4.1.2
The
EIA Report has identified that suspended solids (SS) would be the most critical
water quality parameter during the dredging operations. Marine water quality monitoring for SS
and turbidity is therefore recommended to be carried out at selected WSD
flushing water intakes. The
monitoring should include baseline and impact monitoring. The impact monitoring should be carried
out during the proposed dredging works for cruise terminal construction. Monitoring programme to be implemented
for protection of the coral communities are provided in Section 7.
4.2
Monitoring Schedule and Stations
4.2.1
The proposed water quality monitoring stations are shown in Table 4.1
and Figure 4.1. The monitoring stations proposed in this
section are indicative subject to further review before commencement of the
water quality monitoring works. The
status and locations of water sensitive receivers and the marine activities may
change after issuing this Manual.
If such case exists, the ET Leader shall propose updated monitoring
locations and seek approval from the IEC and EPD.
4.2.2
It
is proposed to monitor the water quality at seven WSD flushing water intakes
along the seafront of the
Table 4.1 Proposed
Marine Water Quality Stations for Baseline and Impact Monitoring
|
Station |
WSD |
Easting |
Northing |
|
WSD9 |
Tai Wan |
838132.71 |
817798.61 |
|
WSD10 |
Cha Kwo
Ling |
841528.70 |
817713.39 |
|
WSD15 |
Sai Wan Ho |
841194.35 |
816520.20 |
|
WSD17 |
|
839863.48 |
817077.46 |
|
WSD21 |
Wan Chai |
836242.94 |
815999.00 |
|
WSD19 |
Sheung Wan |
832488.01 |
816911.92 |
4.3.1
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.
4.3.2
The baseline conditions should be established by measuring turbidity and
suspended solids (SS) levels at the seven selected monitoring stations. The baseline monitoring schedule should be
submitted to EPD at least 4 weeks before commencement of monitoring for
agreement. EPD should also be
notified immediately for any changes in schedule.
4.3.3 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. There should not be any marine construction activities 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.
4.3.4
The baseline monitoring report should be submitted to EPD at least 4
weeks before the commencement of the dredging works for agreement. The baseline monitoring report should be
certified by the IEC before submission to EPD.
4.4.1
During
the period of dredging, monitoring should be undertaken three days per week, at
mid-flood and mid-ebb tides, with sampling / measurement at the designated
monitoring stations as shown in Table 4.1. Silt screens are recommended to be deployed
at these intakes during the dredging period. It is recommended to conduct the
monitoring behind the silt screens and at the appropriate vertical levels of
the abstraction points of these intakes to collect information on the mitigated
water quality condition if practicable.
4.4.2
The
interval between two sets of monitoring should not be less than 36 hours except
where there are exceedances of Action and/or Limit Levels, in which case the
monitoring frequency will be increased.
Table 4.2 shows the proposed monitoring frequency and water
quality parameters. 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.
Table 4.2 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) |
|
During dredging
works for proposed cruise terminal at Kai Tak |
Three days per
week, at mid-flood and mid-ebb tides |
Turbidity,
Suspended Solids (SS) |
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.
4.4.3
The
proposed water quality monitoring schedule should be submitted 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 4.4 are exceeded, appropriate
actions should be taken in accordance with the Event and Action Plan in Table
4.5.
Regular Maintenance of Silt Screens
4.4.4
Silt
screens are recommended to be deployed at the WSD flushing water intakes during
the dredging period. Installation
of silt screens at the seawater intake points may cause a potential for
accumulation and trapping of pollutants, floating debris and refuse behind the
silt screens and may lead to potential water quality deterioration at the
seawater intake points. Major
sources of pollutants and floating refuse include the runoff and storm water
discharges from the nearby coastal areas. 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 at the monitoring stations 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.
4.5.1
Implementation
of regular site audits is to ensure that the recommended mitigation measures are
to be properly undertaken during the proposed dredging works. It can also provide an effective control
of any malpractices and therefore achieve continual improvement of
environmental performance on site.
4.5.2
Site audits should be
carried out by the ET and should be based on the mitigation measures for water
pollution control recommended in Appendix C.
In the event that the recommended mitigation measures are not fully or
properly implemented, deficiency should be recorded and reported to the site
management. Suitable actions are to
be carried out to:
· investigate the problems and 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.
