This section presents the potential air quality impacts during
construction and operation of the wind turbine. Dust emission is the major concern of air pollution during
construction. During operation, no
air quality impact is expected as there is no pollutant generated from the wind
turbine. It is noted that
electricity generated from renewable energy source would substitute emissions
from conventional forms of the equivalent amount of electricity production
which is an environmental benefit.
The principal
legislation for the management of air quality in the HKSAR is the Air Pollution Control Ordinance (APCO) (Cap
311). The APCO lists a set of Air Quality Objectives, (AQOs) for
seven air pollutants, stipulating statutory limits and permissible exceedances,
as detailed in Table 7.1.
Table 7.1 Hong Kong Air Quality Objectives (mgm-3) (a)
|
Air Pollutant |
Averaging Time |
||||
|
|
1 Hour (b) |
8Hour (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. |
|||||
A maximum hourly level of TSP of 500 mgm-3 at ASRs is also stipulated in the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) to control 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 minimised.
The existing air
quality within the vicinity of the Study Area is mainly affected by emissions
from the existing HEC Lamma Power Station. The HEC does operate air quality monitoring stations (AQMSs)
on Lamma Island to monitor the emissions of total suspended particulates (TSP),
nitrogen dioxide (NO2) and sulphur dioxide (SO2) from the
power station. The nearest AQMS
monitored TSP is located at Tai Yuen Tsuen whereas the nearest AQMS monitored
NO2 and SO2 is located at Pak Kok Tsuen. The annual average air quality data
monitored at the HEC AQMSs on Lamma Island for the year 2002 are summarized in Table 7.2.
Table 7.2 Annual
Average Air Quality in 2002
|
Air Pollutant |
Annual Average Concentration in mgm-3
(a) |
|
HEC Pak Kok San
Tsuen AQMS |
|
|
Sulphur Dioxide (SO2) |
11 |
|
Nitrogen Dioxide (NO2) |
25 |
|
HEC Tai Yuen
Tsuen AQMS |
|
|
Total Suspended Particulates (TSP) |
47 |
|
Notes: (a) The annual average concentrations of air pollutants monitored at HEC AQMSs on Lamma Island in 2002 are provided by the HEC. |
|
ASRs have been identified within 500 m from the Project Site in accordance with the EIA Study Brief (ESB-112/2004) and the criteria set out in Annex 12 of the EIAO-TM and through site inspections and review of land use plan. Landuse type, height of buildings, their horizontal distance from the worksite boundary and approximate base elevation (in mPD) are summarised in Table 7.3. The locations of ASRs are shown in Figure 7.1.
Table 7.3 Air Sensitive Receivers
|
ASR |
Location |
Type |
No. of
Storeys |
Distance from Nearest Worksite Boundary (m) |
Approximate
Base Elevation in mPD |
|
A1 |
No.1 Tai Ling Tsuen |
R |
2 |
185 |
79 |
|
A2 |
No.2 Tai Ling Tsuen |
R |
1 |
240 |
69 |
|
A3 |
No.3 Tai Ling Tsuen |
R |
1 |
245 |
69 |
|
A4 |
Tai Wan Kau Tsuen |
R |
3 |
420 |
12 |
|
A5 |
Po Lo Villa, Long Tsai Tsuen |
R |
1 |
415 |
39 |
|
A6 |
Long Tsai Tsuen |
R |
1 – 3 |
470 |
35 |
|
A7 |
Lo Tik Wan Village |
R |
2 - 3 |
430 |
10 |
|
A8 |
Tai Peng |
R |
2-3 |
470 |
42 |
|
Note: (a) The base elevation of the wind turbine is 92 mPD. |
|||||
Dust in terms of Total Suspended Particulates (TSP) is expected to be
the main air pollutant during the construction of the Project. The Project Area covers an area of about
4,400 m2. The
construction works will last for not more than ten months. Construction activities will include
site formation through minor cutting of the hill slope and filling to form the
site platform, foundation construction, cable laying, wind turbine erection and
landscaping works. Approximately
1,300 m3 of excavated materials will be generated and 95% of them
will be temporarily stored on site for backfilling. The remaining portion will be transported by trucks to the
HEC Power Station for offsite disposal.
