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 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
5.24 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(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 The
monitoring results and graphical presentation of water quality at the
monitoring stations is shown in Appendix
H.
5.38 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 |
|
|
|
|
|
|
3/11/2017 |
|
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
IS2 |
Action Level |
|
|
|
|
|
|
|
3/11/2017 |
|
1 |
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
IS3 |
Action Level |
|
|
|
|
|
|
|
|
|
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
IS4 |
Action Level |
|
|
|
|
|
|
|
|
|
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
SR1 |
Action Level |
|
|
|
|
|
|
|
|
|
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
SR2 |
Action Level |
|
|
|
|
|
|
|
|
|
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
SR3 |
Action Level |
|
|
|
|
|
|
|
3/11/2017 |
|
1 |
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
SR6 |
Action Level |
|
|
|
|
|
|
|
|
|
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
ST1 |
Action Level |
|
|
|
|
|
|
|
|
|
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
ST2 |
Action Level |
|
|
|
|
|
|
|
|
|
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
ST3 |
Action Level |
|
|
|
|
|
|
|
|
|
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
SRA |
Action Level |
|
|
|
|
|
|
|
|
|
|
Limit Level |
|
|
|
|
|
|
|
|
|
|
|
Total |
Action Level |
|
|
|
|
|
|
1 |
2 |
3 |
|
Limit Level |
|
|
|
|
|
|
0 |
0 |
0 |
5.39 All
water quality monitoring was conducted as scheduled in the reporting month.
There are three Action Level and no Limit Level exceedances were recorded for
suspended solids. No Action/Limit Level exceedance for dissolved oxygen and
turbidity were recorded.
5.40 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 pollution source
from this Contract was observed and no construction vessel for this Contract
was travelling nearby. Dispersion of sediment plume to the monitoring stations
from the area outside the site boundary (i.e. works area not under and related
to HY/2011/09) was also observed.
5.41 Should
non-compliance of the criteria occur, action in accordance with the Action Plan
in Appendix K shall be carried out.