Melbourne Water as part of the Northern Suburbs Sewerage Strategy is undertaking the Northern Diversion Sewer Project. This $300 million upgrade of the sewer system in Melbourne’s north to improve the health of the Yarra and other Melbourne waterways. The project will help protect the Merri and Moonee Ponds creeks from sewage overflows that can occur after heavy rain. The new sewers will increase the capacity of Melbourne's sewerage system to meet the rapidly growing demand for services in the northern suburbs.

The project involves the construction of 13 km of new sewer pipes ranging in diameter from 1.6 to 2.5 metres. Additionally, five major access shafts of up to 65 metres in depth and 13 metres in diameter will also be constructed.

Stage 1
Stage 1 is a major 8 km-long deep tunnelled sewer that will connect the existing sewerage system near the Merri creek at Coburg and the Moonee Ponds creek in Pascoe Vale to the northwestern sewer in Essendon.

Construction of Stage 1 commenced in early August 2007 with site establishment works at the Brearley Reserve site. Works at other shaft sites commenced through the remainder of last year and will continue this year. So far, the project has commenced (establishment, shaft sinking and launch chamber construction).
The geology is typically siltstone (Silurian age), with intrusions of basalt (Newer Volcanics) and alluvial soil deposits (Brighton group). Crews will use two Herrenknecht EPB TBMs that will erect precast concrete rings of six segments.
Korea Mould has been contracted to design and fabricate steel segment moulds, internal diameter 2.4 m and 3.4 m, a segment lifting and turning device and a segment stacking frame. The segments will be sealed by Phoenix tunnel seals. The mucking-out method consists of a loco with muck cars, a vertical conveyor as well as traditional crane and skips.
There will be three drives from the main TBM work site in Brearley Reserve. One will be heading north (NNW), one south (SSW) and one east. The east drive is at 10 m higher level than the north and south drive. The reception shaft also picks up three drives. In all, there will be eight shafts with maximum depth of 65 m and 13 m in diameter.
Vertical conveyor
At the main tunnelling shaft site TBM drives are undertaken from two different levels. Two drives will be undertaken from the base on the shaft and the final drive some ten meters above the shaft invert. During the lower drives, the muck cars will tip the spoil into a hopper and apron feeder which in turn supplies a 75 m-high elevator conveyor. The intermediate drive will also utilise the apron feeder and vertical conveyor. This vertical conveyor will be designed, produced, supplied and installed by Marti Technik. Stage 2

The geology will principally be high strength basalt with some zones of sand/soils. The tunnel alignment goes through high strength abrasive basalt requiring the use of a hard rock shielded TBM supplied by Robbins, a section of Brighton group and alluvium is anticipated and a Herrenknecht EPB TBM will be used for this section.
In September 2007, John Holland signed the contract with Robbins for a 3 m double shield TBM, back-up, spare parts and cutters.
The Robbins TBM will be launched from a 35 m-deep shaft at the compact Newlands Road job site. The machine will utilise 43.2 cm cutters to bore through basalt rock ranging from low strength to 270 MPa UCS. As the TBM bores, full muck cars will be hoisted up the shaft and dumped into a spoils bin for removal by rubber-tired vehicles. Launch of the TBM is scheduled for late August 2008, after manufacture and factory commissioning in the Robbins facility in Ohio, USA.
Precast concrete segmental lining will be installed as part of the EPB TBM section. Here again, Korea Mould will produce the segment moulds, which will be sealed by Phoenix gaskets.
This is a significant project for the water companies and the State government of Victoria. It will support growth for the north of the city of Melbourne and deliver environmental benefits to the city's rivers and creeks.