Insituform has now lined almost 35 km of 150–300 mm diameter sewers throughout Hunter Water Corporation’s (HWC) significant region of 5,366 square km with a total of 4,477 km of sewer mains.
In August 2010, Insituform was asked to undertake the rehabilitation of a deteriorated 450 mm diameter sewer main through Elermore Vale Public School.
The main was 120 m in length, with initial CCTV revealing that the pipe was suffering from ongoing, large mass-root intrusions, leading to regular blockages and emergency maintenance. Flows were as high as 90 per cent in sections, being fed by 450 mm, 300 mm and 150 mm mains upstream.
To make the project even more interesting, the line ran through a sensitive area in Elermore Vale Public School adjacent to Ironbark Creek. The work site was also going to encroach on the school’s parent drop-off and pick-up zone.
Working together with HWC’s operations and engineering staff, Insituform developed a proposal to overcome the identified risks and complete the rehabilitation of the pipeline with minimal impact to the public or the environment.
Due to the high incoming flows and potential for environmental damage, Insituform decided to set up a significant precautionary bypass prior to lining. This involved running the bypass under busy Croudace Road, through a nearby stormwater culvert.
In order to eliminate the risk of any sewer bypass leaks, the under-road crossing was completed using fully welded 200 mm HDPE pipes.
Insituform said “Thanks to extensive prior communication and planning with the school, the parent drop-off and pick-up zone was isolated and relocated to an alternative safe location for both students and parents, without impacting their normal activities.”
Insituform was then able to successfully install CIPP structural liner using its proprietary air inversion/steam curing technology.
The 9 mm thick liner was installed in a one-day shift, reducing the original pipe diameter by only 2 per cent, while actually increasing flow capacity due to the improved hydraulics through the smooth liner.
A final CCTV inspection of the pipe after lining showed a significant reduction in flow levels. As the Insituform tight-fit CIPP liner is installed in one continuous length, without any joins, it becomes impenetrable to root ingress. This ensures at least 50 years of virtually maintenance free operation of the asset.
“This project is yet another example of the benefit that Trenchless Technology provides to the environment and the community when properly planned and executed in partnership with the asset owner,” Insituform said.
