Project: Tamar Bridge Strengthening
Client: Tamar Bridge & Torpoint Ferry Joint Committee
Contractor: Cleveland Bridge
UK Other firms: Mouchel; Leonhardt, Andr' und Partner; Faber Maunsell; Skanska
The 335m span Tamar Bridge was Britain's first long span suspension structure when completed in 1961.
Four decades on, the reinforced concrete deck was deteriorating and the crossing was seriously congested with 40,000 vehicles a day crossing from Devon to Cornwall - ten times the traffic it carried on opening.
An initial plan, to add external cantilevers carrying temporary decks to allow the main deck to be rebuilt without interrupting traffic, developed into a permanent widening scheme. For about a tenth the cost of a replacement crossing Tamar has now been both strengthened and widened. Weight was saved by replacing the concrete deck with steel, allowing the deck to be expanded from three lanes to four lanes.
Additional stay cables were added to increase the load carrying capacity of the main truss without detracting from the appearance of the suspension structure. All this work has been done with negligible interruption to traffic, claimed to be a world first.
Project: Restoration of Standedge Tunnel, Marsden, West Yorkshire
Client & designer: British Waterways
Construction Cost: £4.5M
Constructed between 1794 and 1811 Standedge remains the longest, at 5.2km, highest above sea level, at 195m, and deepest below the surface, at 180m, canal tunnel in Britain. But the largely unlined tunnel had been abandoned in 1944 and left for nature to take its course. Half a century on, the decision was taken to reinstate the tunnel to form a vital part of the Huddersfield Narrow Canal and Pennine Ring, giving a circular route from Manchester.
Between May 1999 and December 2000 the tunnel was drained, silt pumped out and some 2,000t of fallen rock and spoil removed. To repair 2.2km of deteriorated tunnel some 6,000, 2.2m long stainless steel rock bolts were installed and 6,500m 3of sprayed concrete applied.
Extensive work was also needed to stabilise air shafts and cross passages linking with two disused and one live rail tunnel that run parallel.
The canal reopened in May last year.
Project: Anderton Boat Lift Restoration, Northwich
Client, designer & contractor: British Waterways
Other firms: Aspen Burrow Crocker; Lewin Fryer & Partners; Bosch Rexroth (hydraulic system); R&R Engineering; TI Coatings; SGB
The Anderton Boat Lift was a world first when completed in 1875 with an hydraulic operating mechanism.
It connects the Trent & Mersey Canal and Weaver Navigation over a 17m level difference. Failure of the hydraulics led to the lift's effective replacement in 1908 by a massive steel structure supporting an electro-mechanically operated lift tank arrangement featuring an array of massive exposed gear wheels. But in 1983 the lift was closed and abandoned until the possibility of grant aid made restoration feasible.
For this job British Waterways took on the role of designer and contractor because the scope of work required could not be defined accurately. Then it was discovered that the 1908 part of the Scheduled Ancient Monument was so severely corroded that 70% would have to be replaced to make the lift operational. In a way this was a bonus because it has enabled the lift to be restored to near its original hydraulically driven mechanism as possible.