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page 11 ii. Stormwater - Describe the quantity and quality of stormwater runoff at the site prior to and post construction. Include the routes and receiving water bodies for runoff from the site (major downstream water bodies as well as the immediate receiving waters). Discuss any environmental effects from stormwater discharges. Describe stormwater pollution prevention plans including temporary and permanent runoff controls and potential BMP site locations to manage or treat stormwater runoff. Identify specific erosion control, sedimentation control or stabilization measures to address soil limitations during and after project construction. Under existing conditions the site contains a manufactured housing park with 6.6 acres of impervious surface. Proposed conditions will consist of multi-family residences with 9.6 acres of impervious surface. Existing runoff drains to a depression in the southeast quadrant of the project area and discharges to the Saint Anthony Village stormwater system. The stormwater is then discharged into the City of Minneapolis system and into the Mississippi River. There is a history of flooding on this property and surrounding properties. An XP- SWMM model has been developed to determine the existing conditions runoff rates for the 2-, 10-, and 100-year Atlas-14 storm events (Table 6). This model indicates that the City Stormwater System currently surcharges and flows back into this property. Therefore, backflow preventers may be required to manage stormwater runoff onto this site. Table 6: Existing Discharge Rate into the City Storm Sewer System Storm Discharge Rate (cfs) 2-Year 5.8 10-Year 5.9 100-Year 6.1 The proposed XP SWMM analysis of the proposed development will need to show that there will be no increase in the 100-year, 24-hour storm form the new development into the City of St. Anthony storm sewer. The final grading plan and design will be submitted to the City of Saint Anthony Village for review and approval prior to construction. Stormwater quality requires the capture and retention of the first 1.1 inches of runoff from the new and fully reconstructed impervious surfaces. However, due to the presence of clay soils and the potential for mobilization of contamination, infiltration is discouraged on this site. Therefore, if the site is unable to capture and retain the 1.1 inches the site must achieve the following, per the Mississippi River Watershed Management Organization Watershed Management Plan 2011-2021 (11-09-2016 Revision) Appendix Q:  0.55 inch volume reduction  Remove 75% of the annual Total Phosphorus between pre and post conditions. 46