No repairs to the top of main spillway. the first photo is at a poor angle. the left sidewall was lost during the ‘test’ after the failure was discovered. The main spill way is not failing regressively. the photo makes the gate look closer to the failure point than what it is.
the night time shot has the concrete pumper working in the downstream apron area of the aux/emergency spill way section. there they have been placing riprap into the erosion features and grouting them in place.
Agree. See post 1052.
There still is the item of what was causing a distinct vertical spray from the Main Spillway. This vertical spray was well above the mid section failure spray.
>>>The main spill way is not failing regressively.<<<
The main spillway is failing regressively. The extreme turbulence of the failed mid section of the spillway has been moving upward in breaking off pieces of the concrete slabs. This is from the undercutting of the substructure. The worst effects are from “cavitation erosion”. The secondary undercut erosion is from the tremendous hydraulic turbulence. These are know civil design factors to proper spillway construction. They use large block “spillway aeration devices” to disperse the flow (just as this design has at the bottom of the spillway - large angled concrete pillars/blocks).
This spillway was not constructed on solid bedrock. It was constructed on “weathered” rock. This type of rock is very fractured but may remain stable if no powerful erosive forces are applied.
To prevent any sub erosion of the cement slabs of the spillway, a capture drainage system will redirect small leakages from any faults in the expansion joints et al. This is because the design must be protected from any erosion under the slabs.
There are a numerous images that have shown the progression of this erosion on the main spillway. How quickly it progresses is what the engineers are carefully watching. They don’t have much choice right now. Dump now, fix later & hope nothing progresses too quickly.