4.1.1
This Section presents an assessment of the potential air quality impacts
that could arise from the construction and operation of the Project.
4.2.1
The criteria for evaluating air quality impacts
and the guidelines for air quality assessment are laid out in Annex 4
and Annex 12 of the TM-EIAO.
The principal legislation for the management of air quality in Hong Kong
is the Air Pollution Control Ordinance (APCO) (Cap. 311). The Air Quality Objectives (AQOs) stipulating
statutory ambient limits for air pollutants and the maximum allowable number of
exceedances over specific averaging periods are presented in Table 4.1.
Table 4.1 Hong Kong Air Quality Objectives
|
Air
Pollutant |
Averaging
Time |
Concentration
(mgm-3) (a) |
No.
of Exceedances Allowed per Year |
|
Sulphur Dioxide (SO2) |
10 minutes |
500 |
3 |
|
|
24-hours |
125 |
3 |
|
Respirable Suspended Particulates
(RSP) (b) |
24-hours |
100 |
9 |
|
Annual |
50 |
- |
|
|
Fine Suspended Particulates
(FSP) (c) |
24-hours |
75 |
9 |
|
Annual |
35 |
- |
|
|
Nitrogen Dioxide (NO2) |
1-hour |
200 |
18 |
|
|
Annual |
40 |
- |
|
Ozone (O3) |
8-hours |
160 |
9 |
|
Carbon Monoxide (CO) |
1-hour |
30,000 |
- |
|
|
8-hours |
10,000 |
- |
|
Lead |
Annual |
0.5 |
- |
|
Notes: (a)
Measured at
298K and 101.325 kPa. (b)
Suspended
particles in air with a nominal aerodynamic diameter of 10 μm or less (c)
Suspended
particles in air with a nominal aerodynamic diameter of 2.5 μm or less |
|||
4.2.2
A maximum hourly TSP level of 500 mg m-3
at Air Sensitive Receivers (ASRs) is also stipulated in Section 1, Annex 4 of the EIAO-TM
to assess potential construction dust impacts.
The measures stipulated in the Air
Pollution Control (Construction Dust) Regulation
should also be followed whenever possible to ensure that any dust impacts are
reduced.
4.2.3
Annex 4
of the EIAO-TM has also stipulated that the odour
level at a sensitive receiver should not exceed 5 odour
units based on an averaging time of 5 seconds for odour
prediction assessment.
4.3.1
Clause
3.4.1.2 of the EIA
Study Brief prescribes the Study Area which is generally defined by a distance of 500 m from boundary of the Project, or to
include other project locations as identified in the EIA. Figure 4.1 shows the
Study Area within the 500 m envelope of the Project (including the works areas)
and the identified representative ASRs which have been described in the next
section in details. The Study Area is the same for both the construction and
operation phases.
4.4.1
Air Sensitive Receivers (ASRs) have been identified in
accordance with Annex 12 of EIAO-TM and are summarised in Table 4.2 and shown in Figure 4.1.
Table 4.2 Identified
Representative Air Sensitive Receivers
|
ASR |
Description |
Minimum Distance
away from the Project Site Boundary (m) |
|
ASR01 |
Fortune
Pharmacal Co. Limited |
50 |
|
ASR02 |
Tung
Tau Wai San Tsuen |
12 |
|
ASR03 |
Shan
Pui Chung Hau Tsuen |
10 |
|
ASR04 |
Twin
Regency |
8 |
|
ASR05 |
Yuk Yat Garden |
21 |
|
ASR06 |
Wang
Fu Court |
5 |
|
ASR07 |
Tung
Tau Industrial Area - Yuen Long Hi-Tech Centre |
24 |
|
ASR08 |
Yeung
Uk San Tsuen |
28 |
|
ASR09 |
Yuen
Long Long Ping Estate Wai Chow School |
39 |
|
ASR10 |
The
Spectra |
11 |
|
ASR11 |
Tai Kiu Tsuen |
8 |
|
ASR12 |
Fuk Yip
Building |
1 |
|
ASR13 |
Yuen
Fat House |
