Tring Summit closure

[David Mack]

The other interesting question over the next day or so will be how fast the Tring summit actually falls and how far down it goes. The final canal level will tell us where the groundwater level currently is and the rate of fall will say something about how bad the leaks are.

 

And while the canal level is down, and they don't have to make any provision for boat movements, are BW proposing to do anything towards fixing these leaks, so that the Tring Summit is less susceptible to this in future?

 

David

[BEngo]

I remember Gavin (ex BW water management guru) explaining all this at an open day, but I've forgotten most of the details. According to Alan Faulkener, "Originally the Marsworth engine pumped into the Railway Feeder North and hence into the Marsworth reservoir.... [later] the system was modified for the water to enter the canal above lock 38. From this pound it could be run into the Startopsend reservoir." (Grand Junction Canal. p.92). Is this still happening, I wonder?

 

 

I had seen that, but even the first time I read it it doesn't make sense- lock 38 is the top of Peters Two so the water runs into the Red/White Lion pound, which is lower than Startopsend reservoir (which is the lowest of that group)- there is a paddle on the reservoir headbank which can run water from the reservoir into the Red/White lion pound at the tail of lock 39, practically under the road bridge. When the paddle is up getting into the teashop side of Marsworth bottom is a much more interesting manoeuvre!

 

Levels might allow BW to run the excess into Wilstone Reservoir, but I don't know how this could be done- certainly not off the Aylesbury arm.

 

N

[Proper Job]

And while the canal level is down, and they don't have to make any provision for boat movements, are BW proposing to do anything towards fixing these leaks, so that the Tring Summit is less susceptible to this in future?

 

David

From what I understand, it would be a pointless exercise. The water is leaking out of un-puddled sections of the canal. Under normal circumstances with ground water levels at anything normal, this works in favour fo the canal as ground water seeps into the canal.

 

The problem now is that ground water levels are so low that water is now seeping out of the canal and effectively topping up the water table.

 

If the effected areas were sealed, as soon as the water table rose to its normal levels (when we eventually get some significant rain) and puddling would be 'blown off' by the pressure of water behind it.

 

It's fair to say that these are extra ordinary circumstances

[mayalld]

And while the canal level is down, and they don't have to make any provision for boat movements, are BW proposing to do anything towards fixing these leaks, so that the Tring Summit is less susceptible to this in future?

 

David

 

From reading the information posted, I suspect that the answer to that will turn out to be "not possible".

 

So far as I can tell, the whole design of a long stretch of the summit pound means that it will always leak. It isn't about fixing leaks, because that implies that something is broken, wheras in this case the problem is that the canal was never designed to be watertight. It isn't the canal that neads fixing, but the whole design of the canal.

 

To "fix" this would require the whole canal to be rebuilt, which would be a serious engineering problem, as it would have to withstand the groundwater pressure once the water table comes up again.

[David Mack]

From reading the information posted, I suspect that the answer to that will turn out to be "not possible".

 

So far as I can tell, the whole design of a long stretch of the summit pound means that it will always leak. It isn't about fixing leaks, because that implies that something is broken, wheras in this case the problem is that the canal was never designed to be watertight. It isn't the canal that neads fixing, but the whole design of the canal.

 

To "fix" this would require the whole canal to be rebuilt, which would be a serious engineering problem, as it would have to withstand the groundwater pressure once the water table comes up again.

 

The BW Press Release quoted in post #69 says:

 

From Wednesday 11th January water in the stretch between locks 39 and 49 will be reduced by approximately 300mm in order to take it below the upper section of the canal bank which is often most prone to leaks.

 

Jeff Whyatt, senior waterway manager explains; "The top part of the canal bank is often most susceptible to leaks due to the fact that it is continually wetted and dried and it is also subject to holes or cracks formed by burrowing animals and wave action from boat props."

 

If that is so it would seem that taking the opportunity to repair the upper section of the channel would reduce (but not eliminate) the water loss.

 

And the provision of a drainage layer behind a new impermeable lining would mean that when the groundwater is high, the excess water could be collected and fed into the canal.

