City of Eden Prairie, MN Pond Inventory and Maintenance Assessment

Abstract

The City of Eden Prairie, MN (population 62,409) is a suburb of Minneapolis with an area of approximately 12 square miles. The City’s stormwater system consists of approximately 950 water bodies; including constructed stormwater ponds, wetlands, lakes, infiltration BMPs and creek segments. The next step in the City’s stormwater program is to ensure adequate maintenance of the constructed ponds, infiltration BMPs and wetlands that are either City-owned, under a drainage easement, receive public drainage or are within City rightof- way. The City selected Wenck Associates, Inc. (Wenck) to evaluate 180 water bodies in a portion of the Staring Lake watershed. (The remaining water bodies will be evaluated in subsequent phases.) Wenck spent 2010 reviewing construction records and conducting visual inspections and sedimentation surveys. Wenck collected data using a survey-grade subcentimeter GPS unit to complete bathymetric surveys of the basins; estimate accumulated sediment depth and percent coverage by aquatic vegetation; determine the water surface elevation; and establish basin outlet/overflow data. Data from the survey is being used to determine sedimentation, pollutant removal effectiveness, and, ultimately, which basins need sediment removal. The loadbased removal efficiency will be calculated and compared to NURP design standards. Maintenance will be prioritized by degree of sedimentation, proximity to public waters, potential water quality benefits and budget available. The final phase of the project will include a watershed- wide P8 model and a lake-response model for Staring Lake. The removal efficiency analysis may show that maintenance of individual water bodies is necessary; however, the P8 and lake-response models may show that the system adequately protects Staring Lake even though maintenance is needed. The final report (March 2011) will document methodology, analysis, results, and cost considerations for the recommended maintenance activities.