ten2win
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October 14th, 2010 at 4:07:49 PM permalink
I noticed this article in today's online version of the LAT

Bridge

I've not seen any comments regarding this engineering marvel mentioned in any recent post's. We passed it driving over the dam on our drive to Las Vegas this past August. I was awed when I first saw it! A true feat of American making.

It should really cut down on travel time for those coming from Arizona, New Mexico and Texas.

These pictures are pretty cool too.

Pictures
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Wizard
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October 16th, 2010 at 12:50:13 PM permalink
I plan to see it for myself whenever it opens. I find it rather annoying that they can't give out an exact date when it will be open to the public.
"For with much wisdom comes much sorrow." -- Ecclesiastes 1:18 (NIV)
pacomartin
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October 16th, 2010 at 5:16:29 PM permalink
There are many people who feel that the country needs an interstate not only directly from
Phoenix to Las Vegas, but the thousand miles from Las Vegas to Portland. Not just for tourism,
but to ship goods from Mexico to Canada and in between.

If the turns out to be too ambitious, there is a federal law that is 15 years old:
Quote: Public Law 104-59, November 28, 1995


The CANAMEX Trade Corridor, as defined by Congress in the 1995 National Highway Systems Designation Act, is a High Priority Corridor.

(26) The CANAMEX Corridor from Nogales, Arizona, through Las Vegas, Nevada, to Salt Lake City, Utah, to Idaho Falls, Idaho, to Montana, to the Canadian Border as follows:

(A) In the State of Arizona, the CANAMEX Corridor shall generally follow-- (i) I-19 from Nogales to Tucson; (ii) I-10 from Tucson to Phoenix; and (iii) United States Route 93 in the vicinity of Phoenix to the Nevada Border.

(B) In the State of Nevada, the CANAMEX Corridor shall follow-- (i) United States Route 93 from the Arizona Border to Las Vegas; and (ii) I-15 from Las Vegas to the Utah Border.

(C) From the Utah Border through Montana to the Canadian Border, the CANAMEX Corridor shall follow I-15.

JerryLogan
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October 16th, 2010 at 8:34:48 PM permalink
This bridge is almost too good to be true. I too agree that it's very disturbing not being told exactly when the thing's gonna open for normal traffic. One of the latter reasons they gave for building it is to eliminate the need for checkpoints nearby the dam in Az. and Nv., presumably to keep the bad guys with TNT out. But it seems to me blowing up that incredible piece of architecture would be just as spectacular an act of terrorism as taking out part of the dam.

We don't need any road that comes into this country from anywhere in Mexico. All it does is bring in unsafe trucks driven by drivers who would rather take a thousand chances riding in a rig with sub-par brakes and tires, than stay in that 3rd world hole.
Wizard
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October 16th, 2010 at 10:06:22 PM permalink
Quote: JerryLogan

One of the latter reasons they gave for building it is to eliminate the need for checkpoints nearby the dam in Az. and Nv., presumably to keep the bad guys with TNT out. But it seems to me blowing up that incredible piece of architecture would be just as spectacular an act of terrorism as taking out part of the dam.



I think this is the first time I have agreed with JL about something. Granted, I'm not an expert at blowing things up, but if somebody did have the ability to take out the Hoover Dam, or at least do serious damage to it, couldn't they exact much greater damage exploding the thing by a tall office building, like Tim McVeigh did? I have to question if the dam security for nine years has been a huge waste of money, not to mention the inconvenience to the drivers. Somebody correct me if I'm wrong.
"For with much wisdom comes much sorrow." -- Ecclesiastes 1:18 (NIV)
boymimbo
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October 16th, 2010 at 10:22:59 PM permalink
Quote: JerryLogan

This bridge is almost too good to be true. I too agree that it's very disturbing not being told exactly when the thing's gonna open for normal traffic. One of the latter reasons they gave for building it is to eliminate the need for checkpoints nearby the dam in Az. and Nv., presumably to keep the bad guys with TNT out. But it seems to me blowing up that incredible piece of architecture would be just as spectacular an act of terrorism as taking out part of the dam.

We don't need any road that comes into this country from anywhere in Mexico. All it does is bring in unsafe trucks driven by drivers who would rather take a thousand chances riding in a rig with sub-par brakes and tires, than stay in that 3rd world hole.



True, but those drivers are coming in today and are just driving and extra 150 miles (return) that they no longer will have to drive. That will gives those trucks 2.5 less hours on the road which will probably lead to less fatigue and less accidents as a result of the road.

Blowing up the Hoover Dam would have a much more catastrophic effect than blowing up a bridge.
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mkl654321
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October 17th, 2010 at 12:26:15 AM permalink
Quote: Wizard

I think this is the first time I have agreed with JL about something. Granted, I'm not an expert at blowing things up, but if somebody did have the ability to take out the Hoover Dam, or at least do serious damage to it, couldn't they exact much greater damage exploding the thing by a tall office building, like Tim McVeigh did? I have to question if the dam security for nine years has been a huge waste of money, not to mention the inconvenience to the drivers. Somebody correct me if I'm wrong.



