A507 Stotfold Underpass
| Project name: | A507 Stotfold Underpass |
| Client: | Bedfordshire County Council |
| Business(s): | Civil Engineering |
| Sector(s): | Civil Buildings and Amenities |
| Location: | Bedfordshire |
| Type of contract: | Traditional |
| Contract value: | £500,000 |
| Duration: | May 2004 - August 2004 |
| Contact email: | civilengineering@osborne.co.uk |
In just 11 weeks Osborne built an underpass beneath the busy A507 to give pedestrians and cyclists access to a new area of development on the edge of Stotfold in Bedfordshire. This was achieved with minimum disruption to traffic on the road thanks to an alternative design and construction method that was proposed by Osborne at the tender stage, based on experience the company has gained in the rail sector.
The proposal was to construct the new subway entirely off line and then install it during a weekend road closure, rather than building on line, which would have required half of the carriageway to be closed throughout the construction period. The reinforced concrete underpass was built in two 14m sections inside a casting bay to one side of the A507.
During a weekend road closure the construction team excavated the existing road and transported the two complete portal sections into position one at a time using a special trolley system consisting of three Kamag multi axle trailer units. Once the two portal underpass units had been positioned, the four wing walls - which had been precast on site -were lifted into position using a 500 tonne mobile crane.
With all sections of the structure in place, the excavation around the structure could be backfilled and the existing carriageway reconstructed, allowing the road to be reopened to traffic at 6.00am on the Monday morning.