3 Air Quality impact

3.1 Introduction

3.1.1 This section presents the assessment of potential air quality impacts on air sensitive receivers (ASRs) arising from the construction of the Project. Assessment has been conducted in accordance with criteria and guidelines as stipulated in Annex 4 and Annex 12 of the EIAO-TM as well as the requirements given in Clause 3.4.4 and Appendix B of the EIA Study Brief (No. ESB-332/2020).

3.1.2 The potential dust impact arising from dusty construction activities of the Project have been assessed and appropriate mitigation measures are proposed to alleviate any adverse air quality impact.

3.1.3 The rail system to be employed in the Project will be electric-powered, and air-emission free during the normal operation. Exhaust for general ventilation and smoke extraction facilities will be carefully positioned to avoid causing any nuisance to the ambient. The potential air quality impact during operation phase is thus considered insignificant and is not assessed in this section.

3.2 Environmental Legislations, Standards and Guidelines

Air Quality Objectives & Technical Memorandum on EIA Process

3.2.1 The criteria and guidelines for air quality assessment are laid down in Annex 4 and Annex 12 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM).

3.2.2 The Air Pollution Control Ordinance (APCO) provides the statutory authority for controlling air pollutants from a variety of sources. The Hong Kong Air Quality Objectives (AQOs), which stipulate the maximum allowable concentrations over specific periods for typical pollutants, should be met. The prevailing AQOs was enforced on 1 January 2022 and is adopted in the EIA study. The relevant prevailing AQOs are listed in Table 3.1.

Table 3.1 Hong Kong Air Quality Objectives

Pollutant	Averaging Time	Maximum Average Concentration (µg/m³) ⁽¹⁾	No. of Exceedances Allowed ⁽²⁾
Fine Suspended Particulates (PM_2.5) ⁽⁴⁾	24-hr	50	35
Fine Suspended Particulates (PM_2.5) ⁽⁴⁾	Annual ⁽³⁾	25	NA
Respirable Suspended Particulates (PM₁₀) ⁽⁵⁾	24-hr	100	9
Respirable Suspended Particulates (PM₁₀) ⁽⁵⁾	Annual ⁽³⁾	50	NA
Sulphur Dioxide (SO₂)	10-min	500	3
Sulphur Dioxide (SO₂)	24-hr	50	3
Nitrogen Dioxide (NO₂)	1-hr	200	18
Nitrogen Dioxide (NO₂)	Annual ⁽³⁾	40	NA
Carbon Monoxide (CO)	1-hr	30,000	0
Carbon Monoxide (CO)	8-hr	10,000	0
Photochemical Oxidants (as ozone)	8-hr	160	9
Lead (Pb)	Annual ⁽³⁾	0.5	NA

Notes:

(1) Gaseous pollutant is measured at 293 K and 101.325 kPa.

(2) The number of exceedances allowed per year.

(3) Arithmetic mean.

(4) Suspended particulates in air with a nominal aerodynamic diameter of 2.5 mm or smaller.

(5) Suspended particulates in air with a nominal aerodynamic diameter of 10 mm or smaller.

3.2.3 Apart from AQOs, the limit of hourly Total Suspended Particulates (TSP) concentration should not exceed 500 µg/m³ (measured at 25°C and one atmosphere) for construction dust impact assessment according to Annex 4 of EIAO-TM.

Air Pollution Control (Construction Dust) Regulation

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

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

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

3.3 Description of the Environment and Future Trends

Existing Environment

3.3.1 The Project Site is located in the southern part of Tuen Mun and extends in a generally southward direction from the existing TUM station of the WRL to the existing Tuen Mun Ferry Pier. The existing environment adjacent to the prospective alignment is urbanized, with existing land uses comprising mainly high-density residential developments, government, institution or community (G/IC), green belt and open space.

3.3.2 The dominant existing air pollutants sources within the 500m assessment area are the vehicular emissions from Wong Chu Road, Tuen Mun Road, Lung Fu Road, Hoi Wing Road, Hoi Wong Road and Wu King Road.

3.3.3 The prevailing year background concentrations within the assessment area has been made reference to the EPD’s monitoring data recorded in Tuen Mun Air Quality Monitoring Station (AQMS) published in Air Quality in Hong Kong. The major air pollutants induced from the Project would be the particulates emissions during the construction phase. Therefore, the Fine Suspended Particulates (FSP) and Respirable Suspended Particulates (RSP) monitoring data recorded between Year 2016 to 2020 at the Tuen Mun AQMS are examined and summarized in Table 3.2. It is observed that the highest 24-hour average concentrations of FSP and RSP exceeded the relevant short-term AQO limit value in these five years. However, the 10th highest 24-hour average concentrations of FSP and RSP complied with AQOs since 2016 and 2017 respectively. Annual average concentrations of FSP and RSP in these five years also complied with the AQOs. The results also show that there is a decreasing trend in the pollutants levels in these five years.

Table 3.2 The Air Quality Monitoring Data Recorded at EPD’s Tuen Mun AQMS in Year 2016 – 2020

Pollutant	Averaging Time	AQO^[^1]	Data Summary	Year ^[2]					5-year mean
Pollutant	Averaging Time	AQO^[^1]	Data Summary	2016	2017	2018	2019	2020	5-year mean
Fine Suspended Particulates (FSP)	24-hr	75 (9)	Max.	81	89	103	92	60	85
			10th Max.	63	65	53	53	47	56
			No. of Exceedance(s)	2	3	2	2	0	-
	Annual	35	-	27	27	26	24	20	25
Respirable Suspended Particulates (RSP)	24-hr	100 (9)	Max.	141	134	143	146	101	133
			10th Max.	103	99	87	89	84	92
			No. of Exceedance(s)	10	9	4	4	1	-
	Annual	50	-	44	43	42	41	34	41

Notes:

[1] The former AQO (effective since 2014) at the time of publish of Air Quality in Hong Kong (2016 – 2020). Values in ( ) mean the number of exceedances allowed per year.

[2] Bolded values mean exceedance of the AQOs.

[3] All concentration units are in microgram per cubic metre (µg/m³).

Future Trends

3.3.4 Apart from the air quality monitoring data, EPD has released a set of background levels from “Pollutants in the Atmosphere and their Transport over Hong Kong”, PATH model (PATHv2.1). The PATH model is a regional air quality model developed by EPD to simulate air quality over Hong Kong against the Pearl River Delta (PRD) as background. Year 2025 data of the assessment area extracted from PATHv2.1 model is presented in Table 3.3. The future air quality in these areas predicted by PATHv2.1 are lower than the AQOs.

Table 3.3 PATHv2.1 Model - Air Pollutant Concentrations in Year 2025

Pollutant	Aver-aging Time	AQO^[1]	Data Summary	PATH Grid Cell ^[2]
Pollutant	Aver-aging Time	AQO^[1]	Data Summary	(19,39)	(19,40)	(19,41)	(19,42)	(20,39)	(20,40)	(20,41)	(20,42)
				Year 2025
Fine Suspended Particulates (PM_2.5) ^[3][4]	24-hr	50 (35)	Max.	78	76	75	76	77	78	79	79
			36th Max.	26	26	26	26	26	25	27	26
			No. of Exceedance(s)	11	10	11	11	11	10	10	12
	Annual	25	-	16	16	16	16	16	16	16	16
Respirable Suspended Particulates (PM₁₀)^[4]	24-hr	100 (9)	Max.	95	92	92	93	94	95	96	96
			10th Max.	68	70	71	71	67	69	71	71
			No. of Exceedance(s)	0	0	0	0	0	0	0	0
	Annual	50	-	29	28	28	28	29	28	28	28

Notes:

[1] Values in ( ) mean the number of exceedances allowed per year.

