^tDS% NONPOINT SOIREE S1CEESS STORY VTr 1.0 m Secchi disk depth, < 60 |ig/L total phosphorus, and < 20 |ig/L chlorophylI-o. Because it exceeded eutrophication criteria, the lake was added to the Clean Water Act (CWA) sec- tion 303(d) list of impaired waters in 2002. Story Highlights Actions that contributed to a reduction in phosphorus loading include both in-lake management and external loading reduction by the Riley Purgatory Bluff Creek Watershed District and local partners. Implementation included: • In-lake alum treatment of upstream Round Lake 'MitchelllRpinj Boat Landing RiceilVla^lilUak'elRark! Figure 1. In-lake weed harvesting locations (red outlined areas) in Mitchell Lake, Minnesota. • Stormwater management in Mitchell Lake watershed • Canada goose management • Installation of various stormwater BMPs, including rain barrels, rain gardens and pervious pavement • Shoreland restoration and vegetation projects (Figures 2 and 3) ------- Mitchell Lake Summer Total Phosphorus History 120 80 V ¦ 1 0 2004 2006 2008 2010 2012 2014 State Standard Year Figure 4. Mitchell Lake phoshorus data (Source: City of Eden Prairie). Results Review of recent data (2006-2013) indicates Mitchell Lake had growing season averages of 57 [ig/L total phosphorus, 20.7 |ig/L chlorophyll-o and 1.3 m Secchi disk depth. Based on these results, Mitchell Lake is meeting water quality standards (Figure 4); therefore, it was approved for removal from the draft 2018 CWA section 303(d) list of impaired waters. Partners and Funding Over 500 local stakeholders were involved in the improvement of Mitchell Lake, including community members, the city of Eden Prairie, Mitchell Lake Association, Riley-Purgatory-Bluff Creek Watershed District, University of Minnesota, and Hennepin County. Support for these projects came in the form of public participation, iandowner cooperation, monitoring, the Implementation of BMPs, and more. To keep the progress moving forward, these stakeholders were Involved in the planning for the 10-year period that began 2016. Figure 2. Native wildflowers were re-established along the lake shore. Figure 3. New plantings help to stabilize the shoreland zone of Mitchell Lake. • Curlyleaf pondweed and Eurasian milfoil removal • Annual lake cleanup events • Public participation and outreach In-lake water quality monitoring will continue to evaluate trends over time and to inform the need for modifying in-lake management. Also, opportunities for additional stormwater treatment will continue to be explored. & PROt*° 2 o U.S. Environmental Protection Agency Office of Water Washington, DC EPA 841-F-19-001M April 2019 For additional information contact: Chris Zadak Minnesota Pollution Control 651-757-2837 • chris.zadak@state.mn.us ------- |