Table of Contents

 

4            air quality impacts. 4-1

4.1     Introduction. 4-1

4.2     Environmental Legislation, Polices, Standards and Criteria. 4-1

4.3     Identification Air Sensitive Receivers. 4-2

4.4     Identification of Potential Air Quality Impacts. 4-7

4.5     Assessment Methodologies. 4-9

4.6     Evaluation of Air Quality Impacts. 4-22

4.7     Recommendations for Monitoring and Audit 4-3031

4.8     Conclusions. 4-3031

4  air quality impacts  4-1

4.1  Introduction  4-1

4.2  Environmental Legislation, Polices, Standards and Criteria  4-1

4.3  Identification Air Sensitive Receivers  4-2

4.4  Identification of Potential Air Quality Impacts  4-76

4.5  Assessment Methodologies  4-98

4.6  Evaluation of Air Quality Impacts  4-2220

4.7  Recommendations for Monitoring and Audit  4-312928

4.8  Conclusions  4-31292928

 

 

List of Tables

 

Table 4‑1     Hong Kong Air Quality Objectives

Table 4‑2     Tunnel Air Quality Guidelines (TAQG)

Table 4‑3     Details of the Representative Air Sensitive Receivers (ASRs) - Existing

Table 4‑4     Details of the Representative Air Sensitive Receivers (ASRs) – Planned

Table 4‑5     Vehicle Classification in EMFAC-HK

Table 4‑6     Sensitivity of Emission Inventory

Table 4‑7     Emission Factors for NOx in Year 2015 (g/mile-veh)

Table 4‑8     Emission Factors for RSP in Year 2015 (g/miles-veh)

Table 4‑9     Meteorological Conditions for CALINE4 Model (Worst-case Scenario)

Table 4‑10       Background Air Quality

Table 4‑11       Predicted Cumulative Worst Case Average NO2 Concentrations at Existing ASRs

Table 4‑12       Predicted Cumulative Worst Case Average NO2 Concentrations at Planned ASRs

Table 4‑13       Predicted Cumulative Worst Case Average RSP Concentrations at Existing ASRs

Table 4‑14       Predicted Cumulative Worst Case Average RSP Concentrations at Planned ASRs

Table 4‑15       Predicted Maximum NO2 Concentrations inside Full Noise Enclosures

Table 4‑1  Hong Kong Air Quality Objectives

Table 4‑2  Tunnel Air Quality Guidelines (TAQG)

Table 4‑3  Details of the Representative Air Sensitive Receivers (ASRs) - Existing

Table 4‑4  Details of the Representative Air Sensitive Receivers (ASRs) – Planned

Table 4‑5  Vehicle Classification in EMFAC-HK

Table 4‑6  Sensitivity of Emission Inventory

Table 4‑7  Emission Factors for NOx in Year 2015 (g/mile-veh)

Table 4‑8  Emission Factors for RSP in Year 2015 (g/miles-veh)

Table 4‑9  Meteorological Conditions for CALINE4 Model (Worst-case Scenario)

Table 4‑10  Background Air Quality

Table 4‑11  Predicted Cumulative Worst Case Average NO2 Concentrations at Existing ASRs

Table 4‑12  Predicted Cumulative Worst Case Average NO2 Concentrations at Planned ASRs

Table 4‑13  Predicted Cumulative Worst Case Average RSP Concentrations at Existing ASRs

Table 4‑14  Predicted Cumulative Worst Case Average RSP Concentrations at Planned ASRs

Table 4‑15  Predicted Maximum NO2 Concentrations inside Full Noise Enclosures

Table 4‑1  Hong Kong Air Quality Objectives

Table 4‑2  Tunnel Air Quality Guidelines (TAQG)

Table 4‑3  Details of the Representative Air Sensitive Receivers (ASRs) - Existing

Table 4‑4  Details of the Representative Air Sensitive Receivers (ASRs) – Planned

Table 4‑5  Vehicle Classification in EMFAC-HK

Table 4‑6  Sensitivity of Emission Inventory

Table 4‑7  Emission Factors for NOx in Year 2015 (g/mile-veh)

Table 4‑8  Emission Factors for RSP in Year 2015 (g/miles-veh)

Table 4‑9  Meteorological Conditions for CALINE4 Model (Worst-case Scenario)

Table 4‑10  Background Air Quality

Table 4‑11  Predicted Worst Case Average NO2 Concentrations at Existing ASRs

Table 4‑12  Predicted Worst Case Average NO2 Concentrations at Planned ASRs

Table 4‑13  Predicted Worst Case Average RSP Concentrations at Existing ASRs

Table 4‑14  Predicted Worst Case Average RSP Concentrations at Planned ASRs

Table 4‑15  Predicted Maximum NO2 Concentrations inside Full Noise Enclosures

 

 

List of Figures

 

Figure 4-1           Representative Air Sensitive Receivers Under EIAO

Figure 4-2           Location of Tsuen Wan Air Quality Monitoring Station and Ching Pak House Automatic Weather Station

Figure 4-3           Location of Concurrent Projects

Figure 4-4           Location of Chimneys

Figure 4-5           Pollutant Isopleths – NO2 (1-hour) (At Worst Hit Concentration)Predicted Cumulative Hourly NO2 Concentration At Worst Hit Level (1.5m Above Ground)

Figure 4-6           Predicted Cumulative Daily NO2 Concentration At Worst Hit Level (1.5m Above Ground)Pollutant Isopleths – NO2 (24-hour) (At Worst Hit Concentration)

Figure 4-7           Predicted Cumulative Daily RSP Concentration At Worst Hit Level (1.5m Above Ground)Pollutant Isopleths – RSP (24-hour) (At Worst Hit Concentration)

 

 

List of Appendices

 

Appendix 4-A     Photos of Air Sensitive Receivers

Appendix 4-B     Road Link Map

Appendix 4-C     Adjustments on Exhaust Technology Fractions

Appendix 4-D     Estimated population in year 2015, 2020, 2025, 2030

Appendix 4-E      Trips per VMT

Appendix 4-F      Details of Annual Traffic Census Core Station 5010, 5018, 5026, 5030 and 5035 

Appendix 4-G     Meteorology Information

Appendix 4-H     Sensitivity Test of Emission Inventory and Calculation of Emission Factors

Appendix 4-I       Speed Fraction

Appendix 4-J      Sensitivity Test Speed Fraction

Appendix 4-K     Surface Roughness

Appendix 4-L      Supplementary Information for CALINE4 Model

Appendix 4-M    Calculation of Portal Emission

Appendix 4-N     Photographic Survey for Chimney Inventory

Appendix 4-O     Request Letter and Responses for Chimney Inventory

Appendix 4-P      Chimney Emission Inventory

Appendix 4-Q     Calculation of Air Quality Inside Full Noise Enclosure

Appendix 4-R     Sample Input Files of EMFAC-HK Model

Appendix 4-S      Sample Input Files of CALINE4 Model

Appendix 4-T      Sample Input Files of ISCST3 Model

Appendix 4-U     Predicted Worst Case Average Pollutant Concentrations at ASRs

4                          air quality impacts

4.1                    Introduction

4.1.1              Proposed scope of the Project includes upgrading and widening of Tsuen Wan Road (TWR) for 2.8km between Tuen Mun Road (TMR) and Kwai Tsing interchange, as well as associated improvement works for connected local roads and interchanges.

4.1.2              For the construction stage of the Project with works including civil, structural, drainage, geotechnical and landscaping works, traffic control and surveillance systems, traffic aids and street lighting works etc. would possibly create air quality impact to the adjacent air sensitive receivers (ASRs).  For operational phase, increase of traffic flow due to the upgrading of existing TWR would be also possible to generate additional air quality impact to the surrounding ASR.

4.1.3              Hence, it is necessary to carry out air quality impact assessment to try controlling and minimizing the potential air quality impact to the ASRs associated with the Project.  Besides, necessary air mitigation measures for non-compliance of the Air Quality Objectives (AQOs) should be considered, if necessary.

4.1.4              This section summarizes the identified sources of air quality impact during both the construction and operational phases.  Representative ASRs have been identified and the potential air quality impacts to these receivers arising from associated impacts have been evaluated.  Appropriate mitigation measures have been proposed, as and when required, in order to alleviate the potential air quality impacts to acceptable levels.

4.2                    Environmental Legislation, Polices, Standards and Criteria

Air Quality Objectives

4.2.1              Hong Kong’s air quality is regulated through the Air Pollution Control Ordinance (APCO). The APCO specifies AQOs, which are the statutory limits for a number of pollutants and the maximum allowable number of times that these may be exceeded over specified periods. 

4.2.2              The AQOs form the statutory criteria for evaluating air quality impacts and are reproduced in Annex 4 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) as standards for EIA purposes as shown in Table 4‑1Table 4‑1Table 4‑1Table 4‑1Table 4‑1Table 4‑1Table 4‑1Table 4‑1Table 4‑1Table 4‑1Table 4‑1.

Table 4‑1        Hong Kong Air Quality Objectives

Parameter

Maximum Average Concentration (µg/m3) (1)

1 Hour (2)

8 Hours (3)

24 Hours (3)

Annual (4)

Sulfur Dioxide (SO2)

800

----

350

80

Total Suspended Particulates (TSP)

500 (1) (5)

-----

260

80

Respirable Suspended Particulates (RSP)

-----

-----

180

55

Nitrogen Dioxide (NO2)

300

-----

150

80

Carbon Monoxide (CO)

30,000

10,000

-----

-----

Photochemical Oxidants (as Ozone) (6)

240

----

----

----

Notes:

1)       Measured at 298 K and 101.325 kPa (one atmosphere).

