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| Halcrow designs tunnels for New Zealand's largest road project Halcrow is designing the 13.5m-wide, 340m-long twin-tube tunnels through Johnstone's Hill, north of Orewa, for the Northern Gateway Alliance as part of the NZ$365 million 7.5km Northern Motorway Extension. The two tunnels will eventually be linked to a sweeping 537m viaduct over the Waiwera River at the southern portal. Tunnelling of the south-bound tunnel from the north portal, adjacent to the Puhoi River, commenced on February 20 using a roadheader to excavate the sedimentary deposits. Excavation of the tunnels and cross-passages is expected to take approximately one year with an excavation volume of aprox. 60,000 m³, followed by the construction of the permanent concrete lining. Design continues on the skewed portal structures that are designed to blend into the bush-clad hillside and on the internal fitout of the tunnel. The tunnel is the first large road tunnel to be constructed in 30 years, since Wellington's Terrace Tunnel which was built in the mid-1970s, and is part of New Zealand's largest single road project. write your comments about the article :: © 2006 Construction News :: home page |