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Offices in Illinois, Iowa, Minnesota, and Wisconsin 2901 International Lane, Suite 300, Madison, WI 53704-3133 (608) 242-7779 (800) 446-0679 FAX: (608) 242-5664 WEB ADDRESS: www.msa-ps.com MEMO To: City of Middleton From: Ann Dansart, P.H., Eric Thompson, P.E. Subject: Storm Water Quality Plan Addendum Date: June 5, 2009 This memo is an addendum to the September 19, 2007 Stormwater Quality Plan prepared by MSA Professional Services, Inc. for the City of Middleton, WI. The purpose of this memo is to document the results of updated WinDETPOND and P8 modeling of various City ponds that has occurred since the September 19, 2007 Storm Water Quality report was published. Specifically, the pollutant trapping efficiency of individual ponds has been updated, and the impact of these individual ponds’ changed pollutant trapping efficiency on the City’s overall municipal regulated TSS load reduction has been tabulated. The main differences between the 2007 and 2009 modeling include the following: 1) Minor revisions have been made to a number of ponds, in response to updated modeling guidance from the WDNR, and in order to correct a few modeling (data entry) errors that were discovered since 2007; and 2) The confluence pond model was modeled in P8 and calibrated to match streamflow gauge data at Parmenter street (just of this pond) and hydraulically modeled backwater effects on the pond outlet structure predicted by XP-SWMM and HEC-RAS modeling of the pond and the reach of Pheasant Branch creek. Table 1 below, summarizes the results of the revised modeling on the overall municipal regulated TSS load reduction. The first column of results in Table 1 shows the citywide TSS reduction reported in September 2007. The second column shows the overall change from revising pond models other than the confluence pond in WinDETPOND (scenario 1 above). The third column shows the results of the revised WinDETEPOND models and the calibrated confluence pond model (scenarios 1 and 2 above). ---PAGE BREAK--- Offices in Illinois, Iowa, Minnesota, and Wisconsin 2901 International Lane, Suite 300, Madison, WI 53704-3133 (608) 242-7779 (800) 446-0679 FAX: (608) 242-5664 WEB ADDRESS: www.msa-ps.com Table 1. City of Middleton, WI: Existing TSS Reduction, Municipal Regulated Load June 2009 Addendum September 2007 Report WinDETPOND Model Revised (Sc. 1) WinDETPOND Model Revised + P8 Calibrated Confluence Pond Model (Sc. 1& 2) No Controls Annual Regulated Load 611.7 tons/yr 611.7 tons/yr 611.7 tons/yr TSS Removed by Street Sweeping 15.3 tons/yr 15.3 tons/yr 15.3 tons/yr Additional TSS Removed by Structural BMPs 202.0 tons/yr 184.4.3 tons/yr 237. 