Leaky sandstone at Glen Canyon Dam

Wayne

Administrator
Staff member
There is a leak in the sandstone around the Glen Canyon Dam that has been there for decades. I've read about the studies of the leak and it doesn't jeopardize the dam so far. I remember being at the dam when I was a kid, probably 42 years ago, and saw the leak then. It seems to have a lot more moss growing on it now. There is a small diversion ditch at the base of the leak that directs the water into the river. I don't know the flow rate of the leak, but it's gotta be 5-10 gallons/second.

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I always have a moment of pause when I'm walking on or in front of a big dam. My mind immediately goes to the physics of the thing and how it would crush me like a bug should something go wrong.

The leaking sandstone brings to mind my visit to the Fontana Dam over here in TVA country. The tallest dam east of the Mississippi it has the distinction of being a dam THAT THEY COMPLETELY CUT THROUGH FROM TOP TO BOTTOM every handful of years or so. The concrete is undergoing a reaction that causes it to expand, so they cut a slot through the dam to release the compression on it.

I know...engineering and all, but I want to meet the person who said 'yea, we can chop a slot in it and it will be fine'.

All that said, I love a dam and will stop and look at any I find along my path.

 
I don't understand how they can cut the dam in half and it maintains integrity. Maybe @dnewton3 can explain, being that he is an engineer.
 
I'm not a civil engineer; mechanical engineer. However, I would expect that just a few things contribute to the success of this cutting plan:
- the dam is an arch; water pressure is always pushing against the arch and trying to collapse it (it has the arch in compression)
- as the dam is cut, they do mention that the gap is literally closing as it's being cut (the concrete is relieving into its new shape)
- the concrete "growing" phenomenon is probably used to their advantage; they want the gap to "grow" closed (together)
- the rough surface of the cut probably is a good aid to binding itself together; each side "grips" the other

Those are my thoughts, anyway.
 
I'm not a civil engineer; mechanical engineer. However, I would expect that just a few things contribute to the success of this cutting plan:
- the dam is an arch; water pressure is always pushing against the arch and trying to collapse it (it has the arch in compression)
- as the dam is cut, they do mention that the gap is literally closing as it's being cut (the concrete is relieving into its new shape)
- the concrete "growing" phenomenon is probably used to their advantage; they want the gap to "grow" closed (together)
- the rough surface of the cut probably is a good aid to binding itself together; each side "grips" the other

Those are my thoughts, anyway.
That's pretty much my understanding of how it works.

Still, it is unsettling knowing that and standing at the base of, or on top of the thing and thinking about it.
 
First and only time I've ever been inside a dam was about 6 years ago; here at Cannelton Dam on the Ohio River, just east of Cannelton, Indiana. I like to ride/drive along the state roads in southern IN; very pretty and curvy/hilly. I typically stop at the Cannelton dam as they have locks, and you can often watch big barges go up or down river passing through the locks from the observation tower.

One day I was about to climb the stairs to the tower, and a guy holler's over at me from the locks ...
Worker: "Hey - you wanna come see the dam?"
Me: "Uhhhhh ... Sure !"

So he has me walk across the closed lock, and sign in on a visitor sheet; the dams/locks are operated by the Army Corps of Engineers. I get a full tour of the operations, the locks, the dam, etc. Takes about 2 hours; he shows me all the inner workings. I've heard about these structures, but it's quite interesting to be 50' below river bottom, inside the walkways, and hear the droning of the hyro-generators whirring above your head. Exhilarating and frightening all at the same time. We walked all the way across to the KY side and back, under the river. WOW ! I got to see some of the maintenance guys working on lubricating the massive bearings for the locks, etc. I asked why he invited me over. "Well, you got lucky today. They accidentally scheduled one too many people, and so they have to pay us by contract since we all showed up, and I'm the senior guy so I get to float between jobs today." IOW, just by fluke of me being in that parking lot at the exact moment he saw me walking up the stairs, and he had nothing better to do but waste my tax dollars (kidding; sort of ...), I got the experience of a lifetime!

The observation tower (second photo; red circle) is still accessible from the outside, but you can no longer go inside the tower itself. It used to be that they had a really neat river diorama and informational posters inside the viewing tower. Sadly, after 911, that was closed to the public. But you can still walk the stairs and exterior deck of the tower. One thing I had learned from previous trips to this location is that the amount of "fall" (elevation drop) along the IN portion of the Ohio River is significant. As I recall there are 5 dams along the IN section of the river alone, and Indiana has the first and second most drop of the dam sections in the entire river.


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So he has me walk across the closed lock, and sign in on a visitor sheet; the dams/locks are operated by the Army Corps of Engineers. I get a full tour of the operations, the locks, the dam, etc. Takes about 2 hours; he shows me all the inner workings. I've heard about these structures, but it's quite interesting to be 50' below river bottom, inside the walkways, and hear the droning of the hyro-generators whirring above your head. Exhilarating and frightening all at the same time. We walked all the way across to the KY side and back, under the river. WOW !
What a cool experience! I've been down in Hoover dam and experienced the same droning of the generators while walking in a concrete tunnel somewhere in the dam. We stood next to the penstock that controlled water flow to the generators. It's a huge steel pipe with a huge valve that was built, I guess, in the 1930s. It's still carrying high pressure water and has enough vibration that it makes noise. I'm sure they x-ray test it to make sure there are no fatigue cracks forming, or at least I would hope they do.
 
What a cool experience! I've been down in Hoover dam and experienced the same droning of the generators while walking in a concrete tunnel somewhere in the dam. We stood next to the penstock that controlled water flow to the generators. It's a huge steel pipe with a huge valve that was built, I guess, in the 1930s. It's still carrying high pressure water and has enough vibration that it makes noise. I'm sure they x-ray test it to make sure there are no fatigue cracks forming, or at least I would hope they do.
When I got to tour HD back in 2002 all you could do was ride the elevator down to the generator floor and back. That was the most immersive tour they had, much to my disappointment. I really love big infrastructure 'things' and could easily spend the rest of my life touring stuff like that.
 
There is a leak in the sandstone around the Glen Canyon Dam that has been there for decades. I've read about the studies of the leak and it doesn't jeopardize the dam so far. I remember being at the dam when I was a kid, probably 42 years ago, and saw the leak then. It seems to have a lot more moss growing on it now. There is a small diversion ditch at the base of the leak that directs the water into the river. I don't know the flow rate of the leak, but it's gotta be 5-10 gallons/second.

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View attachment 1952
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5-10 gallons a second in sandstone for decades! I'd worry that it would be eroding constantly and the leak getting bigger.
 
A few dam pictures. Much more picturesque in the spring/summer.

Ohh, also @dnewton3 , not an arch, simple gravity type. Which makes the whole cutting-in-half thing even more interesting. (to me at least)


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