The Water Supplies Department says it needs to double the size of its north Lantau water treatment plant to cope with the development of Tung Chung and the airport district.

It proposes boosting the capacity of the Siu Ho Wan Water Treatment Works from 150,000 cubic metres a day to 300,000 cubic metres daily.

The department has not indicated how much the expansion plan will cost, but it will seek funds from the Legislative Council for research and design early next year and then carry out a study, Oriental Daily reports.

Construction is expected to start in 2021 and will be completed in 2025.

As well as expanding the Siu Ho Wan plant, it will install a pipe along South Lantau Road to increase the flow of water from Shek Pik Reservoir, and build a booster station to improve supply from Tai Lam Chung Reservoir.  It will also increase the capacity of the Pui Oi pumping station.

Under the Tung Chung extension plan its population is expected to increase from approximately 80,000 today to 268,000 in the mid-2020s.