[2] Bolded values mean exceedance of the AQOs.

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

[4] Annual and daily RSP concentration is adjusted by adding 10.3 µg/m³ and 11 µg/m³ respectively with reference to Guidelines on Choice of Models and Model Parameters.

[5] All concentration units are in microgram per cubic metre (µg/m³).

3.4 Identification of Air Sensitive Receivers

3.4.1 In accordance with Annex 12 of the EIAO-TM, any domestic premises, hotel, hostel, hospital, clinic, nursery, temporary housing accommodation, school, educational institution, office, factory, shop, shopping centre, place of public worship, library, court of law, sports stadium or performing arts centre are considered as air sensitive receivers (ASRs). Any other premises or place with which, in terms of duration or number of people affected, has a similar sensitivity to the air pollutants as the aforementioned premises and places is also considered to be a sensitive receiver. In accordance with the EIA Study Brief (No. ESB-332/2020), the boundary of the assessment area for air quality assessment should be 500 m from the Project boundary including works sites and works areas.

3.4.2 The representative ASRs (existing / planned) that may be affected by the Project within the 500 m assessment area have been identified based on the latest Outline Zoning Plans, Layout Plan, Outline Development Plans, Layout Plans and other relevant published land use plans.

3.4.3 The locations of the representative ASRs are shown in Figure No. C1502/C/TME/ACM/M51/101 & 102. The details of the representative ASRs for assessment are presented in Table 3.4 and Table 3.5.

Table 3.4 Representative Air Sensitive Receivers along TME

ASR	Description	Land Use	Approx. Distance between ASR and closest works area/works site (m)	No. of storey
A1	Century Gateway Phase 1	R	38	36
A2⁽²⁾	Tuen Mun Park	O	21	N/A
A3⁽²⁾	Tuen Mun Park	O	16	N/A
A4⁽²⁾	Tuen Mun Park Children Playground	O	1	N/A
A5	Oi Ming House, Yau Oi Estate	R	88	26
A6	Tin Hau Temple	G/IC	144	N/A
A7	Islamic Primary School	G/IC	1	6
A8	Oi Tak House, Yau Oi Estate	R	5	26
A9	Oi Lai House, Yau Oi Estate	R	1	26
A10	The Esplanade	R	75	20
A11	Yan Chai Hospital Ho Sik Nam Primary School	G/IC	87	6
A12	Oceania Heights	R	42	35
A13	Lung Mun Oasis	R	124	32
A14	Lung Mun Oasis	R	117	30
A15	Glorious Garden	R	103	28
A16	Glorious Garden	R	116	28
A17	Sun Tuen Mun Centre	R	129	44
A18	Wu Shan Cycle Park	O	40	N/A
A19	Tuen Mun Wu Hong Clinic	G/IC	25	6
A20	Wu Hong Police Quarters	R	26	21
A21	Yan Chai Hospital Law Chan Chor Si Primary School	G/IC	1	6
A22	Nga Hei House, Siu Hei Court	R	42	38
A23	Pierhead Garden	R	14	30
A24	Richland Garden	R	23	28
A25	Wu Boon House, Wu King Estate	R	17	22
A26	Taoist Ching Chung Primary School (Wu King Estate)	G/IC	7	6
A27	Tung Wah Group of Hospitals Sun Hoi Directors' College	G/IC	12	6
A28	Wu Tsui House, Wu King Estate	R	1	20
A29	Wu Fai House, Wu King Estate	R	29	20
A30	Not used
A31	Not used
A32	Block 13, Yuet Wu Villa	R	20	27
A33	Shine Skills Center (Tuen Mun)	G/IC	100	5
A34	Castle Peak Bay Ambulance Depot	G/IC	1	5
A35	Castle Peak Bay Fire Station	G/IC	15	5
A36	Wu Shan Tennis Court	O	195	N/A
A37	Wu Shan Lawn Bowling Green	O	200	N/A
A38	Tuen Mun Area 44 Joint-user Complex and Wholesale Fish Market	G/IC	270	6
A39	Sunkids Kindergarten	G/IC	240	1
A40	Sun Wah Cold Storage Phase 2	I	240	20
A41⁽³⁾	Tuen Mun Swimming Pool	Recreational	10	3
A42	Yeh King House, Siu Shan Court	R	295	20
A43	The Jockey Club Tuen Mun Butterfly Beach Sports Centre	G/IC	230	4
A44	Block 1, Sun Tuen Mun Centre	R	360	44
P1	Planned Public Housing at Tin Hau Road, Area 17	R	80	37
P2	Planned Public Housing at Hang Fu Street, Area 16	R	40	22
P3	Planned Public Housing at Hang Fu Street, Area 16	R	110	29

Note:

(1) R – Residential; G/IC - Government, institution and community; O – Open Space

(2) As discussed in Section 2.4.4, the maintenance works to be conducted at Tuen Mun Park only include diversion of cycle track and pedestrian walkway (e.g. erection of hoarding/signage, painting of road sign) and minor pruning works at the overgrown trees branches. In view of works nature, there will be no dusty emission from the maintenance works within Tuen Mun Park. Distances are therefore considered from the ASRs to the works site that has major dusty construction activities.

(3) A41 is expected to be demolished in Year 2026, thus it was not considered in Scenario 2 assessment.

Table 3.5 Representative Air Sensitive Receivers in the vicinity of Offsite Works Area

ASR	Description	Land Use	Approx. Distance between ASR and closest works area/works site (m)	No. of storey
OA2	Pillar Point Fire Station	GIC	135	5
OA3	Tuen Mun Vehicle Servicing Station	GIC	180	2
OA4	Admin Building of Customs and Excise Department	GIC	140	5
OA5	Butterfly Beach Laundry	GIC	265	5
OA6	Vehicle Repair Workshop	Workshop	225	1
OA7	Main Control Building of TM-CLK	Office	235	3

Note:

(1) R – Residential; G/IC - Government, institution and community; O – Open Space

3.5 Identification of Environmental Impacts during Construction Phase

Identification of Emission Sources from Construction Activities

Construction Works Sites along TME

3.5.1 As mentioned in Section 2, the major modification works at TUM Station would be conducted at the overrun section. Minor dismantling works at existing structure and concreting works for connection of new elevated viaduct would be conducted. It is anticipated that only minor dust nuisance would arise from these construction activities. Therefore the modification works are not considered in the quantitative assessment.

3.5.2 The bored piling method will be adopted for construction of the pile caps while piers will be built in situ for the viaduct. The use of bored pile foundation will prevent the need for large excavation and subsequent backfilling. The bored piling area for land-based piles is limited in size (approx. 9.5m x 9m) and only minor excavation would be conducted at the commencement of the foundation. Potential dust emission would likely be limited to construction of the pile caps. For the pile across Tuen Mun River Channel, it would all be constructed within the cofferdam. Temporary steel platforms are proposed to be constructed during dry seasons for the standard viaduct between TRB and A16, and for the TRB (back spans and pylon area). The piling works will be carried out using this steel temporary platforms and precast shells for the pile caps. The potential dust emission sources would be limited to the area involved in piling works at river channel. To minimize the impact arising from construction activities on-site, the concrete segments of viaduct will be prefabricated off-site and then will be joined together at their final positions on-site only. Such construction method would cause only minor dust emission from the assembling works and require less construction vehicles within the assessment area. As mentioned in Section 2, these precast concrete segments would be transported to the works areas/works sites by barge. There would be 4 trips of barge per week, which would cause potential marine emission during the construction phase.

