5.1
According to EM&A Manual, impact water quality monitoring shall be
carried out three days per week during the construction period. The interval
between two sets of monitoring will not be less than 36 hours.
5.2
Replicate in-situ measurements and samples collected from each
independent sampling event shall be collected to ensure a robust statistically
interpretable database.
5.3
Impact water quality monitoring was conducted two times per monitoring
day during mid ebb (within + 1.75 hours of the predicted time) and mid
flood tides (within + 1.75 hours of the predicted time) at three depths (i.e. 1m below surface, mid-depth and 1m
above seabed, except where the water depth less than 6m, mid-depth station may
be omitted. Should the water depth be less than 3m, only the mid-depth station
was monitored) Dissolved oxygen, Suspended solids (SS), turbidity, pH, salinity
and temperature were monitored in accordance with the requirements set out in
the EM&A Manual.
5.4
The proposal for changing Action and Limit Levels for water quality
monitoring was submitted to EPD on 15 March 2013. No objection was received
from EPD according to the letter (ref. (10) in Ax(3)
to EP2/G/A/129pt.4) dated 25 March 2013. Therefore, the updated Action and
Limit Levels for water quality monitoring was used for comparison starting from
25 March 2013.
5.5
Appendix B shows the
established Action/Limit Levels for the water quality monitoring works.
5.6
Impact water quality monitoring was conducted at 14 monitoring stations
under the Contract which are summarized in
Table 5.1. The monitoring station is also shown in Figure 4.
Table 5.1 Location
for Marine Water Quality Monitoring Locations
Monitoring Stations |
Coordinates |
|
Easting |
Northing |
|
IS1 |
803474 |
815060 |
IS2 |
804851 |
815715 |
IS3 |
806502 |
815743 |
IS4 |
807008 |
816986 |
CS1 |
801784 |
812711 |
CS2 |
805849 |
818780 |
SR1 |
803126 |
812379 |
SR2 |
807856 |
816953 |
SR3 |
810525 |
816456 |
SR6 |
805837 |
821818 |
ST1 |
802677 |
816006 |
ST2 |
804055 |
818840 |
ST3 |
800667 |
810126 |
SRA |
809872 |
817152 |
Instrumentation
5.7
A multi-parameter meters (Model YSI 6820-C-M) were used to measure DO,
turbidity, salinity, pH and temperature.
Dissolved Oxygen
(DO) and Temperature Measuring Equipment
5.8
The instrument for measuring dissolved oxygen and temperature was
portable and weatherproof complete with cable, sensor, comprehensive operation
manuals and use DC power source. It was capable of measuring:
¡P a dissolved oxygen level in the range of 0-20 mg/L and 0-200%
saturation; and
¡P a temperature of 0-45 degree Celsius.
5.9
It has a membrane electrode with automatic temperature compensation
complete with a cable.
5.10 Sufficient stocks of
spare electrodes and cables were available for replacement where necessary.
5.11 Salinity compensation
was built-in in the DO equipment.
Turbidity
5.12 Turbidity was
measured in situ by the nephelometric method. The
instrument was portable and weatherproof using a DC power source complete with
cable, sensor and comprehensive operation manuals. The equipment was capable of
measuring turbidity between 0-1000 NTU. The probe cable was not less than 25m
in length. The meter was calibrated in order to establish the relationship
between NTU units and the levels of suspended solids. The turbidity measurement
was carried out on split water sample collected from the same depths of
suspended solids samples.
Sampler
5.13 A water sampler,
consisting of a transparent PVC or glass cylinder of a capacity of not less
than two litres which can be effectively sealed with
cups at both ends was used. The water sampler has a positive latching system to
keep it open and prevent premature closure until released by a messenger when
the sampler was at the selected water depth.
Water Depth
Detector
5.14 A portable,
battery-operated echo sounder was used for the determination of water depth at
each designated monitoring station.
pH
5.15 The instrument was
consisting of a potentiometer, a glass electrode, a reference electrode and a
temperature-compensating device. It was readable to 0.1pH in a range of 0 to
14. Standard buffer solutions of at least pH 7 and pH 10 were used for
calibration of the instrument before and after use.
Salinity
5.16 A portable salinometer capable of recording salinity within the range
of 0-40 ppt was used for salinity measurements.
