This section presents the
assessment of potential air quality impacts arising from the
construction and operation of the two proposed submarine gas pipelines and Gas
Receiving Stations (GRSs) to the northeast of the
Black Point Power Station (BPPS). The Study Area is
generally defined by a distance of 500 m from the boundary of the Project site
(Figure 4.1). Representative Air
Sensitive Receivers (ASRs) and emission inventories have been identified and an
assessment of the air quality impacts has been conducted and mitigation
measures and environmental monitoring and audit programme
will be proposed if necessary.
4.2
Legislation
Requirement and Evaluation Criteria
The principal legislation for the
management of air quality in
Table 4.1
|
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 |
|
|
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 |
|||||
A maximum hourly TSP level of 500 mgm-3 at ASR is also stipulated
in the Technical Memorandum on
Environmental Impact Assessment Process (EIAO-TM) to assess potential construction dust impacts.
The
measures stipulated in the Air Pollution
Control (Construction Dust) Regulation
should be followed to ensure that any dust impacts are reduced.
The proposed site is located to the
northeast of the Black Point Headland and the existing BPPS. The area has a very low population
density and the local air quality is influenced by industrial emissions from the
existing BPPS, Castle Peak Power Station (CPPS) and other industrial
facilities, vehicle emissions from
4.3.1
Background Air Quality
CLP
has an Air Quality Management Station (AQMS) at Lung Kwu
Tan since 2005 which measures the Nitrogen Dioxide (NO2) and Sulphur
Dioxide (SO2) in the area.
The monitoring data from CLP’s AQMS has taken
into account all local emission sources including BPPS and CPPS and regional
pollutant fluxes and, therefore, is considered as representative of the
existing NO2 and SO2 concentrations in the Study Area (Figure
4.1). The mean of five years annual average NO2
and SO2 concentrations (2005 – 2009) are summarized in Table 4.2.
Concentrations
of air pollutants other than NO2 and SO2, measured at the
nearest EPD AQMS at Tung Chung, were used as a reference. The 5 years annual average
concentrations (2004 – 2008) of these air pollutants give an indication of the
background air quality and are summarized in Table 4.2.
Table
4.2 Background Air Quality (a)
|
Air Pollutant |
Background Concentration (mg m-3) |
|
Nitrogen Dioxide (NO2) (b) |
28 |
|
Sulphur Dioxide (SO2) (b) |
13 |
|
Total Suspended Particulates (TSP) (c) |
70 |
|
Respirable
Suspended Particulates (RSP) (c) |
56 |
|
Carbon Monoxide (CO) (c) |
837 |
|
Ozone (O3) |
88 (d) |
|
Notes: (a)
Background
Lead concentration is not shown since this Project will not give rise to any
Lead emissions and thus Lead concentration is not relevant to this Project (b)
5
years (2005 to 2009) annual average measured at CLP’s
AQMS at Lung Kwu Tan. (c)
5
years (2004 to 2008) annual average measured at EPD’s
AQMS at Tung Chung. (d)
The
ozone concentration is the mean of 5-year annual average of the daily hourly
maximum concentrations measured at EPD’s AQMS at
Tung Chung between 2004 and 2008. |
|
4.3.2
Contribution of Emissions from BPPS and
CPPS
Air quality in the vicinity may also be
influenced by local emission sources, including BPPS and CPPS.
An EIA
of the Proposed 6,000 MW Thermal Power Station at Black Point: Key Issue Assessment
– Air Quality (hereafter referred to as the BPPS EIA Study) has been used as the basis for quantifying the
contribution of emissions from BPPS and CPPS to local air quality.
The
BPPS EIA Study included wind tunnel
testing to assess the near-field air quality impacts of six gas-fired units,
each with a design generating capacity of 800 MW (Phases I and II) (i.e., a
total generating capacity of 4,800 MW) for BPPS and the CPPS “A” and “B” Units
(CPA and CPB). The findings of the
wind tunnel tests indicated that nitrogen dioxide (NO2) is the major
air pollutant and that higher NO2 impacts occur at higher wind
speeds (refer to Annex D of BPPS EIA Study) ([1]).
NO2 concentrations under different averaging times at Lung Kwu Tan were calculated based on the wind tunnel testing
results, the reported ozone level (i.e. 70 µgm-3) and the NOx/NO2
ratio estimation approach as described in “A
Classification of NO Oxidation Rates in Power Plant Plumes based on Atmospheric
Conditions”, by Janssen, 1983.
Since the assessment in the BPPS EIA was completed, there have been
a number of changes to both the installed generating capacity and the regional
air quality.
