4.1 Introduction
4.1.1 This section presents an assessment of air quality impacts associated
with the construction (qualitative) and operation (quantitative) of the
recreational and residential development proposed at Whitehead and Lee
On area (the Project). Worst-case impacts (i.e. based on the preliminary
Preferred Development Option) on the representative Air Sensitive Receivers
(ASRs) have been assessed. Three major sources of air pollution have been
identified namely construction dust emission, road traffic emissions and
industrial emissions. The sources of air pollutants at the different phases
of the development are categorized as follows:
i) Construction Phase: Construction works include site clearance,
site formation, building works, infrastructure provision and any other
infrastructure activities. The major temporary air pollution is dust generated
as a result of these construction works.
ii) Operational Phase: The major permanent sources of air
pollutants are the vehicle emission from traffic on major roads and the
air pollutants emitted from the vicinity of the industrial stationary
sources. Vehicular emissions from the roads surrounding the Project, including
the future Road T7, widened Sai Sha Road and all internal roads are considered.
Chimneys emissions associated with nearby industrial premises are the
stationary air pollutant sources.
4.2 Air Quality Assessment Criteria
4.2.1 The principal legislation regulating air emissions in Hong Kong
is the Air Pollution Control Ordinance (APCO) [Cap 311] of 1983 and its
subsidiary regulations, and Technical Memorandum on Environmental Impact
Assessment Process (TMEIA). The whole Hong Kong has been covered by Air
Control Zones. The Hong Kong Air Quality Objectives (AQOs) stipulate maximum
acceptable concentrations of four major air pollutants: nitrogen dioxide
(NO2); sulphur dioxide (SO2), total and respirable suspended particulates
(TSP and RSP). The ambient standard for hourly, daily and annual concentrations
of these pollutants are shown in Table 4.1
Table 4.1
Hong Kong Air Quality Objectives (AQOs)
|
Pollutants
|
Concentration in Micrograms per Cubic Metre (m
g/m3)A
|
|
Averaging Time
|
|
1 hourB
|
24 hourC
|
1 yearD
|
|
Nitrogen Dioxide (NO2)
|
300
|
150
|
80
|
|
Sulphur Dioxide (SO2)
|
800
|
350
|
80
|
|
Total Suspended Particulates (TSP)
|
500E
|
260
|
80
|
|
Respirable Suspended Particulates (RSP)F
|
-
|
180
|
55
|
Notes:
A Measured at 298k (25ºC) and 101.325 kPa (one atmosphere).
B One hour criteria not to be exceeded more than three times per year.
C 24 hour criteria not to be exceeded more than once per year.
D Arithmetic means
E This control limit has no statutory basis but is used as a target level
for limiting fugitive dust emissions generated by construction activities.
F Respirable suspended particulates means suspended particles in air with
a nominal aerodynamic diameter of 10 micrometer (mm) or smaller.
4.2.2 There are no statutory criteria for maximum levels of odours in
Hong Kong. EPD's recommended an odour nuisance criterion is 5 odour units
(OUs) based on averaging time of 5 seconds at the sensitive receiver.
4.3 Study Area
4.3.1 The Project is located in the Shatin
- Sai Kung Corridor about midway between Sha Tin Town and Sai Kung Town
and to the east of Ma On Shan area.
4.3.2 Majority of land in this area is used for residential development
(public estate and private residential development), car park, small farm
and scattered villages. No major industrial activities are found within
the Study Area. Sai Sha Road is the major road passing the centre part
of the Study Area. Thus, the major air pollutant source is vehicular emissions
from the roads.
4.4 Baseline Conditions
Meteorology and Topography
4.4.1 The Study Area is located in a meteorological confined area, the
Tolo Airshed where only gaseous fuel is permitted under the Air Pollution
Control (Fuel Restriction) Regulation. Therefore, the majority of the
air pollutants are emitted from the moving vehicles, particularly the
diesel trucks and heavy vehicles.
4.4.2 Figure 4.1 illustrates the wind conditions at Shatin station. The
dominant wind direction is northeasterly due to the channelling effect
associated with the Sha Tin Valley.
