Contents

3 Air Quality Impact

3.1 Introduction

3.2 Environmental Legislations, Standards and Guidelines

3.3 Description of the Environment

3.4 Assessment Area and Identification of Air Sensitive Receivers

3.5 Environmental Impacts during Construction Phase

3.6 Environmental Impacts during Operational Phase

Tables

Table 3.1: Air Quality Objectives  3-1

Table 3.2: Historical Air Quality from EPD’s general monitoring station at Yuen Long  3-3

Table 3.3: Future Background Air Quality from PATH for Year 2030  3-4

Table 3.4: Representative ASRs in the Vicinity of the Project 3-6

Table 3.5: Criteria and Non-criteria Pollutants and Odour Emissions from Chimneys  3-22

Table 3.6: Total Emission in Year 2030, 2033, 2036, 2040, 2043, 2045, 2048 and 2051  3-27

Table 3.7: Summary of Worst Predicted Cumulative Modelling Results During the Operational Phase at Each ASR  3-31

Figures

Figure 3.1	Assessment Area for Air Quality Impact Assessment (with PATH grids)
Figure 3.2A	Location of Representative Air Sensitive Receivers
Figure 3.2B	Location of Representative Air Sensitive Receivers (Sheet 1 of 2)
Figure 3.2C	Location of Representative Air Sensitive Receivers (Sheet 2 of 2)
Figure 3.3	Construction Phasing Plan and Locations of Concurrent Projects
Figure 3.4	Locations of Chimneys
Figure 3.5	Locations of Bus Terminus, Bus Depot and Car Park with Heavy Goods Vehicle and Coach
Figure 3.6A	Contour of Cumulative 10th highest 24-hour Average RSP Concentration (µg/m^3) at 1.5m Above Ground
Figure 3.6B	Contour of Cumulative Annual RSP Concentration (µg/m^3) at 1.5m Above Ground
Figure 3.6C	Contour of Cumulative 36th highest 24-hour Average FSP Concentration (µg/m^3) at 1.5m Above Ground
Figure 3.6D	Contour of Cumulative Annual FSP Concentration (µg/m^3) at 1.5m Above Ground
Figure 3.6E	Contour of Cumulative 19th highest 1-hour Average NO2 Concentration (µg/m^3) at 10.0m Above Ground
Figure 3.6F	Contour of Cumulative Annual NO2 Concentration (µg/m^3) at 1.5m Above Ground
Figure 3.6G	Contour of Cumulative 4th highest 10-min SO2 Concentration (µg/m^3) at 9.2m Above Ground
Figure 3.6H	Contour of Cumulative 4th highest 24-hour Average SO2 Concentration (µg/m^3) at 1.5m Above Ground

Appendices

Appendix 3.1	Details of Representative Air Sensitive Receivers
Appendix 3.2	Fresh Air Intake via Earth Cooling Tube
Appendix 3.3	Traffic Forecast and Speed Profiles
Appendix 3.4	Industrial Emission Sources more than 500m away from Air Sensitive Uses of the Proposed Development
Appendix 3.5	Model Input Parameters for Vehicular Emissions from Open Roads
Appendix 3.6	Composite Emission Factors and Sensitivity Test
Appendix 3.7	Surface Parameters for AERMOD Meteorological Data
Appendix 3.8	Emission Inventory for Chimneys Sources
Appendix 3.9	Emission Inventory for Bus Terminus, Bus Depot and Car Park with Heavy Goods Vehicle and Coach
Appendix 3.10	Derivation of Cumulative Annual Average NOx to NO2 Conversion Using Jenkin Method
Appendix 3.11	Detailed Cumulative Modelling Results during Operation Phase
Appendix 3.12	Assessment of Air Sensitive Uses Within Exceedance Zones

Glossary

AERMET	Meteorological data pre-processor for AERMOD
AERMOD	American Meteorological Society/Environmental Protection Agency Regulatory Model
AP-42	5th edition of Compilation of Air Pollution Emission Factors issued by USEPA
APCO	Air Pollution Control Ordinance
AQMS	Air Quality Monitoring Station
AQO	Air Quality Objective
ASR	Air Sensitive Receiver
CDWE	Comprehensive Development with Wetland Enhancement
CO	Carbon Monoxide
Corinair	Core Inventory Air Emissions
C&D	Construction and Demolition
D.D.	Demarcation District
DPM	Diesel Particulate Matter
DS	Development Site
DSD	Drainage Services Department
EC	Elemental Carbon
EIA	Environmental Impact Assessment
EIAO	Environmental Impact Assessment Ordinance
EIAO-TM	Technical Memorandum on Environmental Impact Assessment Process
EMEP	European Monitoring and Evaluation Programme
EMFAC-HK	Vehicle emission calculation model, EMission-FACtor-Hong Kong (EMFAC-HK) Version 4.3
EPD	Environmental Protection Department
EU	European Union
FSP	Fine Suspended Particulates
H2S	Hydrogen Sulphide
HKO	Hong Kong Observatory
HKPSG	Hong Kong Planning Standards and Guidelines
IDC	Investigation, Design and Construction
LC	Lut Chau
LSPS	Land Sharing Pilot Scheme
MSBs	Multi-Storey Buildings
NH3	Ammonia
NO2	Nitrogen Dioxide
NOx	Nitrogen Oxides
NRMM	Non-road Mobile Machinery
NSW	Nam Sang Wai
NTN	New Territories North
O3	Ozone
OEHHA	Office of Environmental Health Hazard Assessment, California, USA
OLM	Ozone Limiting Method
OSHA	Occupational Safety and Health Administration, USA
OU	Odour Units
PAHs	Polycyclic Aromatic Hydrocarbons
PATH	Pollutants in the Atmosphere and their Transport over Hong Kong Model Version 3.0
Pb	Lead
PCB	Polychlorinated Biphenyls
PEL	Permissible Exposure Limit
PER	Preliminary Environmental Review
PM	Particulate Matter
PM2.5	Fine Suspended Particulates (FSP or PM2.5)
PM10	Respirable Suspended Particulates (RSP or PM10)
PMEs	Powered Mechanical Equipment
RCP	Refuse Collection Point
RCV	Refuse Collection Vehicle
REL	Reference Exposure Levels
RSP	Respirable Suspended Particulates
RTS	Refuse Transfer Stations
SAMP	EPD’s Smart Air Modelling Platform
SO2	Sulphur Dioxide
SP	Specified Process
SPS	Sewage Pumping Station
TAPs	Toxic Air Pollutants
TD	Transport Department
TOC	Total Organic Carbons
UK	United Kingdom
USEPA	United States Environmental Protection Agency
VKT	Vehicle Kilometre Travelled
VOCs	Volatile Organic Compounds
WCP	Wetland Conservation Park
WLP	Wetland Park Station
WRF	Weather Research and Forecasting
YLEPP	Yuen Long Effluent Polishing Plant
YLEPP EIA	Yuen Long Effluent Polishing Plant Environmental Impact Assessment study (AEIAR-220/2019)
YLIE	Yuen Long Industrial Estate

3 Air Quality Impact

3.1 Introduction

3.1.1 This section presents the assessment of potential air quality impacts associated with the construction and operational phases of the proposed comprehensive development with wetland enhancement (CDWE) at Nam Sang Wai (NSW) and Lut Chau (LC).

3.1.2 Representative Air Sensitive Receivers (ASRs) within the 500m Assessment Area have been identified and the worst-case impacts on these receivers have been assessed. Suitable mitigation measures have been recommended accordingly, in order to comply with relevant criteria.

3.2 Environmental Legislations, Standards and Guidelines

3.2.1 Air quality impact assessment has been carried out in accordance with the relevant criteria and standards as specified in the following legislation and guidelines:

● Environmental Impact Assessment Ordinance (EIAO) (Cap. 499), EIAO-TM, Annexes 4 and 12;

● Air Pollution Control Ordinance (APCO) (Cap. 311);

● Air Pollution Control (Construction Dust) Regulation;

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

● Air Pollution Control (Fuel Restriction) Regulation.

Technical Memorandum on Environmental Impact Assessment Process

3.2.2 The criteria and guidelines for evaluating air quality impacts are laid out in Section 1 of Annex 4 and Annex 12 of the EIAO-TM, respectively. Section 1 of Annex 4 stipulates the criteria for evaluating air quality impacts. This includes meeting the Air Quality Objectives (AQOs) and other standards established under the APCO, as well as meeting the hourly Total Suspended Particulate (TSP) concentration of 500 μg/m³ and the 5-second average odour concentration of 5 odour units (ou/m³). Annex 12 provides the guidelines for conducting air quality assessments under the EIA process, including determination of Air Sensitive Receivers (ASRs), assessment methodology as well as impact prediction and assessment.

Air Pollution Control Ordinance

Air Quality Objectives

3.2.3 The principal legislation for the management of air quality is the APCO. The APCO specifies Air Quality Objectives (AQOs) which stipulate the statutory limits of air pollutants and the maximum allowable numbers of exceedances over specific periods. The prevailing AQOs which have been effective since 1st January 2022 are listed in Table 3.1 below.

Table 3.1: Air Quality Objectives

Pollutant	Averaging time	Concentration^[i] (µg/m^3)	Number of exceedances allowed
Respirable Suspended Particulates (PM10) ^[ii]	24-hour	100	9
	Annual	50	Not applicable
Fine Suspended Particulates (PM2.5) ^[iii]	24-hour	50	35 ^[iv]
	Annual	25	Not applicable
Nitrogen Dioxide (NO2)	1-hour	200	18
	Annual	40	Not applicable
Sulphur Dioxide (SO2)	10-minute	500	3
	24-hour	50	3
Ozone (O3)	8-hour	160	9
Carbon Monoxide (CO)	1-hour	30,000	0
	8-hour	10,000	0
Lead (Pb)	Annual	0.5	Not applicable

Notes:    

[i]. All measurements of the concentration of gaseous air pollutants, i.e., sulphur dioxide, nitrogen dioxide, ozone and carbon monoxide, are to be adjusted to a reference temperature of 293 Kelvin and a reference pressure of 101.325 kilopascal.

[ii]. Respirable suspended particulates mean suspended particles in air with a nominal aerodynamic diameter of 10 µm or less.

[iii]. Fine suspended particulates mean suspended particles in air with a nominal aerodynamic diameter of 2.5 µm or less.

[iv]. The allowable exceedance for government projects is 18.

Air Pollution Control (Construction Dust) Regulation

3.2.4 The Air Pollution Control (Construction Dust) Regulation enacted under the APCO defines notifiable and regulatory works activities that are subject to construction dust control. Notifiable works are site formation, reclamation, demolition of a building, construction of foundation and superstructure for a building, and road construction work. Regulatory works are renovation of building, road opening or resurfacing work, slope stabilisation work, and any work involving stockpiling, loading and unloading of dusty material, transfer of dusty material using belt conveyor system, etc.

3.2.5 Notifiable works require that advance notice of activities shall be given to EPD. The Air Pollution Control (Construction Dust) Regulation also requires the works Contractor to ensure that both notifiable works and regulatory works are conducted in accordance with the Schedule of Regulation, which provides dust control and suppression measures.

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

3.2.6 The Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation controls the emissions from non-road vehicle and regulated machines to be used in construction sites. The regulated machines must comply with the emission standards of Stage IIIA of the European Union (EU) or equivalent. Non-road vehicles that are not licensed under the Road Traffic (Registration and Licensing of Vehicles) Regulations (Cap. 374E) are required to comply with the Euro VI / California LEV III emission standards. Upon confirmation of their compliance with the emission requirement, EPD will issue them with an approval label.

