3                  Air qUALITY

3.1             Introduction

3.1.1       This section presents an air quality impact assessment for construction and operation phases of the proposed CWB & IECL, addressing the revised CWB & IECL layout, the latest road networks, the revised traffic forecasts, and the change of emissions from the tunnel portals / ventilation buildings.

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 laid out in Annex 4 and Annex 12 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM), respectively.

3.2.2       The Air Pollution Control Ordinance (APCO) provides the statutory authority for controlling air pollutants from a variety of sources.  The ordinance encompasses a number of Air Quality Objectives (AQOs) which stipulate maximum concentrations for a range of pollutants, of which Carbon Monoxide (CO), Nitrogen Dioxide (NO2), Respirable Suspended Particulates (RSP) and Total Suspended Particulates (TSP) are relevant to this study.  The relevant AQOs are listed in Table 3.1.

Table 3.1        Hong Kong Air Quality Objectives

Parameter

Maximum Average Concentration (µg m-3) (1)

 

1 Hour (2)

8 Hours (3)

24 Hours (3)

Annual (4)

NO2

300

-----

150

80

RSP

-----

-----

180

55

CO

30,000

10,000

-----

-----

TSP

500 (5)

-----

260

80

Note:       (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)      Not an AQO.  However, in addition to the established legislative controls, it is accepted that an hourly-averaged TSP concentration of 500 µg m-3 should not be exceeded.

3.2.3       The criteria for tunnel quality, which are based on EPD’s Practice Note on Control of Air Pollution in Vehicle Tunnels 1995, are presented in Table 3.2.

Table 3.2        Tunnel Air Quality Criteria

Parameter

Maximum Concentration (1)  (2)

CO

115,000 µg m-3

100 ppm

NO2

1,800 µg m-3

1 ppm

SO2

1,000 µg m-3

0.4 ppm

Note:       (1)     Averaging time is 5 minutes.

(2)      Measured at 298 K and 101.325 kPa.

3.2.4       In addition, the visibility in tunnels acts as an indicator of smoke concentration and should be controlled so that extinction coefficient does not exceed 0.005 per meter (over five minutes).

3.3             Description of the Environment

3.3.1       As agreed with the EPD, the annual average concentrations of the pollutants measured at EPD’s Central / Western and Central Station air quality monitoring stations in 1999 have been adopted as the background air quality within and adjacent to the CWB & IECL.  Table 3.3 summaries the annual average concentrations of the pollutants in 1999.

Table 3.3        Annual Average Concentrations of Pollutants in 1999

Pollutant

Annual Average Concentration in 1999 (mg m-3)

Monitoring Stations

CO

1,179

Central

NO2

56

Central / Western

RSP

53

Central / Western

TSP

81

Central / Western

3.3.2       The annual average concentrations of the pollutants were used as the background concentrations for the cumulative impact assessment.

3.4             Sensitive Receivers

3.4.1       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 ASRs are listed in Table 3.4 and the corresponding locations are shown in Figures 3.1.1 and 3.1.2.

Table 3.4        Locations of Air Sensitive Receivers

ASR

Section

Location

Existing / Planned Land Use

No. of floors

 

Horizontal Distance (m)

Alignment*

Ventilation Building

 

 

Existing

 

 

 

 

 

A1

Sheung Wan

Shun Tak Centre

Commercial

30

20

648

(1)

A2

Sheung Wan

Korea Centre

Residential

13

12

654

(1)

A3

Sheung Wan

Wing On Centre

Commercial

24

9

606

(1)

A4

Central

Vicwood Plaza

Commercial

27

32

527

(1)

A5

Central

Harbour Building

G/IC

26

16

407

(1)

A6

Central

Crocodile Building

Commercial

20

214

321

(1)

A7

Central

Hang Sang Bank Headquarters

Commercial

25

260

313

(1)

A8

Central

Exchange Square III

Commercial

26

246

271

(1)

A9

Central

Exchange Square I & II

Commercial

45

208

281

(1)

A10

Central

Exchange Square I & II

Commercial

45

280

341

(1)

A11

Central

Jardine House

Commercial

46

248

360

(1)

A12

Central

Jardine House

Commercial

46

287

384

(1)

A13

Central

Statue Square

Recreation

0

313

510

(1)

A14

Central

Hong Kong Club Building

Commercial

16

282

561

(1)

A15

Central

City Hall

G/IC

11

120

534

(1)

