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:
· 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 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°C 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 |
|
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: 1m below sea surface, mid-depth
and 1m above sea bed. ·
If
the water depth is less than 3m, mid-depth sampling only. ·
If
water depth less than 6m, mid-depth may be omitted. |
·
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°C 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°C 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 |
|
|
|
|
|
|
|
30/12/2016 |
0 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
IS2 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
IS3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
IS4 |
Action Level |
|
|
|
|
|
|
|
30/12/2016 |
0 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
SR1 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
SR2 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
SR3 |
Action Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
SR6 |
Action Level |
|
|
|
|
|
|
30/12/2016 |
30/12/2016 |
1 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
ST1 |
Action Level |
|
|
|
|
|
|
|
30/12/2016 |
0 |
1 |
|
Limit Level |
|
|
|
|
|
|
|
|
0 |
0 |
|
|
ST2 |
Action Level |
|
|
|
|
|
|
|
30/12/2016 |
0 |
1 |
|
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 |
1 |
5 |
6 |
|
|
Limit Level |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
||
5.38 All
water quality monitoring was conducted as scheduled in the reporting month. There
are three six Action
Level and five Limit Level exceedances were
recorded for suspended solids. 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)
Control Station value already exceeded either the Baseline Action or
Limit Levels;
3)
The exceeded results found at the monitoring station which is situated
at the upstream of the construction sites;
4)
Localized sediment plume due to the rough water condition was observed;
and
5)
The exceeded result was similar to the ranges baseline monitoring
results.
5.40
Should non-compliance of the criteria occur, action in accordance with
the Action Plan in Appendix K shall
be carried out.