5
Construction Dust IMPACT
5.1
Potential dust impacts associated with the
construction phase of the Shatin to Central Link
(SCL) protection works at Causeway Bay
Typhoon Shelter (CBTS) are presented in this section. Representative Air Sensitive Receivers (ASRs)
are identified. Potential dust impacts on these receivers
arising from dust emission from the construction activities associated with the
Project have been assessed and appropriate mitigation measures are proposed to
alleviate the impacts.
Environmental
Legislation, Standards and Guidelines
5.2
The criteria for evaluating air quality
impacts and the guidelines for air quality assessment are laid out in Annex 4
and Annex 12 of the Technical Memorandum on Environmental Impact Assessment
Process (EIAO-TM) as well as the requirements set out under Clause 3.4.4 of the
EIA Study Brief (No. ESB-213/2010).
Air Quality Objective & EIAO-TM
5.3
The Air Pollution Control Ordinance (APCO)
provides the statutory authority for controlling air pollutants from a variety
of sources. The Hong Kong Air Quality
Objectives (AQOs), which stipulate the maximum allowable concentrations over
specific periods for a number of criteria air pollutants, should be met. The
relevant AQOs are listed in Table 5.1.
Table 5.1
|
Pollutant |
Maximum
Concentration (µg m-3) (1) |
|
|
Averaging
Time |
||
|
Daily (2) |
Annual (3) |
|
|
260 |
80 |
|
Note:
(1)
Measured at 298 K and 101.325 kPa.
(2)
Not to be exceeded more than once per year.
(3)
Arithmetic mean.
5.4
The EIAO-TM stipulates that the hourly TSP
level should not exceed
Air Pollution Control (Construction Dust)
Regulation
5.5
Notifiable and
regulatory works are under the control of Air Pollution Control (Construction
Dust) Regulation. Notifiable
works are site formation, reclamation, demolition, foundation and
superstructure construction for buildings and road construction. Regulatory works are building renovation,
road opening and resurfacing, slope stabilisation, and other activities
including stockpiling, dusty material handling, excavation, concrete
production, etc. This Project is
expected to include notifiable works (reclamation,
demolition, foundation and superstructure
construction) and regulatory works (temporary stockpile, dusty material
handling, excavation and concrete production).
Contractors and site agents are required to inform EPD and adopt dust
reduction measures to minimize dust emission, while carrying out construction
works, to the acceptable level.
Description of the
Environment
5.6
The SCL Protection Works is located entirely
offshore within the Causeway Bay Typhoon Shelter. The locality of the Project
Area is a developed urban area and the sensitive receivers are located along
the harbour-front area with major land uses including commercial,
residential and open spaces.
5.7
The study area is located in the
5.8
Central/Western
monitoring station is located at Sai Ying Pun at the centre of the hinterland
area. The monitoring station is
surrounded by mixture of commercial as well as densely populated residential
areas and busy local traffic networks in all directions. The TSP recorded at this station would
largely be contributed by the vehicular emissions from the surrounding road
network. Contrastly,
the study area of this Project is a harbour front location facing the Harbour
to the north. Lower TSP levels would be
expected in the study area when wind is blowing in the prevailing
north-easterly direction. Given the
different site characteristic of the study area and EPD’s Central/Western
monitoring station, alternative historic TSP monitoring data are
considered. In order to estimate the
background TSP level in the vicinity of the study area, recent environmental
monitoring data recorded at harbour front locations by the environmental
monitoring and audit (EM&A) programme for other designated project in close
proximity to the study area are referred to.
5.9
Central
Reclamation Phase III (CRIII) is a designated project under the EIA Ordinance
and its project site is located near the northern harbour front of the
5.10
The air quality
monitoring at PLA commenced in April 2005 and data of up to 5 years are
available to represent the background air quality in the surrounding area. Whereas the air quality monitoring at City
Hall only commenced in March 2006 with less than 5 years available data and
thus is not selected for background air quality estimation.
