Costain is currently in the early contractor involvement (ECI) phase of a £70million project to strengthen and refurbish the Hammersmith Flyover in West London on behalf of Transport for London (Tfl).
The project is one of the first tranches of work to be awarded by Tfl as part of the structures and tunnels investment portfolio (STIP), through a four-year highways and tunnels framework awarded in April 2013.
“We are delighted to have the opportunity to work in close collaboration with Transport for London on this strategically important project, which is a first for Costain’s highways sector,” said Barry Woodman, programme director for Costain.
The flyover was closed in 2011 when it was found that water and salt from winter gritting had leaked into the structure corroding the structural post tensioning cables. Five spans were repaired prior to the London 2012 Games.
Costain is now tasked with strengthening the remaining structure, and replacing the existing post tensioning strands with a new system. The bridge deck is supported on a single central row of piers comprising 16 spans – 11 at 42.7m long, two at 30.5m, two of 36.6m and one at 22.6m – giving a total length of 626m. The approach ramps at either end increase the total length to 863m.
The works also include replacing the roller bearings on the 16 piers and replacing the abutment bearings, renewing the bridge deck waterproofing, bridge deck drainage and outfalls, replacing expansion joints, renewing the carriageway surfacing and replacing the existing central reservation safety barrier along the length of the structure.
The project is complicated by the age and size of the flyover, as well as its strategic importance to London’s transport infrastructure. The existing precast concrete segmental post tensioned flyover was originally opened in 1961 and today more than 90,000 vehicles a day use the busy A4 arterial route over the central Hammersmith gyratory system.
“At Hammersmith, our aim is to work closely with Transport for London and our designers to minimise traffic disruption on this technically challenging project,” said Barry.
The project team has been co-located with TfL and designer RPB (Ramboll and Parson Brinkerhoff) in London since April to collaboratively develop the detailed design and construction methodology prior to commencing on site in late October 2013. The works are expected to be completed by summer 2015.