Taking out the dam would cause orders of magnitude more damage and disruption than taking out the bridge, or destroying a more prosaic office building. There would be catastrophic downstream flooding, with the likely failure of all the main-stem dams downstream. Hundreds of thousands of acres of farmland would be flooded, and all of the river towns downstream would be heavily damaged. There would be a major loss of electrical generating capacity as well. To refill Lake Mead would take several years, perhaps decades. The only damage that would no longer occur would be the severing of the US 93 corridor (assuming the new bridge remained intact). But the economic cost would be gigantic. Oh yes, I almost forgot to mention--Southern California's water supply would be severely disrupted for years.

Hoover Dam is a uniquely high-value target, in that its destruction would affect a huge area. No office building's destruction--not even the Twin Towers--could come even close to wreaking the havoc that Hoover Dam's failure or deliberate destruction would cause. I've endured the long waits to get through the checkpoints, but in this case, I heartily agree with the rationale for the increased security.
The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one. The happiness of credulity is a cheap and dangerous quality.---George Bernard Shaw
JerryLogan
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October 17th, 2010 at 12:55:35 AM permalink
I've driven through those checkpoints maybe 20 times in the past 8 years, and each time I got waved through as if I were looking for and were directed to a parking spot at the ballpark. It was always abundantly clear that I could easily have had a trunkful of explosives, as could anyone who travels through those points in normal cars. All they do is make the SUV's and pickups go through a visual inspection. If the Hoover Dam were considered to be such a unique and easy target, the bad guys could have easily gotten a half dozen explosive-laden autos into the dam area in some sort of coordinated effort.

However, when I drove through those checkpoints during the first year after 9-11, it was a vastly different story. Every vehicle got searched and everyone was a suspect. I don't understand what happened to ease up security, but I read that certain experts' analyses that even slamming a 747 fully loaded with fuel into the Dam would not bring it down, may have been the reason. Still, the whole checkpoint thing doesn't make sense to me, at least in the way it's operated.

By the way, I've NEVER had to "endure long waits" since 2002 as mkl654321 says he's had to. It kind of makes one wonder just how much talent he has in order to be so prolific at making things up on the go in so many threads.
Wizard
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October 17th, 2010 at 2:58:59 AM permalink
Quote: mkl654321

Taking out the dam would cause orders of magnitude more damage and disruption than taking out the bridge, or destroying a more prosaic office building. There would be catastrophic downstream flooding, with the likely failure of all the main-stem dams downstream. Hundreds of thousands of acres of farmland would be flooded, and all of the river towns downstream would be heavily damaged. There would be a major loss of electrical generating capacity as well. To refill Lake Mead would take several years, perhaps decades. The only damage that would no longer occur would be the severing of the US 93 corridor (assuming the new bridge remained intact). But the economic cost would be gigantic. Oh yes, I almost forgot to mention--Southern California's water supply would be severely disrupted for years.

Hoover Dam is a uniquely high-value target, in that its destruction would affect a huge area. No office building's destruction--not even the Twin Towers--could come even close to wreaking the havoc that Hoover Dam's failure or deliberate destruction would cause. I've endured the long waits to get through the checkpoints, but in this case, I heartily agree with the rationale for the increased security.



First, I question whether a conventional truck bomb could even take out the dam. As I recall when I did the tour years ago, they built the thing with much more concrete than required to hold back the water on the north side.

Second, even assuming they could destroy the dam, such a bomb should be able to take out not just an office building but half of Manhattan. I would think a terrorist would prefer that.

Third, the dam does not produce that much electricity. A single nuclear plant produces much more.
"For with much wisdom comes much sorrow." -- Ecclesiastes 1:18 (NIV)
Nareed
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October 17th, 2010 at 5:13:12 AM permalink
Quote: Wizard

First, I question whether a conventional truck bomb could even take out the dam. As I recall when I did the tour years ago, they built the thing with much more concrete than required to hold back the water on the north side.



Not a chance. When you did the tour you ought to have noticed how wide the dam is on top. All of that is solid concrete. As you descend along the face of the dam, the concrete only gets wider. Besides, all a truck bomb could so is take a piece off the top, which would be bad but not a disaster.

A bomb on a boat on lake Mead would be much worse, plus you can pack more explosives on a large boat, but that wouldn't bring down the dam either.

Now, if you were to crash a commercial airliner near the base of the dam, who knows what would happen. But that would be difficult to do, as the route involves flying along a narrow canyon.

BTW taking out a bridge with a truck bomb isn't that easy, either. The bypass bridge by Hoover Dam, moreover, is an arch bridge, meaning it's supported by an arch under the roadway. Blow a truck on top and all you can take out is the roadway, which again would be bad but not a disaster.
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mkl654321
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October 17th, 2010 at 8:37:57 AM permalink
Quote: Wizard

First, I question whether a conventional truck bomb could even take out the dam. As I recall when I did the tour years ago, they built the thing with much more concrete than required to hold back the water on the north side.

Second, even assuming they could destroy the dam, such a bomb should be able to take out not just an office building but half of Manhattan. I would think a terrorist would prefer that.

Third, the dam does not produce that much electricity. A single nuclear plant produces much more.



It would take much less explosive than you might think. The trick is to deliver the charge with enough forward velocity that it penetrates to the innards of the dam. It also would help for the weapon to be in the form of a "shaped charge", for better penetration. The target area should be the dam abutment, where the dam joins the rock wall. Those joints are filled with concrete grout, as the rock is rather porous. Take out either abutment and the dam, while remaining mostly intact, would swing outward like a giant door on a hinge--the effect would be the same as if it had totally failed. It would also probably be enough to simply destroy the spillways, especially during a rainy winter/spring.

