11.               Air Quality impact

Introduction

11.1        Potential air quality impacts associated with the construction phase of the Project are presented in this section. Representative Air Sensitive Receivers (ASRs) were identified.  Potential air quality impacts on these receivers arising from construction dust emission and emissions from proposed construction work sites, temporary crushing plants, magazine site, stockpiles and barging facilities have been assessed and appropriate mitigation measures are proposed to alleviate the potential air quality impacts. 

Environmental Legislation, Standards and Guidelines

11.2        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 EIAO-TM, respectively.

Air Quality Objective & EIAO-TM

11.3        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), which stipulate the maximum allowable concentrations over specific periods for typical pollutants, should be met. The relevant AQOs are listed in Table 11.1.

 

Table 11.1         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

-

-

-

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

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

 

11.4        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.  Mitigation measures for construction sites have been specified in the Air Pollution Control (Construction Dust) Regulations.

Air Pollution Control (Construction Dust) Regulation

11.5        Notifiable and regulatory works are under the control of 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 notifiable works (demolition, foundation and superstructure construction) and regulatory works (temporary stockpile, dusty material handling, excavation and concrete production).    Contractors and site agents are required to inform EPD and adopt dust reduction measures to minimize dust emission, while carrying out construction works, to the acceptable level.

Air Pollution Control Ordinance - Control of Emissions from Specified Processes

11.6        Major stationary air polluters such as power plant, incinerator, crushing plant, which are classified as Specified Processes (SP) in the APCO, are subject to a more stringent emission control. The operation of the following facility is classified as SP under the APCO.     

§          Operation of Stone Crushing Plant in which the processing capacity exceeds 5000 tonnes per annum and in which stones are subjected to any size reduction or grading by a process giving rise to dust, not being any works described in any other specified process.

 

11.7        A licence is required for the operation of these processes under Part IV of the ordinance.  Application for licence should be made to EPD. EPD may either grant or refuse to grant a licence subject to whether the applicant can fulfil the environmental standards to avoid causing air pollution. If EPD decides to grant the licence, a set of conditions will be imposed to ensure the adequate prevention of the discharge of air pollutant emissions.

Description of the Environment

11.8        The proposed alignment of the WIL is from Sheung Wan, via Sai Ying Pun and Hong Kong University to Kennedy Town. The main land uses of these areas are residential, commercial and educational institutes.  Traffic emissions are the dominant existing pollutant sources in these areas.

11.9        There is currently a Environmental Protection Department (EPD) fixed air quality monitoring station located within the study area, namely Central/Western monitoring station (situated at the Upper Level Police Station, High Street, Sai Ying Pun).  The annual averages of pollutants in mg m-3 monitored at this station for the Year 2005 & 2006 are summarized in Table 11.2.

 

Table 11.2         EPD Air Quality Monitoring Data at Central/Western Station in 2005 & 2006

 

Pollutant

Annual Average Concentration (μg/m3)

2005

2006

SO2

22

23

NO2

58

54

Ozone

36

38

TSP

81

78

RSP

54

53

Note: Bold value - Exceedance of AQO

 

Identification of Air Sensitive Receivers

11.10    In accordance with Annex 12 of the EIAO-TM, representative air sensitive receivers (ASRs) in the proximity of the construction sites, temporary stockpiles and crushing plants/barging points were identified.  The representative ASRs are listed in Table 11.3 to 11.5 and their locations are illustrated in Figure 11.1 to 11.3.

 


Table 11.3         Representative Air Sensitive Receivers in the vicinity of Kennedy Town Station Work Sites during Construction Phase

 

ID No.

Location

Use

Distance between ASR and closest work boundary(m)

K1

Kam Po Mansion

Residential

12

K2

Urban Council Smithfield Complex

GIC

4

K3

Luen Tak Apartments

Residential

25

K4

University Heights Tower 2

Residential

42

K5

Pokfield Garden

Residential

15

K6

Smithfield Terrace Block D

Residential

24

K7

Kwun Lung Lau Block D

Residential

15

K8

Kennedy Town Playground

Open Space

9

K9

Sincere Western House

Residential

57

K10

Centenary House Block 2

Residential

126

K11

Cadogan Street Temporary Garden

Open Space

38

K12

The Merton Block 1

Residential

28

K13

Cayman Rise

Residential

63

K14

Victoria Road Workshop

Industrial

18

K15

Victoria Public Mortuary

GIC

3

K16

Kennedy Town Police Quarters Block B

Residential

10

K17

Kennedy Town Police Quarters Block B

Residential

11

K18

HKIVE (Tsing Yi) Kennedy Town Centre

Education Institute

25

K19

School at Victoria Road

Education Institute

26

K20

Hong Kong Hostels Association Ma Wui Hall

Recreational

461

 

Table 11.4         Representative Air Sensitive Receivers in the vicinity of University Station Work Site during Construction Phase

 

ID No.

