4.
WATER QUALITY
4.1.1
In accordance with
the EM&A Manual, impact monitoring is conducted for three days per week at
mid-flood and mid-ebb with sampling and measurement at the designated monitoring
stations.
4.2.1
Equipment used for
in-situ measurement and water sampling during impact water quality monitoring
is summarised in Table 4.1. The equipment is in compliance with the requirements set out in the
EM&A Manual. All in-situ monitoring instruments were calibrated by a
HOKLAS-accredited laboratory. Calibration of temperature, DO, salinity, pH and
turbidity is conducted in three month interval.
Calibration certificates for the water quality monitoring equipment are
attached in Appendix D.
4.3.1
All in-situ monitoring instruments shall be checked, calibrated
and certified by a laboratory accredited under HOKLAS before use and
subsequently re-calibrated at three monthly intervals throughout all stages of
the water quality monitoring programme. Responses of sensors and electrodes
shall be checked with certified standard solutions before each use. Wet bulb
calibration for a DO meter shall be carried out before measurement at each
monitoring location.
4.3.2
Sufficient stocks of spare parts shall be maintained for replacements
when necessary. Backup monitoring equipment shall also be made available so
that monitoring is uninterrupted even when some equipment is under maintenance
or calibration etc.
The monitoring parameters and frequency for both in-situ measurement and
laboratory analysis are summarised in Table 4.2.
4.5.1
The position of water monitoring station will be located by the
Differential Global Positioning System (DGPS) or equivalent. The water depth of
water monitoring station will be determined by the echo sounder affixed to the
bottom of the monitoring vessel or a portable echo sounder depth detector.
4.5.2
Once the location and water depth are confirmed, water samples shall be
collected at 3 depths (1m below the surface, mid-depth, and 1m above the
seabed) of the water column at each location, except where water depth is less
than 6m, the mid-depth will be omitted and if the water depth is less than 3m
only the mid-depth station will be monitored. Duplicate marine samples will be
collected in each sampling event. The water samples are decanted from the water
sampler into the water sample bottles. The bottles are labelled, tightly
sealed, placed into a cool-box and packed with ice ready for delivery to the
laboratory.
4.5.3
Two consecutive measurements of water quality data, including pH,
salinity, dissolved oxygen and turbidity will be
recorded according to the monitoring locations. Separate deployment of the
monitoring instruments and water samplers will be conducted for the consecutive
measurements or samplings. The monitoring location / position, time, water depth,
sampling depth, tidal stages, weather conditions, sea condition and any special
phenomena or work underway nearby shall also be recorded. If the difference in
value between the first and second measurement of DO or turbidity parameters is
more than 25% of the value of the first reading, the reading shall be discarded and further readings should be taken.
4.6
Laboratory Measurement / Analysis
4.6.1
Fugro Technical Services Limited (HOKLAS Reg: No.015) has been appointed
to conduct the laboratory measurement or analysis of water sample in this
project.
Quality Assurance / Quality
Control
4.6.2
The laboratory incorporates a variety of QA/QC monitoring programme into
their testing system. Where applicable or available, the quality of the analysis will
be monitored by conducting the following QC analysis:
§ A minimal of 1
laboratory method blank will be analyzed;
§ A minimal of 1
sample duplicate will be analyzed;
§ A minimal of 1
sample matrix spike will be analyzed.
4.7.1
In accordance with
the EM&A Manual, water quality monitoring should be carried out at 3
designated monitoring locations.
4.7.2
The coordinates of
the monitoring location stated in the EM&A Manual is summarised in Table 4.3
and the locations of the water quality monitoring stations shown in Figure 4.
4.8.1
The schedule of water
quality monitoring in reporting month is provided in Appendix E.
4.8.2
Impact water
quality monitoring was conducted at all designated monitoring stations in the
reporting month. Impact water quality monitoring results and graphical
presentations are provided in Appendix F.
4.8.3
The weather and
meteorological conditions during the monitoring are provided in Appendix K.
4.8.4
Number of Action/ Limit exceedance recorded
in the reporting month at each impact stations is summarized in Table 4.4.
4.8.5
During the
reporting period, no Action and Limit Level exceedance was recorded for water quality
monitoring.
4.8.6
The Event and
Action Plan for water quality is given in Appendix
H.
4.9
WetSeps
4.9.1
Three WetSeps are deployed within the site for treatment of the
site runoff prior to disposal in compliance with the conditions stipulated in
the water discharge license (Variation of WPCO Discharge Licence was approved
by EPD on 1 December 2022 with immediate effect).