Decades ago, Thompson Lake was a destination for swimmers, a beach in the developing West St. Paul area.
Today, it's a scenic attraction, a fishing spot and even a place where some harvest snails -- in an urban Dakota County park.
The future of the lake, however, is uncertain.
After decades of serving as a drainage pond as the city evolved around it, Thompson Lake, like many urban lakes and ponds, has a pollution problem.
The sediments that have washed into the lake over the years, settling on the bottom and forming a delta at the lake's northern end, contain a variety of contaminants, including road salt, petroleum products and driveway sealant.
Cleanup, based on a plan that may change as more testing is done, would cost $1.6 million.
"You're seeing long-term impacts of decisions that were made a long time ago about how we deal with storm water," Al Singer, the county's land conservation manager, told Dakota County board members at a meeting last month.
The county, city, a host of other government agencies and even a nearby school are working together to figure out just how harmful the contaminants are to people, to wildlife and to plants.