Moonbeam Canyon was carved in weeks when it should have taken centuries.
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.
Apparently the operating plan is to use the main spillway to drop the res level to just above the spillway use min level.
Then shut off flow and go excavate the river below to allow the powerplant to operate. Repeat as needed.
It's usage, in a pressurized hydraulic water flow, is a very unwise choice. The transition of Bentonite into a "jelly-like mass" from hydration, forms a non-structural component. To "Stuff" this into void areas under the concrete spillway slabs - with a known high pressurized "wash" flow does not make any sense. Worse, the void areas formed under the spillway slabs from hydraulic erosion from a severely deficient drain design*. Emplacing Bentonite into these void areas, especially near the drain pipe voids, could assure bentonite entering and plugging the drains (a low pressure transition point).
The *ONLY* effect bentonite could yield is a superficial one. That is, when the spillway is not in use - in the dry years - bentonite could seal the water weepage (unpressurized state) that was coming out of nowhere in places along the spillway.
There are modern techniques to dealing with the art of concrete spillway crack repairs - such as super-low-viscosity (SLV) epoxy for micro crack healer-sealer and expandable chemical urethane to stop multiple leak sources.
The last issue is that "voids" represent a structural stress risk to the spillway concrete slabs from the extreme weight of water. A "gel-like" state of hydrated Bentonite is not a structural bearing material. A "gel-like" state in voids worsens the flexure stresses on the already flawed "thinned" zone slab design. More flexure means continued failure of concrete surface patching, leading to re-cracking of the patch in addition to surface stresses exposing the seams to spontaneous spalling ("chipping").
Bentonite on a spillway is just "lipstick" to make something look good when not in use.
*Drains emplaced "upward into the slabs" severely "thinned" the concrete slabs. The slabs severely cracked above nearly every single drain line run on the entire spillway. The 50 yr old spillway design does not have seam "water stops". The spillway concrete pour was emplaced upon a washable compacted gravel bed. Thus large crack volume + seams area per slab drives a pressurized waterflow from spillway operation.
Kewel
Quite possible, perhaps even likely, though there is a LOT less debris present this time around since the loose material has already been eroded away.
Another possibility in relation to the plant is the re-routing of the power lines. We only get to see the pictures of the linemen working on assembling the "temporary" structures, but there are also crews working in the power station at the base of the dam. It is quite possible that one or two of the original 3 lines have been taken out of service for a couple of days to allow them to re-terminate the new lines. They cannot do that work while energized. That would limit the amount of power that the plant could produce due to the lack of full line capacity.
It would make sense to coordinate that work with the operation of the spillway as much as possible.
THEY FOUND THE FAILURE CAUSE!!
As the repair bill for the crumbling spillway and the emergency response approached $200 million last week, DWR acting Director Bill Croyle — who has exhibited a troublesome tendency to downplay the incident since it started Feb. 7 — used an inappropriate analogy when asked at a press conference whether the crisis could have been prevented and who was responsible.
“This happened. Stuff happens,” he said. “So, you get a flat tire on your car, you run your car out of oil. I mean, these things happen. We’re going to get into how this happened, why this happened.”
tell me you are being sarcastic, right?
Lol, yes. The entire editorial is a decent read. Every once in a while, the Drive-by Media gets it, and actually performs a worthwhile public service. It appears the Mercury News has figured out the folks at DWR are trying to stall, but aren’t buying it.
Expert consultants are now revealing what should have been figured out years ago. Soon, there will be hard questions asked as to why these issues were not figured out and fixed when they had the opportunity. This article provides more detail on the "spillway design flaw" revelations from experts.
BTW - NO Bentonite clay was used. The "Clay" usage was from "surface grade filling in depressions" in doing the original construction.
Damage, design flaws in Oroville Dam spillway point to lengthy repairs, consultants say
Article clips: (emphasis mine)
1. "Above the crater, consultants described design problems in the intact portion of the chute that are so “gross and obvious” they will have to take priority this year, said J. David Rogers, a dam expert from Missouri, who reviewed the report at The Sacramento Bee’s request. Rogers said the problems the consultants described were so egregious he was surprised the spillway didn’t fail decades ago.
2. "It calls into question the whole design of what’s still there in the upper section,” said Rogers, a professor at the Missouri University of Science and Technology."
3. "The report contradicts DWR officials’ assertions that the 3,000-foot-long spillway can be completely repaired in time for the next rainy season."
4. "The expert panel’s conclusions, based on a review of reports and an on-site inspection earlier this month, provide a first-ever accounting of structural and design problems that might have caused the spillway to essentially split in half Feb. 7."
5. "The consultants described seeing troubling amounts of water flowing from underneath the structure, concrete that was far too thin and dangerous gaps underneath the foundation on which the massive concrete chute sits."
6. "Notably, the panel expressed concern that the concrete chute is only a foot thick, and less so in some places. DWR built the spillway on an uneven mountainside and in some spots used compacted clay to fill in the depressions in the rock foundation beneath the concrete. The consultants described finding evidence of “a number of repair instances” in which portions of the chute were cut away in order to “fill voids beneath the concrete.”
7. “This calls into question whether the portions of the slab that appear undamaged by the failure should be replaced during the restoration,”
8. "The panel report also said that while touring the spillway, consultants spotted “extraordinarily large” amounts of water gushing out of drains designed to move water out from beneath the intact portion of the chute. The water was flowing even though the spillway’s gates were closed and it wasn’t raining,.."
