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Bexley Bridge
 

Description of Works 
Bexley Village Bridge is a critical part of the local infrastructure in Bexley. Carrying the A223 over the River Cray, it is one of the main routes in and out of the high street. First constructed in 1872 to replace an earlier 18th century structure, the bridge was built using Victorian cast iron beams and a mix of brick, concrete and stone parapets. A steel footbridge was later added to the south side of the bridge. 

Following many years of wear and tear, an assessment survey carried out by the London Borough of Bexley showed that the bridge was steadily weakening and was at risk of becoming unsafe.  

As the term maintenance contractor for the borough, FM Conway was commissioned by Bexley Council to carry out a comprehensive upgrade scheme, supported by funding from Transport for London, which would see the existing bridge and parallel footway demolished and rebuilt.  Crucially this would allow the overall width of the bridge to be increased from 9.22m to 9.91m, bringing it within safe limits for modern foot and vehicle traffic. 
 

Delivering Innovation 

The FM Conway team first implemented a temporary footbridge to the south of the existing bridge to allow continued pedestrian access to Bexley High Street throughout the upgrade works. 

Bexley Village Bridge carries a number of services and utilities over the river, including telephone cables, high-voltage electrical cables, medium and low-pressure gas mains and a 750mm high pressure water main that runs alongside the structure. The site team had to take extra care throughout the project to avoid damaging these utilities and to preserve the safety of those working on site. 

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Challenges and Solutions 

During this phase of the works, the site team noticed that the flange bolts that were holding the high pressure collars on the Thames Water main had begun to corrode and were at major risk of failure.  Making the most of the bridge closure, FM Conway and Thames Water took the opportunity to replace these rusty bolts with new stainless ones to maximise the lifetime of this asset.

Vibration monitors were used throughout the upgrade scheme to assess the impact of the works.  The team had to be especially careful not to damage a large 700mm foul sewer main and the 750mm high pressure water main running across the structure. The old bridge was taken down in two phases to allow the team to re-divert the 700mm combined sewer main.  Three-quarters of the structure was demolished before installing 16 of the 20 piles for the new bridge down to a depth of 18 metres. Once this had been completed, 700mm combined sewer from the remains of the structure was diverted into temporary manholes and a new temporary sewer installed.

The precast parapets and beams for the new bridge were lifted into place using a 300-load crane. With these in place, the team then installed the cast institute reinforced deck slab. The deck was sprayed with a Stirling Lloyd Eliminator waterproofing coating to prolong the life of the structure and the steels within it.  FM Conway’s surfacing team laid the bridge’s new carriageway and resurfaced the approaches to it using recycled material from FM Conway’s state-of-the-art asphalt recycling plants.  With this complete, the northern footpath was opened for public use, allowing the team to remove the temporary pedestrian footbridge.