Introduction
1.1.1
This Annex presents an assessment of
fugitive dust emission impact associated with the establishment, operation and
decommissioning of the proposed fill bank in Tuen Mun Area 38.
1.1.2
Based on the nature of the project,
potential dust emission impact was identified to be the key air quality issue
of interest. The fugitive dust
emission impact was evaluated further and presented here with quantitative
assessments using air quality modelling.
The assessment generally covers an area within 500m radius of the project
site, but has been extended to include dust emission sources associated with
the operation of the existing cement works located at more than 500m to the
west of the site in the assessment of potential cumulative dust impact. As the nearest residential development
is situated at more than 2 km from the fill bank, air quality impact on these
air sensitive receivers (ASRs) are unlikely. The ASRs of interest in this assessment are the existing and
planned factories situated in the vicinity of the fill bank.
1.1.3
With consideration of the preliminary
development programme of the fill bank and other concurrent planned
construction activities and operation of C&D material in the vicinity of
the site as shown in Figure A1, the following worst case representative
scenarios were identified and the potential dust impacts were assessed
quantitatively:
Scenario
1:
|
From
mid 2004 to late 2004 when there would be concurrent dust generation
activities associated with the operation/ decommissioning of the fill bank, together
with other offsite sources including construction works at the Recovery Park
Phase I, PAFF and operation of the C&DMRF, PBR2 Sorting Facility and
C&DMSF, and the existing cement works.
|
Scenario
2:
|
In
late 2004 after the commissioning of the Recovery Park Phase I (i.e. an ASR),
including the operation/ decommissioning of the fill bank, construction
activities at PAFF, and operation of C&DMRF, PBR2 Sorting Facility and
C&DMSF and the existing cement works.
|
Scenario
3:
|
From
late 2006 to Feb. 2008 when there would still be dust generation from the
decommissioning of the fill bank but with much reduced truck flows, sources
and strengths, and emissions from other sources including the operation of
the PBR2 Sorting Facility and C&DMSF and the cement plant. The Recovery
Park Phase II and PAFF will have commenced their operation (i.e. ASRs) under
this assessment scenario.
|
1.1.4
If the assessment results predicted
under these worst case assessment scenarios indicated that the planned dust
control measures are able to mitigate the dust impact to acceptable levels, it
is expected that the provision of these measures would be able to effectively
control the potential dust emission impact on the nearby ASRs to acceptable
levels under all other situations.
Assessment Criteria
2.1.1
The principal legislation regulating
air quality in Hong Kong is the Air Pollution Control Ordinance (APCO)
(Cap. 311). Air Quality Objectives
(AQOs) are set for the whole territory which specify statutory concentration
limits for various criteria pollutants and the maximum numbers of times allowed
to exceed over a specified period of time. The 24-hour and annual average Total Suspended Particulates
(TSP) objectives relevant to this study are 260 and 80 mg/m3 respectively.
2.1.2
In addition to the AQOs, EPD requires
for construction dust impact assessment under Annex 4 in the Technical
Memorandum on EIA Process (EIAO-TM) issued under the EIA Ordinance an
hourly TSP limit of 500mg/m3.
2.1.3
The Air Pollution Control
(Construction Dust) Regulation came into effect since 16 June 1997. Stockpiling of dusty materials;
loading, unloading or transfer of dusty materials; transfer of dusty materials
using a belt conveyor system; use of vehicles; debris handling, excavation or
earth moving, and site clearance, etc. are classified as “Regulatory Work”
under the Regulation. A Schedule, which specifies dust control requirements for
a variety of construction activities, is included in the Regulation. The contractor carrying out a
Regulatory Work is required under the Regulation to ensure that the dust
control measures required under the Regulation are being implemented.
Study Area and Air Sensitive Receivers
3.1.1
Figure A2 shows the area falling
within 500m radius of the project site.
The Project Site is a reclaimed land and is topographically flat. Representative Air Sensitive Receivers
(ASRs) situated nearest to the project site have been identified according to
the criteria set out in Annex 12 of EIAO-TM through site inspection and review
of relevant outline zoning plan with respect to individual scenarios. Table 3-1 summarizes the representative
ASRs identified and the representative assessment points (RAPs) selected for
the fugitive emission impact assessment in relation to the 3 assessment scenarios
described above. Locations of the
RAPs are as shown in Figure A3.