The British developed dam-busting technology in 1943, when they successfully destroyed several dams in Germany's Ruhr district using special bombs delivered by Lancaster bombers. The weapons themselves were not that large; it was the point of impact that mattered. There is an excellent book about this called "The Dam Busters". Modern explosives could be delivered to a similar point on Hoover Dam via a number of methods, most obviously by boat.

The destruction of Hoover Dam would not in itself result in the loss of that much electricity, but the loss of Hoover plus all the downstream dams would.

I'll probably have the FBI knocking on my door later today.
The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one. The happiness of credulity is a cheap and dangerous quality.---George Bernard Shaw
Wizard
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October 17th, 2010 at 9:01:55 AM permalink
Well, I don't know the topic of dam construction well enough to contradict your theory. However, your argument still doesn't pass my smell test. I've been Hoover Dam lots of times, and that thing is a massive wall of cement. I just can't picture it swaying like you described.

About the electrical output, the Palo Verde nuclear plant near Phoenix produces six times the power of Hoover dam, and that plant could have been built much bigger (source).' rel='nofollow' target='_blank'>http://www.heartland.org/publications/environment%20climate/article/25799/Mr_Obama_Tear_Down_This_Wall.html]source). The loss of electrical output would pale in comparison to the loss of water supply to Las Vegas and other cities that depend on it as their main water source.

About the FBI, I think it would be the Department of Homeland Security. Otherwise, the same thought crossed my mind too.
"For with much wisdom comes much sorrow." -- Ecclesiastes 1:18 (NIV)
JerryLogan
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October 17th, 2010 at 9:47:18 AM permalink
Quote: mkl654321

It would take much less explosive than you might think. The trick is to deliver the charge with enough forward velocity that it penetrates to the innards of the dam. It also would help for the weapon to be in the form of a "shaped charge", for better penetration. The target area should be the dam abutment, where the dam joins the rock wall. Those joints are filled with concrete grout, as the rock is rather porous. Take out either abutment and the dam, while remaining mostly intact, would swing outward like a giant door on a hinge--the effect would be the same as if it had totally failed. It would also probably be enough to simply destroy the spillways, especially during a rainy winter/spring.

The British developed dam-busting technology in 1943, when they successfully destroyed several dams in Germany's Ruhr district using special bombs delivered by Lancaster bombers. The weapons themselves were not that large; it was the point of impact that mattered. There is an excellent book about this called "The Dam Busters". Modern explosives could be delivered to a similar point on Hoover Dam via a number of methods, most obviously by boat.

The destruction of Hoover Dam would not in itself result in the loss of that much electricity, but the loss of Hoover plus all the downstream dams would.

I'll probably have the FBI knocking on my door later today.



See what I mean about how this know-it-all makes it up on the go? This guy is a study in flowing illogic. It's already been written about, discussed on the news, and talked about by explosives experts how only a small yield tactical nuclear weapon would be the ONLY way to bring that dam down in the castatropic way mkl654321 purports. And there is no special "weak spot" anywhere on that dam. That's why places like Iran have built their nuclear facilities underground and layered them with yards and yards of cement.
PeteM
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October 17th, 2010 at 10:07:24 AM permalink
I was waiting for someone to bring up the "Dambusters". The Brits used use a spinning drum of explosive that had to skip over the torpedo nets spread in front of the dams and then sink right next to the face of the dam before exploding, in order to take advantage of the tamping effect of the water to direct the force of the explosion towards the concrete. It's the tamping effect that's the key. Explosive force follows the line of least resistance, i.e. towards the open air. I suspect that if a fully fueled 747 managed to slide up the Black Canyon and impact on the face of the dam, the damage would be minimal. That's not a hollow(essentially) office building, it's many,many feet of solid concrete. I remember seeing a cross section of Hoover Dam when I visited. The front is fairly sheer, but water side of the wall is basicly a 45 degree slope. The structure is even more massive than it appears to be. Remember, it took the RAF multiple hits to take out the Ruhr dams.

As to shaped charges, a Hellfire or TOW missile blows a hole about the size of a 50 cent coin through its target, by way of example. That's the point of a SHAPED charge, it focuses all the explosive force on a very narrow area. Even if Achmed and his buddies managed to cobble to gether a VERY large shaped warhead they would still have to deliver it (not likely).

Stuff like penetrator bombs, Dibbers, bunker busters, etc. belong to the USAF and other national military entities. If we go to war with the Russians or the Chinese I'd start worrying.

Oh, and Jerry, the first time I tried to visit the dam the traffic was backed up to within a quarter mile of Boulder City, so yeah, delays do happen.
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mkl654321
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October 17th, 2010 at 10:14:10 AM permalink
Quote: Wizard

Well, I don't know the topic of dam construction well enough to contradict your theory. However, your argument still doesn't pass my smell test. I've been Hoover Dam lots of times, and that thing is a massive wall of cement. I just can't picture it swaying like you described.

About the electrical output, the Palo Verde nuclear plant near Phoenix produces six times the power of Hoover dam, and that plant could have been built much bigger (source).' rel='nofollow' target='_blank'>http://www.heartland.org/publications/environment%20climate/article/25799/Mr_Obama_Tear_Down_This_Wall.html]source). The loss of electrical output would pale in comparison to the loss of water supply to Las Vegas and other cities that depend on it as their main water source.

