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.
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"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.
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.
(CD)
