Beach Water Quality Report 2002

Chapter Seven

Beaches on Outlying Islands

7.1	The water quality of the two beaches on Cheung Chau have slight fluctuation during the bathing season In the Outlying Islands District, Lantau, Lamma and Cheung Chau are the outlying islands where popular beaches of good water quality are found. There are altogether nine gazetted beaches on these three islands. In 2002, all except Silvermine Bay had 'Good' water quality. Silvermine Bay was ranked 'Fair' in 2002, which was the same as in 2001. All nine beaches were able to comply with the WQO for bathing water (Figure 7.1).
7.2	Water fluctuation of water quality was observed at Silvermine Bay Beach Most of the beaches on the outlying islands had stable good water quality in 2002. Tong Fuk and Cheung Sha Upper on Lantau and the two beaches on Lamma, viz. Hung Shing Yeh and Lo So Shing had consistent good water quality throughout the whole bathing season. Slight fluctuation in water quality was observed at Cheung Sha Lower and Pui O of Lantau, Kwun Yam Wan and Tung Wan of Cheung Chau. Figure 7.2 shows the distribution of weekly grading recorded in 2002 for all the gazetted beaches in the Outlying Islands District.
7.3	Sullage can be discharged via surface channels to watercourses Among the nine gazetted beaches on outlying islands, wider fluctuation in water quality was observed at Silvermine Bay where its hinterland was relatively more populated (Figure 7.3). Although about 80% of the population of Mui Wo and the surrounding villages are connected to sewerage, some houses in the catchment still use septic tank and soakaway pit systems for sewage treatment and disposal. Many of these houses are at close proximity to streams. If these treatment systems are not properly maintained, sewage may overflow to the nearby streams and rivers leading to the beach. Similarly, sullage from village houses would also be discharged via surface channels to watercourses in the vicinity. Hence the water quality of Silvermine Bay is particularly susceptible to the effect of heavy rain, which may flush pollutants from the hinterland into the beach water.
7.4	In order to prevent pollution of beach water, EPD had conducted frequent inspections to ensure that the septic tank and soakaway pit systems in the beach hinterland are properly maintained and regularly desludged. Advisory letters had been distributed to the companies of holiday bungalows in the Silvermine Bay area to advise the management and the holiday users to maintain their sewage treatment systems and dispose of their waste properly.
7.5	Construction of sewer along Tung Wan Tau Road As provision of sewerage to village houses is the key to mitigate beach pollution, trunk sewer is now being built at Tung Wan Tau to the northeast of Silvermine Bay. The works are scheduled for completion in 2003. Construction of trunk sewers at Tai Tei Tong and Pak Ngan Heung in the catchment of Mui Wo has also been completed, but house connections have yet to be made.
7.6	The upgrading of Mui Wo STP has been proposed to treat also the flow from the south of Lantau Village houses at Pak Ngan Heung will also be connected to sewer in future Provision of village sewerage will improve the water quality of rivers and streams flowing to the beach The existing Mui Wo Sewage Treatment Plant (STP) is located further south from the beach, currently serving part of Mui Wo, including the Silvermine Bay Hotel and most of the Chung Hau Village at the south of the beach. The STP provides secondary level sewage treatment with disinfection. The Outlying Islands Sewerage Master Plan (SMP) Stage II Review Study recommended to expand and upgrade the existing Mui Wo STP for treating sewage from Mui Wo and the south of Lantau (Figure 7.4). Trunk sewerage incorporating a series of pumping stations will be constructed to convey sewage from the south of Lantau to the Mui Wo trunk sewerage system. Branch sewerage will be extended to villages at the south of Lantau as well as to villages around Mui Wo including Wang Tong, Mui Wo Kau Tsuen, and Tsoi Yuen Tsuen. House connections will be provided in Pak Ngan Heung, Luk Tei Tong, Tai Tei Tong, Chung Hau and Tung Wan Tau. The implementation programme for the proposed works has not been finalized. Of the SMP packages that have been developed in the Outlying Islands SMP Review Study, village sewerage connections to the Mui Wo environs is of high priority. By the time when these proposed sewerage works are implemented, the good water quality of the beaches on Lantau will be further safeguarded.