About the FBI, I think it would be the Department of Homeland Security. Otherwise, the same thought crossed my mind too.



The trick is, the dam itself wouldn't have to be destroyed--just one of its anchoring points. The immense hydraulic pressure behind the dam would do the rest. The dam is convex relative to the lake for that reason--to focus the hydrostatic pressure on the inner dam face, and not the abutments. But the whole setup is heavily dependent on how the dam is anchored to the canyon walls. Even a small rotational shift--caused by a manmade or natural event that moves either of the anchoring rock walls and/or the internal grouting--would result in a possibly catastrophic failure; the river would simply shoulder aside the dam. Hoover Dam looks impressive to us humans, but Lake Mead has millions of times the mass of the dam.

Teton Dam in Idaho failed due to the exact effects I just described. And that dam was built fifty years AFTER Hoover Dam.

The relative amount of electricity lost would be small, but downstream generating capacity would be lost as well, either from the failure of those dams as well, or a simple loss of storage. On a hot summer day, the Pacific Southwest often uses 100% of existing generating capacity; losing even, say, 5% of that capacity would result in rolling brownouts, at the very least. Not fun. Though I agree that the effect on California's water supply would be much more serious.
The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one. The happiness of credulity is a cheap and dangerous quality.---George Bernard Shaw
mkl654321
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October 17th, 2010 at 10:23:33 AM permalink
Quote: PeteM

As to shaped charges, a Hellfire or TOW missile blows a hole about the size of a 50 cent coin through its target, by way of example. That's the point of a SHAPED charge, it focuses all the explosive force on a very narrow area. Even if Achmed and his buddies managed to cobble to gether a VERY large shaped warhead they would still have to deliver it (not likely).



See my other post. The dam itself would not have to be destroyed--just its abutments. As a practical matter, the release of all of Lake Mead's water in a matter of several hours would have just as catastrophic an effect as total failure/destruction of the dam.

I brought up the "dam buster" story to illustrate how low-tech targeted explosives can destroy a huge structure. Today's terrorists would have much more effective weaponry and delivery options than the RAF had in 1943. I agree that a simple, bash-away-at-the-face-of-the-dam approach would probably NOT work. However, that would not be the point that anyone with a knowledge of dam construction would attack.

Furthermore, a destruction of just the spillways and outlet works---a much easier task--would disable the dam's generating capacity, and during the rainy season, could provoke a crisis if the upstream dam's reserviors (Glen Canyon, etc.) were already full.
The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one. The happiness of credulity is a cheap and dangerous quality.---George Bernard Shaw
Wizard
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October 17th, 2010 at 11:29:30 AM permalink
It sounds like PeteM knows a lot more on the topic of bombing dams than me, so I'll let him take over on that point.

About the water issue, California could get by without Colorado River water. I believe the major southern California cities gets most of their water from aquifers from northern California. Someone correct me if I'm wrong, but doesn't California use most of their Colorado River allotment on Salton Sea farming, which is not essential. Meanwhile, Vegas gets almost all its water from the Colorado River.
"For with much wisdom comes much sorrow." -- Ecclesiastes 1:18 (NIV)
pacomartin
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October 17th, 2010 at 11:36:44 AM permalink
A shape charge is your primary means of destroying a large submarine with a smaller delivery system
(like a small plane or a helicopter). It is difficult to deliver enough explosive to rupture a hull, so the shape
charge sends a small metal blob into a critical compartment at 22000 mph. It shreds the people and the
electronic equipment as it bounces around the compartment and then the rest of the crew is very worried
about damage containment as the water sprays through the small hole. Ideally they will surface which means
they will be easy to kill or forced to surrender.

I doubt that a shape charge could do much damage to a dam.

I also doubt that the dams were really in much danger of a terrorist attack that would kill massive numbers of people.
I think a terrorist attack on the Hoover dam would do much more psychological damage. Even if you blew up a gaurd shack
there would be experts on tv for years talking about the potential to take out the dam.

The thing that we were most afraid of was an attack on a passenger cruise ship. There are at least 20 cruise ships that
carry more than 3000 passengers, making a succesful attack as devestating as 9-11. Plus the fuel capacity blowing up
in a harbor could do damage to the pier and nearby buildings.

But, I agree that an attack on the Hoover Dam bypass bridge would have equally damaging psychological effect.
JerryLogan
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October 17th, 2010 at 11:40:40 AM permalink
"It sounds like PeteM knows a lot more on the topic of bombing dams than me, so I'll let him take over on that point."

Yes, more than you, me, and everyone else combined....except, of course, for the anonymous one mkl, who can't live with himself unless he brings everyone else over to his side of the fence. But let's hope we never have to test these theories.

On the water and changing the subject a little, what's with the tremendous decline in depth of Lake Mead? Is that thing drying up or what? (I know, if mkl didn't have me on his blocked list I'd get the answer AND THEN SOME!)
pacomartin
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October 17th, 2010 at 11:43:21 AM permalink
Quote: JerryLogan

what's with the tremendous decline in depth of Lake Mead? Is that thing drying up or what?



There was an attention getting study done in early 2008 that said Lake Mead could be empty by 2021.
Melman
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October 17th, 2010 at 11:44:21 AM permalink
Quote: Wizard

I plan to see it for myself whenever it opens. I find it rather annoying that they can't give out an exact date when it will be open to the public.



