4.                  Air Quality

Introduction

4.1              This Section presents the potential air quality impacts associated with the construction and operation of the Project.  Emission of fugitive dust from construction sites would be a key concern during the construction phase.  Vehicle exhaust emissions from traffic on the Project and surrounding road network would be the major source of pollution during operational phase.  Air quality impacts on air sensitive receivers (ASRs) have been predicted.  Mitigation measures required to protect the ASRs are recommended, where necessary, to ensure that the air quality criteria are satisfied.

 

Environmental Legislation and Guidelines

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

4.3              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) should be satisfied at the Hong Kong Special Administrative Region (HKSAR). The AQO stipulate the maximum allowable concentrations for typical pollutants, of which total suspended particulates (TSP), respirable suspended particulates (RSP), nitrogen dioxide (NO2) and carbon monoxide are relevant to this EIA Study.  The relevant AQOs are listed in Table 4.1.

 

Table 4.1         Hong Kong Air Quality Objectives

Pollutant

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

1-Hour (2)

8-Hour (3)

24-Hour (3)

Annual (4)

TSP

-

-

260

80

RSP (5)

-

-

180

55

NO2

300

-

150

80

CO

30,000

10,000

-

-

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.

 

4.4              Annex 4 of the EIAO-TM stipulates that the hourly TSP level should not exceed 500 mgm-3 (measured at 25oC and one atmospheric pressure) for construction dust impact assessments.  Mitigation measures for construction sites are specified in the Air Pollution Control (Construction Dust) Regulations.

 

Baseline Conditions

4.5              The Study Area is located in the Deep Bay Airshed where dispersion is inhibited by the surrounding high hills: Kai Kung Leng and Tai To Yan to the south, Wutong Mountain and Jigong Tou Mountains to the northeast in Shenzhen area.  According to the Hong Kong Observatory Summary of Meteorological Observations in Hong Kong, 2001, the prevailing wind direction of the Study Area is easterly wind (wind data monitored at Lau Fau Shan Station, 2001).

4.6              There is no fixed air quality monitoring station near the Study Area.  The nearest air quality monitoring station is located at Yuen Long.  Air monitoring data from Yuen Long Station for the year 2000 are shown in Table 4.2.

 

Table 4.2         Background Air Quality

Pollutant

Concentration (mg/m3) (1)

NO2

57

SO2

19

TSP

95

RSP

56

(1)            Air Quality in Hong Kong 2000, Environmental Protection Department

 

Air Sensitive Receivers

4.7              A total of fifteen representative Air Sensitive Receivers (ASRs) have been identified for this assessment in accordance with the criteria set out in the EIAO-TM.  All the existing ASRs (A1 to A13) are residential village houses with 2-3 storeys high.  Two planned developments (A14, A15) are also included in this assessment.  Description of the ASRs and their horizontal distance from the Project are listed in Table 4.3.  Locations of the ASRs are shown in Figure 4.1.

 

Table 4.3         Air Sensitive Receivers

ASR

Description

Horizontal Separation from site boundary (m)

A1

Village house near Castle Peak Road

55

A2

Village house near Kwu Tung Road

70

A3

Village house near Kwu Tung Road

100

A4

Village house near Kwu Tung Road

75

A5

Village house near Kwu Tung Road

60

A6

Village house near San Tin Highway

30

A7

Village house near Kwu Tung Road

75

A8

Tsing Lung Tsuen

355

A9

Village house near San Tin Highway

135

A10

Village house near San Tin Highway

5

A11

Village house near Tai Fu Tai

75

A12

Wing Ping Tsuen

240

A13

Tung Chan Wai

260

A14 (1)

Potential village development

2

A15 (1)

Proposed development

220

            (1)           Air sensitive receiver at operation phase only.

 

 

 

 

Evaluation of Impacts

Construction Phase

4.8              The Project comprises six slip roads (slip A through F) aligned along the San Tin Highway and Fanling Highway, connecting to the existing Vehicle Holding Ground (VHG) near the Lok Ma Chau Boundary crossing.  Widening of Castle Peak Road near the San Tin Interchange is also included in the Project.  Major construction activities are:

·         Site clearance and formation;

·         Construct retaining wall, boredpile and abutment;

·         Cast pilecap and pier;

·         Installation of precast concrete road segment; and

·         Road pavements and markings.

