5.1
In
accordance with the Updated EM&A Manual, impact water quality monitoring
shall be carried out three days per week at all the designated monitoring
stations during the construction period. The measurement periods are during the
construction of channel specified in Table 4.1 of the Updated EM&A Manual. The
interval between two sets of monitoring shall not be less than 36 hours.
5.2
Replicate
in-situ measurements of Dissolved Oxygen (DO), temperature, turbidity, pH,
Suspended Solids (SS) and samples for Suspended Solids (SS), ammonia nitrogen,
unionized ammonia, nitrate nitrogen and orthophosphate from each independent
sampling event were collected to ensure a robust
statistically interpretable database.
5.3
Appendix B shows the established Action
and Limit Levels for the water quality monitoring work according to the Updated EM&A Manual and
Baseline Water Quality Monitoring Report (KTN & FLN NDA).
5.4
Table 5.1 summarises the monitoring
parameters, monitoring periods and frequencies of the water quality monitoring.
Table 5.1 Water
Quality Monitoring Parameters and Frequency
|
Parameters, unit |
Depth |
Frequency |
|
·
Temperature(°C) ·
pH(pH
unit) ·
turbidity
(NTU) ·
water
depth (m) ·
salinity
(ppt) ·
DO
(mg/L and % of saturation) ·
SS
(mg/L) ·
Ammonia Nitrogen (NH3-N) (mg NH3-N/L) ·
Unionized Ammonia (UIA) (mg/L) ·
Nitrate-nitrogen (NO3-N) (mg NO3--N/L) ·
Ortho-phosphate (PO4) (mg PO43--P/L) |
· 3 water depths: 1m below water surface, mid-depth and 1m above river
bed. · If the water depth was
less than 3m, mid-depth sampling only. · If water depth was
less than 6m, mid-depth may be omitted. |
3 days per week during construction of channel |
5.5
According to Section
5.6.1.2 of the approved EIA Report,
the potential water quality impact during construction is due to the
alternation of natural streams (i.e. channelization of Ma Tso Lung Stream and
Siu Hang San Tsuen Stream) as these two streams are the ecologically important streams.
5.6
No construction of
channel was carried out at Ma Tso Lung Stream and Siu Hang San Tsuen Stream
during the reporting month. Therefore, no water quality monitoring was
conducted.
Additional Water Quality
Monitoring
5.7
Additional Water
Quality Monitoring shall be carried out at River Beas, River Indus and near Siu
Hang San Tsuen Stream three days per week at all designated monitoring stations
during the construction period. The measurement period are during the
construction site drainage along River Beas, construction of footbridge across
River Beas and during construction of bridge across River Indus.
5.8
Replicate in-situ
measurement and samples from each independent sampling event were collected to
ensure a robust statistically interpretable database. DO, temperature,
turbidity and pH were measured in-situ whereas SS and arsenic were determined
by an accredited laboratory. Other relevant data, including monitoring location
/ position, time, water depth, weather conditions and any special phenomena or
work underway at the construction site were recorded.
5.9
For all the
monitoring stations, sampling were taken at 3 water depths, namely 1m below the
water surface, mid depth and 1m above the river bed. For stations that were less than 3m in
depth, only the mid depth sample was taken. Should the water depth was less than 6m, in
which case the mid-depth station may have been omitted. The
interval between two sampling surveys was not less than 36 hours.
5.10
Appendix B shows the established Action and
Limit Levels for the environmental monitoring works.
5.11
Additional
impact water quality monitoring was conducted at 6 monitoring stations (SYR-CS1,
SYR-IS1, NTR-CS1, NTR-IS1, SHST-IS2, MWR-IS3) which are summarised in Table 5.2. The location of monitoring
stations is shown in Figures 5 and 6.
Table
5.2 Additional Water
Quality Monitoring Stations
|
Station |
Description |
Locations |
Measurement Periods |
|
River Beas |
|||
|
SYR-CS1 |
Control Station |
Upstream of river |
During the construction site drainage
along River Beas and construction of the footbridge
across River Beas |
|
SYR-IS1 |
Impact Station |
Downstream of river |
|
|
River Indus and near Siu Hang San Tsuen
Stream |
|||
|
NTR-CS1 |
Control Station |
Upstream of river |
During construction of the bridge across River Indus |
|
NTR-IS1 |
Impact Station |
Downstream of river |
|
|
SHST-IS2 |
Impact Station |
Water sensitive receiver at near Siu
Hang San Tsuen Stream |
|
|
MWR-IS3 |
Impact Station |
Water sensitive receiver at near
Ma Wat River |
|
5.12
Multi-parameter meters (Model YSI EXO) were used to measure DO, turbidity, salinity,
pH and temperature.
