Pro-vice-chancellor John Malpas, who is chairman of the campus development group, said: 'The public wanted us to preserve this building. We listened to what they had to say and went the extra yard to try to preserve the building in situ.

'It has taken several months of detailed engineering design work and creative thinking to come up with a practical solution.'

The site houses three working reservoirs that serve Western District and which will be relocated without any suspension of water supplies.

The university is spending HK$800 million, one-third of the total cost of the development, to preserve the waterworks buildings and replace the reservoirs - which involves tunnelling deep into the hillside.

Two saltwater reservoirs are being rebuilt underground to minimise the impact on the environment.

Unfortunately, the grade-three-listed treatment works stands right in front of the proposed tunnelling site and is sandwiched between the two reservoirs being demolished.

There are severe technical constraints on the rebuilding plans because of a lack of space and the potential impact of reservoir design on water pressure.

'We have had to play around almost mathematically to find the right shape and get the right capacity for the reservoirs, and also allow the Elliot Treatment Works to remain in situ,' Professor Malpas said.

'We have slightly changed the position of the tunnelling into the hillside. We changed the shape, size and position of the two surface water tanks and made some slight modifications to the road system.

'It is a difficult site to access in general because it is up on the hillside and working around this heritage building will provide an extra challenge to the contractors. Therefore we also have to go through a process of protecting the building during the construction works, which may involve placing a canopy over it.'

He said the university's guiding principles for the project had always been sustainable development and protecting the environment.

Work on the reservoir site started in April and tunnelling will begin at the end of this month. The development group is now looking at possible uses of the treatment works and how it should be adapted for visitors.

'We would like to provide a visitors' centre, a staff and alumni lounge, and a water supplies museum and art gallery for educational purposes,' Professor Malpas said.

Fading glories

Conservationists have urged the government to introduce a heritage policy as soon as possible to protect the dwindling number of historic sites in Hong Kong.

Since 1980, the Antiquities Advisory Board has graded 607 buildings, of which 57 were declared as monuments and 54 Demolished