Missing Detail of joint between wall footing and spillway slab.
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]
BUT... the picture in post #2273
http://www.freerepublic.com/focus/news/3524221/posts?page=2273#2273
certainly does appear to be the other way around...
I just don’t really know.
The only other thing I have to contribute at this time is that
somewhere ... outside of the sidewall, there would have been a
transition from the perforated pipe to a non-perforated pipe.
Missing Detail of joint between wall footing and spillway slab.
There is a slight "flaring" of the remains of the elbow in the spillway wall. This also indicates the bell couplings were aligned appropriately (upslope) - at least for this "missing pipe" section.
OK in the 2273 picture ...
I can’t tell which direction that pipe is running.
I think we are in agreement.
New Evidence reveals a better forensic insight into How & Why the Main Spillway likely Failed. Evidence strongly indicates a substantial presence and flow of water below the under slab drain pipe system. This could cause SubSurface Bedrock Weathering (weakening) and potential Scouring Erosion - besides "missing water from some drain section regions, such as where the blowout failure occurred.
The key to this new evidence was from finding a drain pipe under the centerline of the broken Upper Main Spillway. This Pipe "aligns" with its sister "mirrored" drain pipe for the other side/half of the spillway. This "alignment" is exactly where the left half of the upper spillway fractured in the most recent damage of the Upper Main Spillway. A "top view" of the left half of the fractured spillway shows an angled line ("herringbone pattern" angle) that is straight - as would a fracture follow in a "weak" line in the concrete - such as "thinning" by a drain pipe.
What was originally believed to be a "foundation pour" of concrete (prior posting), now reveals as a unique pattern formed by the concrete impressing upon a Polyethylene sheet of plastic (giving it a "smooth" texture in contrast with the rough slab fracture). The actual slab "was" thicker and is angled and emplaced upon the rough leveled bedrock. Since Vitreous Clay Pipe is fragile, the VCP pipe was likely placed upon a layer of gravel material to keep it off of the rough leveled bedrock. The exact composition of this layer of material is not known, but early pictures of the construction of the Upper Spillway reveal a smooth and leveled layer of packed aggregate. IF so, this would enable placement of the VCP pipe upon a smooth surface (packed aggregate). Images DO reveal that there was round rock emplaced around the sides of the Drain Pipe as some of this has been captured from concrete penetration during the slab pour.
A severe shortcoming of the drainage design is that water must flow or jump "upward" from the aggregate base to enable capture within the perforated drain. This jump "upward" could be up to 2.5 inches above the packed aggregate surface if the drain pipe is supported by the larger diameter Bell Coupling connections of the pipe (including the thickness of the wall of the pipe). This means that there is a minimum of 2 to 2.5 inches of downhill waterflow that the drain pipe would miss - i.e. it would flow below the pipe & not be captured. From the start, any water penetrating under the slabs would have a notable "escape" percentage as the Drains would miss its capture.Worse, this waterflow could have penetrated & scoured the packed aggregate base. This evidence is prominent in the images as waterflow "voids" and "seams" are observable.
The sum of these conditions, combined with a single rebar layer at the top of the slab, would be susceptible to the powerful hydraulic forces of "hydraulic jacking" (Stagnation Pressure), and forcing cracks above in the spillway. The thinning of the concrete slab by the emplaced Drain Piping forms a weak zone. Many spillway concrete images show cracks that follow the drain pipe patterns ("herringbone" pattern). During spillway operation, any waterflow deeper into the SubBase rock could lead to erosion in weathered rock. Voids and scouring erosion would place even greater stress on the concrete slab above.
Given the new evidence, the safety factor of the spillway could be calculated as resting upon limiting "hydraulic jacking", by limiting water penetration, and critically depending on the slab anchor bars to retain the spillway integrity against these forces.
Concrete Fractured along Drain Pipe Emplacement. Angles from centerline of spillway. Centerline point is where sister drain pipe meets/aligns heading to the other half of the spillway side.
Right side of spillway Drain Pipe (under slab) - aligns with left side drain pipe fracture line & angles from centerline of spillway.
West Drain Pipe (missing from slab fracture failure) aligns at the center of the spillway at the junction near the East Drain Pipe (circled under the slab).
West Drain Pipe outline created by Pipe + Polyethylene Plastic + round enveloping gravel. Waterflow seams and Voids deeper under Drain Pipe line. Gravel retained from penetrating concrete during pour.
Evidence of water flow region/seam below drain pipe (possible eroded seam) with gravel layer above deeper water flow area.
Evidence of Voids deeper under Drain Pipe (possible source of "water induced" weathering of rock over 40+ years from seepage, wet weather, infrequent spillway use,…). Large pockets of prior or recent weathered base rock may have eroded easily away from recent spillway backcutting.
Too bad that we have no photos of a slab break at a drain line.
Here’s some stuff from over at Metabunk that’s interesting from a 2009 maintenance project
Notice to Contractors
http://www.water.ca.gov/engineering/Contracts/09-14_Notice.pdf
Bid opening report
http://www.water.ca.gov/engineering/Contracts/09-14_Opening.pdf
Bid summary
http://www.water.ca.gov/engineering/Contracts/09-14_Summary.pdf
Two things I learned on the farm decades ago.
