6.
AIR QUALITY IMPACT
6.1.1 The potential air quality impacts associated with the construction and operation of the proposed Spur Line project (the Project) are assessed according to the requirements stipulated in Section 3.7.1 of the Environmental Impact Assessment Study Brief (ESB-085/2001, October 2001) and presented in the following sections. The major components of the Project are described in detail in Chapter 2. The alignment of the Project, comprising a tunnel section (4.3 km) and an above ground section (3.1 km), will cover areas where existing and future residential development will be located. There is potential for residents to be affected by air quality impacts during the construction stage.
6.1.2 Construction works associated with the Project include:
·
A permanent way of a total route length of 7.4 km between Lok Ma Chau
and Sheung Shui Stations, 4.3 km of which will be constructed in tunnel, 0.9 km
on ramps or at grade, and the remaining 2.2 km on viaduct. The project includes
construction of diaphragm walls as the track descends at Sheung Shui and Chau
Tau, cut and cover and twin bored tunnels from Sheung Shui to Chau Tau and
viaduct construction.
·
Lok Ma Chau Station with Immigration and Customs Facilities and a
two-level footbridge linking Lok Ma Chau and Huanggang Stations.
·
Ventilation building, Kwu Tung station box, Emergency Access Point
shafts, TBM launching shaft, TBM recovery shaft, widening of Lok Ma Chau Road,
diversion of Chau Tau drainage channel.
·
Landscaping works and noise barriers where required. All other
mitigation works as recommended in the EIA.
6.1.3 As the proposed tunnel section will be constructed using a TBM, limited construction nuisance is expected. If no appropriate mitigation measures are followed and implemented, the cut and cover tunnel sections and the other exposed sections, will result in potential dust nuisance due to the proximity to nearby sensitive receivers. The air quality impacts due to the operation of the Project are considered to be minor.
6.1.4 A significant benefit is expected from the operation of the new railway, on local air quality around Man Kam To and Lok Ma Chau.
6.2.1
The principal legislation regulating air emissions in
Hong Kong is the Air Pollution Control Ordinance (APCO) [Cap. 311] and its
subsidiary regulations. The whole of the territory has been covered by Air
Control Zones. The Hong Kong Air Quality Objectives (AQOs) stipulate maximum
acceptable concentration of air pollutants. The AQOs for hourly, daily and
annual concentrations of four major pollutants, that are considered to be
related to the proposed Project, are shown in Table 6.1.
Table 6.1
Hong Kong Air Quality Objectives (AQOs)
|
Pollutants |
Concentration in micrograms per cubic metre (mg/m3) |
||
|
|
Averaging Time |
||
|
|
1 hour a |
24 hour b |
1 year c |
|
Nitrogen
Dioxide (NO2) |
300 |
150 |
80 |
|
Sulphur
Dioxide (SO2) |
800 |
350 |
80 |
|
Total
Suspended Particulates (TSP) |
500 e |
260 |
80 |
|
Respirable
Suspended Particulates (RSP)d |
- |
180 |
55 |
Notes : Concentrations measured at 298K(25oC)
and 101.325kPa (one atmosphere).
a Hourly
criteria not to be exceeded more than 3 times per year.
b Daily
criteria not to be exceeded more than once per year.
c Arithmetic
means.
d Respirable
suspended particulates means suspended particulates in air with a nominal
aerodynamic diameter of 10 micrometer (mm) or smaller.
e This
control limit has no statutory basis but is used as a target level for limiting
fugitive dust emissions generated by construction activities.
6.3.1
The representative air sensitive receivers (ASRs) that
will be impacted by the Spur Line are mainly rural village houses while the
remaining are high-rise residential buildings near Sheung Shui Station. They
are listed in Table 6.2. The location of the ASRs is shown in Figures
6.1 (sheets 1 to 5).
6.3.2 Sheung Shui is an established town containing a number of public and private residential developments, such as Choi Po Court, Choi Yuen Estate, Tai Ping Estate, Sheung Shui Centre, Lung Fung Garden and Tin Ping Estate. North of the existing Sheung Shui Station is Shek Wu Hui and Sheung Shui Wai with mainly traditional village houses.
6.3.3 The areas between Sheung Shui Station and Lok Ma Chau are mainly agricultural uses with villages scattered around Kwu Tung, Ho Sheung Heung, Chau Tau and Pak Shek Au. Within the vicinity of the Study Area are a number of enterprises including several timber mills, a small-scale chemical plant, several car repair shops, rattan factory, pottery factory, umbrella factory, as well as food and sauce factories.
6.3.4 Lok Ma Chau is a boundary control area with restricted access. Most of the land is for agriculture and fishponds use with a few scattered villages.