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

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

4)       Arithmetic mean.

5)       Not an AQO, but an EIAO-TM criterion for construction dust impact assessment. It is accepted that an hourly-averaged TSP concentration of 500 µg/m3 should not be exceeded.

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

 

Tunnel Air Quality Guidelines

4.2.3              In addition to the statutory AQO limits, air pollutant concentration of various common vehicular gaseous emission recommended in Tunnel Air Quality Guidelines (TAQG) specified under the EPD’s “Practice Notes on Control of Air Pollution in Vehicle Tunnel, 1995” should not exceed inside road tunnels or full noise enclosures. Table 4‑2Table 4‑2Table 4‑2Table 4‑2Table 4‑2Table 4‑2Table 4‑2 presents these guideline values.

Table 4‑2        Tunnel Air Quality Guidelines (TAQG)

Air Pollutant

Averaging Time (min)

Maximum Concentration

µg/m3

ppm

Carbon Monoxide (CO)

5

115,000

100

Nitrogen Dioxide (NO2)

5

1,800

1

Sulfur Dioxide (SO2)

5

1,000

0.4

               Note:

                    All limits are expressed at reference conditions of 298K and 101.325kPa.

 

4.2.4              In addition to the foregoing, visibility in tunnels or full noise enclosures should be controlled to a maximum level equivalent to an extinction coefficient of 0.005 m-1 during any 5 minutes interval.

4.3                    Identification Air Sensitive Receivers

4.3.1              ASRs were identified in accordance with Annex 12 of the EIAO-TM. These include any domestic premises, hotels, hostels, temporary housing accommodation, hospitals, medical clinics, educational institutions, offices, factories, shops, shopping centres, places of public worship, libraries, courts of law or performing arts centres.

4.3.2              Existing ASRs were identified with reference to the latest information provided on the survey maps and further confirmed by actual site conditions as per site surveys and inspections in the mid of August 2007.  Planned ASRs have also been identified with reference to the latest published Outline Zoning Plans (OZPs).  Relevant site photos to justify the actual condition of the ASRs are given in Appendix 4-A. 

4.3.3              For the case of the planned residential developments of the Kowloon Canton Railway Corporation (KCRC) at TW5, TW6 and TW7 as well as TWTL 394, the latest approved master layout plans available at the time working on this assessment have been taken into consideration.

4.3.4              Besides, latest comments provided by Planning Department on 25 May 2007 regarding the podium levels and building heights (refer to Appendix 3-B) have been adopted.

4.3.5              Details of the identified representative ASRs and their land uses for the air quality assessment are illustrated in Table 4‑3Table 4‑3Table 4‑3Table 4‑3Table 4‑3Table 4‑3Table 4‑3 and

4.1.1              Table 4‑4

4.1.1              Table 4‑4

4.1.1              Table 4‑4

4.1.1              Table 4‑4

4.1.1              Table 4‑4

4.1.1              Table 4‑4

4.3.6              Table 4‑4, for existing and planned receivers respectively.  Corresponding locations of the identified representative ASRs are shown in Figure 4-1.

Table 4‑3        Details of the Representative Air Sensitive Receivers (ASRs) - Existing

ASR No.

Description

Land Use

No. of Storey

Podium (P) / Site (S) Levels (mPD) (1)

Horizontal Distance to the Site Boundary (m)

Existing ASRs

1

Allway Gardens Block A

Residential

22

57.1 (P)

240

2

Tsuen Wan Adventist Hospital Staff Quarter

Residential

5

44.2 (S)

200

3

Summit Terrace Block 2

Residential

39

37.1 (P)

140

4

Summit Terrace Block 3

Residential

40

37.1 (P)

120

5

Summit Terrace Block 5

Residential

40

37.1 (P)

100

6

Kong Nam Industrial Building

Industrial

26

11.1 (S)

20

7

The Panorama

Residential

43

30.4 (P)

40

8

Wang Fat Ching She

Place of Worship

2

25.3 (S)

210

9

Lok Shun Seaview Factory Building

Industrial

14

4.1 (S)

10

10

Serenade Cove Block B

Residential

32

13.7 (P)

140

11

Golden Bear Industrial Centre

Industrial

25

4.4 (S)

5

12

Wong Siu Ching Secondary School

School

6

4.0 (S)

100

13

Clague Garden Estate Block A

Residential

40

4.0 (S)

20

14

Clague Garden Estate Block B

Residential

40

4.0 (S)

50

15

Clague Garden Estate Block C

Residential

40

4.0 (S)

30

16

Salvation Army Ng Kok Wai Memorial Kindergarten

School

2

5.1 (S)

10

28

Skyline Plaza

Residential

35

23.4 (P)

130

29

Vision City Tower 1

Residential

41

38.4 (P)

230

30

Vision City Tower 2

Residential

43

38.4 (P)

270

31

Tsuen Wan Park

Recreational

-----

5.8 (S)

Within Site Boundary (3)

35

No. 57 Yeung Uk Road

Residential

5

4.0 (S)

280

36

Tsuen Wan Caritas Clinic

Clinic

4

4.0 (S)

310

41

Texaco Road Industrial Centre

Industrial

16

4.0 (S)

60

56

Waterside Plaza Block 1

Residential

37

18.2 (P)

60

57

Waterside Plaza Block 2

Residential

37

18.2 (P)

60

58

Waterside Plaza Block 3

Residential

32

19.5 (P)

70

59

Waterside Plaza Block 4

Residential

31

19.5 (P)

80

60

Shak Chung Shan Memorial Catholic Primary School

School

7

4.5 (S)

160

62

Riviera Gardens Tower 22

Residential

30

22.3 (P)

160

63

165

64

Metropolitan Industrial & Warehouse Building No.2

Industrial

22

4.8 (S)

0 (2)

65

Leader Industrial Centre Phase I & II

Industrial

15

4.9 (S)

0 (2)

66

Tak Fung Industrial Centre

Industrial

26

4.0 (S)

0 (2)

67

Kerry Godown (Tsuen Wan)

Industrial

17

21.8 (S)

20

68

Chun Shing Factory Estate

Industrial

25

20.2 (S)

10

69

Wing Kei Road 5-A-Side Soccer Pitch

Recreational

-----

15.6 (S)

5

70

Broadway Centre

Industrial

23

20.0 (S)

0 (2)

71

S K H Chu Tan Primary School

School

6

61.0 (S)

140

72

Kwai Shing West Estate Block 8

Residential

24

61.0 (S)

130

73

Lee I Yao Secondary School

School

5

26.5 (S)

70

74

Wing Kin Industrial Building

Industrial

26

7.3 (S)

0 (2)

75

Kingsford Industrial Building Phase 1

Industrial

26

7.6 (S)

20

76

Waford Industrial Building

Industrial

12

7.6 (S)

20

77

Marvel Industrial Building Block B

Industrial

16

5.9 (S)

110

78

Kwai Tak Industrial Building Block 2

Industrial

11

5.0 (S)

120

79

Kwai Shun Street Playground

Recreational

-----

5.5 (S)

150

80

Profit Industrial Building

Industrial

15

5.7 (S)

220

81

Kwai Shun Industrial Centre

Industrial

12

5.4 (S)

230

82

Lai King Catholic Secondary School

School

5

7.2 (S)

500

83

Lai King Estate Fung King House

Residential

14

18.3 (S)

500

84

Supermarket at G/F of the Panorama

Commercial

1

11.3 (S)

65

85

Shop at G/F of Skyline Plaza

Commercial

1

4.2 (S)

100

86

Shopping Centre of Vision City

Commercial

-----

4.3 (S)

225

87

Allway Gardens Shopping Arcade

Commercial

2

52.1 (S)

240

88

Shopping Centre of Waterside Plaza

Commercial

1

4.4 (S)

60

89

Riviera Gardens Tower 22 – G/F

Commercial

1

6.9 (S)

160

Notes:

1)       (P) for podium level and (S) for site level.

2)       ASRs are located adjacent to the site boundary, i.e. horizontal distance to the Site boundary equals to 0m.

3)       Since part of Tsuen Wan Park is located beneath the Tsuen Wan Road viaduct, part of this ASR is within site boundary.

 

Table 4‑4        Details of the Representative Air Sensitive Receivers (ASRs) – Planned

ASR No.

Description

Land Use

No. of Storey

Podium (P) / Site (S) Levels (mPD) (1)

Horizontal Distance to the Site Boundary (m)

Planned ASRs

17

Development at TW5 Bayside Tower 1

Residential

49

30.6 (P)

80

18

Development at TW5 Bayside Tower 2

Residential

42

30.6 (P)

90

19

Development at TW5 Bayside Tower 3

Residential

42

30.6 (P)

110

20

Development at TW5 Bayside Tower 4

Residential

39

30.6 (P)

90

21

Development at TW5 Bayside Tower 5

Residential

39

30.6 (P)

60

22

Development at TW5 Bayside Tower 6

Residential

42

30.6 (P)

20

23

Development at TW5 Bayside Tower 7

Residential

42

30.6 (P)

10

24

Development at TW5 Bayside Tower 8

Residential

42

30.6 (P)

10

25

Development at TW5 Bayside Tower 9

Residential

42

30.6 (P)

10

26

Development at TW5 Cityside Tower 10

Residential

50

33.2 (P)

10

27

Development at TW5 Cityside Tower 11

Residential

52

33.2 (P)

70

32

Tsuen Wan Town Lot 394 Tower 1

Residential

44

30.6 (P)

180

33

Tsuen Wan Town Lot 394 Tower 2

Residential

44

30.6 (P)

170

34

Tsuen Wan Town Lot 393

Commercial

-----

4.3 (S)

130

37

Development at TW6 Tower 1

Residential

48

23.5 (P)

40

38

50

39

Development at TW6 Tower 2

Residential

46

23.5 (P)

50

40

50

42

Development at TW7 Tower 1

Residential

44

20.5 (P)

10

43

10

44

Development at TW7 Tower 2

Residential

44

20.5 (P)

10

45

10

46

Development at TW7 Tower 3

Residential

44

20.5 (P)

10

47

10

48

Development at TW7 Tower 4

Residential

42

20.5 (P)

10

49

10

50

Development at TW7 Tower 5

Residential

42

20.5 (P)

10

51

20

52

Development at TW7 Tower 6

Residential

40

20.5 (P)

5

53

10

54

Development at TW7 Tower 7

Residential

40

20.5 (P)

10

55

20

61

Proposed School Site at TW7

School

6

17.5 (S)

80

Note:

1)   (P) for podium level and (S) for site level.