3.5.3 The proposed TMS Station is an elevated station over Wu King Road. Bored pile foundation and pile cap construction will involve excavation which would likely to have potential dust emission impact. The construction activities for the superstructure works as mentioned in Section 2 are considered as less-dusty construction activities. In addition, there is demolition of two existing footbridges and a toilet block at Wu King Road. The demolition of two existing footbridges would pose potential dust emission. The demolition of toilet block involves only taking down of a small surface structure, i.e. no excavation works to be involved, which would cause minor dust impact only. Therefore, the demolition of toilet block is not considered in the quantitative assessment.

3.5.4 The major potential air quality impact during construction phase of the Project would be construction of A16 Station which would involve the following dusty construction activities:

· Demolition of existing Tuen Mun Swimming Pool, Community Green Station (CGS) and nearby structures;

· Site formation works involving excavation, materials handling, spoil removal, bored piling and backfilling works;

· Haul road within the works areas/works sites; and

· Wind erosion of the exposed site area.

3.5.5 Site clearance at Wu King Garden and portions of Pui To Road (South) Rest Garden and Wu Shan Recreation Playground, as well as modification works at Wu King Road are also dusty construction activities which would pose potential dust impact.

3.5.6 Construction vehicles on the haul road within the works areas/works sites would also cause construction dust impact. Dust mitigation measures such as paving and regular watering will be provided to abate the dust emission. Construction vehicle will be required to pass through the wheel washing facilities upon site exit. Thus, the construction vehicle movements outside the works areas/works sites would not cause any significant dust impact. In addition, the concrete segments for viaduct would be prefabricated off-site and then transported by barge, the number of construction vehicle including dump trucks and concrete trucks is estimated to be not more than 20 nos. per hour throughout the construction phase, based on the preliminary engineering design information. With the adoption of dust suppression measures before leaving the construction site, dust nuisance from construction vehicle movement outside the worksite is expected to be insignificant.

Offsite Works Area

3.5.7 An offsite construction works area at Mong Wing Street, which is currently used as a construction works area for the project “Tuen Mun - Chek Lap Kok Link (TM-CLKL),” is proposed to support the construction of the Project. This works area would be handed over by Highways Department in 2024 tentatively. This offsite works area will only be used as site office, material storage for pre-cast unit (non-dusty material) and temporary tree nursery, and there would be no excavation works, earthworks and stockpiling of dusty materials to be conducted at this works area. Considering no excavation works to be involved and only limited traffic induced, its potential dust impact is considered minor, thus it is addressed qualitatively.

Identification of Key Air Pollutants of Emission from Construction Activities

3.5.8 On-site use of diesel-powered engines is also the potential source for other gaseous pollutants such as NO₂ and SO₂ and smoke. The Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation came into effect in June 2015 to control emissions from diesel-powered engines. In addition, the number of such equipment required on-site would be kept to minimum and the equipment would be under normal operation with proper maintenance which is unlikely to cause significant smoke and gaseous emissions. Furthermore, connecting construction plant and equipment to main electricity supply and avoiding use of diesel generator and diesel-powered equipment should be implemented as far as practicable to minimize the air quality impact arising from NRMMs. Thus, particulates from dusty construction activities would be the major air pollutant during construction phase. According to Annex 4 of the EIAO-TM, TSP is the criteria pollutant for construction dust impact assessment. TSP emission impact as well as other particulates, RSP and FSP stipulated in AQOs, were therefore considered in the construction dust impact assessment.

Other Existing Emission Sources

3.5.9 The land uses in the vicinity are mainly residential, industrial, schools, and parks. Vehicular emission from open road is the major source of air pollutants within 500m assessment area from the Project boundary. Major open roads in the vicinity includes Tuen Mun Road. Wong Chu Road, Lung Fu Road. Tuen Mun Ferry Terminal and Tuen Mun Typhoon Shelter also fall within 500m assessment area. Existing marine emission from scheduled ferries and vessels accessing the typhoon shelter also contribute to ambient air quality.

3.5.10 There are also existing industrial chimneys within 500m assessment area. These chimneys have been identified and their locations are illustrated in Appendix 3.7.

3.5.11 Major emission sources within 4km of the quantitative assessment area would also contribute to the ambient air quality. However, no major emission source was found within 4km of the Project boundary.

3.5.12 Based on the available information (Table 2.6 refers), concurrent dusty construction activities of other projects undertaken within 500m assessment area during construction phase of the Project would include the Reprovision of Tuen Mun Swimming Pool and Tuen Mun Golf Centre Practice Green which would be located opposite to Sun Tuen Mun Centre, the Planned Public Housing Development at Wu Shan Road, and the Reprovision of Pet Garden.

3.5.13 Planned Public Housing Development at Yip Wong Road and Planned Public House Development at Hang Fu Street also fall within 500m assessment area. According to their programme, their foundation works are expected to be completed by Year 2021. Their major dusty construction activities would be completed before the commencement of the Project. Thus, they were not considered in the quantitative assessment.

3.5.14 Reprovision of Community Green Station opposite to Lung Mun Oasis also falls within the outermost area of 500m assessment area but only minor construction works (i.e. erection of containers) is expected based on the similar facilities in other district, thus it is not considered in the quantitative assessment.

3.6 Assessment Methodology

General Approach

3.6.1 As mentioned in Section 3.5, particulates from dusty construction activities would be the major air pollutant during construction phase. The major construction activities with significant particulate emission would be construction of A16 Station. However as a conservative approach, the bored piling works with limited excavation area (limited for work sites for foundation of pile caps) between TUM Station and TMS Station, including those across Tuen Mun River Channel, site clearance works at Wu King Road Garden, portions of Pui To Road (South) Rest Garden and Wu Shan Recreation Playground, and modification works at Wu King Road were also included in the quantitative assessment of TSP, RSP and FSP.

3.6.2 According to “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts”, three components of contribution should be considered in evaluating the air quality impact due to the Project upon ASRs, namely primary, secondary and background contributions.

· Primary contributions: Project induced;

· Secondary contributions: pollutant-emitting activities in the immediate neighbourhood. Any emission sources in an area within 500 m radius of the Project area with notable impacts were identified and included in an air quality assessment to cover the short-range contributions using EPD’s approved local-scale Gaussian type model. Vehicular and marine traffic emission were considered in the assessment; and

· Background contributions: Background concentrations from Pollutants in the Atmosphere and their Transport over Hong Kong (PATH) model released from EPD were adopted to estimate future concentrations.

Emission Inventory

Construction Dust from the Project

3.6.3 The concerned major dusty construction activities for the Project that were considered in the modelling assessment include:

· Site clearance, which involves removal of vegetation and surface soil, and ground levelling, modelled as heavy construction activities;

· Demolition works, which is modelled as heavy construction activities;

· Excavation, material handlings, spoil removal, bored piling, backfilling works and haul road within construction site modelled as heavy construction activities; and

· Wind erosion of open active site during non-working hours.

