GLADWIN COUNTY – Work crews on Feb. 24 will begin lowering the Edenville Dam Tobacco River spillway, bringing down water levels behind the structure. As the water recedes, dangerous and unstable ice conditions will develop and pose a significant risk for recreational users. The public is warned to stay off of the ice and the newly exposed bottomlands until further notice.
The spillway will be lowered by more than 20 feet, increasing its capacity to alleviate the risk of future flooding downstream and restoring the natural flow of the Tobacco River. Water levels behind the dam are expected to drop about 12 feet by the second week of March.
The area of unsafe ice conditions is between Dale Road and the remaining portion of the dam west of M-30. As the water level drops and its velocity increases, the ice will become destabilized or could break apart, creating dangerous conditions for anglers or outdoor recreators. The receding water is also expected to expose unstable bottomlands, steep channel slopes and previously unseen debris, tree stumps or other hazards.
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.
EGLE has partnered with the Michigan Department of Natural Resources and the Gladwin County Emergency Management Office to alert the public about the impacts of the water drawdown above and below the dam. As project work is expected to continue into the summer, residents and visitors are warned to stay clear of the dam worksite, as well as the nearby construction site for the M-30 temporary causeway bridge by the Michigan Department of Transportation.
Lowering the spillway is an integral part of the emergency dam work that was started in December to alleviate concerns over the possibility of a future flood that could send a 10-15-foot wave of water downstream should the dam fail a second time. Work is also being done to restore the Tobacco and Tittabawassee Rivers to their natural channels and clear debris and sediment to help protect area residents and businesses.
The Edenville Dam failed in May 2020 after significant rainfall stressed the Edenville Dam, which breached, and the resulting torrent of water overtopped and breached the Sanford Dam further downstream. More than 11,000 people were evacuated and 2,500 structures damaged by the floods.
An independent forensic investigation continues into the cause of the dam failure.
The current emergency work will have no impact on future decisions on whether to rebuild the dam. Four Lakes Task Force, which owns the dam, and local stakeholders will make that determination. EGLE is fully committed to working with stakeholders to make sure any decisions that are made on the future of the dam are carried out in a safe manner and in accordance with applicable laws.
For more information, EGLE has posted a Frequently Asked Questions listed below. EGLE also hosted a webinar in November to outline details of the emergency work.
What work is being done at the spillway and downstream?
The Tobacco River spillway crest will be lowered to reduce the height of the Tobacco impoundment to address dam safety concerns and restore flow to the downstream river. The work will also alleviate river flow strains on the collapsed M-30 causeway (which the Michigan Department of Transportation is replacing with a temporary bridge), minimize upstream impacts and address concerns about the dam’s stability. The Tittabawassee River spillway will be demolished and modified to restore flow to the abandoned river channel. Also, sediment and debris will be removed from the river upstream and downstream of the spillway.
What is the impact on water levels around the dam?
Water levels behind the Tobacco River side of the dam will drop by an estimated 12 feet. Lowering the spillway will allow for more water to flow through the dam and into its natural downstream channel. The Tittabawassee River water levels won’t likely change significantly as its impoundment was nearly fully drawn down when the dam breached in May 2020. The drawdown of the impoundment behind the spillway will increase the rate of the water flow downstream in the Tobacco River channel, but is not expected to have a significant impact on water levels.
How long will it take to lower the water levels?
The approved rate of dewatering is one foot per day, so it will take approximately 12 days to reduce the water of the impoundment to a safe level.
What is the impact on residents of lower the water level?
The biggest danger to the public is the unsteady nature of the ice in the impoundment area. EGLE is urging the public to stay off the ice for the rest of the winter. As the water level drops, the current in the water impoundment area north of the dam will become stronger, causing ice to thin in some places. Additionally, ice that has already formed may break up or become perched, creating gaps below the ice that may not support those fishing or recreating in the area. The area where we caution the public to stay off the ice is from Dale Road south to the dam. Residents south of the dam will notice faster flowing water in the Tobacco River and ice that is breaking up in area where water had been stagnant.
Are there any other impacts?
Once the water level is reduced the public will see larger areas of exposed and unstable bottomlands, which may contain debris, tree stumps, dock pilings or other material that could be dangerous. Area residents will also notice steeper slopes along the Tobacco River impoundment area. It’s best to stay off the ice and off the bottomlands.
How is the public being notified?
EGLE is working with state and local partners to alert the public through a number of resources. Local media has been notified. EGLE and other state agencies are posting messages on social media. EGLE has also posted the information to the Michigan.gov/EdenvilleDamFailure webpage. Highly visible signs have been posted at Department of Natural Resources and other public access areas. Fliers have been distributed around the impacted area at bait shops, retail shops and restaurants.
Will the work affect water wells in the area?
It’s unclear what impact the work related to the safety measures at the Edenville dam will have on the water table and property owners’ wells. Long-term effects of changes in water levels or shifting water tables caused by the collapse of the dams will not be known for some time, but some shallow water wells near the shores of the former lakes have gone dry. There are a number of reasons that residents may be having issues with their wells, including that the depths of the well may not be sufficient. If residents are experiencing troubles with their wells, they should contact the emergency managers for either Midland or Gladwin Counties or the local health department. Local officials may be able to offer help with funding or resources to repair or drill deeper wells.
Why is EGLE doing the work at the dam?
EGLE has significant concerns over the safety of the remaining portions of the Edenville Dam, the continued impact on natural resources and the prospect of a future flood that could send a wave of water that is 10-15 feet downstream, if the dam were to fail again. That amount of water would have a severe impact on residents, infrastructure, homes, businesses and natural resources between Edenville Dam and the Sanford impoundment. Lesser flooding extents would be expected downstream of the Sanford Dam. Modifying the Tobacco River spillway, restoring the Tobacco and Tittabawassee Rivers to their natural channels and clearing debris and sediment will be the best short-term protective measures for area residents and businesses.
What does the emergency work mean for the dam’s future?
The work under the emergency order is necessary to meet time-sensitive needs to address site concerns about the safety of the dam and ongoing impacts to public safety, transportation and natural resources. The work has been coordinated with Four Lakes Task Force, which owns the dam, and does not impact any final decision on the dam’s future or the timeframe to decide how to move forward. Those determinations are to be made by the dam’s owner and not by any state agency or department. EGLE is generally supportive of maintaining or removing existing dams, provided that either option is carried out in a safe manner and in accordance with applicable laws. EGLE is fully committed to working with the dam’s owner and local stakeholders as they work toward a determination of whether or not the Edenville Dam will be restored.