3. Air Quality Impact Assessment
3.1. Introduction
3.2. Environmental
Legislation, Policies, Plans, Standards, and Criteria
3.3. Description of
the Existing Environment
3.4. Identification of
Assessment Area and Air Sensitive Receivers
3.5. Identification of
Pollution Source
3.6. Description of
Assessment Methodology
3.7. Identification,
Prediction and Evaluation of Environmental Impacts (Construction Phase)
3.8. Mitigation of
Environmental Impacts
3.9. Definition and
Evaluation of Residual Environmental Impact
3.10. Identification and Evaluation
of Operational Phase Environmental Impact
3.11. Environmental Monitoring and
Audit
3.12. Conclusions and
Recommendations
This chapter presents the assessment of potential air quality impacts which may arise from the Project. Air quality impacts associated with decommissioning, site formation, temporary drainage works and road works of the west portion and southern edge of the Middle Ash Lagoon are assessed.
3.2.1. The criteria for evaluating air quality impacts and the guidelines for air quality assessment are laid down below:
·
Section
3.4.3, Appendix B and B-1 to B-3 of EIA Study Brief (No. ESB-243/2012)
·
Annex
4 and Annex 12 of the Technical Memorandum on Environmental Impact Assessment
Process (EIAO (TM))
·
Air
Pollution Control Ordinance (APCO) Cap. 311
3.2.2. The “Air Pollution Control Ordinance (Cap. 311)” provides a statutory framework for establishing the Air Quality Objectives (AQOs) and stipulating the anti-pollution requirements for air pollution sources. The AQOs (Table 3.1) stipulates the statutory limits for seven pollutants and dictate the maximum number of allowable exceedance over a specified time periods.
Table 3.1 Hong Kong Air Quality Objectives (AQOs)
|
Pollutants |
Averaging Time[2] |
AQOs |
|
|
Concentration in micrograms per cubic meter (µg/m3)[1] |
No
of Exceedance
Allowed per
Calendar Year |
||
|
Sulphur Dioxide |
10-min |
500 |
3 |
|
24-hr |
125 |
3 |
|
|
Respirable Suspended Particulates
(PM10)[3] |
24-hr |
100 |
9 |
|
Annual |
50 |
N/A[5] |
|
|
Fine Suspended Particulates (PM2.5)[4] |
24-hr |
75 |
9 |
|
Annual |
35 |
N/A[5] |
|
|
Nitrogen Dioxide |
1-hr |
200 |
18 |
|
Annual |
40 |
N/A[5] |
|
|
Ozone |
8-hr |
160 |
9 |
|
Carbon Monoxide |
1-hr |
30,000 |
0 |
|
8-hr |
10,000 |
0 |
|
|
Lead |
Annual |
0.5 |
N/A[5] |
Notes:
[1] Gaseous air
pollutants are measured at 293K (20oC) and 101.35kPa (one
atmosphere)
[2] Refer to Air
Pollution Control (Amendment) Ordinance 2013.
[3] Respirable
suspended particulates mean suspended particles in air with a nominal
aerodynamic diameter of 10µm or less.
[4] Fine suspended
particulates mean suspended particles in air with a nominal aerodynamic
diameter of 2.5µm or less.
[5] “N/A” stands for
“Not Applicable”
3.2.3. The EIAO (TM) stipulates that the hourly TSP level should not exceed 500μg/m3 (measured at 25°C and one atmosphere) for construction dust impact assessment. Mitigation measures for construction site are specified in the Air Pollution Control (Construction Dust) Regulation.
3.2.4. In accordance with the EIAO (TM), odour at an air sensitive receiver should not exceed 5 odour units based on an average time period of 5 seconds for odour prediction assessment.
3.2.5. Notifiable and regulatory works are under the control of the Air Pollution Control (Construction Dust) Regulation. Notifiable works are site formation, reclamation, demolition, foundation and superstructure construction for buildings and road construction. Regulatory works are building renovation, road, opening and resurfacing slope stabilisation, and other activities including stockpiling, dusty material handling, excavation, concrete works etc. This Project is expected to include both notifiable works and regulatory works. Contractor and site agents are required to inform the Environmental Protection Department (EPD) on carrying out construction works and to adopt dust reduction measures to reduce dust emission to the acceptable level.
3.3.1. The Subject Site is located at the existing ash lagoons in Tsang Tsui, Tuen Mun, overlooking the Deep Bay in the north-western New Territories. The Subject Site within area of approximately 30,000m2 (3 hectares) located at the west portion of the Middle Ash Lagoon, was leased to China Light & Power Company Ltd. (CLP) for the storage of pulverized fuel ash (PFA). A location plan of this potential site is shown in Figure 1.1.
