Harbour Area Treatment Scheme (HATS) Stage 2A comprises three major works components, namely (a) the construction of a sewage conveyance system (SCS) to transfer sewage generated from the northern and south-western parts of Hong Kong Island to the expanded Stonecutters Island Sewage Treatment Works (SCISTW), (b) the upgrading of eight preliminary treatment works (PTWs) along the route of the SCS, and (c) the expansion of the SCISTW to increase its treatment capacity and to provide disinfection treatment facilities.
The SCS comprises three sections of deep tunnels with a total length of about 21km, from North Point to Stonecutters Island, Aberdeen to Sai Ying Pun and Ap Lei Chau to Aberdeen. This Project constructs the section of SCS from Aberdeen to Sai Ying Pun with total length of about 7.5km.
Construction of diaphragm wall temporary shafts at Sandy Bay and Sai Ying Pun to provide access for the construction of sewage conveyance system from Aberdeen to Sai Ying Pun. The works also include shear pinning of diaphragm walls and toe grouting underneath diaphragm wall toe.
– Diaphragm walls: (a) 1.2m & 1.5m thick, (b) excavation area 5,976m2
– Shear pins: (a) 86 nos.
– Toe grouting: (a) 138 grout holes