3      aIR qUALITY.. 2

3.1       Introduction. 2

3.2       Environmental Legislation, Policies, Plans, Standards and Criteria. 2

3.3       Description of the Environment 2

3.4       Sensitive Receivers. 2

3.5       Identification of Environmental Impacts. 2

3.6       Assessment Methodology. 2

3.7       Prediction and Evaluation of Environmental Impacts. 2

3.8       Mitigation of Adverse Environmental Impacts. 2

3.9       Evaluation of Residual Impacts. 2

3.10     Environmental Monitoring and Audit 2

3.11     Conclusion. 2

 

List of Tables

 

Table 3.1         Hong Kong Air Quality Objectives. 1

Table 3.2         Tunnel Air Quality Guidelines (TAQG) 2

Table 3.3         Annual Average Concentrations of Pollutants in 2006. 2

Table 3.4         Details of Air Sensitive Receivers. 3

Table 3.5         Emission Factors for Construction Activities and Wind Erosion. 9

Table 3.6         Different Major Dust Generating Activities in the Worst Case Scenarios during Construction Phase  12

Table 3.7         Annual Average Concentrations of Pollutants in Past Five Years. 14

Table 3.8         Vehicle Classes in EMFAC-HK Model 15

Table 3.9         Emission Factors for Year 2016 for Different Vehicle Classes (EMFAC-HK) 20

Table 3.10       Portal and Ventilation Building Emissions. 22

Table 3.11       Design of Ventilation Buildings. 23

Table 3.12       Summary of Odour Patrol Results in Year 2006 Survey. 27

Table 3.13       Summary of Odour Patrol Results in Year 2007 Survey. 28

Table 3.14       Results of Olfactometry Analysis (Year 2006) 32

Table 3.15       Results of Olfactometry Analysis (Year 2007) 32

Table 3.16       Existing Odour Emission Inventory for the Worst Case Scenario. 34

Table 3.17       Conversion Factors to 5-second Mean Concentration. 35

Table 3.18       Predicted Cumulative Maximum 1-hour Average TSP Concentrations at 1.5m above ground  37

Table 3.19       Predicted Cumulative Maximum 24-hour Average TSP Concentrations for at 1.5m above ground  38

Table 3.20       Predicted Cumulative Maximum 1-hour Average TSP Concentrations at 5m above ground  39

Table 3.21       Predicted Cumulative Maximum 24-hour Average TSP Concentrations at 5m above ground  40

Table 3.22       Predicted Cumulative Maximum 1-hour Average NO2 Concentrations at the Representative ASRs at Different Elevations. 42

Table 3.23       Predicted Cumulative Maximum 24-hour Average NO2 Concentrations at the Representative ASRs at Different Elevations. 44

Table 3.24       Predicted Cumulative Maximum 24-hour Average RSP Concentrations at the Representative ASRs at Different Elevations. 46

Table 3.25       Predicted Odour Concentrations at the Representative ASRs (Based on the Existing Odour Emission Rates) Under the Worst Case Condition. 48

Table 3.26       Predicted Odour Concentrations at the Representative ASRs (Mitigated Scenario) under the Worst Case Condition. 51

Table 3.27       Number of Hour Exceeding the Odour Criterion at the Representative ASRs (Mitigated Scenario) in a Year  52

 


3                    aIR qUALITY

3.1              Introduction

3.1.1        This section presents an impact assessment of air quality during the construction and operation phases of the WDII and CWB project.  Compared to the previous scheme, the size of reclamation has been decreased in the latest scheme.  Potential construction dust impact is expected to be less.  However, as the tunnel length of the Central-Wan Chai Bypass has been increased, the operational air quality impact arising from vehicular traffic emissions, tunnel ventilation and portal emissions could be an issue.  Odour nuisance associated with the Causeway Bay Typhoon Shelter is an existing environmental problem.  This Project will not create any new odour source during the operational phase.  However, in order to improve the environment, this Project will take the opportunities to mitigate the potential sources of odour nuisance within the Project area so as to alleviate this existing environmental problem as well as to provide an acceptable environment for the future land uses within the project area (including the proposed open space at the northern breakwater). Appropriate air quality mitigation measures for the proposed development are identified under this Study where necessary.      

3.2              Environmental Legislation, Policies, Plans, Standards and Criteria

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

Air Quality Objective & EIAO-TM

 

3.2.2        The Air Pollution Control Ordinance (APCO) provides the statutory authority for controlling air pollutants from a variety of sources.  The Hong Kong Air Quality Objectives (AQOs), which must be satisfied, stipulate the maximum allowable concentrations of certain pollutants over specific periods.  The relevant AQOs are listed in Table 3.1.

Table 3.1     Hong Kong Air Quality Objectives

Pollutant

Maximum Concentration (µg m-3) (1)

Averaging Time

1 hour (2)

8 hour (3)

24 hour (3)

Annual (4)

Total Suspended Particulates (TSP)

-

-

260

80

Respirable Suspended Particulates

(RSP) (5)

-

-

180

55

Sulphur Dioxide (SO2)

800

-

350

80

Nitrogen Dioxide (NO2)

300

-

150

80

Carbon Monoxide (CO)

30,000

10,000

-

-

Photochemical Oxidants

(as Ozone, O3) (6)

240

-

-

-

Notes:

(1)              Measured at 298 K and 101.325 kPa.

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

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

(4)              Arithmetic mean.

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

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

 


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

3.2.4        In accordance with the EIAO-TM, odour level at an air sensitive receiver should meet 5 odour units based on an averaging time of 5 seconds for odour prediction assessment.

 

Air Pollution Control (Construction Dust) Regulation

 

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

 

Practice Note on Control of Air Pollution in Vehicle Tunnels

 

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

Table 3.2     Tunnel Air Quality Guidelines (TAQG)

        Air Pollutant

Averaging Time

Maximum Concentration

(mg/m3) (1)

ppm

Carbon Monoxide (CO)

5 minutes

115,000

100

Nitrogen Dioxide (NO2)

5 minutes

1,800

1

Sulphur Dioxide (SO2)

5 minutes

1,000

0.4

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

3.3              Description of the Environment

Baseline Conditions

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

Table 3.3     Annual Average Concentrations of Pollutants in 2006

Pollutant

Annual Average Concentration in 2006 (mg m-3)

Monitoring Station

CO

862

Central

NO2

54

Central / Western

RSP

53

Central / Western

TSP

78

Central / Western

 

3.4              Sensitive Receivers

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

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

Table 3.4         Details of Air Sensitive Receivers

ASRs

Section

Location

Existing / Planned Land Use

No. of floors

 

Horizontal Distance (m)

Alignment*

Ventilation Building

Existing

A25

Wanchai

Police Headquarters

G/IC

7

306

357

1

A26

Wanchai

HK Academy for Performing Arts (Office/Performance Hall)

G/IC

9

186

254

1

A27

Wanchai

Arts Centre

G/IC

10

200

175

1

A28

Wanchai

Citic Tower

Commercial

42

160

385

1

A29

Wanchai

Servicemen's Guides Association

Commercial

3

116

228

1

A30

Wanchai

HK Academy for Performing Arts (Open Space)

G/IC

9

160

144

1

A31

Wanchai

Shui On Centre

Commercial

34

190

160

1

A32

Wanchai

Hong Kong Convention & Exhibition Centre (HKCEC)

Commercial

46

60

229

1

A33

Wanchai

Pedestrian plaza

Recreation

0

95

62

1

A34

Wanchai

HKCEC Extension

Commercial

8

100

177

1

A35

Wanchai

Great Eagle Centre

Commercial

27

112

372

1

A36

Wanchai

Causeway Centre (Block A)

Residential

42

178

531

1

A37

Wanchai

Wanchai Swimming Pool

Recreation

3

58

568

1

A38

Wanchai

Wanchai Sports Ground

Recreation

0

74

723

1

A39

Wanchai

SPCA

G/IC

6

62

787

1

A40

Wanchai

Gloucester Road 169-170

Residential

12

306

750

1

A41

Wanchai

Gloucester Road 210

Residential

18

276

870

1

A42

Wanchai

Gloucester Road 226

Residential

22

264

924

1

A43

Causeway Bay

Elizabeth House

Residential

21

231

1023

1

A44

Causeway Bay

Sino Plaza

Commercial

33

182

900

2

A45

Causeway Bay

World Trade Centre

Commercial

34

151

756

2

A46

Causeway Bay

Excelsior Hotel

Commercial

28

147

726

2

A47

Causeway Bay

Riviera Mansion

Residential

15

162

705

2

A48

Causeway Bay

Marco Polo Mansion (northern façade)

Residential

15

174

633

2

A49

Causeway Bay

Marco Polo Mansion (eastern façade)

Residential

15

180

606

2

A50

Causeway Bay

Royal Hong Kong Yacht Club

Recreation

3

59

720

2

A51

Causeway Bay

Police Officers Club (Tennis Courts)

Recreation

0

70

840

2

A52

Causeway Bay

Police Officers Club (Bowling Green)

Recreation

0

116

822

2

A53

Causeway Bay

Police Officers Club

Recreation

3

68

774

2

A54

Causeway Bay

Bowling Green, Victoria Park

Recreation

0

226

438

2

A55

Causeway Bay

Victoria Park Public Swimming Pool

Recreation

0

322

483

2

A56

Causeway Bay

Viking Garden

Residential

25

434

591

2

A57

Causeway Bay

Victoria court

Residential

18

380

534

2

A58

Causeway Bay

Mayson Garden

Residential

24

327

480

2

A59

Causeway Bay

Gordon House

Residential

15

293

471

2

A60

Causeway Bay

Belle House

Residential

24

214

366

2

A61

Causeway Bay

Citicorp Centre

Commercial

36

146

294

2

A62

Causeway Bay

Hoi Tao Building

Residential

30

160

300

2

A63

Causeway Bay

Victoria Centre

Residential

30

63

249

2

A64

Causeway Bay

Seaview Estate

Industrial/

commercial

13

63

282

2

A65

Causeway Bay

Harbour Heights

Residential

44

674

312

2

A66

Causeway Bay

Whitfield Road Rest Garden

Recreation

0

165

318

2

A93

North Point

City Garden (Block 11) (the height of 1st Sensitive Receiver is located at 5m above ground)

Residential

27

16

612

2

A94

North Point

City Garden (Block 6) (the height of 1st Sensitive Receiver is located at 5m above ground)

Residential

27

20

744

2

A95

North Point

Hong Kong Baptist Church Henrietta Secondary School

Educational

N/a

44

810

2

A96

North Point

Provident Centre (Block 1)

Residential

25

46

918

2

A97

North Point

Provident Centre (Block 6)

Residential

25

34

984

2

A98

North Point

Provident Centre (Block 17)

Residential

25

48

1176

2

Future

A70

Central

Central Government Complex

G/IC

N/a

360

564

1

A71

Central

New G/IC site south and east of CITIC Tower

G/IC

20

264

360

1

A73

Central

Waterfront related commercial and leisure uses

Recreation

N/a

42

246

1

A76

Central

Open space at the west of HKCEC

Recreation

N/a

10

132

1

A81

Wanchai

Waterfront related commercial and leisure uses

Commercial

N/a

15

432

1

A91

North Point

A land zone as “CDA(1) near Oil Street

CDA(1)

45

40

414

2

A92

North Point

A land zoned as CDA near Oil Street

CDA

45

32

513

2

A99

Wanchai

OU(Railway Air Intake Location) zone

 

Other use

3.5m above ground

28

246

1

A100

Wanchai

Water Sports Centre

Recreation

N/a

21

894

2

A101

Causeway Bay

Open space at CBTS Breakwater

Other use

N/a

150

306

2

 

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

1 Distance from the Central Ventilation Building.

2 Distance from the exhaust vent shaft of the East Ventilation Building.

 

3.4.3        For construction dust impact assessment, the proposed ASRs under WDII Project including ASRs A71, A73, A76, A81, A99, A100 and A101 would only be occupied after the completion of construction activities of WDII Project, therefore, the construction dust impact assessment does not cover these ASRs.  ASRs A91 and A92 are planned ASRs and there is no construction programme for these two ASRs at the time of this assessment, these two ASRs are therefore also not considered in the construction dust impact assessment.  The planned ASR A70 is Central Government Complex which may be occupied during the construction period of WDII Project.  As a conservative approach, ASR A70 was considered in the construction dust impact assessment.  For operational traffic emission impact, all ASRs listed in Table 3.4 are considered in the assessment.

3.4.4        During construction phase of the Project, dredging activities would be undertaken at the CBTS, and waterfronts along Wan Chai and North Point.  There is potential odour impact associated with the dredging and handling of dredged material from CBTS.  During operational phase, this Project will not create any new odour source.  However, odour nuisance associated with the Causeway Bay Typhoon Shelter is an existing environmental problem.  In order to improve the environment, this Project will take the opportunities to mitigate the potential sources of odour nuisance within the Project area so as to alleviate this existing environmental problem as well as to provide an acceptable environment for the future land uses within the project area (including the proposed open space at the northern breakwater).  The odour impact assessment has assessed the existing odour impact in the vicinity of the Causeway Bay Typhoon Shelter and the potential odour impacts on the planned ASRs proposed under WDII Project during the operational phase.  Odour mitigation measures have been formulated to alleviate this existing environmental problem.  The ASRs considered in the odour impact assessment during operational phase include ASRs A76, A81, A100 and A101.

