The Deputy Head of the Geotechnical Engineering Office (Mainland), Civil Engineering and Development Department, Dr. Richard PANG, and his colleagues visited the deep sewage tunnel project for the Harbour Area Treatment Scheme Stage 2A Construction of Sewage Conveyance System on 5 June 2014.

After a brief presentation by DSD’s consultants on the project and the drill-and-blast and grouting operations for tunnel construction, Assistant Director/Sewage Services Mr. CHAN Pak-Keung, took GEO colleagues on a tour of the deep sewage tunnel being built between Sai Ying Pun and Wan Chai East, which is about 157m below sea level, to further understand the tunnel condition and the operations for tunnel construction.

HATS Stage 2A Construction of Sewage Conveyance System from North Point to Stonecutters Island (Contract No. DC/2007/23) comprises construction of a 12-kilometre tunnel with sections varying from about 140m to 160m below sea level. The drill-and-blast method has been adopted for the shaft and deep tunnel excavation. The section of tunnel between North Point and Wan Chai East, with the lowest point at about 160m below sea level (160m is equivalent to the height of a 50-storey building), is the deepest sewage tunnel in Hong Kong. The contractor for construction of the tunnel is Gammon Construction Limited and the supervising consultants are AECOM Asia Company Limited.

For this challenging tunnel project, GEO delivers the explosives and regulates their use under the Dangerous Goods Ordinance, and exercises geotechnical control audits of the standard of the design and construction in accordance with ETWB TC(W) No.15/2005.