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

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

[EarthResearcher333]

Yes, an interesting perspective.. The finished wall is almost a work of art.

[EarthResearcher333]

RCC "Football field" stage - Rock Islands gone - Vertical Access Pipe - New construction revelation of sub base rebar in Sidewall slab substructure

The progression of the placement of the Roller Compacted Concrete (RCC) has filled in the "rock islands". The large area resembles a flat stage that a football field could fit within. This gives a perspective on the cubic yards of additional RCC required to elevate their progression to the final upper spillway "joining point". Just think of how many layers of "football field" sized "lifts" of RCC to get to the final grade. A football field is 6,000 square yards (includes the end zones). To elevate the grade in the square footage of this "area", although in a diagonal progression shift of the equivalent "field", a 50 foot fill height is 100,000 cubic yards of RCC. The "height distance to go" is well more than 50 feet. So the math becomes impressive on the work that is to be done.

Another interesting reveal. This photo shows long sections of steel reinforcement bar in the substructure area of the lower Sidewall Slab base. Other photographs in the lower spillway had not revealed this. So, this rebar may be consistent with the construction in all of the Sidewall base OR this rebar is unique to this area (for structural reasons). It's possible that there is more "fill layer" concrete to be placed and that the drain system was being constructed that conflicted with the "fill layer" progression. The photo angle does not reveal any easy height distinguishing differences of the "fill layer" on the other side of the top finish layer slabs verses this inner section.

A vertical "access" pipe is observable in the photo. This access pipe, for inspection and maintenance, connects to the drain system below.

The RCC fill process has reached a stage where the rock islands are covered over. The flat fill area is near a "football field" or more. Long rebar in sidewall slab substructure is a new discovery. Vertical Access Pipe to drains below visible.

[EarthResearcher333]

Correction - the noted "Vertical Drain Access" is incorrect. It is most likely a large trash bucket where workers are gathering debris in cleaning/gathering items during construction.

The prior posting of the drain system showed the vertical connection points to the drainage piping for service access. I thought it a bit strange for them to have a tall section installed...

[EarthResearcher333]

Exit Path for Crane off of Upper Spillway - Long protruding steel are "load transfer" bars in the lower part of Spillway Slabs - New Report Hammers DWR - includes the Green Wet Leakage Area issue

Went back through earlier construction photographs and found a consistent construction use of "long bars" in the lower layer of the Spillway Slabs. These smooth surface steel bars are to load balance, or "load transfer", between the seams of the adjacent concrete slabs.

Some here are already versed in concrete construction.

However, for those that are interested in these bars and techniques and the how & why on a dam spillway, here is a little background.

Thermal expansion and contraction of reinforced concrete slabs need a seam that allows for these thermally induced small movements between the "expanding & contracting" slabs. Note: Steel reinforcement "ribbed rebar" keeps the entire individual slabs from forming cracks within the concrete as the slab acts as a solid structure. If the slabs were designed to be too large in dimensions, in length and width, the thermal expansion results in a larger and greater overall expansion/contraction per slab. To distribute this thermal expansion into smaller pieces, more seams are required. Designers place "Contraction Joints" at the slab boundaries to allow for this effect. For continuity in the vertical load stress balance, from having more individual slabs, rows of strong steel bars, with smooth surfaces, facilitates expansion and contraction as the bar slides in its smooth concrete encapsulated shape. These "load transfer" bars are important to keep the Slab surface alignments precise. Any difference of height at these seams could induce undesirable damaging cavitation effects in high velocity and high pressure spillway water flows.

So what could move the slabs in vertical strain when the spillway is under heavy flows? The whole base of the bedrock will deform slightly from the incredible weight of large spillway water flows. That is why specific guidelines are followed in a careful metered ramping up and ramping down rate in a large size spillway. The slow ramping allows for a smoother adjustment of the base bedrock deformation. Included in the deformation is the existence of moisture in the tiny cracks and pores in the bedrock. This is part of the reason for underdrain systems in that spillway loading is able to squeeze moisture through these tiny cracks and pores. A good spillway design will optimize conditions to keep the moisture from accumulating from natural water seepage and also to allow for the dynamic pressure deformation effects.