5.11
All the TSP
monitoring data were recorded in accordance with the requirements stipulated in
the EM&A Manual of CRIII and were reviewed and
submitted as per the requirements of the corresponding environmental permit
issued under the EIA Ordinance. All the TSP
levels were measured in accordance with the standard high volume sampling
method set out in the Title 40 of the Code of Federal Regulations, Chapter 1
(Part 50), Appendix B.
Initial calibration of dust monitoring equipment was conducted upon
installation and thereafter at bi-monthly intervals. The transfer standard is traceable to the
internationally recognised primary standard and was calibrated annually. The calibration and air quality monitoring
was conducted by independent environmental team and led by an environmental
team leader. The calibration data were
also reviewed and validated by independent environmental checker. The collected dust samples were analysed by a
laboratory which had been inspected and audited by the independent
environmental checker as per the EM&A Manual of
CRIII Project to undertake the dust analysis.
5.12
Review of the detailed TSP monitoring results
recorded at PLA was undertaken and it is observed that some unusually low TSP
concentrations were measured on some days.
TSP comprises of suspended particulates of different size including respirable suspended particulates (RSP). The background RSP level in Hong Kong is
largely influenced by regional contribution, thus the spatial variation of RSP
level over the
5.13
The TSP data
recorded at PLA are considered as of acceptable quality and with sufficient
valid data after discarding the unusually low TSP monitoring data. The
estimated background TSP concentration using the PLA
monitoring results is 76.2μg/m3. The past TSP monitoring data recorded at PLA
is attached in Appendix 5.1.
5.14
In accordance with
Annex 12 of the EIAO-TM, any domestic premises, hotel, hostel, hospital,
clinic, nursery, temporary housing accommodation, school, educational
institution, office, factory, shop, shopping centre, place of public worship,
library, court of law, sports stadium or performing arts centre are considered
as air sensitive receivers (ASRs). As stated
in the EIA Study Brief, the boundary of the assessment area for air quality
assessment should be
5.15
The proposed SCL
protection works would be constructed by cut-and-cover methods on the temporary
reclamation land. All associated
construction works would be at ground level.
The air quality impact at the lowest level of each representative ASR
with sensitive use, which is the worst affected level, was assessed in this
assessment. Higher assessment height of
5m above ground level (AGL) was also selected for elevated ASRs to show the
vertical variation of the pollutant concentrations.
Table 5.2 Representative
Air Sensitive Receivers
|
ASRs |
Description |
Land Use |
Distance
from the
nearest dust emission sources (m) |
No. of
storey |
Assessment Height (m AGL) |
|
CHA1* |
World Trade Centre |
Commercial |
80 |
34 |
5 |
|
CHA2* |
|
Commercial |
120 |
33 |
5 |
|
CHA3 |
|
Residential |
150 |
15 |
1.5 & 5 |
|
CHA4 |
Royal |
Recreation |
140 |
3 |
1.5 & 5 |
|
CHA5 |
Police Officers
Club (POC) |
Recreation |
20 |
3 |
1.5 & 5 |
|
CHA6 |
|
Residential |
130 |
14 |
1.5 & 5 |
Note:
* Only non-sensitive use
was observed at the ground level, assessment height was taken as the second level
of 5m AGL.
5.16
The SCL Protection Works involves the
construction of a section of the railway tunnel box by cut-and-cover method at
the crossing above the proposed Central Wanchai
Bypass (CWB) tunnels. Temporary
reclamation would be required to construct the Protection Works. The
construction works included dredging, temporary sea wall construction, filling,
installation of diaphragm wall, excavation, placing a reinforced concrete
tunnel box and removal of temporary reclamation. Construction of temporary seawall and fill
works are the major construction works during reclamation. Excavation, materials handling, wind erosion,
truck haulage on unpaved roads are other major sources of dust impact.
5.17
Apart from the potential dust impact
associated with the temporary reclamation, dredging at the southeast corner of
the CBTS is required to provide space for temporary relocation of anchorage
area for the vessels due to the additional temporary reclamation for the
Protection Works. Since the dredging
activities are not dusty activities and the moisture content of dredging
materials is very high, negligible fugitive dust emissions is expected. Yet in view of the small scale, short
duration and low dredging rate of the proposed dredging works, adverse odour
impact during the dredging operation is not anticipated. The potential odour impact arising from the
dredging process is further discussed in Section 6 of this EIA Report.
