- Whaley Bridge
Manchester Evening News are doing Live Updates https://www.manchestereveningnews.co.uk/news/greater-manchester-news/reservoir-sealed-police-people-told-16681771?Posted 3 months agodeadkennySubscriber
From earlier footage it looks like the reservoir overtopped and ran down the spillway as designed, but the surface has washed away in part. It’s not the dam breached from inside.
Now the dam has stopped overtopping it shouldn’t be so much a risk but heavy rain could wash more away and then concern how much damaged inside. Will be a big tough wall other side though and huge mound of earth still remaining, given victorian engineering so hopefully will hold.
Evacuation is obvious precaution though and to fix it they might have to drain it which means waiting for levels to go down in rivers.Posted 3 months agothenorthwindMember
As deadkenny says… Kinda looks like the bit that’s “collapsed” is just some concrete on a spillway with about a billion tons of earth underneath it. I wouldn’t describe that as a collapse. Bit worrying, yes, and if I lived downstream, I’d be GingTFO, but seems a bit sensationalist.Posted 3 months ago
Surely some duct tape is all that’s required…
Looks like a sticker to me. 🙂
I’m hoping DeadKenny’s assessment is correct. There were certainly a lot of blokes standing around scratching their heads on the bit of the dam most likely to end up in New Mills if it was a proper breach.Posted 3 months agohoneybadgerxSubscriber
The issue is that if the spillway needs to flow due to more heavy rain, etc. then said flow will was away the earth core to the dam. Not something you want to take any risks on – there’s been quite a few incidents like this over the past year or so on older dams.Posted 3 months ago
They’ve closed Union Road in New Mills, presumably because if the dam goes, the Goyt is going to get a massive influx of water and the local bridges are potentially vulnerable.
I know it’s stating the obvious, but there has been a colossal amount of rain in the last couple of days and the local rivers are already close to overflowing or over their banks already.
Fingers crossed nothing happens.Posted 3 months agounovoloMember
Been working over that way today (Higher Disley) and needed to drop property keys off in Chapel en le frith.
Quickest route is straight through Whaley, not a chance!!
All the roads into are shut with Police cordons in place, traffic around the area was crap at 2pm today so god knows what its going to be like at peak times as a lot of people who have been out for the day(myself included) wont have a clue whats going on.
Best bet is avoid it if you canPosted 3 months agothegeneralistMember
As deadkenny says… Kinda looks like the bit that’s “collapsed” is just some concrete on a spillway with about a billion tons of earth underneath it. I wouldn’t describe that as a collapse.
Yeah, cos earth is renowned as being highly resistant to tonnes of water running over it at high speed. The concrete layer on top was just for decoration wasn’t it, to make it look nice.
Words fail me.Posted 3 months agoprojectMember
As Drac said above, huge number of emergency service vehicles parked just where a dam burst is going to wash them away, also if there is another emergency near by whos going to respond, who thought it was a good idea to handball all those sandbags onto the top of the dam havent these mangers ever heard of sack trucks, to transport loads over short distances, and one poor guy stacking bags tied to the railing with a rope. Wheres the army and other armed forces.
Dolgarog in North Wales was the last UK dam collapse in 1925. Some nice rides on a bike round there, and the old wall is still there of the dam.Posted 3 months ago
If the dam fails then it is the Utility’s liability not the standard homeowner property insurance. Most houses affected by this kind of failure are well outside the flood maps. Only a dam burst/failure is probably going to cause this kind of pluvial flooding event.
The concrete spillway is not decoration. It is there to quickly transport the overtopping water away from the reservoir. The absence of concrete on that part of the spillway will exacerbate the situation if they get overtopping again as the scouring effect of the fast moving water will wash away more surface layers. If this happens repeatedly the earth wall dam is at risk.
For those stating that people are “refusing to leave”, I have family about 500m from it. The roads are closed and have been for hours – nobody goes in or out. Even the road over Disley tops.Posted 3 months agofunkrodentMember
Just to add a bit of someone who actually knows what they’re talking about (as opposed to ill informed speculation from people who can’t be arsed/are incapable of doing a bit of research before spouting off) this from the Grauniad –
Such earth embankment dams are at serious risk of being quickly washed away if the concrete spillways that protect them are damaged, according to Mohammad Heidarzadeh, an assistant professor of civil and environmental engineering at Brunel University London. “In embankment dams, spillways are extremely important, because they prevent embankment dams from overtopping,” he said. “Due to heavy rainfall ine the Whaley Bridge area, the spillway is now broken and a big chunk of its concrete structure is damaged. There is a possibility that the spillway could then become fully broken in a few hours. If the spillway is fully gone, the embankment dam will be washed away very rapidly, which could cause a massive flood.”