 

David

[LEO]

 

The other interesting question over the next day or so will be how fast the Tring summit actually falls and how far down it goes. The final canal level will tell us where the groundwater level currently is and the rate of fall will say something about how bad the leaks are.

 

If it falls more than 300mm what will BW do? Holding it at -300mm will still cost water that isn't there.....

 

N

 

Hi,

 

By measurement during the period 11.00am Sunday to 11.00 Monday, I reckon the Cowroast level dropped by about 75mm.

 

I confirm BW have started pumping from the borehole.

 

The stop planks at New Ground may take a time to seal.

 

Leo.

 

PS - It will be interesting to see how water flow from the Wendover feeder holds up - this drains a huge area around Wendover, and flow rates for many years are available somewhere - booklet -'Water from Wendover'.

Edited January 16, 2012 by LEO

[koukouvagia]

Having exchanged some mails this morning with Jim, (Koukouvagia) that first posted this thread, he is again in communication with BW's regional manager, Jeff Whyatt, to try and get definitive answers to a number of questions about BW's intentions.

 

I'm sure Jim will report back here when he learns anything new.

 

OK, here's the latest from Jeff Whyatt:

- The pound is now down 330mm. We have switched on the Cowroast (borehole) pump to bring the level up in the 'marina' section of the canal. It is our intention to attempt today to seal (rack up) the planks to enable the Cowroast section of the pound to maintain a differential head of water from the level on the north side of the planks.

 

- We intend to monitor the levels either side of the planks to establish how effective the seal on the planks is. We will also monitor the hours run per day on any/all pumps used to maintain levels.

 

- It is our intention to maintain the northern side of the planks at no lower than 450mm for the time being. NB – this is likely to need a feed of water to maintain this level, we will look to overpump using Cowroast borehole supply for this, where need be.

 

It is clearly too early to give indications of the water conserved from this action – we will be better placed to inform you of this next week

Car parking at Marsworth – the old BW yard has now been opened up as a temporary car park for displaced moorers

 

How long will these current measures continue ?

 

I recognise that this is a question that is concerning many.

 

If reservoir savings that result are meaningful then possibly throughout February – it is too early to speculate any further than this.

 

We will share results by way of this weekly update and take a view in consultation with the Trade and boaters who are directly affected

 

 

 

 

I'll keep everyone posted as and when I hear any more news.

Jim

[LEO]

I have to say I would not blame lack of rain. I blame poor maintenance and spending money on things that should have been spent on LOCKS. I am near Uxbridge Lock that leaks like a goo dun and Cowley Lock is even worse.

 

Hi,

 

Would not worry about these two locks, lots of water drains down via the Rivers Ver, Colne, Gade and Chess.

 

Leo.

[BEngo]

You clearly know a lot more than I do, so I'd really like to learn more!

 

At which locks between Tring summit, and (say) Stoke Hammond is there actually any back-pump availability, please ?

 

/quote

 

 

 

 

At Fenny there is a pump in the cottage/workshop on the towpath side.

 

At Talbots the pump is in the hip-roofed building across the lock from the cottage.

 

At Stoke Hammond 3 the pump is in the hip-roofed buildings on the opposite side to the pub

 

At Leighton the pump is at the tail of the lock on the cottage side

 

At Grove I don't know

 

At Church the pump is on the offside in the building there- this may suck from below Grove. There is (was last time I passed) a temporary discharge pipe wandering across the remains of the side ponds

 

At Slapton I don't know

 

At Horton the pump is on the offside in the cottage buildings there. It may suck from below Slapton

 

At Ivinghoe the pump is in the building by the cottage at the top lock on the towpath side

 

At Nags Head 3 the pump is in the Southern end of the pump house by the middle lock 35 - it draws from below 34

 

At Peters Two the pump is in the buildings on the Marsworth side of the cottage on the offside.

 

I still don't know how (or if) the water gets up to the Summit except that Tringford pumps are almost certainly involved - is anyone still in touch with Gavin?

 

A good clue for tracking the pumps in many places is to look and see where the electric wires go.