1 |
|
ASR14 |
Healey
Building |
2 |
|
ASR15 |
Wah Shing Mansion |
6 |
|
ASR16 |
CCC
Chun Kwong Primary School |
1 |
|
ASR17 |
Tse King
House |
2 |
|
ASR18 |
On
Ning Building |
1 |
|
ASR19 |
Ho
Wang Building |
1 |
|
ASR20 |
Caritas
Yuen Long Chan Chun Ha Secondary School |
4 |
|
ASR21 |
Sun
Fai Court |
2 |
|
ASR22 |
Ma
Tin Tsuen - Kung Um Road |
2 |
|
ASR23 |
Yuen
Long Villa |
3 |
|
ASR24 |
Lung
Tin Tsuen |
31 |
|
ASR25 |
Wang
Chau Lam Uk Tsuen |
38 |
|
ASR26 |
Wang
Chau Tung Tau Wai |
64 |
|
ASR27 |
Hong
Kong School of Motoring - Yuen Long Road Safety Centre |
188 |
|
R1 |
Sol
City (Planned) |
8 |
4.5.1 Data collected by EPD air quality monitoring programme during the period of 2013 to 2017 were examined with the average period value presented in Table 4.3. It is noted that the 5-year averaged annual and 1-hour concentrations of NO2, 24-hour concentrations of FSP and RSP and 8-hour concentration of O3 exceeded the relevant AQO. The concentrations of SO2 and CO were in relatively low level and well within the AQOs during 2013-2017.
4.5.2
The traffic emissions from Castle Peak Road,
Yuen Long Highway and other local roads, as well as emissions from the Yuen
Long Industrial Estate (YLIE) and Tung Tau Industrial Area (TTIA), are
considered likely to be the key local sources affecting the ambient air quality
within the Study Area.
4.5.3
Discharges of sewage from unsewered villages and
illegal discharges from livestock farms are the main sources of pollution to
the YLTN, leading to the existing water quality nuisance in the area. As indicated by EPD’s water quality
monitoring data in 2017, river water quality of the four monitoring stations
(YL1-4) located within the YLTN, Main Nullah and San Hui Nullah was characterized
by high levels of 5-day Biochemical Oxygen Demand (BOD5) and E. coli (please refer to Section 6.3 for details). Such discharges to the nullah are causing odour nuisance to the surrounding area.
Table
4.3 5-year Averaged Annual Background
Concentration of Air Pollutants recorded at Yuen Long Station by EPD for the
Period of 2013-2017
|
AIR Pollutant |
Averaging Time |
AQO (a) |
Data Description |
UNIT |
Year (b)
(c) (d) |
5-year mean |
||||
|
2013 |
2014 |
2015 |
2016 |
2017 |
||||||
|
Fine
Suspended Particulates (FSP)
(PM
2.5) |
24-hour |
75
(9) |
Max. |
μg m-3 |
140 |
119 |
127 |
76 |
77 |
108 |
|
10th
Max. |
μg m-3 |
106 |
86 |
78 |
63 |
52 |
77 |
|||
|
No.
of Exceedance(s) |
- |
35 |
18 |
12 |
1 |
2 |
14 |
|||
|
Annual |
35 |
- |
μg m-3 |
37 |
35 |
30 |
23 |
22 |
29 |
|
|
Respirable Suspended Particulates (RSP) (PM10) |
24-hour |
100 (9) |
Max. |
μg m-3 |
184 |
156 |
176 |
128 |
111 |
151 |
|
10th Max. |
μg m-3 |
142 |
124 |
102 |
86 |
87 |
108 |
|||
|
No.
of Exceedance(s) |
- |
47 |
21 |
12 |
4 |
2 |
17 |
|||
|
Annual |
50 |
- |
μg m-3 |
56 |
50 |
44 |
37 |
40 |
45 |
|
|
Sulphur Dioxide (SO2) |
10-minute (e) |
500 (3) |
Max. |
μg m-3 |
N/A |
112 |
67 |
77 |
105 |
90 |
|
4th Max. |
μg m-3 |
N/A |
92 |
51 |
58 |
80 |
70 |
|||
|
24-hour |
125 (3) |
Max. |
μg m-3 |
53 |
34 |
20 |
18 |
24 |
30 |
|
|
4th Max. |
μg m-3 |
33 |
27 |
17 |
17 |
20 |
23 |
|||
|
Nitrogen Dioxide (NO2) |
1-hour |
200 (18) |
Max |
μg m-3 |
230 |
227 |
339 |
202 |
214 |
242 |
|
19th Max. |
μg m-3 |
183 |
165 |
162 |
149 |
156 |
163 |
|||
|
No.