3 tons/yr Total TSS Removed 217.3 tons/yr 199.4 tons/yr 252.6 tons/yr TSS Reduction Rate 35.5% 32.6% 41.3% With both the WinDETPOND and P8 modeling revisions, the City’s overall existing load reduction has increased from 35.5% to 41.3%. The City therefore meets the WNDR requirement to reduce TSS in runoff from existing developed areas, by 40% by 2013. Tables 2 and 3, attached, show the TSS reduction achieved by each existing City pond with and without the modified confluence pond, respectively. Note in Tables 2 and 3, that because SLAMM and WinDETPOND are not able to model ponds in series, the cumulative effectiveness of the BMPs is determined algebraically by applying the highest efficiency of any BMP in series with the BMP being considered. This is due to WinSLAMM's inability to track the particle distribution (and hydrograph attenuation) being discharged from any single BMP. This approach and its limitations is described and discussed at length in Section 5.4 of the 2007 report. ---PAGE BREAK--- Table 2. Individual Pond Pollutant Trapping Efficiencies - WinDETPOND Modeling Only Discharge Location Discharge Location (or BMP) Name Direct TSS Load* (lbs/yr) BMP Efficiency** Street Sweeping Area Sweeping Efficiency Max TSS Efficiency TSS Load Attenuated 1 1.01 264,326 50.1% 1 0.025 50.1% 132,427 2 1.02 2,065 18.3% 1 0.025 1 50.1% 1,035 3 1.03 48,343 14.9% 1 0.025 1 50.1% 24,220 4 1.04 1,446 20.3% 1 0.025 1 50.1% 724 5 2.0102 60,200 73.0% 1 0.025 1 73.0% 43,946 6 4.01 14,064 58.9% 1 0.025 58.9% 8,284 7 5.01 2,937 82.0% 1 0.025 82.0% 2,408 8 6.01 3,179 99.5% 1 0.025 99.5% 3,163 9 7.01 913 9.5% 1 0.025 1 50.1% 457 10 7.020304 862 32.4% 1 0.025 1 50.1% 432 11 9.01 2,282 24.0% 1 0.025 1 12 50.1% 1,143 12 9.02 1,267 31.4% 1 0.025 1 50.1% 635 13 9.03 1,974 7.2% 1 0.025 1 50.1% 989 14 11.01 884 50.2% 1 0.025 50.2% 444 15 12.01 690 45.2% 1 0.025 16 45.2% 312 16 12.02 137 16.7% 1 0.025 16.7% 23 17 13.01 86 31.4% 1 0.025 18 20 21 59.0% 51 18 13.02 0 8.2% 1 0.025 20 21 59.0% 0 19 15.01 18,781 26.3% 1 0.025 26.3% 4,939 20 16.01 7,162 59.0% 1 0.025 21 59.0% 4,226 21 16.02 2,885 0.1% 1 0.025 2.5% 72 22 17.01 3,040 64.3% 1 0.025 23 24 81.6% 2,481 23 17.02 460 81.6% 1 0.025 24 81.6% 375 24 17.03 1,408 54.6% 1 0.025 54.6% 769 25 18.01 4,012 38.4% 1 0.025 1 50.1% 2,010 26 18.02 776 24.7% 1 0.025 1 50.1% 389 27 18.03 14,968 20.3% 1 0.025 1 50.1% 7,499 28 18.04 1,895 36.1% 1 0.025 1 27 50.1% 949 29 18.05 2,546 32.8% 1 0.025 1 3 50.1% 1,276 30 20.01 6,381 33.7% 1 0.025 21 33.7% 2,150 31 21.01 13,949 10.0% 1 0.025 10.0% 1,395 32 23.01 2,626 66.2% 1 0.025 1 5 73.0% 1,917 33 23.02 3,094 40.3% 1 0.025 1 5 73.0% 2,259 34 24.01 4,475 48.3% 1 0.025 48.3% 2,161 35 25.01040512 5,019 38.5% 1 0.025 61 38.5% 1,932 36 25.0203 1,673 9.5% 1 0.025 1 5 73.0% 1,221 37 25.06 1,014 2.2% 1 0.025 61 35.2% 357 38 25.0711 4,665 2.2% 1 0.025 63 17.0% 793 39 26.01 4,806 67.1% 1 0.025 67.1% 3,225 40 26.02 3,124 90.0% 1 0.025 90.0% 2,812 41 27.01 13,914 72.2% 1 0.025 72.2% 10,046 42 28.01 32,111 74.0% 1 0.025 74.0% 23,762 43 28.02 455 63.7% 1 0.025 42 74.0% 337 44 29.01 177 93.1% 1 0.025 1 3 93.1% 165 45 29.02 29 100.0% 1 0.025 1 3 100.0% 29 46 31.01 