3 aIR qUALITY

3.1 Introduction

3.2 Environmental Legislation, Policies, Plans, Standards and Criteria

3.3 Description of the Environment

3.4 Sensitive Receivers

3.5 Identification of Environmental Impacts

3.6 Assessment Methodology

3.7 Prediction and Evaluation of Environmental Impacts

3.8 Mitigation of Adverse Environmental Impacts

3.9 Evaluation of Residual Impacts

3.10 Environmental Monitoring and Audit

3.11 Conclusion

3 aIR qUALITY

3.1 Introduction

3.1.1 This section presents an air quality impact assessment of air quality during the construction and operation phases of the Wan Chai Development Phase II Designated Project 2 (DP2) – Road P2 and other roads which are classified as primary/district distributors roads. The potential construction dust and operational traffic emission impacts were identified. Appropriate mitigation measures for the proposed development are proposed under this Study where necessary.

3.2 Environmental Legislation, Policies, Plans, Standards and Criteria

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

Air Quality Objective & 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 must be satisfied, stipulate the maximum allowable concentrations of certain pollutants over specific periods. The relevant AQOs are listed in Table 3.1.

Table 3.1 Hong Kong Air Quality Objectives

Notes:

(1) Measured at 298 K and 101.325 kPa.

(2) Not to be exceeded more than three times per year.

(3) Not to be exceeded more than once per year.

(4) Arithmetic mean.

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

(6) Photochemical oxidants are determined by measurement of ozone only.

3.2.3 The EIAO-TM stipulates that the hourly TSP level should not exceed 500 mgm^-3 (measured at 25^oC and one atmosphere) for construction dust impact assessment. Standard mitigation measures for construction sites are specified in the Air Pollution Control (Construction Dust) Regulations.

Air Pollution Control (Construction Dust) Regulation

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

Practice Note on Control of Air Pollution in Vehicle Tunnels

3.2.1 The Practice Note on Control of Air Pollution in Vehicle Tunnels, prepared by the EPD provides guidelines on control of air pollution in vehicle tunnels. Guideline values on tunnel air quality are presented in Table 3.2.

Table 3.2 Tunnel Air Quality Guidelines (TAQG)

Air Pollutant	Averaging Time	Maximum Concentration
		(mg/m^3) ^(1)	ppm
Carbon Monoxide (CO)	5 minutes	115, 000	100
Nitrogen Dioxide (NO2)	5 minutes	1,800	1
Sulphur Dioxide (SO2)	5 minutes	1,000	0.4

Note: (1) Expressed at reference conditions of 298K and 101.325kPa.

3.3 Description of the Environment

Baseline Conditions

3.3.1 The study area is in Wan Chai, Causeway Bay and North Point. The nearest EPD air quality monitoring stations are in Central and Central/Western. The annual average concentrations of the pollutants measured at EPD’s Central / Western and Central air quality monitoring stations in 2006 adjacent to the WDII development area are summarised in Table 3.3.

Table 3.3 Annual Average Concentrations of Pollutants in 2006

Pollutant	Annual Average Concentration in 2006 (mg m^-3)	Monitoring Stations
CO	862	Central
NO2	54	Central / Western
RSP	53	Central / Western
TSP	78	Central / Western

3.4 Sensitive Receivers

3.4.1 The study area is within 500m from the project boundary. The study area of air quality assessment is shown in Figure 3.1. Existing and planned Air Sensitive Receivers (ASRs) including domestic premises, commercial buildings, educational institutions, and recreational and leisure facilities have been identified for air quality impact assessment.

3.4.2 The identified representative ASRs are listed in Table 3.4 and the corresponding locations are shown in Figures 3.2 and 3.3.

Table 3.4 Details of Air Sensitive Receivers

ASRs	Section	Location	Existing / Planned Land Use	No. of floors	Horizontal Distance (m)
					Alignment^*	Ventilation Building
Existing
A25	Wanchai	Police Headquarters	G/IC	7	306	357	^1
A26	Wanchai	HK Academy for Performing Arts (Office/Performance Hall)	G/IC	9	186	254	^1
A27	Wanchai	Arts Centre	G/IC	10	200	175	^1
A28	Wanchai	Citic Tower	Commercial	42	160	385	^1
A29	Wanchai	Servicemen's Guides Association	Commercial	3	116	228	^1
A30	Wanchai	HK Academy for Performing Arts (Open Space)	G/IC	9	160	144	^1
A31	Wanchai	Shui On Centre	Commercial	34	190	160	^1
A32	Wanchai	Hong Kong Convention & Exhibition Centre (HKCEC)	Commercial	46	60	229	^1
A33	Wanchai	Pedestrian plaza	Recreation	0	95	62	^1
A34	Wanchai	HKCEC Extension	Commercial	8	100	177	^1
A35	Wanchai	Great Eagle Centre	Commercial	27	112	372	^1
A36	Wanchai	Causeway Centre	Residential	42	178	531	^1
A37	Wanchai	Wanchai Swimming Pool	Recreation	3	58	568	^1
A38	Wanchai	Wanchai Sports Ground	Recreation	0	74	723	^1
A39	Wanchai	SPCA	G/IC	6	62	787	^1
A40	Wanchai	Gloucester Road 169-170	Residential	12	306	750	^1
Future
A70	Central	Central Government Complex	G/IC	N/a	360	564	^1
A71	Central	New G/IC site south and east of CITIC Tower	G/IC	20	264	360	^1
A73	Central	Waterfront related commercial and leisure uses	Recreation	N/a	42	246	^1
A76	Central	Open space at the west of HKCEC	Recreation	N/a	10	132	^1
A81	Wanchai	Waterfront related commercial and leisure uses	Commercial	N/a	15	432	^1
A99	Wanchai	OU(Railway Air Intake Location) zone	Other use	3.5m above ground	28	246	^1

*Distance from the edge of Trunk Road/ IECL alignment.

¹ Distance from the Central Ventilation Building.

3.4.3 For construction dust impact assessment, the proposed ASRs under WDII Project including ASRs (A71, A73, A81 and A99) would be only be occupied after the completion of construction activities of WDII Project, therefore, the construction dust impact assessment does not cover these ASRs. The planned ASR A70 is Central Government Complex which may be occupied during the construction period of WDII Project. As a conservative approach, ASR A70 was considered in the construction dust impact assessment. For operational traffic emission impact, all ASRs listed in Table 3.4 are considered in the assessment.

3.5 Identification of Environmental Impacts

Construction Phase

Air Quality Impact from Construction Activities

3.5.1 Construction of Road P2 and other roads which are classified as primary/distributor roads are the only construction works under DP2. Materials handling and wind erosion are the major sources of dust impact. SO₂, NO₂ and smoke emitted from diesel-powered equipment may also affect the air quality of the study area.

