SAN FRANCISCO — The Latest on an independent dam-safety report saying tougher safety reviews could have prevented spillway collapse at tallest U.S. dam (all times local):

3:45 p.m.

Dam safety experts say federal regulations may require the kind of thorough review that could have caught safety problems at the nation’s tallest dam in California.

Dam expert John France revealed the preliminary results Tuesday of an independent industry investigation into this winter’s spillway collapses at Oroville Dam.

The collapses prompted the evacuation of nearly 200,000 people.

The experts say California could have caught the safety problems if dam managers had thoroughly reviewed problems with the original design and construction of the half-century old structure.

France told reporters that existing federal regulations may require that kind of historical review of a dam’s original construction. He later added that industry experts are looking into whether there was “some wriggle room in interpretation” of those federal regulations.

Overall, France says, all the clues to this February’s spillway collapses at Oroville were “in the files” showing the spillway’s original shoddy design and build.

Spokeswoman Erin Mellon says California’s Department of Water Resources agrees with the independent experts that safety review procedures need changing.


11:45 p.m.

Bad design and construction and inadequate state oversight led to a disastrous spillway collapse at the nation’s tallest dam, an independent team of national dam safety experts said Tuesday.

The experts investigating February’s spillway failures at California’s Oroville Dam say the state probably could have detected the problems if dam managers had reviewed the original flaws in the half-century-old dam, using modern engineering standards.

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.

Experts from the national Association of State Dam Safety Officials and the U.S. Society on Dams are conducting their own independent 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 the spillway in the 1960s, including thin concrete, poorly placed drains, and inadequate foundations.

Inspections alone would not have been enough to have dealt with the original flaws, the experts said.

However, a thorough review of flaws built into the dam originally “would likely have connected the dots … by identifying the physical factors that led to failure,” the investigators said.

The independent investigators found no sign that such a review using modern engineering standards had ever been conducted.

State Department of Natural Resources spokeswoman Erin Mellon says officials are reviewing the report.