Replacing a Road Bridge over a Busy Motorway Without Long-Term Closures
Replacing a road bridge over a busy stretch of motorway might conjure up an image of long-term road closures, diversions, disruption and frustrated road users. This was the scenario that Highways England, Osborne and our supply chain partners were determined to avoid on the Romsey bridge replacement project over the M27.
The existing dual-deck bridge had come to the end of its serviceable life and needed to be replaced. The plan adopted aimed to complete the demolition and replacement works during three weekend closures between junctions 3 and 4 of the motorway.
The first phase, to demolish the western section of the bridge, was completed in September 2018. The process was so well organised that the motorway reopened 16 hours ahead of the 5.00am Monday deadline, leaving the remaining deck of the bridge in service. Following the demolition of the first section, preparatory work has begun ready for the installation of the new bridge, which is currently under construction in an offsite location. The offsite methodology means that the bridge can be transported to the site and installed during a single weekend closure .The remaining section of the old bridge is to be demolished, once the new deck has been brought into use.
The fact that the first phase of this ambitious project was achieved so far ahead of schedule is down to the close collaborative working between Highways England, Osborne, and our supply chain partners.
Sustainability is another important consideration. The arisings from the demolished bridge are being crushed to create around 2000 tonnes of clean crushed concrete to provide all of the piling mats and haul roads at Romsey. When the second bridge is crushed next year, any material that is not absorbed in to the project will be sold to a local supplier.
Before work started, extensive surveys led to relocation of several species of animals including grass snakes, slow works and adders. Speed doesn’t have to come at the expense of sustainability or the environment – it’s just a question of careful planning.
The next phase of the project to install the new bridge is scheduled for July 2019. Being able to quickly install a complete bridge over existing transport routes (whether road or rail) within tight closure periods is a capability that Osborne has deployed on several projects. Success depends on meticulous planning, collaboration and a determination to put the needs of road users first.