Construction of the Thames Barrier

Jane Thorniley-Walker’s portrayal of construction of the Thames Barrier illustrates the works at their climax early in 1982 just as the extensive temporary works are being removed to reveal the permanent structures. The view is from the north bank, up-stream from the Barrier with Woolwich in the distance. Mud flats are exposed by the low tide.

The nine river piers can all be seen, with the distinctive hoods and stainless steel cladding under various stages of construction on all the main piers. Concrete works are still being completed on Piers 4 and 5. Piers 1 and 2 are less visible and support dropping (rather than rising) gates along with the elevated permanent Warren truss pedestrian bridge from the North Bank to Pier 3.

Access to the works during construction was generally along the temporary bridge that was constructed on tubular steel piles half way across the river and around each pier during construction. This bridge can be clearly seen on the upstream side of piers 1 to 4 and is in the process of being demolished in the span to Pier 5. Beyond the temporary bridge, small boats were generally used to reach other parts of the site, and these can be seen moored at the mid-stream jetty up stream of Pier 5, at the south landing and elsewhere as safety boats. Cages suspended from the cranes were also used frequently to swing personnel from pier to pier or down onto barges.

Four types of crane can be seen on the main site: Tower cranes are mounted on the piers, a mobile telescopic crane is working on the north river bank, while crawler cranes were used on the temporary bridges. One crawler crane is delivering timber for the hoods to Pier 4 and has been lifting up the deck and extracting the tubular piles of the retreating temporary bridge. Floating barge-mounted cranes were used for the river works and inclined masts can be seen between piers. These would be carrying out a range of tasks such as bedding the sunken concrete sills on sand, laying rock armour to prevent scour, removing temporary works and installing machinery to operate the gates. ‘The Merlin’ between piers 4 and 5, would be driving sheet piles into the river bed for the ‘sill cut-off wall’ to prevent water flowing through the gravels beneath the river bed.

The flat-topped barge in the foreground of the picture with the temporary timber decking was used to deliver steel sheet piles. Sheet and box piles played an important part of both the permanent and temporary works and were used to construct cofferdams around each pier so that the concrete piers could be built up off the bed of the river in the dry. Keeping water seepage to an acceptable level was a constant battle until the concrete pier could be built up. The remains of these cofferdams can be seen in the picture at Piers 3, 4 and 5.

The upstream barge contains one of many airlifts manufactured for various uses during construction. This one cleaned out the insides of the box piles before they were cut once the cofferdams were no longer needed. Airlifts worked by mixing air with water at the bottom of a water-filled open tube, so that the buoyant mixture rushed up the tube sucking debris up with it in the form of an underwater vacuum cleaner.

The apparatus in the down-stream barge, moored in the foreground beyond the flat top barge, was designed to provide shelter from tidal flow for divers cutting off sheet piled walls. Much underwater cutting of steel was carried out by divers in zero visibility using electric arcs, and without protection from the tidal currents, divers could only work for half an hour or so at high and low water.

Between the cofferdams are other temporary sheet piled walls that were installed just to reduce the tidal flow in that working span. Cost and effort were minor considerations when there were opportunities to speed up operations.

While a three-shift system kept the site active for six and half days and five nights a week, the picture captures the site in the few hours rest after the Saturday morning shift. Although the oil on canvass painting was painstakingly created in 2009 from several photographs, Jane has caught the pervading sense of excitement that remains even when the cranes, boats and piling rigs fell silent. During the years of construction there was an ever growing risk that the Barrier might be finished too late to save London from flooding.