4.4                    Identification of Potential Air Quality Impacts

Construction Phase

4.4.1              Potential air quality impacts during the construction phase are primarily due to fugitive dust emission. Typical dust generating construction activities include traffic and utility diversion, piling works, substructure construction, superstructure construction, earthworks for retaining wall construction and finishing works.

4.4.2              Construction work of this Project would commence in June 2011 and until June 2015 tentatively.  In general, it is expected that no extensive underground construction work would be conducted throughout the construction phase, but mainly at-grade road pavement construction and pre-cast viaduct elements for on-site installations.

4.4.3              In addition, construction works would be carried out in different phases to minimize number of parallel operations, in order to avoid the adverse environmental impact to the surrounding sensitive receivers. The tentative construction programme and works areas are shown in Figure 2-3 and Figure 2-4, respectively. Potential fugitive dust emissions for each work stage would be finite as only limited construction plants would be operated in each work area. Hence, it is anticipated that heavy amount of dust emission will not be generated.

4.4.4              With the implementation of proper air quality impact mitigation measures as shown in Section 4.6.3, insignificant adverse air quality impacts would be generated from the construction activities.

4.4.5              Furthermore, referring to the construction programme of the Project, there would be 4 potential interfacing projects (as shown in Figure 4-3) taking place in the proximity of the assessment area (500m from the Project Boundary). The concurrent projects are:

·            Reconstruction and Improvement of Tuen Mun Road (2009 to 2011Anticipated Completion Year: 2011): Construction of noise barriers at sections of Tsuen Wan (close to the Panorama, Belvedere Garden, Greenview Court and Yau Kom Tau Village) and Sam Shing Hui;

·            Property Development at Tsuen Wan West Station TW5 (Anticipated Completion Year: 2015 – 20162011 to 2016): Construction: Construction of residential blocks and relevant facilities;

·            Property Development at Tsuen Wan West Station TW6 (Anticipated Completion Year: 2011 – 20122008 to 2012): Construction of residential blocks and relevant facilities; and

·            Property Development at Tsuen Wan West Station TW7 (Anticipated Completion Year: 2012 – 20142011 to 2014): Construction of residential blocks and relevant facilities.

4.4.6              For Reconstruction and Improvement of Tuen Mun Road, the adjacent construction work areas of the Project include (1) Connections of Viaduct N1, (2) Connections of Viaduct S1, (12) Viaduct N1 and (22) Viaduct S1 (numbers refer to Figure 2-4), which major construction tasks are scheduled from June 2011 to January 2015 (refers to Figure 2-3). Therefore, there would be only a short overlap between the projects. Furthermore, this project aims for the provision of noise barriers and associated works and thus the scale of construction activity is considered as small. Hence, it is anticipated that the cumulative air quality impact associated with Reconstruction and Improvement of Tuen Mun Road would be minor.

4.4.7              For Property Development at Tsuen Wan West Station TW5, the adjacent construction work areas of the Project include (29 to 33) Viaduct S4 to S8 and (16 to 20) Viaduct N4 to N8 (numbers refer to Figure 2-4), which major construction tasks are scheduled from January 2012 to January 2015 (refers to Figure 2-3), while for Property Developments at Tsuen Wan West Station TW6 and TW7, the adjacent construction work areas of the Project include (23, 24, 32 to 34 and 39) Viaduct 7 to 11 and Wall 5 and (13, 19 to 21) Viaduct N7 to N10 (numbers refer to Figure 2-4), which major construction tasks are scheduled from January 2012 to January 2015 (refers to Figure 2-3).

4.4.8              Therefore, the construction works of these property developments would potentially coincide with the Project.

4.4.9              However, these property developments would be confined in small work areas and involve typical construction activities. The scale of the property developments would be relatively small and the number of construction equipment employed would be limited.

4.4.10          It is also noteworthy that it is mandatory for Contractors to implement dust suppression measures as stipulated in the Air Pollution Control (Construction Dust) Regulation.

4.4.11          Moreover, it is remarkable that part of Property Developments TW5 (bay-side) will be constructed above the existing West Rail Station, which structure was designed to cater this future development, and thus the extent of dusty construction activities of TW5 (such as piling and substructure) would be minimized.

4.4.12          As a result, construction dust impact due to these concurrent projects would be localised, temporary and surmountable. Hence, adverse cumulative construction dust impacts due to these property developments would not be anticipated.

Operational Phase

4.4.13          Potential air quality impact during the operational phase of Tsuen Wan Road and other major existing road networks would be dominated by vehicle gaseous emissions arising from road traffic.

4.4.14          Air quality impacts, associated with road traffic are caused mostly by Carbon Monoxide (CO), Nitrogen Dioxide (NO2) and Respirable Suspended Particulates (RSP).  Owing to the much higher AQO limit comparing with other major parameters of air quality impact, non-compliance of CO is not envisaged in general, if the NO2 concentrations are below the AQO standards.  Therefore, only 1-hour and 24-hour concentrations of NO2 and RSP were calculated and compared with the AQO limits.

4.4.15          In order to estimate the cumulative air quality impact, pollutant-emitting activities in the Study Area were considered in the air quality impact assessment. The following emission sources were included in the cumulative air quality impact:

·            Vehicle gaseous emissions from open sections of existing and planned road networks within 500m from the Site Boundary;

·            Portal emission from the proposed and existing full noise enclosures; and

·            Chimney emissions arising from nearby industrial premises within 500m from the Site Boundary.

4.4.16          Besides, length of the proposed full noise enclosures for road traffic noise mitigation in this Project ranges from 58m to 110m.  Owing to the longitudinal transport of pollutants promoted by the movement of traffic, as well as the meteorological condition and the turbulence generated by the passing vehicles, air pollutants arising from vehicles emissions would be confined inside noise enclosure structures.   In this connection, air quality inside the tunnel is also critical and was assessed based on the traffic flow features.

4.5                    Assessment Methodologies

Construction Phase

4.5.1              During the construction phase, manner of work conducted by the Contractor should comply with the statutory practice specified on the Air Pollution Control (Construction Dust) Regulations, which specifies management techniques and practices to control air quality impacts arising from fugitive emissions. Further details of appropriate techniques are presented in Section 4.6.3.  In addition to fugitive emissions, operation of diesel powered mechanical plant and construction vehicles will result in gaseous emissions from construction site activities.

Operational Phase

4.5.2              In general, the assessment area for this air quality impact assessment is defined by a distance of 500m from the project boundary as given under the EIA study brief.  Figure 4-1 illustrates schematically the project boundary and assessment area for air quality impact assessment.

4.5.3              As mentioned in Section 4.4.15, potential air quality impact during the operational phase of Tsuen Wan Road project includes the following potential sources.

·            Vehicle gaseous emissions from open sections of existing and planned road networks in Tsuen Wan Road;

·            Portal emission from the proposed and existing full noise enclosures; and

·            Chimneys emissions arising from nearby industrial premises.

4.5.4              Besides the potential air pollution sources, background air quality levels in this assessment area was considered for the purpose of evaluating the cumulative constructional and operational air quality impacts. Details are further elaborated in Section 4.5.664.5.664.5.664.5.664.5.664.5.664.5.754.5.66.

Vehicle Gaseous Emission from Open Road Sections

Emission Factors of Vehicle Gaseous Emission

4.5.5              The cumulative air quality impact generated by vehicle gaseous emission from open road sections and portals were estimated based on the highest emission strength given by the combination of traffic flow and vehicle mixture. The latest version of “EMFAC-HK” provided by EPD was adopted to determine the total emission inventory, and subsequently generate the appropriate vehicle emission factors for each type of vehicle.  The results were input to open road source dispersion model and portal emission calculation to predict the cumulative air quality impact.

4.5.6              Referring to Appendix I of EMFAC-HK Guideline, details of the procedures and assumptions for the use of “EMFAC-HK” are given following sections, whereas the input files of EMFAC-HK model were given in Appendix 4-R.

Assumptions of adopting EMFAC-HK Model in the EIA Study

Vehicle Classes

4.5.7              Vehicle Classes are referred to all vehicles operating on roads within 500m from the project boundary that were categorized into 16 vehicle classes in accordance to the Appendix I of EMFAC-HK Guideline as shown in Table 4-5.

