3.1.1.1
Monitoring
of the Total Suspended Particulates (TSP) levels shall be carried out by the
Environmental Specialist (ET) (see Section 1) to ensure that construction works
are not generating dust which exceeds the acceptable level. Timely action should be taken to rectify the
situation if an exceedance is detected.
3.1.1.2
1-hour
and 24-hour TSP levels shall be measured to indicate the impacts of
construction dust on air quality. The TSP levels shall be measured by following
the standard high volume sampling method as set out in the Title 40 of the Code
of Federal Regulations, Chapter 1 (Part 50), Appendix B. Upon approval by the Engineer’s
Representative (ER) and the Environmental Protection Department (DEP), 1-hour
TSP levels may be measured by direct reading methods for ad hoc measurements.
3.1.1.3
All
relevant data including temperature, pressure, weather conditions, elapsed-time
meter reading for the start and stop of the sampler, identification and weight
of the filter paper, any other special phenomena and work progress of the
concerned site shall be recorded in detail by the ET. A sample data sheet is shown in Figure 3.1.
3.2.1.1
A high volume sampler in compliance with the
following specifications shall be used for carrying out the 1-hr and 24-hr TSP
monitoring:
(i)
0.6-1.7 m3/min (20-60 SCFM)
adjustable flow range;
(ii)
equipped with a timing/control device
with +/- 5 minutes accuracy for 24 hours operation;
(iii)
installed with elapsed-time meter with
+/- 2 minutes accuracy for 24 hours operation;
(iv)
capable of providing a minimum exposed area
of 406 cm2 (63 in2);
(v)
flow control accuracy: +/- 2.5%
deviation over 24-hr sampling period;
(vi)
equipped with a shelter to protect the
filter and sampler;
(vii)
incorporated with an electronic mass
flow rate controller or other equivalent devices;
(viii)
equipped with a flow recorder for
continuous monitoring;
(ix)
provided with a peaked roof inlet;
(x)
equipped with a manometer;
(xi)
able to hold and seal the filter paper
to the sampler housing in a horizontal position;
(xii)
easy to change the filter; and
(xiii)
capable of operating continuously for
24-hr period.
3.2.1.2
The Contractor is responsible for
provision of the monitoring equipment and shall ensure that sufficient number
of high volume samplers with an appropriate calibration kit are available for
carrying out the baseline monitoring, impact monitoring and ad hoc monitoring.
The high volume samplers shall be equipped with an electronic mass flow
controller and be calibrated against a traceable standard at regular intervals.
All the equipment, calibration kit, filter papers, etc. shall be clearly
labelled by the ET.
3.2.1.3
Calibration of dust monitoring equipment
shall be conducted by the ET upon installation and thereafter at bi-monthly
intervals. The transfer standard shall
be traceable to the internationally recognised primary standard and be calibrated
annually. The calibration data shall be properly documented for future
reference by concerned parties, such as the IEC. All the data shall be
converted into standard temperature and pressure condition.
3.2.1.4
The flow-rate of the sampler before and
after the sampling exercise with the filter in position shall be verified to be
constant and recorded in the data sheet as described in Section 3.1.
3.2.1.5
If the ET proposes to use a direct
reading dust meter to measure 1-hr TSP levels on an ad hoc basis, he shall
submit sufficient information to the IEC to prove that the instrument is
capable of achieving a comparable result as that the High Volume Sampler (HVS)
and may be used for the 1-hr sampling. The instrument should also be calibrated
regularly and the 1-hr sampling shall be checked periodically by the HVS to
check the validity and accuracy of the results measured by the direct reading
method.
3.2.1.6
Wind data monitoring equipment shall
also be provided and set up at suitable locations for logging wind speed and
wind direction near to the dust monitoring locations. The equipment
installation location shall be proposed by the ET and agreed with the ER, in
consultation with the IEC.
3.2.1.7
For installation and operation of wind
data monitoring equipment, the following points shall be observed:
(i)
the wind sensors should be installed on
masts at an elevated level 10 m above ground so that they are clear of
obstructions or turbulence caused by the buildings;
(ii)
the wind data should be captured by a data
logger to be down-loaded for processing at least once a month;
(iii)
the wind data monitoring equipment
should be re-calibrated at least once every six months; and
(iv)
wind direction should be divided into 16
sectors of 22.5 degrees each.
3.2.1.8
In exceptional situations, the ET may
propose alternative methods to obtain representative wind data upon approval
from the ER and agreement from the IEC.
3.3.1.1
A clean laboratory with constant temperature
and humidity control and equipped with necessary measuring and conditioning
instruments shall be used for sample analysis and equipment calibration and
maintenance. The laboratory shall be HOKLAS accredited.
3.3.1.2
If a site laboratory is set up or a non-HOKLAS
accredited laboratory is hired for carrying out the laboratory analysis, the
laboratory equipment shall be approved by the ER, in consultation with the IEC.