4.6.1
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.
4.6.2
A sample data record sheet is shown in Appendix B for reference.
4.7
Monitoring Equipment
Dissolved Oxygen and Temperature Measuring Equipment
4.7.1
The instrument should be a
portable and weatherproof DO measuring instrument complete with cable and
sensor, 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.
4.7.2 It should have a membrane electrode with automatic temperature compensation complete with a cable (for example, YSI model 59 meter, YSI 5739 probe, YSI 5795A submersible stirrer with reel and cable or an approved similar instrument). Sufficient stocks of spare electrodes and cables should be available for replacement where necessary.
4.7.3
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
4.7.4
Turbidity should be measured in situ by the
nephelometric method. The instrument
should be portable and weatherproof using a DC power source complete with
cable, sensor and comprehensive operation manuals. It should have a photoelectric sensor
capable of measuring turbidity between 0 - 1000 NTU (for example, Hach model
2100P or an approved similar instrument).
The cable should not be less than 25m in length. The meter should be calibrated in order
to establish the relationship between NTU units and the levels of suspended
solids. The turbidity measurement
should be carried out on split water sample collected from the same depths of
suspended solids samples.
Sampler
4.7.5
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
4.7.6
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
4.7.7
A portable, salinometer capable of measuring salinity in
the range 0 – 40 mg/L shall be provided for measuring salinity of the water at
each monitoring location.
Sample Containers and Storage
4.7.8
Water samples for SS should be stored in high density
polythene bottles, packed in ice (cooled to 4°C without being frozen) and
delivered to the laboratory and analysed as soon as possible after
collection. Sufficient volume of
samples should be collected to achieve the detection limit.
Monitoring Position Equipment
4.7.9
A hand-held or boat-fixed type digital Differential Global
Positioning System (DGPS) with way point bearing indication or other equipment
instrument of similar accuracy, should be provided and used during water
quality monitoring to ensure the monitoring vessel is at the correct location
before taking measurements. DGPS or
the equivalent instrument, calibrated at appropriate checkpoint (e.g. Quarry
Bay Survey Nail at Easting 840683.49, Northing 816709.55) should be provided
and used to ensure the monitoring station is at the correct position before
taking measurement and water samples.
Calibration of In-Situ Instruments
4.7.10
All in-situ monitoring instruments should be
checked, calibrated and certified by a laboratory accredited under HOKLAS or
any other international accreditation scheme before use and subsequently
re-calibrated at three monthly intervals throughout all stages of the water
quality monitoring programme.
Responses of sensors and electrodes should be checked with certified
standard solutions before each use.
Wet bulb calibration for a DO meter should be carried out before
measurement at each monitoring location.
4.7.11
For the on site calibration of field equipment, the BS
127:1993, Guide to Field and On-Site Test Methods for the Analysis of Water
should be observed.
4.7.12
Sufficient stocks of spare parts should be maintained
for replacements when necessary. Backup monitoring equipment should also be
made available so that monitoring can proceed uninterrupted even when some
equipment is under maintenance, calibration, etc.
4.8
Laboratory Measurement / Analysis
4.8.1
Analysis
of SS level should be carried out in a HOKLAS or other international
accredited laboratory. Sufficient
water samples of not less than 1 liter should be collected at the monitoring stations
for carrying out the laboratory SS determinations. The suggested testing method and lowest
detection limit are provided in Table 4.3.
Table 4.3 Analytical
Methods to be applied to Marine Water Quality Samples
|
Determinant |
Suggested
Method |
Suggested
Detection Limit |
|
Suspended solids |
APHA 2540D* |
1 mg L-1 |
* APHA American Public Health Association
Standard Methods for the Examination of Water and Wastewater
4.8.2
The
testing of SS should be HOKLAS accredited (or if not, approved by EPD) and comprehensive
quality assurance and control procedures in place in order to ensure quality
and consistency in results.
4.8.3
The
ET should provide the Contractor with on copy of the relevant chapters of the
“Standard Methods for the Examination of Water and Wastewater” updated edition
and any other relevant document for his reference.