of Exceedance(s) |
- |
7 |
4 |
5 |
1 |
2 |
4 |
|||
|
Annual |
40 |
- |
μg m-3 |
54 |
52 |
45 |
46 |
41 |
47 |
|
|
Carbon Monoxide (CO) |
1-hour |
30,000 |
Max. |
μg m-3 |
2690 |
2560 |
2460 |
2080 |
1450 |
2248 |
|
8-hour |
10,000 |
Max. |
μg m-3 |
1950 |
2319 |
2143 |
1474 |
1324 |
1842 |
|
|
Ozone (O3) |
8-hour |
160 (9) |
Max. |
μg m-3 |
183 |
304 |
261 |
269 |
272 |
258 |
|
10th Max. |
μg m-3 |
163 |
177 |
164 |
143 |
175 |
164 |
|||
|
No.
of Exceedance(s) |
- |
10 |
15 |
11 |
5 |
13 |
11 |
|||
Notes: (a) Values in ( )
indicate the number of exceedances allowed per year
(b) Data
extracted from EPD Website (http://www.aqhi.gov.hk/en/download/air-quality-reportse469.html?showall=&start=1)
(c) Bolded values represent exceedances of the AQOs.
(d) N/A – Data not available
(e)
The 10-minute averages of SO2 data are only available from 2014 and
hence only 4-year mean result was derived.
4.6.1
The following sources of air pollution are expected during
the construction phase of the Project:
·
Fugitive dust caused by earthworks including site clearance,
excavation, materials handling, loading, unloading and backfilling etc;
·
Gaseous
emissions from diesel-powered construction equipment and vehicles associated
with the construction of the Project; and
·
Odour
from the excavated channel bed materials.
4.6.2
The entire Project will be constructed in sections (Figure
2.1) and hence the exposed area
will be reduced. Dust is expected
to be generated from excavation, backfilling, handling of materials and wind
erosion from the site.
4.6.3
Based on the engineering design, it is estimated that about
15,252 m3 of construction and demolition (C&D) materials and channel
bed material will be excavated from the Project for the whole construction
period. About 4,424 m3 of the
excavated materials will be reused on-site and the rest (about 10,828 m3)
will be temporarily stored in stockpiling areas for subsequent disposal
off-site. Dust generated from construction
vehicle movements to and from the stockpiling areas and works areas will
generally be limited within the work areas.
4.6.4 For site clearance and demolition works, it is estimated that a total of 2 truck trips per day will be required to dispose of the C&D materials/construction waste off-site (please refer to Section 7.5.3 for details). With proper implementation of good site practices and mitigation measures stipulated in the Air Pollution Control (Construction Dust) Regulation, potential unacceptable dust impacts associated with on-site handling and transportation of the public fill and construction waste to disposal sites are not expected to occur.
4.6.5
In view of the relatively small scale of the
construction works, the quantity of excavated materials generated and no
concrete batching on-site, the potential fugitive dust nuisance during the
construction phase should be limited. With
the implementation of typical dust suppression measures and good site practices
stipulated in the Air Pollution
Control (Construction Dust) Regulation, no unacceptable
adverse air quality impacts on the identified representative ASRs are
anticipated during the construction phase.
4.6.6
The potential air quality impacts associated with the
gaseous emissions from diesel-powered construction equipment are expected to be
relatively low as only a small number of generators and vehicles are expected
to be deployed on site. In addition, all
construction plants are required to use ultra-low-sulphur diesel (ULSD)
(defined as diesel fuel containing not more than 0.005% sulphur by weight) as
stipulated in Environment, Transport and
Works Bureau Technical Circular (ETWB-TC(W))
No 19/2005 on Environmental Management on Construction Sites. Therefore, no adverse air quality impacts are
expected from gaseous emissions.
4.6.7
Excavation of the nullah bed material will be
required for the construction of the Project.
Depending on the quality of the nullah bed material, the excavation and
handling of nullah bed material may cause odour impacts
during construction. Hydrogen sulphide (H2S) is the key odour
constituent of the excavated material.
