3. Air Quality

3.1 Introduction

3.1.1 This section presents the assessment for potential air quality impact during construction phase and operation phase of the Project. Construction phase and operation phase air quality impact assessment was conducted in accordance with the requirements set in Annexes 4 and 12 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM), S3.4.4, and Appendices B and B-1 of the Environmental Impact Assessment (EIA) Study Brief No. ESB-356/2022.

3.2 Environmental Legislations, Standards, and Criteria

3.2.1 The Air Pollution Control Ordinance provides the statutory authority for controlling air pollutants from a variety of sources.  The Hong Kong Air Quality Objectives (AQOs), which stipulate the maximum allowable concentrations over specific periods for typical pollutants, should be met.  The prevailing AQOs are listed in Table 3.1.

Table 3.1 Hong Kong Air Quality Objectives (AQOs)

Pollutants	Averaging Time	Concentration Limit^[1] (µg/m^3)	Number of Exceedance Allowed per Year
Sulphur dioxide	10-min	500	3
	24-hour	50	3
Respirable suspended particulates (RSP or PM10)^[2]	24-hour	100	9
	Annual^[4]	50	N/A
Fine suspended particulates (FSP or PM2.5)^[3]	24-hour	50	18^[5]
	Annual^[4]	25	N/A
Nitrogen dioxide (NO2)	1-hour	200	18
	Annual^[4]	40	N/A
Ozone	8-hour	160	9
Carbon monoxide	1-hour	30,000	0
	8-hour	10,000	0
Lead	Annual	0.5	N/A

Note:

1. Gaseous air pollutants are measured at 293K and 101325 Pa.

2. Suspended particulates in air with a nominal aerodynamic diameter of 10µm or smaller.

3. Suspended particulates in air with a nominal aerodynamic diameter of 2.5µm or smaller.

4. Arithmetic mean

5. The new AQO allows 35 days of exceedance per calendar year for daily FSP. However, government and related projects shall adopt a more stringent standard with the number of allowable exceedances of 18 days per calendar year.

Air Pollution Control (Construction dust) Regulation

3.2.2 Notifiable and regulatory works are under the control of Air Pollution Control (Construction Dust) Regulation.  Notifiable works include site formation, reclamation, demolition, foundation and superstructure construction for buildings and road construction.  Regulatory works include building renovation, road opening and resurfacing, slope stabilisation, and other activities including stockpiling, dusty material handling, excavation, concrete production, etc.  This Project is expected to include notifiable works (foundation and superstructure construction and demolition) and regulatory works (dusty material handling and excavation).  Contractors and site agents are required to inform Environmental Protection Department (EPD) and adopt dust reduction measures to minimize dust emission, while carrying out construction works, to the acceptable level.

Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation

3.2.3 The Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation comes into operation on 1 June 2015.  Under the Regulation, Non-road mobile machinery (NRMMs), except those exempted, are required to comply with the prescribed emission standards.  From 1 September 2015, all regulated machines sold or leased for use in Hong Kong must be approved or exempted with a proper label in a prescribed format issued by EPD.  Starting from 1 December 2015, only approved or exempted NRMMs with a proper label are allowed to be used in specified activities and locations including construction sites.  The Contractor is required to ensure the adopted machines or non-road vehicle under the Project could meet the prescribed emission standards and requirement.

Air Pollution Control (Fuel Restriction) Regulation

3.2.4 The Air Pollution Control (Fuel Restriction) Regulation was enacted in 1990 and amended in 2008.  The regulation imposes legal control on the type of fuels allowed for use and their sulphur contents in commercial and industrial processes. Gaseous fuel, conventional solid fuel with a sulphur content not exceeding 1% by weight or liquid fuel with a sulphur content not exceeding 0.005% by weight and a viscosity not more than 6 centistokes at 40°C, such as Ultra Low Sulphur Diesel (ULSD) are permitted to be used in commercial and industrial processes.

Development Bureau Technical Circular (Works) No. 13/2020 Timely Application of Temporary Electricity and Water Supply for Public Works Contract and Wider Use of Electric Vehicles in Public Works Contracts

3.2.5 In response to the carbon emission reduction target as specific in the “Hong Kong Climate Action Plan 2030+”, timely provision of electricity could help reduce carbon emission arising from operation of diesel generators at the construction sites.  At the detailed design stage, project team should timely apply for the temporary electricity with a target that the necessary cables laying works could be completed before the commencement of the works contract.  In addition, timely provision of electricity to construction sites can facilitate the use of Electric Vehicles (EVs) in public works contracts.  The Project team should specify the use of EV(s) as well as the installation of designated medium-speed charger for each EV as a standard provision at the site accommodation in each public works contract.

Development Bureau Technical Circular (Works) No. 1/2015 Emissions Control of NRMM in Capital Works Contracts of Public Works

3.2.6 This Circular promulgates the requirements for the use of non-road mobile machinery (“NRMM”) approved under the Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation (“the Regulation”) in new capital works contracts of public works including design and build contracts, in addition to the statutory requirements of the Regulation.

3.3 Description of the Environment

3.3.1 In accordance with Clause 3.4.4.2 of the EIA Study Brief, the assessment area for air quality impact assessment should be defined by a distance of 500m from the boundary of the Project Area and the works of the Project. The location plan for the Project Site and the 500m air quality impact assessment area is shown in Figure 3.1. It is surrounded by low-rise residential buildings, village houses, temporary structures, and vegetation. The dominant sources of air pollution within 500m assessment area include vehicular emissions and industrial emissions.

3.3.2 The nearest EPD air quality monitoring station is located in Yuen Long. The recent five years of the key air pollutants relevant to the Project is summarized in Table 3.2. According to Table 3.2, there is a general decreasing trend in pollutant concentrations in the past five years.

Table 3.2        Pollutant Concentrations in the recent five years (2018-2022) at Yuen Long Air Quality Monitoring Station

Pollutant	Averaging Time	AQOs	Pollutant Concentrations (μg/m^3)
			2022	2021	2020	2019	2018
SO2	4^th Highest 10-minute average	500	21	24	26	42	52
	4^th Highest 24-hour average	50	7	14	10	11	16
RSP	10^th highest daily average	100	56	73	77	83	75
	Annual average	50	25	30	30	37	37
FSP	19^th Highest daily average	50	38	36	32	39	40
	Annual average	25	16	17	16	20	20
NO2	19^th Highest 1-hour average	200	122	148	135	161	150
	Annual average	40	37	40	32	44	43

Note:

1. Bolded value indicates exceedance of the AQO.

3.3.3 Future background air quality has been predicted based on hourly concentration data extracted from the “Pollutants in the Atmosphere and their Transport over Hong Kong” (PATH v2.1) model. According to Section 2.8, the Project commissioning year is Year 2033. The best available data from PATH v2.1 will be the projected background scenario in Year 2030. Pollutant concentrations in PATH grid (22,44), (22,45), (22,46), (23,45), (23,46), (24,46) projected to Year 2030 were extracted and summarized in Table 3.3.

Table 3.3        Background Air Pollutant in Year 2030 extracted from PATH v2.1

Pollutant	Averaging Time	AQO^[1]	PATH Background Concentrations (μg/m^3)
			(22,44)	(22,45)	(22,46)	(23,45)	(23,46)	(24,46)
RSP^[2]	10^th highest daily average	100(9)	69	71	72	70	70	69
	Annual average	50	27	27	27	26	27	27
FSP^[3][4]	19^th Highest daily average	50(18)^[5]	37	37	39	37	37	40
	Annual average	25	15	15	16	15	15	16
NO2	19^th Highest 1-hour average	200(18)	90	89	90	88	91	94
	Annual average	40	17	17	18	15	17	18

Note:

1. Values in brackets mean the number of exceedances allowed per year.

2. Bolded value indicates exceedance of the AQO.

3. Annual FSP concentration is adjusted by adding 3.5 μg/m³ with reference to ‘Guidelines on Choice of Models and Model Parameters’.

4. 10^th highest daily and annual RSP concentrations are adjusted by adding 11 μg/m³ and 10.3 μg/m³ respectively with reference to ‘Guidelines on Choice of Models and Model Parameters’.

