Oroville Dam Neighbors Fear Hundreds of New Spillway Cracks

Oroville Dam neighbors and downstream residents blasted California officials for claiming they should not worry about hundreds of cracks in the newly reconstructed dam spillway.

The California Department of Water Resources (DWR) public presentation to City of Oroville and downstream Feather River residents deteriorated into a screaming match after the state’s dam experts tried to reassure the community that there was nothing to see in the string of hairline cracks that have developed just weeks after finishing the $275 million first phase of rebuilding of the dam’s spillways.

Residents hammered the DWR with complaints, asking why they ought to believe the State of California after officials were not honest with the community regarding the breadth of safety problems that were known for almost a decade.

Lead contractor Kiewit Corporation poured a 1,700-foot cement top sheet and then roller-compacted and smoothed the spillway’s surfaces shortly before the Nov. 1 contract deadline. The DWR inspected the work and certified the first phase of the massive repair job was completed on time.

But the Sacramento Bee reported in late November that that cracks were first detected in September “when the first phase was nearing completion.”  The Federal Energy Regulatory Commission (FERC), which has federal oversight over the California-owned dam, instructed DWR on October 2 to investigate “cracking of the erosion resistant concrete” and to recommend any further steps necessary to address infrastructure risks.

The California Division of Dams wrote a letter to FERC on November 7 to reassure regulators that “the presence of hairline cracks was anticipated and is not expected to affect the integrity of the slabs.” DWR spokeswoman Erin Mellon added, “All concrete has this result in the placement. It’s just physics of how concrete works,”

State officials acknowledged at the meeting for the first time that there are hundreds of small cracks in spillway’s new concrete. The engineers stated that the cracks are different from the cracks that experts now believe led to the spillway collapse due to water erosion under the original spillway.

But KQED reported last week that Robert Bea, professor emeritus of civil engineering and founder of the respected UC Berkeley Center for Catastrophic Risk Management, stated: “Cracking in high-strength reinforced concrete structures is never to be expected.” He added that when large volumes of water cascade down the spillway at speeds approaching 90 miles per hour, even small cracks can increase stresses on concrete.

One resident complained during the meeting’s public comment period that heavy equipment was driven on the un-reinforced road on top of the dam during repairs. Others voiced concerns that heavy construction materials were staged on the top of the dam this summer and that the rusted spillway gates are not scheduled for repair until next spring.

Oroville resident Genoa Widener protested, according to ChicoER.com: “We heard that in 2009 when we saw DWR fixing cracks on the spillway, that it was completely normal, that it was no concern. And then we were told to run for our lives. So you telling us that it’s normal is not enough.”