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.

[mad_as_he$$]

The word is that Almanor(Canyon Dam) is releasing at full standard capacity(no emergency). Here is a link to the cams about 10 miles below the dam(the only ones I could find).

http://www.dot.ca.gov/dist2/cctv/sm_sr70sr898.shtml

[janetjanet998]

models dump 4-10 inches of precipitation over the basin the next 10 days or so starting this weekend

looks like they are dumping rock opposite side of the main spillway to prevent erosion from that bank I assume..

no update if they still plan to restart them main spillway tomorrow yet

[janetjanet998]

judging by the NWS forecast for the feather river below the dam at Gridley, it appears they plan to open the main spillway midday tomorrow to at least 50,000 cfs

[Ray76]

#OrovilleSpillway press briefing tomorrow at 9 am. Watch via DWR Facebook live. http://www.facebook.com/CADWR/

source: https://twitter.com/CA_DWR/status/842468925384269824

[janetjanet998]

Lake Oroville... Gates will open on the spillway tomorrow starting at 11am. 50,000 cfs outflow for 5-7 days

[Repeal The 17th]

It will take at least 1/2 a day just to get the people and equipment out of the way.
It is going to get interesting again.
Hope we can get some video.

[EarthResearcher333]

Spillway reactivation - Repair Test: Watch the Sidewall Drains…& the failing slip target indicator on sidewall

Oroville spillway's drains & non-modern tech & with no waterstop slab seams have operated as a high "underslab" waterflow structure from early on. Plenty of water, pressurized while the spillway is active, penetrates and flows under the slab. Oroville's current design depends on strong anchor bars, emplaced into rock, to counter "uplift" forces from "hydraulic jacking". Now that the current set of emergency repairs on the spillway have been done, the sidewall drain outlets should give an indication of an improvement to limiting the underslab water penetration.

Below are comparison images of sidewall drain flows from 1968 while operating at 150,000 cfs. The newer picture has sidewall drain flows from 2017 while operating at 100,000 cfs (after the blowout). Both are of the upper section of the spillway near the slope progression.

Last two images are discussion material: Evidence that the Drains have an "escape" flow path under the drainpipe from the bell coupling offset of the body of the main pipe. There is evidence that the drain pipe was also placed upon gravel as the damaged portion shows concrete mortar that has imbedded material (round rock) + a "void seam" below this. This "void seam" may have been from compacted gravel to facilitate a "grade" surface to place the drain pipe upon & keep it from fulcrum pressure points on bare bedrock irregularities. The "uncaptured" subsurface waterflow would pose an erosion condition to any path that would facilitate material migration. A side point is that any "fines" (fine grain material) would be able to migrate through the perforated drain pipe holes as the drain system was not filtered.

Oroville spillway 1968 operating at 150,000 cfs (DWR history photo). Notice the volume of sidewall drain flow in this "newly" constructed timeline.

Oroville spillway 2017 operating at 100,000 cfs after "blowout failure". Both images are near the slope curvature progression of the spillway.

"In the upper slab drain design: Underflow graphic (simplified as hydraulic operating pressure has "uplift" into the drain pipe) - note the un-captured water "underflow access" potential.

Evidence of an erodible layer under the drain pipe & slab - "seam and voids" present. Potential "underflow" regions from "un-captured water" & erosion of "fines" & other pressurized movement of non-solid material

[Ray76]

The ‘68 photo indicts the design. Having just become operational the spillway must have been considered as working as designed.

[meyer]

It will be interesting to see how it works (or doesn’t work) later today when they start spilling. They’re going to ramp up to 50,000 later.

I watched the press conference - one caution that he made repeatedly was “what you see today may not be there tomorrow”, meaning that while they did a lot to strengthen and secure the remaining portion of the spillway, it still might be further damaged when used.

They plan on running for about 5-7 days. They will shut down the plant for the spill. I don’t know if it will stay shut down for the duration, or it it’s a precaution for the initial operation to protect from potential issues.