If I may make a comment that doesn't involve blowing anything up... I believe I read that the reason for not giving the exact date/time of opening is to prevent a crowd of first-across-the-bridge wannabees from showing up.

It also lets them open it just as soon as possible. Until recently, the advertised date was in November. Now they're saying late this week. I bet it's open before that.

Did anyone attend the "open house" event yesterday? It looked to me like fewer people showed up than they were expecting... although I was there early and gone by 10:00. So I don't know if the crowds grew later.
mkl654321
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October 17th, 2010 at 12:28:14 PM permalink
Quote: Wizard

It sounds like PeteM knows a lot more on the topic of bombing dams than me, so I'll let him take over on that point.

About the water issue, California could get by without Colorado River water. I believe the major southern California cities gets most of their water from aquifers from northern California. Someone correct me if I'm wrong, but doesn't California use most of their Colorado River allotment on Salton Sea farming, which is not essential. Meanwhile, Vegas gets almost all its water from the Colorado River.



Los Angeles gets the largest portion of its water from stored runoff (from a long distance away); the northern CA aquifers are in severe deficit from Delta, Sacramento, and San Joaquin Valley farming and the water table there is dropping. There is also a severe pesticide, alkali, and salt contamination problem. The Peripheral Canal (which was the proposed solution to LA's thirst) won't be delivering much usable water at all in the near future. Furthermore, there is increasing political resistance in northern California to sending its water south, which practice has accelerated degradation of local farmland, as above, and has harmed the ecology of the Delta and San Francisco Bay.

California has been borrowing Nevada's share of the Colorado River Compact for some time now. That interstate agreement was, unfortunately, based on runoff figures from the wettest decade on record--the 1920s. Since then, the river has been "in deficit" every year since then, i.e., the allocations exceed the actual usable water available. It is only because Nevada has never insisted on its full allotment from the Compact that California has been able to exceed its own allotment, year after year.

The Imperial Valley does indeed use a large share of California's allotment, but it's debatable whether that area is "not essential" to California's economy (the Salton Sea and immediately surrounding area is not extensively farmed due to high soil alkaline content). If Colorado river water were not available, much of southeastern California would simply dry up and blow away. Also, San Diego is far more dependent on Colorado river water than Los Angeles, because the vast majority of state and federal water projects, starting with the Owens Valley diversions in the 1920s, were targeted toward L.A. San Diego was a relative backwater until quite recently, and never received the benefits of the Central California Project, or any of the other mutil-billion-dollar schemes that were hatched to keep L.A. growing and growing and growing.

A great read on the subject is Marc Reisner's "Cadillac Desert".
The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one. The happiness of credulity is a cheap and dangerous quality.---George Bernard Shaw
mkl654321
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October 17th, 2010 at 12:36:27 PM permalink
Quote: pacomartin

There was an attention getting study done in early 2008 that said Lake Mead could be empty by 2021.



The other problem is that Lake Mead could be FULL by 2050. Full of silt, that is. The amount of silt that comes downstream was vastly underestimated by the dam's builders. It was subsequently thought that Glen Canyon Dam would intercept enough silt to extend Hoover's life by decades. However, the river isn't called "Colorado" for nothing. The river drains a vast area of exposed sandstone and rugged topography. Tributaries dump immense silt loads into the river when storms hit the Colorado Plateau. In the Grand Canyon, the river turns a livid red from the dissolved silt. Fill a glass with that water, and after a few minutes, there will be a half inch or more of silt on the bottom.

That silt has been piling up at the base of all the Colorado main-stem dams for decades. Storage capacity is at 70-80% of original construction levels. The useful life of those dams was originally estimated to be 250-300 years; it now appears to be less than a third of that.
The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one. The happiness of credulity is a cheap and dangerous quality.---George Bernard Shaw
Wizard
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October 17th, 2010 at 1:26:43 PM permalink
Quote: JerryLogan

On the water and changing the subject a little, what's with the tremendous decline in depth of Lake Mead? Is that thing drying up or what? (I know, if mkl didn't have me on his blocked list I'd get the answer AND THEN SOME!)



That is mainly the result of weak snowfalls in the Rockies the last 10-20 years. Contrary to popular belief, it has little to do with rainfall and population growth in Vegas. Southern Nevada gets only a small share of Colorado River water. It will never happen that Lake Mean runs dry. If things get really bad then I imagine we could buy some of California's share. On my list of things to worry about, Lake Mead water levels do not make the top 100.
"For with much wisdom comes much sorrow." -- Ecclesiastes 1:18 (NIV)
Nareed
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October 17th, 2010 at 4:52:23 PM permalink
Quote: Wizard

I have to question if the dam security for nine years has been a huge waste of money, not to mention the inconvenience to the drivers. Somebody correct me if I'm wrong.



Well, we've pretty much established terrorists couldn't blow up the dam. Blowing up a generator, damaging the water intake towers or the control rooms wouldn't be too hard without security.
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mkl654321
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October 17th, 2010 at 5:25:10 PM permalink
Quote: Nareed

Well, we've pretty much established terrorists couldn't blow up the dam. Blowing up a generator, damaging the water intake towers or the control rooms wouldn't be too hard without security.



