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

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

[janetjanet998]

The California Department of Water Resources issued a sudden evacuation order shortly before 5 p.m. Sunday for residents near the Oroville Dam in northern California, warning that the dam’s emergency spillway would fail in the next 60 minutes.

The Oroville Dam is the highest in the nation.

[EarthResearcher333]

Yes it does reveal details.

[meyer]

New Photos added. They are hardening and supporting the area under the end of the spillway (the intact part)....

https://pixel-ca-dwr.photoshelter.com/galleries/C0000OxvlgXg3yfg/G00003YCcmDTx48Y/I00008uMygbUP5dw/KG-oroville-repair-15824-jpg

[meyer]

I would like it very much if they ramped up the output of the generating plant. Perhaps they’re going to assess this morning before they change things. It is just after 8 AM PST, 3 hours behind us here in the eastern zone.

[mad_as_he$$]

Nice. They are moving very fast. Not sure a coating of shotcrete is going to do much but the stuff they put down two weeks ago has had time to cure so there is that. The weather is suppose to get warm again for a few days. If they can’t keep five generators going starting today they may have to open the main spillway again. Beat the clock and rising water, interesting prospect.

[janetjanet998]

good news

GFS model also pushes the wet weather more north like theo the models

that could change stay tuned

[EarthResearcher333]

ShotCrete & Mesh: Sealing rock under broken upper Main Spillway (including plastic drain pipe)

Workers are currently sealing the rock face under the broken slabs of the Upper Main Spillway. Notice the white plastic drain pipes (coated a bit with shotcrete). This is to drain water that is flowing in cracks under the foundation of the Main Spillway & to capture/release any water on the backside of the shotcrete seal.

Other images reveal a very unusual construction choice for the foundation. Images indicate the original construction/design had a Second drain layer of "under-gravel" where-ever a foundation layer was poured to get it to "level" before the Main Slabs were poured. This deep layer of "under-gravel" formed a seam between the irregular rock bed and the poured foundation. This choice was not outlined in the original design specifications. It also forms a serious problem for water that penetrates deeper into this foundation than what the drain pipes were designed for in the upper main slab.

[KC Burke]

Of course we all agree that this work being shown here is just temporary stop gap to mitigate (but not stop) erosion damaging to quickly when they have to turn the spillway back on.

I think any actual significant repair will have to be done beginning the end of June when much of the snow melt has occurred.

[EarthResearcher333]

Of course we all agree that this work being shown here is just temporary stop gap to mitigate (but not stop) erosion damaging to quickly when they have to turn the spillway back on. There may be a disconnect... my additional comments pertain to a foundation threat upstream.

The new images (not this one) reveal an undrained -new layer- source to Stagnation Pressure. This risk could bust an area of the Upper Spillway, including near the gates.

[KC Burke]

If I had to make a snap guess, I bet they only run this thing in the 20k to 40k range and with 10-14k on the power plant, they try and use that to manage the lake for the next five months.

When they feel they can shut this off, they will have staged a complete replacement and hit it in force.

[EarthResearcher333]

Hi KC Burke, This new DWR zoom image illustrates what I may have fell short in wording on the "under-gravel" description. (image marked up- zoom at broken end of main spillway)

Here's the problem: A second potent underflow region in the "foundation pour" was created by putting in a gravel layer between the bedrock and foundation pour in the original construction. (note: some of the foundation pour penetrated into the gravel.)

This was NOT in the original design specifications. The drawings always show the slab poured on top of rock (the mustache wiskers markings). IF they had to backfill up to the slab level, they were to pour concrete and anchor it. Nothing was shown, discussed, or illustrated where a gravel layer was ok to be placed.

This infers that the "gravel" was intended to be a type of secondary drain system - that they did not expect any water to get below the pipe drain system. Since water WAS very profuse in the pipe drain system, and there were numerous fractures/cracks in the upper slabs, water undoubtably penetrated into this gravel & bedrock seam area. Erosion, voids, and "hydraulic jacking" effects would have created serious problems in this seam area.

This would explain the "missing water" in the failed blowout region. It all dumped into this lower seam layer, bypassing the drains, and then caused serious problems to the underlying support to the slabs. It's possible the maintenance engineers likely would not have expected such a deeper layer of flow as all of the specifications, archives, drawings, and notation did not show this "sublayer of gravel".

Only an ol' timer who was part of the construction would had to have passed this on verbally (if asked).

[meyer]

So, if there is a gravel layer, then it needs to be drained. Having the gravel/loose fill under the concrete backfill would for certain be a problem since the drain system was on the bottom of the top concrete layer, not under the fill.

[meyer]

By concrete backfill, I mean foundation.

[EarthResearcher333]

Oops. When Designs go awry: Plastic Sheeting wraps Perf Drain Pipe & round gravel rock shifts - making a "second bulge"

"What were the designers thinking?" pondered the construction workers.. Here is a classic case of a design that goes awry.

DWR provided video shows a Drain Pipe under a slab. The original design intent/drawings was for a nice inverted "V" shape of gravel sloping on both sides to the peak of the upper pipe curvature. Check.

Use round gravel to yield the best pocket seams for waterflow. Check.

Place a sheet of plastic over the arrangement to keep concrete from penetrating into the shaped pyramid of gravel and from into the perforated drain pipe. Check.

Result - The round gravel became like "marbles" when heavy concrete was poured. Oops #1

The round gravel & the drain pipe "shifted" such that the pyramid shape became a "double camel hump" with very little to no gravel on one side. Oops #2

The "shifting gravel" allowed the plastic to wrap around the drain pipe, on one side - restricting/blocking perforated drain pipe hole access. Oops #3

The "double camel hump" from the shifted gravel caused a significant widening of the thinning area of the main slab. Big Oops #4

Of course, there are tell-tale cracks observed above the drain pipe….

The plastic looks to be in great shape. This truly lives up to its irony - plastic tent above the drain pipe repelling waterflow from cracks caused by thinning weak point stresses above drain pipes…

Large Void created by "round rock" (marbles) being shifted during concrete pour - note the significant "hump" created to the right of the drain pipe while the other side has the plastic hugging the pipe (from the "shifting" during pour).

Original drawings, below, showing the designer's intent with a perfect "pyramid" sloping on both sides of the drain pipe.

[Ray76]

Nothing but crumbly brown rock under those slabs.

[KC Burke]

Yes and very jury rigged detail for that type of under slab drain. Never saw one like it in 45 years of reading plans.

[meyer]

A complete spillway rebuild is in order. All the way back to the gates. Maybe those too, but don’t know at this point.

[KC Burke]

One issue is that the re-build is a pretty substantial project and it is only about 40% of the project duration — the site demolition, clean-up and site preparation is going to take longer than placing the 25 million dollar spillway. I would say the spillway is about a 50 million dollar job if the access is as fair as it appears.

[meyer]

I’d almost consider building a new spillway to the left of the main spillway, completely from top to bottom, while keeping the present main spillway in service. It’s a large proposition, but this one might not be salvageable as is. Even if the gates are in good shape, they will need to build so much of it that it might as well be a top-to-bottom job. I think the cost will be a couple of hundred million dollars though.

[KC Burke]

If you were going to add an additional set of gates that will add almost a year. I think they have to have this puppy back to the bowl about five months from June 30.

[meyer]

that’s a good point. Unless they can use the present one for another year (taking a chance though, given the potential for a very wet year again) in its crippled state, while building the new one.

I guess they’ll weigh all the options. Hopefully, they’ll make a good decision rather than a political one.