6.1
According to Section 7.5 of updated EM&A
Manual, an ambient arsenic monitoring is required to be conducted in KTN during
the clean-up processes of arsenic containing soil and the construction phase.
6.2
The Respirable Suspended Particulate (RSP, or
PM10) should be measured by High Volume Sampler (HVS) equipped with PM10
selector following the "Reference Method for the Determination of
Particulate Matter as PM10 in the Atmosphere" Part 50 Chapter 1 Appendix
J, Title 40 of the Code of Federal Regulations of the USEPA.
6.3
The Dust-laden air should be drawn through
PM10 HVS fitted with a conditioned pre-weighting filter paper, at a controlled
rate. After sampling for 24-hour (refer Section 9.5.5 for details on
measurement period), the filter paper with retained PM10 particulates shall be
collected and returned to the laboratory for drying in a desiccators followed
by accurate weighting. 24-hour average RSP levels shall be calculated from the
ratio of the mass of PM10 particulates retained on the filter paper to the
total volume of air sampled.
6.4
The weighted filter paper shall be prepared
for arsenic testing through a "Hot Acid Extraction Procedure". The
extracted material shall be tested for arsenic by using Inductively Coupled
Plasma/Mass Spectrometry (ICP/MS). The extraction and testing will be
referenced to the following methods:
l
Compendium Method 1O-3.1 Selection, Preparation
and Extraction of Filter Material, Center for Environmental Research
Information, Office of Research and Development, USEPA, June 1999; and
l
Compendium Method 1O-3.5 determination of
Metals in Ambient Particulate Matter using Inductively Coupled Plasma/Mass
Spectrometry (ICP/MS., Center for Environmental Research Information, Office of
Research and Development, USEPA, June 1999.
6.5
Ambient arsenic monitoring was conducted at
the monitoring station under the Work Contract, as shown in Figure 5. Table
6.1 describes the locations of the ambient arsenic monitoring station.
Table 6.1 Location of Ambient Arsenic
Monitoring station
|
EP. No |
Contract No. |
Monitoring
Stations |
Location |
|
EP-466/2013 EP-467/2013/A EP-468/2013/A |
ND/2019/01 |
KTN-DMS-4A[1] |
Temporary Structure at Pak Shek Au |
|
EP-468/2013/A |
ND/2019/03 |
Notes:
[1]: Monitoring at original
KTN-DMS-4 (originally proposed in the approved EM&A Manual) was denied as
no electricity supply. An
alternative location (KTN-DMS-4A) was proposed.
6.6
Table 6.2 summarizes the equipment
used in the ambient arsenic monitoring. Copies of calibration certificates are
attached in Appendix C.
Table 6.2 Ambient
Arsenic Monitoring Equipment
|
Monitoring
Stations |
Equipment |
Model and Make |
Quantity |
|
KTN-DMS-4A |
Calibrator |
TISCH Model: TE-5025A |
1 |
|
HVS
Sampler (RSP) |
TISCH Model: TE-6070X |
1 |
6.7
Table 6.3 summarizes the monitoring
parameters and frequencies of ambient arsenic during the clean-up processes of
arsenic-containing soil and construction. The ambient arsenic monitoring
schedule for the reporting month is shown in Appendix D.
Table 6.3 Impact
Ambient Arsenic Monitoring Parameters, Frequency and Duration
|
Parameters |
Frequency |
|
24-hr RSP (Ambient Arsenic) |
Once/ 6 days |
24-hour RSP Monitoring
Instrumentation
6.8
High volume samplers (HVS) (GMW PM10
(TE6070)) complete with appropriate sampling inlets was employed for 24-hour
RSP monitoring. The sampler is
composed of a motor, a filter holder, a flow controller and a sampling inlet
and its performance specification complied with that required by USEPA Standard
Title 40, Code of Federation Regulations Chapter 1 (Part 50).
