4 WATER QUALITY

4.2 Construction Site Audits

4.2.1 Implementation of regular site audits is to ensure that the recommended mitigation measures are to be properly undertaken during proposed construction works. It can also provide an effective control of any malpractices and therefore achieve continual improvement of environmental performance on site.

Site Inspection

4.2.2 Site inspections shall be carried out by the ET and shall be based on the mitigation measures for water pollution control recommended in the implementation schedule as presented in Appendix A. In the event that the recommended mitigation measures are not fully or properly implemented, deficiency shall be recorded and reported to the site management. Suitable actions are to be carried out to:

• Record the problems and investigate the causes;

• Issue action notes to the Contractor who is responsible for the works;

• Implement remedial and corrective actions immediately;

• Re-inspect the site conditions upon completion of the remedial and corrective actions; and

• Record the event and discuss with the Contractor for preventive actions.

Compliance Audits

4.2.3 Compliance audits are to be undertaken to ensure that a valid discharge license has been issued by EPD prior to the discharge of effluent from the Project site. If monitoring of the treated effluent quality from the Works Areas is required during the construction phase of the Project, the monitoring shall be carried out in accordance with the WPCO license which is under the ambit of regional office (RO) of EPD. The audit results reflect whether the effluent quality is in compliance with the discharge license requirements. In case of non-compliance, suitable actions by the relevant parties shall be undertaken to:

• Notify the site management on the non-compliance;

• Identify the sources of pollution;

• Check the implementation status of the recommended mitigation measures;

• Investigate the operating conditions of the on-site treatment systems;

• Implement corrective and remedial actions to improve the effluent quality;

• Increase monitoring frequency until the effluent quality is in compliance with the discharge licence requirements; and

• Record the non-compliance and propose preventive measures.

4.3 Mitigation Measures

4.3.1 The mitigation measures recommended for the construction phase of the Project are summarised below. The implementation schedule of the recommended water quality mitigation measures is presented in Appendix A.

Construction Phase

Construction Runoff and Drainage

4.3.2 The site practices outlined in ProPECC PN 1/94 “Construction Site Drainage” should be followed as far as practicable in order to minimise surface runoff and the chance of erosion, and also to retain and reduce any suspended solids prior to discharge. These practices include the following items :

• Before commencing any site formation work, all sewer and drainage connections should be sealed to prevent debris, soil, sand etc. from entering public sewers/drains.

• Silt removal facilities such as silt traps or sedimentation facilities should be provided to remove silt particles from runoff to meet the requirements of the TM standards under the WPCO. The design of silt removal facilities should be based on the guidelines provided in ProPECC PN 1/94. All drainage facilities and erosion and sediment control structures should be inspected monthly and maintained to ensure proper and efficient operation at all times and particularly during rainstorms.

• Careful programming of the works to minimise surface excavations for the road improvement works during the wet season. If excavation of soil cannot be avoided during the wet season, exposed slope surfaces should be covered by a tarpaulin or other means. Other measures that need to be implemented before, during, and after rainstorms are summarized in ProPECC PN 1/94.

• Exposed soil surfaces should be protected by paving or fill material as soon as possible to reduce the potential of soil erosion.

• Open stockpiles of construction materials or construction wastes on-site should be covered with tarpaulin or similar fabric during rainstorms. These materials should not be placed near water courses.

General Construction Activities

4.3.3 Debris and refuse generated on-site should be collected, handled and disposed of properly to avoid entering the nearby local stormwater drainage system. Stockpiles of cement and other construction materials should be kept covered when not being used.

• Oils and fuels should only be used and stored in designated areas which have pollution prevention facilities. All fuel tanks and storage areas should be provided with locks and be sited on sealed areas, within bunds of a capacity equal to 110% of the storage capacity of the largest tank. The bund should be drained of rainwater after a rain event.

Sewage Effluents

4.3.4 Temporary sanitary facilities, such as portable chemical toilets, should be employed on-site. A licensed contractor would be responsible for appropriate disposal and maintenance of these facilities.

Operation Phase

4.3.5 A surface water drainage system will be provided to collect road runoff. The following measures are recommended to ensure road runoff will comply with the standards stipulated in the TM for discharges into storm water drains:

• The road drainage should be directed through silt traps in the gully inlets to remove silt and grit before entering the public storm water drainage system; and

• The silt traps should be regularly cleaned and maintained in good working condition.