Location

Use

Distance between ASR and closest work boundary(m)

U1

The Kadoorie Biological Sciences Building

Education Institute

7

U2

The Belcher’s, Tower 3

Residential

8

U3

Yam Pak Building

Residential

11

U4

Hillview Garden, Block 5-8

Residential

18

U5

Jadeview Court

Residential

9

U6

Wing Fu Lau

Residential

9

U7

Western Court, Block 1

Residential

3

U8

The Belcher’s, Tower 8

Residential

26

U9

Sun Court

Residential

34

U10

Belcher Bay Park

Open Space

46

U11

New Fortune House, Block A

Residential

59

 


Table 11.5         Representative Air Sensitive Receivers in the vicinity of Sai Ying Pun Station Work Site during Construction Phase

 

ID No.

Location

Use

Distance between ASR and closest work boundary(m)

S1

Bon-Point

Residential

5

S2

No. 18-20 Eastern St

Residential

4

S3

Ivy Tower

Residential

4

S4

Chung Ching House

Residential

3

S5

Ka Yue Building

Residential

14

S6

Hang Lung Building

Residential

2

S7

Ka On Building

Residential

4

 

 

Identification of Emission Sources and Potential Impacts

11.11    The construction tasks in the Project include demolishment of some existing structures, construction of three proposed stations (Kennedy Town Station, University Station and Sai Ying Pun Station), construction of the WIL tunnel from Sheung Wan Station to Kennedy Town Station, permanent vent shafts for WIL and temporary construction shafts. In addition, there are two rock crushers to be installed at surface works areas, one temporary magazine site under the western side of Mount Davis, two temporary stockpiles and three barging points located at Kennedy Town Abattoir site and Western PCWA respectively during construction period.  Locations of worksites, construction shafts, rock crushers, temporary stockpiles, magazine site and barging facilities are illustrated in Figure 11.1 – 11.5.  The details of construction activities and potential emission sources are described as follows.

 

Kennedy Town Abattoir Site

11.12    There is one single stage (secondary crushing) rock crusher with screening process, one temporary stockpile and one barging point (Barging Point 1) at the Kennedy Town Abattoir site.  The rock materials from the Kennedy Town Station site would be transported to this rock crusher for processing.  The rock crusher with screening processing and the receiving point (unloading of rocks/stones) of crushing facility would be enclosed.  Water spraying would be provided at the unloading point.  A dust extraction and collection system would be installed at the rock crushing facility for the treatment of the emissions from rock crushing and screening processes.  The potential emission sources at this rock crushing facility would be the unloading activities (from trucks to receiving point of crushing facility) and the discharge point of this dust extraction system.

11.13    After crushing/screening process, there is an enclosed conveyor belt for transporting the crushed materials to the nearby temporary stockpile area.  No emission is expected during transportation process except the loading point (continuous drop from conveyor to the stockpile).  In order to prevent fugitive emission, water spraying and flexible dust curtains would be provided at this loading point.  As confirmed with the Project Proponent, the active area of this temporary stockpile area would be limited to 20% of the total area and the other inactive area would be well covered with impervious sheeting.  Water spraying system would be applied to the active area.  The material handling and wind erosion at the active stockpile site would be potential dust emission sources.  The spoil at the stockpile would be transported to the Barging Point 1 by trucks and the dusty materials would be well covered.  The material handling and storage pipes within the stockpile site would be one of the potential dust emission sources.

11.14    The haul roads within the Kennedy Town Abattoir site are all paved and water spraying would be provided on the haul roads to keep wet condition.  Vehicles would be required to pass through designated wheel washing facilities before leaving the barging facilities.  The trucks would directly unload the spoils to the barges in enclosed tipping hall.  The unloading activity is considered as one of the potential dust emission sources though water spraying and flexible curtains would be provided at the unloading point.

Kennedy Town Station

11.15    There are two work areas to be considered in the assessment.  One of the work sites is located at Rock Hill Street for construction of the station box and the entrance.  Kennedy Town Swimming Pool would be demolished.  The construction work area for the station box and entrance would include this swimming pool and Forbes Street Playground.  The other work site is located at Ka Wai Man Road for demolishment of the existing Block A and Block C of ex-police Quarters and construction of a construction shaft and a permanent vent shaft.   

11.16    The construction of the station box would require open-cut excavation. The dusty construction activities at these two work areas would include demolishment of concrete structures, soil excavation, material handlings, loading and unloading of excavated materials.  Potential dust impact generated from the work sites would be anticipated.  For the construction vehicle movement, watering facilities would be provided at every designated vehicle exit point.  Since all vehicles would be washed at exit points and vehicle loaded with the dusty materials would be covered entirely by impervious sheeting before leaving the construction site, the dust nuisance from construction vehicle movement outside the work site is unlikely to be significant.

