This Section presents an assessment of the potential air quality impacts
associated with the construction and operation of the Project.
4.2
Legislation
Requirements and Evaluation Criteria
The principal legislation for the management of air
quality in Hong Kong is the Air Pollution
Control Ordinance (APCO) (Cap. 311).
Under the APCO, the Hong
Kong Air Quality Objectives (AQOs), which are
presented in Table 4.1, stipulate the
statutory limits for air pollutants and the maximum allowable numbers of exceedences over specific periods.
Table 4.1 Hong Kong Air Quality Objectives (mg m-3) (a)
|
Air Pollutant |
Averaging Time |
||||
|
|
1 Hour (b) |
8 Hour (c) |
24 Hour (c) |
3 Months (d) |
1 Year (d) |
|
Total Suspended Particulates (TSP) |
- |
- |
260 |
- |
80 |
|
Respirable Suspended Particulates (RSP) (e) |
- |
- |
180 |
- |
55 |
|
Sulphur Dioxide (SO2) |
800 |
- |
350 |
- |
80 |
|
Nitrogen Dioxide (NO2) |
300 |
- |
150 |
- |
80 |
|
Carbon Monoxide (CO) |
30,000 |
10,000 |
- |
- |
- |
|
Photochemical Oxidants (as ozone (O3)) (f) |
240 |
- |
- |
- |
- |
|
Lead (Pb) |
- |
- |
- |
1.5 |
- |
|
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 means (e) Suspended airborne particulates with a
nominal aerodynamic diameter of 10 micrometres or smaller (f)
Photochemical
oxidants are determined by measurement of ozone only |
|||||
In addition, the Technical Memorandum of
Environmental Impact Assessment Ordinance (EIAO-TM) stipulates an hourly
TSP criterion of 500 mg m-3 for
construction dust impact assessment.
The measures stipulated in the Air Pollution Control (Construction Dust) Regulations should be
followed to reduce dust impacts.
The Project area is located at the Hong Kong
boundary. Villages are located to the south
or southeast of the river. No commercial
and industrial developments are identified within the Study Area (i.e. within
500m from the Project Site) in HKSAR.
Schools, residential dwellings and a sewage treatment works are
identified to the north or northwest of the river within Shenzhen region.
Since the Project area is rural and no major air
emission sources are identified, the existing air quality in the vicinity of
the river is affected by general background air quality in the Pearl River
Delta.
There is no EPD Air Quality Monitoring Station (AQMS)
operating in the Study Area. The nearest AQMS operated by EPD is
located at Tai Po. The means of annual
average concentrations of air pollutants recorded at Tai Po’s AQMS from 2005 to
2009 are adopted to characterise the background air quality for the impact
assessment. However, as CO concentration
is not measured at the Tai Po’s AQMS, the CO concentrations measured at Tap Mun’s AQMS are used to establish the background CO
concentration for the Study Area. The
background air quality for the Project is summarised in Table 4.2.
Table 4.2 Background
Air Quality
|
Air Pollutant |
Background Concentration (mg m-3) (a) |
|
Total Suspended
Particulates (TSP) |
67 |
|
Respirable Suspended Particulates (RSP) |
50 |
|
Nitrogen Dioxide (NO2) |
51 |
|
Sulphur Dioxide (SO2) |
16 |
|
Carbon Monoxide (CO) |
745 (b) |
|
Notes: (a)
Arithmetic
mean of annual average data on air pollutant concentrations measured at the
EPD Tai Po AQMS for the period from 2005 to 2009. (http://www.epd-asg.gov.hk/english/report/aqr.php). (b)
Since
CO concentration is not measured at Tai Po’s AQMS, the CO concentrations
measured at Tap Mun’s AQMS are used due to the similar
environment to the Study Area. |
|
4.4
Identification
of Air Sensitive Receivers
The major landuse within the
Study Area is village environs and no commercial or industrial establishments
were identified. Representative Air Sensitive Receivers (ASRs)
were identified in line with the requirements set out in the EIA Study Brief (ESB-199/2004) and Annex 12 of the EIAO-TM. They are summarised
in Table 4.3 and illustrated in Figure
4.1. The list includes existing and planned ASRs within the
Study Area. The Study Area is now
covered by the Development Permission Area (DPA) Plans. The planned ASRs were identified with
reference to the relevant planning studies such as the Land Use Planning for the Closed Area.