3.6.4 According to United States Environmental Protection Agency (USEPA) AP-42^{[^[1]]}, construction dust particles may be grouped into five particle size classes. The particle size distribution as referenced to AP-42, Section 13.2.4 (Aggregate Handling Emission), is normalized to obtain the particle size distribution in PM₃₀ (TSP). Details are shown in Table 3.6. The mass of RSP, which is defined as suspended particulates in air with aerodynamic size of 10 µm or smaller, is estimated to be 47.3% of PM₃₀, i.e. RSP emission = 47.3% × TSP emission. Similarly, the mass of FSP is estimated to be 7.2% of PM₃₀.

Table 3.6 Particle Size Distribution

Size Range (µm)	Average size(µm)	Distribution	Normalized Distribution
15 – 30	22.5	26.0%	35.1%
10 – 15	12.5	13.0%	17.6%
5 – 10	7.5	15.0%	20.3%
2.5 – 5	3.75	14.7%	19.9%
< 2.5	1.25	5.3%	7.2%

3.6.5 According to the preliminary engineering design information, dust control measures would be incorporated into the design, as presented in Table 3.7. These dust control measures were also taken into account in the assessment.

Table 3.7 Dust Emission Design Control Measures

Process	Description	Dust Emission Design Control Measures
Haul road within construction sites facilities	Transportation of spoil	All road surfaces within the construction sites would be paved and watering frequently along the haul road during the working hours.
Trucks	Vehicles leaving the loading/unloading facility	Vehicles would be required to pass through the wheel washing facilities provided at the site exit.
All dusty construction work sites	All heavy construction activities	Watering once every 2 hours on heavy construction work sites to reduce dust emission by 91.7%.
Demolition works sites	All heavy construction activities	Watering once every 2 hours on heavy construction work sites to reduce dust emission by 91.7%.

3.6.6 Construction emission rates were estimated based on emission factors of United States Environmental Protection Agency (USEPA) Compilation of Air Pollution Emission Factors (AP-42), 5th edition and activity data from the engineer design. Activity data considered in the calculation including, but not limited to, percentage active area, and number of construction trucks and truck speed. The latter two were used to determine the dust suppression efficiency applied to the emission factor with mitigation measures. The emission factors for identified dust sources are summarized in Table 3.8.

Table 3.8 Emission Factors for Dusty Construction Activities

Source	Activity	Emission Factor	Remarks
Site Clearance Works Areas/Road Modification Works at Wu King Road/Works Sites for A16 Station and bored piling works (for pile cap) between River Crossing Bridge and TMS Station/ Demolition of the Tuen Mun Swimming Pool and two footbridges	Heavy Construct-ion Activities (including Excavation, materials handling, spoil removal, backfilling, piling works, and truck movement)	E(TSP)=2.69 Mg/hectare /month of activity E(RSP) = 2.69 x 47.3% Mg/hectare/month⁽¹⁾ E(FSP) = 2.69 x 7.2% Mg/hectare/month⁽¹⁾	100% area actively operating for hourly and daily concentration prediction AP-42, Section 13.2.3, 1/95 ed.
Wind Erosion	E(TSP)=0.85 Mg/hectare /year E(RSP) = 0.85 x 47.3% Mg/hectare/month⁽¹⁾ E(FSP) = 0.85 x 7.2% Mg/hectare/month⁽¹⁾	100% area actively operating for hourly and daily concentration prediction AP-42, 5^th ed., Table 11.9.4

Source

Activity

Emission Factor

Remarks

Site Clearance Works Areas/Road Modification Works at Wu King Road/Works Sites for A16 Station and bored piling works (for pile cap) between River Crossing Bridge and TMS Station/ Demolition of the Tuen Mun Swimming Pool and two footbridges

Heavy Construct-ion Activities (including Excavation, materials handling, spoil removal, backfilling, piling works, and truck movement)

E(TSP)=2.69 Mg/hectare

/month of activity

E(RSP) = 2.69 x 47.3%

Mg/hectare/month⁽¹⁾

E(FSP) = 2.69 x 7.2%

Mg/hectare/month⁽¹⁾

100% area actively operating for hourly and daily concentration prediction

AP-42, Section 13.2.3, 1/95 ed.

Wind Erosion

E(TSP)=0.85 Mg/hectare

/year

E(RSP) = 0.85 x 47.3%

Mg/hectare/month⁽¹⁾

E(FSP) = 0.85 x 7.2%

Mg/hectare/month⁽¹⁾

100% area actively operating for hourly and daily concentration prediction

AP-42, 5^th ed., Table 11.9.4

Note:

(1) USEPA AP-42, 5th ed. 11/06 ed. S13.2.3

3.6.7 Construction dust emission factors in United States Environmental Protection Agency (USEPA) AP-42 are expressed in terms of TSP. Fractions of finer particulates were estimated from the TSP emission factor with the size distribution of the concerned process, in order to compare against the AQOs. Construction activity generally involves aggregate handling, therefore the particle size distribution of aggregate handling, which is available in AP-42 by USEPA, was adopted for heavy construction activities. Particle size distribution of construction dust is listed in Table 3.9.

Table 3.9 Fractions of Particulates for Construction Dust

Process	Cumulative % of TSP
Process	RSP	FSP	Reference
Aggregate Handling (equivalent to Heavy Construction Activities)	47.3%	7.2%	Page 13.2.4-4, Section 13.2.4, AP-42, USEPA (Version 11/06)

3.6.8 The construction of the Project would commence in Nov 2023 for completion in 2030. The works to be conducted in 2023 (Appendix 2.3 refers) would be tree felling which would not induce adverse dust impact, while the concerned major dusty activities such as site clearance, demolition and piling works would be conducted between 2024 and early 2028, and all major dusty activities will be completed by early 2028. Following the completion of piling works, less-dusty construction method (using offsite prefabricated component erected by gantry/crane) would be adopted for the construction of pier, viaduct and station (Section 2.3.32 and 2.3.34 refer) to minimise environmental impacts including dust, noise and waste generation. The tentative programme of the concerned major dusty activities is summarised in Table 3.10. Site clearance works will commence in Year 2024, while the piling works and construction of pile caps will follow and to be completed by early Year 2028. Referring to the above identified construction activities with potential dust emissions and the construction period of these dusty construction activities, all major dusty construction activities were grouped into two assessment scenarios, i.e. construction activities within Year 2023 to 2025 as Scenario 1 and construction activities within Year 2026 to 2030 as Scenario 2. The locations of works sites considered in the modelling are presented in Appendix 3.1.

Table 3.10 Tentative Construction Programme

Construction Task	Tentative Works Programme		Assessment Scenario
Construction Task	Start	Completion of works	Scenario 1	Scenario 2
Site Clearance at Wu King Road Garden	Jan 2024	Mar 2024	√	-
Site Clearance at portion of Pui To Road (South) Rest Garden	Feb 2024	Jun 2024	√	-
Site Clearance at portion of Wu Shan Recreation Playground	Nov 2023	Mar 2024	√	-
Road modification works at Wu King Road	Mar 2024	Aug 2024	√	-
Demolition and Reprovision Works of Two Existing Footbridges	Sep 2024	Oct 2025	√
TUM Station Modification Works	Oct 2024	Oct 2025	-	-
Construction of Major Viaduct Civil Works and Finishing Works (Piling Works and Construction of Pile Caps)	Apr 2024	Oct 2027	√	√
Demolition of Tuen Mun Swimming Pool	Aug 2026	Nov 2026	-	√
Construction of Major Civil Works of A16 Station (Piling Works and Construction of Pile Caps)	Jun 2024	Jan 2028	√	√
Construction of TMS Station (Piling Works and Construction of Pile Caps)	May 2025	Nov 2027	√	√

3.6.9 For the prediction of the highest hourly average TSP, the 10^th highest daily average and annual average RSP, the 36^th highest daily average and annual average FSP concentrations, the construction period was assumed as 12-hour (07:00-19:00) a day, 7 days a week for the assessment purpose. Since no construction activity would occur during non-working hours (19:00 to 07:00 of the following day), only wind erosion was assumed for non-working hours.