Therefore, the number of trucks is expected to be minimal. Wind erosion, materials handling and
on-site stockpiling are therefore, the major dust generating activities for the
Project.
Due to the very limited excavated materials generated and small size of
the worksite (3,100 m2), the dust emissions would be minor. In addition, the nearest ASR identified
in Tai Ling Tsuen (A1) is located at 185 m away from the site. Hence, with the implementation of dust
suppression measures in Section 7.5.1, the dust impact would be limited
and no exceedance of dust level would be envisaged.
During the operation of the wind turbine, no air emission is
expected. However, the wind
turbine will displace emissions of greenhouse gases and other emissions from
conventional power generating plant.
Assuming a 600 kW wind turbine producing electricity of 700 MWh/yr, the
emission reduction of major air pollutants compared with that of the same capacity
at the existing turbines is presented in Table 7.4.
Table 7.4 Air
Pollutant Emission Reduction by Wind Turbine (a) (b)
|
Air Pollutants |
Annual Emission Reduced (kg) |
|
Sulphur dioxide (SO2) |
1941 |
|
Nitrogen oxides (NOx) |
1008 |
|
Particulates |
100 |
|
Carbon dioxide (CO2) |
605.5 tonnes/yr (i.e., 605,500 kg/yr) |
|
Note: (a)
Assuming 600 kW
wind turbine produce electricity of 700 MWh/yr. (b)
Based on
average emission generated from the existing coal-fired units including of
2.773 kg/MWhr of SO2, 1.44 kg/MWhr of NOx, 0.143
kg/MWhr of TSP and 865 kg/MWhr CO2 |
|
It can be seen from above table that the operation of the wind turbine
can bring about benefits through the reduction in emissions of air pollutants
such as SO2, NOx, CO2 and particulates.
In order to reduce the dust emissions during construction phase, the
following dust suppression measures stipulated in the Air Pollution Control
(Construction Dust) Regulation will be incorporated into the Particular
Specification and implemented by the Contractor.
·
Covering entirely
by impervious sheet or frequently watering of the on-site stockpile of
excavated materials to keep wet always before backfilling;
·
Frequent watering
of exposed area or worksite of excavation to maintain surface wet, if necessary
and practical;
·
Provision of
vehicle washing to remove any dusting materials from
small village trucks’ body and
wheel at the exit of worksite;
·
Well-maintained diesel-powered
mechanical equipment to avoid black smoke emissions; and
·
Shut-down of diesel-powered mechanical equipment or trucks inside the worksites
when they are not in operation.
No mitigation measures would be required as only reduction of air
emissions is anticipated.
No residual construction and operational phase air quality impacts would
be anticipated.
During the construction phase, regular site auditing is recommended to ensure the recommended mitigation measures are properly implemented.
No EM&A is required during the operational phase.
Dust nuisance is the only potential air quality impact during the
construction of the Project. Site
formation, foundation construction, cable laying, wind turbine erection and
landscaping works are the main construction activities. Wind erosion, materials handling,
on-site stockpiling and vehicles movements are the major dusty activities. Since the site area is small, the
construction period is short with minimal construction activities and the
distance from the ASRs is more than 185 m away, therefore, with the
implementation of dust suppression measures in Section 7.5.1, the
potential for causing dust impacts is very low. However, to protect the ASRs, regular site auditing is
recommended to ensure the recommended mitigation
measures are properly implemented.
No air quality impact would be envisaged during the
operation of the wind turbine. The
wind turbine will displace emissions of greenhouse gases and other emissions
from conventional power generating plant.
Estimates of the potential emission reductions have been presented.