Skip to comments.Emergency: California’s Oroville Dam Spillway Near Failure, Evacuations Ordered
Posted on 02/12/2017 4:26:47 PM PST by janetjanet998Edited on 02/12/2017 9:33:58 PM PST by Admin Moderator. [history]
The Oroville Dam is the highest in the nation.
Seems the Upper Main Spillway has Extensive crack lines in the slabs. Nearly every drain "line" shows surface repair "patching" over the cracks in the slabs. Photos from 2010, when a thin layer of water was present in the spillway chute, reveals the significant extent of the drain-emplacement-thinning slab cracking problem. The Images reveal the repaired cracks as whitish lines of the newer/fresh patch material over the cracks. Cracks nearly every 20 ft (10 crack lines across the width of the spillway for every 4 slabs) for the length of the ENTIRE spillway.
History of posts, discussion, & reference photos:
Extensive Patched Cracks start at Gates of Upper Main spillway (first image). (Oroville's slab design only had a top layer of rebar. Oroville's slab design created up to a 60+% reduction in thinning of the slab from the placement of intervals of drain pipes & gravel - forming a inverted "V" of non-concrete. Aggravating the Oroville design was the lack of a lower layer of rebar in the slab.)
Next segment: Extensive Patched Cracks of Upper Main spillway (second image)
Third segment to near Towers where existing broken section of the Upper Main Spillway.
Blowout Failure region (would be at center of image) showing the patched drain line induced cracks. notice the tree growing directly adjacent to the spillway wall just below the "blowout area". Tree is on the side where the drainage canyon formed.
History information (updated):
The "angled cracks" in the spillway concrete slabs and the "jetting" of water out of the sidewall drains should have set off alarms years ago regarding the integrity of the Oroville Main Spillway.
Why? Both of these signs indicate a serious known failure mode in spillways from Stagnation Pressure (via cracks/voids/water). Two prominent examples are Big Sandy Dam, Wyoming, 1983, (spillway chute failure) - Dickinson Dam, North Dakota, 1954 (spillway chute failure).
Excessive water beneath the concrete slabs causes a very powerful effect dubbed "hydraulic jacking" from under the slab (think of a hydraulic car jack). Called in engineering terms: "Stagnation Pressure" & "Stagnation Pressure Failure".
How does the water get under the slabs? The most potent source is from pressurized water from the top of the spillway being forced below through cracks & non-sealed seams in the concrete chute. The more cracks, the more water, the more water, the greater ability of this water to "wash or erode away material" under the slab. Erosion leads to "voids". Voids + "hydraulic jacking" lead to greater stresses on the slab, thus "cracking".
How do you protect from "Stagnation Pressure Failure"? Drain pipes are placed under the concrete slabs to collect & drain any leakage, thus preventing a pressurized water layer under the slab. A well sealed & healthy spillway would have very little waterflow out of the drains. The Oroville Main Spillway slab design is less than modern standards. (1) Modern slab designs have rebar in the top layer and the bottom layer. Oroville's slab design only had a top layer of rebar. (2) Modern slab designs retain the full thickness of the slab by placing drain pipe & pervious material below the slab. Oroville's slab design created a 61% reduction in thinning of the slab from the placement of intervals of drain pipes & gravel - forming a inverted "V" of non-concrete. (3) Aggravating the Oroville design was the lack of a lower layer of rebar in the slab. Thus (1)(2)(3) should have set off alarms when high waterflow was "jetting" out of the drains.
And no one will be held accountable.
Definition of government (a hybrid of Melvin Udall's definition of women from "As Good As It Gets"):
"Government is free enterprise after you take away reason and accountability."
My apologies to all dedicated and able folks who have worked on government projects. Individual efforts can be golden, but from what I've seen throughout history, the more the government controls the project, the greater the danger and the less the accountability.
Just a few quick notes on the power line situation. The following image was taken prior to the event. This is the original transmission line configuration...
In the original configuration, there are 3 ea. 230 kilovolt transmission circuits that tie to the plant's switchyard and a transmission switching substation roughly west of the plant. 2 circuits are on the lower (downhill, closest to the erosion) tower and 1 on the upper tower. Typically, lines of this voltage are capable of carrying 500-800 Megawatts of power. The plant is rated, with all 6 units on line at full output, at 819 MW. Basically, the station is designed to have 3 circuits to allow for contingency loss of one, or for removing one line from service for maintenance.
Recently, they re-arranged the conductors and removed both circuits from the lower tower in preparation for the possibility that it could be lost to erosion from further damage and use of the main spillway. This resulted in only 2 instead of 3 circuits connecting the plant's generation to the power grid, both of which are located on the upper transmission tower.