3.5.2 The concurrent works for the CRIII project has also been taken into account in assessing the impacts.

Operational Phase

Traffic Emission Impact

3.5.3 The major sources of traffic emissions include the open road sections and various tunnel portals / ventilation shafts. In accordance with the engineering design for CWB Main Tunnel, there will be zero portal emission at the eastern tunnel portal, Slip Road 1 and Slip Road 3. Standby ventilation fans would also be provided to ensure zero portal emission of CWB. Therefore, tunnel portal emission impact on the ASRs in the vicinity is not anticipated. Other than emissions from tunnel portal, long sections of landscape deck/deckovers may also result in portal emissions. Within the study area of the Project, there are some existing and planned deckovers which may have portal emissions. The landscape deckovers identified in the study area are summarized as follows:

· Planned deckover along Road P2

· Landscape deck to HKCEC West

· Existing deckover over Expo Drive

· Deckover (New Atrium Link) between Expo Drive Central and Convention Avenue

· Landscaped deck link to waterfront and ferry pier

· Landscaped deck from Victoria Park to CBTS waterfront

· Landscaped deck over Trunk Road Portal

3.5.4 The landscape deck to HKCEC West (with width of about 8.5m), landscaped deck link to waterfront and ferry pier (with width of about 12m), and landscaped deck from Victoria Park to CBTS waterfront (with width of about 16 m) are very short (see Figure 2.5), therefore, portal emissions from these three landscape decks are not anticipated. For the landscaped deck over Trunk Road Portal, only one side of the deckover is supported by solid wall (near the Oil Street site), columns would be used as a support on the other side, hence, no portal emission from this landscape deck is expected.

3.5.5 The overall traffic emission air quality impact for this Project would result from:

· background pollutant levels based on five years averaged monitoring data from EPD monitoring station at Central/Western

· vehicle emissions from open sections of existing and planned road networks in WDII Project and the CWB

· emissions from Central Ventilation Building and East Ventilation Building

· portal emissions from the existing Cross Harbour Tunnel (CHT)

· portal emissions from the planned deckovers along Road P2

· portal emissions from the existing deckover over Expo Drive

· portal emissions from the proposed deckover (New Atrium Link) between Expo Drive Central and Convention Avenue.

3.5.6 Air quality impacts associated with road traffic are caused mostly by NO₂ and RSP. The fleet average emission factors of various classes of vehicles were calculated by the EMPAC Model and are shown in Appendix 3.8a. According to the emission rates derived from the EMFAC Model, the ratio of the emission rate for NO₂ (as 20% of NO_X) and CO to the corresponding 1-hour average AQO is 0.0041 and 0.0015, respectively. Detailed calculation of the ratio of the hourly average NO₂ and CO emission rates to the corresponding AQO is presented in Appendix 3.8b. The calculation indicates that NO₂ is a more critical criteria air pollutant of concern as compared with CO. In other words, if the predicted NO₂ concentrations comply with the corresponding AQO, CO with lower ratio would also comply with its respective AQO. NO₂ and RSP were selected as the critical traffic air pollutants for the purpose of this assessment.

3.5.7 The tunnel section of the Trunk Road (CWB) is around 3.5km long. As confirmed with the tunnel ventilation design engineer, a ventilation system would be provided to maintain the air quality inside the tunnel so as to achieve the EPD recommended standard of 1ppm NO₂ concentration within the tunnel in accordance with the “Practice Note on Control of Air Pollution in Vehicle Tunnels”. The emission rate of CO is more than 44 times of the NO₂ emission rate with reference to vehicle emission derived from the EMFAC Mode, however, the ratio of guideline standard of CO (5-minutes) concentration to NO₂ (5-minutes) concentration in mg/m³ is 64 to 1. Therefore, CO would also comply with the standard. Under the Air Pollution Control (Motor Vehicle Fuel) Regulation, the sulphur content of diesel fuel is required to be less than 0.005%. In view of the low emission rates relative to the statutory limit, SO₂ would also comply with the tunnel air quality limit.

3.6 Assessment Methodology

Construction Phase

3.6.1 There is potential for SO₂, NO₂ and smoke to be emitted from the diesel-powered equipment and dredgers being used during the construction phase. However, the number of such plant required on-site (land based and water based) will be limited and under normal operation, equipment with proper maintenance is unlikely to cause significant dark smoke emissions and gaseous emissions are expected to be minor. Thus, the AQOs are not expected to be exceeded. Notwithstanding, plant should be regularly maintained to minimise emissions.

3.6.2 The principal source of air pollution during the construction phase will be dust from the dusty activities as mentioned in Section 3.5.1. The impact of fugitive dust sources on air quality depends upon the quantity as well as the drift potential of the dust particles emitted into the atmosphere. Large dust particles (i.e. over 100 mm in diameter) will settle out near the source and particles that are between 30 and 100 mm in diameter are likely to undergo impeded settling. The main dust impacts are likely to arise from particles less than 30 mm in diameter, which have a greater potential to disperse over greater distances.

3.6.3 According to the USEPA AP-42, construction dust particles may be grouped into nine particle size classes. Their size ranges are 0 - 1 mm, 1 - 2 mm, 2 - 2.5 mm, 2.5 - 3 mm, 3 - 4 mm, 4 - 5 mm, 5 - 6 mm, 6 - 10 mm and 10 - 30 mm, and the percentage of particles in each class was estimated to be 4%, 7%, 4%, 3%, 7%, 5%, 4%, 17% and 49%, respectively.

3.6.4 The emission rates adopted in the WDII project assessment for different construction activities were based on the USEPA Compilation of Air Pollutant Emission Factors (AP-42), 5th edition. Table 3.5 gives the relevant clauses for emission factors used in this assessment in AP-42. Detailed calculation of emission rate is presented in Appendix 3.1.

Table 3.5 Emission Factors for Construction Activities

Construction Activities	Emission Rate (g/m^2/s)	Remark
Road Construction, Building Construction and Material Handling (as Heavy Construction)	E = 3.113426E-05	- 50% work area - 75% reduction by water suppression (watering four times a day) -USEPA AP-42 5^th ED., S.13.2.3.3
Wind Erosion	E = 1.347666E-06	- 50% work area - AP-42 5^th ED., S.11.9 Table 11.9.4

3.6.5 The Air Pollution Control (Construction Dust) Regulation specifies that dust suppression measures such as watering should be applied for the construction site. Dust emission from the site would be reduced by 75% if watering with complete coverage of active construction area four times a day. This assumption was adopted in the construction dust impact assessment.

3.6.6 As confirmed with the Project Proponent, 10 working hours per day (08:00-18:00) was assumed for the dusty construction works in the assessment. Wind erosion of open work sites would take place over the whole day.

3.6.7 The following summarises the construction activities within 500m study boundary from WDII DP2 during the construction stage. The locations of the different reclamation sites are shown in Figure 3.4.

Wan Chai Reclamation (WCR)

· Wan Chai Reclamation Stage 1 (WCR1)

· Wan Chai Reclamation Stage 2 (WCR2)

· Wan Chai Reclamation Stage 3 (WCR3)

· Wan Chai Reclamation Stage 4 (WCR4)

· New Ferry Pier Reprovisioning & Demolish Existing Pier

· Helipad Reprovisioning at HKCEC

· Roads

HKCEC Reclamation

· HKCEC Reclamation Stage 1 (Water Channel) (HKCEC1)

· HKCEC Reclamation Stage 2 (HKCEC2E & HKCEC2W)

· MTR Tunnel Crossing

· HKCEC Reclamation Stage 3 (HKCEC3E & HKCEC3W)

· Roads

Cross Harbour Watermains

· Submarine Pipeline

· Land Section

Tunnel Building and Installation

· Administration Building

· Central Ventilation Building

3.6.8 Beside the Wan Chai development, some construction activities would be undertaken within 500 m from the boundary of DP2. The construction period of whole CRIII Project is from February 2003 to September 2012. The interfacing of CRIII dusty construction activities would be from end 2008 to the 1^st quarter of 2012. The concurrent dusty construction activities undertaken within 500 m from the boundary of the DP2 are summarized as follows.