29,740 57.9% 1 0.025 57.9% 17,219 47 33.01 52 83.9% 1 0.025 1 83.9% 44 48 33.02 103 89.9% 1 0.025 1 89.9% 93 49 34.01 355 0.2% 1 0.025 61 35.2% 125 50 35.01 164 54.7% 1 0.025 46 57.9% 95 51 36.01 2,002 63.0% 1 0.025 63.0% 1,261 52 39.01 460 80.0% 1 0.025 1 80.0% 368 53 40.01 400 67.0% 1 0.025 31 67.0% 268 54 41.01 960 15.3% 1 0.025 61 35.2% 338 55 42.01 9,908 71.7% 1 0.025 71.7% 7,104 56 42.02 956 80.2% 1 0.025 80.2% 767 57 43.01 1,568 30.3% 1 0.025 46 57.9% 908 58 44.01 23,833 24.6% 1 0.025 1 3 50.1% 11,940 59 45.01 8,720 27.0% 1 0.025 27.0% 2,354 60 46.01 11,673 57.8% 1 0.025 57.8% 6,747 61 47.01 19,632 35.2% 1 0.025 35.2% 6,910 62 47.02 965 25.9% 1 0.025 25.9% 250 63 47.03 558 17.0% 1 0.025 17.0% 95 64 48.01 1,115 81.2% 1 0.025 19 81.2% 905 65 49.01 9,113 26.6% 1 0.025 26.6% 2,424 66 50.01 1,187 87.1% 1 0.025 1 87.1% 1,034 67 51.01 626 13.8% 1 0.025 1 5 71 72 73.0% 457 68 51.02 1,900 47.6% 1 0.025 1 5 72 73.0% 1,387 69 51.03 1,166 44.2% 1 0.025 1 5 73.0% 851 70 51.04 1,718 30.0% 1 0.025 1 5 72 73.0% 1,254 71 51.05 12,325 17.6% 1 0.025 1 5 72 73.0% 8,997 72 51.06 586 9.7% 1 0.025 1 5 73.0% 428 73 51.07 1,244 18.2% 1 0.025 1 5 73.0% 908 74 52.01 3,454 41.9% 1 0.025 41.9% 1,447 75 52.02 15,086 35.3% 1 0.025 74 41.9% 6,321 76 53.01 725 63.1% 1 0.025 77 63.1% 457 77 53.02 673 55.2% 1 0.025 55.2% 371 78 55.01 192 26.3% 1 0.025 26.3% 50 79 57.01 1,183 57.5% 1 0.025 1 57.5% 680 80 58.01 651 40.9% 1 0.025 31 40.9% 266 81 59.01 1,063 11.1% 1 0.025 1 50.1% 533 82 61.01 558 29.6% 1 0.025 1 50.1% 280 83 61.02 406 23.9% 1 0.025 1 50.1% 203 84 Direct 495,200 0.0% 1 0.025 2.5% 12,380 TOTAL 1,223,320 32.6% 398,760 *Include only TSS generated in the watershed that drains directly to the BMP. Do not include any TSS that first drains to an upstream BMP. **TSS attenuation rate of BMP. Enter if no BMP. ***Enter 1 if located in street sweeping area 1, 2 if in area 2, or 0 if the area is not swept BMPs (Enter # of BMP ---PAGE BREAK--- Table 3. Individual Pond Pollutant Trapping Efficiencies with Confluence Pond Model Calibrated in P8 Discharge Location Discharge Location (or BMP) Name Direct TSS Load* (lbs/yr) BMP Efficiency** Street Sweeping Area Sweeping Efficiency Max TSS Efficiency TSS Load Attenuated 1 1.01 264,326 77.5% 1 2.5% 77.5% 204,853 2 1.02 2,065 18.3% 1 2.5% 1 77.5% 1,600 3 1.03 48,343 14.9% 1 2.5% 1 77.5% 37,466 4 1.04 1,446 20.3% 1 2.5% 1 77.5% 1,121 5 2.0102 60,200 73.0% 1 2.5% 1 77.5% 46,655 6 4.01 14,064 58.9% 1 2.5% 58.9% 8,284 7 5.01 2,937 82.0% 1 2.5% 82.0% 2,408 8 6.01 3,179 99.5% 1 2.5% 99.5% 3,163 9 7.01 913 9.5% 1 2.5% 1 77.5% 708 10 7.020304 862 32.4% 1 2.5% 1 77.5% 668 11 9.01 2,282 24.0% 1 2.5% 1 12 77.5% 1,769 12 9.02 1,267 31.4% 1 2.5% 1 77.5% 982 13 9.03 1,974 7.2% 1 2.5% 1 77.5% 1,530 14 11.01 884 50.2% 1 2.5% 50.2% 444 15 12.01 690 45.2% 1 2.5% 16 45.2% 312 16 12.02 137 16.7% 1 2.5% 16.7% 23 17 13.01 86 31.4% 1 2.5% 18 20 21 59.0% 51 18 13.02 0 8.2% 1 2.5% 20 21 59.0% 