3.4.5        Regarding the corner of CBTS (i.e. the area in the vicinity of POC), in accordance with the RODP, the pavement at that area would not be changed.  The land strip with 1.5m to 4.5m width would not attract pedestrians to stay here.  It is expected that this narrow strip of land will continue to serve as pedestrian walkway, not a sensitive land use.  The area in the vicinity of drainage culvert outfall Q is also a walkway.  No active and passive recreational uses are proposed under the Project along the existing Gloucester Road/Victoria Park Road from the POC to Causeway Bay Flyover.  It is not expected that the land uses along CBTS between POC and Causeway Bay Flyover would be changed.   


3.5              Identification of Environmental Impacts

Construction Phase

Air Quality Impact from Construction Activities

3.5.1        Construction of seawall and filling works are the major construction works during reclamation.  Excavation, materials handling, wind erosion, truck haulage on unpaved roads are other major sources of dust impact.  However, no on-site concrete batching activity will take place within the construction site.  SO2, NO2 and smoke emitted from diesel-powered equipment may also affect the air quality of the study area.

3.5.2        Potential marine traffic emissions from the dredgers would be expected.  However, given that only a maximum of 10 dredgers would be concurrently operated at CBTS and Wan Chai waterfront, the associated emissions should be limited.  In addition, the nearest distance between the dredgers and ASR (A50) at CBTS is 66m while the nearest distance at Wan Chai waterfront is 27m (ASR A32). Therefore, marine traffic emission impact arising from the Project is anticipated to be insignificant.       

3.5.3        For the tunnel works of the Trunk Road, potential dust nuisance is anticipated during excavation and backfilling of the tunnel construction. 

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

Odour Impact from Dredging Activities

3.5.5        The water quality in the typhoon shelter has been polluted by sewage discharges in the past and sediments deposited on the seabed in the vicinity of storm outfalls.  These sediments may contain high concentrations of organic matter and heavy metals.  The sediments in CBTS would be dredged away when carrying out the temporary reclamation.

3.5.6        For the dredging activities carried out in the vicinity of Police Officers’ Club, the dredging operation will be restricted to only 1 small close grab dredger to minimise the odour impact during the dredging activity.  The dredging rate should be reduced as much as practicable for the area in close proximity to the Police Officers’ Club.  As the sediments may contain highly contaminated mud which may be disposed with the use of geosynthetic containers (details shall refer to Section 6), grab dredger has to be used for filling up the geosynthetic containers on barges.  As there is no programme constraint for the removal of the sediments at the south-west corner of the typhoon shelter in the vicinity of Police Officers’ Club for mitigating the existing odour problem, the dredging rate can be slowed down or restricted to specific non-popular hours in weekdays when it is necessary during construction.


Operational Phase

Traffic Emission Impact

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

·                     Planned deckover along Road P2

·                     Landscape deck to HKCEC West

·                     Existing deckover over Expo Drive

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

·                     Landscaped deck link to waterfront and ferry pier

·                     Landscaped deck from Victoria Park to CBTS waterfront

·                     Landscaped deck over Trunk Road Portal

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

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

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

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

·                     emissions from Central Ventilation Building and East Ventilation Building

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

·                     portal emissions from the planned deckovers along Road P2

·                     portal emissions from the existing deckover over Expo Drive

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


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

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

Odour Impact

3.5.12    During operational phase, this Project will not create any new odour source.  An extension / modification of Wan Chai East Sewage Screening Plant is not within the scope of the WDII or CWB project, it is only the reprovisioning of the sewage outfall affected by the reclamation work that is within the scope of the WDII Project.  However, odour nuisance associated with the Causeway Bay Typhoon Shelter is an existing environmental problem.  In order to improve the environment, this Project will take the opportunities to mitigate the potential sources of odour nuisance within the Project area so as to alleviate this existing environmental problem as well as to provide an acceptable environment for the future land uses within the project area.

3.6              Assessment Methodology

Construction Phase

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


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

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

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

 

Table 3.5         Emission Factors for Construction Activities and Wind Erosion

Construction Activities

Emission Rate (g/m2/s)

Remark

Road Construction, Building Construction and Material Handling (as Heavy Construction)

E = 3.113426E-05

- 50%  work area

- 75% reduction by water suppression (watering four times a day)

-USEPA AP-42 5th ED., S.13.2.3.3

 

Wind Erosion

E = 1.347666E-06

 

- 50% work area

- AP-42 5th ED., S.11.9  Table 11.9.4

 

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

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

3.6.7        The following summarises the construction activities during the construction stage of the WDII Project.  The locations of the different reclamation sites are shown in Figure 3.4

Causeway Bay Temporary Reclamation (CBR)

·                     Temporary Relocation Causeway Bay Typhoon Shelter (CBTS)

·                     CBTS Temporary Reclamation Stage 1 (TCBR1W & TCBR1E)

·                     CBTS Temporary Reclamation Stage 2 (TCBR2)

·                     CBTS Temporary Reclamation Stage 3 (TCBR3)

·                     CBTS Temporary Reclamation Stage 4 (TCBR4)

·                     Slip Road 8 & Victoria Park Facilities Reprovisioning

 

Ex-PCWA Temporary Reclamation

·                     Temporary Reclamation PCWA Stage 1 (TPCWAE)

·                     Temporary Reclamation PCWA Stage 2 (TPCWAW)

 

Wan Chai Reclamation (WCR)

·                     Wan Chai Reclamation Stage 1 (WCR1)

·                     Wan Chai Reclamation Stage 2 (WCR2)

·                     Wan Chai Reclamation Stage 3 (WCR3)

·                     Wan Chai Reclamation Stage 4 (WCR4)

·                     New Ferry Pier Reprovisioning & Demolish Existing Pier

·                     Helipad Reprovisioning at HKCEC

·                     Roads

 

HKCEC Reclamation

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

·                     HKCEC Reclamation Stage 2 (HKCEC2E & HKCEC2W)

·                     MTR Tunnel Crossing

·                     HKCEC Reclamation Stage 3 (HKCEC3E & HKCEC3W)

·                     Roads

 

Cross Harbour Watermains

·                     Submarine Pipeline

·                     Land Section

 

North Point Reclamation (NPR)

·                     North Point Reclamation Stage 1 (NPR1)

·                     North Point Reclamation Stage 2 (NPR2E & NPR2W)

 

Construction of IECL

·                     IECL Connection Work

·                     East Portal and IEC Connection

 

Construction of Central Interchange

Tunnel Building and Installation

·                     East Ventilation Building

·                     Administration Building

·                     Central Ventilation Building

 

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

Construction of CWB Tunnel Under CRIII Project

·                     CWB Tunnel at Initial Reclamation Area East

·                     CWB Tunnel at Final Reclamation Area East

 

3.6.9        Based on the construction programme (Appendix 2.5) and the number of dusty activities on site, six worst-case scenarios for the development works have been identified throughout the construction period and are shown in Table 3.6.  Overall, the scenarios presented are considered to be representative of the worst case.  The figures showing locations of dusty construction site areas for each scenario are presented in Figures A3.1 to A3.6 in Appendix 3.1.


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

Period

2009 – Early 2010

Mid 2010 – Early 2011

Mid 2011 – Early 2012

Mid 2012 – Early 2013

Mid 2013 – Early 2014

Mid 2014-2016

Worst month

Jan 2010

Aug 2010

April 2012

Feb 2013

Nov 2013

Apr 2015

Activities

Scenario 1

Scenario 2

Scenario 3

Scenario 4

Scenario 5

Scenario 6

1

TCBRIE–

Filling

TCBR1E –

CWB Tunnel

TCBR1W – CWB Tunnel

TCBR3 – CWB Tunnel

TCBR3 – CWB Tunnel

TCBR4-CWB Tunnel

2

TCBRIW – Filling

TCBR1W – CWB Tunnel

TCBR2 – CWB Tunnel

TCBR4 – Filling

TCBR4 – CWB Tunnel

TPCWAW-CWB Tunnel

3

TCBRIE –

CWB Tunnel

TCBR2 –

CWB Tunnel

TCBR3 – CWB Tunnel

TPCWAW – CWB Tunnel

Slip Rd 8 & Victoria Park Reprovisioning

Realignment Hung Hing Road

4

TCBR2 –

Filling

TPCWAE –  CWB Tunnel

TPCWAE – CWB Tunnel

WCR2 – Promenade

TPCWAW – CWB Tunnel

Road P2 from Fleming Road to Marsh Road

5

TPCWAE – CWB Tunnel

WCR1 - Drainage

WCR2 – CWB Tunnel

WCR3 – Filling

WCR3 – CWB Tunnel

Mainline to IEC

6

WCR1 – Filling

WCR1 – Cooling Water

HKCEC2E – Filling

WCR4 – Filling

WCR4 – CWB Tunnel

 

7

WCR1 – CWB Tunnel

WCR1 – CWB Tunnel

HKCEC2W – Filling

WCR4 – Drainage

HKCEC2E – Drainage

 

8

New Ferry Piers

HKCEC1 – Cooling Water

HKCEC3E – Filling

HKCEC2W – CWB Tunnel

HKCEC2W – Drainage

 

9

HKCEC1 – Cooling Water

MTR - Piling

HKCEC3E – Drainage

HKCEC3W – CWB Tunnel

HKCEC2E – CWB Tunnel

 

10

HKCEC2E - Filling

NPR1 – CWB Tunnel

HKCEC3W – Drainage

HKCEC3E – CWB Tunnel

HKCEC2W – CWB Tunnel

 

11

Cross Harbour Watermains – Land Sections

NPR2E – Filling

HKCEC3E – CWB Tunnel

IEC Connection Work

HKCEC3E – CWB Tunnel

 

12

NPR1 – CWB Tunnel

CRIII – CWB Tunnel at Initial Area East

NPR2W – CWB Tunnel

East Ventilation Building

HKCEC3W – CWB Tunnel

 

13

NPR2E – Filling

CRIII – CWB Tunnel at Final Area West

 

 

 

 

14

NPR2W – CWB Tunnel

CRIII – CWB Tunnel at Final Area East

 

 

 

 

15

CRIII – CWB Tunnel at Initial Area East

 

 

 

 

 

16

CRIII-CWB Tunnel at Final East

 

 

 

 

 


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

·                     Wind speed:                     1 m/s

·                     Wind direction:                        360 wind direction

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

·                     Surface roughness:          1m

·                     Mixing height:                  500 m

 

3.6.11    Daily TSP concentrations were calculated as follows:

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

 

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

Operational Phase

Vehicular Emission Impact (Open Road)

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

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

 

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

 

·                     emissions from Central Ventilation Building and East Ventilation Building

 

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

 

·                     portal emissions from the planned deckovers along Road P2

 

·                     portal emissions from the existing deckover over Expo Drive

 

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


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

Background Concentration

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

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

Table 3.7     Annual Average Concentrations of Pollutants in Past Five Years

Pollutant

Annual Average Concentration in Past Five Years (2000, 2003-2006) at Central/Western Station (mg m-3)

NO2

55

RSP

54

       

Vehicle Emissions from Open Sections of Existing and Planned Road Networks

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

·                     new roads in the WDII

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

·                     the Trunk Road & IECL

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

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


Fleet Average Emission Factors

Vehicle Classes

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

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

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

Table 3.8     Vehicle Classes in EMFAC-HK Model

Vehicle Class

Description

Fuel Type

Gross Vehicle Weight

MC1

Petrol Private Cars (PC) & Light Goods Vehicles (LGV)

Petrol

all

MC3

Diesel Private Cars & Light Goods Vehicles<2.5t

Diesel

<=2.5t

MC4

Diesel Private Cars & Light Goods Vehicles 2.5-3.5t

Diesel

>2.5-3.5t

MC5

Public Light Buses

LPG, Diesel

all

MC6

Light Goods Vehicles >3.5t

Diesel

>3.5-5.5t

MC7

Medium & Heavy Goods Vehicles with GVW 5.5-15t

Diesel

>5.5-15t

MC8

Medium & Heavy Goods Vehicles with GVW >=15t

Diesel

>15t

MC10

Double Deck Franchised Buses

Diesel

all

MC11

Motor Cycles

Petrol

all

Taxi3

Taxi

LPG

all

Taxi4

Private Light Buses <3.5t

LPG, Diesel

<=3.5t

Taxi5

Private Light Buses >3.5t

LPG, Diesel

>3.5t

Taxi6

Non- franchised Buses <6.4t

Diesel

<=6.4t

Taxi7

Non- franchised Buses 6.4-15t

Diesel

>6.4-15t

Taxi8

Non- franchised Buses >15t

Diesel

>15t

Taxi10

Single Deck Franchised Buses

Diesel

all

 


Road Grouping

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

 

Input Assumptions in EMFAC-HK

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

 

Modelling Modes

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

 

Technology Fractions

 

Exhaust Technology Fractions

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

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

 

Evaporative Technology Fractions

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

 

Vehicle Population

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


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

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

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

 

Accrual Rate

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

 

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

 

Diurnal Variation of Daily Trips

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

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

 

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

 

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

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

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


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

 

Hourly Temperature and Relative Humidity Profile

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

 

Speed Fractions

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

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

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

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

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

 


Model Year

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

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

3.6.45    As a conservative approach, the hourly emissions in Year 2016 were first divided by the number of vehicles and the distance travelled to obtain the emission factors in gram per miles per vehicle.  The calculated maximum vehicle emission factors were then selected for incorporation into the air dispersion model.  These conservative vehicle emission factors together with the forecasted Year 2031 peak traffic flow were adopted in this air quality impact assessment, which would be the highest emission strength from road vehicles within the next 15 years upon commencement of operation of the proposed road.  The calculation of fleet vehicle emission is presented in Appendix 3.8.