The spillway structure has to account for the overall deformation effects in acting as a unified balanced load system. That is why it is so important for such heavy anchorage bars/plates, load transfer bars, extensive rebar design within the slabs & sidewalls, high strength construction concrete, and building the structure upon fresh bedrock.

If you overlook any of these details, nature is unforgiving. If you contrast the new spillway design & construction with the old, it becomes very clear how fragile the original constructed design & foundation was done. Yet the spillway is only as sound as the weakest link. Unfortunately, the choice of skipping in addressing issues in the Radial Gate Headworks structure, with large diagonal cracks and differential settling abutment bridge piers, and end-of-life 50 year old cracking steel anchor tendons, the spillway could still be in jeopardy.

A recently released independent report highlights these issues and much more. See the story and link below. The report is easy to read, full of graphics, and is well referenced. This report was in the news, but didn't get much attention.

Oroville Dam highlights California water infrastructure ‘falling apart’

A new independent report that is well written and researched was recently released. A good recommended read on the issues that DWR still face and also what led DWR to the problems & subsequent failures that occurred.

http://www.friendsoftheriver.org/wp-content/uploads/2017/09/The-Oroville-Dam-2017-Spillway-Incident-Lessons-from-the-Feather-River-Basin-Final.pdf

Exit Path for Crane off of Upper Spillway - Long protruding steel are "load transfer" bars in the lower part of Spillway Slabs

Physicist Richard Feynman - a very relevant quote regarding the Spillway failures - No amount of Public Relations can fool Nature

New Report recently released on a wide ranging set of current Oroville Dam and Feather River issues, including the danger of not lining the full Emergency Spillway. Recommended Read.

(New Report Graphic) Preliminary Root Cause Analysis of Failures of the Oroville Dam Gated Spillway. First report out of a set from Professor R.G. Bea. To which has recently been mirrored in the Internal Forensic Team (IFT) interim report.

[The Westerner]

Thanks for posting Prof. Bea’s report. Love the Feynman’s quote:

“No amount of Public Relations can fool Nature.”

[EarthResearcher333]

Alert - NBC Investigates Team - "Is the Dam Safe?" - Special Broadcast tonight at 11pm - Sep 28, 2017

Head's up. A special investigative report is scheduled to air tonight 11 pm Pacific Time on NBC in the Bay Area. Live streaming available to watch.

NBC's youtube promotional teaser reveals an interview from a blurred image source stating "More important than the Spillway... these bolts were cracking and failing".

Another interviewee states "I think it has failed. It just hasn't collapsed".

David Gutierrez, advisory consultant to DWR, states "We're pretty confident that the Dam is Safe".

Oroville Mercury Register News article on the special:

NBC to air special on Oroville Dam tonight - "Is the Dam Safe?" http://www.orovillemr.com/article/NB/20170928/NEWS/170929720

=== Article clip:

Bay Area >> NBC Bay Area (www.nbcbayarea.com ) will air a special segment from its investigative unit on the Oroville Dam at 11 p.m. today posing the question “Is the dam safe?”

The segment will be also be livestreamed at 11 p.m. It will air again at 11 a.m. and 6 p.m. Friday.

A promotional video on YouTube says the team’s six-month investigation has uncovered “new issues with the dam.”

=== end clip

Promotional YouTube: https://www.youtube.com/watch?v=ftYwXEkNGfo&feature=youtu.be

Live Stream: http://www.nbcbayarea.com/news/local/NBC-Bay-Area-News-Live-Stream-Newscasts-243824281.html

[EarthResearcher333]

Correction: Joel Ledesma, DWR's deputy director, is attributed to the statement "We're pretty confident that the Dam is Safe" in the NBC investigative story.

