Stormwater Wetland Reduces Pollutant Loading into Easter Lake

Reducing stormwater runoff and pollutant loading throughout the watershed is a critical part of restoring Easter Lake. As new developments have been built around the lake, sediment and pollutant loading has increased. To protect Easter Lake now and into the future, addressing new urban developments is key.

When a new housing development was planned near the northeast side of the lake that sends stormwater runoff directly to Easter Lake, partners of the watershed project were able to be proactive in developing a solution to protect lake water quality.

In 2016, the Polk Soil & Water Conservation District worked closely with the Polk County Conservation Board and applied for a Water Quality Initiative grant to construct a stormwater wetland and sediment basin forebay within Easter Lake Park. A WQI grant of $72,500 was awarded to the Easter Lake Watershed Project.

A stormwater wetland is a man-made management practice that provides a natural way to treat and remove pollutants from stormwater before it enters a stream, river, or lake. As stormwater is captured within the wetland, the removal of pollutants is naturally promoted through the slowing of water, settling, uptake and filtering by vegetation, and biochemical reactions.

Construction for the wetland began in May of 2017 and finished in late June 2017.  To construct berms and microtopography for the wetland and future sections of the Mark C. Ackelson Trail around Easter Lake, readily available fill dirt from the lakebed was used. The wetland and forebay were seeded with plants native to Iowa and Iowa wetlands providing water quality and habitat benefits.

Today the stormwater wetland helps to treat and slowdown 37 acres of stormwater runoff from an adjacent neighborhood before entering Easter Lake. In total, this wetland helps to reduce 9.1 million gallons of stormwater each year and reduces 70 lbs. of nitrogen and 20 lbs. of phosphorus loading each year*. Improvements like this wetland help to reduce sediment and pollutant loading into Easter Lake, protecting the lake for years to come.

*Estimates come from the Iowa DNR Pollutant Reduction Calculator

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Prior to wetland construction.

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After construction, fall 2018

Sediment Forebay Construction

A sediment forebay captures eroded soil from incoming runoff before entering the wetland. Over time, buildup of eroded soils can be removed from the forebay allowing for easier maintenance preventing damage to the wetland and plants, increasing overall longevity of the wetland.

Stormwater Wetland Construction

Stormwater wetlands are man-made management practices that provide a natural way to treat and remove pollutants from stormwater runoff before it enters a stream, river, or lake. Microtopography of a stormwater wetland creates a “stormwater maze” forcing water to weave slowly through the wetland promoting pollutant removal. Varying depths of water throughout the wetland increases plant diversity, promotes plant growth allowing for biological uptake which helps remove pollutants. Stormwater wetlands help achieve 4 major goals: (1) slows down stormwater, (2) removes pollutants through settling (3) removes pollutants through biological uptake, and (3) supports wildlife habitat.

Wetland Plants & Animals found at the Stormwater Wetland

Animal photos courtesy Polk County Conservation

For more information on the Water Quality Initiative click here. 

 

clean water starts with you

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