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Wetlands basin prevents Lake Superior pollution

A sign at the Poplar Wetland Basin, constructed in 2016, shows how wetlands clean stormwater before it goes to the St. Louis River estuary. Shelley Nelson

Superior is relying on nature to clean pollutants from stormwater runoff at the recently constructed Poplar Wetlands Basin.

The basin was constructed in 2016 at the end of Poplar Avenue north of 12th Street as part of a larger project to manage stormwater coming from Belknap Street when reconstruction of the State Highway 2 from Hill to Banks avenues is completed in 2018.

And it's already showing results.

The basin provides added treatment for stormwater-carrying pollutants from Belknap Street and the surrounding area, said Andrea Crouse, water resource specialist with the Superior Environmental Services Division.

"We have in the city some stormwater detention basins, and those allow sediment to settle out of the stormwater," Crouse said. "Sediment and excess dirt is one of the biggest pollutants that we deal with for Lake Superior. Those basins let sediment settle to the bottom. Then we can clean it out later."

The Poplar Wetland Basin works differently because wetland plants are effective for cleaning the water before it goes back into the St. Louis River estuary, and eventually to Lake Superior.

"They provide additional uptake, as they call it, of pollutants," Crouse said. "Specifically, excess nutrients that run off properties, like phosphorous and nitrogen."

Plants like cattails are planted at the far end of the wetland basin to provide a "final polishing" for the water before it flows into the St. Louis River estuary, Crouse said.

The nutrients, common in lawn fertilizers, have been linked to algae blooms in the Great Lakes.

This week, the site was dedicated after a sign marking the Poplar Wetland Basin and interpretive signs were installed to educate the public on how green infrastructure works and how natural systems clean water.

Mayor Jim Paine said the biggest threat to Lake Superior is people.

"Mother Nature is far better than us at cleaning up the damage that we do," Paine said during the dedication of the site Monday.

He said it's not only important because it takes stormwater off Belknap Street and the surrounding area, but it has created a beautiful site in North End that the public can enjoy.

"A lot of green infrastructure is kind of invisible to people walking down the street," Crouse said. She said the signs help to explain the basin and how it works.

"Without the signs, we're missing an opportunity to let citizens know how these natural systems — and built systems mimicking natural systems — function to keep our lake clean," Crouse said.

The basin, which cost $740,000, was funded by a $400,000 grant from the Wisconsin Department of Natural Resources and a $250,000 green infrastructure grant from the U.S. Environmental Protection Agency. It was part of a $1.9 million project that included installing stormwater sewers from from Belknap Street to the basin. It was constructed in 2016 in anticipation of the two-year reconstruction project started in 2017.

"It adds a green space in an urban area for people to enjoy," Crouse said. The area also provides habitat for animals and insects that help keep down the mosquito population.

"That will only get better over time," Crouse said.