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eggsarascal

Whaley Bridge Evacuated

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2 minutes ago, Woodlover said:

Eggs will prob know if its true but when I was laying drainage a few years ago I was told due to minimum fall levels n that...that pipes full of turds and wet wipes need the piss water to help move em along ...if you just flushed the solids and there was no rain then you may get problems? Also the water must dilute the raw sewage flowing around the system and help control gases and smells? 

A 4"/110mm drain needs a fall of 1' in 40' to self cleanse, old fashioned toilet cisterns were a three gallon flush, way over the top. The new dual flush cisterns are over used on the short flush and don't provide enough water for the drain to clear, this is overcome by most folk showering each day and using washing machines/ dishwashers on a daily basis.

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What I trying to say in my earlier post, re the concrete being the problem, was that the concrete on the surface prevented the erosion beneath being seen, though walking the slabs and thumping them with sommat solid should have detected their "boastness", plus the forward slope of the earthen dam would probably have been stabilized by the grass roots, and again without the concrete, any untoward erosion would have been noticed.

BUT, these issues should? have been considered when the dam face was concreted 50 years ago, but possibly were not.

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1 hour ago, eggsarascal said:

This doesn't happen very often, I'm lost for words.

I'm only giving you my opinion on what I've read and what I know about reservoir design (having actually had a reservoir designed and built for me). I do know that there is a mandatory requirement for inspection on an annual basis and I think I'm correct in saying that an independent reservoir panel engineer has to inspect at least every 10 years. I'm also reasonably sure that I've read somewhere that an independent panel engineer said there was nothing in photos taken prior to the failure that caused them concern and I also think there was a report saying that an IRP engineer inspected and passed the reservoir (which would include the spillway and and any vegetation growth on it) in April of this year. 

 

I'm happy to take on board other peoples views, I was interested in the thread in the first place because of the design issues that came up in my own project and I felt I had something to contribute. I hadn't considered that the lack of maintenance might apply to the lower network of canals resulting in a reservoir being kept over full in order to ensure that there was sufficient water for the canals, rather than the reservoir itself.

 

Clearly if you are lost for words about my comments, you have personal knowledge of the site, the extensiveness of the vegetation and the fact that trees have grown through the spillway slab and rendered it ineffective. If you do have that level of actual factual knowledge that the spillway was fatally damaged before the storm and the overtopping, that might amount to negligence for individuals and the CaRT and that is an extremely serious matter.  

 

 

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38 minutes ago, difflock said:

What I trying to say in my earlier post, re the concrete being the problem, was that the concrete on the surface prevented the erosion beneath being seen, though walking the slabs and thumping them with sommat solid should have detected their "boastness", plus the forward slope of the earthen dam would probably have been stabilized by the grass roots, and again without the concrete, any untoward erosion would have been noticed.

BUT, these issues should? have been considered when the dam face was concreted 50 years ago, but possibly were not.

One thing with concrete, once its in place and surrounded by more concrete, is the friction between pieces is absolutely immense. You try breaking up a concrete driveway. You might crack it but you cant lift pieces out. Once you do make a hole though, it starts to work the other way, the weight of the concrete and the void underneath means that a piece can fall and what was previously seemingly impossible to break now snaps because its brittle. Those photos that I've seen of the damaged spillway, don't appear to show reinforcing bars or mesh in each slab, so its "just" concrete. Once the spillway surface is breached for whatever reason, with that level of water passing over it, there is only going to be one outcome, unless the water flow stops.

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1 minute ago, Chalgravesteve said:

One thing with concrete, once its in place and surrounded by more concrete, is the friction between pieces is absolutely immense. You try breaking up a concrete driveway. You might crack it but you cant lift pieces out. Once you do make a hole though, it starts to work the other way, the weight of the concrete and the void underneath means that a piece can fall and what was previously seemingly impossible to break now snaps because its brittle. Those photos that I've seen of the damaged spillway, don't appear to show reinforcing bars or mesh in each slab, so its "just" concrete. Once the spillway surface is breached for whatever reason, with that level of water passing over it, there is only going to be one outcome, unless the water flow stops.

Drain the reservoir before it gets to that stage?, we've already established the cut and the Goyt could have taken the flow from the reservoir before the predicted rainfall. Why can't you see CaRT didn't/wouldn't start draining before the slipway failed?

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42 minutes ago, eggsarascal said:

Drain the reservoir before it gets to that stage?, we've already established the cut and the Goyt could have taken the flow from the reservoir before the predicted rainfall. Why can't you see CaRT didn't/wouldn't start draining before the slipway failed?

That's the whole point though. Unless you are suggesting deliberate negligence, no one knew or expected that the slip way would fail. Why would they? What crystal ball do you have that they dont have, so you know it was going to fail before it did?

