Cavern fire safety – overview of requirements and pragmatic solutions in Hong Kong

Hong Kong’s steep hilly terrain limits the growth of surface urban areas. In response to the society’s needs for land to support social and economic developments, the Government of Hong Kong Special Administrative Region is actively exploring the use of caverns as one of the innovative measures to supplement Hong Kong’s land resources. The development of cavern space is an attractive option to meet the land demand not only for “not-in-my-backyard” (nimby) type public utilities but also for a wide spectrum of uses including commercial, industrial and community type facilities. The development of cavern fire safety design in Hong Kong evolved from the first cavern project in around 1980s. The design guideline “Guide to Fire Safety Design for Caverns” was jointly established by Building Authority and Fire Services Department in 1994, by referring to overseas and local experience consolidated in the Study of the Potential Use of Underground Space (SPUN) in 1990. This guideline however was developed with a focus on caverns for use by low population public utilities such as sewage treatment works and water service reservoirs where the fire load is generally localised, closely controlled and relatively low. Whereas, other prescriptive fire safety guidelines commonly adopted in the Code of Practice for Fire Safety in Buildings 2011 (FS Code) and the Codes of Practice for Minimum Fire Service Installations and Equipment and Inspection, Testing and Maintenance of Installations and Equipment (FSI Code) were developed for typical surface buildings only. The existing fire design guidelines are found to be not fully compatible with the recent expanding spectrum of cavern usage in Hong Kong. Each cavern development type has its unique site setting and fire safety characteristics under the proposed usage (e.g. government facilities, industrial and commercial facilities like concrete batching/rock processing/asphalt production plants, data centres, logistics/warehouse facilities, etc.). Strictly following the prescriptive fire safety requirements and the design guidelines for typical buildings to these usages in cavern will pose immense technical issues/challenges to cavern projects and could also lead to unwarranted impacts on their functional operations. A more coherent fire safety design approach for new cavern projects is therefore needed to facilitate project proponents to plan cavern projects in the future. This paper provides an overview of fire safety issues for ca