5.18
Alternative
construction methods/phasing programme were described in Chapter 2 of this
report.
Cumulative Dust Impact from Other
Concurrent Project
5.19
Based on the
current programme, the Project would likely interface with Wan Chai Development
Phase II & Central-Wan Chai Bypass (WDII & CWB) in 2012 – 2013.
WDII
& CWB
5.20
The major
construction works for WDII & CWB Project would be the construction of
trunk road and reclamation works. The
proposed trunk road runs from Central Interchange in Central Reclamation Phase
I through the Central Reclamation Phase III and WDII & CWB project areas,
and the Island Eastern Corridor Link (IECL) which provides connection from the
eastern portal of the CWB to the IEC.
5.21
Any above ground
construction activity arising from WDII & CWB that is located within 500m
from the Project boundary were considered in this assessment.
5.22
Referring to the above sections, potential
adverse dust impact would be expected from construction of temporary seawall,
fill works and cut-and-cover tunnel. The potential dust
emission sources considered in the assessment are shown in Appendix 5.2.
Emission Inventory
5.23
The principal source of air pollution during the
construction phase will be dust from the dusty activities as mentioned
above. The impact of fugitive dust
sources on air quality depends upon the quantity as well as the drift potential
of the dust particles emitted into the atmosphere. Large dust particles (i.e. over 100 mm in diameter) will settle near the source
and particles that are between 30 and 100 mm in diameter are likely to undergo impeded
settling. The main dust impacts are
likely to arise from particles less than 30 mm in diameter, which have a greater potential
to disperse over greater distance.
5.24
According to the USEPA AP-42, construction
dust particles may be grouped into nine particle size classes. Their size ranges are 0.5 mm, 1.5 mm, 2.25 mm, 2.75 mm, 3.5 mm, 4.5 mm, 5.5
mm, 8 mm, 20 mm, and the percentage of particles in each
class was estimated to be 4%, 7%, 4%, 3%, 7%, 5%, 4%, 17% and 49%,
respectively.
5.25
Predicted dust emissions are based on
emission factors from AP-42. The major
dusty construction activities for the Project to be considered in the modelling
assessment include:
(A)
Temporary Reclamation areas (modeled as heavy construction)
-
Construction of
seawall
-
Back filling the
spoils
-
Installation of
diaphragm wall
-
Truck haulage on
unpaved roads
(B)
Tunnel Cut & Cover areas
-
Excavation and material handlings within the construction site and truck haulage
on unpaved roads modelled as heavy construction activities
-
Wind erosion of
open active site
5.26
In terms of the construction programme, it
should be noted that the sequencing of works for each works activity over each
works site or area will be determined by the Contractor and is not known at
this stage. However, due to the
constrained size of the works sites and the tight construction programme, it
will be necessary for active construction activities to be undertaken at
multiple work faces spread across each site.
Therefore, it is not feasible to identify the exact location of
individual dust emission source. As
such, for the purpose of predicting annual TSP concentrations, it is assumed
that dust emissions would be distributed across the whole area of each site and
the dust emission rates are estimated based on the annual average percentage
active works area of each works site.
5.27
Whereas for predicting shorter-term TSP
levels including hourly and daily average TSP levels, a more conservative
approach is adopted. It is assumed that
the whole construction site would be 100% actively operated, notwithstanding
that such a scenario would unlikely to occur.
5.28
The emission rates of identified pollutant
sources are summarised in Tables 5.3. Detailed calculations of the emission factors
are given in Appendix 5.2.
Table 5.3 Emission
Factors for Dusty Construction Activities (For Hourly and Daily TSP Concentrations
Prediction)
|
Emission Source |
Activity |
Emission
Rate |
Remarks |
|
Temporary
Reclamation/Tunnel Construction at |
Heavy Construction Activities |
E=2.69 Mg/hectare /month
of activity |
|
|
|
Wind
Erosion |
E=0.85Mg/hectare /year |
|
5.29
Based on the
preliminary engineering design, the annual averaged active area is estimated to
be 6% and would be assumed for predicting the annual concentrations. The justification for the percentage of
annual average active area is presented in Appendix 5.3.
