This Section assesses the potential air
quality impact associated with the construction and operation of the Project.
5.2
Relevant Legislation and
Guidelines
The principal legislation for the
management of air quality in
Table 5.2a Hong Kong Air Quality Objectives (mg m-3) (a)
|
Air Pollutant |
Averaging Time |
|||
|
|
1 Hour (b) |
8 Hours (c) |
24 Hour (c) |
1 Year (d) |
|
|
800 |
- |
350 |
80 |
|
Total Suspended Particulates (TSP) |
- |
- |
260 |
80 |
|
Respirable Suspended Particulates (RSP) (e) |
- |
- |
180 |
55 |
|
Nitrogen Dioxide (NO2) |
300 |
- |
150 |
80 |
|
Carbon Monoxide (CO) |
30,000 |
10,000 |
- |
- |
|
Photochemical Oxidants (as ozone) (f) |
240 |
- |
- |
- |
|
Notes: (a)
Measured
at 298K (25°C) and 101.325 kPa (one
atmosphere) (b)
Not
to be exceeded more than three times per year (c)
Not
to be exceeded more than once per year (d)
Arithmetic
mean (e)
Respirable suspended particulates means suspended particles
in air with a norminal aerodynamic diameter of 10
micrometres or smaller (f)
Photochemical
oxidants are determined by measurement of ozone only. |
||||
The EIAO–TM also stipulates an hourly total
suspended particulates (TSP) concentration of 500 μg
m-3 for construction dust impact assessment.
5.3
Baseline Environmental Conditions
and Sensitive Receivers
5.3.1
Baseline Environmental Conditions
The existing air
quality in the Study Area (Figure 5.3a) is
predominantly influenced by the vehicular emissions from the existing POR,
Table 5.3a Background
Air Quality
|
Air
Pollutants |
Background
Concentration (μg m-3) (a) |
|
Nitrogen Dioxide (NO2) |
60 |
|
Respirable Suspended Particulates (RSP) |
64 (b) |
|
Total Suspended Particulates (TSP) |
103 (b) |
|
Notes: (a)
Annual average data on air pollutant concentrations measured
at EPD Yuen Long AQMS for the past 5 years (2003 – 2007)
(http://www.epd-asg.gov.hk/english/report/aqr.php) (b)
The RSP and TSP levels recorded at EPD Yuen Long
AQMS exceeds the corresponding Air Quality Objective. |
|
5.3.2
Air Sensitive Receivers
Air sensitive
receivers (ASRs) were identified according to Annex 12 of EIAO-TM. Planned developments were identified
with reference to the latest Outline Zoning Plan (No. S/YL/17 gazetted in November 2007). The identified ASRs are presented in Table 5.3b and Figure 5.3a.
The existing
environment of the Study Area is predominantly rural with a number of villages
within its boundary. YOHO Town
Phase I, which is a more recent high-rise development with five residential
blocks, is located to the southwest of the POI. Two planned ASRs (ie
ASRs A3 and A7), which are comprehensive developments with both residential and
commercial uses, have been identified in Yuen Long Areas 15 and 12 to the
northwest and southwest of the POI, respectively.
Table 5.3b Identified Air
Sensitive Receivers
|
ASR |
Location |
Approximate Distance from
Site Boundary (m) |
Type of Uses (a) |
Approximate Maximum Height
of the Building above Ground (m) |
|
A1 |
Wong |
10 |
R |
6 |
|
A2 |
Small Traders New Village |
10 |
R |
6 |
|
A3 |
Planned Development in Yuen Long Area 15 |
30 |
CDA |
117 |
|
A4-1 |
Pok Oi
Hospital |
130 |
Hospital |
18 |
|
A4-2 |
Jockey Club Care and Attention Home |
65 |
Hospital |
18 |
|
A5 |
|
290 |
C |
9 |
|
A6 |
Pond Fish Vegetable Market |
25 |
C |
5 |
|
A7 |
Planned Development in Yuen Long Area 12 |
180 |
CDA |
132 |
|
A8 |
|
30 |
Educational Institute |
15 |
|
A9 |
|
170 |
R |
105 |
|
A10-1 |
Village House |
35 |
R |
6 |
|
A10-2 |
Village House |
70 |
R |
6 |
|
A11 |
Yeung |
260 |
R |
6 |
|
A12 |
Ming Sum Hope for the Aged |
390 |
Home for the aged |
6 |
|
A13 |
|
190 |
R |
9 |
|
A14 |
|
220 |
R |
9 |
|
A15 |
Chuk San Tsuen |
90 |
R |
9 |
|
Notes: (a)
R = Residential developments, C = Commercial
premises, CDA = Comprehensive Development Area |
||||
5.4
Potential Sources of Impact
5.4.1
Construction Phase
The Project involves
the construction of a flyover and a number of new slip roads, resurfacing and
re-marking of existing road sections to provide an additional traffic
lane. The major dust generating
construction activities associated with the Project are the demolition of
existing structures, site formation, minor excavation and filling works,
removing lane markings from the existing road surface, piling, concreting and
road paving works.
