Nine months after a severe blaze temporarily closed the Deans Brook Viaduct, which carries the M1 over part of north London, repair work on the structure and in the surrounding area is complete.
Most of the repair work has taken place under the viaduct with minimum disruption to traffic on the motorway above.
The viaduct was badly damaged when fire broke out in a scrapyard beneath it in April last year, and in the intervening months intensive work has been carried out to assess the damage and carry out the repairs.
Special 3D laser scans and modelling helped engineers to find the best solution and ensure the repairs could be carried out as quickly and safely as possible.
The final part included reinstating a footpath, used mainly by schoolchildren, which had to be temporarily diverted because of the effects of the fire.
Paul Robinson, Highways Agency asset manager, said: "The M1 Deans Brook Viaduct is a key part of one of England's busiest motorways and it was of utmost importance to us to firstly get the M1 open again as soon as safely possible after the fire under the viaduct temporarily closed it, and then, with our contractors, to find the best solution to carry out the repairs with the least possible disruption to road users and the local community.
"Once the motorway re-opened after the fire in April, there was still further work to do to enable us to gain full access to the structure. We then started a thorough, detailed investigation to determine the level of damage and the schedule of repairs.
"The actual repair work started in late September and while we needed some overnight lane closures on the M1, the majority of the repair has taken place under the structure, causing as little disruption as possible to road users on the M1.
"We have also reinstated a footpath used largely by school children, and this week we will hand the site under the viaduct back to its owners. We are grateful to the local community for their patience during the essential work."
The laser scanning system enabled engineers to recreate the underside of the viaduct which bore the brunt of the blaze, revealing the full extent of the damage. This was then used to build a 3D model of the affected area which helped to generate a works programme.
The work included repairs to the concrete underside of the structure, replacement of southbound parapet, bearing replacement and new bridge joints, so the structure can expand and compress with seasonal changes in temperature.
The M1 in this area is managed on behalf of the Highways Agency by Connect Plus and the repair project was managed by Balfour Beatty Major Civil Engineering.
Nick Boyle, technical services director for Balfour Beatty Major Civil Engineering, said:"The laser scanning system provided the key to the repair design and construction programming. The beauty of 3D modelling means you can try out many different options on a computer screen to see which will work best, before you actually get on to site."