Construction of CWB Tunnel Under CRIII Project

· CWB Tunnel at Initial Reclamation Area East

· CWB Tunnel at Final Reclamation Area East

3.6.9 Based on the construction programme (Appendix 2.5), the construction period of road P2 and other roads under WDII DP2 would be from early 2014 to end 2015 which after the HKCEC Reclamation. The major dust generating activities in worst case scenario 5 as identified in Schedule 3 EIA Report included HKECE Reclamation and parts of Wan Chai Reclamation, which having more dusty activities and larger construction area than WDII DP2. Therefore, worst scenario 5 was considered to represent the worst case scenario for construction impacts of WDII DP2. The worst-case scenarios for the development works have been identified throughout the construction period and are shown in Table 3.6. The figures showing locations of dusty construction site areas for each scenario are presented in Figure A3.1 to A3.6 in Appendix 3.1.

Table 3.6 Different Major Dust Generating Activities in the Worst Case Scenario 5 during Construction Phase

Period	Mid 2013 – Early 2014
Worst month	Nov 2013
Activities	Scenario 5
1	TCBR3 – CWB Tunnel
2	TCBR4 – CWB Tunnel
3	Slip Rd 8 & Victoria Park Reprovisioning
4	TPCWAW – CWB Tunnel
5	WCR3 – CWB Tunnel
6	WCR4 – CWB Tunnel
7	HKCEC2E – Drainage
8	HKCEC2W – Drainage
9	HKCEC2E – CWB Tunnel
10	HKCEC2W – CWB Tunnel
11	HKCEC3E – CWB Tunnel
12	HKCEC3W – CWB Tunnel

3.6.10 Fugitive Dust Model (FDM) (1993 version) was used to assess potential dust impact from the construction works. The worst case meteorological data was used to predict the 1-hour and 24-hour average TSP concentrations at representative discrete ASRs close to the construction works. Since the construction activities would be undertaken at ground level and underground level, the worst dust impact on the ASRs would be at the ground floor of the ASRs. The height of 1.5m above ground, which is the breathing level of human, was adopted for the construction dust impact assessment. As there are some ASRs at the podium level, assessment for ASRs at 5m above ground was also included in the assessment. The meteorological data used in the model were:

· Wind speed: 1 m/s

· Wind direction: 360 wind direction

· Stability class: D (daytime) & F (night time)

· Surface roughness: 1m

· Mixing height: 500 m

3.6.11 Daily TSP concentrations were calculated as follows:

Daily TSP concentration = (number of working hour)/24 ´ (1-hour average maximum TSP concentration during working hours) + (number of non-working hour)/24 ´ (1-hour average maximum TSP concentration during non-working hours) + Background

3.6.12 The background TSP concentration of 77 mg/m³, based on the latest five years average monitoring data from EPD Central/Western monitoring station, was adopted as an indication of the future TSP background concentration. As the monitoring data in year 2001 and 2002 were below their respective minimum data requirement of 66% for number of data within the period, therefore, the annual average concentration of TSP was calculated based on the data in Year 2000 and 2003-2006.

Operational Phase

Vehicular Emission Impact (Open Road)

3.6.13 The overall traffic air quality impact for this Project would result from the following sources and the locations of portals and ventilation building emissions are indicated in Figure 3.5.

· background pollutant levels based on five years averaged monitoring data from EPD monitoring stations at Central/Western

· vehicle emissions from open sections of existing and planned road networks (e.g. Trunk Road) in WDII Project and CWB Project

· emissions from Central Ventilation Building and East Ventilation Building

· portal emissions from the existing Cross Harbour Tunnel (CHT)

· portal emissions from the planned deckovers along Road P2

· portal emissions from the existing deckover over Expo Drive

· portal emissions from the proposed deckover (New Atrium Link) between Expo Drive Central and Convention Avenue

3.6.14 The tunnel of Trunk Road Eastbound, CWB Slip Road 3 and Slip Road 1 would be provided with an extraction system with capacity that exceeds the maximum ventilation rate of the tunnel, and the in-tunnel emissions would be exhausted at the vent shaft of East Ventilation Building and Central Ventilation Building. Therefore, the tunnel exit portals of these two slip roads and trunk road eastbound would have zero portal emissions.

Background Concentration

3.6.15 The annual average concentrations of the pollutants measured at EPD’s Central / Western air quality monitoring station in the past five years were adopted as the background air quality within and adjacent to the Project area. As the monitoring data in year 2001 and 2002 were below their respective minimum data requirement of 66% for number of data within the period, therefore, the annual average concentration of NO₂, and RSP were calculated based on the data in Year 2000 and 2003 – 2006.

3.6.16 Table 3.7 summarises the annual average concentrations of the pollutants considered as background concentrations for the cumulative impact assessment.

Table 3.7 Annual Average Concentrations of Pollutants in Past Five Years

Pollutant	Annual Average Concentration in Past Five Years (2000, 2003-2006) at Central/Western Station (mg m^-3)
NO2	55
RSP	54

Vehicle Emissions from Open Sections of Existing and Planned Road Networks

3.6.17 The CALINE4 dispersion model was used for calculation of the 1-hour average NO₂, 24-hour average NO₂ and 24-hour average RSP concentrations. Open sections of existing and planned road networks within 500 m from the boundary of the WDII project area are considered in the model and are listed as follows:

· new roads in the WDII

· new roads in the Central Reclamation Phase III (CRIII)

· the Trunk Road & IECL

· the existing roads (including Island Eastern Corridor, Victoria Park Road, Gloucester Road, Harcourt Road, Causeway Road, Hennessy Road and Queensway).

3.6.18 The predicted morning peak hour traffic flows and vehicle mixes for the road networks in 2031, which is higher than the afternoon peak traffic flow, were used for the assessment of the worst-case air quality scenario. The projected 2031 morning peak hour traffic flows and vehicle compositions are attached in Appendix 3.2.

Fleet Average Emission Factors

Vehicle Classes

3.6.19 EMFAC-HK model was adopted to estimate the vehicle emission rates and inventories of exhaust, carbon monoxide, oxides of nitrogen and particulate matter.

3.6.20 The “vehicle fleet” refers to all motor vehicles operating on roads within this Study Area. The modelled fleet was broken down into 16 vehicle classes based on the information as shown in Table 4.4 (Registration and Licensing of Vehicle by Fuel Type) of the “Transport Monthly Digest (May 2006)” and the vehicle group classification was based on the definition in the “The Annual Traffic Census 2005 – Appendix F Vehicle Classification System”.

