Oroville Dam spillway devastation, ruined hillside, clogged river revealed after water flow is stopped
Outside consultants agree with the state’s plan to spend the next two summers replacing sections of Oroville Dam’s still largely intact upper spillway rather than trying to tear it all out in one season.
But the public can’t see the recommendations the independent board of consultants gave the Department of Water Resources to ensure the work is safe and sound.
In a 16-page report made public late Wednesday, the engineering consultants concur with DWR’s plan to leave the dam’s upper spillway mostly untouched this summer while focusing efforts on the heavily damaged lower spillway.
However, DWR redacted five paragraphs that spell out the consultants’ recommendations for making the plan work.
The consultants’ report, their fourth, was more heavily redacted than the previous memos released by DWR. Erin Mellon, a spokeswoman for the Natural Resources Agency, which oversees DWR, said the latest report contains more information that was considered “critical energy infrastructure information,” or CEII. That rule, intended to prevent terrorist attacks, allows DWR to seal sensitive information.
“There was more CEII in the fourth consultants’ memo,” Mellon said Thursday.
In their memo, the consultants also sign off on DWR’s plan to fill in the gaping chasms in the spillway with fast-drying concrete made from recycled rock that’s been recovered from the Feather River channel below the dam. However, they add that so far the methods used for crushing the rocks don’t produce “suitable material” and need to be refined.
The heavy redaction is the latest example of DWR officials citing security concerns as justification for withholding information from the public following the February crisis, which left the dam’s two spillways badly damaged and prompted the evacuations of tens of thousands of Northern Californians.
Mellon added Thursday that DWR has received a preliminary verbal briefing from a committee of forensics consultants who are studying the possible causes of the spillway fracture. She said DWR plans to release a written report by the consultants within about a week.
She said it remains to be seen whether that report will contain redactions, too.
DWR officials have defended the redactions and the outright withholding of other reports, saying they’re trying to weigh security concerns against the public’s right to know.
“I’m going to be very up front here. It’s going to be a balancing act,” said DWR Chief Deputy Director Cindy Messer at a town hall meeting Wednesday night in Oroville. “I know there’s information that’s already been put out that’s been redacted or blacked out. There will be more very sensitive and confidential information down the road that we have to decide whether we release.”
Assemblyman James Gallagher and Sen. Jim Nielsen, two Republican state lawmakers who represent the area, have complained about the secrecy to the Federal Energy Regulatory Commission, which holds the dam’s license.
In letters to the lawmakers this week, FERC’s acting Chair Cheryl A. LaFleur said the federal officials likewise are trying to strike a balancing act with information. FERC ordered the state to conduct a forensic analysis and hire the board of consultants. The DWR is required to submit reports to the federal agency, which has kept the records confidential.
“Please be assured that commission staff is zealously working with the Oroville Dam officials to restore the facility to its proper working condition and to ensure that such incidents do not take place again in the future,” she wrote in a letter posted Thursday on FERC’s website. “Moreover, commission staff is taking every step to appropriately disclose information related to the Oroville Dam without jeopardizing the security of the facility.”
The Feb. 7 fracture in Oroville’s main concrete spillway prompted the temporary evacuation of 188,000 downstream residents when water levels in Lake Oroville rose to unprecedented heights and water spilled over a never-before-used emergency spillway. Evacuations were called after the hillside below the emergency structure nearly washed away.
In the weeks since, crews have been fortifying both spillways while planning for permanent repairs.
The crisis is expected to cost more than $500 million, including the two-year repair project. Kiewit Corp. of Omaha, Neb., won a $274 million contract to conduct the main repairs. The federal government has pledged to fund at least half of the total bill.