State Line Creek is a small, coldwater stream located in Carlton County, Minnesota within the Nemadji River watershed. Restoration and enhancement of the streams and rivers in this watershed is important to both the restoration of the St. Louis River estuary and Lake Superior and to their coldwater fisheries.
The Carlton County Transportation Department, in partnership with the Carlton County Soil and Water Conservation District, contracted the team of Cardno and LHB, a Minnesota-based engineering firm. Together our teams developed designs for a bridge to replace an existing culvert that was undersized and causing stream instability and creating a barrier to fish and aquatic organism passage.
Cardno designed 500 feet of bank stabilization and channel restoration through the bridge opening and eroding bank downstream of the bridge. LHB was responsible for the design of the free span bridge nearly 140 feet long.
Cardno’s stream design used Natural Channel Design (NCD) to provide a stable channel dimension, pattern, and profile and re-establish floodplain connectivity. A series of riffle-pools were constructed to provide streambed grade control and fish passage through the bridge opening. Toewood and J-hook log vane structures addressed the eroding banks downstream of the bridge crossing that resulted from the undersized culvert.
The project improves Carlton County’s infrastructure and public safety, while reducing sedimentation to the Nemadji River and the St. Louis River estuary and connecting eight miles of headwater and coldwater stream habitat for native brook trout.
Learn more about this project and its results in this video.