Lock 20W HNC

[Mac of Cygnet]

UPDATE (17 April 2012): British Waterways and its contractors are continuing to work in the lock and have experienced severe difficulty in removing the water from the lock floor.

 

This is due to the amount of leakage through the lock and the recent wet weather. Works to repair the floor cannot be commenced until this is done.

 

Whilst there is a possibility that the works could be complete in 14 days but there is a possibility it could take up to a month to repair the lock.

 

This is absolutely bloody ridiculous. The contractors I hope will be paying a penalty for this, if they are the same ones who ballsed up the grouting in the first place, leaving it to solidify on the lock floor and jamming the gates. But a month to clear out a lock!!! Surely dewatering the pound above might just help a little bit?

[safsnowball]

I had a look at what was going on yesterday. They've installed a dam below the lock to try and stop water flowing back into it which seems mostly successful. The stop planks above the lock now seem to be doing their job also.

 

The main problem I could see was that there appears to be a bywash which actually runs back in just below the bottom gates. This is, however, inside the dam they have made which is what seems to be making it difficult if not impossible to drain the lock.

 

Somebody also told me that the next lock up, 21w, is proving extremely difficult to fill. It's always been really slow but apparently it's now a major problem. I've seen nothing from BW about the issue.

Edited April 17, 2012 by safsnowball

[RichardH]

This is bitterly ironic given the great investment in gates on the HNC over the winter.

 

This may start to affect us now as a number of guests have the HNC planned into their holidays.

[Mac of Cygnet]

 

The main problem I could see was that there appears to be a bywash which actually runs back in just below the bottom gates. This is, however, inside the dam they have made which is what seems to be making it difficult if not impossible to drain the lock.

 

 

Diverting a byewash should not be beyond the wit of man. But better would be to dewater the canal at some point above, I can't remember if there are any sluices in the vicinity to allow this. Martin?

[MartinClark]

Diverting a byewash should not be beyond the wit of man. But better would be to dewater the canal at some point above, I can't remember if there are any sluices in the vicinity to allow this. Martin?

 

I don't know, but the river runs alongside the canal on that stretch, so possibly.

[mayalld]

I don't know, but the river runs alongside the canal on that stretch, so possibly.

 

 

Of course, the HNC usually has bed valve drains rather than run-off sluices, and many of them were abandoned a couple of years ago.

[MartinClark]

Just to add to the mystery of what on earth is going on at Lock 20w, I went there late this afternoon to take a few photos. I spoke to the security guard who is stationed in a little cabin there to guard all the pumps and equipment through the night. Bearing in mind that BW today put out a notice saying that the work could take between 2 and 4 weeks, I was a little surprised when the security guard said that BW has told his company that they wouldn't be needed after Thursday! We will have to see...

 

If you are baffled about what has been happening, these photos may (or may not) shed some light.

 

Fabric dam constructed downstream of the lock tail bridge. I couldn't see any stop plank grooves below the lock.

 

Ineffective stop planks above the lock...

 

... allow water to continue to leak through the top gate into the chamber they are trying to de-water.

There seems to be deeper water still in the lock that between the lock and the fabric dam, possibly because the canal below the lock has silted up a bit. The water leaking in through the top gate is being pumped out from the lock chamber and put back in below the fabric dam.

 

The by-wash outlet is the hole on the left, between the bottom gates and the lock tail bridge. Nothing is coming out as the pound above the lock has been lowered slightly and does not top the by-wash weir.

You can see that some smaller dams have been put in on each side of the bottom gates, presumably so that the area around the bottom gates and bottom cill can be drained. Reports from others suggest that leaking concrete grout has solidified in this area. If so, this is certainly not glaringly evident from this photo, so perhaps the depth of any such concrete is not very great and it won't take too long to hack out.

 

Of course that is speculative, as BW are not saying much about it. Indeed, the signs attached to balance beams along the canal say that Lock 20w is closed "for safety reasons"!

[Mac of Cygnet]

Thank you, Martin. You have contributed enormously to the sum of our ignorance of what the hell is going on!

[Davidss]

...

I couldn't see any stop plank grooves below the lock.

...

The by-wash outlet is the hole on the left, between the bottom gates and the lock tail bridge. ...

That picture appears to show some stop plank grooves between the by-wash outlet and the bottom gates, so they are there, just unused on this occasion.

(Possibly in the wrong place for the defect they are attempting to repair?).

 

I would echo the comment from Mac "Thank you, Martin. You have contributed enormously to the sum of our ignorance of what the hell is going on!".

I'd better confirm I read that as a positive comment, quixotically expressed :-)

 

Regards.

[MartinClark]

That picture appears to show some stop plank grooves between the by-wash outlet and the bottom gates, so they are there, just unused on this occasion.

So they are! I saw those but, for some reason, failed to recognise them as stop plank grooves. I don't know what else I thought they might be.

 

Edited to add: Perhaps BW tried using them and found that they were as effective as the stop planks above the lock!

Edited April 18, 2012 by MartinClark

[billh]

So they are! I saw those but, for some reason, failed to recognise them as stop plank grooves. I don't know what else I thought they might be.

 

Edited to add: Perhaps BW tried using them and found that they were as effective as the stop planks above the lock!

 

The situation/farce at this lock is an absolute disgrace! Just look at the hired plant in the photos. Three large diesel pumps , failing to keep the lock empty, a portable dam, hired at great expense, all to remove concrete in the bottom of the lock where it should never have been anyway. Sack the project manager who obviously hasn't a clue about canals, locks or concrete.

Harping back 40 years, we were to do a lock clearance at Fairfield , lock 18. It required first, two sets of stop planks, one at each end of the lock. Ben Wagstaffe was the BW carpenter on the Ashton then, knocked up the two sets of planks, using a handsaw and an adze, in about 90 minutes. Meanwhile 2 other canal men busied themselves clearing the cills that the planks sit on, using a special "stop plank groove cleaning tool" This with the water levels normal . The planks fitted perfectly and a 2HP diesel sludge pump was set to work emptying the lock. As the level started to drop, the planks were "racked up" using cinders off the towpath. The pump ran overnight, but the lock was ready for volunteers to clean out next day- the work proceeded over a couple of weekends, there was a lot of silt and rubbish in the lock.

Basking in past glories? Possibly, but then there were professional practical canal men, mostly poorly paid who knew what they were doing and a gang of very willing volunteers, the job got done at minimal expense and nobody died.

The Lock 20 farce, is repeated endlessly around the canal system, most times we don't get to hear about it. Why did it take 4 days to refloat a sunk boat in Lock 1w last week? Pathetic.

 

Bill

[MartinClark]

Bearing in mind that BW today put out a notice saying that the work could take between 2 and 4 weeks, I was a little surprised when the security guard said that BW has told his company that they wouldn't be needed after Thursday! We will have to see...

 

Well, the security guard was right - BW has just put out a notice to say that Lock 20w has just re-opened to navigation. Where the hell did "14 days" and "a month" come from?

[safsnowball]

Well, the security guard was right - BW has just put out a notice to say that Lock 20w has just re-opened to navigation. Where the hell did "14 days" and "a month" come from?

 

Perhaps it's reverse psychology, if you say it will take 14 days to a month and then you do it much quicker people might think what a good job you've done.