 

Temporary Magazine Site

11.17    The construction of the WIL would involve substantial amount of rock excavation of which majority could be carried out by drill and blast method.  A temporary magazine is proposed to be constructed under the western side of Mount Davis, with a minimum of 20m of rock cover, to support the construction of WIL.  An underground access tunnel to the magazine storage chambers will be constructed.  The tunnel portals of the access tunnel will be built on a flat platform next to Victoria Road.  Excavation and slope works would be conducted for the construction of the magazine site in the initial stage of the construction programme.  Once the magazine storage chambers are constructed, the major activities on the platform would be the vehicles entering/leaving the magazine storage chambers.      

 

University Station

11.18    The work sites would include one station box, five station entrance (Entrance A, B1, B2, C1 and C2), a construction shaft and four permanent vent shafts.

11.19    Construction areas for entrance adits, construction shaft and permanent vent shafts would be limited (see Figure 11.2).  There would be no demolition activities except Station Entrance B1 (an existing 3 storey height toilet block to be demolished).  After site clearance and excavation at the surface area, the secant piles would be installed and then construct overhead gantry crane for mucking out.  An enclosed spoil removal hoist (with bucket hopper) would be provided for mucking out. The excavation work would then be carried out in enclosed area and the excavation level would be from ground level to underground level.  The spoil removal process would also be conducted within the enclosed structure.  No adverse dust impact to the nearby ASRs would be expected.  The dusty materials would be well covered by impervious sheeting and the trucks would be washed before leaving the mucking-out area.  Therefore, no adverse dust impact from the transportation of spoil would be anticipated.

11.20    The station box of University Station would be constructed underground, not involving open-cut excavation.  The spoils at University Station site would be transported to the construction shaft at the open area of Kennedy Town Praya via an underground construction adit and then to Barging Point 3 at Western PCWA via an enclosed conveyor belt system.  The whole transporting process is undertaken in the enclosed system, therefore, no adverse dust emission would be expected arising from the University Station site.          

 

Sai Ying Pun Station

11.21    The work sites would include one station box, six station entrance (Entrance A1, A2, B1, B2, B3 and C), one construction shaft and two permanent vent shafts.

11.22    Construction areas for entrance adits, construction shaft and permanent vent shafts would be limited (see Figure 11.3).  Demolition activities would be carried out for some entrance adits, however, only one building structure to be demolished of each adit site, for example, Tai Shing House for Entrance A1 and A2, Centre Street Market and Centre Street Cooked Food Centre for Entrance B1 and B2, and Hong Kong Government David Trench Rehabilitation Centre for Entrance C.  After site clearance and excavation at the surface area, the secant piles would be installed and then erect a spoil removal hoisting tower at the opening for mucking out purpose.  The hoisting tower would be enclosed.  The excavation work would be carried out in enclosed area and the excavation level would be from the ground level to the underground level.  The spoil removal process would also be conducted within the enclosed structure.  No adverse dust impact to the nearby ASRs would be expected.  The dusty materials would be covered entirely by impervious sheeting and the trucks would be washed before leaving the mucking-out area.  Therefore, no adverse dust impact arising from the transportation of spoil would be anticipated.

11.23    The station box of Sai Ying Pun Station would be constructed underground, not involving open-cut excavation.  The spoils at this station site would be transported to the entrance adits for disposal via underground construction adits.   As mentioned in Section 11.19, the loading of the spoil to the trucks would be undertaken within the enclosed structure.  The dusty materials would be well covered by impervious sheeting and the trucks would be washed before leaving the mucking-out area.  Therefore, no adverse dust impact to the surrounding area would be anticipated.

 

Western PCWA

11.24    There are one single stage (secondary crushing) rock crusher with screening/sorting device, one temporary stockpile and two barging points (Barging Point 2 and 3) at the Western PCWA site.  The rocks from the University Station site and Sai Ying Pun Station site would be transported to this rock crusher for processing.  The rock crusher with screening process and the unloading point of crushing facility would be enclosed and provided with a dust extraction and collection system.  Water spraying would also be provided at the unloading point.  The potential emission sources at this rock crushing facility would be the unloading activities (from trucks to receiving hopper of crushing facility) and the discharge point of dust extraction system (emissions from operation of rock crusher and screening process).

11.25    After rock crushing and screening process, the crushed materials may be transported to nearby stockpile for temporary storage via an enclosed conveyor belt system.  Water spraying and flexible dust curtains would be installed at this loading point.  As confirmed with the Project Proponent, the active area of this temporary stockpile would be 100% and water spraying would be applied on this open area.  The loading point of crushed materials (from rock crushing facility to stockpile), material handling and wind erosion at this active stockpile would be potential dust emission sources.

11.26    The crushed materials from the rock crushers would also be transported to the nearby enclosed tipping hall and then to Barging Point 3 via enclosed conveyor belt system.  As mentioned in Section 11.19, the spoils from the University Station would be transported to the enclosed tipping hall and then discharged at Barging Point 3 via enclosed conveyor belt system.  In addition, the spoils removed from the University Station entrance adits and Sai Ying Pui Station entrance adits/construction shaft would also be transported to the tipping hall by trucks and then discharged at Barging Point 3 via enclosed conveyor belt system. The possible emission sources for these processes would be unloading process at the tipping hall and the unloading point from enclosed conveyor to the barge.  Flexible dust curtains and water spraying would be provided at the unloading point to suppress the dust impact.    

