2.1 As identified in the EIA Report, the key water quality impacts caused by the Project would be associated with the dredging works during the construction phase. The EIA report has identified that suspended sediment is the most critical water quality parameter caused by the dredging works. Marine water quality monitoring shall be carried out during the construction phase to ensure that any unacceptable increase in suspended solids / turbidity and decrease in dissolved oxygen due to the dredging activities or temporary reclamation works could readily detected and timely action be taken to rectify the situation. As presented in the EIA Report, adverse impacts associated with the potential release of contaminants (such as heavy metals) from the marine mud during dredging activities is not expected. As such, no monitoring programme specific for contaminant release is considered necessary.
2.2 Dissolved Oxygen (DO), turbidity and Suspended Solids (SS) levels shall be monitored at designated marine water quality monitoring stations during the construction phase. DO and turbidity should be measured in situ whereas SS should be determined by laboratory.
Monitoring Equipment for Marine Water Quality Monitoring
Dissolved Oxygen and Temperature Measuring Equipment
2.3 The instrument should be a portable and weatherproof dissolved oxygen (DO) measuring instrument complete with cable and senor, and use a DC power source. The equipment should be capable of measuring:
· a DO level in the range of 0 - 20 mg∙L-1 and 0 - 200% saturation; and
· a temperature of 0 - 45 degree Celsius (°C).
2.4 It should have a membrane electrode with automatic temperature compensation complete with a cable.
2.5 Should salinity compensation not be built-in to the DO equipment, in-situ salinity should be measured to calibrate the DO equipment prior to each DO measurement.
Turbidity Measurement Instrument
2.6 The instrument should be a portable and weatherproof turbidity measuring instrument using a DC power source. It should have a photoelectric sensor capable of measuring turbidity between 0 - 1000 NTU (for example, Hach model 2100P or an approved similar instrument).
Sampler
2.7 A water sampler is required. It should comprise a transparent PVC cylinder, with a capacity of not less than 2 litres, which can be effectively sealed with latex cups at both ends. The sampler should have a positive latching system to keep it open and prevent premature closure until released by a messenger when the sampler is at the selected water depth (for example, Kahlsico Water Sampler or an approved similar instrument).
Water Depth Detector
2.8 A portable, battery-operated echo sounder should be used for the determination of water depth at each designated monitoring station. This unit can either be hand-held or affixed to the bottom of the work boat, if the same vessel is to be used throughout the monitoring programme.
Salinity
2.9 A portable salinometer capable of measuring salinity in the range of 0 - 40 parts per thousand (ppt) should be provided for measuring salinity of the water at each monitoring location.
Sample Containers and Storage
2.10 Water samples for SS should be stored in high density polythene bottles with no preservative added, packed in ice (cooled to 4 °C without being frozen) and delivered to the laboratory and analyzed as soon as possible after collection. Sufficient volume of samples should be collected to achieve the detection limit stated in Table 2.1.
Monitoring Position Equipment
2.11 A hand-held or boat-fixed type digital Differential Global Positioning System (DGPS) with way point bearing indication and Radio Technical Commission for maritime (RTCM) Type 16 error message ‘screen pop-up’ facilities (for real-time auto-display of error messages and DGPS corrections from the Hong Kong Hydrographic Office), or other equipment instrument of similar accuracy, should be provided and used during marine water monitoring to ensure the monitoring vessel at the correct location before taking measurements.
Calibration of In-Situ Instruments
2.12 The pH meter, DO meter and turbidimeter shall be checked and calibrated before use. DO meter and turbidimeter shall be certified by a laboratory accredited under HOKLAS or any other international accreditation scheme, and subsequently re-calibrated at 3 monthly intervals throughout all stages of the water quality monitoring. Responses of sensors and electrodes should be checked with certified standard solutions before each use. Wet bulb calibration for a DO meter shall be carried out before measurement at each monitoring location.
2.13 Sufficient stocks of spare parts shall be maintained for replacements when necessary. Backup monitoring equipment shall also be made available so that monitoring can proceed uninterrupted even when some equipment are under maintenance, calibration, etc.