1. Drains should be lower than the area you are addressing. IE, they should of been placed in their own “trench”. No danger of the water having to go up to exit and no thinning of the slab.
2. You don’t use round “river rock” to keep a buried object in place - especially on a slope with a concrete pour over it.
And I am not a civil engineer, just a lowly mechanical engineer.
You are very well correct. Indications are is that the designers were hesitant to carve and then seal capture drain basin “grooves” in the foundation rock. In addition, the bedrock would have to have been sealed to resist/prevent water penetration into the bedrock until it reached the catch drain basin grooves.
Stagnation Pressure Failures of spillways weren’t well documented in the day. Only after 2 dams failed did this issue become a high consideration. However, Oroville was already completed. Then the issue became a discussion on if the anchoring system + crack/seam maintenance repairs would suffice. If not, the cost would be very painful to tear up and replace this (now proven) fatal design.
Engineering judgement in compromises or analysis has led to failures of great magnitude. In the case of a dam, with the destruction and damage it would incur to the State of California, businesses, agriculture, citizens, and even the federal government in bailing it out, the Engineering judgement MUST be such there are very high safety factors and redundancies.
What is worse, competent engineers knew the warning signs and should have raised the alarms years back. Instead, we are witnessing one of the greatest engineering failures in history. No excuses.
btw- good engineers are in all lines of work. I’ve known engineers that were just as good if not better in analysis of designs in cross engineering fields. In fact, a top Weyerhaeuser research PhD who was fearless. He had his degree in mechanical engineering, but was able to apply his skillset in many other fields. He also relied on talking to knowledgeable people to get their input. A fantastic person. Working with classified scientists & engineers, they too rely on sharing expertise. There needs to be more “grey beards” to pass on these characteristics to all so that the wealth of skill, drive, responsibility, and knowledge is given to those that are willing to grow and learn.
I will comment about the characteristics of various engineers who one might consider “good” due to their through application of disciplines. Often that analysis does not take into account their full performance ability.
I have worked with, supervised, employed, built from designs, used for forensic analysis, purchased peer reviews from, and otherwise utilized a large variety of engineers in almost 50 years of construction. Some of the best forensic engineers or peer review engineers, cannot be trusted to complete a design project.
What makes them strong on the task given can make them where they can’t meet a deadline, ever finish the documentation, understand the limitations of field construction, interface as part of a team or otherwise get a design done in a reasonable period of time.
Likewise, I have seen design engineers that design aspects of a project that would be great projects but the owner buys the initial design and then uses government inspectors and engineers and by cutting to original designer out of that administrative process misses the chance for field correction of misunderstandings or a faulty detail being corrected in ink rather than dollars.
Owners set the buying environment for the project. Concept, Budget, design, purchase, administration and deadlines are all set by the Owner. Owners allow a weak facet of that project flow to go off course.
Several new pertinent pics today.
https://pixel-ca-dwr.photoshelter.com/galleries/C0000OxvlgXg3yfg/G00003YCcmDTx48Y/Oroville-Spillway-Incident
Also,
Oroville Dam: Photos taken weeks before spillway broke show something wrong
PUBLISHED: March 11, 2017 at 5:14 am | UPDATED: March 11, 2017 at 5:19 am
Oroville – Something was wrong with the Oroville Dam spillway weeks before the Department of Water Resources noticed a hole in the concrete.
Two photos taken by photographers from this newspaper show discoloration and possible damage to the concrete of the spillway at the spot where a gaping hole opened Feb. 7. Those pictures were taken Jan. 13 and Jan. 27.
When asked for a response to the photos, California Natural Resources Agency deputy secretary for communication Nancy Vogel wrote in an email to this newspaper, “Oroville dam was frequently inspected by multiple state and federal agencies. Reports of those inspections did not reveal any major causes for concern. DWR will soon name a panel of independent experts to investigate the cause of the main spillway failure and ascertain if such a failure could occur again. We hope that what we learn about the cause of this incident and how to prevent it elsewhere will help dam owners around the world.”
She did not ask to view the photos.
So why didn’t the water agency see what the pictures show?
The answer may have to do with inspections of the dam and spillway.
Before Feb. 7, the last inspection on the entire spillway structure by DWR was Feb. 3, 2015. Despite claims the department performed inspections twice per year, the spillway had not been fully inspected with operations and maintenance workers on the concrete in just over two years, according to a DWR spokeswoman, before a worker noticed the concrete breaking up on his way to work this Feb. 7.
After the February 2015 inspection, there were inspections of the dam by the DWR in July 2015 and August 2016, but those didn’t involve workers walking on the spillway getting a close look.
“During annual inspections, the Oroville Dam, and its appurtenances, have been repeatedly found safe for continued use, which includes the emergency spillway,” Vogel wrote.
The reason for the lack of complete spillway inspections is, presumably, safety.
