Tunnels at the heart of Sydney transport vision
Oct 2012
Peter Kenyon, TunnelTalk
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As Sydney prepares to award the major underground construction contract for 15.5km of twin running rail tunnels, attention has shifted to a vision for the historic city's highway network. Last year the Australian Government created Infrastructure New South Wales to advise it on priority projects. As a result of its recommendations projects comprising 30km of traffic tunnels are now set to advance towards the design, planning and funding stages.
- Australia has committed funding towards a new and upgraded 33km highway link in western Sydney that includes 14km of tunnels and up to 4km of cut-and-cover and open-cut excavation.
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Fig 1. Concept alignment for WestConnex Project
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Gaps in Sydney's major traffic arteries
- The Government has given top priority to and committed Aust$1.8 billion in funding towards construction of the newly-named Aust£10 billion WestConnex Project, which integrates key elements of three long-standing projects that have been stuck in the pipeline for more than a decade.
- Following detailed recommendations on a 20-year transport strategy released last week (October, 2012) by the Government's transport advisory body Infrastructure New South Wales (INSW), three road projects in Sydney have been given priority status. They are:
- 1. The WestConnex Project (Fig 1), which includes key elements of long-standing proposals for an Inner Western Bypass, M5 widening and M4 extension, and comprises:
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• Extending the M4 6.4km eastwards towards the city through the suburbs via a mixture of cut-and-cover tunnels and open cut excavations.
• Construction of new 5.3km-long twin tunnels to link the extended M4 and the M5 to the south, and provide better access to Sydney Airport.
• Widening the M5 and constructing a duplicate of the existing 3.8km-long M5 eastern-running tunnel, which cannot handle current traffic levels headed into the city.
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WestConnex concept video from INSW
- The original M5 East and West tunnels were constructed in the 1990s by the Baulderstone/Hornibrook/Bilfinger/Berger JV with Hyder Consulting and Jacobs Associates as project excavation and design consultants. They were constructed as flat-roofed 3.8km twin dual-lane tunnels with a 700m cut and cover river crossing. Six roadheaders were used to drive through ground consisting mostly of Hawkesbury sandstone, at an average advance rate of 6m/day.
- Under the new integrated WestConnex proposal, which still requires the necessary permissions and remains at concept stage, the M4 would extend towards the city centre along the existing Parramatta Road via a 6.4km mixture of cut-and-cover tunnelling, excavated slots and surface alignments. From here it would continue west towards the city and south via the proposed new two or three lane twin 5.3km tunnels, to connect with the M5.
- Excavation and support methods for the main M4-M5 link tunnel are yet to be determined, but given the likely alignment's suburban location and the need for careful monitoring of ground movement, use of TBMs is likely.
Cut and cover tunnels and slot excavations will extend the M4 eastwards along Parramatta Road, one of Sydney's oldest and busiest east-west traffic arteries
- "The State Infrastructure Strategy identifies WestConnex as the State's highest priority project. The New South Wales Government's support of the project is the start; there is now a lot of work that needs to occur to inform the business case which will be finalised by the middle of next year [2013]," INSW spokeswoman Sandy Olsen told TunnelTalk from Australia.
- She added: "This work will include route development, community consultation, preliminary environmental assessment, construction timetable, tolling and finding funding solutions. The business case will also propose strategies for future planning approvals, procurement and delivery. A Sydney Motorway Project Office is being established following the Government's announcement."
- In order to attract private funding for this and other road projects Sydney will be reviewing its tolling structure, including the possible introduction of distance tolling across the network, and the project is likely to be awarded as a concession. The recommendation to Government is that is be "delivered within the next ten years" with all necessary permissions, planning and design completed within five years.
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Fig 2. Preferred M2-F3 link is an 8km tunnel
- 2. The M2-F3 tunnel link
- In 2004 the Australian Government announced a preferred corridor for this important 8km link (Fig 2) in the north-west of Sydney following the outcome of a 2002 study.
- It concluded that an 8km tunnel under Pennant Hills Road, to a depth of 40m, was the preferred option - a decision reinforced during a 2007 review.
- This estimated Aust$3 billion project (2009 prices) is now considered by INSW as being the second most important standalone road project behind WestConnex, subject to it attracting private funding.
- In July this year Transport New South Wales, the Government's highways agency, received an unsolicited proposal to develop this route from Transurban, which already owns five concessions to operate roads and tunnels on Sydney's orbital network. One of these is very close to the proposed M2-F3 link: the Aust$1.1 billion Thiess/John Holland JV-built 3.6km Lane Cove Tunnel. The toll tunnel was acquired by Transurban in 2010 for Aust$630 million from previous operator Connector Motorways when it went into receivership. Transurban also operates a tolled 21km section of the M2 in the Hills district to the west of the Cove Lane Tunnel.
- INSW says Transurban's proposal is currently being assessed by Government transport agencies and that if acceptable it could move to construction within five years.
- 3. CBD dedicated 2km underground bus tunnel
- INSW has earmarked this project for priority construction, subject to the necessary approvals, funding package and design between 2017-2022. The scope includes:
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• refurbishment of the twin-running 850m-long disused Wynyard tram tunnels (currently used as mainly car parking space) that run under the CBD and emerge near the Harbour Bridge.
• construction of two new connecting 900m-long tunnels that will extend the dedicated underground busway alignment to the Town Hall, and
• construction of two new underground bus interchanges. - The concept is similar to the 3km busway that formed part of the package of works as part of Brisbane's Airport Link. Half of that busway's alignment is underground in a cut-and-cover tunnel.
Underground bus tunnel would utilise disused tram tunnels north of Wynyard and a new tunnel to Town Hall
- In a report to the New South Wales transport department last month (September 2012) consultants Evans & Peck estimated the current cost of the Sydney underground busway project at Aust$2 billion. There is scope within the plan for a future westward connection to the Cross City Tunnel, and any new rail link that is built to service the CBD.
- The proposals for the future of Sydney's transport network come as final planning consents were granted for the Aust$8.5 billion North West Rail Link. The full scope of this project, which will require four TBMs, includes laying 23km of new track between Cudgegong Road and Epping, 15.5km of which will be in twin-running segmentally lined tunnels. Advance construction works have already started, and the main tunnelling contracts are expected to be awarded early next year ready for a 2014 start.
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Lane Cove tunnel collapse investigations - TunnelTalk, February 2007
Three vie to build longest rail tunnel in Australia - TunnelTalk, September 2012
Brisbane awards airport highway tunnel link - TunnelTalk, May 2008
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