Study names impaired lakes in northern Dakota County

Thompson Lake in West St. Paul is among four lakes deemed impaired in a study. (Linda E. Andersen/Review)

Thompson Lake in West St. Paul on June 24 was murky and full of algae, especially around the shorelines where grasses grow. (Linda E. Andersen/Review)

Public invited to comment on   findings, fixes

City officials in northern Dakota County had an idea a handful of their lakes were impaired — now it’s official. 

The thick algae tainting the water was one clue at Lake Augusta in Mendota Heights. It turned out it was the lake in need of the most restoration out of the four deemed impaired in a recently-released study.

“Every summer, the surface of Augusta turns green,” said city engineer John Mazzitello. “We knew there was something wrong with Augusta, just because of how it behaved.”

The Minnesota Pollution Control Agency and the Lower Mississippi River Watershed Management Organization recently made available a draft of a report detailing the extent of pollution in Augusta and four other lakes. The report also includes recommendations on what governmental bodies, lake associations and residents can do to improve and protect them.

The public has an opportunity to comment on the draft through July 16.

Setting a cap for pollutants

The Lower Mississippi River Watershed Management Organization is a local unit of government that manages a nearly 35,500-acre watershed in the southeast metro that includes 88 lakes and wetlands, four streams and the Mississippi River.

Rogers Lake in Mendota Heights is the only one of the five the study examined that meets state water quality standards.

Thompson Lake in West St. Paul, Pickerel Lake in Lilydale and St. Paul, Lake Augusta in Mendota Heights and Sunfish Lake in the city of the same name all need restoration.

The report indicates a “total maximum daily load” for the lakes, quantifying the maximum pollutants, including phosphorus, that can be present while still maintaining a quality water body.

“They’re based on use,” said Barb Peichel, an MPCA spokesperson. “If you see a lot of algae in the water, do you want to swim in it? No.”

Other uses could include canoeing, irrigation and sustaining aquatic life.

Phosphorus in inordinate amounts hampers water quality; it boosts algal blooms and sucks up oxygen essential for other plant and animal life to thrive.

Phosphorus enters the water internally, where it’s already been collected at the bottom of lakes over time. It can also creep in externally via fertilizer, pet waste, grass clippings or stormwater runoff.

How polluted are they?

The report recommends the phosphorous levels to be reduced by 22 percent in Thompson, 33 percent in Sunfish and a whopping 64 percent in Augusta. Pickerel Lake, a shallow, 115-acre lake, is greatly affected by flooding of the Mississippi River, so the study put off setting an allocation for the water body, until more data is collected.

Through surveys and at public meetings, community leaders and members have already shown an interest in pitching in, Peichel said.

Citizens living in the watershed have talked about installing rain gardens or barrels to help keep pollutants from trickling straight into the lake, she said. Those who’ll bear the cost have started discussing ways to pay for the solutions, hoping to combat outside contributors or reduce the pollution already trapped in the lake.

“(The report) sets the goals,” Peichel said. “We want these lakes to be picked up, and there are people willing to do the next steps.”

Kick-starting solutions

Some entities have already gotten started on restoration options covered in the report. They may also use the information to apply for state grants to help cover the cost of warding off and getting rid of pollutants.

West St. Paul has already worked out a deal with St. Croix Lutheran School to start addressing the phosphorous problem in its seven-acre lake.

As part of a new dorm project, the school plans to hand over a portion of its property to the city. That will allow the city and Dakota County to install a pond that would treat water before it dumps into Thompson.

According to the study, almost all of the phosphorous polluting the lake flows in from the watershed.

“We’ve been looking at doing something at Thompson since probably 2006,” said Matt Saam, city engineer and director of public works and parks and recreation. “It doesn’t surprise anybody here that it’s classified as impaired. (The report) will probably help to kick-start the treatment project.”

Recent estimates put the cost of the project at $1.5 million, Saam said.

An expensive portion of the project would be removing contaminants from the land, Saam said. The project could also include excavation and habitat restoration.

Lakes a community resource

The property surrounding Sunfish Lake is all in the hands of around 30 or so private owners, including Sunfish Lake Mayor Molly Park and her husband.

She said the lake is used for non-motorized boating, canoeing and ice fishing. If anyone besides lakeshore property owners want to use the 47-acre lake, they need a permit, according to Park.

“We enjoy the beauty of it,” Park said. “I used to swim there to train for triathlons.”

The majority of phosphorus has already built up over time at the bottom of Sunfish Lake; only about 10 percent of pollution comes from external sources, according to the study.

“Ours is embedded,” Park said. “It’s deep; it’s been there a long time.”

That led to the report’s recommendation to treat the lake with alum to isolate the phosphorus. It could cost up to $110,000, according to the draft.

At this point, it’s unclear who will pay for the solution, although it’s usually up to the lake association to execute best practices and solutions for protecting the lake, according to Park.

“We are a very small city,” Park said. “What affects a small part of the community affects everybody. We’ll have to see what we can resolve as a community.”

Kaitlyn Roby can be reached at 651-748-7815 and Follow her at

Public invited to comment

The draft report is online at (click on the orange “Public notices” icon on the homepage). The report, named “Draft Lower Mississippi River WMO Watershed Restoration and Protection Strategy (WRAPS) Study,” is under Monday, June 16 in the list.

It’s also available at the MPCA’s St. Paul office, located at 520 Lafayette Road N.

Comments should be submitted in writing by 4:30 p.m. on July 16 to Barb Peichel, 520 Lafayette Road N., St. Paul, MN 55155, or via email: Peichel is available to answer questions by phone at 651-757-2646.


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