 

Over the years I have seen most if not all of these working but I think they are all locally controlled (so are difficult to manage without a lot of blokes) and are so infrequently needed since Tring Sewage works on was built on the Wendover, that the mud has to be cleared from all the inlets and outlets every time before they will work. Maybe the upgrade will enable them to be run emotely so that a few minutes a week will keep the pipes etc clear.

 

N

[koukouvagia]

 

At Church the pump is on the offside in the building there- this may suck from below Grove. There is (was last time I passed) a temporary discharge pipe wandering across the remains of the side ponds

 

 

I think this is correct. It also explains why the Church to Grove pound is very often shallow. The water bypasses this pound as it is back pumped into the pound above. You only need a few boats from the new marina to lock down below Grove and the level sinks alarmingly. At least no water is lost as it is on the Tring summit - it just needs rebalancing.

 

There are nine Northern Engines, so there isn't one at either Grove or Slapton

Edited January 16, 2012 by koukouvagia

[BlueStringPudding]

OK, here's the latest from Jeff Whyatt:

 

 

I'll keep everyone posted as and when I hear any more news.

Jim

And this morning most of it was nicely frozen over. A few more days and nights of cold temperatures and the ice will hide most of the leaking of the planks till a thaw mucks it all up big time!

[alan_fincher]

You clearly know a lot more than I do, so I'd really like to learn more!

 

At which locks between Tring summit, and (say) Stoke Hammond is there actually any back-pump availability, please ?

 

<snip>

Over the years I have seen most if not all of these working but I think they are all locally controlled (so are difficult to manage without a lot of blokes) and are so infrequently needed since Tring Sewage works on was built on the Wendover, that the mud has to be cleared from all the inlets and outlets every time before they will work. Maybe the upgrade will enable them to be run emotely so that a few minutes a week will keep the pipes etc clear.

<snip>

Thanks!

 

You live and learn!

 

I don't think much of this very often gets switched on, or at least I have never seen a great deal of evidence of it.

 

That said, Fenny did appear to be being back-pumped today, although the rate of flow is very low, (that said, as it is only back-pumping round a 1 foot deep lock, I suppose it can be a lot slower than most!)

 

As to statements about current situation, I took another look at New Ground planks this evening....

 

I'm afraid I can't see anything that proves they have been putting water in on the Cow Roast side of the planks, and letting it drain down on the Bulbourne side.

 

If anything, despite some of the comments just made, the whole level throughout, including the Cow Roast stretch, looks marginally lower than yesterday, but not by very much.

 

There is absolutely no evidence of any level difference at the New Ground planks, or of water getting past them rather than building up.

 

An attempt has been made to hang a plastic sheet on the Cow Roast side of the planks since yesterday, though not a very good one!

 

If there were a level difference, I personally thing a lot of water would escape. Both the condition of the grooves, and the way the boards have woods wedged both sides of them mean I think the edges are really going to leak.

 

As of today, the planks and the padlocks are the only thing stopping the summit being used, I would say, otherwise most boats could still be crossing it.

[matty40s]

oh Alan, go and get some ash and do it properly!!

 

unless there is a significant difference between the levels, the plastic sheet will just float around.

 

Best thing they could do is empty the water from the summit down the Marsworth flight until it reached their required depth instead of waiting for it maybe....in time.....to drop.

 

Then they would find out whether the whole pound was leaking, or just the stretch from New Ground Bridge and Cowroast.

[AJLintern]

Why don't they have double grooves a couple of feet apart and fill the bit in between with clay? Wouldn't have to rely on the sealing of dodgy grooves then as the clay would do the sealing with the planks just to hold it in place.

[sheriff]

Why don't they have double grooves a couple of feet apart and fill the bit in between with clay? Wouldn't have to rely on the sealing of dodgy grooves then as the clay would do the sealing with the planks just to hold it in place.

yeah why not.good idea in theory..sure someone will shoot the idea down.worth a try I would of thought

[RLWP]

Why don't they have double grooves a couple of feet apart and fill the bit in between with clay? Wouldn't have to rely on the sealing of dodgy grooves then as the clay would do the sealing with the planks just to hold it in place.

 

Because they don't need to?

 

The traditional and effective way is to use planed planks and drop ash down where there are leaks. It works - this is how the dry dock at Hillmorton works

 

Richard

[sheriff]

Because they don't need to?

