Capacity Source Assessment Allocations Seasonal Variation Seasonal Variation Margin of Safety TMDL TMDL = WLA Point Sources + WLA MS4 + LA + MOS WLA W A A MOS
Drainage Area Perspective Drainage Area Perspective Watershed Loading
Potential Options Potential Options Allocations “Combination” Approach Equal Percent Reduction Area Export Coefficient Impervious Cover
Subwatershed Groups Approximate Composition Approximate Composition City A B C D E F Plymouth 5% Wayzata 3% Minnetonka Minnetonka 87% 87% 75% 75% St. Louis Park 16% 59% 25% Hopkins 7% 36% 7% Edina 4% 60% 60% Minneapolis 37% 100%
Potential Allocations Equal Percent Reduction Equal Percent Reduction Applied at all points Applied at all points Reduction Allocation Group (lbs) (lbs) lbs lbs % % --- Grays Bay 1,279 0 --- A McGinty (Minnetonka) 640 269 29.6% B W. 34th (Minnetonka, SLP, Hopkins) 584 246 29.6% C Excelsior (SLP, Hopkins) 727 305 29.6% D Browndale 464 195 29.6% ( (SLP, Edina) ) E BD to COL (Edina, Minneapolis) 579 243 29.6% F COL to Hiawatha (Minneapolis) 498 210 29.6% Needed Reduction: 1,468 lbs
Potential Allocations Equal Percent Reduction Equal Percent Reduction Applied at all points Applied at all points
Unit Area Loading Concept Concept Load divided by Area Load divided by Area Area Rate Group Group (acres) (lbs/acre) A McGinty 3,493 0.260 B B W 34th W. 34th 5 101 5,101 0 163 0.163 C Excelsior 1,998 0.517 D Browndale 1,426 0.462 E BD to COL 2,171 0.379 F COL to LH 2,504 0.283
Unit Area Loading Area Export Coefficient Area Export Coefficient Load divided by Area Load divided by Area
Potential Allocations Area Export Coefficient Area Export Coefficient Based on total area (0.209 lbs / acre) Based on total area (0.209 lbs / acre) Reduction Allocation Group (lbs) (lbs) lbs lbs % % --- Grays Bay 1,279 0 --- A McGinty (Minnetonka) 730 177 19.5% B W. 34th (Minnetonka, SLP, Hopkins) 1,067 -237 -28.5% C Excelsior (SLP, Hopkins) 418 614 59.5% D Browndale 298 361 54.7% ( (SLP, Edina) ) E BD to COL (Edina, Minneapolis) 454 368 44.8% F COL to Hiawatha (Minneapolis) 523 185 26.1% Needed Reduction: 1,468 lbs
Potential Allocations Impervious Cover Weighting Impervious Cover Weighting Based on Impervious Area (0.448 lbs / acre) Based on Impervious Area (0.448 lbs / acre) Reduction Allocation Group (lbs) (lbs) lbs lbs % % --- Grays Bay 1,279 0 --- A McGinty (Minnetonka) 595 312 34.4% B W. 34th (Minnetonka, SLP, Hopkins) 886 -56 -6.8% C Excelsior (SLP, Hopkins) 530 502 48.6% D Browndale 279 379 57.7% ( (SLP, Edina) ) E BD to COL (Edina, Minneapolis) 549 273 33.2% F COL to Hiawatha (Minneapolis) 650 58 8.2% Needed Reduction: 1,468 lbs
Potential Allocations “Combination” Approach “Combination” Approach Average of Area Export & Impervious Average of Area Export & Impervious Reduction Allocation Group (lbs) (lbs) lbs lbs % % --- Grays Bay 1,279 0 --- A McGinty (Minnetonka) 663 244 26.9% B W. 34th (Minnetonka, SLP, Hopkins) 976 -145 -17.6% C Excelsior (SLP, Hopkins) 474 558 54.1% D Browndale 289 370 56.2% ( (SLP, Edina) ) E BD to COL (Edina, Minneapolis) 502 320 39.0% F COL to Hiawatha (Minneapolis) 587 121 17.1% Needed Reduction: 1,468 lbs
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