5. The new AQO allows 35 days of exceedance per calendar year for daily FSP. However, government and related projects shall adopt a more stringent standard with the number of allowable exceedances of 18 days per calendar year.

3.4 Identification of Air Sensitive Receivers

3.4.1 In accordance with Annex 12 of the EIAO-TM, any domestic premises, hotel, hostel, hospital, clinic, nursery, temporary housing accommodation, school, educational institution, office, factory, shop, shopping centre, place of public worship, library, court of law, sports stadium or performing arts centre are considered as air sensitive receivers (ASRs).

3.4.2  According to S3.4.4.2 of the EIA Study Brief, the assessment area for the air quality impact assessment shall be defined by a distance of 500 meters from the boundary of the Project area and the works of the Projects as identified in the EIA Study. The ASRs which were closest to the Project boundary are anticipated to be the most affected and therefore considered the most representative ASRs. The representative ASRs were summarized in Table 3.4 and Figure 3.2.

Table 3.4        Representative Air Sensitive Receivers

ASR ID	Description	Land use	Assessment Height (mAG)	Distance from the Project Boundary (m)
Existing ASRs
A1	Temporary Structure at Fuk Hang Tsuen	Residential	1.5 - 5	69
A2	283 Tsoi Yuen Tsuen	Residential	1.5 - 5	237
A3	145 Wo Ping San Tsuen	Residential	1.5 - 5	58
A4	Temporary Structure at Wo Ping San Tsuen	Residential	1.5 - 5	19
A5	174B Tan Kwai Tsuen	Residential	1.5 - 5	<1
A6	345 Tan Kwai Tsuen	Residential	1.5 - 5	21
A7	349 Tan Kwai Tsuen	Residential	1.5 - 5	32
A8	89 Tan Kwai Tsuen Road, Casa Regalia	Residential	1.5 - 10	135
A9	21 Manor Parc	Residential	1.5 - 15	105
A10	370 Tan Kwai Tsuen	Residential	1.5 - 5	14
A11	Buddhist Temple	Place of public worship	1.5 - 5	84
A12	Temporary Structure at Tai Tao Tsuen	Residential	1.5 - 5	<1
A13	House 30 Uptown	Residential	1.5 - 10	17
A14	Agnes Wise Kindergarten	Education	1.5 - 10	24
A15^[1]	Hung Fuk Estate Ancillary Facilities Block	G/IC	4 - 15	255
A16	142 Tai Tao Tsuen	Residential	1.5 - 10	30
A17	House 17 Park Villa	Residential	1.5 - 10	289
A18	House 33 Park Villa	Residential	1.5 - 10	182
A19	176A Fui Sha Wai	Residential	1.5 - 10	15
A20	Jasper Court	Residential	1.5 - 15	29
A21	Tong Yan San Tsuen Garden	Recreational	1.5	77
A22	Sha Tseng Tsuen	Residential	1.5 - 5	80
A23	The Eldorado	Residential	1.5 - 15	124
A24^[2]	Block 1 Parkside Villa	Residential	5 - 40	280
A25	Village House at Lam Hau Yuen	Residential	1.5 - 5	354
A26	175 Fuk Hang Tsuen	Residential	1.5 - 5	412
A27	Shung Tak Catholic English College	Education	1.5 - 10	192
A28	Hung Yuet House	Residential	1.5 - 85	473
A29	Tower 2 Scenic Gardens	Residential	1.5 - 40	428
A30	Hop Hing Building	Industrial	1.5 - 15	1
A31	Tong Yan San Tsuen Playground	Recreational	1.5	350
Planned ASRs
PA1	Proposed School at Long Bin	Education	1.5 - 25	104
PA2	Proposed Public Housing at Long Bin	Residential	1.5 - 140	105
PA3	Planned Residential under Yuen Long South Development	Residential	1.5 - 35	233
PA4	Planned Residential under Yuen Long South Development	Residential	1.5 - 35	297
PA5	Planned Residential under Yuen Long South Development	Residential	1.5 - 15	412
PA6	Proposed Public Housing at Ping Shan South	Residential	1.5 - 150	21
PA7	Proposed Public Housing at Ping Shan South	Residential	1.5 - 130	129
PA8	Proposed School at Tan Kwai Tsuen	Education	1.5 - 25	30
PA9	Proposed Public Housing at Tan Kwai Tsuen	Residential	1.5 - 170	77
PA10	Proposed Public Housing at Lam Tei North	Residential	1.5 - 150	34
PA11	Proposed Public Housing at Lam Tei North	Residential	1.5 - 150	93
PA12	Proposed Residentials under Yuen Long Area 13 & 14	Residential	1.5 - 115	244
PA13	Proposed Residentials under Yuen Long Area 13 & 14	Residential	1.5 - 115	267

Note:

[1] Based on the site visit dated 16 June 2023, Hung Fuk Market is located at 0 – 5 mAG and its fresh air intake is 4 mAG; carpark is located at 5 – 9 mAG and hostel with openable windows is located 9 – 13 mAG. Hence, assessment height are ranged from 4 – 15 mAG.

[2] Based on site survey on 25 November 2022, there is a podium with no air-sensitive use below 5 mAG.

3.5 Identification of Environmental Impacts

Construction Phase

3.5.1 Potential air quality impact during construction phase would be limited to fugitive dust emissions generated work activities such as site clearance, excavation, piling, and handling of construction materials. No major dusty construction activities and only minor earthworks are expected. A maximum of 3 separated work fronts up to 200m long and 15m wide to be taken place at the same time. The tentative construction programme is shown in Appendix 3.1.

3.5.2 Slope works will be required along the northern side of YLH (Eastbound) for site formation and utility diversion for the affected trunk utilities. The extent of areas requiring slope works is limited to 820m² at a time. Therefore, potential fugitive dust emissions arisen from slope work are expected to be limited and localized.

3.5.3 Widening of at-grade road sections will be required along YLH eastbound between Hung Shui Hang Stream and Tin Shui Wai West Interchange, from Hung Tin Road southbound to YLH eastbound, and along YLH westbound between Tong Yan San Tsuen Interchange and Tin Shui Wai West Interchange. The works will not be carried out for the entire section at the same time. Instead, it will be divided into various sub-sections of 200m long and 15m wide where the roadworks will be confined to within relatively small works area at any one time. The potential fugitive dust emissions are expected to be limited.

3.5.4 Construction of about 20m long 6m width elevated road sections will be required at YLH eastbound near Shui Fu Road. The works will involve earthworks and piling. The potential fugitive dust emissions are expected to be limited and localized.

3.5.5 The extent of roadworks, slope works, and bridgeworks is shown in Figure 3.3.

3.5.6 It is estimated that 1 dump truck per hour would be required during normal construction work whilst maximum 5 dump trucks would be needed per hour during peak construction period. In view of the small number of dump trucks, the additional vehicular emissions generated by the dump trucks is considered insignificant.

3.5.7 Fuel combustion from the use of powered mechanical equipment (PME) during construction works is also a source of particulates, NOx, SO₂, and CO. According to the Air Pollution Control (Non-road Mobile Machinery (NRMM)) (Emission) Regulation, starting from 1 December 2015, only approved or exempted NRMMs with a proper label are allowed to be used in specified activities and locations including construction sites. The Air Pollution Control (Fuel Restriction) Regulation also imposes legal control on the type of fuel used for NRMMs. In addition, the Contractor shall timely apply for the temporary electricity with a target that the necessary cables laying works can be completed before the commencement of construction works and avoid on-site use of diesel generator according to DVEB’s TC (W) No. 13/2020. The Contractor is not allowed to use exempted NRMM to ensure the adopted machines or non-road vehicle under the Project could meet the prescribed emission standards and requirements according to DEVB's TC No.1/2015 (Emissions Control of NRMM in Capital Works Contracts of Public Works).

3.5.8 Based on the latest plant inventory list, the maximum number of PME to be used at a time is 9. The Contractor shall follow the regulations and technical circulars listed in Section 3.5.7 during the use of PME. Hence, with the implementation of the said Regulations and technical circular, the emissions from PMEs are considered relatively low and will not cause adverse air quality impact to the surrounding ASRs. 