Table 6.2
Representative Air Sensitive Receivers
|
SR |
mPD
at Ground Level |
Description
of Existing Use |
No.
of Storeys of Existing Use |
|
1
|
+7.6 |
Low rise commercial / residential building at San Fung Avenue |
3*** |
|
2
|
+9.2 |
Choi Pik House, Choi Po Court |
36 |
|
3
|
+9.2 |
Choi Ying House, Choi Po Court |
33 |
|
4
|
+5.9 |
Village House |
3 |
|
5
|
+4.8 |
Village House |
3 |
|
6
|
+9.8 |
Village House |
2 |
|
7
|
+7.9 |
Village House |
1 |
|
8
|
+10.1 |
Village House |
1 |
|
9
|
+10.7 |
Kindergarten |
1 |
|
10
|
+8.5 |
Village House |
2 |
|
11
|
+12.6 |
School |
2 |
|
12
|
+17.5 |
Old People’s Home |
2 |
|
13
|
+19.1 |
Village House |
3 |
|
14
|
+13.3 |
Village House |
3 |
|
15
|
+15.7 |
Village House |
2 |
|
16
|
+24.0 |
Village House |
2 |
|
17
|
+9.0 |
Village House |
2 |
|
18
|
+6.4 |
Village House |
1 |
|
19
|
+6.4 |
Village House |
2 |
|
20
|
+5.3 |
Village House |
1 |
|
21
|
+3.5 |
Village House |
3 |
|
22
|
+5.3 |
Village House |
1 |
|
23
|
+4.5 |
Village House |
1 |
|
24
|
+9.1 |
Village House |
1 |
|
25
|
+7.2 |
Village House |
1 |
|
26
|
+3.4 |
Village House |
1 |
|
27
|
+3.2 |
Village House |
2 |
|
28
|
+3.2 |
Village House |
2 |
|
29
|
+2.9 |
Village House |
1 |
*** 3
storeys dwelling on top of 3 commercial storeys
Meteorology and Topography
6.4.1
The Study Area is situated in the northwest corner of
Hong Kong and falls within the Deep Bay Airshed. There are several hills higher
than 400 m in the Shenzhen area to the northeast (Wutong Mountain and Jigong
Tou Mountain) and two hills to the east (Kai Kung Leng and Tai To Yan) (Figure6.2).
6.4.2
Figure 6.3
illustrates the wind conditions at Lau Fau Shan Station of Hong Kong Observatory
which is close to the Study Area and will be taken as an indication of the
conditions that prevail at the western end of the alignment. During the winter
season, the dominant wind direction is northeasterly. For the rest of the
season, 45-50% of the winds are from the east while about 15-20% come from
the southwestern direction
[1]
. The wind pattern characteristic is the result of the blocking
effect of hills over the western part of the New Territories. Topographic
barriers also create eddies that change the direction and speed of the air.
6.4.3
In addition to these wind patterns, the Study Area
generally exhibits a limited dispersive capacity because of the occurrence of
an inversion layer in the morning and evening over this area[2].
In other words, the stable layer associated with the inversion layer acts as a
lid thereby trapping the pollutants[3].
Thus the occurrences of frequent and extensive inversions make it very
difficult for the air pollutants to disperse from the Deep Bay area.
6.4.4
Figure 6.4
illustrates wind conditions at the Hong Kong Observatory’s Ta Kwu Ling Station,
which is representative of the eastern part of the Study Area. The prevailing
wind direction in the Study Area is southeasterly, due to the channelling
effects of nearby mountain ridges.
Existing Conditions
6.4.5
There is no baseline air quality data available for
the entire site. EPD's latest data from the air quality monitoring station at
Yuen Long has been used to estimate the ambient air quality over the western
part of the Study Area. According to Air
Quality in Hong Kong (2000), the concentration levels of the NO2,
SO2, TSP and RSP for Yuen Long Station during 2000 are shown in
Table 6.3[4].
Table 6.3
Air Pollutants Concentrations at Yuen Long EPD Station (2000)
|
Pollutant |
Concentration in micrograms per cubic metre (mg/m3) |
|||||
|
1 hour |
24 hour |
Annual |
||||
|
Maximum |
AQOs |
Maximum |
AQOs |
Measured |
AQOs |
|
|
TSP |
N/A |
500 |
288 |
260 |
95 |
80 |
|
RSP |
281 |
N/A |
176 |
180 |
56 |
55 |
|
NO2 |
260 |
300 |
148 |
150 |
57 |
80 |
|
SO2 |
251 |
800 |
79 |
350 |
19 |
80 |
Note : N/A means Not Applicable.
6.4.6
Table 6.3 indicates that the concentrations of NO2
and SO2 are below the AQOs. The daily average maximum concentrations
of RSP are close to the AQOs while the daily average maximum concentration of
TSP and annual average of TSP and RSP concentrations exceed the AQOs.
6.4.7
The high TSP and RSP levels recorded at EPD's Yuen
Long Station were probably attributed to the intensive construction activities
in the vicinity of the station including works for Village Flood Protection for
Yuen Long, Kam Tin & Ngau Tam Mei (30CD), Drainage Channels for Yuen Long
& Kam Tin (43CD and 60CD), infrastructure provision for Yuen Long South
development, West Rail and the heavy industrial activities near Shenzhen. In
the long term, TSP and RSP levels in the Yuen Long area are likely to remain
high as construction and industrial activities continue to develop.
6.4.8
The closest EPD air quality monitoring station within
the eastern part of the Study Area is at Tai Po. Although there are only a
small number of industrial establishments, in comparison to the Tai Po Area,
scattered around Sheung Shui, pollutants associated with heavy industrial
activities in Shenzhen are believed to significantly influence air quality in
the Sheung Shui basin. Thus the air quality data from Tai Po Station is used
only as a reference to the general air quality for the eastern section of the
Study Area. Similarly, as reported in the Air
Quality in Hong Kong (2000), the concentration levels of the NO2,
SO2, TSP and RSP for Tai Po Station during 2000 are shown in Table
6.4[5].
