ENG-1990 — Page 272

LAND, PUBLIC WORKS AND UTILITIES

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outfall into the Dangan Channel. Under 'existing schemes' four sewage screening plants with submarine outfalls at To Kwa Wan, Wan Chai East, North Point and Shau Kei Wan were completed thus providing treatment for sewage from a population of 1.2 million around the eastern half of Victoria Harbour. This should have a significant beneficial effect on its water quality. Making resolute progress towards completion by 1992 is the largest 'existing project', the North West Kowloon Sewage Treatment and Disposal Scheme. This scheme will collect, treat and discharge sewage from a population of 1.1 million in Sham Shui Po, Mong Kok and Yau Ma Tei. All the construction contracts have been awarded. The second largest project in this category is the scheme to 'export' the sewage effluent from the Sha Tin and Tai Po Sewage treatment works and discharge it into Victoria Harbour. The first contract in this scheme which is for the construction of a 3.2 metre- diameter, 7.5 kilometre long sewer tunnel under Tsz Wan Shan was awarded in July. This is the first government project in which it is proposed to use a tunnel boring machine. Under the 'sewerage masterplan scheme' the first contract for sewer refurbishment in the Southern District of Hong Kong Island was awarded towards the end of the year and detailed design was being carried out on sewerage improvements in East Kowloon. Under the 'strategic network schemes' detailed engineering feasibility studies were commenced in June.

With the commissioning of each additional item of infrastructure there is a consequential increased commitment in operations and maintenance. By the end of the year, throughout the territory, some one million cubic metres per day of sewage were receiving grit removal and screening and another 250 000 cubic metres were receiving full biological treatment, and a 1 400 cubic metre-capacity purpose-designed vessel was built as part of a five-year contract for dumping at sea the sludges from the Sha Tin and Tai Po sewage treatment works and the Sha Tin water treatment works. Plans were made to carefully monitor the environmental effect of such dumping.

Following a number of floods in recent years a territory-wide study was carried out by consultants to review rainfall stream flow and flooding predictions, and the measures which government was taking to reduce the extent and risk of flooding. This study was completed during the year and confirmed the appropriateness of most of the measures which government either had taken or was proposing to take and it made a number of recommendations both for structural and non-structural measures. Foremost among the latter was the need to draw up basin management plans. Therefore towards the end of the year work started on drawing up basin management plans for the river basins in the North and North-west New Territories and to examine at a more detailed level what local flood mitigation measures can be taken. In addition, pamphlets giving advice on flooding situations were widely distributed through the district administration to people living in flood-prone areas. Among structural measures which government has already put in hand are the construction of main drainage channels in the northern flood plains and local works to protect low-lying villages which are difficult to drain. Construction of 6.5 kilometres of channels for the Tin Shui Wai hinterland was 50 per cent complete at the end of the year and design was in hand for another 14 kilometres of channels in Yuen Long, Kam Tin and Ngau Tam Mei with a view to starting work on-site in 1991. Four flood pumping stations together with earth embankments and other ancillary flood protection works were also completed near the villages of Kiu Tau Wai, Sik Kong Tsuen, Sik Kong Wai and Sheung Shui, and more than 120 flap gates were installed in various channels at problem locations.