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


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

Vehicle Class

Description

Emission Factors for 2016, g/mile-veh

NOx

RSP

Trunk Road

Other Road

Trunk Road

Other Road

MC1

Petrol Private Cars (PC) & Light Goods Vehicles (LGV)

0.1433

0.1545

0.0047

0.0063

MC3

Diesel Private Cars & Light Goods Vehicles<2.5t

0.4012

0.4157

0.1284

0.1516

MC4

Diesel Private Cars & Light Goods Vehicles 2.5-3.5t

0.2642

0.2702

0.0813

0.0896

MC5

Public Light Buses

0.1208

0.1163

0.0887

0.0835

MC6

Light Goods Vehicles >3.5t

2.1532

2.2242

0.1547

0.1836

MC7

Medium & Heavy Goods Vehicles with GVW 5.5-15t

4.4177

4.6047

0.2553

0.3066

MC8

Medium & Heavy Goods Vehicles with GVW >=15t

5.4535

6.0203

0.3635

0.4121

MC10

Double Deck Franchised Buses

2.7890

2.8216

0.0808

0.0902

MC11

Motor Cycles

1.1216

1.0611

0.0487

0.0503

Taxi3

Taxi

0.2376

0.2585

0.0188

0.0252

Taxi4

Private Light Buses <3.5t

0.0000#

0.0000#

0.0000#

0.0000#

Taxi5

Private Light Buses >3.5t

0.3270

0.3390

0.1972

0.2421

Taxi6

Non- franchised Buses <6.4t

0.0000#

0.0000#

0.0000#

0.0000#

Taxi7

Non- franchised Buses 6.4-15t

3.7716

4.7213

0.1433

0.1790

Taxi8

Non- franchised Buses >15t

7.1778

3.6599

0.1433*

0.1790*

Taxi10

Single Deck Franchised Buses

2.5173

2.4728

0.1631

0.1126

Note:

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

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

 

Model Assumptions for Open Road Vehicle Emission

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

·                     Wind speed              :     1 m s-1

·                     Wind direction         :     360 wind directions

·                     Resolution               :     1°

·                     Wind variability       :     24°

·                     Stability class           :     D

·                     Surface roughness   :     1 m

·                     Mixing height           :     500 m


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

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

Portal and Ventilation Building Emissions

3.6.50    The Industrial Source Complex Short Term 3 (ISCST3) dispersion model was used to predict the portal and ventilation building emissions.

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

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

·                     tunnel portal emissions from the existing CHT

·                     portal emission from deckover over Expo Drive

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

·                     portal emissions from the planned deckovers along Road P2.

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

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

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

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


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

Table 3.10   Portal and Ventilation Building Emissions

Type

NOX  (g/s)

RSP (g/s)

Portal Emission

Trunk Road Eastbound

0

0

Slip Road 1

0

0

Slip Road 2 under HKCEC Atrium Link Deckover

1.455E-02

7.956E-04

Slip Road 3

0

0

Cross Harbour Tunnel

1.110E+00

6.828E-02

Expo Drive Central

1.024E-02

5.787E-04

P2 Road (Eastbound) Under HKCEC Atrium Link Deckover

9.892E-03

6.026E-04

P2 Road (Westbound) Under HKCEC Atrium Link Deckover

1.319E-02

8.972E-04

Central Wan Chai Bypass (Westbound) Under HKCEC Atrium Link Deckover

8.654E-03

6.781E-04

Convention Avenue Under HKCEC Atrium Link Deckover

1.527E-02

9.951E-04

Expo Drive

6.476E-02

4.335E-03

P2 Road between Tim Wa Ave, and Tim Mei Ave

2.060E-02

1.482E-03

Ventilation Building

East Ventilation Building (Trunk Road Eastbound)

2

2.258E-02#

Central Ventilation Building

3.966

3.003E-01

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

 

3.6.54    The preliminary design of the ventilation buildings (including minimum mid-discharge heights, exhaust directions, exhaust area of ventilation buildings and exit velocity) is summarised in Table 3.11.  The tunnel ventilation schematic diagram is indicated in Appendix 3.15.  The approximate dimensions of the exhaust vent shaft, the discharge height and stack area are shown in the illustrations annexed in Appendix 10.1.   For a worst case scenario in the air quality assessment, the minimum height of stack was used in modelling.

Table 3.11       Design of Ventilation Buildings

 

Cross-sectional area of stack (m2)

Exit velocity

(m s-1)

Minimum mid-discharge height (meter above ground)

Exhaust direction

East Ventilation Building (EVB)

- Vent shaft at the breakwater

94

8

16.25

Inclined 45 degree upward (discharge towards sea direction)

Central Ventilation Building (CVB)

219

8

17.5

Vertical

 

3.6.55    The emission from EVB is discharged from the louvre on the side of the vent shaft over 250 degree laterally with exit velocity of 8m/s at inclined 45 degree upward direction.  Since the ISCST3 dispersion model employed in this assessment cannot simulate the dispersion from an inclined discharge, the EVB discharge at the vent shaft is therefore simulated as four numbers of discrete point sources with vertical discharge.  The four point sources are evenly located around the 250 degree discharge louver.  The discharge heights of the point sources are set at the middle height of the discharge louvre and the total discharge area of the four point sources is equivalent to the area of the discharge louver.  The exit velocities of the point sources are set as the vertical component of the inclined discharge velocity of 8/ms, i.e. 5.66m/s vertically upward.  The horizontal component of the inclined discharge velocity was not simulated in the ISCST3 mode.  This may result in some deviations in the initial dispersion pattern of the discharged plume, yet the final form of the discharged plume and hence the level of impact associated with the final plume predicted by the ISCST3 model on far field air sensitive receivers should be very much the same as that of the inclined discharge.  For those near field air sensitive receivers that are on the opposite side of the inclined discharge, the ISCST3 model prediction based on the source simulation described above should be on the conservative side, and vice versa for those near field air sensitive receivers facing the inclined discharge.  In this assessment, all the air sensitive receivers facing the inclined discharge are located at far field (say at more than 300m from the discharge) except some air sensitive receivers located at the eastern end of the breakwater.  Yet the height of the air sensitive receiver on the breakwater is only 1.5m above ground which is much lower than the discharge height of the vent shaft at 16.25m and these air sensitive receivers should not be subject to the direct impingement of the plume discharged from the vent shaft of EVB.  For all the other near field air sensitive receivers (say air sensitive receivers within 300m from the discharge), they are located on the opposite side on the inclined discharge and the ISCST3 model prediction should produce results on the conservative side with regards to the impacts of the EVB discharge.  To summarise, the simulation approach described above should produce representative impact prediction at the identified air sensitive receivers with regards to the EVB discharge at the vent shaft.

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


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

3.6.58    As mentioned in Section 3.6.47, 360 predetermined meteorological conditions were used.  The following summarises the meteorological conditions adopted in the air quality modelling using the ISCST3 model:

·                     Wind speed                    :     1 m s-1

·                     Wind direction               :     360 wind directions

·                     Resolution                     :     1°

·                     Stability class                 :     D

·                     Mixing height                 :     500 m

·                     Emission temperature    :     7° above ambient

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

Cumulative Impact

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

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

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

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

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

 

Vehicular Emission Impact (Inside the CWB Tunnel/ deckover)

3.6.63    In accordance with the “Practice Note on Control of Air Pollution in Vehicle Tunnels”, the air quality inside the tunnel should achieve the EPD recommended standard of 1ppm NO2 concentration.  As advised by the ventilation engineer, the air quality inside the CWB Tunnel would comply with the above standard, which is the design requirement for the tunnel ventilation system. 

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

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

 

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

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

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

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

3.6.67    The air quality under the planned deckover on HKCEC Atrium Link was calculated based on the empirical formulas of fluid dynamics.  A conversion factor of 12.5% including tailpipe NO2 emission (taken as 7.5% of NOx) plus 5% of NO2/NOx for tunnel air recommended in PIARC for air expelled from the tunnel was taken in this assessment as the inside tunnel conversion factor.  Two scenarios were considered in the assessment, i.e. normal traffic flow condition and congested traffic flow condition.  It was assumed that under normal traffic flow condition, the vehicles are at a speed of 50 kph, whereas under congested mode, the vehicles are at a speed of 10 kph, the separation between vehicles is assumed to be 1 m.  Different emission factors for normal condition (which presented in Table 3.9) and congestion condition (emission factor with traffic speed at 10kph) are used to calculate the air quality under the deckover.  The calculation of in-tunnel air quality for section of deckover on planned HKCEC Atrium Link and emission factor of 10 kph are presented in Appendix 3.12.  As per the discussion in Section 3.5.11, only NO2 was assessed for the existing/planned deckover. 

Odour Impact

Odour Emission Source

3.6.68    During operational phase, this Project will not create any new odour source.  However, odour nuisance associated with the Causeway Bay Typhoon Shelter is an existing environmental problem.  In order to improve the environment, this Project will take the opportunities to mitigate the potential sources of odour nuisance within the Project area so as to alleviate this existing environmental problem as well as to provide an acceptable environment for the future land uses within the project area. Therefore, the assessment was focused on the existing odour emission sources within the study area and formulated practicable odour mitigation measures to alleviate this existing odour problem.  In order to identify the existing odour emission sources and determine the extent and level of existing odour impacts, odour surveys including odour patrols and air sampling on existing odour source area for olfactometry analysis were carried out by the Hong Kong Polytechnic University (HKPU) in September 2006 and July 2007.


Odour Patrol

3.6.69    Odour patrols were carried out in September 2006 and July 2007 by two qualified odour panel members from the Odour Laboratory of HKPU.  They used their olfactory senses to detect/identify any odour problems and the locations of odour sources along/at the ex-PCWA and CBTS (including the areas in the vicinity of storm outfall P, Q, R and S), Northern Breakwater and Eastern Breakwater.  The patrol members were free from any respiratory illnesses and do not normally work at or live in the area in the vicinity of CBTS and any typhoon shelter.

3.6.70    Each patrol day consisted of two patrol exercises in two different time periods (morning and afternoon/evening) and at least one patrol exercise of each patrol day was conducted during the low tide period of the day.

3.6.71    During the odour patrol, the patrol members recorded the weather condition including wind direction and temperature, location where odour was detected, possible source of odour, perceived intensity of the odour, duration of odour and characteristics of the odour detected. 

3.6.72    The perceived intensity detected by odour patrol members was divided into 5 levels which are ranked in order as follows.  The staying time at each patrol location was at least 2 -3 minutes to detect the odour intensity and the patrol location was at downwind direction of potential odour source area.  The highest perceived intensity at each location during patrol was recorded.

0

Not detected

No odour perceived or an odour so weak that it cannot be easily characterised or described

 

1

Slight

Identifiable odour, slight

 

2

Moderate

Identifiable odour, moderate

 

3

Strong

Identifiable odour, strong

 

4

Extreme

Severe odour

3.6.73    In conjunction with the odour patrol, on-site H2S measurement was conducted at the locations where odour was detected during the odour patrol.  The purpose of the measurement was to provide initial idea about the strength of odour emission in terms of H2S concentration.  The H2S concentration was measured by a portable H2S analyzer (Jerome 631-X H2S analyzer) at the odorous locations identified by the odour patrol members.

3.6.74    There were a few clusters of yachts/vessels at moorings.  The patrol routes covered the whole water surface at CBTS as far as possible.  The odour patrol areas are indicated in Figure 1 and 1a of Appendix 3.13.  The odour patrol at Northern Breakwater and Eastern Breakwater were conducted at the downwind direction of CBTS.  The detailed odour patrol procedures and results are presented in Appendix 3.13.  The mean odour intensity levels and the odour characteristics recorded at the patrol locations in the 2006 survey and 2007 survey are summarized in Table 3.12 and 3.13 respectively.


Table 3.12       Summary of Odour Patrol Results in Year 2006 Survey

 

Site ID

Location

Mean Odour Intensity

Odour Character

Duration

On-site H2S Conc.

(ppb)

Possible Sources

1

CBTS near Victoria Park

0

n.d.

n.d.

3-5

n.d.

1a

CBTS near Fire Station

0.5

Rotten organics + sea wind blow

Intermittent

5

Sea water and refuse near the bank

2

CBTS near Victoria Park Road

0.06

Rotten organics + sea wind blow*

Intermittent

3-10

Sea water and refuse near the bank

2a

CBTS near Noonday Gun

0.25

Rotten organics + sea wind blow*

Intermittent

7-10

Sea water and refuse near the bank

3

CBTS near Police Officers’ Club

1.44

Rotten organics/

decayed sediment + diesel smell

Persistent

7-15

Sea water and boats at CBTS

4

CBTS near carpark of Police Officers Club

0.75

Rotten organics/

decayed sediment + diesel smell

Persistent/

intermittent

4-7

Sea water and boats at CBTS

5

Ex-PCWA , GFS Temporary Helipad

0

n.d.

n.d.

