Everyone who lives in Golden Valley — or shops there, or works there, or drives through — leaves a little something behind in Sweeney Lake.

Lawn fertilizer. Road salt and oil drips. Dirt from construction sites. All the organic and chemical debris of 2,400 urbanized acres eventually drains toward the 67-acre lake, tucked away near the intersection of Hwys. 55 and 100 less than five miles from downtown Minneapolis.

Sweeney Lake has been designated as "impaired" by both the federal Environmental Protection Agency and the state Pollution Control Agency. Several projects are underway, aimed at improving drainage in the area and restoring natural wetlands that help filter out sediment and chemicals before they reach the lake.

But long before government agencies got involved, the 40 or so households on Sweeney Lake began their own fight to preserve every Minnesotan's birthright: a clean lake for swimming, boating and enjoyment. It's a fight that continues today.

In September, Sweeney Lake residents turned out in force to support a land use plan that would preserve several areas near the lake as permanent conservation easements. As each resident finished addressing the Golden Valley City Council, the rest applauded so vigorously that council members finally asked them to stop. The council ultimately passed the plan.

Later that month, residents packed a state Department of Natural Resources hearing on the future of the lake. Nearly 20 neighborhood members — representing about half of the lake's residents — expressed their support for ongoing aeration in the lake, which helps replenish oxygen and support aquatic life. The department hasn't yet acted on the issue.

Long before government agencies got involved, the 40 households on Sweeney Lake began their own fight to preserve it.

Algae bloom takes over lake

Dave Hanson, a retired engineer who's lived on the lake for nearly 50 years, recalled the incident that really brought home the dangers posed by development and chemicals. One summer in the early 1970s, a massive algae bloom took over the lake.

"It was such a beautiful lake, and all of a sudden it had green guck on it," said Hanson, now 86. The ongoing transition of Golden Valley from lightly settled countryside to full-fledged suburb had reached a tipping point, and the lake was feeling the effects.

Hanson responded the way you'd expect an engineer to: He researched the problem and took action. Hanson began visiting other lakes and streams in the area, "traipsing through a lot of water." He looked at the topography and studied the water, plant life and sediment.

Then he bought a generator, hooked it to an air compressor and ran a hose out into the lake, creating Sweeney Lake's first aerator. Over the coming years, he'd install eight more. The shallow lake, he explained, is like a fishbowl. It needs help creating enough oxygen to support fish and reduce the phosphorus buildup that causes algae and other plant life to grow wildly.

"Dave is a hero," said his neighbor of 25 years, Jane McDonald Black. "He has saved this lake."

A group effort

But he didn't do it alone. After the first big algae bloom, residents formed the Sweeney Lakeshore Owners Association. Over the years, the association has repeatedly mobilized to fight threats to the lake and encourage efforts to improve its water quality. Nearly all the lake residents are members, paying $150 in annual dues.

When a developer proposed building a new subdivision of more than 600 homes on nearby Twin Lake, the association pushed for a smaller development. In the end, about 150 homes went up at Twin Lake, "all done in a very environmentally sensitive manner," said McDonald Black.

When Schaper Park was built near the south end of Sweeney Lake, the association asked for — and got — a holding pond included in the project, giving runoff another place to settle before reaching the lake. Work is set to begin soon on a project to improve the pond's capacity and performance.

Several Sweeney Lake residents have also served on the Bassett Creek Watershed Management Commission, which represents nine cities in the west metro area.

Sweeney Lake is an affluent neighborhood; a home on the lake can easily go for a million dollars. But the lake isn't used only by residents — there's public access for canoeing and other nonmotorized uses. Residents believe their fight benefits more than just the people who live there.

"The Sweeney Lake Association has always been ready to jump up and fight off threats to the health of the lake," said McDonald Black. "I didn't grow up as an environmentalist, but this lake has made me one."

John Reinan • 612-673-7402