Wow!
A lot of information swept under the rug, or attempted to be swept under the rug.
My take, and I don’t know how big a job it is, would be the systematic replacement of a portion of the rods each year with the stipulation that if repetitive problems are found in an area, then it gets increased attention. I’m just looking at it from a maintenance point of view.
As I said, I don’t know what replacement entails, and I don’t know the extent of issues that might be found.
I believe DWR fully desires to replace ALL of the anchor tendons in the new upgrade to the spillway. Why? Why fix the main spillway with flowing monies available and then have another crisis from 50-year-old dying Anchor Tendons blowing out? However, replacing these Anchor Tendons requires (1) removal of the Radial Gates. Removal of the Radial Gates poses a safety problem if the reservoir rises. (2) They would have to build a coffer dam to protect against not having the Radial Gates installed. (3) a coffer dam poses a safety risk if not properly built and sealed (piping issues). (4) Head pressure to the coffer dam requires a sizable structure if primarily using gravity mass. (5) The Inlet geometry design of the Flood Control gates needs to be restored if laminar flow (non turbulent flow) is to be insured to original design conditions.
Because of (1)(2)(3)(4)(5), I believe they may build a new RCC based inlet structure that facilitates a temporary RCC coffer dam. When the temporary RCC coffer dam is removed, the RCC inlet structure will remain. This inlet structure would help with regard to controlling piping issues as the current inlet design is erodible. Having an RCC inlet structure (when done) also gives the added benefit of being able to drain the reservoir via the Main Spillway Gates to a lower elevation without the "scouring erosion" problem they have to avoid with the current erodible inlet. (I believe they are limited to a 22 ft margin 835ft reservoir to 813.6ft gate inlet floor).
This raises the question if they are able to work on the ES & MS simultaneously. Using the existing modified Emergency Spillway would have to be a backup in case the repair work on the Main Spillway is not ready in time for an unexpected filling -or- and unexpected failure of the Hyatt power plant.
They should tell the public if this is their plan - Many people would want to know that the Emergency Spillway would become a primary contingency in this case.
Oroville Spillway Anchor Tendon Blueprint - notice the density of the array of Tendons. Anchored endpoints, of the 24 tendons & their anchors in the concrete, are spaced radially in a "fan arc" shape.