 

Table 4‑5        Vehicle Classification in EMFAC-HK

Vehicle Class

EMFAC-HK Notation

Descriptions

Gross Vehicle Weight

MC 1

PC+LGV(1)

Petrol Private Cars & Light Goods Vehicles

ALL

MC 3

PC+LGV(3)

Diesel Private Cars & Light Goods Vehicles <=2.5 tonne

<=2.5ton

MC 4

LGV(4)

Light Goods Vehicles >2.5-3.5 tonne

>2.5-3.5ton

MC 5

PLB

Public Light Buses

ALL

MC 6

LGV(6)

Light Goods Vehicles >3.5 tonne

>3.5ton – 5.5ton

MC 7

HGV(7)

Medium Goods Vehicles with GVW <15 tonne

>5.5ton – 15ton

MC 8

HGV(8)

Medium & Heavy Goods Vehicles with GVW >=15 tonne

>15ton

MC 10

FBDD

Double Deck Franchised Buses

ALL

MC 11

MC

Motor Cycles

ALL

TAXI 3

Taxi

Taxi

ALL

TAXI 4

PV(4)

Private Light Buses <=3.5 tonne

<=3.5ton

TAXI 5

PV(5)

Private Light Buses >3.5 tonne

>3.5ton

TAXI 6

NFB(6)

Non-franchised Buses <=6.4 tonne

<=6.4ton

TAXI 7

NFB(7)

Non-franchised Buses 6.4-15 tonne

>6.4ton – 15ton

TAXI 8

NFB(8)

Non-franchised Buses >15 tonne

>15ton

TAXI 10

FBSD

Single Deck Franchised Buses

ALL

 

Road Grouping

4.5.8              Roads within the Study Area were grouped into two types, namely Trunk Roads and Local Roads, which were characterised by continuous flow and interrupted flow respectively. Hence two sets of emission factors for the two road types were calculated. The associated Road Link Map is shown in Appendix 4-B.

Exhaust Technology Fractions

4.5.9              The underlying assumptions in EMFAC-HK are that the vehicle can be categorized into unique technology groups with each technology group representing vehicles with distinct emission control technologies, which have similar in-use deterioration rates, and respond the same to repair. 

4.5.10          Exhaust Technology Fraction for each vehicle class has adopted from the information provided in the Up to Date Vehicle Licensed Number by Age and Technology Group Fractions from EPD's website. However, since there is no further information available after year 2003, exhaust technology fraction for each vehicle class are then assumed to be the same as proportion in year 2003 as a conservative approach. In addition, some adjustments have been made according to Appendix II of the EPD Guideline on Modelling Vehicle Emissions, Implementation Schedule of Vehicle Emission Standards in Hong Kong (Updated as at 17 August 2005). Details of adjustments in each vehicle class are shown in Appendix 4-C.

Evaporative Technology Fractions

4.5.11          Default values and compositions are adopted in this Study, referring to the EPD Guideline on Modelling Vehicle Emissions.

Vehicle Population

4.5.12          Refer to the EPD Guideline on Modelling Vehicle Emissions, the latest vehicle age distribution data provided in the EPD’s website (Year 2003) has been adopted in this study with exception to the population of private car, taxi, public light bus and private light bus >3.5ton.  Corresponding population has been calculated and shown in Appendix 4-D. Details on the assumptions adopted for the abovementioned vehicle population are presented below.

Private Car  

4.5.13          As the implementation of Vehicle Emission Standards, there was no new registration of diesel private car in Hong Kong after 1998. Hence, population of private car is considered 100% using petrol fuel in this Study, and number of diesel private car subsequent to year 1998 is then regrouped into petrol type.

Taxi

4.5.14          As the implementation of Vehicle Emission Standards, new registration of diesel taxi was banned in Hong Kong on 1st August 2001. 100% of LPG taxies were therefore assumed in this study and diesel taxi subsequent to 1st August 2001 was then regrouped into LPG fuel type.

Public Light Bus (PLB)

4.5.15          An incentive scheme has been implemented by Environmental, Transport and Works Bureau (ETWB) to encourage the replacement of diesel light buses with LPG type since 2002. Refer to the Up to Date Vehicle Licensed Number by Age and Technology Group Fractions provided in EPD's website, 28% of diesel and 72% of LPG public light buses were newly registered in 2003, however there was no further information available after 2003. Proportions of diesel and LPG PLB were then assumed as same as year 2003 for those vehicles registered after 2003 as a conservative approach. 

 

 

Private Light Bus >3.5ton

4.5.16          An incentive scheme has been implemented by Environmental, Transport and Works Bureau (ETWB) to encourage the replacement of diesel light buses with LPG type since 2002. Refer to the Up to Date Vehicle Licensed Number by Age and Technology Group Fractions provided in EPD's website, 50% of diesel and LPG private light buses (>3.5ton) were newly registered in 2003. Since there was no further information available after 2003, proportions of diesel and LPG were then assumed 50% respectively for those vehicles registered after 2003 as a conservative approach. 

 Accrual Rate

4.5.17          Since there was absence of forecast information in the model year and hence “Default values and compositions” are adopted referred to EMFAC-HK Guideline.

Daily Trips

4.5.18          With reference to the EPD Guideline on Modelling Vehicle Emissions, the diurnal variation of daily trips is used to estimate the cold start emission of petrol vehicles. Hence, trips for vehicle other than petrol type vehicle would be assumed zero.  In contrast, estimations on number of trips for petrol type vehicle in different road types are considered as following, where associated Road Link Map is shown in Appendix 4-B.

Trunk Road Sections

4.5.19          It was assumed that number of trips in the trunk road sections would be zero, as no cold start would be considered in the trunk road section under normal circumstance.

Local Road Sections

4.5.20          It was assumed that the number of trips equal to the number of cold start in these sections. For assuming number of trips is direct proportion to VMT and pattern is similar throughout Hong Kong territory. Number of trips in this Study Area was then estimated by multiplying VMT within Study Area and Trips per VMT within Hong Kong .

4.5.21          Trips per VMT within Hong Kong  were calculated based on the default data of EMFAC-HK, whereas VMT within Study Area was calculated by multiplying the number of vehicle and the length of road travelled in this Study Area. Corresponding trips per VMT are shown in Appendix 4-E.

Daily Vehicle Mile Travelled (VMT)

4.5.22          Vehicle-Mile-Travelled (VMT) was inputted in the model, which represents the total distance travelled on a weekday. The regional specific VMT was calculated by multiplying vehicle flow and section length with reference to the Final TIA Report issued by Scott Wilson in January 2007 in association with MVA Hong Kong Ltd.

4.5.23          Diurnal traffic pattern was inputted to simulate the effect of different traffic pattern. In order to determine the proportion of estimated daily traffic flow variation, hourly traffic flow at Kwai Chung Road (KCR), Core Station No. 5030 was adopted, as it is the nearest available core station to the Study Area and directly interfaces with the TWR, according to Annual Traffic Census 2006 by Transport Department (TD).  Location of nearby core stations and extracted information from Transport Department are shown in Appendix 4-F.

4.5.24          It should be noted that information from other stations No. 5010, 5018, 5026 and 5035 were not adopted since their comparatively remote locations to the assessment area (please refer to Figure 1 in Appendix 4-F.), as well as the difference of vehicle proportion (characteristic), which do not match with the TIA report that already endorsed by TD.

4.5.25          Diurnal traffic variation for various vehicle types are then estimated based on the "Table of Vehicle Classification and Occupancy" extracted from Appendix A1 of Annual Traffic Census 2006. Those assumptions of referencing information from core station 5030 were adopted with no comment from TD. 

Hourly Temperature and Relative Humidity Profile

4.5.26          According to the information provided by Hong Kong Observatory, nearest meteorological station of this Project is Ching Pak House Automatic Weather Station, with anemometer height of 136m. By considering the characteristic of Ching Pak House Automatic Weather Station would be representative to this Study Area, annual and monthly hourly average ambient temperature and relative humidity obtained from this station are adopted in the model. The adopted values are shown in Appendix 4-G.

Model Year

4.5.27          For the purpose of finding the worst scenario year, sensitivity test for emission inventory among 15 years after the commencement of the Project is carried out, which are Year 2015, 2020, 2025 and 2030. Based on emission control schemes in the testing years with varied VMT of corresponding years, four sets of emission inventory with emission factors were produced and provided in Appendix 4-H. Emission Factors in the year that with the largest emission inventory is used as the model year of the air quality impact assessment (AQIA) for worst-case scenario prediction associated with vehicular gaseous emission.

4.5.28          The peak hour travel speeds for Yr 2015, 2020, 2025 and 2030 were adopted in the sensitivity test, which were calculated based on the peak traffic flow of the corresponding year & V/C ratio. By using the peak hour flow in each year, it was found year 2015 is the worst scenario year and hence emission factors in year 2015 would be adopted in this Study.

4.5.29          Default value 45 years (between Starting Model Year and Final Model Year) was used to include 45 model years. The Calendar Years were set as  “2015”, “2020”, “2025”, and “2030” respectively.

Speed Fractions

4.5.30          To simulate the effect of different road speed during the rush and non-rush hour, sensitivity test had been carried out. The design road speed limits were assumed for representing the situation during non-rush hour; while the vehicle speed of peak hour flow was adopted representing the situation during the rush hour. The estimated speed fractions of year 2015, 2020, 2025 and 2030 were shown in Appendix 4-I.

4.5.31          The peak flow hour travel speeds were calculated based on the peak traffic flow in Year 2015 and volume/capacity ratio of different road types. To obtain the speed fractions of each vehicle type, the vehicle speeds of each road were first calculated and weighed by VMT. The estimated speed fractions of model year in 2015 were adopted in the sensitivity test, as it was the worst scenario year among assessment years according to the model year sensitivity test described in Section 4.5.284.5.284.5.284.5.284.5.284.5.284.5.294.5.28.

4.5.32          In the model, same road speeds were applied to all hours to demonstrate the effect of using peak flow speed and design speed. The worst emission factors were selected for predicting the vehicle emissions. Results of Sensitivity Test are shown in Appendix 4-J.

