The West Drainage Tunnel project is now in full swing with the launch of its second tunnel-boring machine today.

The machine, and the first one launched in March, will bore the east and west section of the tunnel simultaneously until early 2011. The tunnel will be commissioned in 2012.

Director of Drainage Services Lau Ka-keung said at the launch ceremony today the $3 billion project will enhance the drainage system in the northwestern part of Hong Kong Island and prevent flooding.

The 11km tunnel runs from Tai Hang to Cyberport. Thirty-four intakes will be constructed in Wan Chai, Central and Western Districts to intercept and convey the run-off mid-hill through dropshafts and the connecting tunnel for discharge into the sea near Cyberport.

Most of the intakes will be constructed with the raise boring method to reduce public nuisance. The contractor will build the tunnel first and a drilling reamer will then be installed inside the tunnel for subsequent dropshaft excavation works from the bottom upwards.

"As the works are to be carried out underground, this method can confine the noise and dust within the dropshafts and tunnel. Since excavation materials will be collected in the tunnel during dropshaft construction, spoil disposal can be carried out via the tunnel portals, thus reducing the construction traffic impact to the nearby road networks," Mr Lau said.