3.2.7 According to the regulation, mobile machine and equipment (regulated machines) means any mobile machine or transportable industrial equipment that is powered by an internal combustion engine with a rated engine power output that is greater than 19 kW but less than or equal to 560 kW. Non-road Mobile Machinery (NRMM) is intended to be used in a private road that is within an area wholly or mainly used for the carrying on of construction work/industry. Regulated machines include crawler cranes, excavators, etc., while non-road vehicles mean private cars, goods vehicles, etc. Therefore, this regulation is applicable to the regulated machines and non-road vehicles (if any) to be deployed for construction activities of the Project.

Air Pollution Control (Fuel Restriction) Regulation

3.2.8 The Air Pollution Control (Fuel Restriction) Regulation specifies the legal control on the type of fuels to be allowed for use and the sulphur contents of the fuels. With the exception of Shatin district, the fuels to be used should comply with the following respective requirements:

● Gaseous fuel; and

● 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”)

3.3 Description of the Environment

Local Environment

3.3.1 The Project consists of two separate sites located in NSW and LC, Yuen Long. These mainly consists of wetlands and fishponds. Yuen Long Industrial Estate is approximately 120m west of the NSW site. There is no major road in the vicinity of the Project Site.

Baseline Condition

3.3.2 Historical background air quality has been referenced from EPD’s general air quality monitoring station (AQMS) located in Yuen Long, which is closest to the NSW site. The recent five years’ monitoring data (Year 2019 – 2023) recorded at the AQMS in Yuen Long is presented in Table 3.2.

Table 3.2: Historical Air Quality from EPD’s general monitoring station at Yuen Long

Pollutant	Averaging Period	Concentration (µg/m^3)						Corresponding AQOs (µg/m^3)
		2019	2020	2021	2022	2023	5-year annual average
Respirable Suspended Particulates (RSP or PM10)	24-hour - 10^th highest	83	77	73	56	59	70	100
	Annual	37	30	30	25	26	30	50
Fine Suspended Particulates (FSP or PM2.5)	24-hour - 36^th highest	34	28	31	30	30	31	50
	Annual	20	16	17	16	16	17	25
Nitrogen Dioxide (NO2)	1-hour -      19^th highest	161	135	148	122	130	139	200
	Annual	44	32	40	37	37	38	40
Sulphur Dioxide (SO2)	10-minute - 4^th highest	42	26	24	21	20	27	500
	24-hour -     4^th highest	11	10	14	7	10	10	50
Ozone (O3)	8-hour -      10^th highest	200	154	178	194	155	176	160
Carbon Monoxide (CO)	1-hour	2,150	1,530	2,090	1,700	1,580	1,810	30,000
	8-hour	1,903	1,279	1,591	1,519	1,273	1,513	10,000

Notes:

[i]. Data extracted from EPD’s Smart Air Modelling Platform (SAMP) v2.0.

[ii]. Monitoring results that exceeded prevailing AQO criteria are shown in bold characters.

3.3.3 The predicted future background air pollutant concentrations within the Assessment Area are extracted from relevant grids of the Pollutants in the Atmosphere and their Transport over Hong Kong (PATH) v.3.0 model for Year 2030 and are summarised in Table 3.3 below. Year 2030 is referenced being the planned Phase 1 population intake year of the Project.

Table 3.3: Future Background Air Quality from PATH for Year 2030

Pollu-tant	Averaging Period	Concentration (µg/m^3)												Corres-ponding AQOs (µg/m^3)
		25, 48	25, 49	25, 50	25, 51	26, 48	26, 49	26, 50	26, 51	27, 48	27, 49	27, 50	27, 51
RSP/ PM10	24-hour - 10^th Highest	53	53	54	54	53	53	53	53	55	52	52	53	100
	Annual	20	20	20	20	20	20	20	20	21	20	20	20	50
FSP/ PM2.5	24-hour - 36^th Highest	26	26	26	26	26	26	26	26	28	26	26	26	50
	Annual	12	12	12	12	12	12	12	12	13	12	12	12	25
NO2	1-hour - 19^th Highest	76	74	74	75	75	75	76	76	74	73	73	74	200
	Annual	16	15	14	14	15	14	14	14	14	14	14	14	40
SO2	10-min -   4^th Highest	25	25	25	25	24	25	25	25	24	24	24	24	500
	24-hour - 4^th Highest	7	7	7	7	7	7	7	7	7	7	7	7	50
O3	8-hour -      10^th Highest	190	190	189	186	186	188	189	186	181	184	189	190	160
CO	1-hour	522	522	522	523	520	521	521	522	522	523	523	523	30,000
	8-hour	487	487	485	484	489	490	489	489	491	491	491	492	10,000

Notes:    

[i]. Data extracted from EPD’s Smart Air Modelling Platform (SAMP) v2.0.

3.3.4 As shown in Table 3.3, future background levels of hourly and annual NO₂, daily and annual RSP and FSP and 10-min and daily SO₂ would be below their corresponding AQOs by 2030. The improvement in future ambient air quality can be attributed to the government’s commitment to implement various planned emission reduction measures, as published on EPD’s website^[1].

3.4 Assessment Area and Identification of Air Sensitive Receivers

3.4.1 The Assessment Area is defined as an area within 500m from the Project Boundary, as shown in Figure 3.1.

3.4.2 Referring to 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 should be classified as Air Sensitive Receivers (ASRs). Any other premises or place with similar duration or number of people to be affected as the above premises and places should also be considered as ASRs.

3.4.3 Representative ASRs (both existing or planned) that may be affected by the Project within the 500m Assessment Area are shown in Figure 3.2A to Figure 3.2C. A summary and details of representative ASRs are presented in Table 3.4 and Appendix 3.1.

3.4.4 In order to minimise the impact from Yuen Long Industrial Estate (YLIE) on the planned residential development at NSW Development Site (DS), particularly to the planned air-conditioned Visitor Centre (P01), the fresh air intake for this building will be designed to be located further away from the industrial estate via an earth cooling tube. The tentative fresh air-intake location is presented in Appendix 3.4. Therefore, no openable window is provided for the Visitor Centre. It is not uncommon to have fresh air drawn into a building via an earth cooling tube. An example of this practice would be the CIC Zero Carbon Park as presented in Appendix 3.2. The exact location of the Visitor Centre or its fresh air intake will be further reviewed during the detailed design stage. In any case, the air-sensitive uses of the visitor centre including openable window and fresh air intake shall not be located within 500m of the air emission sources during the detailed design stage.

Table 3.4: Representative ASRs in the Vicinity of the Project

ASR ID	Description	Type of Use	Approximate Horizontal Distance from Project Boundary (m)	Approximate Horizontal Distance from Phase 1 Construction (m)	Approximate Horizontal Distance from Phase 2 Construction (m)	Approximate Horizontal Distance from Phase 3 Construction (m)	Assessment Height Above Ground (mAG)	Construction Phase	Operational Phase
Existing ASRs
A01	Nestle Hong Kong Ltd	I	422	718	847	855	1.5 - 10.0	ü	ü
A02	Hong Kong Petrochemical Co., Ltd	I	268	816	978	1,008	1.5 - 10.0	ü	ü
A03	Viva Manufacturing	I	210	569	724	751	1.5 - 20.0	ü	ü
A04	Chiho-Tiande Group Limited	I	297	509	524	524	1.5 - 10.0	ü	ü
A05	Nin Jiom Medicine Manufactory HK Ltd	I	307	491	491	453	1.5 - 10.0	ü	ü
A06	Shan Pui Chung Hau Tsuen	R	360	637	637	493	1.5 - 10.0	ü	ü
A07	Transitional Housing - United Court	R	199	539	539	346	1.5 - 10.0	ü	ü
A08	Village House near United Court	R	307	737	680	464	1.5 - 10.0	ü	ü
A09	The Parcville Tower	R	382	800	747	530	1.5 - 35.0	ü	ü
A10	Shan Pui Hung Tin Tsuen	R	263	719	628	396	1.5 - 10.0	ü	ü
A11	Shan Pui Tsuen	R	234	661	567	351	1.5 - 10.0	ü	ü
A12	Zen River	R	200	654	560	334	1.5 - 10.0	ü	ü
A13	Houses near Yuen Long Road Safety Centre	R	44	475	415	200	1.5 - 10.0	ü	ü
A14	Yuen Long Road Safety Centre	E	129	431	394	256	1.5	ü	ü
A15	Houses near Yuen Long Road Safety Centre	R	37	308	286	180	1.5	ü	ü
A16	Chung Hau Yu Man San Tsuen	R	11	353	263	28	1.5 - 10.0	ü	ü
A17	Nam Sang Wai village houses	R	302	581	581	634	1.5 - 10.0	ü	ü
A18	Fairview Park	R	480	1,772	1,939	2,116	1.5 - 10.0	ü	ü
A19	Lut Chau	R	126	1,381	1,518	1,679	1.5	ü	ü
A20	Leeman Hydraulic	I	145	186	241	246	1.5 - 10.0	ü	ü
A21	Fortune Pharmacal	I	27	298	298	303	1.5 - 10.0	ü	ü
A22	Village House near Lut Chau	R	368	1,560	1,742	1,810	1.5 - 10.0	ü	ü
A23	Village House near Fairview Park	R	274	1,652	1,816	1,981	1.5 - 10.0	ü	ü
A24	59 Wang Lok Street (near car park)	I	14	266	299	278	1.5 - 20.0	ü	ü
Planned ASRs
C01	Private Housing Development at D.D. 115 at Chung Yip Road, Nam San Wai *	R	66	499	468	316	1.5 - 10.0	ü	ü
P01	Fresh air intake for Visitor Centre	Rec	Within Project Site	Phase 1 development	613	660	1.5 - 9.2	Phase 2 & 3	ü
P02	Elderly Centre	HE	Within Project Site	Phase 1 development	185	254	1.5 - 22.0	Phase 2 & 3	ü
P03	Residential Development 25 Floors (Phase 1) **	R	Within Project Site	Phase 1 development	105	171	1.5 - 82.8	Phase 2 & 3	ü
P04	Residential Development 25 Floors (Phase 1) **	R	Within Project Site	Phase 1 development	16	76	1.5 - 82.8	Phase 2 & 3	ü
P05	Residential Development 22 Floors (Phase 3) **	R	Within Project Site	NA	NA	Phase 3 development	1.5 - 73.2	×	ü
P06	Residential Development 19 Floors (Phase 3) **	R	Within Project Site	NA	NA	Phase 3 development	1.5 - 63.6	×	ü
P07	Residential Development 19 Floors (Phase 3) **	R	Within Project Site	NA	NA	Phase 3 development	1.5 - 63.6	×	ü
P08	House (3-storey) (Phase 2) **	R	Within Project Site	NA	Phase 2 development	10	1.5 - 12.4	Phase 3	ü
P09	House (3-storey) (Phase 2) **	R	Within Project Site	NA	Phase 2 development	10	1.5 - 12.4	Phase 3	ü
P10	Residential Development 22 Floors (Phase 2) **	R	Within Project Site	NA	Phase 2 development	10	1.5 - 73.2	Phase 3	ü
P11	House (3-storey) (Phase 1) **	R	Within Project Site	Phase 1 development	20	178	1.5 - 12.4	Phase 2 & 3	ü
P12	Residential Development 20 Floors (Phase 1) **	R	Within Project Site	Phase 1 development	10	166	1.5 - 66.8	Phase 2 & 3	ü
P13	House (3-storey) (Phase 1) **	R	Within Project Site	Phase 1 development	10	174	1.5 - 12.4	Phase 2 & 3	ü
P14	Proposed Public Park	Rec	Within Project Site	Phase 1 development	353	405	1.5	Phase 2 & 3	ü
P15	Proposed Public Park	Rec	Within Project Site	Phase 1 development	53	75	1.5	Phase 2 & 3	ü

Notes:    

ü             Applicable to all phases (Phase 1, Phase 2 and Phase 3) of the construction phase, respectively

×              Not applicable

*ASR C01 is assumed to be included during the construction phase, as a conservative approach, since the population intake year for this ASR is unknown.