[EarthResearcher333]

A Must Watch - "NBC Investigates" Uncovers Major Oroville Dam Safety issues - Three Ex-DWR engineers reveal inside information

NBC Investigates has performed a six month investigation into Oroville dam. They have reviewed 20 years worth of reports, and nearly 10,000 pages of documents. What they've found is startling.

The news report starts with a statement in the opening: "Now we've uncovered more problems with the Oroville Dam. The entire Dam could fail which could impact our water supply."

NBC's investigative lead reporter, Stephen Stock, stated that DWR has still not replied on critical information as to why DWR has not addressed such high priority safety issues even though FERC and DSOD had noted these issues for years. DWR's Joel Ledesma said that they would provide these answers to NBC during the interviews.

Watch the full news reports, videos, and sets of interviews at the link:

http://www.nbcbayarea.com/investigations/Records-Raise-Safety-Questions-Surrounding-Oroville-Dam-448318083.html

Fig 1 and Fig 2 below are images in a video sequence, courtesy of NBC Investigates link, that reveal the failure mode of the catastrophic collapse of Oroville Dam.

=== NBC news report link (clips from story): (emphasis mine)

A six-month investigation by NBC Bay Area that reviewed two decades’ worth of safety documents uncovers questions about the dam’s safety beyond the spillway that failed in February By Stephen Stock, Rachel Witte and Michael Horn

A six-month investigation by NBC Bay Area that reviewed two decades’ worth of safety documents uncovers questions about the dam’s safety beyond the spillway that failed in February. Senior Investigative Reporter Stephen Stock reports in a video that first aired on Sept. 28, 2017.

An NBC Bay Area examination of 20 years’ worth of Federal Energy Regulatory Commission (FERC) and California Division of Safety of Dams (DSOD) inspection reports, engineering studies, Federal Part 12D independent consultant inspection reports, consultant letters and memos—nearly 10,000 pages of documents in all—repeatedly identified problems with the stability, safety and monitoring of Oroville Dam.

These issues raise concern among seven engineers who reviewed the materials at NBC Bay Area’s request. Several of those engineers, who asked to remain anonymous, currently work in structural engineering, including the design, monitoring and review of dams. One engineer served on the National Dam Safety Review Board.

All of the engineers told NBC Bay Area that the documents they reviewed raise serious safety concerns that they say must be addressed sooner rather than later or risk failure of Oroville Dam itself.

…

For many of the engineers, that last issue is the most troubling problem. In a 2010 report, federal inspectors ordered the California Department of Water Resources (DWR) to “establish a long-term plan to monitor the flow” of water through the earthen dam—what’s known as the phreatic surface. This issue subsequently appears as the top priority to be addressed in the past five years of DSOD inspection reports, yet DWR has, thus far, failed to create such a plan.

According to the structural engineers who specialize in dam design, construction and safety, if the phreatic surface comes out at the wrong place and the wrong speed, it could erode the structure from the inside, and if enough force is created, it could wash away the entire dam.

==== end clips More at link above

Fig 1. Courtesy NBC: Normal seepage migration within an Earth Dam forms a "Phreatic Surface" or underneath water level within the earthen dam. DWR has no working piezometers to determine this critical Phreatic level - even when FERC has been asking for these instruments for years.

Fig 2. Courtesy NBC: Failure of the Dam from internal Phreatic water levels compromising the structural integrity of the Zone 3 embankment. Dam collapses and sends a massive wall of water to towns below.

[KC Burke]

And if that was the only uncertainty, we would be lucky.

[EarthResearcher333]

The other two major concerns in this NBC investigative report were the cracked and failing anchor tendons and the large 16 ft diagonal crack in Pier 10 of Gate 8. DWR refused to let them see this crack on an on-site visit.