 

Their expectation is that it will do the job that it was built and designed for, 50 years earlier. Even if they allowed the reservoir to continue to fill once every year or so, until the water overtopped the spillway and flowed down it, the volume of water passing down the spillway in that "test" would be nowhere near the volume that came over in the storm. You cannot simulate that storm because the normal inflowing river only carries are certain volume of water in and the same volume would flow out over the spillway in the same time. 

 

As someone said earlier, if Cart had emptied the reservoir because a thunderstorm was predicted and then it rained for a bit but there was now not enough water for the canal network, they would have been ridiculed.

 

I would have thought that if they tried to use the canal network to empty the reservoir into (as they must have some mechanism for getting water out of the reservoir and into the upper reaches of the canal to top it up all the time - is that gravity or pumped?) there is no way that the canal network could absorb that volume of water because of lock gates and sluices etc. Its a system that needs a controlled level of water. The river Goyt on the other hand, is more capable of handling a higher level of waterflow, 

 

Clearly though, given the fact that they have been pumping water out of the reservoir for a week, there is no direct controlled gravity feed discharge from the reservoir to the Goyt. They might be able to divert the inlet source but once its in the reservoir they appear to be stuck. You would hope that whatever solution they come up with to make the bank above Whaley Bridge safe, and the spillway safe, that this would incorporate a means of being able to discharge volumes from the reservoir safely.

 

  

 

 

Edited by Chalgravesteve

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16 minutes ago, Chalgravesteve said:

no one knew or expected that the slip way would fail. Why would they? What crystal ball do you have that they dont have, so you know it was going to fail before it did?

If core drill samples of the spillway were taken then the lack of re-bar and voids beneath would have been discovered and it would never have been allowed to be used. 

Why would they do this...because in California US a few years ago a very similer incident occoured at the Oroville Dam that was on all the UK news and obviously big news for any people who manage Dam`s. The US incident had plants/trees growing on there spillway in google pics taken from before it failed, and it failed where the plant growth was, just like this one.

Also the US spillway was not constructed with enough re-bar or proper foundations, the thickness of the concrete ect was not up to modern standards and rules and if know pre-fail then it would have been changed. 

After the US incident at the least send someone up to drill a few holes to see the condition and why not de-weed it and grout the joins.

I honestly just do not understand why they did not learn from the US incident...They certainly missed a trick there,at the least a few executives could have had a free holiday there on a fact finding mission...maybe that's to come.

 

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10 minutes ago, Woodlover said:

If core drill samples of the spillway were taken then the lack of re-bar and voids beneath would have been discovered and it would never have been allowed to be used. 

Why would they do this...because in California US a few years ago a very similer incident occoured at the Oroville Dam that was on all the UK news and obviously big news for any people who manage Dam`s. The US incident had plants/trees growing on there spillway in google pics taken from before it failed, and it failed where the plant growth was, just like this one.

Also the US spillway was not constructed with enough re-bar or proper foundations, the thickness of the concrete ect was not up to modern standards and rules and if know pre-fail then it would have been changed. 

After the US incident at the least send someone up to drill a few holes to see the condition and why not de-weed it and grout the joins.

I honestly just do not understand why they did not learn from the US incident...They certainly missed a trick there,at the least a few executives could have had a free holiday there on a fact finding mission...maybe that's to come.

 

I don't disagree with any of this - except that if the engineering inspections say its all OK, why would they query that? The experts whose job it is to inspect and ensure the safety say its all ok! 

 

You would expect the engineering inspections teams to be absolutely aware of the California spillway failure and to be more stringent on inspections on anything constructed in a similar manner or a similar age etc. All we are doing of course, is speculating on what might have happened and what information people might have had. The one thing I really don't think anyone could have done, is accurately predict the volume of water that cascaded into the reservoir in the first place. If the wind had blown that storm 50 miles to the east or west, it would have saved 10 pages on an arbtalk forum as well as the reservoir!

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47 minutes ago, Chalgravesteve said:

I don't disagree with any of this - except that if the engineering inspections say its all OK, why would they query that? The experts whose job it is to inspect and ensure the safety say its all ok! 

 

You would expect the engineering inspections teams to be absolutely aware of the California spillway failure and to be more stringent on inspections on anything constructed in a similar manner or a similar age etc. All we are doing of course, is speculating on what might have happened and what information people might have had. The one thing I really don't think anyone could have done, is accurately predict the volume of water that cascaded into the reservoir in the first place. If the wind had blown that storm 50 miles to the east or west, it would have saved 10 pages on an arbtalk forum as well as the reservoir!

Why would they query it?,  possibly because people who have worked the cut, and the reservoir have been warning them for years of its potential to fail due to lack of maintenance, the maintenance that everyone apart from you can seem to see. When you've worked in the water industry and see the infrastructure that's passed as fit for purpose when it's crumbling you'll understand. Like I said earlier, it's not your house, business under it.

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