Existing Air Quality
4.4.3 The baseline air quality data within the Study Area has been based
on the EPD's monitoring station in Shatin. According to "Air Quality
in Hong Kong (2000)", the concentration levels of NO2, SO2, TSP,
RSP and O3 at Shatin are shown in Table 4.2:
Table 4.2
Measured Concentrations at Shatin EPD Station (2000)
|
Pollutant
|
Hourly
|
Daily
|
Annual
|
|
Maximum
|
AQO
|
Maximum
|
AQO
|
Average
|
AQO
|
|
TSP
|
N/A
|
500
|
223
|
260
|
58
|
80
|
|
RSP
|
N/A
|
N/A
|
164
|
180
|
46
|
55
|
|
NO2
|
254
|
300
|
146
|
150
|
46
|
80
|
|
SO2
|
185
|
800
|
72
|
350
|
18
|
80
|
|
O3
|
265
|
240
|
N/A
|
N/A
|
N/A
|
N/A
|
Notes: N/A means Not Applicable
Concentration in micrograms per cubic metre (µg/m³)
4.4.4 The table indicates that the concentration of SO2 is well below
the AQO. The short-term and long-term maximum concentration of NO2, TSP
and RSP are below the AQOs.
4.4.5 The fairly high concentration of NO2, TSP and RSP was mainly contributed
by heavy traffic in the Shatin area. The construction of the Ma On Shan
(MOS) Rail also increase the particulates concentration in the regional
area.
Future Air Quality
4.4.6 From the latest findings of the Third Comprehensive Transport Study
(CTS3), the projection of future baseline air quality data at Shatin Station
is used. According to CTS3 Study, the annual average concentrations of
nitrogen dioxide (NO2) and Respirable Suspended Particulates (RSP) are
predicted to be 52.4 mg/m3 and 55.0 mg/m3 respectively for the high growth
scenario in 2016. This worst case scenario gives rise to an increase of
around 6.4 mg/m3 for NO2 and 9 mg/m3 for RSP in comparison with EPD's
monitoring data at Shatin in 2000. As the predicted future concentration
of sulphur dioxide (SO2) is not available in CTS3, the data from EPD's
Shatin Station (18 mg/m3) is assumed for this assessment.
4.5 Representative Air Sensitive Receivers
4.5.1 The representative air sensitive receivers (ASRs) within the Study
Areas will represent the future and existing sensitive receivers likely
to be affected by the Project. They are described in detail under the
noise chapter.
4.6 Construction Impact
Introduction
4.6.1 The principal potential source of air quality impact arising from
the construction of the Project will be fugitive dust. The temporary dust
nuisance, measurable as Total Suspended Particulates (TSP) and Respirable
Suspended Particulates (RSP), would be generated as a result of construction
activities during the construction phase of the Project.
4.6.2 The construction programme of the Project is yet to be finalized.
Tentatively, the construction programme is likely to commence in 2003
and completed in 2008. Thus the construction period is expected to last
for about six years. It is noted that the site formation for the Wu Kai
Sha (WKS) station development is not part of this Project. The station
development will be constructed on the platform of the MOS Rail - Wu Kai
Sha Station, which is currently under construction by KCRC.
4.6.3 The potential dust sources associated with construction activities
is likely to be generated from loading and unloading, top soil removal,
travel over dirt roads and wind erosion. Concrete batching plants and
rock crushing plant with a processing capacity exceeds 5,000 tonnes per
annum are not necessary for this Project. Blasting is not required. However,
stockpiling areas and working areas may be required.
Construction Programme
4.6.4 The construction works associated with the development are broadly
divided into three categories:
(i) Wu Kai Sha Station residential development - (2002-2006);
(ii) Site formation and infrastructure works - (2003-2008); and
(iii) Residential development at Lok Wo Sha and Whitehead and Recreation
development - (2004 - 2008).
4.6.5 Among all construction activities, site formation has the highest
potential of causing dust nuisance to the nearby ASRs. In brief, the site
formation works will commence in 2003 and likely to be finished by 2004.
Representative Air Sensitive Receivers
4.6.6 During the construction of the Project, some existing
residence may be subject to the potential construction dust impacts. Table
4.3 shows these air sensitive receivers and the shortest distance between
the ASRs and the construction areas. The location of the sensitive receivers
is shown in Figure 3.4.1 of Chapter 3 (Noise Impact Assessment).
