Silver Bridge closure

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hikeaz
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Silver Bridge closure

Post by hikeaz »

The Silver Bridge crosses the Colorado River at the bottom of the Bright Angel Trail - It is closed "until further notice" due to "structural concerns". During the closure, hikers will need to cross the Colorado River exclusively via Black Bridge, which is at the bottom of the South Kaibab trail. From the South Rim - If hiking the Bright Angel Trail to Phantom Ranch (and beyond), hikers should anticipate being redirected along the River Trail, and the Black Bridge which will add approximately 1.5 miles to their trip.
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hikeaz
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Re: Silver Bridge closure

Post by hikeaz »

nonot wrote: Sep 09 2020 12:10 pm This is utter nonsense, scouring is a problem for pillars in the waterflow. The silver bridge is cable-stayed with no pillars in the waterway.
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nonot
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Re: Silver Bridge closure

Post by nonot »

The nuns should be happy I spelled it correctly :D
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hikeaz
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Re: Silver Bridge closure

Post by hikeaz »

nonot wrote: Sep 09 2020 12:23 pm The nuns should be happy I spelled it correctly :D
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Canyonram
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Re: Silver Bridge closure

Post by Canyonram »

@nonot

Hello noitall,

I know that the Silver Bridge is a suspension bridge and I never said anything in my post about pillars in the river.

Do you agree that the Canyon is a monument to the power of erosion to sculpt the landscape? If you agree to that, what is so unusual to suggest that repeated HFR experiments from Glen Canyon Dam is going to have an effect on the undercutting processes of running water against the Inner Canyon wall that anchors the suspension bridge? Especially when the water is at 4X the normal water flow and containing a high sand content as well? Scouring action from rushing water occurs along the Inner Canyon walls and does not require a pillar in the river.

The Silver Bridge south anchor site sits close to the River and exits onto the River Trail built by the CCC to connect Bright Angel Trail to the South Kaibab. At the beginning of this youtube video (link below), you can see how the River curves into the sidewall of the Canyon. Go to about 1:20 to 2:10 for a view of the swirling water undercutting the bank. Use the 360 control in the upper left. That south rim anchor site might as well be a 'pillar in the river.'

[ youtube video ]

This is under normal reduced flow since Glen Canyon Dam construction. Imagine 4X the flow slamming under here during HFR experiments.

There’s been recent engineering work to replace the water pipeline from the North Rim that crosses the river and provides for the 4.5 million visitors to the South Rim. The wastewater treatment plant below Phantom Ranch is in need of major repair/replacement. Wonder if either of these two projects revealed any impact of the HFR? Any engineering firm looking to design a replacement for the water pipeline is going to evaluate the integrity of the Silver Bridge to hold the new water line. They could have discovered the impacts of about 60 years of rushing Colorado and/or several HFR experiments.

https://www.nationalparkstraveler.org/2 ... r-pipeline

This makes the second detailed response I have given to you. You challenged me on my ‘Stop Smoking’ teaching method and now you call out my guess/theory on what may be happening with the Silver Bridge. In both cases, you have provided no information of your own. I’ll be glad to discuss these issues with you but I expect the courtesy of some effort on your part to provide the basis for your opinion. Simply sneering is not enough.
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sidhayes
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Re: Silver Bridge closure

Post by sidhayes »

@Canyonram
"That's how the canyon was formed." Really?
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chumley
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Re: Silver Bridge closure

Post by chumley »

So in the 1960s engineers designed and built a bridge in a canyon that they know has been eroding for millions of years, primarily getting wider (vs deeper), and set the footings into the hardest of the layers of rock in the canyon (Vishnu group?). But they didn't take into account the erosive power of water, and a mere 55 years after it was built, their engineering has failed--primarily due to high water flows generated during 9 or 10 separate High Flow Experiments cumulatively totaling ~40 days?

I don't know a dam : wink : thing about bridge building or river erosion, but it seems like this would be an incredibly short-sighted engineering fiasco. Who knows though, it will be interesting to learn more in the weeks ahead. At least it didn't sway like the Tacoma Narrows 25 years earlier! :o

But look, I found some cool photos!
https://www.flickr.com/photos/grand_can ... 9331614885
https://www.flickr.com/photos/grand_can ... 9560893265
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Canyonram
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Re: Silver Bridge closure

Post by Canyonram »

@sidhayes
sidhayes wrote:"That's how the canyon was formed." Really?
Yup. Even if you want to go with Noah's Flood---it would still be erorison. Brief description provided by NPS on the geological processes:

https://www.nps.gov/grca/learn/nature/g ... cut%20down.