Laboratory Measurement / Analysis for Marine Water
2.14 Duplicate samples from each independent sampling event are required by EPD for all parameters. Analysis of suspended solids shall be carried out in a HOKLAS or other international accredited laboratory. Sufficient water samples shall be collected at the monitoring stations for carrying out the laboratory SS determinations, with detection limit shown in Table 2.1. The SS determination work shall start within 24 hours after collection of the water samples. The analyses shall follow the standard methods according to Table 2.1 and as described in “American Public Health Association (APHA) Standard Methods for the Examination of Water and Wastewater”, 19th edition, unless otherwise specified.
Table 2.1 Analytical Methods to be applied to Marine Water Quality Samples
|
Determinant |
Standard Method |
Detection Limit |
|
Suspended Solids (mg L-1) |
APHA 2540 D |
0.1 mg L-1 |
2.15 If a site laboratory is set up or a non-HOKLAS and non-international accredited laboratory is hired for carrying out the laboratory analysis, the laboratory equipment, analytical procedures, and quality control shall be approved by EPD. All the analysis shall be witnessed by the ER. The ET Leader shall provide the ER with one copy of the relevant chapters of the “APHA Standard Methods for the Examination of Water and Wastewater”, 19th edition and any other relevant document for his reference.
2.16 For the test methods of other parameters as recommended by EIA or required by DEP, detailed testing methods, pre-treatment procedures, instruments use, QA/QC details (such as blank, spike recovery, number of duplicate samples per batch, etc.), detection limit and accuracy shall be submitted to EPD for approval prior to the commencement of monitoring programme. The QA/QC shall be in accordance with the requirements of HOKLAS or international accredited scheme. The QA/QC results shall be reported. EPD may also request the laboratory to carry out analysis of known standards provided by EPD for quality assurance. Additional duplicate samples may be required by EPD for inter laboratory calibration. Remaining samples after analysis shall be kept by the laboratory for 3 months in case repeat analysis is required. If in-house or non-standard methods are proposed, details of the method verification may also be required to submit to EPD. In any circumstance, the sample testing shall have comprehensive quality assurance and quality control programmes. The laboratory shall prepare to demonstrate the programme to DEP or his representatives when requested.
Marine Water Monitoring Locations
2.17 The locations of water monitoring stations during construction phases of the Project are shown in Figure No. NEX2213/C/331/ENS/M62/510 and Table 2.2.
Table 2.2 Proposed Marine Water Quality Stations for Baseline and Impact Monitoring
|
Station |
Description |
Easting |
Northing |
|
8 |
Cooling Water Intake for Excelsior Hotel
& World Trade Centre / |
837036.23 |
816007.92 |
|
9 |
Cooling Water Intake for |
837222.84 |
816149.67 |
2.18 Station 8 will be located within the temporary embayment created by the temporary reclamations for the Protection Works and TS4. The DO levels at Station 8 will be monitored during the construction period to avoid aggravation of odour nuisance from seawater arising from temporary reclamation in the CBTS. In case the temporary reclamation for the Protection Works is found during the water quality monitoring and audit programme to cause unacceptable oxygen depletion (e.g. <2 mg/L) at Station 8, mitigation measures (e.g. use of aeration method to improve the DO levels in the marine embayment) will be considered and implemented in the CBTS as necessary to improve the problems.
Baseline Marine Water Monitoring
2.19 Baseline conditions for marine water quality should be established and agreed with EPD prior to the commencement of marine works. The purpose of the baseline monitoring is to establish ambient conditions prior to the commencement of the dredging works and to demonstrate the suitability of the proposed monitoring stations.
2.20 The baseline conditions should be established by measuring dissolved oxygen, turbidity and suspended solids levels at the selected monitoring stations as shown in Figure No. NEX2213/C/331/ENS/M62/510. The proposed monitoring frequency and water quality parameters for the baseline monitoring are shown in Table 2.3. The baseline monitoring schedule should be submitted to EPD at least 2 weeks before commencement of monitoring for agreement. EPD should also be notified immediately for any changes in schedule.
2.21 The measurements should be taken at all designated monitoring stations, 3 days per week, at mid-flood and mid-ebb tides, for at least 4 weeks prior to the commencement of dredging works. Any marine construction works should be avoided in the vicinity of the stations during the baseline monitoring. The interval between 2 sets of monitoring should not be less than 36 hours. Duplicate in-situ measurements and water sampling should be carried out in each sampling event. For selection of tides for in-situ measurement and water sampling, tidal range of individual flood and ebb tides should be not less than 0.5 m.