Compared
to the ozone level in 1993 (70 µgm-3), the mean of annual average of
the daily one-hour maximum concentrations measured at Tung Chung AQMS in years
2004 to 2008 has increased to 88 µgm-3 (see Table 4.2).
For assessing the contribution of the
BPPS, an adjustment was made to account for the current generating capacity
which is 2,500 MW. There is no
confirmed programme for the Phase II expansion, as was assumed in the BPPS EIA Study.
For
assessing the contribution of the CPPS, an allowance was made for the fact that
low NOx burners are now operating in the
CPA and CPB. A further NOx reduction is anticipated for CPB and the
indicative date of the implementation of the further NOx
reduction measures will be over the period of 2009 to 2011 according to the
approved EIA for Emission Control Project
to CPPS “B” Units.
Taking
into consideration the latest information for BPPS and CPPS as well as the
higher ozone level of 88 µgm-3, the adjusted NO2
concentrations are summarized in Table
4.3 and were utilised in the assessment of the cumulative air quality
impacts in the Lung Kwu Sheung
Tan and Ha Pak Nai areas.
Detailed calculations are provided in Annex
4A-1.
Table
4.3 Adjusted Maximum Hourly,
Daily Average and Annual Average NO2 Concentrations Contributed by
BPPS and CPPS
|
Location |
Adjusted NO2
Concentration (mgm-3)
(a) |
||
|
|
Maximum Hourly
|
Daily Average (c) |
Annual Average
(c) |
|
Lung Kwu Tan |
55.0 (b) |
21.3 |
0.6 |
|
Ha Pak Nai |
106.5 |
19.8 |
0.5 |
|
Notes: (a)
Adjustment
is based on the mean of annual average of the daily hourly maximum ozone
concentration (88 mgm-3)
in 2004-2008. Refer to Annex 4A-1
for detailed calculation. (b)
Only the BPPS contribution is considered. No CPPS contribution is considered due
to opposite wind angles from GRS and from the CPPS to Lung Kwu Sheung Tan area. (c)
Both BPPS and CPPS contributions are considered, no
adjustment has been made to account for the reduced power generation capacity
of BPPS, existing licence limit requirement or the future NOx
reduction at CPB due to the implementation of the Emission Control Project. |
|||
In accordance with the EIA
Study Brief, a general study area for the air quality assessment is defined by
a distance of 500 m from the boundary of the Project site. Within the 500 m study area, there are
no residential developments and only one ASR identified (
The nearest identified ASRs
in the surrounding environment are summarized in Table 4.4 and shown in Figure 4.1.
Table 4.4 Identified
Air Sensitive Receivers
|
Area |
ASR |
Location |
Approximate Distance from
the Project site (m) |
Type of Uses |
Maximum Height |
|
Black Point and Lung Kwu Sheung Tan |
A1 |
Black Point Power Station –
|
490 |
Office |
10 |
|
A2 |
Karting Track |
1,780 |
Recreational |
1.5 |
|
|
A3 |
Open Storage – Site |
1,400 |
Office |
10 |
|
|
A4 |
Concrete Batching Plant –
Site |
1,300 |
Office |
1.5 |
|
|
A5 |
Hong Kong Oil - Site |
1,550 |
Office |
10 |
|
|
A6 |
Open Storage – Site |
1,700 |
Office |
1.5 |
|
|
Ha Pak Nai |
A7 |
Sludge Treatment Facility –
Site |
1,400 |
Office |
10 |
|
A8 |
WENT Landfill Extension –
Site |
1,400 |
Office |
10 |
4.5
Potential Sources
of Impact
4.5.1
Construction Phase
The
major construction works include site clearance, dredging, reclamation,
pipeline trench and GRSs construction works. These would have the potential to
generate dust and gaseous emissions from diesel-driven plant.
Site
Clearance Works
Co-location
of the new GRS with the existing GRS of BPPS will require land clearance within
the existing GRS site boundary to accommodate the new GRS facility. Any dust impact during site clearance is
expected to be localized. Together
with the implementation of the dust control measures stipulated in Air Pollution Control (Construction Dust)
Regulation, the amount of dust arising from site clearance is predicted to
be minor and is not anticipated to exceed the dust criterion.
Dredging
and Reclamation Works
Dredging
works will be required for seawall construction and reclamation. Dredging is planned to be undertaken
within the first 5 months of the works, depending on the programme for the Foreshore and Seabed (Reclamations)
Ordinance (FSRO) approval.
Marine sediment will be dredged and disposed of at designated marine
disposal sites by barge. The
moisture content of dredged materials is very high,
therefore, no fugitive dust emissions are anticipated during the works. This applies to marine dredging works
for pipeline trenching works as well ([2]).
During
reclamation, rocks will be imported for seawall construction. Marine sand and public fill will be
imported for the reclamation works.