Table 6.4
Air Pollutants Concentrations at Tai Po EPD Station (2000)
|
Pollutant |
Concentration in Micrograms per Cubic Metre (mg/m3) |
|||||
|
1 hour |
24 hour |
Annual |
||||
|
Maximum |
AQOs |
Maximum |
AQOs |
Measured |
AQOs |
|
|
TSP |
N/A |
500 |
174 |
260 |
63 |
80 |
|
RSP |
237 |
N/A |
165 |
180 |
48 |
55 |
|
NO2 |
259 |
300 |
156 |
150 |
47 |
80 |
|
SO2 |
153 |
800 |
59 |
350 |
12 |
80 |
Note : N/A means Not Applicable.
6.4.9
The data indicates that in 2000 the measured
concentration of TSP, RSP, NO2 and SO2 were well below
the AQO, except the medium-term average of NO2 which is exceeded the
AQO. The high NO2 levels were probably due to the emissions from
traffic utilizing the Fanling Highway and heavy industrial activities on Tai Po
Industrial Estate. These trends are expected to continue as the development of
the areas and the heavy utilization of Fanling Highway continues.
Future Air Quality
6.4.10 Due to rapid
development and heavy vehicular load near the Deep Bay area, both the Hong Kong
side and the Shenzhen side, it is likely that the air quality of the area will
deteriorate further, particularly if emissions to the atmosphere from future
developments are not properly controlled.
6.4.11 The proposed
development of the Kwu Tung NDA, currently being studied by TDD and PlanD, may
impact the local air quality. The findings and recommendations of the current study
should be considered in the evaluation of overall impacts of the area and the
development of suitable mitigation measures in other studies.
Introduction
6.5.1
The principal potential source of air quality impact
arising from the construction of the Spur Line will be fugitive dust. The
temporary dust nuisance, measurable as TSP (Total Suspended Particulates) and
RSP (Respirable Suspended Particulates) would be generated as a result of
construction activities, especially from excavation works where large quantity
of silty material movement may be involved. However, the nuisance from emission
of construction vehicles and plants is likely to be negligible because it is
anticipated that the number of these vehicles and plant will be relatively
small for the area involved.
Construction Programme
6.5.2 The tentative construction programme of the project is scheduled to start construction in mid 2002 and be complete in mid 2007. However, it is expected that the major construction activities that will result in major dust generation will take place during the site formation of the proposed Lok Ma Chau Station, the cut and cover tunnel sections and excavation and filling for the proposed Kwu Tung Station.
6.5.3 Potential fugitive dust sources from the construction of the Spur Line are expected from the following activities:
·
vehicular movement at the haul roads within the works
area and along the exposed track alignment;
·
material handling and stockpiling;
·
wind erosion of unpaved works areas;
·
earthworks in excavation of foundations and pilecap of
viaduct piers;
·
earthworks in cut and cover tunnel sections, launching
and recovery shaft (west of Sheung Shui area and area near Chau Tau);
·
earthworks in excavation and filling for the enabling
works for the future Kwu Tung Station;
·
earthworks in excavation and filling for the proposed
Lok Ma Chau Station.
6.5.4 The volumes of cut and fill to be generated within the alignment and station sites have been estimated from the engineering drawings produced at this stage. An approximate estimate of material volumes is given in Table 6.5.
Table 6.5
Estimated Material Quantities for the Spur Line
|
Construction
Activities |
Spoils
Generated (m³) |
Fill Required
(m³) |
|
Tunnel Alignment : |
||
|
Eastern Open Ramp |
22,000 |
0 |
|
Eastern Cut and Cover
Tunnel |
181,000 |
15,000 |
|
Launching Shaft at East (including diaphragm walls) |
83,000 |
26,000 |
|
East Approach EAP |
Minimal |
0 |
|
Eastern Ventilation
Building |
9,000 |
0 |
|
Eastern EAP Shaft (Shaft) |
3,000 |
0 |
|
Eastern EAP Shaft (Building
Foundation) |
3,000 |
0 |
|
Kwu Tung Station Box |
256,000 |
18,000 |
|
Western EAP Shaft (Shaft) |
3,000 |
0 |
|
Western EAP Shaft (Building
Foundation) |
3,000 |
0 |
|
Bored-Tunnel |
390,000 |
0 |
|
Western Ventilation
Building |
500 |
0 |
|
TBM Exit Shaft |
41,000 |
6,000 |
|
Western Cut and Cover Tunnel (including diaphragm walls) |
103,000 |
31,000 |
|
Western Open Ramp |
40,000 |
4,000 |
|
Total Estimated
Quantity for Tunnel |
1,137,500 |
100,000 |
|
Viaduct Alignment : |
||
|
Foundations |
27,500 |
0 |
|
Maintenance Access |
7,000 |
20,000 |
|
EAP |
2,000 |
5,000 |
|
Total Estimated
Quantity for Viaduct |
36,500 |
25,000 |
|
Terminus : |
||
|
Foundations |
24000 |
0 |
|
Terminus Platform |
0 |
450,000 |
|
Surrounding Areas
(including reedbeds & Marshland) |
0 |
227,000 |
|
EVA |
20,000 |
23,000 |
|
Total Estimated
Quantity for Terminus |
44,000 |
700,000 |
Lok Ma Chau Station
6.5.5 During the foundation cutting works associated with the Lok Ma Chau Station, the dust impact is expected to be relatively insignificant as the excavated material of that area will be mainly from fishponds that have a high moisture content. Some of this may be transferred to other areas of the site such as Ecological Mitigation Areas. As shown in Table 6.5, about 450,000 m3 of fill material will need to be imported for the terminus platform. The river will probably be used as the route for transportation, thus minimising the distance for movement of materials, hence minimising dust generation. Implementation of appropriate mitigation measures is required to minimize dust generation. If road transportation is required for import of material, mitigation measures described below will be required to minimize dust impacts on the sensitive receivers at Lok Ma Chau (ASR 29).