11.27    There is another barging point (Barging Point 2) located within Western PCWA.  The spoils disposed from mucking out areas of University Station entrance adits and Sai Ying Pui entrance adits/construction shaft would also be transported to enclosed tipping hall of Barging Point 2 by trucks.  The potential dust emission source would be the unloading point from the truck to the barge.  Flexible curtains and water spraying would be provided at this unloading point to reduce the potential dust impact. 

11.28    The haul roads within the Western PCWA are all paved and water spraying would be provided on the haul roads to keep wet condition.  Vehicles would be required to pass through designated wheel washing facilities before leaving the barging facilities.

 

WIL Tunnel

11.29    The construction works for WIL Tunnel would be bored tunnelling and would be performed underground, potential dust impacts from tunnel works would not be anticipated.

 

Cumulative Dust Impact

11.30    According to the construction programme, some construction activities of the proposed stations sites would be overlapped.  However, these three construction sites would be located at least 500m away from each other.  There is no other major concurrent project undertaken within the study area. Therefore, potential cumulative dust impacts generating from the operation of Kennedy Town Abattoir Site, Western PCWA, temporary magazine site and Kennedy Town Station site would be expected and considered in this assessment.

Assessment Approach and Methodology

11.31    Referring to Section 11.11 – 11.30, potential adverse dust impact would be expected during operation of Kennedy Abattoir Site, Western PCWA and construction work activities at Kennedy Town Station site and magazine site.  For the other two study areas, University Station site and Sai Ying Pun Station site, no adverse dust impact at nearby sensitive receivers would be expected due to limited dusty construction activities and the excavation works and spoil loading/unloading would all be undertaken within enclosed structure.  With the implementation of dust suppression measures as stipulated in Air Pollution Control (Construction Dust) Regulation, no adverse dust impacts would be expected from the construction activities at the University Station site and Sai Ying Pun Station site. Therefore, quantitative assessment was only conducted for Kennedy Town Station site, taking into account of cumulative dust impacts from operation of Kennedy Town Abattoir Site, temporary magazine site and Western PCWA.

Emission Inventory

11.32    Predicted dust emissions were based on emission factors from USEPA Compilation of Air Pollution Emission Factors (AP-42), 5th Edition.  The major dusty construction activities for the Project to be considered in the modelling assessment include:

Kennedy Town Abattoir Site

-                      Discharge point from dust extracting system at enclosed rock crushing facility and its emission include unloading of rocks to the receiving hopper of rock crushing facility operation of rock crusher and screening process

-                      Loading point (loading crushed materials from rock crushing facility onto stockpile)

-                      Material handlings and wind erosion at the active temporary stockpile area

-                      Transportation of the spoils from the active stockpile area to the enclosed tipping hall of Barging Point 1 by trucks on the paved haul road

-                      Unloading point (Barging Point 1) to the barge

-                       

Kennedy Town Station Site

-                      Heavy construction activities including demolition and excavation within the construction site

-                      Wind erosion of open active site

 

Temporary Magazine Site

-                      Heavy construction activities including excavation and slope works within the construction site

-                      Wind erosion of open active site

 

 

 

Western PCWA

-                      Discharge point from dust extracting system at enclosed rock crushing facility and its emission include unloading of rocks to the receiving hopper of rock crushing facility, operation of rock crusher and screening process

-                      Loading point (loading crushed materials from rock crushing facility onto stockpile)

-                      Material handlings and wind erosion at the active temporary stockpile area

-                      Transportation of spoils to the rock crushing facilities/barging point within Western PCWA

-                      Unloading point inside the tipping hall (from truck unloading to conveyor leading to Barging Point 3)

-                      Unloading points at Barging Point 2 and 3.

 

11.33    According to the preliminary engineering design information, the processing capacity of the rock crushing plants would exceed 5000 tonnes per annum.  The operation of crushing plant is therefore classified as SP.  The Contractor should apply the SP license under APCO.  The requirements and mitigation measures stipulated in the Guidance Note on the Best Practicable Means for Mineral Works (Stone Crushing Plants) BPM 11/1 should be followed and implemented.  The dust control measures have been incorporated into the design of the crushing plant, barging facilities and stockpile areas, as presented in Table 11.6, 11.7 and 11.8.  These dust control measures have also been taking into account in the assessment.

 

Table 11.6     Rock Crushing Plants – Dust Emission Design Control Measures

 

Process

Description

Dust Emission Design Control Measures

Unloading of raw materials

Unloading of stone/rock at the receiving hopper

The unloading process would be undertaken within enclosed rock crushing facility. Water spraying would be provided at the unloading point.

 

Crushing of raw materials

Crushing the stone/rock with rock crusher.

