Posted on 02/12/2017 4:26:47 PM PST by janetjanet998
Edited on 02/12/2017 9:33:58 PM PST by Admin Moderator. [history]
The Oroville Dam is the highest in the nation.
This finding also tells us that when the spillway is put back in service until next years dry period when the upper portion is only then replaced another spillway failure can occur due to problems known in advance.
I also wonder why when discussing hidden public documents and future dangers the name Christie Jones comes to mind....
Curious.
Article clip: === Will Oroville Spillway Gates Fail in Heavy Flows? Design Flaws & Fixes Risk Gate Binding?
Has DWR missed for over 40 years the accumulation of mud, debris, and silt that ended up jamming a Radial Gate? For many years Inspectors believed that extensive leaking from Gates were normal. What changed this belief in the failure of a binding Gate during a test? Are the Gates closer to Failure with these new findings?
LOS ANGELES, CA (California Network) - In 2007, during an official Federal Energy Regulatory Commission (FERC) Inspection, Radial Gate 4 jammed after only lifting 6 feet of its 33 foot travel [1]. From the perspective that all components of the Spillway Radial Gates are considered a High-Reliability System, what ensued in the subsequent Engineering Failure Analysis Report findings could only be read as an engineering nightmare. Quoting the Report: "During Federal Energy Regulatory Commission required operational testing Spillway Gate No. 4 would only open to approximately 7 feet at which time the motor would trip offline from overload." "Initial inspection found heavy galling marks on the right side wall plates as well as protruding bolts on the seal assembly directly adjacent to the wall plates. A bronze plate was also found between the wall and seal. This plate was later determined to be from a retrofit done in 1974." "The seal assemblies were removed and disassembled. A large amount of mud and debris was found behind the seal. The seal inflation piping was completely filled with mud and debris also. One bronze guide shoe was damaged beyond repair." "Two main items were attributed to the gate binding: 1. Lack of maintenance caused the system to degrade and become clogged with mud and debris. 2. Due to irregularities in the seal assemblies - it appears they were not properly adjusted for the proper clearance over the entire length of the seal."
This event uncovered an astonishing amount of damage, broken parts, and design issues so serious that it led to the complete refurbishment to all eight of the Spillway Radial Gates. These issues are considered FERC Category 1 Failure modes that are of the highest rated level. Failures of Radial Gates have been known to lead to potential catastrophic outcomes including dam failures [10][11]. DWR's own report to FERC noted that a major cause was from "Lack of maintenance" - which caused the system to degrade and become clogged with mud and debris. How could a High-Reliability System be neglected to the degree to where the accumulation of mud and debris became a contributing failure mode? How many years of this type of maintenance neglect of this mud and debris have been going on? Forty years?
DWR Engineers also discovered that silt had entered into the piping that pressurizes the rubber seals, rendering the inflation/deflation system inoperable. The hydraulically operated piping & rubber seal systems did not have any silt filtering nor any method of flushing the tubing for maintenance cleaning. This design flaw wasn't discovered for forty years until gate 4 failed. Apparently, there was no maintenance inspection program nor were there a DSOD inspection program of the hydraulic tubing systems that could have alerted engineers to this internal pipe & seal clogging issue.
The most severe findings were loose bolts and heavy scraping wear on the stainless steel side plates and the bronze guide shoe bars (see Fig 5). The stainless steel plates are imbedded into the pier concrete column walls to form a smooth surface for the inflatable rubber seals and the bronze guide shoes to slide upon. The scraping and galling marks were so significant that the stainless steel plate surfaces had to be repaired. How could DSOD or Maintenance miss these dramatic scraping marks for so many years? It finally took a broken bronze shoe plate becoming jammed into the sidewall seam for the combined failure of Gate 4 to awaken DWR to these serious and numerous issues. DSOD did a "special spillway" inspection report soon after the Gate 4 failure and found that most of the gates had visible sign of "galling" (rubbing wear) on the side seal stainless steel plates [2]. DSOD and Maintenance further discovered that the side seal assemblies were highly irregular, bent, unaligned, and were conducive to be "imprecise to where seal leakage can be expected" [2].
Evidence suggests that DSOD inspectors had become accustomed to excessive gate seal leakage for many years [4][5][6][7][8][9]. Yet this "extensive leakage" was considered normal. In a High-Reliability System, this should have triggered alarms as the seals were designed to be water tight with minimal seepage. But, this serious multi-gate failure mode was considered "normal" by the consistent "satisfactory" approvals in the decades of Inspection reports. This is very difficult to fathom in a high quality engineering background.