DWR's deputy director (according to NBC), Joel Ledesma, repeatedly went on the record saying the crack in the 5ft thick Gate 8 pier has not grown. Yet I'm going to post 2005 and 2015 DSOD photographs that show this is not true. This does not bode well for DWR in gaining the trust of the people when such a significant structural Headworks question is answered to where it is easily disproven.

[EarthResearcher333]

DWR's Deputy Director - Misled NBC on 14ft Crack not growing? - 2005 & 2015 DSOD photographs show 2+ft extension growth - Will this hurt public trust?

Perhaps the most significant event in the "NBC Investigates" news report was on the structural uncertainty of a large diagonal crack in a 5 foot thick concrete pier that secure the trunnion pins for Radial Gate 8 (Pier 10).

DWR's deputy director Joel Ledesma repeatedly noted that the large crack is not growing [1]. Fig 1. to Fig 2. clearly shows a significant growth in the length of the crack. These photos are from DSOD 2005 and DSOD 2015 inspection reports respectively.

NBC's Stephen Stock was able to get Joel to admit that If the crack was growing that would this be something of a serious issue. With the evidence below, how does DWR answer this question. Was the paint mistakenly placed on the 2+ foot extension to the concrete chamfer? If so, is DWR's O&M grossly in error and cannot accurately distinguish and paint a crack on such a critical structure (i.e. mistaken paint placement)? Is DWR now going to correct the record on either case of a gross error or a serious extension of a crack that they say "did not occur"?

Why did DWR refuse to let NBC see the crack?

Comparing DSOD's 2005 report and their close up photograph their identification of the crack end is accurate. In fact DSOD Inspectors noted that the identification paint was either not extended to cover the increase OR that calcite deposits had possibly masked the paint (Fig 1). In either case, the end of the crack was clearly noted and observable in their photograph. The end of this crack lines up perfectly with the dashed red arrow of the 2015 DSOD report where the new extension of the crack is over 2+ feet going all of the way down to the chamfer seam in the concrete wall. The Inspector notes in detail the extension of the crack in the main body of the 2015 report stating "The long standing crack in the left pier for gate 8 appears to have extended to the concrete chamfer below the old telltale paint mark, as evidenced by the length of the recently applied red telltale paint, photograph 8. Visual monitoring of the crack should continue. A significant extension of the crack would warrant an investigation into the cause." (Fig 3).

[1] === "NBC investigates" news story - clip from link (regarding answer to "diagonal crack") (emphasis mine) http://www.nbcbayarea.com/investigations/Records-Raise-Safety-Questions-Surrounding-Oroville-Dam-448318083.html

But DWR’s Ledesma says his engineers do know what it is. When asked specifically about the inspection report that noted growth in the crack, he said it was “probably a miscommunication.” Ledesma says his own conversations with the agency’s dam engineers indicate the crack—what he calls a “stress crack” that occurs when concrete is poured—has not grown.

“It’s not changing and it's not posing any risk to the structure,” he said.

=== end clip

Fig 1. DSOD Oct 12, 2005 Inspection photograph noting the small mismatch in telltale paint to the end of the diagonal crack. This "end" location is an exact match to the dashed red arrow in the 2015 DSOD Inspection report (see Fig 2). Thus, in 10 years, the crack has telltale paint noting a 2+ foot growth.

Fig 2. DSOD Feb 3, 2015 Inspection photograph revealing a large 2+ foot growth in the diagonal crack in the headworks 5ft thick Pier to Gate 8. The dashed red arrow matches the location of the "end" from the 2005 DSOD photo (see Fig 1). How can DWR say that there was no growth? Did they paint a mistake?

Fig 3. DSOD Feb 3, 2015 Inspection notes on the extension of the diagonal crack as noted from prior inspection information and the new telltale paint of the 2+ foot extension. Will DWR tell the public what is going on? Why keep NBC from seeing the large crack?

[EarthResearcher333]

NBC Interview - Unbalanced Gates from Large Crack in Pier - Anchor Tendon Relaxation-Cracks-Breakage - Evidence confirming Imbalance in the Gates? Failure Mode of Spillway?

