ENG-1989 — Page 396

THE ENVIRONMENT

sewage treatment works for Stanley, a screening plant at Shek O, and a sewage pumping station at Repulse Bay to replace the existing facilities in the area.

As part of the Tolo Harbour action plan, the treatment processes at the Sha Tin and Tai Po sewage works are being modified to reduce the amount of nitrogen in the effluent. This will significantly reduce the impact the effluents make on the natural environment. A scheme to remove these two effluents entirely from Tolo Harbour to a neighbouring, less sensitive catchment is being designed.

Sewerage improvements needed in both East Kowloon and Hong Kong Island South have been started and will be completed in the next four years.

Primary treatment plants at Deep Water Bay, Repulse Bay and Stanley will be replaced by new facilities as part of the Hong Kong Island South improvements.

Treated sludges from sewage treatment and drinking water production processes will be deposited at sea for a five-year trial period commencing late in 1990. Investigations at sea to ensure that there will be no pollution as a result of this scheme were completed in 1989, and construction of the facilities began. Work should be finished in good time to allow the disposal operation to begin on schedule, thereby removing a considerable pollution load from the Tolo catchment.

Landfills

The waste disposal strategy for municipal solid waste requires the establishment of three very large landfills to replace urban incinerators and small local landfills. These landfills will be served by a network of transfer stations. They will transfer the waste from small refuse collection vehicles to bulk transporters, reducing cost and environmental problems.

Two of the long-term disposal facilities, the West New Territories Landfill and the North-east New Territories Landfill, are now being designed in detail. Environmental impact assessments for both these projects have recommended, among other things, that leachate, a highly-polluting liquid residue from the decomposition of the waste, should be carefully contained within an impermeable lining in the landfill and piped away for treatment and disposal. Extensive laboratory and field experiments have been undertaken to determine the best type of containment liner for the West New Territories Landfill. A similar experimental programme will soon commence for the North-east New Territories Landfill. A proposal to treat leachate from the North-east New Territories Landfill at Shek Wu Hui sewage works is currently under investigation. Detailed design has commenced on the works for the disposal of leachate from the West New Territories Landfill via the proposed North-west New Territories sewage effluent outfall at Urmston Road. A feasibility study and environmental impact assessment is being carried out on a proposal to develop a third regional landfill. This South-east New Territories Landfill is planned to be operational by 1994. The three regional landfills will provide sufficient disposal capacity for Hong Kong's needs over the next 20 years.

Urban development has virtually surrounded several small closed landfills in north- east Kowloon. There is a risk that flammable and possibly explosive gases arising from the decomposition of the waste might migrate to surrounding areas. The government has investigated this problem and found that control facilities should be built both on and around the former Sai Tso Wan landfill. Construction has begun and a further study is in progress to examine the potential for using the landfill gas as an energy resource. Transfer Stations

Almost without exception, the incinerators operating in Hong Kong are poorly located, many being in residential areas. Although electrostatic precipitators fitted to the Lai Chi

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