ENG-1990 — Page 426

THE ENVIRONMENT

Works are in progress to modify the sewage treatment processes at the Sha Tin and Tai Po sewage treatment works to enhance nitrogen removal from the effluent, under the Tolo Harbour Action Plan. Works for the Effluent Export Scheme started in 1990 and are scheduled to be completed in 1994. When this scheme is commissioned, the treated effluent from the Sha Tin and Tai Po sewage treatment works will be discharged to the Kai Tak Nullah. This will remove the effluent from the nitrogen sensitive Tolo Harbour as well as dilute the organic pollution in the Kai Tak Nullah and Kowloon Bay Typhoon Shelter.

Under the Marine Disposal of Sludges Scheme, treated sludges from Sha Tin from the drinking water purification and sewage treatment processes will be disposed of by tankering to the open sea for a five-year trial period commencing 1991. Baseline ecological studies on the designated marine dumping area were completed in 1989. Construction of the sludge pumping, temporary holding facilities and the specially-designed sludge disposal vessel is well underway.

Landfills

As part of the Waste Disposal Plan, three large-capacity landfills are being developed to provide the necessary capacity for disposal of waste in the territory for the next 20 years. 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 at detailed design stage and construction of the 4.5-kilometre access road to the West New Territories Landfill has commenced. A feasi- bility study and environmental assessment of the third regional landfill, the South-east New Territories Landfill, should be completed early in 1991. Inclusion of state-of-the-art technology to attain high environmental standards at these landfills is among the basic requirements in developing these sites. Extensive laboratory and field experiments have been undertaken to determine the best type of containment liner for the West New Territories Landfill and a similar experimental programme has commenced for the North-east New Territories Landfill. A leachate disposal study for the North-east New Territories Landfill has recommended that the leachate be pre-treated at the landfill site before pumping to the Shek Wu Hui Sewage Treatment Works for further treatment. The environmental impact assessment of the South-east New Territories Landfill has also recommended that leachate generated at the South-east New Territories Landfill be pre-treated prior to its discharge to the Tseung Kwan O Sewage Treatment Works for further treatment. Detailed design of the disposal facilities for leachate from the West New Territories Landfill via the proposed North-west New Territories sewage effluent outfall at Urmston Road is in progress.

Landfill gas and leachate investigations at the Tseung Kwan O Landfill Stages I and II/III have begun. The investigations will lead to recommendations on the best approach to manage the landfill gas and leachate problems at the two landfills as well as provide valuable design data for the development of the South-east New Territories Landfill.

Studies have also begun to consider work requirements for retrofitting pollution control systems to existing and completed landfills and reinstating these sites to allow future development. The first to be examined are the urban sites and the major work is expected to include leachate and landfill gas control and surface restoration.

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