3.6.21 Referring to “Transport Monthly Digest (May 2006)”, there were only 0.5% of private car using diesel fuel. It was therefore assumed that all private cars would be grouped as “petrol private car” in the model in view of negligible value. The “Transport Monthly Digest (May 2006)” also indicated that there were 3% light good vehicle using petrol fuel. Besides, in accordance with the Up to Date Vehicle Licensed Number by Age and Technology Group Fractions launched on EPD’ website, the % of LGV under MC1 is less than 7% of the total vehicle of MC1. Moreover, refer to EPD’s Guideline on Modelling Vehicle Emissions Appendix 2 Implementation Schedule of Vehicle Emission Standards in Hong Kong, the implementation schedule of diesel LGV emission standards were later than petrol private car. As a conservative approach, all light good vehicles would be grouped as “diesel light good vehicle”. The 16 vehicle classes which were modelled in EMFAC-HK are summarized in Table 3.8.

Table 3.8 Vehicle Classes in EMFAC-HK Model

Vehicle Class	Description	Fuel Type	Gross Vehicle Weight
MC1	Petrol Private Cars (PC) & Light Goods Vehicles (LGV)	Petrol	all
MC3	Diesel Private Cars & Light Goods Vehicles<2.5t	Diesel	<=2.5t
MC4	Diesel Private Cars & Light Goods Vehicles 2.5-3.5t	Diesel	>2.5-3.5t
MC5	Public Light Buses	LPG, Diesel	all
MC6	Light Goods Vehicles >3.5t	Diesel	>3.5-5.5t
MC7	Medium & Heavy Goods Vehicles with GVW 5.5-15t	Diesel	>5.5-15t
MC8	Medium & Heavy Goods Vehicles with GVW >=15t	Diesel	>15t
MC10	Double Deck Franchised Buses	Diesel	all
MC11	Motor Cycles	Petrol	all
Taxi3	Taxi	LPG	all
Taxi4	Private Light Buses <3.5t	LPG, Diesel	<=3.5t
Taxi5	Private Light Buses >3.5t	LPG, Diesel	>3.5t
Taxi6	Non- franchised Buses <6.4t	Diesel	<=6.4t
Taxi7	Non- franchised Buses 6.4-15t	Diesel	>6.4-15t
Taxi8	Non- franchised Buses >15t	Diesel	>15t
Taxi10	Single Deck Franchised Buses	Diesel	all

Road Grouping

3.6.22 Based on different road speed limits in local road and trunk road, two sets of emission factors for the two road types were calculated. Gloucester Road, Cross Harbour Road and Central Wan Chai Bypass Trunk Roads (except Tunnel Section), with speed limit of 70kph, were grouped as trunk roads. Other roads within the Study Area, with design speed limit of 50kph, were grouped as local roads. The emission rates of the Trunk Roads Tunnel Section would be calculated by the tunnel engineer. Their calculations would not apply the fleet emission factor generated by EMFAC-HK model. Details of the classification of road type are presented in Appendix 3.3.

Input Assumptions in EMFAC-HK

3.6.23 The latest model version EMFAC-HK v1.2 provided by EPD was employed in this Study. The input parameters and model assumptions made in EMFAC-HK model are summarized as follows.

Modelling Modes

3.6.24 As suggested in EPD guideline, “Burden mode” which can provide hourly vehicular emissions according to the diurnal variations of traffic flow, temperature, relative humidity and speed, was selected for this Project. Both CVS and MVE17G CVS output file formats were produced.

Technology Fractions

Exhaust Technology Fractions

3.6.25 Each vehicle class had diverse technological factors in different years. According to the underlying assumption in EMFAC-HK, each vehicle class could be modelled by the individual behaviour of unique technology groups. Each technology group represented the same vehicle class had distinct emission control technologies, similar in-use deterioration rates and responded the same to repair. It means that the vehicles from the same class had the same emission standards or specific equipment installed on them (e.g. multi-port fuel injection, three-way catalyst, adaptive fuel controls, etc) which gave them the same performance.

3.6.26 According to the “EPD Guideline on Modelling Vehicle Emissions”, it mentioned that the existing vehicle emission control programmes were included in the EMFAC-HK. No other vehicle emission control measures were assumed in the assessment, thus the default data was adopted in the model.

Evaporative Technology Fractions

3.6.27 Evaporative technology fraction in the model was based on the default value.

Vehicle Population

3.6.28 As recommended in the “EPD Guideline on Modeling Vehicle Emissions”, the latest vehicle age distribution data provided in EPD’s website, that is, the Vehicle Population in Year 2003, was used except the population of diesel private car, taxi and public light bus.

3.6.29 After the implementation of stringent emission standard in 1998, there was no new certification of diesel private car registration in Hong Kong. Thus, the number of diesel private car was extracted and grouped into the “petrol private car”. Since diesel Taxi started to switch to LPG from Year 2001, 100% LPG taxi was therefore assumed for assessment years namely 2016 to 2031.

3.6.30 Environment, Transport and Works Bureau (ETWB) implemented an incentive scheme to encourage the early replacement of diesel light buses with LPG or electric ones since 2002. According to report published by EPD, around 80% of newly registered public light buses are operating on LPG. However, as a conservative approach, the ratio of LPG and diesel public light bus in 2003 was adopted for the vehicle population in future year in the assessment.

3.6.31 According to the above assumptions, vehicle population in Year 2016 is calculated and is presented in Appendix 3.4.

Accrual Rate

3.6.32 The default accrual rates in EMFAC-HK were estimated from the local mileage data adjusted to reflect the total vehicle-mile-travelled (VMT) for each vehicle class. The default value was used.

Diurnal Variation of Daily Trips and Daily Vehicle-Mile-Travelled (VMT)

Diurnal Variation of Daily Trips

3.6.33 The diurnal variation of daily trips was used to estimate the start emissions of petrol vehicles, thus the trips of other vehicles would be zero. The number of trips per day of petrol vehicle was equal to the number of cold starts per day. For IEC trunk road, CWB trunk road, some slip roads of CWB and Road P2, there would not be cold start at the middle of the above roads, thus, zero vehicle trip per day was assumed for those roads. For other roads, the diurnal variation of daily trips could be estimated based on the ratio of trip/VMT in the entire territory and the Study Area. For other roads, the number of vehicle trips was calculated by the following equation:

Vehicle Trip of Class 1 in the Study Area at hour 1 = Vehicle trip of Class 1 in the territory* at hour 1 ´ VMT for vehicle class 1 in the Study Area at hour 1 / VMT for vehicle class 1 in the territory

* where the trip and VMT in the territory could be read from the default data of EMFAC-HK model

Diurnal Variation of Daily Vehicle-Mile-Travelled (VMT)

3.6.34 Vehicle-mile-travelled (VMT) represents the total distance travelled on a weekday. The VMT was calculated by multiplying the number of vehicle which based on the forecasted hourly traffic flow in Year 2031 and the length of road travelled in the Study Area. The input in the model was by vehicle/fuel/hour.

3.6.35 The hourly profile of traffic flow was made reference to the “Annual Traffic Census 2005”. The major core station along Gloucester Road (No. 1028) was selected for representing the hourly profile of all roads within the Study Area. However, the same traffic breakdown in % would be applied to all hours.

3.6.36 Those assumptions of producing the hourly traffic flow and the traffic breakdown were approved by the Transport Department. The adopted daily trips and VMT in year 2031 are summarized in Appendix 3.5.