9. "Paul Tullis, a dam safety consultant ... agreed that it found the original design and construction inadequate."
DWR's response to the FERC expert consultants statements:
10. "Bisnett, the DWR spokeswoman, said the agency plans over the long haul to “rebuild or replace” both spillways “with the latest design, technology and materials, with public safety as our top abiding concern.” She added that the main spillway “met the design and construction standards of its time half a century ago. Through the decades, the spillway has been inspected repeatedly and been found to be well maintained and satisfactory for continued use.”
I'm sure the experts will have something to say about "competent" recognition of alarming conditions (seemingly a non-issue with CA inspectors) - the money quote: "the spillway has been inspected repeatedly and been found to be well maintained and satisfactory for continued use".
Temporary Fix For Oroville Dam Spillway Could Involve Making Water Jump Gap
By Drew Bollea
March 23, 2017 11:10 PM
SACRAMENTO (CBS13) — Officials with the Department of Water Resources are mulling over temporary and permanent solutions to the Oroville Dam Spillway crisis. They were presented with the findings from a group of engineering experts who analyzed the problems and potential fixes to the beaten and battered spillway.
“I think it’s one of the most urgent infrastructure things you could imagine,” said Jay Lund, a civil engineering professor at UC Davis.
Lund read over the panel’s report, which outlines issue with the spillway and suggested solutions.
“They point out that there is potential for additional things to go wrong on the remaining portion of that spillway,” said Lund.
“It’s a minor miracle that it’s working pretty well given its state,” he continued.
The panel identified faulty piping, deteriorated concrete, and cracks that may have weakened the spillway foundation. Now they’re proposing some unique solutions.
One temporary recommendation is building an angled flip just above the collapse site. If water needs to be released from the lake down the spillway, the flip would launch the water away from the hole, preventing further erosion.
“I think it makes a lot of sense,” said Lund.
Lund says it’s a typical practice at other dams, but this would likely be the first attempt to jump a hole.
“They’re not holding back,” he continued.
A spokesperson for the Department of Water Resources says “We are in the process of analyzing alternative approaches, both temporary and permanent”
Experts are suggesting a two-phase solution. A fix through this year, with a complete rebuild of the main spillway in the future.
“It’s just a matter of how much time it takes and to what expense you want to go,” said Lund.
I am speechless. Where do they find these idiots?
(note: the "flip" buckets at the end of the original spillway looked to have plenty of hard Amphibolite to anchor to)
*The end of the broken spillway revealed a heavy layer of weathered rock.
What is Amphibolite?
Amphibolite is a coarse-grained metamorphic rock that is composed mainly of green, brown, or black amphibole minerals and plagioclase feldspar. The amphiboles are usually members of the hornblende group. It can also contain minor amounts of other metamorphic minerals such as biotite, epidote, garnet, wollastonite, andalusite, staurolite, kyanite, and sillimanite. Quartz, magnetite, and calcite can also be present in small amounts.
How Does Amphibolite Form?
Amphibolite is a rock of convergent plate boundaries where heat and pressure cause regional metamorphism. It can be produced through the metamorphism of mafic igneous rocks such as basalt and gabbro, or from the metamorphism of clay-rich sedimentary rocks such as marl or graywacke. The metamorphism sometimes flattens and elongates the mineral grains to produce a schistose texture.
Amphibolite
Amphibolite: Some amphibolites are greenish, as determined by the color of the amphibole minerals. This specimen is actually an igneous rock. Some geologists call an igneous rock composed primarily of amphibole minerals an amphibolite or “hornblendite.” USGS image.
Uses of Amphibolite
Amphibolite has a variety of uses in the construction industry. It is harder than limestone and heavier than granite. These properties make it desirable for certain uses. Amphibolite is quarried and crushed for use as an aggregate in highway construction and as a ballast stone in railroad construction. It is also quarried and cut for use as a dimension stone.
Higher quality stone is quarried, cut, and polished for architectural use. It is used as facing stone on the exterior of buildings, and used as floor tile and panels indoors. Some of the most attractive pieces are cut for use as countertops. In these architectural uses, amphibolite is one of the many types of stone sold as “black granite.”
Some amphibolite deposits, such as the one at Gore Mountain in the Adirondacks of New York, contain significant amounts of garnet. If enough garnet is present and of proper quality, the amphibolite can be mined and the garnet recovered for use as an abrasive.
http://geology.com/rocks/amphibolite.shtml
“Comment #2,634 Removed by Moderator”
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Uh-oh, someone must have used the word “Dam”!
Moonbeam Canyon was carved in weeks when it should have taken centuries.
However, the erosion debris field reveals how materials became collision shatter instruments from the significant forces of hydraulic turbulence in the blowout flow (canyon). Thus, all of the broken spillway concrete, all of the highly fractured weathered rock, and even ultimately "shattered" pieces of the amphibolite essentially "jackhammered" a "fresh rock erosion" down the canyon.
Throughout all of the geologic reports, the definition of "fresh rock" and "adequate bedrock" applied to the hard amphibolite (and was noted as Amphibolite).
The article discussed “building an angled flip just above the collapse site”, not at the end of the spillway.
on the ground in that area
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