Article: Major engineering hurdles remain for new rail tunnel beneath city

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From the Melbourne Age click here!

Major engineering hurdles remain for new rail tunnel beneath city

Major engineering hurdles remain for new rail tunnel beneath city
February 28, 2013 Adam Carey

SILTY soil, the cancer centre currently being built, the City Loop's four tunnels and aquifers beneath the murky bottom of the Yarra River are all major hurdles to building a proposed new rail tunnel beneath the city.

Investigative work is well under way on building the proposed Melbourne Metro tunnel, before the required federal funding to help pay for the major project has been secured.

But project planners have yet to solve a number of engineering challenges, the greatest of which is how to tunnel beneath the Yarra River, which is risky due to the presence of aquifers and softer ground.

Cracks have previously appeared in CityLink's Burnley tunnel near the river, leaking water and costing hundreds of thousands of dollars to repair.

Public Transport Victoria is also contemplating running the tunnel over the City Loop near Melbourne Central station, just metres below the earth's surface.

This option is preferred as it would cost less than digging beneath the Loop, some 50 metres below ground. It would also save passengers a very long escalator ride to street level.

Five years after Melbourne Metro was first proposed in Sir Rod Eddington's Victorian transport report, project manager Paul Beavis conceded engineers had not yet solved the puzzle of how the tunnel would be built, in a presentation to the Railway Technical Society of Australasia in November, details of which were posted online last month.

Mr Beavis told the gathering Public Transport Victoria was also contending with changes brought about by the construction of the Victorian Comprehensive Cancer Centre in Parkville. ''They've had to change their plans because one of the options they were thinking of using was not there any more,'' said Michael Angelico, a society member who attended the presentation.

Further west at the proposed Arden station in North Melbourne, the presence of silty soil meant watertight diaphragm walls would be needed, Mr Beavis said, while sandy soil at Domain station beneath St Kilda Road was also a potential problem.

Ray Kinnear, director of network planning at PTV, said on Wednesday: ''The construction of Melbourne Metro presents a number of logistical challenges ... New underground railways are successfully constructed in the heart of cities around the world ... We are actively applying [lessons] from these projects in the planning of Melbourne Metro.''