Table 4.3
Representative ASR around the Project during Construction Phase
|
ASR
|
Status *
|
General Description
|
No. of Storey
|
Shortest Distance to the boundary of Construction
area (m)
|
|
1
|
E
|
Village house in To Tau
|
1
|
45
|
|
2
|
E
|
Village house in Lok Wo Wu Kai Sha
|
3
|
65
|
|
3
|
E
|
Li Po Chung United World College
|
3
|
65
|
|
4
|
E
|
Block 1, Symphony Bay
|
5
|
50
|
|
5
|
E
|
Village house at Cheung Muk Tau
|
3
|
150
|
|
6
|
E
|
Block 15, Monte Vista
|
30
|
20
|
|
7
|
F
|
Wu Kai Sha Station development
|
50
|
55
|
Note:
* E - Existing ASR; F - Future ASR.
Assessment Results
4.6.7 The residential buildings of the Wu Kai Sha Station development
will be build on the platform of the Wu Kai Sha station. The platform
is currently being constructed during the construction of MOS Rail. Thus,
no further site formation works will be required for Wu Kai Sha station
development.
4.6.8 For the Lok Wo Sha development, the site formation work will be
conducted by the private developer. As the existing ground level of the
Study Area is averaging at 6 mPD, the proposed site formation level will
likely to be ranging from 7 to 9 mPD based on a balanced out and fill
approach, resulting in relatively less quantity of excavation. In addition,
currently majority area of the existing Lok Wo Sha have been leveled for
purpose of carpark use and thus no extensive site formation is expected
to be required.
4.6.9 Under this Project, site formation work will be conducted by Government
at the Whitehead Sites 1, 2 and 3, the school sites at Whitehead, and
all the proposed roads. As the existing landuses for the Whitehead Sites
1 to 3 and proposed schools are golf course and previous detention camp,
extensive site formation work is unlikely required. According to the engineering
assessment, most of the excavated material can be reused within the Project.
The movement of the cut and fill materials within the Project is summarized
in Table 4.4. With the reuse of excavated material, there will be limited
fill material required to be imported for site formation. Broad estimation
shows that there would likely be no more than 50 to 70 trucks moving out
or in materials from the construction site within a day.
Table 4.4
Movement of Cut and Fill Material within Project
|
Site
|
Cut (cu.m)
|
Fill (cu.m)
|
Net (cu.m)
|
|
Whitehead Site 1
|
85,822
|
92,173
|
(6,352)
|
|
Whitehead Site 2
|
73,380
|
46,309
|
27,071
|
|
Whitehead Site 3
|
35,282
|
83,554
|
(48,273)
|
|
Central Spine
|
12,780
|
7,797
|
4,983
|
|
Schools at Whitehead Site 3
|
12,030
|
12,893
|
(863)
|
|
Road L1
|
23,443
|
15,615
|
7,828
|
|
Road D1
|
1,090
|
94,134
|
(93,044)
|
|
Total
|
243,826
|
352,475
|
(108,649)
|
Note : number in bracket means import material quantity
4.6.10 Most of the construction dust will be generated from the movement
of construction vehicles on dirt roads. Uploading and removal of spoil
material will also be the potential source for dust nuisance. According
to the preliminary site investigation, the moisture content of the material
to be excavated will be relatively low. Thus the most direct and effective
dust suppression measures are regular watering or the pavement of main
haul roads within each individual site formation area. With the help of
regular watering over all the exposed area, at least twice a day, a 50%
reduction on the dust contribution from the exposed surface can be reduced.
However, it is our experience from other similar sites in Hong Kong when
undertaking the Environmental Monitoring and Audit Phase that a much more
acceptable degree of dust suppression can be achieved. For example, the
pavement of haulage can further reduce the potential dust nuisance. With
the aid of regular watering and haulage pavement, the construction dust
levels at representative ASRs, hence all nearby ASRs, will likely to be
complied with the requirement of AQOs.
4.6.11 Construction of drains, sewers and water mains will require excavation
of trenches. Laying these new infrastructures are likely to be conducted
section by section, thus the quantity of the excavated material is unlikely
to be large enough to cause dust nuisance. It is anticipated that excavated
material will only be stockpiled on each local works area. The duration
of stockpiling will be as short as possible as most of the material will
be used as backfill material for the open cut trenches. Given the limited
scale of construction works and with the implementation of proper standard
dust suppression measures, no adverse impact is expected and compliance
with the AQOs is achieved at ASRs at all time.
4.6.12 Construction of building blocks and recreation facilities should
not generate excessive dust, as the construction works are mainly associated
with framework and concrete pouring. Leveling, compacting and resurfacing
new areas within these developments will not involve significant material
movement. Hence dust impacts will be insignificant. Proper watering of
exposed dirt will be undertaken throughout the construction phase and
dust generation will be minimized. It is expected that compliance with
the AQOs can be achieved at ASRs at all time.
