The NZ Transport Agency says excavation work for the first of the Waterview Connection's two 2.4 kilometre-long motorway tunnels beneath suburban Auckland is on-track to begin next year, with today's ceremonial ground-breaking for a 30 metre deep trench needed for the construction of the project's twin tunnels.
The Prime Minister, John Key, officially turned the first soil for the excavation of the tunnels' southern approach trench in the west Auckland suburb of Owairaka this morning.
The trench, which will be excavated to a depth of 30 metres, will be where the 85 metre-long tunnel boring machine will be assembled before beginning work excavation of the tunnels next year.
NZTA State Highways Manager for Auckland and Northland, Tommy Parker said a range of preparatory works and environmental controls have already been put in place to facilitate the start of construction. These include the provision of alternative open space, realignment and rehabilitation of parts of Oakley Creek and the relocation of local wildlife and plant life to new habitats.
The five kilometre Waterview Connection, including two 2.4km tunnels between Owairaka and Waterview, will provide a new six-lane motorway link between SH16 (the Southwestern Motorway) and SH20 (the Northwestern Motorway) to complete Auckland's Western Ring Route. It is New Zealand's largest and most complex roading project to date, and one of the seven Roads of National Significance identified as key to enabling economic growth for New Zealand.
Mr Parker said when the southern approach trench was complete, the tunnel boring machine would descend to 45 metres beneath the surface, passing below hard volcanic rock and leaving intact the open space, communities and commercial precincts above.
"To create the launch pad for the machine, we first have to excavate through a significant chunk of this basalt to reach the softer soil conditions below, and that is the process we have officially begun today," Mr Parker said.
Excavation of the trench will involve a series of controlled explosions to fragment hard rock.
"This not only allows the excavation to be carried out faster, it also significantly decreases the impact felt by local residents as it reduces the amount of traditional rock-breaking activity required. Basalt retrieved through this process will be used throughout the project, and for landscaping."
Mr Parker said the project strikes a balance between contributing to the economic development of Auckland and New Zealand, and meeting the needs of the project's surrounding communities.
"In addition to local landscaping initiatives around Owairaka and Waterview, the project will, in partnership with Auckland Council, also provide enhanced walking and cycle ways between the two communities. These elements are vital components of the overall project scope, as we work to deliver this key transport link for Auckland."