And of course, back in 2005 someone pointed out that EXACTLY THIS could happen if they didn’t armor the earthen auxiliary spillway with concrete.
Cliffs: Big reservoir dam has too much water, they start releasing some down the concrete emergency spillway. That gets a small crater in it, which quickly becomes a huge crater, so they have to dial back the water release. This causes water to start spilling over the earthen auxiliary spillway that has never seen water go over it since the dam was built in 67. As the 2005 lawsuit predicted, the earth quickly erodes and threatens to collapse the concrete lip of auxiliary spillway and release a 30’ wall of water on 200k people. They turn the water rate back up on the emergency spillway and cross their fingers and luckily manage to lower the water below the lip of the auxiliary spillway, at least for now. More storms predicted for Wednesday though.
I’ve been wondering the same thing. I think their concern is it’s also eroding uphill and if it compromises the control gates they’ll then have no way to control it.
The damage is REALLY far uphill though. It sounds like it is being throttled, so I don’t think it’s a capacity issue. Maybe they are worried that it will fail closer to the dam as well.
In the 2nd image notice how much worse the damage is on the right side, and more importantly, how the hillside on the left has started to erode as well. I’m no geologist but my guess is they’re concerned if they keep using it, at least at the level they needed to prevent the water from reaching the emergency spillway, the whole hillside will give way and they’ll lose the control gate.
So they throttled it, let the water go over the auxiliary spillway, then realized how that was going to fail in a hurry. At which point they turned the flow rate back up on the emergency spillway and hoped for the best.
When I was in college during 9/11 I had a bunch of classes with people from other countries. They got call after call from their relatives asking how close they were to the debris/were they safe.
I think that image confirms my theory as to why. It’s so much water and eroding so much at the damage point that i they keep using it before long the whole hillside would fail taking the control gate with it.
Sounds like they almost have it under control right now with no water coming down the emergency spillway and the main spillway dumping 100k cubic feet per second. Hopefully they can figure out a way to shore up the emergency spillway before the rains Wednesday.
This is a better photo of how much land is left, it really is a good amount. I think the fear was in regards to the portion to the right of the emergency release. If that part didn’t hold up, it would let water out. Just the little bit that flowed over seems to have done minor damage.
I think the real issue is that they are about to get hammered with another storm and if they can’t release water fast enough due to the damage, they might have another issue.
This while situation reminds if the Kinzua dam all over again.
Yeah, they’ve cleaned up some of the terminology being used now. The press (as usual) is getting all kinds of stuff wrong. The key things you need to understand are.
1: The concrete slide looking thing with the giant crater in it is the “Main Spillway”. This morning they were calling it the emergency spillway.
2: The dirt to the left of it (in the pictures with the lake behind it), with the concrete lip, is the “Emergency Spillway”, or the proper term for it, “Auxilary Spillway”. That’s the one that has never been used since the dam was built and the one they were sued in 2005 because someone had the foresight to say, “Hey, if water ever did spill over this thing it would just wash away the dirt and before very long the concrete lip would wash away, all the water would come crashing through, and everyone drowns”.
I thought when they said this morning that they had stopped the water on the emergency spillway they mean the concrete structure, which would be good because they could repair it or at a minimum the erosion would be stopped. That’s not the case Water is still blasting into that crater at 100k cu/ft per second, the rate they had to increase it to from 55k in order to stop the water from continuing to overflow the auxiliary spillway. They had decreased it from 100k to 55k because they were concerned the erosion happening to the concrete was going to cause THAT spillway to fail.