Table 4.3 Representative
Air Sensitive Receivers (ASRs)
|
ASR |
Location |
Type
of Uses (a) |
Approx.
Distance from the nearest Project Site Boundary (m) |
Approx.
Max. Height of Building |
|
A1 |
Muk Wu Chuen
Yiu |
R |
400 |
10 |
|
A2 |
Ta Ku Ling Ling Ying Public School |
G/IC |
387 |
3 |
|
A3 |
Chow Tin Tsuen |
R |
458 |
10 |
|
A4 |
Fung Wong Wu |
R |
390 |
10 |
|
A5 |
Ta Kwu
Ling Village |
R |
11 |
10 |
|
A6 |
Ta Kwu
Ling Police Station |
G/IC |
72 |
10 |
|
A7 |
Ta Kwu
Ling Fire Station |
G/IC |
115 |
6 |
|
A8 |
ArchSD Property Services
Branch |
G/IC |
100 |
3 |
|
A9 |
Kan Tau Wai |
R |
240 |
10 |
|
A10 |
Kaw Liu Village |
R |
11 |
10 |
|
A11 |
Tsung Yuen Ha |
R |
232 |
10 |
|
A12 |
Chuk Yuen
Village Resite (b) |
R |
320 |
10 |
|
A13 |
Proposed
Future Recreation Use (c) |
Re |
77 |
10 |
|
A14 |
Kan Tau Wai
Village House |
R |
352 |
10 |
|
Notes: (a)
R = Residential premises, G/IC =
Government/Institution/Community, Re = Recreation (b)
With reference to the EIA of the proposed Liangtang/Heung Yuen Wai
Boundary Crossing Point (LT/HYW BCP), the relocation of Chuk
Yuen Village will be completed by early 2013, before the commencement of the
Shenzhen River Regulation Stage 4 works and the construction of the LT/HYW
BCP Project. Therefore instead of the
existing Chuk Yuen Village, the future Chuk Yuen Village Resite will
be included in the dust modelling and impact assessment. (c)
With reference to the Land
Use Planning for the Closed Area – Feasibility Study, recreational use
was proposed in the area by the Planning Department. While detailed plans for air sensitive uses
are not readily available, this location is chosen for assessment of
potential air quality impacts in the proposed recreation area. |
||||
4.5
Potential
Sources of Impact
4.5.1
Construction Phase
The construction phase of the Project
will last for 44 months (ie August 2013 to March
2017, tentatively). An advance work
contract on the reprovisioning of boundary fence and patrol
road on Hong Kong side, as part of this Project, will last for about 36 months
between the period of February 2012 and January 2015, tentatively.
Advanced Works – Reprovisioning
of Boundary Fence and Patrol Road on Hong Kong Side
Reprovisioning of patrol road and boundary
fence within the Project Site boundary has been described in Section 3.2. The major construction activities may include
excavation, footing construction, fence installation, road construction and
demolition/relocation of existing boundary fence. Given that the reprovisioning
works will be carried out section by section and the road is narrow, the volume
of excavated materials or filled materials required will be limited at any one
time. With the implementation of dust
mitigation measures stipulated in Air
Pollution Control (Construction Dust) Regulation, the dust impact will be
alleviated and the advanced works will not cause any adverse air quality
impact.
River Modification and Associated Works
River diversion will be carried out before the
commencement of the construction of the regulation works. The main construction works include dredging
of river sediment, soil excavation, embankment construction, dry weather flow
interception works, and landscaping works.
Detailed construction methodology has been described in Section 3.4.
The Project Site will be divided into four works
areas along the river as shown in Figure
4.1.
The construction works will be carried out from the
downstream to upstream of each works area.
In accordance with the works programme, latest engineering design and
the experience from Shenzhen River Stage 3 regulation works, the maximum size
of the active construction areas at any one time will not be larger than 150m
long along the river at each works area.