4.8.4
Detailed
testing methods, pre-treatment procedures, instrument use, Quality Assurance /
Quality Control (QA/QC) details (such as blank, spike recovery, number of
duplicate samples per batch, etc.), detection limits and accuracy should be
submitted to EPD for approval prior to the commencement of monitoring
programme. EPD may also request the
laboratory to carry out analysis of known standards provided by EPD for quality
assurance. The QA/QC should be in accordance with the requirement of HOKLAS or
international accredited scheme.
The QA/QC results should be reported. The testing methods and related proposal
should be checked and certified by IEC before submission to EPD for approval.
4.8.5
Additional
duplicate samples may be required by EPD for inter laboratory calibration.
Remaining samples after analysis should 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
should have comprehensive quality assurance and quality control programmes. The laboratory should prepare to
demonstrate the programmes to EPD or EPD’s representatives when requested.
4.9.1
The water quality assessment criteria, namely Action and Limit Levels are
shown in Table 4.4. If the monitoring
results of the water quality parameters at any designated monitoring stations
indicate that the water quality assessment criteria are exceeded, the actions
in accordance with the Event and Action Plan in Table 4.5 should be
carried out.
4.9.2
The
ET Leader should assess the potential dredging impacts 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 4.4 Action
and Limit Levels for Marine Water Quality at the WSD
|
Parameters |
Action |
Limit |
|
SS in
mg L-1 |
95
percentile of baseline data See Note 1 or 10 mg/l |
99 percentile of baseline data See Note 1 or 10 mg/l |
|
Turbidity
in NTU |
95
percentile of baseline data See Note 1 |
99 percentile
of baseline data See Note 1 |
Remarks: 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 EPD may amend the figures whenever it
is considered as necessary.
Note
1: More than
1 set of baseline data should be derived to take account the seasonal
fluctuation of the background SS level (refer to Section 4.9.3).
4.9.3
The
proposed dredging works would likely cover both dry and wet seasons. Given the
rather short duration for baseline data collection (refer to Section 4.3), it
is recommended that the EPD routine marine water quality monitoring data at the
relevant stations should be used to determine the monthly variation of the SS
level in the Victoria Harbour. The monthly SS pattern derived from the EPD monitoring data should
be used to adjust the baseline data collected at the intake points to take account the seasonal fluctuation in the background SS level. At least
two sets of Action and Limit levels (for dry and wet seasons respectively)
should be derived for each intake. The ET should approach the Water Quality
Assessment Section of EPD for the data.
4.10
Mitigation of Adverse Environmental Impacts
4.10.1
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.
4.10.2
Recommended
mitigation measures to minimize the adverse impacts on water quality during the
proposed dredging are listed in the implementation schedule given in Appendix C.
Table 4.5 Event
and Action Plan for Marine Water Quality
|
EVENT |
ACTION |
|||
|
|
ET |
IEC |
ER |
CONTRACTOR |
|
Action level being exceeded by one sampling day |
1.
Repeat in-situ measurement to confirm
findings; 2.
Identify source(s) of impact; 3.
Inform IEC and Contractor; 4.
Check monitoring data, all plant, equipment
and Contractor's working methods; 5.
Discuss mitigation measures with IEC and
Contractor; 6.
(The above actions should be taken within 1
working day after the exceedance is identified) 7.
Repeat measurement on next day of exceedance. |
1.
Discuss with ET and Contractor on the
mitigation measures; 2.
Review proposals on mitigation measures
submitted by Contractor and advise the ER accordingly; 3.
Assess the effectiveness of the implemented
mitigation measures. 4.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1.
Discuss with IEC on the proposed mitigation
measures; 2.
Make agreement on the mitigation measures to
be implemented. 3.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1.
Inform the ER and confirm notification of the non-compliance
in writing; 2.
Rectify unacceptable practice; 3.
Check all plant and equipment; 4.
Review the working methods and consider additional measures such as use
of frame-type silt curtain, deployment of double silt curtains, slowing down,
or rescheduling of works; 5.
Discuss with ET and IEC and propose mitigation
measures to IEC and ER; 6.
Implement the agreed mitigation measures. 7.
(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 |
1.
Identify source(s) of impact; 2.
Inform IEC and Contractor; 3.
Check monitoring data, all plant, equipment
and Contractor's working methods; 4.
