CONTENTS

3 Air Quality Impact.. 3-1

3.1 Introduction.. 3-1

3.2 Relevant Legislation, Standards and Guidelines. 3-1

3.3 Baseline Condition.. 3-2

3.4 Air Sensitive Receivers. 3-3

3.5 Identification of Key Air Pollutants. 3-5

3.6 Assessment Methodology.. 3-8

3.7 Prediction and Evaluation and Environmental Impacts. 3-16

3.8 Mitigation Measures. 3-17

3.9 Residual Impacts. 3-20

3.10 Monitoring and Audit Requirement.. 3-20

3.11 Conclusion.. 3-20

TABLES

Table 3.1 Hong Kong Air Quality Objectives. 3-1

Table 3.2 5-year Averaged Annual Background Concentration of Air Pollutants recorded at Sham Shui Po Station by EPD for the Period of 2015-2019.. 3-2

Table 3.3 Air Pollutants Concentrations at the Project Site in 2020 Predicted from PATH-2016 Model 3-3

Table 3.4 Representative Air Sensitive Receivers. 3-4

Table 3.5 Key Concurrent Projects for Construction Dust Assessments. 3-7

Table 3.6 Individual Construction Activities during Construction.. 3-9

Table 3.7 Emission Factor for Dust Emitting Construction Activity.. 3-10

Table 3.8 Preliminary Design of Ventilation System at the Portal 3-12

Table 3.9 Vehicular Classes in EMFAC-HK Model 3-12

Table 3.10 Summary of Cumulative Dust Emission Concentration (Unmitigated Scenario). 3-16

Table 3.11 Summary of Dust Suppression Measures. 3-17

Table 3.12 Summary of Cumulative Dust Emission Concentration (Mitigated Scenario). 3-18

3 Air Quality Impact

3.1 Introduction

3.1.1 This Section provides an evaluation of the potential air quality impacts arising from the construction and operation of the proposed Project, with accordance to the EIA Study Brief No. ESB-317/2019, Appendix B Clause 3(ii) of the EIA Study Brief. Additional modelling guidelines is taken according to the Appendix B-1 of the EIA Study Brief. Mitigation measures have been proposed if considered necessary.

3.2 Relevant Legislation, Standards and Guidelines

3.2.1 The relevant legislations, standards and guidelines applicable to the assessment of air quality impacts include.

· Air Pollution Control Ordinance (APCO) (Cap 311);

· Air Pollution Control (Construction Dust) Regulation;

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

· EIAO-TM Annex 4 and Annex 12; and

· Technical Circular (Works) No. 13/2020 of Development Bureau (DEVB TC(W) No. 13/2020)

3.2.2 The criteria for evaluating air quality impacts and the guidelines for air quality assessment are laid out in Annex 4 and Annex 12 of the TM-EIAO. The principal legislation for the management of air quality in Hong Kong is the Air Pollution Control Ordinance (APCO) (Cap. 311). The Air Quality Objectives (AQOs) stipulating statutory ambient limits for air pollutants and the maximum allowable number of exceedances over specific averaging periods are presented in Table 3.1.

Table 3.1 Hong Kong Air Quality Objectives

Air Pollutant	Averaging Time	Concentration (mgm^-3) ^(a)	No. of Exceedances Allowed per Year
Sulphur Dioxide (SO2)	10 minutes	500	3
	24-hours	125	3
Respirable Suspended Particulates (RSP) ^(b)	24-hours	100	9
	Annual	50	-
Fine Suspended Particulates (FSP) ^(c)	24-hours	75	9
	Annual	35	-
Nitrogen Dioxide (NO2)	1-hour	200	18
	Annual	40	-
Ozone (O3)	8-hours	160	9
Carbon Monoxide (CO)	1-hour	30,000	-
	8-hours	10,000	-
Lead	Annual	0.5	-
Notes: (a) Measured at 298K and 101.325 kPa. (b) Suspended particles in air with a nominal aerodynamic diameter of 10 μm or less (c) Suspended particles in air with a nominal aerodynamic diameter of 2.5 μm or less

3.2.3 A maximum hourly TSP level of 500 mg m^-3 at Air Sensitive Receivers (ASRs) is also stipulated in Section 1, Annex 4 of the EIAO-TM to assess potential construction dust impacts. The measures stipulated in the Air Pollution Control (Construction Dust) Regulation should also be followed whenever possible to ensure that any dust impacts are reduced.

3.2.4 Annex 4 of the EIAO-TM has also stipulated that the odour level at a sensitive receiver should not exceed 5 odour units based on an averaging time of 5 seconds for odour prediction assessment.

3.2.5 The Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation requires 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.

3.2.6 DEVB TC(W) No. 13/2020 stimulated the public works contracts will be required to observe the requirements of timely application of temporary electricity to minimise the use of diesel generators.

3.3 Baseline Condition

Prevailing Air Quality

3.3.1 Sham Shui Po Air Quality Monitoring Station (AQMS) is the nearest monitoring station operated by EPD to the Project Site. Air quality data collected in Sham Shui Po AQMS during the period of 2015 to 2019 were examined with the average period value presented in Table 3.2. It is noted that annual NO₂ emission for all five years did not complied with AQOs requirement. The 8-hour concentration of O₃ in 2019 was exceeded the relevant AQO. The concentrations of SO₂ and CO were in relatively low level and well within the AQOs during 2015-2019.

Table 3.2 5-year Averaged Annual Background Concentration of Air Pollutants recorded at Sham Shui Po Station by EPD for the Period of 2015-2019

Air Pollutant	Averaging Time	AQO^(a)	Data Description	UNIT	Year ^(b) (c)					5-year mean
					2015	2016	2017	2018	2019
Fine Suspended Particulates (FSP) (PM 2.5)	24-hour	75 (9)	10th Max.	μg m^-3	58	48	46	41	36	46
	Annual	35	-	μg m^-3	25	23	21	21	18	22
Respirable Suspended Particulates (RSP) (PM10)	24-hour	100 (9)	10th Max.	μg m^-3	80	77	72	59	65	71
	Annual	50	-	μg m^-3	38	35	33	33	33	34
Sulphur Dioxide (SO2)	10-minute	500 (3)	4th Max.	μg m^-3	186	126	76	98	41	105
	24-hour	125 (3)	4th Max.	μg m^-3	28	26	25	21	14	23
Nitrogen Dioxide (NO2)	1-hour	200 (18)	19th Max.	μg m^-3	215	161	194	152	176	180
	Annual	40	-	μg m^-3	63	58	54	49	48	54
Ozone (O3)	8-hour	160 (9)	10th Max.	μg m^-3	143	106	130	147	164	138

Notes: (a) Values in ( ) indicate the number of exceedances allowed per year

(b) Data extracted from EPD Website (http://www.aqhi.gov.hk/en/download/air-quality-reportse469.html?showall=&start=1)

(c) Bolded values represent exceedances of the AQOs.

3.3.2 The tentative construction programme of the Project will commence in 2022 and complete by 2027. As a general reference, the future prevailing background concentrations can be made reference to the EPD’s Pollutants in the Atmosphere and the Transport over Hong Kong-2016 (PATH-2016) modelling results for Year 2020. 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. PATH is set up on a three-dimensional grid system with horizontal nesting. The PATH results for the Project site in 2020 are summarised in Table 3.3.