3.6.10 Works activities and plant would not be concentrated in certain areas of the site close to ASRs for an extended period of time during the construction period. However, notwithstanding that such a scenario would not be expected to occur, a hypothetical approach assuming working in full capacity (100% active) at a construction site of the Project with mitigation measures (as mentioned in Table 3.7) in place has been undertaken for the assessment purpose.

Secondary Contributions

3.6.11 Secondary contributions are the air pollutant emissions immediate neighbourhood of the works sites contributing further to the local air quality impact. Any particulate emission sources within 500 m of the works sites boundary with notable impact were identified and considered in the construction phase impact assessment. Potential sources for secondary contribution in particulates mostly come from vehicular emission by nearby open roads, marine emission from nearby ferry terminal and typhoon shelter, and chimneys. These sources were considered in the cumulative impact assessment.

Vehicular Emission and Start Emission from Open Road

3.6.12 The dust pollutants associated with traffic emission are TSP, RSP and FSP in cumulative dust impact assessment. The projected 24-hour traffic flows and vehicle compositions, including the dump trucks induced by the construction of the Project, were adopted in this air quality assessment. Vehicular emission burden of each construction year, namely Year 2023 – 2025 for Scenario 1 and Year 2026 – 2030 for Scenario 2, was estimated based on the traffic forecast and EMFAC-HKv4.3. Year 2025 and Year 2028 are the highest emission years with respect to vehicular emissions, thus vehicular emissions from these years were adopted as the worst-case assessment year for Scenario 1 and Scenario 2 respectively. A Technical Note illustrating the methodology to produce the traffic data (include 24-hr traffic flow, trips, daily vehicle-kilometer-travelled (VKT) & speed fraction) had been agreed by Transport Department (TD).

3.6.13 EMFAC-HK v4.3 was adopted to estimate the vehicular emission factors in TSP, RSP and FSP in various travelling speed, ambient condition such as temperature and relative humidity.

3.6.14 The traffic data of each road within 500m assessment area, which comprises 24-hour traffic flow with fleet percentage, travelling speed of each of 18 vehicle classes is the basis for the estimation of vehicular emission. The traffic flow data is presented in Appendix 3.2. With reference to the traffic data, hourly emission factor of each open road was determined by summation of emission by each vehicle class which is product of traffic flow and emission factor at specific speed and ambient condition. The vehicular emission factor at specific traveling speed was extracted from EMFAC-HK v.4.3 in EMFAC mode with the lowest temperature and relative humidity in a year. The hourly emissions factors of TSP, RSP and FSP were then further divided by the hourly flow to obtain a composite emission rate in gram per miles per vehicle, ready for input to the dispersion model. The summary of vehicular emission factors and the emission inventory of vehicular emission sources are presented in Appendix 3.3 and Appendix 3.4 respectively.

3.6.15 Start emission refers to the air pollutants generated due to the ignition of the vehicle engines which is released at vehicle tailpipes. Roadside parking on local roads in the assessment area was reviewed and identified. These roads with roadside parking are shown in Appendix 3.4. For the vehicle class other than public transport, including franchised bus, coach, minibus and taxi, and heavy goods vehicle, startup emission was applied on these roads with roadside parking in a broad-brush approach. In broad-brush approach, start emission was assumed at all local roads irrelevant to the actual location of engine start. Frequency of start emission of a vehicle type on a road was estimated by its forecasted VKT and Trips/VKT ratio extracted from Traffic Census. Start emission factors of 18 vehicle classes at various soak times were extracted from EMFAC-HK v4.3, among which the highest factor is adopted for a vehicle class. The emission factors concerning start emission at local road with roadside parking is presented in Appendix 3.3.

Emission Associated with Bus and Minibus Termini, Heavy Goods Vehicle and Coach Parking Sites

3.6.16 Among all 18 vehicle classes, start emissions of public transport, including franchised bus, coach, minibus and taxi, and also heavy goods vehicle are the highest and of concern. In particular, the facilities of concern would be bus termini, bus depot, minibus termini, and heavy goods vehicle and coach parking sites. Kowloon Motor Bus Tuen Mun (South) Depot, and Citybus Tuen Mun Depot are located adjacent to the works areas/works sites for A16 Station. Bus termini and heavy goods vehicle and coach parking sites within assessment area were identified and their locations are illustrated in Appendix 3.5. Data concerning engine start at these concerned locations, such as the frequency and soak time, were collected by traffic survey. The observations in engine start frequency and soak time are presented in Appendix 3.5. Start emission factors of concerned public transport at various soak times were extracted from EMFAC-HK v4.3. The detailed calculation of start emission is also presented in Appendix 3.5.

Marine Emission

3.6.17 Based on the latest design, 4 trips of barge per week would be required for the transport of precast concrete segment to be used in the construction of pile caps and viaducts. 1 barge was assumed to berth at the barging point for unloading operation during the construction hours between 07:00 and 19:00.

3.6.18 Tuen Mun Ferry Terminal and Tuen Mun Typhoon Shelter fall within the assessment area as shown in Figure No. C1502/C/TME/ACM/M51/101. Existing marine emission from scheduled ferries and vessels accessing the typhoon shelter was included in the assessment. A 2-day vessel count survey was conducted for existing marine traffic flows within Tuen Mun Typhoon Shelter, while the marine traffic at Tuen Mun Ferry Terminal was derived from the latest ferry schedule.

3.6.19 With reference to the Study on Marine Vessels Emission Inventory (MVEIS) by HKUST, the marine emission was estimated in activity-based approach. The emission factors were derived in units of works (gram per kilowatt-hour), dependent on fractional load of the equipment during different vessel activity modes. The calculation is summarized as below:

Emission = P x FL x T x EF

where P is the installed power of equipment;

FL is fractional load of equipment in a specific mode;

T is operation time-in-mode; and

EF is fractional load emission factor of equipment

3.6.20 Detailed assumptions and parameters adopted for the assessment was determined according to the findings of the vessel survey and is presented in Appendix 3.6.

Chimney Emission

3.6.21 Chimneys were identified within 500m assessment area in a site survey conducted in November 2021. Their locations are illustrated in Appendix 3.7. The emission rates and stack parameters refer to the approved EIA Report of Sludge Treatment Facilities (Register No.: AEIAR-129/2009). The emission inventory in details is also presented in Appendix 3.7.

Construction works of Concurrent Project

3.6.22 The concurrent projects include Reprovision of Tuen Mun Swimming Pool and Tuen Mun Golf Centre Practice Green which would commence in 2022 for completion in 2026, and Planned Housing Development at Wu Shan Road which would be built between 2023 and 2026. Reprovision of Pet Garden would be undertaken in Year 2028 – 2029, and the demolition and site clearance would be carried out earlier in Year 2024. These concurrent projects were therefore considered in both Scenario 1 and 2. Heavy construction activities with typical dust mitigation measures, e.g. watering every 2 hours, were assumed. The detailed calculation of these construction dust sources is presented in Appendix 3.8.