Excavation and backfilling will be required for site formation and foundation
works. About 32,000 m3
of materials (ie, about a total of 74 m3 per day of excavated
materials) ([1]) will be excavated
from different construction works throughout the construction phase and about
23,300 m3 of which will be surplus materials to be transported
off-site (ie about 13 truckloads per day of excavated
materials will be transported off-site per day ([2])). HyD has estimated that The excavated materials are
generated from the 9th month to the 21st month
(tentatively scheduled for the period from August 2010 to August 2011). Since the construction of slip
roads will be carried out in small sections, the works area for each section
will be small and confined. The
quantity of excavated materials generated from each construction worksite will
therefore be limited. In view of the
nature of the Project and the small area of works sites for each section, it is
not anticipated that dust emissions will cause adverse air quality impacts
within the Study Area with the implementation of the good site practices and
dust control measures recommended in Section
5.7.
Potential air
quality impacts may arise from the use of Powered Mechanical Equipment (PME)
during the construction works.
Since the number of PMEs required on-site will
be limited, the gaseous emissions associated with the operation of such
equipment on site are expected to be minor and will not cause adverse air
quality impacts.
5.4.2
Operational Phase
Vehicular
emissions are the potential sources of impact during the operation of the Project. Vehicular emission sources within the
Study Area are dominated by road traffic on the proposed new road sections and
the existing road network including POR,
The objective of
the Project is to relieve the traffic pressure and traffic queue of the
existing POR. The design flow of
POI,
Nitrogen dioxide
(NO2) and respirable suspended particulates
(RSP) are the key air pollutants of concern.
5.4.3
Cumulative Impacts
As indicated in Section 2.3, Kau Hui Development - Engineering Works in Area 16, Yuen Long
Phase 2 - Extension of Road L3 (Project No. 7721CL/A) and Proposed
Left-Turn Lane at Pok Oi Interchange
for the Development at YOHO Town Phase II are identified as concurrent
projects that may cause cumulative environmental impact with this Project in
the vicinity.
The scope of Kau Hui Development - Engineering Works in Area
16, Yuen Long Phase 2 - Extension of Road L3 (Project No. 7721CL/A) mainly
comprises the extension of an existing carriageway by about 220m and its
associated drainage and landscape works.
The proposed project is under tender assessment stage. The construction is expected to commence
in end 2008 and end in 2011.
A dedicated left-turn lane for access to
the planned private development of YOHO Town Phase II from
Construction Phase
The construction programme of the Project
will have an overlap of about 10 months and 1 year with the above-mentioned
concurrent projects, respectively.
No major excavation works are expected to be required for the concurrent
projects, hence, adverse cumulative dust impacts are not anticipated.
Operational Phase
The Kau Hui Development and the dedicated left-turn lane for access
to the planned private development of YOHO Town Phase II from
5.5.1
Construction Phase
As discussed in Section 5.4.1, no adverse dust impact is
expected, and therefore no quantitative assessment is required.
5.5.2
Operational
Phase
Vehicular Emission Rate Estimation
As discussed in Section 5.4.2, NO2 and RSP
are the concerned air pollutants from vehicular emissions. The EMFAC-HK model was adopted to
estimate the NO2 and RSP emission rates for the input to the
subsequent dispersion model for the assessment of the air pollutant
concentrations in the vicinity of the Project.
The Guideline on Modelling Vehicle Emissions by EPD was used as a reference
to develop the assumptions and parameters for the EMFAC-HK for this Project.
The methodology
and assumptions were developed with reference to the adopted for the approved EIA of Widening of Tuen Mun
Road at Tsing Tin Interchange
(EIA-142/2007). Some assumptions
were made in accordance with published information from the EPD and relevant
Government departments.
Vehicle Classes
Based on the information in Table 4.4 (Registration and Licensing of
Vehicle by Fuel Type) of the Transport
Monthly Digest (Apr 2008) and the vehicle population provided by EPD, the
modelled “vehicle fleet” (ie, all motor vehicles
operating on roads within the Study Area) was broken down into 16 vehicle
classes as shown in Table 5.5a. The vehicle group classification was
based on the definition in The Annual
Traffic Census 2006 – Appendix F Vehicle Classification System.
