Polluted stormwater running off of Twin Cities buildings and streets normally isn't cleaned up very much — if at all — before it enters a series of pipes that flow into the Mississippi River.
The pollution can lead to algae blooms and other problems in the river, and if it's bad enough, state regulators force cities to do something about it.
The Mississippi Watershed Management Organization is looking to get ahead of that with a new stormwater treatment and research facility that will capture and treat about 169 million gallons of polluted stormwater each year. Runoff from a 600-acre area in the southern part of St. Anthony Village will be routed through the facility, and stormwater managers hope it will cut pollution from that area by half.
While the facility could help the watershed address a state designation that its part of the Mississippi River is impaired, watershed managers also hope it will help determine what methods of stormwater treatment work the best.
Stormwater enters the $1.6 million facility and first gets swirled around in a chamber to allow heavier particles to be filtered out. The cleaner water moves through another filter that removes debris and pollutants like oil before the water makes one of two last stops: a filtration chamber that uses iron and sand to get rid of fine and dissolved pollutants, or a chamber containing special cartridges that filter pollutants out of the stormwater.
The Mississippi Watershed Management Organization put together a video showing how it works.
The facility's main target is phosphorus, a nutrient that is able to bind with sediment and is a key food source for algae.
"The part that's been difficult for stormwater professionals to deal with is the dissolved component of phosphorus in stormwater, and so both of these treatment systems are designed to remove a greater portion of that," said Doug Snyder, executive director of the Mississippi Watershed Management Organization.
Snyder says urban watersheds must decide how to get the most bang for their buck in reducing stormwater pollution.
"We're trying to do that in the most efficient way possible. So this is going to allow us to have field operations where we can actually see which of these kinds of practices are actually working for us," he said.
A ribbon-cutting ceremony for the facility is being held at the corner of Lowry Avenue Northeast and Coolidge Street Northeast in Minneapolis on Thursday evening.