Hourly Temperature and Relative Humidity Profile

3.6.37 According to the information provided by the Hong Kong Observatory (HKO), there is no meteorological station at Hong Kong Island, except South Hong Kong Island. Thus, King’s Park (anemometer height of 90m) and Hong Kong Observatory (anemometer height of 74m) meteorological stations are the nearest station to the Project area. The characteristic of HKO meteorological station was considered to be more similar to the Study Area, thus the hourly temperature and relative humidity of HKO meteorological station were adopted for the model input.

Speed Fractions

3.6.38 The speed limits of each road were made reference to the Traffic AIDs from the Transport Department. Referring to the Traffic AIDs, the speed limits of all road links within the Study Area (except Trunk Road Tunnel Section) would not exceed 70kph. In the assessment, as a conservative approach, the speed limit of 70 kph was assumed for Trunk Road. Therefore, all vehicle classes were assumed to have the same speed profile in the model.

3.6.39 To simulate the effect of different road speed during the rush and non-rush hour, sensitivity test had been carried out. The design road speed limits were assumed for representing the situation during non-rush hour; while the vehicle speed of peak hour flow in Year 2031 would be representing the situation during rush-hour.

3.6.40 The flow speeds were calculated based on the peak traffic flow in Year 2031 and volume/capacity ratio of different road type. To obtain the speed fractions of each vehicle type, the vehicle speeds of each road link were first calculated and weighed by VMT. If the road links are in two-way direction, the vehicle speeds were calculated by weighing vehicle speeds of each direction. In addition, the design speed limits of Victoria Park Road (section between Top Glory Tower and Prospect Mansion) eastbound and westbound are different, as a conservative approach, this section would be grouped as local road.

3.6.41 In the model, same road speeds were applied to all hours to demonstrate the effect of using peak flow speed and design speed. Based on the comparison of the total daily emission rate, the worst road speed fraction was applied for predicting the vehicle emissions. Model year of 2031 was adopted in the sensitivity test.

3.6.42 From the results of the sensitivity test, it indicated that higher total daily NO_x and RSP emissions would be obtained at lower road speed, only the total daily NO_x emissions of trunk roads under design speed fractions were slightly greater than that under peak hour flow speed fractions. However, the dominant NO_x emissions were obtained on other roads under all scenarios. Thus, the peak hour flow speed in Year 2031 was applied to all hours for predicting the total daily emissions in this assessment as a conservative approach. The sensitivity test results are presented in Appendix 3.6.

Model Year

3.6.43 For the purpose of finding the worst emission year, 15 sets vehicle emissions based on the emission control schemes from Year 2016 to 2031 by using the same VMT in 2031 were produced. The emission standards of each vehicle class were the major factor influencing the vehicle exhaust emission. According to the implementation schedule of emission standards, the latest program was up to Year 2006 or 2009. Vehicles with better emission control (Euro IV and V) would replace the old pre-Euro diesel/petrol vehicles. The vehicle exhaust emissions of Year 2016 to Year 2031 were calculated. Sensitivity tests were undertaken to calculate the vehicle exhaust emissions in different year by using the VMT of each road category and the flow speed fractions in Year 2031. By using the peak hour flow speed in Year 2031 at all hours, the total daily NO_x emissions by 16 vehicle classes in different vehicle exhaust emission year from 2016 to 2031 were summarized in Appendix 3.7.

3.6.44 Comparing the total daily NO_x and RSP emissions under different vehicle exhaust emission years from Year 2016 to 2031, the highest vehicle emissions were found in Year 2016 using emission control scenario and were decreased from Year 2016 to 2031. Therefore, as a conservative approach, the emissions using emission control scenario in Year 2016 were adopted for this Study.

3.6.45 As a conservative approach, the hourly emissions in Year 2016 were first divided by the number of vehicles and the distance travelled to obtain the emission factors in gram per miles per vehicle. The calculated maximum vehicle emission factors were then selected for incorporation into the air dispersion model. These conservative vehicle emission factors together with the forecasted Year 2031 peak traffic flow were adopted in this air quality impact assessment. The calculation of fleet vehicle emission is presented in Appendix 3.8.

3.6.46 The calculated vehicular emissions for different vehicle categories were listed in Table 3.9.

Table 3.9 Emission Factors for Year 2016 for Different Vehicle Classes (EMFAC-HK)

Vehicle Class	Description	Emission Factors for 2016, g/mile-veh
		NOx		RSP
		Trunk Road	Other Road	Trunk Road		Other Road
MC1	Petrol Private Cars (PC) & Light Goods Vehicles (LGV)	0.1433	0.1545		0.0047		0.0063
MC3	Diesel Private Cars & Light Goods Vehicles<2.5t	0.4012	0.4157		0.1284		0.1516
MC4	Diesel Private Cars & Light Goods Vehicles 2.5-3.5t	0.2642	0.2702		0.0813		0.0896
MC5	Public Light Buses	0.1208	0.1163		0.0887		0.0835
MC6	Light Goods Vehicles >3.5t	2.1532	2.2242		0.1547		0.1836
MC7	Medium & Heavy Goods Vehicles with GVW 5.5-15t	4.4177	4.6047		0.2553		0.3066
MC8	Medium & Heavy Goods Vehicles with GVW >=15t	5.4535	6.0203		0.3635		0.4121
MC10	Double Deck Franchised Buses	2.7890	2.8216		0.0808		0.0902
MC11	Motor Cycles	1.1216	1.0611		0.0487		0.0503
Taxi3	Taxi	0.2376	0.2585		0.0188		0.0252
Taxi4	Private Light Buses <3.5t	0.0000^#	0.0000^#		0.0000^#		0.0000^#
Taxi5	Private Light Buses >3.5t	0.3270	0.3390		0.1972		0.2421
Taxi6	Non- franchised Buses <6.4t	0.0000^#	0.0000^#		0.0000^#		0.0000^#
Taxi7	Non- franchised Buses 6.4-15t	3.7716	4.7213		0.1433		0.1790
Taxi8	Non- franchised Buses >15t	7.1778	3.6599		0.1433*		0.1790*
Taxi10	Single Deck Franchised Buses	2.5173	2.4728		0.1631		0.1126

Note:

^# - Since there is no private light buses <3.5t and non-franchised buses <6.4t travelled within the study area, the calculated emission factors for these two vehicle classes are zero.

* - Since the VMT of non-franchised buses >15t is too small (only 4 vehicles within the study area in Year 2031), the calculated RSP emission factor for this vehicle class is zero in the EMFAC output model file. As a conservative approach, the RSP emission factor of non-franchised buses 6.4-15t would be adopted for non-franchised buses >15t.

Model Assumptions for Open Road Vehicle Emission

3.6.47 In order to calculate the cumulative pollutant concentrations from different sources using different models (CALINE4 and ISCST3) in the later part of the assessment, the dispersion modelling was undertaken assuming 360 predetermined meteorological conditions and the highest predicted pollutant concentration amongst the 360 wind directions were identified. The following summarises the meteorological conditions adopted in the air quality modelling using the CALINE4 model:

· Wind speed : 1 m s^-1

· Wind direction : 360 wind directions

· Resolution : 1°

· Wind variability : 24°

· Stability class : D

· Surface roughness : 1 m

· Mixing height : 500 m

3.6.48 The CALINE4 model calculates hourly concentrations only. With reference to the Screening Procedures for Estimating the Air Quality Impact of Stationary Source (EPA-454/R-92-019), a conversion factor of 0.4 is used to convert the 1-hour average concentrations to 24-hour average concentrations.

