Relocation of Sham Tseng Sewage Treatment Works to Caverns Feasibility Study

In 1995, the first cavern sewage treatment works (STW) in Hong Kong was established at Stanley. It is a secondary STW with a design sewage treatment capacity of 11,600m³/day, and currently receiving about 9,000m3/day of sewage arising from 27,000 residents. It is housed in three caverns of 120m long, 15m wide and 17m high that are connected by access of over 450m long, ventilation tunnels and shafts.

The experience with Stanley STW demonstrates that STW in caverns not only blends in with the nearby environment, but also spares the local residents undesirable environment impacts during construction and daily operation.

In 2009, the Western Salt-water Service Reservoirs at the University of Hong Kong was relocated to rock caverns that are 50m long, 17.6m wide and 17m high. The Salt-water Reservoir has a capacity of 12,000m³ and serves a population of more than 120,000 in the Central, Western and Peak areas. The precious surface land was released for the University's Centennial Campus development. The design helped preserve three graded historic buildings and minimised tree felling.

The Island West Transfer Station, commissioned in 1997, involved the construction of a waste transfer facility in a rock cavern near Kennedy Town waterfront. It provides service to Central and Western District and Southern District (part). As there was difficulty in identifying a suitable site for the refuse transfer station within the area, cavern development provided a good and feasible solution. The rock cavern is about 65m long, 27m wide and 12m high.

The Oset Water Treatment Complex, which was implemented in 1971, was constructed inside 5 parallel caverns. Following the upgrading works in 2008, the treatment plant became one of the largest water treatment plants in Europe. Nowadays, it serves 90% of Oslo's population and supplies 391,000 m³/day of potable water.