An eroded emergency spillway in Northern California prompted the evacuation of hundreds of thousands of people over the weekend, a surprise development that came after days of authorities' assurances that there was no danger.
The Oroville Dam, the tallest in the nation, was not close to collapse, but its emergency spillway was in danger of caving in after a hole was discovered — the second spillway hole at the dam. The deterioration came as a surprise to Lori Spragens, executive director of the Association of State Dam Safety Officials (ASDSO), because she said California is usually on top of inspecting its dams.
Unlike with U.S. bridges, there is no one place that makes information on dam safety and conditions available to the public, giving anyone concerned about the safety record of their local dam a few places to check.
“It’s not that easy to find out,” Spragens said. “Some states are good about posting [information], some aren’t.”
In 2013, the American Society of Civil Engineers gave the nation's 84,000 dams a collective grade of D, noting they average 52 years old, with more than 4,000 deficient dams.
Dams can be owned by federal, state or local governments, along with public utilities or private agents, according to the U.S. Army Corps of Engineers. While there are federal dam safety guidelines, states are responsible for monitoring their respective dams, and would be the resource to call for information on any given dam in the state.
States are not necessarily responsible for maintaining them, however. According to the ASDSO, about 64 percent of dams are privately owned. Private owners can include utility companies, farmers, mining companies and neighborhood associations.
State dam safety programs reported nearly 175 dam failures between Jan. 1, 2005, and June 2013, according to the ASDSO.
One way to track down dam information is to use the U.S. Army Corps of Engineers' dam search engine. Each entry provides basic information on the dam, as well as the agency responsible for its oversight and a government representative of the dam's area.
Dams that are considered “highly hazardous” are monitored closely and are usually inspected about once a year, Spragens said. But sometimes, states simply don’t have the funding to keep up with the demands of eroding dams.
“In most states, the resources are just not there,” she said.