**For P03 to P13, (Phase X) means population intake phase

Type of use: I – Industrial; R – Residential; E – Educational; Rec – Recreational; HE – Home for the elderly

Assessment height intervals for A01 – A24 & C01 are at 1.5m, 5m, and at 5m intervals from then on, as applicable. For details refer to Appendix 3.1.

Assessment height intervals for the planned development (P01 – P15) were determined according to floor level plans. For details refer to Appendix 3.1. The full range of assessment heights have been covered for each ASR.

3.5 Environmental Impacts during Construction Phase

3.5.1 Referring to the tentative construction programme as shown in Appendix 2.1, the construction works consist of four phases of pond enhancement at the LC site and wetland enhancement at the NSW site, construction of the proposed bridge, three phases of residential development at NSW DS and construction of a visitor centre cum public park in parallel with Phase 1 of the DS. The locations of the tentative construction phases are shown in Figure 2.8. The population intake will be phased in line with the construction phases of the residential development. Each phase will begin to be occupied upon completion of its construction works.

Identification of Pollution Sources

3.5.2 The major potential pollution sources of air quality impact during the construction phase would be fugitive dust arising from site clearance, site formation, excavation and piling works. Potential dust emission sources of the Project are identified as follows:

● Construction works within the works site including bulk excavation works, handling of dusty materials and temporary stockpiling of dusty materials;

● Wind erosion from excavated areas and stockpiles; and

● Use of construction/ dump trucks for construction works.

3.5.3 Potential odour may be generated from the excavation of bed materials of fishponds and wetland.

3.5.4 On-site use of diesel-powered engines is a potential source for particulate matter (PM) and gaseous pollutants (e.g., NO₂ and SO₂). A phased programme would be adopted during the construction phase to minimise construction air quality impact. Diesel Powered Mechanical Equipment (PMEs) would be mainly used in the area for the DS. The PME would have separation distances of at least 186m, 241m and 28m from non-Project ASRs during the construction of Phase 1, Phase 2 and Phase 3 respectively, and a separation distance of at least 10m from its own Project ASRs (i.e., population intake of the DS). However, no more than 31 numbers of PMEs (including diesel PME) would be operated at the same time under normal operation and only about 10% of the construction period would use more than 28 numbers of PME at a time. Given that the area of Phase 1 is the largest in the DS, it is expected that the highest number of PMEs would be employed during said phase. As mentioned, the separation distance of Phase 1 from non-Project ASRs is 186m and there would be no population intake of Project ASRs during Phase 1. During the construction of Phase 2 and Phase 3, hoarding higher than 2.4m will be erected along the boundary as planned ASRs would be closer to the works boundary.

3.5.5 With proper maintenance of PMEs, limited gaseous emissions and smoke would be generated from such equipment. In addition, the Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation came into effect in June 2015 to control emissions from diesel-powered engines, fuel with sulphur content not exceeding 0.005% by weight will be used to minimize SO₂ emission in accordance with the Air Pollution Control (Fuel Restriction) Regulation. The use of NRMMs with exempted label under the Air Pollution Control (NRMM) Regulation will be avoided as far as practicable. Also, electrified NRMMs will be employed as far as practicable, which are unlikely to cause significant smoke and gaseous emissions. Alternative power supply such as off-grid power storage, e.g., AMPD Enertainer, will also be considered where feasible. With the abovementioned regulations being followed, together with the Air Pollution Control (Smoke) Regulation, the limited number of diesel-powered engines employed, their limited operation hours, and with the implementation of good site practices and the control measures as presented in Paragraph 3.5.27, the air quality impact from the operation of on-site diesel PMEs is considered to be limited and localised.

3.5.6 In view of the minor impact by NRMMs, fugitive dust (particulates) and odour would be the primary concerns of air quality impact during the construction phase.

Prediction and Evaluation of Air Quality Impacts during Construction Phase

Fugitive Dust

3.5.7 There are no demolition and road improvement works of existing roads proposed for the Project. Apart from the area for the DS and proposed public park, the rest of Project Site would be for wetland and pond enhancement works which involve modification of wetlands during the creation of the Wetland Enhancement Area at NSW site and LC Nature Reserve. No percussive piling works would be conducted to minimise the disturbance on the area and excavated materials from the area will be generally wet. The average excavation area would be around 100 m² at each of the sites at any time. In addition, the enhancement works will be well-controlled by the implementation of dust suppression measures as presented in Paragraph 3.5.27. Hence, dust nuisance from wetland and pond enhancement works is anticipated to be limited. The amount of excavation material for the construction of the proposed bridge is approximately 4,000 m³ only. The impact of construction work for the proposed bridge across Shan Pui River is also considered as minimal due to limited excavation works, piling works and the use of prefabricated building parts. No excavation work is proposed at Shan Pui River.

3.5.8 The major dust generation works are considered to be the site formation and excavation works in the DS which will be conducted in 3 phases (Phase 1 to Phase 3) as shown in Figure 3.3. The total area of the development of the DS is approximately 11.6 ha. Phase 1 to Phase 3 would include site formation and excavation works, substructure works, civil and road works for the residential development and landscaping works. Phase 1 of the development would also include enhancement works of the existing public park adjacent to Shan Pui River and the construction of a visitor centre and Sewage Pumping Station (SPS). Construction works for the public park are mainly landscaping works. The excavation area of the visitor centre will be around 680 m² only. With reference to Table 3.4, the major dust generation works (e.g., site formation and excavation works) are about 28m away from the closest existing ASR and 10m away from the planned ASRs. In order to minimise the fugitive dust impact, the 3 phases of the site formation and excavation works would not be carried out concurrently. Each of the excavation work areas would be around 100 m² in size to minimise construction dust impact. In addition, proper programming arrangement shall be considered to maximise separation distances between dust generating works and planned ASRs (e.g., conduct dust generating works near planned ASRs prior to their population intake). Moreover, dust suppression measures should be properly implemented, such as regular watering and erection of solid barrier with a height of 3.5m (subject to site constraints) in front of the air sensitive façade facing the work site to shield off concerned ASRs from nearby dust emission sources. Based on the above, no adverse impact from dust generation works is anticipated.

3.5.9 According to the engineering design, the estimated total amount of construction and demolition (C&D) materials to be deposited for the whole construction period at NSW site is about 372,200 m³ and the LC site is about 3,300 m³. 65,000 m³ of inert material will be reused on-site for the LC site. The remaining inert material will be delivered to the public fill reception facility or other concurrent construction projects for reuse. The recyclable non-inert C&D materials will be recycled and the remaining non-recyclable portion will be disposed of at landfill. Based on information provided by the Design Engineers, it can be estimated that there would be around 50 no. of trips of dump truck per day for transporting waste serving for both sites during peak construction period. All construction vehicles will be wheel-washed thoroughly, and dusty contents will be well covered before leaving the site. Hence, the dust impact from use of dump trucks is considered to be insignificant. C&D materials exclude excavated pond mud as all excavated pond mud is proposed to be reused onsite.

3.5.10 Moreover, construction dust monitoring is also proposed as part of the EM&A programme for the Project (Chapter 14), to confirm that the recommended mitigation measures are properly implemented and are effective in ensuring that no nearby ASRs are subjected to adverse air quality impact.

Odour

3.5.11 Depending on the quality of the bed material of fishponds and wetland, odour may be generated from their excavation. In order to minimise odour impact, excavation works for fishponds and wetland should be conducted in the shortest time span possible. Programming of the excavation works of bed materials should be minimised. As mentioned in Chapter 4, the proposed habitat modification works will be restricted to no more than four ponds, mostly adjacent to each other, at any one time. The duration of the works at each pond will be less than one month. The separation distance between the pond enhancement works at Lut Chau and the nearest ASR (A19) is approximately 126 m as shown in Table 3.4 and Figure 3.3. The distance between the closest ASR (A16) and the Nam San Wai wetland enhancement works area is 11 m as presented in Table 3.4 and Figure 3.3. If necessary, the Contractors should also liaise with local resident to inform them of the duration of potential odour nuisance, and efforts made to minimise and mitigate odour nuisance. Odorous excavated material should be placed as far away from ASRs as possible. Temporary stockpiles of odorous excavated material should be covered with impervious sheet. With the implementation of good site practice recommended in Paragraph 3.5.27, no unacceptable odour nuisance is anticipated.

Cumulative impacts from concurrent projects

3.5.12 As mentioned in Section 2.9, there are few concurrent projects within the Assessment Area which may have cumulative impacts. The locations of the concurrent projects and the construction works area of the Project are shown in Figure 3.3, where available. Close liaison with contractors of the concurrent projects will be conducted to avoid overlapping of dusty activities as far as possible.

Yuen Long Barrage Scheme (AEIAR-228/2021)

3.5.13 According to the tentative construction programme under the approved EIA (AEIAR-228/2021), construction works for the section of the barrage scheme within the Assessment Area started in Q2 2023 and will be completed by 2030. Between the commencement year of the construction works of the proposed NSW DS in 2025 and Year 2030, the potential overlapping construction works of the barrage scheme will be superstructure works of pumping stations, installation of tidal barrier and widening and deepening of the Yuen Long Nullah. The construction air quality impact of superstructure works is considered as minimal. The tidal barrier installation is considered small scale with limited impact. Adverse air quality impact from the enhancement of the nullah is also not anticipated with the implementation of air quality control measures as stipulated in the Air Pollution Control (Construction Dust) Regulation under the APCO. Potential odour from construction activities related to the enhancement of the nullah such as excavation and handling of nullah bed material are also expected to be localised and minimal given the scale of the Project. Hence, the cumulative impact with this Project is anticipated to be limited.

Yuen Long Effluent Polishing Plant (AEIAR-220/2019)

3.5.14 Based on the latest information available, the construction works of YLEPP started in November 2022 and will be completed by 2026/2027. The YLEPP project is about 130 m from the NSW site (1 km from the DS) and approximately 400 m from the LC site. Between the commencement year of the construction works of the proposed NSW DS in 2025 and Year 2027, most of the YLEPP construction works in Phase 1 will be superstructure and small scale demolition works (i.e., of a 2-storey building, gas holders and sediment tanks). During Phase 2 construction of YLEPP, the main air quality impact of the proposed Project will be site formation and excavation works at the NSW DS which is approximately 1 km from YLEPP. In addition, sediment and sludge tanks of YLEPP will be cleaned before demolition. Hence cumulative impact is anticipated to be minimal.

Improvement of Yuen Long Town Nullah (Town Centre Section) (AEIAR-223/2020)

3.5.15 With reference to the EIA study for this project (AEIAR-223/2020), construction is expected to commence in Q2 2024 for completion in Q1 2027. The works for the improvement of Yuen Long Nullah within the Project’s Assessment Area will be mainly construction of rising main, with sections that will use trenchless method. The air quality impact of the project is considered to be limited due to the relatively small scale of its construction works and quantity of excavated material. Therefore, the cumulative impact of this project is anticipated to be minimal.

Proposed Private Residential Development in D.D.115 at Chung Yip Road, Nam Sang Wai, Yuen Long (Approved Planning Application No. A/YL-NSW/282)

3.5.16 The Lands Department announced on 17 August 2021 the land tender award of the site. However, there is no publicly available information on this development's construction and occupation programme. The site is approximately 1.5 ha. This proposed private residential development is approximately 160 m from the Project Boundary and more than 250 m away from the DS.

