The massive task of removing 160,000 cubic metres of rock and earth to form the trench for the Victoria Park Tunnel is underway -enough to fill a hole eight stories deep and as large as a rugby field.
Excavators and long-reach diggers moved onto the central Auckland site on Monday to begin digging a 700-metre trench which includes a 450-metre covered tunnel under Victoria Park and its entry and exit.
The NZTA’s Regional Director for Auckland and Northland, Wayne McDonald, says the start of excavation is a major milestone for the Victoria Park Tunnel project, which will remove the last major bottleneck on the central Auckland motorway network.
“It signals that the project is well on track to have the tunnel structure built and work moved underground by the time of next year’s Rugby World Cup.”
The tunnel is due to be opened to three lanes of northbound traffic and the existing Victoria Park Viaduct reconfigured to carry four southbound traffic lanes by mid-2012.
The Victoria Park Tunnel project is one of the country’s seven roads of national significance, identified by the Government as essential to future economic growth. As well as the tunnel, it includes motorway widening through St Marys Bay, improved bus priority measures and better walking and cycling access to the Auckland CBD.
The tunnel is being built using the cut-and-cover method, which means the walls of the tunnel are built first followed by installation of roof beams, excavation of the tunnel trench below the beams, pouring the floor and roof panels and finally the installation of tunnel operating systems and services.
The construction sequence is being varied where the tunnel will run under local roads, Beaumont Street and Victoria Street West. Here, the tunnel roof will be fully completed so that traffic can run on top before the trench below is excavated.
Mr McDonald says construction of the tunnel began in April. “Progress has been rapid in spite of the extremely tight working space and very wet winter.”
The depth of the excavation will be 13 metres at the tunnel’s lowest point. The material being removed will be mainly natural marine sediment, the fill used to reclaim Freemans Bay in the early 1900s, and the underlying East Coast Bays sandstone. Procedures are in place for recovering anything of historic significance found during the operation, and for the possibility of contaminated materials.