A16

Central

City Hall

G/IC

11

244

530

(1)

A17

Central

Furama Hotel

Commercial

23

260

619

(1)

A18

Central

Hutchison House

Commercial

18

257

683

(1)

A19

Central

Bank of America Tower

Commercial

33

256

723

(2)

A20

Central

PLA Headquarters

Others

4

92

604

(2)

A21

Central

PLA Headquarters

Others

21

204

648

(1)

A22

Central

Far East Financial Centre

Commercial

40

310

630

(2)

A23

Central

Admiralty Centre

Commercial

48

341

579

(2)

A24

Central

Harcourt Garden

Recreation

0

328

423

(2)

A25

Wanchai

Police Headquarters

G/IC

7

306

322

(2)

A26

Wanchai

HK Academy for Performing Arts

G/IC

9

186

212

(2)

A27

Wanchai

Art Centre

G/IC

10

200

196

(2)

A28

Wanchai

Citic Tower

Commercial

42

160

327

(2)

A29

Wanchai

Servicemen's Guides Association

Commercial

3

116

169

(2)

A30

Wanchai

HK Academy for Performing Arts

G/IC

9

160

132

(2)

A31

Wanchai

Shui On Centre

Commercial

34

190

228

(2)

A32

Wanchai

Hong Kong Convention & Exhibition Centre (HKCEC)

Commercial

46

60

356

(2)

A33

Wanchai

Pedestrian plaza

Recreation

0

95

146

(2)

A34

Wanchai

HKCEC Extension

Commercial

8

100

276

(2)

A35

Wanchai

Great Eagle Centre

Commercial

27

112

494

(3)

A36

Wanchai

Causeway Centre

Residential

42

178

396

(3)

A37

Wanchai

Wanchai Swimming Pool

Recreation

3

58

281

(3)

A38

Wanchai

Wanchai Sports Ground

Recreation

0

74

144

(3)

A39

Wanchai

SPCA

G/IC

6

62

95

(3)

A40

Wanchai

Gloucester Road 169-170

Residential

12

298

364

(3)

A41

Wanchai

Gloucester Road 210

Residential

18

276

300

(3)

A42

Wanchai

Gloucester Road 226

Residential

22

266

290

(3)

A43

Causeway Bay

Elizabeth House

Residential

21

242

303

(3)

A44

Causeway Bay

Sino Plaza

Commercial

33

206

368

(3)

A45

Causeway Bay

World Trade Centre

Commercial

34

168

493

(3)

A46

Causeway Bay

Excelsior Hotel

Commercial

28

160

525

(3)

A47

Causeway Bay

Riviera Mansion

Residential

15

166

564

(3)

A48

Causeway Bay

Marco Polo Mansion (northern facade)

Residential

15

152

663

(3)

A49

Causeway Bay

Marco Polo Mansion (eastern facade)

Residential

15

148

703

(3)

A50

Causeway Bay

Royal Hong Kong Yacht Club

Recreation

3

40

317

(3)

A51

Causeway Bay

Police Officers Club (Tennis Courts)

Recreation

0

96

301

(3)

A52

Causeway Bay

Police Officers Club (Bowling Green)

Recreation

0

140

370

(3)

A53

Causeway Bay

Police Officers Club

Recreation

3

88

375

(3)

A54

Causeway Bay

Bowling Green, Victoria Park

Recreation

0

124

1006

(3)

A55

Causeway Bay

Victoria Park Public Swimming Pool

Recreation

0

190

1169

(3)

A56

Causeway Bay

Viking Garden

Residential

25

304

1247

(3)

A57

Causeway Bay

Victoria court

Residential

18

262

1251

(3)

A58

Causeway Bay

Mayson Garden

Residential

24

213

1243

(3)

A59

Causeway Bay

Gorden House

Residential

15

184

1232

(3)

A60

Causeway Bay

Belle House

Residential

24

122

1205

(3)

A61

Causeway Bay

Citicorp Centre

Commercial

36

126

1163

(3)

A62

Causeway Bay

Hoi Tao Building

Residential

30

120

1257

(3)

A63

Causeway Bay

Victoria Centre

Residential

30

16

1224

(3)

A64

Causeway Bay

Seaview Estate

Residential

13

21

1277

(3)

A65

Causeway Bay

Harbour Heights

Residential

44

17

1319

(3)

A66

Causeway Bay

Whitfield Road Rest Garden

Recreation

0

64

1153

(3)

 

 

