 Pine River is one of about 75 places around Minnesota where these rock rapids have replaced dams. The State Department of Natural Resources has helped cities design and pay for the projects to improve safety and habitat for fish and other aquatic species. Amy Childers is a river ecologist and outreach coordinator with the DNR. She says more and more communities are having to decide what to do with aging dams. A lot of these are designed for a 50-year lifespan, and they're way beyond 50 years.