Modelling Modes

Scenario Type   

4.5.33          “Burden Mode” was the only scenario that can consider and provide the hourly vehicular emissions according to the diurnal variations of vehicle-kilometer-travelled (VKT), trips, ambient temperature, relative humidity and speed.

Output Frequency

4.5.34          Hourly average emission factors were derived for the purpose of obtaining worst emission factor.

Procedure of EMFAC-HK Applications

Emission Inventories

4.5.35          For trunk road sections, only “Run Exhaust” was considered as it was characterised by continuous flow, whereas “Start Exhaust” and “Run Exhaust” were considered for local road sections because of the cold start emissions including. 

Calculation of Emission Factors

4.5.36          Further as the results from EMFAC-HK were given in different type of fuel, hourly emission factors were then calculated by dividing total emission inventory by total VKT in each vehicle class in each hour, in order to obtain representative and generic emission factors for these vehicle categories. For example: Emission Factor of LGV is:

 

 

 

 

 

Emission Factor = Σ(Emission Inventory)i / Σ(VKT)i

 

 

 

where            NCAT = Non Catalyst;           

CAT = Catalyst; and

DSL= Diesel

4.5.37          The maximum value of calculated hourly emission factors in grams per miles per vehicle were then selected for the incorporation into the air quality impact assessment for a conservative approach.

Emission Factors for Each Road Link

4.5.38          Composite emission factors for road links were calculated by the weighted average of the emission factors of sixteen different types of vehicles. Contribution of total emission factors by all identified line-sources (road links) within 500m-assessment area has been included in the sensitivity test. Details of the sensitivity analysis are shown in Appendix 4-H and Table 4‑6Table 4‑6Table 4‑6Table 4‑6Table 4‑6Table 4‑6Table 4‑6 summarizes the findings.

Table 4‑6        Sensitivity of Emission Inventory

Total Emission Inventory (g/s)

 

Yr 2015

Yr 2020

Yr 2025

Yr 2030

NOx (TR)

8.97

6.43

5.61

5.84

NOx (LR)

4.54

3.21

2.85

3.03

RSP (TR)

0.47

0.24

0.22

0.24

RSP (LR)

0.37

0.19

0.17

0.19

 

4.5.39          In Table 4‑6Table 4‑6Table 4‑6Table 4‑6Table 4‑6Table 4‑6Table 4‑6, it was noted that greater emission inventory is resulted for both NOx and RSP in Year 2015. Therefore, Year 2015 was selected as the worst-case model year for the air quality impact assessment, whereas the calculated emission factors for different vehicle categories were list in Table 4‑7Table 4‑7Table 4‑7Table 4‑7Table 4‑7Table 4‑7Table 4‑7 and Table 4‑8Table 4‑8Table 4‑8Table 4‑8Table 4‑8Table 4‑8Table 4‑8.

Table 4‑7        Emission Factors for NOx in Year 2015 (g/mile-veh)

Vehicle Class

Description

NOx E.F. g/mile-veh

Trunk Road

Local Road

MC 1

Petrol Private Cars & Light Goods Vehicles

0.127

0.178

MC 3

Diesel Private Cars & Light Goods Vehicles <=2.5 tonne

0.421

0.455

MC 4

Light Goods Vehicles 2.5-3.5 tonne

0.285

0.308

MC 5

Public Light Buses

0.173

0.162

MC 6

Light Goods Vehicles >3.5 tonne

2.441

2.637

MC 7

Medium Goods Vehicles with GVW <15 tonne

4.934

5.258

MC 8

Medium & Heavy Goods Vehicles with GVW >=15 tonne

6.116

6.520

MC 10

Double Deck Franchised Buses

3.276

3.784

MC 11

Motor Cycles

1.150

1.229

TAXI 3

Taxi

0.231

0.289

TAXI 4

Private Light Buses <=3.5 tonne

0.000*

0.000*

TAXI 5

Private Light Buses >3.5 tonne

0.252

0.255

TAXI 6

Non-franchised Buses <=6.4 tonne

1.796

1.933

TAXI 7

Non-franchised Buses 6.4-15 tonne

4.222

4.559

TAXI 8

Non-franchised Buses >=15 tonne

4.487

4.856

TAXI 10

Single Deck Franchised Buses

2.777

3.229

*There is NO Private Light Bus <3.5t within this Study Area

 

Table 4‑8        Emission Factors for RSP in Year 2015 (g/miles-veh)

Vehicle Class

Description

RSP E.F. g/mile-veh

Trunk Road

Local Road

MC 1

Petrol Private Cars & Light Goods Vehicles

0.004

0.008

MC 3

Diesel Private Cars & Light Goods Vehicles <=2.5 tonne

0.104

0.180

MC 4

Light Goods Vehicles 2.5-3.5 tonne

0.063

0.110

MC 5

Public Light Buses

0.097

0.151

MC 6

Light Goods Vehicles >3.5 tonne

0.147

0.255

MC 7

Medium Goods Vehicles with GVW <15 tonne

0.243

0.415

MC 8

Medium & Heavy Goods Vehicles with GVW >15 tonne

0.223

0.380

MC 10

Double Deck Franchised Buses

0.079

0.154

MC 11

Motor Cycles

0.041

0.065

TAXI 3

Taxi

0.016

0.033

TAXI 4

Private Light Buses <=3.5 tonne

0.000*

0.000*

TAXI 5

Private Light Buses >3.5 tonne

0.140

0.224

TAXI 6

Non-franchised Buses <=6.4 tonne

0.053

0.093

TAXI 7

Non-franchised Buses 6.4-15 tonne

0.145

0.254

TAXI 8

Non-franchised Buses >15 tonne

0.131

0.229

TAXI 10

Single Deck Franchised Buses

0.093

0.184

*There is NO Private Light Bus <3.5t within this Study Area

 

Traffic Flow Condition

4.5.40          Forecasted AM peak traffic flow and vehicle mixture of the major roads related to this Project in Year 2015 was adopted as the basis of worst-case scenario traffic condition (refer to Final TIA Report, issued by Scott Wilson Ltd in January 2007 in association with MVA Hong Kong Ltd., as attached in Appendix 3-H). In accordance with the endorsed Final TIA Report, the AM peak traffic flow would larger in volume than PM peak traffic flow. The AM peak traffic flows were hence adopted in the assessment of nighttimes traffic flows of selected year of assessment, as a conservative approach. 

Open Road Emission

4.5.41          Dispersion model CALINE4, based on the Gaussian diffusion equations employing a mixing zone concept to characterise pollutant dispersion over roadways, was used to assess the operational traffic air quality impacts upon the identified representative ASRs.

Meteorological Condition

4.5.42          Due to its incapability of CLAINE4 in handling lengthy data, the meteorological conditions adopted to predict the worst-case pollutant concentrations at identified ASRs are presented in Table 4-9. The estimation of surface roughness is presented in Section 4.5.434.5.434.5.434.5.434.5.434.5.434.5.484.5.43.

Table 4‑9        Meteorological Conditions for CALINE4 Model (Worst-case Scenario)

Meteorological Parameter

Daytime Scenario

Nighttime Scenario

Time Period

7:00 AM – 7:00 PM

7:00 PM – 7:00 AM (Next Day)

Stability class

D

F

Standard deviation of wind direction

22.79o

6.93o

Wind speed

1 m/s

Wind direction

Worst case for each receiver

Worst case for each receiver

Surface roughness height

302 cm

Mixing height

500 m

Temperature

298 K

 

Surface Roughness Height in the Study Area

4.5.43          Since the Project area is adjacent to urban area and water surface, a weighted surface roughness length with respect to prevailing wind direction was evaluated, which was considered to be the best describing the actual surface roughness that could be adopted in this assessment. The weighted surface roughness length shown in Table 4-9 was estimated by considering the ratio of water surface area to urban area portion within the 500 m assessment area for air quality impact assessment. Justifications on the determination of the surface roughness length are provided in Appendix 4-K.

Methodology of CALINE4 Computer Modelling

4.5.44          Due to the wide range of road segments elevated from +3.5mPD to +60mPD within the Study Area, whereas identified ASRs with the elevation ranged from ground level (+5mPD) up to +61mPD, open road emission was modelled in separated files. Details of methodologies are elaborated as follow.

Road Elevations

4.5.45          In view of default input settings of CALINE4 computer simulation analysis for free-flow vehicular line source emission in open air environment, maximum acceptable range of vertical height input on road segments for valid computation is positive altitude within a 10m bandwidth (e.g. 0mPD to +10mPD, +10mPD to +20mPD etc.)  In other words, input of road segment height at negative altitude or out of the range of that 10m bandwidth would be considered as null input for valid computation.

4.5.46          As wide range of road segments elevated from +2mPD to +60mPD 88mPD were presented in this assessment, road sections were divided into eight nine categories according to their height, which were 0-6mPD, 6-16mPD, 16-26mPD, 26-36mPD, 36-46mPD, 46-56mPD and 56-66mPD 0-10mPD, 10-20mPD, 20-30mPD, 30-40mPD, 40-50mPD, 50-60mPD, 60-70mPD, 70-80mPD,and 80-90mPD respectively.

ASRs Elevations

4.5.47          In order to assess the worst scenario of air quality impact to human, assessments for portal emission from full noise enclosures were conducted at 1.5m, 5m, 10m 15m and 20m above ground level or podium level and 3 additional assessment levels covering the building heights to obtain the worst hit concentration.

4.5.48          Another limitation of CALINE4 program is that the input of air impact assessment receptors must be either within the 10m bandwidth abovementioned in accordance with the elevation of road segments, or at any higher elevations.  In other words, input of the receptors lower than the bandwidth of road segment category in consideration was not able to be model from the simulation program.

