In June 2007, Caboolture Shire Council (CSC) invited tenders for the rehabilitation of 1,543 m of 200 mm ductile iron cement lined (DICL) sewer pressure main between Aerodrome Road and Lower King Street, Caboolture Qld.

The original DICL main was commissioned in 2003, but as a result of aggressive industrial trade waste discharges (food processing) from the catchment, the original cement lining was quickly eroded from the pipe to the extent that the pipe’s DI wall was beginning to corrode.

CSC received a total of ten submissions from five companies and the contract was awarded to Insituform Pacific Pty Limited (IPPL) in August 2007, based on the company’s conforming offer to rehabilitate the pipe using its exclusive PolyFlex system.

The Bruce Highway runs through the middle of the project and to make it even more critical, $40 million worth of widening works to the highway and approaches were recently completed prior to the rehabilitation project being let. The rehabilitated pipe runs directly under the upgraded six lanes of highway and then adjacent to the upgraded approaches on Lower King Street.

The client therefore opted for the specification of a structural trenchless rehabilitation system with a positive test pressure of 800 kPa, a minimum finished internal diameter of 180 mm, and a design life of 50 years.

The client’s specification was highly innovative by Australian standards as very little close-fit pressure pipe rehabilitation has been carried out in Australia. While the pressure pipe rehabilitation market is well established in Europe, led by the UK, it is only starting to gather momentum in Australia and North America.

Insituform, with its original foundations going back 35 years to the UK, was in an excellent position to bring a number of pressure pipe rehabilitation systems and extensive experience to the Australian market.

The PolyFlex system was developed by Insituform and uses standard Australian manufactured high density polyethylene (HDPE) pipe to create a new internal liner within a pipe. The HDPE pipe is temporarily reduced in size on site using the PolyFlex roller reduction machine which allows the pipe to be easily inserted and pushed through the host pipe. The compressed pipe is then re-rounded within the host pipe using hydrostatic pressure to provide a close fit pipe liner.

A total of 22 small excavations were proposed on the pipe to allow access for lining and the removal of all scour, air, reflux, and stop valves, as well as various 22.5, 45 and 90 degree bends along the pipe route. The liner was able to comfortably deal with 11.25 degree bends with the longest single installation being 288 m. IPPL received excellent site support from its UK and US colleagues during the project to ensure the transfer of global experience to the Australian crew.

One of the key challenges on this project was the required flow bypass system, a complex project in itself. IPPL decided to design a two stage overland bypass system which mirrored the pipe and fittings in the ground in order to keep the pump stations operating as normal without the need for constant manning.

The bypass system was complex in that it had to negotiate several major road crossings and incorporate a number of valves as well as drainage and test points to allow the bypass to be decommissioned without the risk of spillage. Each bypass stage was approximately 750 m long using the same grade HDPE pipe being utilised for lining.

This project will be strategically important to the continued growth of the pipeline rehabilitation market in Australia by establishing the foundations for a pressure pipe rehabilitation market through its success.