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.
5.7
The Proposal for Change of Marine Water Quality
Monitoring Station was submitted to EPD on 12 July 2017.
No objection was received from EPD according to the letter (ref. (22) in Ax(4) to EP2/G/A/129pt.4) dated 28 July 2017. Therefore, the
updated Water Quality Monitoring Station was used for water quality monitoring starting
from 31 July 2017.
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 |
CS2(A)# |
805232 |
818606 |
SR1 |
803126 |
812379 |
SR2 |
807856 |
816953 |
SR3 |
810525 |
816456 |
SR6 |
805837 |
821818 |
ST1 |
802677 |
816006 |
ST2 |
804055 |
818840 |
ST3 |
800667 |
810126 |
SRA |
809872 |
817152 |
#Alternative station for CS2 starting from 31st
July 2017, after the approval of the Proposal for Change of Marine Water
Quality Monitoring Station by EPD on 28th July 2017.
Instrumentation
5.8
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
5.9
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.
5.10
It has a membrane electrode with automatic
temperature compensation complete with a cable.
5.11
Sufficient stocks of spare electrodes and cables
were available for replacement where necessary.
5.12
Salinity compensation was built-in in the DO
equipment.
Turbidity
5.13
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
5.14
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
5.15
A portable, battery-operated echo sounder was used
for the determination of water depth at each designated monitoring station.
pH
5.16
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
5.17
A portable salinometer
capable of recording salinity within the range of 0-40 ppt
was used for salinity measurements.
Monitoring
Position Equipment
5.18
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
5.19
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
5.20
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.
5.21
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.
5.22
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.
5.23
The equipment used for impact water quality
monitoring is shown in Table 5.2. 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 |
Sonar Water Depth Detector |
Garmin Fishfinder 140 |
Monitoring Position Equipment |
KODEN
DGPS (KGP913MKIID,
GA-08 & BA-03) |
Multi-parameter
Water Quality System |
YSI EXO |
Water
Sampler |
Kahlsico Water-Bottle Model 135DW 150 |
Monitoring
Parameters, Frequency
5.24
Table
5.3 summarizes the monitoring parameters, monitoring period and frequencies
of the water quality monitoring.
Table
5.3 Water Quality Monitoring Parameters
and Frequency
Monitoring Stations |
Parameters, unit |
Depth |
Frequency |
IS1, IS2, IS3 IS4, CS1, CS2(A),
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 |
5.25
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.
5.26
A multi-parameter meters (Model YSI 6820-C-M) were
used to measure DO, turbidity, salinity, pH and temperature.
Operating/Analytical
Procedures
5.27
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.
5.28
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.
5.29
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.
5.30
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
5.31
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
5.32
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.
5.33
The laboratory determination works were started
within 24 hours after collection of the water samples.
Quality Control
Measures for Sample Testing
5.34
The samples testing were performed by CMA Testing
and Certification Laboratories.
5.35
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.
5.36
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.
5.37
As the Construction Phase EM&A Programme under
HY/2011/09 have been terminated since 24th October 2018, no
impact monitoring for water quality was carried out in the reporting month.
5.38 Post-construction monitoring for
water quality was carried out after the termination of Construction Phase
EM&A Programme. Summary of post-construction
water quality monitoring results are summarized in Table 5.5 and the corresponding report is provided in Appendix I.
