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]

Explosive Failure of an Anchor Tendon Rod - shoots out of concrete..

Here is an example of what happens to old anchor tendons that fail. Images are from an Oklahoma Dam. The sudden tensile stress release from a failed anchor tendon causes an explosive force that "shoots" the rod out of the concrete. This dam used rods that were 50 ft in length. Oroville's Radial Trunnion Gates use 30+ feet length rods.

Oklahoma dam with similar (to Oroville design) post-tension steel anchor tendons. Anchor Tendon rods strengthen the concrete to endure the forces from the pivot anchoring plates of the Trunnion (Radial Trunnion Gate design).

Explosive failure result: Zoom: Oklahoma dam with similar (to Oroville design) post-tension steel anchor tendons.

[KC Burke]

California has a long history of law suits and action causing delays and studies in lieu of action. Brown trying to avoid such delays uses declaration of emergency powers.

Someone may file suit due to lack of sunshine on dam problems — would serve them right.

I bet the documents for bids are 90 percent complete.

[Bobsvainbabblings]

EarthResearcher333, take care of your ticker. I have three stints but am other wise healthy.

I have lived near Seattle for over 40 years. My wife and 3 neighbors are conservative. That is how I feel talking with the rest of the population.

Jaun’s latest, 6 April Update The ‘New’ Spillway Design Revealed!

https://www.youtube.com/watch?v=QAY-4-NeB18

[janetjanet998]

sounds like they plan to increase flows from 9800 to max 13,000 here soon(why did they decrease in the first place?)

Oroville >> Flows in the Feather River were to be increased Friday evening by the state Department of Water Resources.

DWR said that at 7 p.m., the flows in the stretch of the river past downtown Oroville would increase from 1,600 cubic-feet per second to 5,000 cfs, and warned the water would be deeper and swifter.

An additional 8,750 cfs were to be released into the river at the Thermalito Afterbay outlet downstream, for a total river flow of 13,750 cfs, up from 10,350 cfs.

The extra water will be coming through the Hyatt Powerhouse underneath Oroville Dam, which will be increasing releases from 9,800 cfs to 13,000 cfs.

No water is being released through the damaged main spillway.

Inflow into the lake has risen with the current storm, and is in the 35,000-40,000 cfs range. That’s about double the inflow on Thursday.

At 4 p.m. Friday the lake surface was at 848.6 feet above sea level, an increase of more than 3 feet in 24 hours.

http://www.orovillemr.com/general-news/20170407/feather-river-flows-increase-friday-night?utm_source=dlvr.it&utm_medium=twitter

[meyer]

Thanks for posting the video update. I enjoy them.

Not sure that anything but a complete rebuild will be sufficient here, but if they do it right, it is a tried-and-true design, isn’t it?

According to the video, they will repair/rebuild the top portion first and will for certain have that done by November 1. The bottom portion will maybe be done by then also, but maybe not.

He had no information on whether or not they would rebuild the spillway gate portion. I suspect that it will get significant maintenance anyway.

[meyer]

Thanks for the update. I also wonder why they reduced the Hyatt output, but there might be operational considerations in the plant that they were dealing with. Or maybe, speculation on my part, maybe they wanted a slower river flow while they were dredging a certain area.

[meyer]

Is that the Kerr Dam?

[meyer]

Hyatt plant flow up to 12,800. Good sign.

Side note - Juan Browne’s video said that he asked about using the river release valve system, which should be capable of moving something on the order of 4000 additional cfm through the dam. No answer, but they will look into it and get back to him.

[EarthResearcher333]

The Report did not identify which Oklahoma Dam. I looked through the entire report. Thought it was odd.

[EarthResearcher333]

Wet Area - DWR-FERC correspondence - DWR asking to relocate drill hole to facilitate DWR's to help figure out Green Wet Area

DWR is seeking to determine the cause of the Green - Wet Spot area on the left midslope area of the dam. Here is a snip from 2016 DWR's response to FERC in asking to move the FERC requested toe monitoring drill site where DWR is asking if it could be instead drilled near the Wet Spot area. DWR notes that this hillside should have "severely fractured weathered rock". This evidence points to DWR suspecting penetration into the left embankment from percolating ground table water - thus causing the Wet Area. This Wet Area still needs a horizontal component to distribute the seepage - that is where the "layer 2 and layer 3" construction history may indicate a residual clay "fines" mixed in with the Zone 3 embankment layer compaction (forming a "flow shelf").

2016 FERC doc - DWR wants to relocate (from FERC request) a proposed drill hole to 670ft Left Bank near Green Wet Area to help understand the cause of the Seepage.

Map from DWR to FERC on relocation request for piezometer sensor based drill/test/monitoring hole.

[jpal]

Maybe I missed something, and would appreciate clarification from those who are more astute, but it appeared to me that DWR is planning work on 4 separate projects: 1) the emergency spillway, 2) the main spillway gates, 3) the remaining section of the upper main spillway, and 4) the lower main spillway.

