Powderhorn Lake removed from most polluted waters list

Categories: Environment
Flickr Creative Commons: bigwibble6, left, and bdunnette
Powderhorn Lake is a community center during the Powderhorn Art Fair, left, and May Day festivities.
Floating trash, blooming algae, deteriorating shoreline. For years, activists have been trying to clean up Powderhorn Lake, the 11-acre, 24-foot-deep body of water at the center of Powderhorn Park and the surrounding community.

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The city has sunk more than $800,000 into improving the lake's infrastructure. Neighbors have implemented innovative solutions, from planting rain gardens that purify storm runoff, to using barley straw bushels to suppress algae.

The rehab efforts might be paying off: on Tuesday, Powderhorn Lake was removed from a long list of the state's "impaired" (polluted) waters. Which means it's healthier, right? Kind of.

There's some history behind the lake's new stamp of cleanliness. It starts in the 1960s, when 35W was constructed and Powderhorn Lake, already man-made from a marsh, was cut off from its freshwater supply. Today, the lake's water comes from an aquifer tap and from storm runoff -- which includes all the trash, fertilizers, and other debris that trickle down from surrounding streets and lawns.

In winter 1998, a broken oxygen pump led to a bunch of the lake's fish dying off, and some concerned neighbors got together to form Save Our Lakes! To hear Michael Kehoe, the leader of the group, tell it, the members lobbied the Park Board, the City Council, and the state until, after a few years, everyone involved was ready to roll up their sleeves.

The government spent about $550,000 to install five "grit chambers," which use centrifugal force to separate storm water from garbage and sediments. The new work meant a jump in aesthetics: less trash floating around. But there was still all that garden fertilizer getting into the water, polluting the lake with excess nutrients that led to algae everywhere.

So in 2004, the park system began lining the shore with barley straw, which fuels organisms that feed on algae. More recently, neighbors planted nearly 100 rain gardens.

Today, there are two species of native plants back in the lake, plus new types of stocked fish, like channel catfish. On warm days, anglers line the waters, and many of them eat what they catch.
Minneapolis Parks
A city parks brochure on caring for Powderhorn Lake includes this map of improvement projects.
Now that the lake is off the impaired waters list, it has hit a milestone. But it's not as though Powderhorn Lake has suddenly experienced drastic improvements. In order to determine which bodies of water are clean and which aren't, the state Pollution Control Agency looks at a decade of data.

Powderhorn was on the list for just one reason: too-high levels of phosphorus, the nutrient that causes the excess algae. The lake's phosphorus levels have been decreasing for years, and water clarity increasing to match. Plus, Powderhorn seems to have a knack for getting clearer than its phosphorus levels suggest it should be. "It's like a person who can take in more calories and still not gain as much weight," says Chris Zadak, a project manager at the PCA.

For his part, Kehoe, the Save Our Lakes! leader, is skeptical that the delisting is much more than superficial. "I would jump for joy if the new measurements show that it's improved markedly, but I'd be surprised," he says. "It's certainly good news that the lake is off the list of the worst lakes, but I suspect that it's still very low."

So for now, Powderhorn Lake might look a little clearer, and have the label to match. But don't expect to see a swimming beach installed in the park anytime soon.

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