The project, commissioned by the Water Corporation, called for the rehabilitation of the gravity fed sewer system along St Georges Terrace, the only road that bisects the city centre east to west without interruption.
The challenge was to complete the works with minimal disruption to the flow of traffic while maintaining the integrity of the reline. The works program called for the CIPP relining of 650 m of gravity fed sewers to be broken into seven portions, each portion including jet washing, pre and post reline CCTV surveys, reinstatement of junctions and refurbishment of the access chambers.
Each of the seven portions required multiple lane closures in the east-bound lanes of St Georges Terrace and a number of street closures including the overnight closure of William Street, the only direct north-south route through the city centre. That involved the rerouting of 29 bus routes to the city centre bus port. Due to the one-way nature of many of Perth’s inner city streets and the two pedestrian malls in its centre the detours were complicated, and in many cases lengthy, requiring traffic to travel up to an extra six blocks through the city.
Anyone familiar with the Perth CBD layout will attest to the fact that the combination of a grid layout, pedestrian malls and one way streets results in any disruption to the flow of traffic affecting all of the city centre traffic and, during rush hour, the arterial roads leading out of the city.
In order to minimise the effects of the lane and street closures, Drilline were restricted by the City of Perth to 12 hour work periods from 7 pm to 7 am on Thursday, Friday and Saturday nights. Drilline were permitted to begin the set-up at 7 pm and were required to be off road by 7 am, including all traffic diversions and bypasses. As a response to the time constraints imposed Drilline broke the works down further, with a typical works program comprising Jetwashing and pre-reline CCTV survey on Thursday, CIPP reline, reinstatement of junctions and access chamber refurbishment on Friday, and post-reline CCTV with report on Saturday. The exception to this program was the 139 m section requiring the closure of William Street, where all works were completed on the Friday night between 9 pm and 9am.
Outside of the complicated traffic management, the CBD location added other obstacles including lengthy negotiations with the City of Perth for access, work permits and additional public advertisement of road closures and detours affecting both general traffic and public transport.
The project was further complicated by the need to access, monitor and King Vac (vacuum recovery) the private pumping stations servicing each of the office buildings along St Georges Terrace during the bypass periods, including Perth’s largest building, Central Park. Drilline liaised with building management of each of the buildings prior to the commencement of the project and in the lead up to each new section. Working at night and weekends did reduce the flow, resulting in reduced risk to Drilline personnel and other stakeholders in the bypass component of the project.
Drilline successfully completed the St Georges Terrace Sewer Rehabilitation Project in a highly visible location, to exacting deadlines, within extreme time constraints and additional complex third party liaison without compromising the integrity of the oviform CIPP relining works or the safety of its personnel, proving that its project management capabilities are on par with its technical expertise.