Despite extensive coastal reclamation in recent years the small territory of Hong Kong is still short of easily-developed flat land. Evaluation of the use of underground space is worthwhile in land-use planning studies. Geological conditions in Hong Kong are generally favourable for the construction of rock caverns. The dominant Mesozoic volcanic and granitic rocks are generally very strong and have few major structural weaknesses. Evolving from a long tradition of hard rock tunnelling, a number of caverns have been built in Hong Kong during the last fifteen years for water supply, rail transport, sewage treatment, refuse transfer and storage of explosives. Two types of geotechnical studies are being used to make preliminary assessments of the potential for cavern development. In a Cavern Area Study (CAS) the suitability of land for cavern development is broadly classified from existing information on surface and underground developments, engineering geology and topography. Once a potential cavern site is identified, a Preliminary Engineering Geology Study (PEGS) is undertaken to determine a suitable location, geometry and access for the cavern and to provide a rough cost estimate. A PEGS includes both desk study and field assessment of engineering geology. CAS and PEGS have been formally included in the Hong Kong Government's Planning Standards and Guidelines.
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