The traditional home to the Royal Train when not in use by members of the Royal Family, the transfer of the Royal Train left the Wolverton Rail Works open for development. Subsequently housing developments and the refurbishment of the 300 year old building were planned.

As part of the development works, a potentially unstable area of ground, carrying a 900 mm diameter surface water sewer, needed to be stabilised. The sewer ran 14 metres below the historic building and is the responsibility of Anglian Water. Obstructing the sewer The property developers used historical drawings to map the sewer to be rehabilitated, which ran in a straight line between two manholes for a distance of just over 100 metres. In accordance with this information, the developers proceeded to drill a bore hole which was pumped full of concrete to stabilise the ground below.

However, the historical drawings were found to be incomplete, with the sewer running with a slow long bend with part of its course running directly below where the bore hole operation had taken place. This meant that the bore hole had been drilled directly into the sewer, which had subsequently been completely filled with concrete. CIPP saves the day High pressure jetting, man entry and water lancing techniques all proved to be ineffective solutions. As the works needed to be completed concurrently with the property development works, Anglian Water contracted OnSite to fix the problem using Trenchless Technology.

OnSite initially proposed to use its high-specification robot cutter unit to grind out the concrete, but after initial attempts with this system progressed slowly, OnSite decided to rehabilitate the sewer using a technique that would allow crews to work safely to excavate the concrete while remaining fully protected in the pipe.

OnSite’s rehabilitation method involved installing a series of structural CIPP repair patches inside the pipe up to the face of the concrete. The concrete excavation team could then work safely within the ‘patched’, and therefore supported, area of the pipe whilst further concrete was removed. A new patch was installed after every 0.5 metres of concrete were removed, enabling safe working to continue. As the operation progressed a constant appraisal of procedures was carried out with new ideas and suggestions being put forward all the time. Such suggestions included the installation of a temporary support heading where the concrete had been poured into the pipe. It took seven days to completely remove the eight metre long concrete obstruction.

OnSite subsequently fully lined the damaged area using the Premier-Pipe CIPP lining system in order to ensure the long term structural integrity of the pipe, particularly around the damaged area caused by the bore hole.