Potential cumulative impacts during construction phase

3.5.9 Potential concurrent projects with the 500m air quality study area and their respective tentative implementation programs were listed in Table 3.5 and in Figure 3.4.

Table 3.5        Potential Concurrent Projects and their implementation programs

No	Potential Concurrent Projects	Tentative construction time	Shortest Separation distance, m
1	Environmentally Friendly Transport Services in Hung Shui Kiu / Ha Tsuen New Development Area and Adjacent Areas	Phase 1: Year 2027 – 2030/31 Phase 2: Year 2032 – 2036 Phase 3: Year 2034 – 2038	50
2	Route 11 (Section between Yuen Long and Lantau)	No later than Year 2033	10
3	Site Formation and Infrastructure Works for Public Housing Developments at Long Bin, Yuen Long	Year 2020 - 2026	45
4	Site Formation and Infrastructure Works for Public Housing Development near Tan Kwai Tsuen, Yuen Long	Year 2022 - 2027	<1
5	Yuen Long South Development	2022 – 2038	<1
6	Hung Shui Kiu / Ha Tsuen New Development Area	2020 – 2038	50
7	Potential Sites in Yuen Long Areas 13 & 14 for Housing Development	Year 2025 - 2032	230

3.5.10 As shown in Appendix 3.1, the tentative construction period will be Year 2028 – 2032. There will be no overlapping construction period between this Project and potential concurrent projects no. 3 and 4. Cumulative construction dust impact between this Project and the two projects is not anticipated.

3.5.11 For potential concurrent project no. 7, the potential dusty work may include site formation and excavation. The Contractor of this Project shall closely liaise with the corresponding parties of these two projects to avoid dusty activities within 200m of each other. Should such work in close proximity be unavoidable, the corresponding parties shall work closely to schedule the construction works at different periods of the day to minimize concurrent works.

3.5.12 As this Project is separated by 10 m with the potential concurrent project no. 2, the Contractors of this Project and potential concurrent project no. 2 shall liaise to arrange dusty works and roadworks to be carried out by sections and be separated by at least 200m. Hence, cumulative construction dust impact from these two projects is controlled and minimized.

3.5.13 The potential concurrent projects no. 1, 5 and 6 cover a substantial amount area and long construction period such that the Contractor this Project shall closely liaise with the corresponding parties of these three potential concurrent projects to arrange dusty activities being carried out by sections and avoid works areas to be located within 200m of each other. Hence, cumulative construction dust impact from these two projects is controlled and minimized.

3.5.14 In view of close proximity construction site to some ASRs (i.e., A5, A12, A30), a site hoarding of height not less than 4 m shall be provided between the closest construction site and the ASRs to mitigate construction dust impact to these ASRs. A comprehensive dust monitoring plan which includes, but not limited to continuous monitoring of RSP and FSP concentrations by sensors, will be proposed to ensure compliance of relevant AQOs.

3.5.15 With the adoption of careful scheduling between concurrent construction works, both within the Project itself and with other interfacing projects, comprehensive dust monitoring programme, good site practices, and mitigation measures, adverse cumulative construction dust impacts are not expected. Quantitative dust impact assessment is not necessary.

Interim Phase

3.5.16 Referring to the environmental permit (EP) of “Deep Bay Link” (EP-163/2003/H) and the EP of “Widening of Yuen Long Highway between Tan Kwai Tsuen and Shap Pat Heung Interchange” (EP-141/2002/A), the existing noise mitigation measures covered in the two EPs will need to be removed for the purpose of this Project. In general, the future Contractor of this Project is not allowed to remove any existing noise barriers until either permanent noise barriers or temporary noise barriers with the same geometry as the one to be demolished are erected and connected to the other existing noise barriers seamlessly. i.e., the existing noise barriers will be demolished only after the erection of permanent or temporary noise barrier and connected to the existing ones seamlessly.

3.5.17 Some noise barriers stipulated in the EP of “Widening of Yuen Long Highway between Tan Kwai Tsuen and Shap Pat Heung Interchange” (EP-141/2002/A) would be reprovisioned. In case of other constraints when reprovisioning the noise barriers before demolishing existing ones are not feasible, a temporary noise barrier of the same geometry as the existing one will be erected and connected to the existing ones seamlessly. The noise barriers to be reprovisioned is listed in Table 3.6 and depicted in Figure 3.5a, 3.5b, and 3.5c.

Table 3.6       Extent and Locations of Existing Noise Barriers to be Reprovisioned

ID	Barrier Type	Concerned EP	Approximate Length, m
N5	5m Vertical Barrier	EP-141/2002/A	590
N6	5.5m high with 1.5m cantilever at 45^o	EP-141/2002/A	180
N7	4m Vertical Barrier	EP-141/2002/A	140
N8	5.5m high with 1.5m cantilever at 45^o	EP-141/2002/A	160
N9	5.5m high with 2.5m cantilever at 45^o	EP-141/2002/A	140
N10	4m Vertical Barrier	EP-141/2002/A	120
N11	5.5m high with 2.5m cantilever at 45^o	EP-163/2003/H	110
N12	5m Vertical Barrier	EP-547/2018	40

3.5.18 Proposed noise barriers listed in Table 3.7 and noise barriers to be upgraded listed in Table 3.8 are shown in Figure 3.5a and Figure 3.5b. Since there is a change in the geometry of the noise barriers stipulated in the EPs of “Deep Bay Link” (EP-163/2003/H) and “Widening of Yuen Long Highway between Tan Kwai Tsuen and Shap Pat Heung Interchange” (EP-141/2002/A), a quantitative assessment would be carried out to demonstrate that there is no material change with respect to the two EPs.

Table 3.7       Extent and Locations of Proposed Noise Barriers

ID	Barrier Type	Height	Figure
N1	Vertical Barrier	3m	Figure 3.5b
N2	Y-shape Cantilever Barrier	8m high with 4m cantilever at 45^o	Figure 3.5a

Table 3.8       Extent and Locations of Noise Barriers to be Upgraded

ID	Existing Barrier Type	Concerned EP	Upgraded Barrier Type	Figure
N3	5m Vertical Barrier and 5.5m Vertical Barrier with 2.5m cantilever at 45^o	EP-141/2002/A and EP-163/2003/H	8m vertical barrier with 4m cantilever at 45^o	Figure 3.5a
N4	6m Vertical Barrier, 3m Vertical Barrier, and 5.5m high with 2.5m cantilever at 45^o	EP-141/2002/A and EP-163/2003/H	8m vertical barrier with 4m cantilever at 45^o	Figure 3.5a

3.5.19 Regarding to the quantitative assessment for the interim scenario, as identified in the approved EIA Report on Widening of Yuen Long Highways between Lam Tei and Shap Pat Heung Interchange (AEIAR-059/2002) and Deep Bay Link (AEIAR-064/2002), the air pollutants of prime concern from vehicular emission are nitrogen dioxide (NO₂) and RSP. In addition, FSP will be assessed for the purpose of comparison against AQOs. Therefore, the quantitative assessment for interim phase will focus on NO₂, RSP, and FSP on the representative air sensitive receivers.

Operation Phase

3.5.20 Potential air quality impact during operation phase of the Project will be associated with background pollutant concentrations, open road vehicular emissions within 500m from the Project Boundary, emissions associated with bus and minibus public transport interchanges and heavy goods vehicle and coach parking sites, portal emissions, and industrial emissions. Vehicular emission will be the dominant source of air pollution within 500m assessment area.

3.5.21 Vehicular emission comprises several pollutants, including nitrogen oxides (NOx), RSP, FSP, sulphur dioxide (SO₂), carbon monoxide (CO), lead (Pb), etc.  According to “An Overview on Air Quality and Air Pollution Control in Hong Kong” published by EPD, one of the major air pollution issues is the local street-level pollution.  Motor vehicles, especially diesel vehicles, are the main sources of these pollutants at street level in Hong Kong.  For other pollutants such as Diesel Particulate Matters (DPMs), Polycyclic Aromatic Hydrocarbons (PAHs) and Volatile Organic Compounds (VOCs), due to the low concentration in vehicular emission, they are not considered as key pollutants for the purpose of this study.