Table 3‑1 Air Sensitive Receivers located within the 500m
Study Area
|
Air
Sensitive Receiver
|
Nature
of Use
|
RAPs
|
Assessment
Scenario
|
|
1
|
2
|
3
|
|
River Trade
Terminal (Existing)
|
Industrial
|
A1 – A3
|
Ö
|
Ö
|
Ö
|
|
Shiu Wing
Steel Mill (Existing)
|
Industrial
|
A4 – A6
|
Ö
|
Ö
|
Ö
|
|
Recovery
Park Phase I building (Planned)
|
Industrial
|
A7
|
|
Ö
|
Ö
|
|
Recovery
Park Phase II building (Planned)
|
Industrial
|
A8
|
|
|
Ö
|
|
Permanent
Aviation Fuel Facility (PAFF) (Planned)
|
Industrial
|
A9
|
|
|
Ö
|
3.1.2
Amongst the identified representative ASRs,
the River Trade Terminal and Shiu Wing Steel Mill are existing land uses. RAPs, A1 through A6, have been selected
to represent these existing land uses.
3.1.3
According to the latest information
provided by DEP, the RPPI and RPPII would commence construction in mid 2004 and
mid 2006 respectively. These
planned industrial uses were assumed to be operational as early as in late 2004
and late 2006 as a conservative approach, and the potential dust impact was assessed
under Scenarios 2 (for RPPI) and 3 (for RPPI and RPPII). Based on the programme presented in the
EIA carried out for the PAFF approved in August 2002, the PAFF was also assumed
to be operational at the end of 2005 and the potential dust impact on the facility was
assessed under Scenario 3. Indicative
assessment points (A7 through A9) have been selected to represent these planned
land uses in the air quality modelling study. TSP concentrations were predicted at the RAPs at 1.5m, 4.5m
and 7.5m above ground.
3.1.4
To the north of Lung Mun Road there is
an area zoned as “Other Specified Use” annotated “Container Storage &
Repair Depot” under the Outline Zoning Plan No. S/TM/16. The site is vacant at present and
according to the Planning Department, there is currently no definite
implementation programme for this area.
4.
Baseline air quality
Baseline air quality
4.1.1
The fill bank site is situated in an
undeveloped, newly reclaimed land with some nearby industrial premises,
including Shui Wing Steel Mill and the River Trade Terminal, which are situated
within 500m of the site and other industrial operations including a cement
works and Castle Peak power station at further distance. The background TSP level resulted from
dust emissions from vehicular exhaust emissions as well as other industrial
sources in the region has also been assumed to be 87 mg/m3 by making reference to the EPD’s “Guidelines on
Assessing the ‘Total’ Air Quality Impacts”.
5.
dust emission sources
dust emission sources
Dust Emissions from the
Fill Bank
5.1.1
The principal sources of air pollution
associated with the operation/ decommissioning of the fill bank will include
dust emissions from truck movement on haul roads, wind erosion, and material
handling including the loading of public fill to the storage area and load out
of public fill from the fill bank.
Effective dust control measures have been derived based on the
requirements stipulated in the Air Pollution Control (Construction Dust)
Regulation to control these dust emission sources as presented in
Attachment I of the project profile.
These measures include standard practices as required under the
Regulation, as well as provision of a truckload control zone covering an area
of 100m x 100m at the north-eastern corner of the site. Restriction on number
of tucks travelling to that region would be imposed during the operation and
decommissioning of the fill bank to minimise dust generation and potential
cumulative air quality impact on the air sensitive land uses at the River Trade
Terminal (see Attachment I for details).
5.1.2
With the provision of the dust control
measures, the mitigated dust emission levels associated with the principal dust
emission sources have been estimated based on the typical emission factors
reported in the Complication of Air Pollutant Emission Factors (AP-42) 5th
Edition published by U.S. Environmental Protection Agency (USEPA),
and estimated dust control efficiency achievable with the dust control measures
presented in Attachment I. A
summary of the dust emission sources, estimated dust emission rates associated
with different types of sources, and the references in the USEPA AP-42 are
presented in Appendix I.