Table 5.5a Vehicle
Classes in EMFAC-HK Model
|
Vehicle Class |
Description |
Fuel Type |
Gross Vehicle Weight |
|
MC1 |
Petrol Private
Cars (PC) & Light Goods Vehicles (LGV) |
Petrol |
All |
|
MC3 |
Diesel Private Cars & Light Goods
Vehicles <2.5t |
Diesel |
<=2.5 t |
|
MC4 |
Diesel Private Cars & Light Goods
Vehicles |
Diesel |
>2.5–3.5 t |
|
MC5 |
Public Light Bus |
LPG, Diesel |
All |
|
MC6 |
Light Goods Vehicles |
Diesel |
>3.5-5.5 t |
|
MC7 |
Medium & Heavy Goods Vehicles with
GVW 5.5-15t |
Diesel |
>5.5-15 t |
|
MC8 |
Medium & Heavy Goods Vehicles with
GVW >=15t |
Diesel |
>15 t |
|
MC10 |
Double Deck Franchised Buses |
Diesel |
All |
|
MC11 |
Motor Cycles |
Petrol |
All |
|
Taxi3 |
Taxi |
LPG |
All |
|
Taxi4 |
Private Light Buses < 3.5t |
LPG, Diesel |
<=3.5 t |
|
Taxi5 |
Private Light Buses > 3.5t |
LPG, Diesel |
>3.5 t |
|
Taxi6 |
Non- franchised
Buses <6.4t |
Diesel |
<=6.4 t |
|
Taxi7 |
Non- franchised
Buses 6.4-15t |
Diesel |
>6.4-15 t |
|
Taxi8 |
Non- franchised
Buses >15t |
Diesel |
>15 t |
|
Taxi10 |
Single Deck
Franchised Buses |
Diesel |
All |
According to the Transport Monthly Digest (Apr
2008), 0.5% of private cars operated on diesel fuel and 3% of the light
goods vehicles (LGV) in
Road Grouping
With reference to the current road links
and design scheme within 500m of the site boundary, the speed limits on (i) Yuen Long Highway; (ii) newly proposed northbound
flyover, (iii) Castle Peak Road and (iv) road links merging with POR and main
roads and other local roads are 80 kph, 70 kph, 50 kph and <8kph,
respectively. Details of the
current road design scheme and road classifications are presented in Figure
5.5a.
Modelling Modes
The latest version
of the model, EMFAC-HK v1.2, provided by EPD was employed in this Project. “Burden mode” was selected as it is the
one that can provide the hourly vehicular emissions according to the diurnal
variations of vehicle-mile-travelled (VMT), trips, ambient temperature,
relative humidity and speed. Model
output files in both TextFile (CSV) and MVE17G (CSV)
formats were generated.
Exhaust Technology
Fractions
Each vehicle class had diverse
technological factors in different years.
According to the underlying assumption in EMFAC-HK, each vehicle class
could be modelled by individual characteristics of unique technology groups. Each technology group representing the
same vehicle class had the same emission control technologies, similar in-use
deterioration rates and responded the same to repair. In short, emission performances from the
same class of vehicles would be identical due to same emission standards and
emission control measures installed.
The Up
to Date Vehicle Licensed Number by Age and Technology Group Fractions
listed on the EPD website had been adopted in the model run. While the exhaust technology fractions
are only provided up to Year 2003, data after 2003 have been projected in
accordance with EPD Guidelines on
Modelling Vehicle Emissions Appendix II ‘The Implementation Schedule of Vehicle
Emission Standards in
According to the EPD’s Guideline on Modelling Vehicle Emissions,
all emission control programs implemented in
In accordance with EPD’s Guideline on Modelling Vehicle Emissions
Appendix II, emission standard of diesel franchised buses would be upgraded
to Euro III since 1 October 2001.
However, franchised bus – single deck (FBSD) in 2001 was not upgraded to
Euro III in the technology group fraction table provided by EPD. As a conservative approach, the emission
standards of FBSD in Year 2001 - 2005 were therefore assumed to be Euro II and
the emission standards of FBSD after Year 2005 had followed those provided in
the Implementation Schedule of Vehicle
Emission Standards in
Evaporative Technology
Fractions
Default values in EMFAC-HK were adopted.
Vehicle Population
As recommended in the EPD’s Guideline on Modelling Vehicle Emissions,
the Vehicle Population in Year 2003 were used except for private cars and
taxis. After the implementation of
stringent emission standards in 1998, new certification of diesel private cars
registration ceased. The number of
diesel private car was therefore extracted and grouped as petrol private car,
while LGV < 2.5t and LGV 2.5t – 3.5t was also extracted and grouped as
diesel LGV < 2.5t and LGV 2.5t – 3.5 respectively. Since the implementation of a subsidy
program in 2001, 99.9% of the taxis in
The Environment, Transport and Works
Bureau (ETWB) implemented an incentive scheme that encouraged replacement of
diesel public light buses with LPG or electric ones since 2002. According to the EPD’s
information ([4]), about 58% of the registered public light
buses are currently operating on LPG, while 2,500 public light buses have
switched from diesel to LPG with reference to information regarding LPG Vehicle
Scheme from EMSD ([5]).
As a conservative approach, the incentive scheme for public light buses
was not considered in this assessment.
The vehicle population in Year 2011 was calculated and is summarized in Annex
D2.
Accrual Rate
The accrual rates in the EMFAC-HK model
are estimated from the local mileage data adjusted to reflect the total
vehicle-mile-travelled (VMT) for each vehicle class. The default rates were used in this
Study.