Dust Mitigation Measures
4.6.13 In order to comply with Air Pollution Control Ordinance (APCO),
the Contractor should at all times prevent dust nuisance as a result of
his activities. The Contractors are required to follow all the requirements
for dust control stipulated in the Air Pollution Control (Construction
Dust) Regulation. Site formation works are likely to cause short-term
unacceptable dust impacts on all of the representative ASRs close to the
Project development. Therefore, dust suppression measures, such as regular
watering the exposed area and haulage pavement, should be installed as
part of good construction practice, and they should be incorporated in
the Contract Specification and implemented to minimize dust nuisance to
within acceptable levels arising from the works. Measures which are employed
to minimize impacts on sensitive receivers in the Study Area are also
relevant for the protection of ecologically sensitive areas. Other dust
suppression measures are highlighted below:
(i) The Contractor shall observe and comply with the Air Pollution Control
Ordinance and its subsidiary regulations, particularly the Air Pollution
Control (Construction Dust) Regulation.
(ii) The Contractor shall undertake at all times to prevent dust nuisance
as a result of his activities. Effective dust suppression measures shall
be employed to ensure that the air quality, at the boundary of his site
and at any ASRs, complies with the Hong Kong Air Quality Objectives.
(iii) The Contractor shall ensure that there will be adequate water supply
/ storage for dust suppression purposes.
(iv) The Contractor shall frequently clean and water the site to minimize
fugitive dust emissions.
(v) Effective water sprays shall be used during the delivery and handling
of aggregate, and other similar materials, when dust is likely to be created
and to dampen all stored materials during dry and windy weather.
(vi) Watering of exposed surfaces shall be exercised as often as possible
depending on the circumstance.
(vii) Areas within the site where there is a regular movement of vehicles
shall be regularly watered.
(viii) Where dusty materials are being discharged to vehicle from a conveying
system at a fixed transfer point, a three-sided roofed enclosure with
a flexible curtain across the entry shall be provided. Exhausted fans
shall be provided for
this enclosure and vented to a suitable fabric filter system.
(ix) The Contractor shall restricted all motorized vehicles within the
site, excluding those on public roads, to a maximum speed of 15 km per
hour and confine haulage and delivery vehicles to designated roadways
inside the site.
(x) Wheel washing facilities shall be installed and used by all vehicles
leaving the site (Figure 4.2). No earth, mud, debris, dust and the like
shall be deposited on public roads. Water in wheel cleaning facility shall
be changed at frequent intervals and sediments shall be removed regularly.
The Contractor shall submit detailed proposals for the wheel cleaning
facilities to the Engineer prior to construction of the facility. Such
wheel washing facilities shall be usable prior to any earthworks excavating
activity on the site. The Contractor shall also provide a hard-surfaced
road between any washing facility and the public road.
(xi) The Contractor shall devise, arrange methods of working and carrying
out the works in such a manner so as to minimize dust impacts on the surrounding
environment, and shall provide experienced personnel with suitable training
to ensure that these methods are implemented.
(xii) All site vehicles' exhausts shall be directed vertically upwards
or directed away from the ground.
(xiii) Any stockpile of dusty material shall be either: (a) covered entirely
by impervious sheeting; (b) placed in area sheltered on the top and the
three sides; or (c) sprayed with water or a dust suppression chemical
so as to maintain the entire surface wet.
Cumulative Impacts
4.6.14 Projects that have potential cumulative construction
dust impacts would be works due to MOS Rail and Road T7. The construction
of these two projects is currently being undertaken. It is anticipated
that most of the site formation works of the two projects should have
been completed in 2004. Therefore, potential cumulative dust impact from
these projects is minor.
Monitoring and Audit Requirement
4.6.15 Air quality monitoring should be carried out at selected ASRs
during the construction period to monitor compliance with AQOs for the
construction activities being undertaken for the proposed development.
Monitoring is also required to check the effectiveness of the recommended
mitigation measures. Ad-hoc monitoring and audit
should also be carried out at other ASRs in case of complaints, and measures
taken to ensure acceptable dust levels are met as far as possible.
4.6.16 It is recommended that the following representative ASRs be monitored
during construction stage of the Project development. These ASRs are selected
to represent a particular area likely to be worst affected by the construction
works.