Measurement performed by the laboratory shall be demonstrated to the
satisfaction of the ER and the IEC. The IEC shall conduct regular audits of the
measurements performed by the laboratory to ensure the accuracy of the results.
The ES shall provide the ER and the IEC with one copy each of the Title 40 of
the Code of Federal Regulations, Chapter 1 (Part 50), Appendix B for reference.
3.3.1.3
Filter paper of size 8"x10"
shall be labelled before sampling. It shall be a clean filter paper with no pin
holes and shall be conditioned in a humidity controlled chamber for over 24-hr
and be pre-weighed before use for the sampling.
3.3.1.4
After sampling, the filter paper loaded
with dust shall be kept in a clean and tightly sealed plastic bag. The filter paper shall then be returned to
the laboratory for reconditioning in the humidity controlled chamber followed
by accurate weighing by an electronic balance with a readout down to 0.1
mg. The balance shall be regularly
calibrated against a traceable standard.
3.3.1.5
All the collected samples shall be kept
in a good condition for 6 months before disposal.
3.4.1.1
The air quality sensitive receivers, as
determined by the EIA, are shown in Figure 3.2
and these will also form the recommended dust monitoring locations. The status and locations of dust sensitive
receivers may change after issue of this manual. If this happens, the ET shall propose updated
monitoring locations and seek approval from the ER and agreement from IEC.
3.4.1.2
When alternative monitoring locations
are proposed, the following preferred locations and factors shall be
considered:
(i)
the site boundary or locations close to
the major dust emission source;
(ii)
close to the sensitive receptors; and
(iii)
the prevailing meteorological
conditions.
3.4.1.3
The ET shall agree with the ER, in consultation
with the IEC, the position of the high volume samplers. When positioning the samplers, the following
points shall be noted:
(i)
a horizontal platform with appropriate
support to secure the samplers against gusty wind shall be provided;
(ii)
the distance between the sampler and an
obstacle, such as buildings, shall be at least twice the height that the
obstacle protrudes above the sampler;
(iii)
a minimum of 2 metres of separation from
walls, parapets and penthouses is required for rooftop samplers;
(iv)
a minimum of 2 metres separation from
any supporting structure, measured horizontally is required;
(v)
no furnace or incinerator flue is
nearby;
(vi)
airflow around the sampler is
unrestricted;
(vii)
the sampler is more than 20 metres from
the dripline;
(viii)
any wire fence and gate, to protect the
sampler, shall not cause any obstruction during monitoring;
(ix)
permission must be obtained to set up
the samplers and to obtain access to the monitoring stations;
(x)
a secured supply of electricity is
needed to operate the samplers; and
(xi)
no two samplers should be placed less
than 2 metres apart.
3.4.1.4
Prior to construction, the dust
monitoring schedule shall be developed by the ET based upon the construction
schedule supplied by the Contractor. The
ET shall inform the IEC of the impact monitoring programme such that he can
conduct on-site audits to ensure accuracy of the impact monitoring results. The
environmental monitoring schedule shall be approved by the ER.
3.1.1.1
The ET
shall carry out baseline monitoring at all the representative dust monitoring
locations. The monitoring at these
locations shall be undertaken for at least 14 consecutive days prior to the
start of the construction works to obtain daily 24-hr TSP samples. 1-hr sampling shall also be carried out at
least 3 times per day during the same period.
Monitoring shall take place within a 3 week period prior to the
commencement of construction works.
3.1.1.2
During
the baseline monitoring, there should not be any construction or dust
generation activities in the vicinity of the monitoring stations.
3.1.1.3
In
case the baseline monitoring cannot be carried out at the designated monitoring
locations during the baseline monitoring period, the ET shall carry out the
monitoring at alternative locations which can effectively represent the
baseline conditions at the impact monitoring locations. The alternative
baseline monitoring locations shall be approved by the ER, IEC and agreed with
DEP.
3.1.1.4
In the
event that insufficient baseline monitoring data or questionable results are
obtained, the ET shall liaise with the DEP to agree on an appropriate set of
data to be used as a baseline reference and submit this data to the ER and IEC
for approval.
3.1.1.5
Ambient
conditions may vary seasonally and shall be reviewed at three monthly
intervals. If the ET considers that the
ambient conditions have changed and a repeat of the baseline monitoring is
required to be carried out for obtaining updated baseline levels, the monitoring
should be at times when the Contractor's activities are not generating dust, at
least in the proximity of the monitoring stations. Should a change in ambient
conditions be determined, the baseline levels and, in turn, the air quality
criteria, shall be revised. The revised baseline levels and air quality
criteria shall be agreed with the DEP and supplied to the IEC.