3.6.49 Secondary air quality impacts arising from the implementation of roadside noise barriers and enclosures were also incorporated into the air quality model. For the proposed cantilever noise barrier and noise semi-enclosure along the IECL (as shown in Figures 4.11 and 4.12), it was assumed that dispersion of the traffic pollutants would have effect similar to assuming that traffic pollutants would be emitted from the top of the canopies and semi-enclosures at a point close to the central divider of the road. A figure showing the concerned open road sections considered in the model and the calculation of open road emissions are summarised in Appendix 3.9.

Portal and Ventilation Building Emissions

3.6.50 The Industrial Source Complex Short Term (ISCST3) dispersion model was used to predict the portal and ventilation building emissions.

3.6.51 The followings are the portal and ventilation building emissions in and around the study area:

· tunnel portal and ventilation building emissions from the tunnel section of the Trunk Road

· tunnel portal emissions from the existing CHT

· portal emission from deckover over Expo Drive

· portal emission from proposed deckover (New Atrium Link) between Expo Drive Central and Convention Avenue

· portal emissions from the planned deckovers along Road P2.

3.6.52 Three ventilation buildings have been proposed for Trunk Road to discharge the polluted tunnel air:

· West Ventilation Building (WVB): for extracting polluted tunnel air from the Trunk Road Westbound

· Central Ventilation Building (CVB): for extracting polluted tunnel air from the Trunk Road Westbound, Trunk Road Eastbound, Slip Road 1 and Slip Road 3

· East Ventilation Building (EVB): for extracting polluted tunnel air from the Trunk Road Eastbound.

3.6.53 The location of the WVB is outside the study area of this EIA, therefore, only emissions from the CVB and EVB were considered in this assessment. The portal emissions from Trunk Road Eastbound and CWB slip roads, and ventilation building emissions provided by the ventilation design engineers are summarised in Table 3.10. Portal emissions from other existing / planned deckovers predicted by EMFAC model are also presented in Table 3.10.

Table 3.10 Portal and Ventilation Building Emissions

Type	NOX (g/s)	RSP (g/s)
Portal Emission
Trunk Road Eastbound	0	0
Slip Road 1	0	0
Slip Road 2 under HKCEC Atrium Link Deckover	1.455E-02	7.956E-04
Slip Road 3	0	0
Cross Harbour Tunnel	1.110E+00	6.828E-02
Expo Drive Central	1.024E-02	5.787E-04
P2 Road (Eastbound) Under HKCEC Atrium Link Deckover	9.892E-03	6.026E-04
P2 Road (Westbound) Under HKCEC Atrium Link Deckover	1.319E-02	8.972E-04
Central Wan Chai Bypass (Westbound) Under HKCEC Atrium Link Deckover	8.654E-03	6.781E-04
Convention Avenue Under HKCEC Atrium Link Deckover	1.527E-02	9.951E-04
Expo Drive	6.476E-02	4.335E-03
P2 Road between Tim Wa Ave, and Tim Mei Ave	2.060E-02	1.482E-03
Ventilation Building
East Ventilation Building (Trunk Road Eastbound)	2	2.258E-02^#
Central Ventilation Building	3.966	3.003E-01

Note: # Electrostatic precipitator will be installed, dust removal efficiency of 80% has been considered in the calculation.

3.6.54 The preliminary design of the ventilation buildings (including minimum mid-discharge heights, exhaust directions, exhaust area of ventilation buildings and exit velocity) is summarised in Table 3.11. The tunnel ventilation schematic diagram is indicated in Appendix 3.15. For a worst case scenario in the air quality assessment, the minimum height of stack was used in modelling.

Table 3.11 Design of Ventilation Buildings

	Cross-sectional area of stack (m^2)	Exit velocity (m s^-1)	Minimum mid-discharge height (meter above ground)	Exhaust direction
East Ventilation Building (EVB) - Vent shaft at the breakwater	94	8	16.25	Inclined 45 degree upward (discharge towards sea direction)
Central Ventilation Building (CVB)	219	8	17.5	Vertical

3.6.55 The portal emissions (NO₂, and RSP) of the existing CHT, the existing underpasses and the planned deck-over were calculated based on the vehicle emission derived from the EMFAC model and vehicle flows in 2031. A figure showing the locations of the tunnel/enclosures portal emissions and ventilation buildings, and the calculations of portal emissions is attached in Appendix 3.10.

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

3.6.57 As mentioned in Section 3.6.48, 360 predetermined meteorological conditions were used. The following summarises the meteorological conditions adopted in the air quality modelling using the ISCST3 model:

· Wind speed : 1 m s^-1

· Wind direction : 360 wind directions

· Resolution : 1°

· Stability class : D

· Mixing height : 500 m

· Emission temperature : 7° above ambient

3.6.58 For the calculation of the NO₂ concentrations, the vehicular emission factor for NO_x was used and the conversion factor from NO_x to NO₂ for all roads and portal emissions of tunnels and ventilation building was based on the Ambient Ratio Method (assuming 20% of NO_x to be NO₂) which is one acceptable approach as stipulated in EPD “Guidelines on Choice of Models and Model Parameters”. The locations of open road emission sources, portal and ventilation buildings are shown in Appendix 3.11.

Cumulative Impact

3.6.59 As mentioned in Section 3.6.15, background pollutant levels within and adjacent to the WDII, vehicle emissions from open sections of the existing and planned road networks, tunnel portal and ventilation building emissions from the Trunk Road, and portal emissions from the existing CHT, the existing underpasses and the planned deckovers will contribute to the cumulative impact.

3.6.60 The pollutant concentrations at the ASRs at different wind directions (1 degree resolution) were predicted by both CALINE4 and ISCST3 models, where

· the CALINE4 model was used to predict the open road emissions from the existing and planned road networks

· the ISCST3 model was used to predict all the portal emissions (Trunk Road, CHT, existing underpasses and planned deckover) and ventilation shaft emissions.

3.6.61 The cumulative pollutant concentrations at the ASRs at each specific wind direction were calculated by summing the results from the two models. The highest pollutant concentrations at the ASRs amongst the 360 wind directions were identified as the worst predicted cumulative pollutant concentrations.

Vehicular Emission Impact (Inside the deckover of HKCEC Atrium Link)

3.6.62 Under the proposed deckover for planned HKCEC Atrium Link, the road considered in the assessment including (i) Expo Drive Central; (ii) CWB Slip Road 2; (iii) Road P2 eastbound; (iv) Road P2 westbound; (v) CWB Slip Road 3 including tunnel section; and (vi) Convention Avenue.