The crushing process is the secondary crushing.  The rock crushing plant is enclosed and water spraying system would be installed.  Dust extraction and collection system (80% dust removal efficiency) would be provided. 

 

Screening process

Screening the crushed stone/rock

The crushed stone/rock would be screened by the screening and sorting facility before transporting to the temporary stockpile via enclosed conveyor.  Water spraying system would be installed.  Dust extraction and collection system (80% dust removal efficiency) would be provided. 

 

 

Table 11.7     Temporary Stockpiles – Dust Emission Design Control Measures

 

Process

Description

Dust Emission Design Control Measures

Kennedy Town Abattoir Site

Loading point

Loading of crushed materials from rock crushing facility onto stockpile

The transportation would be via an enclosed conveyor belt system and water spraying and flexible dust curtains would be provided at the loading point to suppress the dust impact.

 

Storage of materials

Active area for loading & unloading materials

The active area would be minimized to 20% of the total area of the stock piles.  The 80% inactive area would be well covered with impervious sheeting.  Water spraying system would be applied on the active area and watering with complete coverage of active area four times a day would be required.

 

Trucks

Transportation of materials to Barging Point 1

Wheel wash facilities provided at the site exit. The vehicles would be washed before leaving the stockpiles.  The spoils would also be well covered before leaving the site in order to minimise generation of dusty materials.

 

The haul roads within the site would be all paved and water spraying would be provided to keep the wet condition.

 

Western PCWA

Loading point

Loading of crushed materials from rock crushing facility onto stockpile

The transportation would be via an enclosed conveyor belt system and water spraying and flexible dust curtains would be provided at the loading point to suppress the dust impact.

 

Storage of materials

Active area for loading & unloading materials

Water spraying system would be applied on the active area and watering with complete coverage of active area four times a day would be required.

 

Trucks

Transportation of materials to Barging Point 2

The vehicles would be washed before leaving the stockpiles.  The spoils would also be well covered before leaving the site in order to minimise generation of dusty materials.

 

The haul road would be all paved and water spraying would be provided to keep the wet condition.

 

 

Table 11.8     Barging Facilities – Dust Emission Design Control Measures

 

Process

Description

Dust Emission Design Control Measures

Kennedy Town Abattoir Site

Haul road within barging facilities

Transportation of spoils to Barging Point 1

All road surfaces within the barging facilities would be paved and water spraying would be provided to keep the wet condition.

 

unloading of materials

unloading of spoil materials

The unloading process would be undertaken within enclosed tipping hall.  Flexible dust curtains and water spraying would be provided at the discharge point for dust suppression.

 

Trucks

Vehicles leaving the barging facility

Vehicle wheel washing facilities provided at site exit.

 

Western PCWA

Haul road within barging facilities

Transportation of spoils to Barging Point 2

All road surfaces within the barging facilities would be paved and water spraying would be provided to keep the wet condition.

 

Unloading of materials

Unloading of spoil materials from trucks to Barging Point 2

The unloading process would be undertaken within the enclosed tipping hall.  Flexible dust curtains and water spraying would be provided at the discharge point for dust suppression.

 

Unloading of spoil materials from enclosed tipping hall to Barging Point 3

The tipping hall would be enclosed structure.  The conveyor from tipping hall to the Barging Point 3 would be enclosed.  Water spraying and flexible dust curtains would be provided at the receiving point of the tipping hall.  Flexible dust curtains and water spraying would be provided at the discharge point of barging facilities for dust suppression.

 

Trucks

Vehicles leaving the barging facility

Vehicle wheel washing facilities provided at site exit.

 

 

11.34    The excavation rate, material handling rate, moisture content, silt content, number of trucks and truck speed are based on the preliminary engineering design for Kennedy Town Abattoir Site, Kennedy Town Station site and Western PCWA.  The emission rate of identified pollutant sources in these sites are summarised in Table 11.9, 11.10 and 11.11.  Detailed calculations of the emission factors are given in Appendix 11.1.

Table 11.9         Emission Factors for Dusty Construction Activities at Kennedy Town Abattoir Site

 

Emission Source

Activity

Emission Rate

Remarks

Rock Crushing Plant at Kennedy Town Abattoir Site

 

Unloading of rock/stone to the receiving hopper of rock crushing plant

E = 9.93611 x 10-5 g/s

Maximum crushing rate: 85 Mg/hr, 12 operation hours per day.

75% reduction with water spray

AP42, Section 11.19.2

Secondary Crushing

E =0.0006 g/Mg

=2.83889 x 10-3 g/s

 

Maximum crushing rate: 85 Mg/hr, 12 operation hours per day.