5.1.3
Usage frequency of the fill bank is
expected to vary in a similar way as the existing operation of the public
filling area at Tuen Mun Area 38.
Based on the existing data gathered in the operation of the public
filling area at Tuen Mun Area 38, peak hour public fill delivery truck traffic
is expected to occur before lunch time at 11:00 to 12:00 when the truckload
volume is predicted to reach its maximum of 13% of the daily truck flows. This gave an estimated public fill
delivery truck arrival rate of 156 vehicles/hr in 11:00 to 12:00, and an
average public fill delivery truck arrival rate of 109 vehicles/hr, which were
calculated from the maximum daily truck arrival rate of 1,200 vehicles/day for
the operational phase of the fill bank. During the operation-decommissioning
overlapping period, removal of all public fill from the site will be carried
out by barges at the PBR2 Sorting Facility. During the decommissioning period after the fill bank has
terminated to receive further public fill, the marine route will remain as the
major route for delivery of stockpiled material offsite. The barging points at
the PBR2 Sorting Facility will be used but an additional barging point with a
processing capacity of about 4,860 tonnes per day (i.e., 450 truckloads per
day) would be erected at the fill bank.
On a need basis, there would also be land-based delivery of stockpiled
fill material offsite by trucks and a truck flow of 50 vehicles per day was
assumed to be generated at Lung Mun Road. Both the daily average and highest
hourly number of trucks were considered in the air quality modelling in the
prediction of the highest 1-hour TSP concentrations and daily average TSP
concentrations at the RAPs for comparison with the 1-hour and 24-hour TSP
criteria, respectively.
Concurrent Dust Emission
Sources Offsite
5.1.4
During the operation/ decommissioning
of the fill bank, there will be other dust emission sources offsite generated
from:
·
the operation of the existing
Construction and Demolition Material Recycling Facility (C&DMRF) located to
the north-west of the site;
·
the operation of the temporary public
fill sorting facility for Penny’s Bay Reclamation Stage 2 (PBR2 Sorting
Facility) located to the south-east of the site;
·
the operation of the temporary
Construction and Demolition Material Sorting Facility (C&DMSF) located to
the immediate east of the PBR2 Sorting Facility;
·
dust generating construction
activities at Recovery Park Phase I located to the immediate west of the site;
·
dust generating construction
activities associated with the construction of Recovery Park Phase II located
within the fill bank site;
·
dust generating construction
activities associated with the construction of the Permanent Aviation Fuel
Facility (PAFF) located to the west of the site;
·
dust generated from the operation of
the existing cement works located at more than 500m to the west of the site.
5.1.5
While the contractors of these nearby
construction sites and operations would be required to control fugitive dust
emissions in accordance with the requirements of the relevant regulation and/or
guidelines, the potential cumulative dust emission impact on the ASRs have been
assessed by estimation of the mitigated dust emission rates associated with
these sources. Figure A1 shows the
activity periods associated with each of these offsite activities in relation
to the identified assessment scenarios 1, 2 and 3.
5.1.6
The temporary C&DMSF is planned to
receive mixed C&D material containing an average of about 50% waste. A vehicular access to the temporary
C&DMSF will be provided along the eastern boundary of the fill bank. The
access will be retained for the sole use of the C&DMSF and will not serve
as access to the fill bank, the PBR2 Sorting Facility and the C&DMRF. The
sorted public fill will be transported to the fill bank and the separated waste
material will be delivered to landfill for proper disposal. Similar direct vehicular access to the
PBR2 Sorting Facility will not be provided to minimise the potential cumulative
dust impact on the air sensitive land uses of the nearby River Trade
Terminal. The PBR2 Sorting
Facility will receive public fill delivered from the fill bank site. Operation of the both sorting facilities
would primarily involve dust emissions generated from truck movement, loading
and unloading activities. The
pre-sorting and sorting areas provided for temporary storage of material would
be enclosed at least on three sides to minimise wind erosion. The main screens at the sorting
facilities will be housed in enclosed structures served by bag filters. Operation of the existing C&DMRF
involved the intake of large sized inert C&D material for crushing and
sorting to produce aggregates for reuse.