No fugitive emissions are expected from rock and marine sand filling;
however, fugitive dust emissions are possible from the handling of public
fill. In accordance with the
construction method, the filled area will be compacted immediately after
filling and therefore, fugitive dust emissions will be reduced. Furthermore, due to the large separation
distance from the ASRs and with the implementation of the dust control measures
stipulated in Air Pollution Control
(Construction Dust) Regulations, the dust impact from filling activities is
very limited.
GRSs Construction Works
The
GRSs will be delivered to site as discrete
subassemblies or pre-fabricated structures and will be assembled on-site. Piping and equipment will generally be skid-mounted
(size permitting) and placed on prepared concrete footings. Larger piping and equipment assemblies
will be delivered to site as discreet subassemblies and assembled on-site. Sensitive instrumentation will be housed
in air-conditioned instrument enclosures that are commonly prefabricated
portable buildings. With
consideration of the works nature, it is considered that limited dust emissions
will be emitted from the GRSs construction works with
the implementation of the dust control measures stipulated in the Air Pollution Control (Construction Dust)
Regulation.
Gaseous
Emissions from Construction Plants
Gaseous
emissions from construction plants will arise during the construction
phase. With reference to the
construction programme, the numbers of diesel-driven powered-mechanical
equipment (PMEs) operating simultaneously on-site for
land-based works will be limited.
The potential gaseous emissions from these PMEs
are expected to be minimal and unlikely to cause adverse air quality
impacts.
Offshore PMEs such as dredgers, jetting
machine, barges and tugboats will be distributed at the area of dredging,
reclamation and pipeline trench.
Referring to the preliminary construction plant (equipment) inventory, a
total of 2 dredgers are required for reclamation and up to 14 dredgers and/ or
one jetting machine are required for pipeline trench. These vessels are located in different
marine works areas and may not all be operating simultaneously; therefore, the
air emissions from the offshore PMEs over an overall
large marine works area will be low.
With the consideration of the large separation distance from the ASR, no
adverse air quality impact due to offshore PMEs is
anticipated.
4.5.2
Operation Phase
Emissions from the operation of pipeline
gas heaters of the GRSs are the key air pollution
sources from the Project. No
additional traffic will be generated from this Project during operation and
Lung Kwu Tan Road and Nim
Wan Road are located outside the 500 m Study Area. In addition, the traffic emission
impact, if any, is localized and at low elevation. Therefore, unacceptable road traffic
impacts are not anticipated.
The following other existing and future
emission sources were identified to cause cumulative air quality impacts in the
vicinity during the operation of the Project:
·
Black
Point Power Station (BPPS) and
·
·
Shiu
Wing Steel Mill;
·
Eco-Park;
·
Existing
WENT Landfill and proposed WENT Extension;
·
Marine
vessels along navigation channel outside WENT Landfill; and
·
Proposed
Sludge Treatment Facilities.
The status and the time frame of the
Integrated Waste Management Facilities (IWMF) are unknown at this stage and
hence this project is not considered in the cumulative air quality impact
assessment.
Emissions from Pipeline Gas Heaters of GRSs
Two new GRSs are
proposed, one co-located with the existing GRS on existing land and the other
one on newly reclaimed land.
Including the existing GRS, a maximum of three GRSs
are expected to be in operation and they are hereafter called GRS complex in
the following assessment. Their
locations are shown in Figure 4.1.
Since
the detailed design of the two future GRSs will be
determined at a later stage, the exact number of pipeline gas heaters proposed
is not yet confirmed but it will be within 3 – 7 for each location (i.e., 2 – 6
heaters in operation and 1 heater for standby at each location). The pipeline gas heaters are assumed to
be in operation continuously over 24 hours. The heaters use pipeline gas as their
fuel source and NOx and CO are the
principal air pollutants from the combustion process. An individual stack is connected to each
of the gas heaters. The total flowrate of the exhaust gas is estimated to be 73,900 Nm3hr-1. The exhaust gas temperature of new gas
heaters will be about 280°C
as a minimum. The stack height of
the new gas heaters is expected to be approximately 15 m above ground. A maximum of 8.22 kg of NOx and 5.14 kg of CO in total will be emitted
in an hour (i.e., approximately 72 tonnes of NOx
and 45 tonnes of CO a year) from the whole GRS complex. The NOx
and CO emissions are estimated based on their emission factors in the
preliminary engineering specification of the gas heater and the anticipated
total flowrate of exhaust gas (please refer to Annex
4A-2). The exit velocity will be designed to be
at least 10 ms-1 which is similar to that of the existing gas
heaters. The stack diameter will be
designed to be in a range of 0.94 m and 1.63 m. The stack information is summarized in Annex
4A-3.
