Naturalizing a Stormwater Retention Basin
Improves Water Quality
Retrofitting and naturalizing a retention basin in Indiana improved water quality by filtering out sediments and pollutants from stormwater, decreasing the harmful impact of storms, and improving aquatic wildlife habitats.
One of the biggest threats to the Great Lakes is polluted runoff that occurs when heavy rains wash pesticides, fertilizer, sediment, animal waste, oil and other pollutants into nearby rivers and streams—and eventually the Great Lakes. Several years ago, to control stormwater flow within a local watershed, the City of Valparaiso, Ind., constructed a traditional concrete detention basin. The basin itself is roughly 2 acres in area, but is responsible for collecting stormwater from approximately 330 acres, most of which are commercial, industrial, or residential. The basin, as originally designed, only held excess water but did nothing to slow down flow or filter out sediments and pollution. Thanks to a grant from the Great Lakes Restoration Initiative, the City of Valparaiso and nonprofit Save the Dunes have partnered to naturalize and retrofit the Thorgren Basin by removing concrete and naturalizing landscaping and vegetation in the swale. They aim to expand the basin’s functionality, having it treat stormwater and provide aquatic habitat in addition to redirecting storm flows. At each inlet to the basin, sediment traps were constructed to remove much of the sediment picked up by the stormwater. The channels were reconstructed to give them a meandering path that slows down the flow of stormwater, allowing sediments and pollutants to settle out. Crews removed the concrete lining the channels, replacing it with bio-swales of native vegetation. Crews also landscaped the basin to provide a varied topography for wildlife habitats, creating clay-lined permanent pools, transitional wetland zones, and upland infiltration areas. Native vegetation was planted throughout the basin to naturalize its hydrology.
Resource Challenges Addressed
- Polluted storm runoff
- Lack of suitable aquatic habitats.
THORGREN BASIN NATURALIZATION
Location: Valparaiso, Ind.
Approximate cost: $815,000 including $607,000 provided by the Great Lakes Restoration Initiative.
Key partners: The City of Valparaiso, Indiana Department of Environmental Management, Salt Creek Watershed Group, Valparaiso University, U.S. Environmental Protection Agency, G.E. Marshall, Soil Solutions, Inc., TestAmerica Laboratories, Inc., A & L Great Lakes Laboratories, Amereco Engineering, and Stat Analysis Corporation.
Types of jobs created: Local environmental contractors, professors, and general labor.
Results and Accomplishments
This project is expected to annually prevent 402 pounds of nitrogen, 130 pounds of phosphorus, 3,590 pounds of biochemical oxygen demand, and 23 tons of sediment from entering the Salt Creek watershed, which eventually flows into Lake Michigan. This has significantly improved the water quality for both the people and wildlife in the area.