I’m wondering if they were able to seal effectively near the top of the spillway, given that there was always a small flow of water coming out of the gates. Still, to me, it seems that the water flowing out of the drains is significantly less than it was in the days just prior to shutting it off, when they were maintaining 50,000 cfs.
We’ll see, over the next few days, if the work was effective and sufficient to harden the remaining spillway for the duty of flowing water as necessary. If it makes it through the spring melt, that should be a tribute to the efforts of the engineers, geologists, and workers that scrambled to get this thing under control.
Hi Meyer, just for discussion...if they weren't able to seal effectively near the top of the spillway (near the gate region), then the first set of drains "output" should reveal this (each set of drains sequentially service a section of the spillway).
Regarding "less flow": Until the "drains" flow is reduced to a trickle, hydraulic jacking may create net forces upward greater than the weight of the water. Even when slabs were rebar anchored in the blue/grey hard amphibolite bedrock, the slabs revealed consistent fractures along the concrete flexure "weak point" of the drain lines (post 2,421). This reveals the power of hydraulic jacking forces.
The rock bolt array emplacement is in rock that reveals as "weathered" (fractured & weaker than the hard amphibolite). There is a reason why DWR is saying “what you see today may not be there tomorrow”..
My keen interest in the upper main spillway is from the depth of weathered rock revealed from the Emergency Spillway erosion. This weathered rock depth (to an elevation) was adjacent to the head of the gate outlet area of the main spillway. Archive documents confirm this similar geology where it is stated that there are sections in the upper main spillway that are emplaced upon "lesser quality rock".
I believe they have adequate monitoring to be able to respond to any sudden anomalies. If nature cooperates, they have windows of time for repairs. However, in engineering, you become accustomed to Murphy's law...