Dissolved Oxygen
(DO) and Temperature Measuring Equipment
5.13
The instrument
for measuring dissolved oxygen and temperature should be portable and
weatherproof complete with cable, sensor, and use DC power source. The
equipment was capable of measuring:
·
A dissolved
oxygen level in the range of 0-20mg/L and 0-200% saturation; and
·
The temperature
within 0-45 degree Celsius.
5.14
The equipment
had a membrane electrode with automatic temperature compensation complete with
a cable.
5.15
Sufficient stocks
of spare electrodes and cables were available for replacement where necessary.
5.16
Salinity
compensation was built-in in the DO equipment. In-situ salinity was measured to calibrate the DO equipment prior
to each DO measurement.
5.17
Turbidity was
measured in situ by using the nephelometric method. The instrument was
portable and weatherproof using a DC power sources 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.
5.18
A portable
salinometer capable of recording salinity within the range of 0-40 parts per
thousand (ppt) was used for salinity measurement.
5.19
A portable,
battery-operated and hand held echo sounder was used for the determination of
water depth at each designated monitoring station.
pH
5.20
The instrument consisted
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.
Water
Sampling for Laboratory Analysis
5.21 A water
sampler, consisting of a transparent Polyvinyl Chloride (PVC) of a capacity of
not less than two litres which can be effectively sealed with cups at both ends
was used. The water sampler had 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. In addition, a sampling cup attached to a fixed or
extendable rod was also used for sampling at the monitoring stations with
swallow water.
Sample
Container and Storage
5.22 Following
collection, water samples for laboratory analysis were stored in high density
polyethylene bottles with appropriate preservatives added, packed in the ice
(cooled to 4oC without being frozen). The samples were delivered to WELLAB Limited (HOKLAS
Registration No. HOKLAS083)
and analysed as soon as possible after collection of the water samples.
Sufficient volume of samples was collected to achieve the detection limit.
Calibration
of In Situ Instruments
5.23 The pH
meter, DO meter and turbidimeter were checked and calibrated before use. DO
meter and turbidimeter were certified by WELLAB Limited before use and
subsequently re-calibrated at quarterly basis throughout all stage of water
quality monitoring programme. Response 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 station.
5.24 For
on-site calibration of field equipment (Multi-parameter Water Quality System),
the standard BS 1427:2009 “Guide to on-site test
methods for analysis of waters” was observed.
Back-up
Equipment
5.25 Sufficient
stocks of spare parts were maintained for replacements when necessary. Backup
monitoring equipment was also be made available so that monitoring could proceed uninterrupted even when some
equipment was under maintenance, calibration, etc.
5.26 Table 5.3 summarises the equipment used in the water quality
monitoring programme. Copies of the calibration certificates of the multi-parameter water quality systems are shown in Appendix C.
Table 5.3 Water
Quality Monitoring Equipment
|
Equipment |
Model and Make |
Qty. |
|
|
|
|
|
Water
sampler and sampling cup |
A
2-Litre transparent PVC cylinder with latex cups at both ends and sampling
cup for monitoring stations with swallow water |
1 |
|
Sonar
Water Depth Detector |
Garmin
Striker plus 4 |
1 |
|
Multi-parameter
Water Quality System |
YSI
EXO 1 |
2 |
5.27 Table 5.4 summarises the monitoring parameters and
frequencies of the additional water quality monitoring. The water quality
monitoring schedule for the reporting month is shown in Appendix D.
Table
5.4 Additional Water
Quality Monitoring Parameters and Frequency
|
Monitoring
Station(s) |
Parameters,
unit |
Depth |
Frequency |
|
|
River
Beas |
SYR-CS1 SYR-IS1 |
·
Temperature (oC) ·
pH (pH unit) ·
Turbidity (NTU) ·
Water depth (m) ·
Salinity (ppt) ·
Dissolved Oxygen (DO) (mg/L and % of
saturation) ·
Suspended Solids (SS) (mg/L) ·
Arsenic (As) (µg/L) |
·
3 water depths: 1m below water surface,
mid-depth and 1m above river bed. ·
If the water depth was less than 3m,
mid-depth sampling only. ·
If water depth was less than 6m,
mid-depth might be omitted. |
3 days per
week |
|
River Indus
and near Siu Hang San Tsuen Stream |
NTR-CS1 NTR-IS1 SHST-IS2 MWR-IS3 |
·
Temperature (oC) ·
pH (pH unit) ·
Turbidity (NTU) ·
Water depth (m) ·
Salinity (ppt) ·
Dissolved Oxygen (DO) (mg/L and % of
saturation) ·
Suspended Solids (SS) (mg/L) |
||
5.28 Monitoring
location and position, time, sampling depth, weather conditions and any special
phenomena or work underway nearby was also recorded.