5.30
With reference to
the proposed construction method of both SCL Protection Works and CWB,
temporary seawall construction will be first conducted to enclose each phase of
the temporary reclamation. Installation
of diaphragm wall on temporary reclamation land as well as any bulk filling
will proceed behind the completed seawall.
After the temporary reclaimed land was formed, tunnel box construction by
cut-and-cover method down to below water level will be conducted. Then all construction works would be carried
out below water level and adverse dust impact would not be anticipated. Finally, the temporary reclamation will be
removed after completion of all tunnel construction works. According to the assumption made under WDII
& CWB EIA, the maximum percentage of active construction works area is 50%,
the remaining 50% of the works area is just exposed to air without any construction
works. Therefore, as the worst-case
assumption, the annual exposed area is assumed to be 50% for predicting the
annual concentrations.
5.31
There will be no construction activity
carried out at the southwest retained temporary reclamation after the land was
formed. The land will be covered or
paved once the filling is completed. In
accordance with the tentative construction programme, the filling activities of
the whole temporary reclamation authorized under SCL Protection Works would
take 2 months. As a conservative
assumption, the duration for filling the retained temporary reclamation is also
assumed to be 2 months in the model. The
dust emission rates for the filling activities are estimated based on a
conservative estimate of daily maximum percentage active works area of 20% for
predicting the annual TSP concentration.
5.32
The averaged emission rate of general construction activities for predicting the annual concentrations are summarised in Table 5.4.
Table 5.4 Averaged
Emission Factors for Dusty Construction Activities (For Annual TSP
Concentrations Prediction)
|
Emission Source |
Activity |
Emission
Rate |
Remarks |
|
Temporary
Reclamation/Tunnel Construction at |
Heavy Construction Activities |
E=2.69 Mg/hectare /month
of activity |
|
|
|
Wind
Erosion |
E=0.85Mg/hectare /year |
|
|
Retained Temporary
Reclamation – Filling (only for 2 months duration) |
Heavy Construction Activities |
E=2.69 Mg/hectare /month of activity |
|
|
|
Wind
Erosion |
E=0.85Mg/hectare /year |
|
5.33
The SCL Protection Works would be carried out
under the CWB project. The same working
hours of 10 hours per day was assumed for dusty construction during 08:00 to 18:00 in this assessment.
Wind erosion of open work sites was assumed to take place over the whole
day.
5.34
According to the updated information
presented in the Environmental Permit of WDII & CWB Project, the
construction period of the whole WDII & CWB Project is from 2010 to
2017. It is expected that the
construction of SCL Protection Works would only occur concurrently with the
construction of WDII & CWB project from 2012 to mid 2013. The short-term dust impact arising from the
construction of WDII & CWB in early 2012 (namely scenario 1 in this
assessment) and mid 2012 to early 2013 (namely scenario 2 in this assessment)
were predicted and presented in the approved WDII & CWB EIA Report. Therefore, for the purpose of predicting the
cumulative short-term (hourly and daily average) dust impacts, the contribution
of dust impacts from WDII & CWB at the ASRs were taken as the predicted
worst-case dust impacts at the respective ASR presented in the approved WDII
& CWB EIA Report.
5.35
However, annual average TSP concentrations
were not predicted in WDII & CWB EIA.
