Given the lack of land resources in Hong Kong, it has all along been our policy objective to develop underground space and enhance the use of rock caverns systematically so as to promote the sustainable development of Hong Kong.  I am glad to share with you that the International Tunnelling and Underground Space Association (ITA) has earlier awarded the Civil Engineering and Development Department (CEDD) and the Planning Department (PlanD) the Innovative Underground Space Concept of the Year in the ITA Tunnelling Awards 2017 for their concerted efforts in formulating the Cavern Master Plan (CMP) for Hong Kong.

Founded in 1974, the ITA currently has 74 member states and has officially launched its Tunnelling Awards Programme in 2015 to commend the most ground-breaking achievements and innovations in underground infrastructure worldwide.  The Awards, dubbed the Oscars of the industry, never fails to attract elite experts in the engineering sector from around the world.  In mid-November, Chief Geotechnical Engineer of the CEDD, Mr HO Ying-kit, Tony, and Chief Town Planner of the PlanD, Mr LO Wai-ming, Edward, represented the two departments to attend the international conference cum awards ceremony in Paris and presented the panel of judges on the cross-departmental collaboration in formulating the CMP.

Cavern development for various uses

This time I have invited representatives of the two winning departments to share with us the promotion of rock cavern development in Hong Kong.  Mr Edward LO told us that they had a very good experience at the international conference, which enabled them to learn more about the innovative concepts for the use of underground space around the world.  According to him, the CMP may have won because what they presented to the panel of judges is not a single development project, but a holistic and strategic planning tool for underground space which helped promoted the use of rock caverns for development of different land uses, complementing Hong Kong’s pursuit of sustainable development.  This direction for development was recognised by the panel.

Our steep terrain has led to the high concentration of urban development on the flat land of Hong Kong.  However, about 80 percent of the land in Hong Kong is formed by hard igneous rocks (i.e. granitic and volcanic rocks) with great potential for cavern development.  This, coupled with Hong Kong’s advanced cavern construction technology, means that there is sufficient geological justification to support the use of these hidden land resources to create new space.

48 strategic cavern areas identified

To formulate a long-term strategy for cavern development, we started to compile the CMP in 2013.  After a detailed assessment of the geological conditions and careful consideration of the land uses, transport networks and spatial context of the surrounding areas, 48 Strategic Cavern Areas (SCVAs) with potential have been identified.  However, the development potential of individual cavern areas is still subject to their uses, actual site settings and other various constraints. 

The CMP provides systematic guidelines for cavern development and helps us gain a better understanding of its potential to enhance land supply for the sustainable development of Hong Kong in future.  Mr Tony HO told us that his colleagues always paid particular attention to overseas examples of rock cavern development whenever they are on vacation or business trips.  Overseas experience demonstrates that cavern development can be applied to a wide variety of effective uses, such as (1) community and recreational facilities (sports centres, swimming complexes); (2) storage facilities (archives, food and wine storage); (3) commercial and industrial facilities (data centres, logistics/warehousing, maintenance depots); and (4) special facilities (e.g. columbarium, testing laboratories), which are worthy of reference.

Early examples of cavern development in Hong Kong

Back in the mid-1990s, in order to address the needs of the community and due to the shortage of suitable sites in particular localities, a number of public facilities were built in rock caverns, including the Stanley Sewage Treatment Works, the Island West Transfer Station and the Kau Shat Wan Government Explosives Depot.  In 2009, the University of Hong Kong constructed rock caverns to re-house the Western Salt Water Service Reservoirs to make room for the Centennial Campus development.  These projects have demonstrated that rock caverns can be a cost-effective alternative, while yielding additional safety, environmental and security benefits.

Minimise impacts on the surrounding areas

The Stanley Sewage Treatment Works, which I particularly want to show you, is actually built in rock caverns.  After four years of construction, the sewage treatment works came into operation in 1995 with a current daily capacity of 8 000 m3 to provide sewage treatment services for about 30 000 residents of the Stanley Peninsula, Tai Tam, Chung Hom Kok and the Redhill Peninsula.  To preserve the unique landscape in the area, the facility is housed inside three large caverns, each about 120m long, 15m wide and 17m high, connected with over 450m of access paths, ventilation tunnels and shafts.  The treatment works thus constructed would not cause disturbances to the nearby residents in the construction process and during the daily operation of the facility.

The Drainage Services Department has decided that the relocation of the Sha Tin Sewage Treatment Works to caverns will be conducted in phases.  The facility will be relocated to the proposed rock caverns in Nui Po Shan, a hill across the Shing Mun River.  The original site will then be released for other purposes that will enhance residents’ quality of life and bring long-term benefits to the community and the environment.

Long lead time calls for a multi-pronged strategy and long-term planning

Cavern development takes time, so it is positioned as one of the sources of long-term land supply under the Government’s multi-pronged strategy to increase land supply.  Regarding cavern development proposals, any development projects, whether they are located inside or outside the SCVAs, should be carefully planned according to individual circumstances.  Planning and Engineering feasibility studies and other assessments, including their impacts on the environment and the traffic, should also be conducted.  No matter which approach is adopted for developing new land resources in the future, we shall continue to strengthen our communication with the community and together, use our creativity to build Hong Kong into a more liveable city.