Michigan, Department of Environment, Great Lakes & Energy issued the following announcement on Sept. 21.
The Michigan Department of Environment, Great Lakes, and Energy issued an emergency order to Boyce Hydro Power LLC to perform critical repairs at the Edenville Dam. The dam’s remaining earthen embankment sustained significant damage during May’s flooding at both the Tobacco and Tittabawassee Rivers, requiring urgent action to increase public safety.
Since the dam failed, the Tobacco River has not followed its natural path and instead has been flowing along the dam, through the breach and down the Tittabawassee River channel. This makes it difficult to temporarily repair the destroyed M-30 causeway bridge due to continuously changing river dynamics and also has had a negative impact on natural resources in now dry riverbeds. Without work on the spillway and river channels, residents downstream face a threat of another flood if the remaining portion of the weakened dam is unable to impound water from a combination of spring rains and snow melt.
“The continued rerouting of the Tobacco River is delaying necessary safety measures and fixes that are important to stabilize the area affected by the Edenville Dam’s failure,” said Liesl Clark, director of EGLE. “We don’t want residents who live downstream to face another devastating flood. Boyce needs to step up and do what’s right for the community and property owners, make sure that no further damage is done to natural resources and allow for critical infrastructure work.”
The Edenville Dam is still classified as a High Hazard Dam, which means that should there be another collapse it could result in severe impacts and even a loss of life downstream from the dam. Without a way to relieve pressure from water held back by the Tobacco side of the dam – which could be exacerbated by just a one- to two-year flood event, which is highly likely over the next year – a collapse could unleash a 10- to 15-foot wave of water that would severely affect properties and infrastructure downstream.
The emergency order instructs Boyce, which owns the Edenville Dam in Gladwin County, to expedite modifications to the Tobacco spillway, which will lower the water level in the impoundment area to a safe height and restore downstream flow. Boyce must also restore the Tittabawassee River to its former channel below the spillway and divert the river away from the breach through the dam. Finally, sediment and debris in the river from the spillway to approximately 3,000 feet downstream must be removed.
The time-sensitive work plan was developed by engineering firm AECOM, hired by EGLE and the Michigan Department of Transportation (MDOT) to assess the dam’s condition. The plan will alleviate strain on the collapsed M-30 bridges, minimize upstream impacts, address dam safety concerns and relieve ecological impacts, from stagnation and potential dewatering of a part of the Tobacco River to continuous elevated levels of sediment in the diverted water.
EGLE has instructed Boyce numerous times since May 22 to undertake sufficient engineering analyses and perform necessary short-term repairs and cleanups. Boyce has not adequately addressed the ongoing hazards to the public, transportation infrastructure and natural resources.
The chosen work plan is the highest rated of four alternatives provided by AECOM engineers, who conducted a site inspection after Boyce submitted a report from an engineering firm hired by the company and which acknowledged it did not fulfill the requirements of a June 15 Temporary Restraining Order.
The emergency order instructs Boyce to immediately hire a contractor to do the work and submit to EGLE proof of a contract by Sept. 21, complete by Sept. 25 applications for any necessary EGLE permits and start construction by Oct. 19. If Boyce fails to meet its deadlines, EGLE will have the work done and seek to recoup the costs from Boyce.
The temporary safety and protective measures will be in place until a more permanent solution is decided upon for the future of the dam by its owners.
The emergency work plan is separate from an ongoing independent forensic investigation of the causes behind the collapse of the Edenville and Sanford Dams and recommendations for future action. That in-depth investigation by five subject matter experts is expected to be completed next year.
Keep up with developments at EGLE’s Edenville Dam Failure webpage.
Original source can be found here.
Source: Michigan, Department of Environment, Great Lakes & Energy
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