Table 3.3 Air Pollutants Concentrations at the Project Site in 2020 Predicted from PATH-2016 Model

Air Pollutant	Averaging Time	AQO	Data Description	UNIT	Predicted Background Concentration in Year 2020 ^[1]
					(41, 36)	(42, 36)
FSP ^[2]	24-hour	75 (9)	10th Max.	μg m^-3	53	52
	Annual	35	-	μg m^-3	22	22
RSP ^[3]	24-hour	100 (9)	10th Max.	μg m^-3	70	71
	Annual	50	-	μg m^-3	31	31
NO2	24-hour	200	19th Max	μg m^-3	115	112
	Annual	40	-	μg m^-3	19	17

Notes:

1) Extracted from PATH grids (41, 36) and (42, 36) in which the Project site is located.

2) With reference to EPD’s Guidelines on the Estimation of PM2.5 for Air Quality Assessment in Hong Kong, the following conservative formulae are adopted to calculate background FSP concentration from the RSP concentration extracted from the PATH model:

· Annual (µg/m³): FSP = 0.71 × RSP

· Daily (µg/m³): FSP = 0.75 × RSP

3) With reference to the EPD’s Guidelines on Choice of Models and Model Parameters, PATH-2016’s output of RSP concentration is adjusted as follows:

· 10^th highest daily RSP concentration: add 26.5 µg/m³

· Annual RSP concentration: add 15.6 µg/m³

3.4 Air Sensitive Receivers

3.4.1 In accordance with Annex 12 of the Technical Memorandum on Environmental Impact Assessment Process (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 classified as air sensitive receivers (ASRs).

3.4.2 Representative existing, planned and committed ASRs within the Study Area have been identified based on the topographic maps supplemented by site surveys, Outline Zoning Plans (OZPs), other published plans in the vicinity of the Project Site. Reference has been made to the Approved Kowloon Tong Outline Zoning Plan No. S/K18/21, the Draft Wang Tau Hom & Tung Tau Outline Zoning Plan No. S/K8/21 and the Approved Tsz Wan Shan, Diamond Hill & San Po Kong Outline Zoning Plan No. S/K11/29 in identifying appropriate ASRs. In addition, site visits have been conducted to verify the ASRs and its assessment point.

3.4.3 Clause 3.4.3.2 of the EIA Study Brief prescribes the Study Area which is generally defined by a distance of 500 m from boundary of the works areas of the Project as identified in the EIA. Figure 3.1 highlights the ASRs within the 500m quantitative assessment area for detailed quantitative assessment. For area outside the 500m quantitative assessment area, a 500m qualitative assessment area is defined for qualitative assessment. The assessment areas are presented in Figure 3.2. The justification of the quantitative and qualitative assessment areas is illustrated in Section 3.6. Details of the ASRs are presented in Table 3.4.

Table 3.4 Representative Air Sensitive Receivers

ASR ID	Description	Types of ASRs	No. of Floors	Base Elevation (mPD)	Ass. Height (mAG)	Minimum Distance (m)
						Access Tunnel Portal	Water Main	Access Tunnel & Cavern	Works Boundary
ASR 1	Lion Rock Park	Recreational	-	93.6	1.5	54	107	68	54
ASR 2	Tennis Court near Tin Ma Court	Recreational	-	60.3	1.5	25	14	132	14
ASR 3	Block B, Peninsula Heights	Residential	14	67.0	1.5, 3.0, 6.1, 9.1, 12.2, 15.2, 18.2, 21.3. 24.3. 27.4, 30.4, 33.4, 36.5, 39.5. 42.6, 45.6	38	72	220	38
ASR 4	Block 1, Meridian Hill	Residential	9	62.5	1.5, 2.8, 5.5, 8.3, 11.1, 13.9, 16.6, 19.4, 22.2, 24.9, 27.7	38	25	210	25
ASR 5	Chun Sing House, Tin Ma Court	Residential	37	54.5	1.5, 2.7, 5.4, 8.1, 10.8, 13.5. 16.2, 18.9, 21.6, 24.3. 27.0, 29.7, 32.4, 35.1, 37.8, 40.5, 43.2, 45.9, 48.6, 51.3, 54.0, 56.7, 59.4, 62.1, 64.8, 67.5, 70.2, 72.9, 75.6, 78.3, 81.0, 83.7, 86.4, 89.1, 91.8, 94.5, 97.2, 99.9, 102.6	86	40	155	40
ASR 6	Chun Wai House, Tin Ma Court	Residential	37	54.5	1.5, 2.7, 5.3, 8.0, 10.6, 13.3, 15.9, 18.6, 21.2, 23.9, 26.5, 29.2, 31.8, 34.5, 37.1, 39.8, 42.4, 45.1, 47.7, 50.4, 53.1, 55.7, 58.4, 61.0, 63.7, 66.3, 69.0, 71.6, 74.3, 76.9, 79.6, 82.2, 84.9, 87.5, 90.2, 92.8, 95.5, 98.1, 100.8	83	27	146	27
ASR 7	Grace Methodist Church Kindergarten	Educational	1	60.0 [*]	1.5 [*]	98	10	131	10
ASR 8	Wang King House, Tin Wang Court	Residential	21	54.1	1.5, 2.7, 5.4, 8.2, 10.9, 13.6, 16.3, 19.0, 21.7, 24.5, 27.2, 29.9, 32.6, 35.3, 38.1, 40.8, 43.5, 46.2, 48.9, 51.6, 54.4, 57.1, 59.8	202	10	235	10
ASR 9	Block 6, Tsui Chuk Garden	Residential	22	92.3	1.5, 2.8, 5.5, 8.3, 11.0, 13.8, 16.6, 19.3, 22.1,24.8, 27.6, 30.4, 33.1, 35.9, 38.7, 41.4, 44.2, 46.9, 49.7, 52.5, 55.2, 58.0, 60.7, 63.5	141	74	128	74
ASR 10	Ma Chai Hang Recreation Ground	Recreational	-	45.7	1.5	358	104	381	104
ASR 11	Baptist Rainbow Primary School	Educational	7	45.6	1.5, 2.9, 5.7, 8.6, 11.4, 14.3, 17.1, 20.0, 24	447	32	453	32
ASR 12	Pang Ching Court	Residential	34	69.9	N/A	532	25	417	25
ASR 13	Chung Yuen House, Chuk Yuen North Estate	Residential	34	63.9	N/A	657	14	473	14
ASR 14	Wah Yuen House, Chuk Yuen South Estate	Residential	34	50.9	N/A	632	13	529	13
ASR 15	Mui Yuen House, Chuk Yuen North Estate	Residential	34	55.4	N/A	1021	23	778	23
ASR 16	Our Lady of Maryknoll Hospital	Care Centre	7	46.0	N/A	1115	1	888	1
ASR 17	Our Lady's College	Educational	7	39.0	N/A	1124	3	943	3
ASR 18	Evangel Children's Home	Care Centre	6	58.2	N/A	1137	6	811	6
ASR 19	Wing Shing House	Residential	6	43.8	N/A	1292	5	982	5
ASR 20	Ying Fuk Court	Residential	37	55.5	N/A	1043	54	698	54
ASR 21	Diamond Hill Kwong Yum Home for the Aged	Care Centre	7	62.5	N/A	1144	12	810	12
ASR 22	St. Bonaventure College and High School	Educational	8	46.7	N/A	1202	3	942	3
ASR 23	Wu York Yu Health Centre	Care Centre	4	55.0	N/A	1276	6	928	6
ASR 24	Twghs Wong Tai Sin Hospital	Hospital	5	66.5	N/A	1172	31	783	31
ASR 25	Ho Lap Primary School	Educational	7	60.9	N/A	1349	23	962	23
ASR 26	Lok Shing House, Tsz Lok Estate	Residential	40	67.8	N/A	1363	22	957	22
ASR 27	Fat Chong Temple	Temple	4	129.5	N/A	1044	62	550	62
ASR 28	Wo Tin House	Residential	41	126.5	N/A	1130	5	651	5
ASR 29	CCC Kei Tsz Primary School	Educational	9	131.0	N/A	1297	24	772	24
ASR P1	Proposed Departmental Quarters for Customs & Excise Department	Residential	27	62.0	N/A	1320	7	924	7

Remarks:

[*] The kindergarten is a one floor building with the bottom being a car park. Base elevation has been taken at the elevation of the kindergarten classrooms. The assessment height of the car park and roof are not assessed.