Background Contributions

3.6.23 As suggested by “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts”, an integrated modelling system PATH which is developed and maintained by EPD was applied to estimate the background pollutant concentrations. The background concentrations from PATH model (Pollutants in the Atmosphere and their Transport over Hong Kong) (PATHv2.1) were adopted to estimate future concentrations during the construction years. Dataset of Year 2025 was adopted for Scenario 1 and 2.

3.6.24 Dataset of PATH has no TSP background. TSP background concentration was assumed to constitute of 100% of PM₁₀ concentration. PM₁₀ concentration from PATH was directly adopted as TSP background concentration for the assessment.

3.6.25 The assessment area covers 8 grid cells of PATH, namely grid (19,39), (19,40), (19,41), (19,42), (20,39), (20,40), (20,41) and (20,42). PATH dataset of these 8 grid cells were adopted as the background concentration for the assessment.

3.7 Dispersion Modelling & Modelling Approach

Construction Dust Emission

3.7.1 According to Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts by EPD, an integrated modelling system PATH which is developed and maintained by EPD was applied to provide background pollutant concentrations in assessing the total impact in the assessment area. In addition, Weather Research and Forecast (WRF) meteorological data were adopted for modelling.

3.7.2 American Meteorological Society (AMS) and U.S. Environmental Protection Agency (EPA) Regulatory Model (AERMOD), the EPD approved air dispersion model, was employed to predict the air quality impacts due to emission from construction activities. The air pollutants concentrations were predicted at each identified ASRs at various assessment height at 1.5 mAG, 5mAG, 10mAG, 20mAG and so on of the respective ASRs, according to its physical height.

3.7.3 Hourly meteorological conditions including wind data, temperature, relative humidity, pressure, cloud cover and mixing height were extracted from the WRF meteorological data adopted in the PATH system (PATHv2.1). The dataset by WRF should be intact and consistent among parameters. In order to avoid any hours misidentified as missing data by AERMOD and its associated components, the WRF met data is handled manually to set wind direction between 0° – 0.1° to be 360°. The height of the input data is assumed to be 9 metres above ground for the first layer of the WRF data as input.

3.7.4 The wind speed and mixing heights in the WRF data were further adjusted before meteorological pre-processing by AERMET. The minimum wind speed is capped at 1 metre per second. The mixing height is capped between 131metres and 1941 metres according to the observation by HKO, i.e. in Year 2015 or the relevant. After pre-processed by AERMET, the mixing height is verified once again and adjusted to the capped range if necessary.

3.7.5 Surface characteristic parameters such as albedo, Bowen ratio and surface roughness are required in the AERMET. The parameters were determined according to land use classified for the surrounding and the latest AERMOD Implementation Guide. Details refer to Appendix 3.9. Flat terrain option was applied in AERMOD because the urban area of Tuen Mun is flat in general.

3.7.6 As particulates are concerned, dry deposition was applied in the model run. Particle size distribution was assigned for particles with aerodynamic diameters smaller than 10 µm to each type of source in the AERMOD in order to account for the particle deposition. The particle size distributions for construction dust are summarized in Table 3.11.

Table 3.11 Particle Size Distribution of Aggregate Handling (equivalent to Heavy Construction Activities and Wind Erosion)

Average Particle Diameter (µm)	Normalized Distribution
1.25	7%
3.75	20%
7.5	20%
12.5	18%
22.5	35%

Remark:

(1) Reference from Table of Aerodynamic Particle Size Multiplier (k) for Equation 1, Section 13.2.4-4, AP-42, USEPA

Vehicular Emission from Open Road

3.7.7 CALINE4, the USEPA approved line source air dispersion model developed by the California Department of Transport was used to assess the secondary contribution due to vehicular emission from road networks within 500 m assessment area.

3.7.8 The surface roughness is dependent on the land use characteristics, which is estimated to be 10% of average height of physical structure within 1 km radius of the Project Site. Typically, the value is assumed to be 370 cm and 100 cm for urban and new development respectively. The assessment area comprises abundant high-rise buildings and also open waters and park, thus surface roughness of 100 cm was assumed.

3.7.9 Under the current EPD guideline, the hourly meteorological data including wind speed, wind direction, and air temperature from the relevant grids from the WRF Meteorological data (same basis for PATH model), were employed for the model run. PCRAMMET was applied to generate Pasquill-Gifford stability class for the meteorological input to CALINE4 model based on the WRF meteorological data.

Cumulative impact of Criteria Air Pollutants

3.7.10 Cumulative air pollutant concentration at ASR was derived by the sum of contributions by various sources, and background contribution from PATHv2.1 system on hour-by-hour basis. Averaging results, namely daily and annual, were derived from the cumulative hour-by-hour results in accordance with Title 40, Code of Federal Regulations, US Environmental Protection Agency (USEPA 40 CFR) Part 51 “Revision to the Guideline on Air Quality Models, January 2017”. If the total number of valid hours is less than 18 for 24-hour average, the total concentration should be divided by 18 for the 24-hour average. For annual average, the sum of all valid hourly concentrations was divided by the number of valid hours during the year. For daily average, cumulative results at each ASR amongst 365 days were ranked by highest concentration and compared with the maximum allowable concentration to determine the number of exceedance throughout a year. The air quality impact on ASRs was then evaluated by number of exceedance per annum against the criteria of EIAO-TM and AQOs.

3.8 Prediction and Evaluation of Environmental Impacts

Construction Works Sites along TME

3.8.1 The cumulative air quality impact due to construction activities of the Project and concurrent projects, open roads, chimneys and marine emission within 500m assessment area at representative ASRs in Scenario 1 and Scenario 2 were predicted. It is noted that exceedance in hourly TSP, 10^th highest daily and annual RSP, 36^th highest daily FSP were predicted at the representative ASRs, thus mitigation measures are deemed necessary. The detailed predictions of unmitigated Scenario 1 and 2 are presented in Appendix 3.10 and Appendix 3.11 respectively.

Offsite Works Area

3.8.2 The offsite works area at Mong Wing Street is proposed to be used as site office, storage for pre-cast unit (non-dusty material) and temporary tree nursery. The site is being used as a construction works area for the project “Tuen Mun - Chek Lap Kok Link (TM-CLKL). No excavation works is anticipated to prepare the area. Tree nursery would not involve any earthworks. Storage for pre-cast unit does not involve stockpiling of dusty material, which would not cause any fugitive dust emission. According to latest design, only one crane is required at the off-site works site for loading/unloading of precast unit. Lorry crane is required for loading and unloading tree plants. There would be only 1 – 2 overall truck movement per hour involved for delivery during peak construction period. Given no excavation works and minor traffic induced, in additional to limited no. of machinery operating on-site, its potential air quality impact on the ambient is consider negligible.

3.9 Mitigation of Adverse Environmental Impacts

3.9.1 In order to minimize the construction dust impact, the following dust mitigation measures should be implemented during the dusty construction activities including the site clearance and piling works:

· Watering once every 2 hours on heavy construction work areas to reduce dust emission by 91.7%. Any potential dust impact and watering mitigation would be subject to the actual site condition. For example, a construction activity that produces inherently wet conditions or in cases under rainy weather, the above water application intensity may not be unreservedly applied. While the above watering frequency is to be followed, the extent of watering may vary depending on actual site conditions but should be sufficient to achieve the removal efficiency. The dust levels would be monitored and managed under an EM&A programme as specified in the EM&A Manual.