3-6

n.d.

                     Note: n.d. – Not detected; * only detected on 11 September 2006.


Table 3.13       Summary of Odour Patrol Results in Year 2007 Survey

Location

Odour Intensity Level #

Odour Nature #

Duration #

On-site H2S Conc. (ppb) #

Possible Sources #

P1

2 / 2

Oily & decayed waste

Persistent

5 – 9 / 3 – 4

Floating debris, sediment

P2

2 / 2

Oily & decayed waste

Persistent

5 – 11 / 4 – 6

Floating debris, sediment

P3

1 / 1

Oily & decayed waste

Persistent

4 – 6 / 2 – 3

Floating debris, sediment

P4

1 / 1

Oily & decayed waste

Intermittent

2 – 4 / 2 – 3

Floating debris, sediment

P5

0 / 0

- / -

n.d.

0 – 1 / 2 – 3

- / -

P6

0 / 0

- / -

n.d.

1 / 2

- / -

P7

0 / 0

- / -

n.d.

1 / 2

- / -

P8

0 / 0

- / -

n.d.

1 – 2 / 2

- / -

P9

0 / 0

- / -

n.d.

1 / 2

- / -

P10

0 / 1

- / Rotten-egg

n.d. / Intermittent

1 / 0 – 1

- / Air bubbles from sediment were noted at nearby area

P11

0 / 2.5

- / Rotten-egg

n.d. / Intermittent

0 – 2 / 7 – 11

- / Floating debris

P12

1 / 3

Sewage + rotten-egg 

Persistent

2 – 27 / 11 - 44

Outfall + air bubbles from sediment

P13

2.5 / 2

Sewage + rotten-egg

Persistent

14 – 37 / 42 - 70

Outfall + air bubbles from sediment

P14

3 / 2

Rotten-egg

Persistent

10 – 57 / 41 - 81

Air bubbles from sediment

P15

1 / 0

Oily and decayed wastes

Intermittent / n.d.

4 – 12 / 2 - 3

Floating debris / -

P16

0 / 0

- / -

n.d.

2 – 3 / 2

- / -

P17

0 / 0

- / -

n.d.

2 – 3 / 1 - 2

- / -

P18

0 / 0

- / -

n.d.

1 – 2 / 0 – 1

- / -

P19

0 / 0

- / -

n.d.

0 – 1 / 0 - 1

- / -

P20

0 / 0

- / -

n.d.

0 – 1 / 1 – 2

- / -

P21

0 / 0

- / -

n.d.

1 – 2 / 1 - 2

- / -

P22

0 / 0

- / -

n.d.

1 – 3 / 1 – 3

- / -

P23

0 / 1

- / Oily and wastes

n.d. / Intermittent

2 – 7 / 2 -4

- / Floating debris

P24

0 / 0

- / -

n.d.

2 – 5 / 1 – 2

- / -

P25

1.5 / 0

Rotten-egg / -

Intermittent / n.d.

5 – 27 / 2 - 5

Air bubbles from sediment at nearby area / - 

P26

0 / 0

- / -

n.d.

0 – 2 / 1 – 2

- / -

P27

0 / 0

- / -

n.d.

1 / 2 - 5

- / -

P28

0 / 0

- / -

n.d.

1 – 2 / 2 – 4

- / -

P29

0 / 0

- / -

n.d.

0 – 1 / 1

- / -

P30

1 / 0

Rotten-egg / -

Intermittent / n.d.

0 – 1 / 0 - 1

Air bubbles from sediment at nearby area / -

P31

2 / 1

Sewage + rotten-egg

Persistent /Intermittent

2 – 13 / 5 – 13

Outfall + air bubbles from sediment

P32

0 / 0

- / -

n.d.

1 – 2 / 3 – 4

- / -

P33

0 / 0

- / -

n.d.

2 – 3 / 2 – 4

- / -

P34

0 / 0

- / -

n.d.

1 – 6 / 1 – 4

- / -

P35

1 / 0

Decayed wastes

Intermittent / n.d.

9 – 10 / 1 - 2

Floating debris / -

P36

0 / 0

- / -

n.d.

2 / 2 - 6

- / -

                     Note: # - morning result / afternoon result;  n.d. – Not detected.

 


3.6.75    Odour patrol results indicated that no odour nuisance was detected at ex-PCWA, the areas in the vicinity of Northern Breakwater and Eastern Breakwater, the areas in the vicinity of storm drain outfall R and S.  High odour intensity levels were recorded at the corner of CBTS (near Police Officer’s Club) and the area in the vicinity of Outfall Q.  Based on the findings of the odour surveys, the following four existing odour sources found at CBTS are identified and the possible causes of odour are summarized below.

(a)            Sediment at the corner of CBTS and areas in the vicinity of Storm Drain Outfall Q

3.6.76    CBTS receives discharges from several drainage systems from Causeway Bay and Happy Valley.  There are four outfalls including outfall P, Q, R and S discharging into CBTS as shown in Figure 5.3B.  Currently these systems primarily receive stormwater and street runoffs.  Odour patrol results indicated that odour nuisance was detected at the corner of CBTS (near Police Officers’ Club) and areas in the vicinity of storm drain outfall Q.  It is likely that polluted sewage/wastewater has been discharged to this storm drain through some expedient connections made in the past.  The sewage/wastewater discharged from these expedient connections contained high levels of pollutants, which together with the stagnant water system at the corner of CBTS, resulted in the deposition of a contaminated sediment layer today. 

3.6.77    Under normal conditions, the organic matter is decomposed by micro-organisms aerobically using the oxygen in the water and also diffused to the sediment.   The resultant products are carbon dioxide and water:

Organic matter + oxygen energy + carbon dioxide + water

 

3.6.78    When the organic load exceeds the carrying capacity, oxygen is not available for aerobic respiration and sulphate in seawater is used as the agent for anaerobic respiration by micro-organisms.

3.6.79    Hydrogen sulphide is formed when the organic rich sediments act as a substrate for the action of sulphate-reducing bacteria (SRBs) which reduce the sulphate in the absence of oxygen.  Organic sulphur compounds, such as mercaptans, also contribute partly to the odour with process similar to hydrogen sulphide:

Organic matter + sulphate energy + hydrogen sulphide + water

 

Organic matter with sulphide energy + mercaptans + water (minor pathway)

 

3.6.80    This is also reflected by the observations made during the odour patrols that high concentration of hydrogen sulphide was detected in the air samples collected above the water surface at the corner of CBTS and the area in the vicinity of Outfall Q by the handheld H2S detector.

 

(b)           Polluted discharges from Outfall P and Q

3.6.81    In accordance with the site observation during odour patrol, polluted discharge from storm drain outfall P and sewage-like discharge from storm drain outfall Q into CBTS were noted in the odour patrols and causing odour nuisance.  During odour sampling exercise in the 2007 odour survey, very high odour concentration and hydrogen sulphide concentrations were detected at the area in the vicinity of Outfall Q and its headspace.  This supports the observation that the polluted discharge from outfall Q consisted of sewage which likely came from expedient connections.

 


(c)            Slime attached on the shoreline seawall

3.6.82    Oil and greases discharged from the storm drain outfall P and Q were accumulated at the south-western corner of CBTS due to stagnant water flow and poor water circulation and some of the oil and greases were attached on the shoreline seawall.  As there was no cleaning of the shoreline seawall before, the slime attached on the seawall caused odour nuisance in particular during low tide periods.

 

(d)           Floating Debris

3.6.83    Floating debris at CBTS was observed during odour survey.  The debris might be disposed from the boats at CBTS or in the discharges from outfalls.  The quantity of floating refuse collected was higher in the summer months (See Table 6.5) which may be attributed to the heavy rains and typhoons bringing more refuse into the harbour.  In the summer, the wind direction is from the south-west which also brings more refuse into the harbour.

 

Air Sampling and Olfactometry Analysis

3.6.84    Based on the findings of the odour patrols, the odour intensity level recorded at some locations within CBTS was equal to or higher than 1, which is classified as identifiable odour.  However, the site observation indicated that the odour detected at these locations was intermittent with duration less than 1 minute.  These locations are unlikely to be odour sources as the duration of odour detected at source location should be persistent (at least 2 – 3 minutes).  The intermittent odour was most likely due to wind dispersion from nearby odour source areas.  Hence, the potential odour sources locations should fulfil the following two criteria:

(i)                 Mean odour intensity level equal to or higher than 1 during patrol exercise; and

(ii)               The duration of odour detected was persistent during patrol.

 

3.6.85    Based on the above two criteria, Site ID 3 (corner of CBTS) in Year 2006 odour patrol and Locations P1 (corner of CBTS, similar location of Site ID3 in Year 2006 odour patrol), P2, P3,  P12, P13, P14 and P31 in Year 2007 odour patrol were considered as existing odour source locations.  In order to determine the level of odour impact under the existing situation,  source air samples were collected from these existing odour source locations and ambient air samples were collected along the CBTS waterfront for olfactometry analysis.  The air sampling exercises were conducted on 15 September 2006 and 28 July 2007 during noon/afternoon and at low tide condition.  The sampling periods are considered to represent the reasonable worst case condition as more hydrogen sulphide would be released from sediment under high temperature (hot season) and low water depth (low tide condition).  In the 2007 odour survey, air sample inside headspaces of storm outfall P and Q were also collected to demonstrate whether the discharge from these two outfalls is a potential source contributing to the existing odour nuisance.

3.6.86    The air sampling and subsequent olfactometry tests were conducted by Odour Research Laboratory of HKPU which is an accredited laboratory in Hong Kong to conduct such odour sampling and olfactometry test.


3.6.87    Source air sampling above potential odorous water surface were based on “hood” methods[1], whereby a flux hood type apparatus was placed on the odour emitting surface of potential source locations, and air was blown through it.  A dynamic flux hood was employed in the sampling work to collect odour samples from water surfaces, in which an odour-free gas from a nitrogen gas cylinder was supplied to generate an air flow at 20L/min inside the flux hood.  The emission rate was then given by airflow through the hood and the odour concentration of the exit air.  The ambient air samples were collected via a sampling tube connecting to an odour sampling system (i.e. air pumps and Tedlar bags).  The empty sample bag was placed in a rigid plastic container and the container was then evacuated at a controlled rate and the bag was filled.  The air sampling locations of the Year 2006 and 2007 odour surveys are indicated in Figure 1 and 2 of Appendix 3.13.  The collected samples were sent to the Odour Research Laboratory of the Hong Kong Polytechnic University for olfactometry analysis within 24 hours.

3.6.88    The odour concentration of the air samples were determined by a forced-choice dynamic olfactometer with a panel of human assessors being the sensor in accordance with the European Standard Method (EN13725).  Each odour testing session comprised at least six qualified panellists.  All the panellists were screened beforehand by using a 50 ppm solution/mixture of certified n-butanol standard gas.  Their individual odour thresholds of n-butanol in nitrogen gas were in the range of 20 to 80 ppb/v as required by EN13725.  The odour panellists were all free from any respiratory illnesses and were not normally working at or living in the area in the vicinity of CBTS and typhoon shelters.

Existing Odour Emission Inventory

3.6.89    Based on the findings of the odour surveys in September 2006 and July 2007, existing odour nuisance was identified at the corner of the CBTS near the Police Officers’ Club and the water surface area in the vicinity of Outfall P and Q.  No existing odour nuisance was detected at the east and centre of CBTS, ex-PCWA, Northern Breakwater, Eastern Breakwater and nearby areas and the areas in the vicinity of Outfall R and S.

3.6.90    The odour concentration (in terms of ou/m3) of the collected air samples were determined by olfactometry analysis.  The specific odour emission rate (SOER) of each existing area source was calculated by the following equation:

    SOER (ou/m2.s) =      Odour concentration(ou/m3) x Air flow rate inside hood (m3/s)

                                      Covered water surface area (m2)

                                          =        OC x (0.02/60) / (0.2 x 0.2 x 3.14) = OC x 0.00265

3.6.91    The odour concentrations and odour emission rates of the existing source areas estimated from the 2006 and 2007 survey results are summarised in Table 3.14 and 3.15 respectively.