Table 5.5 Summary
of Post-Construction Water Quality Monitoring Results
Station |
DO (mg/L) |
Turbidity (NTU) |
SS (mg/L) |
|||||||
Mean |
Min. |
Max. |
Mean |
Min. |
Max. |
Mean |
Min. |
Max. |
||
IS1 |
Surface |
6.9 |
6.4 |
7.7 |
4.1 |
1.3 |
7.6 |
9.0 |
4.8 |
19.3 |
Middle |
6.7 |
6.4 |
7.4 |
7.2 |
1.5 |
17.8 |
9.2 |
4.9 |
14.4 |
|
Bottom |
6.6 |
6.3 |
7.0 |
19.8 |
2.8 |
64.4 |
10.4 |
5.0 |
19.8 |
|
IS2 |
Surface |
6.9 |
6.5 |
7.6 |
6.8 |
2.0 |
17.0 |
9.6 |
3.8 |
28.3 |
Middle |
6.8 |
6.4 |
7.5 |
8.9 |
2.4 |
23.1 |
10.5 |
5.1 |
30.9 |
|
Bottom |
6.6 |
6.3 |
7.2 |
18.2 |
3.5 |
50.8 |
10.2 |
5.2 |
38.0 |
|
IS3 |
Surface |
6.8 |
6.2 |
7.6 |
5.4 |
2.1 |
14.3 |
9.3 |
6.3 |
20.3 |
Middle |
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
Bottom |
6.7 |
6.1 |
7.6 |
9.5 |
3.3 |
19.8 |
9.1 |
5.3 |
16.0 |
|
IS4 |
Surface |
6.8 |
6.3 |
7.5 |
5.8 |
1.9 |
12.4 |
9.3 |
4.0 |
17.7 |
Middle |
6.8 |
6.3 |
7.5 |
6.6 |
2.0 |
13.0 |
8.8 |
4.1 |
17.5 |
|
Bottom |
6.7 |
6.2 |
7.3 |
9.6 |
2.2 |
27.2 |
9.5 |
5.6 |
15.5 |
|
CS1 |
Surface |
6.8 |
6.3 |
7.9 |
4.6 |
1.0 |
16.1 |
9.1 |
4.5 |
19.2 |
Middle |
6.6 |
6.2 |
7.4 |
6.0 |
1.5 |
25.4 |
9.6 |
5.4 |
20.8 |
|
Bottom |
6.5 |
6.1 |
7.0 |
16.4 |
4.0 |
44.6 |
9.2 |
5.2 |
18.7 |
|
CS2(A) |
Surface |
7.0 |
6.4 |
8.1 |
5.1 |
1.9 |
14.7 |
9.2 |
4.7 |
17.4 |
Middle |
6.8 |
6.3 |
8.1 |
6.4 |
2.5 |
16.3 |
8.8 |
5.9 |
14.5 |
|
Bottom |
6.7 |
6.2 |
7.6 |
11.5 |
3.5 |
35.7 |
10.0 |
5.6 |
16.4 |
|
SR1 |
Surface |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Middle |
6.7 |
6.3 |
7.2 |
8.5 |
2.5 |
21.8 |
10.9 |
6.0 |
21.5 |
|
Bottom |
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
SR2 |
Surface |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Middle |
6.6 |
6.1 |
7.4 |
6.8 |
1.1 |
12.4 |
9.7 |
3.0 |
17.1 |
|
Bottom |
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
SR3 |
Surface |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Middle |
6.8 |
6.0 |
7.9 |
6.4 |
3.4 |
12.3 |
10.6 |
5.7 |
22.4 |
|
Bottom |
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
SR6 |
Surface |
6.9 |
6.3 |
7.7 |
5.0 |
1.3 |
10.9 |
9.4 |
6.0 |
21.9 |
Middle |
- |
- |
- |
- |
- |
- |
- |
- |
- |
|
Bottom |
6.7 |
6.1 |
7.4 |
8.4 |
1.6 |
19.1 |
10.5 |
5.0 |
22.8 |
|
SRA |
Surface |
6.7 |
6.1 |
7.7 |
5.5 |
1.2 |
11.4 |
10.7 |
4.5 |
28.1 |
Middle |
6.6 |
6.0 |
7.8 |
6.4 |
1.8 |
14.2 |
10.3 |
3.9 |
25.1 |
|
Bottom |
6.5 |
5.9 |
7.8 |
8.0 |
1.9 |
27.4 |
9.3 |
4.0 |
21.2 |
|
ST1 |
Surface |
6.9 |
6.4 |
7.4 |
6.7 |
2.3 |
17.9 |
10.6 |
7.0 |
26.1 |
Middle |
6.7 |
6.3 |
7.3 |
9.5 |
2.9 |
23.0 |
11.1 |
4.7 |
27.2 |
|
Bottom |
6.6 |
6.3 |
7.1 |
18.3 |
3.5 |
50.0 |
11.1 |
6.5 |
22.8 |
|
ST2 |
Surface |
7.0 |
6.4 |
7.9 |
5.3 |
1.3 |
13.8 |
9.1 |
5.4 |
16.7 |
Middle |
6.8 |
6.3 |
7.5 |
7.2 |
2.5 |
20.6 |
10.1 |
5.2 |
16.8 |
|
Bottom |
6.6 |
6.3 |
7.4 |
14.8 |
3.8 |
37.8 |
9.7 |
5.5 |
17.7 |
|
ST3 |
Surface |
6.8 |
6.4 |
8.4 |
4.8 |
1.6 |
12.0 |
9.5 |
5.2 |
21.0 |
Middle |
6.6 |
6.3 |
7.3 |
7.9 |
2.5 |
23.7 |
9.2 |
4.8 |
20.5 |
|
Bottom |
6.5 |
6.2 |
7.1 |
17.9 |
3.3 |
55.1 |
9.2 |
4.3 |
15.6 |
5.39
Should non-compliance of the criteria occur, action
in accordance with the Action Plan in
Appendix C shall be carried out.