3.6.63 As Convention Avenue and Expo Drive Central are located far away from the other four road sections (Road P2 Eastbound & Westbound and CWB Slip Road 2 & Slip Road 3), good mixing of air pollutants from Road P2 and CWB under the deckover would be anticipated. However, mixing of vehicular emissions from Convention Avenue and Expo Drive Central would not be expected, so these two road sections were considered as separate tunnel sections in the assessment. In total, three separated tunnel sections under the deckover were assumed for the in-tunnel air quality model run:

(i) Deckover along Expo Drive Central – emissions contributed from Expo Drive Central

(ii) Deckover along Road P2 Eastbound & Westbound and CWB Slip Road 2 & Slip Road 3 - emissions contributed from Road P2 Eastbound & Westbound, CWB Slip Road 2 & Slip Road 3 (open road section under the deckover)

(iii) Deckover along Convention Avenue – emissions contributed from Convention Avenue

3.6.64 As the representative ASRs are located along the Convention Avenue, except tunnel portal emission from CWB westbound was included in the emission of its “tunnel” tube, the tunnel portal emission was also included in the emissions from “tunnel” tube of Convention Avenue, so as to provide highly conservative results. No ventilation system was assumed.

3.6.65 The air quality under the planned deckover on HKCEC Atrium Link was calculated based on the empirical formulas of fluid dynamics. A conversion factor of 12.5% including tailpipe NO₂ emission (taken as 7.5% of NO_x) plus 5% of NO₂/NOx for tunnel air recommended in PIARC for air expelled from the tunnel was taken in this assessment as the inside tunnel conversion factor. Two scenarios were considered in the assessment, i.e. normal traffic flow condition and congested traffic flow condition. It was assumed that under normal traffic flow condition, the vehicles are at a speed of 50 kph, whereas under congested mode, the vehicles are at a speed of 10 kph, the separation between vehicles is assumed to be 1 m. Different emission factors for normal condition (which presented in Table 3.9) and congestion condition (emission factor with traffic speed at 10kph) are used to calculate the air quality under the deckover. The calculation of in-tunnel air quality for section of deckover on planned HKCEC Atrium Link and emission factor of 10 kph are presented in Appendix 3.12. As per the discussion in Section 3.5.7, only NO₂ was assessed for the existing/planned deckover.

Level of Uncertainty in the Assessment

Construction Dust and Road Traffic Emission Impact Assessments

3.6.66 The emission rates adopted in the construction dust impact assessment are in accordance with the USEPA Compilation of Air Pollutant Emission Factors (AP-42), which had previously been applied in similar situations in other EIA studies.

3.6.67 The Fugitive Dust Model (FDM) for construction dust impact assessment, Caline4 model for open road traffic emission impact assessment, and Industrial Source Complex Short Term 3 (ISCST3) dispersion model for portal/vent shaft emission impact assessment are generally accepted models for use in assessing construction dust impacts and road traffic emission impacts.

3.6.68 There would be some limitations such as the accuracy of the predictive base data for future conditions e.g. traffic flow forecasts, plant inventory for the proposed construction works and sequences of construction activities. Uncertainties in the assessment of impacts have been considered when drawing conclusions from the assessment.

3.7 Prediction and Evaluation of Environmental Impacts

Construction Phase

3.7.1 Construction activities for WDII, Trunk Road and CRIII Project will cause a cumulative dust impact on the nearby sensitive receivers.

3.7.2 Since most of the construction activities are at ground level, the likely cumulative dust impacts of the WDII on the ASRs at 1.5 m and 5 m above ground were modelled.

3.7.3 The predicted cumulative maximum 1-hour average TSP and 24-hour average TSP during construction are shown in Tables 3.12 - 3.13.

Table 3.12 Predicted Cumulative Maximum 1-hour Average TSP Concentrations at 1.5m & 5m above ground

ASR	Predicted Concentration (mg m^-3) *
	1.5mAG	5mAG
A25	172	174
A26	252	248
A27	199	199
A28	226	230
A29	408	364
A30	277	266
A31	193	192
A32	421	367
A33	366	311
A34	328	308
A35	278	257
A36	200	199
A37	358	344
A38	214	219
A39	190	190
A40	148	151
A70	174	180

Note: * Background concentration is included.

Hourly TSP criteria (EIAO-TM): 500 mg m^-3

Table 3.13 Predicted Cumulative Maximum 24-hour Average TSP Concentrations for at 1.5m & 5m above ground

ASR	Predicted Concentration (mg m^-3) *
	1.5mAG	5mAG
A25	121	122
A26	158	154
A27	134	133
A28	147	147
A29	229	204
A30	169	162
A31	131	129
A32	235	206
A33	210	183
A34	193	181
A35	168	158
A36	134	132
A37	207	199
A38	143	144
A39	132	131
A40	110	111
A70	124	126

Note: * Background concentration is included.

24-hour TSP criteria (AQO): 260 mg m^-3

3.7.4 Based on results indicated in Tables 3.12 and 3.13, no exceedance of 1-hour average and 24-hour average TSP guideline and AQO is predicted at the ASRs at 1.5m and 5m above ground. The predicted cumulative maximum 1-hour average and 24-hour average TSP concentration contours at 1.5m and 5.m above local ground are shown in Figures 3.10 and 3.16. Exceedances of the 1-hour average TSP guideline of 500 mg/m³ and the 24-hour average TSP AQO of 260 mg/m³ are noted in some areas at 1.5m above ground including:

Exceedance of the 1-hour average TSP guideline of 500 mg/m³

sea area, area underneath New Atrium Link (Extension of HKCEC), area in the vicinity of existing Wan Chai Pier and nearby PTI, area next to Servicemen’s Guides Association

Exceedance of the 24-hour average TSP AQO of 260 mg/m³

sea area, part of waterfront near Causeway Bay Flyover, area underneath New Atrium Link (Extension of HKCEC), area in the vicinity of existing Wan Chai Pier and nearby PTI, area next to Servicemen’s Guides Association

3.7.5 Exceedances were noted at the above identified areas but they are not the ASRs and no any air sensitive areas are located within these exceedance areas.

Operational Phase

Traffic Emission Impact (Open Road)

3.7.6 Taking into account vehicle emissions from open road networks, portal and ventilation building emissions from the Trunk road, portal emissions from the CHT, existing underpasses and planned deckovers, and the background pollutant concentrations, the cumulative 1-hour average NO₂, 24-hour average NO₂ and 24-hour average RSP concentrations were predicted and the highest pollutant concentrations at each ASR under the worst wind directions were calculated.

3.7.7 In order to determine the potential impacts on the upper level receivers, pollutant concentrations at various levels (1.5 m, 5m, 10 m, 20m, 30m and 40m above ground) were calculated. Tables 3.14, 3.15 and 3.16 summarise the predicted cumulative maximum 1-hour average NO₂, 24-hour average NO₂ and 24-hour average RSP concentrations at different elevations respectively.

