Expert performed autopsy on Oroville spillway collapse. Here’s what he found.

The Sacramento Bee –

As state officials clamp down on records at Oroville Dam, one of the country’s foremost experts on catastrophic engineering failures has used state inspection reports, photographs and historical design specifications to piece together an autopsy detailing why the spillway at the country’s tallest dam failed so spectacularly this winter.

The independent analysis by Robert Bea, of the Center for Catastrophic Risk Management at UC Berkeley, points to design and construction flaws dating back to the spillway’s construction in the 1960s. Bea said the gaping crater that formed in the spillway on Feb. 7 was all but inevitable given that the design problems were compounded by inadequate upkeep and maintenance.

Bea’s 78-page report, which he has shared with The Sacramento Bee and other media outlets, says the spillway was undermined by a variety of factors, including thin concrete, the presence of “soils and incompetent rock” below the concrete and evidence of water undermining that material. Bea’s findings dovetailed with the conclusions made last month by four consultants advising the state on Oroville’s repairs.

Subsequent reports by those consultants have been sealed, along with several other documents connected to the Oroville recovery effort. Bea said he’s troubled that federal and state officials are citing terrorism concerns to block access to these reports. Greater third-party scrutiny could help guide the $275 million repair job at Oroville and point to flaws in other dams, he said.