Using trenchless technology to seal private lateral connections to mainlines-post rehabilitation (Lateral junction repairs)

The rehabilitation of sewers using trenchless technology in is growing rapidly in New Zealand. Within the last few years several different lining technologies have become available for the rehabilitation of pipelines. The uptake in the use of trenchless rehabilitation methods is due to the reduction in costs (both direct and environmental costs) and the reduction of inconvenience to the public. The annual spending and turnover on trenchless rehabilitation has almost doubled in past five years.

The North Shore City Council (NSCC), since 1998 have been implementing “Project Care”, a 20 year project to reduce wastewater overflows and beach closures. As part of this project, NSCC is using trenchless technology to rehabilitate sewers to reduce inflow/infiltration into the sewer network. All the public network assets’ including mainlines, public laterals and public manholes in the leakiest mini catchments are rehabilitated.

The lateral connections on all rehabilitated mainlines are cut open using remote cutting technology after the mainline lining has been completed. However the re-opened junctions are not sealed and have potential risk of infiltration, as the gaps between the new liner and the host pipe are not sealed at this point. The sealing and repair at these connections is known as “Lateral Junction Repair” (LJR).

ProjectMax Ltd, has been working closely with North Shore City Council in providing the most suitable and practicable engineering solutions to control inflow/infiltration issues. This paper will discuss a case study on sealing the incoming lateral connections onto the rehabilitated sewers in North Shore City.