Further information from the "NBC Investigates" TV episode [1] on retired DWR insiders speaking out. The former employees starkly commented on the Large Crack in the Gate Structure [2][Fig1] and the "cracking & failing" anchor tendons that secure the Radial Gate Trunnion Pins [3].

Photographs (Fig. 2 & Fig. 3), during the spillway crisis, may confirm NBC's interview statements of DWR sources identifying "twisting" of Gates from structural weakening and/or stress effects. This may be directly evidenced by DWR's abnormal operation of the gates (Fig. 2 & Fig. 3) nearest the 16+ foot (Fig.1) Large Crack in the Headworks Gate structure.

NBC's interview of retired insider DWR sources noted the issue of this exact problem of an "unbalanced" or asymmetry in force balance on trunnion anchorage to the pivot pins that results in a "shift" in the gate side edge to where it "jams" [2]. Note: The tolerances come out to just a 0.017 inch shift of a Trunnion anchorage/pin would cause the gate to lose its 0.040 inch gap spacing to the side plates. Bronze guide shoes would eventually rub against the stainless steel slide plates with greater and higher forces, causing a "jam". A "stuck" gate is a Failure mode to the Headworks. DWR noted in the NBC interview that any loss of control of the Gates is a serious problem and risks loss of control of the structure itself.

The other retired DWR source spoke to malfunctions stating “Here you'll have a catastrophic structural failure that's not going to allow you to operate the facility the way it's supposed to,” [1]. Both DWR sources, plus other engineers, spoke to the Large Crack and the end-of-life 50 year old Anchor Rods/Tendons stating concerns of "weakening the structure" and "Gate Anchorage" [2][3].

DWR states in the NBC interview that they say that they still have "life" in the anchor tendons - that still allows flows at normal rates. Yet why is DWR operating the gates in an abnormal sequence? (Fig. 2) Why was DWR operating at a heavy 100,000 cfs spillway flow with Gates 7 and 8 non-operating? (Fig. 3) Certainly the dramatic hydraulic turbulence to the "open" gates, via skin plate force transfers from a powerful whirlpool, is not a standard operating condition. DWR was risking further damage to the open gates as the whirlpool has the ability to pull any floating log debris down below and it could slam against the gate skin plates. Why was DWR taking these risks? Is it because they had no choice in that Gates 7 and/or 8 had structural problems/risks (jamming from twisting)?

DWR may be facing a larger problem in the structural weakness of Gate 8 from the 16+ foot crack. Photos from years of DSOD inspections show water streaks originating from the crack. This evidences water entering into this crack, in the 5 foot thick pier. Water accelerates corrosion to where the steel re-inforcement bar (rebar) in the 5 foot thick pier could be "corroding itself" into two sections (i.e. a "loss" of tensile "hold together" strength of one side of the concrete to the other via the rebar - the "crack" in the middle). This would result in even greater stresses on the anchor tendons to flex during spillway flows on Gate 8, and thus make it very prone to dynamic twisting, and possibly radial gate structural damage (if the twisting goes beyond absorbing elements to result in a "bent" structure).

The NBC interviewee DWR insider source was correct in stating the "balanced" condition of a normal operating gate. Even if there is some "life" left in the overage 50yr old steel tendons, any imbalance of the steel relaxation in the sum of both sides risks a notable degradation to this "balance".

This issue of "imbalance" in the anchorage via the Large Crack uncertainty & internal corrosion combined with the 2014 US Army Corps of Engineers study finding of up to 70% variance in 39 year old shorter steel tendons (Fig. 4) (verses Oroville's 50 year old longer steel tendons), makes for a potentially serious issue for Oroville.