6.5.6 For the construction of other superstructure sections of the station, the amount of spoil generated and filling material required is estimated to be about 44,000 m3 and 250,000 m3 respectively. Construction of various government control offices such as Immigration and Customs facilities, security facilities, quarantine facilities and Department of Health facilities involve only minor generation of waste and requirement for filling of materials. It is anticipated that the associated construction dust impacts to the sensitive receivers will not be significant because the material movement involved will be minor. Any materials dropped on sealed roads must be cleaned up immediately to prevent any dust nuisance.
6.5.7 Widening the Boundary Patrol/Control Road and Lok Ma Chau Road to serve as emergency vehicle access for the proposed Lok Ma Chau Station is required. The major potential construction dust impact due to the road widening including the associated drains, sewers and water distribution mains in the Lok Ma Chau Boundary Crossing Area is the dust arising from breaking up the existing road surface. Construction of drains, culverts, sewers and water distribution mains will require excavation of trenches. Laying this new infrastructure will be conducted section by section and spoil will only be stockpiled at each local works area; thus the quantity of the excavated material will be very limited.
6.5.8 The duration of stockpiling will be short as most of the material will be re-used as backfill material for the open cut trenches. Levelling, compacting and resurfacing of the new roads will not involve significant movement of materials; hence dust impacts will not be significant. However, proper watering of exposed spoil should be undertaken throughout the construction phase to minimize cumulative impacts of these and other concurrent works such as Shenzhen River Regulation Phase III and San Tin MDC East Channel, and enable air quality to comply with the AQO at all times.
6.5.9 A footbridge connecting the Huanggang Station and proposed Lok Ma Chau Station will accommodate the smooth passenger flow upon the commissioning of Spur Line. Bored piling will be required to provide foundations for the footbridge. As the construction activities will only involve minor cutting and filling of materials, it is anticipated that the dust impacts to the sensitive receivers will not be significant.
Open Ramp Section
6.5.10 Open ramp section is proposed at the western approach of the tunnel. The construction method will be fairly straightforward, namely excavation from the top to the desired levels, followed by construction of diaphragm walls. It is estimated that the amount of spoil generated and fill required at western ramp is about 40,000 m3 and 4,000 m3 respectively. Only limited local stockpiles will be needed for the finishing back-filling processes, while the majority of the excavated materials will be exported to suitable sites for final disposal.
6.5.11 Preliminary information from geotechnical studies reviews indicates that the majority of the excavated portion will be beneath the groundwater table. Thus the moisture content of the excavated materials will be relatively high, in the order of 30%. Given the high moisture content of the excavated materials, the dust impacts are likely to be minor. As both sites are located near to existing traffic networks, stockpiles of such excessive materials and haulage will be minimised to prevent unnecessary dust nuisance. Meanwhile, with good site housekeeping practices maintained on site during the whole construction stage, dust impacts at nearby sensitive receivers will be controlled within AQO criteria.
6.5.12 With consideration of the high moisture content of the excavated materials, limited stockpile duration, short haulage involved and implementation of sufficient watering of the site areas throughout the construction stage, the potential dust arising from the construction activities can be significantly reduced. Hence with suitable mitigation, associated nuisance will be insignificant and compliance with AQOs can be achieved at the representative sensitive receivers at all times.
Cut and Cover (C&C) Tunnel Sections
6.5.13 As the eastern C&C tunnel site in Sheung Shui is within an industrial area, no ASRs are identified in the immediate vicinity, the nearest ASRs identified are the residential premises in Choi Po Court, Sheung Shui (ASR 3) and a village house in Long Valley (ASR 4). The buffer distances between the works areas to these two ASRs are about 200 and 600m respectively. The western C&C tunnel site in the Chau Tau area is near to scattered village houses. The nearest identified ASR is a village house (ASR 20), about 20m distance from the works site in Chau Tau.
6.5.14 For the construction of the eastern and western cut and cover tunnel sections, the quantities of spoil generated are estimated to be 181,000 and 103,000 m3 respectively. Due to the nature of the proposed works, the quantity of imported material will be insignificant in comparison with the quantity of excavation. Only small amount of excavated materials will be needed to be stockpiled locally for the back-filling processes, while the majority of the excavated material will be exported to suitable sites for final disposal.