3.5 Identification of Key Air Pollutants

Surrounding Environment

3.5.1 There is an LPG chimney identified at 8 Chui Chuk Street which is 300m away at the eastern side of the portal area.  For the portal of Lion Rock Tunnel, it is about 300m away, north-west to the portal area. The location of the LPG chimney and the surrounding environment is shown in Figure 3.3.

3.5.2 The traffic emissions from Lung Cheung Road and other local roads (such as Chuk Yuen Road) are considered to be the key local emission sources affecting the ambient air quality within the Study Area.

Pollution Sources

Construction Phase

3.5.3 Heavy construction activities such as excavation, material handling and wind erosion of exposed site area would contribute to the construction dust.

3.5.4 Potential sources of air quality impacts would be dust emissions including total suspended particulates (TSP), respirable suspended particulates (RSP) and fine suspended particulates (FSP) generated during heavy construction activities. Fuel combustion from the use of powered mechanical equipment (PME) during construction works would be a source of NO₂, SO₂ and CO. As the number of equipment used on site is limited and the equipment used would be subject to the Air Pollution Control (Non-road Mobile Machinery (NRMM)) (Emission) Regulation of meeting the prescribed emission standards and requirement, the emissions from the equipment used are therefore considered insignificant. Therefore, only TSP, RSP and FSP will be considered in the construction dust impact assessment.

Transportation and Routings

3.5.5 Transportation activities are also a potential dust source. The routings, means of the transportation of the Project and the dust control measures are shown below:

· Transportation Routes of Materials

Ø The proposed disposal outlets of inert C&D materials and non-inert C&D materials will be disposed to the public fill reception facility at TKO Area 137 Fill Bank and SENT landfill by trucks respectively via Lung Cheung Road, Kwun Tong Road, Tseung Kwan O Road and Wan Po Road. Chemical waste will be collected by licensed collectors and dispose to Chemical Waste Treatment Centre (CWTC) at Tsing Yi or licenced facility via Lung Cheung Road, Ching Cheung Road, Tsing Kwai Highway, Kwai Tsing Road, Tsing Yi Road and/or waste transfer/disposal facilities. The general refuse generated will be collected by a waste collector and disposed of at waste transfer/disposal facilities and then to designated landfill.

Ø The relocated DHSRs are mainly for the storage and pumping of fresh water and flushing water. The relocated DHSRs and the other ancillary facilities will be unmanned during operation, only small amount of general waste would be generated during regular inspection and maintenance. The general refuse generated will be collected by a waste collector and disposed of at waste transfer/disposal facilities and then to designated landfill. In addition, small amount of chemical waste will be generated which will be collected by licensed collector for the disposal of at licensed treatment facilities.

· Dust Control Measures

Ø Vehicles would be required to pass through the wheel washing facilities provided at site exit. No earth, mud, debris, dust and the like shall be deposited on public roads. Watering will be provided once per hour and vehicles leaving a site loaded with dusty materials should be covered by tarpaulin or other impervious sheeting (please refers to Section 3.8 of EIA). With the implementation of the dust control measures, dust generated from the transportation activities would not cause significant emission. Regular site inspections and audit is recommended to ensure the effectiveness of the proposed mitigation measures. No dust and odour impact are anticipated during the operation of the Project.

Consideration of Alternatives Construction Methods, Means of Transportation for Construction Materials, Phasing Programmes and Alternative Modes of Operation

3.5.6 To reduce the air quality impact to the surrounding ASRs around the Project site, considerations of alternatives construction methods have been considered as follow, to reduce the air quality impact to the surroundings:

· Construction Methods: The design of the Project has undergone a detailed evaluation of different arrangements to arrive at the optimum planning, engineering and environmental solutions which fit together in a coherent manner (please refers to Section 2.6 of the EIA). The location of the cavern and the alignment of the access tunnel have been carefully planned to avoid encroachment into the Lion Rock Country Park (LRCP) and nearby sensitive receivers. With further reduction of tunnel length and emergency exit tunnel near Shatin Pass Road, the potential dust quality impact to Tsz Wan Shan portal area (of emergency exit) and generation of construction & demolition material can be greatly minimised. For the construction methods of tunnel and caverns, it is proposed to adopt drill and break/drill and blast method for the tunnel/ cavern excavation. Other construction method such as tunnel boring machine (TBM) has also been considered but they are not recommended due to the site constraint and project nature (please refers to Section 2.8 of the EIA).

· Means of Transportation for Construction Materials: The construction materials will be transported by trucks to the construction site. The inert and non-inert C&D materials generated from the Project will be disposed to the public fill reception facility, recycling companies and/or landfill by trucks. Chemical waste will be collected by licensed collector and dispose to licenced facility and waste transfer/disposal facilities to Chemical Waste Treatment Centre (CWTC) at Tsing Yi by truck. Other means of transportation are considered not applicable due to site location and constraints.

· Phasing Programmes: The access tunnels would be excavated first from the tunnel portal area towards to the cavern area. This would be followed by excavation of the caverns. The excavated tunnels would be used as construction access for transportation of materials by trucks and plants ingress and egress of the construction site. Ancillary building will be constructed adjacent to the tunnel portal afterwards. For water mains laying at carriageways/footpath, their extent of excavation, unloading/loading of spoils, material handling, and site area exposed to wind erosion are very limited. In addition, they will be constructed by section to minimise the potential traffic and environmental impacts. As there is only single route to cavern, there is not much room to divide the construction programme in phases/packages.

· Operation Mode of Relocated DHSRs: The relocated DHSRs only involve routine inspection and maintenance of ventilation system, pumping system, electrical system, detection/ alarm system, pipeworks and civil structures. No special alternative operation mode is required.

Other Emission Sources within the Study Area

3.5.7 Apart from the construction dust emission, cumulative air quality impact at the representative ASRs would also be expected due to the background pollutant concentrations, vehicular emissions from existing open roads, portal emissions from the Lion Rock Tunnel and the existing LPG chimney locating at Chui Chuk Street within the assessment area.

Dust Emission associated with the Concurrent Projects / Dust Sources

3.5.8 For any concurrent projects with overlapping construction works, such as those shown in Table 3.5, the associated dust emission sources and emission strength are referenced to their respectively approved EIA Studies and/or the best available information.

Table 3.5 Key Concurrent Projects for Construction Dust Assessments

Project Name	Project Scope	Remarks
HyD’s Improvement of Lion Rock Tunnel	The scope of the Project comprises the construction of a new tunnel tube to facilitate the subsequent rehabilitation/reconstruction of the two existing tunnel tubes, widening of the connecting roads and the associated works.	Project details is not available for consideration at time of reporting.
CE 28/2017 (HY) - Pedestrian Link near Chuk Yuen North Estate – Design and Construction	The scope of the Project comprises the main construction of covered pedestrian link, pedestrian subway and covered walkway. The project also includes road realignment and other associated works, which include provision of barrier free facilities.	Works area of tunnel portal and ancillary building is away from this concurrent project, only the small scale watermain laying shall be considered relevant.

3.5.9 EIA study brief (ESB-323/2019) of the project “Improvement of Lion Rock Tunnel” was issued in November 2019. Based on the latest information, the target work commencement date of the project “Improvement of Lion Rock Tunnel” is mid of 2024, which is a concurrent project with this Project during construction. Further discussion has been provided in Section 3.6.27-3.6.28.