3.5.17 Control measures and good site practices will be implemented by both parties to minimize construction air quality impacts and close liaison will be maintained to avoid heavy/ dusty construction activities being carried out simultaneously, as far as practicable. Dust monitoring work will also be implemented by the proposed Project during the construction stage to ensure there is no adverse air quality impact.

3.5.18 Therefore, with the implementation of typical air quality control measures and good site practices at the proposed DS, adverse cumulative construction air quality impact of both sites is not anticipated.

Agreement No. CE3/2016(CE) Study on Proposed Multi-storey Buildings in Yuen Long Area for Brownfield Operations - Feasibility Study

3.5.19 According to the Environmental Assessment Report, the construction activities for setting up multi-storey buildings (MSBs) are limited and the scale of construction works would be minor. Based on the latest information, construction is expected to commence in 2024 for completion in 2028/ 2029. It is anticipated that the construction of the project will not give rise to adverse construction air quality impact on nearby ASRs with the implementation of the recommended control measures. Moreover, the proposed MSBs are located about 500 m from the NSW site (more than 550 m from the DS) and approximately 1.2 km from the LC site.

3.5.20 Hence, with the implementation of the recommended mitigation measures and proposed dust monitoring as part of the EM&A programme, adverse cumulative construction air quality impact from the Project and the concurrent projects would not be expected.

Proposed Public Housing Development in Sha Po

3.5.21 Based on the Preliminary Environmental Review (PER) of Agreement No. CE 10/2020 (CE) for Site Formation and Infrastructure Works planned for proposed public housing developments at Sha Po, Shap Pat Heung, and Tai Kei Leng in Yuen Long, it has been determined that sub-phase work arrangement will be implemented such that the active work front at any one time will be minimized to limit potential air quality emissions during site formation works. The PER also indicates that dust monitoring at existing ASRs close to the project will be conducted throughout the construction period to ensure no adverse construction air quality impact and the necessary control measures are implemented. Furthermore, the public housing development is located approximately 1,100 meters away from the Project Boundary. Therefore, no unacceptable air quality impact is anticipated during the construction phase, and no adverse cumulative construction air quality impact is anticipated.

Proposed Development under Land Sharing Pilot Scheme (LSPS) Application No. LSPS/002

3.5.22 Based on the Gist of LSPS Application No. LSPS/002, the development involves the construction of nine composite blocks, with a maximum building height ranging from 24 to 26 storeys. The anticipated date for the commencement of statutory procedures on planning and road works is 2023, while the expected completion date for site formation works for the Public Housing/ Starter Homes Portion is by the end of 2026. Furthermore, the project site at Ho Chau Road is located approximately 500 meters away from the Project Boundary. With the implementation of recommended mitigation measures and the proposed dust monitoring as part of the EM&A programme, cumulative adverse construction air quality impact from the Project and the concurrent project would not be expected.

Proposed Residential and Community Hub Development in Tung Shing Lei (Approved Planning Application No. A/YL-NSW/274)

3.5.23 According to the Gist of the approved planning application for the project with reference A/YL-NSW/274, the development comprises of eight domestic blocks with eight to 21 storeys and three non-domestic blocks with three to four storeys, providing 1,518 flats for residential use. There is no publicly available information on its construction and occupation programme. However, since the Tung Shing Lei proposed development is located approximately 680 meters away from the Project Boundary, with the implementation of recommended mitigation measures and the proposed dust monitoring as part of the EM&A programme, cumulative adverse construction air quality impact from the Project and the concurrent project would not be expected.

Northern Metropolis Highway

3.5.24 According to the “Hong Kong Major Transport Infrastructure Development Blueprint” in December 2023, the Northern Metropolis Highway comprises four main road sections, namely the Tin Shui Wai Section, San Tin Section, Kwu Tung Section, and the New Territories North (NTN) New Town Section, with a view to linking the core developments in NTN. Based on the information from Highways Department, the alignment of Northern Metropolis Highway and the implementation programme will be reviewed in the upcoming Investigation Study. There is no further publicly available information on the construction programme.

3.5.25 Control measures and good site practices will be implemented by both parties to minimize construction air quality impacts and close liaison will be maintained to avoid heavy/ dusty construction activities being carried out simultaneously, as far as practicable. Dust monitoring work will also be implemented by the proposed Project during the construction stage to ensure there is no adverse air quality impact.

Sam Po Shue Wetland Conservation Park

3.5.26 The proposed Sam Po Shue Wetland Conservation Park (WCP) under the Northern Metropolis Development Strategy is recommended as a mitigation measure for the potential loss of wetland habitats for the San Tin Technopole Development. The proposed area of Sam Po Shue WCP is approximately 338 ha. Sam Po Shue WCP will be established in phases, with Phase 1 works anticipated to commence in 2026/2027 for completion in 2031 and the remaining phases scheduled for completion by 2039. The proposed Sam Po Shue WCP is located about 270 m from the LC site and approximately 1.4 m from the NSW site. With the implementation of the recommended mitigation measures and proposed dust monitoring as part of the EM&A programme, adverse cumulative construction air quality impact would not be expected.

Air Quality Mitigation Measures for Construction Phase

3.5.27 It is recommended that the relevant air quality control measures as stipulated in the Air Pollution Control (Construction Dust) Regulation, good site practices and odour control measures should be adopted to further reduce the construction impacts of the Project. These practices include:

Good Site Management

● Good site management is important to help reduce potential air quality impact down to an acceptable level. As a general guide, the Contractor should maintain high standards of housekeeping to prevent emissions of fugitive dust. Loading, unloading, handling and storage of raw materials, wastes or by-products should be carried out in a manner so as to minimise the release of visible dust emission. Any piles of materials accumulated on or around the work areas should be cleaned up regularly. Cleaning, repair and maintenance of all plant facilities within the work areas should be carried out in a manner minimising generation of fugitive dust emissions. The material should be handled properly to prevent fugitive dust emission before cleaning.

● Hoarding at least 2.4m high from ground level along the works boundary.

● Hoarding with a height of 3.5m (subject to site constraints) shall be erected for Phase 2 and Phase 3 construction works boundary as planned Phase 1 and Phase 2 ASRs would be closer to the works boundary.

● Placing stockpile and machinery away from ASRs as far as possible.

Disturbed Parts of the Roads

● Main temporary access points should be paved with concrete, bituminous hardcore materials or metal plates and be kept clear of dusty materials; or

● Unpaved parts of the road should be sprayed with water or a dust suppression chemical so as to keep the entire road surface wet.

Exposed Earth

● Exposed earth should be properly treated by compaction, hydroseeding, vegetation planting or seating with latex, vinyl, bitumen within six months after the last construction activity on the site or part of the site where the exposed earth lies.

● Covering stockpiling area with impervious sheets and spraying all dusty material with water immediately prior to any load transfer operations to keep dusty materials wet during material handling at the stockpile areas.

● Any excavated or stockpile of dusty material should be covered entirely with impervious sheeting or sprayed with water to maintain the entire surface wet and then removed or backfilled or reinstated where practicable within 24 hours of the excavation or unloading.

Loading, Unloading or Transfer of Dusty Materials

● All dusty materials should be sprayed with water immediately prior to any loading or transfer operation so as to keep the dusty material wet.

Debris Handling

● Any debris should be covered entirely by impervious sheeting or stored in a debris collection area sheltered on the top and the three sides.

● Before debris is dumped into a chute, water should be sprayed onto the debris so that it remains wet when it is dumped.

Transport of Dusty Materials

● Vehicles used for transporting dusty materials/ spoils should be covered with tarpaulin or similar material. The cover should extend over the edges of the sides and tailboards.

Wheel Washing

● Vehicle wheel washing facilities should be provided at each construction site exit. Immediately before leaving the construction site, every vehicle should be washed to remove any dusty materials from its body and wheels.

Use of Vehicles

● The speed of the trucks within the Project Site should be controlled to about 10 km/hour in order to reduce dust impacts and secure the safe movement around the Project Site.

Control of Construction Plant and Equipment Emissions

● Provide power supply for on-site machinery and avoid the diesel generators and machinery during the construction stage as far as practicable.

● Deploy electrified NRMMs as far as practicable.

● Use of exempted NRMMs should be avoided as far as practicable.

● Regular maintenance of construction equipment deployed on-site should be conducted.

Odour Control

● Limit the number of ponds (i.e., no more than four ponds) to be excavated at a time. The duration of the works of each pond will be less than one month.

● Fishpond/wetland excavated materials shall be kept in watertight container on site and transported off site within 24 hours.

● During transportation, odorous materials on the trucks should be properly covered by tarpaulin sheets.

Evaluation of Residual Impacts for Construction Phase

3.5.28 With proper implementation of the above recommended mitigation measures during the construction phase, no adverse residual impact would be anticipated during the construction phase of the Project.

Environmental Monitoring and Audit Requirements for Construction Phase

3.5.29 Dust monitoring is considered necessary during the construction stage of the Project and regular site audits are also required to ensure the mitigation measures are properly implemented. Details of the EM&A programme are presented in the separate EM&A Manual.

Conclusions and Recommendations for Construction Phase

3.5.30 Potential air quality impacts from the construction works of the Project would mainly be related to construction dust from site formation, foundation works and excavation. With proper implementation of the recommended mitigation measures, adverse construction air quality impact would not be anticipated. Since limited PMEs would be operated at the same time under normal operation, with proper maintenance, air quality emissions from such equipment would be limited. Exhaust emission from NRMMs would also be minimised with the implementation of measures such as avoiding exempted NRMMs, deploying electrified NRMMs and using alternative power supply, as far as practicable.

3.5.31 Potential odour impacts from the construction works of the Project would mainly be related to excavation works for fishponds and wetland. With proper implementation of the recommended mitigation measures, adverse construction odour impact would not be anticipated.

3.6 Environmental Impacts during Operational Phase

3.6.1 Potential air quality impact during the operational phase would be associated with the following sources:

● Vehicular emissions from the road networks within the Assessment Area, including project induced traffic;

● Potential odour may be generated from the proposed SPS and Refuse Collection Points (RCPs) of the proposed DS;

● Industrial emissions from Yuen Long Industrial Estate (YLIE), including odour impact;

● Vehicular emissions associated with the existing bus depot, bus terminus, heavy goods vehicle and coach car park; and

● Background pollutant concentrations.

Identification of Pollution Sources and Key Air Pollutants

Project-induced emissions

Vehicular Emissions

3.6.2 Vehicular emissions from all existing roads and the proposed bridge within the Assessment Area are the major Project induced air pollution sources on surrounding ASRs during the operational phase of the Project.

3.6.3 For the proposed bridge, the approved bridge alignment in the planning application overlaps with the site area of the DSD Yuen Long Barrage Scheme Project. As a result, a revised bridge alignment is proposed which is shown in Figure 2.3. The revised bridge alignment is still awaiting approval from the relevant government department at this stage of the Study. As the revised bridge alignment landing is at the Car Park with Heavy Goods Vehicle at Wang Lok Street (23WLO), part of the car park may be closed. Should there be a change to the bridge alignment in the future, further assessment of vehicular emission impact will be considered during the detailed design.

3.6.4 Other project induced sources are vehicular emission through ventilation shafts from the basement car park of the proposed development. However, the proposed basement carpark will mainly be for private cars and not for heavy goods vehicles and coaches. Emissions from vent shafts are therefore anticipated to be limited since vehicular emission factors for private cars are relatively small. Exhausts from vent shafts shall be located and facing away from ASRs, as far as practicable, and fitted with effective fabric filters or equivalent air pollution control systems. In addition, start emissions for all 18 vehicle classes are considered on all roads in the assessment by broad-brush approach, as a conservative approach. Hence, emissions from vent shafts are not included in the model assessment.

