Note size of people to the left of the initial break.
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 hill seems to be mainly that brown crumbly rock with lumps of the harder gray rock here and there. Even the gray rock took a lot of erosion.
Video won’t show up. I’ll look for another source.
I wouldn’t be surprised if the hole is 80-100 feet deep.
Thanks, JanetJanet!
Quite a bit of debris to dredge out of there, but it looks like they’re going to attack it from upstream and downstream. It’s interesting how far the water went down just from shutting down the spillway.
And that is a huge ravine carved into the hillside.
Note size of people to the left of the initial break.
Great image, Ray76. Watching the video, I was amazed at the size of the debris pile at the bottom of the spillway. Its size was masked by the 50,000 g/s flow. It’s a significant island.
it cut a channel through the “bedrock” under that bottom road on the right
I noticed that when they were shutting it down, it started spilling onto some dirt on the left that hadn’t been eroded yet. Thus, the muddy water.
I think that for now, they might want to build up the fall area and just let it use the new eroded channel but with a limited flow of 50,000 tops. Now that all the soft stuff is out of the way, that would be a possible temporary solution until after the spring melt season.
Also, being able to run the plant will help lot in getting water out of the reservoir. I thought I had read that at peak, it can pull almost 17,000 g/s of water out, but they keep saying like 14,000 or 15000. Maybe because one generator appeared to be out for maintenance in the one photo.
Latest local news....
Well, the engineers don’t have to speculate anymore
on the location of the good rock, bad rock, and no rock...
You’ve got that right! :)
I wonder if they can build a suitable spillway bridge over that gap. Half kidding, but I don’t know. I’ve seen some interesting spillways and penstocks out there.
“... DWR spokesperson Lauren Bisnett said the department estimated there
was 500,000 to 1 million cubic yards of debris in the Diversion Pool.
The higher figure is the equivalent of a football field
stacked 470 feet high with debris, she said.
Figuring that mass in terms of dump truck loads that must be hauled away,
the average commercial dump truck can carry up to 18 cubic yards of material.
That’s 55,556 truck loads that will be hauled away and dumped near the dam ...”
That’s a LOT of debris. Essentially, that’s the rock and concrete that the river cut away. I suspect that there’s some silt there, but a lot of it went downstream.
Here’s the Chickamauga Dam, which is near where I live. I’ve been inside a few times (since I work for the entity that operates it). It’s older, built around 1940, but it’s a tried-and-true design. There are 3 or 4 dams of very similar design along the Tennessee River including Watts Bar and Nickajack.
https://en.wikipedia.org/wiki/Chickamauga_Dam
At some point, perhaps more than once, they’ve cut the concrete of the dam and grouted to relieve pressures caused by expansion. They’ve done this at most of the TVA dams along the Tennessee River, as well as the dams run by the Corp of Engineers along the Cumberland river.
The one thing that sets the local dams apart from the Oroville (well, one of many things really) is that the height difference between the head water and the tail water is a lot less. It’s listed as 139 feet for Chickamauga, versus hundreds for Oroville. That makes spilling water a lot less violent at Chickamauga.
I’ve seen them spilling huge amounts of water once or twice. The river looks like Lake Erie on a choppy day!
I guess we will see in a day or so where they decided
to dump 1/2 million cubic yards of dredged material.
I think it’s going to take longer than a couple of days to clear out that mess. Maybe they can re-purpose it as aggregate along with boulders and mucho grout somewhere.
Another one of our dams, Fontana - drawings.
It shows an “emergency” spillway, but I am pretty certain that it has never been used.
https://upload.wikimedia.org/wikipedia/commons/5/5b/Fontana-dam-design-tva1.jpg
Cross posting from other thread, your reply to oldexpat where he talked about the close call on the emergency spillway:
http://www.freerepublic.com/focus/news/3529609/posts?page=20#20
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