Other Existing and Future Emission Sources
identified in the Vicinity
The Black Point Power Station (BPPS) is
considered as the nearest existing air emission source, contributing to the air
quality within the Study Area. In
addition, the Castle Peak Power Station (CPPS) also contributes to the local
air quality. The contribution from
BPPS and CPPS has been presented in Tables
4.2 and 4.3.
Green Island Cement (GIC) is located at
more than 5km from the Project site.
The potential emissions assessed included the major stack emissions from
fuel combustion as listed in its Specified Process Licence. The potential emission source from GIC
stated in the Specified Process Licence was included in the assessment and the
detailed emission inventory and stack parameters are summarized in Annex
4A-3.
Shiu
Wing Steel Mill is located at about 5km from the Project site. The major emission sources considered in
this assessment are the two major stacks with in the mill, i.e., the air
furnace stack and the reheat furnace stack described in the EIA for Shiu Wing
Steel Mill Tuen Mun Area 38. NO2 is one of the key air
pollutants from the stack emissions.
The detailed emission inventory and stack parameters are summarized in Annex
4A-3.
The
Eco-Park is also located at 5km away from the Project site. The potential emissions of Eco-Park
considered in this assessment include the major stack emissions from fuel
combustion. By reviewing the
approved EIA for Development of an EcoPark in Tuen Mun Area 38 (Table 3.25), source location A2 would
result in the highest NO2 concentration at nearby ASRs. Since NO2 is the critical
pollutant in this Study, source location A2 was therefore adopted as the
worst-case emission location of Eco-Park for the purpose of this
assessment. The detailed emission
inventory and stack parameters are summarized in Annex
4A-3.
Gaseous emissions from operation plants
including ammonia stripping plant (ASP) of leachate
treatment plant (LTP), landfill gas (LFG) power generators and flare system are
the potential sources from the operation of existing WENT landfill and the
proposed WENT landfill extension in accordance with the approved EIA for West New Territories (WENT) Landfill Extensions
– Feasibility Study. The
detailed emission inventory and stack parameters of these emission sources are
summarized in Annex 4A-3.
Emissions from marine vessels transporting
waste from refuse transfer stations (RTSs) to
existing and future WENT Landfill would be a concern. These RTSs
included Island East Transfer Station (IETS), Island West transfer Station
(IWTS), Outlying Island Transfer Station (OITS), West Kowloon Transfer Station
(WKTS) and North Lantau Transfer Station (NLTS). Emission from future marine vessels that
may be operated to transport sludge from Stonecutters Island Sewage Treatment
Works (SCISTW) to existing WENT landfill or STF for disposal is also considered
in this Study. According to the
approved EIA for West New Territories
(WENT) Landfill Extensions – Feasibility Study, the future operation
schedule of the above-mentioned marine vessels would be the same as the current
one. The operation schedule is
summarized in Table 4.5.
Table
4.5 Operation
Schedule for Marine Vessels
|
|
Barging Point in Existing WENT Landfill |
|||||
|
|
IETS |
IWTS |
OITF |
WKTS |
NLTS |
STF |
|
Round Trips (nos/day) |
1 |
1 |
1 |
1 |
1 |
1 |
|
Iding
Period |
2130 – 1700 |
2100 – 1800 |
1100 – 1430 |
0730 – 1930 |
0830 – 0920 |
0600 - 2000 |
|
Engine during Idling |
Auxiliary Engine |
Auxiliary Engine |
Auxiliary Engine |
No |
Only Generator |
No |
|
Notes: (a)
Reference
to Approved EIA for West New Territories
(WENT) Landfill Extensions – Feasibility Study (b)
Take
IETS as an example, 2130 refers to the time when the marine vessel
arrives. When it arrives, it
would wait until daytime period when the loading/unloading process starts. The process would be completed by 1700
and the marine vessel would leave by 1700. Therefore, the manoeuvring would be
occurred at 1 hour before 2130 and 1 hour after 1700. |
||||||
The detailed emission inventories and stack
parameters of these marine vessel emissions are summarized in Annex
4A-3.
NO2 will be emitted from
chimney during the incineration process of the STF. The emission inventories and chimney
information of STF stacks presented in the approved EIA for Sludge Treatment Facilities are summarized in Annex
4A-3.
4.6
Assessment
Methodology
(Operation Phase Only)
4.6.1
Worst Case Assessment Scenarios for
Project Emissions
Although a maximum of 21 heaters will be
present in the GRS complex, with reference to the current operation of the
existing GRS, it is not expected that more than 6 heaters will be operated at
full load at the same time in the future.
