
As the cavity in the Oroville Dam spillway continued to erode, California Department of Water Resources (DWR) staff today ramped up flows down the concrete spillway to 35,000 cubic feet per second after conferring with state and federal dam safety officials.
“There is no imminent or expected threat to public safety or the integrity of Oroville Dam,” DWR Director Bill Croyle and other officials have repeatedly said.
However, with inflows into the lake more than anticipated, it’s likely that DWR will increase flows to 55,000 cfs to avoid the use of the dam’s never-used emergency spillway.
Overnight flows of 20,000 cfs caused additional lower spillway erosion, as expected, officials said. The staff halted spillway flows again for a few hours this morning to evaluate the integrity of the structure.
DWR staff first noticed erosion on the spillway Tuesday morning and shut off flows to investigate.
“More erosion is expected, but the releases will help operators absorb the inflow of the storm expected today and tomorrow,” the agency stated.
After posting online a news release about the spillway rupture, DWR sent out a notice for today’s noon media phone briefing on the Oroville Dam spillway rupture at 12:07 p.m, seven minutes after it was supposed to have begun. This apparently haphazard approach to media outreach during a dam spillway failure has baffled a number of reporters at a time when the state agency should be clearly communicating with the press and the public.
There were also some technical problems with the call, including music suddenly intruding into the call and the line going mute for no apparent reason. It was also difficult to understand officials speaking and answering questions without identifying themselves.
Nonetheless, the Department reported it is releasing 35,000 cubic feet a second of water around the clock using the Oroville Dam’s erosion-damaged gated spillway. “The flow – reduced from controlled spills before the erosion damage was discovered Tuesday – is calculated to avoid the necessity of using the dam’s ungated, emergency spillway,” DWR stated.
An estimated 121,000 cfs was flowing into Lake Oroville at the time of the press conference.