California officials are keeping another document on the Oroville Dam recovery sealed from public view but promise to release a redacted version within a week.
The Department of Water Resources filed an update Thursday from the outside consultants advising DWR on Oroville repairs. The report was filed with the Federal Energy Regulatory Commission, or FERC, which licenses the dam and ordered DWR to hire the consultants shortly after the crisis erupted at Oroville in February.
DWR officials say the consultants’ reports contain information that could compromise national security. The group’s first report wasn’t sealed, which DWR called a mistake. The second and third reports were initially sealed but DWR released redacted versions in response to an outcry from elected officials and others.
Erin Mellon, a spokeswoman for the Natural Resources Agency, which oversees DWR, said the fourth report will be released to the public in about a week with sensitive information blacked out.
The first three reports shed light on the severity of the damage to Oroville Dam, including the likelihood that repairs would take two years, and offered insights into possible reasons why its main spillway fractured in two Feb. 7.
After the structure fractured, dam operators curtailed water releases to limit the damage. A heavy storm raised water levels to the point that water flowed over the adjacent emergency spillway – a concrete lip over an unlined hillside – for the first time. Severe erosion on the hillside nearly caused the emergency structure to fail, triggering an evacuation of 188,000 residents. Dam operators dramatically ramped up the outflows from the battered main spillway, which lowered lake levels and arrested the flow of water over the emergency spillway, averting disaster.