Future

 

 

 

 

 

A67

Central

Comprehensive Development Area Site

Commercial

N/a

103

108

(1)

A68

Central

Airport Railway Hong Kong Station

Commercial

N/a

30

54

(1)

A69

Central

Future Commercial Buildings and landscaped deck east of new outlying Islands Ferry Piers (CDA site)

Commercial

N/a

58

219

(1)

A70

Central

Proposed Central Government Complex

G/IC

N/a

68

500

(2)

A71

Central

New G/IC site south and east of CITIC Tower (to include the redeveloped HK Red Cross Headquarters)

G/IC

N/a

219

314

(2)

A72

Central

New G/IC site north of CITIC Tower

G/IC

N/a

27

244

(2)

A73

Central

Waterfront related commercial and leisure uses

Commercial

N/a

14

185

(2)

A74

Central

Open space promenade along new reclamation edge

Recreation

N/a

11

512

(2)

A75

Central

Waterfront related commercial and leisure uses - Festival Market

Commercial

N/a

49

516

(1)

A76

Wanchai

Waterfront related commercial and leisure uses

Commercial

N/a

14

86

(2)

A77

Wanchai

Waterfront related commercial and leisure uses

Commercial

N/a

18

82

(2)

A78

Wanchai

Grade A Office

Commercial

N/a

68

37

(2)

A79

Wanchai

Helipad

Others

N/a

196

517

(3)

A80

Wanchai

Pier

Others

N/a

94

304

(3)

A81

Wanchai

Exhibition Station – future CDA development

Commercial

N/a

22

400

(3)

A82

Wanchai

Waterfront related commercial and leisure uses

Commercial

N/a

22

266

(3)

A83

Wanchai

Waterfront related commercial and leisure uses

Commercial

N/a

28

174

(3)

A84

Wanchai

Waterfront related commercial and leisure uses

Commercial

N/a

39

66

(3)

A85

Wanchai

Harbour Museum

G/IC

N/a

93

132

(3)

A86

Wanchai

Indoor games hall and training pool

G/IC

N/a

16

129

(3)

A87

Wanchai

5-Star hotel / Commercial

Commercial

N/a

52

399

(3)

A88

Wanchai

5-Star hotel / Commercial

Commercial

N/a

130

455

(3)

A89

Causeway Bay

Tin Hau Temple

G/IC

N/a

38

1068

(3)

A90

Causeway Bay

Indoor Entertainment Centre

G/IC

N/a

36

1061

(3)

*Distance from the main CWB & IECL alignment.

(1) Distance from the West Ventilation Building.

(2) Distance from the Central Ventilation Building.

(3) Distance from the East Ventilation Building.

3.5             Assessment Methodology

Construction Phase

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 emitting 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.

3.5.2       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.

3.5.3       Fugitive Dust Model (FDM) was used to predict the TSP concentration levels.  The emission rates 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.

Table 3.5        Emission Factors for Construction Activities

Construction Activities

Reference*

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

S.13.2.3.3

Material Handling (Excavation and Backfilling)

S.13.2.4

Truck Haulage

S.13.2.2

Wind Erosion

S.11.9 Table 11.9.4

* AP-42, 5th Edition

3.5.4       The 1997 meteorological data from the Hong Kong Observatory (Central Station) was used in the FDM to predict the 1-hour and 24-hour averaged TSP concentrations.  The data includes hourly-averaged wind speed, wind direction, stability class, ambient temperature and mixing height.

3.5.5       The following summarises the construction stages of the CWB & IECL project.  The locations of different construction works are shown in Figures 3.2.1 and 3.2.2.

·        CWB & IECL Work Packages (excluding entrusted works):

-    Tunnel Section of the Central Interchange (Central Interchange (Tunnel));

-    Bridge Section of the Central Interchange (Central Interchange (Building));

-    Demolition of part of Rumsey Street Flyover;

-    East Section of the IECL (IECL-East);

-    West Section of the IECL (IECL-West);

-    Tunnel Buildings (includes West Ventilation Building, Central Ventilation Building, East Ventilation Building and Administration Building); and

-    E&M and Tunnel Installation.

·        CWB entrusted works in Wan Chai Development Phase II (WDII):

-    CWB tunnel;

-    Slip roads; and

-    Tunnel building foundation and ducting structures.

·        CWB entrusted works in Central Reclamation Phase III (CRIII):

-    CWB tunnel.