6.5.15 A review of geotechnical studies indicated that the majority of the excavated portion will be beneath the groundwater table. Thus the moisture content of the excavated materials will be relatively high. As both of the C&C tunnel sites are located near to existing traffic networks, stockpiles of such excessive materials and haulage will be minimised to prevent unnecessary dust nuisance.
6.5.16 With consideration of the high moisture content of the excavated materials, limited stockpile duration, short haulage involved and implementation of sufficient watering of the site areas throughout the construction stage, the potential dust arising from the construction activities can be significantly reduced. Hence with suitable mitigation, associated nuisance will be insignificant and compliance with AQOs can be achieved at the representative sensitive receivers at all times.
Bored-Tunnel Section
6.5.17 A twin bored-tunnel, with an external diameter of 8.4m and a length of 4.3km, is proposed to be constructed as one of the key components of the proposed Project. The bored-tunnel will be constructed using the TBM method, which has been successfully used to construct Tsing Tsuen Tunnels of West Rail Phase I.
6.5.18 As the proposed bored-tunnel alignment is beneath the groundwater table, the moisture content of the mucked out material, in the form of paste, will be very high. Before being loaded into trucks for disposal, the paste has to be specially treated to lower the water content. The treatment plant will be located at the Sheung Shui works area that facilitates vehicular access to Fanling Highway. Due to the wet nature of the mucked out spoil from the TBM operation, dust nuisance will not be significant.
6.5.19 From the preliminary design information, the bored-tunnel will be constructed at the rate of about 10m per day, i.e. around 560 m3 per day. Based on the average truck load capacity of 6m3, it is estimated that the maximum number of loaded trucks will be about 10 per hour. Even with the consideration of the return trip, the estimated traffic generated is about 20 veh/hr. Given such a small number of truck trips for transportation and the fact that limited haulage will be required, due to the availability of easy access to Fanling Highway, haulage dust nuisance is expected to be insignificant if the standard site housekeeping practice is in place.
TBM Shaft Sections
6.5.20 During the construction of the bored-tunnel, two shafts are proposed: one at the western side, the TBM recovery shaft, located next to the Chau Tau and the other at the eastern side, the TBM launching shaft, located at the Shek Sheung Ho area. The TBM Launching Shaft is located in the industrial area at Sheung Shui, the nearest ASR is the village house in Long Valley (ASR 4), at a distance of about 100 m.
6.5.21 The spoil generated, estimated to be 83,000 and 41,000 m3 for TBM Launching Shaft and TBM Recovery Shaft respectively, are expected to be high in moisture content. Thus the associated dust nuisance from the excavation of such materials will be minor. Meanwhile, as the site is located near to the existing traffic networks, the possible haulage involved will be limited. Hence dust nuisance related to the haulage will also be limited.
6.5.22 Given the high moisture content of the excavated materials, short haulage involved and implementation of sufficient watering of the site areas throughout the construction stage, the potential dust impacts arising from the construction activities can be significantly reduced. Hence with suitable mitigation, associated nuisance will be insignificant and compliance with AQOs can be achieved at the representative sensitive receivers at all times.
Kwu Tung Station Box Section
6.5.23 The Kwu Tung Station Box is proposed around the midway of the bored-tunnel, which is located in the future town centre of the proposed Kwu Tung NDA. The area is characterised by scattered low-rise houses, either used for residential or industrial uses. The nearest identified ASR is the village house immediately next to the works area (ASR 14, with a buffer distance of about 10 m).
6.5.24 For the construction of the Kwu Tung Station Box, the quantity of spoil generated is estimated to be 256,000 m3. Only a small amount of excavated materials will be needed to be stockpiled locally for back-filling processes, while the majority of the excavated materials will be exported to suitable sites for final disposal.
6.5.25 As the site is located near to the existing traffic networks, served by both Castle Peak Road and Fanling Highway, limited haulage along site road will be involved. The site haul road is proposed to be paved to further control the potential haulage dust. As the majority of the excavation will be beneath the groundwater table, the moisture content of the excavated materials will be relatively high. Thus minor dust nuisance is expected in association with this excavation process.
6.5.26 Given the high moisture content of the excavated materials, limited stockpile needed, short haulage involved and implementation of sufficient watering of the site areas throughout the construction stage, the potential dust arising from the construction activities can be significantly reduced. Hence with suitable mitigation, associated nuisance will be insignificant and compliance with AQOs can be achieved at the representative sensitive receivers at all times.
Construction of Ventilation Building and Emergency Access Point Shaft
6.5.27 Two Ventilation Buildings, (VBs, located at chainage 31+080 and chainage 34+850) and two Emergency Access Point Shafts (EAPs, located at chainage 32+100 and chainage 33+900) are being proposed. The estimated quantity of the excavated material for the eastern VB is 9,000 m3, while for the western VB, the quantity of additional excavated material is expected to be minimal as the majority of its excavation will be conducted as a part of the Western C&C tunnel section. The estimated spoil generated for each EAP is about 3,000 m3 and 3,000 m3 for the building foundation respectively.
6.5.28 As all these excavated materials are expected to have a high moisture content, the associated dust nuisance from the excavation of such materials will be minor. Meanwhile, as the sites are located near to the existing traffic networks, the possible haulage involved will be limited. Hence dust nuisance related to the haulage will be limited too.