3.5.10 According to the best available information, the project “Pedestrian Link near Chuk Yuen North Estate” will commence in mid-2023 for completion in mid-2029. As the proposed works area of tunnel portal and ancillary building is about 1 km away from this concurrent project and the cavern/tunnel construction works is mainly inside cavern, watermain laying is the only construction work with potential cumulative impact with this concurrent project.

3.5.11 The construction of each watermains section of the Project will be using open cut method or trenchless method by sections. Each section will be about 40m long at maximum and any two sections will be separated by at least 200m. With the implementation of the mitigation measures and good site practices, no adverse dust impact is anticipated during construction. Referring to the latest information provided by HyD on the Pedestrian Link near Chuk Yuen North Estate, detailed construction programme is not yet available. The major scopes include pedestrian link with escalation and pedestrian subway(s) between Chuk Yuen North Estate and the Public Transport Terminus (PTT) near Wong Tai Sin Road, covered walkway, road / junction realignment, barrier free facilities and associated works. With implementation of pollution control measures during construction, no adverse dust impact is anticipated. To further minimise the potential cumulative impacts during construction phase, it is recommended that the contractor shall plan the works area of the close proximity water mainlaying sections which will not overlap with the works area of Pedestrian Link near Chuk Yuen North Estate project as far as practical.

Operation Phase

3.5.12 As the DHSRs and DHPS are mainly for the storage and pumping of fresh water and salt water and associated watermains are underground pipelines, no dust and odour emission impact during the operation of the Project is expected.

3.6 Assessment Methodology

Construction Phase

Assessment Area

3.6.1 Construction works of the Project include construction of cavern and access tunnel, construction of ancillary building and tunnel portal, structural works for the relocated DHSRs, watermain laying and E&M installation. The major emission from the Project are emitted from the ventilation shaft of the portal area (which emits all emissions inside cavern), the 500m quantitative assessment area is therefore defined particular for the quantitative construction dust impact assessment (i.e. 500m from the portal area boundary).

3.6.2 For area outside the quantitative assessment area (i.e. 500m from the portal area boundary) but within the Study Area (i.e. 500m from the project site boundary), water mainlaying works are proposed. Since water mainlaying works will be constructed by sections by open cut method on footpaths/carriageways, the extent of excavation, unloading/loading of spoils, material handling, and site area exposed to wind erosion are very limited. It is believed these construction work would give insignificant construction dust impacts to the surrounding ASR. Qualitative assessment has been conducted to address these potential construction dust impact to ASRs by comparing/making reference to the quantitative air quality assessment results.

Emission Inventory

3.6.3 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 Contribution

3.6.4 Primary contributions are the project-induced emission which contributes to the local air quality impact. Thus, construction dust emission associated with the construction works of the Project is the primary contributions during the construction phase.

3.6.5 Construction activities with significant particulate emission are identified from the construction method suggested by engineering design. Construction dust emission rate are estimated based on emission factors of US Environmental Protection Agency (USEPA) Compilation of Air Pollution Emission Factors (AP-42), 5th edition and activity data from the engineer design. The major dust emitting construction activities for the Project considered in the modelling assessment include:

a. Site formation for Portal Enclosure, Auxiliary Buildings and Infrastructure Works for Watermain Laying

· Excavation and material handling within the construction site; and

· Wind erosion of open active area.

b. Drill & Blast / Drill & Break for Caverns and Access Tunnel

· Drill & Blast operations

· Excavation and material handling within the construction;

· Wind erosion of open active area;

· Rock crusher with loading, crushing and screening;

· Materials handling of excavated material; and

· Vehicle movements on unpaved site roads.

c. Stockpiling of Excavated Material

· Stockpiling and material handling within the construction site; and

· Wind erosion of open active area.

3.6.6 The assumptions made for the construction activities are presented in Table 3.6 below:

Table 3.6 Individual Construction Activities during Construction

Activity	Description	Details
Blasting	Area and the depth of each blasting	For drill and break per event, depth is assumed to be 1.5m; For drill and blast per event, depth is assumed to be 3m; Approximate area is assumed to be 14.7m x 11.2m = 165m^2
	Number of blasting per day	1 time
	Planned time for blasting in each working day	Blasting could have happened anytime between 7am to 7pm – Monday to Saturday (subject to condition)
	Procedures	1) Before blasting, blast nets / canvas will be installed at the blasting area inside the tunnel/cavern. 2) Blast door will be installed near to the blasting area and keep closed which can withstand the air pressure generated inside the tunnel/cavern and minimise the dust emission during blasting. Ventilation system will be turned off before blasting. All other construction activities inside tunnel/cavern (e.g. rock crushing, wet drilling, material handling, vehicle movement) will be ceased. 3) After blasting, all dust emitted will be confined with the tunnel/cavern. 4) Blast door will be opened. Water spraying will be provided to facilitate initial dust settlement after blasting. Ventilation system will be turned on to remove the dust emitted.
Bulldozing	Any bulldozing activity	No bulldozing activity is anticipated
Material Handling	Working hours per day	24 hours in tunnel
	Handling rate per hour	21 m^3/hr
	Material moisture content in percent	0.7% for crushed limestone
	Density of material	Ranging between 2500kg/m^3 and 2700kg/m^3 (subject to lab test report)
	Wind speed inside cavern	0.1m/s
Tertiary Crushing	Crushing Rate	3.9 ton/hr
Truck Unloading	Loading Rate	3.9 ton/hr
Vehicle Movements on Unpaved Site Roads	The net weight and the gross weight of each truck	10 tonnes
	Truck flow in each direction (1. from the portal to the blasting location and 2. from the blasting location to the portal)	The truck flow in one way is 3.5 truck per hour
	The weight of the materials to be carried by each truck	20 tonnes
	Average one-way travel distance within site	750m is a conservative estimation
	Surface material slit content	8.5%
Wet Drilling	Handling rate per hour	21 m^3/hr

