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"You note that each anchor tendon is a 6 inch thick steel rod."

Perhaps there is a misunderstanding of the text... The text of 37' 6" is a length - thirty seven feet six inches long. The diameter of each steel rod is 1 3/8 inches. (Oroville specs). In the Oroville Radial Trunnion Gate anchor tendons, in reference to this picture, anchor tendon (150), encased within a steel sleeve (158), anchor plate (154), nut (156) -(or in other cases a wedge type "grip nut"). Oroville's spillway has 24 anchor tendons to secure the operating loads from each Trunnion Pin (136) (forces from). note: This drawing only shows 1 anchor tendon to each Trunnion Pin. Oroville's construction emplaced grout inside the steel sleeve (158) that encapsulated the anchor tendon (150) after the tendon was tightened to load design tension.

Anchor Tendon example image - for discussion.

Board worried - DWR keeping this from the public - "failing" anchor tendon scenario (engineers working on)

This is being kept from the public. No news stories on this. Not even a peep in the "rebuild" press conference in addressing a potential serious issue - DWR engineers are quietly calculating how much damage the spillway could be weakened by "snapped" anchor tendons (they don't know right now i.e. tendons snapped and/or loss of tension). Here is an April 8, 2016 letter to FERC from DWR regarding this matter. DWR is keeping anchor tendon history related information (report data) as CEII secret.

The Board of DWR is concerned, even expecting the failure of Anchor Tendons within the Radial Trunnion Gate Structure. As of this moment, they don't have the results back from Dispersal Wave Testing and do not know if any of them have failed. They performed Dispersal Wave Injection tests in late 2016, but the parent company contracted for this (FDH-Velocitel) has not been able to compare the waveform refraction/reflection data to a sample 40ft long "test" anchor rod in the lab. DWR has requested a delay in the report back to FERC until late in 2017 until they can get a reference model built properly. The first steel rod manufactured for this lab test bed reference came back with problems. They are in the process of re-doing another reference steel anchor rod. More later.

Board worried - DWR keeping this from the public - "failing" anchor tendon scenario anticipation (engineering analysis of). Letter to FERC on the affairs of the 50 year old, end-of-life, anchor tendons & anticipation of "breakages" and "loss of tensile tension".

Thanks for the pictures and the diagram of the radial gates. That really helps clear up the issues that you’re bringing to our attention.

Intuitively, I would think the trunnion pins would be more of an concern then the anchors that hold it in place being as it’s an exposed moving part where the stress is concentrated versus the anchors which are encapsulated, static, and where is the stress is distributed. However, your documentation shows otherwise. It is greatly appreciated that you’re willing to share your expertise within this forum.

Perhaps this is why DWR indicated that they would be upgrading the FCO.
They can bury this work in with everything else and hope that no one will notice, or be allowed to do to security reasons. I still don’t see how they can work on the FCO until they can use Hyatt alone to get and keep the water level down below the gates, unless they’re planning on building a cofferdam, which would be quite an undertaking and in itself.