4.9              It is understood that the fabrication of precast concrete segments will be conducted off-site.

4.10          Foundation works, including excavation and materials handling, would be the major dust-emitting activity.  The foundation works at the three zones, zone A (Slip A, E and F), zone B (Slip B and C) and zone C (Slip D, link bridge and widening castle peak road) would be conducted in parallel, and the length of each work site of the slip roads is estimated to be 50m. It is expected that about a total volume of 29 m3 spoil (11 m3/day for zone A, 15 m3/day for zone B and 3 m3/day for zone C) would be handled per day. Based on the average truck load capacity of 7m3, it is estimated that the number of loaded trucks would be about 1-2 trips per hour. Given such a small number of truck trips for transportation and the fact that limited haulage would be required, due to the availability of easy access to existing traffic network such as Kwu Tong Road, Castle Peak Road and Fanling Highway, haulage dust nuisance is expected to be minor.

4.11          The excavated materials would be delivered to a temporary stockpile area near slip Road D. It is expected that more than 50% of the spoil would be utilized by this Project. 

Operation Phase

4.12          Vehicle exhaust emissions, including NO2 and RSP, from the traffic on the San Tin Interchange and associated road network and queuing of vehicle before the kiosks at Lok Ma Chau Boundary Crossing would be the major pollutants during operation phase. It is understood that the Project would be heavily used by heavy good vehicles and container trucks.  In addition, these vehicles tend to use mainland diesel fuel, which is of lower quality than the fuel marketed in Hong Kong.

4.13          The forecast traffic flows around the study area with the proposed Project are similar to the forecast traffic flows without the proposed Project.  With rapid development and heavy vehicular load nearby the Lok Ma Chau Boundary Crossing, the proposed Project would improve the capacity of San Tin Interchange and segregate the cross border goods vehicles at Lok Ma Chau corridor so as to reduce the resulting adverse traffic impact of cross-boundary traffic queues on the strategic and local networks. It is considered that without the Project, the worsening traffic congestion would result in increased vehicle exhaust emissions and associated adverse impacts on the local air quality.

 

 

 

Assessment Methodology

Construction Phase

4.14          Dust emission is one of the major concerns related to the construction activities.  The major dust emitting sources are identified to be materials handling, excavation and wind erosion of open sites.

4.15          The emission factors for dusty activities are estimated based on USEPA Compilation of Air Pollution Emission Factors (AP-42), 5th Edition, and are presented in Table 4.4.  Detailed calculation of emission rates of construction activities are shown in Appendix 4.1. 

4.16          TSP concentrations were predicted using the Fugitive Dust Model (FDM).  The Air Pollution Control (Construction Dust) Regulation specifies that mitigation measures such as watering should be applied for the construction site.  This measure could reduce dust emission from the site by 50% and were incorporated in the FDM model.

4.17          Particle size distributions were determined based on AP42.  Hourly meteorological data of Lau Fau Shan Weather Station (including wind speed, wind direction, stability class and temperature) for the year 2000, as measured by the Hong Kong Observatory, are used for the model run.

4.18          Hourly average TSP concentrations were predicted at the ASRs.  A twelve-hour working day was assumed for the assessment.

 

Table 4.4         TSP Emission Rates for Construction Activities

Location

Activity

Emission Rate

Remarks

Slip A,E and F

(Zone A)

Material handling

E = 13.7 mg/s

   =0.274 mg/s/m

·       Volume of material: 11 m3/day

·       Moisture content: 25%

·       Density: 2000 kg/m3

·       50% reduction by water suppression

·       AP42, Section 13.2.4

Excavation

E = 42.8 mg/s

   = 0.856 mg/s/m

·       Volume of material: 11 m3/day

·       Density: 2000 kg/m3

·       AP42, Section 11.19.2

Wind erosion

E = 1.35 mg/s/m2

·       50% reduction by water suppression

·       AP42, Section 11.9

Slip B and C

(Zone B)

