· a DO level in the range of 0 ‑ 20 mg L-1 and 0 ‑ 200% saturation; and
· a temperature of 0 ‑ 45 degree Celsius.
Table 4.1 Action and Limit Levels for Water Quality
Parameters |
Action |
Limit |
DO in mg/L (mid-depth) |
5 %-ile of baseline data
|
4 mg/L
|
SS in mg/L (mid-depth) |
95 %-ile of baseline data or 120% of control station’s SS on the same day of measurement |
99 %-ile of baseline or 130% of control station's SS on the same day of measurement
|
Turbidity in NTU (mid-depth)
|
95 %-ile of baseline data or 120% of control station’s turbidity on the same day of measurement |
99 %-ile of baseline or 130% of control station's turbidity on the same day of measurement |
Notes: 1. For DO, non-compliance of the water quality limits occurs when monitoring result is lower than the limits.
2. For SS and turbidity, non-compliance of the water quality limits occurs when monitoring result is higher than the limits.
Table 4.2 Event and Action Plan for Water Quality
Event |
ET Leader |
IC(E) |
ER |
Contractor |
Action level being exceeded by one sampling day |
Repeat in situ measurement to confirm findings; Identify reasons for non-compliance and source(s) of impact; Inform IC(E) and Contractor; Check monitoring data, all plant, equipment and Contractor's working methods; Discuss mitigation measures with IC(E) and Contractor; Repeat measurement on next day of exceedance. |
Discuss with ET and Contractor on the mitigation measures; Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly; Assess the effectiveness of the implemented mitigation measures. |
Discuss with IC(E) on the proposed mitigation measures; Make agreement on the mitigation measures to be implemented. Assess the effectiveness of the implemented mitigation measures. |
Inform the ER and confirm notification of the non-compliance in writing; Rectify unacceptable practice; Check all plant and equipment; Consider changes of working methods; Discuss with ET and IC(E) and propose mitigation measures to IC(E) and ER; Implement the agreed mitigation measures. |
Action level being exceeded by more than two consecutive sampling days |
Repeat in situ measurement to confirm findings; Identify reasons for non-compliance and source(s) of impact; Inform IC(E) and Contractor; Check monitoring data, all plant, equipment and Contractor's working methods; Discuss mitigation measures with IC(E) and Contractor; Ensure mitigation measures are implemented; Prepare to increase the monitoring frequency to daily; Repeat measurement on next day of exceedance. |
Discuss with ET and Contractor on the mitigation measures; Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly; Assess the effectiveness of the implemented mitigation measures. |
Discuss with IC(E) on the proposed mitigation measures; Make agreement on the mitigation measures to be implemented; Assess the effectiveness of the implemented mitigation measures. |
Inform the ER and confirm notification of the non-compliance in writing; Rectify unacceptable practice; Check all plant and equipment; Consider changes of working methods; Discuss with ET and IC(E) and propose mitigation measures to IC(E) and ER within three working days; Implement the agreed mitigation measures. |
Limit level being exceeded by one sampling day |
Repeat in situ measurement to confirm findings; Identify reasons for non-compliance and source(s) of impact; Inform IC(E) Contractor and EPD; Check monitoring data, all plant, equipment and Contractor's working methods; Discuss mitigation measures with IC(E), ER and Contractor; Ensure mitigation measures are implemented; Increase the monitoring frequency to daily until no exceedance of Limit level. |
Discuss with ET and Contractor on the mitigation measures; Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly; Assess the effectiveness of the implemented mitigation measures. |
Discuss with IC(E), ET and Contractor on the proposed mitigation measures; Request Contractor to critically review the working methods; Make agreement on the mitigation measures to be implemented; Assess the effectiveness of the implemented mitigation measures. |
Inform the ER and confirm notification of the non-compliance in writing; Rectify unacceptable practice; Check all plant and equipment; Consider changes of working methods; Discuss with ET, IC(E) and ER and propose mitigation measures to IC(E) and ER within three working days; Implement the agreed mitigation measures. |
Limit level being exceeded by more than two consecutive sampling days |
Repeat in situ measurement to confirm findings; Identify reasons for non-compliance and source(s) of impact; Inform IC(E) Contractor and EPD; Check monitoring data, all plant, equipment and Contractor's working methods; Discuss mitigation measures with IC(E), ER and Contractor; Ensure mitigation measures are implemented; Increase the monitoring frequency to daily until no exceedance of Limit level for two consecutive days. |
Discuss with ET and Contractor on the mitigation measures; Review proposals on mitigation measures submitted by Contractor and advise the ER accordingly; Assess the effectiveness of the implemented mitigation measures. |
Discuss with IC(E), ET and Contractor on the proposed mitigation measures; Request Contractor to critically review the working methods; Make agreement on the mitigation measures to be implemented; Assess the effectiveness of the implemented mitigation measures; Consider and instruct, if necessary, the Contractor to slow down or to stop all or part of the construction activities until no exceedance of Limit level. |
Inform the ER and confirm notification of the non-compliance in writing; Rectify unacceptable practice; Check all plant and equipment; Consider changes of working methods; Discuss with ET, IC(E) and ER and propose mitigation measures to IC(E) and ER within three working days; Implement the agreed mitigation measures; As directed by the ER, to slow down or to stop all or part of the construction activities. |
Construction Phase
Construction run-off and Drainage
· 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 Technical Memorandum standard under the Water Pollution Control Ordinance. 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 of more than 50m3 should be covered with tarpaulin or similar fabric during rainstorms. These materials should not be placed near water courses.
· A Drainage Management Plan (DMP) should be prepared by the Contractor and submitted to EPD before the commencement of any construction works to detail the procedures for control of construction site runoff. The DMP should at least cover the construction works areas for slip roads E and F and for Bridge A, and the local widening of the existing Castle Peak Road. No site run-off nor drainage should enter fishponds.
General Construction Activities
Sewage from Construction Workforce
Operation Phase