Crews will begin lowering a spillway connected to a dam that failed last year and contributed to massive flooding in parts of mid-Michigan.
The Edenville Dam Tobacco River spillway will be lowered by more than 20 feet (6 meters) starting Feb. 24 to help prevent future flooding, according to Michigan’s Department of Environment, Great Lakes, and Energy.
Water levels are expected to drop about 12 feet (3.6 meters) behind the dam — and less upstream — by the second week in March, the agency said Wednesday.
That will increase capacity in the spillway that runs through Gladwin and Midland counties.
More than 11,000 people in the Midland area had to be evacuated last May after heavy rains stressed the Edenville Dam, about 140 miles (225 kilometers) north of Detroit, and the Sanford Dam, about 7 miles (11 kilometers) downriver.
About 2,500 homes and businesses were damaged.
Emergency dam work was started in December to alleviate concerns over the possibility of a future flood that could send a 10-15-foot (3-4.5-meter) wave of water downstream should the dam fail a second time.
Officials warned Wednesday that as the water level drops and velocity increases, ice on the waterway will become destabilized or could break apart, creating dangerous conditions for anglers or outdoor recreators.
“Caution also should be taken on the Tittabawassee River above the breached section of the dam — where the drawdown could lead to shifting and unstable ice — and below the dam on the Tobacco River, as increased flow over the spillway and through the newly cleared river channel is expected to change water velocity and ice conditions,” the agency said.
Work also is also being done to restore the Tobacco and Tittabawassee rivers to their natural channels and clear debris and sediment to help protect residents and businesses.
The nearly century-old Edenville Dam had been the target of lengthy investigations by federal regulators. The Federal Energy Regulatory Commission said it repeatedly raised concerns about the dam’s ability to prevent flooding because of its inadequate spillway capacity.
Boyce Hydro Power had been authorized to run the dam. The company has filed for bankruptcy protection and has blamed the state and residents, accusing them of insisting on high water levels.
