Hong Kong secretary for development Carrie Lam led a breakthrough ceremony for the Hong Kong West Drainage Tunnel on 17 February.

The 6.25-7.25m diameter, 11km-long tunnel featured the first use in Hong Kong of raise boring and reverse circulation drilling to construct dropshafts.

Supervising consultant Arup said, “The logistics for delivery of explosives, removal of spoils generated by both TBMs and blasting operations, and arrangement of working and supervisory staffs inside the tunnel, was one of the most complicated processes ever for the Hong Kong construction industry.”

Breakthrough occurred in January beneath Stubbs Road, Wan Chai and marked entry to the final phase. Construction began under the Dragages-Nishimatsu JV in 2007 and will be completed in 2012.

“The HKD 3bn (USD 385.4bn) project is the biggest flood prevention project implemented by the Drainage Services Department so far,” said Chan Chi-Chiu, Hong Kong director of drainage services.

The project also involved some 34 intakes and eight adits of 1km, constructed by drill and blast, to connect intakes to the main drainage tunnel. Two TBMs excavated the tunnel from either end simultaneously to shorten construction time.

“The government is implementing various flood prevention and sewerage infrastructure projects with a total cost of HKD 36.6bn (USD 4.7bn), in order to create a quality living environment in Hong Kong,” said Lam. “Other major projects with a total value of HKD 20.6bn (USD 2.65bn) are also under planning.”

When completed, the tunnel will divert 30 per cent of stormwater from northern Hong Kong.