DWR Failed Dam - Radial Gate 2 - Failed Anchor Tendons -Clifton Court Forebay Dam 2013
In 2013, Clifton Court Forebay Dam Failed. Emergency Repairs were initiated to fix Radial Gate No. 2. Searching Contractor website "accomplishments" revealed report information of corrosion damage in Anchor Tendons prior to failure of Radial Gate 2. This type of information is typically not available through the FERC website on DWR filings (CEII secret status). DWR's Clifton Court Forebay Dam could be noted as the first Radial Gate failure linked to Anchor Tendons. Built in 1969, this Dam is 2 years younger than Oroville Dam. As this failure occurred in 2013, it is not surprising that the Board (DWR) expressed concern regarding Oroville's anchor tendons as noted the 2014 Inspection Report.
In 2016, DWR put out a bid to have a full repair & replacement of Anchor Tendons on Gates 1, 3, and 5 at Clifton Court Forebay Dam (See second image below). note: Gate 2 was repaired in an emergency fix in 2013. Emergency Repair bid awarded July 24, 2013.
2013 Failure of Radial Gate No 2 in Clifton Court Forebay Dam - Report data obtained from using website search (contractor's website - touting accomplishments). This data not typically available through FERC/DWR as a CEII rating would make the data/results "secret".
2016 DWR Bid announcement defining specifications for repair & replacement of Anchor Tendons in Clifton Court Forebay Dam.
Oroville has a problem: Failed Anchor Tendons in Oroville Radial Gates from 1999 archive FERC reports - Corrosion & misapplied grout in construction
Archive reports, not made CEII secret, reveal Anchor Tendons have failed as far back as 1999 at the Oroville Radial Trunnion Gates. Further, ultrasonic testing to detect "imminent failure" Anchor Tendons, is unable to test 90% of the length of the Anchor Tendons. Reflection attenuation, impedance changes, and artifacts occlude the clarity of the injected signals' return reflection content. Reports state that only 4 feet is testable of the near 40' long tendons. Since the two failed tendons were near the testing end of the grip nut anchors (within 7 inches), the DWR engineers have presented FERC with the theory basis that any potential failures should be detected with the ultrasonic technique (that works for the 4 foot length). However, this "theory" discounts the possible grout voids in the deeper 90%. The forensic analysis of the Clifton Court Forebay Dam anchor tendon failures revealed construction deficiencies where the grout was not properly emplaced fully around the tendons (voids). THE SAME finding was discovered in the two failed tendons at Oroville (voids in grout from poor construction emplacement). Corrosion developed in these voids which led to the failing of the tendon(s). note: Alkali based grout was used in the original construction intended to counter any corrosion reaction. Any "voids" in the emplacement of the encapsulating grout would defeat the protective sealing grout & alkali measure if moisture were to penetrate.
This means that DWR has made an engineering failure scenario assumption for the 90% of the untestable lengths of the Anchor Tendons from Ultrasonic testing. Indeed, Division of Safety of Dams have noted "satisfactory" Anchor testing results in all of the Inspection reports (up & to 2016) - (i.e. all 384 tendons ok) - from this limited depth Ultrasonic testing AND the engineering assumption of failure in only the first 7 inches justification/reasoning. Based on the Clifton Court Forebay data & the Oroville Anchor tendon failure data, there is a high possibility that grout voiding occurred in the other 90% of the length of the anchor tendons, exposing them to corrosion failure. Thus DWR cannot assure that the tendons are 100% "safe" (or in their vernacular "satisfactory").
Critically, DWR "hides" the mention of grout "voids" to a response letter to FERC. Why is this critical? This DWR letter cleverly defines the basis of "satisfactory" in future testing, using ultrasound, where it identifies anchor tendons as "safe". However, the grout "voiding" findings (from original construction) could exist in areas of the full near 40ft length of the Anchor tendon, to which the ultrasonic testing is admitted to be limited to the first 4 feet. It is DWR's responsibility to bring up this limiting fact of uncertainty in possible corrosion areas in these deeper grout "voidings" where the ultrasound testing cannot verify. Yet this is not stated in the FERC supplied response from DWR.
A perfect example of engineering maneuvering "slight of hand" to dodge responsibility of "there are no excuses" & you must "know" or "find out"
Look Carefully: This original supplemental report identifies missing grout that wasn't properly emplaced completely around the corrosion failed Anchor Tendon(s). These grout "voids" are from the original construction.
Page 1 of DWR's letter to FERC on the Oroville Anchor Tendon Failures - and summarization of the failure + ultrasonic testing limits to detection of faults to within 4 feet of the Tendon rod.
Page 2 of DWR's letter to FERC on the Oroville Anchor Tendon Failures - DWR Fails to mention deeper grouting "voiding" areas beyond the ultrasound testing reach (instead - makes an engineering assumption to give assurance they are adequate in their testing & methods).