· ASR 1 (To Tau Village)
· ASR 3 (Li Po Chun United World College)
4.6.17 Details of the monitoring and audit for construction dust are
presented in the separate EM&A Manual.
4.7 Operational Impact
Operational Impact Assessment
Introduction
4.7.1 During the operational phase of the Project, two major sources of
air pollution have been identified in the neighbourhood of the site. The
first source is vehicular exhaust from the road traffic in and around
the Study Area. The second source is emission from chimneys in the immediate
area.
Vehicular Emission
4.7.2 One of the major sources of potential air pollution is the vehicular
emission from traffic. In this assessment, the predicted traffic flow
in the year 2023 has been used. Traffic emission impacts has been undertaken
using CALINE4. The emissions from the predicted traffic flows on the following
major roads have been modelled, namely future Road T7, Sai Sha Road and
nearby internal roads.
4.7.3 The traffic air pollution is mainly from NO2 and RSP. Only maximum
hourly concentrations of NO2 and the maximum daily concentration of NO2
and RSP need assessment to check the compliance with the AQOs. These are
predicted using CALINE4.
Assessment Methodology
(a) The assessment has been based on the 2023 traffic flow
data provided by traffic consultant. A detailed breakdown of the types
of vehicles is given in Table D1 of Annex D in terms of the percentage
of passenger cars (%P.Car), taxi (%taxi), public bus (%PuBus), private
bus (%PrBus), public light bus
(%PuLB), light goods vehicle (%LGV), medium goods vehicles (%MGV) and
heavy goods vehicles (%HGV) plus the emission rates of RSP and NO2.
(b) Gases have been assumed to be inert, and concentrations of NO2 have
been taken as 20 percent of the total NOx concentration.
(c) The assumed vehicular emissions factor for pollutants such as particulates
and NO2 in the year 2011 have been supplied by the Vehicle Emission Control
Section of EPD. These factors originated from the USEPA MOBILE IV program.
The emission factors in 2023 are extrapolated from these data and are
assumed to be same as the emission factor of heavy vehicle is predicted
to be levelling off after 2008.
(d) The following worst-case meteorological conditions have been assumed:
Wind speed : 1 m/s at 10m height
Wind direction : (worst case for individual receiver)
Stability class : D
Mixing height : 500m
(e) The associated noise barriers of the future widened Sai Sha Road
and that of Road T7, which is currently being constructed, have been taken
into account in the assessment. This assessment assumes that the source
of the air pollutants will be evaluated from the road surface to be on
top of the proposed barriers.
(f) The background concentrations of pollutants have been based on the
modelling results of CTS-3 Report under the high growth scenario, i.e.
the background concentration of NO2 and RSP are 52.4 and 55.0 µg/m³
respectively.
(g) As a conservative approach, a conversion factor 0.6 is used to calculate
the daily air pollutant concentration from hourly value.
Vehicular Emission (NO2 and RSP) Impacts
4.7.4 The traffic impact assessment shows that the majority of traffic
and the heavy vehicle (HV) within the Study Area will flow along the major
highways namely Road T7 (5610 veh/hr and about 11.2% of HV) and Sai Sha
road (2060 veh/hr and 11.2% of HV). In comparison, the traffic predictions
of the internal local roads within the Project are relatively less, ranging
from 140 to 1010 veh/hr with about 10-20 % Heavy Vehicle. Therefore, it
is expected that Sai Sha Road and Road T7 would constitute the most air
quality impact associated with the traffic emission.
4.7.5 Figures 4.3 to 4.5 show the predicted concentration
of NO2 and RSP in the Study Area at pedestrian level. The contour plots
show that buffer distance between the major highways and the surrounding
residential areas is adequate to alleviate the vehicular emission impacts.
The predicted NO2 and RSP concentration levels at the representative ASRs
are shown in Table D2 (including background NO2 and RSP concentrations)
of Annex D. It is expected that the hourly and daily NO2 concentrations
and daily RSP concentrations of the ASRs in the Study Area will comply
with the AQOs.
Vehicle Exhaust Emission from proposed Underpass
4.7.6 In this Project, a section of Road L1 of about 80m in length will
be depressed to create a pedestrianized area near the proposed recreational
site (Figure D1 of Annex D). As it is less than 230m in length, no mechanical
ventilation system would be provided for the underpass and thus the underpass
air pollutants will be dispersed via the underpass portal.
