4. WATER QUALITY MONITORING
4.1 Monitoring Locations
4.1.1 The water monitoring works for the Contract are covered by Contract No. HY/2010/02 “Hong Kong-Zhuhai-Macao-Bridge HKBCF – Reclamation Works”. The ET of the Contract or another ET of the HZMB project is required to conduct impact water quality monitoring at the stations shown in Table 4.1 and Figure 3.
Table 4.1 Water Quality Monitoring Stations
|
Station |
Description |
East |
North |
|
IS5 |
Impact Station (Close to HKBCF construction site) |
811579 |
817106 |
|
IS(Mf)6 |
Impact Station (Close to HKBCF construction site) |
812101 |
817873 |
|
IS7 |
Impact Station (Close to HKBCF construction site) |
812244 |
818777 |
|
IS8 |
Impact Station (Close to HKBCF construction site) |
814251 |
818412 |
|
IS(Mf)9 |
Impact Station (Close to HKBCF construction site) |
813273 |
818850 |
|
IS10(N) |
Impact Station (Close to HKBCF construction site) |
812569 |
821475 |
|
IS(Mf)11 |
Impact Station (Close to HKBCF construction site) |
813562 |
820716 |
|
IS(Mf)16 |
Impact Station (Close to HKBCF construction site) |
814328 |
819497 |
|
IS17 |
Impact Station (Close to HKBCF construction site) |
814539 |
820391 |
|
SR3 |
Sensitive receivers (San Tau SSSI) |
810525 |
816456 |
|
SR4(N) |
Sensitive receivers (Tai Ho) |
814705 |
817859 |
|
SR5(N) |
Control Station |
812569 |
821475 |
|
SR6 |
Sensitive receivers (Sha Chau and Lung Kwu Chau Marine Park) |
805837 |
821818 |
|
SR7 |
Sensitive receivers (Tai Mo Do) |
814293 |
821431 |
|
SR10A(1) |
Sensitive receivers(Ma Wan FCZ) 1 |
823741 |
823495 |
|
SR10B(N)(1) |
Sensitive receivers(Ma Wan FCZ) 2 |
823683 |
823187 |
|
CS(Mf)3(N) |
Control Station |
808814 |
822355 |
|
CS(Mf)5 |
Control Station |
817990 |
821129 |
|
CS4 |
Control Station |
810025 |
824004 |
|
CS6 |
Control Station |
817028 |
823992 |
|
CSA(2] |
Control Station |
818103 |
823064 |
Note:
(1) Additional monitoring station for ma Wan FCZ
(2) Additional control monitoring station for Ma Wan FCZ
Remarks:
The ET of the Contract should conduct impact water quality monitoring at the WQMs listed in the table as part of EM&A programme according to latest notification from ENPO if water quality monitoring is no longer covered by another ET of the HZMB project. The ET of the Contract shall communicate and share the monitoring data to the ET(s) of the other contracts if the water quality monitoring station(s) is/are as part of EM&A programme.
4.2...... Monitoring Requirements
4.2.1... The monitoring requirements, monitoring equipment, monitoring parameters, frequency and duration, monitoring methodology, monitoring schedule, meteorological information are detailed in the monthly EM&A Reports prepared by Contract No. HY/2010/02.
4.2.2... The event and action plan is provided in Appendix D.
4.2.3... The Action and Limit Levels for Water Quality are provided in Table 4.2.
...........
........... Table 4.2 Action and Limit Levels for Water Quality
|
Parameters |
Action |
Limit |
|
DO in mg/L (Surface, Middle & Bottom) |
Surface and Middle 5.0 Bottom 4.7 |
Surface and Middle = 4.2 (except 5 mg/L for FCZ) Bottom = 3.6 |
|
SS in mg/L (depth-averaged) at all monitoring stations and control stations |
23.5 and 120% of upstream control station's SS at the same tide of the same day* |
34.4 and 130% of upstream control station's SS at the same tide of the same day and 10mg/L for WSD Seawater intakes* |
|
Turbidity in NTU (depth-averaged) |
27.5 and 120% of upstream control station's turbidity at the same tide of the same day* |
47.0 and 130% of upstream control station's turbidity at the same tide of the same day* |
* Remarks: Reference is made to EPD approval of adjustment of water quality assessment criteria issued and became effective on 18 February 2013.
