Michigan’s environmental department plans to issue Boyce Hydro an emergency orderto alter the Tobacco River spillway near Midland before year’s end after officials studied alternatives that would best address dam safety concerns and reduce stream impacts following the May breach of the Edenville Dam.
The work detailed in a Monday preliminary report would lower or breach the Tobacco River spillway to divert water that’s been draining east into the lower Tittabawassee River and streaming through the earthen embankment breached amid historic rains in mid-May.
The design would restore partial flow to the Tobacco River, ensure the Tittabawassee River is restored to where it flowed prior to the flood and alleviate strain on M-30 bridges, which collapsed during the flood, according to the report.
The temporary measure to secure the site may lead to some lowered water levels in the Tobacco segment of the Wixom Lake impoundment, said dam safety engineer Luke Trumble.
“There is a sizable impoundment on the Tobacco side still intact,” Trumble said. “There would be some lowering of the water level on the Tobacco side. We would not expect any changes to the Tittabawassee River side of the impoundment.”
Once the design is complete, “EGLE will issue an emergency order to Boyce to complete the construction phase of the project this year,” the department said in its report. The environmental department doesn’t expect the company to comply with the order, in which case it would undertake the work itself.
“It will be an expedited process, and we will give the owner some chance to comply. But I think like you stated earlier, we’re not hopeful that’s going to happen,” Trumble said.
The state said it believes the project may be eligible for grant funding that would cover 75% of construction costs and 7.5% of engineering costs.
The inspection of the Tobacco River side of the dam was undertaken by the state in August after it said the dam’s owners, Boyce Hydro, failed to complete a comprehensive review of the structures’ safety.
Boyce Hydro filed preliminary engineering reports in June noting tension cracks, erosion and sloughing on the Tobacco River side of the dam, but a judge ordered the company to perform additional inspections.
The state took those over in August, citing Boyce’s bankruptcy and alleged unresponsiveness to the court’s order.
The findings were presented in the first of several reports expected to stem from the May 19 Edenville Dam failure, in which historic rains broke through the earthen embankment of the dam to send a surge of water down the Tittabawassee River. The surge overtopped the Sanford Dam and flooding Midland area.
Besides the investigation undertaken by the Department of Environment, Great Lakes and Energy, three other reviews are being undertaken by an independent forensic investigation team, the Michigan Dam Safety Task Force and the Association of State Dam Safety Officials. The latter two investigations will look at Michigan’s dam safety program, and the independent forensic review will look at the factors that led to the dam failure.
The state, in its Monday report, also concluded the Dow Midland Plant did not have “a material impact on contamination,” noting that levels found after the flood were “consistent with levels seen after non-2020 seasonal flooding events.”