Vandalism not the cause
I THINK Canal & River Trust needs to look further than ‘a drained lock through vandalism' to seek the cause of the movement in the lock wall. [Wolverhampton 21] writes the, Chairman of the Grantham Canal Society, Mike Stone.
On the Grantham Canal Lock 18 suffered a similar problem. Once the wall was dismantled the cause was easily discovered. Water had entered through the brickwork above the lock gates; working its way through the brickwork of the quoin; running behind the wall and then, possibly, freezing. The ice had sought the easy way of expanding and pushed the wall towards the empty lock.
Enlarged
Once we dismantled the wall the hole enlarged by the water flow was very apparent! It is clearly visible below the balance beam in the attached photo. Yes the water had enlarged it to the diameter of a hard hat!
So that's one possible cause; there may be others.
For example—what has been taking place in Oxley railway sidings beyond the towpath? In the general area have any land drains or ditches been blocked or moved? Has there been any experimental fracking for oil within 20 miles of the lock? When did the area last experience a mini earthquake? Were there old mine working in the area?
I see that it has been noted that this lock was constructed after the flight was built. However, as this was in the early 1780's no doubt the construction techniques were still pretty sound.
Lack of maintenance
Wait until the wall comes down to find the real answer—which just might be, as in our case, lack of maintenance to the wall above the top gate.
Our problem cost over £200,000 to repair which was met by generous donations and sponsorship. I anticipate CaRT will have to find a similar figure. So don't expect the flight to re-open quickly and I suggest it will not do so during 2013.
Regrettably, boaters and CaRT are reaping the rewards of a maintenance backlog, which even as I write, is probably generating further problems which have yet to surface, caused by many years of under resource and neglect.