Construction dust is the
major air quality concern during the construction phase. Truck movements, excavation works, embankment
construction, dry weather flow interception works,
patrol road and boundary
fence re-provisioning and wind erosion were identified to be the major dust generating activities.
Based on the latest engineering design, it
is estimated that about 51,000 m3 of construction and demolition
(C&D) materials and sediments will be excavated from the Project during the
peak construction month. About 8,500m3
of the excavated materials will be reused on-site and the rest (about 42,500m3)
of excavated materials will be temporarily stored in the four stockpiling areas
located on the
Shenzhen side of the river bank (see Figures 3.14 to 3.17)
for subsequent disposal off-site. Dust emission from construction vehicle
movements to and from the stockpiling areas and works areas will generally be
limited within the work areas.
During peak construction period, the disposal of
surplus C&D materials and sediments will generate a maximum of 34 truck
trips per hour to Yan Fang Road on the Shenzhen side ([1]).
Wheel washing facilities will be provided at all designated vehicular exit points and the dusty
materials will be transported by vehicles with mechanical cover/tarpaulin. With the implementation of the dust control
measures recommended in Section 4.8.1,
dust nuisance from construction vehicle movement outside the work areas is
unlikely to be significant.
Dredging of river sediment
will be required for the river modification works. Depending on the quality of the river
sediment, the dredging and handling of river sediment may cause
odour impact during construction.
Hydrogen sulphide (H2S) is the key odour constituent of the
dredged sediment. With the
implementation of good site practice recommended in Section 4.8.1, the odour nuisance is not anticipated.
4.5.2
Operation Phase
As mentioned in Section 3.5, the frequency and scale of
maintenance dredging required along the river channel and the flood retardation
pond is anticipated to be very small compared with the dredging works during
the capital works. Besides, the dry weather flow interception works under this
Project will convey the untreated sewage from the Shenzhen side, which
currently are discharging into the Shenzhen River, into the Luo
Fang sewage treatment work. Therefore it
is expected that the water and sediment quality will be improved after
completion of the Project. Thus adverse
odour impacts on ASRs due to maintenance dredging are not expected.
Access to the reprovisioned
Boundary Patrol Road (BPR) is controlled by the Frontier Closed Area (FCA)
Permits issued under Section 37(2) of the Public
Order Ordinance and only limited numbers of vehicle with valid permit can
access to the Study Area. Based on the
approved “Construction of a Secondary
Boundary Fence and New Sections of Primary Boundary Fence and Boundary Patrol
Road – EIA Report”, it is anticipated that the traffic flow of the BPR will
not exceed 50 vehicles per hour in 15 years after commissioning. Adverse air quality impact due to traffic
emission from the BPR is therefore, not envisaged.
4.5.3
Concurrent Projects
Construction Phase
The works area
of the planned LT/HYW BCP is located adjacent to the Works Area II and III of
this Project and the EIA for LT/HYW BCP is ongoing. Based on the latest best available
information from the Design Engineer of LT/HYW BCP, the construction of the
LT/HYW BCP and connecting roads will commence at the end of 2013 and be
completed in end 2018. It is anticipated
that the LT/HYW BCP will be constructed concurrently with this Project. With close liaison with the LT/HYW BCP
project team, the latest best available dust emission sources information of
the LT/HYW BCP project have been incorporated into the construction phase
cumulative air quality impacts assessment of this EIA study.
Based on the approved EIA report of the Construction of a Secondary Boundary Fence and New Sections of Primary
Boundary Fence and Boundary Patrol Road (BPR) (Register No.: AEIAR-136/2009), the construction
works will be carried out in phase and therefore the fugitive dust impact
during construction will be minimal. Of
particular note, the construction of the section of fence and patrol road
within the Project Area will be carried out under this Project and will be
considered in this construction dust impact assessment.
Operation Phase
Within 500m study area, it is
identified that the operation of the future LT/HYW BCP and reprovisioned
BPR may cause cumulative impact with this Project.
Since the potential air
quality impact from the operation of the BPR is also minimal as mentioned in Section 4.5.2 above, the cumulative impact
on air quality is considered to be minimal.