Discuss mitigation measures with IEC and
Contractor; 5.
Ensure mitigation measures are implemented; 6.
Prepare to increase the monitoring frequency
to daily; 7.
(The above actions should be taken within 1
working day after the exceedance is identified) 8.
Repeat measurement on next working day of
exceedance. |
1.
Discuss with ET and Contractor on the
mitigation measures; 2.
Review proposals on mitigation measures
submitted by Contractor and advise the ER accordingly; 3.
Assess the effectiveness of the implemented
mitigation measures. 4.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1.
Discuss with IEC on the proposed mitigation
measures; 2.
Make agreement on the mitigation measures to
be implemented; 3.
Assess the effectiveness of the implemented mitigation
measures. 4.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1.
Inform the Engineer and confirm notification
of the non-compliance in writing; 2.
Rectify unacceptable practice; 3.
Check all plant and equipment; 4.
Review the working methods and consider additional measures such as use
of frame-type silt curtain,
deployment of double silt curtains, slowing down, or rescheduling of
works; 5.
Discuss with ET and IEC and propose mitigation
measures to IEC and ER within 3 working days; 6.
Implement the agreed mitigation measures. 7.
(The above actions should be taken within 1
working day after the exceedance is identified) |
|
Limit level being exceeded by one sampling day |
1.
Repeat in-situ measurement to confirm
findings; 2.
Identify source(s) of impact; 3.
Inform IEC, Contractor and EPD; 4.
Check monitoring data, all plant, equipment
and Contractor's working methods; 5.
Discuss mitigation measures with IEC, ER and
Contractor; 6.
Ensure mitigation measures are implemented; 7.
Increase the monitoring frequency to daily
until no exceedance of Limit Level. 8.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1.
Discuss with ET and Contractor on the
mitigation measures; 2.
Review proposals on mitigation measures
submitted by Contractor and advise the ER accordingly; 3.
Assess the effectiveness of the implemented
mitigation measures. 4.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1.
Discuss with IEC, ET and Contractor on the
proposed mitigation measures; 2.
Request Contractor to critically review the
working methods; 3.
Make agreement on the mitigation measures to
be implemented; 4.
Assess the effectiveness of the implemented mitigation
measures. 5.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1.
Inform the Engineer and confirm notification
of the non-compliance in writing; 2.
Rectify unacceptable practice; 3.
Check all plant and equipment; 4.
Review the working methods and consider additional measures such as use
of frame-type silt curtain, deployment of double silt curtains, slowing down,
or rescheduling of works; 5.
Discuss with ET, IEC and ER and propose mitigation
measures to IEC and ER within 3 working days; 6.
Implement the agreed mitigation measures. 7.
(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 |
1.
Identify source(s) of impact; 2.
Inform IEC, Contractor and EPD; 3.
Check monitoring data, all plant, equipment
and Contractor's working methods; 4.
Discuss mitigation measures with IEC, ER and
Contractor; 5.
Ensure mitigation measures are implemented; 6.
Increase the monitoring frequency to daily
until no exceedance of Limit level for two consecutive days. 7.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1.
Discuss with ET and Contractor on the
mitigation measures; 2.
Review proposals on mitigation measures
submitted by Contractor and advise the ER accordingly; 3.
Assess the effectiveness of the implemented
mitigation measures. 4.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1.
Discuss with IEC, ET and Contractor on the
proposed mitigation measures; 2.
Request Contractor to critically review the
working methods; 3.
Make agreement on the mitigation measures to
be implemented; 4.
Assess the effectiveness of the implemented
mitigation measures; 5.
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. 6.
(The above actions should be taken within 1
working day after the exceedance is identified) |
1. Inform
the ER and confirm notification of the non-compliance in writing; 2. Rectify
unacceptable practice; 3. Check
all plant and equipment; 4. Review
the working methods and consider additional measures such as use of frame-type silt curtain, deployment of double silt curtains,
slowing down, or rescheduling of works; 5. Discuss
with ET , IEC and ER and propose mitigation measures to IEC and ER within 3
working days; 6. Implement
the agreed mitigation measures; 7. As
directed by the Engineer, to slow down or to stop all or part of the marine
work or construction activities. 8.
(The above actions should be taken within 1 working
day after the exceedance is identified) |