3.3.2. In accordance with the Guidelines on assessing the “TOTAL” Air Quality Impacts as detailed in Appendix B-2 of the EIA Study Brief (No. ESB-243/2012), the recent five years (2009-2013) monitoring data are adopted as the background concentration. There is currently no EPD-operated air quality monitoring station near the Subject Site. Hence background air quality levels is obtained from the data of air quality monitoring station setup by China Light & Power Company Limited (CLP) located at Lung Kwu Tan. The background air pollutant concentrations adopted from CLP Lung Kwu Tan monitoring station are tabulated in Table 3.2. Results indicate that the background concentration of SO2 and NO2 at the monitoring station setup by CLP at Lung Kwu Tan complies with the AQO.
3.3.3. In addition, air quality levels are obtained from air quality monitoring station setup by Airport Authority Hong Kong (AA) located at Lung Kwu Chau and Sha Chau for the recent five years (2009-2013). The background air pollutant concentrations adopted from AA Lung Kwu Chau/Sha Chau monitoring station are tabulated in Table 3.3. Exceedances of pollutant concentration at monitoring station are shown in bold in Table 3.3.
Table 3.2 Air Pollutant
Concentration measured at CLP’s Lung Kwu Tan Air
Quality Monitoring Station
|
Pollutant |
Averaging Time |
AQOs |
CLP Lung Kwu Tan Air Quality Monitoring
Station |
||||
|
2009 |
2010 |
2011 |
2012 |
2013 |
|||
|
(µg/m3) |
(µg/m3) |
(µg/m3) |
(µg/m3) |
(µg/m3) |
(µg/m3) |
||
|
Sulphur Dioxide |
10-minute |
500 |
N/A[2] |
N/A[2] |
N/A[2] |
N/A[2] |
N/A[2] |
|
24-hour |
125 |
N/A[1] |
60 |
38 |
31 |
34 |
|
|
Nitrogen Dioxide |
1-hour |
200 |
N/A[1] |
149 |
153 |
134 |
149 |
|
Annual |
40 |
28 |
26 |
30 |
26 |
28 |
|
Source: China Light &
Power Company Limited (CLP)
Note:
[1] 2009 Hourly Data of
Sulphur Dioxide and Nitrogen Dioxide are not available. Annual average of Sulphur Dioxide and Nitrogen
Dioxide in 2009 are 19 And 28 respectively according to CLP.
[2] No Data is available for
10-minute Sulphur Dioxide
Table 3.3 Air Pollutant Concentration measured at
AA’s Lung Kwu Chau/Sha Chau Air Quality Monitoring Station
|
Pollutant |
Averaging Time |
AQOs |
AA Lung Kwu Chau Air Quality Monitoring Station |
||||
|
2009 |
2010 |
2011 |
2012[3,4] |
2013[3] |
|||
|
(µg/m3) |
(µg/m3) |
(µg/m3) |
(µg/m3) |
(µg/m3) |
(µg/m3) |
||
|
Sulphur Dioxide |
10-minute |
500 |
N/A[6] |
N/A[6] |
N/A[6] |
N/A[6] |
N/A[6] |
|
24-hour |
125 |
56 |
55 |
44 |
32 |
32 |
|
|
PM10 |
24-hour |
100 |
105 |
119 |
113 |
90 |
125 |
|
Annual |
50 |
48 |
50 |
53 |
44 |
48 |
|
|
PM2.5 |
24-hour |
75 |
N/A[5] |
N/A[5] |
N/A[5] |
66 |
91 |
|
Annual |
35 |
N/A[5] |
N/A[5] |
N/A[5] |
30 |
32 |
|
|
Nitrogen Dioxide |
1-hour |
200 |
145 |
148 |
117 |
101 |
185 |
|
Annual |
40 |
38 |
35 |
29 |
28 |
41 |
|
|
Ozone |
8-hour |
160 |
225[7] |
217[7] |
240[7] |
198[7] |
235[7] |
|
Carbon Monoxide |
1-hour |
30,000 |
2049 |
2894 |
2271 |
2107 |
2132 |
|
8-hour |
10,000 |
1738 |
2453 |
2239 |
1551 |
2032 |
|
Source: Airport
Authority Hong Kong
Note:
[1] 2009
– 2011 Annual averages were calculated based on figures obtained from Lung Kwu
Chau air quality monitoring station from Jan 2009 – Dec 2011
[2]
Monitoring results that exceed the new AQOs are shown in bold
[3]
2012 and 2013 annual average calculated based on figures obtained from Sha Chau monitoring Station
[4]
The monitoring station set up by AA at Lung Kwu Chau has been moved to Sha Chau
since July 2012. 2012 annual average calculated based on figures obtained from
Sha Chau monitoring Station from July 2012 – Dec 2012.