4.5.49          In order to take into account all identified ASRs within the 500m assessment area boundary with the elevation ranged from ground level (+5mPD) up to +61mPD, all input height of the identified ASRs originally lower than the bandwidth of road segment category in consideration were set with reference point at the lowest level of that bandwidth +1.5m (simulate the normal elevation from ground).  Supplementary information provided in Appendix 4-L illustrates schematically the abovementioned ASRs input methodology.

4.5.50          The estimated pollutant concentrations from every category were then accumulated at each ASR respectively. Consequently, the vehicular emissions contributed from every road sections would be taken into account at each ASR, and hence the total concentration level at each ASR by vehicular emissions by all roads within 500m from work boundary was obtained.

Effects of Noise Mitigation Measures

4.5.51          Potential air quality impacts arising from the implementation of roadside noise mitigation measures (vertical barriers, cantilever noise barriers, semi-enclosures and full-enclosures) were also incorporated into the air quality model.  Locations of existing and proposed noise mitigation measures on the Tsuen Wan Road are shown in Figure 3-5, Appendices 3-I and 3-J.

4.5.52          It was assumed that, with the installation of vertical noise barriers, all the traffic pollutants generated from the mitigated road section would be emitted from the top of the noise barriers as a worst-case consideration. In the CALINE4 model, the elevation of the mitigated road section was set to the elevation of the barrier top, and the road type was set to 'fill'. No correction or adjustment to the receiver heights was made in the model.

4.5.53          For the cantilever noise barriers or semi-enclosures, it was assumed that the dispersion of the traffic pollutants would be adjusted to physically shifting the mitigated road section towards edge of the canopies horizontally. Vehicular gaseous pollutant was assumed to be emitted from the top of the canopies as a worst-case consideration.  In the CALINE4 model, alignment of the mitigated road section was shifted by a distance equal to the covered extent, the elevation of the mitigated road section was set to the elevation of the barrier top, and the road type was set to 'fill'. No correction or adjustment to the receiver heights is required for the model.

Portal Emission from Full Noise Enclosures

4.5.54          In order to assess the worst scenario of air quality impact to human, assessments for portal emission from full noise enclosures were conducted at 1.5m, 5m, 10m 15m and 20m above ground level or podium level and 3 additional assessment levels covering the building heights to obtain the worst hit concentration.

4.5.55          Portal emissions from full noise 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 of portal emission and the locations of portal emissions considered in the assessment are given in Appendix 4-M.

4.5.56          The closest and most representative Hong Kong Observatory (HKO) meteorological station to the Project area is Ching Pak House (with anemometer height 136 metres above mean sea level) automatic weather station.  The hourly meteorological data in year 2006 obtained from this station was used as the meteorological inputs for the modelling of portal emissions due to the implementation of full noise enclosures.  The portal emissions were modelled as volume sources by using the Industrial Source Complex Short Term (ISCST3).  The location of meteorological station is shown in Figure 4-2.

Chimney Emissions from Industrial Premises

4.5.57          Since the Project is located in the vicinity of the industrial premises in Tsuen Wan and Kwai Chung, cumulative impact of potential industrial chimney emissions were considered necessary and included in the cumulative air quality impact assessment.

4.5.58          Within the air quality assessment area (500 m from the Project Boundary), chimney inventory was achieved from Technical Appendices - Environmental Impact Assessment Reports of Section 16 Application for Development Tsuen Wan West (TW5, TW6 and TW7) West Rail, Phase 1 by Kowloon-Canton Railway Corporation.

4.5.59          The chimney inventory has been validated and updated by conducting site photographic survey (at both ground and elevated levels) and checking with the management offices/tenants of the subjected industrial premises by sending request letters, which are shown in Appendix 4-O and Appendix 4-P respectively.

4.5.60          There are totally 94 106 chimney emission sources identified and the chimney locations are summarized and presented in Figure 4-3.

4.5.61          In order to assess the worst scenario of air quality impact to human, assessments for chimney emissions from nearby industrial premises were conducted at 1.5m, 5m, 10m 15m and 20m above ground level or podium level and 3 additional assessment levels covering the building heights to obtain the worst hit concentration.

4.5.62          Since only SO2 was evaluated in these EIA Reports, therefore it is necessary to deduce the fuel consumption rates by SO2 emission rates in accordance with Table 1.3-1 Criteria Pollution Emission Factors for Fuel Oil Combustion of USEPA AP-42.  The detail calculation and assumptions made on chimney emission inventory are given in Appendix 4-P. The ISCST3 dispersion model was used to predict the chimney emission (as point source) from nearby industrial premises. Same set of meteorological data in 2006 at Ching Pak House automatic weather station was used for simulation.

Determination of Proportion of NO2 from NOx

4.5.63          CALINE4 dispersion model is used for calculation of NOx and RSP concentrations by open road traffic. For the calculation of NO2 concentrations, the vehicular emission factors for NOx were used and the conversion factor from NOx to NO2 is assumed to be 20% for open road emission sources.

4.5.64          ISCST3 dispersion model was used to calculate the NOx and RSP concentration from portal emission of full noise enclosures and chimney emissions. Same NO2 conversion factor of 20% is adopted for chimney emissions and portal emission.

4.5.65          In order to obtain the daily average air pollutant concentrations, a factor 0.4 was used to convert the maximum hourly levels to daily average concentrations as suggested by Brode, R.W., 1988 – “Screening Procedures for Estimating the Air Quality Impact of Stationary Sources”. On the other hand, referring to EPA-450/4-88-010, U.S. Environmental Protection Agency, Research Triangle Park, N.C., U.S.A., p 4-17, this factor applies to convert the short-term concentrations estimated by screening models to long terms concentrations.

Background Air Quality Levels

4.5.66          With reference to the latest five years averaged monitoring data from EPD monitoring station at Tsuen Wan, background air pollutant concentrations are shown in Table 4‑10Table 4‑10Table 4‑10Table 4‑10Table 4‑10Table 4‑10Table 4‑10, which have been adopted in this air quality impact assessment.  The 5-year-average background air quality levels were obtained from year 2001 to year 2006, except that of year 2003 (since data in 2003 is not representative) in the nearest EPD air quality monitoring station located in Tsuen Wan (i.e. Princess Alexandra Community Centre, 60 Tai Ho Road).  The location of air quality monitoring station is given in Figure 4-2.

Table 4‑10      Background Air Quality

Air Pollutant

5-year Average Concentration (μg/m3)(1)

Sulfur Dioxide (SO2)

24.0

Total Suspended Particulates (TSP)

77.2

Respirable Suspended particulates (RSP)

56.4

Nitrogen Dioxide (NO2)

64.2

Carbon Monoxide (CO)

747.2

Note:

1)       Due to the close proximity of the monitoring station to the project area, the figures can be adopted as background air quality data in Tsuen Wan.

 

Cumulative Operational Air Quality Impacts

4.5.67          Cumulative air quality impacts at all identified ASRs for NO2 and RSP were calculated by the summation of the modelling results of vehicular emission from free-flow road links (by CALINE4), emission from openings of full noise enclosures (ISCST3) and chimney emission from the nearby industries (ISCST3), together with the respective background concentrations.

Air Quality inside Full Noise Enclosures

4.5.68          Full noise enclosures were proposed in this EIA study along the proposed Tuen Mun and Kowloon bound viaducts. Location of these enclosures is provided in Figure 3-5.

4.5.69          Air quality inside the sections of the full noise enclosures was studied as the case similar to tunnels, since the air pollutants could be confined in the enclosed space inside the enclosures with longitudinal transport of pollutants.  A conversion factor of 12.5% including tailpipe NO2 emission (taken as 7.5% of NOx) plus 5% of NO2/NOx for tunnel recommended in PIARC91 for air expelled from the tunnel was adopted in this assessment as the inside enclosure conversion factor. 

4.5.70          Two scenarios were considered for the air quality evaluation inside the full noise enclosures – normal traffic flow condition and congested traffic flow condition.  Appendix 4-Q shows the detailed calculation of the inside tunnel air quality assessments for the sections of the full enclosures, after the implementation of the proposed noise mitigation measures.

4.6                    Evaluation of Air Quality Impacts

Construction Phase

4.6.1              Among those works mentioned in Section 4.4.1, work stages / activities which will generate fugitive dust emission would include the following:-

·            Traffic and utility diversion;

·            Piling works;

·            Substructure construction;

·            Superstructure construction;

·            Earthworks for retaining wall construction; and

·            Finishing works.

4.6.2              In general, it is anticipated that no extensive underground construction work and piling work would lead to massive fugitive dust emission, since all these works are mainly confined for at-grade road pavement construction and pre-cast viaduct elements ready for on-site installations.

4.6.3              The following site practices are recommended to be fully implemented by Contractor, in order to suppress dust emissions during construction work.  Recommendations are represented in the form of contractual clauses:

·            The Contractor shall undertake at all times to prevent dust nuisance as a result of his activities. Dust suppression measures such as water spraying are necessary and should be installed to ensure that the air quality at the boundary of the site and at any sensitive receivers complies with the AQOs.

·            The Contractor shall notify any specific construction work as stated in the Air Pollution Control (Construction Dust) Regulation to the Authority before the commencement of such work.

·            The Contractor shall apply for a license or permit under the requirements of the relevant legislation (e.g., Air Pollution Control Ordinance and its subsidiary regulations) wherever applicable.

·            Watering of unpaved areas, access roads, construction areas and dusty stockpiles shall be undertaken at least eight times daily during dry and windy weather. Watering of the haul road shall be undertaken four to eight times daily during dry or windy weather. Water sprays may be either fixed or mobile to follow individual areas to be wetted as and when required. Application of suitable wetting agents, such as dust suppression chemicals, shall be used in addition to water, especially during the dry period (November to March).

