I suspect the leaking seams were from various cracks in these concrete monoliths at the mid to upper height levels of the concrete. They were built with a 4ft shell layer of enriched concrete. Penetrating water in the "build" seam layers are likely where the linear cracks exist that allowed water to seep into the base concrete.
DWR has "blacked out" information on discussion revealing any of the Ogee Weir "flaws", other than a non-blacked out section discussing a way to drill & anchor the Weir to the footing rock (was just a passing "idea" that was abandoned). The discussion then evolved and became the new proposed concept design using massive buttressing with RCC.
At least they can control the integrity of the RCC Buttress construction, thus the envelope of the RCC will secure the "flaws" of shear & anchoring.
Their decisions are "triage" driven. It is the best choice given the time and circumstances.
I'm confident that there is discussion of improving the seal at the front side rock, called a "grout curtain". Their current drilling at the front of the ES will determine what they will need to do to seal off any "piping" channels under the Weir.
I will give the BOC credit. They are driving the issues & specifications to be met correctly.
Thank you for the reply. I lost track of whether it was anchored or not. It seems to me that the existing weir serves no purpose, the buttress does the work.
http://www.latimes.com/local/lanow/la-me-oroville-spillway-20170424-story.html
Water under Oroville spillway probably caused February collapse, state consultants say
Bettina Boxall
4/24/17
Official reports released Monday say the catastrophic damage to Oroville Dam’s main spillway probably stemmed from swift water flows under the concrete chute, which was cracked and of uneven thickness.
The observations, contained in consultants’ reports prepared for the state Department of Water Resources, echo much of an independent assessment made for UC Berkeley’s Center for Catastrophic Risk Management.
An official verdict on the cause is not due until the fall, when a separate forensics team investigating the February spillway break will submit its report.
But a Board of Consultants reviewing the state’s repair plans noted several problems with the spillway’s original design and construction.
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New pictures have been added showing, among other things, debris removal on the lake side of the main spillway gates.