Notes:
1.”depth-averaged" is calculated by taking the arithmetic means of reading of all three depths.
2. For DO, non-compliance of the water quality limits occurs when monitoring result is lower than the limits.
3. For turbidity, SS, non-compliance of the water quality limits occurs when monitoring result is higher than the limits.
4. All the figures given in the table are used for reference only and the EPD may amend the figures whenever it is considered as necessary.
5. The 1%-ile of baseline data for dissolved oxygen (surface and middle) and dissolved oxygen (bottom) are 4.2mg/L and 3.6mg/L respectively.
4.2.4... If exceedance(s) at these stations is/are recorded by the ET of the Contract or referred by the other ET under the HZMB project to the Contract, the ET of the Contract will carry out an investigation and findings will be reported in the monthly EM&A Report.
4.3...... Monitoring Results
4.3.1... The monitoring results for the monitoring stations shown in Table 4.1 are reported in the monthly EM&A Report prepared for Contract No. HY/2010/02. There were two Action Level exceedances of suspended solids recorded at station SR3 during mid-ebb tide on 12 July 2017 and station IS7 during mid-flood tide on 14 July 2017. After investigation, it was concluded that the two exceedances were not relevant to Contract No. HY/2013/03.
4.3.2... Regarding the exceedance on 12 July 2017, marine-based construction works were undertaken in Box Culvert B and there was one derrick lighter delivered sand to the work site of Three Runway Project on 12 July 2017 under Contract No. HY/2013/03. Both marine-based construction works and the route of marine transportation were far away from the concerned WQM station SR3. There was no notification of exceedance received at the WQM stations closer to the marine-based construction works areas, such as IS(Mf)11, IS10, IS17 and SR7. Besides, the SS exceedance was recorded at 13:49. The derrick lighter was deposited at HKBCF from morning until 16:00. Therefore, it was unlikely to generate any suspended solids to cause the SS exceedance recorded at the concerned WQM station SR3 during mid-ebb tide on 12 July 2017. Besides, the water quality mitigation measures as mentioned in EM&A Manual and EP were fully implemented in Contract No. HY/2013/03. Hence, the exceedance on 12 July 2017 was not related to Contract No. HY/2013/03.
4.3.3... Regarding the exceedance on 14 July 2017, marine-based construction works were undertaken in Box Culvert B and there were two derrick lighters delivered sand to the work site of Three Runway Project on 14 July 2017 under Contract No. HY/2013/03. Both marine-based construction works and the routes of marine transportation were undertaken in the north side of HKBCF while the concerned WQM station IS7 was in the south-west side. As the concerned monitoring station was far away from both marine-based construction works and the routes of marine transportation and there was no notification of exceedance received at the WQM stations closer to the works areas, such as IS(Mf)11, IS10, IS17 and SR7, it was unlikely to generate any suspended solids to cause the SS exceedance recorded at the concerned WQM station IS7 during mid-flood tide on 14 July 2017. Besides, the water quality mitigation measures as mentioned in EM&A Manual and EP were fully implemented in Contract No. HY/2013/03. Hence, the exceedance on 14 July 2017 was not related to Contract No. HY/2013/03.
4.3.4... After investigation, it was concluded that the exceedances were not related to Contract No. HY/2013/03 due to the above reasons. The investigation reports 002 & 003 (including the causes of exceedance, action taken and recommendation for mitigation) for Action or Limit Level Non-compliance were provided in Appendix J. There was no Action and Limit Level exceedance recorded on other monitoring dates at the monitoring stations shown as shown at Table 4.1 by the Environmental Team of Contract No. HY/2010/02 during the reporting period.
4.3.5... Although the exceedances were not relevant to Contract No. HY/2013/03, the Contractor was reminded to continue to fully maintain all water quality mitigation measures and ensure the silt curtain is fully maintained to prevent any water quality impact to seawater.