01.01.07
Kilburn High Road bridge project completed
Network Rail has been responsible for the design and construction of a £6.5m project with Galliford Try to replace a four span overbridge at Kilburn High Road in north London which is owned by Network Rail. The structure carries the A5 over the West Coast Main Line railway. At this point the A5 is the direct arterial route from Marble Arch in central London to the start of the M1 motorway.
The bridge comprised three spans of cast iron beams dating from the 1850's and a fourth more recent span of steel construction. The three cast iron spans failed their Bridgeguard 3 assessment and needed replacing in order to carry modern 40 and 44 tonne HGV traffic. The fourth span required strengthening. The road bridge was the central one of three. The adjacent parallel bridges carry footways, shops and Kilburn High Road station, meaning that access to the site was extremely restricted.
The scheme to replace the bridge was further complicated by the presence of a large number of utility pipes and cables. In particular two 450mm diameter gas pipes, two 450mm diameter and one 300mm diameter water pipes and over 50 BT ducts had to be temporarily diverted or worked around.
The planning and sequencing of the works were crucial to the success of the project which had to be completed whilst minimising disruption to vehicle and pedestrian movements. Through detailed liaison and planning with Camden council and Transport for London, Network Rail was able to devise a scheme that saw the bridge replaced with modern precast concrete units over a 106 hour possession of the railway using a 500 tonne crane at each end of the bridge and a third service crane.
The overall cost of the scheme was £6.5 million which included £2 million of service diversion costs. At the height of the possession weekend there were around 100 engineers on site and approximately 1,500 m3 of debris was removed from site. The project was a logistical success and saw a large bridge carrying one of the busiest roads in London over the busiest mainline railway completed on time and to budget.
During the main weekend, 45m long temporary bridges long were used to support some of the BT cables in situ, reducing the cost of diverting them. Pedestrian access around the site was maintained at all times through careful planning and shops and premises remained open throughout.
The possession was handed back 30 minutes early and the eight week road closure was given up one day early.
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