Ha! Yes, the posts after their tweet show that the public does NOT believe anything that they say.
In your image from 1997, there is some green in the area that ER noted in earlier posts, so that dampness has been going on a while. As ER said, the source should be investigated before it turns into something disastrous. If it’s nothing, then prove it’s nothing.
IIRC, ER333 was the first to notice the issue and document it right here on FR.
They don't know. DWR even asked FERC in 2015 to allow them to relocate a test drill hole (put in in 2016) with a water sensing piezometer up by the abutment near the Seepage area to help them try to figure this out.
More alarmingly, a DSSMRs report identified a 2x settlement difference on the dam. DWR was asked by the Board to get an answer to this 2x differential settlement and respond with an updated DSSMRs report to FERC.
This 2x finding is a significant sign of "differential settlement" issues. Differential Settlement are Dam killers.
The Greening Seepage area is in a classic "sharp abutment" transition from a flat abutment zone. Stress forces from this characteristic are warned in Earthen Dam designs as a failure mechanism as "differential settlement" will occur at this transition. Thus, potentially large differential compaction differences will create longitudinal cracks in the core - causing leakage.
Read on a photographers blog that the waterfalls in Yosemite will be near record runs during May of this year. I may drive up to see the snow melt and waterfalls in Kings Canyon and Yosemite. May cross over to Mono and Mammoth as well as the dry lake areas in Owens.
I don’t know that I will get as far north as Oroville.
My wife likes to do needlework as I drive, but there are only so many days in the car that she can tolerate.
I think they may be of the mind that they need to be shown it is dangerous first. As in "Whoops, looks like the dam failed..."