The Delavan Lake North Inlet Restoration Project
The Town of Delavan, WI completed a $1.46 million sediment removal project in 2011 to help restore the ability of the 210-acre North Inlet area to filter eroded topsoil and nutrients that enter Delavan Lake through Jackson Creek. Sixty-eight percent of the water entering the lake flows through the Inlet and the 3,000-foot channel leading to it. As a result of sediment and phosphorus laden runoff from the watershed, the North Inlet had accumulated so much sediment that it lost approximately 56 percent of its natural storage capacity and therefore became less effective at trapping sediment and phosphorus prior to flowing into the main body of Delavan Lake. Approximately 45,330 cubic yards of sediment were hydraulically dredged from the Inlet and mechanically dewatered within an extremely small area behind the Town fire station using a mobile dewatering system that included a course material shaker/separator, a hydro-cyclone to remove sand, a clarifier to floc out fine grained silts and clays, and a series of belt filter presses to rapidly remove excess water from the sediment. The dewatered sediment was temporarily stock piled and hauled off-site on a daily basis since space was extremely limited. The recovered Wisconsin topsoil was hauled to a nearby sand and gravel facility to be beneficially reused for reclamation and landscape purposes. The clear effluent water was returned to the lake via pipeline and consistently satisfied all Wisconsin DNR regulatory water quality requirements.