[5] No
data is available for PM2.5 from 2009 to 2011.
[6] No
Data is available for 10-minute Sulphur Dioxide
[7]Denotes the 10th highest 8-hour average concentration.
3.4.1. As defined in Section 3.4.3.2 of the EIA Study Brief (ESB-243/2012), the assessment area for construction air impact assessment includes all areas within 500m from the boundary of the Subject Site. Generally speaking, air impact generated at distances beyond 500m would not be significant. Figure 3.1 shows the assessment area for air quality impacts.
3.4.2. According to Section 2 of Annex 12 of the EIAO (TM), “all domestic premises, hotel, hostel, hospital, clinic, nursery, temporary housing accommodation, school, education institution, office, factory, shop, shopping centre, place of public worship, library, court of law, sports stadium or performing arts centres shall be considered to be an air sensitive receiver (ASRs)”. In addition, “any other premises or place with which, in terms of duration or number of people affected, has a similar sensitivity to the air pollutants as the aforelisted premises and places shall be considered to be a sensitive receiver”.
3.4.3. Existing ASRs within the area of concern have been confirmed through site visits conducted on 10 July 2012 and 11 December 2013, along with the review of the survey map. Planned ASRs within the area of concern have been reviewed with reference to relevant Outline Zoning Plans, Outline Development Plans, Layout Plans and other published plans.
3.4.4. A total of 2 representative ASRs have been identified for this assessment in accordance with the criteria set out in the EIAO (TM). The details of the representative ASRs are summarised in Table 3.4 and locations of the ASRs are shown in Figure 3.1.
Table 3.4 Identified Air
Sensitive Receivers
|
ASR |
Description |
Land Use |
Horizontal Separation from
Site (m) |
|
ASR1 |
EPD WENT Landfill Site office |
Industrial |
217 |
|
ASR2 |
Sludge Treatment Facilities Site Office |
Industrial |
290 |
Note:
The horizontal separation distance from site is measured from the nearest point
of the site boundary.
3.4.5. Aside from the identified air sensitive receivers in Table 3.4, a Hung Shing Temple was also located within the Study Area. According to the latest site visit conducted on 11 December 2013, the temple entrance was covered by wild grass. Incense burner was covered in dust while Buddha worship supplies were removed, suggesting it was unattended for a period of time. There was no encounter with any acolyte or visitors during the course of the site visit. As such, it was believed that the temple was abandoned and thus not considered as an air sensitive receiver. Photographic records of the Hung Shing Temple visit on 11 December 2013 are shown in Figure 3.2.
3.5.1. Major potential air quality impact during decommissioning would be fugitive dust arising during construction phase of the Project, including following activities:
·
Excavation
and levelling of pulverized fuel ash;
·
Formation
of Construction Access Road
·
Vehicular
movement on unpaved construction access roads;
·
Covering
of 1m thick general fill above the final PFA surface;
·
Construction
of retaining structure for slope stabilization;
·
Drainage
and road works; and
·
Wind
erosion of open sites and stockpiling areas.
3.5.2. With reference to the approved Sludge Treatment Facilities (STF) EIA Report (EIA-155/2008),WENT Landfill Extensions (WLES) EIA Report(EIA-171/2009) and Integrated Waste Management Facilities (IWMF) (EIA-201/2011), the construction period of these three projects would not overlap with the construction activities of the Project. Therefore, cumulative dust impact from other EIA designated projects is not expected. The construction programmes of the Project and other approved EIA are given in Table 3.5 below.
Table 3.5 Construction Programme of the Project and other Approved EIA
|
EIA Designated Project |
Construction Period |
Completion |
|
Decommissioning of West Portion
of the Middle Ash Lagoon (the “Project”) |
Sep
2015 |
Mar
2016 |
|
Sludge Treatment Facilities (EIA-155/2008)[1] |
Sep 2010 – Early 2015 |
Early 2015 |
|
WENT Landfill Extensions (EIA-171/2009) |
2016 - 2028 |
2028 |
|
Integrated Waste Management
Facilities (EIA-201/2011)[2] |
Mar 2013 (According to IWMF EIA Report
approved on 17 Jan 2012) |
2019 (According to
IWMFEIA Report approved on 17 Jan 2012) |
Note:
[1] With
reference to the information from EPD, The construction of the STF is expected
to be completed in early 2015.