3.6.7 The emission factor for dust emitting construction activity and their location are presented in Table 3.7 below:

Table 3.7 Emission Factor for Dust Emitting Construction Activity

Activity	Emission Factor	Remarks	Location
Heavy Construction Activities i) Site formation for Portal Enclosure and Auxiliary Buildings, operating area = 2050m^2 and ii) Water mains laying works	E = 2.69 Mg/hectare/month of activity (TSP) TSP-to-RSP factor = 0.473 TSP-to-FSP factor = 0.072 E = 2.0756E-04 g/s (TSP) E = 9.8177E-05 g/s (PM10) E = 1.4944E-05 g/s (PM2.5)	USEPA AP-42, Section 13.2.3, 1/95 ed. USEPA AP-42, 5th ed. 11/06 ed. S13.2.4 USEPA AP-42, 5th ed. 11/06 ed. S13.2.4 Assumed total area of 7889.15m^2	Outside Cavern
Wind Erosion	E = 0.85 Mg/hectare/year (TSP) TSP-to-RSP factor = 0.473 TSP-to-FSP factor = 0.072 E = 2.6953E-06 g/s (TSP) E = 1.2749E-06 g/s (PM10) E = 1.9406E-07 g/s (PM2.5)	USEPA AP-42, 5th ed., Table 11.9.4 USEPA AP-42, 5th ed. 11/06 ed. S13.2.4 USEPA AP-42, 5th ed. 11/06 ed. S13.2.4 Assumed total area of 7889.15m^2	Outside Cavern
Blasting	E = 1.3203E-01 g/s (TSP) E = 6.8654E-02 g/s (PM10) E = 3.9608E-03 g/s (PM2.5)	USEPA AP-42, Section 11.9, Table 11.9-1	Inside Cavern
Loading Point of Rock Crusher within Portal Enclosure	E = 8.0000E-06 kg/Mg (PM10) TSP-to-RSP factor = 2.1[1] E = 1.6405E-05 g/s (TSP) E = 7.8119E-06 g/s (PM10) E = 7.8119E-06g/s (PM2.5)	USEPA AP-42, 5^th ed. 8/04 ed., Section 11.19.2, Table 11.19.2-1 100% actively operating AP-42 Section 11.19.2	Inside Cavern
Tertiary Crushing by Rock Crusher within Portal Enclosure	E = 2.6365E-03 g/s (TSP) E = 1.1718E-03 g/s (PM10) E = 1.1718E-03 g/s (PM2.5)	USEPA AP-42, 5^th ed. 8/04 ed., Section 11.19.2, Table 11.19.2-1 100% actively operating USEPA AP-42, 5^th ed. 8/04 ed., Section11.19.2, Table 11.19.2-1 Adopt PM10 Emission Factor as upper bound	Inside Cavern
Fine Screening by Rock Crusher (controlled with wet suppression) within Portal Enclosure	E = 1.7577E-03 g/s (TSP) E = 1.0741E-03 g/s (PM10) E = 1.0741E-03 g/s (PM2.5)	100% actively operating USEPA AP-42, 5^th ed. 8/04 ed., Section11.19.2, Table 11.19.2-1 USEPA AP-42, 5^th ed. 8/04 ed., Section11.19.2, Table 11.19.2-1 PM2.5 Emission Factor Adopt PM10 Emission Factor as upper bound	Inside Cavern
Materials Handling	RSP-TSP factor = 0.52 FSP-TSP factor = 0.03 E = 1.4581E-03 g/s (TSP) E = 6.8964E-04 g/s (PM10) E = 1.0443E-04 g/s (PM2.5)	USEPA AP-42, Section 11.9, Table 11.9-1 USEPA AP-42, 5^th ed, Section 13.2.4.1	Inside Cavern
Vehicle movements on unpaved site roads (with loading)	E = 2.3298E+00 g/s (TSP) E = 6.6568E-01 g/s (PM10) E = 6.6568E-02 g/s (PM2.5)	USEPA AP-42, 5^th ed, Section 13.2.2.2	Inside Cavern
Vehicle movements on unpaved site roads (without loading)	E = 1.4211E+00 g/s (TSP) E = 4.0603E-01 g/s (PM10) E = 4.0603E-02 g/s (PM2.5)	USEPA AP-42, 5^th ed, Section 13.2.2.2	Inside Cavern
Wet Drilling	E = 6.3000E-03 g/s (TSP) E = 6.3000E-04 g/s (PM10) E = 6.3000E-04 g/s (PM2.5)	USEPA AP-42, Section 11.19.2, Table 11.19.2-1	Inside Cavern

3.6.8 The detailed calculation of dust emission rates and areas of construction work sites are presented in Appendix 3A and Appendix 3F. Activity data including blasting frequency, drilling rate, excavation rate, material handling rate, moisture content, silt content, number of construction trucks and truck speed are based on the engineering design.

3.6.9 The emission of all construction activities outside cavern is a series of area source emission around the portal area and water mains area, which forms the total area of 7,900m². During working hours, it is assumed within 7am to 7pm daily. For the non-working hours, dust emission will occur due to wind erosion.

3.6.10 The assumption of emission from all construction activities inside cavern which will be emitted from the ventilation shaft located at the tunnel portal. The preliminary design, location and the inventory of the ventilation shaft is presented in Table 3.8. For worst case scenario, it has set to assume all construction activities which will be conducted in 24 hours. Blasting works which is set to be conducted anytime within 7am to 7pm (Monday to Saturday). This can stimulate the worst case scenario contributed by the primary dust emission at the construction phase.

Table 3.8 Preliminary Design of Ventilation System at the Portal

Design	Emission Type	Coordinates		Design Dimension			Temp	Emission velocity (m/s)	Building Height (m)
		X	Y	Length (m)	Width (m)	Height (m)
Roof monitor structure	POINT (CAPPED)	837094.8	822795.8	1.5	1.5	0.5	Ambient	3	14.5m above ground (ground level: 75.7 mPD)

Secondary Contribution

3.6.11 Secondary contribution is the air pollutant emitted from the neighborhood of the Project site contributing to the local air quality. Any emission sources within 500m of the portal area boundary shall be considered in the construction phase impact assessment. The main source of secondary contribution are the vehicular emissions, such as Lung Cheung Road, Chuk Yuen Road and the Lion Rock Tunnel. Aside from vehicular emission, the other nearby dust emission sources are also considered (e.g. chimney operation).

Vehicular Emission within the Quantitative Assessment Area

3.6.12 The roads included for the vehicular assessment is presented in Figure 3.4.

Determination of Worst Assessment Year

3.6.13 Based on the tentative construction programme as indicated in Appendix 2A, the construction work will be conducted in between 2022 to 2027. Worst assessment year for vehicular emission modelling is chosen based on the conservative approach. For a conservative estimation of vehicular emission, the vehicle emission factor is chosen by using the first year of the construction programme (i.e. 2022), and predicted traffic flow of 2027. This combination represents the worst case scenario for the vehicular emission.

3.6.14 EMFAC-HK 4.2 model is adopted to estimate the emission rates of 16 types of vehicles, presented in Table 3.9, and the inventories of exhaust oxides of nitrogen and particulate matter for worst-case scenario (year 2022). “EMFAC” mode is used for predicting the vehicular emission of 16 vehicle classes with different speed profiles. Vehicular emission factors of each road section of each hour of a day were derived using EPD’s EMFAC-HK v4.2 software.

Table 3.9 Vehicular Classes in EMFAC-HK Model

Vehicle Class	Description	Fuel	Gross Vehicle Weight
PC	Private Cars	ALL	ALL
TAXI	Taxi	ALL	ALL
LGV3	Light Goods Vehicles (≤2.5t)	ALL	≤2.5t
LGV4	Light Goods Vehicles (2.5-3.5t)	ALL	>2.5-3.5t
LGV6	Light Goods Vehicles (3.5-5.5t)	ALL	>3.5-5.5t
HGV7	Medium & Heavy Goods Vehicles (5.5-15t)	ALL	>5.5-15t
HGV8	Medium & Heavy Goods Vehicles (≥15t)	ALL	>15t
PLB	Public Light Buses	ALL	ALL
PV4	Private Light Buses (≤3.5t)	ALL	≤3.5t
PV5	Private Light Buses (>3.5t)	ALL	>3.5t
NFB6	Non-franchised Buses (<6.4t)	ALL	≤6.36t
NFB7	Non-franchised Buses (6.4-15t)	ALL	>6.36-15t
NFB8	Non-franchised Buses (15-24t)	ALL	>15t
FBSD	Single Deck Franchised Buses	ALL	ALL
FBDD	Double Deck Franchised Buses	ALL	ALL
MC	Motor Cycles	ALL	ALL

3.6.15 For estimating the worst possible hourly vehicular emission factors, EMFAC model is adopted to use the lowest temperature and relative humidity data to calculate the vehicular emission factors in the corresponding period on hourly basis and then simulate the air quality impact assessment. Meteorological data from the Hong Kong Observatory (HKO) are found representative for the assessment.

· Minimum temperature extracted from Wong Tai Sin weather station = 9.9 deg.C

· Minimum relative humidity extracted from King's Park weather station = 18%

3.6.16 Details of the HKO data, the assumption used for EMFAC and the emission factors generated are given in Appendix 3C. The technical note of traffic forecast for environmental impact assessment and Traffic Department’s agreement letter are given in Appendix 3D. Using the generated EMFAC emission factor, the input emission factor corresponding to the estimated traffic flow and speed for can also be found in Appendix 3D.

