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.
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
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/
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: ·
If the water
depth is less than ·
If water depth
less than |
·
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
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
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 |
|
|
|
|
|
11/03/2013 18/03/2013 |
08/03/2013 13/03/2013 |
|
2 |
2 |
Limit Level |
|
|
|
|
08/03/2013 15/03/2013 |
01/03/2013 04/03/2013 13/03/2013 15/03/2013 20/03/2013 |
15/03/2013 |
06/03/2013 15/03/2013 |
3 |
7 |
|
IS2 |
Action Level |
|
|
|
|
|
15/03/2013 |
|
|
0 |
1 |
Limit Level |
|
|
|
|
08/03/2013 15/03/2013 |
01/03/2013 13/03/2013 |
15/03/2013 |
04/03/2013 06/03/2013 |
3 |
4 |
|
IS3 |
Action Level |
|
|
|
|
18/03/2013 |
13/03/2013 |
01/03/2013 27/03/2013 |
|
3 |
1 |
Limit Level |
|
|
|
|
08/03/2013 23/03/2013 |
08/03/2013 15/03/2013 |
20/03/2013 |
06/03/2013 23/03/2013 |
3 |
4 |
|
IS4 |
Action Level |
|
|
|
|
15/03/2013 |
|
18/03/2013 |
04/03/2013 11/03/2013 |
2 |
2 |
Limit Level |
|
|
|
|
|
|
15/03/2013 |
06/03/2013 |
1 |
1 |
|
SR1 |
Action Level |
|
|
|
|
|
25/03/2013 |
27/03/2013 |
06/03/2013 |
1 |
2 |
Limit Level |
|
|
|
|
06/03/2013 08/03/2013 11/03/2013 13/03/2013 15/03/2013 |
01/03/2013 13/03/2013 15/03/2013 |
01/03/2013 13/03/2013 15/03/2013 20/03/2013 |
04/03/2013 11/03/2013 15/03/2013 25/03/2013 |
9 |
7 |
|
SR2 |
Action Level |
|
|
|
|
|
20/03/2013 |
|
|
0 |
1 |
Limit Level |
|
|
|
|
06/03/2013 08/03/2013 13/03/2013 15/03/2013 20/03/2013 23/03/2013 |
04/03/2013 06/03/2013 08/03/2013 11/03/2013 13/03/2013 15/03/2013 |
01/03/2013 08/03/2013 11/03/2013 15/03/2013 18/03/2013 20/03/2013 23/03/2013 |
04/03/2013 08/03/2013 11/03/2013 13/03/2013 23/03/2013 |
13 |
11 |
|
SR3 |
Action Level |
|
|
|
|
|
08/03/2013 |
20/03/2013 |
|
1 |
1 |
Limit Level |
|
|
|
|
08/03/2013 11/03/2013 15/03/2013 18/03/2013 23/03/2013 |
04/03/2013 06/03/2013 |
08/03/2013 11/03/2013 15/03/2013 18/03/2013 23/03/2013 |
06/03/2013 11/03/2013 23/03/2013 |
10 |
5 |
|
SR6 |
Action Level |
|
|
|
|
08/03/2013 15/03/2013 |
08/03/2013 20/03/2013 |
|
|
2 |
2 |
Limit Level |
|
|
|
|
|
01/03/2013 13/03/2013 15/03/2013 |
08/03/2013 |
11/03/2013 23/03/2013 |
1 |
5 |
|
ST1 |
Action Level |
|
|
|
|
18/03/2013 |
11/03/2013 |
|
06/03/2013 |
1 |
2 |
Limit Level |
|
|
|
|
06/03/2013 08/03/2013 13/03/2013 15/03/2013 23/03/2013 |
01/03/2013 04/03/2013 13/03/2013 15/03/2013 20/03/2013 |
08/03/2013 15/03/2013 |
13/03/2013 15/03/2013 |
7 |
7 |
|
ST2 |
Action Level |
|
|
|
|
11/03/2013 18/03/2013 |
04/03/2013 20/03/2013 |
11/03/2013 |
20/03/2013 |
3 |
3 |
Limit Level |
|
|
|
|
06/03/2013 08/03/2013 13/03/2013 15/03/2013 |
01/03/2013 08/03/2013 13/03/2013 |
08/03/2013 13/03/2013 15/03/2013 23/03/2013 |
06/03/2013 08/03/2013 11/03/201323/03/2013 |
8 |
7 |
|
ST3 |
Action Level |
|
|
|
|
|
|
13/03/2013 |
|
1 |
0 |
Limit Level |
|
|
|
|
06/03/2013 08/03/2013 11/03/2013 13/03/2013 15/03/2013 |
11/03/2013 13/03/2013 15/03/2013 |
15/03/2013 |
|
6 |
3 |
|
SRA |
Action Level |
|
|
|
|
|
11/03/2013 15/03/2013 20/03/2013 23/03/2013 |
18/03/2013 |
18/03/2013 |
1 |
5 |
Limit Level |
|
|
|
|
06/03/2013 08/03/2013 15/03/2013 23/03/2013 |
08/03/2013 |
08/03/2013 15/03/2013 20/03/2013 |
06/03/2013 08/03/2013 11/03/2013 23/03/2013 |
7 |
5 |
|
Total |
Action Level |
0 |
0 |
0 |
0 |
7 |
16 |
10 |
6 |
|
|
Limit Level |
0 |
0 |
0 |
0 |
40 |
35 |
31 |
31 |
5.38
All
water quality monitoring was conducted as scheduled in the reporting month. There
are twenty-three Action Level exceedances and
seventy-five Limit Level exceedances for turbidity
were recorded. Sixteen Action exceedances and
sixty-two Limit Level exceedances for suspended
solids were recorded.
5.39
According
to the investigation, no major marine construction activities were conducted
during the monitoring period between 1 and 19 March 2013. No pollution
discharge from the marine works after 19 March 2013 (casing installation works)
were observed. Therefore, all exceedances are
considered not due to the Contract. Water quality impact sources during the
water quality monitoring were the nearby construction activities and operating
vessels by other parties.
5.40
Should
non-compliance of the criteria occur, action in accordance with the Action Plan
in Appendix K shall be carried out.