·            Effective water sprays shall be used during the delivery and handling of all raw sand and aggregate, and other similar materials, wet dust is likely to be created and to dampen all stored materials during dry and windy weather.

·            Stockpiles of sand, aggregate or any other dusty materials greater than 20m3 shall be enclosed on three sides, with walls extending above the pile and 1 metre beyond the front of the pile.

·            Suitable chemical wetting agent such as dust suppression chemical shall be used on completed cuts and fills to reduce wind erosion.

·            Areas within the construction site where there is a regular movement of vehicles shall have a paved surface and be kept clear of loose surface material.

·            The Contractor shall restrict all motorized vehicles within the construction site, excluding those on public roads, to maximum speed of 20 km per hour and confine haulage and delivery vehicles to designated roadways inside the Site.

·            Construction working areas will be restricted to a minimum practicable size.

·            The Contractor shall ensure that no earth, rock or debris is deposited on public or private rights of way as result of his activities, including any deposits arising from the movement of plant or vehicles.

·            The Contractor shall provide a wheel washing facility at the exits from work areas to the satisfaction of the Engineer. Water in wheel washing facilities and sediment shall be changed and removed respectively at least once a month.

·            The Contractor shall submit details of the wheel washing facilities; such shall be usable prior to any earthworks excavation activity on the construction site. The Contractor shall also provide a hard-surfaced road between any washing facility and the public road.

·            In the event of any spoil or debris from construction works being deposited on adjacent land, or streams, or any silt being washed down to any area, then all such spoil, debris or material and silt shall be immediately removed and the affected land and areas restored to their natural state by the Contractor to the satisfaction of the Engineer.

·            If spoil cannot be immediately transported out of the Site, stockpiles should be stored in sheltered areas.

·            Plant and vehicles shall be inspected annually to ensure that they are operating efficiently and that exhaust emissions are not causing a nuisance. All Site vehicle exhausts should be directed vertically upwards or directed away from ground.

·            Dust monitoring will be included in the EM&A Manual at the most affected ASRs.  In general, 24-hour total suspended particulates and 1-hour total suspended particulates are required to be measured at the most affected ASRs.

·            Path for complaints and handling procedures should be set up and implement.With the strict application of the Air Pollution Control (Construction Dust) Regulations, the cumulative impacts associated with the construction of the Tsuen Wan Road Upgrading project and the identified interfacing projects including “Yeung UK Road Widening” and “Reconstruction and Improvement of Tuen Mun Road Eastern Section”, are not anticipated to cause unacceptable impacts. (to be deleted)

Operational Phase

Air Quality from Open Roads

4.6.4              Taking into account vehicular exhaust emission from open road networks, portal emission from full noise enclosure, chimney emission from industrial premises and the background pollutant concentration, the worst cumulative 1-hour NO2, 24-hour NO2 and 24-hour RSP concentrations among the four assessment levels of each ASRs were calculated and are presented in Table 4‑11Table 4‑11Table 4‑11Table 4‑11Table 4‑11Table 4‑11Table 4‑11 to Table 4‑14Table 4‑14Table 4‑14Table 4‑14Table 4‑14Table 4‑14Table 4‑14, whereas the details could be found in Appendix 4-U.

Table 4‑11      Predicted Cumulative Worst Case Average NO2 Concentrations at Existing ASRs

ASR No.

Description

NO2 (μg/m3)

Existing ASRs

Hourly

(Day time)

Hourly

(Nighttime)

Daily

1

Allway Gardens Block A

98.65

121.02

86.93

2

Tsuen Wan Adventist Hospital Staff Quarter

106.84

139.93

94.49

3

Summit Terrace Block 2

99.69

131.01

90.92

4

Summit Terrace Block 3

102.79

137.02

93.33

5

Summit Terrace Block 5

106.94

144.08

96.15

6

Kong Nam Industrial Building

135.38

188.88

114.07

7

The Panorama

112.39

133.67

91.99

8

Wang Fat Ching She

119.74

129.93

90.49

9

Lok Shun Seaview Factory Building

167.04

234.36

132.27

10

Serenade Cove Block B

108.26

128.39

89.88

11

Golden Bear Industrial Centre

137.00

178.85

110.06

12

Wong Siu Ching Secondary School

123.19

155.95

100.90

13

Clague Garden Estate Block A

144.56

185.33

112.65

14

Clague Garden Estate Block B

124.25

164.87

104.47

15

Clague Garden Estate Block C

145.17

190.18

114.59

16

Salvation Army Ng Kok Wai Memorial Kindergarten

154.95

203.54

119.94

28

Skyline Plaza

112.47

153.47

99.91

29

Vision City Tower 1

108.12

135.20

92.60

30

Vision City Tower 2

104.14

130.91

90.88

31

Tsuen Wan Park

206.18

257.58

141.55

35

No. 57 Yeung Uk Road

126.18

165.10

104.56

36

Tsuen Wan Caritas Clinic

135.31

168.76

106.02

41

Texaco Road Industrial Centre

181.97

196.68

117.19

56

Waterside Plaza Block 1

128.55

142.95

95.70

57

Waterside Plaza Block 2

125.30

139.18

94.19

58

Waterside Plaza Block 3

123.60

140.31

94.64

59

Waterside Plaza Block 4

124.30

138.99

94.12

60

Shak Chung Shan Memorial Catholic Primary School

119.60

134.86

92.46

62

Riviera Gardens Tower 22

119.06

131.24

91.02

63

122.11

134.81

92.44

64

Metropolitan Industrial & Warehouse Building No.2

184.30

246.76

137.22

65

Leader Industrial Centre Phase I & II

172.37

227.64

129.57

66

Tak Fung Industrial Centre

151.26

173.59

107.96

67

Kerry Godown (Tsuen Wan)

168.35

197.49

117.52

68

Chun Shing Factory Estate

174.35

248.54

137.94

69

Wing Kei Road 5-A-Side Soccer Pitch

150.43

191.32

115.05

70

Broadway Centre

160.20

229.17

130.19

71

S K H Chu Tan Primary School

104.70

122.37

87.47

72

Kwai Shing West Estate Block 8

106.46

130.56

90.74

73

Lee I Yao Secondary School

141.58

200.92

118.89

74

Wing Kin Industrial Building

174.63

236.63

133.17

75

Kingsford Industrial Building Phase 1

124.45

178.09

109.75

76

Waford Industrial Building

138.23

174.39

108.28

77

Marvel Industrial Building Block B

147.99

176.81

109.24

78

Kwai Tak Industrial Building Block 2

140.58

196.71

117.21

79

Kwai Shun Street Playground

169.71

242.69

135.60

80

Profit Industrial Building

171.36

193.71

116.01

81

Kwai Shun Industrial Centre

134.64

192.49

115.52

82

Lai King Catholic Secondary School

145.47

188.45

113.90

83

Lai King Estate Fung King House

172.78

248.88

138.07

84

Supermarket at G/F of the Panorama

122.10

150.96

98.90

85

Shop at G/F of Skyline Plaza

118.32

160.09

102.55

86

Shopping Centre of Vision City

123.42

164.80

104.44

87

Allway Gardens Shopping Arcade

100.44

125.36

88.66

88

Shopping Centre of Waterside Plaza

131.11

147.70

97.60

89

Riviera Gardens Tower 22 – G/F

127.33

144.98

96.51

Notes:

1)       All pollutant concentrations include the background concentration ([NO2] = 64.2 μg/m3).

 

 

 

 

 

 

Table 4‑12      Predicted Cumulative Worst Case Average NO2 Concentrations at Planned ASRs

ASR No.

Description

NO2 (μg/m3)

Planned ASRs

Hourly

(Day time)

Hourly

(Nighttime)

Daily

17

Development at TW5 Bayside Tower 1

117.71

145.33

96.65

18

Development at TW5 Bayside Tower 2

115.40

142.38

95.47

19

Development at TW5 Bayside Tower 3

110.95

136.22

93.01

20

Development at TW5 Bayside Tower 4

111.81

140.62

94.77

21

Development at TW5 Bayside Tower 5

114.77

148.06

97.74

22

Development at TW5 Bayside Tower 6

126.87

178.10

109.76

23

Development at TW5 Bayside Tower 7

131.45

186.86

113.27

24

Development at TW5 Bayside Tower 8

131.83

184.03

112.13

25

Development at TW5 Bayside Tower 9

133.92

183.78

112.03

26

Development at TW5 Cityside Tower 10

130.34

169.41

106.28

27

Development at TW5 Cityside Tower 11

118.63

150.91

98.88

32

Tsuen Wan Town Lot 394 Tower 1

118.84

152.50

99.52

33

Tsuen Wan Town Lot 394 Tower 2

125.32

158.48

101.91

34

Tsuen Wan Town Lot 393

133.34

180.54

110.74

37

Development at TW6 Tower 1

131.31

158.48

101.91

38

133.83

158.91

102.08

39

Development at TW6 Tower 2

137.78

157.90

101.68

40

136.57

155.79

100.83

42

Development at TW7 Tower 1

162.25

193.40

115.88

43

163.73

192.96

115.70

44

Development at TW7 Tower 2

164.53

193.58

115.95

45

161.82

189.21

114.20

46

Development at TW7 Tower 3

160.47

190.09

114.55

47

153.63

192.06

115.34

48

Development at TW7 Tower 4

148.75

194.26

116.22

49

142.59

183.32

111.85

50

Development at TW7 Tower 5

140.46

180.31

110.64

51

141.40

176.14

108.97

52

Development at TW7 Tower 6

156.88

197.79

117.64

53

149.73

194.81

116.45

54

Development at TW7 Tower 7

149.24

194.72

116.41

55

147.22

192.68

115.59

61

Proposed School Site at TW7

139.19

150.08

98.55

Notes:

1)       All pollutant concentrations include the background concentration ([NO2] = 64.2 μg/m3).

