SAN FRANCISCO (AP) — Bad design and construction of the tallest U.S. dam a half-century ago, and inadequate state and federal oversight since then, led to a disastrous spillway collapse at the nation’s tallest dam, an independent team of national dam safety experts said Tuesday in urging tougher safety reviews at dams nationwide.
The experts investigating February’s spillway failures at California’s Oroville Dam say the state probably could have detected the problems that led to the collapse if dam managers had assessed the original construction flaws in the 1960s-era dam in light of modern engineering standards.
Clues to the crisis at Oroville Dam “were all in the files” of California officials showing the original flaws in the spillways’ foundation, concrete and drainage, said John France, speaking for the expert panel formed by national dam-safety associations.
At Oroville Dam, “there has never been an evaluation completely that went back thoroughly in the files,” as far as the outside experts can tell, France said.
Erin Mellon, a spokeswoman for California’s Department of Water Resources, the owner of the 770-foot-high (235-meter-high) dam, said state officials “are committed to applying lessons learned from Oroville.
“The reconstruction efforts at Oroville will bring the spillway design and construction up to today’s standards to ensure we address the physical causes that led to the February failure,” Mellon said.
Assessing whether similar problems lie unseen in other old dams nationally will depend partly on authorities budget the money for those historical reviews, France said.
Authorities ordered nearly 200,000 people to evacuate Feb. 12 after both spillways at Oroville Dam collapsed. Authorities feared an uncontrolled release of massive amounts of water, which did not happen. Residents and farms downstream have filed more than $1 billion in claims for damage they blame on the state’s heavy releases of water from the dam to deal with the crisis.
Experts from the national Association of State Dam Safety Officials and the U.S. Society on Dams are conducting their own joint review of the causes of the Oroville crisis for any safety lessons the California crisis holds for dam managers nationally.
State and federal officials also have initiated investigations.
Tuesday’s report says water entering through cracks or repair seams in the main spillway may have triggered crumbling of the spillway. It cites a series of problems with the original construction of…