Diurnal Variation
of Daily Trips
Calculation
of Diurnal Variation of Daily Trips : The diurnal variation of daily trips was used to
estimate the start emissions of petrol vehicles, thus the trips of those
vehicles other than petrol vehicles were assumed to be zero. The number of trips per day of petrol
vehicle was equivalent to the number of cold starts per day. Cold starts were expected at those road
links merging with the POI and at the Pok Oi
Vehicle Trip of Class 1 in the Study Area at hour 1 =
[VMT for Vehicle Class 1 in the Study Area at hour 1] X [Vehicle Trip of Class
1 in the territory (default in model)] / [VMT for Vehicle Class 1 in the
Territory (default in model)]
Diurnal Variation of Daily Vehicle Mile
Travelled (VMT)
The VMT represents the total distance
travelled by vehicles on a weekday.
The VMT was calculated by multiplying the number of vehicles based on the
forecast hourly traffic flow in Year 2026 and the length of road travelled in
the Study Area. The input in the
model was in terms of vehicle/fuel/hour.
The calculation of VMT for Public Light
Bus (PLB) had taken in the assumption that LPG PLB and Private Light Bus (PrLB) made up 58% and 13%of the total light bus population,
respectively with reference to Table 4.4
(Registration and Licensing of Vehicles by Fuel Type)
of the Transport Monthly Digest
(Apr 2008). All PrLBs were also assumed to be operating from 07:00 to
19:00, and therefore the VMTs during the other hours
were taken to be zero. The
calculated VMTs for all vehicle classes are
summarized in Annex D4.
The
Speed Fraction
Reference was made to the information
provided by the Highways Department for the speed limits of each road and was
approved by the Transport Department (Annex B). The design speed limits for most road
links within the Study Area are 50kph, whereas the limit on the newly proposed
northbound flyover and Yuen Long Highway are 70 kph and 80 kph, respectively
(refer to Figure 5.5a). The vehicles at the road junctions
connecting to the POR and
Among all daily emission rates, the road
speed fractions that led to the worst case emissions were applied to predict
emission factor. The total daily NOx and RSP emissions from vehicles travelling
at the design flow speed and the peak hour flow speed in 2026 were therefore
compared in the sensitivity test.
The NOx and RSP emissions predicted
from non-peak and peak hours were compared and the road speed that generating
higher NOx and RSP emissions were applied
to all hours in the prediction of total hourly emissions in this Study as a
conservative approach.
Sensitivity Test for Identification of
Worst Speed Limit for EMFAC-HK Model
A sensitivity test was conducted using the
traffic flow in 2026 to simulate the effect on the total daily NOx and RSP emissions during the peak (ie, peak-hour flow speed) and non-peak hours (ie design speed).
The results of the sensitivity test for different road groups are
summarized in Tables 5.5b to 5.5e.
Table 5.5b Total
Daily NOx and RSP Emissions under Non-peak
and Peak Hour on Road Links of 80 kph during Year 2026
|
Vehicle Type |
Total Daily NOx Emission (ton/day) |
Total Daily RSP Emission
(ton/day) |
||
|
|
Non-peak Hour (Design
Speed) |
Peak Hour (Peak-hour Flow Speed) |
Non-peak Hour (Design
Speed) |
Peak Hour (Peak-hour Flow Speed) |
|
PC&LGV |
0.004799 |
0.004856 |
0.000159 |
0.000165 |
|
PC&LGV - <2.5t |
0.000332 |
0.000306 |
0.000068 |
0.000074 |
|
LGV 2.5-3.5t |
0.001625 |
0.001501 |
0.000291 |
0.000315 |
|
Public Light Bus |
0.000369 |
0.000340 |
0.000161 |
0.000173 |
|
LGV>3.5t |
0.013131 |
0.012128 |
0.000217 |
0.000235 |
|
HGV<15t |
0.098707 |
0.094458 |
0.002457 |
0.002712 |
|
HGV>15t |
0.011210 |
0.010727 |
0.000197 |
0.000217 |
|
FBDD |
0.017314 |
0.016354 |
0.000279 |
0.000307 |
|
MC |
0.001144 |
0.001101 |
0.000042 |
0.000040 |
|
Taxi - Taxi (LPG) |
0.000996 |
0.001008 |
0.000066 |
0.000069 |
|
PrLB<3.5t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
PrLB>3.5t |
0.000218 |
0.000219 |
0.000083 |
0.000098 |
|
NFB<6.4t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
NFB6.4-15t |
0.002540 |
0.002431 |
0.000058 |
0.000064 |
|
NFB>15t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
FBSD |
0.000681 |
0.000643 |
0.000015 |
0.000016 |
|
Total |
0.153066 |
0.146072 |
0.004093 |
0.004485 |
Table 5.5c Total
Daily NOx and RSP Emissions under Non-peak
and Peak Hours on Road Links of 70kph during Year 2026
|
Vehicle Type |
Total Daily NOx Emission (ton/day) |
Total Daily RSP Emission
(ton/day) |
||
|
|
Non-peak Hour (Design
Speed) |
Peak Hour (Peak-hour Flow Speed) |