 

Table 4‑13      Predicted Cumulative Worst Case Average RSP Concentrations at Existing ASRs

ASR No.

Description

RSP (μg/m3)

Existing ASRs

Daily

1

Allway Gardens Block A

62.77

2

Tsuen Wan Adventist Hospital Staff Quarter

64.70

3

Summit Terrace Block 2

63.80

4

Summit Terrace Block 3

64.40

5

Summit Terrace Block 5

65.22

6

Kong Nam Industrial Building

70.94

7

The Panorama

64.32

8

Wang Fat Ching She

63.60

9

Lok Shun Seaview Factory Building

75.06

10

Serenade Cove Block B

63.74

11

Golden Bear Industrial Centre

68.98

12

Wong Siu Ching Secondary School

67.40

13

Clague Garden Estate Block A

69.74

14

Clague Garden Estate Block B

67.73

15

Clague Garden Estate Block C

69.51

16

Salvation Army Ng Kok Wai Memorial Kindergarten

71.28

28

Skyline Plaza

66.88

29

Vision City Tower 1

64.63

30

Vision City Tower 2

64.12

31

Tsuen Wan Park

76.02

35

No. 57 Yeung Uk Road

69.37

36

Tsuen Wan Caritas Clinic

69.58

41

Texaco Road Industrial Centre

71.58

56

Waterside Plaza Block 1

65.35

57

Waterside Plaza Block 2

64.95

58

Waterside Plaza Block 3

64.62

59

Waterside Plaza Block 4

64.43

60

Shak Chung Shan Memorial Catholic Primary School

64.48

62

Riviera Gardens Tower 22

63.83

63

63.98

64

Metropolitan Industrial & Warehouse Building No.2

77.82

65

Leader Industrial Centre Phase I & II

75.75

66

Tak Fung Industrial Centre

68.32

67

Kerry Godown (Tsuen Wan)

71.20

68

Chun Shing Factory Estate

77.65

69

Wing Kei Road 5-A-Side Soccer Pitch

70.20

70

Broadway Centre

76.63

71

S K H Chu Tan Primary School

63.14

72

Kwai Shing West Estate Block 8

64.04

73

Lee I Yao Secondary School

72.80

74

Wing Kin Industrial Building

74.97

75

Kingsford Industrial Building Phase 1

70.21

76

Waford Industrial Building

69.81

77

Marvel Industrial Building Block B

69.19

78

Kwai Tak Industrial Building Block 2

71.64

79

Kwai Shun Street Playground

76.38

80

Profit Industrial Building

70.64

81

Kwai Shun Industrial Centre

71.19

82

Lai King Catholic Secondary School

69.85

83

Lai King Estate Fung King House

77.46

84

Supermarket at G/F of the Panorama

67.44

85

Shop at G/F of Skyline Plaza

68.23

86

Shopping Centre of Vision City

69.14

87

Allway Gardens Shopping Arcade

63.25

88

Shopping Centre of Waterside Plaza

65.92

89

Riviera Gardens Tower 22 – G/F

65.62

Notes:

1)       All pollutant concentrations include the background concentration ([RSP] = 56.4 μg/m3).

 

Table 4‑14      Predicted Cumulative Worst Case Average RSP Concentrations at Planned ASRs

ASR No.

Description

RSP (μg/m3)

Planned ASRs

Daily

17

Development at TW5 Bayside Tower 1

65.28

18

Development at TW5 Bayside Tower 2

65.00

19

Development at TW5 Bayside Tower 3

64.44

20

Development at TW5 Bayside Tower 4

64.95

21

Development at TW5 Bayside Tower 5

65.74

22

Development at TW5 Bayside Tower 6

68.82

23

Development at TW5 Bayside Tower 7

69.70

24

Development at TW5 Bayside Tower 8

69.51

25

Development at TW5 Bayside Tower 9

69.42

26

Development at TW5 Cityside Tower 10

67.20

27

Development at TW5 Cityside Tower 11

65.94

32

Tsuen Wan Town Lot 394 Tower 1

66.53

33

Tsuen Wan Town Lot 394 Tower 2

66.84

34

Tsuen Wan Town Lot 393

69.92

37

Development at TW6 Tower 1

66.75

38

66.70

39

Development at TW6 Tower 2

66.45

40

66.35

42

Development at TW7 Tower 1

70.77

43

70.84

44

Development at TW7 Tower 2

70.88

45

70.21

46

Development at TW7 Tower 3

69.77

47

69.63

48

Development at TW7 Tower 4

69.70

49

68.85

50

Development at TW7 Tower 5

68.64

51

67.99

52

Development at TW7 Tower 6

70.11

53

70.03

54

Development at TW7 Tower 7

70.04

55

69.69

61

Proposed School Site at TW7

65.56

Notes:

1)       All pollutant concentrations include the background concentration ([RSP] = 56.4 μg/m3).

 

4.6.5              In Table 4‑11Table 4‑11Table 4‑11Table 4‑11Table 4‑11Table 4‑11Table 4‑11 and Table 4‑12Table 4‑12Table 4‑12Table 4‑12Table 4‑12Table 4‑12Table 4‑12, the simulated results at ASRs show that the nighttime NO2 concentrations are higher than the concentrations during daytime. Thus, nighttime condition was considered as the worst-case condition and the hourly averaged result during daytime nighttime was used to calculate the daily concentration.

4.6.6              Referring to the results shown in Table 4‑11Table 4‑11Table 4‑11Table 4‑11Table 4‑11Table 4‑11Table 4‑11 to Table 4‑14Table 4‑14Table 4‑14Table 4‑14Table 4‑14Table 4‑14Table 4‑14, it can be noted that the concentration of all predicted air quality parameters (1-hour NO2, 24-hour NO2 and 24-hour RSP) at all the representative ASRs would comply with the AQO limits under worse-case scenario.  All existing and proposed noise mitigation for this Project such as vertical noise barriers, cantilever noise barriers, semi-enclosures and full noise enclosures have been adopted in this air quality impact assessment.  Appendix 4-S and Appendix 4-T presents the input/output files of CALINE4 and ISCST3 models.

4.6.7              For ease of visualisation, contour plots of hourly and daily average concentrations of NO2 at worst hit concentration level (1.5m above ground) are presented in Figures 4-4 5 and 4-56.  Contours for daily average concentrations of RSP at worst hit concentration level (1.5m above ground) are plotted in Figure 4-67. As illustrated in Figures 4-5, 4-6 and 4-7, there areis no ASR within the contours of exceeding air quality criteria.

Air Quality inside Full Enclosures

4.6.8              Air quality inside the sections of full enclosures during normal traffic condition and congested traffic condition was assessed.  Results are presented in Table 4-15.

Table 4‑15      Predicted Maximum NO2 Concentrations inside Full Noise Enclosures

Full Enclosure No. (1)

Maximum NO2 Concentration (μg/m3)

Normal Traffic Condition

Congested Traffic Condition

F1

404303

611510

F2

329255

444370

F3

310231

491412

Note:

1)      Full enclosure numbers are shown in Figure A4-M1 in Appendix 4M.

 

4.6.9              Table 4-15 indicates that the maximum NO2 concentration inside all full noise enclosures under both normal and congested traffic conditions is well below the recommended level of 1,800 mg/m3 specified on the guideline.  Therefore, it is anticipated that no adverse air quality impact inside all full noise enclosures associated with the on-road traffic would be resulted.

4.7                    Recommendations for Monitoring and Audit

4.7.1              With the implementation of the proposed dust suppression measures, good site practices and dust monitoring and audit programme, no adverse dust impact would be expected at the ASRs.  Details of the monitoring requirements such as monitoring locations, frequency of baseline and impact monitoring are presented in the EM&A manual separate for this report.

4.8                    Conclusions

4.8.1              As construction works are controlled under the Air Pollution Control (Construction Dust) Regulations, it is mandatory that the construction works are implemented in accordance with the legislative requirements and hence the potential for causing dust nuisance is kept to a minimum level.  Monitoring and audit requirements would recommend in order to ensure that the air quality level is in compliance with the statutory requirements.

4.8.2              Typical construction works and the major dust generating activities have been identified and reviewed.  Good site work practices based on the statutory requirements laid down in the Air Pollution Control (Construction Dust) Regulations should be conveyed to site staff to ensure effective implementation of dust control measures during the construction phase. Provided these recommendations are followed, it is anticipated that there should be no adverse air quality impact during the construction to the adjacent ASRs along the project area.

4.8.3              Total air quality level associated with the operational phase, which is contributed mainly by vehicular gaseous emission, portal emission from full noise enclosures and chimney emission from industrial premises has been assessed, with the consideration of background air quality level.  Existing and proposed noise mitigation measures for this Project have been taken into account in this air quality impact assessment. 

4.8.4              Results indicate that the predicted maximum hourly and daily concentrations of NO2 shall comply with the corresponding AQO hourly and daily limits of 300 µg/m3 and 150 µg/m3 respectively at all ASRs.  On the other hand, results of the predicted maximum daily RSP concentration is well below the AQO limit of 180 µg/m3.   In other words, it is anticipated that no potential air quality impact to the ASRs will be resulted associated with the operation phase of this Project, and no mitigation measures for air quality impact during operational phase would be deemed necessary.