When sewage arrives at SCISTW, it is lifted from the deep tunnels to the surface via two very large main pumping stations, one serving the Stage 1 flow and the other one for the Stage 2 flow respectively. The two pumping stations are interconnected by a tunnel to allow flow to be diverted if needed to enhance the reliability of the operation of these main pumping stations.
Both pumping stations have an internal diameter of over 50 metres and are about 40 metres below ground, involving deep excavation within a diaphragm wall. Massive pumps driven by variable speed drives are installed at the bottom of the pumping station to lift sewage from the tunnels to the sedimentation tanks.
Exterior View of Main Pumping Station No.2