Material handling

E = 18.7 mg/s

   =0.374 mg/s/m

·       Volume of material: 15 m3/day

·       Moisture content: 25%

·       Density: 2000 kg/m3

·       50% reduction by water suppression

·       AP42, Section 13.2.4

Excavation

E = 58.3 mg/s

   = 1.17 mg/s/m

·       Volume of material: 15 m3/day

·       Density: 2000 kg/m3

·       AP42, Section 11.19.2

Wind erosion

E = 1.35 mg/s/m2

·       50% reduction by water suppression

·       AP42, Section 11.9

Slip D, link bridge and widening castle peak road

 

(Zone C)

Material handling

E = 3.74 mg/s

   =0.0748 mg/s/m

·       Volume of material: 3 m3/day

·       Moisture content: 25%

·       Density: 2000 kg/m3

·       50% reduction by water suppression

·       AP42, Section 13.2.4

Excavation

E = 11.7 mg/s

   = 0.233 mg/s/m

·       Volume of material: 3 m3/day

·       Density: 2000 kg/m3

·       AP42, Section 11.19.2

Wind erosion

E = 1.35 mg/s/m2

·       50% reduction by water suppression

·       AP42, Section 11.9

Stockpile

Material handling

E = 36.2 mg/s

   =0.0302 mg/s/m2

·       Volume of material: 29 m3/day

·       Moisture content: 25%

·       Density: 2000 kg/m3

·       50% reduction by water suppression

·       AP42, Section 13.2.4

Wind erosion

E = 1.35 mg/s/m2

·       50% reduction by water suppression

·       AP42, Section 11.9

 

Operation Phase

4.19          The USEPA approved CALINE4 dispersion model was employed to predict the concentrations of NO2 and RSP due to vehicle emissions.  The hourly average concentration of NO2 and RSP were modeled at the worst affected height, 1.5m above ground level, at the ASRs.

4.20          Fleet emission factors based on EURO IV/V criteria have been developed by EPD for the cross boundary vehicles using fuel complying with the standard of Mainland China.  Emission factors beyond 2011 are not available and 2011 vehicle emission factors were therefore assumed for traffic beyond 2011, as a worst-case scenario.

4.21          Hourly traffic flows within 15 years after the operation of the Project have been forecasted for this Project.  Comparison of vehicle emission for different scenario year has been conducted for the Project and results are shown in Table 4.5 below. Year 2007 pm traffic forecast would produce the highest level of pollutant and were employed in this air quality assessment as the worst-case scenario.  Appendix 4.2 shows the detail calculation of comparison of vehicle emission.

4.22          Traffic forecast for the Project are shown in Section 2.  Calculations of emission for each road segments are shown in Appendix 4.3.

 

Table 4.5         Comparison of Vehicle Emission for Different Scenario Year

Year

Road

Segment

Length

(m)

Traffic Flow

(veh/hr)

Total Emission Rate (g/hr)

NOx

RSP

2007

Slip A

39

530

501

4714

706

41

460

828

Slip B

12

320

307

40

720

327

2011

Slip A

39

530

359

3131

457

41

460

634

Slip B

12

320

258

40

720

274

2016

Slip A

39

530

402

3462

505

41

460

702

Slip B

12

320

282

40

720

300

2022

Slip A

39

530

456

3811

556

41

460

792

Slip B

12

320

282

40

720

321

 

4.23          Queuing of vehicle at the kiosks at Lok Ma Chau Boundary Crossing will also contribute to the background pollutant levels of the study area. Queuing forecast of kiosks are presented in Appendix 4.4. Queuing of vehicle at all the kiosks has been assumed in the assessment as a worst-case scenario. The existing vehicle holding area is limited to emergency situation. Therefore, queuing of vehicles at that area would not be expected during normal operation.

4.24          The emission factors for idling vehicles have been provided by EPD, and are shown in Table 4.6. EPD advised that vehicle using china fuel should be used in the model.  Calculation of emission factors for queuing lanes are shown in Appendix 4.4.

