Brawoliner used at cathedral site
Difficulty of access meant a pipe repair job required a trenchless solution. On behalf of CJ Kelly, Ian Clarke explains
Dalrod UK has successfully completed a trenchless lining job near historic Ely Cathedral in Cambridgeshire.
Pipeline survey works highlighted that ground movement has caused deterioration and cracking in sewers the vicinity of the cathedral and that the sewers were now in need of relining. In this instance, one particular 225mm-diameter sewer system, which was approximately 2.8 to 3.0m deep, had particularly difficult access problems. The pipeline runs below a terrace of pre-war houses with no rod-able access points from most of the lateral connections. There is also poor access to most of the gardens, which made it difficult to reopen the lateral connections subsequent to the main line lining work.
Most of the properties comprised threestorey buildings that had live systems which could not be shut down. This meant that Dalrod had to reline the sewers whilst the system was live and over-pump to make sure that no flooding occurred in the basements of any of the buildings. This was clearly a case for a trenchless solution.
Dalrod’s lining expert, Mike Pollard, says: “We knew that only one product would do the job and that was Brawoliner as it is a strong, flexible material which would fill all of the cavities, smooth out joint displacements preventing any further movement within the sewer itself. Not only that, but it also meant that we would eliminate the need for expensive excavations.”
Brawoliner was chosen because of its capacity to negotiate multiple bend and joint displacement situations, whilst offering a 50-plus year life-expectancy. The company also used its latest acquisition on the project, a lateral cutter robotic system which was used to reopen all of the 24 lateral connections along the lined main sewer route.
The three liners installed comprised two relatively short sections of 10m and 15m length respectively, which used the inversion drum system. The longest lining of some 68m used a scaffold tower inversion set-up, with the scaffold being some 6.5m high.
This height was necessary to ensure tight fitting of the liner against the host pipe wall whilst balancing the high pressure head of the live flows in the laterals feeding the main sewer being lined. All liners were completed using hot water curing techniques. At one point the crew was accompanied by a security guard as they accessed the rear of a local bank to complete the lining project.