Table 3.14       Results of Olfactometry Analysis (Year 2006)

Sample ID

Ambient Air

or Source Sample

Odour Concentration

(ou/m3)

Odour

Emission Rate

(ou/m2/s)

1-A

Ambient air sample

19

-

1-E

Source sample above water surface

61

0.16

2-A

Ambient air sample

32

-

2-E

Source sample above water surface

82

0.22

3-A

Ambient air sample

42

-

3-E

Source sample above water surface

143

0.38

4-A

Ambient air sample

37

-

4-E

Source sample above water surface

134

0.36

5-A

Ambient air sample

20

-

5-E

Source sample above water surface

75

0.20

 

Table 3.15       Results of Olfactometry Analysis (Year 2007)

Sample ID

Odour Nature

Possible Source

In-situ H2S (ppb)

Odour Concentrations (ou/m3)

Odour Emission Rate (ou/m2/s)

1

Oily & decayed wastes + rotten-egg

Floating debris + sediment + sewage

120 – 130

5792

15.32

2

Oily & decayed wastes + rotten-egg

Floating debris + sediment + sewage

5 – 6

164

0.43

3

Oily & decayed wastes + rotten-egg

Floating debris + sediment + sewage

11 – 12

889

2.35

4

Oily & decayed wastes + rotten-egg

Floating debris + sediment + sewage

3 – 4

484

1.28

5

Oily & decayed wastes + rotten-egg

Floating debris + sediment + sewage

3 – 4

469

1.24

8

Septic sewage + rotten-egg

Outfall + sediment with gas bubbling

2400

30,530

80.77

9

Septic sewage + rotten-egg

Outfall + sediment with gas bubbling

15

670

1.77

10

Septic sewage + rotten-egg

Outfall + sediment with gas bubbling

370 – 380

6208

16.42

11

Septic sewage + rotten-egg

Outfall + sediment with gas bubbling

12 - 13

433

 

1.15

 


3.6.92    Comparing the results of the two odour surveys, higher odour emission rates were obtained in the 2007 odour survey.  This might be due to the fact that the sampling day in 2007 was very hot and the sampling exercise was conducted at the lowest tide ( below 0.5mPD) and during period with very high temperature (31 – 33 degrees Celsius).  Discharges from Outfall Q with sewage-like smell were noted during the entire odour sampling period.  The odour emission rates derived from the 2007 odour survey were considered as reasonable worst case emission rates and were therefore adopted in the assessment for the prediction of the worst odour concentrations at the representative ASRs.  However, the odour emission rate derived from Sample ID 8 (Year 2007) was unreasonably high (80.77 ou/m2/s).  The emission rates derived from other air samples collected in the vicinity of outfall Q such as Sample ID 9 (the closest point to the outfall Q) and Sample ID10 were significantly lower.  These two air sample locations were also close to Sample ID8.  In accordance with the past experience in other odour projects, the odour emission rates for sewage and sludge related sources were not higher than 40 ou/m2/s.  It was therefore suspected that the air sample of Sample ID8 might be contaminated in the laboratory analysis.  The result for this sample was therefore discarded and the emission rate used in the modelling was based on the second highest odour emission rate (i.e. 16.42 ou/m2/s) derived from Sample ID10 which was also close to Sample ID8.

3.6.93    The odour concentrations of air samples collected inside the headspaces of outfall P and Q were 884 ou/m3 and 71320 ou/m3, respectively.  The results indicated that high odour concentrations were detected in the headspace of outfall Q.  Under the worst case condition as identified by the odour surveys during low tide, the rate of change in tide level is very slow and hence the rate of displacement of the headspace air volume from the outfalls to the atmosphere, if any, would also be very low.  Therefore, no air displacement from the headspace of the outfalls was considered in the odour modelling.  During other tidal conditions, the rate of displacement of the headspace air volume from the outfalls to the atmosphere might be higher, yet the odour emissions from other potential odour source locations would be significantly less and are therefore not considered as worst case conditions.  

3.6.94    Based on the findings of the odour surveys, the locations of potential odour source areas considered in the odour modelling for the worst case scenario are shown in Appendix 3.14.  Besides, with reference to the results of the odour surveys carried out in 2006 and 2007, it is noted that the odour emission rates of the identified odour source areas would be lower under lower ambient temperature.  The recorded ambient temperature during the sampling period in 2006 and 2007 was in the range of 25-29 oC and 31-34 oC respectively.  The estimated odour emission rates based on the 2006 odour survey results are significantly lower than those derived based on the 2007 odour survey results.  The highest odour emission rate derived from the 2006 odour survey results is 0.38 ou/m2/s whereas the highest odour emission rate derived from the 2007 odour survey results is 16.42 ou/m2/s.  For the purpose of this assessment to produce reasonable prediction under different ambient temperature, the odour emission rates during periods with ambient temperature equal to or greater than 30 oC were derived from the 2007 odour survey results, whereas the odour emission rates during periods with ambient temperature less than 30 oC were taken as the highest odour emission rate derived from the 2006 odour survey results, i.e. 0.38 ou/m2/s.  The emission factors of the existing source areas under different temperature ranges are summarized in Table 3.16.


Table 3.16      Existing Odour Emission Inventory for the Worst Case Scenario

Sample ID

Odour Emission Rate (ou/m2/s)

(for ambient temperature <30 oC)

(for ambient temperature >= 30 oC)

1

0.38

15.32

2

0.38

0.43

3

0.38

2.35

4

0.38

1.28

5

0.38

1.24

8

0.38

16.42

9

0.38

1.77

10

0.38

16.42

11

0.38

1.15

 

Air Dispersion Model

3.6.95    Odour impacts were assessed using air dispersion model, ISCST3.  Hourly meteorological data for the year 2005 (including wind speed, wind direction, air temperature, Pasquill stability class and mixing height) of the Hong Kong Observatory Weather Station were employed for the model run.  The study area is in an urban area, “Urban” model was adopted in the model.

 

3.6.96    The modelled hourly odour concentrations at the ASRs were converted into the 5-second odour concentration so as to compare with the EIAO-TM odour criteria.  In accordance with EPD’s “Guidelines on Choice of Models and Model Parameters”, it is recommended to follow the methodologies proposed by Duffee et al.[2]  and Keddie[3]   in performing the conversion from hourly and 5-second average concentration.  However, it is noted that these methodologies are based on findings of earlier researches on dispersion of odour emissions from point sources.  More recent researches indicated that the peak-to-mean ratio of odour dispersion would depend upon the type of source, atmospheric stability and distance downwind.  Depending on the physical source configuration, the peak-to-mean ratio of odour dispersion from area source could be far smaller than that from point source.  In this assessment, the potential odour sources to be studied are in the form of area sources in CBTS.  Therefore, for the purpose of this assessment to produce more reasonable predictions for odour dispersion from area sources, reference was made to the peak-to-mean ratio for area source stipulated in “Approved Methods for Modelling and Assessment of Air Pollutants in New South Wales” published by the Department of Environment and Conservation, New South Wales, Australia (NSW Approved Method).


3.6.97    The dispersion modelling techniques employed for this assessment followed those described in EPD’s “Guidelines on Choice of Models and Model Parameters” using ISCST3 model except the use of alternative peak-to-mean ratios discussed above.  However, it should be noted that the peak-to-mean ratios stated in the NSW Approved Method are derived based on experimental and theoretical analyses and assuming a 0.1% exceedance level (Ref.: Statistical Elements of Predicting the Impact of a Variety of Odour Sources, Peter R. Best, Karen E. Lunney and Christine A. Killip, Water Science and Technology, Australia, 44: 9 pp 157-164 2001).  In other words, there would be a 0.1% probability that the actual peak concentration would be higher than those derived with the peak-to-mean ratios stated in the NSW Approved Method.  The residual odour impact associated with this 0.1% probability is addressed in Sections 3.8 and 3.9 below.

3.6.98    In accordance with the NSW Approved Method, the conversion factors are used for converting the 1-hour average concentrations to 1-second average concentrations.  As a conservative approach, these conversion factors were directly adopted for converting the 1-hour average concentrations predicted by the ISCST3 model to 5-second average concentrations for compliance checking with the odour criteria.  Besides, in this case, the potential odour sources are located in the vicinity of the ASRs, therefore, the ASRs are considered to be located in the near field region with regards to the odour sources as per the NSW Approved Method.  The conversion factors adopted in this assessment for different stability classes are shown in Table 3.17.

  Table 3.17     Conversion Factors to 5-second Mean Concentration

Pasquill Stability Class

       Conversion Factor (1 hour to 5 seconds)

A

2.5

B

2.5

C

2.5

D

2.5

E

2.3

F

2.3

 

Presentation of Assessment Results

3.6.99    The predicted odour concentrations within the study area under the existing scenario were presented in the form of contour plots and are attached in Appendix 3.14.   

Level of Uncertainty in the Assessment

Construction Dust and Road Traffic Emission Impact Assessments

3.6.100The emission rates adopted in the construction dust impact assessment are in accordance with the USEPA Compilation of Air Pollutant Emission Factors (AP-42), which had previously been applied in similar situations in other EIA studies.

3.6.101The Fugitive Dust Model (FDM) for construction dust impact assessment, Caline4 model for open road traffic emission impact assessment, and Industrial Source Complex Short Term 3 (ISCST3) dispersion model for portal/vent shaft emission impact assessment are generally accepted models for use in assessing construction dust impacts and road traffic emission impacts.

3.6.102There would be some limitations such as the accuracy of the predictive base data for future conditions e.g. traffic flow forecasts, plant inventory for the proposed construction works and sequences of construction activities.  Uncertainties in the assessment of impacts have been considered when drawing conclusions from the assessment.

Odour Impact Assessment

3.6.103The degree of uncertainty of the predicted odour impacts depends on the accuracy of the estimated odour emission rates and the air dispersion modelling.  The number of air samples collected as well as the intrinsic limitations of the air sampling technique and the olfactometry analysis would also affect the accuracy of odour emission rate estimation.

3.6.104The odour patrol was conducted over a limited number of days to identify the potential odour source locations, however, the patrol days were all sunny days in very hot season and the patrol period covered the low tide condition.  It is believed that the potential odour source locations at CBTS have been identified.  Besides, given that the odour surveys were carried out in a limited number of days at worst-case weather and tidal conditions, the measured odour concentrations are basically worst-case snapshot values.  Given the above, the estimated odour emission rates are considered to represent reasonable worst case conditions.  

3.6.105Air sampling is an important step in the process of measuring the odour concentrations of the sources, as is the quality and reliability of the results.  All the odour sampling was carried out by the odour sampling team of HKPU which has the most extensive local experience in odour sampling.  The potential error associated with odour sampling process is considered to be on the low side.     

3.6.106It should be noted that all the odour concentrations (in ou/m3) and hence area source emission rates (in ou/m2/s) were measured by olfactometry analysis carried out at the Odour Research Laboratory of HKPU in accordance with the European Standard Method (EN13725).  This European Standard Method specifies a method for the objective determination of the odour concentration of a gaseous sample using dynamic olfactometry with human assessors.  The detection limit for this European Standard Method is 10 ou/m3.  Yet the detection limit of this European Standard Method could vary between laboratories.  Therefore, in reviewing the odour concentration results (in ou/m3), it should be noted that a measured low odour concentration value would normally has a higher degree of error due to the inherent properties of the olfactometry analysis method.

3.7              Prediction and Evaluation of Environmental Impacts

Construction Phase

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

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

3.7.3        The predicted cumulative maximum 1-hour average TSP and 24-hour average TSP during construction are shown in Tables 3.18 - 3.21.


Table 3.18       Predicted Cumulative Maximum 1-hour Average TSP Concentrations at 1.5m above ground

ASR

Predicted Concentration (mg m-3) *

Scen. 1

Scen. 2

Scen. 3

Scen. 4

Scen. 5

Scen. 6

Max.

A25

123

107

172

162

172

92

172

A26

151

130

252

247

252

94

252

A27

195

135

199

196

199

101

199

A28

132

120

222

204

226

91

226

A29

170

154

409

402

408

94

409

A30

216

175

277

276

277

99

277

A31

208

138

193

192

193

106

208

A32

221

186

394

434

421

155

434

A33

378

232

367

269

366

107

378

A34

246

173

328

224

328

103

328

A35

141

126

240

278

278

149

278

A36

124

121

175

205

200

117

205

A37

214

213

329

414

358

256

414

A38

241

228

235

292

214

173

292

A39

225

206

199

238

190

184

238

A40

113

112

131

152

148

105

152

A41

120

118

129

150

142

113

150

A42

121

120

129

147

138

120

147

A43

127

125

125

138

134

132

138

A44

150

149

149

163

151

139

163

A45

189

189

189

218

209

192

218

A46

193

193

193

230

223

206

230

A47

180

180

180

226

222

208

226

A48

158

158

158

224

224

218

224

A49

151

150

151

219

219

215

219

A50

306

306

306

193

192

174

306

A51

212

212

212

210

204

180

212

A52

201

199

200

191

179

163

201

A53

280

277

277

216

204

184

280

A54

147

145

156

185

320

164

320

A55

125

123

129

153

237

127

237

A56

111

108

113

133

148

115

148

A57

116

114

119

141

194

117

194

A58

123

121

128

148

277

120

277

A59

129

128

137

154

183

122

183

A60

148

147

160

166

167

126

167

A61

183

182

193

181

181

132

193

A62

166

162

162

155

153

118

166

A63

221

212

174

195

152

119

221

A64

194

175

165

223

140

113

223

A65

185

172

166

254

132

109

254

A66

170

170

184

184

184

135

184

A70

217

210

168

162

174

88

217

A95

225

220

102

238

99

159

238

A96

167

162

99

185

98

139

185

A97

149

145

98

167

97

125

167

A98

121

117

95

132

95

95

132

Note:      * Background concentration is included.

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


Table 3.19       Predicted Cumulative Maximum 24-hour Average TSP Concentrations for at 1.5m above ground

ASR

Predicted Concentration (mg m-3) *

Scen. 1

Scen. 2

Scen. 3

Scen. 4

Scen. 5

Scen. 6

Max.

