Maple Grove’s Fish Lake Coming Off Impaired Waters List
After years of water treatment, Maple Grove’s Fish Lake is moving off the state’s list of polluted waters.
Located in a Three Rivers regional park, the lake is a popular spot for anglers, swimmers, canoers and kayakers.
The lake has been on the Minnesota Pollution Control Agency’s (MPCA) Impaired Water list for more than a decade due to high levels of nutrients.
Typically, when lakes are on the impaired waters list, “you have recreational opportunities that are impaired or become inhibited,” said Brian Vlach, water resource manager with Three Rivers Park District. “It may not be desirable [to make] direct contact [with] the water.”
According to Vlach, phosphorus in the lake has caused issues with algae.
“It’s had severe algae blooms during the summer time,” Vlach said. “High nutrients and poor water clarity conditions have resulted for the lake to be put on the impaired waters list.”
Water Treatment Helps Fish Lake
The situation made the lake a good candidate for an alum treatment.
Vlach said alum is a non-toxic compound that binds to phosphorus.
“It kind of forms a blanket over the sediments,” Vlach said. “That alum blanket essentially keeps that phosphorus from being released into the water column .. it causes a significant improvement in water quality right away.”
The treatment proved to be successful. Vlach said Fish Lake is now slated to move off the MPCA Impaired Waters list.
“To remove a lake off the impaired waters list is extremely difficult — it takes years to do,” Vlach said.
But, new issues can arise after an improvement to water quality.
“Improvements in clarity results in more plant growth,” Vlach said. “Because of that, sometimes you may have to manage for the aquatic plant community in the lake. So, your work isn’t necessarily done. But once you do meet water quality standards, that is a huge undertaking.”
The water quality improvement project at Fish Lake required many partners, according to Vlach. Elm Creek Watershed Management Commission, Hennepin County, the Fish Lake Area Residents Association, Three Rivers Park District and the Minnesota Board of Water and Soil Resources all were involved in the project.
In 2022, the Minnesota Department of Natural Resources and Three Rivers found invasive zebra mussels in Fish Lake.