Wirth Lake - Excess Nutrients: TMDL Project

Wirth Lake is located in Hennepin County with most of its watershed within the city of Golden Valley. The remaining portion of the watershed south of the lake is in Minneapolis and all of the shoreline around the lake is owned and managed by the Minneapolis Park and Recreation Board (MPRB). Wirth Lake is an important recreational resource to residents of north Minneapolis and surrounding inner-ring suburbs and it is used extensively for swimming, fishing, non-motorized boating, and aesthetic viewing. This lake is surrounded by significant wetland vegetation which provides excellent wildlife habitat. The Wirth Lake watershed is essentially fully developed and has a total area of 348 acres (excluding landlocked areas). As noted in the Bassett Creek Water Management Commission (BCWMC) Watershed Management Plan (WMP, 2004) the city of Golden Valley, Minneapolis, the MPRB, and the BCWMC have been partners working to improve the water quality of Wirth Lake for several years. MPRB has worked on improving Wirth Lake for decades.

In 2004, Wirth Lake was placed on the Minnesota Pollution Control Agency's list of impaired waters in need of a Total Maximum Daily Load (TMDL) study for excess nutrients, based primarily on data collected by the MPRB and the BCWMC. The data indicated that Wirth Lake had a total phosphorus concentration in excess of the MPCA's state water quality narrative standard of 40 micrograms per liter for the growing season mean. The MPCA partnered with BCWMC and MPRB to develop the work products necessary to complete a TMDL and implementation plan for Wirth Lake.

In 2012, the BCWMC (in cooperation with the MPRB and the City of Golden Valley and with a grant from the Clean Water Legacy Fund) completed a project which modified the Wirth Lake outlet to prevent backflow from Bassett Creek into Wirth Lake during periods of high water in the creek. This project, along with other improvements in the watershed, reduced total phosphorus levels in the lake considerably. The lake was removed from the Impaired Waters List for phosphorus in 2014. The lake remains on the Impaired Waters List for high mercury and chloride levels.

Map and location

Wirth Lake is located in Hennepin County, within the Mississippi River - Twin Cities watershed of the Upper Mississippi River basin.

     

    Map of Wirth Lake

    TMDL report and implementation plan

    Other documents

    Previous reports/plans for Wirth Lake

    Meetings and events

    Links

    Information contact

    Rachel Olmanson, Project Manager
    Minnesota Pollution Control Agency
    520 Lafayette Road N
    St. Paul, MN 55155
    651-757-2473
    rachel.olmanson@state.mn.us