A25

98

91

122

117

121

84

122

A26

111

102

158

156

158

84

158

A27

131

105

134

133

134

88

134

A28

102

98

145

136

147

83

147

A29

119

113

229

226

229

85

229

A30

141

124

169

169

169

87

169

A31

137

106

131

130

131

90

137

A32

143

129

221

241

235

111

241

A33

213

149

210

168

210

90

213

A34

154

122

193

145

193

88

193

A35

106

101

152

169

168

109

169

A36

99

98

122

136

134

95

136

A37

140

140

192

231

207

156

231

A38

152

146

151

178

143

119

178

A39

145

137

136

154

132

124

154

A40

94

94

103

112

110

89

112

A41

97

97

102

111

108

93

111

A42

97

98

102

110

106

96

110

A43

100

100

100

107

104

101

107

A44

111

111

111

119

113

104

119

A45

129

129

129

143

139

128

143

A46

130

130

130

148

145

134

148

A47

124

124

124

146

144

135

146

A48

114

115

115

144

144

139

144

A49

111

111

112

142

142

138

142

A50

180

183

183

132

132

120

183

A51

139

141

141

139

136

122

141

A52

134

134

135

132

126

115

135

A53

171

170

170

144

138

124

171

A54

109

108

113

127

187

116

187

A55

99

99

101

113

151

99

151

A56

92

92

94

103

110

94

110

A57

95

94

97

107

132

95

132

A58

98

97

101

111

170

96

170

A59

101

100

105

114

126

97

126

A60

109

109

116

120

120

99

120

A61

125

125

132

127

127

101

132

A62

118

117

118

115

114

95

118

A63

142

142

124

132

113

95

142

A64

130

124

119

145

107

93

145

A65

126

122

118

159

104

91

159

A66

120

120

127

129

128

102

129

A70

141

139

121

118

124

82

141

A95

144

145

89

153

88

113

153

A96

117

118

88

128

87

104

128

A97

109

110

87

119

86

98

119

A98

97

97

86

103

86

85

103

 

Note:      * Background concentration is included.

                   Daily TSP (AQO): 260 mg m-3

 


Table 3.20       Predicted Cumulative Maximum 1-hour Average TSP Concentrations at 5m above ground

ASR

Predicted Concentration (mg m-3) *

Scen. 1

Scen. 2

Scen. 3

Scen. 4

Scen. 5

Scen. 6

Max.

A25

125

104

175

163

174

93

175

A26

153

122

248

242

248

95

248

A27

194

125

199

196

199

102

199

A28

135

115

226

207

230

92

230

A29

173

142

364

354

364

95

364

A30

213

155

266

266

266

100

266

A31

206

127

192

195

192

107

206

A32

219

167

318

390

367

154

390

A33

323

187

312

270

311

109

323

A34

229

151

308

224

308

104

308

A35

143

120

234

259

257

148

259

A36

125

114

178

203

199

118

203

A37

203

182

258

371

344

208

371

A38

222

186

234

291

219

166

291

A39

214

176

202

241

190

183

241

A40

115

108

134

155

151

106

155

A41

122

114

132

153

145

113

153

A42

124

115

132

150

141

120

150

A43

130

120

128

141

134

132

141

A44

152

138

151

167

155

141

167

A45

185

167

185

221

211

193

221

A46

188

170

188

231

224

206

231

A47

176

160

176

226

223

207

226

A48

158

145

157

221

221

215

221

A49

152

139

152

216

216

211

216

A50

259

230

259

195

195

176

259

A51

202

179

200

208

202

176

208

A52

199

178

197

196

182

165

199

A53

265

233

263

220

206

186

265

A54

148

134

156

188

209

167

209

A55

127

117

130

157

216

130

216

A56

113

105

115

136

151

117

151

A57

118

109

121

144

191

119

191

A58

124

115

131

152

223

122

223

A59

130

121

140

159

179

124

179

A60

148

136

163

171

171

129

171

A61

180

163

196

186

185

135

196

A62

168

150

166

158

157

120

168

A63

219

190

177

196

155

121

219

A64

194

161

167

222

143

115

222

A65

186

157

167

248

135

111

248

A66

169

154

186

189

188

137

189

A70

201

174

173

167

180

88

201

A93

410

354

115

432

107

167

432

A94

301

258

106

299

102

169

301

A95

228

199

104

239

101

147

239

A96

171

152

101

189

99

132

189

A97

152

137

99

171

98

123

171

A98

124

113

96

135

96

96

135

Note:      * Background concentration is included.

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

 

 

 

Table 3.21       Predicted Cumulative Maximum 24-hour Average TSP Concentrations at 5m above ground

ASR

Predicted Concentration (mg m-3) *

Scen. 1

Scen. 2

Scen. 3

Scen. 4

Scen. 5

Scen. 6

Max.

A25

100

90

122

117

122

84

122

A26

112

98

154

152

154

85

154

A27

131

100

133

132

133

88

133

A28

105

95

146

137

147

83

147

A29

122

108

205

200

204

85

205

A30

140

114

162

162

162

87

162

A31

136

100

129

132

129

90

136

A32

142

119

185

219

206

111

219

A33

186

126

182

167

183

91

186

A34

145

111

181

144

181

89

181

A35

108

98

148

158

158

108

158

A36

99

95

123

134

132

95

134

A37

134

125

160

209

199

135

209

A38

142

126

149

176

144

116

176

A39

139

123

136

155

131

124

155

A40

95

92

104

113

111

90

113

A41

99

95

103

112

109

93

112

A42

100

96

103

111

107

96

111

A43

103

98

101

108

104

101

108

A44

112

106

111

120

114

105

120

A45

126

119

126

144

139

128

144

A46

127

119

127

148

145

134

148

A47

122

115

122

145

144

134

145

A48

114

109

114

142

142

138

142

A49

112

106

112

140

140

136

140

A50

158

145

157

132

132

121

158

A51

136

126

135

138

135

120

138

A52

133

124

132

134

127

116

134

A53

163

149

161

145

138

125

163

A54

110

104

113

128

137

117

137

A55

100

96

102

115

140

100

140

A56

94

90

95

104

111

95

111

A57

96

92

98

109

129

96

129

A58

99

95

102

113

144

97

144

A59

101

97

106

116

125

98

125

A60

110

104

117

122

122

100

122

A61

124

117

132

129

129

102

132

A62

119

111

119

116

115

96

119

A63

143

131

125

132

115

96

143

A64

132

118

119

143

109

94

143

A65

128

115

119

155

105

92

155

A66

118

112

128

131

130

104

131

A70

134

122

123

120

126

82

134

A93

224

200

95

235

91

117

235

A94

181

162

91

179

89

118

181

A95

148

135

90

152

89

108

152

A96

122

114

89

129

88

101

129

A97

113

106

88

121

87

97

121

A98

99

95

86

105

86

85

105

Note:      * Background concentration is included.

                   Daily TSP(AQO): 260 mg m-3

 

                          


3.7.4        Based on results indicated in Tables 3.18 to 3.21, no exceedance of 1-hour average and 24-hour average TSP guideline and AQO is predicted at the ASRs 1.5m and 5m above ground.  The predicted cumulative maximum 1-hour average and 24-hour average TSP concentration contours at 1.5m and 5m above local ground are shown in Figures 3.6 to 3.17.  Exceedances of the 1-hour average TSP guideline of 500 mg/m3 and the 24-hour average TSP AQO of 260 mg/m3 are noted in some areas at 1.5m above ground including:

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

 

Scenario 1 – sea area, area next to Cross Harbour Tunnel and area next to HKCEC, IEC

Scenario 2 – sea area and IEC

Scenario 3 – sea area, area next to Cross Harbour Tunnel, area next to HKCEC, area underneath New Atrium Link (Extension of HKCEC)

Scenario 4 -  sea area, IEC, part of waterfront in the vicinity of Causeway Bay Flyover, area underneath New Atrium Link (Extension of HKCEC), area in the vicinity of existing Wan Chai Pier and nearby PTI, area next to Servicemen’s Guides Association

Scenario 5 – sea area, area underneath New Atrium Link (Extension of HKCEC), area in the vicinity of existing Wan Chai Pier and nearby PTI, area next to Servicemen’s Guides Association

Scenario 6 – sea area and part of waterfront in the vicinity of Causeway Bay Flyover 

 

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

 

Scenario 1 – sea area, area next to Cross Harbour Tunnel and area next to HKCEC, IEC

Scenario 2 – sea area, IEC and area next to Cross Harbour Tunnel

Scenario 3 – sea area, area next to Cross Harbour Tunnel, areas next to Servicemen’s Guides Association and HKCEC, area underneath New Atrium Link (Extension of HKCEC)

Scenario 4 -  sea area, IEC, part of waterfront in the vicinity of Causeway Bay Flyover, GFS Helipad, area underneath New Atrium Link (Extension of HKCEC), area in the vicinity of existing Wan Chai Pier and nearby PTI, area next to Servicemen’s Guides Association

Scenario 5 – sea area, part of waterfront near Causeway Bay Flyover, area underneath New Atrium Link (Extension of HKCEC), area in the vicinity of existing Wan Chai Pier and nearby PTI, area next to Servicemen’s Guides Association

Scenario 6 – sea area and part of waterfront in the vicinity of Causeway Bay Flyover

 

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

Operational Phase

Traffic Emission Impact (Open Road)

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


3.7.7        In order to determine the potential impacts on the upper level receivers, pollutant concentrations at various levels (1.5 m, 5m, 10 m, 20m, 30m and 40m above ground) were calculated.  Tables  3.22, 3.23 and 3.24 summarise the predicted cumulative maximum 1-hour average NO2, 24-hour average NO2 and 24-hour average RSP concentrations at different elevations respectively.

Table 3.22       Predicted Cumulative Maximum 1-hour Average NO2 Concentrations at the Representative ASRs at Different Elevations

ASRs

Predicted 1-hour averaged Concentration (mg m-3) *

1.5m AGL

5m AGL

10m AGL

20m AGL

30m AGL

40m AGL

A25

100

95

87

87

87

87

A26

79

78

77

77

77

77

A27

81

78

77

77

77

77

A28

81

80

78

78

78

78

A29

77

76

75

75

75

75

A30

81

79

77

77

77

77

A31

85

82

79

79

79

79

A32

83

82

80

79

79

79

A33

77

75

75

74

74

74

A34

74

74

74

74

73

73

A35

79

79

78

78

78

78

A36

96

93

88

88

88

88

A37

94

87

83

83

82

82

A38

98

94

89

88

88

87

A39

95

94

93

93

91

90

A40

130

124

113

113

113

112

A41

126

123

116

115

114

113

A42

132

128

119

118

117

115

A43

131

127

118

116

113

110

A44

170

152

129

120

108

99

A45

175

154

125

114

106

106

A46

167

149

122

114

106

106

A47

143

135

119

114

106

102

A48

118

114

107

105

102

99

A49

110

107

102

101

99

97

A50

194

189

174

135

101

83

A51

255

245

218

163

118

100

A52

178

175

164

132

101

101

A53

250

239

208

136

94

94

A54

97

93

89

89

89

89

A55

84

83

82

82

82

82

A56

90

79

75

75

75

74

A57

94

85

79

79

79

79

A58

96

86

82

82

82

82

A59

96

87

83

83

83

83

A60

91

83

81

81

80

80

A61

91

84

81

81

81

80

A62

88

83

79

79

79

79

A63

78

78

77

77

77

77

A64

77

77

76

76

76

75

A65

76

76

75

75

75

75

A66

83

83

82

82

82

82

A70

75

74

73

73

73

73

A71

79

78

77

77

77

77

A73

104

89

81

81

81

81

A76

90

86

81

81

81

81

A81

89

86

82

82

82

82

A91

78

80

84

84

84

85

A92

77

77

76

76

76

77

A93

84

84

82

82

82

82

A94

82

82

81

81

81

81

A95

78

78

78

78

78

78

A96

75

75

75

75

75

75

A97

76

75

74

74

74

74

A98

76

76

74

74

74

74

A99

86

84

80

80

80

80

Note:      *  Background concentrations are included.

                   1-hr NO2 criteria (AQO): 300 mg m-3

 

 


Table 3.23       Predicted Cumulative Maximum 24-hour Average NO2 Concentrations at the Representative ASRs at Different Elevations

ASRs

Predicted 24-hour averaged Concentration (mg m-3) *

1.5m AGL

5m AGL

10m AGL

20m AGL

30m AGL

40m AGL

A25

73

71

68

68

68

68

A26

65

64

64

64

64

64

A27

65

64

64

64

64

64

A28

66

65

64

64

64

64

A29

64

64

63

63

63

63

A30

66

65

64

64

64

64

A31

67

66

65

65

65

65

A32

66

66

65

65

65

65

A33

64

63

63

63

63

63

A34

63

63

62

62

62

62

A35

65

64

64

64

64

64

A36

71

70

68

68

68

68

A37

71

68

66

66

66

66

A38

72

70

68

68

68

68

A39

71

71

70

70

70

69

A40

85

83

78

78

78

78

A41

84

82

79

79

79

78

A42

86

84

81

80

80

79

A43

85

84

80

80

78

77

A44

101

94

85

81

76

73

A45

103

94

83

79

76

76

A46

100

93

82

78

76

76

A47

90

87

81

78

75

74

A48

80

79

76

75

74

72

A49

77

76

74

73

72

72

A50

111

109

103

87

73

66

A51

135

131

120

98

80

73

A52

104

103

98

86

74

73

A53

133

128

116

87

70

70

A54

72

70

69

69

69

68

A55

67

66

66

66

66

66

A56

69

64

63

63

63

63

A57

71

67

65

65

65

65

A58

71

67

66

66

66

66

A59

71

68

66

66

66

66

A60

69

66

65

65

65

65

A61

69

66

65

65

65

65

A62

68

66

65

65

65

65

A63

64

64

64

64

64

64

A64

64

64

63

63

63

63

A65

63

63

63

63

63

63

A66

66

66

66

66

66

66

A70

63

63

62

62

62

62

A71

65

64

64

64

64

64

A73

75

69

66

66

66

66

A76

69

67

65

65

65

65

A81

69

67

66

66

66

66

A91

64

65

67

67

67

67

A92

64

64

63

63

64

64

A93

67

66

66

66

66

66

A94

66

66

65

65

65

65

A95

64

64

64

64

64

64

A96

63

63

63

63

63

63

A97

63

63

63

63

63

63

A98

64

63

63

63

63

63

A99

67

67

65

65

65

65

 

Note:      *  Background concentrations are included.