3.5.6       Besides the CWB & IECL project, the following is a list of interfacing projects from 2002 to 2012 within 500 m from the study boundary.  The locations of different construction works are shown in Figures 3.2.1 and 3.2.2.

·        Wan Chai Development Phase II (WDII):

-    HKCEC Reclamation Stage 1 – Water Channel (HKCEC1);

-    HKCEC Reclamation Stage 2 – West (HKCEC2W);

-    HKCEC Reclamation Stage 2 – East (HKCEC2E);

-    Wanchai Reclamation Stage 1 – (WCR1);

-    Wanchai Reclamation Stage 2 – West (WCR2W);

-    Wanchai Reclamation Stage 2 – East (WCR2E);

-    Wanchai Reclamation Stage 3 – West (WCR3W);

-    Wanchai Reclamation Stage 3 – East (WCR3E);

-    Causeway Bay Reclamation Stage 1 – West (CBR1W);

-    Causeway Bay Reclamation Stage 1 – East (CBR1E);

-    Causeway Bay Reclamation Stage 2 – West (CBR2W);

-        Causeway Bay Reclamation Stage 2 – East (CBR2E);

-        PCWA Basin Reclamation;

-        Pier Construction;

-        MTR Tunnel Construction;

-        Helipad Construction; and

-        Hung Hing Road Flyover Construction.

 

·        Central Reclamation Phase III (CRIII):

-        Stage 1 (includes Hinterland Areas, Initial Reclamation Area West (IRAW));

-        Stage 2 (includes Hinterland Areas, IRAW and Initial Reclamation Area East (IRAE));

-        Stage 3 (includes Hinterland Areas, IRAE, IRAW);

-        Stage 4 (includes Hinterland Areas, FRAW, IRAE);

-        Stage 5 (includes Hinterland Areas, IRAE, Final Reclamation Area West (FRAW) and Final Reclamation Area East (FRAE));

-        Stage 6 (includes FRAW and FRAE);

-        Stage 7 (includes FRAW, FRAE and all areas);

-        Stage 8 (includes FRAW);

-        North Hong Kong Island Line (NHKIL) protection works (within CRIII area); and

-        Extended Overrun Tunnel (EOT) entrusted works (within CRIII area).

3.5.7       Public fill is to be used in the reclamation work in WDII area.  The major dust generating activities for the public fill are summarised in Appendix 3.1.  Based on the sequence of potentially dusty activities on site, ten worst-case scenarios for the public fill are identified and shown in Table 3.6.


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

Period

2002 – 2004

2005

2006

2007

2008

2009 - 2012

Worst month

Oct. 2004

Feb. 2005

May. 2005

Aug. 2005

Jul. 2006

Mar.2007

Aug.2007

Feb.2008

Aug.2008

Jun.2009

Activities

Scenario 1

Scenario 2

Scenario 3

Scenario 4

Scenario 5

Scenario 6

Scenario 7

Scenario 8

Scenario 9

Scenario 10

1

CRIII –

Stage 5

CRIII –

Stage 5

CRIII –

Stage 6

CRIII –

Stage 6

CRIII –

Stage 7

Central Interchange

(Tunnel)

Central Interchange (Tunnel)

Central Interchange (Tunnel)

IEC – East

IEC – West

2

CBR1E – Filling

CBR1E – Filling

CBR1W – Filling

CBR1W – Filling

Central  Interchange (Tunnel)

CBR2W – Filling

CBR2W – Filling

WCR2 – Drainage

WCR2 – Drainage

Tunnel Buildings

3

WCR1 –

Filling

CBR1 –

Cooling Water

CBR1 – Drainage

CBR1 – Drainage

Central Interchange (Bridge)

CBR2 – Drainage

CBR2 – Drainage

WCR2W – CWB Tunnel

WCR2W – CWB Tunnel

 

4

WCR1 –

Cooling Water

 WCR1 –

Filling

CBR1 –

Cooling Water

CBR1 –

Cooling Water

CBR1 – Drainage

WCR2 – Drainage

WCR2W – Filling

WCR3 – CWB Tunnel

WCR3 - Drainage

 

5

HKCEC2 – Cooling Water

PCWA Basin

Construction

WCR1 –

CWB Tunnel

WCR1 –

CWB Tunnel

CBR2E – Filling

WCR2E – CWB Tunnel

WCR2 – Drainage

HKCEC2W – CWB Tunnel

HKCEC2 – Drainage

 

6

 