For considering worse case impacts at Lung Kwu
Sheung Tan/Black Point and Ha Pak Nai,
four worst case scenarios on different source locations within the GRS complex
have been developed and the description and maximum hourly emission rate of
each emission source are summarized in Table
4.6. The locations of emission
points are shown in Figure 4.2.
Table
4.6 Worst
Case Scenario
|
Scenario |
Number of heaters operating |
Location of heater (b) (c) |
Emission Rate of Each Source (kg/hr) (a) |
|
|
|
|
|
NOx |
CO |
|
1 |
2 |
Co-located area |
4.11 |
2.57 |
|
2 |
6 |
Co-located area |
1.37 |
0.86 |
|
3 |
2 |
Reclamation area |
4.11 |
2.57 |
|
4 |
6 |
Existing GRS |
1.37 |
0.86 |
|
Notes: (a)
The
maximum total emissions of NOx and CO
are 8.22 kg and 5.14 kg per hour, respectively (i.e., 72 tonnes and 45 tonnes
per year, respectively) assuming 24-hour operation. (b)
Locations
of emission points are illustrated in Figure
4.2. (c)
The
location of emission points is for worst case assessment purpose. It does not represent the future exact
location of the heaters. |
||||
4.6.2
Emission Rate Estimation & Stack
Information
Pipeline gas heaters are
fuelled by natural gas and hence NOx and
CO are the principal air pollutants.
As discussed in Section 4.5.2, the pipeline gas heaters
are assumed to be operating 24 hours and 365 days in the modeling assessment
and hence this is a worst-case approach.
The estimated emission rates
of NOx and CO under different scenarios
are summarized in Table 4.7 and detailed calculations are
presented in Annex 4A-3.
Table 4.7 Summary
of Stack Information and Emission Rates of NOx
and CO
|
Parameter |
Unit |
Pipeline Gas
Heater (a) |
|||
|
|
|
Scenario 1 |
Scenario 2 |
Scenario 3 |
Scenario 4 |
|
No. of Source |
- |
2 |
6 |
2 |
6 |
|
Location |
- |
Co-located Area |
Co-located Area |
Reclamation Area |
Existing GRS |
|
Stack height |
metre above ground |
15 |
15 |
15 |
9.4 |
|
Stack diameter |
m |
1.63 |
0.94 |
1.63 |
0.90 |
|
Exit
temperature |
°C |
280 |
280 |
280 |
300 |
|
Exit velocity |
ms-1 |
10 |
10 |
10 |
11.3 |
|
NOx emission rate |
gs-1 |
1.14 |
0.38 |
1.14 |
0.38 |
|
CO emission
rate |
gs-1 |
0.71 |
0.24 |
0.71 |
0.24 |
|
Note: (a)
All the stack information and emission rates are for
1 gas heater only. |
|||||
The estimated emission rates
of NOx from different other emission
sources and the stack information discussed in Section 4.5.2 are also presented in Annex 4A-3.
4.6.3
Modelling Approach
An air dispersion model, Industrial Source Complex Short Term (ISCST3),
recommended in the EPD’s Guideline of Choice of Models and Model
Parameter, was employed to predict the air quality impacts from project’s
emissions and emissions from GIC, Eco-Park, Shiu Wing
Steel Mill, Existing WENT Landfill, future WENT Landfill extension, marine
vessels along navigation channel outside WENT Landfill and proposed STF.
The pipeline gas heaters have been assumed to be operated continuously in
the modeling assessment for a worst case assessment.
The NOx
and CO impact assessments under different scenarios as presented in Table
4.6 above have been conducted.
As the site area is classified as “rural”
in accordance with the EPD’s Guidelines on Choice
of Models and Model Parameter, a “rural” dispersion mode was used in the
model. In addition, the local
terrain within 500 m study area has been incorporated into the model to account
for terrain-induced impacts to dispersion.
It has been assumed that the background
ozone present in the vicinity of the Project site is elevated, and so the Ozone
Limiting Method (OLM) was used to estimate the hourly conversion ratios of NOx to NO2. As a worst-case assumption, the mean of
daily hourly maximum ozone concentrations measured at EPD’s
Tung Chung AQMS in 2004 to 2008 (i.e., 88 µgm-3) were utilized.
Since most of the emissions are from
elevated sources, air pollutant concentrations were predicted at 1.5 m above
ground at all identified ASRs and at 5 m and 10 m for the elevated ASRs.
A worst-case assumption of continuous
emission from pipeline gas heaters was adopted, a high
background ozone level and a whole year of meteorological data were used in the
air dispersion model. Maximum
hourly, daily average and annual average NO2 and CO concentrations
were predicted at the identified ASRs and represent worst case conditions.
