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5) BENNETT LAKE WATER QUALITY REPORT Ryan Johnson, Environmental Specialist, introduced himself to the commission. Johnson provided the definitions of two terms that would be used during his presentation on the Bennett Lake Water Quality. The two terms are listed below: Impaired: When a water body fails to meet standards set by the MPCA, it is listed as an impaired on the MPCA 303(d) Impaired Waters List and a Total Maximum Daily Load (TMDL) study is required o Required by Section 303(d) of the Federal Clean Water Act TMDL – Total Maximum Daily Load: Water quality study to determine allowable pollutant loading from point and nonpoint sourcesdetermine allowable pollutant loading from point and nonpoint sources to lakes/rivers so as to achieve the water quality standards. o Approved by both the MPCA and the USEPA The brief history and overview of Bennett Lake consist of the following details: Drainage Area = ~780 acres Primarily single family residential Lake area = 25 acres Maximum depth = 9 feet During the 1940’s Bennett Lake area was only a wetland Algae blooms happen during the summer months happen as a result of contaminants. One of the main is Phosphorous. For Bennett Lake Phosphorous sources include: External o Stormwater runoff from hard (impervious) surfaces o Soil erosion o Pet/animal waste o Leaves & grass clippings o Fertilizers o Point discharges Internal o Phosphorus can be stored in lake bottom sediments and released when oxygen levels are low o Bottom sediment can also be re suspended and bring phosphorus into the water column o Carp can stir up lake sediments, causing turbidity and phosphorus release o Macrophyte die off Staff provided graphs showing the rates ofChlorophyll(1985-2019)Phosphorus (ug/l) (2003-2019) and Secchi Disk Transparency (2003-2019) in Bennett Lake. 3