New Zealand concedes proposed park route
Nov 2011
Peter Kenyon, TunnelTalk
- An interim concession by New Zealand's Department of Conservation is granted to a private company to build and operate a controversial 11.4km single lane bus tunnel through national park land on its South Island.
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Existing route, a trap for rockfalls and avalanches
- The Milford Dart company has been battling for more than five years to get the green light for its ambitious plan to link Mount Aspiring and Fiordland National Parks under the Humboldt and Ailsa mountain ranges of New Zealand South Island's Southern Alps.
- The NZ$170 million proposal is to excavate the 11.4km roadway by TBM, making the so-called Milford Passage comfortably the longest bored tunnel in the country.
- As part of its application Milford Dart presented a technical design carried out by URS, whose experience includes working on the 9km-long, 10m-diameter TBM-bored Second Manapouri Tailrace Tunnel in the same area of New Zealand’s South Island near Queenstown.
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The plan comprises:
• A 100m drill+blast tunnel at the Hollyford Valley (Milford Sound) end, with most of the tunnelling operations being carried out from this side.
• A 468m drill+blast tunnel at the Routeburn Valley (Queenstown) end.
• On-site assembly of a TBM to bore a 5m o.d (4.65m i.d.) to excavate the 11.3km drive at 3% gradient;
• Dispersal of the 268,000m3 of spoil on the nearby Hollyford Airstrip, raising its level by 7-7.5m.
• Construction of a new access road at the Queenstown side and widening of carriageways on both main roads near the service road access points.
11.3km Dart Passage will cut the 12 hour Queenstown to Milford Sound journey to 4 hours
- The new route is intended for buses only and would cut journey times from Queenstown to the isolated but extremely popular tourist destination of Milford Sound, to just two hours for the shorter 240km route. Currently road traffic reaches the area via a 12-hour 1,200km round trip using the SH-6 and SH-94 highways, both of which are prone to avalanches and rockfalls. The route is designated the third most dangerous in New Zealand.
- Milford Dart proposes to use a fleet of zero-emission diesel-electric hybrid coaches, running 40 buses daily in the Summer, or an average of 23/day throughout the year. It anticipates an 18-month construction period for the two drill+blast portals, during which a final geotechnical survey would also be carried out. This would be followed by 3-4 years of tunnelling and site remedial works.
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Longitudinal section of the proposed tunnel alignment
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Routeburn portal plan
- The commercial viability of the scheme is backed by recent studies that have shown Milford Sound attracts more than 550,000 visitors a year, a figure expected to rise to 750,000 by 2012. Because planning regulations have limited the construction of tourist accommodation in Milford Sound an estimated 90% of visitors come on day trips, the journey time resulting in short stays.
- Earlier this month, following an inquiry, summarised in a 168-page report, the Minister for Conservation gave notice of her intention to grant concessions under section 17Q of the Conservation Act 1987 to Milford Dart Limited to investigate, construct, operate and maintain a bus tunnel from the Routeburn Road in Mount Aspiring National Park to the Hollyford Road in Fiordland National Park. A period for written objections to the plan closes on 27 January 2012.
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Up to 40 buses a day would use the tunnel
- Although the Department of Conservation has granted an interim concession for the project, there will now be a formal public consultation. A previous stumbling block had been that construction of an access road had encroached on the National Park itself, but Milford Dart has satisfied government officials by increasing the length of the tunnel to 11.3km from the originally 10.2km length.
- If built, the Milford Passage, as it would be called, will be the longest bored tunnel in New Zealand, overtaking the 8.9km Kaimai rail tunnel on the East Coast main trunk railway near Apata that opened in 1978.
- Currently the longest road tunnel is the 1,900m long tunnel between Lyttelton and Christchurch that opened in 1964.
- Construction of a 14m diameter twin tube TBM bored tunnel is required on the estimated NZ$1.4 billion Waterview Connection project around Auckland to complete a 4.8km section of six-lane highway on the city's Western Ring Route. In August the Fletcher Construction, McConnell Dowell, Obayashi Corporation, Beca, Parsons Brinckerhoff, and Tonkin & Taylor group, with sub consultant SICE of Spain, was selected as the preferred design-build partner for construction of the large diameter EPBM undertaking.
- New Zealand awards mega-TBM undertaking - TunnelTalk, August 2011
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