11-19-2024 Planning Commission Packet

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Idyllvale Shores – Conservation Design Master Plan October 2024 Civil Methods, Inc.Page | 5 Wetland 3 is a direct connection to Lake Minnetonka, receiving runoff from both the site and additional upland areas. Additional information about the existing drainage system can be found in the wetland delineation report as well as the stormwater management plan prepared for the project. 3.2 STORMWATER MANAGEMENT SYSTEM The proposed development includes the construction of two cul-de-sac roads, a shared walking path, five single-family homes with associated driveways, septic systems, wells, and necessary site grading and landscaping. A small portion of wetland (less than 400 square feet) will be impacted to accommodate a driveway culvert for Lot 4. However, no other wetlands will be affected, and existing wetlands will be protected during construction. The overall site drainage pattern will remain unchanged, with all runoff eventually discharging southeast into Lake Minnetonka. The project will increase the impervious area by approximately 1.82 acres, bringing the total to 2.37 acres. To manage stormwater runoff, three stormwater basins will be installed to capture, infiltrate, and treat the runoff before it reaches the lake. The stormwater management system proposed for the site will be highly effective at mitigating any potential hydrologic impacts of the project. As required by the Minnehaha Creek Watershed District (MCWD), the stormwater BMPs will reduce runoff volume from the site in an amount equal to one inch over all final site impervious area. They will also provide rate control, ensuring that for all regulated storms, the peak flow rate from the site in aggregate will not increase under proposed conditions. The analysis and additional documentation of the stormwater management system is provided in the project stormwater management plan. 3.3 MANAGEMENT OF INVASIVE AND DISEASED VEGETATION Two prevalent invasive species were identified in the project area: buckthorn and reed canary grass. Buckthorn, a non-native shrub, can outcompete native plants and degrade habitat quality. Reed canary grass, a tall perennial, can form dense stands that displace native vegetation. To effectively manage these invasive species, a combination of mechanical, chemical, and biological control methods may be employed. The following resources may be consulted for specific guidance on management of these species: https://www.dnr.state.mn.us/invasives/terrestrialplants/woody/buckthorn/index.html https://www.dnr.state.mn.us/invasives/terrestrialplants/grasses/reedcanarygrass.html Additionally, the emerald ash borer (EAB) poses a significant threat to ash trees in the region. Given the presence of EAB, it is anticipated that all ash trees on the site will eventually die. Therefore, the removal of ash trees should not be considered a negative impact of the 120