Monitoring
Position Equipment
5.17 A hand held
Differential Global Positioning System (DGPS) was used during water quality
monitoring to ensure the monitoring vessel is at the correct location before
taking measurements.
Sample Container
and Storage
5.18 Following collection,
water samples for laboratory analysis were stored in high density polythene
bottles (250ml/1L) with no preservatives added, packed in ice (cooled to 4¢XC without being frozen) and kept
in dark during both on-site temporary storage and shipment to the testing
laboratory. The samples were delivered to the laboratory as soon as possible
and the laboratory determination works were started within 24 hours after
collection of the water samples. Sufficient volume of samples was collected to
achieve the detection limit.
Calibration of In
Situ Instruments
5.19 All in situ
monitoring instruments were checked, calibrated and certified by a laboratory
accredited under HOKLAS or other international accreditation scheme before use,
and subsequently re-calibrated at 3 monthly intervals throughout all stages of
the water quality monitoring programme. Responses of
sensors and electrodes were checked with certified standard solutions before
each use. Wet bulb calibration for a DO meter was carried out before
measurement at each monitoring event.
5.20 For the on site calibration of field equipment (Multi-parameter
Water Quality System), the BS 1427:2009, "Guide to on-site test methods
for the analysis of waters" was observed.
5.21 Sufficient stocks of
spare parts were maintained for replacements when necessary. Backup monitoring
equipment was also being made available so that monitoring can proceed
uninterrupted even when some equipment was under maintenance, calibration, etc.
5.22 The equipment used for
impact water quality monitoring is shown in Table 5.2 and copies of the calibration certificates are shown in Appendix C. All the monitoring equipment complied
with the requirements set out in the EM&A Manual.
Table 5.2 Water Quality Monitoring Equipment
Equipment |
Model and Make |
Qty |
Sonar Water Depth Detector |
Garmin
Fishfinder 140 |
2 |
Monitoring Position Equipment |
KODEN
DGPS (KGP913MKIID,
GA-08 & BA-03) |
2 |
Multi-parameter
Water Quality System |
YSI EXO |
2 |
Water
Sampler |
Kahlsico Water-Bottle Model 135DW 150 |
2 |
Monitoring Parameters, Frequency
5.23 Table 5.3 summarizes the monitoring
parameters, monitoring period and frequencies of the water quality monitoring.
The water quality monitoring schedule for the reporting month is shown in Appendix D.
Table 5.3 Water Quality Monitoring Parameters and Frequency
Monitoring Stations |
Parameters, unit |
Depth |
Frequency |
IS1, IS2, IS3 IS4, CS1,
CS2, SR1, SR2, SR3, SR6, ST1, ST2, ST3, SRA |
¡P
Temperature(¢XC) ¡P
pH(pH unit) ¡P
turbidity (NTU) ¡P
water depth (m) ¡P
salinity (ppt) ¡P
dissolved oxygen (DO) (mg/L and % of saturation) ¡P
suspended solids (SS) (mg/L) |
¡P
3 water depths: 1m below sea surface,
mid-depth and 1m above sea bed. ¡P
If the water depth is less than 3m, mid-depth sampling only. ¡P
If water depth less than 6m, mid-depth may be omitted. |
¡P
Impact monitoring: 3 days per week,
at mid-flood and mid-ebb tides during the construction period of the Contract |
5.24 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 were recorded.
5.25 A multi-parameter
meters (Model YSI 6820-C-M) were used to measure DO, turbidity, salinity, pH
and temperature.
Operating/Analytical Procedures
5.26 The monitoring
stations were accessed by the guide of a hand-held Differential Global
Positioning System (DGPS) during water quality monitoring in accordance with
the EM&A Manual. The depth of the monitoring location was measured using
depth meter in order to determine the sampling depths. Afterwards, the probes
of the in-situ measurement equipment were lowered to the predetermined depths
(1 m below water surface, mid-depth and 1 m above seabed) and the measurements
were carried out accordingly.
5.27 At each measurement,
two consecutive measurements of DO concentration, DO saturation, salinity,
turbidity, pH and temperature were taken.
The probes were retrieved out of the water after the first measurement
and then re-deployed for the second measurement. Where the difference in the value
between the first and second readings of each set was more than 25% of the
value of the first reading, the reading was discarded and further readings were
taken.
