Built in the late 1800s, the Grayling Mill Pond Dam on the Au Sable River was a relic of northern Michigan’s lumbering industry. Originally constructed of log timber, the dam was used by lumber mill operators to store logs. Although the lumber industry eventually declined, the dam remained and was renovated with steel sheet pilings in 1933. The structure gradually deteriorated, collected mounds of sediment and roadway runoff from an adjacent bridge, and nearly failed in 1994 during a record flood.
The dam also threatened the river’s trout fishery. Fishery biologists from the Michigan Department of Natural Resources (MDNR) determined that the 85-acre Mill Pond upstream from the dam impoundment created a “thermal pool.” The shallow pond produced a considerable temperature gradient in comparison to the river, often making the pond too hot in the summer and too cold in the winter to support a thriving trout species. While the Mill Pond was considered a community asset, maintaining a healthy trout fishery was viewed as a more important element to promote local recreation and attract sports enthusiasts.
Initially, a number of local residents spoke out in favor of keeping the dam and Mill Pond. Surrounded by a City Park, the dam was perceived as a community focal point of historical significance. Early opposition required the Michigan Department of Transportation (MDOT), MDNR and the City of Grayling to clearly outline the benefits of dam removal and develop a solution that retained the site as a community asset.
Significant obstacles to dam removal included incomplete records regarding ownership of the dam weir and a structural connection to the bridge carrying the I-75 Business Loop over the Au Sable River. With no clear owner of the dam weir, neither the City of Grayling nor MDOT were willing to accept ownership of a new dam.
The community chose a partial removal of the dam to retain an important local point of interest. This solution promoted a healthy stream ecosystem by restoring free movement of aquatic organisms and water quality to nearly pre-dam conditions while managing in-stream sediments. The partial removal was completed in 2005 by replacing the steel weir structure with a network of boulders and naturally reinforced stream channel. The City of Grayling partnered with MDOT and the MDNR to coordinate the removal of the weir structure without negatively impacting the bridge.