The Melbourne Main Sewer Replacement (MMSR) is a vital infrastructure project employing a LOVAT tunnel boring machine (TBM) to meet the future growth of Melbourne.

The MMSR is a major urban infrastructure project that will replace a section of Melbourne’s main sewer that has been servicing the city and inner southern suburbs for over 100 years.

MMSR project scope

The original Melbourne main sewer was built between 1894 and 1897. The old sewer requires replacing, due to its age and capacity, to keep up with urban growth. The capacity of the new sewer will be four times greater than the existing sewer.

Managing Director of Melbourne Water Rob Skinner said “This massive engineering project will also deliver health and environmental benefits, cutting the risk of sewage leaks into Melbourne’s waterways including the Yarra River and reducing the need for running repairs.”

Construction work for the MMSR will include the replacement of approximately 2.214 kilometres of the existing Melbourne main sewer from the Docklands in the north to connect with the Hobsons Bay main sewer in Port Melbourne. The diameter of the replacement sewer tunnel will be between 1.5–1.8 metres at a depth of between 10–15 metres.

The MMSR will also involve the removal of the North Wharf pump station and a staged sheet piling process for the Yarra River.

A TBM called Lucy Loo

The TBM will bore through Coode Island silt, sand and other materials, and has been named ‘Lucy Loo’ after a competition among students at the local Port Melbourne Primary School.

While you could be forgiven for thinking the TBM has been named after the famous actress, Lucy Liu, it was in fact a grade six student, Lucy Goudie, who named it after herself and the slang term for a toilet.

The TBM is a specially designed earth pressure balance machine of 2.952 metres in diameter that will construct a 2.4 metre ID segmental tunnel lining. The TBM has an 11 metre shield length and measure 92 metres in total length, including backup. The TBM is being designed to be capable of cutting a maximum of 150 mm per minute.

Six vertical access shafts 10–15 metres deep will be excavated along the sewer corridor providing access for ‘Lucy Loo’ to be inserted and retrieved. These shafts will then act as future manholes.

The TBM will bore into the ground at the key construction site of Fennel Reserve in Port Melbourne. The northern section of the project, around Docklands and the Charles Grimes Bridge, will use pipe jacking technology.

Contractors

John Holland Group has been appointed lead contractor for the project on behalf of Melbourne Water. Other project team members include designer GHD and project manager Connell Wagner.

John Holland Managing Director David Stewart said “This is the second project to reach the construction stage under John Holland’s six year agreement with Melbourne Water to provide tunnel construction services. We are excited about getting started on this vital piece of Melbourne infrastructure.”

The Yarra River crossing

Melbourne Water has identified a major component of the MMSR to be the crossing of the Yarra River, upstream from the Charles Grimes Bridge.

The river crossing will be completed by a three stage cofferdam construction, commencing from the south bank and progressing north. The company said that this will ensure two-thirds of the river will remain open to traffic at all times.

The cofferdam construction involves the installation of steel sheet piling to create a closed area in which to work. Some river silt will be removed to allow concrete pipes to be laid under the river bed. Once the silt has been removed, a concrete slab will be poured within the sheet piling as a base upon which a pipe will be laid and fitted together by divers. The pipe will then be encased in concrete, secured into place and back filled to the existing river bed level. The sheet piling arrangement will then be moved further across the river to allow the next stage to be laid.

Melbourne Water said that strict environmental controls in accordance with the Environmental Protection Association of Victoria, Melbourne Water and Parks Victoria requirements will be implemented and maintained throughout the duration of the project to protect the health of the waterways and aquatic life.

Branch sewers

The MMSR project will also involve the construction of approximately 2.5 kilometres of new local branch and reticulation sewers to connect the existing sewer system into the new MMSR. The company said that these works will be undertaken mostly by Trenchless Technology using small diameter pipes between 300–500 mm. Small short term shaft sites in local streets will be utilised to complete the works.

Melbourne Water said that construction of the MMSR is expected to be completed in 2012.

The Sugarloaf Pipeline

The $A750 million ($US618 million), 70 kilometres Sugarloaf Pipeline – also known as the North-South Pipeline – will connect the Goulburn River to Melbourne’s Sugarloaf Reservoir to allow the transfer of 75 billion litres of water to Melbourne by 2010 as part of the Food Bowl Modernisation Project.

The pipeline will have a maximum diameter of 1.75 metres. John Holland has been awarded the contract to construct the pipeline. The contract is an alliance between Melbourne Water, John Holland and designers Sinclair Knight and Mertz and GHD. The initial development phase of the project commenced in early 2008, with construction commencing in November 2008. The pipeline will be completed in 2010.

Ollie the TBM

An $A8 million ($US6.6 million) remote controlled TBM (pictured page 51) has completed an 830 metre tunnel under the Toolangi State Forest to make way for the water pipeline.

The TBM, named ‘Ollie” after the world’s biggest earthworm the Giant Gippsland Earthworm (Oligochaetra), was manufactured especially for the rock encountered in the area.

An Herrenknecht AVN 1800 TD (with an extension kit to suit 2000 ID / 2400 OD pipes) was used to excavate the tunnel, 700 metres of which was through rock with strengths ranging from 80 to 250 MPa. The final 130 metres was excavated through soft colluvial material.

‘Ollie’ mixes the excavated material with slurry for transport back to the surface, where it is segregated by a large Slurry Treatment Plant onsite. Some of the rock has been used elsewhere on the Sugarloaf Pipeline. The majority is disposed of at the old Castella Quarry.

Alliance Project Manager Rob Cranston said the successful completion of the tunnel marked a major milestone in the pipeline project. Mr Cranston congratulated the Project Manager for the tunnel, Sam Jones, and his team on successfully completing the tunnel earlier than expected.

Tunnelling began on 1 April and took ten weeks. A crew of ten worked 24 hours a day, six days a week to complete the drive.