The Issue with the Woolen Mill Dam
The Issue with the Woolen Mill Dam
The Wisconsin Department of Natural Resources and statute requires dam owners to be compliant with NR 333. Every dam receives a Hazard Rating of Low, Significant, or High. In 2024, the Woolen Mill dam was assigned a Hazard Rating of High after a Dam Failure Analysis was completed. The ratings are based on a failure event and the impact one would cause downstream. A high Hazard Rating means the Woolen Mill dam must have the minimum capacity to handle a 1,000-year flood event without failing. It currently can handle about the 10-year flood event.
There are very few options to greatly increase the dam's capacity and all of them should be considered cost prohibitive. The dam cannot be made longer because there is no space available. The height of the dam could be lowered significantly, but doing so would create a low-head dam, also known as a "drowning machine." The dam could be razed and perhaps a larger one could be built with a different design that includes very large, unsightly gates. But, it needs to be asked and answered, what for? Why do we need a wildly expensive do-nothing dam? Why not just restore this area of our river?
Many local officials incorrectly tell residents that this dam is historic and many residents believe them. Ironically, the only historic component of this dam is the privately-owned limestone mill race wall, and any dam repair scenario will require its destruction. It is original to the first dam that was built in 1864, which washed out in 1881. It would be replaced with concrete stamped to "give the impression of stone," like in the photo below.
Top: Original, still existing mill race wall at the Woolen Mill dam, built in 1864.
Bottom: The mill race wall at the Columbia Mill dam, built in 2019, with stamped concrete to give the impression of stone.