3.6.5 Tailpipe emission comprise a number of pollutants, including Nitrogen Oxides (NOx), RSP, FSP, SO₂, CO, O₃, Toxic Air Pollutants (TAPs), Pb, etc. The determination of key pollutants for vehicular emissions is discussed as below.

NO_X

3.6.6 According to the 2022 Hong Kong Emission Inventory Report published by EPD in June 2024, which is the latest available information at the time of preparing this report, NOx emission from vehicles was the 3^rd largest, accounting for 19% of the total. NOx would be converted to NO₂ in the presence of O₃ and Volatile Organic Compounds (VOCs). Increasing of traffic flows would increase the roadside NO₂ concentration. Hence, NO₂ is one of the key air pollutants included in the assessment for vehicular emissions.

RSP and FSP

3.6.7 RSP and FSP refer to suspended particulates with a nominal aerodynamic diameter of 10µm or less and 2.5µm or less, respectively. According to the 2022 Hong Kong Emission Inventory Report, RSP and FSP emissions from vehicles contribute for 10% and 11% of the total emissions. They are therefore both considered as key pollutants for the increase in traffic flows due to the Project.

SO₂

3.6.8 Road transport contributes to 1% of the total emissions as per the results of the 2022 Hong Kong Emission Inventory Report. The low contribution is due to the use of ultra-low sulphur fuel for all types of vehicles in Hong Kong. Therefore, SO₂ is not a key pollutant and is not included in the assessment for vehicular emissions.

CO

3.6.9 With reference to Air Quality in Hong Kong 2023 Statistical Summary published by EPD, the highest 1-hourly and 8-hourly average CO concentrations were measured at North station and Central roadside station, respectively. These were 2390µg/m³ and 1546µg/m³, respectively and are 8% and 15% of their respective AQOs. As the concentrations are well below their respective AQOs, CO is not considered as a key pollutant.

O₃

3.6.10 O₃ is formed from the photochemical reaction between NO_X and VOCs in the presence of sunlight. O₃ concentrations are governed by both precursors and atmospheric transport from other areas. When precursors transport under favourable meteorological conditions and sunlight, ozone will be produced. This explains why higher ozone levels are generally not produced in the urban core or industrial area but rather at some distance downwind, after photochemical reactions have taken place. In the presence of large amounts of NOx in the roadside environment and industrial estate, O₃ reacts with NO to give NO₂ and thus results in O₃ removal. O₃ is therefore not considered as a key pollutant for this assessment.

TAPs

3.6.11 TAPs are pollutants found in vehicular exhaust. With reference to EPD’s Assessment of Toxic Air Pollutant Measurements in Hong Kong Final Report, monitored TAPs in Hong Kong include diesel particulate matter (DPM), toxic elemental species, dioxins, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), carbonyls, and VOCs. According to the results of the report and Sources of PCB emissions by European Monitoring and Evaluation Programme (EMEP) / Core Inventory Air Emissions (Corinair), vehicular emission is not considered as a primary source of dioxins, PCBs, carbonyls and most toxic elemental species. Therefore, these pollutants are not considered as key pollutants for the operational phase of the Project.

3.6.12 As recommended by EPD’s Assessment of Toxic Air Pollutant Measurements in Hong Kong Final Report, 2003, elemental carbon (EC) is used as a surrogate for DPM, and with reference to the Final Report for Chemical Separation of PM_2.5 Filter Samples 2022[2], EC showed a decrease in concentration from 2018 to 2022 in Hong Kong, i.e. -37.0%, -41.8%, -39.8%, -48.5% and -39.5% at Mong Kok Air Quality Monitoring Station (AQMS), Clear Water Bay Air Quality Research Site (AQRS) at Hong Kong University of Science and Technology, Tsuen Wan AQMS, Yuen Long AQMS and Kwai Chung AQMS, respectively. With the continual efforts by EPD to reduce particulate emission from vehicular fleet, a discernible decreasing trend is noted in the level of particulate matter. Therefore, DPM is not a key pollutant for the Project.

3.6.13 The most important PAH is Benzo[a]pyrene and is often selected as a marker for PAHs. The EU Air Quality Standards for PAHs (expressed as concentration of Benzo[a]pyrene) is 1ng/m³ for annual average. With reference to “Air Quality in Hong Kong 2022”, annual average concentrations of Benzo[a]pyrene measured at EPD’s Tsuen Wan and Central/Western stations were 0.03ng/m³ and 0.04ng/m³, which is far below the EU Standards. Hence, PAHs are not considered as key pollutants for the Project.

3.6.14 According to Assessment of Toxic Air Pollutant Measurements in Hong Kong Final Report, 2003, among the VOC compounds, benzene and 1,3-butadiene are the most significant ones for Hong Kong. The UK National Air Quality Objectives for benzene and 1,3-butadiene are 5µg/m³ and 2.25µg/m³, respectively. With reference to “Air Quality in Hong Kong 2022”, annual average concentrations of benzene at EPD’s monitoring stations at Tsuen Wan and Central/Western were 0.50µg/m³ and 0.70µg/m³, respectively. The level of 1,3-butadiene was 0.03µg/m³ for both Tsuen Wan and Central/Western stations. The concentrations are far below the UK AQOs. Thus, VOCs are not considered as key pollutants for vehicular emission.

Pb

3.6.15 Pb is not considered as a key air pollutant of concern since the sale of leaded petrol has been banned in Hong Kong since April 1999. According to the Air Quality in Hong Kong 2022, the annual averages ranged from 6ng/m³ (at all stations except Yuen Long and Tuen Mun) to 8ng/m³ (at Yuen Long and Tuen Mun). The measured concentrations were well below the AQO limit of 500ng/m³.

Summary

3.6.16 Based on the above, the air pollutants of concern for vehicular emissions are therefore NO₂, RSP and FSP. The location of the roads links is presented in Appendix 3.3 together with their traffic forecast data.

Odour Emissions

3.6.17 Odour emission from the proposed Sewage Pumping Station (SPS) and refuse collection within the proposed development are also potential Project induced air pollution sources on surrounding ASRs. These are discussed below.

Sewage Pumping Station (SPS)

3.6.18 A SPS is proposed for the Project (with a maximum capacity of 4,000m³ per day) and sewage generated from the Project will be discharged to the public sewerage system. The SPS will be fully enclosed and located underground with air- and water-tight covers for potential sources, e.g., inlet chamber, coarse screen channel, distribution chamber and wet well. The exhaust from the SPS will be equipped with a high efficiency odour removal system (of at least 95% odour removal efficiency and at least 99.5% removal for hydrogen sulphide (H₂S)) at the exhaust vent to limit odour impact. Screening waste will be stored in enclosed containers. The SPS will maintain negative pressure to prevent foul air from flowing out to the surrounding area. The exhaust vent of the proposed SPS will be located more than 10m and facing away from the nearest sensitive receiver, as shown in Figure 3.3. The separation distance between the exhaust vent of the proposed SPS and the nearest air sensitive uses will be 14.0m and 16.3m for the public park and closest residential building, respectively.

3.6.19 With reference to the approved EIA for the Sai O Trunk Sewer Sewage Pumping Station (AEIAR-230/2021), site visits were conducted in July 2017 to several typical SPSs in Hong Kong with design capacities ranging from about 12,100 to 36,900 m³ per day and odour removal efficiency of at least 99.5% for H₂S. Site observations revealed that odour was not noticed at the site boundaries of these SPSs, which were less than 10m away from the SPS’s exhausts. Site visits were also conducted to Tai Po Tai Wo Road SPS (12,100m³ per day[3]), Yuen Long Kau Hui SPS (20,650m³ per day[4]) and Yuen Long South SPS (36,900 m³ per day[5]) between August and September 2024. Odour was not noticed at the site boundaries of these SPS, which are less than 10m away from their respective SPS exhausts. Furthermore, the contour plots from the quantitative odour assessment for the Sai O Trunk Sewer Sewage Pumping Station (with an installed capacity of 20,600m³ per day, odour removal efficiency of at least 99.5% for H₂S and deodorizer exhaust height at 4mAG), indicated no adverse odour impact at a location 10m away from the exhaust vent of that SPS. Given that the proposed SPS will have a maximum capacity less than 5 times that of the Sai O Trunk SPS; it is concluded that with the implementation of appropriate mitigation measures commonly adopted in other existing SPSs in Hong Kong, adverse odour impact from the proposed SPS is not anticipated. The proposed SPS’s exhaust vent will be designed at a location and height acceptable to the EPD in the detailed design stage. It is anticipated that the height of the SPS’s exhaust vent will follow the design of other similar exhaust vent approved by EPD such as the one in Sai O Trunk SPS which is approximately 4mAG.

Refuse Collection Points (RCPs)

3.6.20 RCPs are proposed for the Project, but their locations and design are also not available at this stage. With reference to the practical solutions recommended on waste handling and refuse room in EPD’s website[6], loaded waste container should be removed daily (i.e., no overnight accumulation/ storage of waste) and refuse bins, refuse rooms and RCPs should be cleaned daily. The proposed RCPs will be located away from ASRs, as far as possible. Proper ventilation, exhaust and deodourisation system with odour removal efficiency at 90% or above will be provided to minimize odour impact upon nearby ASRs. High levels of odour removal efficiency may be achieved by use of activated carbon (i.e. 99.5% for H₂S)[7] or other technologies such as Nano Confined Catalytic Oxidation (NCCO) and Nano Plasma-Driven Catalysis (PDC) technology. The suitability of adopting NCCO and PDC will be assessed during the detailed design. Test results for these two technologies indicate that they have an efficacy of over 99% in removing sulphur dioxide, ammonia and volatile organic compounds in the air, and could effectively deodorize and purify the air inside RCPs[8]. Good hygiene at RCPs will be enhanced through frequent washing, proper covering of refuse bins, closing of roller shutters, good housekeeping and proper maintenance of ventilation, exhaust and deodorisation system. A fully enclosed design with ventilation system to ensure negative pressure will be considered for RCPs during the detailed design stage. Municipal solid waste will be transported by fully-enclosed Refuse Collection Vehicles (RCVs) equipped with metal tailgate cover and waste water tank/sump tank, and in compliance with the Code of Practice on the Operation of RCVs. Routes between RCPs and Refuse Transfer Stations (RTS) would be designed to minimise potential odour impact from RCVs to ASRs in the vicinity of the routing.

Summary

3.6.21 Whilst the proposed SPS, RCPs and their respective ventilation/ deodorising systems to be installed will be further studied in the Investigation, Design and Construction (IDC) stage, with the implementation of the deodourisation measures as described above, potential adverse odour impact from these sources on nearby ASRs is not anticipated. Therefore, odour is not considered as a key pollutant of concern arising from this Project.

Pollutant-emitting activities in the immediate neighbourhood

Industrial Emissions from Chimneys

3.6.22 A number of existing chimneys were identified in YLIE through site visits, review of SP licenses and the EIA of Yuen Long Effluent Polishing Plant (YLEPP EIA) (AEIAR-220/2019). Site visits were conducted in February and June 2022, June 2023, and January 2024. No major point source was identified within 4 km from the Project Boundary. AQO criteria and non-criteria pollutants as well as odour emissions emitted from the chimneys of YLIE are discussed in this section.