Non-peak Hour (Design
Speed) |
Peak Hour (Peak-hour Flow Speed) |
|
PC&LGV |
0.000269 |
0.000277 |
0.000009 |
0.000010 |
|
PC&LGV - <2.5t |
0.000001 |
0.000001 |
0.000000 |
0.000000 |
|
LGV 2.5-3.5t |
0.000002 |
0.000002 |
0.000000 |
0.000000 |
|
Public Light Bus |
0.000019 |
0.000015 |
0.000073 |
0.000073 |
|
LGV>3.5t |
0.000019 |
0.000019 |
0.000000 |
0.000000 |
|
HGV<15t |
0.002039 |
0.001951 |
0.000051 |
0.000056 |
|
HGV>15t |
0.000226 |
0.000216 |
0.000004 |
0.000004 |
|
FBDD |
0.000500 |
0.000472 |
0.000008 |
0.000009 |
|
MC |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
Taxi - Taxi (LPG) |
0.000071 |
0.000073 |
0.000005 |
0.000005 |
|
PrLB<3.5t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
PrLB>3.5t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
NFB<6.4t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
NFB6.4-15t |
0.000077 |
0.000073 |
0.000002 |
0.000002 |
|
NFB>15t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
FBSD |
0.000022 |
0.000021 |
0.000000 |
0.000001 |
|
Total |
0.003245 |
0.00312 |
0.000152 |
0.000160 |
Table 5.5d Total
Daily NOx and RSP Emissions under Non-peak
and Peak Hours on Road Links of 50kph during Year 2026
|
Vehicle Type |
Total Daily NOx Emission (ton/day) |
Total Daily RSP Emission
(ton/day) |
||
|
|
Non-peak Hour (Design
Speed) |
Peak Hour (Peak-hour Flow Speed) |
Non-peak Hour (Design
Speed) |
Peak Hour (Peak-hour Flow Speed) |
|
PC&LGV |
0.003986 |
0.005000 |
0.000159 |
0.000336 |
|
PC&LGV - <2.5t |
0.000238 |
0.000287 |
0.000075 |
0.000123 |
|
LGV 2.5-3.5t |
0.001246 |
0.001503 |
0.000343 |
0.000562 |
|
Public Light Bus |
0.000376 |
0.000450 |
0.000246 |
0.000391 |
|
LGV>3.5t |
0.009476 |
0.011430 |
0.000241 |
0.000395 |
|
HGV<15t |
0.026973 |
0.032536 |
0.000882 |
0.001447 |
|
HGV>15t |
0.003071 |
0.003705 |
0.000071 |
0.000116 |
|
FBDD |
0.009098 |
0.012026 |
0.000195 |
0.000355 |
|
MC |
0.001246 |
0.001097 |
0.000046 |
0.000058 |
|
Taxi - Taxi (LPG) |
0.001594 |
0.002006 |
0.000127 |
0.000268 |
|
PrLB<3.5t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
PrLB>3.5t |
0.000240 |
0.000290 |
0.000141 |
0.000229 |
|
NFB<6.4t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
NFB6.4-15t |
0.001358 |
0.001639 |
0.000041 |
0.000067 |
|
NFB>15t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
FBSD |
0.000352 |
0.000465 |
0.000010 |
0.000018 |
|
Total |
0.059254 |
0.072434 |
0.002577 |
0.004365 |
Table 5.5e Total
Daily NOx and RSP Emissions under Non-peak
and Peak Hours on Road Links of 50kph (with cold starts) during Year 2026
|
Vehicle Type |
Total Daily NOx Emission (ton/day) |
Total Daily RSP Emission
(ton/day) |
||
|
|
Non-peak Hour (Design
Speed) |
Peak Hour (Peak-hour Flow Speed) |
Non-peak Hour (Design
Speed) |
Peak Hour (Peak-hour Flow Speed) |
|
PC&LGV |
0.000115 |
0.000115 |
0.000017 |
0.000017 |
|
PC&LGV - <2.5t |
0.000007 |
0.000007 |
0.000004 |
0.000004 |
|
LGV 2.5-3.5t |
0.000035 |
0.000035 |
0.000015 |
0.000015 |
|
Public Light Bus |
0.000001 |
0.000001 |
0.000001 |
0.000001 |
|
LGV>3.5t |
0.000283 |
0.000283 |
0.000012 |
0.000012 |
|
HGV<15t |
0.000982 |
0.000982 |
0.000051 |
0.000051 |
|
HGV>15t |
0.000111 |
0.000111 |
0.000004 |
0.000004 |
|
FBDD |
0.000377 |
0.000377 |
0.000013 |
0.000013 |
|
MC |
0.000016 |
0.000016 |
0.000002 |
0.000002 |
|
Taxi - Taxi (LPG) |
0.000016 |
0.000016 |
0.000005 |
0.000005 |
|
PrLB<3.5t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
PrLB>3.5t |
0.000001 |
0.000001 |
0.000001 |
0.000001 |
|
NFB<6.4t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
NFB6.4-15t |
0.000043 |
0.000043 |
0.000002 |
0.000002 |
|
NFB>15t |
0.000000 |
0.000000 |
0.000000 |
0.000000 |
|
FBSD |
0.000013 |
0.000013 |
0.000001 |
0.000001 |
|
Total |
0.002000 |
0.002000 |
0.000128 |
0.000128 |
The sensitivity test
results indicate that the total daily NOx
emissions are higher during the peak hour at lower speeds (<50kph) and
during the non-peak hour at higher speeds (70-80kph). On the other hand, the total RSP
emissions at all speeds are higher during the peak hour. The sum of emissions for NOx and RSP of all road groups during the peak
hour is higher than that of the non-peak hour. As a result, the peak-hour flow
speed was adopted for the estimation of the worst-case NOx
emissions on low speed road links (50kph (with cold starts) and 50kph) and RSP
emissions at all road links (50kph (with cold starts), 50kph, 70kph and 80kph)
in the EMFAC-HK model. The non-peak
hour flow speed was adopted for the estimation of the worst case NOx emissions on high speed roads (70kph and
80kph).