Which theory on the formation do you subscribe to.
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Canyonram
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Re: Silver Bridge closure

Post by Canyonram »

@chumley

Great photos.

Never underestimate the ability of human beings to get it wrong (either someone speculating on the problem or the engineers who designed the bridge).

You have any guess? Has to be some sort of major issue to ban hiker traffic over the bridge. What is going on to halt a few hundred pounds of hikers on the bridge?

Wonder if something is going on in regards to the intergrity of the water line? That is the weight burden crossing the bridge. If the water line goes, South Rim will be in big trouble. Will need water tankers/train and a parade of trucks to deliver water to support the tourist traffic and Village and refill the backup water silos. Even with Covid-19 cutting into the tourist numbers.
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ShatteredArm
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Re: Silver Bridge closure

Post by ShatteredArm »

If the scouring were weakening the actual walls, wouldn't they have to close off the trail near the bridge as well? And yeah, 40 days of high flow doesn't seem like enough to alter something that took hundreds of millions of years to reach its current state naturally...
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Re: Silver Bridge closure

Post by Canyonram »

ShatteredArm wrote:If the scouring were weakening the actual walls, wouldn't they have to close off the trail near the bridge as well? And yeah, 40 days of high flow doesn't seem like enough to alter something that took hundreds of millions of years to reach its current state naturally...
Yo ShatteredArm,

Good point. Not closing the River Trail itself might be a good clue as to what might be going on—we have NPS reporting that it is a structural issue but only closed the bridge but not the trail itself. That might put the damage on the North side of the River. From the pictures Chumley linked, it looks as if the North side is a less secure anchor. You can block the approach trail leaving Phantom Ranch to the Silver Bridge a good distance away from the bridge but still allow hikers along the River Trail to continue hiking while blocking the access to the bridge.

Canyon continues to crumble. In March 2017 the River Trail between the Silver Bridge and Pipe Creek was closed for repairs due to the collapse of a retaining wall.

When man sticks his big clumsy thumb into the ecological web, the millions of years that went into establishing a given ecosystem is reduced to years—or weeks. Our activities are changing the world’s climate—so it should be no surprise that putting a dam across the Colorado has dramatically cranked up the clock on change. The Silver Bridge doesn’t belong in the discussion of natural processes that take millions of years. We should anticipate a single human lifetime at most for this man-made structure. Expect it to be damaged when we take the plug out of the Lake Powell bathtub and blow water through the Canyon so we can reetablish sandbars that we destroyed in the first place.

Pre-dam floods used to flush tremendous amounts of alluvial fan debris from along the River and literally reshape the shore line and the various rapids. 1 day of HFR is sufficient to carve and reshape the Inner Canyon. It is the whole rationale for blowing open the Glen Canyon Dam in the first place—reestablish the sandbars and rid the shore of invasive plants (tamarisk for example) and restore the ‘natural’ habitat for a host of Canyon native species; 40 days of HFR is plenty of time for water to do its work (hey, isn’t that the same time frame for Noah’s Boat Ride?) 40 days of HFR is also plenty of time to damage structures engineered to a reduced flow after the dam construction.
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Re: Silver Bridge closure

Post by hikeaz »

Reopened!
-
During the closure, National Park Service crews performed stabilization work. Federal Highway Administration (?) engineer Hugo First deemed the bridge safe for pedestrian use after the work was completed.
Last edited by hikeaz on Sep 11 2020 7:41 pm, edited 1 time in total.
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chumley
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Re: Silver Bridge closure

Post by chumley »

@hikeaz
They just gave it some Prozac and now it's a lot more stable than it was before.
(I don't think they care about pedestrian use. Is it safe for the water pipe?)
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ShatteredArm
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Re: Silver Bridge closure

Post by ShatteredArm »

@Canyonram
40 days of high flow is not a lot of time to further a process that normally takes millions of years. It kinda sounds like you read about erosion once and now you think everything happens because of erosion. It's speculative nonsense.

And I guess it's reopened, so obviously you were wrong, and 40 days of high flow didn't, in fact, manage to compromise the integrity of those walls that have managed to remain intact through thousands of years of naturally occurring floods.
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Re: Silver Bridge closure

Post by Canyonram »

ShatteredArm wrote:40 days of high flow is not a lot of time to further a process that normally takes millions of years. It kinda sounds like you read about erosion once and now you think everything happens because of erosion. It's speculative nonsense.

