The Stonecutters Island Sewage Treatment Works was designed to handle a huge sewage flow of 2.45 million cubic meters per day under HATS Stage 1 & 2A.  For this purpose, a lot of sedimentation tanks occupying a large area would be required.  In order to save space, double-decked sedimentation tanks are adopted.  In total, there are 46 double-decked sedimentation tanks, each with a plan area of 60m by 7m.

Longitudinal section of a double-decked sedimentation tank

View of a row double-decked sedimentation tanks