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Idyllvale Shores – SWMP October 2024 <br />Civil Methods, Inc.Page | 2 <br />2.EXISTING SITE CONDITIONS <br />Under existing conditions, the property contains a house and several accessory structures, <br />landscaped areas, woods, wetlands, other green space, and open water pertaining to Lake <br />Minnetonka (North Arm). The total impervious area on site is approximately 24,016 SF. Soil <br />mapping for the area indicates a prevalence of Hydrologic Soil Group (HSG) Type C or C/D soils of <br />limited infiltration capacity (Soil Map, Appendix A). A low infiltration rate of 0.25 IN/HR is <br />assumed for the site soils. <br />Stormwater runoff from the overall site drains to the southeast to Lake Minnetonka. Runoff flow <br />in the interior of the site is governed by local topography, which is generally steep in the upland <br />areas. Drainage area boundaries and flow directions at the site are illustrated in Appendix B. <br />Three wetlands have been identified and delineated on the property and are described in detail <br />in the project wetland delineation report. Runoff from the site flows to these wetlands before <br />discharging into Lake Minnetonka. There is an existing overland overflow channel connecting <br />Wetland 1 (upstream) to Wetland 2 (downstream); Wetland 2 discharges at the southern <br />property boundary, with flow proceeding southeast to Lake Minnetonka. Wetland 3 is the open <br />water and surrounding area at the southeast corner of the property. It receives runoff from the <br />additional connected upland on the property, and it is directly connected as part of the Lake <br />Minnetonka open water area. <br />3.PROPOSED SITE CONDITIONS <br />The proposed conditions include the construction of two cul-de-sac roads, five single-family <br />homes with associated driveways, septic fields, and wells, and all associated grading, landscaping, <br />and stormwater management features. A small amount of wetland (less than the de minimis <br />amount of 400 SF) is expected to be filled or impacted for placement of the driveway culvert <br />serving Lot 4. Aside from that, no other wetland impacts are expected to occur, and the wetlands <br />will be protected during construction. <br />The overall site drainage patterns will remain the same, with all runoff from the site eventually <br />discharging southeast to Lake Minnetonka. The overall project is expected to result in a total of <br />85,746 SF (1.97 AC) of impervious area on the site. Three stormwater basins are proposed to <br />capture and infiltrate runoff from the project area, providing rate control, volume control, and <br />associated water quality treatment prior to discharge downstream. These basins are illustrated <br />in Appendix B. <br />144