4.6.4
Meteorological Condition
Representative hourly meteorological data
from the Hong Kong Observatory (HKO)
station located at Lau Fau Shan, for the year 2006,
were used in the model. The
meteorological data included hourly wind speed, wind direction, ambient
temperature and stability class.
While the mixing height information is obtained from HKO station at
King’s Park.
4.6.5
Modelled NO2 Concentration
Calculation
The
hourly, daily and annual average NO2 concentrations at each ASR due
to each source group were predicted.
As discussed above, OLM was applied to each source group individually in
estimating the NO2 concentrations. The total modelled NO2
concentrations were then calculated by arithmetic sum of the predicted NO2
concentrations at each ASR due to each source group.
4.6.6
Total NO2 and CO Concentrations
General
background NO2 concentration presented in Table 4.2 and NO2 concentrations contributed from the
operation of BPPS and CPPS (presented in Table
4.3) will be added to the total modelled NO2 concentrations to
give an overall total NO2 concentration at each ASR. Worst assessment scenario will be
selected based on the overall NO2 concentration predicted at
ASRs. Contours showing the overall
NO2 concentrations at 1.5m, 5m and 10m above ground in the vicinity
will be plotted for the worst assessment scenario.
General background CO concentration
presented in Table 4.2 will be added
to the modelled CO concentration to give an overall total CO concentration at
each ASR.
The overall maximum hourly, daily average
and annual average concentrations of NO2 and the maximum hourly and
8-hour average concentrations of CO were predicted under the 4 worst-case
scenarios. The predictions of
overall NO2 and CO concentrations are summarized in Table 4.8 and
4.9, respectively. Detailed
results contributed by project emission and other individual emission sources
are presented in Annex 4A-4.
Table 4.8 Predicted
Overall Maximum Hourly, Daily Average and Annual Average Concentrations of NO2
at ASRs under 4 Worst-case Scenarios
|
ASRs |
Predicted NO2 Concentrations (mgm-3)(a) |
||||||||
|
Maximum
Hourly |
Daily
Average |
Annual Average |
|||||||
|
1.5m
above ground |
5m above
ground |
10m
above ground |
1.5m
above ground |
5m above
ground |
10m
above ground |
1.5m
above ground |
5m above
ground |
10m
above ground |
|
|
Scenario 1 |
|||||||||
|
A1 |
137 |
137 |
137 |
59.2 |
59.3 |
59.4 |
30.6 |
30.6 |
30.7 |
|
A2 (b) |
138 |
- |
- |
59.0 |
- |
- |
30.9 |
- |
- |
|
A3 |
117 |
117 |
117 |
58.6 |
58.6 |
58.6 |
30.5 |
30.5 |
30.5 |
|
A4 (b) |
120 |
- |
- |
58.8 |
- |
- |
30.4 |
- |
- |
|
A5 |
120 |
120 |
120 |
59.3 |
59.3 |
59.4 |
30.2 |
30.2 |
30.2 |
|
A6 (b) |
129 |
- |
- |
56.1 |
- |
- |
30.3 |
- |
- |
|
A7 |
153 |
153 |
153 |
58.4 |
58.8 |
61.8 |
31.8 |
31.9 |
32.3 |
|
A8 |
141 |
141 |
141 |
58.8 |
59.4 |
61.3 |
31.1 |
31.1 |
31.5 |
|
Scenario 2 |
|||||||||
|
A1 |
137 |
137 |
137 |
62.9 |
62.9 |
63.5 |
31.2 |
31.3 |
31.3 |
|
A2 (b) |
138 |
- |
- |
59.2 |
- |
- |
30.9 |
- |
- |
|
A3 |
117 |
117 |
117 |
59.0 |
59.0 |
59.1 |
30.7 |
30.7 |
30.7 |
|
A4 (b) |
120 |
- |
- |
58.8 |
- |
- |
30.5 |
- |
- |
|
A5 |
120 |
120 |
120 |
59.3 |
59.3 |
59.4 |
30.3 |
30.3 |
30.3 |
|
A6 (b) |
129 |
- |
- |
56.3 |
- |
- |
30.3 |
- |
- |
|
A7 |
160 |
160 |
161 |
59.0 |
59.0 |
62.0 |
32.0 |
32.1 |
32.5 |
|
A8 |
148 |
148 |
148 |
59.8 |
59.8 |
61.6 |
31.2 |
31.3 |
31.6 |
|
Scenario 3 |
|||||||||
|
A1 |
137 |
137 |
137 |
59.1 |
59.2 |
59.3 |
30.6 |
30.6 |
30.7 |
|
A2 (b) |
138 |
- |
- |
56.0 |
- |
- |
30.9 |
- |
- |
|
A3 |
117 |
117 |
117 |
56.0 |
59.4 |
59.9 |
30.4 |
30.4 |
30.4 |
|
A4 (b) |
120 |
- |
- |
58.4 |
- |
- |
30.3 |
- |
- |
|
A5 |