DWR is holding new test data "CEII secret" on Oroville's anchor tendons. The engineering details were discussed in a prior post:

Anchor Rod Update - DWR has test "results" - Won't say how bad it is - They are holding a "workshop" to discuss the results (keeping the data secret via CEII)

=== clip from post 4192

Ominous results from another DAM, West Point Dam in Georgia, reveal that engineers & scientists are startled by "extreme variances" in tension loss in aging anchor tendons. At this dam they discovered tension losses of up to 70% (See Fig 4.). This does not bode well for Oroville. Oroville's steel tendons in the Radial Gates, that are critical to the flood release load capacity, have a known population of cracks in the tendons (See Fig 6.). Some of these cracks are very close to the "critical sudden failure" size. Yet, DWR can only test 2% of the tip of the 40 foot long tendons. 98% of the steel tendons are "unknown" in detectable cracks and thus "unknown" in the risk of failure.

Because of this 98% uncertainty, and the "end of life" 50 year old tendons posing a real threat to Radial Gate failures (that have been failing at this age at other dams around the country), DWR partnered with FDH-Velocitel to use a new experimental test method called Dispersal Wave Testing. Essentially, DWR is putting all of their "eggs in a basket" hoping that the steel tendons haven't lost much of their tension and thus prolonging the maintenance costs of replacing. However, this is a huge risk, as now revealed from West Point Dam test data of similar post-tensioned steel rods (Fig 4). The crucial revelation of West Point's data is that the engineering & scientific community had their first glimpse of what actually happens to the steel rods over time (in this case 39 years). Before this data, engineers had believed that there would be a uniform reduction of losses (via steel stress relaxation, for example). What they found is alarming. There were wild variations of losses in the tensions. This means that the full phenomena to tension loss causality is not fully understood in the industry. Thus any "prediction" of future tension loss performance has to be considered "unknown".

Yet DWR is going to hold a "workshop" to do just that - to "try to" predict the future performance (to "consider the future reliability of the anchor rods"). DWR is playing with fire - here are the list of issues….

=== end clip from post 4192 see link for rest of engineering discussion.

[1] === "NBC investigates" news story - clips from link (regarding answer to "diagonal crack") (emphasis mine)

http://www.nbcbayarea.com/investigations/Records-Raise-Safety-Questions-Surrounding-Oroville-Dam-448318083.html

Over the course of the six-month investigation, the NBC Bay Area Investigative Unit spoke with two retired DWR insiders. The former employees, both engineers by trade, asked to be called by different names because they’re worried they could lose their pensions after speaking out publicly about what they say are serious problems at Oroville Dam. Both men recently retired from the department and say they were already aware of the issues found repeatedly in the inspection reports.

One man asked to be called “Mark.” The other asked to be called “Tony.”

“They're not addressing issues that have been pointed out and documented in previous Division of Safety of Dams inspection reports,” said Mark, who worked within DWR as a high-level administrator. Mark also worked as a field engineer on the State Water Project, of which Oroville Dam is a key component.

“My driving force [for speaking out] is out of concern for the public,” he said.

The other retired DWR engineer, Tony, says DWR’s delayed response to these issues may be due in large part to the agency’s culture.

“They have a tendency to try to reduce their maintenance costs by trying to do things themselves and not getting adequate technical help,” he said.

Tony says that approach could lead to another failure, like the spillway collapse in February, but he worries this time it would be worse.

“Here you'll have a catastrophic structural failure that's not going to allow you to operate the facility the way it's supposed to,” he said.

. . .[2]

Another major point of concern that engineers point to as problematic is a roughly 15-foot-long crack on the concrete at gate eight of the spillway headworks. Inspectors have been monitoring the crack with red spray paint, and a report from February 2015 indicates the crack appeared to have grown in length and needed to be addressed immediately.