4.7.7 For the worst-case scenario of air quality within the underpass,
a congested condition is considered i.e. traffic moving slowly and the
separation between vehicles is assumed to be 1m. For the worst-case scenario
of air quality due to the openings of the depressed road, traffic pollutants
are assumed to be emitted from both ends of the underpass (portal).
Representative Air Sensitive Receivers
4.7.8 The major landuses around the depressed Road L1 are the pedestrianised
area and low-rise residential developments. The details of the representative
air sensitive receivers (rASRs) are shown in Table 4.5 and on Figure D1
of Annex D.
Table 4.5
Description of the Representative Sensitive Receivers (rASRs)
|
rASRs
|
Landuse
|
Floor
|
|
1
|
Low-rise Residential Development
|
Pedestrian Level
|
|
2
|
Visitor Centre
|
Pedestrian Level
|
Methodology
4.7.9 In the absence of mechanical ventilation, the exhaust gases emitted
from the portal of the depressed road will be dragged out by cars leaving
the portal. The ISCST3 air dispersion model has been used to assess the
impact due to the portal emission on the surrounding area.
4.7.10 In the air quality model, it was assumed that the
open road emission would behave as line sources in accordance with the
procedure stated in the Section III of the Permanent International Association
of Road Congresses (PIARC), 1991. The sources of the portal emission have
been modelled as a line source represented by adjacent area sources. The
length of the line source was taken as 100m at each opening of the depressed
road. As there is no force ventilation, it is assumed that half of the
air pollutants' concentration inside the decking will be emitted out from
each opening. It is also assumed that 1st half of 100m consists of 2/3
of the emitted mass and 2nd half of 100m consists of 1/3 of the emitted
mass. Annex D1 shows a calculation. Similar to road emission, it is assumed
that 20% of NOx will be converted to NO2.
4.7.11 In addition to the portal emission, the sensitive receivers near
Road L1 will also be impacted by the traffic emission from the nearby
roads. This assessment has calculated the cumulative NO2 concentration
at the rASR from portal emission and road emission. The methodology used
for the traffic emission calculation is based on the CALINE4 model. It
is assumed that 20% of NOx will be converted to NO2.
4.7.12 The associated NO2 emission rate are thus calculated and shown
in Table 4.6 together with the physical parameters of each decking section.
Table 4.6
NO2 Emission Rates
|
Decking Section I.D.
|
Composite Emission Factor
|
Decking Length (m)
|
Traffic Flow (veh/hr)
|
NOx Emission Rate (g/s)
|
|
Road L1
|
1.394 (NOx)
|
80
|
180
|
0.0028
|
| |
0.118 (RSP)
|
80
|
180
|
0.0004
|
Assessment Results
4.7.13 The modelling results are shown in Table 4.7. The findings indicate
that the predicted pollutants' concentration at the air sensitive receivers
due to the portal emission from the sunken road will be well below the
AQOs.
Table 4.7
Predicted Traffic Emission from Portal Emission at the rASR
|
rASR
|
Floor
|
NO2(a)
|
RSP(b)
|
|
1hr
|
24hr
|
1hr
|
24hr
|
|
1
|
1
|
55.4
|
52.9
|
56.3
|
55.2
|
|
1
|
3
|
53.1
|
52.4
|
55.3
|
55.0
|
|
2
|
1
|
56.8
|
53.8
|
56.8
|
55.6
|
Note:
(a) Background concentration 52.4 µg/m³ is included. 1hr AQO
of NO2 is 300 µg/m³; 24hr AQO of NO2 is 150 µg/m³
(b) Background concentration 55.0 µg/m³ is included. There is
no 1hr AQO of RSP; 24hr AQO of RSP is 180 µg/m³
Carparks
4.7.14 Carparks are proposed under the podium of the high-rise residential
developments (1 storey podium at Whitehead Development and 2 storeys podium
at Lok Wo Sha Development). The integrated carparks are all above the
ground levels. This layout will enhance the natural air movements across
the carparks. Therefore, the air quality associated with most of the carparks
is expected to be acceptable.
4.7.15 It is expected that for those carparks whose parking spaces exceeding
500 units, their air qualities may exceed the air quality guidelines listed
in ProPECC PN 2/96 (Table 4.8). Mitigation measures such as installation
of ventilation systems may be required in order to minimize the emissions
from vehicles inside the carparks. With these measures and design consideration,
the air quality associated with the proposed carparks is expected to meet
the air quality guidelines as given in Table 4.8.