Impact Marine Water Monitoring
Table 2.3 Proposed Marine Water Quality Monitoring Frequency and Parameters
|
Activities |
Monitoring Frequency Note 1 |
Key Parameters Note 2 |
|
During the 4-week baseline monitoring period |
Three days per week, at mid-flood and mid-ebb tides |
Turbidity, Suspended Solids (SS), Dissolved Oxygen (DO), pH, temperature, salinity |
|
During marine construction works |
Three days per week, at mid-flood and mid-ebb tides |
Turbidity, Suspended Solids (SS), Dissolved Oxygen (DO), pH, temperature, salinity |
|
After completion of marine construction works |
Three days per week, at mid-flood and mid-ebb tides |
Turbidity, Suspended Solids (SS), Dissolved Oxygen (DO), pH, temperature, salinity |
Notes:
1. For selection of tides for in-situ measurement and water sampling, tidal range of individual flood and ebb tides should be not less than 0.5 m.
2. Turbidity should be measured in situ whereas SS should be determined by laboratory.
2.23 The proposed water quality monitoring schedule should be passed to EPD at least 1 week before the first day of the monitoring. EPD should also be notified immediately for any changes in schedule. If the monitoring data collected at the flushing water intakes indicate that the Action or Limit levels as shown in Table 2.4 are exceeded, appropriate actions should be taken to stop the dredging works and mitigation measures such as slowing down, or rescheduling of works should be implemented as necessary.
Regular Maintenance of Silt Screens
2.25 As a mitigation measure to avoid the pollutant and refuse entrapment problems and to ensure that the impact monitoring results are representative, regular maintenance of the silt screens and refuse collection should be performed by the contractor at the silt screens at regular intervals on a daily basis. The Contractor should be responsible for keeping the water behind the silt screen free from floating rubbish and debris during the impact monitoring period. The contractor should be responsible for keeping the water behind the silt screen from floating rubbish and debris before the silt screens are removed.
Post-construction Marine Water Monitoring
2.26 Upon completion of all marine-based construction activities, a post-project monitoring exercise on water quality shall be carried out for four weeks in the same manner as the impact monitoring as described in Section 2.22 to 2.24.
Field Log for Marine Water Monitoring
2.27 Other relevant data should also be recorded, including monitoring location / position, time, water depth, sampling depth, pH, salinity, DO saturation, water temperature, tidal stages, weather conditions and any special phenomena or work underway nearby.
2.28 A sample data record sheet is shown in Appendix B1 for reference.
2.29 Implementation of regular site audits is to ensure that the recommended mitigation measures are to be properly undertaken during proposed marine construction works. It can also provide an effective control of any malpractices and therefore achieve continual improvement of environmental performance on site.
Site Inspection
2.30 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 attached 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
2.31 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 should 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 should 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 license requirements; and
· Record the non-compliance and propose preventive measures.
Event and Action Plan for Construction Water Quality
2.32 The water quality assessment criteria, namely Action and Limit levels are shown in Table 2.4. When exceedances of water quality assessment criteria are detected at any designated monitoring stations, carry out the actions in accordance with the Action Plan in Table 2.1 is recommended.
2.33 The ET Leader should assess the potential impacts caused by dredging works on the seawater intakes based on the monitoring data. The performance of the environmental management system (i.e. of the overall EM&A programme) should be reviewed by the ET Leader on a quarterly basis. The findings of this review should be included in the quarterly EM&A summary reports, together with any recommendations to improve the performance of the EM&A programme.
Table 2.4 Action and Limit Levels for Marine Water Quality at Seawater Intakes
|
Parameters |
Action |
Limit |
|
SS in mg∙L-1 |
95 percentile of baseline data |
99 percentile of baseline data |
|
Turbidity in NTU |
95 percentile of baseline data |
99 percentile of baseline data |
|
DO in mg/L |
5 percentile of baseline data |
1 percentile of baseline data or 2mg/L |
Notes
1. It is recommended to conduct the monitoring behind the silt screens and at the appropriate vertical levels of the abstraction points of these intakes
2. For turbidity and SS, non-compliance of the water quality limits occurs when monitoring result is higher than the limits.
3. 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.
2.34 If monitoring results indicate that the dredging or filling works have caused an adverse impact on water quality at the cooling water intakes, it is recommended that the contractor should inform the owners of cooling water intakes. Additional mitigation measures should be recommended to rectify the non-compliance or the construction programme should be carefully reviewed to slow down the rate of dredging.