Model Year
EMFAC-HK model was
run for the year from 2011 to 2026 using the VMT of each road link and the
peak-hour flow speed in Year 2026.
A summary of the predicted total daily NOx
and RSP emissions are summarized in Annex D5 and the highest total daily NOx and RSP emissions would occur in year
2011. Therefore, the hourly
emissions of each vehicle type in 2011 were divided by the corresponding total
VMT to determine the emission factors in gram per miles per vehicle and maximum
emission factors which are summarized in Annex D6. The maximum emission factor for each
vehicle type was adopted in the subsequent CALINE4 air dispersion model for the
prediction of pollutant concentrations at the Air Sensitive Receivers (ASRs).
Sensitivity Test for AM and PM Peak Hourly
Traffic Flow and Vehicle Mix
A sensitivity test
between the AM and PM peak traffic flows and vehicle mixes was conducted to simulate
the total vehicular emissions. A
summary of the predicted NOx and RSP
emission factors by adopting the AM and PM traffic data was presented in Annex
D7. The sensitivity test
results indicate the AM peak hourly traffic flow and vehicle mix produce higher
NOx and RSP emissions and hence the AM
peak hourly traffic flows and vehicle mixes in 2026 (ie
15 years after the Project completion) are used for the worst case
estimation.
Assessment of Air Pollutant Concentrations
The EPD-approved
air dispersion model, CALINE4, was used to predict the maximum hourly and daily
concentrations of NO2 and RSP at 1.5m to 20m above ground of the
identified ASRs. The CALINE4 model
calculates hourly concentrations only.
With reference to Screening
Procedures for Estimating the Air Quality Impact of Stationary Source
(EPA-454/R-92-019), a conversion factor of 0.4 was used to convert the maximum
hourly concentrations to daily average concentrations.
The forecasted AM
peak hourly traffic flow, vehicle mixes for relevant road links and fleet
emission factors of NO2 and RSP in 2026 for the CALINE4 model
prediction are presented in Annex D8. In accordance with EPD’s
Guidelines on Choice of Models and Model
Parameters, 20% of NOx was assumed to
be converted into NO2 for the purpose of this assessment.
The following daytime worst-case
meteorological conditions were adopted in the model run:
·
Wind
speed 1
ms-1
·
Wind direction worst
case for each ASR
·
Stability
class D
·
Standard
deviation of wind direction 12
·
Surface
roughness 100
cm
·
Mixing
height 500
m
·
Ambient
temperature 25.5
°C
Background NO2
and RSP concentrations, as presented in Table
5.3a, were added to the predicted concentrations to obtain cumulative air
pollutant concentrations to check against the respective AQO criteria.
Existing and future noise barriers, if
installed for the road links considered, have also be taken into account in the
model by shifting the road height to the top of the noise barrier.
Isopleths showing hourly and daily NO2
and RSP concentrations within the Study Area were also plotted to show the
general impacts of the air pollutants in the vicinity of the Project.
5.6.1
Construction Phase
As discussed in Section 5.4.1, in view of the nature,
relatively small scale of the Project and small construction works area, it is
not anticipated that dust emissions will cause adverse air quality impacts within
the Study Area with the implementation of good site practices and the dust
control measures recommended in Section
5.7.
5.6.2
Operational Phase
Cumulative maximum hourly concentrations of NO2 and daily
average concentrations of NO2 and RSP, taking the background
concentrations of the respective pollutants into account, were predicted at 1.5
to 20m above ground level. The
results are shown in Tables 5.6a to 5.6c.