3.6.23 The planned MSBs at YLIE are also a potential source for cumulative air quality impact. As referenced from Paragraph 3.5.19, the planned MSBs are located over 550m from the air-sensitive uses of the proposed DS. Even the planned air-conditioned Visitor Centre (P01), is located about 500m away from the planned MSBs as shown in Figure 3.3. With reference to the approved EA Report of the MSBs at YLIE, no major/ special emissions are expected within the proposed MSBs. In addition, as mentioned in said EA Report, if there are any special emission sources identified within the MSBs in future, an assessment will be conducted accordingly. There is no further updated information of the specific use of the MSBs at the time of report preparation. Therefore, the planned MSBs development is not considered as an emission source in the model assessment. The existing Car Park with Heavy Goods Vehicle at Fuk Wang Street and Yuen Long Industrial Estate Bus Terminus (22FW) is included in the model assessment instead, as a conservative approach. (See Paragraph 3.6.33)

3.6.24 Criteria and non-criteria air pollutants and odour emitted from chimneys of YLIE and YLEPP within 500m from the Project Boundary are detailed in Table 3.5. Determination of key pollutants for industrial emissions from chimneys is discussed as follows.

Table 3.5: Criteria and Non-criteria Pollutants and Odour Emissions from Chimneys

Name	Criteria Air Pollutants (under AQO)	Non-criteria Air Pollutants (non-AQO)	Odour Emissions (under EIAO-TM)	Source
Hong Kong Petrochemical Co. Ltd	NO2, RSP, FSP, SO2	Total Organic Carbons (TOCs), Styrene, Ethyl benzene, Dibutyl Phthalate	Styrene, Ethyl benzene, Dibutyl Phthalate	SP Licence
Dunwell Industrial (Holdings) Ltd	NO2, RSP, FSP, SO2	H2S, TOCs	Odour, H2S
Saint-Gobain Weber (Hong Kong) Building Material Co. Ltd	NO2, RSP, FSP, SO2	--	--
Nestlé Hong Kong Limited	NO2, RSP, FSP, SO2	--	--	YLEPP EIA (AEIAR-220/2019)
Vogue Laundry Service Limited	NO2, RSP, FSP, SO2	--	--
Yuen Long Effluent Polishing Plant (YLEPP)	NO2, RSP, FSP, SO2	Ammonia (NH3)	Odour, NH3
Fortune Pharmacal Company Limited	NO2, RSP, FSP, SO2	--	--	Pollutants identified based on industrial processes involving fuel combustion
Nin Jiom Medicine Manufactory Hong Kong Limited	NO2, RSP, FSP, SO2	--	--

Notes:

Odour thresholds: Styrene (0.32 ppm)[9], Dibutyl phthalate (0.26 mg/m³)[10], Ethyl benzene (2.3 ppm)[11], H₂S (0.00047 ppm) and NH₃ (0.037 ppm) [12]

NO₂, RSP and FSP

3.6.25 NO₂, RSP and FSP were found to be emitted from chimneys of YLIE and YLEPP within 500m from the Project Boundary. Considering that there are a number of emission sources for said air pollutants, these were regarded as key pollutants of concern and considered in the quantitative cumulative assessment.

SO₂

3.6.26 SO₂ was also found to be emitted from chimneys of YLIE and YLEPP within 500m from the Project Boundary. There are no SO₂ emission sources contributed from the proposed Project. Considering that some of the SO₂ emission sources are within 500m from Project ASRs (i.e., Saint-Gobain Weber (Hong Kong) Building Material Co. Ltd. and Nestlé Hong Kong Limited), SO₂ is regarded as a key air pollutant for the Project and its cumulative impact on Project ASRs is evaluated quantitatively.

TOCs

3.6.27 Total organic carbons (TOCs) encompass a wide range of organic compounds that includes both volatile and non-volatile compounds. Emission of volatile organic compounds (VOCs) may potentially lead to air quality impact. As referenced from the “Air Quality in Hong Kong 2022”, concentrations of benzene, formaldehyde and perchloroethylene contributed most of the measured organic substances in Hong Kong in 2022. However, since TOC emission sources from YLIE (i.e., CH1_1B and CH2_S1) are more than 500m away from Project ASRs as indicated in Appendix 3.4, TOC impact from YLIE is regarded as limited. There will be no TOC emission from the Project. Therefore, TOC is not considered as a key air pollutant of concern for the Project.

Styrene, Ethyl benzene, Dibutyl phthalate and H₂S

3.6.28 As indicated in Appendix 3.4, the emission sources for styrene (i.e., CH1_6A, CH1_6B, CH1_26A and CH1_37A), ethylbenzene (i.e., CH1_26A and CH1_37A), dibutyl phthalate (i.e., CH1_14) and H₂S (i.e., CH2_S1, CH2_S4 and CH2_S5) are more than 500m away from Project ASRs. Also, there will be no styrene, ethyl benzene, dibutyl phthalate and negligible H₂S emission from the Project. Therefore, the impact of these non-criteria air pollutants on the Project is considered as limited and they are not regarded as air pollutants of concern for the Project.

NH₃

3.6.29 With reference to the YLEPP EIA, the predicted pollutant concentration of NH₃ at surrounding sensitive receivers of the proposed YLEPP is far below the criteria with a maximum annual average concentration of 1.4µg/m³ (standard: 200µg/m³) and hourly average concentration of 30µg/m³ (standard: 3,200µg/m³). The predicted annual average and maximum hourly average concentrations at an air sensitive use (A05 in YLEPP EIA), which is next to Shan Pui River and at the Project Boundary of Nam Sang Wai, are 0.1μg/m³ and 9μg/m³ respectively. As confirmed by site survey, since there are no additional NH₃ emission sources identified within the 500m Assessment Area than those assessed in the YLEPP EIA, and there has been no update to the design of the YLEPP’s chimneys, the results in the YLEPP EIA are applicable to this Project. The YLEPP EIA assessment methodology and assumptions remain valid.

3.6.30 Moreover, there are no Project ASRs within 500m from the emission sources for NH₃ from YLEPP as indicated in Appendix 3.4. The emission sources for NH₃ (i.e. CHP01, CHP02, BO, CHP03, CHP04 and ASP) are more than 500m from Project ASRs as indicated in Appendix 3.4. Therefore, the impact of NH₃ from YLEPP on the Project is regarded as limited and NH₃ is not considered as a key pollutant of concern for the Project.

Odour

3.6.31 A number of odour sources were identified from the chimneys of YLIE and YLEPP. The emission sources for odour (i.e., CH2_S1, CH2_S2, CH2_S3_1, CH2_S3_2, CH2_S3_3, CH2_S6 to CH2_S15 and DO1 to DO6) are more than 500m from Project ASRs as indicated in Appendix 3.4. Therefore, adverse odour impact from the YLIE and YLEPP to the planned Project ASRs is not anticipated. Odour is not considered as a key pollutant of concern for the Project.

Summary

3.6.32 Based on the above, the pollutants of concern for industrial emissions from chimneys are therefore NO₂, RSP, FSP and SO₂. The locations of the chimneys are indicated in Figure 3.4.

Vehicular emissions associated with the existing Bus Terminus, Bus Depot and Car Park with Heavy Goods Vehicle and Coach

3.6.33 Four existing open area bus terminus/ bus depot/ car park with heavy goods vehicle and coach have been identified within the 500m Assessment Area from the Project Boundary as summarised below and indicated in Figure 3.5.

● 19WLE - KMB Bus Depot at Wang Lee Street

● 22FW - Car Park with Heavy Goods Vehicle at Fuk Wang Street and Yuen Long Industrial Estate Bus Terminus

● 23WLO - Car Park with Heavy Goods Vehicle at Wang Lok Street

● 24TY - Bus Terminus at Tak Yip Street

3.6.34 As referenced from Paragraph 3.6.3, even though it is likely that part of the Car Park with Heavy Goods Vehicle at Wang Lok Street (23WLO) may be closed due to the revised bridge alignment’s landing, the entire car park's footprint is considered in this assessment, as a conservative approach. Similarly, the existing Car Park with Heavy Goods Vehicle at Fuk Wang Street and Yuen Long Industrial Estate Bus Terminus (22FW) may be replaced by the planned MSBs development. Given that there is no updated information on the specific use and emissions from the proposed MSBs (see Paragraph 3.6.23), the existing car park is considered in this assessment, as a conservative approach.  

3.6.35 In addition to the above, start emissions from Yuen Long Road Safety Centre and other parking sites (i.e., the proposed basement carpark, parking spaces inside industrial buildings, metered parking spaces and residential parking) also were considered within the 500m Assessment Area. The start emissions from YL Road Safety centre and other parking sites are calculated by broad brush approach.

Summary

3.6.36 Based on the above, air pollutants of concern for vehicular emissions from the abovementioned sources are also NO₂, RSP and FSP, in line with those identified for vehicular emissions as presented in Paragraph 3.6.16.

Summary of key air pollutants

3.6.37 As a result, cumulative NO₂, RSP and FSP impact on all ASRs is assessed quantitatively; and cumulative SO₂ impact on Project ASRs is assessed quantitatively.

Assessment Methodology

Operational Phase – Vehicular Emissions from Open Roads

Traffic Forecast Data

3.6.38 Traffic forecast data for roads within the 500m Assessment Area was provided by the Traffic Consultant for 8 years: Year 2030 (Phase 1 population intake), Year 2033 (Phase 2 population intake), Year 2036 (Phase 3, full population intake), Year 2040 (interim year 1), Year 2043 (interim 2), Year 2045 (15 years after Phase 1 population intake), Year 2048 (15 years after Phase 2 population intake) and Year 2051 (15 years after the full population intake). Traffic from all existing roads and induced traffic from the Project, including the proposed bridge, have been considered in the traffic forecasts. Details of the 24-hour traffic patterns are presented in Appendix 3.3. Transport Department’s (TD’s) agreement on the traffic data has also been provided in Appendix 3.3.

Speed

3.6.39 24-hourly average speeds of each road link were provided by the Traffic Consultant. All 18 vehicle classes on the same road link were assumed to travel at the same hourly speed. The location of the road links and their individual road segments are also shown in Appendix 3.3.

Dispersion Model for Open Roads

3.6.40 AERMOD model was used to assess vehicular emissions from open roads. These were modelled as line sources within AERMOD.

Hourly Temperature and Relative Humidity

3.6.41 Temperature and relative humidity (RH) data were extracted from the meteorological output in Smart Air Modelling Platform (SAMP) v2.0 of the PATH grids where the road segments are located. For details refer to EPD’s User Guide for the ROAD tool in SAMP v2.0.

3.6.42 For short-term and long-term impact, daily profile of lowest temperature and RH data in each hour for the whole year (i.e. 24 hours data in a year) were used to calculate the vehicular emission factors on an hourly basis, as a conservative approach. These are presented in Appendix 3.5.

Estimation of Vehicular Emission Inventory

3.6.43 For each scenario year as shown in Table 3.6, emission rates ready for AERMOD input and annual vehicular emissions were calculated using SAMP v2.0 and the corresponding year’s traffic data. To demonstrate the worst-case scenario, zero emission vehicles were not considered in the calculation.

3.6.44 EMFAC-HK V4.3 model was used to determine the fleet average emission factors for 18 vehicle classes, for all the existing roads and the proposed bridge within the 500m Assessment Area. EMFAC mode was selected in the model for hourly vehicular emission outputs. Under this mode, emissions factors of NO, NO₂, RSP and FSP were computed for each vehicle class based on temperature, relative humidity, average speed and soak time. Start emissions were considered on all roads in the assessment and for all 18 vehicle classes by broad-brush approach, as a conservative approach. Maximum start emission factor among different soak time for each vehicle class is used in the calculation of start emission as a conservative approach.