3.9.2 With the implementation of the above measures, the predicted cumulative hourly TSP, 10^th highest daily and annual RSP, 36^th highest daily and annual FSP concentrations at the representative ASRs are summarized in Table 3.12 and Table 3.13. The predictions showed that the hourly average of TSP, daily and annual averages of RSP and FSP at representative ASRs would comply with the criteria as stipulated in the EIAO-TM and the AQOs. The detailed prediction results are presented in Appendix 3.12 and Appendix 3.13.

Table 3.12 Worst Predicted Cumulative Air Quality Impact at Representative ASRs (Scenario 1 with Dust Mitigation Measures)

ASR ID	Maximum Hourly Average TSP Conc. (µg/m³) (EIAO-TM: 500 µg/m³)	10^th Highest Daily Average RSP Conc. (µg/m³) (AQO: 100 µg/m³)	Annual RSP Conc. (µg/m³) (AQO: 50 µg/m³)	36^th Highest Daily Average FSP Conc. (µg/m³) (AQO: 50 µg/m³)	Annual FSP Conc. (µg/m³) (AQO: 25 µg/m³)
A01	146	74	31	28	18
A02	167	74	31	28	17
A03	188	74	31	28	17
A04	242	78	34	28	17
A05	147	72	29	27	17
A06	149	74	30	27	17
A07	269	78	35	28	17
A08	284	79	35	28	18
A09	299	81	36	28	18
A10	144	74	33	28	17
A11	149	71	30	27	17
A12	148	71	30	27	17
A13	143	73	32	27	17
A14	143	73	32	27	17
A15	143	74	32	27	17
A16	143	74	31	27	17
A17	144	74	32	27	17
A18	172	74	33	28	18
A19	254	74	35	28	18
A20	240	75	35	28	18
A21	302	80	39	29	18
A22	192	73	32	27	17
A23	238	74	34	28	18
A24	236	81	37	29	18
A25	264	83	41	30	19
A26	363	91	46	31	20
A27	390	91	47	31	20
A28	439	91	47	31	20
A29	194	76	36	28	18
A32	304	73	33	27	17
A33	147	71	30	27	17
A34	149	73	31	27	17
A35	148	73	30	27	17
A36	161	72	32	29	18
A37	160	72	32	29	18
A38	146	72	33	30	19
A39	145	72	31	28	18
A40	144	71	31	28	17
A41	247	79	34	28	17
A42	225	76	33	28	17
A43	497	80	37	29	18
A44	208	76	33	28	18
P1	146	75	33	28	18
P2	148	71	30	27	17
P3	147	71	30	27	17

Table 3.13 Worst Predicted Cumulative Air Quality Impact at Representative ASRs (Scenario 2 with Dust Mitigation Measures)

ASR ID	Maximum Hourly Average TSP Conc. (µg/m³) (EIAO-TM: 500 µg/m³)	10^th Highest Daily Average RSP Conc. (µg/m³) (AQO: 100 µg/m³)	Annual RSP Conc. (µg/m³) (AQO: 50 µg/m³)	36^th Highest Daily Average FSP Conc. (µg/m³) (AQO: 50 µg/m³)	Annual FSP Conc. (µg/m³) (AQO: 25 µg/m³)
A01	146	73	30	27	17
A02	147	72	29	27	17
A03	147	72	29	27	17
A04	147	72	29	27	17
A05	147	72	29	27	17
A06	147	72	29	27	17
A07	147	72	29	27	17
A08	147	72	29	27	17
A09	147	73	30	27	17
A10	144	74	32	28	17
A11	202	71	30	27	17
A12	223	72	31	27	17
A13	175	74	33	27	17
A14	228	74	31	27	17
A15	166	73	30	27	17
A16	162	73	30	27	17
A17	144	73	30	27	17
A18	143	73	30	27	17
A19	147	72	31	28	18
A20	146	72	31	28	17
A21	149	72	31	27	17
A22	146	71	31	27	17
A23	151	72	31	27	17
A24	145	72	32	28	17
A25	145	73	33	28	18
A26	145	73	33	28	17
A27	145	73	32	28	17
A28	144	73	34	28	18
A29	161	73	30	27	17
A32	147	71	30	27	17
A33	172	71	30	27	17
A34	332	84	35	29	18
A35	283	79	33	28	18
A36	148	71	31	29	18
A37	147	71	31	29	18
A38	146	71	32	30	19
A39	145	71	31	28	18
A40	144	71	31	28	17
A42	225	76	32	28	17
A43	497	79	36	28	18
A44	209	76	33	28	18
P1	166	74	33	28	18
P2	229	71	30	27	17
P3	187	71	30	27	17

3.9.3 According to the discrete results, the worst affected level of TSP, RSP and FSP would be 1.5 metres above ground (mAG). The contour plots of TSP, RSP and FSP at 1.5mAG are illustrated in Figure Nos. C1502/C/TME/ACM/M51/103 - C1502/C/TME/ACM/M51/112 respectively. Exceedance in particulates concentrations, including hourly TSP, 10^th highest daily and annual RSP, was generally be predicted at the proposed works area and works areas of concurrent projects under the two scenarios. Given that these works areas would be under construction, thus no air sensitive use would exist within these works areas, and also no air sensitive use within these exceedance zones arising from works areas of concurrent projects. In Scenario 1, exceedance in annual RSP at 1.5mAG was predicted at the junction of Wu King Road and Wu Yuet Street, nearby basketball court in Tung Wah Group of Hospitals Sun Hoi Director's College and soccer pitch, while the building of Tung Wah Group of Hospitals Sun Hoi Director's College is outside the exceedance zone of annual RSP. The soccer pitch and the basketball court do not have long-term air sensitive uses such as snack kiosk within the exceedance zone of annual RSP. Given that the air sensitive uses at the soccer pitch and the basketball court are in transient nature, and thus long-term RSP impact is not applicable to these air sensitive uses. The prediction results also indicate that there would be no exceedance of the short-term AQOs (i.e. hourly TSP, daily RSP and FSP) at these soccer pitch and basketball court. No exceedance in 36^th highest daily and annual FSP was predicted within the assessment area under the two scenarios. With the implementation of the proposed dust mitigation measures, i.e. watering once every 2 hours on heavy construction work areas, it is anticipated that there would be no adverse dust impact during the construction of the Project.

3.10 Evaluation of Residual Impacts

3.10.1 With the implementation measures specified in the Air Pollution Control (Construction Dust) Regulation together with the design control measures such as water frequency (with dust removal efficiency of 91.7%) on the works sites and exposed surface, i.e. once every 2 hours, no adverse residual impact would be expected from the construction of the Project.

3.10.2 Dust suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation and good site practices listed below should be carried out to further minimize construction dust impact.

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

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

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

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

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

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

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

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

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

3.10.3 Although there is no long-term air sensitive use within the exceedance zone of annual RSP at 1.5mAG, as a good practice, the following measures would be implemented at the works sites located at the junction of Wu King Road and Wu Yuet Street:

· Proper planning of site layout to locate the machinery and dusty activities (e.g. haul roads and stockpiling areas) away from nearby air sensitive uses such as soccer pitch and basketball court as far as practicable;

· Provision of at least 2.4 m or higher hoarding from ground level along works site boundary close to the basketball court; and

· Adopt more frequent watering (e.g. once every hour) to reduce dust emissions from the exposed site surfaces, if any.

3.10.4 To minimize the exhaust emission from NRMMs during the construction phase, below measures should be applied as far as practicable:

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

· Avoid exempted NRMMs as far as practicable; and

· Deploy electrified NRMMS as far as practicable.