6.9
The following guidelines were adopted during
the installation of HVS:
l a horizontal platform with appropriate
support to secure the samplers against gusty wind was provided;
l no two samplers was placed less than 2 meters
apart;
l the distance between the sampler and an
obstacle, such as buildings, was at least twice the height that the obstacle
protrudes above the sampler;
l a minimum of 2 meters of separation from
walls, parapets and penthouses was required for rooftop samplers;
l a minimum of 2 meters separation from any
supporting structure, measured horizontally was required;
l no furnace or incinerator flue was nearby;
l airflow around the sampler was unrestricted;
l the sampler was more than 20 meters from the
dripline;
l any wire fence and gate, to protect the
sampler, were not cause any obstruction during monitoring;
l permission was obtained to set up the
samplers and to obtain access to the
l monitoring stations; and
l a secured supply of electricity was needed to
operate the samplers.
Operating/analytical procedures for the operation
of HVS
l
Prior
to the commencement of the dust sampling, the flow rate of the high volume
sampler will be properly set (between 1.1 m3/min. and 1.4 m3/min.)
in accordance with the manufacturer's instruction to within the range
recommended in USEPA Standard Title 40, CFR Part 50.
l
The
power supply was checked to ensure the sampler worked properly. On sampling, the sampler was operated
for 5 minutes to establish thermal equilibrium before placing any filter media
at the designated air monitoring station.
l
The
filter holding frame was then removed by loosening the four nuts and a weighted
and conditioned filter will be carefully centered with the stamped number
upwards, on a supporting screen.
l
The
filter was aligned on the screen so that the gasket formed an airtight seal on
the outer edges of the filter. Then
the filter holding frame was tightened to the filter holder with swing bolts.
The applied pressure were sufficient to avoid air leakage at the edges.
l
The
shelter lid was closed and secured with the aluminum strip.
l
The
timer was then programmed.
Information was recorded on the record sheet, which included the
starting time, the weather condition and the filter number (the initial weight
of the filter paper can be found out by using the filter number).
l
After
sampling, the filter was removed and sent to the Wellab
Ltd. for weighing. The elapsed time
was also recorded.
l
Before
weighing, all filters were equilibrated in a conditioning environment for 24
hours. The conditioning environment
temperature was between 25°C and 30°C and not vary by more than ±3°C; the
relative humidity (RH) was < 50% and not vary by more than ±5%. A convenient
working RH was 40%. Weighing results were further analysis of RSP
concentrations collected by each filter.
6.10
The following maintenance/calibration was
required for the HVS:
l
The
high volume motors and their accessories were properly maintained. Appropriate
maintenance such as routine motor brushes replacement and electrical wiring
checking were made to ensure that the equipment and necessary power supply were
in good working condition.
l
High
volume samplers were calibrated at bi-monthly intervals using TE-5025A
Calibration Kit throughout all stages of the ambient arsenic monitoring.
6.11
Quartz filters of size 8” x 10” were labelled
before sampling. A HOKLAS accredited laboratory, Wellab
Ltd., is responsible for the preparation of 24-hr conditioned and pre-weighed
filter papers for the monitoring team.
The balance for weighting filter paper was regularly calibrated against
a traceable standard.
6.12
All filters, which were prepared by Wellab Ltd., were equilibrated in the conditioning
environment for 24 hours before weighing.
The conditioning environment temperature was around 25 °C and not
variable by more than ±3 °C; the relative humidity (RH) was < 50% and not
variable by more than ±5%. A
convenient working RH was 40%.
6.13
Wellab
Ltd. (HOKLAS Registration No. 083), is responsible for the extraction and
testing procedure for Arsenic and comprehensive quality assurance and quality
control programmes were conducted.
6.14
The ambient arsenic monitoring results are
summarized in Table 6.4. Detailed monitoring results and test report are
shown in Appendix E.
Table 6.4
Summary Table of 24-hour RSP Monitoring Results (Ambient Arsenic) during
the Reporting Month
|
Monitoring Date |
Monitoring
Station |
Concentration (ng/m3) |
Action Level (ng/m3) |
Limit Level, (ng/m3) |
|
03/08/2020 |
KTN-DMS-4A |
0.15 |
9.36 |
11.7 |
|
07/08/2020 |
0.91 |
|||
|
13/08/2020 |
0.56 |
|||
|
19/08/2020 |
0.30 |
|||
|
25/08/2020 |
1.08 |
|||
|
31/08/2020 |
3.09 |
6.15
All ambient arsenic monitoring was conducted
as scheduled in the reporting month. No Action/Limit Level exceedances were
recorded.
6.16
Should project-related non-compliance of the
criteria occur, action in accordance with the Action Plan in Appendix J shall be carried out.