 

The traditional and effective way is to use planed planks and drop ash down where there are leaks. It works - this is how the dry dock at Hillmorton works

 

Richard

seen the Hillmorton dry dock myself...and it works.....that's answered that question

[bizzard]

Volunteers volunteers,thousands and thousands of em all st that's whats needed

[Pluto]

Volunteers volunteers,thousands and thousands of em all st that's whats needed

... and two buckets each.

[Ray]

I'm told that the Stoke Hammond pump runs eight hours a day every day by one of the local residents and that was last Autumn before the current problem was identified.

 

Grove lock leaks (as does Church) although whether at both ends I'm not sure. They both drain fairly quickly after use. There are also ongoing problems either with or in the area of both Ivinghoe locks which seem to have defeated BW last winter.

 

I've been told that the pumps at Peter's Two have been used although I've never witnessed it.

 

BW were working on a leak in the pound below Slaptopn last Autumn. However, the pound below Peter's Two regularly drops about a foot probably because the moored boats further down are lifting paddles overnight to re-float their boats. BW then come down the following day and top the levels up, presumably from the Marworth end judging by the direction of the water flow which makes me wonder whether the back pumps further north are working.

[sheriff]

I'm told that the Stoke Hammond pump runs eight hours a day every day by one of the local residents and that was last Autumn before the current problem was identified.

 

Grove lock leaks (as does Church) although whether at both ends I'm not sure. They both drain fairly quickly after use. There are also ongoing problems either with or in the area of both Ivinghoe locks which seem to have defeated BW last winter.

 

I've been told that the pumps at Peter's Two have been used although I've never witnessed it.

 

BW were working on a leak in the pound below Slaptopn last Autumn. However, the pound below Peter's Two regularly drops about a foot probably because the moored boats further down are lifting paddles overnight to re-float their boats. BW then come down the following day and top the levels up, presumably from the Marworth end judging by the direction of the water flow which makes me wonder whether the back pumps further north are working.

Thinking about it there's not many locks south or north of Tring that don't leak more than the average,and a fair few leak many many locks of water over 24hours,even when closed up

[alan_fincher]

Today's very boring New Ground Bridge stop plank pictures!

 

Plastic sheeting added to Cow Roast side,(sort of!....)

 

 

The following is one of the reasons why I am not confident about the ability of this lot to seal - is the brickwork that bad under the water ?

(And "yes", this is the side it needs to seal against).

 

 

Comparing to yesterday's pictures, I would say it has dropped by less than an inch since then, (both sides, as I don't think there was any level difference either day).

[sheriff]

I was considering getting on train to Tring to take some SLR photos myself to post to our counter parts across the channel to see how Great we are in Britain of doing things ........you spend all this money...and this is it.

 

why is there no BW aware tape....slacking (normaly placed on unfinished jobs).

 

I am aware that those working chaps up north seem to be more enthusiastic when it comes to doing these types of jobs.

 

with less money and time allocated to them..........you see a marked contrast in workmanship...up there..seen it myself and asked why.....:and less money/time/and manpower allocated:is the reply

[jenlyn]

I was considering getting on train to Tring to take some SLR photos myself to post to our counter parts across the channel to see how Great we are in Britain of doing things ........you spend all this money...and this is it.

 

why is there no BW aware tape....slacking (normaly placed on unfinished jobs).

 

I am aware that those working chaps up north seem to be more enthusiastic when it comes to doing these types of jobs.

 

with less money and time allocated to them..........you see a marked contrast in workmanship...up there..seen it myself and asked why.....:and less money/time/and manpower allocated:is the reply

Frozen in at tescos, where you?

[koukouvagia]

Someone with greater mathematical ability than mine ought to be able to predict how far the canal will have dropped if it loses water at the rate of 60 megalitres a week. It's a bit like those O level maths problems that I used to struggle with in the dim and distant past:

 

"If a tank of water 4.13km long and 5m wide loses water at the rate of 60 megalitres a week, how long will it take to lower the level by 400 cm?"

 

 

 

Will it take days/weeks to drop the level?

Edited January 16, 2012 by koukouvagia