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.
Northern California may face ‘significant risk’ from Oroville Dam
AN FRANCISCO (AP) —
California is courting a “very significant risk” if a damaged spillway on the nation’s tallest dam is not operational by the next rainy season, and the state’s plan leaves no time for any delays, a team of safety experts has warned in a report obtained Wednesday by The Associated Press.....
Water was even seeping from seemingly undamaged stretches of the main spillway, the experts said. Only 12 inches thick, the concrete spillway is heavily patched, at some places by clay stuffed into holes below the concrete.
“This calls into question whether the portions of the slab that appear undamaged by the failure should be replaced,” the consultants said, raising the prospect of a much bigger long-term repair job.
Fully repairing the spillway will likely take two years, the consultants said. California still has at least a month left in the current, unusually wet rainy season. A record snowfall in the Sierra Nevada will send more and more runoff into Lake Oroville as weather warms.....
http://www.kcra.com/article/heres-what-flying-over-mars-might-look-like/9172131
Northern California may face ‘significant risk’ from Oroville Dam
AN FRANCISCO (AP) —
California is courting a “very significant risk” if a damaged spillway on the nation’s tallest dam is not operational by the next rainy season, and the state’s plan leaves no time for any delays, a team of safety experts has warned in a report obtained Wednesday by The Associated Press.....
Water was even seeping from seemingly undamaged stretches of the main spillway, the experts said. Only 12 inches thick, the concrete spillway is heavily patched, at some places by clay stuffed into holes below the concrete.
“This calls into question whether the portions of the slab that appear undamaged by the failure should be replaced,” the consultants said, raising the prospect of a much bigger long-term repair job.
Fully repairing the spillway will likely take two years, the consultants said. California still has at least a month left in the current, unusually wet rainy season. A record snowfall in the Sierra Nevada will send more and more runoff into Lake Oroville as weather warms.....
http://www.kcra.com/article/heres-what-flying-over-mars-might-look-like/9172131
Northern California May Face Significant Risk From Oroville Dam
This statement was from independent expert(s) selected by the state (CA) at the request of the Federal Energy Regulatory Commission (FERC). Good Grief - who in their right minds would be stuffing clay under the spillway slabs?
The admission of this significant point, by independent experts requested by FERC, is very damaging. The act of "stuffing" implies an intentional act of emplacement. DWR engineers must have been aware of this. My oh my.
A few clips from the KRCA article (my emphasis):
....
"Water was even seeping from seemingly undamaged stretches of the main spillway, the experts said. Only 12 inches thick, the concrete spillway is heavily patched, at some places by clay stuffed into holes below the concrete."
.....
"The experts called it "absolutely critical" that the dam's state operators not use the faulty emergency spillway again."
.....
"The state should start work now redesigning a new emergency spillway for the 50-year-old dam, the consultants said."
....
Do you think some misguided person thought some bentonite clay would stay in place ignoring drainage?
Should have copied you my 2605 question as well.
I have no idea (answer to your query). The only link I can think of, by a person or person(s), is how Bentonite is used as a low permeable barrier in lining landfills. But to be amiss in knowledge of the pressurized drain waterflow dynamics is very revealing.
I can't imagine an experienced contracting company specializing in dams and concrete spillway repairs would ever do this (unless there is a formulation & technique to a void repair technology that may have been interpreted as a "clay" by error). If you exclude the experienced contracting concrete specialist companies, this leaves DWR engineers directing custom repairs.
I believe you nailed the thinking. The constant repairs of leaking cracks in the concrete would drive to this solution space (thinking). Without understanding the cause of the constant re-cracking (repairs) from slab flexure (top layer rebar only, drain design thinning of the slab, high levels of subslab waterflow, hydraulic jacking..) a flexible type of Sodium Bentonite water seal fits.
The irony is that pressurized waterflow & other underslab waterflow would defeat this approach. It will be telling to find out what more information comes out from the independent consulting experts (FERC recommended).
The MS was improperly maintained, the ES was poorly designed, river valves have been inoperative for years, somehow water entered the powerhouse....
What a mess.
More likely governor Moon Beam's high speed rail project.
Regards,
GtG
The use of bentonite would also explain why there were a few drains not draining at all with apparent hydrolic build up of water pressure above.
For others — bentonite clays can be used as pond liners or other use where you don’t want water to run like sealing a well.
As of 4 pm California time on March 23rd, the lake level is at 846 feet
It has dropped 2 feet in the previous 24 hours.
The target for shutting off the flow is 835 feet.
It might be a 5 or 6 day wait to see what happens next.
A significant amount of water is going down the remnants of the bottom of the spillway on March 17th. On March 21st almost no water is going down the remnants.
If the release rate is approximately the same each day then the channel must have grown enough to handle all of the flow that was previously spilling over onto the remnant of the spillway.
I am certainly not an expert on dams. Another possibility, of course, is that flow has decreased enough to account for the difference. It would have to be a pretty big change.
Interesting observation.
The captions on both pictures say 40,000 cfs.
It is strange to think that we won’t really know what is going on
until Juan Browne gets back from Brazil! (lol)
I think the caption is wrong and the 1st pic on the 17th is 50,000
you can tell by the spray (more of it) plus on the 17th total out flow was 50,000 in the afternoon according to the data and they turned the power plant off at first until that evening......not 100% sure though
in any case, assuming a steady 40000 out of the main spillway the outflow from the power plant has been slowly decreasing over time and is now around 5000 cfs ....a few days ago it was 6800...
I suspect more debris is being washed in to the pool and they have to cut back to prevent the water backing up
another decent rain the next 24 hours and a weaker, cooler system Sunday
inflows caught up with outflows for a short time Tuesday so that delayed the drop
inflows still around 30,000 now still so I suspect they will catch up with inflows again over the weekend
but after that the long range looks dry for a awhile
Related article:
http://www.freerepublic.com/focus/f-news/3537581/posts?page=1#1
They need to have it fixed by the next rainy season .
Bentonite is a “clay” and typically a good seal, if hydrated.
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