So in layman’s terms, if the concrete skin goes, the risk is that the water scoops away the earth underneath, thereby compromising the structural integrity of the earth wall. This may already have happened, maybe not. I certainly wouldn’t be chancing it. Fingers crossed for all affectedPosted 3 months agonwilkoMember
Whoever’s responsible for maintaining the dam is in major problem.Posted 3 months ago
The still images and video here..
Clearly show some sizeable plants growing on the spillway which given their size must have roots which pass completely through the concrete skin of the spillway.
The fact the plants arent being washed away in the video despite the volume of water passing by suggests the roots are sizeable.
Failure of the joints between the seperate concrete slabs allowing the clay earth underneath to be washed away eventually leading to the slabs failling themselves.
Maintenance failure will be pretty hard to talk their way out of.singletrackmindMember
IANACE, but surely the danger is water percolating through the breach in the concrete topping and down the underside of the remaining unbroken concretePosted 3 months ago
This would have a 2 fold effect. Wetting and loosening the earth bank so in the event of a structual failure it washes away very , very quickly
Increasing pressure on the underside of the remaing sound concrete , by adding mass / density to the earth . If the inceased weight on the underside of the spillway increases then a larger , potentialy catastrophic failure could occur with huge chunks of concrete being dislodged and then a river of wet mud de -stabilising the remaining earth bank
or perhaps not?singletrackmindMember
Have you forgotten where you are .Posted 3 months ago
This is STW where everyone becomes an instant exprt on absolutely everything despite having zero prior knowledge or having stuudied for and passed exams pertaining to a subject even mildly related to the hot topic of the day
and there are actual real life people on here who are experts in whatever particular feild is up for discussion, who know what they are talking about , and they still get told they are wrong , even if tey are right . because even if you are right, on the interent most things drop down to a difference of opions . .
Well, watching the BBC News and the reporter says that one theory is that the water is being driven through from the inside out by pressure. You have to think, that if that is the case, it doesn’t sound great.
More practically, anyone trying to drive through New Mills from the A6 end of the world can pretty much forget it, though you can get in from the Hayfield side and over the top from Marple Bridge. Anything with a bridge over the Goyt or low lying enough to be threatened by any sort of potential flood surge is shut off by the police.
It was possible to sneak through the Torrs apparently and bypass the police cordon, but some idiot called Crazy Fingers or such like tipped them off and ruined it for everyone. What a nonber, now I can’t get to the chippy 🙁Posted 3 months ago
There seems to be a lot of confusion from poor reporting, I have heard the phrase dam has collapsed used etc. When people stop and think about the unfolding scene they provide sensible comment when they react to the emotive headlines then their imagination runs wild. (not aimed at STW posters).
My take (acknowledging previous posts) is that the engineers are concerned that more rain will cause further overflow resulting in hydraulic action on the damaged spill way section. This will undercut the top of the dam causing a collapse. Then the water running though the breech will cause more erosion at an increasing rate. The result will be a tsunami like wave followed by a large river running through the village.
An evacuation had to be carried out, the possible consequences otherwise are unthinkable.Posted 3 months agoWaderiderMember
Not having read all the above I’ll jump in here as a civil engineer.
Earthfill dams always have a water cut off built in – watertight upstream face, internal clay waterstop etc. Earth on its own won’t hold back water, water will move through the pores saturating the whole structure until it fails by a mechanism such as a rotational slump or piping. Think of building dams of sand as a child on the beach – they’d always ultimately fail as the sand became saturated.
In dams of this era the waterstop is nearly always clay. The initial failure has been the concrete of the spillway, but it is particularly interesting to read that a clay layer beneath the spillway has been eroded. I’d be surprised if this clay layer was the main waterstop for the structure, common sense says the less of the structure with saturated pore spaces generally the more stable the earth fill shall be. The clay layer here may have been designed to stop water running down the spillway from saturating the downstream face of the embankment – the joints in the concrete slabbed spillway may not have been waterproof as designed.
In summary if the waterstop is gone piping failure is a very real risk. I think in any case the earth fill embankment is now saturated in this area so that sudden collapse through a slip or slump is a very real risk. This would be a very sudden event.
The water level will need to drop substantially for this risk to reduce.
Regarding the condition of the dam and spillway, the Reservoirs Act means all such structures must be inspected by an qualified engineer, who can force maintenance obligations on the owner. Hence the buck may stop with a Reservoir Panel Engineer rather than the owner, if there is judged to be liability due to poor maintenance.
Disclaimer – others know more!Posted 3 months ago
So, to sum up – the earth behind that concrete may already be saturated enough to collapse, and further overflow only increases that risk?
Terrifying. My thoughts are with the people having to work tonight in proximity to the dam or in Whaley with that thing hanging over them.Posted 3 months ago
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