5.28 Water sampler was
lowered into the water to the required depths of sampling. Upon reaching the
pre-determined depth, a messenger to activate the sampler was then released to
travel down the wire. The water sample was sealed within the sampler before
retrieving. At each station, water samples at three depths (1 m below water
surface, mid-depth and 1 m above seabed) were collected accordingly. Water
samples were stored in a cool box and kept at less than 4¢XC but without frozen and sent to
the laboratory as soon as possible. In addition, field information as described
in Section 5.23 was also recorded.
5.29 The testing of all
parameters was conducted by CMA Testing and Certification Laboratories (HOKLAS
Registration No.004) and comprehensive quality assurance and control procedures
in place in order to ensure quality and consistency in results. The testing
method, reporting limit and detection limit are provided in Table 5.4.
Table 5.4 Methods for
Laboratory Analysis for Water Samples
Determinant |
Instrumentation |
Analytical Method |
Detection Limit |
Suspended Solid (SS) |
Weighing |
APHA 21e 2540D |
0.5 mg/L |
Decontamination Procedures
5.30 Water sampling
equipment used during the course of the monitoring programme
was decontaminated by manual washing and rinsed clean seawater/distilled water
after each sampling event. All disposal equipment was discarded after sampling.
Sampling Management and
Supervision
5.31 All sampling bottles
were labelled with the sample I.D (including the indication of sampling station
and tidal stage e.g. IS1_me_a), laboratory number and sampling date. Water
samples were dispatched to the testing laboratory for analysis as soon as
possible after the sampling. All samples were stored in a cool box and kept at
less than 4¢XC but without frozen.
All water samples were handled under chain of custody protocols and
relinquished to the laboratory representatives at locations specified by the
laboratory.
5.32 The laboratory
determination works were started within 24 hours after collection of the water
samples.
Quality Control Measures for
Sample Testing
5.33 The samples testing
were performed by CMA Testing and Certification Laboratories.
5.34 The following quality
control programme was performed by the CMA Testing
and Certification Laboratories for every batch of 20 samples:
² One set of quality control (QC) samples.
5.35 All in situ
monitoring instruments were checked, calibrated and certified by a laboratory
accredited under HOKLAS or other international accreditation scheme before use,
and subsequently re-calibrated at 3 monthly intervals throughout all stages of
the water quality monitoring programme.
5.36 The monitoring
results and graphical presentation of water quality at the monitoring stations
is shown in Appendix H.
5.37 The summary of exceedance
record in reporting month is shown in Appendix
L and summarized in the Table 5.5.
Table 5.5 Summary
of Water Quality Exceedances
Station |
Exceedance Level |
DO (Surface & Middle) |
DO(Bottom) |
Turbidity |
SS |
Total Number of Exceedances |
|||||
Mid-Ebb |
Mid-Flood |
Mid-Ebb |
Mid-Flood |
Mid-Ebb |
Mid-Flood |
Mid-Ebb |
Mid-Flood |
Mid-Ebb |
Mid-Flood |
||
IS1 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
01/03/2017 |
0 |
1 |
|
IS2 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
01/03/2017 |
0 |
1 |
|
IS3 |
Action Level |
|
|
|
|
|
|
15/03/2017 |
|
1 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
IS4 |
Action Level |
|
|
|
|
|
|
|
01/03/2017 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR1 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
15/03/2017 |
|
1 |
0 |
|
SR2 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR6 |
Action Level |
|
|
|
|
|
|
|
01/03/2017 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
ST1 |
Action Level |
|
|
|
|
|
|
|
01/03/2017 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
ST2 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
01/03/2017 |
0 |
1 |
|
ST3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SRA |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Total |
Action Level |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
3 |
4 |
|
Limit Level |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
3 |
4 |
5.38 All water quality
monitoring was conducted as scheduled in the reporting month. There are four Action
Level and four Limit Level exceedances were recorded for suspended solids. No
Action/Limit Level exceedance for dissolved oxygen and turbidity were recorded.
5.39 According to the investigation,
the exceedances are considered not due to the Contract due to the following
reasons:
1) No pollution
discharge from construction activity was observed;
2) The exceeded results
were similar or within the ranges baseline monitoring results;
3) Sediment plume due to
natural fluctuation of shallow water was observed;
4) Adverse water quality
outside the site boundary was observed while no construction vessel for this
Contract was travelling nearby.
5.40 Should non-compliance
of the criteria occur, action in accordance with the Action Plan in Appendix K shall be carried out.