Within enclosed system and wet suppression

Dust extraction and collection system (80% dust removal efficiency)installed at the rock crushing facility and the discharge point is located at least 39m away from the west boundary of the rock crushing facility under the preliminary design

0                         AP42, Section 11.19

Screening

E =0.0011 g/Mg

=5.20463 x 10-3 g/s

Stockpile at Kennedy Town Abattoir Site

Loading point from rock crushing facility to temporary stock pile

E = 1.32697 x 10-2 g/s

Maximum handling rate: 85Mg/day

AP-42, S13.2.4, particle size < 30 um, 1/95 ed

AP-42, Table 13.2.4-1, 1/95 ed

 90% dust reduction with watering spraying and flexible dust curtains provided at the loading point 

 

Material Handling and storage piles

E = 0.00561 kg/Mg

= 8.27736 x 10-5 g/m2/s

E=k´0.0016´[(U/2.2)^1.3/(M/2)^1.4]

Maximum Material Handling rate: 85 Mg/hr

Particle size multiplier: 0.74

Moisture content: 0.7 %

Average wind speed: 2.35 m/s

80% inactive area (well covered by impervious sheeting) and 20 % active area

75% reduction by water suppression

(complete coverage of active area four times a day)

AP42, Section 13.2.4

Wind Erosion

E = 0.85 Mg/hectare/year

= 2.69533 x 10-6 g/m2/s

80% inactive area (well covered by impervious sheeting) and 20 % active area

Watering on the active area during operation hours

AP42, Section 11.9.4

Barging Point at Kennedy Town Abattoir Site

Paved haul road -Transport the spoil from the stockpile to the Barging Point 1

 

E = 1850 g/VKT

=4.54004 x 10-4 g/m/s

E=k´(sL/2)^0.65´(W/3)^1.5

Particle size multiplier: 24g/VKT

Silt content: 12%

Averaged truck weight: 25tons

No. of truck: 106 trucks/day (including return trip),

 90% reduction by water spraying to keep wet condition

AP42, Section 13.2.1.

 

Unloading process within enclosed tipping hall.

E = 1.32697 X 10-2 g/s

AP-42, S13.2.4, particle size < 30 um, 1/95 ed

AP-42, Table 13.2.4-1, 1/95 ed

 Watering spraying and flexible dust curtains provided at discharging point.  90% reduction of dust emission assumed.

 

 

Table 11.10       Emission Factors for Dusty Construction Activities at Kennedy Town Station Site and Temporary Magazine Site

 

Emission Source

Activity

Emission Rate

Remarks

Construction Site (Kennedy Town Station)

Heavy Construction Activities

E=2.69 Mg/hectare

/month of activity

=2.59452 x 10-5 g/m2/s

50% area actively operating

75% reduction by water suppression

(complete coverage of active construction area four times a day)

AP42, Section 13.2.3

Wind Erosion

(night time)

E=0.85Mg/hectare

/year

=1.34767 x 10-6 g/m2/s

 

50% active site

AP42, Section 11.9.4

Magazine Site

(open works area)

Heavy Construction Activities

E=2.69 Mg/hectare

/month of activity

=5.18904 x 10-5 g/m2/s

50% area actively operating

50% reduction by water suppression

(complete coverage of active construction area two times a day)

AP42, Section 13.2.3

 

Wind Erosion

(night time)

E=0.85Mg/hectare

/year

=1.34767 x 10-6 g/m2/s

 

50% active site

AP42, Section 11.9.4

 

Table 11.11       Emission Factors for Dusty Construction Activities at Western PCWA

 

Emission Source

Activity

Emission Rate

Remarks

Rock Crushing Plant at Western PCWA

Unloading of rock/stone to the receiving hopper of rock crushing plant (Crusher Loading Point)

 

E = 1.27361 x 10-4 g/s

Maximum crushing rate: 109 Mg/hr, 12 operation hours per day.

75% reduction With water spray

AP42, Section 11.19.2

Secondary Crushing

E =0.0006 g/Mg

=3.63889 x 10-3 g/s

Maximum crushing rate: 109Mg/hr

Within enclosed structure and wet suppression

Dust extraction and collection system (80% dust removal efficiency)installed at the rock crushing facility

AP42, Section 11.19

Screening

E =0.0011 g/Mg

=6.67130 x 10-3 g/s

Handling rate: 109Mg/hr

Within enclosed structure and wet suppression

Dust extraction and collection system (80% dust removal efficiency)installed at the rock crushing facility

AP42, Section 11.19

Stockpile at Western PCWA

Loading point from rock crushing facility to temporary stock pile

E = 1.70092 x 10-2 g/s

Handling rate: 109Mg/hr, 12 operation hours

AP-42, S13.2.4, particle size < 30 um, 1/95 ed

AP-42, Table 13.2.4-1, 1/95 ed

 90% dust reduction with watering spraying and flexible dust curtains provided at the loading point 

 

Material Handling and storage piles

E =  0.00561 kg/Mg

= 1.16643 x 10-4 g/m2/s

E=k´0.0016´[(U/2.2)^1.3/(M/2)^1.4]

Material Handling rate: 109 Mg/hr

Particle size multiplier: 0.74

Moisture content: 0.7 %

Average wind speed: 2.35 m/s

100 % active area

75% reduction by water suppression

(complete coverage of active area four times a day)

AP42, Section 13.2.4

Wind Erosion

E = 0.85 Mg/hectare/year

= 2.69533 x 10-6 g/m2/s

Watering on the active area during operation hours

AP42, Section 11.9.4

Barging Point 2 at Western PCWA

Paved Haul Road within Western PCWA

 

E = 1850 g/VKT

=6.852893 x 10-4 g/m/s

E=k´(sL/2)^0.65´(W/3)^1.5

Particle size multiplier: 24g/VKT

Silt content: 12%

Averaged truck weight: 25tons

No. of truck: 160 truck/day (including return trip)

 

90% reduction by water spraying to keep wet condition AP42, Section 13.2.1

 

Unloading of spoils to the barge within enclosed tipping hall.

