(maggief OP)
The Los Angeles Times revealed a stark dichotomy in "before" and "after" statements by DWR concerning their engineering assessment & lack of awareness of critical design aspects of the Emergency Spillway. DWR should not have been surprised that the ES was not anchored. It is in the design construction blueprint drawings and described as a "gravity ogee weir" in the construction/design archives. DWR also should have been aware of the geology + construction reports specifically noting "lower quality rock than anticipated" in areas of the "saddle region" - thus, the inaccuracy of stating "Solid Rock" at the Feb 11 briefing.
= = Article Title:
"Government severely misjudged strength of Oroville emergency spillway, sparking a crisis"
http://www.latimes.com/local/california/la-me-oroville-spillway-failure-20170216-story.html
Before (at Feb 11 briefing): = = excerpt:
"Bill Croyle stood in front of an aerial photo of Lake Oroville and swept his hand across the top of the emergency spillway that was helping drain water out of the brimming reservoir.
“Solid rock. All this is rock,” Croyle, acting director of the Department of Water Resources, said with an air of confidence at the Feb. 11 briefing.
....
"Some 27 hours later, state officials told Butte County Sheriff Kory Honea that erosion was chewing away at the base of the spillway’s concrete lip. It was on the verge of collapse, threatening to send a towering wall of flood water surging through downstream communities, endangering tens of thousands of people. Honea ordered a mass evacuation."
...
"Interviews and records suggest that the near-catastrophe grew out of fundamental problems with the original design of the emergency spillway that were never corrected despite questions about its adequacy."
...
"The concrete weir at the top of the emergency spillway was “just plopped on top of that ridge." ...
"Vogel confirmed that the weir, which she said ranges in height from 25 feet to 45 feet, was not anchored."
...
= = end excerpts
It should be noted that the article states "soft rock" where as the rock is "highly fractured hard rock". There is an important difference in the different erosion characteristics & swiftness of erosion (fractured chunks breaking off verses small pieces eroding at a different pace via hydraulic turbulence).
It’s a long discussion thread, but there is a lot of good information and drawings linked within, all pertaining to the dam...
https://www.metabunk.org/oroville-dam-spillway-failure.t8381/
The aloofness and arrogance of big government is breathtaking, and yet we continue to put in their hands what private enterprise, small government, and reasonable accountability could do so much better.