With the implementation of good site practice recommended in Section 4.9, unacceptable odour nuisance is not anticipated.
4.7.1
Maintenance would be necessary for the Project to remove
excessive silts, vegetation, debris and obstructions in order to maintain its
hydraulic performance and structural integrity.
Moderate siltation will generally be allowed to accumulate, and removal
of excess silt would be carried out at locations where it would impede water
flow. Such small-scale
maintenance would require only light mechanical equipment such as a small
loader and/or a small crane truck.
Hand-held equipment will be used for vegetation removal. Therefore, unacceptable
impacts from dust and gaseous emission are not expected to occur.
4.7.2
The main odour nuisances from DWF pumping station can
be attributed to the wet wells/ retention tanks of the pumping station. To reduce potential odour impacts, the
pumping station will be enclosed inside building structure equipped with
adequate odour control measures (i.e. installation of deodourization
unit with 99.5% odour removal efficiency.
The vent will be located away from ASRs as far as practicable.
4.7.3
The closest ASR to the DWF pumping station is ASR04
with the separation distance of 23m from the ventilation louvre of the pumping
station. The EIA report of “Tuen Mun Area 54
Sewage Pumping Station (TM54SPS)” (AEIAR-122/2008) has been reviewed. The design
capacity of the TM54SPS is about 1.03 m3/s (88,992 m3/d)
and the average dry weather flow is 0.32 m3/s (27,648 m3/d). The
nearest distance of the identified ASR to the site boundary of the TM54SPS was
10m. With installation of deodourizer (with 90% odour removal efficiency),
the predicted odour levels at all representative ASRs
would comply with the odour criterion. Considered
expected lower odour strength of DWF compared with
sewage, longer separation distance and installation of deodourization unit with higher odour removal
efficiency (99.5%) under this Project, the odour impacts to the ASRs (including
ASR04) in the vicinity is expected to be acceptable.
4.7.4
It is expected that odour
nuisance of the YLTN will be alleviated due to the operation of the Project
since the polluted DWF originally discharged into the Project Site will be
diverted to the YLSTW. This is being
considered as a beneficial impact of the Project.
4.8.1
Relevant dust control measures stipulated in the Air Pollution Control (Construction Dust)
Regulation, and good site practices will be incorporated as the Contract
Specifications for implementation throughout the construction period. These
include:
·
The works area for site clearance and excavation should
be sprayed with water before, during and after the operation so as to maintain the entire surface wet.
·
Where a vehicle leaving a construction site is carrying a load of dusty materials,
the load should be covered entirely by clean impervious sheeting to ensure that
the dusty materials will not leak from the vehicle.
·
Erection of hoarding along the site boundary, where
appropriate.
·
All dusty materials should be sprayed with water
immediately prior to any loading, unloading or transfer operation so as to maintain the dusty materials wet.
·
Reduce the traffic induced dust dispersion and
re-suspension, the travelling speed of vehicles within the site should be
controlled.
·
Regular maintenance of construction equipment deployed
on-site should be conducted to prevent black smoke emission.
4.8.2
Excavated nullah bed
materials that are placed on trucks for disposal should be properly covered
with tarpaulin sheets during transportation to minimise the release of any potential
odour. The odorous excavated material should
be placed as far away from the sensitive receivers as possible. Odorous river bed material excavated during
construction phase should be removed off-site as soon as practicable within 24
hours to avoid any odour nuisance.
4.8.3
During operation phase, mitigation measures are
considered necessary when materials generated from the maintenance works are
found to be odorous, and the following measures should be implemented by the
Contractor.
·
Temporarily stockpile odorous material as far away
from ASRs as possible; and
·
Temporary stockpiles of odorous material will be properly
covered with tarpaulin and should be removed off-site as soon as practically
possible within 24 hours to avoid any odour nuisance arising.
4.8.4
To reduce odour
impacts from the DWF pumping station, the following measures should be
implemented.
·
The DWF pumping station should be enclosed inside
building structure and maintained with negative pressure;
·
The DWF pumping station should be equipped with deodourization unit using activated carbon or other
equivalent odour removal techniques with odour removal efficiency of 99.5%;
·
The exhaust outlet of the deodourization
unit should be located in a direction away from the
nearby ASRs, with a view to maximizing the separation distance between the
exhaust outlet and the nearest ASR; and
·
Regular maintenance of the deodourization
unit should be conducted to ensure its effectiveness.