6.5.29 Given the high moisture content of the excavated materials, short haulage involved, limited quantity of excavation involved and implementation of sufficient watering of the site areas throughout the construction stage, the potential dust impacts arising from the construction activities can be significantly reduced. Hence with suitable mitigation, associated nuisance will be insignificant and compliance with AQOs can be achieved at the representative sensitive receivers at all times.
Diversion of Chau Tau Drainage Channel
6.5.30 The upstream tributary of the Chau Tau Channel at chainage 34+850 km will also need a temporary and permanent diversion. The main Chau Tau drainage channel at chainage 35+400 km does not require diversion as part of the works. However, it is close to the abutment for the viaduct and a box structure of the railway. As only minor cutting and filling of materials is expected, it is anticipated that the associated dust impacts will not be significant.
Viaduct Foundation Excavation
6.5.31 The viaduct section of the Spur Line will start at the end of the western open ramp section (i.e. chainage 35+420) and finish at the proposed Lok Ma Chau Station. For the construction of the viaduct sections, a series of viaduct piers will be constructed, including the excavation of pilecaps foundation, construction of pilecaps, construction of piers and followed by the erection of the pre-cast viaduct sections.
6.5.32 Only the construction of foundations will involve excavation, which has the potential to create dust nuisance. The remaining construction activities are relatively minor in terms of dust nuisance. Based on the preliminary engineering design information, the estimated spoil generated is about 36,500 m3.
6.5.33 Based on the preliminary findings of the geotechnical studies, the groundwater level of the proposed viaduct section areas is quite high. Hence all these excavated materials are expected to have high moisture content. Thus the associated dust nuisance from the excavation of such materials will be relatively minor. Meanwhile, given the small quantity of the excavation and the spread along the whole viaduct section (about 2.2 km in total), the possible haulage involved in each local area will be very limited. Hence dust nuisance related to the haulage will be insignificant.
6.5.34 Given the high moisture content of the excavated materials, limited haulage involved, limited quantity of excavation involved and implementation of sufficient watering of the site areas throughout the construction stage, the potential dust impacts arising from the construction activities can be significantly reduced. Hence with suitable mitigation, associated nuisance will be insignificant and compliance with AQOs can be achieved at the representative sensitive receivers at all times.
Other Activities
Concrete Batching Plant
6.5.35 From the latest design information, concrete batching plants are unlikely to be needed in the Project. However, if a concrete batching plant is needed at any stage of the Project, a licence from the Authority will be required prior to the operation of the plant. As the operation of such plant, if presented, is strictly controlled under the licence, potential dust impact on the nearby sensitive receivers will be reduced to acceptable levels.
6.5.36 According to the Air Pollution Control (Specified Processes) Regulations, concrete batching plants with a silo capacity greater than 50 tonnes will be considered as a specified process and require a licence to be operated. Under this regulation, an Air Pollution Control Plan for the batching plant will be prepared in an effort to control the fugitive dust.
Mortar Plant
6.5.37 According to the preliminary engineering design information, mortar plant is proposed to facilitate the operation of the TBM tunnelling, such as waterproofing of the tunnel lining. Under the TBM works, special additives will be used in the mortar plant to facilitate the tunnel lining works. The number of proposed mortar plants will depend on the number of TBM machine being employed under the Project. For example, if two TBM machines are used, two mortar plants will be set-up. Based on preliminary design information, the output capacity of the plant is likely to be less than 350 m3/day and the silo capacity involved may exceed 50 tonne. To support the TBM operation and to minimize the potential dust impact associated with the proposed plant, the plant(s) is proposed at the Sheung Shui area, because it is well-served by existing traffic networks (Fanling Highway), easy for construction operation (located next to the proposed TBM Launching Shaft) and relatively separated from nearby sensitive receivers.
6.5.38 Under the Air Pollution Control (Specified Processes) Regulations, a mortar plant may be classified as Cement Works, which is a Specified Process and requires a licence for operation. The licence requirement also applies to the process if the silo capacity of the plant exceeds 50 tonnes. As both of these definitions are likely to be fulfilled, the proposed mortar plant is likely to require a licence for operation and control under this Regulation. To fulfil the requirement of the Regulation, an Air Pollution Control Plan for the plant will be prepared to control the dust. Thus, operation of plant will comply with the strict dust controls so as to reduce the potential dust impact on the nearby sensitive receivers.
6.5.39 The remaining construction activities are not expected to produce any dust nuisance to the air sensitive receivers. Landscaping areas within the Spur Line alignment will not involve significant movement of earth materials; hence dust impacts are expected to be insignificant.
6.5.40 Proper dust suppression measures, as stipulated by Air Pollution Control (Construction Dust) Regulation, are always required when handling exposed spoil throughout the construction phase to ensure that the compliance of AQOs is achieved at the ASRs. For example, proper watering of exposed spoil will need to be undertaken throughout the construction phase so that dust generation is minimised and compliance with the AQOs can be achieved at the representative ASRs.
6.5.41 Cumulative dust impacts as a result of concurrent construction activities both within the Study Area and surrounding areas are not expected to be significant provided that proper dust suppression measures are implemented. These are highlighted below.