= end clip More at link -Article link:
Will Oroville Spillway Gates Fail in Heavy Flows? Design Flaws & Fixes Risk Gate Binding?
Fig 1. DSOD Inspection photograph of "alignment bolts" that secure the Side Seal Assembly and are intended to maintain a precise alignment gap during the operation of the heavy approx 20 to 30 ton Radial Gates. This image reveals a better alignment, or minimal offset, of the welded radial gate mounting flanges/plates. Other Gates have very large offsets of these mounting points with respect to the bolt holes in the Side Seal Assembly - thus creating the "fix" extensions and spacers employed by DWR. The base design is a poor design as torsional or operational side forces may "shift" the eyelet at the "hold bolt" - thus opening a gap for mud and debris to wedge into while in flow conditions.
Fig 2. DSOD 2015 Feb 3 Inspection photograph reveals a Gate Failure Binding Risk in the angled attachment "fixes" to secure the Gate Side Seal assembly strips to a Radial Gate. Any strong forces from Gate Flow operation may risk shifting of the alignment bolting design of the side seal assembly, resulting in excessive frictional forces from side seals and bronze guide shoes on the sidewalls.
Fig 3. Radial Gate Design Flaw. A series of bolts are used to align the side seal assembly to the approx 20 to 30 ton Radial Gate. Poorly aligned gate mounting flanges and side seal assembly bolt holes have led to bolt bending, eyelet bolts with spacers, and extensions of bar or metal. Any vibration or torsional forces by the massive gate could shift these mounting points to where there could be a risk of binding of the gate via excessive frictional forces on the sidewalls.
Fig 4. DWR Gate 4 2008 Failure analysis report identifying past used bent bolts due to alignment problems. New bolts wouldn't fit until eyelets used with spacers. DWR notes that the reassembled side assemblies pressed hard against the sidewalls while noting this as a source of a potential gate binding issue in the past and present. DWR worked the array of adjustment bolts to get both sides aligned to 0.040 inch gap from the sidewalls.
Fig 5. Severe scraping damage and heavy wear (drag marks) to a bronze guide shoe on the failed Gate 4 (binding failure). Bolts found to be scraping the sidewalls and were cut away to remove the guide shoe. Mud and debris found caked within the inflation seal assemblies rendering the seals inoperable.
Now we are talking some serious rebar!
According to DWR/FERC documentation, all Gates have been refurbished in their inflatable side seals & other hardware problems found in 2007 (DSOD 2015 report). So why is Gate 3 "streaming" in a leak? The circular "splash" reveals the streaming nature of the flow. The curvature or angle cannot be from a gravity flow (drain) directly above. Clues are revealed in photographs of fine floating debris. Divers were required to "unseal" the gates for a new flow on March 17 (boat/diver pic taken March 16). DSOD Inspection reports and DWR O&E reports detail the difficulty in "tuning" the side seal spacing against the stainless steel sidewall plates (embedded in the concrete gate walls).
Evidence infers that this design of "tuning" is easily knocked out of alignment from gate operation. Heavy bronze slide shoes (3 to each side) - called "guide shoes" - rub on the stainless steel plates as part of the side seal assembly. Yet, the side seal assembly is a weak structure that can be "shifted" with respect to the forces of the approx 33 ton Radial Gate body that they are "eyebolt" compression linked to. Gate 3 is also the gate with the highest number of known cracks in the 50 yr old anchor tendons.
I suspect a piece of debris lodged into a side seal causing an unusual stream opening that may be causing the unusual "arc stream" revealed in the photograph.
This issue also answers why DWR has never been able to seal the gates. Even after documenting all of the eight gate refurbishments to FERC, the gates still cannot properly seal. DWR cannot filter all of the fine debris during flows - even their log boom system is not functioning.
Debris jamming in the side seal assemblies were linked to multiple occasions of gates binding. I suspect this is a weakness that will not be brought to light.
Unusual "arc stream" observed in Gate 3 near the sidewall concrete column of the gate. Picture taken before March 16 "diver" crew work to unseal gates.
Divers "unsealing" debris caught in the side seal assemblies of the gates. Gates will "jam" if too much debris is wedged into the sidewalls. DWR image taken March 16, one day before reopening the flow on March 17. DWR photo metadata notes "unsealing" of the gates.