“Cracks like that could really weaken the structure to the point where you could lead to a failure,” said “Tony,” the recently retired DWR engineer. Colson was more blunt about what that crack might mean when the NBC Bay Area Investigative Unit showed him pictures found in several inspection reports. “This really bothers me,” Colson said. “I think we could debate [its merits]. I really believe that it's a function of the trunnion anchorages putting stress and causing tension. The interior gates, they’re all balanced. But, that end one [gate eight], on both ends is asymmetry, not balance. So there's a twist. When you get a crack like this that’s growing. You don't know what it is.”

. . .[3]

Independent engineers who spoke to NBC Bay Area also point to another concern: cracks in the trunnion rods, or tendons that support the flood control gates. Initial tests conducted back in 2000 and repeated several times since then show 28 of the 384 trunnion rods used to operate the eight flood control gates, or 14 percent, have cracks of 1/32 of an inch or bigger. Six of those cracks are larger than 1/16 of an inch.

Both DWR insiders and external experts say that more precise and comprehensive tests of these cracks are necessary to better understand the issue.

The problem is something the agency has been monitoring for nearly two decades, says DWR insider “Tony.”

“Back ten-fifteen years ago when we were looking at it, these bolts were cracking and failing,” he said. “If this gate fails you're not going to be able to control the releases out of Oroville.”

=== end NBC clips

Fig. 1 16+ Foot crack (adding 14+ ft to 2+ ft growth extension - red paint marked) in 5 foot thick concrete Gate Pier number 10 (for Gate 8). Years of corrosion likely of reinforcement rebar evidenced from DSOD photos showing leakage (moisture) in this large crack. Resulting in a significant Structural Degradation to Gate 8? Explains "offset" shift in massive pier?

Fig. 2 Abnormal Gate operation by DWR. Operating specifications require gates to be opened in pairs together from the center outwards. Here Gate 7 is fully shut. A hydraulic force balancing "trick", using Gate 7, to get Gate 8 to properly open? Note: Gate 7 was opened last after Gate 8 was operating.

Fig. 3 Gate 7 and Gate 8 not operating during heavy 100,000 cfs flow. Extreme sharp hydraulic flow "bend" from Gate7&8 off causes huge whirlpool to form. An extreme abnormal Gate operating condition during the crisis. Was Gate 8 having problems? Is this why DWR had to operate Gate 7 off to open Gate 8 later? (Fig. 2).

Fig. 4 Army Corps of Engineers found up to a 70% variance in 39 year old anchor tendons at another dam. Scientists/engineers were mystified - steel phenomenon not understood - defied expectations of a fairly "even" loss. With Oroville's 50 year old anchor tendons, are they worse than 70% in losses & variance?

[KC Burke]

The issue is that the bulk of the population of California has too many concerns about the Kardashians to really devote a lot of time to understand what NBC is trying to point out.

[EarthResearcher333]

It’s unfortunate if serious News, that could have a disastrous outcome (New Oroville crisis or worse) for California, that has to compete with reality TV.

[WestSide70]

Been following the discussion here since the Metabunk forum went quiet and this is the first time I’ve decided to comment.

I’m puzzled about how the rest of the RCC is going to be laid as what is happening doesn’t seem to me to tie up with what DWR originally announced some months back.

At present, the RCC that fills the former “plunge pool” area appears to be laid flat/level and forms a sort of plateau. I reckon there’s at least 150 feet height difference between that and the cutoff wall where the RCC will meet the rebuilt section of the upper spillway. How will the RCC be sloped upwards to reach that point? I’d guess that at some point soon the fill will have to be sloped back across the plateau from the rock base that needs to be covered. Maybe that’s already started but I can’t detect it in any photos.

One thing I don’t get is how these new layers will bond with the RCC already there. Essentially won’t they end up with the existing flat area over which a triangular (viewed from the side) construct is created? And wouldn’t these be two distinct masses of material?

I might have been naive but I thought that from DWR’s original plan that this whole area would be sloped with the RCC built up in uniform layers.

[EarthResearcher333]

Hi WestSide70, As the continual process of new RCC layers are placed, the spillway "slope" edge is angled with a tilted blade on a dozer and compressed using a flat bladed head on a custom excavator.

