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 6820-C-M and YSI 6920-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 |
¡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 |
|
|
|
|
|
|
|
07/05/2016 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
IS2 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
07/05/2016 |
0 |
1 |
|
IS3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
IS4 |
Action Level |
|
|
|
|
|
|
|
07/05/2016 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR1 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR2 |
Action Level |
|
|
|
|
|
|
20/05/2016 |
|
1 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR6 |
Action Level |
|
|
|
|
|
|
|
07/05/2016 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
ST1 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
07/05/2016 |
0 |
1 |
|
ST2 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
07/05/2016 |
0 |
1 |
|
ST3 |
Action Level |
|
|
|
|
|
|
20/05/2016 |
|
1 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SRA |
Action Level |
|
|
|
|
|
|
20/05/2016 |
|
1 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Total |
Action Level |
0 |
0 |
0 |
0 |
0 |
0 |
3 |
3 |
6 |
|
Limit Level |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
3 |
3 |
5.38
All water quality
monitoring was conducted as scheduled in the reporting month except the water
quality monitoring scheduled on 27th May 2016 which was re-scheduled
to 28th May 2016 due to the adverse weather condition (Strong Wind
Signal, No. 3). There are six Action Level and three Limit Level exceedances for
suspended solids were recorded. 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 was observed from the site;
2) Adverse water quality outside the site boundary and
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) were observed;
3) Sediment
plume due to natural fluctuation of shallow water was observed; and
4) Localized
sediment plume due to the rough water condition was observed.
5.40 Should
non-compliance of the criteria occur, action in accordance with the Action Plan
in Appendix K shall be carried out.