117 |
117 |
117 |
56.2 |
56.2 |
56.2 |
30.2 |
30.2 |
30.2 |
|
A6 (b) |
129 |
- |
- |
56.3 |
- |
- |
30.3 |
- |
- |
|
A7 |
153 |
153 |
153 |
58.3 |
58.7 |
61.8 |
31.7 |
31.9 |
32.3 |
|
A8 |
142 |
142 |
142 |
58.7 |
59.3 |
61.1 |
31.0 |
31.1 |
31.4 |
|
Scenario 4 |
|||||||||
|
A1 |
137 |
137 |
138 |
63.4 |
63.8 |
65.0 |
31.6 |
31.6 |
31.7 |
|
A2 (b) |
138 |
- |
- |
59.7 |
- |
- |
31.0 |
- |
- |
|
A3 |
117 |
117 |
117 |
58.9 |
58.9 |
59.0 |
30.6 |
30.6 |
30.6 |
|
A4 (b) |
120 |
- |
- |
58.8 |
- |
- |
30.4 |
- |
- |
|
A5 |
117 |
117 |
117 |
56.7 |
56.7 |
56.9 |
30.3 |
30.3 |
30.3 |
|
A6 (b) |
129 |
- |
- |
56.1 |
- |
- |
30.3 |
- |
- |
|
A7 |
158 |
158 |
158 |
58.3 |
58.9 |
61.8 |
31.9 |
32.1 |
32.5 |
|
A8 |
157 |
158 |
157 |
58.8 |
59.4 |
61.3 |
31.3 |
31.3 |
31.7 |
|
AQO |
300 |
300 |
300 |
150 |
150 |
150 |
80 |
80 |
80 |
|
Notes: (a)
Refer to Annex
4A-4 for detailed results. (b)
As A2, A4 and A6 are not elevated
ASRs and therefore, no assessment was performed at 5m and 10 m above ground
at these ASRs. |
|||||||||
Table 4.9 Predicted
Overall Maximum Hourly and 8-hour Average Concentrations of CO under 5
Worst-case Scenarios
|
ASRs |
Predicted
CO Concentrations (mgm-3) (a) |
|||||
|
Maximum
Hourly |
8-hour
Average |
|||||
|
1.5m
above ground |
5m above
ground |
10m
above ground |
1.5m
above ground |
5m above
ground |
10m
above ground |
|
|
Scenario 1 |
||||||
|
A1 |
844 |
844 |
845 |
841 |
841 |
841 |
|
A2 (b) |
840 |
- |
- |
838 |
- |
- |
|
A3 |
844 |
844 |
844 |
840 |
840 |
840 |
|
A4 (b) |
842 |
- |
- |
839 |
- |
- |
|
A5 |
841 |
841 |
841 |
838 |
838 |
838 |
|
A6 (b) |
843 |
- |
- |
838 |
- |
- |
|
A7 |
844 |
844 |
844 |
841 |
841 |
841 |
|
A8 |
841 |
841 |
841 |
840 |
840 |
840 |
|
Scenario 2 |
||||||
|
A1 |
855 |
855 |
855 |
849 |
849 |
849 |
|
A2 (b) |
844 |
- |
- |
839 |
- |
- |
|
A3 |
852 |
852 |
852 |
843 |
844 |
844 |
|
A4 (b) |
848 |
- |
- |
842 |
- |
- |
|
A5 |
845 |
845 |
845 |
839 |
839 |
839 |
|
A6 (b) |
850 |
- |
- |
840 |
- |
- |
|
A7 |
853 |
853 |
853 |
843 |
843 |
842 |
|
A8 |
846 |
846 |
846 |
841 |
841 |
841 |
|
Scenario 3 |
||||||
|
A1 |
844 |
844 |
845 |
840 |
840 |
841 |
|
A2 (b) |
843 |
- |
- |
839 |
- |
- |
|
A3 |
841 |
841 |
841 |
839 |
839 |
839 |
|
A4 (b) |
844 |
- |
- |
839 |
- |
- |
|
A5 |
843 |
843 |
843 |
839 |
839 |
839 |
|
A6 (b) |
841 |
- |
- |
839 |
- |
- |
|
A7 |
844 |
844 |
844 |
840 |
840 |
840 |
|
A8 |
841 |
841 |
841 |
840 |
840 |
840 |
|
Scenario 4 |
||||||
|
A1 |
870 |
870 |
872 |
855 |
855 |
855 |
|
A2 (b) |
851 |
- |
- |
844 |
- |
- |
|
A3 |
850 |
850 |
850 |
843 |
843 |
843 |
|
A4 (b) |
854 |
- |
- |
840 |
- |
- |
|
A5 |
854 |
854 |
854 |
841 |
841 |
841 |
|
A6 (b) |
848 |
- |
- |
839 |
- |
- |
|
A7 |
852 |
852 |
852 |
842 |
842 |
842 |
|
A8 |
851 |
851 |
851 |
842 |
842 |
842 |
|
AQO |
30,000 |
30,000 |
30,000 |
10,000 |
10,000 |
10,000 |
|
Notes: (a) (b) As
A2, A4 and A6 are not elevated ASRs and therefore, no assessment results were
presented at 5m and 10 m above ground at these ASRs. |
||||||
The results indicate that the worse case cumulative
NO2 and CO impacts under different time averaging meet the AQOs at all identified ASRs. With the consideration of contribution
from project emissions only, the highest NO2 concentrations are
predicted at Black Point and Lung Kwu Sheung Tan areas (i.e., A1 – A6) under Scenario 4 and at Ha
Pak Nai area (i.e., A7 and A8) under Scenario 2. For cumulative NO2 impacts,
the highest prediction at each ASR is contributed to mainly by emissions from
the future operation of the ST. The
contribution from project emission is minimal except at A7 and A8 under
Scenario 4. Therefore, isopleths of
NO2 concentration contributed by the project emission only and
