Re-branded SSDS stage two in HK

Hong Kong's Drainage Services Department (DSD) is kicking off the HK$19bn (US$2.43bn) second stage of the territory's deep tunnel sewerage scheme in August with an invitation to engineering consultants to apply to bid for the preliminary design contract.

The project, now known as the Harbour Area Treatment Scheme, involves the construction of about 20km of tunnels on the northern and western shores of Hong Kong Island. The tunnels will be some of the deepest in Hong Kong, built at depths of up to 130m below sea level.

Outlining the challenges that lie ahead, DSD said, "there is little existing information about ground conditions at this depth. It is necessary to carry out an extensive programme of ground investigation at this early stage of the project to provide suitable information for the planning, design, tendering and construction of the tunnel works".

Legislators approved HK$166M (US$21.4M) in early July to finance the design consultancy, which includes investigation and construction supervision, plus a separate environmental impact assessment and ground investigation works. Parties will be asked to prequalify to bid for the EIA in September. Work on the 18 month assessment is expected to start next March.

Under current plans the DSD will invite contractors to bid towards the end of next year for the design and construct contract to build the deep tunnel network. The department has been persuaded to adopt design and construct after the disastrous experience on the 25km phase one tunnel network in Kowloon and the New Territories. Detailed design was done by MWH in association with Mott Connell under a contract from the DSD, which awarded a separate contract for construction.

The result left the contractor with little latitude to modify tunnelling work according to the poor ground conditions. As a result, the original contractor, a jv between Campenon Bernard and Maeda, stopped work, was thrown off the project and the government rebid the job as three separate contracts. The completion contractors also ran into problems and the last claims have only just been settled. As a result of delays caused by the poor ground conditions and the contractual problems, completion of the tunnels were 3.5 years late and were finished in December 2001.

No details of how many tunnelling contracts DSD plans to award for this latest phase have been released. Plans envisage one tunnel along the northern shore of Hong Kong Island from North Point to Central. A second tunnel would run from Lamma Island across to the south side of Hong Kong skirting the western edge of the island to Central. A third tunnel would run under the western entrance of the harbour from Central to connect with the treatment works at Stonecutters Island built under stage one.

Construction of the tunnel network is due to start in 2007 for completion in about 2011-12.