3.11 Environmental Monitoring and Audit

3.11.1 EM&A for potential dust impacts are recommended during the construction phase of the Project so as to check compliance with legislative requirements. Details of the monitoring and audit programme are presented in a stand-alone EM&A Manual.

3.12 Conclusion

3.12.1 Potential construction dust impact would arise from the construction of the Project. Cumulative dust impact from construction activities, vehicular emission and start emission from open road, emission associated with bus and minibus termini, marine emission, nearby chimneys and concurrent projects were evaluated. With the implementation design control measures such as watering once every 2 hours during the dusty construction activities, the prediction results concluded that cumulative TSP, RSP and FSP concentrations at all ASRs would comply with the criteria in EIAO-TM and AQOs, no adverse construction dust impact is anticipated.

^{^[1]}USEPA, AP-42 Compilation of Air Pollution Emission Factors (AP-42), Section 13.2.4.3, 1^st Table, November 2006

C1502/C/TME/ACM/M51/101	Locations of Representative Air Quality Sensitive Receivers (Sheet 1 of 2)
C1502/C/TME/ACM/M51/102	Locations of Representative Air Quality Sensitive Receivers (Sheet 2 of 2)
C1502/C/TME/ACM/M51/103	Contour of Predicted Maximum Cumulative Hourly TSP Concentration at 1.5 mAG (µg/m³) (Scenario 1)
C1502/C/TME/ACM/M51/104	Contour of Predicted 10th Highest Cumulative Daily RSP Concentration at 1.5 mAG (µg/m³) (Scenario 1)
C1502/C/TME/ACM/M51/105	Contour of Predicted Cumulative Annual RSP Concentration at 1.5 mAG (µg/m³) (Scenario 1)
C1502/C/TME/ACM/M51/106	Contour of Predicted 36th Highest Cumulative Daily FSP Concentration at 1.5 mAG (µg/m³) (Scenario 1)
C1502/C/TME/ACM/M51/107	Contour of Predicted Cumulative Annual FSP Concentration 1.5mAG (µg/m³) (Scenario 1)
C1502/C/TME/ACM/M51/108	Contour of Predicted Maximum Cumulative Hourly TSP Concentration at 1.5 mAG (µg/m³) (Scenario 2)
C1502/C/TME/ACM/M51/109	Contour of Predicted 10th Highest Cumulative Daily RSP Concentration at 1.5 mAG (µg/m³) (Scenario 2)
C1502/C/TME/ACM/M51/110	Contour of Predicted Cumulative Annual RSP Concentration at 1.5 mAG (µg/m³) (Scenario 2)
C1502/C/TME/ACM/M51/111	Contour of Predicted 36th Highest Cumulative Daily FSP Concentration at 1.5 mAG (µg/m³) (Scenario 2)
C1502/C/TME/ACM/M51/112	Contour of Predicted Cumulative Annual FSP Concentration 1.5mAG (µg/m³) (Scenario 2)

3 Air Quality impact

3.1.2 The potential dust impact arising from dusty construction activities of the Project have been assessed and appropriate mitigation measures are proposed to alleviate any adverse air quality impact.

3.2.1 The criteria and guidelines for air quality assessment are laid down in Annex 4 and Annex 12 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM).

3.2.3 Apart from AQOs, the limit of hourly Total Suspended Particulates (TSP) concentration should not exceed 500 µg/m3 (measured at 25°C and one atmosphere) for construction dust impact assessment according to Annex 4 of EIAO-TM.

3.3 Description of the Environment and Future Trends

3.3.2 The dominant existing air pollutants sources within the 500m assessment area are the vehicular emissions from Wong Chu Road, Tuen Mun Road, Lung Fu Road, Hoi Wing Road, Hoi Wong Road and Wu King Road.

3.4.2 The representative ASRs (existing / planned) that may be affected by the Project within the 500 m assessment area have been identified based on the latest Outline Zoning Plans, Layout Plan, Outline Development Plans, Layout Plans and other relevant published land use plans.

3.4.3 The locations of the representative ASRs are shown in Figure No. C1502/C/TME/ACM/M51/101 & 102. The details of the representative ASRs for assessment are presented in Table 3.4 and Table 3.5.

3.5 Identification of Environmental Impacts during Construction Phase

3.5.4 The major potential air quality impact during construction phase of the Project would be construction of A16 Station which would involve the following dusty construction activities:

3.5.5 Site clearance at Wu King Garden and portions of Pui To Road (South) Rest Garden and Wu Shan Recreation Playground, as well as modification works at Wu King Road are also dusty construction activities which would pose potential dust impact.

3.5.10 There are also existing industrial chimneys within 500m assessment area. These chimneys have been identified and their locations are illustrated in Appendix 3.7.

3.5.11 Major emission sources within 4km of the quantitative assessment area would also contribute to the ambient air quality. However, no major emission source was found within 4km of the Project boundary.

3.6.2 According to “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts”, three components of contribution should be considered in evaluating the air quality impact due to the Project upon ASRs, namely primary, secondary and background contributions.

3.6.3 The concerned major dusty construction activities for the Project that were considered in the modelling assessment include:

3.6.5 According to the preliminary engineering design information, dust control measures would be incorporated into the design, as presented in Table 3.7. These dust control measures were also taken into account in the assessment.

Secondary Contributions

3.6.13 EMFAC-HK v4.3 was adopted to estimate the vehicular emission factors in TSP, RSP and FSP in various travelling speed, ambient condition such as temperature and relative humidity.

3.6.20 Detailed assumptions and parameters adopted for the assessment was determined according to the findings of the vessel survey and is presented in Appendix 3.6.

3.6.24 Dataset of PATH has no TSP background. TSP background concentration was assumed to constitute of 100% of PM10 concentration. PM10 concentration from PATH was directly adopted as TSP background concentration for the assessment.

3.6.25 The assessment area covers 8 grid cells of PATH, namely grid (19,39), (19,40), (19,41), (19,42), (20,39), (20,40), (20,41) and (20,42). PATH dataset of these 8 grid cells were adopted as the background concentration for the assessment.

3.7.7 CALINE4, the USEPA approved line source air dispersion model developed by the California Department of Transport was used to assess the secondary contribution due to vehicular emission from road networks within 500 m assessment area.

3.8 Prediction and Evaluation of Environmental Impacts

3.9.1 In order to minimize the construction dust impact, the following dust mitigation measures should be implemented during the dusty construction activities including the site clearance and piling works:

3.10.2 Dust suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation and good site practices listed below should be carried out to further minimize construction dust impact.

3.10.3 Although there is no long-term air sensitive use within the exceedance zone of annual RSP at 1.5mAG, as a good practice, the following measures would be implemented at the works sites located at the junction of Wu King Road and Wu Yuet Street:

3.10.4 To minimize the exhaust emission from NRMMs during the construction phase, below measures should be applied as far as practicable:

3.11.1 EM&A for potential dust impacts are recommended during the construction phase of the Project so as to check compliance with legislative requirements. Details of the monitoring and audit programme are presented in a stand-alone EM&A Manual.

3.2.3 Apart from AQOs, the limit of hourly Total Suspended Particulates (TSP) concentration should not exceed 500 µg/m³ (measured at 25°C and one atmosphere) for construction dust impact assessment according to Annex 4 of EIAO-TM.

3.6.24 Dataset of PATH has no TSP background. TSP background concentration was assumed to constitute of 100% of PM₁₀ concentration. PM₁₀ concentration from PATH was directly adopted as TSP background concentration for the assessment.