The vehicular emissions from
open roads and emissions from kiosks, loading and unloading (L&UL) areas
and public transport interchange (PTI) arising from the operation of the future
LT/HYW BCP may cause potential cumulative impacts with this Project. Nitrogen dioxide (NO2) and respirable suspended particulates (RSP) are the key
pollutants. Based on the latest best
available information from the project team of LT/HYW BCP, the predicted NO2
and RSP impacts at the identified ASRs are well within the AQOs. As mentioned in Section 3.5 of
this Project, the frequency and scale of maintenance dredging required along
the river channel is low and the dredged sediments will be disposed of by marine
vessels or trucks at Shenzhen side. With
respect to the small quantity of sediments to be dredged, a small number of
truck trips will be generated from the handling and transportation of the
dredged sediments. It should be noted
that the dredged sediments will be delivered to a pier in Shenzhen via the
local route network in Shenzhen. It is
not anticipated that there will be adverse cumulative air quality impacts to
the identified ASRs due to the minor NO2 and RSP emissions generated
from such infrequent and small number of truck trips.
An on-site sewage treatment
work (STW) is proposed to be built at the LT/HYW BCP to treat the sewage
generated from the operation of BCP and the Chuk Yuen
Village Resite and odour generated from the proposed
STW at the BCP may also pose odour impact on nearly ASRs. Based on the latest best available
information from the project team of LT/HYW BCP, the STW is designed with odour
containment and control measures to avoid or minimise odour emission from the
operation of the STW. With proper
implementation control measures, no adverse odour impact is anticipated due to
the operation of STW. Again, as the frequency and scale of maintenance
dredging required along the river channel is low, the quantity of dredged
sediments will be much less than that to be dredged during the construction
phase. The dredged sediments will be
disposed off-site immediately and no on-site stockpile of dredged sediment is
required. Cumulative odour impact is
therefore considered to be minimal and would not cause adverse odour impacts at
the nearby ASRs.
4.6.1
Construction Dust
The key dust emission sources during construction
phase of the Project include:
·
heavy construction (including excavation, embankment construction, dry weather
flow interception works, construction of boundary fence and patrol road,
on-site traffic etc.);
·
material
handling at stockpiling area; and
·
wind erosion of open sites.
The dust (in terms of Total Suspended Particulates
(TSP)) emission rates associated with the principal dust sources during the
construction phase of the Project have been estimated based on the typical
emission factors reported in the Compilation
of Air Pollution Emission Factors (AP-42)
5th Edition published by US Environmental Protection Agency (USEPA)
and are presented in Annexes A1 and A2. Unmitigated
and mitigated scenarios were assessed.
Mitigation measures stipulated in the Air Pollution Control (Construction Dust) Regulations were considered
in estimating the mitigated dust emission rates. The unmitigated and mitigated dust emission
factors are summarised in Table 4.4.
Table 4.4 Dust
Emission Factors
|
Works Sites |
Source Type |
Dust Emission Factors |
Remarks |
|
Active
work areas |
Heavy Construction |
E = 2.69 Mg/hectare/month
(unmitigated) E = 0.269 Mg/hectare/month
(mitigated) |
· AP-42, S13.2.3 1/95 Ed. · applied to all
active works area · 90% dust suppression (reference to Control of Open Fugitive Dust Sources,
Section 3.3.3) |
|
|
Wind Erosion |
E = 0.85 Mg/hectare/year |
· AP-42, Table 11.9-4, 7/98 Ed. |
|
Stockpiling
Areas |
Earth
Handling / Loading & Unloading |
E=
k x (0.0016) x ((U/2.2)1.3) / ((M/2)1.4) E
= 2.87E-04 kg/Mg (unmitigated) E
= 8.62E-05 kg/Mg (mitigated) |
· AP-42, S13.24, 11/06 Ed. · Particle size multiplier, k = 0.74 · 1.9 U, average wind speed, U = 1.9 ms-1
(Annual mean wind speed record at TKL weather station in 2008) · materials moisture content (%), M = 4.8% · 70% dust suppression by
watering at least 8 times a day |
|
|
Wind Erosion |
E = 0.85 Mg/hectare/year (unmitigated) E = 0.255 Mg/hectare/year (mitigated) |
·
AP-42,
Table 11.9-4, 7/98 Ed. ·
70% dust suppression by watering at least 8 times
a day |
Hourly and Daily Average TSP
Based on the latest engineering design information,
plant inventory presented in Annex B and
the experience of Shenzhen River Stage 3 regulation works, the maximum active
construction areas at any one time will not be larger than 150m long along the
river at each Works Area. For the
assessment of maximum hourly and daily TSP concentrations at the identified
ASRs, it is assumed that each Works Area will have a 150m long active working
area at any one time during construction phase as a conservative approach. In order to estimate the reasonable worst
case for the ASRs, these active working areas will be located closest to the
particular ASRs under two modelling scenarios:
·
Scenario
1: all active working areas are located to the southern part of Works Areas or
closest to the ASRs A1 to A10 and A12 to A14 to assess the worst dust impacts;
and
·
Scenario
2: all active working areas are located to the northern part of Works Areas or
closest to the ASR A11 to assess the worst dust impacts.