Dust
Mitigation Measures
6.5.42 The following dust control measures as part of good construction site practice should be incorporated in the Contract Specification and implemented to minimize dust nuisance arising from the works to within acceptable levels:
(i)
The Contractor shall undertake
at all times to prevent dust nuisance as a result of his activities. Effective
dust suppression measures, as necessary, should be installed to minimize air
quality impacts, at the boundary of the site and at any sensitive receivers.
(ii)
The Contractor shall frequently clean and water the
site to minimize fugitive dust emissions.
(iii)
Effective water sprays shall be used during the
delivery and handling of all raw sand, aggregate and other similar materials,
when dust is likely to be created, to dampen all stored materials during dry
and windy weather.
(iv)
Watering of exposed surfaces shall be conducted as
often as possible depending on the circumstances.
(v)
Areas within the site where there is a regular
movement of vehicles shall have an approved hard surface, be kept clear of
loose surface materials and / or regularly watered.
(vi)
Where dusty materials are being discharged to vehicle
from a conveying system at fixed transfer point, a three-sided roofed enclosure
with a flexible curtain across the entry shall be provided. Exhaust fans shall
be provided for this enclosure and vented to a suitable fabric filter system.
(vii)
The Contractor shall confine haulage and delivery
vehicles to designated roadways inside the site. If in the opinion of the Engineer,
any motorised vehicle is causing dust nuisance, the Engineer may require that
the vehicle be restricted to a maximum speed of 15 km per hour while within the
site area.
(viii)
Wheel cleaning facilities shall be installed and used
by all vehicles leaving the site. No earth, mud, debris, dust and the like
shall be deposited on public roads. Water in the wheel cleaning facility shall
be changed at frequent intervals and sediments shall be removed regularly. The
Contractor shall submit details of proposals for the wheel cleaning facilities
to the Engineer prior to construction of the facility. Such wheel cleaning
facilities shall be usable prior to any earthwork excavation activity on site.
The Contractor shall provide a hard-surfaced road between any cleaning facility
and the public road.
(ix)
Any stockpile of dusty material shall be either: a)
covered entirely by impervious sheeting; b) placed in an 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.
(x)
Chemical wetting agents shall only be used on
completed cuts and fills to reduce wind erosion.
(xi)
All site vehicular exhausts should be directed
vertically upwards or directed away from ground to minimize dust nuisance.
(xii)
Ventilation system, equipped with proprietary filters,
should be provided to ensure the safe working environment inside the tunnel.
Particular attention should be paid to the location and direction of the
ventilation exhausts. The exhausts should not be allowed to face any sensitive
receivers directly. Consideration should also be given to the location of
windows, doors and direction of prevailing winds in relation to the nearby
sensitive receivers.
6.5.43 In addition, based on the Air Pollution Control (Construction Dust) Regulation, any works involved regulatory and notifiable works, such as stockpiling, loading and unloading of dusty materials, shall take precautions to suppress dust nuisance. Examples of dust suppression methods are:
·
The working area of any excavation or earthmoving
operation shall spray with water or a dust suppression chemical immediately
before, during and immediately after the operation so as to maintain the entire
surface wet;
·
Exposed earth shall be properly treated by compaction,
turfing, hydroseeding, vegetation planting or sealing with latex, vinyl,
bitumen or other suitable surface stabiliser within six months after the last
construction activity on the construction site or part of the construction site
where the exposed earth lies; and
· Any stockpile of dusty materials shall be either covered entirely by impervious sheeting or placed in an area sheltered on the top and three sides; and sprayed with water or a dust suppression chemical so as to maintain the entire surface wet.
· Other suitable dust control measures as stipulated in the Air Pollution Control (Construction Dust). Regulation, where appropriate, should be adopted.
Concurrent
Construction Activities
6.5.44 A summary of the projects on-going in the area of the Spur Line Project is listed below and shown in Figure 2.3.
Table 6.6
Summary of Major Committed Projects Adjacent to the Spur Line
|
Project |
Commencement Date |
Completion Date |
|
Shenzhen River Training Phase
III |
Mid 2001 |
Late 2004 |
|
San Tin Eastern Main Drainage |
September
2002 |
2005 |
|
Fanling, Sheung Shui &
Hinterland Main Drainage |
1999 |
2003 |
|
Planning & Development
Study on Northeast New |
Programme not yet confirmed |
- |
|
Lok Ma Chau Control Point
Expansion Project |
Mid 1999 |
2003 |
6.5.45 Currently there are three major public works projects scheduled near the Sheung Shui to Lok Ma Chau Spur Line. The projects are the Fanling, Sheung Shui & Hinterland Main Drainage Channel Realignment Works, the San Tin Eastern Main Drainage Channel at Lok Ma Chau and the Expansion of Kiosks at Lok Ma Chau Boundary Crossing. The former is almost completed and the second will start in 2002. Although the construction programmes of San Tin Eastern Main Drainage Channel and the Spur Line are in the same time frame, the cumulative impacts is expected to be very minor. This is because the major site formation of the channel and the Lok Ma Chau Terminus will take place in the area which is far away from the nearby air sensitive receivers. As a result, the potential dust impact from the channel is anticipated to be insignificant. In addition, the construction works associated with the drainage improvement work are relatively minor in terms of site formation, The dust impacts are considered to be limited provided that the control measures stipulated under the Air Pollution Control (Construction Dust) Regulations are properly followed. Therefore, the potential cumulative dust impacts arising from these projects are considered to be not significant.
