Officials have promised that tunnelling work needed to replace reservoirs near the University of Hong Kong as it expands its campus will not affect a grade-three-listed waterworks in the middle of the site.
Two saltwater reservoirs are being rebuilt underground to minimise the impact on the environment.
The 77-year-old Elliot Treatment Works has been protected with extra structures and wrapped in a protective screen while workers labour around the clock to drill a 70-metre-long cavern into hard granite and sandstone.
Officials said regular monitoring had found no signs of subsidence, cracks or displacement of the treatment works.
'We have made heavy structures to protect the building. No matter how the contractor digs the caverns, it will remain steady and will not collapse,' Chan Tze-ho, senior engineer of the Water Supplies Department, said.
Mr Chan said the cavern would be dug with machines only and no explosives would be used.
The treatment works, which is owned by the department, is being preserved along with two other historic structures on a site in Pok Fu Lam where the university will build its Centennial Campus.