The locations of the active working areas under the
two scenarios are shown in Figures A1 and A2 of Annex A1. The implementation of dust control measures
has also considered in the dust emission rate estimation. The mitigated dust emissions are also
summarised in Annex A1.
Annual Average TSP
Since the active working area will not be larger than
150m long along the river at any one time in each Work Area, the active working
areas over the entire year will be about 10.5% of the works area for the whole
project for predicting the annual TSP levels (please refer to Annex A2).
The implementation of dust control measures presented
in Section 4.8.1 has also considered
in the dust emission rate estimation.
The mitigated dust emissions are summarised in Annex A2.
Modelling Approach
The cumulative unmitigated and mitigated 1-hour,
24-hour and annual average TSP concentrations at the representative ASRs due to
the construction of the Project and the LT/HYW BCP have been predicted using
the EPD approved air quality model Fugitive
Dust Model (FDM). During day-time
(07:00 – 19:00 hrs), the dust emission rates from all potential construction
activities have been considered while during remaining period (ie 19:00 – 07:00 hrs of the next day, hereafter referred to
the night-time period), only dust emission from wind erosion of stockpiling
areas has been considered as no construction works will be undertaken during
the night-time period ([2])
. As identified ASRs are elevated, the TSP
concentrations at 1.5m, 5m and 10m above ground at the ASRs were modelled.
A set of meteorological data of the year of 2008
(with more than 90% valid data) were obtained from Hong Kong Observatory and
used for the dust modelling:
·
Hourly
wind direction and speed, air temperature and atmosphere Pasquill
stability class obtained from Ta Kwu Ling Automatic
Weather Station; and
·
Daily
morning and maximum mixing heights based on the radiosonde
ascent at King’s Park.
Particle size distribution is made
reference to Section
13.2.4.3 of Compilation of Air Pollution Emission Factors (AP-42)
5th Edition. The particle size distribution adopted in
this assessment is presented in Table 4.5.
Table 4.5 Particle
Size Distribution
|
Particle size (mm) |
Distribution (%) |
|
1.25 |
7 |
|
3.75 |
20 |
|
7.5 |
20 |
|
12.5 |
18 |
|
22.5 |
35 |
The highest unmitigated and mitigated maximum hourly
TSP concentrations predicted at each ASR for day-time and night-time period
were selected to represent the worst hourly TSP concentration at the ASR. The daily averaged TSP concentrations
predicted for day-time and night-time periods were summed up to obtain the
24-hour average TSP concentrations at the ASR.
Similar approach was adopted to obtain the annual average TSP
concentrations.
The background TSP presented in Table 4.2 was added to the 1-hour, 24-hour and annual average
results to obtain the overall TSP concentrations.
4.6.2
Odour Emission from Dredged River Sediment
Sediment samples were taken
at 3 locations along the river (see Figure
4.2). The levels of acid
volatile sulphide (AVS) in the river sediment of the Project Site were analysed
to assess the potential odour impact during dredging and handling of the river
sediment. These sampling locations
covered the upstream, middle and downstream sections of the river within the
Study Area.
In general,
sediment with a high AVS concentration has the potential to emit odorous
hydrogen sulphide (H2S) gas.
