Since the longer replacement submarine outfall at Pillar Point was commissioned in early 1999, the general water quality of all the six gazetted beaches in the Tuen Mun District had improved to the "Fair" rank and met the WQO for bathing water. In 2001, the same rank was maintained at all the Tuen Mun beaches including the closed Castle Peak Beach (Figure 6.1).

Figure 6.1    Annual ranks of Tuen Mun beaches in 2001

Butterfly Beach

The five opened beaches in the district showed some fluctuations of water quality in 2001. Among them, Butterfly and Golden Beaches had comparatively better and less fluctuating water quality than the others. Though they were also susceptible to the rainfall effect, the deterioration of water quality after rain was less severe. This was also reflected in their weekly grading (Figure 6.2).

Figure 6.2    Distribution of the weekly grading at the Tuen Mun beaches during the bathing season

The other three opened beaches in Tuen Mun viz. Kadoorie, Cafeteria New and Cafeteria Old, showed greater fluctuations of water quality, occasionally very poor weekly grading had been recorded (Figure 6.2). As most domestic premises and beach facilities in the hinterland of these beaches were already connected to public sewers, the fluctuations of water quality at these beaches were most likely related to pollutants flushed down from the Tuen Mun River and the Castle Peak Typhoon Shelter during heavy rain, and to a lesser extent, the marine background of the Tuen Mun area.

Tuen Mun River

After the completion of related improvement works recommended under the Tuen Mun SMP (Figure 6.3) and through EPD's enforcement efforts, the water quality of the Tuen Mun River had significantly improved. However, the E. coli level of the river water was still high ranging from 10³ to 10⁵ per 100mL at the lower reach. Pollutants from the river together with those accumulated in the Castle Peak Typhoon Shelter at the mouth of the river, could contribute to the fluctuating water quality observed at the beaches during heavy rain.

Figure 6.3    Sewerage works in Tuen Mun

Sewer construction

One of the major pollution sources of the Tuen Mun River is the sewage from the unsewered villages at the upper reach. These unsewered villages use septic tank and soakaway systems for sewage treatment. In the years ahead, the Tuen Mun sewerage system will eventually be extended to these unsewered areas so that sewage from the village houses would be collected for treatment and disposal at suitable sewage treatment facilities. When the project is implemented, the water quality of the Tuen Mun River and hence, of the beaches in the vicinity is expected to improve further.

Village houses at the upper reach of Tuen Mun River

The marine background of the Tuen Mun area was affected by discharges from the Northwest New Territories (NWNT) and the Pillar Point submarine outfalls, which discharged into Urmston Road and the sea area facing Pillar Point respectively. EPD's marine monitoring results indicated that the E. coli levels of the water at Urmston Road and Pillar point were around 400 to 500 and 300 to 400 per 100mL respectively. To further improve the marine water quality in Tuen Mun, a study has been completed to upgrade the treatment level of the Pillar Point and San Wai Sewage Treatment Works from preliminary screening level to chemically enhanced primary treatment with disinfection. The overall water quality of the Tuen Mun beaches is expected to improve after the completion of these upgrading works.

Screw pumps at Pillar Preliminary Treatment Works