And I guess it's reopened, so obviously you were wrong, and 40 days of high flow didn't, in fact, manage to compromise the integrity of those walls that have managed to remain intact through thousands of years of naturally occurring floods.
Yup. I bow down at the Alter of Erosion. I give it my respect and appreciation for forming the Canyon. What exactly do you think you are witnessing when you hike or raft through the Canyon??? Have you witnessed Redwall Cavern (about rivermile 33)? Have you looked down on Horseshoe Bend (just outside Page Arizona)? What force do you credit for these formations? Might be time for you to read up a little on Erosion.

40 days of HRF could be the final nudge for the process that has been on going for millions of years. Just need to create enough movement to destabilize the support structure for the bridge. It doesn’t require a total collapse of the side of the Canyon or a total washout of the anchor.

Did you bother to look at the pictures of the construction that Chumley posted? Why are you finding it so hard imagine that the fragile and flimsy man-made structure placed within reach of a swollen Colorado River is not going to be impacted? It is much easier for me to believe that over granting some sort of immunity that the damage is going to require millions of years to occur.

You state “. . .and I guess it's reopened, so obviously you were wrong, and 40 days of high flow didn't, in fact, manage to compromise the integrity of those walls that have managed to remain intact through thousands of years of naturally occurring floods.” Do you have access to the engineering report that provides this conclusion? What facts do you have that the HFR didn’t damage/destabilize the bridge? If not, you are guilty of the speculative nonsense that you accuse me of. I put my theory forward as a guess—you are making a definitive statement that I am wrong. Hope you appreciate the difference.

Do a search of Youtube for videos for ‘Bridge collapse river flood’ (do one with Salt River Phoenix Arizona). You can witness the dramatic impacts that can take only hours of high water flow against a man-made structure.

I’m curious to see if NPS is going to release any description of what was found and what was repaired by the NPS trail crew. I wonder how often the Bridge was getting inspected? Was a routine inspection done immediately before a release experiment and immediately after—that would be one way to tie the structural damage to the bridge to the HFR.
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ShatteredArm
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Re: Silver Bridge closure

Post by ShatteredArm »

@Canyonram
How am I guilty of speculation by stating that there is no evidence that HFS is the cause of the issue?
Canyonram wrote:Why are you finding it so hard imagine that the fragile and flimsy man-made structure placed within reach of a swollen Colorado River is not going to be impacted?
You're speculating that the rock is being eroded though, not the actual bridge. Why does the structure have anything to do with it if your while point is that HFS somehow compromises the walls?

You're the only one here who's speculating. I haven't said what I think the issue is because, just like you, I have no information.
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Canyonram
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Re: Silver Bridge closure

Post by Canyonram »

@ShatteredArm

I supported my guess. I don’t want to retype the same argument over-and-over again. Other posters have offered up their guess and speculation as to why the bridge had to be closed. Please read the entire thread for the different ideas that have gone into the mix. Speculation and imagination are foundations in creative problem-solving and a key component of science. Creative problem-solving requires getting past a rigid ‘No’ as a first step. Have to knock the rust off not just a bridge but brain-cells as well.

I’d like to hear your rationale—after all, we do know that the bridge was closed for structural reasons, NPS trail crew came in to stabilize the bridge, a highway engineer was brought in to pass judgment that it was safe for hikers, etc. Do you have an idea to throw into the brainstorming session? Or have your brain cells rusted in place?
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Re: Silver Bridge closure

Post by azbackpackr »

@Canyonram
My brain cells washed away in the last High Flow Experiment.
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Re: Silver Bridge closure

Post by chumley »

Canyonram wrote:Speculation and imagination are foundations in creative problem-solving and a key component of science
Wild speculation void of facts is also the foundation of 99.6% of all internet posts. (See? I made that up! :D )
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Canyonram
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Re: Silver Bridge closure

Post by Canyonram »

@chumley
Here’s some facts for you. 99.6% is the concentration of oxalic acid used to clean wooden decks and remove rust from metal structures. At first glance, 99.6% looks to match the percentage of your responses on the forum that are three sentences or less in length. Shorter if you judge on informational content. Even shorter if you judge on creative effort.

PS. Erosion created the Canyon. It is also a process that can destabilize a man-made structure. It is pretty wild what running water can accomplish. That’s a fact.
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