California Drought

[EddieWalker]

For all you guys who keep repeating that the spillway is rock, why do you think that will stop the water?

Rock is one of the worse materials for holding water in a pond because of all the cracks. Rushing water over it will break it apart in time. Yosemite is an excellent example of what water does to solid rock.

What is protecting the solid rock from the rushing water? and how long will it remain solid rock?

 

[dickfoster]

The spillway is NEXT to the dam, NOT ON the dam. The area that the spillways are in is a shoulder of rock. That is why they built it there
If you look at the main spillway, it has scoured out the clay and the reclaimed tailings that they used for fill and the area is down to rock (other than the corners of the bottom end of the upper spillway which are still eroding uphill a little), this can be seen by comparing the reddish flume coming off the main spillway for the first day or two to the white flume coming off now.
See Oroville Dam Spillway Failure | Page 3 | Metabunk for comparison pictures.
The emergency spillway is 20 feet lower than the top of the actual dam, it is not likely that there will be enough water to fill the lake to where it over tops the emergency spillway by 20 feet.

Aaron Z

Wrong, the spillway is on and is a part of the dam. That concrete bit to the right of the spillway is just the concrete bit for the power house etc. Earthen dam flanks that part of the dam on each side.
It's right down the road from me and I've been there. Maybe 65 miles away if that far. Make that 63 miles, I just looked it up.
Of course I might not be able to get there now due to road closures due to mud slides and stuff so I'll sit tight up here at 3600'. There's been a lot of that kinda thing going on lately. A huge mudslide even closed I 80 in both directions just last Friday. A few thousand cars somehow managed to find the little road I live on called Scotts Flat road Friday night in a futile attempt to avoid the backup on CA20 which is a two lane road that winds through the mountains. I wonder how they liked the unpaved portion of Scott Valley road further down the hill. LOL Them city folks were sure bound and determined to go skiing. At 2AM they were still goin at it. At least CalTrans would not let the big rigs attempt the CA20 detour due to snow and ice.

 

[houstonscott]

Here's the nightmare scenario at Oroville Dam that officials are fighting to prevent - LA Times

Check out far left side of emergency spillway, looks like drawing.

 

[TomSeller]

Oroville Dam: Feds and state officials ignored warnings 12 years ago

They knew.

A lot of small government people like to bring up things like this at times like this, yet when the funds were requested "back when", they don't support the tax money being spent.

 

[TomSeller]

For all you guys who keep repeating that the spillway is rock, why do you think that will stop the water?

Rock is one of the worse materials for holding water in a pond because of all the cracks. Rushing water over it will break it apart in time. Yosemite is an excellent example of what water does to solid rock.

What is protecting the solid rock from the rushing water? and how long will it remain solid rock?

Is it dirt or rock under the top of a waterfall? How long have the world's waterfalls been there?

 

[EddieWalker]

Is it dirt or rock under the top of a waterfall? How long have the world's waterfalls been there?

Is that a trick question? They have been there as long as the rock holding the water back lasts? Or maybe until all the rock under the water fall erodes to the point that the rock holding the water back up on the mountain fails?

Or did you mean that with all the rock debris at the bottom of every waterfall that I've been to, they are continually eroding and all that rushing water hitting the rock below is constantly eroding that rock away.

Or are you saying that the dam is like a waterfall and the water will just keep going over the dam and falling forever?

 

[aczlan]

Wrong, the spillway is on and is a part of the dam. That concrete bit to the right of the spillway is just the concrete bit for the power house etc. Earthen dam flanks that part of the dam on each side.

Ummm, the power house is way down the hill at the bottom of the dam (it appears that it is even on the other side of the Feather river). Nowhere near the spillway.
Here is a graphic showing where things are:

Source: Compromised Oroville Dam Auxiliary Spillway Leads To Mass Evacuation: SFist
The main spillway is cut into the rock as seen in the picture I posted earlier.

For all you guys who keep repeating that the spillway is rock, why do you think that will stop the water?
Rock is one of the worse materials for holding water in a pond because of all the cracks. Rushing water over it will break it apart in time. Yosemite is an excellent example of what water does to solid rock.
What is protecting the solid rock from the rushing water? and how long will it remain solid rock?

There is clay and fill dirt/riprap/concrete (depending on where you are talking) on the lake side keeping the water out of the (mostly solid) rock. What the rock downhill from the spillway does is resist erosion. Yes, it can be worn away, no it wont hold as well as good concrete, but it will hold a lot better than dirt does.
If you follow the link in my last post, you can see where the water coming down the main spillway has cleaned the dirt out and the water coming down the hill is white (no mud/clay unlike the bottom of the emergency spillway).

Aaron Z

 

[bcp]

Another map and photo showing where things are.

Bruce

 

[Raspy]

This dam is 'old' but is completely sound, HOWEVER the dam can only hold back water so long as the water remains below its top. The reason the emergency spillway exists is because there is a larger threat from a dam being overtopped and then failing. The emergency spillway is being used for the first time ever and it is evident that no maintenance or updating to make sure it too was 'sound' was ever done. Additionally, the long period of drought, would have killed off trees, grasses and other stabilizing growth and left the earth weakened along the emergency spillway. Also, the main spillway, which has a gaping hole, thus allowing water to undermine it and erode the area adjacent to the main spillway is also not sound. It seems that no money at all had been spent to study/evaluate/strengthen the main spillway ever. It's only purpose in life is to guide water to the river, but in your time of need, it fails as a result of water that it should have been designed to withstand.

I will never understand how CA does things.

Well, not quite.

According to a report on PBS today, there was a study done on the Oroville Dam that found the auxiliary spillway was unsound. Unsound for the very reasons we've now seen. A dirt hillside that could undermine and fail. The feds are in charge of the dam, not CA. The Feds decided that it wasn't a problem, based on what I don't know, and moved on. Now it is a problem.

 

[buckeyefarmer]

Don't confuse people with more pictures and facts, they haven't looked at the ones already posted. Lol