The annual TSP impact is therefore assessed by adding the WDII & CWB
dust emission sources to dust model of this Project. Based on the available construction programme
and plant inventory of WDII & CWB, an annual average active area of 6% and
watering on CWB work areas of TCBR1W and TPCWAE once per working hour were
assumed for predicting the annual concentrations. The
justification for the percentage of annual average active area is presented in Appendix 5.3. Detailed
calculations of the emission factors for WDII & CWB are presented in Appendix 5.4. According
to the WDII & CWB EIA, dust suppression measures shall be implemented, thus
emission factors of mitigated scenario are considered. The major dusty construction activities
located within the assessment boundary of SCL Protection Works during the period
interfacing with the Project were extracted from WDII & CWB EIA Report
Table 3.6 and its EP, EP-356/2009 as follows:
Table 5.5 Different Major Dust Generating
Activities in the Worst Scenarios during Construction Phase of WDII & CWB
|
Activities |
Scenario
1 |
Scenario
2 |
|
1 |
TCBR1E – CWB Tunnel |
TCBR1W – CWB Tunnel |
|
2 |
TCBR1W – CWB Tunnel |
TCBR2 – CWB Tunnel |
|
3 |
TCBR2 – CWB Tunnel |
TCBR3 – CWB Tunnel |
|
4 |
TPCWAE – CWB Tunnel |
TPCWAE – CWB Tunnel |
|
5 |
WCR1 – Drainage |
|
|
6 |
WCR1 – Cooling
Water |
|
Dispersion Modeling and
Concentration Calculation
5.36
Fugitive Dust Model (FDM) (1993 version) was
adopted to assess potential dust impact from the construction works. The worst case meteorological condition is
used to predict the maximum hourly and daily average TSP concentrations at
representative discrete ASRs in the vicinity of the construction sites which
are the same as those selected in the WDII & CWB EIA. Assessment heights are taken as 1.5m or the
lowest air sensitive level, and 5m above ground level.
·
Wind direction: 360 wind directions
·
Wind direction resolution: 1°
·
Stability class: D
(daytime, 8:00-18:00) & F (night time, 18:00-8:00)
·
Surface roughness: 1m
5.37
Daily TSP concentrations were calculated as
follows:
Daily TSP concentration = (number of working hour)/24 ´ (1-hour average maximum TSP concentration during working hours) +
(number of non-working hour)/24 ´ (1-hour average maximum TSP
concentration during non-working hours) + Background
5.38
For prediction of
the annual TSP concentrations due to the Project, hourly meteorological data
including wind speed, wind direction, air temperature and Pasquill
stability class from the Hong Kong Observatory for year 2008 were employed for
the model run.
5.39
No construction
activities would be operated on Sundays and the public holidays. Dust emissions from active construction
activities were assumed for the hours from 0800 to 1800 in the year excluding
Sundays and public holidays. Whereas for
the hours from 1800 to 0800 in the year and the hours during Sundays and the public
holidays, only dust emissions due to wind erosion were assumed.
5.40
As described in Sections 5.7 - 5.11 above, a background TSP level of 76.2 mg/m3 was
adopted to represent the future TSP background concentration.
Prediction and Evaluation of Dust Impacts
Unmitigated Scenario
5.41
The predicted unmitigated cumulative maximum hourly, daily average and annual TSP concentrations at the
representative ASRs during construction in scenario 1 and scenario 2 are summarized in Tables 5.6.
Table 5.6 Predicted Cumulative Maximum Hourly,
24-hour and Annual Average TSP Concentrations at Representative Air Sensitive Receivers
(Unmitigated)
|
ASRs |
Assessment
Height (mAG) |
Cumulative
Maximum TSP Concentrations
in mg/m3 |
|||||
|
Hourly Average |
24-hour Average |
Annual Average |
|||||
|
Sc.1 |
Sc.2 |
Sc.1 |
Sc.2 |
Sc.1 |
Sc.2 |
||
|
CHA1 |
1.5 |
734 |
734 |
362 |
362 |
78.0 |
78.0 |
|
|
5 |
640 |
658 |
319 |
326 |
77.6 |
77.7 |
|
CHA2 |
1.5 |
537 |
537 |
279 |
279 |
77.9 |
77.9 |
|
|
5 |
516 |
529 |
269 |
274 |
77.6 |
77.7 |
|
CHA3 |
1.5 |
387 |
387 |
215 |
215 |
77.1 |
77.2 |
|
|
5 |
370 |
382 |
206 |
211 |
77.0 |
77.1 |
|
CHA4 |
1.5 |
566 |
566 |
295 |
295 |
79.8 |
79.8 |
|
|
5 |
481 |
510 |
252 |
264 |
79.3 |
79.3 |
|
CHA5 |
1.5 |
1969 |
1969 |
894 |
894 |
84.5 |
84.4 |
|
|
5 |
1320 |
1350 |
608 |
620 |
79.7 |
79.7 |
|
CHA6 |
1.5 |
507 |
507 |
264 |
264 |
77.4 |
77.5 |
|
|
5 |
468 |
484 |
246 |
253 |
77.2 |
77.4 |
Notes: (1)
A
background TSP level of 76.2 mg/m3 has
been included in the above results.