HKCEC2 – Cooling Water

WCR3E – Filling

WCR3E – Filling

WCR2E - Filling

WCR3W – Filling

WCR2E – CWB Tunnel

 

HKCEC2E – CWB Tunnel

 

7

 

 

HKCEC1 – Filling

HKCEC1 – CWB Tunnel

WCR2 – Drainage

HKCEC2W – Filling

WCR3 – CWB Tunnel

 

 

 

8

 

 

 

MTR Tunnel

Pier Construction

Helipad

HKCEC2E – Filling

 

 

 

9

 

 

 

 

 

 

Helipad

 

 

 

10

 

 

 

 

 

 

Hung Hing Road Flyover

 

 

`


3.5.8       The working hours of all construction sites were assumed to be 12 hours. Truck speed within the sites was limited to 10 km per hour.

3.5.9       Daily TSP concentrations were calculated as follows:

Daily TSP concentration = 12/24 x (1-hour average maximum TSP concentration during working hours) + 12/24 x (1-hour average maximum TSP concentration during non-working hours) + Background

3.5.10    Appendix 3.2 shows the calculation of the dust emission factors and Appendix 3.3 provides sample computer outputs from the FDM model used for the construction dust impact assessment.

Operational Phase

3.5.11    Potential air quality impact during the operational phase of the CWB & IECL is likely to arise from the following pollutant sources:

·        background pollutant levels within and adjacent to the CWB & IECL as described in Section 3.3;

·        vehicle emissions from open sections of existing and planned road networks;

·        tunnel portal and ventilation building emissions from the CWB & IECL;

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

·        portal emissions from the existing underpasses along Connaught Road Central; and

·        portal emissions from the planned deckovers along Road P1, Road P2 and Connaught Road Central.

Vehicle Emissions from Open Sections of Existing and Planned Road Networks

3.5.12    The CALINE4 dispersion model was used for calculation of the 1-hour NO2, 24-hour NO2, 24-hour RSP and 1-hour CO concentrations.  Open sections of existing and planned road networks within 500 m from the boundary of the CWB & IECL are considered in the model and are listed as follows:

·        the CWB & IECL;

·        new roads in the Wan Chai Development Phase II (WDII);

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

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

3.5.13    The predicted morning peak hour traffic flows and vehicle mixes for the road networks in 2027 were used for the assessment of the worst-case air quality scenario.  Figures 3.3.1 to 3.3.6 show the projected 2027 morning peak hour traffic flows and vehicle compositions.

3.5.14    The most up-to-date vehicular emission factors (Fleet Average Emission Factors – EURO3 Model) available from the EPD are for the year 2011 and these were adopted for the assessment.  It is, however, considered that the 2027 emission rates will be lower than those of 2011, as more stringent vehicle emission control will have been in place by that time.  The predicted results will therefore be conservative.

3.5.15    The composite emission factors for the road links were calculated as the weighted average of the emission factors of different types of vehicles.  Four vehicle categories have been adopted.  As a worst-case scenario, the maximum emission factor within the same category was used for the assessment.  The vehicular emissions for different vehicle categories are listed in Table 3.7.  Detailed calculations of the emission factors are shown in Appendix 3.4.

Table 3.7        Emission Factors for Year 2011 for Different Vehicle Categories (EURO3)

Pollutant

Emission Factors for 2011 (EURO3), g/km-veh

PV (1)

LGV (2)

HGV (3)

PT (4)

NOx

0.73

1.53

3.84

6.8

RSP

0.03

0.16

0.53

0.69

CO

1.87

2.25

6.45

7.38

Note:      (1)      Private Vehicles (PV) include taxi and private car.

(2)        Light Goods Vehicles (LGV) include passenger van and light goods vehicle.

(3)        HGV stands for Heavy Goods Vehicles.

(4)        Public Transport (PT) includes all types of buses.

3.5.16    Peak hour traffic flows within and adjacent to the CWB & IECL will occur during daytime.  The night time traffic flows will be low (about 10% of peak flow) and the worst-case scenario will therefore not be encountered during night time.

3.5.17    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

3.5.18    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.

3.5.19    Potential air quality impacts from the implementation of proposed roadside noise barriers along the CWB & IECL were also incorporated into the air quality model.  According to the findings in Section 4, semi-enclosure, cantilever barrier and vertical barrier have been proposed on the Trunk Road to mitigate the noise impacts at Causeway Bay.  With the barriers in place, pollutants will tend to accumulate and disperse at a higher elevation (immediate above the barrier height).

