The sewage conveyance system (SCS) comprises a network of interconnected sewage tunnels and vertical shafts. The vertical shafts collect sewage from the preliminary treatment works in North Point, Wan Chai East, Central, Sandy Bay, Cyberport, Wah Fu, Aberdeen and Ap Lei Chau. The collected sewage is conveyed to the Stonecutters Island Sewage Treatment Works via a total of 21km of deep tunnels with depths varying from 70m to 160m below sea level. The system essentially operates as a siphon
How Are The Sewage Tunnels Built?
Drill and blast method is chosen for constructing the sewage tunnels. In addition to providing more working spaces for temporary support installation, yielding a more controllable programme: and resulting in higher value of excavated rocks for re-use, this method is more versatile in controlling groundwater during construction, especially for deep tunnels under sea.