3.5.22 CO is one of the primary pollutants emitted by road transport. However, monitoring results from all the EPD’s air quality monitoring stations show that background CO concentrations are well below the respective AQO criterion.  CO is therefore considered to be non-critical, and it is not considered necessary to be quantitatively assessed. In Hong Kong, vehicles are restricted to use Ultra Low Sulphur Diesel with a sulphur content of less than 0.001%. Therefore, emission of SO₂ from vehicles is considered minor and no further assessment is considered necessary. Ozone is formed from photochemical reactions between NOx and VOCs in the presence of sunlight. It is not a primary pollutant and thus is not considered as a key criteria pollutant for this Project. Leaded petrol has been banned in Hong Kong since 1999. As such, it is not considered a critical air pollutant of concern and not necessary to be further assessed.

3.5.23 As discussed above, CO, SO₂, ozone, and lead are not considered as critical pollutants of concern in this Project. Thus, operation phase air quality impact assessment will focus on NO₂, RSP, and FSP concentrations on the representative air sensitive receivers.

3.6 Assessment Methodology

3.6.1 The assessment of interim phase and operation phase air quality impact followed the technical requirements set in Appendix B of the EIA Study Brief.

Background Contributions

3.6.2 As suggested by “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts”, an integrated modelling system, PATH v2.1 which is developed and maintained by EPD was applied to estimate the background pollutant concentrations.

3.6.3 The assessment area covered 6 grid cells of PATH v2.1, namely grid (22,44), (22,45), (22,46), (23,45), (23,46), and (24,46).  Based on the construction programme shown in Appendix 3.1, the works for removal and reprovision of noise barrier will commence in Year 2030. Therefore, the best available data from PATH v2.1 was the projected background scenario in Year 2030 for interim phase assessment.

3.6.4 For operational phase assessment, based on the latest information, the Project commission year will be Year 2033. Therefore, the best available data from PATH v2.1 was the projected background scenario in Year 2030.

Vehicular Emissions from Open Roads

3.6.5 Open section of existing and planned road networks within 500m Study Area of the Project were identified.  The predicted 24-hour traffic flow and vehicle compositions at the identified roads during operation phase provided by the traffic consultant were adopted to assess the potential air quality impact from the open roads.  The traffic data adopted for the assessment is presented in Appendix 3.2. The traffic data has been endorsed by the Transport Department and the endorsement letter is enclosed in Appendix 3.2.

3.6.6 With reference to Section 3.5.19 and 3.5.23, NO₂, RSP, and FSP are identified as the key pollutants of concern during interim phase and operation phase. EMFAC-HK v4.3 model was adopted to estimate the vehicular emission rates of NOx, NO₂, RSP, and FSP.  The “vehicle fleet” refers to all motor vehicles operating on roads within this assessment area.  The modelled fleet is broken down into 18 vehicle classes based on the information in the Appendix 1 of Guideline on Modelling Vehicle Emissions published by EPD.  The detailed input parameters and model assumptions made in EMFAC-HK model are summarized in Appendix 3.3. The emission factors for NO were derived by assuming NOx consists of NO and NO₂ only. Temperature and relative humidity data from the nearest weather station with both temperature and relative humidity measurement, i.e., Hong Kong Wetland Park, in Year 2022 was obtained from the Hong Kong Observatory (HKO) for EMFAC modelling.

3.6.7 CALINE4, the EPD approved line source air dispersion model developed by the California Department of Transport was be used to assess the contribution due to vehicular emissions from the open roads within 500 m study area. 

3.6.8 According to Appendix 3.1, the works for removal and reprovision of noise barrier will tentatively commence in Year 2030. Therefore, adopting Year 2030 vehicular emission factors and the road network in Year 2033 would be the worst-case scenario representing the whole interim phase.

3.6.9 The operation phase vehicular emission burdens of NOx, RSP, and FSP from commencement year (Year 2033) to 15 years (Year 2041 and Year 2048) afterwards were estimated using EMFAC-HK v4.3 model as a sensitivity test to identify the worst assessment year for subsequent CALINE4 modelling. The results for the sensitivity test are presented in Appendix 3.3. Based on the results of the sensitivity test, the adoption of Year 2033 vehicular emission factors and road network in Year 2041 yielded the highest vehicular emission burden. Therefore, this combination was adopted as the worst-case scenario for operation phase.

3.6.10 Open sections of existing road networks within the study area will be considered in the model. Surface roughness coefficients of 100cm for each grid will be taken in CALINE4 model.

3.6.11 Under the current EPD guideline, the hourly meteorological data including wind speed, wind direction, and air temperature from the relevant grids in the WRF Meteorological data (same basis for PATH v2.1 model), was employed for the model run. Pasquill-Gifford stability class from the relevant grids provided in the WRF meteorological data was adopted as the meteorological input to CALINE4 model.

3.6.12 The secondary air quality impacts arising from semi-enclosure, underpass, and the existing, proposed, reprovisioned, or upgraded vertical noise barriers or cantilevered noise barrier listed in Table 3.6 to Table 3.8 were incorporated into the interim phase and operation phase air quality model. The locations of all existing, proposed, reprovisioned, or upgraded vertical noise barriers, cantilevered noise barriers, semi-enclosures, and full enclosures within 500m study area are depicted in Figure 3.5, Figure 3.5a, Figure 3.5b, and Figure 3.5c.

3.6.13 It is assumed that, with the installation of vertical noise barriers, all traffic pollutants generated from the mitigated road section are emitted from the top of the noise barriers. In the CALINE4 model, elevation of the mitigated road section was set to the elevation of the barrier top.

3.6.14 For cantilever barriers and semi-enclosures, it is assumed that dispersion of traffic pollutants is in effect similar to physically shifting the mitigated road section towards the central divider.  The traffic pollutants are assumed to emit from the top of the canopies.  In the CALINE4 model, the alignment of the mitigated road section was shifted by a distance equal to the covered extent, elevation of the mitigated road section was set to the elevation of the barrier top.

3.6.15 There is a height limitation for line sources in CALINE4, i.e., road height higher than 10 metres above ground is considered as 10 metres high above ground for assessment purpose. As a rule of thumb, the vertical height difference between road source and receptor in the model should not be larger than their actual vertical difference to avoid underestimation of air quality impact. For the YLH section between Tin Shui Wai West Interchange and Lam Tei Quarry, the YLH is higher than the general area of Tai Tao Tsuen and Tan Kwai Tsuen. Thus, this section of YLH was considered as filled road with the height being set to the elevation of the barrier top plus height difference between the receivers and the road. However, for some receivers situating on terrain and higher than YLH (e.g., A1, A5, A7, A10, A18, A21, A26, PA8, and PA9), the receiver height was adjusted according to the height of the nearest section of YLH in model by the following equation:

Actual height of ASR, mPD – (Actual road elevation, mPD – road elevation set in CALINE4 model, m)

3.6.16 The NO, NO₂, RSP, and FSP running exhaust and start emission factors of 18 vehicle classes predicted by EMFAC-HK are presented in Appendix 3.4. The 24-hour traffic flows and composite emission factors for each road link adopted in air dispersion modelling for vehicular emissions from open roads are presented in Appendix 3.5.

Vehicular Emission from Portals

3.6.17 Vehicular emissions from full enclosures and underpasses proposed by other projects (i.e., portal emissions) were be modelled by the AERMOD model, the EPD approved air dispersion model.

3.6.18 The portal emissions (NO, NO₂, RSP, and FSP) were calculated based on the 24-hour vehicle emission factors predicted by EMFAC-HK v4.3 model and vehicle flows were provided by the traffic consultant. Yearly lowest temperature and relative humidity (5^oC and 20% respectively) from the nearest weather station with both temperature and relative humidity measurement, i.e., Hong Kong Wetland Park, in Year 2022 was obtained from the Hong Kong Observatory (HKO) for EMFAC modelling.

