We are restructuring an earthen dam to slowly drain 53-acre Rasmussen Lake and restore the North Mill Creek stream channel.
The water quality of Rasmussen Lake is very poor. The Illinois Environmental Protection Agency has classified the lake as unsupportive for aquatic life, swimming and recreation. Rasmussen Lake is currently ranked by the Lake County Health Department as 161 of 162 in terms of water quality in the county.
From 2001 to 2006, we studied restoration options with an advisory committee made up of officials from the Illinois Department of Natural Resources, Illinois Environmental Protection Agency, Lake County Health Department, Lake County Stormwater Management Commission, U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, and U.S. Geological Survey. In February 2007, our Board of Commissioners approved dam modification and channel restoration of North Mill Creek.
The project consists of two phases. During the first phase, we restructured the existing earthen dam to slowly expose the lake sediment. The result was a 14-acre shallow wetland that acts as a sediment catch. Slowly draining the lake allowed North Mill Creek to cut a shallow swale through the lake sediment, while allowing the sediments to stabilize and prevent them from moving downstream.
The second phase of the project, which started in October 2017, will drain the remaining 14 acres. Once complete, we will create pools and riffles in a newly developed stream channel. Eroded slopes and the original dam will be addressed during this phase, and the concrete spillway will be removed. The floodplain will then be seeded with native plant species. Finally, we will connect with the stream below the project area to allow fish passage.
The new stream channel will improve water quality, sediment transport, water oxygen levels, and fish habitat. Project completion is anticipated in spring 2019.
Funding assistance for this project was provided by Section 319(h) of the Clean Water Act—Grant funds by the Illinois Environmental Protection Agency and the U.S. Environmental Protection Agency.