Table 3.14 Predicted Cumulative Maximum 1-hour Average NO₂ Concentrations at the Representative ASRs at Different Elevations

ASRs	Predicted 1-hour averaged Concentration (mg m^-3) *
	1.5m AGL	5m AGL	10m AGL	20m AGL	30m AGL	40m AGL
A25	100	95	87	87	87	87
A26	79	78	77	77	77	77
A27	81	78	77	77	77	77
A28	81	80	78	78	78	78
A29	77	76	75	75	75	75
A30	81	79	77	77	77	77
A31	85	82	79	79	79	79
A32	83	82	80	79	79	79
A33	77	75	75	74	74	74
A34	74	74	74	74	73	73
A35	79	79	78	78	78	78
A36	96	93	88	88	88	88
A37	94	87	83	83	82	82
A38	98	94	89	88	88	87
A39	95	94	93	93	91	90
A40	129	124	113	113	112	112
A70	75	74	73	73	73	73
A71	79	78	77	77	77	77
A73	104	89	81	81	81	81
A81	89	86	82	82	82	82
A99	86	84	80	80	80	80

Note: * Background concentrations are included.

1-hr NO₂ criteria (AQO): 300 mg m^-3

Table 3.15 Predicted Cumulative Maximum 24-hour Average NO₂ Concentrations at the Representative ASRs at Different Elevations

ASRs	Predicted 24-hour averaged Concentration (mg m^-3) *
	1.5m AGL	5m AGL	10m AGL	20m AGL	30m AGL	40m AGL
A25	73	71	68	68	68	68
A26	64	64	64	64	64	64
A27	65	64	64	64	64	64
A28	66	65	64	64	64	64
A29	64	64	63	63	63	63
A30	65	65	64	64	64	64
A31	67	66	65	65	65	65
A32	66	66	65	65	65	65
A33	64	63	63	63	63	63
A34	63	63	62	62	62	62
A35	65	64	64	64	64	64
A36	71	70	68	68	68	68
A37	71	68	66	66	66	66
A38	72	70	68	68	68	68
A39	71	71	70	70	70	69
A40	85	83	78	78	78	78
A70	63	63	62	62	62	62
A71	65	64	64	64	64	64
A73	75	69	66	66	66	66
A81	69	67	66	66	66	66
A99	67	67	65	65	65	65

Note: * Background concentrations are included.

24-hr NO₂ criteria (AQO): 150 mg m^-3

Table 3.16 Predicted Cumulative Maximum 24-hour Average RSP Concentrations at the Representative ASRs at Different Elevations

ASRs	Predicted 24-hour averaged Concentration (mg m^-3) *
	1.5m AGL	5m AGL	10m AGL	20m AGL	30m AGL	40m AGL
A25	59	58	58	58	58	58
A26	57	57	57	57	57	57
A27	57	57	56	56	56	56
A28	57	57	57	57	57	57
A29	57	56	56	56	56	56
A30	57	57	57	57	57	57
A31	57	57	57	57	57	57
A32	57	57	57	57	57	57
A33	57	56	56	56	56	56
A34	56	56	56	56	56	56
A35	57	57	57	57	57	57
A36	59	58	58	58	58	58
A37	59	58	57	57	57	57
A38	59	59	58	58	58	58
A39	59	59	59	59	58	58
A40	62	62	61	61	61	60
A70	56	56	56	56	56	56
A71	57	57	56	56	56	56
A73	60	58	57	57	57	57
A81	58	58	57	57	57	57
A99	58	57	57	57	57	57

Note: * Background concentrations are included.

24-hr RSP criteria (AQO): 180 mg m^-3

3.7.8 Based on the above prediction, no exceedance of the 1-hour average NO₂, 24-hour average NO₂ and 24-hour average RSP AQOs would occur at any representative ASR in the Study Area. From the results, it is found that the maximum pollutant concentrations would occur at 1.5m above ground (the lowest assessment height). The predicted cumulative maximum hourly average NO₂, 24-hour average NO₂ and RSP concentration contours at 1.5m above local ground are shown in Figures 3.18 to 3.20.

Vehicular Emission Impact (Inside the deckover of HKCEC Atrium Link)

3.7.9 For the air quality assessment inside the planned deckover on future HKCEC Atrium Link, the predicted maximum NO₂ concentrations under normal traffic flow and congested traffic flow would be 114 mg/m³ and 130 mg/m³ respectively, and would comply with the Tunnel Air Quality Objective (1800 mg/m³). Detailed calculations and results are presented in Appendix 3.12.

3.8 Mitigation of Adverse Environmental Impacts

Construction Phase

3.8.1 As shown in Tables 3.12 and 3.13, the cumulative maximum 1-hour average and 24-hour average TSP concentrations are predicted to comply with the TSP criteria at all representative ASRs with watering on the active work area four times a day. The area within study area of WDII DP2 would also meet the TSP criteria. In order to further ensure compliance with the AQOs at the ASRs at all time, requirements of the Air Pollution Control (Construction Dust) Regulation shall be adhered to during the construction period. In addition, the following mitigation measures, good site practices and a comprehensive dust monitoring and audit programme are recommended to minimise cumulative dust impacts.

· Strictly limit the truck speed on site to below 10 km per hour and water spraying to keep the haul roads in wet condition;

· Watering during excavation and material handling;

· Provision of vehicle wheel and body washing facilities at the exit points of the site, combined with cleaning of public roads where necessary; and

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

Operational Phase

Traffic Emission Impact

3.8.2 The predicted air quality impacts on the ASRs are within the Air Quality Objectives. Exceedances of AQO criteria were predicted at some areas in the vicinity of Cross Harbour Tunnel, however, there would be no air sensitive uses in these areas. No mitigation measures will be required during the operation phase.

3.9 Evaluation of Residual Impacts

Construction Phase

3.9.1 With the implementation of the proposed mitigation measures and the dust suppression measures stipulated in Air Pollution Control (Construction Dust) Regulation during the construction phase, no adverse residual air quality impact would be expected.

Operational Phase

3.9.2 No adverse residual traffic emission impact was predicted.

3.10 Environmental Monitoring and Audit

Construction Phase

3.10.1 With the implementation of the proposed dust suppression measures, good site practices and dust monitoring and audit programme, acceptable dust impact would be expected at the ASRs. Details of the monitoring requirements such as monitoring locations, frequency of baseline and impact monitoring are presented in the stand-alone EM&A Manual.

Operational Phase

3.10.2 Since the predicted air quality due to traffic emission in the study area complies with the AQO, no environmental monitoring and audit is proposed.

3.11 Conclusion

Construction Phase

3.11.1 During construction of Road P2 and other roads under WDII DP2, materials handling and wind erosion were identified as the major dust sources. The worst case scenario have been identified and assessed. The findings of the construction phase air quality assessment indicate that no exceedences of the 1-hour and 24-hour total TSP criteria are predicted at ASRs in the vicinity of the construction sites. In order to ensure compliance with the TSP criteria at the ASRs at all times, the dust suppression measures and requirements of the Air Pollution Control (Construction Dust) Regulation should be adhered to during the construction period. In addition, a comprehensive dust monitoring and audit programme are recommended to ensure the effective implementation of dust suppression measures.

Operational Phase

3.11.2 The cumulative effect arising from the background pollutant levels within and adjacent to the WDII development area, vehicle emissions from open road networks, tunnel portal and ventilation building emissions from the Trunk Road, tunnel portal emissions from the CHT and portal emissions from existing underpasses and planned deckovers have been assessed. Results show that the predicted air quality at the ASRs would comply with the AQO. No mitigation measures are requried. The air quality inside the planned deckovers at the HKCEC Atrium Link, Road P2 and Expo Drive would also comply with EPD in-tunnel air quality standards.