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