Major dust would be generated from activities including loading to the
receiving hoppers, crushing and screening activities, unloading to the storage
piles, and wind erosion associated with the stockpiles.
5.1.7
Based on the design processing
capacity of 2,400 tonnes/day, 9,000 tonnes/day and 600 tonnes/day in the
operation of the C&DMRF, PBR2 Sorting Facility and C&DMSF,
respectively, the dust emission rates associated with truck movements, material
handling (primarily loading/ unloading activities), crushing, screening and
mixing activities, where applicable at these facilities were estimated based on
the dust emission factors presented in USEPA AP-42 accordingly. Dust emissions associated with the
construction works at PAFF and RPPI were estimated with consideration of the
estimated quantity of excavated material handled. Wind erosion associated with stockpiling of significant
quantity of material on exposed surface at the C&DMRF, PAFF and RPPI were
estimated and considered in the model.
Details of the dust emission sources, the estimated dust control
efficiency, mitigated dust emission rates, and the references in USEPA AP42
associated with these dust emission sources offsite are also presented in
Appendix I.
5.1.8
Dust emissions associated with the
operation of the cement works were predicted by making reference to the
emission limits specified as licence conditions for the operation of the cement
works available at EPD (local control office).
Dust Emission Modelling
6.1.1
The potential cumulative dust impact
on the ASRs arising from the operation/ decommissioning of the fill bank, as
well as the other concurrent dust emission sources has been assessed using the
air quality model Fugitive Dust Model (FDM). Dust emissions from the existing cement works were estimated
using the air quality model Industrial Source Complex – Short Term (ISCST3).
The models were developed based on the widely used Gaussian plume formulae for
estimation of pollutant concentrations and designed to predict dispersion of
particulate from point, line, area and volume sources.
Taking into account the nature of the activities, dust emissions from
truck movement on paved/ unpaved roads were modelled as line sources, material
handling as multiple point sources or area sources, and wind erosion as area
sources.
6.1.2
The following relevant meteorological
data of the year 2001 were obtained from Hong Kong Observatory and used in the
air quality modelling study. Parameters used include:
·
Hourly wind direction and speed, air temperature
together with atmospheric Pasquill stability class obtained at Tuen Mun
Automatic Weather Station;
·
Daily morning and maximum mixing
heights based on the radiosonde ascent at King’s Park; and
·
Hourly total sky cover, cloud amount
and cloud based height of the 1st - 4th layers observed at the Hong Kong
International Airport in Chep Lap Kok
6.1.3
The fill bank is planned to be in
operation daily from 8:00 a.m. to 8:00 p.m. The dust concentrations predicted at the RAPs would be over
estimated if dust emissions associated with all activities at the fill bank and
the nearby facilities are considered to be present 24 hours a day in the air
quality modelling. Therefore, in
the prediction of the cumulative 24-hr TSP levels using the FDM and ISCST
modelling, it was assumed in the FDM modelling that, except for dust emissions
associated with wind erosion, all other activities and associated dust
emissions were restricted to 8:00 a.m. to 8:00 p.m. Dust emission rates were calculated based on the daily
averaged truck volume and activity levels. Similarly, the ISCST model was
carried out taking into account the hours when activities associated with the
various dust emission sources at the cement works are expected. The highest 24-hr average TSP
concentrations predicted by the FDM and ISCST modelling under Scenarios 1, 2
and 3 were modelled and reported.
The summation of the 24-hr TSP concentrations modelled by the FDM and
ISCST models at each RAP, after adding the background TSP level, represent the
highest 24-hr TSP concentrations predicted at the RAPs under the worst-case
situations.
6.1.4
Number of public fill delivery trucks
arriving at the fill bank will vary as experienced in the operation of the
existing public filling area at Tuen Mun Area 38 and other public filling areas
in the past. The existing data
collected in the past 12 months revealed that truck volume varied from an
average of 5.1% to 12.2% during the operating hours 8:00 a.m. to 6:00 p.m., and
drop to 0.5% to 4.7% during the operating hours 6:00 p.m. to 8:00p.m. The highest truck flows recorded
occurred between 11:00 and 12:00.