What they're doing now is installing "temporary" wood poles to allow the relocation of one or two circuits farther up the hill to less risky ground. I use quotations on "temporary" because in the power industry, things like this tend to stay in service for decades. What this will allow is to have the full complement of 3 circuits tying the plant to the grid (which will come in handy when they finish maintenance on the 6th generating unit), and will take one or two circuits well out of harm's way if the main spillway experiences more damage or erosion.
They are also removing the lowest tower, and it appears that they're digging up the footers as well, so a tower is not likely to occupy this spot again. Image from ER333's post above...
EarthResearcher333, you probably already said this, but were those four pictures taken recently or years ago? If these are recent pictures, is there an old picture(s) that shows what should have been a red flag?
BTW, great pictures, analysis and updates.
If there’s a hearing, maybe they’ll call on you to testify. :)
...if you don’t like that prospect
According to ER333, the photos in # 2421 are from 2010.
Regarding the 4th image in #2421:
“...notice the tree growing directly adjacent to the spillway wall just below the “blowout area”...”
The fairly regular crack pattern looks different at that location.
Here is a copy of the actual "Notice to Contractors" Bid request by DWR detailing all of the Repair work requirements for the Oroville Dam Main Spillway (bid includes 3 other dams).
Now compare this to the 2017 post blowout "emergency repair work" being done on the spillway. Identical wording. (except for the shotcrete work, over a million cubic yards of river debris excavation, 180,000 people evacuated, 4.7 million dollars a day in emergency work, and needing a "new spillway").
Before any contractor could bid, they had to personally attend an inspection of the spillway. The original estimated cost for this project was generated by a DWR engineer who defined all of the work required, including his own cost estimate for each category of repair work detailed in the Bid request.
You would think that SOMEONE would start putting 2+2 together on the extensive herringbone pattern fractures for the full length of the spillway.
btw- the 2009 bids submitted ranged from $776,055.00 to $954,475.00 for the complete Oroville spillway repair work. Emergency repair work is costing $4.7 million dollars a day.
note: abb credit for originally noting the 2009 bid request information.
“...2009 bids ranged from $776,055.00 to $954,475.00
for the complete Oroville spillway repair work ...”
But what? ... None of the bids were accepted?
Am I seeing wet spots on the shot-create vertical wall at the end of the broken spillway?
(last picture in that post)
That wall is not going to hold up if they did not put in proper drainage.
The wet spots are from the drilling activity. There are multiple drill locations that had spill coming over the concrete lip and down the face of the shotcrete. Indicators are there have been at least seven drillings in an "array" pattern.
The water in middle section of the spillway is the same type: water running off of the surface of the lip of the spillway and onto the face of the shotcrete. They may have drilled at that location too, but the zoom does not show any residual indicator (other than an orange safety cone).
"That wall is not going to hold up if they did not put in proper drainage."
White PVC type drain pipe was emplaced into the backside rock before the shotcrete was applied. The drain pipe has been cut flush since then and is less visible unless you have a good resolution pic to zoom with (even then the flush cut ends are pixellated). The pic in the FRpost below shows four of these pipes protruding under the scaffolding. This is before they were cut flush to the shotcrete surface. (zoom indicates near six total pipes installed).
Regarding the "bids" and awarding. Post summary information indicate that the award went to the lowest bid cost of $776,055.00.
Hi Abb, thanks for the info on the tailings or "borrow" area.
= = For those that are curious: I believe "hydraulic mining" and "tailings" are mixed metaphors here. Hydraulic mining is usually done in higher elevations to strip overburden & "pay" off of a hillside or mountain. They used high pressure water jets to wash and erode material down hill. This material is then "sluiced" for gold.
Dredge Mining is different. Dredge machines are ideal in areas that are low lying historic river bed areas, such as a type of a "basin". The "basin" where this "tailing" material was collected for the dam follows the historic flow of the Feather River. The river would have "meandered" over time in this basin, including wide swath flow from periodic floods. Gold deposits settled in this basin area and would have settled at/near the bedrock layer.
You notice in the images you have linked to that this area remains green from the ready presence of water from the Feather river. It's a low area formed by the historic dredging machines which followed the gold deposits of the river.
Gold Mining Dredge machines are simply "floating barges". These monster machines had large chain of "bucket lines" that are designed to dig and scrape down to the bottom to the hardest layer of rock (fresh bedrock). Weak weathered rock would be broken up and gathered into the buckets as they had chisel type edging on the front edge of each bucket. The overburden of soil & clay would also be gathered into the chain link type of bucket system. Materials are then washed, separated, and "sluiced" for gold inside the dredge. The unwanted rock material is conveyor belt dropped out the back end of the dredge. Soils and clay are deposited out the back in a waterflow chute.