3.6.19 Portal emissions were modelled in accordance with the Permanent International Association of Road Congress Report (PIARC, 1991).  Pollutants are assumed to eject from the portal as a portal jet such that 2/3 of the total emissions were dispersed within the first 50 m of the portal and 1/3 of the total emissions within the second 50 m.

3.6.20 Hourly meteorological conditions including wind data, temperature, relative humidity, pressure cloud cover and mixing height of Year 2015 were extracted from the WRF meteorological data adopted in the PATH v2.1 system.  The minimum wind speed was capped at 1 metre per second.  The mixing height was capped between 131 metres and 1941 metres according to the observation in Year 2015 by HKO. The height of the input data was assumed to be 9 metres above ground for the first layer of the WRF data as input.  In order to avoid any missing hours misidentified by AERMOD and its associated components, the WRF met data was handled manually to set wind direction between 0° – 0.1° to be 360°.  The meteorological data was inputted as on-site data into AERMET.

3.6.21 Surface characteristic parameters such as albedo, Bowen ratio and surface roughness are required in the AERMET (the meteorological pre-processor of AERMOD).  The land use characteristics of the surrounding were classified, and these parameters of each land use were determined by AERMET by default according to its land use characteristics. The determination of the surface characteristics parameters is presented in Appendix 3.6.  Flat terrain in AERMOD was adopted for this assessment as a conservative approach.

3.6.22 The locations and detailed calculations of portal emissions are presented in Figure 3.6, Figure 3.6a, Figure 3.6b and Appendix 3.7.

Industrial Emissions and 4km Major Point Source

3.6.23 Industrial emissions within 500m air quality assessment area were considered as potential sources of air pollution. According to the “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts”, a major point source with 4km from a receiver should be evaluated. Based on desktop survey and site survey dated on 25 November 2022 and 1 December 2022, the following industrial emissions sources consisted of 4 chimneys and 3 concrete batching plant were identified. The asphalt plant identified within 4km near Lam Tei Quarry (AP-2) was obstructed by terrain and had no direct line-of-sight to the air sensitive receivers. Therefore, the contribution from this major emission point to the cumulative air quality impact was considered insignificant and excluded from this assessment. According to the information provided by CEDD in March 2023, the area occupied by the concrete batching plants at Golik Concrete Ltd. and Redland Concrete Ltd. would be resumed in Year 2025. Therefore, these two concrete batching plants were excluded from operation phase air quality impact assessment. The locations of industrial emission sources are shown in Figure 3.7.

Industrial Emissions included in operation phase air quality impact assessment:

· Chimney at Wing Kai Destruction & Recycle Co.

· Chimney at Hop Hing Oil Factory

· Chimney at Hang Sun Chemical Manufacturing Ltd.

· Chimneys at Pun Chun Sauce & Preserved Fruit Factory Ltd.

· Concrete Batching Plant at Hong Kong Concrete Co. Ltd.

Industrial Emissions excluded from operation phase air quality impact assessment:

· Concrete Batching Plant at Golik Concrete Ltd. (Due to land resumption by Yuen Long South Development Project)

· Concrete Batching Plant at Redland Concrete Ltd. (Due to land resumption by Yuen Long South Development Project)

· Asphalt plant near Lam Tei Quarry (AP-2) (Due to obstruction by terrain near Tan Kwai Tsuen)

3.6.24 Letters were issued on 31^st January 2023 to the respective chimney operator to obtain the latest emission information and parameters of each chimney and the latest specified process license of the concrete batching plant was obtained. Of the 4 chimney operators, 2 of them responded and the information has been used for compiling the emission inventory for industrial emissions. The emission inventory for the remaining 2 chimneys without response was referenced to the approved EIA Report for “Housing Sites in Yuen Long South”. Site survey was conducted on 25 November 2022 and 1 December 2022 on the chimneys and were found to be valid. The emission inventory for industrial emissions is presented in Appendix 3.8.

3.6.25 AERMOD was used to assess the air quality impact arisen from industrial emissions. The hourly meteorological conditions and surface characteristic parameters were prepared as the same method as stated in Section 3.6.20 and Section 3.6.21.

3.6.26 Dry deposition was applied for particulate emissions from the concrete batching plant. The particle size distribution was defined with reference to USEPA AP-42.

Emissions associated with the existing bus and minibus termini, heavy goods vehicle and coach parking sites

3.6.27 Start emissions refers to the air pollutants generated from the ignition of vehicle engines and released at vehicle tailpipes. Start emission generally occurs on local road where there is a potential trip start, while no start emission along district distributor, expressway, or trunk road is anticipated.  Table 3.9 shows road sections within the assessment area which were classified as district distributor, expressway, or trunk road according to the Annual Traffic Census 2022 published by Transport Department.

Table 3.9        Road Sections Classified as District Distributor, Expressway, or Trunk Road

Road Name	From	To	Road Type
Yuen Long Highway	Tong Yan San Tsuen Interchange	Lam Tei Interchange	Expressway
Hung Tin Road	Tin Shui Wai West Interchange	Ping Ha Road	District Distributor
Kong Sham Western Highway	Yuen Long Highway	Section of Kong Sham Western Highway near Yick Yuen Road	Expressway
Castle Peak Road – Ping Shan	Ping Ha Road	Tin Ha Road	Rural Trunk Road

3.6.28 For the purpose of this assessment, start emissions generated from private cars, taxi, light goods vehicles, private light buses, heavy goods vehicles, non-franchised bus (NFB) (<6.4t), and motorcycles were assumed on all local roads irrelevant to the actual location of engine start. (i.e., using broad-brush approach, allocating the start emissions on open local roads, using CALINE4). Based on site survey on 22 March 2023 and 24 March 2023, on-street parking of public light bus (PLB), non-franchised bus (NFB) (6.4t – 15t), NFB (15t – 24t), NFB (>24t), franchised bus single deck (FBSD), and franchised bus double deck (FBDD) was not observed on all local roads within 500m study area. Therefore, start emissions generated by PLB, NFB (6.4t – 15t), NFB (15t – 24t), NFB (>24t), FBSD, and FBDD were excluded from start emission modelled by broad-brush approach. Nevertheless, start emissions induced by bus and minibus termini, heavy goods vehicle and coach parking sites were modelled to avoid underestimation of air quality impact. The start emissions, running exhaust emissions, and idling emissions associated with franchised buses, public light buses, heavy goods vehicles, and non-franchised buses (>6.4t) at the existing termini and parking sites within the study area (NO2, RSP, and FSP) were calculated based on the start emission and running exhaust emission factors predicted by EMFAC-HK v4.3 model, cold idling emission factors from the Calculation of Start Emissions in Air Quality Impact Assessment published by EPD, warm idling emission factors from Road Tunnels: Vehicle Emissions and Air Demand for Ventilation published by World Road Association, and traffic data obtained by site survey.

3.6.29 Calculations of emissions associated with the bus and minibus termini, heavy goods vehicle and coach parking sites were referenced to the Calculation of Start Emissions in Air Quality Impact Assessment published by EPD.  Start emissions for diesel vehicles fitted with selective catalytic reduction (SCR) devices vehicles and LPG vehicles were adjusted based on the idling emission and were released over a total spread distance of 700 m and 150m respectively from where the start takes place, while running exhaust and idling emissions were released on the spot. The area occupied by the bus depot at 71 Shan Ha Road and the HGV carpark near 95 Tong Yan San Tsuen Road will be resumed by Yuen Long South Second Phase Development, which the site formation and engineering infrastructure works will tentatively commence in Year 2025. Therefore, this bus depot and HGV carpark were excluded from interim phase and operation phase air quality impact assessment. The HGV carpark at Tai Tao Tsuen was found to be abandoned during site survey on 17 March 2023. Hence, this HGV carpark was not considered in interim phase and operation phase air quality impact assessment. The HGV carpark at Shan Ha Road will be resumed under “Potential Housing Sites for Yuen Long Area 13 & 14” Project, which the site formation and engineering infrastructure works will tentatively begin in Year 2029. Start emissions from this HGV carpark were excluded from interim phase and operation phase air quality impact assessment. The locations of these bus and minibus termini, heavy goods vehicle and coach parking sites with consideration of start emissions by precise approach are listed below and shown in Figure 3.8.