                   24-hr NO2 criteria (AQO): 150 mg m-3

 

 


Table 3.24      Predicted Cumulative Maximum 24-hour Average RSP Concentrations at the Representative ASRs at Different Elevations

ASRs

Predicted 24-hour averaged Concentration (mg m-3) *

1.5m AGL

5m AGL

10m AGL

20m AGL

30m AGL

40m AGL

A25

59

58

58

58

58

58

A26

57

57

57

57

57

57

A27

57

57

56

56

56

56

A28

57

57

57

57

57

57

A29

57

56

56

56

56

56

A30

57

57

57

57

57

57

A31

57

57

57

57

57

57

A32

57

57

57

57

57

57

A33

57

56

56

56

56

56

A34

56

56

56

56

56

56

A35

57

57

57

57

57

57

A36

59

58

58

58

58

58

A37

59

58

57

57

57

57

A38

59

59

58

58

58

58

A39

59

59

59

59

58

58

A40

62

62

61

61

61

60

A41

62

62

61

61

61

61

A42

63

63

61

61

61

61

A43

63

63

62

61

61

60

A44

69

66

63

62

61

59

A45

69

66

63

61

60

60

A46

68

66

62

61

60

60

A47

65

64

62

61

60

60

A48

62

61

60

60

60

59

A49

61

60

60

60

59

59

A50

71

70

69

64

60

57

A51

78

77

74

67

61

59

A52

69

69

67

63

60

59

A53

78

76

73

64

59

59

A54

59

59

58

58

58

58

A55

58

57

57

57

57

57

A56

58

57

56

56

56

56

A57

59

58

57

57

57

57

A58

59

58

57

57

57

57

A59

59

58

57

57

57

57

A60

58

57

57

57

57

57

A61

58

58

57

57

57

57

A62

58

57

57

57

57

57

A63

57

57

57

57

57

57

A64

57

57

57

57

57

56

A65

57

57

57

56

56

56

A66

57

57

57

57

57

57

A70

56

56

56

56

56

56

A71

57

57

56

56

56

56

A73

60

58

57

57

57

57

A76

58

58

57

57

57

57

A81

58

58

57

57

57

57

A91

57

57

58

58

58

58

A92

56

56

56

56

56

56

A93

57

57

57

57

57

57

A94

57

57

57

57

57

57

A95

56

56

56

56

56

56

A96

56

56

56

56

56

56

A97

57

57

56

56

56

56

A98

57

57

56

56

56

56

A99

58

57

57

57

57

57

Note:      *  Background concentrations are included.

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

 

 

3.7.8        Based on the above prediction, no exceedance of the 1-hour average NO2, 24-hour average NO2 and 24-hour average RSP AQOs would occur at any representative ASR in the Study Area.  From the results, it is found that the maximum pollutant concentrations would occur at 1.5m above ground (the lowest assessment height).  The predicted cumulative maximum hourly average NO2, 24-hour average NO2 and RSP concentration contours at 1.5m above local ground are shown in Figures 3.18 to 3.20.    Exceedances of 1-hour average and 24-hour average NO2 concentrations are noted at part of the building of the POC in the contour plots, however, the building of the POC is provided with central air conditioning and there is no fresh air intake at these areas, i.e. no air sensitive areas are located within the exceedance areas. 

 


Vehicular Emission Impact (Inside the Tunnel/deckover)

3.7.9        For the air quality assessment inside the planned deckover on future HKCEC Atrium Link, the predicted maximum NO2 concentrations under normal traffic flow and congested traffic flow would be 114 mg/m3 and 130 mg/m3 respectively, and would comply with the Tunnel Air Quality Objective (1800 mg/m3).  Detailed calculations and results are presented in Appendix 3.12.  The in-tunnel air quality inside the proposed trunk road should be complied with the Tunnel Air Quality Objective with proper engineering design (as mentioned in section 3.6.62).

Odour Impact

3.7.10    Odour nuisance associated with the Causeway Bay Typhoon Shelter is an existing environmental problem.  This Project will not create any new odour source during the operational phase.  However, in order to improve the environment, this Project will take the opportunities to mitigate the potential sources of odour nuisance within the Project area so as to alleviate this existing environmental problem as well as to provide an acceptable environment for the future land uses within the project area.

3.7.11    In order to identify the existing odour emission sources and determine the extent and level of existing odour impacts, odour surveys including odour patrols and air sampling on existing odour source area were undertaken.  The odour patrol was conducted in a limited number of days to identify the existing odour source locations.  The patrol days were all sunny days in very hot season and the patrol period covered the low tide condition.  It is believed that the existing odour source locations at CBTS have been identified.  Besides, given that the odour surveys were carried out in a limited number of days, the measured odour concentrations are basically snapshot values.  Yet, given that all the odour surveys were carried out during hot season and low tide conditions, the estimated odour emission rates are considered representing reasonable worst case conditions.

3.7.12    The odour contour plot for the study area under the existing scenario with worst case odour emission rates is presented in Appendix 3.14.  The odour modelling results indicate that the existing odour levels in the vicinity of CBTS are far higher than the odour criterion of 5 ou/m3 averaged over 5 seconds.  This concurs with the findings of the 2006 and 2007 odour surveys that moderate to high odour intensity levels were sometimes observed at some locations in the vicinity of CBTS.

3.7.13    The odour concentrations predicted at the planned ASRs under WDII Project based on the worst case existing odour emission rates are summarized in Table 3.25.  It is noted that the proposed planned air sensitive uses in Central, Wan Chai and Causeway Bay area would also exceed the odour criterion of 5 ou/m3 averaged over 5 seconds under the worst case condition.

Table 3.25       Predicted Odour Concentrations at the Representative ASRs (Based on the Existing Odour Emission Rates) Under the Worst Case Condition

ASRs

Section

Location

Odour Concentration (ou/m3 averaged over 5 seconds)

A76

Central

Open space at the west of HKCEC

4.9

A81

Wanchai

Waterfront related commercial and leisure uses

12.1

A100

Wanchai

Water Sports Centre

44.0

A101

Causeway Bay

Open space at Northern Breakwater

96.7

Note:  There is 0.1% probability of exceeding the predicted odour concentration inherent in the calculation method. 

3.7.14    It should be noted that the predicted odour impacts presented for the existing scenario are worst case predictions based on worst case odour emissions estimated from survey data recorded under very hot season and low tide conditions as well as worst case atmospheric dispersion conditions assumed in the odour model.  The worst case predictions are not representing the general situation under the existing scenario.  The chance for all these worst case conditions to occur concurrently is considered to be remote.  The model predictions only represent the worst case condition at a limited period of time.  Whereas the odour surveys were carried out at particular days with very hot season and low tide conditions, the findings of the odour survey are also specific to the conditions on those odour survey days.  With reference to the observations of the odour surveys and above odour assessment results, practicable odour mitigation measures are formulated with an objective to alleviate the existing odour problem in the vicinity of CBTS.  Details of the proposed odour mitigation measures are described in the next section.

3.8              Mitigation of Adverse Environmental Impacts

Construction Phase

3.8.1        As shown in Tables 3.18 to 3.21 and explanation given in Section 3.7.4, the cumulative maximum 1-hour average and 24-hour average TSP concentrations are predicted to comply with the TSP criteria at all representative ASRs with watering on the active works area four times a day.  The area within study area of WDII Project would also meet the TSP criteria.  In order to further ensure compliance with the AQOs at the ASRs at all time, requirements of the Air Pollution Control (Construction Dust) Regulation shall be adhered to during the construction period.  In addition, the following mitigation measures, good site practices and a comprehensive dust monitoring and audit programme are recommended to minimise cumulative dust impacts.

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

·                     Watering during excavation and material handling;

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

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

 

Operation Phase

Traffic Emission Impact

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

Odour Impact

3.8.3        The Project itself would not introduce any additional odour emission sources within the study area.  However, as indicated in the odour assessment presented in Section 3.7 above, odour nuisance associated with the Causeway Bay Typhoon Shelter is an existing environmental problem and adverse odour impacts in the vicinity of CBTS would be expected during worst case conditions.  Without any further measures, the possible future status of the existing odour pollution sources are described as follows:

 


Polluted sewage from drainage outfall

3.8.4        The Drainage Services Department (DSD) has conducted the Causeway Bay Typhoon Shelter Expedient Connection Surveys during August 1997 and January 1999.  According to the “Final Report of the Causeway Bay Typhoon Shelter Expedient Connection Surveys” under Agreement No. CE 78/94 Wan Chai East and North Point Sewerage issued in October 2000, DSD was responsible to rectify 6 number of expedient connection in Causeway Bay area.  Five of the 6 expedient connections had been blocked / rectified.  The remaining one is scheduled to be completed in early 2008.  Except these 6 expedient connections, the report also identified a list of buildings where polluted flows into stormwater system which would require the Building Department to follow up or improper discharges causing pollution to stormwater system which would involve EPD’s pollution control.  It is expected that most of the expedient connections to storm water outfall would be rectified in future, the odour generated from sewage discharged from outfall would be reduced comparing with the existing scenario.

 

Floating debris discharged from the boats 

3.8.5        As advised by the Marine Department, it is a routine exercise that they collect the floating refuse at CBTS every day.  In view of no significant increase in the number of boats mooring at CBTS during operation year of the Project, it is expected that any odour impact that may be generated from floating refuse in future would be similar to the existing condition.

 

Slime attached on the shoreline seawall and sediment at CBTS

3.8.6        The shoreline of CBTS would not be changed under the Project, therefore, dredging activities would be focused on the proposed Trunk Road area.  As most of the expedient connections within the study area are expected to be rectified in future with follow up action by DSD, EPD, FEHD and BD as proposed in the “Final Report of the Causeway Bay Typhoon Shelter Expedient Connection Surveys”, the flow of raw sewage discharged from the outfall would be significantly decreased.  Less odour emission generated from the sediment and the slime in future would be expected.

3.8.7        In addition to the rectification works on expedient connections and the regular floating refuse collection described above, the Project Proponent would like to take the opportunity to mitigate the existing sources of odour nuisance within the Project area by implementing an enhancement proposal.  The objective of the enhancement proposal is to alleviate the existing odour problem as well as to provide an acceptable environment for the future land uses within the project area.

3.8.8        Details of the enhancement proposal shall refer to the separate paper on “Enhancement Package for Existing Odour Sources Identified at Causeway Bay Typhoon Shelter” (see Appendix 15.1). Dredging would be conducted at the corner of CBTS to remove the sediment (see Figure 3.21) and the slime attached on the shoreline seawall would be cleaned during implementation of harbour-front enhancement.    Dredging inside the CBTS for the construction of the Trunk Road as shown in Figure 3.21 will also improve the existing odour conditions at CBTS.


3.8.9        With the concerted efforts from various government departments, including DSD, EPD, FEHD, BD, MD, HyD and CEDD, on the implementation of the above enhancement package, the existing accumulated sediments and slimes on the seawall would be removed, the expedient connections would be rectified, the floating refuse would be removed by the regular harbour cleansing service, illegal discharge and dumping into the CBTS and misconnection of drainage system would be controlled by enforcement of relevant ordinance with patrol, the potential odour sources would be substantially reduced and the future situation would be improved as compared to the existing condition.  Taking into account the potential effect of the above measures in reducing odour nuisance, including complete removal of the major generator of odour namely the sediment at the corner of CBTS by dredging and the dredging inside the CBTS for the construction of the Trunk Road, the future mitigated odour emission strength of the identified odour sources is estimated to be reduced by 70%.  This odour reduction efficiency is considered to be reasonable and conservative.

3.8.10    The odour contour plot for the study area under the future scenario with 70% reduction in odour emissions is presented in Appendix 3.14.  The odour modelling results indicate that with the implementation of the proposed enhancement package, the predicted odour levels in the vicinity of CBTS would be reduced significantly by about 70% in general.  In other words, this Project will alleviate the existing odour problems in the vicinity of CBTS to a large extent by implementing the proposed enhancement measures.

3.8.11    With regards to the planned ASRs under WDII Project, the modelling results also showed marked reduction in the predicted odour levels after the implementation of the proposed enhancement measures.  The modelling results under the future mitigated scenario are shown in Table 3.26.  