Table 4.8
Air Quality Guidelines of Carparks
|
Air Pollutants
|
Maximum Concentration Not to be exceeded*
|
|
5 Minutes Average (¦Ìg/m3)
|
|
Carbon monoxide
|
115,000
|
|
Nitrogen dioxide
|
1,800
|
* Expressed at the reference condition of 25°C and 101.325 kPa (one
atmosphere)
Source: ProPECC PN 2/96 - Control of Air Pollution in Car Parks
4.7.16 In addition, a public carpark with maximum capacity of 600 capacity
for private car is proposed under the cycle park / visitor information
centre located in Whitehead Site 1 (Recreational Site). At this stage,
there is no layout for the underground carpark. When designing this car
park layout, the E&M designer (the Developer) should refer to Table
4.8 and ProPECC PN 2/96 for guidelines on ventilation system and air monitoring
system so as to ensure good air quality within the carpark. The outlet
of the ventilation system should be properly located so as to avoid imposing
nuisance, if any, to the nearby air sensitive receivers, taking into account
the prevailing condition of the area (namely northeasterly wind) and flat
coastal area. The coastal wind will provide a natural dispersion of the
air pollutants. With these measures, it is expected that the potential
air quality impact associated with the underground carpark to the nearby
environment is minimal.
4.7.17 An open coach parking with maximum capacity of 20 nos. is proposed
adjacent to the Visitor Information Centre. Given the peak projection
of only 10 coach per hour along the road leading to the visitor centre,
air quality impact due to vehicle emission from parking areas is expected
to be insignificant.
Industrial Emission Impact Assessment
Chimneys Information
4.7.18 According to EPD's inventory of chimneys information, there are
65 chimneys within the vicinity of the Project. Majority of these chimneys
are located at the Tai Po Industrial Estate which is about 5km from the
Study Area. EPD's data set are given in Table D3 of Annex D. Figure 4.6
shows the locations of these chimneys. Of these chimneys, 37 chimneys
consume light diesel fuel or boiler diesel oil, and 9 chimneys has no
fuel consumption information. In addition, 19 chimneys which use naphtha
fuel and emit NO2 gas are in the Tai Po Industrial Estate. One chimney
uses other fuels such as kerosene, charcoal, coke and wood.
4.7.19 The measurable environmental parameters due to the industrial
chimneys are mainly related to sulphur dioxide and nitrogen dioxide. Screening
model (ISC3) has been used to assess their operational impacts on the
representative air sensitive receivers at the potential development areas
at Whitehead. Local meteorological variations due to the topographical
influence have been taken into account by using the local meteorological
data from Shatin station.
Assessment Methodology
4.7.20 The measurable environmental parameters due to the industrial
chimney emissions have been evaluated for SO2 and NO2 impacts by using
ISC3 Model. For this air quality assessment of the chimney emission impact,
the following assumptions have been made:
(i) As the industrial emissions are mainly due to the combustion
of diesel fuels, the impacts due to the light diesel fuel and the boiler
diesel oil have been modelled. Also, the LPG gas chimneys consuming naphtha
fuel (19 chimneys) have been included in the assessment. The other minor
fuels have not been considered for this assessment. Also excluded from
this assessment are those chimneys whose technical information are not
available and chimneys that no longer exist. For SO2, there are 37 chimneys
modelled in this assessment, while there are 56 chimneys are modelled
for NO2 emission in this assessment.
(ii) The maximum fuel consumption has been assumed during the entire
emission period. A 24 hour emission period and 140oC exit temperature
have been assumed for chimneys whose emission period and exit temperature
are not available. However, in order to prevent over prediction, a general
fuel consumption factor, 41 percentage and 23 percentage has been applied
for daily and night operation respectively.
(iii) The emission rate, efflux velocity and volumetric flow rate are
calculated based on the UK's memorandum on Method of Calculating Chimney
Heights. A diesel fuel oil with 0.5 % sulphur content has been assumed
. The emission factor of nitrogen dioxide is based on AP42 . As the diesel
fuel contains low nitrogen content, the emission factor of 0.0024 kg/litre
has been used. It is assumed that 30% of nitrogen oxides emitted are NO2.
For the boiler diesel oil, the emission factor of SO2 is based on AP42.
(iv) The pollutants do not react chemically. There is instantaneous and
perfect mixing of the air within the Study Area.
(v) Based on the USEPA's guidelines published in Section 8.2.8 of the
Guideline on Air Quality Models (Revised), the rural dispersion mode has
been used for modelling the chimney emissions.
