By Paul Rogers
February 12, 2017 Updated February 13, 7:14 AM [I'll assume PST]
The Mercury News [Serves California Bay Area]
[The Latest: State officials await dawn to inspect spillway]
More than a decade ago, federal and state officials and some of California’s largest water agencies rejected concerns that the massive earthen spillway at Oroville Dam — at risk of collapse Sunday night and prompting the evacuation of 185,000 people — could erode during heavy winter rains and cause a catastrophe.
The groups filed the motion with FERC, the Federal Energy Regulatory Commission. They said that the dam, built and owned by the state of California, and finished in 1968, did not meet modern safety standards because in the event of extreme rain and flooding, fast-rising water would overwhelm the main concrete spillway, then flow down the emergency spillway, and that could cause heavy erosion that would create flooding for communities downstream, but also could cause a failure, known as “loss of crest control.”
“A loss of crest control could not only cause additional damage to project lands and facilities but also cause damages and threaten lives in the protected floodplain downstream,” the groups wrote.
FERC rejected that request, however, after the state Department of Water Resources, and the water agencies that would likely have had to pay the bill for the upgrades, said they were unnecessary. Those agencies included the Metropolitan Water District of Southern California, which provides water to 19 million people in Los Angeles, San Diego and other areas, along with the State Water Contractors, an association of 27 agencies that buy water from the state of California through the State Water Project. The association includes the Metropolitan Water District, Kern County Water Agency, the Santa Clara Valley Water District and the Alameda County Water District.
Federal officials at the time said that the emergency spillway was designed to handle 350,000 cubic feet per second and the concerns were overblown.
“It is important to recognize that during a rare event with the emergency spillway flowing at its design capacity, spillway operations would not affect reservoir control or endanger the dam,” wrote John Onderdonk, a senior civil engineer with FERC, in the Federal Energy Regulatory Commission’s San Francisco Office, in a July 27, 2006, memo to his managers.
“The emergency spillway meets FERC’s engineering guidelines for an emergency spillway,” he added. “The guidelines specify that during a rare flood event, it is acceptable for the emergency spillway to sustain significant damage.”
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