3.5.20    Appendix 3.5 shows the sample computer outputs from the CALINE4 model used for the vehicle emissions impact assessment.

Portal and Ventilation Building Emissions

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

3.5.22    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 CWB & IECL;

·        tunnel emissions from the existing CHT;

·        portal emissions from the existing underpasses along Connaught Road Central; and

·        portal emissions from the planned deckovers on Road P1, Road P2 and Connaught Road Central.

3.5.23    The configuration of the tunnel section of the CWB & IECL consists of:

·        CWB Tunnel;

·        Wanchai Bypass Tunnel; and

·        Slip Road F Tunnel.

3.5.24    Vehicle emissions accumulated inside the tunnel sections are required to be extracted or diluted.  In order to reduce the potential impacts from the portal emissions, three ventilation buildings have been proposed for the CWB to discharge the tunnel vitiated air:

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

·        Central Ventilation Building (CVB): for extracting vitiated tunnel air from Slip Road F and Wanchai Bypass Westbound; and

·        East Ventilation Building (EVB): for extracting vitiated tunnel air from Trunk Road Eastbound and Wanchai Bypass Eastbound. 

3.5.25    Locations of the portals and ventilation buildings emissions are shown in Figures 3.4.1 and 3.4.2.  The proposed portal and ventilation building emissions provided by the ventilation design engineer are summarised in Table 3.8.


Table 3.8        Portal and Ventilation Building Emissions

Type

Emission Rate (g s-1)

NO2 *

CO

RSP

Portal Emission

Trunk Road Eastbound

0

0

0

Wanchai Bypass Eastbound

0.02050

0.90250

0.00725

Slip Road F

0

0

0

Wanchai Bypass Westbound

0.09225

4.47750

0.02602

Trunk Road Westbound

0.11750

4.60500

0.03819

Ventilation Building Emission

EVB - Trunk Road Eastbound

0.84271

18.14583

0.26674

EVB - Wanchai Bypass Eastbound

0.05668

2.49515

0.02176

CVB - Slip Road F

0.12222

2.35556

0.01092

CVB – Wanchai Bypass Westbound

0.04884

2.37044

0.00867

WVB – Trunk Road Westbound

0.38364

14.23364

0.11457

Note:      * Based on 20% NO2/NOx conversion in ambient condition.

3.5.26    The preliminary design of the ventilation buildings (including minimum discharge heights, exhaust directions, handling capacity of ventilation buildings and exit velocity) is summarised in Table 3.9.  For a worse case scenario in air quality assessment, the minimum height of stack was used in modelling.

Table 3.9        Design of Ventilation Buildings

 

Maximum capacity

(m3 s-1)

Exit velocity

(m s-1)

Minimum discharge height (meter above ground)

Exhaust direction

EVB - Trunk Road Eastbound

570

8

25

vertical

EVB - Wanchai Bypass Eastbound

200

8

25

vertical

CVB - Slip Road F

180

8

15

vertical

CVB - Wanchai Bypass Westbound

100

8

15

vertical

WVB - Trunk Road Westbound

420

8

15

vertical

3.5.27    The portal emissions (NO2, RSP and CO) of the existing CHT, the existing underpasses and the planned deckover are calculated based on the vehicle emissions (EURO3) and vehicle flows in 2027.  Appendix 3.6 shows the calculations of portal emissions.

3.5.28    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.

3.5.29    As mentioned in Section 3.5.17, 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

3.5.30    Sample computer output is shown in Appendix 3.7.

Model Adjustment

3.5.31    As discussed in “Technical Note on Model Calibration for Cross Harbour Tunnel and Its Nearby Roads”([1]), NO2/NOx ratio varies from the CHT portal to sensitive receivers along Gloucester Road.  As a result, different NO2/NOx ratios were adopted in the vicinity of the CHT.  Near the CHT portal, the NO2/NOx ratio was based on the measured values.  For those far away from the portal, a more conservative value of 0.2 was used. To summarise, the following factors were used:

NO2 /NOx for section of Gloucester Road                  : 0.13

between Tonnochy Road and IECL

NO2/NOx for local roads near CHT                           : 0.13

NO2/NOx for other roads                                         : 0.2

NO2/NOx for portal emissions of other tunnels           : 0.2

and ventilation buildings

3.5.32    The spatial distribution of the NO2/NOx due to CHT portal emissions in the vicinity of the CHT was found to be:

(NO2/NOx) = 0.948 ´ 10-4 ´ (Distance from Portal in metre) + 0.0957

3.5.33    According to on-site measurements in early 2001([2]), the concentration of NO2 inside the tennis court of the Police Officers Club was far lower than that at the roadside of the Police Officers Club. The observed discrepancy was attributed to the presence of the boundary wall near the portal and the use of tarpaulin along the site boundary of the Police Officers Club, which together provide a physical barrier restricting the dispersion of pollutants into the tennis court.  Besides, as the CHT is located very close to the seafront, sea breeze is expected to play an important role in diluting the pollutants. Therefore, appropriate dilution factor has been applied to the modelling result to reflect the situation.

3.5.34    Other locations towards the seaward side of the CHT, e.g. Yacht Club and the planned hotel site, are expected to be similarly screened by the boundary wall of the tunnel and influenced by sea breeze in the daytime.  As discussed in “Technical Note on Model Calibration for Cross Harbour Tunnel and its Nearby Roads”, the dilution factors at Yacht club (A50), Police Officers’ Club (A51-A53), Planned Hotel site (A87, A88) are likey to be lower or similar to that at the tennis court.  As a conservative estimate, a dilution factor of 0.56 was applied to all those receivers in the vicinity of the CHT.

3.5.35    The effect of the boundary wall near the tunnel portal on the dilution factor will diminish with increasing height.  In this respect, a dilution factor of 0.56 will be applied to those ASRs below 10m.  For those ASRs above 10m, no dilution factor is applied to the modelling result.

Cumulative Impact

3.5.36    As mentioned in Section 3.5.11, background pollutant levels within and adjacent to the CWB & IECL, vehicle emissions from open section of existing and planned road networks, tunnel portal and ventilation building emissions from the CWB & IECL, portal emissions from the CHT, the existing underpasses and the planned deckovers will all contribute to the cumulative impact.

3.5.37    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 emission from the existing and planned road networks; and

·        the ISCST3 model was used to predict all the portal emissions (CWB & IECL, CHT, underpasses and deck-over) and ventilation shaft emissions.

3.5.38    The cumulative pollutant concentrations at the ASRs at each specific wind direction are 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.

3.6             Identification of Environmental Impacts

Construction Phase

3.6.1       Potential dust nuisance will be the major concern from the construction of CWB & IECL. Public fill has been proposed for use in the reclamation works in WDII area. Major dust generating activities on site will be ground excavation, material handling, truck haulage on unpaved road and building construction.  However, no on-site concrete batching activity will be taken place within the construction site.

3.6.2       The tunnel section of the CWB & IECL will be constructed by diaphragm wall method on the reclaimed land.  The excavated rate of material is small and the stockpiling of material is not expected.  However, as a worst-case scenario, dust nuisance is expected during excavation and backfilling of the tunnel construction. 

3.6.3       The reclamations and road works by the Territory Development Department (TDD) for the CRIII and the WDII were also taken into account in assessing the impacts.

Operational Phase

3.6.4       The major sources of traffic emissions include the open road sections and various tunnel portals / ventilation shafts.

3.6.5       As mentioned in Section 3.5.11, potential air quality impact during the operational phase of the CWB & IECL includes the following pollutant sources:

·        background pollutant levels within and adjacent to the CWB & IECL as described in Section 3.3;

·        vehicle emissions from the open sections of existing and planned road networks;

·        tunnel portal and ventilation building emissions from the tunnel section of the CWB & IECL;

·        tunnel portal emissions from the existing CHT;

·        portal emissions from the existing underpasses along Connaught Road Central; and

·        portal emissions from the planned deckovers along Road P1, Road P2 and Connaught Road Central.

3.6.6       Air quality impacts associated with road traffic are caused mostly by NO2, RSP and CO.  The 1-hour NO2, 24-hour NO2, 24-hour RSP and 1-hour CO were calculated and compared with the AQO limits.

3.7             Prediction and Evaluation of Environmental Impacts

Construction Phase

3.7.1       Construction activities for CWB & IECL, WDII and CRIII will cause a cumulative 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 CWB & IECL on the ASRs at 1.5 m above ground were modelled.  Detailed breakdown of the dust impacts from different construction activities is shown in Appendix 3.8.

3.7.3       The cumulative 1-hour TSP and 24-hour TSP due to the construction of CWB & IECL is shown in Table 3.10 and Table 3.11.