(vi) No building downwash analysis has been made. Gradual plume rise
mode has been applied.
(vii) The Study Area has been covered by twelve domains. The domain is
divided into a 15 x-grids and 16 y-grids with equal grid spacing of 100
m.
(viii) The assessment has been based on 1998 sequential meteorological
data from the stations at Shatin. The station contains the hourly wind
direction, wind speed, stability and temperature.
(ix) The background value of NO2 is based on the modelling results of
CTS-3 report under the high growth scenario and that of SO2 is based on
the concentrations at Shatin EPD station (2000). The average concentrations
of NO2 and SO2 are 52.4 and 18.0 µg/m3 respectively.
(x) The emission rates of SO2 and NO2 calculated based on the above assumptions
are constant over time.
4.7.21 The emission rates of SO2 and NO2 calculated based on the above
assumptions are listed in Table D5 and D6 of Annex D.
Industrial Emission (SO2 and NO2)
4.7.22 Figures 4.7 to 4.9 show the maximum hourly concentration levels
of sulphur dioxide (SO2) and nitrogen dioxide (NO2) at pedestrian level.
There are no black spots where there is likelihood of exceeding Air Quality
Objectives of SO2 and NO2 found within the Study Area. It is expected
that concentration levels of SO2 and NO2 at the pedestrian level will
be within the AQO limit.
4.7.23 Representative air sensitive receivers at the Study Area have
been evaluated and shown in Table D7 of Annex D. For future high-rise
residential developments within the Project, different heights of the
ASRs have been selected, namely pedestrian level, 1st floor, 5th floor
and every 10th floor up to the each proposed top floor. The modelling
results show that all the predicted air pollutant concentrations at the
ASRs are below the AQOs. Therefore, the buffer distances among the chimneys
and the Project are sufficient to protect the proposed residential developments
from industrial emission of surrounding chimneys.
Cumulative Impact Assessment
4.7.24 The cumulative impact for SO2 is mainly generated from the chimneys
and has been assessed to be below the AQOs. The cumulative impact for
RSP is mainly generated from the traffic and has been assessed to be below
the AQOs.
4.7.25 The cumulative impact for NO2 is generated from the chimneys and
the traffic. The major contribution to the cumulative NO2 level is from
the traffic. The predicted cumulative NO2 levels are shown in Table D8
of Annex D. Generally, the predicted cumulative NO2 concentration at pedestrian
level is higher than that of upper evaluation. Therefore, pedestrian level
is expected to be the worst affected level from vehicular and industrial
emission pollution in terms of NO2 concentration. Figures 4.10 and 4.11
show the predicted cumulative hourly and daily NO2 concentration at the
pedestrian level (worst level). It is expected that there will be no exceedance
of the AQOs found within the residential development areas of Project.
4.8 Conclusion
Construction Dust - Impacts
4.8.1 The construction dust impact assessment has identified Air Sensitive
Receivers (ASRs) within the Study Area and the works with the potential
to generate substantial dust have been identified.
4.8.2 Site formation and haul road traffic would potentially be the main
causes of construction dust impact. With adequate dust suppression measures,
dust levels from the Project will not exceed the Air Quality Objectives
(AQOs) at nearby ASRs.
4.8.3 Mitigation measures such as watering of exposed areas or pavement
of haulage route have been proposed to suppress dust generation. With
the implementation of the recommended mitigation backed up by an EM&A
programme, the Project should comply with the AQOs.
Operational Air Quality - Impacts
4.8.4 Assessment of the vehicular emission due to the major roads shows
that the proposed buffer areas adjacent to the major traffic corridors
such as Road T7, Sai Sha Road and proposed local roads are adequate. The
predicted air pollutant concentrations at all the air sensitive receivers
due to vehicular emission will comply with the AQOs. No mitigation measure
will be required.
4.8.5 The air quality due to the chimney emissions within the vicinity
of the Study Area will comply with the AQOs. Tai Po Industrial Estate
will have minor impact on the Project. The predicted air pollutant concentrations
at all the air sensitive receivers from industrial emission will comply
with the AQOs.
4.8.6 Assessment of cumulative effect from traffic emission and industrial
emission shows that the air quality within Study Area is acceptable and
below the AQOs.
4.8.7 The air quality associated with the proposed carparks is expected
to be acceptable provided the design considerations stipulated in ProPECC
PN2/96 - Control of Air Pollution in Car Parks are adhered to.
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