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Politics & Government

Water Quality of Blackhawk and Thomas Lakes Discussed

The second of three public meetings took place Tuesday to update residents on the Blackhawk Lake and Thomas Lake Clean Water Partnership Agreement.

A dozen Eagan residents who live on or near Blackhawk and Thomas Lakes gathered at Eagan City Hall to learn the results of a water quality study conducted this summer.

Using a grant from the Minnesota Pollution Control Agency and storm water utility fees, Eagan's Water Resources staff spent the summer working with consultants from landscape architectural firm Wenk Associates to assess the water quality of Blackhawk and Thomas lakes in Eagan. 

The project, part of the city's Water Quality and Wetland Management Plan, is aimed at determining not only the water quality, but also the various sources of pollutants in the two lakes and arriving at recommendations for reducing them.

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Residents who turned out for Tuesday's public meeting were mostly concerned with the growth of algae and weeds in the two lakes.

Long-time Blackhawk Lake resident Ross Kramer, who says the lake is a beautiful area and the wildlife is "unbelievable," also believes there is a "tremendous weed problem" and wanted to see what the city was planning on doing to clean up the lake.

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Nancy and Gary Blasberg say they have witnessed the water quality declining on Thomas Lake, where they have lived for 20 years and they, too, were curious to see where the city is headed in clean-up efforts.

The Blasberg's neighbor, John Bolduc, who has lived on Thomas Lake for about 5 years, admitted he has been frustrated with the algae growth that keeps him from kayaking and otherwise being able to enjoy the lake except for a few times during the season. 

Algae is largely caused by phosphorus. And that, according to Eagan Water Resources Coordinator Eric Macbeth occurs in nature, enters the lakes through the watershed and also can come from processes within a lake itself.  

Phosphorus promotes algae growth and causes lake water to become turbid, or cloudy. Eagan's lakes are classified as clear-water lakes, which means someone standing in chest-deep water should be able to see their feet. 

Eagan's water management plan aims to keep them that way. However, according to Macbeth, the city's lakes are shallow water lakes which makes them difficult to manage because so little is known about how they operate. 

Preliminary results of the summer's research indicate that Thomas Lake should reduce phosphorus by approximately 5 percent and Blackhawk Lake requires a 20 percent reduction.

Further research is being conducted and a third public meeting will be held in early November to announce recommendations outlining the next steps for improving the water quality of both lakes.

Joe Bischoff, water ecologist with Wenk Associates, said the research has shown that 93 percent of the phosphorus in Blackhawk Lake and 83 percent in Thomas Lake come from the local watersheds, for example, the more than 7,000 acres of land that drain into Blackhawk Lake. (The Environmental Protection Agency defines a watershed as "the area of land where all of the water that is under it or drains off of it goes into the same place.")

Although increased phosphorus runoff in the city lakes is an unavoidable result of urbanization, Macbeth says homeowners can help decrease the amount that ends up in the watershed by removing grass clippings and leaves from their driveways and streets.

Residents who want to learn more about the project can view both the April 27 and the August 30 meetings on Eagan Webcast Central.

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