Best idea: Attacking local pollutants regionally
MIKE EASTLING, PE
DIRECTOR OF PUBLIC WORKS
In the Land of 10,000 Lakes, keeping one 12-acre lake clean, clear, and fishable is near and dear to Mike Eastling's heart.
Taft Lake is the only recreational body of water in the Minneapolis-St. Paul suburb of Richfield. Excessive nitrogen and phosphate can cause an imbalance that encourages algae blooms in the lake that deprive wildlife of oxygen. To keep that from happening, Eastling holistically manages the inflow.
His team improvised “a dumpster-size device you can haul on-site, pump in runoff water, add a flocculent that precipitates phosphorous into clumps that drop to the bottom, then pump out the clean water into a lake,” he says. “You can then dispose of the phosphorous in the sanitary sewer system, where it can be removed and landfilled. You don't have to hope for rain to clean up the water because this cleans water offline.”
Stormwater tends to flow to one point before it leaves Richfield and enters the lake, so his plan calls for installing the devices in one location instead of relying on upstream rain gardens, wetlands, porous pavement, or shoreline plants to remove phosphorous. “It's similar to bringing all the sanitary sewage to one centralized treatment plant instead of putting septic systems on each lot,” he says. “Topography and a positive cost/benefit analysis drive the idea.”
It also helps that the city has a stormwater utility, so everyone in the Richfield-Bloomington Watershed District will help pay for the devices. “This isn't all my idea,” says Eastling. “It's a large, collaborative effort with many agencies, including the district, involved.”
Also, the lake is home to 12 varieties of fish. “I caught a nice bass out there myself,” he says.