Table 5.6a Predicted
Maximum
|
ASR |
Predicted
Maximum |
||||
|
|
1.5m
Above Ground |
5m
Above Ground |
10m
Above Ground |
15m
Above Ground |
20m
Above Ground |
|
A1 (b) |
282 |
282 |
271 |
- |
- |
|
A2 (b) |
207 |
203 |
177 |
- |
- |
|
A3 |
203 |
199 |
192 |
177 |
162 |
|
A4-1 |
128 |
124 |
120 |
120 |
113 |
|
A4-2 |
150 |
146 |
139 |
131 |
120 |
|
A5 (b) |
135 |
131 |
128 |
- |
- |
|
A6 (c) |
282 |
263 |
- |
- |
- |
|
A7 |
162 |
158 |
154 |
143 |
135 |
|
A8 |
214 |
210 |
199 |
184 |
- |
|
A9 |
139 |
139 |
139 |
135 |
131 |
|
A10-1 (b) |
143 |
143 |
139 |
- |
- |
|
A10-2 (b) |
169 |
169 |
158 |
- |
- |
|
A11 (b) |
101 |
101 |
101 |
- |
- |
|
A12 (b) |
128 |
128 |
124 |
- |
- |
|
A13 (b) |
120 |
120 |
120 |
- |
- |
|
A14 (b) |
116 |
116 |
113 |
- |
- |
|
A15 (b) |
158 |
154 |
154 |
- |
- |
|
AQO |
300 |
300 |
300 |
300 |
300 |
|
Notes: (a)
Background concentrations of NO2 (i.e. 60
µgm-3) have been included. (b)
As the maximum heights of ASRs A1, A2, A5, A10 to A15
are all below 10 m above ground, therefore, the impact was assessed at 1.5m,
5m and 10m above ground only. (c)
As ASR A6 is a one-storey building, the impact was
only assessed at 1.5m and 5m above ground. |
|||||
Table 5.6b Predicted
24-hour Average NO2 Concentrations
|
ASR |
Predicted
24-hour Average NO2Concentration (µgm-3) (a) |
||||
|
|
1.5m
Above Ground |
5m
Above Ground |
10m
Above Ground |
15m
Above Ground |
20m
Above Ground |
|
A1 (b) |
149 |
149 |
144 |
- |
- |
|
A2 (b) |
119 |
117 |
107 |
- |
- |
|
A3 |
117 |
116 |
113 |
107 |
101 |
|
A4-1 |
87 |
86 |
84 |
84 |
81 |
|
A4-2 |
96 |
95 |
92 |
89 |
84 |
|
A5 (b) |
90 |
89 |
87 |
- |
- |
|
A6 (c) |
149 |
141 |
- |
- |
- |
|
A7 |
101 |
99 |
98 |
93 |
90 |
|
A8 |
122 |
120 |
116 |
110 |
- |
|
A9 |
92 |
92 |
92 |
90 |
89 |
|
A10-1 (b) |
93 |
93 |
92 |
- |
- |
|
A10-2 (b) |
104 |
104 |
99 |
- |
- |
|
A11 (b) |
77 |
77 |
77 |
- |
- |
|
A12 (b) |
87 |
87 |
86 |
- |
- |
|
A13 (b) |
84 |
84 |
84 |
- |
- |
|
A14 (b) |
83 |
83 |
81 |
- |
- |
|
A15 (b) |
99 |
98 |
98 |
- |
- |
|
AQO |
150 |
150 |
150 |
150 |
150 |
|
Notes: (a)
Background concentrations of NO2 (i.e. 60
µgm-3) have been included. (b)
As the maximum heights of ASRs A1, A2, A5, A10 to
A15 are all below 10 m above ground, therefore, the impact was assessed at
1.5m, 5m and 10m above ground only. (c)
As ASR A6 is a one-storey building, the impact was
only assessed at 1.5m and 5m above ground. |
|||||
Table 5.6c Predicted
24-hour Average RSP Concentrations
|
ASR |
Predicted
24-hour Average RSP Concentration (µgm-3) (a) |
||||
|
|
1.5m
Above Ground |
5m
Above Ground |
10m
Above Ground |
15m
Above Ground |
20m
Above Ground |
|
A1 (b) |
99 |
99 |
97 |
- |
- |
|
A2 (b) |
85 |
85 |
82 |
- |
- |
|
A3 |
90 |
88 |
84 |
81 |
78 |
|
A4-1 |
78 |
77 |
76 |
75 |
74 |
|
A4-2 |
83 |
83 |
81 |
79 |
77 |
|
A5 (b) |
82 |
81 |
80 |
- |
- |
|
A6 (c) |
104 |
99 |
- |
- |
- |
|
A7 |
82 |
82 |
80 |
78 |
76 |
|
A8 |
90 |
90 |
87 |
84 |
|
|
A9 |
78 |
78 |
77 |
77 |
76 |
|
A10-1 (b) |
78 |
77 |
77 |
- |
- |
|
A10-2 (b) |
82 |
82 |
80 |
- |
- |
|
A11 (b) |
73 |
73 |
72 |
- |
- |
|
A12 (b) |
80 |
80 |
79 |
- |
- |
|
A13 (b) |
74 |
74 |
74 |
- |
- |
|
A14 (b) |
73 |
73 |
73 |
- |
- |
|
A15 (b) |
80 |
80 |
80 |
- |
- |
|
AQO |
180 |
180 |
180 |
180 |
180 |
|
Notes: (a)
Background concentrations of RSP (i.e. 64 µgm-3)
have been included. (b)
As the maximum heights of ASRs A1, A2, A5, A10 to
A15 are all below 10 m above ground, therefore, the impact was assessed at
1.5m, 5m and 10m above ground only. (c)
As ASR A6 is a one-storey building, the impact was
only assessed at 1.5m and 5m above ground. |
|||||
The predictions show that there are no exceedance
of the AQOs for maximum hourly and 24-hour average
concentrations of NO2 and 24-hour average concentrations of RSP at
all identified ASRs taking into account the background concentrations and the
existing and future noise barriers.