2.35 Where necessary, EPD routine marine water quality monitoring data at the relevant station(s), dry and wet seasons inclusive, could also be used to establish the baseline water quality.
Mitigation of Adverse Environmental Impacts
2.36 Mitigation measures for water quality control have been recommended in the EIA Report. The Contractor should be responsible for the design and implementation of these measures.
2.37 Recommended mitigation measures to minimize the adverse impacts on water quality during the proposed dredging are listed in the implementation schedule given in Appendix A.
Table 2.5 Event and Action Plan for Marine Water Quality
|
EVENT |
ACTION |
|||
|
ET |
IEC |
ER |
CONTRACTOR |
|
|
Action
level being exceeded by one sampling day |
Repeat in-situ
measurement to confirm findings; Identify source(s) of
impact; Inform IEC and
Contractor; Check monitoring data,
all plant, equipment and Contractor's working methods; Discuss mitigation
measures with IEC and Contractor; (The above actions
should be taken within 1 working day after the exceedance is identified) 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. (The above actions
should be taken within 1 working day after the exceedance is identified) |
Discuss with IEC on the
proposed mitigation measures; Make agreement on the
mitigation measures to be implemented. (The above actions
should be taken within 1 working day after the exceedance is identified) |
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 IEC
and propose mitigation measures to IEC and ER; Implement the agreed
mitigation measures. (The above actions
should be taken within 1 working day after the exceedance is identified) |
|
Action
level being exceeded by more than one consecutive sampling days |
Identify source(s) of
impact; Inform IEC and
Contractor; Check monitoring data,
all plant, equipment and Contractor's working methods; Discuss mitigation
measures with IEC and Contractor; Ensure mitigation
measures are implemented; Prepare to increase the
monitoring frequency to daily; (The above actions
should be taken within 1 working day after the exceedance is identified) Repeat measurement on
next working 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. (The above actions
should be taken within 1 working day after the exceedance is identified) |
Discuss with IEC on the
proposed mitigation measures; Make agreement on the
mitigation measures to be implemented; Assess the effectiveness
of the implemented mitigation measures. (The above actions
should be taken within 1 working day after the exceedance is identified) |
Inform the Engineer 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 IEC
and propose mitigation measures to IEC and ER within 3 working days; Implement the agreed
mitigation measures. (The above actions
should be taken within 1 working day after the exceedance is identified) |
|
Limit level being exceeded by one sampling day |
Repeat in-situ
measurement to confirm findings; Identify source(s) of
impact; Inform IEC and
Contractor and EPD; Check monitoring data,
all plant, equipment and Contractor's working methods; Discuss mitigation
measures with IEC and Contractor; Ensure mitigation
measures are implemented; Increase the monitoring
frequency to daily until no exceedance of Limit level. (The above actions
should be taken within 1 working day after the exceedance is identified) |
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. (The
above actions should be taken within 1 working day after the exceedance is
identified) |
Discuss
with IEC, 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. (The
above actions should be taken within 1 working day after the exceedance is
identified) |
Inform
the Engineer 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 , IEC and ER and propose mitigation measures to IEC and ER within 3
working days; Implement
the agreed mitigation measures. (The
above actions should be taken within 1 working day after the exceedance is
identified) |
|
Limit
level being exceeded by more than one consecutive sampling days |
Identify source(s) of
impact; Inform IEC, contractor
and EPD; Check monitoring data,
all plant, equipment and Contractor's working methods; Discuss mitigation
measures with IEC, ER and Contractor; Ensure mitigation
measures are implemented; Increase the monitoring
frequency to daily until no exceedance of Limit level for two consecutive
days. (The above actions
should be taken within 1 working day after the exceedance is identified) |
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. (The above actions
should be taken within 1 working day after the exceedance is identified) |
Discuss with IEC, 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
marine work until no exceedance of Limit level. (The above actions
should be taken within 1 working day after the exceedance is identified) |
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 , IEC
and ER and propose mitigation measures to IEC and ER within 3working days; Implement the agreed
mitigation measures; As directed by the
Engineer, to slow down or to stop all or part of the marine work or
construction activities. (The above actions
should be taken within 1 working day after the exceedance is identified) |