18 June 2012

Following 18 months of major utilities strengthening and replacement works on one of London’s busiest streets, the Costain Laing O’Rourke joint venture, as part of the Bond Street Station Upgrade for London Underground, has re-opened Oxford Street to two-way traffic.

The work was required prior to the tunnelling works that will connect the existing station into the new Crossrail route across the capital. It had to be completed in time for the Olympics, due to the Transport for London embargo that will be in place between late June and September.

Oxford Street sits on top of a dense network of sewer, gas, water, electricity and telecommunications systems. Many – notably a 30-inch diameter water main – date from the early or mid-19th century and are made of cast iron. The station upgrade works will require tunnelling under them, starting in 2013.

“Because they’re old pipes there’s concern that they could crack,” explained Deputy Project Director David Whiteford. “The 30-inch main is one of the main water feeds into London and the consequences of that breaking in the middle of Oxford Street would be horrendous.”

The remedy was to insert plastic sleeves that would be more tolerant of any ground movement inside the iron pipes. However, getting to the existing pipes often meant cutting through huge quantities of old concrete backfilling.

“We used hydro-demolition techniques to get the concrete out as quickly and safely as we could, without using excavators,” said David.

“We were working 24/7 but had to restrict our breaking-out activities so we weren’t jack-hammering right through the night because there are residents and a hotel right by the worksite. Throughout the works we have made it a priority to engage closely with the local community.”

Drawing the plastic sleeves through the pipes also proved problematical because of the number of bends in the pipes, which meant the sleeves had to be inserted in sections, then joined up. In all, more than 1.2km of piping had to be replaced with plastic equivalents.

The works required extensive traffic management operations diverting up to 110 buses an hour away from Europe’s busiest retailing street and were successfully delivered without a single lost-time incident. This achievement contributed to the project receiving a Considerate Constructors’ Silver award, a London Underground Silver Star and ROSPA Gold Award.

The position of utilities could not be assumed only from existing plans and so “We had to be flexible in dealing with the unexpected,” said David.

“We carried out radar surveys before we started, followed by hand-dug trial holes to confirm these surveys. In total, over 1000 Permits to Dig had to be issued over the 18 months. The fact this was done without a significant service strike is a testimony to the diligence of the responsible persons issuing them.”

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