hydro dams including the next dam downriver from Mio, the Alcona Dam built in 1924. AU SABLE CANOE MARATHON: The Mio dam is one of 6 dams portaged by canoe race teams during the 120-mile long overnight Au Sable River Canoe Marathon that happens each summer requiring two years to build. Technical Information According to page 113 of the book "The Lower Peninsula of Michigan: An Inventory of Historic Engineering and Industrial Sites" by Charles K Hyde the Mio dam is an earth embankment dam utilizing a reinforced concrete core wall creating a head of 29 feet of water. The original installation is still in operation today including the two Allis-Chalmers vertical turbines and two Allis-Chalmers generators each producing 2,500 KW, 2,500-volts, and operating at 80 R.P.M. The powerhouse is a rectangular flat-roofed brick building measuring 30 ft wide by 75 ft long. The isolated location for the construction of the dam was miles from the closest rail lines in Luzerne thereby complicating the transportation of supplies including concrete, steel, and some machinery weighing over 30 tons which would need to ship by horse-drawn wagons those last miles. Furthermore, the narrow space available in the channel required the use of a then-innovative "conduit spillway" design patented by William W. Tefft who became the Chiel Engineer for Consumers Power Company. This spillway utilized two 60-inch steel tubes to direct the water under the powerhouse. In addition, the dam has one small concrete spillway with a single tainter gate. Consumers Energy, who owns and operates the Mio Dam, installed a cool water upwelling system in 2009 to reduce river water temperatures on hot days as negotiated with a comprehensive settlement agreement with multiple resource agencies to improve habitat for fish and other aquatic life downstream. Studies showed that some fish species, like Trout, became stressed as water temperatures increased. The current system in place at Mio and other Consumers Energy Dams uses an underwater air bubbler to lift/mix colder lower-lying water to the intake pipes for the turbines. Consumers Energy's operating license requires the water to be 68 degrees. When water temperatures rise, the compressors are activated typically for 6 hours a day to mimic evening cooling cycles but has been run as long as 24-hours a day at Mio. River Flow and Safety Since the mid-1960s, the Mio Dam has operated as a run-of-the-river hydroelectricity dam. The river flow leaving the