(2)
The hourly, 24-hour and annual average TSP EIAO-TM /
AQO criteria are 500 mg/m3, 260mg/m3
and 80mg/m3 respectively.
(3) Boldfaced value presents the predicted TSP
concentration exceeding the respective criteria.
Abbreviations: Sc.1 Scenario
1
Sc.2 Scenario
2
5.42
Based on the results indicated in Tables 5.6, the
predicted cumulative maximum hourly and daily average TSP at most representative ASRs would exceed the criteria
in EIAO-TM and AQO. Hence, proper dust
mitigation measure should be implemented.
Recommended
Air Quality Mitigation Measures
5.43
In order to minimise the construction dust
impact, the following dust mitigation measures should be implemented:
Ÿ Watering
once every working hour on the temporary reclamation area of SCL Protection
Works to reduce dust emission by 91.7%[2]; and
Ÿ Covering/paving
the southwest retained area of temporary reclamation once filling is completed
5.44
In additional to
the dust mitigation measures described above, dust suppression measures stipulated in the
Air Pollution Control (Construction Dust) Regulation and good site practices
should be carried out to further minimize construction dust impact.
Ÿ Use of
regular watering, with complete coverage, to reduce dust emissions from exposed
site surfaces and unpaved roads, particularly during dry weather.
Ÿ Use of
frequent watering for particularly dusty construction areas and areas close to
ASRs.
Ÿ Side
enclosure and covering of any aggregate or dusty material storage piles to
reduce emissions. Where this is not
practicable owing to frequent usage, watering shall be applied to aggregate
fines.
Ÿ Open
stockpiles shall be avoided or covered.
Where possible, prevent placing dusty material storage piles near ASRs.
Ÿ Tarpaulin
covering of all dusty vehicle loads transported to, from and between site
locations.
Ÿ Establishment
and use of vehicle wheel and body washing facilities at the exit points of the
site.
Ÿ Provision
of wind shield and dust extraction units or similar dust mitigation measures at
the loading points, and use of water sprinklers at the loading area where dust
generation is likely during the loading process of loose material, particularly
in dry seasons/ periods.
Ÿ Provision of not less than 2.4m high hoarding from ground level along
site boundary where adjoins a road, streets or other accessible to the public
except for a site entrance or exit.
Ÿ Imposition
of speed controls for vehicles on site haul roads.
Ÿ Where
possible, routing of vehicles and positioning of construction plant should be
at the maximum possible distance from ASRs.
Ÿ Every
stock of more than 20 bags of cement or dry pulverised fuel ash (PFA) should be
covered entirely by impervious sheeting or placed in an area sheltered on the
top and the 3 sides.
Ÿ Instigation of an environmental monitoring and auditing program to
monitor the construction process in order to enforce controls and modify method
of work if dusty conditions arise.
Mitigated
Scenario
5.45
The predicted mitigated cumulative maximum hourly, daily average and annual TSP concentrations
at the representative ASRs during construction in scenario 1 and
scenario 2 are
summarized in Tables 5.7.
