Floating islands to help clean Spring Lake

Share this:
September 12, 2011
By: Dylan Thomas
Dylan Thomas
A pollution fighter floating on dirty water

Still searching for the upside of this summer’s state government shutdown? You might find it floating on one of the City of Lakes’ least-known bodies of water.

In August, seven artificial floating islands made of shredded plastic were anchored in Lowry Hill’s tiny, algae-covered Spring Lake. If all goes as planned, the buoyant gardens covered in peat moss and native plants will help clean some of the water passing through the lake, which is located in the Bassett Creek watershed.

Proponents of the technology say they provide sanctuary for hungry microbes that gobble up excess nutrients, such as the phosphorous and nitrogen polluting Spring Lake. The project is one of the first applications in Minnesota of the artificial islands, manufactured locally by Midwest Floating Island of St. Paul.

If not for the state government shutdown that began July 1, though, the islands’ local debut would have been on the Mississippi River. They were one component of a Park Board-led riverfront redesign project just getting underway, said Lowry Hill resident Craig Wilson, who serves on the project’s steering committee.

Wilson said there was no telling if the right permits could be acquired in time after state offices shuttered. And Wilson had a deadline: As the incoming president Minnesota’s chapter of the American Society of Landscape Architects, he needed some type of event to mark Aug. 17, a day when landscape architects nationwide planned to bring attention to the profession.

Wilson, also member of the Lowry Hill Neighborhood Association (LHNA) Board of Directors, quickly rallied the neighborhood behind a floating island project on Spring Lake, the target of years of neighborhood cleanup efforts. LHNA donated $25,000 to the project, paying also for a new, permanent dock on Spring Lake’s north shore.

Tucked between Kenwood Parkway, Interstate 394 and the Parade Ice Garden, Spring Lake is easy to overlook. Even bicyclists who take the spur off the Cedar Lake Trail that rings the lake might not notice the water, which is often obscured by thick clusters of
buckthorn.

The Park Board designated the lake a wildlife refuge in 1893. Today, no fish live in its murky waters, but neighbors said it attracts an assortment of urban-adaptable critters, such as turkeys, herons, muskrats, foxes and turtles.

Like many urban lakes, Spring Lake is impacted by nutrients swept in with the storm water flowing off of neighboring lawns and roadways. And it’s a small lake — just less than 2 acres in size and about 30 feet deep — with a watershed estimated to be about 15 times larger by the Park Board.

A storm water system running beneath nearby I-394 pours out just yards from the lake, and huge piles of snow are stored in a lot on the other side of the highway. Both highway runoff and snowmelt carry additional salts into the lake, Wilson and Reul said.

The lake has another quirk. It’s meromictic, meaning its waters don’t regularly turn over like in other lakes. As Crabb explained, “Spring Lake is almost like two different lakes: a shallow, freshwater lake on top of a really, really nutrient-rich, anoxic lake below.”

Trockman said samples his students have pulled up from the bottom “smell like an outhouse.”

Crabb said the stratification might be more or less natural, more due to its sheltered location than human intervention.

If its murky depths rarely stir, Spring Lake’s surface water does, flowing through an outlet into Bassett Creek, and from there on to the Mississippi River. And that’s where the floating islands come in.

Project consultant Todd Gattino of Maryland-based BlueWing Environmental Solutions and Technologies said the islands mimic naturally occurring floating bogs found in places like northern Wisconsin’s Chippewa Flowage.

Those produced by Midwest Floating Island are made of shredded, non-toxic plastic from recycled water bottles. Woven into thick mats, the same material is used to make floor buffer pads, Gattino said.

He said 250 square feet of islands was enough to clean about 1 acre of water.

“You could potentially see some strong improvement next year,” he predicted.