Instrumentation
5.29 Multi-parameter meters (Model YSI EXO) were used to measure DO, turbidity, salinity,
pH and temperature.
Operating/Analytical Procedures
5.30 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.
Laboratory Analytical Methods
5.31 Duplicate
samples from each independent sampling event were
required for all parameters.
Analysis of suspended solids and arsenic were carried out by WELLAB Ltd. and
comprehensive quality assurance and control procedures were in
place in order to ensure the quality and consistency in results. The analysis methods and limits of reporting are
provided in Table 5.5.
Table 5.5 Method
for Laboratory Analysis for Water Samples
|
Determinant |
Proposed
Method |
Limit of
Reporting |
|
Total Suspend Solids (SS) |
APHA 17ed 2540 D |
2.5 mg/L |
|
Arsenic (As) |
In-house method SOP022 (ICP-AES)
and SOP076 (ICP-MS) |
1 µg/L |
5.32 Water
sampling equipment used during the course of the monitoring process was
decontaminated by manual washing and rinsed with distilled water after each
sampling event. All of the disposal equipment was discarded after the sampling.
Sampling
Management and Supervision
5.33 All
sampling bottles were labelled with the sample I.D.
(including sampling station), laboratory
number and sampling date. Water samples were dispatched to the testing
laboratory for analysis as soon as possible. All the collected samples were
stored in a cool box to keep the temperature less than 4oC 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.
Quality
Control Measures for Sample Testing
5.34 The
samples testing and following QC programmes
were performed by WELLAB Ltd. for
every batch of 20 samples:
·
One method blank; and
·
One set of QC sample.
5.35 All
additional water quality monitoring was conducted as scheduled in the reporting
month except 2 July 2022. According to Hong Kong Observatory, Typhoon Signal
No.8 was hoisted whole day on 2 July 2022. Due to safety reason, water quality
monitoring scheduled for the day was cancelled. The water quality monitoring
schedule for this reporting month is shown in Appendix D.
5.36 The
monitoring results and graphical presentation of additional water quality
monitoring are shown in Appendix G.
5.37 The summary of exceedance recorded in the
reporting month is shown
in Appendix O and
summarised
in the Table 5.6.
Table 5.6 Summary
of Water Quality Exceedances
|
Station |
Exceedance Level |
DO |
Turbidity |
SS |
Total Number of Non-project
Related Exceedances |
Total Number of project
Related Exceedances |
|
SYR-IS1 |
Action Level |
0 |
0 |
0 |
0 |
0 |
|
Limit Level |
2 |
0 |
0 |
2 |
0 |
|
|
NTR-IS1 |
Action Level |
0 |
0 |
0 |
0 |
0 |
|
Limit Level |
0 |
3 |
3 |
6 |
0 |
|
|
SHST-IS2 |
Action Level |
2 |
0 |
0 |
2 |
0 |
|
Limit Level |
0 |
4 |
3 |
7 |
0 |
|
|
MWR-IS3 |
Action Level |
0 |
0 |
0 |
0 |
0 |
|
Limit Level |
4 |
2 |
3 |
9 |
0 |
|
|
Total |
Action Level |
2 |
0 |
0 |
2 |
0 |
|
Limit Level |
6 |
9 |
9 |
24 |
0 |
* Exceedances record date: 04/07, 06/07, 08/07 and 29/07/2022
5.38 Two (2)
Action Level and Six (6) Limit Level for DO, Nine (9) Limit Level for
turbidity, and Nine (9) Limit Level for Suspended Solids of impact water
quality monitoring were recorded. Exceedances were recorded on 4, 6, 8 and 29
July 2022. After investigation, all exceedances were considered due to the
other external factors rather than the contract works due to the following
reasons:
1.
No pollution discharge from site area was
observed.
2.
Water from upstream of Ng Tung River, Siu
Hang San Tsuen River and Ma Wat River which outside the project site boundary
were observed muddy and may led to the increase of turbidity and SS level in
the water body. Organic material is anticipated in adverse water quality
causing reduction in DO levels due to decomposition of organic matter by
microorganisms.
3.
Water quality mitigation measures at the
nearby construction site (i.e., Contract No. ND/2019/02 and ND/2019/04) were
observed properly maintained including silt curtain, green barriers with
impervious sheeting to direct site runoff to water pump to the treatment
facilities and hydro-seeding surrounding the works etc.
4.
Typhoon
Chaba reached Hong Kong in the first few days of July, rainfall in Northern
District was recorded before the water quality monitoring which led to
increased surface runoff and hence adverse water quality. Heavy rainfall in
Northern District was recorded on sampling date 29/07/2022 also.
5.39 Should any non-compliance of the
criteria occur, actions in accordance with the Event/Action
Plan in Appendix N shall be carried
out.