The Lai Chi Kok Drainage Tunnel captured rainwater from the upper catchment in West Kowloon and discharged it into Victoria Harbour to alleviate flooding in Cheung Sha Wan, Lai Chi Kok and Sham Shui Po which are at the downstream area of west Kowloon.
The project provided for the design and construction of two storm water drainage tunnels (the main tunnel and the branch tunnel) with a total length of 3.7 kilometres, each with an internal diameter of 4.9 metres.
The work also included six intake shafts, a stilling basin, an outfall structure, approximately 270 metres of three metre internal diameter connection adits and surface connecting drainage pipelines installed by pipe jacking.
The main function of the intakes was to capture rainwater from streams and open channels and then convey them to the stilling basin via the drop shafts and branch tunnel.
The branch tunnel was constructed within a rock stratum while the main tunnel passed through rock, mixed ground and soft ground strata.
The tunnels were constructed by means of a tunnel boring machine (TBM) and the intake shafts were constructed using traditional methods, drill and split or by blasting. The connection adits were constructed using blasting techniques.
The project is located in an urban area and therefore possible impacts on the public during construction was an issue that the joint venture had paid considerable attention to during the planning and development of the proposed construction methods. The joint venture implemented mitigation measures to control noise, dust and site run-off, such as the use of temporary noise barriers and silenced plant to reduce noise generation, water-spraying to reduce dust emissions and controls on diversions of streams within the site area.