The AVS levels of the river sediment samples were then compared with
that measured from sediment considered to have minimum odour impact to the
surrounding environment to evaluate the potential odour impact. Reference to other similar projects was also
made.
4.7.1
Construction Phase
Construction Dust
The cumulative unmitigated and mitigated 1-hour, 24-hour
and annual average TSP concentrations were predicted at the identified ASRs and
they are presented in Tables 4.6 and 4.7. Detailed calculation of TSP modelled results was presented in Annex A3.
Table 4.6 Predicted
Cumulative Unmitigated TSP Concentrations at ASRs
|
ASR |
Predicted Cumulative
Unmitigated TSP Concentrations (µg m-3) (a) – (d) |
||||||||
|
|
Maximum 1-hour TSP |
24-hour Average TSP |
Annual Average TSP |
||||||
|
|
1.5m |
5m |
10m |
1.5m |
5m |
10m |
1.5m |
5m |
10m |
|
A1 |
233 |
241 |
223 |
99 |
102 |
100 |
74 |
74 |
74 |
|
A2 |
432 |
450 |
407 |
94 |
96 |
93 |
70 |
70 |
70 |
|
A3 |
647 (e) |
664 |
582 |
131 |
134 |
129 |
71 |
71 |
71 |
|
A4 |
712 |
721 |
611 |
166 |
167 |
154 |
73 |
73 |
73 |
|
A5 |
3063 |
1559 |
865 |
998 |
587 |
300 |
103 |
92 |
83 |
|
A6 |
1826 |
1316 |
709 |
354 |
292 |
181 |
89 |
86 |
81 |
|
A7 |
1369 |
1161 |
626 |
313 |
248 |
198 |
82 |
80 |
78 |
|
A8 |
863 |
805 |
568 |
290 |
276 |
219 |
85 |
81 |
78 |
|
A9 |
878 |
801 |
542 |
247 |
238 |
195 |
76 |
76 |
75 |
|
A10 |
1569 |
1346 |
773 |
466 |
396 |
245 |
97 |
92 |
85 |
|
A11 |
1091 |
965 |
587 |
292 |
274 |
213 |
77 |
77 |
76 |
|
A12 |
408 |
414 |
363 |
135 |
137 |
131 |
75 |
75 |
75 |
|
A13 |
861 |
834 |
656 |
175 |
174 |
159 |
96 |
95 |
89 |
|
A14 |
411 |
416 |
363 |
136 |
138 |
131 |
75 |
75 |
75 |
|
TSP Criteria |
500 |
260 |
80 |
||||||
|
Notes: (a)
Scenario 1 for A1 to A10 and A12 to A14; Scenario 2 for A11 (b)
Background TSP concentration of 67 µg m-3 has been
included. (c)
Detailed results are presented in Annex A3. (d)
Mitigated emission rates of LT/HYW project are adopted. (e)
Bold figures are exceeding the relevant criteria. |
|||||||||
Table 4.7 Predicted
Cumulative Mitigated TSP Concentrations at ASRs
|
ASR |
Predicted Cumulative
Mitigated TSP Concentrations (µg m-3) |
||||||||
|
|
Maximum 1-hour TSP |
24-hour Average TSP |
Annual Average TSP |
||||||
|
|
1.5m |
5m |
10m |
1.5m |
5m |
10m |
1.5m |
5m |
10m |
|
A1 |
108 |
112 |
108 |
74 |
75 |
74 |
68 |
68 |
68 |
|
A2 |
134 |
139 |
132 |
73 |
73 |
73 |
67 |
67 |
67 |
|
A3 |
154 |
160 |
150 |
77 |
78 |
77 |
68 |
68 |
68 |
|
A4 |
144 |
148 |
140 |
83 |
83 |
81 |
68 |
68 |
68 |
|
A5 |
394 |
265 |
186 |
174 |
128 |
95 |
72 |
71 |
70 |
|
A6 |
257 |
202 |
143 |
102 |
95 |
86 |
72 |
71 |
70 |
|
A7 |
307 |
185 |
147 |
151 |
98 |
87 |
72 |
70 |
69 |
|
A8 |
361 |
160 |
149 |
107 |
93 |
86 |
75 |
70 |
69 |
|
A9 |
176 |
159 |
143 |
94 |
92 |
85 |
69 |
69 |
69 |
|
A10 |
230 |
205 |
149 |
114 |
106 |
94 |
72 |
71 |
70 |
|
A11 |
332 |
300 |
229 |
131 |
123 |
103 |
69 |
69 |
69 |
|
A12 |
175 |
166 |
144 |
102 |
103 |
98 |
70 |
70 |
69 |
|
A13 |
197 |
200 |
180 |
91 |
91 |
88 |
73 |
73 |
71 |
|
A14 |
168 |
166 |
144 |
103 |
104 |
99 |
70 |
70 |
69 |
|
TSP Criteria |
500 |
260 |
80 |
||||||
|
Notes: (a)
Scenario 1 for A1 to A10 and A12 to A14; Scenario 2 for A11 (b)
Background TSP concentration of 67 µg m-3 has been
included. (c)
Detailed results are presented in Annex A3. |
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Without implementing any mitigation measures, exceedances of TSP criteria were predicted at A3 to A11 and
A13. After implementing mitigation
measures recommended in Table 4.4 and Section 4.8.1, no exceedance of TSP criteria was predicted at all identified
