Dakota County outlines $50 million Bilsby Dam upgrade, safety and emergency plans

Dakota County officials described a multi-year upgrade of the Bilsby Dam near Cannon Falls that nearly doubles the dam’s electricity output while adding structural and safety improvements and updated emergency planning.

Mark Ryan, senior water resources engineer for Dakota County, told local residents that the completed powerhouse upgrade will produce about 4 megawatts at maximum output, roughly double the roughly 2.3 megawatts the site produced with older equipment. “The output of the plant, once we’re fully up and running here is gonna be about 4 megawatts,” Ryan said.

The upgrade, Ryan said, encompasses new vertical Kaplan turbines, added concrete and a rebuilt downstream powerhouse to extend the facility’s service life and improve dam stability. The project also included a separate 2014 spillway upgrade with 65-foot-long, 14-foot-high crest gates designed to pass far larger floods than the dam could previously handle. Ryan said the overall project cost is now about $50,000,000, and that inflation and pandemic-era supply chain delays significantly increased costs and pushed schedules.

Why it matters: Bilsby Dam sits about two miles upstream of Cannon Falls and is considered a high-hazard facility because failure could inundate downstream neighborhoods and infrastructure. The upgrades aim to reduce breach risk, increase controlled flood capacity and maintain the reservoir relied on by local…