“DWR (operations and maintenance) could not inspect the flood control spillway by walking it immediately before and after the spillway was used in March 2016, because the lake elevation was too high — there was water behind the radial arm gates at the top of the flood control spillway,” Vogel wrote. “Typical DWR safety protocol does not allow people to walk in the spillway when water is against the radial gates on the lake side.”
Nearly a year ago, on March 24, 2016, the flood control gates at the top of the spillway opened for the first time in five years.
The spillway was not fully inspected by DWR before or after that event. It took nearly five months before the department checked the dam structure in August 2016, and only a visual check was performed on the concrete spillway.
The Federal Energy Regulatory Commission inspected the dam May 25-26, 2016, and found nothing wrong at that time. But because DWR’s July 2015 review was a joint inspection with FERC and the July 2015 DWR review did not fully inspect the spillway, it’s unclear whether the commission’s annual 2016 inspection fully reviewed the spillway.
A five-year review board also didn’t find anything wrong.
“The most recent 2014 Oroville Dam federal and state board of independent experts concluded that there was no reason to expect either spillway to fail under operation,” wrote Maggie Macias of the Department of Water Resources public affairs office.
Two years after that board met, water was released for the first time in five years. Three years after the board met, the spillway broke and the structure was ruined. It has been more than a month, and the cost is estimated to be $4.7 million per day, or about $150 million to date.
Early rough estimates by DWR acting Director Bill Croyle put the cost to either fix the existing spillway or build a new one are between $100 million and $200 million.
This reveals that there is a concern regarding this section of the upper main spillway where they want to carefully monitor any early warning sign of further downslope sliding. Erosion has compromised some of the lower end of this wall's anchor bars, including significant voids of subsurface rock.
It was expected that drilling/coring would be done. This allows access below the spillway concrete slab to subsurface rock and zones. A common practice to facilitate pumping of "backfill" material to repair voids or to improve the integrity of subsurface conditions (pumping grout). The image denotes a light blue colored "line" marked on the concrete slab. (note: this line angles to the spillway wall, not unlike the drain pipe alignment).
A "two piece" black and white striped optical target has been bolted to a Main Spillway Side wall. Any further movement would reveal a shift in the black and white stripes. This wall & nearby main spillway slab has already shifted a number of inches as noted by the significant width of the gaps that were repaired.
= = clip (my emphasis):
When asked for a response to the photos, California Natural Resources Agency deputy secretary for communication Nancy Vogel wrote in an email to this newspaper, “Oroville dam was frequently inspected by multiple state and federal agencies. Reports of those inspections did not reveal any major causes for concern. DWR will soon name a panel of independent experts to investigate the cause of the main spillway failure and ascertain if such a failure could occur again. We hope that what we learn about the cause of this incident and how to prevent it elsewhere will help dam owners around the world.”
= = end article clip
"They" already know what was wrong... so do other "dam owners around the world" too, by now.
Wow. Greater than this "engineer" failure?
I see lawyers... Lots of lawyers... I see litigation, claims...
I can’t help but wonder about the sheer vastness of scale of this project dealing with such incredible masses of water and dynamic force.
At the time, was there anything comparable to this project meant to artificially contain such force and scale of dynamic-water force?
One wonders if part of the problem may have been possible miscalculation of the incredible, tremendous force of water at full load on this enormous spillway.
Hard to see how that slab stays in place under the two months or more of constant pounding its likely to see this spring.
When/if it goes the slabs to its side are likely to go shortly thereafter.
If it goes, let’s hope the next slab up from there stays put. It’s easy to see a domino effect if the slabs in general are not anchored well enough for that slope and volume of water.
Wildcard: If the rock underneath the slabs has been exposed to “weathering” over the last few decades it may no longer be as strong as it was when the spillway was first built. Based on the great pictures you have so kindly provided, portions of that rock look pretty fractured.
Another wildcard: Significant new erosion is certain if that slab goes. Lots more debris in the channel. At some point the generators would have to be shut down again, leading to the need for even higher flow through the spillway. A bit like an unstable feedback loop I heard about recently...
Hi KC Burke, Well stated. By the wisdom of your words, you embody what leadership qualities & characteristics that fearless technical people need to rise to - even if it is realizing cleaning house on some engineers. This is the negative side, but necessary at times.
General Norman Schwarzkopf, in his book, wrote about the frustrations he faced in the infrastructure of leadership & conditions (after the Vietnam war). As a very driven person, he was at a point of resigning from this weariness. A close peer, stated to him as to who will fight against all of this for the good soldiers that need him. Schwarzkopf realized the truth of it and stayed in the service.
My response using the word “good” was to uplift those that may feel limited by the modern day meme “are you an expert”? Too often I’ve seen this ploy used in a method to criticize or dismiss input from people outside of an engineering circle. Some of the greatest scientists in history were self taught in new fields of learning. Nowadays, the turf has to be protected... thus the “who are you to criticize..are you an expert?...” ploy.
I’ve personally witnessed scientists/researchers seeking to sabotage another scientist/researcher in revenge for a negative peer review on a proposed research project that was shot down. Yet, you have to fight through this type of “bleep” - and even “mentor” others in the challenges you so aptly wrote of.
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