I suppose the truth of that assertion would depend on what you meant by "blow up the dam". They probably couldn't reduce it to rubble, but they wouldn't need to do that to make the dam fail; destroying its support would be enough. It's like a cork in a champagne bottle. In terms of scale, if Lake Mead was a swimming pool, Hoover Dam would be the width and thickness of a fingernail. The potential energy stored in the lake is immense, and it isn't held back by much at all, in terms of relative mass.

I'm not sure it is necessarily foremost in the minds of the terrorists as a target, though in terms of the damage its failure could cause, it probably SHOULD be. But they seem to want to go after symbolic targets rather than the ones whose destruction would inflict the most damage.
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PeteM
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October 17th, 2010 at 6:25:22 PM permalink
Just got back from watching football(49ers FINALLY won). Interesting the way this thread bounces from destruction to water consumption and back.

Granted that the potential energy of the water in Lake Mead is immense,(incalcuable?) I would imagine that even the areas where the dam abuts solid rock are still too tough for any "nongovernmental" action. Those highscalers back in the 30's spent a long time taking the canyon walls down to bedrock before pouring any concrete; and if the explosion isn't tamped, wether by water or drilling, all you get is a smallish crater.

Paco, I don't know if the navy uses shaped charges in its anti-sub torpedoes or not. I do know that they were originally developed as an anti-tank weapon by the Germans in WW II and copied by us and the Brits (God bless the Krauts, they've given us Beethoven, Schwarzwalder cake and the Blitzkrieg!). Sorry to sound pedantic, it's that 20 years in the Infantry and the amateur military history buff in me that won't shut up. I always enjoy your posts about Vegas in general.
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Wizard
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October 17th, 2010 at 10:20:12 PM permalink


Picture from Glitz to Natural Bliss article.
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odiousgambit
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October 18th, 2010 at 12:52:43 PM permalink
Quote: PeteM

Paco, I don't know if the navy uses shaped charges in its anti-sub torpedoes or not.



boned up on torpedoes not too long ago, and the long and the short of it is if we ever get into a war where the state of the art is used, it won't resemble WW2 that much . The developments include "cavitation" for extraordinary velocity and a now evidently favored technique of breaking the back of ship ... the latter comes from study of how a ship is lifted up and then the ends being left with no support as the explosion changes shape, the initial charge going off somewhat below the ship.

this assuming the torpedoes don't go nuke as in the movie "The Bedford Incident", the kind of stuff they used to terrify us with in the 60s
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pacomartin
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October 18th, 2010 at 1:18:05 PM permalink
Quote: PeteM

Paco, I don't know if the navy uses shaped charges in its anti-sub torpedoes or not. I do know that they were originally developed as an anti-tank weapon by the Germans in WW II and copied by us and the Brits (God bless the Krauts, they've given us Beethoven, Schwarzwalder cake and the Blitzkrieg!). Sorry to sound pedantic, it's that 20 years in the Infantry and the amateur military history buff in me that won't shut up. I always enjoy your posts about Vegas in general.



I used to design torpedos. The principal means of killing a submarine with a lightweight torpedo (think air delivery)
since the 1970's was to follow the submarine (i.e. wake homing) and blow up the screws.

The problem came with the invention of the "Typhoon Class" ballistic submarine (the most famous was the
fictional Red October in the Tom Clancy novels). They have two pressure hulls with nuclear missiles between
the hulls. If you hit their screws probably no one will die and they still have plenty of time to fire all their missiles
before additional torpedos hit them. If the crew knows they will probably die after repeated hits, they may be
more incentivized to fire their missiles. We felt that shape charges would be the only way to create enough havoc
inside the pressure hulls so that the crew had more important problems trying to save their own lives.

Quote: odiousgambit

boned up on torpedoes not too long ago, and the long and the short of it is if we ever get into a war where the state of the art is used, it won't resemble WW2 that much . The developments include "cavitation" for extraordinary velocity and a now evidently favored technique of breaking the back of ship ... the latter comes from study of how a ship is lifted up and then the ends being left with no support as the explosion changes shape, the initial charge going off somewhat below the ship.

this assuming the torpedoes don't go nuke as in the movie "The Bedford Incident", the kind of stuff they used to terrify us with in the 60s



This comment is essentially correct. With a heavyweight torpedo you do not detonate the torpedo on the hull, but instead
detonate it underneath the ship. By blowing a big airbubble, you remove the support of the water under the hull. The ship is
designed to be supported by water, and the weight will crack the hull permitting rapid sinking.

We would develop explosives that used a lot of aluminimum mixed into the mix.
Aluminimum vaporizes and creates a lot of gas which allows the bubble to be extra large, increasing the damage to the hull.

======
As a side note:

You may remember the USS Stark which was hit by an Iraqi bomb on 17 March 1987. Much of the damage was caused because
the Stark the fire in the berthing compartment was so hot the aluminum ladders, bulkheads, and decks melted. The aluminimum vaporized into deadly gas which may have killed more of our sailors than shrapnel damage.

Incredibly, Hazard Perry FFG-7, Spruance DD-963, and Ticonderoga CG-47 ships were largely, constructed of aluminum. The Stark incident lead to Arleigh Burke DDG-51 having a steel hull and superstructure.
rxwine
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October 18th, 2010 at 2:06:40 PM permalink
Above ground airplane hangers which have been made to withstand anything but direct hits from a military grade explosive (usually on the end of a large projectile) -

- well anyway, I'm been in them, and I've been in Hoover Dam, and I'd choose Hoover first if I had a choice.

