Consultant Halcrow is lobbying Transport for London (TfL) to start planning an underground replacement for the Hammersmith flyover rather than maintaining the existing 51-year-old structure.
The call for longer-term thinking for the area comes just weeks after TfL issued a contract notice for the next phase of rehabilitation works for the flyover in the Official Journal of the European Union. The structure carries around 90,000 vehicles a day.
The flyover was closed at the end of December after structural defects in the cable tensioning were discovered, causing considerable traffic disruption both locally and regionally. Although the route was partially reopened to cars and light vehicles in January, it was only fully reopened at the end of May.
TfL said completion of the next phase of work to upgrade cables in the remaining 11 spans and carry out bearing maintenance by 2016, along with the £16M first phase on five spans, will extend the service life of the flyover by 100 years.
But Halcrow global head of tunnelling, Martin Knights, said: “We need to start thinking further ahead to what will replace the ageing flyover and consider putting the road underground to reduce the impact on the local area.” He was speaking to GE ahead of the official launch of the “flyunder” concept at the London Architecture Festival which runs from 23 June to 8 July.
The concept is a development of an initiative by Hammersmith-based Chartered Practice Architects, which asked Halcrow’s Hammersmith office to give its technical backing to the launch.
Knights said the concept had been used on the M30 in Madrid and the principles are also being applied to the Alaskan Highway in Seattle. Up to half the cost of the $4bn (£6.4bn) project in Seattle will be funded by selling off land freed up by the new tunnelled route. Knights said the same approach could be used at Hammersmith.
Knights stressed that the scheme is still a concept at this stage, although he said the solution is likely to be a bored tunnel, rather than cut and cover. He added that it must gain public support before the technical detail is worked out.
“If we can deliver a technical solution to the scale of tunnelling needed for Crossrail, then we can engineer a solution for Hammersmith too,” he said.
The scheme has already attracted the attention of the London Borough of Hammersmith and Fulham and its recently appointed leader Nick Botterill is in favour. “There is no scheme of replacement currently being planned, however, it is our strong view that this needs to be looked at starting now,” he said. “Is it really a good policy to keep patching up a 50-year-old structure, which has declining resilience and capacity at ever more considerable cost?
“While construction would take a number of years the benefits of a tunnelled replacement would be considerable. The whole area would be reunited with the riverside which would also have profound economic and environmental benefits.”
Knights said he hoped the event at the London Architecture Festival, to which a number of local politicians and stakeholders have been invited, will help the concept to gain momentum. “This level of interest will be key for a feasibility study to be commissioned, let alone funding or design details to be considered,” he said.
He added that the scheme was viable and that other infrastructure issues in the UK could be dealt with in a similar way. “Civil engineers need to be more proactive and use their technical knowledge to look for solutions and approach clients directly rather than waiting for instructions,” he said.