Dam safety article here, talking about regular maintenance as a contributing factor to dam failure. Interesting stuff!
From the WRRI newsletter (March/April 1999):
Aging dams pose threat to life, property, and water quality
by Carl Weaver
In 1997 and again this year, Oklahoma Congressmen Frank Lucas and Wes Watkins introduced bills to authorize the Secretary of Agriculture to provide cost share assistance to rehabilitate certain dams built by local governments on private land using federal cost share assistance. Lucas and Watkins are acutely aware of a problem that other lawmakers will soon be hearing about. They represent the state that is home to the first flood control dam built under what has long been known as the Small Watershed Program (implemented first under Public Law 534 and subsequently under PL 566) administered by the Natural Resources Conservation Service (NRCS, formerly Soil Conservation Service)...
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Cloud Creek Watershed Site 1, built in 1948 near Cordell, OK, and designed to last 50 years, celebrated its 50th anniversary in July 1998. Cloud Creek is the first of more than 10,400 small watershed dams that local entities—mainly counties and cities in partnership with soil conservation districts—must rehabilitate over the coming decades, and most have not set aside the money to do so.
Although later project dams were designed to last 100 years, many of the earlier small watershed dams were built with a 50-year lifespan. NRCS says that almost 1,000 will reach the end of their evaluated lifespan in the next 10 years. When a dam reaches the end of its evaluated lifespan, major renovations will likely be necessary. The actual lifespan, though, depends on regular maintenance and may also be affected by land use changes, such as urbanization, in the watershed.
North Carolina has 74 small watershed dams between the ages of 9-45 years, with an average age of 29.6 years. Some of these dams are popular attractions, such as Raleigh's Shelley Lake and Lake Lynn, both built in the mid-1970s along Crabtree Creek.
State Dam Safety Engineer Jim Leumas says that North Carolina's small watershed dams are generally in good condition, but many of them need maintenance and minor repairs which can easily become larger problems if left unattended. Leumas says that when an agency plans on spending a certain amount of money on a dam, it looks mainly at construction costs and not costs of repair and maintenance. Although the small watershed program has been of great benefit in creating dams for multiple purposes—flood prevention, water supply and irrigation—the program does not provide for maintenance of the structures.
The Army Corps of Engineers has classified 42% of the state's small watershed dams as having a high hazard potential, meaning that, in the event of a breach, loss of human life would be expected. Thirty-five per cent would cause significant economic loss, environmental damage, or cause disruption to lifeline services, and only 23% of the dams would cause little to no damage outside of the owner's property.
Leumas points out that one factor that makes dams more of a potential hazard is population growth. As areas grow and new people move in, new developments have to be built, and many of these new developments encroach on dam spillways. In the event of a breach, this encroachment could spell disaster.
North Carolina has dam failures every year. While most of these incidents do not end in fatalities, they are serious. The most recent dam failures in North Carolina that resulted in fatalities were one in the early part of the century in Winston-Salem and in 1976 when a family of four was killed in Buncombe County. With so few recent fatal incidents, it may be easy to forget the danger that dams pose for those who live downstream.
In testimony before the U.S. House Committee on Transportation and Infrastructure Subcommittee on Water Resources and the Environment, NRCS Chief Pearlie S. Reed reminded Congressmen that small watershed dams protect billions of dollars in transportation infrastructure such as highways and bridges.
In addition to threatening life and property, older dams may pose threats to water quality. In Oklahoma, a group of landowners has sued the Lincoln County Conservation District saying that polluted waters from a small watershed dam killed their livestock. As is often the case, the local conservation district owns the easement for the project and holds the legal right to enter private land for dam maintenance. The plantiffs say that makes the conservation district responsible for water quality in the dam. The case is now with the Oklahoma Supreme Court.
Recent research by UNC-Charlotte investigators documented that aging ponds and dams in the Charlotte area have become sources of pollution to surface waters. In dams with severe sedimentation, sediment—along with attached metals, nutrients, and other contaminants— is constantly in suspension, and when runoff from storms displaces resident water, that water is often much more polluted than the runoff itself.
NRCS Chief Reed reports that his agency's fiscal year 2000 budget includes $1 million to educate the public about the condition of aging watershed structures. Small watershed dams are not the only dams in need of repair and maintenance. The Federal Emergency Management Agency (FEMA) will devote some of the extra $1 million it received for the 1999 National Dam Safety Program to educate dam owners and the public about the regulatory and repair needs of the country's 75,000 dams for which states and local governments are largely responsible.
However, neither NRCS nor FEMA is offering major funding to help with dam repair and renovation. (NRCS has committed some funds to a pilot rehabilitation project in Oklahoma.) Even if Reps. Lucas and Watkins are successful in getting some funding for small watershed dam rehabilitation, local governments will still be the main responsible parties.
UNC-Charlotte researchers Randall Forsythe, Craig Allen, and John Diemer suggest that rehabilitation of aging ponds and dams should be considered as part of required urban stormwater management programs—perhaps trading rehabilitation of old structures for construction of new ones where water quality would be better served. Leumas suggests the state needs to think about a revolving loan fund for local governments that need to rehabilitate aging dams.
Reps Lucas and Watkins' current bill is H.R. 728, The Small Watershed Rehabilitation Amendments of 1999.
Forethought
