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Restoration drama

Foxton locks Restoration of one of the man-made wonders of the world is moving closer thanks to works now underway on the Grand Union canal. Jon Young reports.

Currently sitting with four out of five stars on the BBC search for the seven wonders of the man-made world, Foxton Locks in the West Midlands is unarguably a thing of intrigue.

Built in 1810, the flight of locks allows barges to ascend the 23m hill on the journey from London to the north. It takes 45 minutes for a barge to pass through all 10 locks. But it hasn't always been this way.

From 1900 to 1911 the Foxton inclined plane lift shimmied barges up the slope in just 12 minutes (see box). But in 1911 the lift was mothballed to save money and by 1928 the machinery had scrapped.

Close to a century on, work is under way to restore as much of the site as possible to its former glory. Although the lift itself is not being reinstated at this stage, contractor Morrison, on behalf of client British Waterways is carrying out major works on the lower basin and the canal's upper arm - located at the bottom and top of the former lift (see diagram).

Work on the lower basin began with the construction of a 400t stone dam across its entrance from the canal, explains Morrison site agent Stuart Johnson.

The dam enabled dewatering of the lower basin - necessary for restoration work to go ahead.

Once dewatered, a large amount of the silt that lines the basin was also temporarily removed to expose the brickwork for repair.

In the lower basin a timber walkway once separated the two landings of the lift.

Johnson explains that the walkway is being reconstructed using like for like materials from the large oak beams to the small steel bolts.

Because the site is a Scheduled Ancient Monument, locally sourced brickwork and copings that best match the original are being used in the repair of basin, adds British Waterways senior engineer Simon Hughes.

But it is the upper arm that needs the greatest civil engineering attention. When the lift was closed, this stretch of canal was sealed off at a stop lock. Morrison arrived on site at the upper arm with little more than an overgrown ditch to mark the path of the old canal.

It took the excavation of some 3,000m 2 of earth to shape the upper arm. Johnson explains that '8.5m long sheet piles have been used to shore up the left [east] bank after badgers had undermined it by digging their sets over the years'.

The 6.5m sheet piles used to seal the front of the upper arm, where the barges would have entered the lift, have been deliberately left undisguised to make it clear to tourists that they are not replicas.

Unexpected ground conditions meant the sheet piles were not able to be vibrated to their full depth as initially planned. A second rig was brought in to hammer them to depth.

A butyl membrane has been used to line the upper arm up to the stop lock, laid over a drainage bed that guides any leakage to side ponds.

A concrete coating is now being applied to the membrane and, once complete, revetment blocks will be installed on the banks. Through the stop lock traditional puddle clay is being used for a lining because it is easier to mould round the lock's features than the membrane, claims Hughes.

The upper arm should be completed in February and both Johnson and Hughes believe the entire £2.6M project will be completed in late November.

It is hoped funding to reinstall the lift itself will be found in time for a reopening in 2011, 100 years after its closure.

How the inclined plane lift worked Designed by Gordon Cale Thomas and built by W H Gwynne of Hammersmith London, the lift was an attempt to protect the canal from the booming rail industry. It consisted of two tanks or caissons on separate rails, each capable of holding two narrow boats or a barge.

The tanks were kept full of water and balanced each other.

Powered by a 25hp engine, one tank ascended the slope as the other descended. It took just 12 minutes for two boats up and two down, a drastic improvement on the 45 minutes per narrow boat on the locks. And less water was lost through the system because the tanks did not need to be emptied.

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