Project #16 Multi-Purpose Wetland Dam Complex – 2016

The Lake Pelican Waster Project District in partnership with the Upper Bix Sioux River Watershed Project, constructed a multi-purpose wetland complex along an unnamed tributary to the Big Sioux River. This complex is located in Lura Township in Grant County in sections 2 and 3. The project consists of four structures: two small earthen dams and two rock check dams with an effective area of approximately 20 acres.

The priority was to first remove an old bridge structure on the township road that was no longer meeting its purpose and replace it with the upstream earthen dam.  This dam’s purpose is to provide a way to cross the tributary with modern trucks and farm machinery.  Additionally, it holds a small permanent pool, which allows the enhancement of the wetland and a location for sediment and nutrients to settle from upstream sources.  Also, this structure allows high flows to pass.  However, with its high freeboard, the high flows pass through slowly enough to protect downstream property.

The item to construct was the two rock ckeck dams which cross the tributary in locations that allow cattle to cross at specific locations whereby keeping them from wallowing in the muddy wetlands and allow the landowners easy access to a crossing when monitoring their livestock.  These check dams also reduce the flow velocity and allow sediments to drop out and nutrients to be removed.

The final downstream earthen dam was constructed to create a permanent pool for livestock watering wetland enhancement and nutrient removal.  This structure is also designed similar to the first structure to reduce the velocity of downstream flow.

Because of the .4 acres of existing wetlands disturbed, the Army Corps of Engineers required that the wetland damage be mitigated.  This was accomplished in section 18 of Lake Township in Codington County.  A three-acre wetland mitigation project was constructed and continues to be monitored to ensure the development of wetland ecology, soils and plants.