Ran across a tidbit concerning a system that tapped into cold water near the bottom of the reservoir, used to manage temperatures of discharged water for the fish population downstream of the dam.
Seems there was an accident leading to a flooding of the control room for this diversion system, a result of malfunctioning equipment. An emergency valve stopped the flooding; but, per the story, the sub-system was never repaired.
Neither of these is the lost source of the previous comment; but, add background and detail to the ongoing story—a story which might get hot about next Tuesday once more.
http://www.sacbee.com/news/state/california/water-and-drought/article131941279.html
https://www.peakprosperity.com/podcast/107126/expert-what-need-know-about-oroville-dam-crisis
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
Look up poster Mat_Helm and do an “in forum” search on his posts. He posted about it a few times.