ASRs with the implementation of the recommended mitigation measures.
The highest cumulative unmitigated and mitigated TSP
concentrations were both predicted at 1.5m above ground. Besides, contour plots showing cumulative
unmitigated and mitigated 1-hour, 24-hour and annual average TSP concentrations
at 1.5m above ground in the vicinity were plotted. Contours showing cumulative unmitigated TSP
concentrations under different time averaging at 1.5m above ground are shown in Figures 4.3 to 4.7 while contours showing cumulative mitigated
TSP concentrations under different time averaging at 1.5m above ground are
shown in Figures
4.8 to 4.12.
The contour plots show that cumulative mitigated TSP concentrations
within most of the Study Area complied with the respective TSP criteria but exceedance of TSP criteria is predicted at small areas
immediately adjacent to the Project’s works area. However, no ASRs are identified within the
affected areas and therefore, no adverse dust impact is anticipated.
Odour from Dredged Sediment
The levels of AVS in the
river sediments of the Project Site were analysed to identify the potential
odour strength from the dredged sediment.
The AVS levels of the sediment samples were in the range of 2 to 30 mg
kg-1. The laboratory analysis
report of AVS level in the sediment samples is attached in Annex A4.
The AVS levels of remediated
sediments, which are considered to have minimum odour impact to the surrounding
environment, stated in an approved EIA report are in the range of 50 to 500 mg
kg-1 ([3]). These levels were used to compare with the
AVS levels of the river sediments to be dredged under this Project to determine
the potential odour impacts from dredging and handling of the sediment.
The AVS concentrations in the
sediment samples for this Project are significantly lower than the reference
level. In addition, the dredged sediment
will be stored in enclosed tanks and will be delivered off-site for disposal
every day. It is therefore expected that
the potential odour emissions from the dredging and handling of river sediments
would be minimal.
4.7.2
Operation Phase
Odour from Maintenance Dredging
As discussed in Section
4.5.2, the frequency and scale of maintenance dredging required along the
river channel and the flood retardation pond is anticipated to be very small
compared with the dredging works during the capital works. Hence, by adopting similar mitigation
measures as in the construction stage, adverse odour impacts at the ASRs due to
maintenance dredging are not expected.
As mentioned above, the dredged sediments will be
disposed of by trucks or marine vessels at Shenzhen side and the number of
truck trips or marine vessels generated will be minimal. With limited quantity of sediments dredged
and the small number of truck trips at Shenzhen side or marine vessels
generated in this Project, no adverse cumulative air quality impacts are
anticipated at the identified ASRs.
4.8.1
Construction Phase
The following dust
control measures stipulated in the Air
Pollution Control (Construction Dust) Regulation will be implemented to
reduce the fugitive dust emission as much as possible:
·
Water
spaying on haul roads and dusty areas for every hour during the construction,
·
Covering
the stockpile areas of at least 70% area with tarpaulin sheet or impervious
sheet;
·
Covering
of dusty materials/spoils on trucks by impervious sheets;
·
Controlling
the dropping height of fill materials;
·
Covering
or storing all debris and materials in a sheltered debris collection area;
·
Storing
dredged sediment in a separate enclosed tank; and
·
Providing
wheel washing facility at each exit of the works site.