Table 3.10      Predicted Cumulative 1-hour Average TSP Concentration for Scenarios 1 to 10 (Unmitigated)

ASR

Predicted Concentration (mg m-3) under different scenarios *

Scen. 1

Scen. 2

Scen. 3

Scen. 4

Scen. 5

Scen. 6

Scen. 7

Scen. 8

Scen. 9

Scen. 10

Max.

A1

145

321

339

189

557

229

289

150

113

98

557

A2

147

324

345

186

618

239

309

157

113

98

618

A3

149

339

360

190

742

249

322

165

114

99

742

A4

153

369

394

197

607

267

347

179

116

100

607

A5

155

405

433

210

734

295

375

206

118

100

734

A6

182

532

591

238

446

341

439

236

127

101

591

A7

195

568

637

255

448

333

433

224

130

100

637

A8

220

649

728

284

501

364

466

249

134

100

728

A9

578

922

1006

424

624

376

464

246

143

102

1006

A10

629

722

780

345

510

327

438

211

136

104

780

A11

289

845

906

385

605

366

487

238

140

106

906

A12

290

763

807

340

537

356

472

217

140

107

807

A13

241

788

882

332

496

398

494

227

153

109

882

A14

264

932

1039

360

594

421

502

226

162

112

1039

A15

354

2582

2668

851

1310

445

587

245

168

113

2668

A16

276

1046

1153

401

696

436

537

242

163

112

1153

A17

292

1124

1251

382

608

445

554

235

170

115

1251

A18

326

1318

1457

389

556

448

589

218

178

116

1457

A19

336

1382

1501

395

539

480

595

219

195

116

1501

A20

556

2134

2307

585

998

570

653

257

213

121

2307

A21

350

1915

2056

443

729

465

556

220

184

118

2056

A22

324

975

1185

375

517

417

584

193

178

128

1185

A23

296

762

930

326

452

429

583

203

180

119

930

A24

326

578

824

337

515

526

731

229

218

113

824

A25

365

550

980

398

525

532

978

232

256

122

980

A26

436

578

1296

494

647

793

1282

320

390

167

1296

A27

391

607

1339

517

808

923

1529

358

414

168

1529

A28

506

731

1337

479

700

936

918

340

285

151

1337

A29

595

712

1802

639

822

1326

1561

424

552

191

1802

A30

406

616

1732

629

813

1100

1715

394

576

175

1732

A31

390

623

1384

534

904

875

1728

321

405

151

1728

A32

508

699

2773

938

1746

1251

1862

562

582

189

2773

A33

393

677

2513

880

1033

1170

2738

412

613

270

2738

A34

337

548

1593

721

1680

1043

3371

463

503

166

3371

A35

692

810

1783

665

1189

1041

1622

448

463

190

1783

A36

593

708

1280

531

993

960

1087

355

295

219

1280

A37

1466

1522

1937

908

1743

1842

1613

616

427

274

1937

A38

1509

1550

1026

982

1853

1908

1470

726

391

360

1908

A39

1401

2550

943

907

1443

1963

1310

736

340

450

2550

A40

535

655

819

455

710

682

669

277

223

192

819

A41

608

664

559

502

650

758

678

305

231

199

758

A42

465

773

580

495

658

825

763

310

242

203

825

A43

443

836

582

534

646

996

997

312

259

209

997

A44

327

816

614

634

617

1171

1175

293

248

226

1175

A45

372

704

714

710

880

1243

1348

239

270

253

1348

A46

404

661

869

864

921

1311

1418

234

291

265

1418

A47

434

659

1014

1008

733

1237

1333

218

303

262

1333

A48

478

604

1045

1045

895

1201

1243

161

304

272

1243

A49

540

590

1033

1036

1023

1224

1244

139

305

279

1244

A50

292

2973

703

701

829

1850

2109

376

287

616

2973

A51

507

1419

642

634

739

2252

2452

357

273

364

2452

A52

390

974

755

752

780

1635

1751

269

268

290

1751

A53

354

1124

684

675

994

2402

2567

322

289

389

2567

A54

3022

3041

1554

1556

888

403

423

106

433

172

3041

A55

1301

1309

1151

1151

353

291

302

101

448

134

1309

A56

813

820

683

682

431

254

271

99

250

125

820

A57

823

835

949

949

291

254

268

99

340

124

949

A58

883

890

641

642

322

284

296

101

225

134

890

A59