WORK on the centrepiece of the Ewingsdale to Tintenbar Pacific Highway upgrade - the St Helena tunnel - has finally begun.

In a joint statement, Federal Transport Minister Anthony Albanese and NSW Roads Minister Duncan Gay said workers building the 434-metre long tunnel are expected to dig through rock that has not been disturbed since it flowed as magma from Mt Warning about 23 million years ago.

"The tunnelling is expected to take 10-12 months and when complete in 2014, will accommodate three lanes of traffic in each direction," Mr Albanese says in the statement.

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

"This is state of the art technology which will help break though rock that is believed to have originated from lava flows from a volcano centred on Mount Warning roughly 23 million years ago."

Mr Gay spelled out the enormous logistics of the project.

"The tunnels will require 30,000 cubic metres of permanent concrete, more than 40,000 square metres of waterproofing membrane, contain more than 3000 steel rock bolts, and have 32 reversible jet fans for ventilation and 2.4 million litres of water stored in tanks to supply the tunnel's fire deluge system," Mr Gay said.

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

The tunnel was a source of controversy when the first route options for the upgrade were proposed, partly because it anchored the upgrade's northern end and limited the ability to look for alternate routes.

The Ewingsdale to Tintenbar upgrade is expected to be finished next year and will create an uninterrupted dual carriageway motorway between Ballina and Brisbane.

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