Termini and carpark included in interim phase and operation phase air quality impact assessment:

· Hung Fuk Estate Bus PTI

· Hung Shui Kiu (Hung Yuen Road) Bus PTI

· Hung Fuk Estate Minibus PTI

· Tan Kwai Tsuen Minibus PTI

· MTR Bus Depot

· HGV Carpark at Forefront Cyber Centre

· HGV Carpark at Energy Industrial Centre

· HGV Carpark at Ping Kwai Road

Termini and carpark excluded from interim phase and operation phase air quality impact assessment:

· Bus Depot at 71 Shan Ha Road (Due to land resumption by Yuen Long South Development Project)

· HGV Carpark near 95 Tong Yan San Tsuen Road (Due to land resumption by Yuen Long South Development Project)

· HGV Carpark at Tai Tao Tsuen (Due to the fact that it was found to be abandoned during site survey dated 17 March 2023)

· HGV Carpark at Shan Ha Road (Due to land resumption by Potential Sites in Yuen Long Areas 13 & 14 for Housing Development Project)

3.6.30 Emissions associated with existing bus and minibus termini, and heavy goods vehicles and coach parking sites were modelled by AERMOD. The modelling methodology follows the descriptions in Sections 3.6.20 – 3.6.21. The number of starts per hour of the concerned vehicle class were derived from on-site observation and operator’s published schedule, if applicable, on a normal day for 24 hours and the sitting time and idling time were obtained based on on-site observation at the PTIs, parking sites, and bus depots. The emission inventory is presented in Appendix 3.9.

Ozone Limiting Method for Short-term Cumulative NO₂ Assessment

3.6.31 For the short-term cumulative NO₂ assessment (i.e., predictions of hourly average NO₂ concentration), Ozone Limiting Method (OLM) was adopted for conversion of NO from vehicle-related source (i.e., emissions from open roads, portals, bus and minibus termini, heavy goods vehicle and coach parking sites) and NOx from industrial emission sources to NO₂ based on the predicted O₃ level from PATH v2.1.  For the industrial emissions, the initial NO₂/NOx ratios was assumed as 10% according to the Heathrow Airport EIA Report [1].  The predicted initial NO concentrations from open roads (from CALINE4), portals, bus and minibus termini, heavy goods vehicle and coach parking sites, and 90% of the predicted NOx concentrations from industrial emissions (from AERMOD) was firstly added together on an hour-to-hour basis and OLM was applied subsequently. The NO₂/NOx conversion was calculated as follows:

[NO₂]_predicted = [NO₂]_vehicular + 0.1 ´ [NOx]_industrial + MIN {[NO]_vehicular + 0.9 ´ [NOx]_industrial, or (46/48) ´ [O₃]_PATH}

where

[NO₂]_predicted    is the predicted NO₂ concentration

[NO₂]_vehicular    is the sum of predicted initial NO₂ concentration from open roads, portals, bus and minibus termini, heavy goods vehicle and coach parking sites

[NO]_vehicular     is the sum of predicted initial NO concentration from open roads, portals, bus and minibus termini, heavy goods vehicle and coach parking sites

[NOx]_industrial    is the initial NOx concentration from industrial sources

MIN                means the minimum of the two values within the brackets

[O₃]_PATH          is the representative O₃ PATH concentration (from other contribution)

(46/48)           is the molecular weight of NO₂ divided by the molecular weight of O₃

Jenkin Method for Long-term Cumulative NO₂ Assessment

3.6.32 For the long-term cumulative NO₂ assessment (i.e., predictions of annual average NO₂ concentration), Jenkin method was adopted for the conversion of cumulative NO_x to NO₂ by using the functional form of annual mean of NO₂-to-NOx with reference to the Review of Methods for NO to NO₂ Conversion in plumes at short ranges[2].  The mentioned functional form is referenced from (Jenkin, 2004)[3] and is presented as follows:

where

[NO₂]             is the NO₂ concentration

[NO_x]             is the NOx concentration

[OX]               is the sum of NO₂ concentration and O₃ concentration (i.e. [OX] = [NO₂] + [O₃])

J                    is the photolysis rate of NO₂

k                    is the rate constant for reaction between NO and O₃

3.6.33 The above functional form was used to analyse the annual mean data obtained from EPD’s air quality monitoring stations including Yuen Long general station, Tap Mun general station, and three roadside stations (i.e., Causeway Bay, Central and Mong Kok roadside stations). The Yuen Long general station is the nearest station and therefore chosen as the representative station. Tap Mun general station and three roadside stations were also included in order to cover a wider range of NOx concentration.

3.6.34 A scatter plot for latest 5 years annual means of NO₂ versus NOx obtained from relevant air quality monitoring stations was created to obtain a best-fit function form curve. The functional form curve would fit the annual mean data when [OX] = 102 µg/m³ and J/k = 22 µg/m³. The value of [OX] and J/k are considered reasonable as they are within typical value range for Hong Kong. The range of annual average [OX] from the selected air quality monitoring stations is 75 – 116 µg/m³. The empirical functional form curve was adopted for the cumulative annual average NOx to NO₂ conversion. The data analysis and derivation of cumulative annual average NOx to NO₂ conversion equation using Jenkin Method for this assessment are shown in Appendix 3.10.

Cumulative Air Quality Impact

3.6.35 Cumulative air quality impacts at the representative ASRs were derived from the sum of predictions by local air quality models (i.e., AERMOD and CALINE4 model) and background concentration from PATH v2.1 projected to Year 2030 on hour-by-hour basis.

3.6.36 The future prevailing RSP and FSP background concentrations was extracted from Year 2030 PATH v2.1 model projection results.  With reference to the EPD’s Guidelines on Choice of Models and Model Parameters, PATH v2.1 output of RSP and FSP concentrations require the following adjustment:

· 10^th highest daily RSP concentration: add 11.0 µg/m³

· Annual RSP concentration: add 10.3 µg/m³

· 19^th highest daily FSP concentration: Nil

· Annual FSP concentration: add 3.5 μg/m³

3.6.37 Cumulative air pollutant concentration at the representative ASRs was derived by the sum of contributions by vehicular emission, portal emissions, industrial emissions, emissions associated with bus and minibus termini and heavy goods vehicles and coach parking sites, and background contribution from PATH v2.1 system on an hour-by-hour basis. For annual average, the sum of all valid hourly concentrations is divided by the number of valid hours during the year.  For daily average, cumulative results at each ASR amongst 365 days are ranked by highest concentration and compared with the maximum allowable concentration to determine the number of exceedances throughout a year.  The air quality impact on ASRs is evaluated by number of exceedances per annum against the AQO criteria.

3.7 Prediction and Evaluation of Environmental Impacts

Construction Phase

3.7.1 As discussed in Section 3.5.1 to Section 3.5.15, potential fugitive dust nuisance during construction phase should be limited due to the small scale work front at a time, nature of the construction works, and close liaison with the Contractors of other potential concurrent projects to arrange dusty activities being carried out by sections and avoid works areas to be located within 200m of each other. Hence, construction dust emission from the works area to the ASRs can be controlled and minimized, and adverse construction dust impact to the ASRs is not anticipated. Nevertheless, dust suppression measures recommended in Section 3.8.1 and mitigation measures stipulated in Air Pollution Control (Construction Dust) Regulation shall be implemented to minimize the potential dust emission from the construction of the Project.

3.7.2 Fuel combustion from the use of PME during construction works is also a source of particulates, NOx, SO2, and CO. Considering the small number of PME to be used at a time and the implementation of Air Pollution Control (Non-road Mobile Machinery (NRMM)) (Emission) Regulation, DVEB’s TC (W) No. 13/2020, and DEVB's TC No.1/2015 (Emissions Control of NRMM in Capital Works Contracts of Public Works), the emissions from PME are considered relatively small. Hence, adverse air quality impact arising from the use of PME to the ASRs is not anticipated.

