Stormwater treatment projects

Stormwater treatment projects
St. Cloud, Minn.

St. Cloud, Minn., straddles the Central Minnesota banks of the Mississippi River and uses it as its sole source of water. When city leaders observed brown sediment trails in the water following heavy rainfall, they traced the plumes to a sub-watershed in northeastern St. Cloud, which they found had been industrialized prior to the city’s water treatment quality standards becoming widespread. City leaders thus decided to bring the area up to par with modern water standards in order to address its stormwater management issues and adequately treat the runoff.

City employees completed a plan in 2012 that included in-ground stormwater treatment projects, education measures, ordinance enforcement and property owner meetings. Eventually, one stormwater management project was completed in 2015, while four projects were started at different dates in 2016. Throughout the construction process, the city educated the community on stormwater through informal meetings, conferences, bus tours, neighborhood grill-outs, one-on-one meetings with industrial properties and over 960 newsletters.

Between 2015 and 2016, four sump catch basins were installed in places where other treatment methods wouldn’t have been feasible. In spring 2016, a street sweeper was purchased and a GIS-based street sweeping program developed. In May, impervious surfaces within city right-of-ways began being converted to pervious green space with depressed boulevards to promote infiltration. This project also entails ongoing involvement of property owners.

The fourth project entailed converting a gravel parking lot directly connected to the Mississippi River to a paved parking lot with a rain garden and an underwater infiltration system. Finally, St. Cloud partnered with the Benton County Soil and Water Conservation District to build an underground regional treatment system for a 45 acre industrial and residential drainage area. The drainage area included 34 acres of impervious surfaces and was also directly connected to the river. This project in particular encountered challenges in addressing existing utilities and getting an easement from nearby property owners.

Each project involved a different contractor, and altogether, the projects cost $1.3 million. The Minnesota Pollution Control Agency and the Minnesota Board of Water and Soil Resources each issued grants that funded the majority of all five projects.

The resulting infrastructure from these projects treats over 21.6 million gallons of stormwater annually. In doing so, the projects prevent 24,400 pounds of sediment and 34.2 pounds of phosphorus from entering the Mississippi River.

“This project is another example of the great accomplishments that can be made when agencies and people from the community work together,” says Benton County Soil and Water Conservation District Supervisor Wade Bastion. “This project not only benefits St. Cloud-area water quality, but every community downstream.”

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