“DNR staff inspected or had contact with the owners of more than 200 dams during the flooding. The good news is that, for the most part, the dams held up well and did what they were supposed to do,” says Meg Galloway, Department of Natural Resources Dam Safety Chief.
“There was no loss of life, and the five dams that were breached were low hazard, rural dams, with only minor damage reported downstream.”
Heavy rains that started June 7 and continued for much of the next two weeks led to record flows on waters including major rivers such as the Baraboo, Rock, Milwaukee, Bark and Root. A portion of five dams in southern Wisconsin were breached and unable to hold back the impounded waters, Galloway says. Those dams were: the Cushman Dam on the Bark River, the Carlin Dam on Upper Spring Creek, and the Lower Spring Creek Dam in Jefferson County. The Wyocena Dam on Duck Creek also was breached, as was the Figor Dam on the Middle Branch of Duck Creek, and an unauthorized dam in Grant County.
Lake Delton drained when floodwaters washed out a section of road, but the dam itself held.
The five dams that were breached are rated “low hazard” because they have few people and buildings downstream, and thus a lower potential for loss of life or property damage.
Another 23 dams are estimated to have substantial damage, while at least 31 others suffered minor damage. Damage assessments are still to come on about 20 more dams once the water recedes to allow for such inspections, Galloway says.
Regional engineers are now working with the owners of damaged dams on repair or reconstruction, and for those owners who no longer want the liability of owning dams, removing them. DNR has ordered owners of some of the damaged dams to draw down water levels to allow inspections to be completed, or to reduce the risk of failure and damage should more flooding occur before work is done to repair, replace or remove the dams.
Many of the 200 dams DNR inspected or contacted dam owners about during the June flooding had been inspected by DNR during last August’s flooding. “We ordered a handful of dam owners to draw down water levels, and we think that probably prevented more breaches from occurring during June’s flooding,” she says.
The department also has been focusing on getting dam owners – many of them private citizens or companies – to prepare their required emergency action plans. Such plans identify the area potentially affected by a dam failure, who to call, and the people and local officials responsible for responding in case of a dam failure.
“The past year’s been a textbook example of why it’s important for dam owners to meet their responsibility for developing an emergency action plan and making sure the appropriate people are aware of it and can carry it out,” Galloway says.
In August 2007, for instance, evacuations were ordered below seven dams in Vernon County as precautionary measures. The fact that Vernon County has done a good job in preparing those plans for all its dams enabled those evacuations to occur quickly and safely, she says. The upstream dams held and the residents were allowed to return to their homes in those cases.
Dam Fast Facts:
Wisconsin has about 3,800 dams. Since the late 19th century, more than 700 dams have been built, then washed out or removed. Since 1967, about 100 dams have been removed.
Dams are classified as “Low,” “Significant” or “High” hazard, with the hazard rating based on the potential for loss of life or property damage should the dam fail, not on the physical attributes, quality or strength of the dam itself.
A dam with a structural height of over 6 feet and impounding 50 acre-feet or more, or having a structural height of 25 feet or more and impounding more than 15 acre-feet is classified as a large dam. There are approximately 1,160 large dams in the State of Wisconsin. These are required to be inspected by DNR once every 10 years.
The federal government has jurisdiction over most large dams in Wisconsin that produce hydroelectricity - about 5 percent or nearly 200 dams. The DNR regulates the rest of the dams.
Almost 60 percent of the dams in Wisconsin are owned by a company or private individual, about 9 by the State of Wisconsin, 17 percent by a municipality such as a township or county government, and 14 percent by other ownership types.
Roughly one-third of Wisconsin’s dams were built before 1940; the next third have been constructed since then, with 851 dams built between 1960 and 1970, the busiest dam-building period. The age of dams is unknown on the remaining third of dams.
Half of Wisconsin’s dams were built primarily for recreation purposes; about 13 percent to provide power; 10 percent to create farm ponds and ponds to aid in fire control; 7 percent to aid in flood control. The primary reasons that the remaining dams were built is unknown.
The Association of State Dam Safety Officials in its October 2003 report estimated that $10 billion would be needed to repair the most critical dams in the nation over the next 12 years. Out of this, needed repairs at publicly-owned dams are estimated at $5.9 billion with the remaining $4.1 billion needed for privately-owned dams.
More information about Wisconsin’s dam safety program can be found online at Wisconsin´s Dam Safety Program.
FOR MORE INFORMATION CONTACT: Meg Galloway (608) 266-7014; Bill Sturtevant (608) 266-8033