HONG KONG — To address Hong Kong’s constant need for more space to build upon, the government in November proposed the usual method of creating new land by filling in more of the surrounding waters with trash, as well as a less conventional solution: underground rock caverns.
It would be akin to digging big basements in solid rock. Even though Hong Kong uses underground space extensively for the subway system, only five other purpose-built caverns are currently in use. These include a sewage treatment plant and a salt-water reservoir, both featuring walls and ceilings of exposed rock.
At a recent press conference, Secretary of Development Carrie Lam called Hong Kong’s rock formations a “unique geological asset” and urged the city to take caverns into consideration. The government's feasibility study, which examines a variety of facilities that might be built underground, highlights that one added benefit of rock caverns is to hide unattractive structures (also known as NIMBY-type facilities) such as water-treatment plants or mortuaries.
Norway and Finland in particular have successfully used underground rock space for facilities ranging from subway stations to swimming-pool complexes. The scandinavian countries' need to go this route is partly due to their cold climate.
Ray Su, a civil engineering associate professor at the University of Hong Kong, said it makes sense in congested, urban areas to move some existing government facilities into a cave and then use the vacated land to build residential or commercial buildings.
But he said underground space should only be used if land really is insufficient. “Making a cave is expensive, and also it is not really environmentally friendly. Therefore, if we can find other means to solve the same problem, then we should avoid using caves,” he said.
Even though land reclamation through filling in coastlines has a bad rap for high costs and disruption of marine life, Su said it might be preferable if approached with environmental sensitivity. "But we need more detailed studies before we can come to any kind of conclusion,” he added.
Photo: Hong Kong Civil Engineering and Development Department