3.2.1.1
The ET
shall carry out impact monitoring during the course of the works. For regular impact monitoring, the sampling
frequency of at least once in every six days shall be strictly observed at six
of the designated monitoring stations for 24-hr TSP monitoring. For 1-hr TSP
monitoring, the sampling frequency of at least three times in every six days
should be undertaken at six locations when the highest dust impact occurs. The stations to be monitored should be
selected based on the prevailing wind direction and their proximity to the
active construction works.
3.2.1.2
The
specific time to start and stop the 24-hr TSP monitoring shall be clearly
defined for each location and be strictly followed by the operator.
3.2.1.3
In
case of non-compliance with the air quality criteria, more frequent monitoring,
as specified in the Action Plan in Section 3.7, shall be conducted within 24
hours after the non-compliance is detected. This additional monitoring shall be
continued until the excessive dust emission or the deterioration in air quality
is rectified.
3.3.1.1
The baseline monitoring results will
form the basis for determining the air quality criteria for the impact
monitoring. The ET shall compare the impact monitoring results with air quality
criteria set
up for 24-hour TSP and 1-hour TSP. Table 3.1 shows the air quality
criteria, namely Action and Limit levels to be used. Should non-compliance with the air quality
criteria occur, the ET, the IEC and the ER and the Contractor shall undertake
their specified actions in accordance with the Action Plan shown in Table 3.2.
Table 3.1 Action
and Limit Levels for Air Quality
|
Parameters
|
Action
|
Limit
|
|
24 Hour TSP Level in µg/m³
|
For baseline level 200 µg/m³, Action level = (Baseline *1.3+ Limit
level )/2;
For baseline level >200 µg/m³, Action level = Limit level
|
260
|
|
1 Hour
TSP Level in µg/m³
|
For baseline level 384 µg/m³, Action level = (Baseline *1.3+ Limit
level )/2;
For baseline level >384 µg/m³, Action level = Limit level
|
500
|
3.3.1.2
In case of non-compliance with the air
quality criteria, more frequent monitoring exercise, shall be conducted within
24 hours after the result is obtained. This additional monitoring shall be
continued until the excessive dust emission or the deterioration in air quality
is rectified. The Event/Action Plan for air quality is given in the attached Table 3.2.
3.3.1.3
The Independent Environmental Checker
(IEC) shall be empowered to audit the environmental performance of
construction, all aspects of the EM&A programme, validate and confirm the
accuracy of monitoring results, monitoring equipment, monitoring locations and
procedures. If any exceedances occur,
the IEC shall follow the actions stated in the Event and Action Plan in Table 3.2.
3.4.1.1
The EIA report has recommended dust
control and mitigation measures. The Contractor shall be responsible for the
design and implementation of the following measures. The recommended construction
dust mitigation measures are summarised in the Air Quality Environmental
Mitigation Implementation Schedule provided in Appendix A.
(i)
all
unpaved roads/exposed area shall be watered which results in dust suppression
by forming moist cohesive films among the discrete grains of road surface
material. An effective watering
programme of twice daily watering with complete coverage, is estimated
to reduce by 50%. This is recommended for all areas in order to reduce dust
levels to a minimum;
(i)
watering
of the construction area 8 times per day is recommended to reduce dust
emissions by 87.5% and shall be undertaken;
(ii)
The Contractor shall, to the
satisfaction of the Engineer, install effective dust suppression measures and
take such other measures as may be necessary to ensure that at the Site
boundary and any nearby sensitive receiver, dust levels are kept to acceptable
levels;
(iii)
The Contractor shall not burn debris or
other materials on the works areas;
(iv)
in hot, dry or windy weather, the
watering programme shall maintain all exposed road surfaces and dust sources
wet;
(v)
where breaking of oversize rock/concrete
is required, watering shall be implemented to control dust. Water spray shall
be used during the handling of fill material at the site and at active cuts,
excavation and fill sites where dust is likely to be created;
(vi)
open dropping heights for excavated
materials shall be controlled to a maximum height of 2m to minimise the
fugitive dust arising from unloading;
(vii)
during transportation by truck, materials
shall not be loaded to a level higher than the side and tail boards, and shall
be dampened or covered before transport.
Materials having the potential to create dust shall not be loaded to a
level higher than the side and tail boards, and shall be covered by a clean
tarpaulin. The tarpaulin shall be
properly secured and shall extend at least 300mm over the edges of the side and
tail boards;
(viii)
no earth, mud, debris, dust and the like
shall be deposited on public roads.
Wheel washing facility shall be usable prior to any earthworks
excavation activity on the site;
(ix)
areas of exposed soil shall be minimised
to areas in which works have been completed shall be restored as soon as is
practicable; and
(x)
all stockpiles of aggregate or spoil
shall be enclosed or covered and water applied in dry or windy condition.
3.4.1.2
If the above measures are not sufficient
to restore the air quality to acceptable levels upon the advice of the ET, the
Contractor shall liaise with the ET regarding other mitigation measures and consult
the IEC for their effectiveness, and then propose these measures to the ER for
approval prior to the implementation of
the measures.