Table 3.26       Predicted Odour Concentrations at the Representative ASRs (Mitigated Scenario) under the Worst Case Condition

ASRs

Section

Location

Odour Concentration (ou/m3 over 5 second average)

A76

Central

Open space at the west of HKCEC

1.5

A81

Wanchai

Waterfront related commercial and leisure uses

3.6

A100

Wanchai

Water Sports Centre

13.2

A101

Causeway Bay

Open space at Northern Breakwater

29.0

 Note:  There is 0.1% probability of exceeding the predicted odour concentration inherent in the calculation method. 

 

3.8.12    As shown in Table 3.26 with the implementation of the proposed enhancement measures, exceedances of the odour criterion are still predicted at two planned ASRs A100 and A101 under the worst case condition. It is noted that odour exceedance predicted at the waterfront in CBTS, however, the residual odour impact is considered as of transient nature for the visitors along the waterfront in CBTS.


3.8.13    In order to investigate the frequency of exceedance of the odour criterion at the two planned ASRs, odour modelling was conducted for every hour of a year based on year 2005 meteorological data.    The modelling results indicated that out of 8760 hours in a year, only 1 hour (or 0.01% of time) and 9 hours (or 0.1% of time) with exceedances of the odour criterion are predicted at ASR A100 and A101 respectively.  However, as discussed above in Section 3.6.96, the peak-to-mean ratios stated in the NSW Approved Method employed in this odour assessment has assumed a 0.1% exceedance level.  Therefore, there is a 0.1% probability that the actual peak concentration would be higher than those derived with the peak-to-mean ratios stated in the NSW Approved Method.  Conservatively, if we assume all of this 0.1% actual peak concentration (which are higher than the predicted peak concentration) exceeded the odour criterion, then there would be 0.1% more of time exceedance in year at the two planned ASRs.  For the other ASRs, there is also a 0.1% probability that the actual odour levels as perceived at the ASRs would exceed the predicted odour concentration.  A summary of the predicted frequency of exceedance, including the additional 0.1% due to intrinsic uncertainty of the modelling approach, at the two planned ASRs are shown in Table 3.27. 

Table 3.27       Number of Hour Exceeding the Odour Criterion at the Representative ASRs (Mitigated Scenario) in a Year

ASRs ID

A100

A101

% of time exceedance in a year

0.11%

0.2%

 

3.9              Evaluation of Residual Impacts

Construction Phase

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

Operational Phase

3.9.2        No adverse residual traffic emission impact was predicted.

3.9.3        The odour modelling results indicate that with the implementation of the proposed enhancement package, the predicted odour levels in the vicinity of CBTS would be reduced significantly by about 70% in general.  In other words, this Project will alleviate the existing odour problems in the vicinity of CBTS to a large extent by implementing the proposed enhancement measures.   However, exceedances of the odour criterion are still predicted at two planned ASRs A100 and A101 under the worst case condition.  The following points should be noted with reference to EIAO-TM Clause 4.4.3 with regards to the residual odour impacts at these planned ASRs: 

(i)                 Effects on public health and health of biota or risk to life

 

In this assessment, the odour emission rates obtained from the survey in Year 2007 were under worst case conditions with the sampling exercise carried out at noon with very low tide (below 0.5mPD) and extremely high ambient temperature (around 33 degrees Celsius).  The predicted maximum odour concentrations at the planned ASR (CBTS breakwater), which is the nearest to the existing odour sources, would be about 29 ou/m3 over 5 second average.  If we assume the dominant odorant is H2S, 29 ou/m3 is equivalent to H2S concentration of about 0.0145 ppm.  In terms of human health effects of hydrogen sulphide[4] exposure of 0 – 10 ppm would cause irritation of the eyes and nose; while exposure of 10 – 50 ppm would cause headache.  Therefore, it is expected that no adverse health impact to human for exposure under such a low concentration of H2S.  

 

(ii)               The magnitude of adverse environmental impacts

 

Based on the modelling results, the predicted worst odour concentration at representative planned ASRs are:

 

Representative ASRs ID

A76

A81

A100

A101

Worst Odour Conc.
(ou/m3 over 5-second averaged)

1.5

3.6

13.2

29.0

Note:  There is 0.1% probability of exceeding the predicted odour concentration inherent in the calculation method. 

 

(iii)             The geographic extent of the adverse environmental impacts

 

The extent of exceedance of odour criterion indicated in Figure A3.14-3 of Appendix 3.14.

 

(iv)              The duration and frequency of the adverse environmental impacts

 

The exceedance of odour criterion would occur:

 

ASRs ID

A100

A101

Total no. of hour exceeding the criterion in a year

1

9

% of time exceedance in a year

0.01%

0.1%

% of time exceedance in a year  (taking into account of 0.1% probability of exceeding the predicted odour concentration inherent in the calculation method)

0.11%

0.2%

 

(v)                The likely size of community or the environment that may be affected by the adverse impacts

 

As indicated in Figure A3.14-2 and A3.14-3 of Appendix 3.14, with the implementation of proposed enhancement package, the odour concentrations in Central, Wan Chai and Causeway Bay area would be reduced substantially as compared with the existing scenario, however, exceedance of the odour criterion of 5 ou/m3 over 5 second average  would still be predicted in part area of Wan Chai and Causeway Bay (about 60,000 residents) under the worst case condition.  Adverse odour impact (i.e. exceeding the EIAO-TM odour criterion) at the planned ASRs would only occur for less than 0.2% of time in a year (taking into account of 0.1% probability of exceeding the predicted odour concentration inherent in the calculation method). 

 


(vi)              The degree to which adverse environmental impacts are reversible or irreversible.

 

Under the future scenario, odour nuisance would be a very short-tem impact for two planned ASRs (ASR A100 and A101) based on the assumption of 70% odour reduction efficiency for the proposed enhancement measures.  It is very likely that the proposed enhancement measures would result in higher odour reduction efficiency and the odour impact at the two planned ASRs would be further minimized.    

 

(vii)            The ecological context

 

The exceedance would not involve any ecological context.

 

(viii)          The degree of disruption to sites of cultural heritage

 

The exceedance would not involve any cultural heritage context. 

 

(ix)              International and regional importance

 

The exceedance would not involve any international and regional importance.

 

(x)                Both the likelihood and degree of uncertainty of adverse environmental impacts

 

The modelling results indicated that out of 8760 hours in a year, only 1 hour (or 0.01% of time) and 9 hours (or 0.1% of time) with exceedances of the odour criterion are predicted at ASR A100 and A101 respectively.  However, as discussed above in Section 3.6.96, the peak-to-mean ratios stated in the NSW Approved Method employed in this odour assessment has assumed a 0.1% exceedance level.  Therefore, there is a 0.1% probability that the actual peak concentration would be higher than those derived with the peak-to-mean ratios stated in the NSW Approved Method.  Conservatively, if we assume all of this 0.1% actual peak concentration (which are higher than the predicted peak concentration) exceeded the odour criterion, then there would be 0.1% more of time exceedance in year at the two planned ASRs.  For the other ASRs, there is also a 0.1% probability that the actual odour levels as perceived at the ASRs would exceed the predicted odour concentration.

 

The degree of uncertainty of the predicted odour impacts depends on the accuracy of the estimated odour emission rates and the air dispersion modelling.  The number of air samples collected as well as the intrinsic limitations of the air sampling technique and the olfactometry analysis would also affect the accuracy of odour emission rate estimation.

 

The odour patrol was conducted over a limited number of days to identify the potential odour source locations, however, the patrol days were all sunny days in very hot season and the patrol period covered the low tide condition.  It is believed that the potential odour source locations at CBTS have been identified.  Besides, given that the odour surveys were carried out in a limited number of days at worst-case weather and tidal conditions, the measured odour concentrations are basically worst-case snapshot values.  Given the above, the estimated odour emission rates are considered to represent reasonable worst case conditions.  

 


Air sampling is an important step in the process of measuring the odour concentrations of the sources, as is the quality and reliability of the results.  All the odour sampling was carried out by the odour sampling team of HKPU which has the most extensive local experience in odour sampling.  The potential error associated with odour sampling process is considered to be on the low side.     

 

It should be noted that all the odour concentrations (in ou/m3) and hence area source emission rates (in ou/m2/s) were measured by olfactometry analysis carried out at the Odour Research Laboratory of HKPU in accordance with the European Standard Method (EN13725).  This European Standard Method specifies a method for the objective determination of the odour concentration of a gaseous sample using dynamic olfactometry with human assessors.  The detection limit for this European Standard Method is 10 ou/m3.  Yet the detection limit of this European Standard Method could vary between laboratories.  Therefore, in reviewing the odour concentration results (in ou/m3), it should be noted that a measured low odour concentration value would normally has a higher degree of error due to the inherent properties of the olfactometry analysis method.

 

3.9.4        Referring to the points discussed in Section 3.9.3 above, no adverse health or risk impact is expected at the planned ASRs under WDII Project (i.e. proposed open space at Northern Breakwater and proposed Wan Chai Water Sport Centre) though its odour levels exceed the EIAO-TM criteria in accordance with the air modelling results (13 - 29 ou/m3 over 5 second average) under the worst case condition.  The time of exceedance of the odour criterion at these two planned ASRs is expected to be less than 0.2% of time in a year.  Therefore, the residual odour impact at the planned ASRs is not persistent.  It is supported by the odour patrol results that no odour nuisance detected at the ex-PCWA and Northern Breakwater (i.e. the locations of proposed open space at Northern Breakwater and proposed land uses at Wan Chai North new waterfront) during odour patrols conducted in Year 2006 and Year 2007 Odour Survey.  Hence, no unacceptable odour impact is expected at the future WDII ASRs.

3.10          Environmental Monitoring and Audit

Construction Phase

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

Operational Phase

3.10.2    Since the predicted air quality due to traffic emission in the study area complies with the AQO, no environmental monitoring and audit is proposed.  Nevertheless, the operator for the proposed CWB tunnel, HyD, will conduct air quality monitoring for the operation performance of the EVB and associated East Vent Shaft.  Regarding the odour issue, monthly (from July to September) monitoring of odour impacts, for a period of 5 years, is proposed during the operational phase of the Project to ascertain the effectiveness of the Enhancement Package over time, and to monitor any on-going odour impacts at the ASRs.  If residual odour impact is still found at the end of the odour monitoring programme, further investigation would be carried out to review the odour problem and to identify the parties responsible for further remedial action.

 


3.11          Conclusion

Construction Phase

3.11.1    During construction, reclamation, filling and surcharging were identified as the major dust sources.  Trunk Road tunnel works would also generate dust.  Due to the complex sequencing of the construction activities, six worst case scenarios of the construction schedules have been identified and assessed.  The findings of the construction phase air quality assessment indicate that no exceedance of the 1-hour and 24-hour total TSP criteria are predicted at ASRs in the vicinity of the construction sites.  In order to ensure compliance with the TSP criteria at the ASRs at all times, the dust suppression measures and requirements of the Air Pollution Control (Construction Dust) Regulation should be adhered to during the construction period.  In addition, a comprehensive dust monitoring and audit programme are recommended to ensure the effective implementation of dust suppression measures.

Operational Phase

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

3.11.3    With the Trunk Road tunnel ventilation system designed for zero portal emission at the eastern portal, at North Point, potential air quality impacts from the tunnel portal emission would be avoided.  In addition, the air quality at the eastern portal area would be enhanced by locating the vent shaft at the end of the eastern breakwater of the CBTS and by the introduction of an electrostatic precipitator system at the East Ventilation Building to screen RSPs from the tunnel emissions.

3.11.4    During operational phase, this Project will not create any new odour source.  However, odour nuisance associated with the CBTS is an existing environmental problem.  In order to improve the environment, this Project will take the opportunity to mitigate the potential sources of odour nuisance within the Project area so as to alleviate this existing environmental problem, as well as to provide an acceptable environment for the future land uses within the project area.  Enhancement measures have been formulated to alleviate this existing odour problem.  These include rectification of expedient connections, regular collection of floating debris, dredging to remove the polluted and odorous sediments at the corner of CBTS and clean up the slime attached on CBTS seawall.  With the implementation of these enhancement measures, the predicted odour levels in the vicinity of CBTS would be reduced significantly.  In other words, this Project will alleviate the existing odour problems in the vicinity of CBTS to a large extent by implementing the proposed enhancement measures.  However, some exceedances of the odour criterion are still predicted at two planned ASRs A100 and A101 under the worst case condition.  Nevertheless, the residual odour impact at these planned ASRs is not persistent, with a time of exceedance of the odour criterion expected to be less than 0.2% of time in a year.  In view of this infrequent likelihood of occurrence, no unacceptable adverse odour impact would be expected at the planned ASRs within the study area.


3.11.5    Monthly monitoring (from July to September) of odour impacts, for a period of 5 years, is proposed during the operational phase of the Project to ascertain the effectiveness of the Enhancement Package over time, and to monitor any on-going odour impacts at the ASRs.  If residual odour impact is still found at the end of the odour monitoring programme, further investigation would be carried out to review the odour problem and to identify the parties responsible for further remedial action.  

 



[1] Sampling for Measurement of Odours, P.Gostelow, P. Longhurst, S.A. Parsons and R.Mstuetz, 2003.

[2] Richard A. Duffee, Martha A. O”Brien and Ned Ostojic (1991).  Odour Modelling – Why and How, Recent Developments and Current Practices in Odour Regulation, Controls and Technology, Air & Waste Management Association.

[3] Keddie, A. W, C(1980). Dispersion of Odours, Odour Control – A concise Guide, Warren Spring Laboratory.