E = 3.56089 x 10-2 g/s

AP-42, S13.2.4, particle size < 30 um, 1/95 ed

90% reduction by water spray and flexible dust curtain at discharging point

AP-42, Table 13.2.4-1, 1/95 ed

Barging Point 3 at Western PCWA

Unloading of spoils from truck to the conveyor within tipping hall

E = 1.66675 x 10-3 g/s

AP42, Section 11.19.2

Handling capacity: 2743 Mg/day

75% reduction by water spraying

Unloading of spoils from the conveyor to the barge

E = 3.56089 x 10-2 g/s

AP-42, S13.2.4, particle size < 30 um, 1/95 ed

90% reduction by water spraying and flexible dust curtain provided at discharging point

AP-42, Table 13.2.4-1, 1/95 ed

 

11.35    In accordance with the preliminary engineering design for both rock crushing facilities, the dust emission in the rock crushing and screening processes would be extracted to the dust extraction and collection system which would have 80% dust removal efficiency for treatment before discharging into the atmosphere.  As advised by the Project Proponent, an active operating area of 50% for Kennedy Town Station construction site and temporary magazine site are assumed at any one time.  12-hour (07:00-19:00) is assumed for the construction period in the assessment.   

 

Dispersion Modelling & Concentration Calculation

 

11.36    Fugitive Dust Model (FDM) (1993 version) was adopted to assess potential dust impact from the construction works.  The worst case meteorological condition was used to predict the 1-hour and 24-hour average TSP concentrations at representative discrete ASRs in the vicinity of the construction sites.   The height of 1.5m (the breathing level of human), 5m, 10m, 15m and 20m above ground were adopted for the construction dust impact assessment.  The meteorological data used in the model were:

§          Wind speed:                                    1 m/s

§          Wind direction:                                360 wind directions

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

§          Surface roughness:                          1m

§          Mixing height:                                  500 m

 

11.37    The background TSP level of 78 mg/m3, based on the latest five years (2000, 2003 – 2006) average monitoring data from EPD Central/Western monitoring station, was adopted as an indication of the TSP background concentration during the construction phase.  The monitoring data in Year 2001 and 2002 were not considered as their monitoring data were below their respective minimum data requirement of 66% for number of data within that period.

 

 

Prediction and Evaluation of Impacts

Kennedy Town Abattoir Site, Kennedy Town Station Construction Site, Temporary Magazine Site & Western PCWA

11.38    The predicted cumulative hourly and daily average TSP concentrations at the representative ASRs due to construction activities at Kennedy Town Abattoir Site, Kennedy Town Station site, temporary magazine site and Western PCWA under the worst case scenario are presented in Table 11.12 and 11.13.

11.39    Based on the results indicated in Table 11.12 and 11.13, the predicted 1-hour and 24-hour average TSP at all representative ASRs would comply with the criteria in EIAO-TM and AQO.  It is noted that the worst levels would be at 1.5m above ground level.  The contour plots of 1-hour and 24-hour average TSP concentrations at 1.5m above ground level are indicated in Figure 11.6 and 11.7.  There are no ASRs found to have non-compliance of the 1-hour and 24-hour average TSP criteria in the contour plots.  

 

Table 11.12       Predicted Cumulative Hourly Average TSP Concentrations at Representative Air Sensitive Receivers

 

ASRs

 

Cumulative Hourly Average TSP Concentrations in mg/m3

1.5m AGL

5m AGL

10m AGL

15m AGL

20m AGL

K1

369

215

140

114

101

K2

398

232

135

100

96

K3

282

218

138

100

96

K4

271

243

176

131

107

K5

350

253

162

120

100

K6

308

232

138

102

94

K7

408

270

164

118

96

K8

385

293

181

130

104

K9

204

195

161

130

109

K10

141

141

130

118

107

K11

114

115

111

106

101

K12

109

109

107

103

99

K13

130

126

111

102

97

K14

283

211

116

100

93

K15

312

228

129

121

101

K16

354

211

124

99

92

K17

335

179

108

100

92

K18

293

210

122

98

93

K19

366

275

152

100

90

K20

95

96

95

93

91

U10

323

269

165

108

98

U11

259

241

188

140

107

            Note:    The background TSP level of 78 mg/m3, have been included in the above results.