 

Table 4.6         China Fuel Vehicle Idling Emission Factors

 

Vehicle Type

Idling emission factor (g/min-veh)

NOX

RSP

Passenger Car

0.21

Negligible

Good Vehicle

2.1

0.06

Bus

2.1

0.06

 

4.25          Vehicle emissions from the queuing of vehicles were modeled as “parking lot” in the CALINE model.

4.26          The following meteorological conditions were used in the CALINE4 model:

 

·        Wind speed:                                                      1 ms-1

·        Wind direction:                                      worst case for each receivers

·        Stability class:                                                   D

·        Mixing height:                                                    500 m

·        Standard deviation of wind direction:                 18 degree

·        Surface roughness:                                            100 cm

·        Temperature:                                                     25 oC

 

4.27          The NOx gas is assumed to be inert and the levels of NO2 were taken as 20% of total NOx emissions.

4.28          Modelling was undertaken to establish worst-case 1-hour average NO2 and RSP concentrations at the ASRs.  The 24-hour average NO2 and RSP concentration was assumed to be 40% of the respective hourly average, in accordance with the EPA’s Screening Procedures for Estimating the Air Quality Impact of Stationary Sources.

4.29          The annual average concentrations of pollutants recorded at the EPD Yuen Long air monitoring station for the year 2000 were taken as the existing background of this Study.

 

Evaluation of Impact

Construction Phase

4.30          Construction dust impacts have been predicted at the ASRs and the results are shown in Table 4.7 below.  Both the hourly and daily TSP concentrations at the worst impacts level, 1.5 m above ground, are shown in the table.  Dust mitigation measures as stipulated in the Air Pollution Control (Construction Dust) Regulation were assumed to be in place for the prediction. 

 

Table 4.7         Predicted TSP Concentration at ASR (With Mitigation)

ASR

TSP Concentration (mg/m3)

1 hr average

24 average

A1

102

102

A2

98

98

A3

99

99

A4

100

100

A5

103

103

A6

109

108

A7

102

102

A8

98

98

A9

100

100

A10

110

110

A11

102

102

A12

100

100

A13

99

99

Criteria

500

260

Note:   Background concentration included in the predicted figure.

 

4.31          The predicted hourly TSP concentration ranges from 98 mg/m3 to 110 mg/m3, and the daily concentrations between 98 mg/m3 and 110 mg/m3 have been predicted at the ASRs.  Highest dust impacts are expected at A10. It has been predicted that the dust level would be satisfied at all the ASRs.  Contours of hourly and daily TSP concentration at 1.5m above ground are shown in Figure 4.2 and 4.3 respectively.  It indicated that the dust criteria would be satisfied at all ASRs. 

4.32          ASR A14 and A15 are planned receivers and are not identified as air sensitive receivers during construction phase.  Dust impacts at these two receivers are therefore not included in this construction phase assessment.

4.33          Mitigation measures, in accordance with Air Pollution Control Ordinance, to be adopted for the Project are listed in Section 4.41.

 

 

Cumulative Impacts

4.34          Construction of the San Tin Interchange would likely coincide with the construction of the following projects:

 

Table 4.8 Concurrent Project

Project

Anticipated Construction Programme

East Rail Extension – Sheung Shui to Lok Ma Cha Spur Line (KCRC Spur Line)

December 2002 to September 2006

San Tin Eastern Main Drainage Channel (EMDC)

October 2002 to June 2006

Proposed Drainage Channel NTM04 under the Northern NT DMP Study  (NTM04)

October 2005 to October 2009

 

 

4.35          As indicated above, the construction of Spur Line would likely coincide with this Project. Based on the KCRC Spur Line EIA, the construction of Spur Line is divided into different stages. Major civil works of the section of Spur Line within our Study Area would be completed before 2005. It is expected that the remaining works for the Spurline are not dusty. Cumulative dust impact from Spurline would not be expected.

4.36          Concurrent air quality impacts from the San Tin EMDC works may likely occur.  The worksites of the San Tin EMDC are located at more than 300m away from the representative ASRs of this Project. The latest construction programme of the San Tin EMDC indicated that major civil works would be completed before March 2005. It is therefore anticipated that cumulative air quality impact associated with the San Tin EMDC would not be expected.

