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 flow rating of the Palermo tunnel is 40 cfs.
Interesting...
If the water is coming through the earthen dam from the reservoir, I would think it is an unfixable problem without draining the swamp so to speak (maybe in more ways than one). It would seem to me that once water found its way into the interior of the earthen dam the gig is up. I know water inside of things can go every which way but loose.
I would think that the swamp would need to be completely drained so they could either do some major repair of the earthen dam or the build a new one.
Is there a better alternative to a dam made of earth when the dam is this massive size?
What other alternatives? A series of smaller dams?
Based on my limited ability to check, the California DWR has NOT released any information on three critical issues.
First: They have yet to release any pictures showing the gauges they installed to measure slab movement. The videos they have released have been edited to avoid showing this as well. They most certainly have this information, and have chosen not to release it.
Second: I have not seen any estimates of the amount of new debris washed into the river. Looking at the pictures the DWR has released, it seems to be far more than just a few odds and ends left over from the previous release. Enough newly eroded gray rock is visible in the river to conclude significant additional erosion has occurred, even without an “official” estimate of the amount.
Third: How thick is “gray” rock layer, and what is below it? Assuming a minimal level of competency, they should most certainly know this by now.
More debris in the river than I thought there would be.
I still can’t see a clear view of the shotcrete
at the edge of the broken spillway to see how it held up.
Looks like a l-o-t of concrete now on the emergency spillway.
They need better Public Relations.
They were advertising for Public Relations persons specifically for the Oroville Dam situation. I don’t know if the positions have been filled.
Earthfill embankment dams are known to "settle" in time. All embankment dams have some seepage. Some of the seepage will affect the internal compacted materials if the seepage flow does not destructively erode into internal "channels" or form cracks. An interesting case is revealed in the early days of Oroville Dam. The first photo was taken shortly after the completion of the dam where the reservoir was filled. Notable in this image is dark discoloration markings in stratified areas of the back surface of the dam. The dark discolorations are inferred to be from seepage.
Later, during early operation of Dam, two sections of the backside surface of the dam show remarkable wet areas. Both areas have in common a thin horizontal seam above or upslope. This may infer an internal water seepage flow within the pervious (waterflow capable) fill on the outer zone fill that resulted in the dark discoloration & partial greening of the downslope areas. Note the branching horizontal strips that infer to be branching out from a common layer seam in the construction of the earthfill embankment layering. Today, these areas are dry and have been dry since images going back to the early 2000's. The only area that has persisted is the current "wet area" in the left mid-slope of the dam. (noted per the recent Dam Safety Inspector reports on "investigating" and "taking action" based upon findings).
Photo taken shortly after the completion of the dam where the reservoir was filled. Notable in this image is dark discoloration markings in stratified areas of the back surface of the dam. The dark discolorations are inferred to be from seepage.
Photo taken in early operation of the dam. Notable in this image is two large dark discoloration areas with some greening hue + stratified branching in areas of the back surface of the dam. Note that each has a top horizontal seam above. All of the dark discolorations are inferred to be from seepage.
source: https://twitter.com/CA_DWR/status/837067623066042368
Thanks.
Those rigs look like giant flamingos or cranes drinking the water and foraging for food.
Oroville dam designers included "overdesign" in the thickness, depth, and dimensions of the layers of the earthfill embankment design. Thus there is a built in safety factor. All earthfill embankment designs have seepage. They just need to be on top of anything that develops.
The problem that I have is that there is an inaction behavior that seems to be ignoring the Dam Inspectors recommendations (inferring from multiple Inspection reports).
They should have a requirement of a skilled technical background (engineering, construction, geology, project management, etc). (someone who is a straight shooter & is experienced).
What if any preferable alternatives are there to earthen-made dams of this size?
Somehow the happy font “We’re Hiring!” text above a disaster picture.. + stating “information officer” engenders a meme of “how to talk happy & creatively during a crisis”. :-) Definitely a job that would be challenging given worldwide attention (and DWR’s rapport history with the public & press).
The “surface erosion channels” shown in your 2670 post are a very significant concern. These channels appear to be new, in that they weren’t indicated in previous DWR dam inspection reports, and appear to only be directly below the the horizontal seepage areas, indicating they weren’t caused by surface erosion from the recent heavy rains.
The flow through these seepage pathways would be the greatest when the dam head is the highest. So when the dam was topping out last month, and the cameras were trained on the failure of the main and emergency spillways, the surface of the dam itself may have been eroding on the flip side of the channel. Once you start to get actual movement of material, things can escalate exponentially and uncontrollably, as was shown dramatically with the main spillway.
This would indicate that even if the do expend the mega to gigabucks over a couple years to adequately repair one or both spillways, once the lake level rises enough for those spillways to be operationally used again, there may be sufficient head on the dam to blow it out.
DWR must be aware of whatever dam seepage has or is taking place, as these wet spots were mentioned in previous inspection reports. Yet, they have repeatedly said “the dam is fine”; the only public safety issues are with the spillways.
This would be good fodder for questions at a DWR press conference, or better yet, for one or more of the “independent experts” whom, without CYA issues, might be more objective and honest.
I’ve been checking in to see the ground radar mapping results. I don’t trust assumptions made based on the exposed area which suffered unique damage.
Appreciate the updating.
That’s funny! You’re right though - the person should have a technical background.
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