Interim Phase

3.7.3 The cumulative air quality impacts due to background pollutant concentrations, vehicular emissions from open roads, portal emissions, industrial emissions, and emissions associated with bus and minibus termini, heavy goods vehicle, and coach parking sites in the vicinity of the Project at the representative ASRs during interim phase were evaluated.  The predicted cumulative air quality impacts at the ASRs were summarized in Table 3.10. The detailed assessment results are presented in Appendix 3.11.

Table 3.10     Predicted cumulative concentrations at representative air sensitive receivers during interim phase

ASR	NO2 Concentration (µg/m^3)		RSP Concentration (µg/m^3)		FSP Concentration (µg/m^3)
	19^th Highest Hourly Average	Annual Average	10^th Highest Daily Average	Annual Average	19^th Highest Daily Average	Annual Average
AQO	200	40	100	50	50	25
A1	108 - 110	18	69	27	37	15
A2	111	19	69	27	37	15
A3	106 - 112	21 - 24	71	27	38	16
A4	111 - 116	22 - 24	71	27 - 28	38	16
A5	109 - 110	21 - 22	71	27	38	16
A6	112 - 113	23	71	27 - 28	38	16
A7	104	15	70	27	38	15
A8	106 - 109	20 - 21	71	27	38	16
A9	109 - 112	21 - 23	71 - 72	27	38	16
A10	115 - 120	21 - 22	70	27	38	15 - 16
A11	110 - 111	20	70	27	38	15
A12	125 - 126	23 - 24	70	27	38	16
A13	116 - 132	22 - 26	70 - 71	27 - 28	38	16
A14	121 - 129	24 - 25	71	27 - 28	38	16
A15	115 - 149	22 - 31	72 - 73	28	40	16 - 17
A16	110 - 118	23 - 25	70	27 - 28	38	16
A17	102 - 109	18 - 19	70	27	37	15 - 16
A18	108 - 118	18 - 20	70	27	37	15 - 16
A19	122 - 128	23 - 25	70	27 - 28	38	16
A20	114 - 134	21 - 26	69	28	40 - 41	16
A21	118	22	69	28	40	16
A22	117 - 118	22	69	28	40	16
A23	106 - 122	19 - 22	69	28	40	16
A24	98 - 150	17 - 28	69 - 70	27 - 28	40	16
A25	141 - 143	26 - 27	69	28	41	16
A26	99 - 100	16	69	27	37	15
A27	108 - 109	21 - 22	72	28	40	16
A28	91 - 115	16 - 23	72	28	39 - 40	16
A29	95 - 142	17 - 24	69	27 - 28	40	16
A30	121 - 143	22 - 28	70	27 - 28	38	16
A31	113	21	69	28	40	16
PA1	113 - 144	21 - 29	69	28	40 - 41	16 - 17
PA2	94 - 151	16 - 31	69	27 - 28	40 - 41	16 - 17
PA3	101 - 126	18 - 24	69 - 70	27 - 28	40	16
PA4	100 - 134	17 - 27	69 - 70	27 - 28	40	16
PA5	100 - 101	16	70	27	38	15
PA6	90 - 110	15 - 22	71	27	37 - 38	15 - 16
PA7	90 - 106	15 - 20	71	27	37 - 38	15 - 16
PA8	97 - 108	16 - 18	71	27	37	15
PA9	89 - 101	15 - 17	71	27	37	15
PA10	89 - 120	15 - 24	71 - 72	27 - 28	37 - 38	15 - 16
PA11	90 - 102	15 - 19	69	27	37	15
PA12	94 - 147	16 - 28	69	27 - 28	40	16
PA13	94 - 145	16 - 26	69	27 - 28	40	16

3.7.4 According to the results in Table 3.10, the prediction results indicated that the 19^th highest hourly average NO₂, annual average NO₂, 10^th highest daily average and annual average of RSP, and 19^th highest daily average and annual average of FSP concentrations at all representative ASRs would comply with the respective AQOs.

3.7.5 According to the predicted results, the worst hit level at the representative ASRs generally appears at the first air sensitive use level. 1.5mAG was considered the best representing the lowest level of most of the air sensitive uses within the Study Area.  Contour plots of the 19^th highest hourly average, annual average NO₂ concentrations, 10^th highest daily average, annual average RSP concentrations, 19^th highest daily average, and annual average FSP concentrations at 1.5mAG are depicted and presented in Figure 3.9 to Figure 3.14.

3.7.6 Referring to the contour plots Figure 3.9 and Figure 3.11 to Figure 3.14, no exceedance zone was found for the 19^th highest hourly average NO₂ concentration, 10^th highest daily averaged RSP concentration, annual averaged RSP concentration, 19^th highest daily averaged FSP concentration, and annual averaged FSP concentration.

3.7.7 Referring to Figure 3.10, 2 small exceedance zones were found near the portal exits of Enclosures F and G and on the road near PA4 for annual averaged NO₂ concentration. No air sensitive use, fresh air intake of ventilation system, or recreational uses in open space is situated in the exceedance zones.

3.7.8 Contour plots of annual averaged NO₂ concentrations at 5 mAG was presented in Figure 3.15. Referring to Figure 3.15, a small exceedance zone was found on the elevated section of Hung Tin Road near A15 for annual averaged NO₂ concentration at 5 mAG. No air sensitive use, fresh air intake of ventilation system, or recreational uses in open space is situated in the exceedance zones.

3.7.9 Contour plots of annual averaged NO₂ concentrations at 10 mAG was presented in Figure 3.16. Referring to Figure 3.16, no exceedance zone was found for annual averaged NO₂ concentration at 10 mAG.

Operation Phase

3.7.10 The cumulative air quality impacts due to background pollutant concentrations, vehicular emissions from open roads, portal emissions, industrial emissions, and emissions associated with bus and minibus termini, heavy goods vehicle, and coach parking sites in the vicinity of the Project at the representative ASRs during operation phase were evaluated.  The predicted cumulative air quality impacts at the ASRs were summarized in Table 3.11.  The detailed assessment results are presented in Appendix 3.11.

Table 3.11     Predicted cumulative concentrations at representative air sensitive receivers during operation phase

ASR	NO2 Concentration (µg/m^3)		RSP Concentration (µg/m^3)		FSP Concentration (µg/m^3)
	19^th Highest Hourly Average	Annual Average	10^th Highest Daily Average	Annual Average	19^th Highest Daily Average	Annual Average
AQO	200	40	100	50	50	25
A1	106	17	69	27	37	15
A2	106	18	69	27	37	15
A3	104 - 106	19 - 22	71	27	38	16
A4	107 - 108	21 - 22	71	27 - 28	38	16
A5	105 - 107	19 - 20	71	27	38	16
A6	110	21	71	27	38	16
A7	101 - 102	15	70	27	38	15
A8	104 - 106	19 - 20	71	27	38	16
A9	106 - 108	20 - 21	71	27	38	16
A10	110 - 113	19 - 20	70	27	38	15 - 16
A11	108	19	70	27	38	15
A12	119 - 120	21 - 22	70	27	38	16
A13	122 - 145	21 - 25	70 - 71	27 - 28	38	16
A14	125 - 130	23 - 24	70 - 71	27	38	16
A15	117 - 158	21 - 30	72 - 73	28	39 - 40	16 - 17
A16	116 - 122	23 - 24	70	27	38	16
A17	101 - 110	18 - 19	70	27	37	16
A18	105 - 121	18 - 20	70	27	37	16
A19	117 - 121	22 - 23	70	27 - 28	38	16
A20	111 - 125	20 - 24	69	28	40	16
A21	114	23	69	28	40	16
A22	113 - 115	22	69	28	40	16
A23	104 - 117	19 - 22	69	28	40	16
A24	97 - 149	17 - 26	69	27 - 28	40	16
A25	139	25	69	28	40	16
A26	98	15	69	27	37	15
A27	108	21	72	28	39 - 40	16
A28	91 - 115	16 - 22	72	28	39 - 40	16
A29	95 - 134	16 - 23	69	27 - 28	40	16
A30	113 - 132	21 - 26	70	27 - 28	38	16
A31	110	20	69	28	40	16
PA1	108 - 138	20 - 27	69	28	40 - 41	16
PA2	94 - 145	16 - 29	69	27 - 28	40 - 41	16
PA3	101 - 118	17 - 24	69 - 70	27 - 28	40	16
PA4	100 - 130	17 - 26	69	27 - 28	40	16
PA5	101 - 104	16	70	27	38	15
PA6	90 - 109	15 - 21	71	27	37 - 38	15 - 16
PA7	90 - 103	15 - 19	71	27	37 - 38	15 - 16
PA8	94 - 104	16 - 17	71	27	37	15
PA9	89 - 99	15 - 17	71	27	37	15
PA10	89 - 113	15 - 22	71	27	37 - 38	15 - 16
PA11	90 - 99	15 - 18	69	27	37	15
PA12	94 - 143	16 - 26	69	27 - 28	40	16
PA13	94 - 139	16 - 25	69	27 - 28	40	16

3.7.11 According to the results in Table 3.8, the prediction results indicated that the 19^th highest hourly average NO₂, annual average NO₂, 10^th highest daily average and annual average of RSP, and 19^th highest daily average and annual average of FSP concentrations at all representative ASRs would comply with the respective AQOs.

