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 |
|
|
|
|
|
|
|
18/04/2018 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
IS2 |
Action Level |
|
|
|
|
|
|
|
18/04/2018 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
IS3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
IS4 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR1 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR2 |
Action Level |
|
|
|
|
|
|
|
02/04/2018 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SR6 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
ST1 |
Action Level |
|
|
|
|
|
|
|
02/04/2018 |
0 |
1 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
ST2 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
ST3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
SRA |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Total |
Action Level |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
4 |
|
|
Limit Level |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
5.39 All water quality monitoring was
conducted as scheduled in the reporting month. There are four 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 major marine construction activity was conducted;
2)
No pollution discharge from construction activity was observed;
3)
Sediment plume due to natural fluctuation of shallow water was observed;
and
4) 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 observed.
5.41 Should non-compliance of the
criteria occur, action in accordance with the Action Plan in Appendix K shall be carried out.