No Looming Oroville But Michigan's Aging Dams Pose Real Flood Risks
By Keith Matheny
While Michigan faces no potential dam collapse disasters like the worsening situation in Oroville, Calif., the Great Lakes State has thousands of dams that are aging, under-maintained and pose localized risks.
The Michigan Department of Environmental Quality oversees 88 potential high-hazard dams in the state, and all but six of them are approaching or past 50 years old, the average engineered life span for a dam. Overall, more than 90% of Michigan's nearly 2,600 dams will reach or exceed their design life by 2020, the American Society of Civil Engineers (ASCE) stated in a 2009 report giving Michigan a D grade on the condition of its dams.
The group has a new infrastructure report card in the works for this spring, and the grade for the state's dams "won't be getting any better," said Jeff Krusinga, a co-author of the upcoming, updated report card and a geotechnical engineer and senior consultant at SME in Kalamazoo.
"There have been some improvements, in that some dams have been removed and addressed," he said. "But in the last eight years, think about all of the dams that are in poor shape that are eight years older and haven't had much of anything done with them."
While the possible collapse of the Oroville Dam has prompted the evacuation of more than 200,000 people, the scale of the potential disaster there dwarfs what would be possible with dams in Michigan, Krusinga noted.
"You've got to remember, that dam is over 700 feet high," he said. "Most of our dams are less than 25 feet high. There are some over 100 feet, but that's just a handful.
"You've got water at such a high elevation (in Oroville), think of it as stored energy in that reservoir behind the dam. We don't have any impoundments behind our dams that are that high. That's not to say we couldn't have some dams in Michigan fail."
Among the biggest concerns in Michigan is the Hamilton Dam, on the Flint River in the heart of the city's downtown. Surrounded by the University of Michigan-Flint campus, it's considered a high-hazard dam -- meaning if it failed, people likely would die and significant structural damage could occur. The DEQ rates the Hamilton Dam as "unsatisfactory," state inspectors' worst rating, a condition calling for "immediate or emergency remedial action." That needed action hasn't occurred for years, as the dam continues to crumble. Huge chunks of concrete are missing in portions, the inner rebar exposed. Three of six floodgates no longer work.
The DEQ in recent years ordered the water impoundment behind the Hamilton Dam lowered to alleviate pressure on the crumbling infrastructure and risk to the public. But every spring, rains and snowmelt swell the river, and knuckles whiten for those aware of the Hamilton Dam's condition.
"I just hope we never have to figure out what would happen if that dam goes -- I don't want to see what could possibly happen if there was a failure," said Rebecca Fedewa, executive director of the nonprofit Flint River Watershed Coalition.
Grant money from the Hagerman Foundation in the fall of 2015 funded pre-engineering for a proposed project to completely remove the Hamilton Dam and create a series of drops and pools that would provide better fish habitat, human access to the river and recreation opportunities, Fedewa said. The proposal is in the hands of Genesee County Parks, which is seeking grant money to make the plan happen.
Most Michigan dams no longer serve the purpose for which they were built in the late 1800s or early to mid-1900s -- power for things such as grist and sawmills and, later, hydropower for small communities whose increasing power needs have since led them to tap into the electric grid.
A 2007 study on the growing crisis of aging dams in Michigan, prepared by Public Sector Consultants and Prein and Newhof for the Michigan Municipal League Foundation, said Michigan has nearly 120 dams in need of an estimated $50 million to address their repair or removal.
But the risk of failing dams in Michigan isn't just theoretical. During the "Great Flood of '86," when torrential rain fell across the central Lower Peninsula from Sept. 10-15, 1986, 14 dams failed and another 19 were near failing, according to U.S. Geological Survey.
The flooding killed six, injured 89, left about 30,000 homes flooded and caused about $500 million in damage. A 30-county area of Michigan was declared a federal disaster area. The Silver Lake Dam, 30 miles upstream of Marquette in the Upper Peninsula, failed on May 14, 2003, when nearly 5 inches of rain fell within 48 hours. It forced the evacuation of 1,800 people and resulted in more than $100 million in damage, with economic losses downstream of $1 million per day, according to ASCE. The dam was rebuilt in 2008.
More than half of the state's dams are privately owned, often mom-and-pop-type organizations -- maybe a condominium association that had a dam installed for their lake, said the DEQ's Lane. The cost of dam repairs, often exceeding $100,000, is a "huge hit" for most. The limited grant funds available aren't typically to repair dams but to remove them and restore the river's natural flows and fish habitat.
Four state-managed, high-hazard dams are rated in poor or unsatisfactory condition:
--The Hamilton Dam in Flint.
--The Otsego and Trowbridge dams on the Kalamazoo River in Allegan County. There, the issue isn't so much the flood potential behind the dams, but the toxic polycholorinated biphenyls, or PCBs, a vestige of the former paper mills along the river, now held in the sediments built up behind the crumbling dams, said Byron Lane, the DEQ's dam safety chief. A stopgap, temporary dam was completed last year upstream of the Otsego dam to alleviate pressure upon it, after inspectors found its condition rapidly worsening.
--The Boardman Dam, owned by Grand Traverse County on the Boardman River. The removal of this dam is to begin this spring.
For those without a trout stream waiting to happen behind their private dam, finding money for removal is very difficult, Krusinga said. The upcoming update to the ASCE's dam report card will recommend finding financial assistance for private dam owners to remove their crumbling infrastructure even if there's not a significant ecological benefit, he said.
A dam can last centuries if it's properly inspected and maintained, Lane said. What's happening now to dams in Michigan and nationwide, as is the case with roads and bridges, stems from neglect.
"Infrastructure needs attention; it needs financial attention," he said.
(c)2017 the Detroit Free Press
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