3.2    During the bathing season in 2001, all the gazetted beaches showed some fluctuations of water quality, which were reflected by their weekly grading. Figure 3.2 showed the variation of weekly grading recorded in 2001 for all the gazetted beaches on the outlying islands. Most water quality fluctuations recorded at these beaches were related to heavy rainfall, which flushed out the accumulated pollutants in the beach hinterland.

Figure 3.2   Distribution of the weekly grading at beaches on the Outlying Islands during the bathing season

 

Silvermine Bay Beach

Wang Tong River leading to Silvermine Bay

3.3    Among the nine gazetted beaches on the outlying islands, the water quality of Silvermine Bay Beach was more susceptible to the rainfall effect and therefore was more fluctuating. The pollution sources of the Silvermine Bay beach are the septic tank and soakaway pit systems of the village houses. If these systems are not properly maintained, sewage may overflow from them and find its way to the nearby rivers leading to the beach. This problem may become more serious during heavy rainfall. Other pollution sources for the beach are the direct discharge of sullage from the unsewered village houses and the seepage from the soakaway pit system in the beach hinterland.

3.4    The pollution of the beach can be greatly mitigated by the provision of sewer connection to individual village houses and the direction of sullage flows to the foul sewers in the beach hinterland. A programme to expand and upgrade the existing Mui Wo sewerage system is being developed under the Outlying Islands Sewerage Master Plan Stage II Review. EPD had also conducted frequent inspections in the beach hinterland to ensure that the septic tank and soakaway pit systems of the village houses were properly maintained. As a result, the water quality of the Silvermine Bay Beach has improved since 1999. It is expected that the water quality of Silvermine Bay Beach will improve further when the other village houses are gradually connected to the sewerage network.

Cheung Sha Lower Beach		Stream flowing into Cheung Sha Lower Beach

3.5    Fluctuations of water quality were also recorded at the Cheung Sha Lower Beach during the wet weather in April to June 2001 (Figure 3.4). Since the village houses in the beach hinterland are served by septic tank and soakaway pit systems, overflow of the systems may occur during heavy rainfall resulting in transient deterioration of beach water quality. Under the Outlying Islands SMP Stage II (Figure 3.3), sewers will be provided along the southern coast of Lantau Island for collecting and conveying sewage to the Mui Wo sewage treatment works for treatment and disposal. When these sewerage works are completed, the water quality of beaches on the south of Lantau including the Cheung Sha Lower Beach will improve.

 

 

Rainfall warning notice board

3.6    In order to alert the bathers about the rainfall effect on the beach water quality, LCSD has displayed advisory notices at those beaches susceptible to the rainfall effect including the Silvermine Bay and Cheung Sha Lower Beaches (Appendix 3). The public is advised not to swim in beach water for up to 3 days after rain stops.