By AMANDA PROSCIA
Capital News Service
LANSING — The recent failure of a northern Michigan dam puts a spotlight on the rest of the state’s aging inventory of water control structures.
The dam on Big Sucker Creek in Emmet County’s Bliss Township forced the Department of Natural Resources (DNR) to draw down the water of O’Neal Lake to investigate the cause of the failure. That left dry areas of the lake once used for fishing, canoeing and boating.
O’Neal Lake dam’s failure raises questions about dams that inspectors have labeled “high hazard.”
Eighty-eight dams in Michigan previously received “high hazard” status following mandatory inspection.
High hazard doesn’t mean a dam is about to fail. According to the Federal Energy Regulatory Commission, a dam is high hazard if its failure or misoperation “will probably cause loss of human life.”
Before it failed in September, the O’Neal Lake dam was classified as “low hazard.”
Like the DNR-owned O’Neal Lake dam, four of the high hazard dams are owned by public agencies: the Otsego and Trowbridge dams in Allegan County; the Hamilton dam in Flint; and the Boardman dam in Grand Traverse County.
According to Michigan law, dams are required to be inspected by a professional engineer every three, four or five years, depending on how much their failure could threaten public safety.
Inspectors identify deficiencies like misalignment and deterioration, said Luke Trumble, the DNR safety specialist for the Otsego, Trowbridge and Hamilton dams.
“To my knowledge, removal is the only option on the table” for those three dams, Trumble said. Often it is cheaper to remove a dam than to repair it.
As long as a dam meets state standards, the ultimate decision whether to remove a dam lies with its owner, he said.
An inspector identified the deteriorating concrete spillway on the Hamilton dam on the Flint River as deficient, Trumble said. The city of Flint owns the dam, and city officials drew down the water behind it following an inspection in 2012 for fear it would fail.
The city also made temporary repairs, including steel sheet-piling installation upstream to hold back more water, Trumble said.
To bring the Hamilton dam into compliance with inspection standards, “extensive repairs” would have to be made, Trumble said.
The dam was formerly used for water supply, but is no longer Flint’s primary source of water, Trumble said.
Its removal is in the early stages of planning, he said. No official plans or permits have been filed.
The Otsego and Trowbridge dams are also in poor structural condition, he said.
Unlike the Hamilton dam, they underwent modification in the 1970s that removed some gates and altered the concrete spillways.
The modification actually elevated the risk of failure due to “inadequate spillway capacity” because water could overflow in the earthen portions of the dams, Trumble said.
Any attempts at repair or removal of the Otsego and Trowbridge dams have increased complications due to their location within the Kalamazoo River Superfund site.
That’s an 80-mile stretch of the river contaminated with PCBs and is being cleaned up by the Environmental Protection Agency. PCBs, or polychlorinated biphenyls, have been linked to cancer and other health problems.
“Everyone wants to make sure that projects are done right so that contamination is remediated and not spread,” Trumble said.
The PCB contamination upstream of the dam must be cleaned up before the dam is removed so it doesn’t spread downstream, according to the EPA.
However, if the dam were to fail before being removed, PCBs would travel further downstream.
The DNR Wildlife Division manages the state-owned Otsego and Trowbridge dams. The agency has made minor repairs to the Otsego dam pending a permanent solution, Trumble said. The Trowbridge Dam has been relatively stable.
Both dams no longer generate hydroelectricity, their original purpose. They are in the planning and design phase for removal.
State officials are removing the Boardman dam on the Boardman River in Traverse City, said Jim Pawloski, a DNR dam safety engineer.
An inspection identified its “inadequate storage capacity” for water as a deficiency, Pawloski said.
Removing it is the second step in the Boardman River project. The first was removal of the Brown Bridge dam, upstream of the Boardman dam.
The Brown Bridge dam failed in 2012 and caused “significant flooding,” according to a state report.
Traverse City owns the Boardman dam and plans to apply to remove it at the beginning of 2015, Pawloski said.
Traverse City also plans to remove the Sabin dam and modify the Union Street dam, all on the Boardman River, Pawloski said.
According to the Massachusetts Institute of Technology, dams have a lifespan of approximately 50 years. More than 90 percent of the dams in the Michigan will be older than that by 2020.
By AMANDA PROSCIA