Deep tunnels used to move excavated materials out of the West Island Line construction site could be kept and converted for other purposes like wine cellars, a veteran geotechnical engineer says. Edwin Chung Kwok-fai, geotechnical division chairman of the Hong Kong Institution of Engineers, said shafts and tunnels in Western district had been built at a depth of about 60 metres and had high potential for other uses. 'These shafts and tunnels provide excellent underground space for storage of wine and they are large enough for that purpose. It would be a waste if they were just filled in after the construction,' he said. Some wine cellars have already taken up underground spaces like air raid shelters abandoned after the second world war. The underground railway construction corridors, one near Hill Road and another near Belcher, are up to eight metres in diameter and between 170 and 340 metres long, the MTR Corporation says. The rail operator said that under the existing agreement on the rail project, it was required to backfill the tunnels and return the sites to the government. 'There is no change to that agreement at the moment,' a spokeswoman said. The Civil Engineering and Development Department, which is in charge of vetting temporary tunnel construction, said it was open-minded about the potential uses of these underground spaces. 'Various options of after-use including backfilling, beneficial reuse, or other sustainable options are under consideration. But there is no firm arrangement yet,' a spokeswoman said. The government has already commissioned a consultancy study to gauge the potential of using underground space to free up prime sites above ground now occupied by various public facilities. The study is expected to be completed by the end of this year at the earliest. The government and the Institute of Planners will co-organise a conference next month to promote the idea. In theory, Hong Kong is ideal for developing underground spaces because the city has so many hills near existing developments that are suitable for excavation. But whether it was cost-effective would largely depend on the future uses of the vacated sites, Chung said. 'It mainly ties in with the land prices of the vacated sites. The higher the prices, the more attractive the option is,' he said. Chung worked on a project involving a salt water reservoir that was hidden in a man-made cavern next to the Centenary Campus of the University of Hong Kong. While the project could be significantly more expensive to develop and maintain afterwards, it helped to preserve sites on the surface for campus development, while protecting two heritage buildings near the site and hundreds of trees on slopes. The cavern, created by drilling and blasting, cost about HK$100 million to build between 2006 and 2009.