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Lake Hiawatha in south Minneapolis is supposed to be a swimming lake, with a public beach on its eastern shore. But an unrelenting aesthetic problem makes swimming tough in practice: trash buildup from a storm sewer pipe that drains runoff from the surrounding neighborhoods into the lake's northwest corner.

Sean Connaughty, a University of Minnesota art instructor who founded Friends of Lake Hiawatha in 2015 to organize resident-led trash removal efforts, has been collecting, weighing and sorting the garbage by brands for nearly a decade. One year the group filled 103 bags weighing more than 2,000 pounds. Another year, a crew of 40 volunteers removed 226 pounds of trash in three hours.

On Saturday, Connaughty and neighbors watched workers attach a three-tier floating barrier around the mouth of the 5-by-6-foot box culvert. The boom is the latest — and they hope, ultimate — solution to controlling the lake trash problem.

"It's dangerous and bad and it just has been a huge labor for us," Connaughty said.

About 340,000 people live upstream of Lake Hiawatha, a reservoir of Minnehaha Creek that flows from Lake Minnetonka to the Mississippi River. Plastic bottles, pet poop and yard waste is propelled by rainwater through a storm water network that passes through several west metro suburbs before reaching the lake.

Stantec Consulting Services produced a report on Lake Hiawatha in April with recommendations for the city to increase trash bins along bus routes, sweep streets more frequently in areas that generate litter and explore banning single-use plastics. Unlike some states, Minnesota does not regulate litter with total maximum daily loads or municipal storm sewer permits, according to the report.

Much of the city and Park Board's efforts to mitigate Lake Hiawatha's trash problem have revolved around education campaigns, including street drain stencils reminding people that what goes in the drain spits out into Minnehaha Creek.

The city has installed a series of trash screens in manholes upstream of the lake. And in 2016, there was an unsuccessful attempt to install a trash curtain at the lake's northwest pipe. But heavy rains kept dislodging its anchors, so the curtain had to be reinstalled twice. It ultimately intercepted just three bags of trash during a month-long pilot.

"There's a pretty significant pipe there and what we had originally tried wasn't able to sustain what was coming out of there," said Paul Chellsen, supervising storm water technician for Minneapolis Public Works.

In 2021, the St. Paul nonprofit Freshwater Society received a grant from the Coca-Cola Foundation — the brand on many of the plastic bottles washing up in Lake Hiawatha — to install a litter capture device, customized by Alabama-based Osprey Initiative, to withstand the high velocity of the storm water rushing from the lake's northwest pipe.

Freshwater intends to transfer ownership of the physical boom to Minneapolis, which would in turn pay a local crew to maintain it and analyze the trash it collects. The boom cost $22,400 and the maintenance budget is $29,300 for the nonfrozen months, said Kris Meyer, Freshwater's community engagement coordinator.

"Freshwater was privileged to be the coordinator, to amplify the concerns and the activism that Friends of Lake Hiawatha and the communities that use the lake," said Meyer. "We're not solving all the pollution problems here, but we are taking a big step forward."

The boom installed Saturday has three layers: one to knock the turbulence out of the water coming out of the pipe, a second to contain the litter and a third to catch anything that gets past the others, said Osprey owner Don Bates.

Osprey is hiring part-time local workers to maintain the boom. After it rains, the crew would check the gear, scoop up the trash and categorize it on shore. The condition of the litter can shed light on how long it's been exposed to the elements and how far it's traveled. Knowing the brands of the most common items can unlock corporate sponsorships for the cost and labor of cleanup.

"There is a chance that the energies here are just too crazy and everything tears up," Bates said. "I'm not envisioning that. We're working in much higher energy environments with this gear in other places. Until you see how it works, it's hard to tell, but typically it's the routine maintenance [that] affects the effectiveness of traps."

The Osprey boom is considered a pilot project. After the first year, the city will assess how things worked, Chellsen said. If successful, it could be permanently maintained by city employees.