St Helena Tunnel Blast

Australia has commenced tunnelling work below St Helena Road in New South Wales (NSW) as part of the Tintenbar to Ewingsdale Pacific Highway upgrade project, which is estimated to be worth A$862m ($830.7m).

The tunnel will measure 434m long, 19m wide and will be located 46m below St Helena Road.

Federal Infrastructure and Transport Minister Anthony Albanese said that the tunnelling, which is expected to take 10-12 months, will accommodate three lanes of traffic in each direction when completed.

"In the coming days, workers will begin excavating the tunnel using drill and controlled blast methods to get through the strong basalt rock," Albanese said.

These proposed tunnel will require 30,000m³ of permanent concrete, over 40,000m² of waterproofing membrane, and contain more than 3,000 steel rock bolts and 32 reversible jet fans for ventilation.

"The tunnel will measure 434m long, 19m wide and will be located 46m below St Helena Road."

The tunnel will also have around 2.4 million litres of water stored in tanks to supply the fire deluge system.

NSW Roads and Ports Minister Duncan Gay said that the tunnel will be temporarily supported with steel rock bolts and reinforced concrete in order to ensure a safe working environment.

"Safety features of the tunnel will include three emergency exit cross passages between the twin tunnels, an automatic fire deluge system, a ventilation system and air quality monitors," the minister said.

The Tintenbar to Ewingsdale section of the Pacific Highway upgrade, when completed, will reduce travel times, freight transport costs and improve safety for the 12,500 motorists and truck drivers that use this section of road every day.

Jointly funded by the Federal and NSW Governments, the project is expected to be completed in the second half of 2014.

Image: The tunnelling, which is expected to take in 10-12 months, will accommodate three lanes of traffic in each direction when completed. Photo: courtesy of Commonwealth of Australia.