[meyer]

Spillway is coming back. No good pictures yet that I have seen....

http://www.kcra.com/article/water-will-flow-again-down-still-damaged-oroville-spillway/9146468

[Repeal The 17th]

Looks like they opened the gates between 11 and noon local time.
https://cdec.water.ca.gov/cgi-progs/queryF?ORO
Outflow is over 40,000, now.

[EarthResearcher333]

"The ‘68 photo indicts the design. Having just become operational the spillway must have been considered as working as designed.

Yes to the 2nd statement. As to the first, there wasn't much technical history on Stagnation Pressure dam spillway failures (only one prior in 1954). Later on, more dam spillway failures occurred & were determined to be from Stagnation Pressure issues. Since Oroville was in "maintenance mode" by then, and not an "engineering analysis" mode, someone would have needed to escalate the question of "do we have a risk in this design?". The only proof of this concern would be if there was a "risk assessment & analysis" done.

One of the failure analysis experts named to the Oroville FERC panel has spent many years going to dams, working with engineers and doing Stagnation Pressure Failure risk analysis. It would be an honest question for someone to ask if there was any concern or thought of doing a risk assessment analysis for the Oroville spillway some time ago.

[janetjanet998]

I don;t see any water jetting out of the side drains yet

https://www.facebook.com/OrovilleNewsOnly4firesAccidentsEventsCrimes/posts/735921796578889

[meyer]

https://twitter.com/CA_DWR

Pictures in their latest tweet.

[meyer]

And a short video at the Sacramento Bee web site...

http://www.sacbee.com/news/state/california/water-and-drought/article139117943.html

[Repeal The 17th]

There was a quick drone fly-by at 3:25 in that video.

[EarthResearcher333]

“what you see today may not be there tomorrow”

I believe they know the stress that the West corner of the sliding & partially rotating sidewall & slab have sustained and/or are under. A conservative estimate of the downslope shift is from 3 inches to 5 inches judging from the repaired sidewall and spillway gaps.

Now translate that movement into the combined retention force against 16 to 20 anchor bars of #11 steel (1.41" dia) rebar emplaced within NX grouted holes (2.15" dia) drilled into 5 feet of sound rock (or what the blueprints state as determined to be "sound rock").

I'm intentionally discounting the large number of anchor bars in the sidewall itself as there was notable sign of potential of subsurface compromising of these anchors via erosion.

IF the slab anchor bars experienced a "bend" from the downslope movement, there should be a slight shift of the slab height (minor drop). However, the photos did not indicate a slab height shift (best estimate of zoom). If not a "bending" force, then the shift occurred from either a pulling of the anchor bar(s) out of their emplacement -OR- a fracturing of the concrete within the slab around the anchor bars -OR- a structural integrity loss of the "sound rock" around all/most of the anchor bars.

In any case, the forces are significant. No surprise they bolted on a precision optical movement detection target on the shifted sidewall.

[EarthResearcher333]

"I don't see any water jetting out of the side drains yet"

Excellent repair results. The video reveals exactly what it should be - just a trickle (wet mark on the sidewall concrete).

[janetjanet998]

but what is that water coming from the left side LEFT of the wall at the beginning of the video?

It is slightly upstream on the main break....you can really see at 28sec before the zoom to the bottom

[EarthResearcher333]

"but what is that water coming from the left side LEFT of the wall at the beginning of the video?"

Good catch. That is a drain pipe that normally would go to the sidewall outlet. The connecting pipe to the left sidewall outlet was broken away from this point from either the backfill erosion damage and/or from the sidewall & slab shift.

The video only gives a good view of the right sidewall drains. So this "catch" on this drain demonstrates there is water penetration about 100 to 200 ft further up the spillway -OR- there is a subsurface flow that is coming from an unexpected "piping" path within the lower rock. Something to keep an eye on.