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:
·
a dissolved oxygen level in the
range of 0-20 mg/L and 0-200% saturation; and
·
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°C 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 6820-C-M |
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 |
·
Temperature(°C) ·
pH(pH unit) ·
turbidity (NTU) ·
water depth (m) ·
salinity (ppt) ·
dissolved
oxygen (DO) (mg/L and % of saturation) ·
suspended
solids (SS) (mg/L) |
·
3 water depths: 1m below sea surface, mid-depth and 1m above sea bed. ·
If the water
depth is less than 3m, mid-depth sampling only. ·
If water depth
less than 6m, mid-depth may be omitted. |
·
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°C 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°C 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 |
|
|
|
|
16/05/2014 |
|
|
16/05/2014 |
1 |
1 |
|
Limit Level |
|
|
|
|
|
16/05/2014 |
|
|
0 |
1 |
|
|
IS2 |
Action Level |
|
|
|
|
|
16/05/2014 |
|
|
0 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
IS3 |
Action Level |
|
|
|
|
|
16/05/2014 |
|
14/05/2014 16/05/2014 |
0 |
3 |
|
Limit Level |
|
|
|
|
|
|
|
26/05/2014 |
0 |
1 |
|
|
IS4 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
SR1 |
Action Level |
|
|
|
|
|
|
|
14/05/2014 |
0 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
SR2 |
Action Level |
|
|
|
|
|
|
|
14/05/2014 |
0 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
SR3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
SR6 |
Action Level |
|
|
|
|
|
16/05/2014 |
|
|
0 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
ST1 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
ST2 |
Action Level |
|
|
|
|
|
16/05/2014 |
|
|
0 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
ST3 |
Action Level |
|
|
|
|
|
16/05/2014 |
|
|
0 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
SRA |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
Total |
Action Level |
0 |
0 |
0 |
0 |
1 |
5 |
0 |
5 |
|
|
|
Limit Level |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
1 |
|||
5.38
All
water quality monitoring was conducted as scheduled in the reporting month. There
are five Action Level and one Limit Level exceedances
for suspended solids were recorded. In addition, there are six Action Level and
one Limit Level exceedances for turbidity were recorded.
No Action/Limit Level exceedance for dissolved oxygen
was recorded.
5.39
According
to the investigation, no pollution discharge was observed from the site. In
addition, some of the exceeded results were similar or within the ranges
baseline monitoring results and sediment plume which is considered due to the
movement of vessel was observed. Therefore, the exceedances
are considered not due to the Contract.
5.40
Should
non-compliance of the criteria occur, action in accordance with the Action Plan
in Appendix K shall be carried out.