A Maryland community’s step pool systems are able to slow down and treat storm flow so that the negative effects on Chesapeake Bay are lessened

Anne Arundel County, Maryland, is one of a number of jurisdictions using the Step Pool Conveyance System (SPCS) approach to reduce stormwater runoff and the resulting pollution.

“We’re using this approach for most of the outfall restoration, and for many of the local development projects, as well,” says Erik Michelsen, administrator for the Anne Arundel County Watershed Protection and Restorations Program, which aims to reduce negative impacts on Chesapeake Bay.

Step pool systems have proven to be effective in safely conveying, slowing down, and treating storm flow.

Related: Water Environment Federation Releases Future of Stormwater Report

The systems utilize a series of constructed shallow aquatic pools, riffle grade control, native vegetation, and an underlying sand/woodchip mix filter bed media. The pools drop in elevation (like big stairs), with cobble riffles in between. The water is slowed down and water collected by the pools seeps back into the ground, while the pollutants are removed by the filter media and vegetation.

Not only do the pools trap pollutants and prevent them from flowing downstream, they tend to look better in the neighborhoods where they are built than the original streams.

Michelsen says the county has had good results, not only in halting erosion, but monitoring indicates that the projects are also effective in trapping sediment and providing nutrient processing.

Related: WEF Announces Winners of MS4 Stormwater, Green Infrastructure Awards

“Depending on local hydrology, some pools may end up holding water more persistently than others,” says Michelsen. “Research has shown that these projects can bring local groundwater up significantly, and end up creating small wetland complexes in what were once eroded gullies.

“Occasionally,” he adds, “the persistent wetness will raise concern about mosquitoes, but we’ve found that once healthy ecosystems get established at these sites, predators generally keep nuisance insects in check.”

Michelsen says anyone with questions about implementing step pools is welcome to get in touch with Anne Arundel County.

Related: Can Worms Combat Stormwater?

Read more about Anne Arundel County in this full profile featured in the February 2017 issue of Municipal Sewer & Water magazine.

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