Emergency: California’s Oroville Dam Spillway Near Failure, Evacuations Ordered

Breitbart ^ | Feb 12, 2017 | Joel B. Pollak1

[janetjanet998]

The California Department of Water Resources issued a sudden evacuation order shortly before 5 p.m. Sunday for residents near the Oroville Dam in northern California, warning that the dam’s emergency spillway would fail in the next 60 minutes.

The Oroville Dam is the highest in the nation.

[meyer]

Croyle Canyon has a nice ring to it. And he seems to be stepping into the role of bureaucrat quite nicely.

[WildHighlander57]

Mad_as_he$$,

Credit EarthResearcher333 for that post; he’s been doing an awesome job keeping us up-to-date on the situation.

[meyer]

Credit EarthResearcher333 for that post; he’s been doing an awesome job keeping us up-to-date on the situation.

Ditto that! He and a few others.

[mad_as_he$$]

Absolutely. Outstanding job!

[Jim W N]

First and foremost, the Engineering responsibilities on the Dam is in a space where there are no excuses.

As I've posted earlier on this thread, this seems to come under the heading of "strict liability" (liability even if no negligence) in common law because building a dam is considered an "abnormally dangerous activity".

in failure analysis for 30 years

Must be a very interesting field. I used to work near Failure Analysis Associates (now Exponent Failure Analysis Associates) off of Marsh Road in Menlo Park, California. You guys familiar with that? (Always loved the building http://www.exponent.com/about/about-us.)

[Jim W N]

Bridge cables are accessible for inspection and repair & not buried in concrete.

Except for the anchored ends of the cable and the bridge center which are in concrete blocks - but maybe the cables inside those blocks are accessible. Would make sense that they would be I guess.

Another interesting thing about the GGBridge as I understand it, is at some point after its opening, painting has gone on non-stop.

[Jim W N]

What is going to be the name this new Canyon?

We've already christened it Moonbeam Canyon. I hope that name sticks.

[meyer]

I think he’s speaking of the future canyon below the emergency spillway. I was thinking Croyle Canyon might be fitting.

[Jim W N]

So maybe “Moonbeam Canyon” in the upper part and Croyle Canyon below the emergency spillway? Sounds good to me.

[EarthResearcher333]

Hi Jim 0216, that's why I included txt in the post "(excluding the bridge Cable anchoring)". i.e. the anchoring in concrete. I believe your original question was regarding a "tensile" loss in the "suspending" steel of the bridge (over time) verses Oroville Spillway Radial Gate Anchor Tendons.

Yes the main suspension cable is anchored in concrete. The cable is split into many subsection termination points to distribute the stress loading and facilitate the termination technique in the concrete. Even in the concrete the bridge cable maintains its "tensile" stress from the "pull" of the suspension bridge. For longevity the anchoring of the steel cable bundles in the concrete must have superior corrosion protection & maintenance. Below is a cross section piece of one of the dual main suspension cables.

[Jim W N]

Thanks.

Have you ever visited the GGBridge? The cable shown is on the SF side of the walk you can take across the bridge. On a warm day in SF - not a frequent occurrence - it is a delightful walk.

[EarthResearcher333]

My point to the image was to visually convey the looming engineering disaster (potential) that DWR is not mentioning. I'm just trying to drive the point home on the "damage to be expected" buried wording that is not being spoken by DWR in this promoted new ES concept design. (i.e. keep mum on the elephant in the room: severe hillside erosion).

Until spec numbers are translated into a visual scenario, people tend to overlook the magnitude of a lurking problem. The new "concept design" is a disaster in waiting if applied to BOC's required specifications. Yet, DWR is not speaking of the hillside damage contingency/issue (i.e. why is armoring not placed for the full hillside?). Have you seen the concept drawing? Note that there is a specific boundary transition to -> "soil".

In engineering, specifications are everything. However, if Chief Engineers & DWR's management do not communicate the true significance of what the specification(s) really mean, verses their "concept design", they could be stated to be "less than forthcoming". (they need to explain this to the public).

The image of the significant hydraulic turbulence down the hillside is exactly what will happen in the BOC specified design flow of 369,000 cfs from the new emergency spillway. The MAJOR disconnect in what is being presented in aesthetic concept pictures of the RCC buttress & a mini-apron design is "what is going to happen to the rest of the 90% of the severely erodible hillside?". DWR has not addressed this scenario of the massive erosion failure mode (i.e. haven't pointed out that the mini-apron does not address a full apron hillside secure design - that a one-time use of the spec flow of the ES will recreate another risk of a main dam failure, via back flow eddy swirl toe erosion).