3.6.45 For each hour in a day, running and starting emissions (g/s-m²) were determined according to the following equations, for each road segment which were modelled as line sources within AERMOD:

3.6.46

3.6.47

3.6.48 Default trips and VKT values from EMFAC-HK are used in SAMP v2.0. For the proportion of local and rural roads within Hong Kong (14.34%), the 2022 Annual Traffic Census data from TD is used in the calculations within SAMP v2.0.

3.6.49 Source release height above ground for all roads was determined as follows:

3.6.50

3.6.50.1 where:

3.6.50.2

3.6.50.3 Road surface height is 0 for all roads except the proposed bridge which has a height of 10mAG.

3.6.50.4 Average vehicle height is a traffic volume-weighted average for each road segment, and it was determined in SAMP v2.0 according to the following equation:

3.6.50.5

3.6.50.6 where:

3.6.50.7

3.6.51 The initial vertical dimension coefficient, Szinit, was estimated by dividing the top of plume height by 2.15, which is equivalent to 0.79 times the weighted-average vehicle height.

3.6.52 The road width is equal to the physical road width plus 3m on both sides of the road, without the presence of physical barriers or obstructions, where the additional width accounts for mechanical turbulence from travelling vehicles.

3.6.53 Source parameters for all years are presented in Appendix 3.5 and their corresponding emission inventories are summarised in Appendix 3.6.

Determination of Worst Scenario Year

3.6.54 Vehicular emissions of NOx, RSP and FSP for Years 2030, 2033, 2036, 2040, 2043, 2045, 2048 and 2051 are presented in Appendix 3.6. The emission factors for NO assume NOx consists only of NO and NO₂. The emission strength of each scenario year is calculated based on the vehicular emission factor coupled with traffic flow of the same scenario year. According to the Climate Action Plan 2050, the Government aims to have zero vehicular emission before 2050 and hence the emission burden for Year 2051 is for reference only.

3.6.55 A sensitivity test was conducted to compare the emission strength for the 8 years, as presented in Appendix 3.6 and summarised in Table 3.6.

Table 3.6: Total Emission in Year 2030, 2033, 2036, 2040, 2043, 2045, 2048 and 2051

Year	Total NOx (tonne/year)	RSP (tonne/year)	FSP (tonne/year)
2030	11.076	0.266	0.244
2033	8.840	0.212	0.195
2036	7.486	0.183	0.169
2040	7.592	0.184	0.169
2043	7.690	0.187	0.173
2045	7.731	0.187	0.172
2048	7.713	0.186	0.172
2051	7.649	0.187	0.173

3.6.56 Year 2030 represents the worst-case scenario where the total NO_X (i.e., NO+NO₂), RSP and FSP emissions are the highest among all scenario years. Therefore, traffic data and emission factors for year 2030 are used for the prediction of air quality impacts due to vehicular emissions, as a conservative approach.

Meteorological Data

3.6.57 WRF meteorological data was extracted from the PATH model via SAMP v2.0 at the relevant grids (25,48), (25,49), (25,50), (26,48), (26,49), (26,50), (27,48) and (27,50) for the representative ASRs. Mixing heights greater than 2,009m and smaller than 119m were set to 2,009m and 119m, respectively, in line with Hong Kong Observatory’s measurement in 2019. The minimum wind speed was capped at 0.5m/s for the treatment of calm hours.

3.6.58 The anemometer height was set at the mid-layer height of the relevant PATH grid in the AERMET model (the meteorological pre-processor of AERMOD), i.e., at 8.5 m, in accordance with EPD’s Guidelines on Choice of Models and Model Parameters.

Geophysical Data

Land use and Surface Characteristics

3.6.59 Surface characteristic parameters such as albedo, Bowen ratio and surface roughness length are also required in AERMET. These were obtained from SAMP v2.0.

3.6.60 In accordance with USEPA’s AERMOD Implementation Guide, albedo and Bowen ratio are determined from a domain defined by a 10km-by-10km area centred on the measurement site. Albedo is based on a simple unweighted arithmetic mean for the representative domain, whereas Bowen ratio is based on a simple unweighted geometric mean for the same representative domain. Surface roughness length is determined for a 1km area centred on the measurement site. It is based on an inverse distance weighted geometric mean. The land use characteristics of each relevant PATH grid are classified into sectors no smaller than 30 degrees in width. The parameters of each sector were then calculated in accordance with their land use characteristics. Detailed of the surface parameters are presented in Appendix 3.7.

Definition of Urban or Rural

3.6.61 The ‘urban’ option in AERMOD is selected to account for the more convective boundary layer from the urban heat island effect by enhancing the turbulence for urban night-time conditions. The latest available 2023 census data is referenced for the population of Yuen Long district (i.e., 670,000[13]), since it is where the Project Site is located. 

Terrain

3.6.62 Given the flat nature of the Project Site, which primarily consists of wetlands and fishponds, the ‘flat’ terrain option is selected in the model.

Operational Phase – Industrial Emissions from Chimneys

Specified Process (SP) and Non-SP License Chimneys

3.6.63 Chimneys from both SP and non-SP Licence within the 500m Assessment Area are considered in the assessment. Based on records kept in EPD’s Specified Process Register at the time of report preparation, the approved YLEPP EIA and site visits conducted in February and June 2022, June 2023 and January 2024, a number of chimneys were identified within the 500m Assessment Area.

3.6.64 The locations of the chimney sources for NO₂, RSP, FSP and SO₂ considered in the modelling assessment are as shown in Figure 3.4. Details of industrial emission sources, including emission inventory and chimney parameters input into the AERMOD model for NO₂, RSP, FSP and SO₂ emissions, are presented in Appendix 3.8.

Dispersion Model for Industrial Emissions from Chimneys

3.6.65 AERMOD model was used to assess emission impacts from industrial sources within the 500m Assessment Area. No dry deposition option was selected for modelling deposition of particulate matter from chimneys.

3.6.66 Meteorological and geophysical data in line with that for vehicular emissions from open roads was adopted.

Operational Phase – Vehicular Emissions from Bus Depot/ Bus Terminus/ Car Park with Heavy Goods Vehicle and Coach

Methodology and Assumptions

3.6.67 Start, idling and running emissions within the identified bus terminus, bus depot and car park with heavy goods vehicle and coach (refer to Paragraph 3.6.33) are assessed using precise approach in accordance with EPD’s guideline “Calculation of Start Emissions in Air Quality Impact Assessment”. Start emissions are also distributed on all roads within the Assessment Area for all 18 vehicle classes as a conservative approach by the broad-brush approach.  

3.6.68 Traffic flows of the bus terminus, bus depot and car park with heavy goods vehicle and coach were provided by the Project Traffic Consultant. Relevant traffic data, including number of trips, idling time and soaking time were obtained by 24-hour site survey conducted on a normal working day, as provided by Project Traffic Consultant. Idling was only observed for buses at bus terminus (i.e., 22FW and 24TY). No idling was observed at car parks and the bus depot, in line with the Motor Vehicle Idling (Fixed Penalty) Ordinance.

3.6.69 Start emissions and running exhaust emissions associated with the vehicles at identified bus terminus, bus depot and car park with heavy goods vehicle and coach were predicted by EMFAC-HK model. Cold idling emission factors were calculated as per EPD published guideline “Calculation of Start Emissions in Air Quality Impact Assessment”. For any idling emission factors which were not provided by the guideline, warm idling emission factors from “Road Tunnels: Vehicle Emissions and Air Demand for Ventilation” as published by World Road Association 2019 were adopted. Detailed calculations of the emissions are presented in Appendix 3.9.

3.6.70 There were a limited number of private cars, taxis and motorcycles recorded at the car parks at both Fuk Wang Street and Wang Lok Street (i.e., 22 FW and 23WLO) during the 24-hour site survey. They are therefore considered by broad-brush approach in all roads around both car parks. Similarly, there were trips for a few private cars and light goods vehicles (LGV4 and LGV6) recorded during the 24-hour site survey conducted at the bus depot (i.e., 19WLE). Given the limited number of trips for these vehicle classes, they were considered by broad-brush approach in which their emissions were allocated along the concerned roads around 19WLE.

3.6.71 As mentioned in the vehicular emissions methodology (i.e., Paragraph 3.6.44), start emissions of all 18 vehicle classes and modelled roads within the Assessment Area were assessed by broad-brush approach. Start emissions from Yuen Long Road Safety Centre[14] and all other parking sites within the 500m Assessment Area (i.e., the proposed basement carpark, parking spaces inside industrial buildings, metered parking spaces and residential parking) have therefore been considered in the air quality impact assessment by broad-brush approach due to the limited number of heavy good vehicles parked inside them. Total traffic flow at the ingress and egress of the Yuen Long Road Safety Centre (i.e., including running and start emission by broad-brush approach) were considered for each internal road within Yuen Long Road Safety Centre, as a conservative approach.

Hourly Temperature and Relative Humidity

3.6.72 Temperature and RH data were extracted from the meteorological output of the PATH grids where the bus terminus, bus depot and car park with heavy goods vehicle and coach are located (i.e., PATH grids (25,49) and (26,48)).

3.6.73 Annual minimum temperature and RH values for each of the corresponding PATH grids were compared and the minimum temperature and RH values among these grids (i.e., 10°C and 16%) were used to calculate vehicular emission factors for grids (25,49) and (26,48), as a conservative approach. These are also presented in Appendix 3.9.

Dispersion Model for Bus Terminus, Bus Depot and Car Park with Heavy Goods Vehicle and Coach

3.6.74 AERMOD model was used to assess emission impacts from bus terminus, bus depot and car park with heavy goods vehicle and coach within the 500m Assessment Area.

3.6.75 Meteorological and geophysical data in line with that for vehicular emissions from open roads was adopted. 

NOx to NO₂ Conversion

1-hour Average NO₂

3.6.76 The Ozone Limiting Method (OLM) as described in EPD’s Guidelines on Choice of Models and Model Parameters has been adopted to estimate the conversion of NO (from open roads, bus terminus, bus depot, car parks with heavy goods vehicles emissions and industrial emissions) to NO₂, based on the future hourly background ozone concentrations for year 2030. These were extracted from the relevant PATH grids (25,48), (25,49), (25,50), (26,48), (26,49), (26,50), (27,48) and (27,50) within which the representative ASRs are located (see Figure 3.2A to Figure 3.2C).

3.6.77 For industrial emissions, an NO₂-to-NOx ratio of 10% was adopted as referenced from the “Air Quality Studies for Heathrow: Base Case, Segregated Mode, Mixed Mode and Third Runway Scenarios modelling using ADMS-Airport, Cambridge Environmental Research Consultants, 2007”.

3.6.78 The NOx/NO₂ conversion was estimated as follows and adopted for short-term cumulative NO₂ emissions:

[NO₂] _total  =  [NO₂] _vehicular + [NO₂] _{bus depot and car park} + 0.1 x [NO_x] _chimney

+ minimum of {([NO] _vehicular + [NO] _{bus depot and car park} + 0.9 x [NO_x] _chimney)

or (46/48) x [O₃]_PATHv3.0}

Annual Average NO₂

3.6.79 Jenkin Method has been adopted to estimate the conversion of the cumulative NOx (from open roads and bus terminus, bus depot and car park emissions) and NOx (from industrial emissions) to NO₂ for the annual mean NOx to NO₂ using SAMP v2.0. The platform makes reference to the “Review of Methods for NO to NO₂ Conversion in Plumes at Short Ranges (Jenkin, 2004a)” by UK Environmental Agency. The calculation equation it uses is presented as below.

