Perhaps this is the origin of the anecdote about a valve failure. It describes lots of neglect in certain parts of the dam. A mishap during equipment testing of 72 inch valves in 2009 is described as generating a near vacuum; and, generated a 100 mph wind flow deep within the dam. A five man crew narrowly escaped being sucked into the flow when a neglected steel safety bulkhead collapsed.
http://www.chicoer.com/article/zz/20100223/NEWS/100227917
I posted a link abut the 2009 incident days ago. A flow limiting ring was not installed for the testing of the ‘river valve’, and workers were instructed to open the valve to 100% for the test, also unusual, and workers expressed concerned about doing that. At 85% things fell apart and one worker was hurt badly.
Having a hard time verifying that the river valve control room is or is not still flooded...
https://www.dir.ca.gov/dosh/citations/CA%20Water%20Resources%20313228637Summary.pdf
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=202489431