Rogers Lake Water Quality Deemed Good, Not Great

St. Thomas Academy’s Advanced Placement environmental science class has concluded that the water quality of Rogers Lake is in good condition and safe for swimming, though there is room for improvement.

The class, taught this year by Tony Kinzley, creates an annual report on the water quality of the lake. The results were presented to the Mendota Heights City Council May 17.

Throughout the fall, the students take nine water quality tests at six sites on the lake weekly for ten weeks, said junior student Kevin Gust.

The overall quality of the lake is toward the bottom of the good range. Its overall score has dropped to 70.7, according to the student data.

A score of 90-100 indicates excellent quality; the “good” range is 70-89.9. 

Dissolved oxygen and fecal coliform (bacteria), two particularly important readings for lake health, both came back good. The reading for fecal coliform came back at 9.3 colonies per million. The reading needs to be below 200 for safe swimming.

Two tests came back borderline: pH and temperature change.

The pH readings came back at 6.17, or slightly acidic. The healthy range is 6.5-8.5. The slightly low reading could be due to a probe calibration, or acidic rain water, according to student Andrew Litwin.

The average variation in water temperature measured between the six testing sites in the fall was 1.1 degrees Celsius, just a fraction higher than the range of 0-1 considered ideal. This could be due to variations in the shade between the sites, and could also be attributed to tree removal that would encourage thermal pollution, according to the report.

Readings for phosphorous and total suspended and dissolved solids were elevated, but still fell in the good range.  Total solids could be attributed to road salt and runoff from Wagon Wheel Trail.

“The most important solution we can implement as a community would be to promote buffer zones around the lake,” said student Sean Byom. “In some ways, buffer zones act as a cure-all for most of our problems through all of these nine different tests.”

By creating zones of natural vegetation surrounding the lake, residents and the city can slow erosion and runoff. Educating the residents who live on Rogers Lake is another important solution, said Byom.

Where Wagon Wheel crosses the lake, road salt and water heated by the road can wash off directly into the water.

The council discussed how the installation of curb and gutter along Wagon Wheel may improve the quality of the water. City Engineer John Mazzitello said that when the road repair is complete, a curb will be installed and the slope down to the lake will be planted.

The re-construction of Wagon Wheel is scheduled to be completed in September.

Council member Liz Petschel said that a “before and after” of the total solids may be particularly valuable in determining the benefits of the curb installation.