It was this particular fault that had resulted in scouring of the backfill and the subsequent subsidence in the bitumen. Other faults included exposed reinforcement and displaced joints, also allowing scouring. The structural integrity of the drainage system was good, however at this point it was over 2.5 m deep and running under a major road.

The City of Tea Tree Gully was looking for an alternative solution to replacing this section of drainage. The competitive cost of CIPP lining compared to traditional open trench excavation was attractive. A CIPP liner can be significantly more cost effective when other costs such as disruption to services, roads, paving and damage to the surrounding environment are factored in.

Pipeline Technology Services were consulted to see if the repairs required could be completed without excavation. At the time, they had previously only patch lined up to 300 mm. Marc Berry, Pipeline Technology Services Manager viewed the initial CCTV, did some further research and remembered an article in the March 2005 edition of Trenchless Australasia, “Record repair in record time for Launceston City Council”, about a similar project in Launceston where the joint was over one metre in diameter and six metres underground. He contacted KRE and, feeling confident that it was possible, proposed a solution utilising the KRE patch in a box system to supply and install seven cured in place patch liners (CPPL) of 525 mm diameter. The council accepted the proposal and Pipeline Technology Services arranged the required plant and material to carry out the installation.

As the pipework was on the downstream end of a substantial stormwater collection system, the work could only be attempted in good weather conditions. The work was carried out over four days, during which Pipeline Technology Services successfully installed all seven of the CPPLs.

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On completion of works, the post installation CCTV confirmed that the CPPLs had provided a sealed, effective solution. The City of Tea Tree Gully was happy that the rehabilitation in fact resulted in a cost saving compared to replacing the pipework.

In all, cured in place patch liners represented a cost effective, environmentally and socially responsible alternative to the replacement of the section of drainage for the asset owners. The advantages of relining over replacement of the section of drainage included:

• Works completed in far shorter time frame; • Less disruptions to residents and traffic; • Cost effectiveness; • Elimination of risks to other services, such as electrical lines in the deep excavation process; and, • Elimination of high safety risks to pipeline technicians and others.

Pipeline Technology Services have the philosophy that rehabilitation of existing drainage is a superior option not only in cost effectiveness, but importantly in regard to environmental and social impacts. Asset owners will recognise the value of a preventative management program covering sewer and stormwater drain assets knowing that repairing collapsed pipes in an emergency can far exceed the costs of preventative maintenance.