3.6.17 As recommended in the EPD’s Guideline on Modelling Vehicle Emissions for cold start emissions, default vehicle populations forecast in EMFAC-HK is used. The default accrual rates in EMFAC-HK are estimated from the local mileage data adjusted to reflect the total VKT for each vehicle class. The default value has been used. Cold start emissions are assumed to be relevant to the roads with a speed limit of 50 km/hr for conservative approach. The percentage of minor roads within the HKSAR are estimated using the data published by the Transport Department, which is used to estimate the trips per VKT for the roads with cold start emissions. The maximum starting emission (g/trip) among different durations (from 5 min to 720 min) is used to reflect the worst case scenario. The details of the calculations are presented in Appendix 3D.

3.6.18 For running emissions, the hourly running exhaust emission rate (RSP and FSP) for each vehicle class was determined by the running exhaust emission rate for the average road speed of the concerned road link. The complete calculation result are displayed in Appendix 3D. The hourly composite running exhaust emission rate (RSP, FSP) was determined by:

3.6.19 Aside for the regular open road traffic, traffic emission including portal emission from the enclosure of the Lion Rock Tunnel has included in the cumulative assessment. It is assumed the exist portal of the Lion Rock Tunnel (Shatin to Diamond Hill direction) has the contribution to dust emission. The peak traffic hour of the tunnel has applied in the 24 hours emission values to offer the most conservative emission scenario. The following formula has applied in the calculation:

3.6.20 The emission height is set to be half of the tunnel height. Portal emissions from the tunnel enclosures were modelled in accordance with the Permanent International Association of Road Congress Report (PIARC, 1991). Pollutants are assumed to be ejected from the openings of full noise enclosures as a portal jet such that two-third (2/3) of the total emission is dispersed within the first 50 m of the portal and the remaining one-third (1/3) of the total emission within the second 50 m. Details of the calculation and results are presented in Appendix 3E and Appendix 3F respectively.

Other Dust Emission Sources within the Quantitative Assessment Area

3.6.21 Apart from the vehicular emission sources, nearby dust emission sources have been reviewed and assessed in the air quality assessment, if required. A LPG plant locating at 8 Chui Chuk Street with chimneys are identified near Tsui Chuk Garden. According to the USEPA, particulate emissions from LPG combustion are very low[2].

3.6.22 Since the emission factor of the LPG chimney is not obtainable, assumption has been made based on the emission factor disclosed by USEPA, which the emission factor of propane and butane are 0.7 lb/10³ gal and 0.8 lb/10³gal respectively. Referring to the approved EIA report, LPG is a pressurised mixture of propane and butane in Hong Kong (ratio 3:7)[3]. The model of the LPG chimney has a flow of 990,000 BTU/hr based on the brand design. As 1 gallon of propane equals to 92,500 Btu and 1 gallon of butane equals to 130,000 Btu[4], the flow of propane and butane of the LPG chimney are estimated about 3.21 and 5.33 gal/hr respectively. Applying the emission factor from USEPA, the calculated sum of butane and propane emitted from LPG chimney is about 8.2052E-04 g/s. Based on the operation mode provided by the operator, the LPG chimney combustion is operating based on the temperature range of the water boiler (i.e. turns on when water temperature <70 °C and turn off >80 °C), indicating the actual emission factor of the mentioned chimney will be lower than the above predicted value.

3.6.23 Referring to the Table 3.12 of Section 3.8, the cumulative impacts to the nearest ASRs closes to the LPG chimney (i.e. ASR8 and ASR10) have at least 25% to buffer to the TSP criteria as stipulated in the EIAO-TM and RSP and FSP criteria in the AQOs. USEPA literature also revealed that dust is not the major emission from LPG combustion, and the actual emission would be smaller than the estimated value with on-off operation mode, the emission impact of LPG chimney is therefore not included in the quantitative assessment.

3.6.24 For the other emission outside the 500m quantitative assessment area, the following major dust sources within 4km from the project boundary are included in the assessment as point source for dust emission according to their perspective SP license:

· Fu Shan Crematorium

· Diamond Hill Crematorium

3.6.25 Site visit has been conducted to investigate the chimney design of the above crematoriums, confirming the parameters to be inputted into AERMOD model, which is presented in Appendix 3F.

3.6.26 For industrial chimneys of HK & China Gas Co. Ltd. locating at To Kwa Wan (Chimney ID 2049, 2054-2057 and Figure 3.4)^[5], Kai Tak Multi-purpose Sports Complex EIA Report have been reviewed. As stated in the Appendix 3.5 of the EIA report and SP Licence (No. L-8-004(1)), it stated that RSP and FSP emission from chimneys were zero. Therefore, it is not considered as cumulative dust source and will not include in the cumulative construction dust impact assessment.

Concurrent Project – HyD’s Improvement of Lion Rock Tunnel (LRT)

3.6.27 Based on the latest project information obtained from HyD on 13^th April 2021, the detailed information of the concurrent project is not yet available, thus its dust impact cannot be estimated and included in the cumulative assessment.

3.6.28 Some tentative information gathered from the LRT project are as follows:

· A road tunnel will be constructed in between the two existing tunnels, approximately 1.4 km long;

· Tunnel Boring Machine (TBM) will be adopted as the road tunnel construction method;

· Tunnel excavation will commence from Shatin side to Kowloon side;

· Most of the excavated material will dispose offsite at Shatin side portal; and

· Tentative TBM excavation programme will commence from 2024 at Shatin side and expect to reach the Kowloon side by 2027 or later.

Since this concurrent LRT project will commence at the Shatin side, most of the construction dust will be emitted from the Shatin side portal, instead of the Kowloon portal, during the tunnel excavation. Nevertheless, the LRT project shall take into account this concurrent relocation of DHSRs project in their EIA study.

Air Dispersion Model and Meteorological Data

3.6.29 California Line Source Dispersion Model, version 4 (CALINE4), the USEPA approved line source air dispersion model developed by the California Department of Transport is used to assess the secondary contribution due to vehicular emission. Surface roughness of 100cm is chosen with reference to EPD’s Guidelines on Choice of Models and Model Parameter (hereafter refer as “the Model Guidelines”). The 500m quantitative assessment area is considered to be not entirely within city center around half of it covers the Lion Rock Hill, the surface roughness of new development is adopted to prevent under-estimation.

3.6.30 Flat terrain approach was adopted in CALINE4 to assume all road links to be at-grade. To correspond with this assumption, the assessment height for ASRs has also been set to be at ground level (i.e. base elevation: 0), this shall give the most conservative result showing the direct impact of vehicular emission to the ASRs. Width of the roads are added by 3m on both sides to represent the mixing zone.

3.6.31 According to the Model Guidelines, the steady-state Gaussian dispersion model United States Environmental Protection Agency (USEPA) AERMOD model was adopted for assessing the potential air quality impact arising from the construction activities. The assessment area mostly falls under PATH-2016 Grid (41,36) and (42,36), with the edge covered part of Grid (41,35). Hourly meteorological data from the concerned grids will be adopted in the model run. Mixing heights from the PATH-2016 which are lower than the minimum mixing height recorded by the Hong Kong Observatory (HKO) in Year 2010 (i.e. 121m) are capped at 121m. For the treatment of calm hours, the wind speeds are capped at 1m/s for those from PATH-2016 below 1m/s.