3.7.12 According to the predicted results, the worst hit level at the representative ASRs generally appears at the first air sensitive use level. 1.5mAG was considered the best representing the lowest level of most of the air sensitive uses within the Study Area.  Contour plots of the 19^th highest hourly average, annual average NO₂ concentrations, 10^th highest daily average, annual average RSP concentrations, 19^th highest daily average, and annual average FSP concentrations at 1.5mAG are depicted and presented in Figure 3.17 to Figure 3.21.

3.7.13 Referring to the contour plots Figure 3.17, Figure 3.19, Figure 3.21 and Figure 3.22, no exceedance zone was found for the 19^th highest hourly average NO₂ concentration, 10^th highest daily averaged RSP concentration, 19^th highest daily averaged FSP concentration, and annual averaged FSP concentration.

3.7.14 Referring to Figure 3.18, 2 exceedance zones were found near the portal exits of Enclosures F and G, and near Hung Fuk Estate Bus PTI. No air-sensitive use including fresh air intake of ventilation system, openable window or recreational uses in open space is situated in the exceedance zones.

3.7.15 As shown in Figure 3.20, a small exceedance zone was found near the concrete batching plant near Hong Kong Concrete Ltd. for annual averaged RSP. The major contribution to the exceedance zone was emissions from the concrete batching plant at Hong Kong Concrete Ltd. Within the exceedance zone was a concrete batching plant. No air sensitive use was situated within the exceedance zone.

3.7.16 Contour plots of annual average NO₂ concentrations, 10^th highest daily average RSP, and annual average RSP concentrations at 5 mAG were presented in Figure 3.23 to Figure 3.25.

3.7.17 Referring to Figure 3.23, a small exceedance zone was located on the elevated section of Hung Tin Road near A15. No air sensitive use is situated within the exceedance zone.

3.7.18 Referring to Figure 3.24 to Figure 3.25, no exceedance zone was found for 10^th highest daily averaged RSP and annual averaged RSP at 5 mAG.

3.7.19 Contour plots of annual average NO₂ concentrations at 10 mAG were presented in Figure 3.26. Referring to Figure 3.26, no exceedance zone was found for annual averaged NO₂ concentrations at 10 mAG.

3.8 Mitigation of Adverse Environmental Impacts

Construction Phase

3.8.1 In order to mitigate dust impact to the ASRs, the following dust suppression measures and good site practices shall be implemented.

· Use of regular watering to reduce dust emissions from exposed site surfaces and unpaved roads, particularly during dry weather.

· Use of frequent watering for particularly dusty construction areas and areas close to ASRs.

· Side enclosure and covering of any aggregate or dusty material storage piles to reduce emissions.  Where this is not practicable owing to frequent usage, watering shall be applied to aggregate fines.

· Open stockpiles shall be avoided or covered.  Where possible, prevent placing dusty material storage piles near ASRs.

· Tarpaulin covering of all dusty vehicle loads transported to, from and between site locations.

· Establishment and use of vehicle wheel and body washing facilities at the exit points of the site.

· Provision of wind shield and dust extraction units or similar dust mitigation measures at the loading area 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.

· Provision of not less than 2.4m high hoarding from ground level along site boundary where adjoins a road, streets or other accessible to the public except for a site entrance or exit.

· Imposition of speed controls for vehicles on site haul roads.

· Where possible, routing of vehicles and positioning of construction plant should be at the maximum possible distance from ASRs.

· Instigation of an environmental monitoring and auditing program to monitor the construction process in order to enforce controls and modify method of work if dusty conditions arise.

· Temporarily stockpile odorous material as far away from ASRs as possible.

· Temporary stockpiles of odorous material will be properly covered with tarpaulin to avoid any odour nuisance arising.

· Connecting construction plant and equipment to mains electricity supply and avoid use of diesel generators and diesel-powered equipment;

· Exempted NRMMs are not allowed; and

· Provision of site hoarding (>4m) for ASRs located in close proximity to works areas (e.g., A5, A12, and A30)

Operation Phase

3.8.2 No adverse air quality impact is anticipated during the operation phase of the Project. Thus, mitigation measure is deemed not necessary.

3.9 Evaluation of Residual Impact

Construction Phase

3.9.1 With the implementation of the mitigation measures as stipulated in the Air Pollution Control (Construction Dust) Regulation together with the recommended dust suppression measures and good site practices on the work sites as described in Section 3.8.1, no adverse residual impact would be expected during the construction phase of the Project.

Operation Phase

3.9.2 No adverse residual air quality impact arising from the Project is anticipated during the operation phase of the Project.

3.10 Environmental Monitoring and Auditing

Construction Phase

3.10.1 EM&A for potential dust impacts should be conducted during construction phase to check compliance with the legislative requirements. Continuous monitoring of RSP and FSP is recommended at various monitoring locations during construction phase of the Project. Details of the monitoring and audit programme are contained in a stand-alone EM&A Manual.

3.10.2 Regular site audits for potential dust impact are recommended to be conducted during the entire construction phase of the Project to ensure the dust mitigation measures and the dust suppression measures stipulated in Air Pollution Control (Construction Dust) Regulation are implemented in order.

Operation Phase

3.10.3 No unacceptable adverse impact arising from the Project is anticipated during the operation phase of the Project. Therefore, the EM&A work for the operation phase is considered unnecessary.

3.11 Conclusion

Construction Phase

3.11.1 Potential dust impact generated from construction works of the Project would mainly be related to construction dust from site clearance, excavation, roadworks, and wind erosion of exposed work area.  With the implementation of mitigation measures specified in the Air Pollution Control (Construction Dust) Regulation together with the recommended dust suppression measures and good site practices, no adverse dust impact at ASRs is anticipated due to the construction activities of the Project. The Contractor of this Project shall liaise with the corresponding parties of potential concurrent projects to avoid dusty activities from being carried out in close proximity.

Interim Phase

3.11.2 Cumulative air quality impact arising during the Interim Phase of the Project was assessed. The results conclude that the predicted cumulative NO₂, RSP, and FSP concentrations at all ASRs would comply with AQOs.  No adverse air quality impact is anticipated arising during the interim phase of the Project.

Operation Phase

3.11.3 Cumulative air quality impact arising from the operation of the Project was assessed for the operation phase of the Project. The results conclude that the predicted cumulative NO₂, RSP, and FSP concentrations at all ASRs would comply with AQOs.  No adverse air quality impact is anticipated arising from the operation of the Project.

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[1] Department for Transport. (2007). Air Quality Studies for Heathrow: Base Case, Segregated Mode, Mixed Mode and Third Runway Scenarios modelled using ADMS-Airport. Cambridge Environmental Research Consultants.

[2] Middleton, D.R., Luhana, L., & Sokhi, R.S. (2007, November). Review of methods for NO to NO₂ conversion in plumes at short range. Bristol; Environmental Agency.

[3] Jenkin, M.E. (2004). Analysis of sources and partitioning of oxidant in the UK – Part 1: The NOx-dependence of annual mean concentrations of nitrogen dioxide and ozone. Atmospheric Environment, 38(30), 5117-5129.