Laserfiche WebLink
the extent feasible or offset new and expanded discharges by constructing Best <br />Management Practices (BMPs) at an offsite location to achieve compliance with <br />Non-degradation requirements. <br />Table 17-1 summarizes the total pollutant loads for each development scenario <br />compared to the baseline condition. <br />Table 17-1: Annual Estimated Pollutant Loads <br /> <br />Development Scenario Annual Runoff <br />Volume (ac-ft) Annual TP <br />Load (Ibs) <br />Annual TSS Load (Ibs) <br />Baseline Condition - 1988 61 83 25,639 <br />Scenario 1 209 208 80,932 <br />Scenario 2 259 252 108,561 <br />Scenario 3 320 309 133,692 <br />To achieve compliance with nondegradation requirements, future development <br />must provide annual volume and pollutant load reductions in the amounts <br />presented in Table 17-2. These values represent reductions from the post- <br />development condition and are comparable to the City's current stormwater <br />management standards. <br />Table 17-2: Required Annual Pollutant Load Reductions to Achieve Baseline Condition (1988) <br /> <br />Development Scenario Annual Runoff <br />Volume (ac-ft) Annual TP Load <br />(Ibs) Annual TSS Load <br />(Ibs) <br />Scenario 1 71% 60% 68% <br />Scenario 2 77% 67% 76% <br />Scenario 3 81% 73% 81% <br />Potential Impact to Downstream Receiving Waters <br />In addition to other stormwater management requirements, future development <br />within the Study Area maybe required to maintain 1988 baseline conditions for <br />runoff volume and pollutant loads. If these requirements are met on site, it is not <br />anticipated that any significant impacts to downstream water quality will result <br />from development. <br />Water Quantity and Quality Mitigation Plan <br />• Infiltration best management practices will be required to meet volume control <br />goals as listed in Table 17-2. Group A soils within the Study Area will likely <br />provide sufficient infiltration capacity to achieve these goals. <br />' • Design considerations for comprehensive storm water management should <br />include regional ponding, individual site underground infiltration systems and a <br />perforated trunk storm sewer conveyance system. <br />City of Elk River <br />Draft Alternative Urban Areawide Review <br />July 2011 <br />Page 41 of 84 <br />