[NO₂]    = sum of predicted NO₂ concentration from all sources

[NOx]    = sum of predicted NOx concentration from all sources

[OX]      = sum of the NO₂ concentration and O₃ concentration

J           = photolysis rate of NO₂

K          = the rate coefficient for reaction between NO and O₃

3.6.80 [OX] and J/K were derived from the analysis of the recent 5 years of annual mean monitoring NOx, NO₂ and O₃ concentrations from relevant EPD’s AQMS. The details of the derivation and AQMS referenced are shown in Appendix 3.10.

Prediction and Evaluation of Air Quality Impacts during Operational Phase

3.6.81 The predicted air quality modelling results have included the background pollutant levels as extracted from the PATH model for year 2030 based on the PATH v3.0 model and the cumulative impacts of the following emissions within the 500m Assessment Area:

● Vehicular emissions from the road networks within the Assessment Area (including project induced traffic);

● Identified industrial emissions from Yuen Long Industrial Estate; and

● Vehicular emissions associated with the existing bus terminus, bus depots, and car park with heavy goods vehicle and coach.

3.6.82 Since there is no SO₂ emission source contributed from the Project, the impact of SO₂ from surrounding sources is only considered upon Project ASRs. The worst predicted cumulative air quality impact at representative ASRs is presented in Table 3.7. Detailed results are presented in Appendix 3.11. It can be seen from Table 3.7 that the worst predicted cumulative results for RSP, FSP and NO₂ at all ASRs are well below their relevant AQOs. Also, no exceedance of SO₂ concentrations is predicted at Project ASRs.

3.6.83 Contour plots of the cumulative pollutant concentrations at the worst affected levels are presented in Figure 3.6A to Figure 3.6J for RSP, FSP, NO₂ and SO₂. The worst assessment height for annual and daily RSP and FSP, annual NO₂ and daily SO₂ is 1.5m above ground. For 10-min SO2, the worst assessment height is 9.2m above ground. For hourly NO₂ the worst assessment height is 10.0m above ground. Exceedance zones of daily and annual RSP at 1.5m above ground, hourly NO₂ at 10.0m above ground, and 10-min SO₂ at 9.2m above ground and daily SO₂ at 1.5m above ground are observed in Figure 3.6A, Figure 3.6B, Figure 3.6E, Figure 3.6G and Figure 3.6H but no air sensitive uses including openable window / fresh air intakes of the ventilation system or recreational uses in open space are situated within the exceedance zones. A site survey was conducted in January 2024 to confirm no air sensitive uses are within the exceedance zones, at the corresponding assessment heights. In any event, since exceedance zones are predicted, contour plots at levels above and below those levels with exceedance zones have been plotted, as applicable, until no exceedance zones are observed, and to confirm that no air sensitive uses are located within exceedance zones. The additional contours plots are presented in Appendix 3.12.

Table 3.7: Summary of Worst Predicted Cumulative Modelling Results During the Operational Phase at Each ASR

ASR ID	RSP		FSP		NO2		SO2
	10th highest 24-hour Average Concen-tration (μg/m^3)	Annual Average Concen-tration (μg/m^3)	36th highest 24-hour Average Concen-tration (μg/m^3)	Annual Average Concen-tration (μg/m^3)	19th highest 1-hour Average Concen-tration (μg/m^3)	Annual Average Concen-tration (μg/m^3)	4th highest 10-minute Average Concen-tration (μg/m^3)	4th highest 24-hour Average Concen-tration (μg/m^3)
Existing ASRs
A01	56.9	21.9	26.9	12.8	112.6	23.1	--	--
A02	62.0	26.6	29.2	14.7	93.0	23.7	--	--
A03	54.4	21.1	26.7	12.6	99.2	20.5	--	--
A04	54.2	21.7	26.9	12.9	101.4	24.8	--	--
A05	55.3	21.2	27.1	12.9	90.1	24.3	--	--
A06	53.6	20.7	26.6	12.6	89.4	18.1	--	--
A07	53.2	20.4	26.5	12.5	85.0	16.1	--	--
A08	53.1	20.3	26.6	12.5	87.6	17.2	--	--
A09	53.2	20.3	26.5	12.5	80.8	16.1	--	--
A10	53.1	20.2	26.5	12.4	78.3	15.0	--	--
A11	53.1	20.2	26.5	12.4	77.0	14.7	--	--
A12	53.2	20.3	26.6	12.5	83.9	16.4	--	--
A13	53.1	20.3	26.5	12.5	79.5	15.1	--	--
A14	53.3	20.6	26.7	12.6	90.1	17.7	--	--
A15	53.2	20.6	26.8	12.6	91.8	17.8	--	--
A16	53.1	20.3	26.5	12.5	78.6	14.9	--	--
A17	54.8	21.0	28.1	13.2	75.6	13.6	--	--
A18	52.3	20.0	26.4	12.3	74.1	13.2	--	--
A19	53.5	20.0	26.2	12.2	78.7	13.3	--	--
A20	53.5	21.2	26.9	12.8	100.3	19.6	--	--
A21	56.3	22.2	27.5	13.3	129.6	33.3	--	--
A22	54.2	20.5	26.5	12.4	82.9	14.4	--	--
A23	53.4	20.0	26.2	12.2	76.4	13.1	--	--
A24	56.3	22.9	27.4	13.4	142.3	28.6	--	--
Planned ASRs
C01	53.3	20.6	26.6	12.6	88.8	17.5	--	--
P01	53.7	20.6	26.4	12.4	87.2	15.6	109.8	24.8
P02	53.6	20.2	26.1	12.3	81.2	14.4	99.2	16.5
P03	53.2	20.5	26.6	12.5	82.2	15.7	122.7	19.9
P04	53.2	20.4	26.6	12.5	80.4	15.6	123.3	19.2
P05	53.2	20.4	26.6	12.5	81.3	15.6	110.4	20.4
P06	53.2	20.4	26.5	12.5	80.9	15.4	92.6	19.0
P07	53.2	20.3	26.5	12.5	80.0	15.2	99.0	16.7
P08	53.1	20.3	26.5	12.5	79.2	14.9	78.1	13.4
P09	53.2	20.4	26.5	12.5	80.2	15.2	95.4	17.5
P10	53.2	20.4	26.5	12.5	80.3	15.4	100.9	18.4
P11	53.2	20.3	26.5	12.5	79.1	15.1	97.2	15.6
P12	53.1	20.3	26.5	12.5	78.7	14.8	82.1	12.9
P13	53.1	20.2	26.5	12.5	78.6	14.7	74.1	11.9
P14	53.6	20.4	26.2	12.3	88.0	15.3	107.8	20.1
P15	53.2	20.5	26.6	12.5	82.2	16.0	115.7	22.1
AQOs	100	50	50	25	200	40	500	50

Note:      

Cumulative SO₂ impact is assessed on Project ASRs only, as there is no SO₂ contribution from the proposed Project.

Air Quality Mitigation Measures for Operational Phase

3.6.84 It has been assessed that the predicted cumulative air quality impacts on all identified ASRs due to industrial emissions; vehicular emissions from open roads, bus terminus, bus depots and car park with heavy goods vehicle and coach; and background concentration within the 500m Assessment Area would comply with the corresponding AQOs for NO₂, RSP, FSP and SO₂. Therefore, no further mitigation measures for such emissions during the operational phase are required. For the planned air-conditioned visitor centre, no air sensitive uses including openable window/ fresh air intakes of the ventilation system or recreational uses in open space (e.g. sitting area) and any other air-sensitive uses of the proposed development would be located within the 500m buffer from TOC, NH₃, H₂S, styrene, ethyl benzene and dibutyl phthalate related emission sources, as shown in Appendix 3.4. Otherwise, further assessment will be conducted during detailed design stage to demonstrate no adverse air quality impact to the air sensitive use of the planned visitor centre or any other air-sensitive uses of the proposed development.

Evaluation of Residual Impacts for Operational Phase

3.6.85 During the operational phase, it has been assessed that the predicted cumulative NO₂, RSP, FSP and SO₂ concentrations at all ASRs due to industrial emissions; vehicular emissions from open roads, bus terminus, bus depots and car park with heavy goods vehicle and coach; and background concentration would comply with the relevant AQOs. Hence, no adverse residual air quality impacts are anticipated for the Project during the operational phase.

Environmental Monitoring and Audit Requirements for Operational Phase

3.6.86 During the operational phase, no ASRs are predicted to exceed the relevant criteria under the AQOs. Hence, the EM&A programme for the operational phase is considered not necessary.

Conclusions and Recommendations for Operational Phase

3.6.87 During the operational phase, based on the cumulative results from industrial emissions; vehicular emissions from open roads, bus terminus, bus depots and car park with heavy goods vehicle and coach; and background concentration, it is concluded that all the identified ASRs would be in compliance with the AQOs for daily RSP, annual RSP, daily FSP, annual FSP, hourly NO₂, annual NO₂ and 10-minute and daily SO₂. Hence, no adverse air quality impacts are anticipated during the operational phase. For the planned air-conditioned visitor centre, no air sensitive uses including openable window/ fresh air intakes of the ventilation system or recreational uses in open space (e.g. sitting area) and any other air-sensitive uses of the proposed development would be located within the 500m buffer from TOC, NH₃, H₂S, styrene, ethyl benzene and dibutyl phthalate related emission sources, as shown in Appendix 3.4. Otherwise, further assessment will be conducted during detailed design stage to demonstrate no adverse air quality impact to the air sensitive use of the planned visitor centre or any other air-sensitive uses of the proposed development.

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[1] Environmental Protection Department, Air Pollution Control Strategies, June 2022 http://www.epd.gov.hk/epd/english/environmentinhk/air/prob_solutions/strategies_apc.html

[2] Environmental Protection Department. Measurements and Validation for the Twelve-month Particulate Matter Study in Hong Kong, 2022, Appendix A. (https://www.epd.gov.hk/epd/sites/default/files/epd/english/environmentinhk/air/studyrpts/files/final_report_mvtmpms_2022.pdf)

[3] PP-334/2007 - Tai Po Tai Wo Road Sewage Pumping Station

[4] PP-371/2008 - Yuen Long Kau Hui No. 2 Sewage Pumping Station

[5] PP-068/1999 - Yuen Long South Sewage Pumping Station

[6]Pollution Problems & Practical Solutions on Waste Handling & Refuse Room
https://www.epd.gov.hk/epd/english/greenproperty/poll_pro/popup_whrr_air.html#3

[7] https://cleanawater.com.au/odour-control/carbon-filters

[8] https://www.legco.gov.hk/yr2023/english/panels/fseh/minutes/fseh20230404.pdf. NCCO has already been adopted in various building in Hong Kong (https://www.rhtind.com.hk/ncco-air-cases). PDC is also commercially available https://www.nami.org.hk/en/technologies/plasma-driven-catalysis-pdc-air-purification-with-downstream-disinfection-1

[9] Styrene Fact Sheet, USEPA, https://www.epa.gov/sites/default/files/2020-05/documents/styrene_update_2a.pdf

[10] National Center for Biotechnology Information (2024). PubChem Compound Summary for CID 3026, Dibutyl Phthalate, https://pubchem.ncbi.nlm.nih.gov/compound/Dibutyl-Phthalate

[11] Ethylbenzene Fact Sheet, USEPA, https://www.epa.gov/sites/default/files/2016-09/documents/ethylbenzene.pdf

[12] Iowa State University Extension (May 2004). "The Science of Smell Part 1: Odor perception and physiological response" (PDF). PM 1963a.

[13] Population and Household Statistics Analysed by District Council District, 2023 Edition, released on 5 April 2024.

[14] Yuen Long Road Safety Centre mainly provide vehicle training for motorcycle, private cars and light goods vehicles, whilst the training on medium goods vehicles and buses is limited.