Good site practices such as regular maintenance and
checking of the diesel powered mechanical equipment will be adopted to avoid
any black smoke emissions and to minimize gaseous emissions.
Dredged
sediment placed on truck or marine vessel for disposal should be properly
covered during transportation to minimise the potential odour. In the event that dredging material are found
to be odorous, the odorous dredged sediment should be placed as far away from
the identified ASRs as practically possible and should be removed off-site as
soon as practicable to avoid any potential odour nuisance arising.
4.8.2
Operation Phase
The maintenance dredging may be undertaken by
land-based or marine-based plants depending on the maintenance dredging
strategy to be developed in future. In order to minimize the potential odour
emissions, if any, the dredged sediment placed on truck or marine vessel for
disposal should be properly covered as far as practicable during
transportation. In the event that
dredging material are found to be odorous, the odorous dredged sediment should
be placed as far away from the identified ASRs as practically possible and
should be removed off-site as soon as practicable to avoid any potential odour
nuisance.
4.9.1
Construction Phase
No residual impact is anticipated after the
implementation of the recommended mitigation measures described in Section 4.8.1.
4.9.2
Operation Phase
No residual impact is anticipated.
4.10
Environmental
Monitoring and Audit (EM&A)
4.10.1
Construction Phase
Regular environmental audit will be conducted to
ensure the implementation of the recommended dust control measures for both the
Advanced Works and River Modification and Associated Works. Besides, dust levels, in terms of TSP will be
monitored, at Ta Kwu Ling Village (AM1) and
Tsung Yuen Ha (AM2) during River Modification Works in works area III or
IV and works area I or II, respectively.
The location of proposed dust monitoring stations is shown in Figure
4.13. Monitoring of 24-hour and
1-hour TSP levels will be conducted once every six days throughout the
construction period. Detailed EM&A
requirements for dust monitoring are presented in the EM&A Manual.
4.10.2
Operation Phase
Since no adverse air quality and odour impacts are
anticipated, no EM&A will be required.
4.11.1
Construction Phase
Construction dust generating from the soil excavation, embankment construction,
dry weather flow interception works, landscaping works, patrol road and boundary
fence re-provisioning and odour
from dredging and handling of river sediment are the key air quality concerns
during construction phase.
With the implementation of the recommended dust
control measures and good construction site practices as recommended in Section 4.8.1, the construction of the
Project will not cause adverse dust and air quality impacts.
The measured AVS concentrations in the sediment
samples of the Project Site were well below of that for the remediated
sediments, which are considered to have minimum odour impact to the surrounding
environment. The dredged sediment will be
stored in enclosed tanks and will be delivered off-site for disposal at regular
interval. Therefore, potential odour
impact due to dredging and handling of river sediment will be minimal.
It is recommended that regular environmental site
audit should be conducted to ensure the implementation of recommended dust
control measures and monitoring of 24-hour and 1-hour TSP levels should be
carried out at the proposed dust monitoring stations at Ta Kwu Ling
Village (AM1) and Tsung Yuen Ha
(AM2) throughout the construction
period to ensure no adverse dust impacts to the ASRs.
The frequency and
scale of maintenance dredging required along the river channel and the flood
retardation pond is anticipated to be very small compared with the dredging
works during the capital works. Besides, the
dry weather flow interception works to be carried out under this Project will
convey the untreated sewage from Shenzhen side, which are currently discharging
to the Shenzhen River, to the sewage treatment work at Shenzhen. It is therefore expected that the water and
sediment quality of the Study Area will be improved after completion of the
Project. The potential odour emissions
due to the dredging and handling of sediment associated with maintenance
dredging will be minimal. With the
infrequent dredging activities required, limited quantity of sediments dredged
and limited number of truck
trips at Shenzhen side or marine vessels required, no adverse cumulative air
quality impact is anticipated.