For the emergency spillway, they are planning on going some indeterminate distance below the existing weir to where they can dig down to “blue bedrock”, put in a cutoff wall, and fill in between the wall and weir with roller compacted concrete, as well as use RCC for some indeterminate distance below the wall. I’m certainly no expert, but I assume to place roller compacted concrete, you’d need a flat enough surface to roll upon. Wouldn’t they first need to fill in and smooth out a lot of the rough surfaces they just made with uncompacted rock and concrete before they could use RCC?

To work on the main spillway (FCO) gates, wouldn’t they have to get the lake level below the gates first and keep it that way using only the Hyatt powerhouse? It seems that they’d have to wait to start until they were sure the total inflow to the lake would stay under 13k cfs, which may not be until late this summer.

They plan to “upgrade” the remaining upper main spillway so it can handle 270k cfs. Wasn’t the original design specification for 270k? Aren’t they implicitly admitting that the spillway wasn’t up to spec?

My understanding is that they plan to work on the lower (missing) spillway section in 2 phases. This year, they plan to knock back and stabilize the massive side slopes of the new ravine to ward off further erosion, and to place some concrete in the plunge pool to channelize flow so that the the ravine can better handle up to 100k cfs. Next year, they plan to use RCC to rebuild the lower spillway up to it’s original height so that it too can handle 270k cfs. This would make the nations tallest earthen dam with perhaps the world’s tallest concrete spillway.

Am I missing something in their plan?

This is a tough nut to crack. No matter what they do, it ain’t going to be easy. An once of prevention could have saved a few killotons of cure.

[Repeal The 17th]

So what does this mean?
Do they think the Palermo tunnel might be leaking?

[Repeal The 17th]

The “roller compacted concrete” confuses me as well.
It is a concrete mix that is laid down in a thin layer
and compacted by a steam roller, similar to the way
asphalt is laid-down for highway pavement.
I don’t understand how that is done on a non-level surface.

[EarthResearcher333]

"Do they think the Palermo tunnel might be leaking?"

No. The Palermo tunnel is lower than the wet area by around 100ft. The slope of the tunnel in the bedrock is not much - so the tunnel wouldn't be a source for water seepage 100ft higher.

The test drill hole will have a piezometer sensor for analyzing for water presence & pressure. This is to monitor for seepage in the hillside next to the dam embankment. I too was suspecting a possible water table percolation from somewhere on the hillside as the wet area greening doesn't always follow/appear based on reservoir levels. There seems to be another component in the mix (spring?, water percolation delay from pore pressure compaction de-compaction from reservoir levels?, hillside pooling?,)

[Ray76]

Here's a tidbit:

Two major shear areas exist beneath the Dam, which are about mid-height on each abutment. Both are steeply dipping and strike normal to the axis of the Dam.

Fresh rock was exposed on the bank of the river channel and in minor outcrops on the abutments. Weathering of rock approached 100 feet in depth in the sheared zones.

California State Water Project, Bulletin 200, Vol 3 (1974)

The proposed new drill hole location is about "mid-height".

Additional information about the geology of the site is spread throughout the chapter.

[EarthResearcher333]

The Main spillway had a max design rating of 296,000 cfs. However, HYD-510 model testing found that at 277,000 cfs water would splash over the side walls (see post link). DWR announced a 270,000 cfs number (7,000 different than the BOC required 277,000). DWR noting that the sidewalls of the chute will be raised answers the "overspill" findings/concerns of the HYD-510 testing.

RCC placement requires a relatively flat surface, but since it is typically placed in 1 foot layers, the irregularities of the surface may be tolerated to a % of the thickness and the resulting roller compaction level grade results. Steel Drum or Rubber tire roller compactors are used in the compaction. Then successive layers are compacted quickly as the material is analogous to asphalt (zero slump, i.e. compresses hard with compactor roller in contrast to sloppy concrete pours).

The Spillway dispersal chute (end of spillway) was designed for 296,000 cfs. So they won't have to do any redesigning of the existing Feather river junction and opposite side bank.

Expert Board of Consultants swizzled flow number specifications for the New Main Spillway and the New Emergency Spillway. Why?

[abb]

Roller Compacted Concrete (RCC) is a mix that uses only enough water to hydrate the Portland cement. The consistency is not like ordinary concrete (slurry), but is just barely dampened aggregate and cement.

Cement takes very little water to activate the hydration process. And excess water severely weakens the finished product. I used to fight with contractors all the time over how much water to use in the mix. They wanted a thin slurry because it’s much easier to work.

https://en.wikipedia.org/wiki/Roller-compacted_concrete

Roller-compacted concrete (RCC) or rolled concrete is a special blend of concrete that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of fly ash for Portland cement.[2] RCC is a mix of cement/fly ash, water, sand, aggregate and common additives, but contains much less water. The produced mix is drier and essentially has no slump. RCC is placed in a manner similar to paving; the material is delivered by dump trucks or conveyors, spread by small bulldozers or specially modified asphalt pavers, and then compacted by vibratory rollers.

[abb]

[KC Burke]

From an equipment stand point, I haven’t seen it placed on slopes greater than about ten percent. I imagine it is all based on how you set up delivery but if you can’t tailgate it in you begin to loose some of its economic advantages.

Emergency spillway makes sense. Main spillway chute as the main surface, you are going to have to show me the plans and specs.

[hal ogen]

Wow...post 3000!