The predicted maximum hourly and 24-hour average NO2
concentrations and 24-hour average RSP concentrations range from 101 - 282 µg m-3,
77 - 149 µg m-3 and 72 – 104 µg m-3, respectively and the
worst affected height is predicted at 1.5m above ground at all identified ASRs.
Figures 5.6a to
5.6f show the maximum hourly and 24-hour average NO2 and 24-hour
average RSP concentrations at 1.5m and 10m above ground level. The different time averaged NO2
and RSP concentrations are well within the respective AQOs
at all ASRs taking into account the background concentrations. Exceedance of
maximum hourly and daily NO2 concentration was predicted along
YLH. The affected areas are YLH and
the embankment of YLH and no ASRs are located within the affected area. Hence, the air quality impact due to the
Project and the current road links are acceptable.
It must be emphasized that the objective of the Project is only to
relieve the traffic pressure and traffic queues of the existing POR and that
the design traffic flow / capacity ratio will be maintained. There will not be any increase in
traffic as a result of this Project.
The levels of NO2 and RSP predicted for YLH are mainly due to
the existing high traffic volume on that particular road section.
5.7.1
Construction Phase
The construction
of the Project will involve site formation, piling, concreting and road paving
works. The dust impact during the construction
phase will be minimized with the implementation of good site practices and dust
control measures stipulated in the Air
Pollution Control (Construction Dust) Regulation, which are summarised as follows:
·
Any stockpile of dusty material will be covered
entirely with impervious sheeting or sprayed with water so as to maintain the
entire surface wet;
·
Where a site boundary adjoins a road, or other area
accessible to the public, hoarding shall be provided a long the entire length of
that portion of the site boundary;
·
All dusty materials will be sprayed with water
immediately prior to any loading, unloading or transfer operation so as to
maintain the dusty materials wet;
·
Where a vehicle leaving the works site is carrying a
load of dusty materials, the load will be covered entirely with clean
impervious sheeting to ensure that the dusty materials do not leak from the
vehicles;
·
The working area of any demolition, excavation or
earth moving operation will be sprayed with water or dust suppression chemicals
immediately after the operation so as to maintain the entire surface wet;
·
The construction plants will be regularly maintained
to avoid the emissions of black smoke; and
·
The construction plants will be switched off when not
in use to avoid gaseous emissions.
5.7.2
Operational Phase
No mitigation
measures are required as no exceedances of the
respective criteria are predicted.
5.8
Environmental Monitoring and
Audit (EM&A)
Regular site audit
during the construction phase is recommended to ensure that mitigation measures
recommended in Section 5.7 are
carried out.
No EM&A for
air quality is required during operational phase.
The key dust
generating construction activities associated with the Project are site
formation, minor excavation and filling works, demolition of the existing
structures, removal of lane markings on existing road surface, piling,
concreting and road paving works.
In view of the nature and sequencing of the Project, and the small scale
of the construction works, air quality impact due to dust emissions is not
anticipated with the implementation of good site practices and dust control
measures stipulated in the Air Pollution
Control (Construction Dust) Regulations. Air quality impact due to gaseous
emissions from the use of PMEs during construction
works is expected to be insignificant due to the limited use of such equipment
and the adoption of good site practices.
Regular site audits are recommended to ensure the implementation of the
prescribed dust control measures and the adoption of good site practices.
Upon completion of the Project, vehicular emission from the traffic on
the open roads is the main potential source of air quality impacts. The key air pollutants from vehicular
emissions include NO2 and RSP.
A quantitative assessment has been conducted with the peak hourly
traffic flow of the proposed new roads and the existing road network and their
fleet emission factors estimated using the EMFAC-HK model. The prediction indicated no exceedance of hourly and daily average concentrations of NO2
or daily average concentrations of RSP in the vicinity of the Project.
It must be
emphasized that the objective of the Project is to relieve the traffic pressure
and traffic queues of the existing POR and the design traffic flow / capacity
ratio will be maintained. There is
not expected to be any increase in traffic as a direct result of this Project.
The vehicular
emissions associated with road traffic with the implementation of the Project
are expected to comply with the respective AQOs, and
therefore will not cause any unacceptable adverse air quality impacts.
([1])
Assuming 24 working days a month, the daily
generation rate of excavated materials = 32,000 m3 / 18 months / 24 days = 74
m3 per day.