Table 5.7 Predicted Cumulative Maximum Hourly,
24-hour and Annual Average TSP Concentrations at Representative Air Sensitive
Receivers (Mitigated)
|
ASRs |
Assessment Height (mAG) |
Cumulative Maximum TSP
Concentrations in mg/m3 |
|||||
|
Hourly Average |
24-hour Average |
Annual Average |
|||||
|
Sc.1 |
Sc.2 |
Sc.1 |
Sc.2 |
Sc.1 |
Sc.2 |
||
|
CHA1 |
1.5 |
234 |
234 |
154 |
154 |
77.1 |
77.2 |
|
|
5 |
206 |
224 |
138 |
145 |
76.9 |
77.0 |
|
CHA2 |
1.5 |
180 |
180 |
131 |
131 |
77.0 |
77.0 |
|
|
5 |
169 |
182 |
124 |
129 |
76.9 |
76.9 |
|
CHA3 |
1.5 |
176 |
176 |
127 |
127 |
76.7 |
76.8 |
|
|
5 |
163 |
175 |
119 |
124 |
76.7 |
76.8 |
|
CHA4 |
1.5 |
327 |
327 |
195 |
195 |
78.9 |
78.9 |
|
|
5 |
250 |
279 |
156 |
168 |
78.5 |
78.4 |
|
CHA5 |
1.5 |
417 |
417 |
247 |
247 |
78.6 |
78.6 |
|
|
5 |
322 |
352 |
192 |
204 |
77.7 |
77.7 |
|
CHA6 |
1.5 |
206 |
206 |
139 |
139 |
76.9 |
77.1 |
|
|
5 |
185 |
201 |
128 |
135 |
76.8 |
77.0 |
Note: (1) A background TSP level of 76.2 mg/m3 has been included in the above results.
(2) The hourly, 24-hour
and annual average
TSP EIAO-TM / AQO criteria are 500 mg/m3, 260mg/m3
and 80mg/m3
respectively.
(3)
Boldfaced value presents the predicted TSP concentration exceed the respective
criteria.
Abbreviations: Sc.1 Scenario 1
Sc.2 Scenario 2
5.46
Based on the results indicated in Table 5.7, the cumulative maximum hourly, daily and annual average TSP levels at all ASRs
would comply with the criteria in EIAO-TM and AQO with implementation of
proposed dust mitigation measures. The
worst-hit level would be at 1.5m AGL. The contour plots
of cumulative maximum hourly, daily and annual average TSP concentrations
at 1.5m above ground level
for scenario 1 and 2 are presented in Figure
Nos. NEX2213/C/331/ENS/M60/502 –
NEX2213/C/331/ENS/M60/507. Marginal exceedance
of 24-hour and annual average TSP concentrations are predicted at part of the
building of POC in the contour plots, however, the building of the POC is
provided with central air conditioning and there is no fresh air intake at
these areas, i.e. no air sensitive areas are located within the exceedance areas.
Potential impacts at dwelling vessels within the CBTS have also been
examined for the purposes of being comprehensive as they do not have exact addresses and are movable
within the anchorage area. As known,
the area for dwelling vessels anchored within the CBTS would be at about 40m
setback from the temporary reclamation area.
No exceedance of 1-hour and 24-hour average
TSP concentrations is predicted at the anchorage area for the dwelling vessels
for the dwelling vessels due to the works under this Project. Marginal exceedances
of annual average TSP concentration are predicted at a relatively small part
outside the works area as shown in the contour plots, i.e. near the proposed
temporary jetty and along the southern works boundary. In view of the small
area and narrow navigation channel at these locations, the dwellings will
unlikely be anchored within these exceedance zones.
Also, in view of the fact that the dwelling vessels do not have exact addresses
and are movable within the anchorage area, the predicted annual average impacts
are not relevant.
Evaluation
of Residual Impacts
5.47
With the implementation of the recommended
mitigation measures as well as the dust suppression measures and good site
practices stipulated in the Air Pollution Control (Construction Dust)
Regulation, the predicted dust impact at ASRs would comply with the hourly,
daily and annual average TSP criteria in the EIAO-TM and AQO.
Environmental
Monitoring and Audit Requirements
5.48
Environmental monitoring and audit for dust
emission should be conducted during the construction phase of the Project so as
to check compliance with legislative requirements. Details of the monitoring and audit programme
are contained in a stand-alone EM&A Manual.
5.49
Potential air quality impacts from the
construction works for the Project would mainly be related to construction dust
from temporary reclamation, excavation, materials handling, spoil removal and
wind erosion. With the implementation of
the recommended mitigation measures as well as the dust suppression measures
and good site practices stipulated in the Air Pollution Control (Construction
Dust) Regulation, no adverse dust impact on the ASRs in the vicinity of the
construction sites would be anticipated.