3.6.32 Dominant or representative land use in the vicinity of the assessment area was identified with the land utilization information (version 2019) disclosed by the Planning Department. Details of assumptions and methods to determine the surface characteristics of the grids is recorded in Appendix 3G.

3.6.33 Guided by a Working Group consisting of experts in air quality modelling, PATH-2016 has gone through extensive testing. It was determined that PATH-2016’s output of RSP concentrations should be adjusted as follows before being applied for EIA to account for the limited information on pollutant emissions on a larger scale:

· 10^th highest daily RSP concentration: add 26.5 μg/m³.

· Annual RSP concentration: add 15.6 μg/m³

3.6.34 Combining all dust emission from various sources, and the extensive use of air dispersion models, the emission considered in this quantitative air quality impact assessment are summarised in Appendix 3F.

Operation Phase

3.6.35 As mentioned in Section 3.5.12, there is no identified dust and odour emission sources of the Project during operation phase.

3.7 Prediction and Evaluation and Environmental Impacts

3.7.1 The summarised assessment result showing the anticipated dust impact to the ASRs are presented in Table 3.10. The detailed result of unmitigated scenario can be found in Appendix 3H.

Table 3.10 Summary of Cumulative Dust Emission Concentration (Unmitigated Scenario)

ASR ID	Description	TSP	RSP			FSP			Comply with AQO or EIAO-TM (Y/N)
		Hourly (Max)	Daily (10^th Highest)	No. of Daily exceedance	Annual	Daily (10^th Highest)	No. of Daily exceedance	Annual
		(µg/m^3)	(µg/m^3)		(µg/m^3)	(µg/m^3)		(µg/m^3)
ASR1	Lion Rock Park	2421	187	111	74	57	2	28	N
ASR2	Tennis Court near Tin Ma Court	3732	238	148	92	68	5	30	N
ASR3	Block B, Peninsula Heights	3469	139	49	55	58	2	26	N
ASR4	Block 1, Meridian Hill	3631	144	72	59	60	2	26	N
ASR5	Chun Sing House, Tin Ma Court	4542	125	28	51	57	2	25	N
ASR6	Chun Wai House, Tin Ma Court	4738	119	27	49	57	2	25	N
ASR7	Grace Methodist Church Kindergarten	3548	133	27	52	56	2	25	N
ASR8	Wang King House, Tin Wang Court	2492	106	16	47	57	2	25	N
ASR9	Block 6, Tsui Chuk Garden	2672	100	9	43	55	2	24	N
ASR10	Ma Chai Hang Recreation Ground	1188	82	2	36	53	1	23	N
ASR11	Baptist Rainbow Primary School	1255	79	2	36	54	1	23	N
Notes: [1] Bolded value represents non-compliance to AQO or EIAO-TM criteria.

3.7.2 Table 3.10 shows a general non-compliance to the AQO’s hourly TSP emission criteria. More than half of the ASRs are not able to comply with the AQO requirement for RSP.

3.7.3 The worst impact level is predicted at ASR2 (60.3m base elevation + 1.5m assessment height). Contours for the cumulative unmitigated emission for TSP, RSP and FSP are plotted in Figure 3.5 to Figure 3.9. Based on the contour plot, the main source of impact is the exhaust of the tunnel portal. It suggested the ASR closer to the exhaust, the more impact it would have experienced. Since all of the ASRs within the quantitative assessment area have not complied with the AQO criteria, it is concluded that proper dust mitigation measures must be implemented. Qualitative assessment has been conducted at Section 3.8 regarding the air quality impacts experienced by the ASRs within the qualitative assessment area.

Operation Phase

3.7.4 As the DHSRs and DHPS are mainly for the storage and pumping of fresh water and salt water, no air pollutant emission source (including odour) is expected during the operation of the Project.

3.8 Mitigation Measures

Construction Phase

3.8.1 Dust suppression measures, including watering once per hour, will be incorporated in accordance with the requirements of the Air Pollution Control (Construction Dust) Regulation. Dust filter will be installed at the ventilation system of the emission source at the tunnel portal chimney. The calculated dust suppression efficiency with dust suppression measures is provided in Appendix 3I. Mitigation measures have been proposed and presented in Table 3.11.

Table 3.11 Summary of Dust Suppression Measures

Process	Description	Dust Control Measure	Remarks
Site Formation	Heavy construction	· Watering will be provided once per hour. Assume dust removal efficiency at 91.7%.	USEPA’s Control of Open Fugitive Dust Sources, s3.3.3, equation 3-2
Rock Crusher	Truck unloading, tertiary crushing, fines screening	· The rock crushing plant is configured as an enclosed system with dust collector. · Dust collector will be provided at the exhaust of the rock crusher during rock crushing. Assume typical dust removal efficiency at 95%^[1].	USEPA’s Control Techniques for Particulate Emission from Stationary Sources Vol.2, S9.7.1.2.2
Blasting	-	Before blasting, blast nets / canvas will be installed at the blasting area inside the tunnel/cavern. Blast door will be installed near to the blasting area and keep closed during blasting. The tunnel ventilation system will be provided with built-in filters for dust removal.	-
Trucks	Material handling, vehicle leaving the works area	· Vehicles would be required to pass through the wheel washing facilities provided at site exit. · Watering will be provided once per hour. Assume dust removal efficiency at 91.7%.	USEPA’s Control of Open Fugitive Dust Sources, s3.3.3, equation 3-2
Overall Emission inside Cavern
Dust filter in ventilation system	All emissions inside cavern	· A dust filter is installed at the ventilation shaft of the tunnel portal to filter all emissions emitted inside cavern. · Assume typical dust removal efficiency at 80%^[2].	-
Remarks: [1] The USEPA’s Control Techniques for Particulate Emission from Stationary Sources Vol.2, S9.7.1.2.2 indicates typical fabric filter, regardless of the type are greater than 99%. However, the efficiency is conservatively reduced to 95% in the construction phase assessment, which is suggested in the same document to be the suppression efficiency of other common dust suppression methods. [2] Blasting shall not reduce the performance of the dust filter, as the ventilation system will be shut down during the blasting process, and blast door will be installed during the blasting process to ensure the change in air pressure during blasting would not affect the dust filter efficiency.

3.8.2 The summarised result showing the anticipated dust impact to the ASRs after imposing mitigation measures are presented in Table 3.12. The detailed result of mitigated scenario can be found in Appendix 3J.

Table 3.12 Summary of Cumulative Dust Emission Concentration (Mitigated Scenario)

ASR ID	Description	TSP	RSP			FSP			Comply with AQO or EIAO-TM (Y/N)
		Hourly (Max)	Daily (10^th Highest)	No. of Daily exceedance	Annual	Daily (10^th Highest)	No. of Daily exceedance	Annual
		(µg/m^3)	(µg/m^3)		(µg/m^3)	(µg/m^3)		(µg/m^3)
ASR1	Lion Rock Park	254	71	2	35	53	2	23	Y
ASR2	Tennis Court near Tin Ma Court	361	77	2	36	54	2	24	Y
ASR3	Block B, Peninsula Heights	232	74	2	34	54	2	24	Y
ASR4	Block 1, Meridian Hill	276	75	2	34	55	2	24	Y
ASR5	Chun Sing House, Tin Ma Court	223	72	2	33	53	2	23	Y
ASR6	Chun Wai House, Tin Ma Court	229	72	2	33	53	2	23	Y
ASR7	Grace Methodist Church Kindergarten	274	73	2	33	54	2	23	Y
ASR8	Wang King House, Tin Wang Court	198	73	2	33	54	2	23	Y
ASR9	Block 6, Tsui Chuk Garden	197	71	2	32	53	2	23	Y
ASR10	Ma Chai Hang Recreation Ground	199	71	1	32	53	1	22	Y
ASR11	Baptist Rainbow Primary School	199	71	1	32	53	1	22	Y

3.8.3 In general, the worst impact level is predicted at ASR2 (60.3mPD base elevation, 1.5mAG assessment height). Contour plots showing the mitigated dust impact to the surrounding ASRs are drawn in Figures 3.10 to Figure 3.14.