The variation in truck flows reflects the typical work pattern of the
construction industry and associated public fill delivery.
6.1.5
To predict the highest 1-hr TSP
concentrations at the RAPs under each Scenario 1 through 3, two separate models
were set up in both the FDM and ISCST modelling:
(i)
Day Time Hours : the first set of
model assessed worst-case dust emission levels during the daytime hours from
8:00 a.m. to 6:00 p.m. Maximum
dust emission levels associated with the sources at the fill bank, PBR2 Sorting
Facility, C&DMSF and C&DMRF were estimated based on the peak activity
hour (i.e. 11:00 to 12:00) when the incoming land-based public fill delivery
truck flow is expected to reach 13% of the daily maximum flow of 1,200 vehicles
per day. The ISCST modelling was
carried out accordingly for the same modelling hours. Meteorological conditions encountered during the daytime
hours, including typical Pasquill stability classes (A through D), were
considered in the modelling run through adopting the data obtained from Hong
Kong Observatory in year 2001;
(ii)
Evening Time Hours: the second set of
model assessed worst-case dust emission levels during the evening hours from
6:00 p.m. to 8:00 p.m. Maximum
dust emission levels associated with the sources at the fill bank, PBR2 Sorting
Facility, C&DMSF and C&DMRF were estimated assuming similar level of
public fill delivery by barges but much reduced land-based public fill delivery
trucks i.e. 5% of the daily maximum flow of 1,200 vehicles per day. The ISCST modelling was carried out
accordingly for the same modelling hours.
Meteorological conditions encountered during the evening hours,
including typical Pasquill stability classes (D through F), were considered in
the modelling run through adopting the data obtained from Hong Kong Observatory
in year 2001
6.1.6
The 1-hr TSP concentrations predicted
by the two sets of models were then compared and the highest 1-hr TSP
concentrations predicted by the models were then reported. At RAPs A1 though A3, which are located
at similar downwind directions of all sources, the 1-hr TSP concentrations
predicted by the FDM and ISCST models were considered to be directly additive
to give the worst case highest 1-hr TSP concentrations at these RAPs. At RAPs A4 through A9, the 1-hr TSP
concentrations predicted by the FDM and ISCST models under the daytime and
evening hours were compared for each RAP, and the maximum 1-hr concentrations
predicted were reported as the highest 1-hr TSP concentrations at that RAP.
Air Quality Modelling Results
7.1.1
The mitigated highest 1-hour TSP
concentrations and 24-hour average TSP concentrations predicted by the FDM and
ISCST models at the RAPs under the 3 scenarios studied are presented in Table
7-1.
With the addition of the background TSP concentrations, the overall 1-hr
and 24-hr TSP concentrations are reported. As discussed above, the highest 1-hr TSP concentrations at
RAPs A1 through A3 were predicted by summation of the FDM and ISCST modelling
results. The maximum highest 1-hr
TSP concentration was predicted to be 478mg/m3 at A2 under both Scenarios 1 and
2. The highest 24-hr TSP
concentration was predicted to be 181mg/m3 under Scenario 1 at A5. Appendix II presents the typical FDM
and ISCST modelling result files.
7.1.2
Figure A4 through
Figure A9 present the pollutant isopleths for highest 1-hr TSP and 24-hr
average TSP generated from FDM and ISCST modelling results obtained at regular
grid points. Similar to the approach adopted in the prediction of the highest
1-hr TSP concentrations at A1 through A3, the 1-hr TSP concentration contours
modelled at the grid points on the eastern side of the site were predicted by
summation of the FDM and ISCST modelling results, while for the grid points
located on the western side of the fill bank, the 1-hr TSP concentrations
obtained by the FDM and ISCST models at each grid point were compared, and the
highest value was adopted in the preparation of a separate 1-hr TSP pollutant
contour map for the study area to the west of the fill bank.
7.1.3
The air quality
modelling undertaken based on consideration of worst case situations revealed
that, with the implementation of the recommended dust control measures, the
mitigated TSP concentrations should be controlled to within the 1-hr and 24-hr
TSP criteria.