So it is a given on the forces of the Stagnation pressure as it has proven out on the slab evidence. Recent emergency repairs will help keep water from penetrating underneath, thus helping to reduce the "hydraulic jacking". But, there may be other source paths to the water penetration.
The original designers stated that the upper spillway area has rock that is not of good quality. They put in extra effort using rock bolts, chain mesh, and pigtail bolts to fortify the anchoring in these seam problem areas.
Spalling or "chips" in the upper spillway also reveal the "hydraulic jacking" forces as the seams chipped to the layer do the top level rebar (at/near). This again tends to reaffirms the upward bending stresses on the slab from Stagnation Pressure "hydraulic jacking".
So this equation is a balance of how much structural integrity has been affected in weathering of the "weak rock areas", of how much water penetration will recur, and how strong is the anchor bar matrix. Stagnation Pressure Failures have taken out many spillways. Oroville DWR engineers and/or management should have signaled the alarm years ago on these "spillway signs" - instead of putting out contracts to band-aid the fundamental design flaws.
Agreed. The bandaids haven’t been effective. Maybe for occasional use, which is the history of this spillway, but the kind of use it has had this year (and will have again soon), that’s just not good enough. And really, considering the cost of a complete failure (people live and work downstream), a quality spillway is what’s needed.
It’s going to be a very interesting spring - they’ve done a fantastic job of getting things in order after the major wash-out. But the spillway will be used again, and they will have to work out how to rebuild/replace it.
Oh, I appreciate your input and observations. You and others have done a great job of illustrating the situation in-depth.