The Drinking Water Safety Advisory Committee (DWSAC) today accepted an investigation report by the Water Supplies Department (WSD) concerning a recent water quality incident at Queen's Hill Estate and Shan Lai Court.

It asked the WSD to expedite implementation of improvement measures and said it expected the department to provide further progress updates before the end of this year.

At a meeting today, the DWSAC received a briefing from the WSD on the report, outlining the department's tracing of the entire fresh water supply network from the Ping Che Fresh Water Service Reservoir to Queen's Hill Estate and Shan Lai Court, along with related analysis and findings, and recommendations to prevent similar incidents in the future.

DWSAC Chairman Chan Hon-fai said the tracing work was objective and scientific.

The DWSAC agreed with the WSD's findings that black sediments in the water supply, identified as bituminous materials, originated from a 400m-long steel pipe with internal bituminous protective lining at Ping Che Road, which is located upstream of the estates.

The sediments also contained a trace amount of blue fragments, which were identified as resin from the internal protective coating on valves in the pipelines. A source of the fragments was found to be a valve located at Lung Ma Road, outside the estates.

The DWSAC agreed to continue the identification and replacement of any defective valves in the estates.

It also noted that the WSD and the Housing Department had carried out a series of joint operations over the past month.

These included increasing the frequency of flushing underground fresh water pipes along Lung Ma Road and within the estates, cleansing the water tanks in each building on the estates, and installing additional strainers on existing filtering devices within the estates.

The DWSAC said that the prevailing water quality had been restored to normal.

Meanwhile, the WSD will explore whether new technologies can be adopted to ensure effective cleansing and eliminate the possibility of sediment in water pipes.

In addition, the DWSAC agreed with several recommendations put forward by the WSD, including the gradual replacement of steel water pipes with bituminous protective lining, which can effectively prevent recurrence of similar incidents in the future.

The department also reported to the DWSAC that it had promptly replaced a section of the underground water pipe with bituminous protective lining at Ping Che Road with an exposed temporary water pipe, and would strive to complete the laying of a new permanent underground water pipe by the end of this year.