This image reveals just how serious the gate problems are in the side seal assemblies. Massive pressurized leakage observed from wide gaps in the side seal. DWR found that the side seals were irregular in gap to wall seal spacing, even though the design had "J-bolts" that were intended to allow fine tuning the spacing to the wall to the spec setting of 0.040 inches (all along the 38+ foot arc on each side assembly).
DSOD Inspectors noted that significant leakage from the gates to be a common condition ("extensive leakage" was considered normal). Problem is - these "gaps" allow lodging or wedging of debris. A "frozen" gate (unmovable) is a Category 1 Failure Mode and is extremely serious. The root of the problem goes to the mechanical stability of the side seal assemblies - note the angled connection bolts in Gate 3. These are "bent" bolts (in the pre-fix design). A very weak alignment mechanical design when considering the forces the approx 33 ton main radial gate may apply in dynamic forces (0.017 inch effective axis "vibration" causes complete loss of the 0.040 specified "gap" spacing").
The side assemblies may be outgunned in the mechanical forces from the heavy radial gate - thus "shifting" the gap alignment constantly.
Even after the divers worked to clean out and "unseal" the gates March 16 (see post above), Gate 7 is observed closed in the March 17 flow. (perhaps it was jammed and causing the lift motor circuit breakers to trip from excessive current?). The other possibility is that DWR is having gate issues to where they are sequencing neighboring gates to shift the hydrostatic pressure to allow "lifting" of a sensitive gate (i.e. keeping 7 closed to allow a differential flow reduction on Gate 8 - and thus allowing an easier lift of Gate 8). However, information will likely not be flowing like water on these issues.
Massive leakage gushing from a supposedly "sealed" Gate 3. DWR prepping closing the inlet to Gate 3 to figure out the problem.
DWR keeps Gate 7 closed during startup for some reason (jam on 7 or alleviating issue on 8). Flows start in paired gate openings from the middle and are paired outward until the desired base flow startup is achieved. This photo is an abnormal condition.
New pictures are up (currently 959 images)
Work has begun on the “cut-off wall”.
The number of images displayed dropped from 959 to 958.
They removed one of the images for some reason.
Impossible to know which one...
Juan deserves some kind of journalism award for his work on the Oroville Dam. Just the facts and no BS with a great delivery.
He does a good job.
One thing seemed a little vague. He asked about the RCC in the canyon having retaining walls on the left side (7:10). The answer was “the design has training walls on both sides”. This sounds like there is an intention to use the canyon, that the canyon will be filled with RCC to an already determined level, that it will have walls, and that it will be used. I thought the plan was to reconstruct the lower spillway and join it to the upper spillway, that the canyon would be used if they were behind schedule. Also, that the RCC was to establish a competent foundation for the reinforced concrete spillway, to fill the plunge at the break, not to completely fill the canyon.
Then again, maybe I misunderstand the plan.
I understood it to be phase 1(this year) and phase 2(next year). But I think they are counting on the canyon for relief beyond a certain flow rate. Not sure how they are going to get the water to go where they want since so far the have shown a complete inability to do that.
Phase 2 is repair/replacement of the upper spillway. I thought the halves were to be joined in the interim. We’ll see.
Thanks for the reminder. But the first question Juan asked was about P1/P2 and wall height. I think my ADHD kicked in(or lack of coffee) but the DWR people seemed to not answer that subject clearly or concisely.
They are making up mats that they will fly in place with a crane. The giveaway is the wooden 4x4.
I would say that is #6 bar or less as it is two guys handling it. When you get up to #8 and 9, then you are talking Steel.
I have had column or pier steel so dense you had to change the mix to pea gravel aggregate because normal 3/4 diameter aggregate would leave air pockets because the steel was so packed together.
Understood. That said this is way more than the original construction amount seen during the failure of the floor.
Thanks, Ray76. Another great video by Juan Browne. I’m enjoying his videos about the spillway, and even enjoyed his departure into discussing the heat and flying. He is a pilot in his real job BTW.
I think the best thing is if we see a mat a the lower level of the slab and at the upper level. That, and drain system element placed where it did not thin the slab, are the most important features in the slab field. Jointing is being more closely placed, which will help with shrink cracking and how far joints open as the slab cures. Joint construction is important because sealant deteriorates in all cases. Possibly we will se a waterstop crossing the joint.
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