0 19 15.01 18,781 26.3% 1 2.5% 26.3% 4,939 20 16.01 7,162 59.0% 1 2.5% 21 59.0% 4,226 21 16.02 2,885 0.1% 1 2.5% 2.5% 72 22 17.01 3,040 64.3% 1 2.5% 23 24 81.6% 2,481 23 17.02 460 81.6% 1 2.5% 24 81.6% 375 24 17.03 1,408 54.6% 1 2.5% 54.6% 769 25 18.01 4,012 38.4% 1 2.5% 1 77.5% 3,109 26 18.02 776 24.7% 1 2.5% 1 77.5% 601 27 18.03 14,968 20.3% 1 2.5% 1 77.5% 11,600 28 18.04 1,895 36.1% 1 2.5% 1 27 77.5% 1,469 29 18.05 2,546 32.8% 1 2.5% 1 3 77.5% 1,973 30 20.01 6,381 33.7% 1 2.5% 21 33.7% 2,150 31 21.01 13,949 10.0% 1 2.5% 10.0% 1,395 32 23.01 2,626 66.2% 1 2.5% 1 5 77.5% 2,035 33 23.02 3,094 40.3% 1 2.5% 1 5 77.5% 2,398 34 24.01 4,475 48.3% 1 2.5% 48.3% 2,161 35 25.01040512 5,019 38.5% 1 2.5% 61 38.5% 1,932 36 25.0203 1,673 9.5% 1 2.5% 1 5 77.5% 1,297 37 25.06 1,014 2.2% 1 2.5% 61 35.2% 357 38 25.0711 4,665 2.2% 1 2.5% 63 17.0% 793 39 26.01 4,806 67.1% 1 2.5% 67.1% 3,225 40 26.02 3,124 90.0% 1 2.5% 90.0% 2,812 41 27.01 13,914 72.2% 1 2.5% 72.2% 10,046 42 28.01 32,111 74.0% 1 2.5% 74.0% 23,762 43 28.02 455 63.7% 1 2.5% 42 74.0% 337 44 29.01 177 93.1% 1 2.5% 1 3 93.1% 165 45 29.02 29 100.0% 1 2.5% 1 3 100.0% 29 46 31.01 29,740 57.9% 1 2.5% 57.9% 17,219 47 33.01 52 83.9% 1 2.5% 1 83.9% 44 48 33.02 103 89.9% 1 2.5% 1 89.9% 93 49 34.01 355 0.2% 1 2.5% 61 35.2% 125 50 35.01 164 54.7% 1 2.5% 46 57.9% 95 51 36.01 2,002 63.0% 1 2.5% 63.0% 1,261 52 39.01 460 80.0% 1 2.5% 1 80.0% 368 53 40.01 400 67.0% 1 2.5% 31 67.0% 268 54 41.01 960 15.3% 1 2.5% 61 35.2% 338 55 42.01 9,908 71.7% 1 2.5% 71.7% 7,104 56 42.02 956 80.2% 1 2.5% 80.2% 767 57 43.01 1,568 30.3% 1 2.5% 46 57.9% 908 58 44.01 23,833 24.6% 1 2.5% 1 3 77.5% 18,471 59 45.01 8,720 27.0% 1 2.5% 27.0% 2,354 60 46.01 11,673 57.8% 1 2.5% 57.8% 6,747 61 47.01 19,632 35.2% 1 2.5% 35.2% 6,910 62 47.02 965 25.9% 1 2.5% 25.9% 250 63 47.03 558 17.0% 1 2.5% 17.0% 95 64 48.01 1,115 81.2% 1 2.5% 19 81.2% 905 65 49.01 9,113 26.6% 1 2.5% 26.6% 2,424 66 50.01 1,187 87.1% 1 2.5% 1 87.1% 1,034 67 51.01 626 13.8% 1 2.5% 1 5 71 72 77.5% 485 68 51.02 1,900 47.6% 1 2.5% 1 5 72 77.5% 1,473 69 51.03 1,166 44.2% 1 2.5% 1 5 77.5% 904 70 51.04 1,718 30.0% 1 2.5% 1 5 72 77.5% 1,331 71 51.05 12,325 17.6% 1 2.5% 1 5 72 77.5% 9,552 72 51.06 586 9.7% 1 2.5% 1 5 77.5% 454 73 51.07 1,244 18.2% 1 2.5% 1 5 77.5% 964 74 52.01 3,454 41.9% 1 2.5% 41.9% 1,447 75 52.02 15,086 35.3% 1 2.5% 74 41.9% 6,321 76 53.01 725 63.1% 1 2.5% 77 63.1% 457 77 53.02 673 55.2% 1 2.5% 55.2% 371 78 55.01 192 26.3% 1 2.5% 26.3% 50 79 57.01 1,183 57.5% 1 2.5% 1 77.5% 917 80 58.01 651 40.9% 1 2.5% 31 40.9% 266 81 59.01 1,063 11.1% 1 2.5% 1 77.5% 824 82 61.01 558 29.6% 1 2.5% 1 77.5% 432 83 61.02 406 23.9% 1 2.5% 1 77.5% 315 84 Direct 495,200 0.0% 1 2.5% 2.5% 12,380 TOTAL 1,223,320 41.3% 505,268 *Include only TSS generated in the watershed that drains directly to the BMP. Do not include any TSS that first drains to an upstream BMP **TSS attenuation rate of BMP. Enter if no BMP. BMPs (Enter # of BMP