[2] There is no programme for the IWMF project at the Tsang Tsui site from September 2015 to March 2016 under which the proposed decommissioning works would be carried out. Hence it is not considered as a concurrent project under EIA.
3.5.3. Pollutant emission from the Project and concurrent sources were evaluated to determine the cumulative air quality impacts. A number of concurrent sources which were taken into account are summarised below:
·
Construction
works of the Project (detailed in Section 3.5.1);
·
Existing
WENT Landfill; and
·
Operation
of the STF
3.5.4. WENT Landfill is one of the key disposal sites for garbage from business, industry and residences. The major air quality impact associated with the existing WENT Landfill would arise from the gaseous emissions from ammonia stripping plant, LFG power generator and flaring systems. Vehicular emissions from Lung Kwu Tan Road and Nim Wan Road and marine vessel emissions would be anticipated during the transportation of waste. WENT Landfill adopts air quality mitigation measures such as the use of active extraction system, plastic sheet cover at inactive tipping phase to reduce adverse air quality impact.
3.5.5. The air pollution sources identified during the operational phase of the STF will come from chimney emission of the STF. The chimney emissions from STF shall comply with the limits as stipulated in “A Guidance Note on the Best Practicable Means for Incinerator (Municipal Waste Incineration) BPM 12/1” published by EPD, European Commission’s Waste Incineration Directive and US’s Emission Limits in Title 40 Part 503 of CFR on Sewage Sludge Incineration. With reference to the Sludge Treatment Facilities EIA Report (EIA-155/2008), air pollution and stack monitoring system will be installed for the STF to ensure that the emissions from the STF stacks will meet the stringent emission limits equivalent to those stipulated in Hong Kong and the European Commission for waste incineration. With the implementation of recommended mitigation measures, adverse air quality impact during the operation of STF is not expected.
3.6.1. With reference to the STF EIA Report (EIA-155/2008) and WLES EIA Report (EIA-171/2009), cumulative air quality impacts associated with the operation of STF, existing WENT Landfill, proposed WENT Landfill Extension and vehicular emissions etc. have been included in the air quality impact assessment in each of the respective EIA reports.
3.6.2. Construction works shall be carried out 12-hours per day, 26 days per month during the 6-month construction period. Major potential air quality impact during decommissioning and construction phase of the Project would be dust arising from the following works:
·
Excavation
and levelling of pulverized fuel ash;
·
Formation
of Construction Access Road
·
Vehicular
movement on unpaved construction access roads;
·
Covering
of 1m thick general fill above the final PFA surface;
·
Construction
of retaining structure for slope stabilization;
·
Drainage
and road works; and
·
Wind
erosion of open sites.
3.6.3.
Table 3.6 summarizes the works and number of construction plants used during
construction. The construction works at the Subject Site shall be carried out
upon completion of works at the Construction Access Road Area.
Table 3.6 Construction Works and
Plant Equipment Schedule
|
Location |
Works |
Equipment Type |
Number of Equipment |
|
Subject
Site |
l
Erection of site hoarding l
Installation of temporary drainage system l
Slope stabilization works at embankment l
Site formation works |
Backhoes |
4 |
|
Compaction Rollers |
4 |
||
|
Dozers |
1 |
||
|
Construction
Access Road Area |
l
Erection of site hoarding l Installation of temporary drainage system |
Backhoes |
2 |
|
Vibratory Roller |
2 |
3.6.4. Apart from levelling and filling operations, majority of the ash stored at the Subject Site would be left in-situ. Extensive excavation and transportation of ash would not be required and there will be no off-site disposal of PFA in this Project. Based on the Project’s preliminary design, it is estimated that 15,000m3 PFA in total would be handled during construction. Assuming that construction shall be carried out 12-hours per day, 26 days per month, the volume of excavated materials handled per day during the construction period would be approximately 83m3. The air sensitive receivers located within the Study Area include the EPD WENT Landfill Site Office and STF Site Office. The nearest air sensitive receiver is the EPD WENT Landfill Site Office located approximately 217m from the Site boundary. However, office areas of WENT Landfill and STF are equipped with air-conditioning and the dust filter associated with the air-conditioning system would reduce the TSP level.
3.6.5. As such, with effective implementation of practicable dust suppression measures as shown in Section 3.8 as well as measures stipulated in the Air Pollution Control (Construction Dust) Regulation, adverse construction dust impact at the ASRs are not expected during construction of the Project. Quantitative assessment is therefore considered not necessary.
