Removing a dam that is beloved by many should not be considered lightly, but on October 6, 2020, the Forest Preserve District of DuPage County made the right decision in entering into an agreement to remove the dam at the Graue Mill in Fullersburg Woods. Fundamentally, two systems of ethics were in apparent conflict – historic preservation vs. restoration of a our natural heritage. If District Commissioners ever earn their pay, it’s when making difficult decisions like these.
Still, some misconceptions arose in the discussion by the District’s Board of Commissioners prior to its 5-2 vote in favor of restoring Salt Creek. Let me explain.
The District’s fundamental purpose is to “to acquire, preserve, protect and restore the natural resources in DuPage County while providing opportunities for people to connect with nature.” This mission statement comes into play, but restoring Salt Creek is also driven by the federal Clean Water Act, which is concerned with pollutants like fecal coliform and “nutrients” like phosphorus and nitrogen.
The presence of stagnant water with these nutrients can cause excess algae growth in the presence of sunlight. At night the algae and phytoplankton consume oxygen as a natural part of the process of photosynthesis, which can cause fish kills. If impounded, water becomes too warm and this issue becomes more pronounced. This is why the dam must be removed.
Back to the Clean Water Act, it’s about the fish and other stream health indicators. The quality of an aquatic system like Salt Creek is a function of the diversity of plants and animals, including fish and insects. They serve as indicators for how the U.S. EPA evaluates the health of the ecosystem to see if it meets the goals of the Clean Water Act.
But even if the quality of Salt Creek was good just above the dam, 16 native species of fish cannot pass through the dam. Installing a fish ladder, widely judged as probably ineffective, would not alter the fundamental problem: the buildup of sediment and algae, and the associated drops in dissolved oxygen above the dam that could cause fish kills. The dead zone will remain.
Commissioner Whelan stated that restoring the stream will destroy the current ecosystem. In fact, the impoundment of water above the dam is not currently a high quality ecosystem, the presence of ducks and geese notwithstanding. Removing the dam and restoring the stream to more natural conditions will lead to an impressive enhancement to the local ecosystem. There will be more diverse wildlife and plant communities after restoration. We will see a new form of historic preservation while preserving both the Graue Mill and reclaiming our natural heritage. It will be stunning and may even increase visitors to the Graue Mill who will see what Salt Creek may have looked like to our early settlers and the Potawatomie tribe who once lived on its banks.
Applying science to public policy decisions is important. It leads to better policy decisions for the benefit of people and environment.