= = From post 2,675 (link below)

The New "Board of Consultants (BOC)", of advising experts to DWR, has stated a requirement of restoration of the rated 646,000 cfs flood capacity of the combined spillway flows (see March 10, 2017 report below). HOWEVER, the new "upped" rating of a huge 396,000 cfs requirement of a new Emergency Spillway includes the caveat: "damage below the Emergency Spillway to be expected". This directly implies that there will be erosive damage. Given the known geology and the actual alarming erosion of "rotten rock" & debris from the last Emergency Spillway incident, the only method to prevent a repeat of this is to armor the hillside all of the way to the Feather River.

We will see how this "damage to be expected" is translated into a new design. Is the "damage" limited to the "armoring itself" or is it damage to an unconsolidated hillside further below an "armoring apron" (or both)? The latter is what could engender a very problematic sequence. (1) If the max rated 396,000 cfs destroys the hillside, a "dam" would form in the Feather River channel. (2) The main spillway chute is upstream, thus flows from the main spillway likely would "backflow" towards the "toe" of the earthen dam. (3) This backflow would form an "eddy swirl" at the "toe" terminus. (4) dangerous destabilizing erosion of the backside toe of the earthen dam would occur. (5) to prevent this "eddy swirl" or partially limit its intensity, the main spillway would need to be slowed or shut off. (6) Further erosion would occur from the Emergency Spillway handling "flood control". This is an inverse repeat of what is currently going on at the dam - BUT- with the exception of a lesser eddy back flow towards the dam (has since been mitigated by the excavation of most of the 1.7 million cubic yards of rock/debris).

The only clean design that "preserves the safety of redundancy" is by fully armoring the Emergency Spillway for the full length of the hillside to the Feather River. But the associated costs for this may become a difficult "political" funding issue.

= =

DWR's 1960's Split spillway "engineering political solution" coming back to haunt the future? (new Failure mode of the entire dam)

Expert Board of Consultants swizzled flow number specifications for the New Main Spillway and the New Emergency Spillway. Why?

[Jim W N]

Thanks EarthResearcher333. Keep up the good work.

Dang man, what would happen if you published an “exposé” book on all of this? An exposé by someone with enough technical knowledge to withstand the critics. The best weapon here looks like it would be widespread public awareness that would put pressure on any corruption and hopefully usher in good-faith officials with analysis and remedies that could, if not save money, at least save lives.

[EarthResearcher333]

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).

[meyer]

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.

[EarthResearcher333]

Repair of a post-tension design Anchor Tendon involves the removal of the Tendon and it's Anchor deep within the concrete column (usually by a coring of the concrete). When the 2 failed Oroville tendons were replaced, it's unclear if they bored out within the "sleeve" or if they cored out the sleeve in the process (no documentation available). The tough part is the anchor. The size of the anchor "Tee" plate is around 7" in the larger dimension. Thus, the "Tee" anchor + the nut & washer would need to be cored out from the side of the Gate concrete column. To gain access to the side of the Gate concrete column could require the removal of a massive Radial Trunnion Gate - depending on which anchor location in the "arc" needs to be replaced.

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.

[EarthResearcher333]

More Discussion: Looking at the Radial Gate Outlet Blueprints, it's possible that all of the Anchors to the tendons are accessible for "side coring" removal & new tendon installation repair if the Radial Trunnion Gate is fully raised.

This would greatly simplify the project as only "stop logs" would be needed to dewater the entrance to the spillway gate. (No coffer dam).

I suspect they would have to sequence the timing of tendon removal & replacement as some "alignment support" is required to keep the trunnion pin secure (via the trunnion anchor beam). Before the new Anchor Tendons may be post-tensioned to tensile loads, the anchor concrete must reach curing to "design strength". Any staggering of the "curing to design strength" timing could widen a completion window.

Then there is the "parallel factor". To do all of the anchor tendons in an optimized window of time requires teams of workers working in parallel on all of the gates simultaneously. Big bucks in equipment & expertise all at the same time...... A challenge in Logistics.

[meyer]

That would be a much larger undertaking than I had thought. My conception of the project was simply to unbolt and remove one rod at a time, re-bore and prep the hole, and slide in a new one.

I wasn’t fully aware of the design and in my mind, the other end of the anchor tendon was an exposed bolt/plate type assembly where it could be accessed. I suppose that if that were true, they could have been systematically replacing them over the last few years (provided they felt like doing maintenance prior to an incident).

[meyer]

More images are up on the Cal DWR web site......

https://pixel-ca-dwr.photoshelter.com/galleries/C0000OxvlgXg3yfg/G00003YCcmDTx48Y/I0000X4WweroQXoM/DK-oroville-spillway-7635-04-10-2017-jpg

Interesting to note that it looks like they might be working on adding shotcrete to the area at the end of the upper spillway, where it ramps down into the plunge pool.

They’re also taking core samples around the emergency spillway, for geological assessment.

I’m also noting that inflows have been a bit lower, between about 23,000 and 28,000 resulting in a slowing down of the increase in water levels in the Oroville Reservoir.

[KC Burke]

(provided they felt like doing maintenance prior to an incident).

Were you asleep these last 30 years of Democrat west coast dominance? LOL