9                      hazARd to life review

9.1                  Yau Kom Tau Water Treatment Works (YKTWTW)

9.1.1              The YKTWTW is located approximately 1km to the west of Tsuen Wan and is situated on a level platform cut into the hillside immediately above Tuen Mun Road. To the east and southwest of the YKTWTW, there lie high rise residential developments including Greenview Terrace, Greenview Court, One Kowloon Peak, Bayview Garden, Belvedere Garden, Hanley Villa, Sunny Villa, Grandview Villa, etc. The YKTWTW is located approximately 800m to the west of the Project site (refer to Figure 9.1).

9.1.2              With reference to the Hazard to Life assessment of the approved EIA for “Tsuen Wan Bypass, widening of Tsuen Wan Road between Tsuen Tsing Interchange and Kwai Tsing Interchange and Associated Junction Improvement Works” (EIA-152/2008), it was confirmed that there is delivery, on-site storage and handling of chlorine at the YKTWTW.

9.1.3              In accordance with Appendix H of the EIA Study Brief (ESB-343/2021), Hazard to Life assessment is required to evaluate potential hazard associated with the storage, use and on-site transport of liquid chlorine at the YKTWTW during construction and operation phases of the Project. According to the latest PHI register, YKTWTW has been delisted and no longer considered as PHI. No hazard to life assessment for liquid chlorine related issue is required for YKWTW.

9.2                  Hazard to Life Review for OSCG Operation in YKTWTW

9.2.1              The OSCG plants generate chlorine gas on demand by using electrolysis technology. The process uses salt and water to generate chlorine gas and sodium hypochlorite, with hydrogen gas as a by-product.

9.2.2              The major hazards associated with operation of the OSCG plants include:

·         Failures associated with the chlorine system pipework; and

·         Hydrogen gas leak from pipes and flanges before vented to outdoor area

9.2.3              Highways Department (HyD) subsequently took over the project from CEDD. HyD’s traffic review study on TWR traffic conditions conducted in 2016 revealed that the widening of TWR and improvement of associated junctions were needed to cope with the future traffic demand.

9.2.4              With reference to the Hazard to Life assessment conducted in approved EIA for Agreement No. CE 69/2001(HY) Tsuen Wan Bypass, Widening of Tsuen Wan Road between Tsuen Tsing Interchange and Kwai Tsing Interchange and Associated Junction Improvement Works (Register No.: AEIAR-124/2008), the failure of chlorine system pipework was represented by gas leakage from 4.5mm hole, resulted in 0.027 kg/s release to atmosphere under normal ventilation and 0.011 kg/s release under “door left open” situation. Both releases will not result in off-site hazard.

9.2.5              In case of hydrogen gas leak within the chlorine store, the hydrogen gas will be mixed with air to concentration lower than its Lower Flammable Limit (LFL), i.e. 4%, and vented outside the chlorine store at the roof top level of the chlorine store. No off-site risks are thus anticipated.