6.5.46 Based on the latest construction programme for the Expansion of Kiosks at the Lok Ma Chau Boundary Crossing, the expansion works will be completed in 2003. It is expected that the main construction period for the viaduct section of the Spur Line will begin in 2003 and will coincide with the final stages of Lok Ma Chau Boundary Crossing construction. Consequently, the cumulative air impact arising from Lok Ma Chau Boundary Crossing is expected to be very minor as far as the Spur Line Project is concerned.
Potential cumulative impacts due to the works of the Shenzhen River Training Scheme are expected to be very minor as the project is almost complete in the vicinity of the Spur Line Project. No details are available at this stage for the works to be carried out or the programming of the Planning and Development Study on NENT.
6.5.47 Potential cumulative impacts due to the works of the Shenzhen River Training Scheme Phase III are expected to be very minor as the project is almost complete in the vicinity of the Spur Line Project. No details are available at this stage for the works to be carried out or the programming of the Planning and Development Study on NENT.
6.5.48 The Sheung Shui to Lok Ma Chau Spur Line will be constructed between 2002 and 2007 and is unlikely to cause any cumulative construction dust impact with these project.
Vehicular
Emission
6.6.1
There are no major air quality impacts associated with
the operation of the Spur Line as only Electric Multiple Units (EMU), which
would not emit atmospheric pollutants, will be used. Used air inside the
station will be removed through ventilation facilities and no adverse air
quality impacts to nearby ASRs are expected.
6.6.2 Ventilation fans and air ventilation systems should be provided to ensure sufficient local air movement within the station concourse. Smoke extraction vents should also be provided in the event of fire. The vents for all ventilation systems should be directed away from nearby sensitive receivers.
6.6.3 As such, none of the areas will likely be subject to adverse air quality impact due to the operation of the proposed Spur Line.
6.6.4 The additional traffic flow around Sheung Shui Station as a result of the proposed Spur Line is expected to be minimal, as passengers will generally reach the station on foot or by means of public transport. No more trains than at present will pass through Sheung Shui Station; some trains will simply be diverted onto the proposed Spur Line. Works vehicles are not expected to be increased significantly above present traffic flows.
6.6.5 The road leading to the proposed Lok Ma Chau Station is a restricted access road, for which a permit is required to cross into the Closed Boundary Area. The road will be widened within the Closed Boundary Area for use as an Emergency Vehicle Access (EVA) route. Vehicles will therefore continue to be restricted in the area, and the additional traffic due to the presence of the proposed station will be minimal. No public access to the proposed station will be permitted.
Operational Impacts
6.6.6 Operationally, the new railway is likely to offer a significant beneficial impact on local air quality at Lok Ma Chau, Man Kam To and the arterial approach roads.
6.6.7 Intercity bus, minibus and coach crossings at the Lok Ma Chau and Man Kam To crossings are expected to reduce as the Spur Line offers a more convenient and air conditioned direct entry into the Shenzhen Metro System.
6.6.8 Currently, queuing and transit of these vehicles at the major crossings contributes to the poor air quality around these crossings and their approaches.
Construction
Dust Impact
6.7.1
The construction dust impact assessment has identified
Air Sensitive Receivers (ASRs) within the Study Area. It has also identified
those works that have potential to generate substantial dust impact to the
nearby ASRs.
6.7.2 The transportation of earth material by trucks over site haul roads is likely to be the dominant dust generation during the excavation of the construction stage. With the implementation of the recommended dust suppression measures and backed up by a proper designed EM&A programme, the construction of Spur Line is expected to comply with the Air Quality Objectives.
Operational Air Quality Impact
6.7.3 Air quality impacts arising from the operational phase of the proposed Spur Line are not considered to be of concern as limited potential sources have been identified. No adverse residual impacts due to the operation of the Spur Line are anticipated.
Environmental Monitoring and Audit (EM&A) Requirements
6.7.4 Dust impacts during the construction phase can be readily mitigated through implementation of standard mitigation measures and good housekeeping practices.
6.7.5 However, if the proposed construction dust mitigation measures are not fully implemented, it is likely that some nearest air sensitive receivers would suffer unacceptable impact. It is therefore recommended that an Environmental Monitoring & Audit (EM&A) programme in respect of dust issues is carried out at four locations. The first location is at Lok Ma Chau (ASR 29) due to the proximity to the “Special Measures Zone” of Deep Bay. The second one is at Chau Tau (ASR 20). The third one is at Kwu Tung (ASR 14) and the fourth one is at Sheung Shui (ASR 4). All these four representative sensitive receivers are very close to the construction works areas and hence, are the mostly likely being impacted if dust suppression measures are not properly implemented.
[1] Royal
Observatory Hong Kong, 1981: A Preliminary Report on the Meteorological
Conditions in the Deep Bay Area.
[2] Royal Observatory Hong Kong, 1984: Meteorological
Assessment of Atmospheric Transport Condition in the Deep Bay Airshed.
[3] Roland, B.S. (1988): An Introduction to Boundary Layer
Meteorology, Kluwer Academic Publishers, p.666.
[4] EPD 2000: Air Quality in Hong
Kong 2000, HKSAR Government
[5] EPD 2000: Air Quality in Hong
Kong 2000, HKSAR Government
