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

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

[abb]

Very good catch.

https://www.gladdingmcbean.com/sites/default/files/attachments/PipeBrochure_0.pdf

6” dia pipe has an OD of 7-7/8” and the bell end has an OD of 10-7/16”

I suspect those are industry-wide standards.

[meyer]

There ma be some variation to inflows based on releases upstream. There are other reservoirs.

Just noticed last hour that they finally brought on a third generator, bringing the flows up to around 5300 cfs.

[Repeal The 17th]

Based on that chart, the profile of the vcp actually stood
over 9 inches tall, suspended up on the bell.

[EarthResearcher333]

Oroville Slab Design - 6" Drain Pipe causes drastic thinning from O.D. & Bell Joint dimensions..

Hat Tip: meyer, abb, Repeal The 17th..

Specifications for the outside diameter and the bell coupling diameter of the Vitreous Clay Drain Pipe used on the Oroville spillway creates severe thinning zones in the Spillway slab. To confirm the original specs on the 4" drain pipe dimensions, detailed measurements on documents & scale revealed a near perfect match to a modern Pipe catalog of the same type of pipe for the 4 inch Inside Diameter (4" I.D.). This means that the actual thickness of the outer dimensions of the pipe need to be factored for a net slab thinning. Thus, shifting to the catalog 6" drain pipe specs (6" I.D. was used in the Oroville slab design) the thinning results were stark. Unless there was a cutting into the foundation layer to compensate for the larger diameter pipe, there was not much spacing in the thin zones for rebar (~2.5" down - centered) at the "bell coupling" areas.

Worse, penetration of water into such thin region(s) could cause persistent cracking, and even spalling (chipping) of the slab concrete surface from Stagnation Pressure ("hydraulic jacking").

[EarthResearcher333]

Repeal The 17th, abb, meyer, Sorry I couldn't get back to you on your questions & discussion (an emergency came up). I looked at the original Oroville scale drawings and was able to extract good values on the I.D., O.D., and thickness of the 4" drain pipe in the original design.

Rather than catch up individually on posts, I put a single image post together as a response & new graphic of the slab thinning.

Good Work --- back to one of the questions...

"I do not understand the logic of making a permeable drain and then deciding to cover it with an impermeable plastic wrap. It just does not make sense to me."

If you look at "Standard Perforated Pipe", on page 5 of the catalog, the drain perforation holes are oriented in the lower half of the pipe. I do not know if this was the case with the Oroville drain pipe as only one hole is visible in the image (at the 9 o'clock position). Using Polyethylene plastic to cover the crest of the drain pipe would serve the designer's intent IF the surrounding drain rock were to maintain its intended sloping shape, like a pyramid.

The drain system is intended to capture any water that penetrated into the lower seam, or the bottom, of the spillway slab (via cracks, or leaks in the abutting slab seam edges). Drainage also is to target any water that seeps into this seam from sources below the spillway slab.

Modern drain designs have a lower notched capture area below the slab bottom layer (see post 2,239 for Modern Drain design). This is what Oroville should have done. But, doing a notched system for the full 3,055ft length of the spillway would have been a significant construction effort as it would have needed to be cut into the foundation pours and the bedrock areas.

I really wonder what type of discussion occurred on the Oroville slab drain design....

[janetjanet998]

outflow 5300..looks like they got a 3rd turbine going

so far it looks like 1700 cfs per turbine
5 turbines(a 6th is down for repair) so 8500 max?

[mad_as_he$$]

Related:

http://www.freerepublic.com/focus/f-news/3532636/posts

[meyer]

outflow 5300..looks like they got a 3rd turbine going

so far it looks like 1700 cfs per turbine
5 turbines(a 6th is down for repair) so 8500 max?

I seem to recall that they were able to run up to 2300 or so on a single unit the other day. I think they might have 3 running but at less than full output, maybe in a cautious approach. They can vary the output by adjusting the wicket gates (more or less, valves where the water enters the turbine). Normally, we use them on our hydro generation plants to regulate the power output of the generator, but the side effect is that it also controls the amount of water passing through the generator's turbine.

But I'm seeing the same thing - 1700-1750 per unit at the present level of generation.

[meyer]

Information on the Hyatt Powerplant located in the Oroville Dam.....

http://www.water.ca.gov/swp/facilities/Oroville/hyatt.cfm

According to the chart, 3 generators are able to pass 2800 cfs at full output, and the other 3 2850 cfs. So they are definitely not running them at full capacity.

I think they want to see the effects of each additional unit on river flows. They seem to be starting them in the evening and letting them run overnight before making a morning assessment.

[meyer]

More updated images. Refresh occasionally if needed...

https://pixel-ca-dwr.photoshelter.com/galleries/C0000OxvlgXg3yfg/G00003YCcmDTx48Y/I0000AKdgnlH5Szc/FL-Oroville-8866-jpg

[meyer]

Based on the images, they’re making good progress on clearing the river channel below. Also, they seem to be progressing along nicely at reinforcing the end of the remaining spillway for future use. My hope would be that they harden it sufficiently that they can use the spillway with little to no erosion. It will remain a significant tool through the thawing season.

I noticed that they were also doing work to temporarily relocate a power transmission line. I think that 1 of the 3 lines coming out of the plant powerhouse has been removed, and another relocated to the tower higher up the hill.

From an electrical standpoint, 2 lines (I think that they are 230 kV circuits ((which should make them roughly capable of 600-800 MW capacity per circuit, depending on wire size)), but not 100% sure) should be able to carry the plant’s output, but with insufficient redundancy. We always try to operate the power system to the next single contingency, and the failure of one of those two lines would limit plant output. Getting the third circuit back in service would be very helpful to add reliability to the plant’s output (purely from the electrical standpoint).

[janetjanet998]

outflow now 7000 cfs at 8am local time

[meyer]

7080 cfs through the plant for hour ending 0900 PST. They’re ramping up. Not sure if they’re running the 3 units up to full output, or if they’ve brought a 4th unit on line.

[meyer]

You beat me by seconds. :)

[WildHighlander57]

Thanks for the link!

From post by hijinx

http://www.freerepublic.com/focus/f-news/3532636/posts?page=10#10

they plan to start releasing from main spillway; water level in the lake is near that point.

[meyer]

860 feet is their magic number, but I think that they might hold off. If they use it now, they will be bringing down a lot of debris from the unscrubbed area just below the end of the intact portion of the main spillway. If they can hold off a few more days and get that area contoured and hardened, they will have time to clear out a better path down at the bottom in the retention pool. And they will have a much more secure surface for passing water which will result in less loose debris carried down into the river below.

The bulk of the eroded area is already scrubbed down to bedrock so it shouldn’t erode much if spilling isn’t extreme. Its just that area directly under the intact part of the spillway that is a very potential area for erosion.

I think that they could ramp up the plant enough now to carry the average incoming water and perhaps a bit more. Barring wet weather or a significant thaw up on the mountains, they should have several days to work with. They’ve gotten over 1/3 of the debris removed from the pond already.

[mad_as_he$$]

Hold on! It could get bumpy.

[meyer]

You can say that again.

Actually, it’s been pretty bumpy there for several weeks now. But they’ve made an amazing amount of progress in that time. Shows what Americans can do when motivated!

[mad_as_he$$]

Nice warm Spring day upstream.

[abb]

Shows what Americans can do when motivated!

In another life when I used to work for wages, we all in the engineering department said that plant operators never wanted to take downtime or spend the money to do proper preventive maintenance, yet invariably spent more money and lost more time when the equipment cratered.

They never learn. Ever.