The dozer has twin GPS type sensors on the outer tips of the blade. With that, and an accurate reference compensator, the dozer can lay the RCC at the exact grade of the dozer's location (elevation and grade).

The large plateau is this "moment" of maximum horizontal surface area during construction. This is a result of the "meeting" up of the deep and wide plunge pool that was/is the original location of the massive clay seam & highly weathered to weathered rock.

The constant application of RCC layers "bond" with the lower "lift" layers in the curing process. They keep the concrete moist to facilitate the "cure" even though the RCC is considered "zero slump" (structurally able to support instead of soupy traditional concrete).

A time lapse video would show the spillway slope angle growing as the horizontal area is rising vertically in placed lifts. When the elevation to slope progress (triangular side view), the volume of RCC to complete the last section will quickly reduce. But it does look like a slow progression of the spillway slope end in this phase of a large area plateau.

There should be a dramatic difference observed in the progress by mid-October photographs.

[WestSide70]

Thanks, now I think I get the picture - subject as noted below.

I saw the GPS-guided laying of RCC on the lower spillway section. I assumed that the individual lifts of RCC were being laid parallel to the underlying angled rock slopes rather than flat with only the lower end of each lift angled/chamfered. This may have been a wrong impression on my part although it’s what I thought DWR originally planned.

However above that area and in the RCC side walls the lifts are truly horizontal, at least to judge by the DWR photos posted today. In one of them it looks like a new lift on the “plateau” has been started and in another the markings on the not yet covered rock surface also indicate more horizontal lifts will be laid.

If this is right there’s a massive amount of RCC yet to be put down in 1 foot lifts and the whole construct will be very thick in places, particularly over the formerly vulnerable area of the plunge pool. I suppose it only makes sense for it to be laid flat for the dead weight of the material to be straight down on the base. (Sorry, I am not an engineer!)

[EarthResearcher333]

The massive amount of RCC, today, reveals what DWR should have done in building the original spillway. Original specifications called for digging down to strong bedrock. The original DWR spillway designers correctly required that excavation was to be done to where the excavation equipment encountered this strong and sound rock and could not excavate further.

Then, per the original spillway design blueprints, the deeper excavation of the incompetent (clay & unstable weathered rock) was to be back filled with concrete to the spillway "grade level".

Somewhere, someone changed the rules and ordered the contracting excavation workers to dig "only to spillway grade" and not dig deeper to this strong and sound rock.

DWR had full knowledge of the large clay/clayey seams as these were surveyed and marked well in the Final Geology Report spec 65-09.

So it can be inferred that the "changing of the rules or specs" may have been an engineering compromise (fatal to the spillway) that could save much cost and minimize a schedule impact.

This is how engineering disasters are created. They thought that hard pan clay could "hold" the anchorage of the slabs (30,000 psi pull test) without considering the water penetration and foundation erosion.

What is not in documentation is whether these decisions were made without consulting with the original designers. I've been in the middle of "engineering" tradeoff decisions, but the worst enemy to good decisions is when politics enters.

You cannot get away with fooling the laws of nature, even if politics & PR desires such.

Note: You can imagine the huge cost overruns, i.e. original budget, and schedule impacts if they properly dug out and backfilled these large areas with back fill concrete (placing the entire spillway on fresh bedrock).

Note2: Another side factor, during the original construction that came into play, was that the sharp edges of the fresh amphibolite rock were cutting into and "popping" the rubber tires of non-track construction equipment. That is likely why a "layer" of gravel aggregate was placed. However, this too was a poor choice as the material is erodible and would keep the spillway slabs from having a solid base all of the way to bedrock.

[janetjanet998]

We might have to turn some of our attention to the lake Okeechobee dike/Dam if it doesn’t stop raining in FL

[janetjanet998]

A thread for Okeechobee

http://www.freerepublic.com/focus/f-news/3591006/posts