3.8.4 Based on the contour plot, the main source of impact is the exhaust of the tunnel portal. It suggested the ASR closer to the exhaust, the more impact it would have experienced. As all ASR within the 500m assessment area show full compliance to AQO or EIAO-TM requirement, it is also anticipated that qualitative assessed ASRs outside the 500m quantitative assessment area but within the 500m qualitative assessment area (i.e. ASR12 to ASR29, ASR P1), shall experience an even lower air quality impact. Therefore, it is concluded that no adverse impact would be made to both quantitatively assessed ASR (ASR1 to ASR11) and qualitatively assessed ASR (ASR12 to ASR29, ASR P1).

3.8.5 With the implementation of standard dust suppression measures as stipulated in the Air Pollution Control (Construction Dust) Regulation and recommended measure in Section 3.8.1, it is believed that there would be no adverse dust impacts on the ASRs in the vicinity of the construction sites. Although no adverse construction phase air quality impacts are anticipated, as a best practice measure to ensure compliance with the Air Pollution Control (Construction Dust) Regulation, it is suggested that the following control measures, but not limited to, be incorporated into contract documents:

· The contractor shall observe and comply with Air Pollution Control (Construction Dust) Regulation and implement all the required mitigation measures;

· The contractor shall undertake precautions at all times to prevent dust nuisance and smoke as a result of his activities;

· The contractor shall ensure a highly efficient dust filter (at least 80% efficiency) to be installed at the ventilation exhaust to treat the exhausting air from cavern;

· The contractor shall frequently clean and water the site to minimise fugitive dust emissions;

· The contractor shall ensure that there will be adequate water supply/storage for dust suppression;

· The working area of any pavement breaking, excavation or earth moving operation should be sprayed with water immediately before, during and after the operation to avoid dust generation;

· Any stockpile of dusty material should be properly covered by tarpaulin or other impervious sheeting;

· Vehicles leaving a site loaded with dusty materials should be covered by tarpaulin or other impervious sheeting;

· Wheel washing facilities shall be installed and used by all vehicles leaving the site. No earth, mud, debris, dust and the like shall be deposited on public roads. Water in the wheel cleaning facility shall be changed at frequent intervals and sediments shall be removed regularly. The contractor shall submit details of proposals for the wheel cleaning facility. Such wheel washing facilities shall be usable prior to any earthworks excavating activity on the site. The Contractor shall also provide a hard-surfaced road between any washing facility and the public road;

· Any materials dropped on paved roads shall be cleaned up immediately to prevent dust nuisance;

· The contractor shall devise, arrange methods of working and carrying out the works in such a manner so as to minimise dust impacts on the surrounding environment, and shall provide experienced personnel with suitable training to ensure that these methods are implemented; and

· The contractor shall plan that the works areas of the close proximity water mainlaying sections will not overlap with the works are of Pedestrian Link near Chuk Yuen North Estate” project as far as practical. The WSD’s contractor shall further liaise with HyD’s contractor on the interfacing issue during construction is required.

3.8.6 Apart from the general dust suppression measures, the contractor shall also implement specific dust mitigation measures for excavation, drilling and blasting activities during the construction of tunnel portal. These include the use of blast nets / canvas covers and ensure blast door is properly installed inside tunnel / cavern.

3.8.7 Before the commencement of any works, the Engineer may require the contractor to submit the methods of working, construction plant or equipment and air pollution control measures to be used on the site to be made available for inspection and approval. This will ensure that the construction works are undertaken in an environmentally acceptable manner.

3.8.8 It is observed that the Project construction activities will not contribute to significant NO₂ emission. However, the contractor is advised to use the precautionary measures to avoid burdening the surrounding NO₂ concentration. Therefore, as a best practice measure, it is suggested that the following control measures, but not limited to, be incorporated into contract documents:

· The contractor shall avoid the use of diesel power machines and generators as far as practicable;

· The contractor shall avoid the use of non-road mobile machineries which exempt by the Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation, and seek the ones with proper label issued by EPD; and

· The contractor shall observe the requirement of DEVB TC(W) No. 13/2020, to apply a temporary electricity and water supply with a target that the necessary cables/water mains laying works could be completed before the commencement of the works contract.

Operation Phase

3.8.9 As no air quality impact is expected during operation of the service reservoirs and pumping station and associated watermains, no mitigation measure is required.

3.9 Residual Impacts

Construction Phase

3.9.1 No adverse residual air quality impact is anticipated from the construction of the Project with the implementation of the recommended mitigation measures and good construction site practices.

Operation Phase

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

3.10 Monitoring and Audit Requirement

Construction Phase

3.10.1 With the implementation of the dust control measures, no unacceptable dust impact is expected during construction of the Project. Nonetheless, given the potential concerns raised by nearby residents, air quality monitoring during construction phase is considered recommended. Regular site inspections and audit is recommended to ensure the effectiveness of the proposed mitigation measures. Details of the monitoring and audit programme are provided in a stand-alone EM&A Manual.

Operation Phase

3.10.2 Given no air quality impact including odour is anticipated during the operation of the Project, monitoring during operation phase is considered not necessary.

3.11 Conclusion

3.11.1 The potential sources of air quality impacts associated with the construction of the Project have been identified and the potential impacts were evaluated. Fugitive dust may arise from the construction activities such as site clearance, rock drilling, blasting operation, breaking works, excavation works, handling and transportation of C&D materials, stockpiling and wind erosion. With the implementation of recommended dust suppression measures as specified in Section 3.8 mitigation measures and EM&A programme. No exceedance of air quality standard is anticipated.

3.11.2 As the DHSRs and DHPS are mainly for the storage and pumping of fresh water and salt water and associated watermains are underground pipelines, air quality impact during the operation of the Project is not envisaged.

END OF TEXT

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[1] The conversion factor has also been included in the following EIA reports:

· Sha Tin Cavern Sewage Treatment Works (Register No.: AEIAR-202/2016) https://www.epd.gov.hk/eia/register/report/eiareport/eia_2402016/01_EIA/Appendix/Appendices/Appendix%203.02c.pdf

· West Island Line (Register No.: AEIAR-126/2008)

https://www.epd.gov.hk/eia/register/report/eiareport/eia_1532008/EIA-pdf/Appendix/app%2011.1.pdf

[2] From USEPA AP-42, 5^th ed. 11/06 ed, Section 1.5 Liquefied Petroleum Gas Combustion, s2.3

https://www.epa.gov/sites/production/files/2020-09/documents/1.5_liquefied_petroleum_gas_combustion.pdf

[3] Chai Wan Government Complex and Vehicle Depot (Reigster No.: AEIAR-(AEIAR-191/2015)

https://www.epd.gov.hk/eia/register/report/eiareport/eia_2302015/Web/HTML/Ch%2010%20Hazard.htm

[4] From University of Connecticut Department of Plant Science and Landscape Architecture, Approximate Heating Value of Common Fuels

http://ipm.uconn.edu/documents/raw2/Approximate%20Heating%20Value%20of%20Common%20Fuels/Approximate%20Heating%20Value%20of%20Common%20Fuels.php?aid=230

[5] Kai Tak Multi-purpose Sports Complex EIA Report (Register No.: AEIAR-204/2017)

https://www.epd.gov.hk/eia/register/report/eiareport/eia_2472016/html/EIA/Appendix/Appendix_3.5.pdf