3.6.6. In view of the large separation distance (>200m) of the nearby ARSs from the Project Site, no dust monitoring is considered necessary. Yet, regular site environmental audits during the construction phase of the Project as described in the Environmental Monitoring and Audit Manual prepared under this study should be conducted to ensure that the recommended dust suppression measures are implemented properly.
The likely air quality impacts arising from the construction works are dust nuisance from construction and vehicle emissions. It is anticipated that dust would mainly be generated from levelling, filling and material handling works. With effective implementation of practicable dust suppression measures as shown in Section 3.8 as well as measures stipulated in the Air Pollution Control (Construction Dust) Regulation, the construction works are not expected to generate significant amount of construction dust. In addition, the large separation distance (>200m) of the nearby ARSs from the Project Site is considered to provide sufficient buffer and hence potential construction dust impact is anticipated to be insignificant.
3.8.1. Measures have been taken into consideration in the planning of the Project to abate the air pollution impacts. Good site practice and air quality management techniques are recommended to minimize potential air quality impact from construction site activities on nearby ASRs. Dust mitigation measures stipulated in the Air Pollution Control (Construction dust) Regulation should be incorporated to control dust emission from the Subject Site. The proposed dust mitigation measures would be specified in the works contract for the Project, for implementation by contractor. Some of these precautionary measures relevant to the Project are listed as follows:
·
Dust
Suppression by watering of construction area at least 10 times per day;
·
Provide
covering of 50% of open area with impervious materials or concrete paving;
·
Limited
working period to 180 days.
·
Provision
pavement to Construction access road with concrete paving and provide wheel
washing facility at entrance and exit.
·
Skip
hoist for material transport should be totally enclosed by impervious sheeting;
·
Vehicle
washing facilities should be provided at every vehicle exit point;
·
The
area where vehicle washing takes place and the section of the road between the
washing facilities and the exit point should be paved with concrete, bituminous
materials or hardcore surfaces;
·
Where
a site boundary adjoining a road, streets or other areas accessible to the
public, hoarding of not less than 2.4m high from ground level should be
provided along the entire length except for a site entrance or exit;
·
Every
main construction access road should be paved with concrete and kept clear of
dusty materials or sprayed with water so as to maintain the entire road surface
wet;
·
The
portion of road leading only to a construction site that is within 30m of a
designated vehicle entrance or exit should be kept clear of dusty materials;
·
Every
stock of more than 20 bags of cement should be covered entirely by impervious
sheeting placed in an area sheltered on the top and the 3 sides;
·
All
dusty materials should be sprayed with water prior to any loading, unloading or
transfer operation so as to maintain the dusty materials wet;
·
Every
vehicle should be washed to remove any dusty materials from its body and wheels
before leaving the construction sites;
·
The
load of dusty materials carried by vehicles leaving a construction site should
be covered entirely by clean impervious sheets to ensure dusty materials do not
leak from the vehicle;
·
Provision
of wind shield and dust extraction units or similar dust mitigation measures at
the loading points, and use of water sprinklers at the loading area where dust
generation is likely during the loading process of loose material, particularly
in dry seasons/ periods;
·
Imposition
of speed controls for vehicles on unpaved site roads. Ten kilometres per hour
is the recommended limit;
·
Where
possible, routing of vehicles and positioning of construction plant should be
at the maximum possible distance from ASRs; and
·
Instigation
of an environmental auditing program to monitor the construction process in
order to enforce controls and modify method of work if dusty conditions arise.
3.8.2. Environmental monitoring and audit should be conducted to ensure that the recommended dust suppression measures are implemented properly. With proper implementation of dust control measures, significant construction dust impacts at ASRs during the construction phase of the Project is not expected.
Residual environmental impact is the net impact remained with the mitigation measures in place. With implementation of dust mitigation measures specified in Air Pollution Control (Construction Dust) Regulation and incorporation of an EM&A programme, adverse residual dust impact during the construction phase is not expected.
As defined in Section 2.5.2, operational phase shall be defined as the period when the decommissioning works as detailed in Section 2.6 are completed. The operational phase of the Project shall be an idle buildable land to cater for any future developments by the government. Since the operational phase does not involve any equipment operation or human activities, adverse air quality impact is not expected.
Further details of the specific EM&A requirements are detailed in Section 12 of this report and in the EM&A Manual, together with event action plans and procedures for complaints.
Air quality impacts from the construction works for the Project would mainly involve the construction dust arising from materials handling, construction access roads, filling activities, wind erosion of open sites and stockpiling areas. With the implementation of mitigation measures specified in the Air Pollution Control (Construction Dust) Regulation, dust impact on air sensitive receivers would be minimal.