4.37          The NTM04 project may be undertaken in parallel with this Project. According to the Environmental Review Report of Drainage Master Plan Study[1], it indicated that minor dust impact would be generated from site clearance, excavation and road work. In view of the small scale of construction activities and the high water content of spoil, dust impact would be localised and temporary. It is therefore anticipated that cumulative air quality impact associated with the NTM04 would be minor and would be unlikely to cause adverse cumulative dust impact with the Project provided that the control measures stipulated under the Air Pollution Control (Construction Dust) Regulations are properly followed.

Operation Phase

4.38          Maximum 1-hour average NO2, 24-hour average NO2 and 24-hour average RSP concentrations have been predicted at the ASRs.  The San Tin Interchanges and the surrounding road networks have been included in the model.  Tables 4.9 shows the predicted NO2 and RSP Concentrations at the ASRs.

 

Table 4.9         Predicted NO2 and RSP Concentrations

ASR

NO2 concentration (mg/m3)

RSP concentration (mg/m3)

1 hr

24 hr

24-hr

A1

217

121

101

A2

140

90

78

A3

129

86

75

A4

126

85

74

A5

154

96

82

A6

265

140

114

A7

221

122

102

A8

123

83

75

A9

215

120

100

A10

250

134

111

A11

204

116

97

A12

117

81

73

A13

106

77

70

A14

207

117

98

A15

108

77

70

AQO

300

150

180

 

Note:       Background concentrations included in the predicted figure.

 

4.39          The above table indicates that A6 would receive highest NO2 impact, with 1-hour and 24-hour average NO2 concentrations of 265 mg/m3 (88% AQO) and 140 mg/m3 (94% AQO) respectively.  Maximum 24-hour average RSP of 114 mg/m3 (63% AQO)would be expected at A6. As shown by the modelling results of the air quality impacts due to the Project, no exceedance of the AQOs was predicted for the assessed air pollutants at the representative ASRs.

4.40          Figures 4.4 - 4.6 show the contour plots of 1-hour average NO2,24-hour average NO2 and RSP.  The modeling results indicated that the AQO would be satisfied in the Study Area.

Mitigation Measures

Construction Phase

4.41          The assessment of air quality impacts during the construction phase is based on the assumption that the dust mitigation measures stipulated in the Air Pollution Control (Construction Dust) Regulation are implemented accordingly.  The relevant dust control measures are listed below:

·           skip hoist for material transport should be totally enclosed by impervious sheeting;

·           every vehicle should be washed to remove any dusty materials from its body and wheels before leaving the construction site;

·           the area where vehicle washing takes place and the section of the road between the washing facilities and the exit point should be paved with concrete, bituminous materials or hardcores;

·           where a site boundary adjoins a road, streets or other accesses to the public, hoarding of not less than 2.4 m high from ground level should be provided along the entire length except for a site entrance or exit;

·           every stock of more than 20 bags of cement should be covered entirely by impervious sheeting placed in an area sheltered on the top and the 3 sides;

·           all dusty materials should be sprayed with water prior to any loading, unloading or transfer operation so as to maintain the dusty materials wet;

·           all stockpiles of aggregate or spoil should be covered and water applied;

·           the height from which excavated materials are dropped should be controlled to a minimum practical height to limit fugitive dust generation from unloading; and

·           the load of dusty materials carried by vehicle leaving a construction site should be covered entirely by clean impervious sheeting to ensure dust materials do not leak from the vehicle.

Operation Phase

4.42          The modelling results showed that during the operation phase of the Project, the concentration of the criteria pollutants at all the ASRs would satisfy the requirements of the AQOs and hence mitigation measures would not be required.

Residual Environmental Impacts

4.43          With the implementation of proper dust control and suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation, as described in Section 4.41, adverse residual impacts from the construction activities of the Project would not be expected.   There would be no adverse impacts associated with the operation phase of the Project.

Environmental Monitoring and Audit Requirements

4.44          With the implementation of mitigation measures stipulated in the Air Pollution Control (Construction Dust) Regulation, dust levels at all ASRs would comply with the dust criteria.  Details of the monitoring and audit requirements during the construction phase are presented in Section 12.

4.45          The predicted air quality at the ASRs complies with the criteria.  EM&A during operation phase of this Project would not be required.

 

 



[1] Maunsell (May 2000). Environmental Review Report, Drainage Master Plan Study in the Northern New Territories