The dredge swings from side to side using cables and pivot anchor feet. This creates a back & forth pattern of rock pile tailings behind. After all of the gold has been "dredged", the remaining sight would have been a mass of rock tailings equal to the area of the entire gold basin. Re-claiming this material for the Oroville Earthen Dam was very unique as it had all of the material types required - especially the clay. (the clay was used for the thick and tall impervious core -i.e. water barrier- of the earthen dam).
Gold Mining Dredge (bucket chain deep in the water & to the right of machine). The "tailings" conveyor structure (left) deposited washed rock cleaned of gold. The soils and clay were dumped out the back ends of the dredge (you can see the little spillway outlets next to and below the origin of the tailings conveyor system).
Side note: Interesting that this old 1966 archive newspaper link had a story in the middle of this page reporting on a widespread observed (witnesses) glowing light - thought to be a UFO... only to be reported by authorities (FAA and Air Force) as "Glowing Gas" and not a UFO..... Right out of the X-files. :-)
Article clip: "The FAA said its stations at Red Bluff, Marysville, Oakland, Fresno and at Edwards, Travis and McClellan Air Force bases sighted the illumination as did airplanes over the Pacific 500 miles west of San Francisco."
Re: post 2415 - worth a watch if you didn’t already view it. The river valve system would be of significant help right now, although probably only to buy more time to make temporary repairs. However, it’s reportedly out of service for “fire protection upgrades” right now. Seems to me that this would be a good time to expedite that work, or put it on hold, but what do I know...
The link, again...
Well, I guess $3/4 million doesn’t really buy much these days...
The repair contract was awarded to: Truesdell Corporation of California, Inc. 1310 West 23rd Street Tempe, AZ 85282 on August 17, 2009. The spillway images were taken July 9, 2010. This gives a period of close to 11 months for the construction repair work to be completed before the image shots.
Truesdell Corp has a history of high tech experience and repair of concrete structures including dams & dam structures. I would imagine they completed the project before the images, although I've been unable to find a specific completion date. (see Clips below on Truesdell Corp website).
= = = Truesdell Corporation: Reference info & experience:
The Truesdell Corporation has built a solid reputation nationwide by providing quality repair, restoration, strengthening, protection, and maintenance of concrete structures. Services range from initial diagnosis to final completion. Headquartered in Phoenix, AZ, Truesdell has successfully completed a wide variety of national and international repair projects ranging from high-rise buildings, nuclear power generating plants, airports, residential projects, water treatment facilities, and a sizeable amount of public agency and DOT work.
Among its more notable projects, Truesdell has completed the Arizona Dam Spillway Rehabilitation projectrecipient of the prestigious Award of Excellence presented by the International Concrete Repair Institute (ICRI). This $2.5 million project consisted of repair and restoration of two spillway structures situated near the top of a damthat houses a hydroelectric power generating station. It was a significant project due to the remote location, difficult access, and the multitude of methods and materials specified and used. Products included lithium nitrate to treat alkali-silica reaction (ASR), super-low-viscosity (SLV) epoxy for micro crack healer-sealer, expandable chemical urethane to stop multiple leaks, and a variety of conventional products including bagged dry-mix shotcrete with added fibers. The spillways were situated on a shear 300-ft-tall cliff, where the only access available was from the top of the dam.
Construction began in the summer with temperatures on the spillway slab reaching 130 °F and continuing into the winter where mild freezing conditions were encountered. Dry process shotcrete was determined to be the most efficient and cost-effective method to perform the repairs for logistical and quality reasons. Ultimately 11,000 bags of material were placed successfully without a single loss-time injury or accident, even though much of the work was performed from ropes, swing stages, and custom system scaffolding.
I think that the primary problem with this spillway, and something that would probably cost more than 775,000 to repair, involved the underlying earth and fill, particularly under the section that failed. By all rights, the section below that (although battered by the 100,000 CFS flows crashing into it) as well as the area above were built on solid bedrock. Despite the cracking, the upper part has held up fairly well.
So it is a given on the forces of the Stagnation pressure as it has proven out on the slab evidence. Recent emergency repairs will help keep water from penetrating underneath, thus helping to reduce the "hydraulic jacking". But, there may be other source paths to the water penetration.
The original designers stated that the upper spillway area has rock that is not of good quality. They put in extra effort using rock bolts, chain mesh, and pigtail bolts to fortify the anchoring in these seam problem areas.
Spalling or "chips" in the upper spillway also reveal the "hydraulic jacking" forces as the seams chipped to the layer do the top level rebar (at/near). This again tends to reaffirms the upward bending stresses on the slab from Stagnation Pressure "hydraulic jacking".
So this equation is a balance of how much structural integrity has been affected in weathering of the "weak rock areas", of how much water penetration will recur, and how strong is the anchor bar matrix. Stagnation Pressure Failures have taken out many spillways. Oroville DWR engineers and/or management should have signaled the alarm years ago on these "spillway signs" - instead of putting out contracts to band-aid the fundamental design flaws.
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