I too, believe, maybe they're more worried about potentially enough damage to cause problems to power generation, or shut down operations from a bomb, than complete failure. But I don't know that much about the weakest points of the dam, though I imagine by any standard it's got to be pretty formidable
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PeteM
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October 18th, 2010 at 3:12:32 PM permalink
Fascinating stuff. Is that "Air bubble" effect the same as the "water hammer" effect that torpedo designers were trying for at the start of WWII? Doctrine back then was to try and explode the torp under the target in order to "break its back". Unfortunately the magnetic detonators in use were so unreliable that there were many more duds than hits. Probably not an issue today,yes?
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Ayecarumba
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October 18th, 2010 at 5:01:33 PM permalink
Quote: rxwine

Above ground airplane hangers which have been made to withstand anything but direct hits from a military grade explosive (usually on the end of a large projectile) -

- well anyway, I'm been in them, and I've been in Hoover Dam, and I'd choose Hoover first if I had a choice.



As we are all well aware, the dam is not solid, but permeated by elevator and ventilation shafts, utility conduits, walkways and service corridors. I suspect a device detonated inside the structure could do significant, perhaps catastrophic, damage. There is a reason the dam was put on the high profile list, perhaps vulnerability is one of the considerations, or the Las Vegas visit by members of the "Detroit Sleepercell". Although the charges were later discoverd to be trumped up, many of the details remain cloaked. See a 2005 Washington Post article about the Detroit procecutorial shenanigans here.
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rxwine
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October 18th, 2010 at 5:40:48 PM permalink
It was overbuilt apparently

From fastfacts databank I found here

http://www.pbs.org/wgbh/buildingbig/wonder/structure/hoover.html

Quote:

The Hoover Dam is so thick and heavy, it doesn't even need to be curved. It's heavy enough to resist the weight and thrust of the water pushing behind it, but designers thought people would feel safer with a curved design.

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rxwine
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October 18th, 2010 at 5:49:46 PM permalink
I wonder if we've attracted the attention of Homeland security filters by now?

bomb, dam...

"I know nothing. I see nothing." as Schultz use to say.
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mkl654321
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October 18th, 2010 at 6:11:21 PM permalink
Quote: rxwine

It was overbuilt apparently

From fastfacts databank I found here

http://www.pbs.org/wgbh/buildingbig/wonder/structure/hoover.html



That's untrue. The curvature of the dam is absolutely integral to its function, i.e., that of holding back the water. How heavy (massive) it is isn't the issue; after all, even a very massive object can be SLID by a relatively modest force, because all that that force has to overcome is the object's (coefficient of) static friction relative to the surface on which it rests. The dam is not even close to massive enough to hold back the water by its weight alone.

The curve functions much the same way an arch does; it distributes the force/weight of the water out toward the anchoring points in the walls of the canyon. That way, the static friction that must be overcome is that of the entire mass of the rock walls. That is why when a dam is breached (transferring the burden back to the dam itself), portions of it often dissolve completely, because the mass of the dam is so inadequate by itself to hold back the water.
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rxwine
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October 19th, 2010 at 2:42:49 AM permalink
Quote: mkl654321

That's untrue. The curvature of the dam is absolutely integral to its function



The Bhakra-Nangal (gravity) Dam in India versus Hoover (arch/gravity) Dam

http://en.wikipedia.org/wiki/Hoover_Dam
http://en.wikipedia.org/wiki/Bhakra_Dam

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JerryLogan
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October 19th, 2010 at 6:22:36 AM permalink
Mr. know-it-all BUSTED again.
Wizard
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October 19th, 2010 at 7:39:29 AM permalink
How about the Three Gorges Dam as well, the largest dam in the world.

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Nareed
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October 19th, 2010 at 7:48:13 AM permalink
The arch is one of the strongest known structures. How strong? It was incorporated in the design of suspension bridges like the Golden Gate and the Brooklyn Bridge. Ancient Roman bridges built 2,000 years ago still stand in some places.

Plus the materials and methods available in the 30s were different from what's available today.
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thecesspit
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October 19th, 2010 at 10:28:32 AM permalink
You'll also find that the Grand Coulee Dam is in two straight lines :



neither of which links into a high rock wall like the Hoover Dam. However these are all long wide gravity dams rather than a high arc dam of the type at the end of Lake Mead. Both are valid forms of dam construction.

Grand Coulee is an awesome sight (it's bigger in terms on concrete poured than the Hoover Dam, makes a profit and has a wonderful son et lumiere displayed on it. In fact a tour down the Columbia is a nice holdiay if your into large scale civil engineering projects, a few rounds of municipal golf and a wander around the back area of Washington and Orgeon.
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sunrise089
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October 19th, 2010 at 10:40:39 AM permalink
Quote: Nareed

Plus the materials and methods available in the 30s were different from what's available today.



Are they really? I mean, of course they couldn't have made a carbon fiber dam back then, but my impression is that dams are pretty much piles of concrete. They're certainly impressive in SCALE, but I don't think they're on the bleeding edge of design-innovations-per-cubic-inch-of-finished-product, like a jetliner or a microchip is.

