The project comprised the installation of Rotaloc structural liners in 5 km of deteriorated sewers with diameters of 915, 1,065 and 1,220 mm. Also included was 380 m of 760 mm diameter pipeline to be lined with Rib Loc Expanda Pipe.

The Sydney Water specification for the project classified the host pipelines as either fully deteriorated, partially deteriorated or intact. The structural capacity of each liner was designed accordingly.

The project presented Interflow with numerous logistical challenges. The deepest pipelines were 9 m deep, many of the sections to be lined had distances between manholes greater than 150 m, with the longest single section being 228 m, and the pipeline route included numerous bends with angles up to 90º. Silt levels varied, but were typically about 10 per cent of pipe diameter and required removal before lining commenced.

A particular challenge was that, being such a vital pipeline in Sydney Water’s sewer system, services had to be maintained at all times during the project. Allowance also had to be made for emergency increases in flow caused by storm events anywhere in the upstream catchment, as sewer overflows were obviously unacceptable. Interflow’s previous experience with rehabilitating large diameter pipelines convinced Sydney Water that they had the experience and resources to successfully complete the project.

Rotaloc is an Australian developed spiral wound lining system which is installed by feeding a single continuous strip of plastic profile down the manhole opening to a winding machine in the deteriorated pipeline. The winding machine takes the plastic profile strip and winds it, locking the edges together as it moves along the pipeline. The winding machine can alter its diameter as it rotates, providing a liner in firm contact with the host pipe, even if the pipe diameter varies along its length through deterioration, displaced joints, or missing sections.

A range of Rotaloc plastic profiles is available, and cement grouting is incorporated where necessary to meet the structural requirements of design specifications. While Rotaloc can be installed with some flow in the pipeline, this project required Interflow to deal with instantaneous flows in excess of 400 litres per second on some portions of the work. Bypass pumping was therefore necessary to maintain sewer services.

Interflow’s flow control arrangement required bypass pumping around lengthy sections to be lined, with flow being taken from upstream access chambers and bypassed to downstream access chambers. The longest length bypassed in a single operation during the Smithfield project was 1,700 m. For the downstream portions of the pipeline, it was possible to divert flows directly into the adjacent Kenyons Road carrier.

Bypass set up and monitoring was a critical aspect of the work as much of the bypass pipeline passed through environmentally sensitive parklands and along a creek. The pipeline routes required several temporary creek crossing bridges to be constructed.

The increasing demand for lining of large diameter sewers has led to Interflow investing significant capital in the purchase of bypass pumping equipment. The company now owns a large number of sewage bypass pumps, including two new 12 inch pumps, as well as more than 6,000 m of HDPE pipe ranging in diameter from 200 to 315 mm.

This equipment was used on the Sydney Water project, so there was minimal reliance on pump hire. Security arrangements were put in place to reduce the risk of vandalism and tampering in environmentally sensitive areas.

Lining was an around-the-clock operation. Two crews worked in 10-hour shifts, typically lining around 70 m of pipe per shift. The record for a single shift was 157 m. In the 4 hour break between lining shifts, a standby crew was on hand to provide security and also to be ready to remove the lining machine in the event of storms or a sudden increase in flow.

The liner was installed from the 600 mm diameter standard manholes. The machine was disassembled, passed through the top of the manhole, and then re-assembled at the base. No excavation was needed.

Bends in the pipeline were of ‘lobster-back’ or segmental construction, with original construction being from straight pipe sections cut at an angle and joined in-situ. The Rotaloc system negotiated several such bends by taking advantage of the strain capacity of the PVC liner. In some of the severe bends where this was not possible, lining was stopped just prior to the deviation. The diameter of the machine was reduced, and it was manually moved just past the deviation where lining continued. The small remaining unlined fillet was later lined with a structural epoxy mortar to create a continuous lining through the bends.

Work commenced in November 2004 and is expected to be fully complete by the end of June this year. The completed project will result in structural renewal of an important, large diameter deep sewer main, accomplished without the need for excavation, and without causing undue disruption to the community. This is a type of Trenchless Technology project carried out using Australian initiative that would not have been possible as recently as a few years ago.