Massive rock threatening to crash into base of Arizona dam

[Judi Lynn]

Source: Associated Press

Massive rock threatening to crash into base of Arizona dam
Felicia Fonseca, Associated Press
Updated 3:51 pm, Friday, September 4, 2015



FLAGSTAFF, Ariz. (AP) — A massive piece of rock is at risk of crashing down from a canyon wall to the base of an Arizona dam, prompting the government to send in a crew of rappelers to keep the slab in place.

The 500,000-pound slab — weighing more than many jumbo jets — began to break away from the canyon wall last week in what the U.S. Bureau of Reclamation attributes to erosion that is typical for that type of rock. The area below the slab includes a passageway to a boat ramp, a machine shop and water and power facilities for the dam.

The Bureau of Reclamation has cut off access to the boat ramp, putting some rafting trips on hold until the rock can be secured.

A three-person crew has been scaling the towering walls to drill bolts that range from 6 feet to 8 feet into the sandstone. Six bolts were placed in the canyon wall a week ago before a small chunk broke loose and crashed to the ground, hitting a building and leaving a pile of rubble, said Bureau of Reclamation spokesman Chris Watt.

Read more: http://www.chron.com/news/us/article/Rock-threatening-to-crash-down-at-base-of-Arizona-6485124.php

[djean111]

1. Seems to me it would be safer (after it is bolted in) to then start chipping away a few feet at a

time - controlled crashing.

[rusty quoin]

12. Yes, and from the top down.

[muriel_volestrangler]

2. "the dam, which is not in danger of being hit by the rock"

Not your fault, but their headline implied danger to the dam itself. It's the buildings around its base that are at risk.

[Hortensis]

3. What a picture. Thanks, Judi. And what a way to make a living.

[Hortensis]

3. What a picture. Thanks, Judi. And what a way to make a living.

[ret5hd]

5. OkK, OK, I'll say it: "Thanks Obama!"

[awoke_in_2003]

8. It wasn't him...

I am blaming that damn Coyote

[passiveporcupine]

6. This is like trying to stop nature from happening

They need to move or ignore the structures at the bottom and let this thing come down. And it looks like once it is down, there will be more to follow.

Mother nature is awesome!

[Cal Carpenter]

9. Yeah, it seems any effort to 'secure' it would be temporary

Without having any expertise at all, my gut is telling me you are right - that whatever is in the path of this should be considered unsafe.

But if engineers and geologists determine otherwise, well, what do I know? Nothing, really.

[Helen Borg]

7. What can they do"?

Superglue it?

[daleo]

10. Duct tape has awesome powers

[Owl]

11. Let it fall and deal with the consequences.

It'll fall eventually. Who would want to work under a 500,000 pound rock dangling from 6 bolts?

[Hoppy]

13. I told yiz so. It's God's reaction to gay marriage.

[shenmue]

16. Ding

[Agony]

14. Bolts! this is the 21st century...

epoxy it and forget about it.

[hunter]

15. Glen Canyon Dam has been a catastrophe from the beginining.

It's a nasty thing that ought never have been built.

In 1983 floodwaters nearly ripped it open along one of the spillways.

https://en.wikipedia.org/wiki/Risks_to_the_Glen_Canyon_Dam#1983

That catastrophe was averted by a few truckloads of lumber, and problems with the spillway design were fixed.

Still...

...because the dam is built within porous, erosion-prone Navajo Sandstone; an overtopping would likely lead to erosion of the dam abutments and a subsequent failure. In 1990, the Bureau of Reclamation prepared a study for a Glen Canyon Dam failure, predicting that the resulting flood would scour the bottom few hundred feet of the Grand Canyon, overtop Hoover Dam, and cause severe damage all along the lower Colorado River.

In an optimistic future, removing this dam and dealing with all the sediment it has collected is going to be an incredible engineering feat.

But it seems much more likely our economic system will collapse along with our ability to pursue such grandiose engineering projects, in which case the dam will eventually fail, making it a very bad day for everyone living within a few hundred miles of the dam, the lower Colorado River, and the river's delta in the Salton Trough.