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2021_0125_CCPacket
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2021_0125_CCPacket
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1/13/2022 1:40:37 PM
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Roseville City Council
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Council Agenda/Packets
Meeting Date
1/25/2021
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5) BENNETT LAKE WATER QUALITY REPORT <br />Ryan Johnson, Environmental Specialist, introduced himself to the commission. Johnson provided <br />the definitions of two terms that would be used during his presentation on the Bennett Lake Water <br />Quality. The two terms are listed below: <br /> Impaired: When a water body fails to meet standards set by the MPCA, it is listed as an impaired <br />on the MPCA 303(d) Impaired Waters List and a Total Maximum Daily Load (TMDL) study is <br />required <br />o Required by Section 303(d) of the Federal Clean Water Act <br /> TMDL – Total Maximum Daily Load: Water quality study to determine allowable pollutant <br />loading from point and nonpoint sources determine allowable pollutant loading from point and <br />nonpoint sources to lakes/rivers so as to achieve the water quality standards. <br />o Approved by both the MPCA and the USEPA <br />The brief history and overview of Bennett Lake consist of the following details: <br /> Drainage Area = ~780 acres <br /> Primarily single family residential <br /> Lake area = 25 acres <br /> Maximum depth = 9 feet <br /> During the 1940’s Bennett Lake area was only a wetland <br /> <br />Algae blooms happen during the summer months happen as a result of contaminants. One of the <br />main is Phosphorous. For Bennett Lake Phosphorous sources include: <br /> External <br />o Stormwater runoff from hard (impervious) surfaces <br />o Soil erosion <br />o Pet/animal waste <br />o Leaves & grass clippings <br />o Fertilizers <br />o Point discharges <br />Internal <br />o Phosphorus can be stored in lake bottom sediments and released when oxygen levels are <br />low <br />o Bottom sediment can also be re suspended and bring phosphorus into the water column <br />o Carp can stir up lake sediments, causing turbidity and phosphorus release <br />o Macrophyte die off <br />Staff provided graphs showing the rates of Chlorophyll (1985-2019) Phosphorus (ug/l) (2003-2019) <br />and Secchi Disk Transparency (2003-2019) in Bennett Lake. <br /> <br /> <br />3 <br /> <br /> <br />
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