4.9.1
The potential for cumulative air quality impact during
the construction and operation phase of the YLTN improvement works has been
checked against the following concurrent projects identified in Section 2.6:
·
Yuen Long Barrage Scheme;
·
Elevated Pedestrian
Corridor in Yuen Long Town Connecting with Long Ping Station; and
·
Housing Sites in Yuen
Long South.
4.9.2
For Yuen
Long Barrage Scheme, the construction period will overlap with that of the
Project during 2021 to 2026. According
to its Project Profile, dust impact is anticipated during construction, but it
would be minimal if dust suppression measures stipulated in the Air Pollution Control (Construction
Dust) Regulation is implemented.
4.9.3
For Elevated Pedestrian Corridor in Yuen Long Town
Connecting with Long Ping Station, the construction period will overlap with
that of the Project during late 2021 to 2025. According
to its EIA report, no adverse dust, gaseous emissions and odour
impacts are anticipated during construction with proper implementation of mitigation
measures.
4.9.4
For Housing Sites in Yuen Long South, the
construction period will overlap with that of the Project during 2021 to 2026. According to its EIA
report, dust impact would arise from the construction activities such as soil
excavation, site formation and wind erosion. No adverse residual air quality
impact is anticipated with implementation of mitigation measures during construction.
4.9.5
In
consideration of both the Project and concurrent projects will not generate
significant air quality impact, unacceptable adverse cumulative dust and
gaseous emissions impact is not anticipated.
4.9.6
Operation of the YLTN improvement works will only involve
limited scope of maintenance works to remove excessive silts, vegetation,
debris and obstructions. As such,
unacceptable cumulative impact to air quality is not anticipated during
concurrent operation with other projects.
4.10.1 No unacceptable
residual impact is anticipated from the construction and operation of the
Project with the implementation of the recommended mitigation measures and good
construction site practice.
4.11.1 Although no unacceptable air quality impacts have been identified, it is recommended to carry out odour monitoring during the construction phase to verify that the Project works will not result in any unacceptable impacts to the surrounding sensitive receivers. The Environmental Monitoring and Audit (EM&A) requirements are discussed in Section 10.
4.11.2 Weekly site inspections and audits will be conducted to ensure that the recommended mitigation measures are properly implemented during the construction stage to reduce the air quality impacts from the Project.
4.12.1 The
potential sources of air quality impacts associated with the construction and
operation of the Project have been identified and the potential impacts were
evaluated.
4.12.2 Construction
works of the Project will inevitably generate some fugitive dust, especially
during the excavation of the YLTN. With the
sectioning construction approach, the areas of excavation works should be limited
in scale. Regular water spraying will
also help to control dust nuisance.
4.12.3 Through
proper implementation of dust control measures required under the Air Pollution Control (Construction Dust)
Regulation, construction fugitive dust should be controlled at source to
satisfactory level.
4.12.4
Maintenance works for the Project will be small-scale in nature. During the operation phase, the
Project will unlikely cause any unacceptable air quality impacts in terms of
dust and odour. In addition, it is expected that odour nuisance of the YLTN will be alleviated due to
operation of the Project since the polluted DWF originally discharged into the
Project Site will be diverted to the YLSTW.
This is being considered as a beneficial impact of the Project.
4.12.5 With
the implementation of the recommended mitigation measures, it is expected that
the residual impacts from the construction and operation of the Project will
not exceed any relevant air quality criteria.
As such, no unacceptable residual air quality impacts are envisaged from
the construction and operation of the Project.
4.12.6 Cumulative
air quality impacts associated with concurrent projects within the Study Area
have been considered, no unacceptable impacts are anticipated.
4.12.7 In order
to ensure and demonstrate that mitigation measures are properly implemented
during the construction stage for reducing the air quality impacts from the
Project, weekly site inspections and audits as well as odour monitoring will be
conducted as part of the EM&A Programme of the Project.
1)
CEDD
(2008) – EIA Report for “Tuen Mun Area 54 Sewage
Pumping Station” (AEIAR-122/2008).