cumulative NO2 concentrations under Scenario 4 were plotted at 1.5m,
5m and 10m above ground in the Black Point and Lung Kwu
Sheung Tan areas and are shown in Figures 4.3a to 4.8c. The isopleths show that no exceedance is predicted at any of the ASRs.
It is noted from the contour plots that no exceedance of daily and annual average NO2
criteria is predicted in the vicinity of Black Point but exceedance
of the hourly NO2 criteria is predicted at the headland south of the
GRS site (refer to Figures 4.3a, 4.4a and 4.5a).
For the cumulative impact situation, apart from the
above, exceedance of the hourly NO2
criteria is also predicted at the headland between BPPS and Lung Kwu Sheung Tan and a small area
opposite to
Following a detailed review it is noted that there
are no existing and / or future ASRs in the aforementioned areas. It is also noted that the area opposite
to
4.8.1
Construction Phase
Dust control measures stipulated in the Air Pollution Control (Construction Dust)
Regulation will be implemented during the construction of the GRSs to control the potential fugitive dust emissions.
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.
4.8.2
Operation Phase
No exceedances of the NO2
and CO are anticipated at the ASRs and thus no mitigation measures are
considered necessary.
4.9.1
Construction Phase
With the implementation of the recommended dust control
measures, no adverse residual impacts are anticipated.
4.9.2
Operation Phase
No exceedances of the NO2
and CO are anticipated at the ASRs, therefore, adverse
residual operational air quality impact is not expected.
4.10
Environmental
Monitoring and Audit
4.10.1
Construction Phase
Regular site inspections will be carried out in order
to confirm that the mitigation measures are implemented and are working
effectively.
4.10.2
Operation Phase
A commissioning test for heaters will be conducted to
ensure the stack design, heater operation and the emission information adopted
in the assessment is maintained.
Potential nuisance from dust generating activities
and gaseous emission during construction of the two proposed submarine gas
pipelines and GRSs have been considered. With the implementation of standard
mitigation measures, no unacceptable dust impact is anticipated. The gaseous emissions from the
construction equipment are also minimal and no unacceptable impact is
anticipated.
During the operation of the existing and
two proposed GRSs (hereafter called GRS complex), air
emissions from pipeline gas heaters are potential sources of air quality
impacts. The detailed design of the
future GRSs will be determined at a later stage hence
the number of gas heaters of each GRS has been assumed to be within a range of
3 to 7 and the exit velocity of gaseous emissions is designed to be 10 ms-1. Four worst case scenarios were developed
that cover an expected range of worst case impacts at Black Point/Lung Kwu Sheung Tan and Ha Pak Nai areas. With
this set of assumptions and considering the background air quality and the
contributions from existing and future facilities in the vicinity, the
assessment indicated that no exceedance of the AQOs are expected at the ASRs. Although exceedance
of cumulative NO2 hourly and daily AQOs is
predicted at some areas of BPPS, Black Point Headland and small area opposite
to the
During construction phase, regular site inspections
will be carried out in order to confirm that the mitigation measures are
implemented and are working effectively.
Before operation, a commissioning test for heaters will be conducted to
ensure the stack design, heater operation and the emission information adopted
in the assessment is maintained.