Re: the arch idea, I have to think that examples of non-arched dams plus the above quote suggests that while arches are one route to a strong dam they are hardly the only route. Even the explanation given (the arch shifts the load to the canyon sides) doesn't strike me as that powerful. The dam is 1,244ft wide, 726ft tall, and 660ft thick at the base narrowing to 45ft thick at the top. If friction is what holds it in place then the base surface area is ~821,000sq ft. The sides are (combined and very approximately) 479,000sq ft. That doesn't suggest to me side friction is of overwhelming importance, though I'm sure every little bit helps by adding to the margin of error.
thecesspit
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October 19th, 2010 at 11:32:29 AM permalink
I've seen it written that the Hoover dam is a arc-and-gravity type of dam, where both parts of the design are important to keep a large mass of water contained behind.
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Nareed
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October 19th, 2010 at 12:24:57 PM permalink
Quote: sunrise089

Are they really? I mean, of course they couldn't have made a carbon fiber dam back then, but my impression is that dams are pretty much piles of concrete. They're certainly impressive in SCALE, but I don't think they're on the bleeding edge of design-innovations-per-cubic-inch-of-finished-product, like a jetliner or a microchip is.



Absolutely. Concrete is centuries old, if not older, but both cement and agregate, and our understanding of them, have come a long way. So have design and engineering, although such things can be more subtle.

If you were to build Hoover Dam today, though, the main differences are you'd use less people, more machines, and overall conditions would be safer. It would take longer and cost more, too, but that's a political matter; assuming it could be built at all, that is.
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pacomartin
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October 19th, 2010 at 12:49:24 PM permalink
Operation Chastise was the World War II operation to blow up dams in Germany.
The article has a good technical description of the design of the bombs to blow up the dams.


Of interest is an article on Lake Mead Water levels .
mkl654321
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October 19th, 2010 at 4:38:02 PM permalink
Quote: rxwine

The Bhakra-Nangal (gravity) Dam in India versus Hoover (arch/gravity) Dam

http://en.wikipedia.org/wiki/Hoover_Dam
http://en.wikipedia.org/wiki/Bhakra_Dam



Sure. There are dams with both designs. I'd like to know what the capacity of the reservoir behind the dam in India is vs. the capacity of Lake Mead.

An arched dam would be stronger than a straight "gravity" dam, all other things being equal. However, it would be a waste of effort and money to build an arch dam where a straight gravity dam would do. I doubt that the engineers who built Hoover Dam built it the way they did just as a redundant safety measure. For one thing, the arch design used about 50% more concrete (foot-for-foot of span) than other similar main-stem dams of the period on equivalent rivers, such as Bonneville and Grand Coulee. Also, the concrete inside a larger dam takes that much longer to cure (Hoover still hasn't fully cured). So there are penalties for the additional strength of an arch dam, and most dam designers of the period refused to pay that penalty. But Lake Mead was unique.
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mkl654321
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October 19th, 2010 at 4:49:06 PM permalink
Quote: sunrise089

Are they really? I mean, of course they couldn't have made a carbon fiber dam back then, but my impression is that dams are pretty much piles of concrete. They're certainly impressive in SCALE, but I don't think they're on the bleeding edge of design-innovations-per-cubic-inch-of-finished-product, like a jetliner or a microchip is.



There are a lot of technologies like that, that have been improved in incremental, nondramatic ways, but haven't fundamentally changed. The internal combustion engine, for example. The orbital payload rocket (which really hasn't changed much since the Apollo program). The television. The bicycle. Etc.

I agree that concrete itself is a very old technology, but its applications have evolved. Going back to Hoover Dam, the use of prefabricated forms and the embedding of pipes in the poured concrete to run refrigerated water through were absolute cutting-edge, brilliant innovations. I'm sure that there have been similarly remarkable advances in the technology since then, though maybe not in the US since in the 1930-1970 era we dammed almost every river and stream that was more than two feet wide.
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EvenBob
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October 19th, 2010 at 5:14:49 PM permalink
Quote: mkl654321

1930-1970 era we dammed almost every river and stream that was more than two feet wide.



In my area, they must have been dam crazy in the 30's and 40's. Every river has multiple dams, like every couple of miles. Hardly any of them produce electricity anymore, they just sit there, giant concrete eyesores. Almost every small town is on a river and there is always a dam there, always. I'm sure its that way in every state east of the Mississippi.
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JerryLogan
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October 19th, 2010 at 7:06:04 PM permalink
Quote: mkl654321

There are a lot of technologies like that, that have been improved in incremental, nondramatic ways, but haven't fundamentally changed. The internal combustion engine, for example. The orbital payload rocket (which really hasn't changed much since the Apollo program). The television. The bicycle. Etc.

I agree that concrete itself is a very old technology, but its applications have evolved. Going back to Hoover Dam, the use of prefabricated forms and the embedding of pipes in the poured concrete to run refrigerated water through were absolute cutting-edge, brilliant innovations. I'm sure that there have been similarly remarkable advances in the technology since then, though maybe not in the US since in the 1930-1970 era we dammed almost every river and stream that was more than two feet wide.



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October 20th, 2010 at 1:53:20 AM permalink
Quote: EvenBob

In my area, they must have been dam crazy in the 30's and 40's. Every river has multiple dams, like every couple of miles. Hardly any of them produce electricity anymore, they just sit there, giant concrete eyesores. Almost every small town is on a river and there is always a dam there, always. I'm sure its that way in every state east of the Mississippi.



I lived near the Patapsco River in Baltimore County from 1992-2001. There were four dams along that river, and I always wondered why. This web site says they built them for power around the turn of the century, and there are plans to remove them.
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