Melbourne’s Northern Sewerage Project Commissioned
On Friday November 11, 2011, the final section of the last shaft cover was lowered into place at Newlands Road, at an event marking the successful commissioning of the Northern Sewerage Project (NSP). This five-year, $650 million project began in August 2007 and completed six months ahead of schedule and $135 million under budget. It involved the excavation and construction of 12.5 kilometers (7.8 mi) of new sewer to increase the capacity of the sewerage system for Melbourne’s growing northern suburbs, and to help protect local creeks from the damaging impacts of sewage overflows that can occur after extreme wet weather events.
The project was delivered jointly by Melbourne Water (Stage 1) and Yarra Valley Water (Stage 2). Project partners for both stages included John Holland as contractor, Aurecon as superintendent/project manager, and Sinclair Knight Merz in association with Jacobs Associates as designers. Working with Sinclair Knight Merz, Jacobs Associates led the tunnel and shaft design for both stages of the project and provided construction services through project completion. Melbourne Water’s Mike Filby, NSP Stage 1 project director, acknowledged the scope of this project and the dedication of the team: “The NSP has been the single largest sewerage tunneling project undertaken in Melbourne. Having such a strong and dedicated design team has been one of the cornerstones for its successful delivery.”
Most construction work for the new sewer took place between 15 and 64 meters (50 and 210 ft) underground. Three specially assembled tunnel boring machines (TBMs) were used to construct seven tunnels through a variety ground conditions ranging from basalt to weak, interbedded siltstone and sandstone. The TBMs included a 3-meter-diameter (10 ft) hard rock machine and two earth pressure balance machines, one 3 meters and the other 4 meters (13 ft) in diameter.
A fiberglass reinforced polymer (FRP) pipe lining was installed within the new sewer tunnels that connect the project’s eight main access shaft sites. This lining provides a finished diameter ranging from 1.6 to 2.5 meters (5.2 to 8.2 ft) across the system. Works also include smaller connections to the existing sewerage system, several of which were installed using trenchless methods.
John Holland is now reinstating the construction sites to their previous condition through revegetation and landscaping. Soon, the only evidence of construction will be several inconspicuous circular manhole covers.
