Cause of Impact
Potential water pollution sources during construction phase will include construction runoff, runoff from tunneling activities and underground works, sewage effluent due to workforce on site, drainage diversion, groundwater seepage, discharge of groundwater pumped out from potential contaminated area, and accidental spillage of chemicals.
During the operational phase, there will be no direct discharge of wastewater into the Tolo Harbour and Victoria Harbour. Potential water pollution sources during the operational phase are runoff from rail track and operational tunnel drainage.
In order to minimize the impact on water quality during construction phase, the following remedies will be applied:
- Applicable mitigation measures in accordance with ProPECC PN 1/94;
- Open stockpiles of construction materials should be covered with tarpaulin or similar fabric during rainstorms;
- Site runoff discharge should pass through sedimentation tanks prior to off-site discharge;
- For tunneling and underground works, direct discharge of the bentonite slurry is not allowed. It should be reconditioned and reused wherever practicable;
- Portable toilets should be provided for handling the construction sewage generated by the workforce;
- Any contaminated groundwater shall be treated before discharge; and
- Disposal of chemical wastes should be to comply with the requirements in the Waste disposal (Chemcial Waste) (General) Regulation.
In order to minimize the impact on water quality during operational phase, the following remedies will be applied:
- Track drainage channels discharge should pass through oil/grit interceptors/chambers to remove oil, grease and sediment before discharging into public storm drainage / foul sewerage systems
- Silt traps and oil interceptors should be cleaned and maintained regularly;
- Oily contents of the oil interceptors should be transferred to an appropriate disposal facility, or to be collected for reuse, if possible;
- Connection of domestic sewage generated should be diverted to the foul sewer wherever possible, or ensure all discharge comply with the requirements stipulated in the Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters; and
- The practices outlined in ProPECC PN 5/93 should be adopted where applicable.
No adverse water quality impact is anticipated with the provision of mitigation measures during construction and operational phase, including covering excavated materials and providing sedimentation tanks on-site etc.