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]
>>>And the Dam<<<
Y’all have to pardon me. I’m expressing a bit of frustration on what the performance of the dam has been reduced to. The main dam itself is well constructed.
But, if there is ever a situation where a capacity of 650,000 cfs is needed, the risk of severe erosive damage at the top of both spillways is the main concern. Then the emergency turns to protecting the berm between the main spillway and the edge of the top of the earthen dam. A secondary emergency would be to prevent “swirling” erosion at the toe of the main dam from backflow pool filling & motion of the feather river.
Ray or Maggie, this picture...is it the spillway completely torn up? Is this the condition of the slab now? And the man who took the photo, is he an employee of DWR? I must have missed the story if so.
The spillway picture is from several days ago. I don’t know what the spillway looks like now.
I saw live video at 7 AM PT today, it did not show the spillway but it did show billowing clouds of mist so the spillway must still be in use.
This link will always give the latest hour-by-hour run of the spillway. See Out Flow. It also has lake levels and then calculates In Flow.
https://cdec.water.ca.gov/cgi-progs/queryF?ORO
Do you recall offhand the elevation of the bottom of the main spillway?
Below that level, the only way to get water out is through the powerhouse.
They seem to doing a good job of maintaining their 850 foot lake level goal.
I recall 813.6
Thanks!
I believe that the floor of the top of the main spillway is 811 feet, +/-. Below that, the water MUST go through the dam unless they’re planning on pumping it out somehow.
Thanks!
Hi RT17,
>>Do you recall offhand the elevation of the bottom of the main spillway?<<
I’m assuming you’re asking what is the lowest level they can use the main spillway. Theoretically they can drain the lake to the height of the entrance of the main spillway. It is noted at 813.8ft.
An important detail - they have to be very careful in slowing down any lowering of the reservoir level to this 814ft as “too fast” of waterflow may cause turbulence erosion of the aggregate/soil entrance of the Main Spillway Sluice Gate.
>>Below that level, the only way to get water out is through the powerhouse.<<
Correct. But they do have a bypass river release valves at the bottom of the dam that are independent of the powerhouse. There was an accident in 2009 in a test of the system that injured employees. No info on when these will be in operation again. IIRC there was discussion on replacement parts or new parts that are part of getting this back online.
==
Article: DWR planning study on worrisome river valves blamed in 2009 Oroville Dam accident:
excerpt:
The accident happened around 7:30 a.m. July 22, 2009, after employees working in the river valve chamber, deep below the dam and Lake Oroville, began to test the valves.
When the valves were opened to 85 percent, a break-away wall pulled away and swept downstream into the 35-foot river diversion tunnel, according to a 2010 California Division of Occupational Safety and Health report.
Cal OSHA concluded opening the valves without an energy dispersion ring, which reportedly was absent, “created water flow with such great turbulence, that it blocked an air vent and created a vacuum.”
==
http://www.orovillemr.com/article/zz/20120912/NEWS/120917443
Thanks!
I’m under the understanding that the ‘bypass river release valve’ has been repaired. See the last page of this document...
To add, I think that the issues that affect flow through the generation turbines also affects the relief valve system - there is a need to dredge and clear the river below. Lots of debris remains that was washed down through the damaged area below the main spillway.
Speaking of pumping....
Mt St Helens created a huge problem when the eruption lahar & debris avalanche dammed up Spirit Lake below. The lake became a giant with thousands of blown down logs forming a “giant mat” on the lake surface.
pics at article: http://www.amusingplanet.com/2015/01/a-gigantic-mat-of-floating-tree-trunks.html
This giant debris dam was unstable and had to be emergency pumped to safe levels. They anticipated the lake would overtop its ashen based material and then release a mudflow that would bury cities 40 miles downstream (Toutle River into the Cowlitz river). The Army Corp of Engineers did a herculean job in setting up some monster pumps. The head of uplift was amazing to get the water up and over the nearest ridge from the lake (into a separate watershed).
The corp built a remedial “mitigation dam” to help control the surges of runoff from winter rains and help protect the levy systems in the towns of Kelso and Longview.
The permanent solution to preventing this avalanche dam from bursting was done by building a tunnel through a mountain to the lake to continually drain it at a certain elevation.
Recently, the tunnel had to have emergency repairs performed as the tunnel was mysteriously narrowing. They stated that “the earth shifted” in causing this narrowing. Keep in mind, this tunnel was bored/cut in rock. Thus the “tunnel floor shifting upward” is not a good sign. (btw- Mt St Helens is starting to come back to life in activity - magma is stated to be moving up).
I monitor the volcanoes in the PNW. Mt St Helens is beautiful. It has a natural spring that is amazing. It is just like a small pristine river flows out of the base footing of the mountain - Kalama River. I’ve been near the headwaters of the spring to get water samples for sulphur & mineral testing. For fun, I did a few “whoop” calls to see what might respond.
The herds of Elk are amazing. They flow up mountainsides with grace and speed that I couldn’t even stagger up. At the top of the ridge they just looked down at me like the scenes in movies where natives are perched all along a sight ridge....
=== Article clip
http://www.usatoday.com/story/news/2015/05/14/mt-saint-helens-volcano-spirit-lake-tunnel-overflow/27326173/
PORTLAND, Ore. — A tunnel dug to help drain a lake whose natural outlet was blocked when Mount St. Helens erupted in 1980 is narrowing. Experts say if it fails, Interstate 5 in Washington state could be inundated.
The Spirit Lake Tunnel was built after the 1980 Mount St. Helens eruption, when ash and debris blocked the lake’s natural outlet into a local creek.
When lake levels began to rise, the U.S. Army Corps of Engineers bored a 1.6-mile tunnel through bedrock to provide Spirit Lake a new outlet.
The tunnel opened in 1985. Last fall and spring, inspections found that the tunnel floor was rising. Geologists say shifting rock formations under the surface are to blame.
It looks like they have removed the generator turbines/pumps as you can see the large empty area with the blue walkway. Normally there is a row of 6 of these huge units flush with each blue circular walkway zone. Crane rail booms above in the power house likely were used to pull these out (i.e protection measure of some very expensive generators & equipment).
Ping to 1856
The picture is from February 16th.
http://pixel-ca-dwr.photoshelter.com/galleries/C0000OxvlgXg3yfg/G00003YCcmDTx48Y/I0000Ds3Gc4QPH_4/KG-oro-spillway-damage-12406-02-16-2017-jpg
Perhaps (just a wild ass guess on my part) they are re-configuring
the 3 units they pump upstream to allow them to pump downstream?
(I don’t even know if that is possible...)
No small task pulling the generators/pumps from their mounts. All six would of been a significant task. Have you found a wider shot image with all six holes open? Could it be that one was already down for maintenance? Removing them would be the prudent thing to do.
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