                         The 1-hour average TSP EIAO-TM criterion: 500 mg/m3.

 

 

 

 

 

 

 

 

 

 

   Table 11.13    Predicted Cumulative 24-Hour Average TSP Concentrations at Representative Air Sensitive Receivers

 

ASRs

Cumulative 24-Hour Average TSP Concentrations in mg/m3

1.5m AGL

5m AGL

10m AGL

15m AGL

20m AGL

K1

235

149

110

96

90

K2

250

158

107

90

87

K3

189

151

108

89

87

K4

185

166

129

105

93

K5

225

170

121

99

89

K6

203

158

109

90

86

K7

258

179

122

98

87

K8

247

192

131

104

91

K9

149

142

121

105

94

K10

114

113

106

99

93

K11

98

99

96

93

90

K12

95

95

93

91

89

K13

107

104

96

91

88

K14

185

146

98

90

86

K15

201

155

104

100

90

K16

228

147

102

89

85

K17

216

130

94

90

86

K18

195

147

101

89

86

K19

230

179

116

90

85

K20

88

88

87

86

85

U10

202

175

123

93

88

U11

170

161

134

109

93

            Note:    The background TSP level of 78 mg/m3, have been included in the above results.

                        The 24-hour average TSP AQO criterion: 260 mg/m3.

 

University Station Construction Site

11.40    In view of limited work site areas and most of excavation activities carried out underground level and within covered area, no adverse dust impact to the surrounding environment would be expected with the implementation of standard dust suppression measures stipulated in Air Pollution Control (Construction Dust) Regulation and good site practices.  An underground construction adit and enclosed conveyor belt system would be provided for transportation of spoil from University Station box to the Barging Point 3 via the construction shaft.  The whole process would be undertaken in enclosed system and no adverse dust impact would be expected.  For the entrance adits/construction shaft, the spoil removal process would be conducted within the enclosed mucking-out area.  The dusty materials would be well covered by impervious sheeting and the trucks would be washed before leaving the mucking-out area.  Insignificant dust impact arising from transportation of spoils would be anticipated.    

Sai Ying Pun Station Construction Site

11.41    Similar to University Station construction site, the work areas at the above ground level are limited and most construction activities would be carried out underground at Sai Ying Pun Station.  Demolishment of some structures at some entrance adits would be required, however, adverse dust impacts would not be anticipated at the nearby ASRs with the implementation of standard dust suppression measures stipulated in Air Pollution Control (Construction Dust) Regulation and good site practices.  Minimal spoil would be removed from the entrance adits sites and construction shaft.  The spoil loading activity would be undertaken within enclosed mucking-out area.  The spoil materials would be covered entirely by impervious sheeting and the trucks would be washed before leaving the mucking-out area, insignificant dust impacts from the transportation of spoil would be anticipated. 

Recommended Air Quality Mitigation Measures

11.42    Dust control measures have been incorporated into the engineering design as presented in Tables 11.6 to 11.8.  For rock crushing plants, the requirements and mitigation measures stipulated in the Guidance Note on the Best Practicable Means for Mineral Works (Stone Crushing Plants) BPM 11/1 should be followed and implemented.  In addition, implementation of dust suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation and good site practices should be carried out to further minimize construction dust impact.   

§          Use of regular watering, with complete coverage, to reduce dust emissions from exposed site surfaces and unpaved roads, particularly during dry weather.

§          Use of frequent watering for particularly dusty construction areas and areas close to ASRs.

§          Side enclosure and covering of any aggregate or dusty material storage piles to reduce emissions.  Where this is not practicable owing to frequent usage, watering shall be applied to aggregate fines.

§          Open stockpiles shall be avoided or covered.  Where possible, prevent placing dusty material storage piles near ASRs.

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

§          Establishment and use of vehicle wheel and body washing facilities at the exit points of the site.

§          Provision of wind shield and dust extraction units or similar dust mitigation measures at the loading points, and use of water sprinklers at the loading area where dust generation is likely during the loading process of loose material, particularly in dry seasons/ periods.

§          Imposition of speed controls for vehicles on unpaved site roads.  8 kilometers per hour is the recommended limit.

§          Where possible, routing of vehicles and positioning of construction plant should be at the maximum possible distance from ASRs.

§          Every stock of more than 20 bags of cement or dry pulverised fuel ash (PFA) should be covered entirely by impervious sheeting or placed in an area sheltered on the top and the 3 sides.

§          Cement or dry PFA delivered in bulk should be stored in a closed silo fitted with an audible high level alarm which is interlocked with the material filling line and no overfilling is allowed.

§          Loading, unloading, transfer, handling or storage of bulk cement or dry PFA should be carried out in a totally enclosed system or facility, and any vent or exhaust should be fitted with an effective fabric filter or equivalent air pollution control system.

 

Evaluation of Residual Impacts

11.43    With the implementation of the mitigation measures as stipulated in the Air Pollution Control (Construction Dust) Regulation, dust control measures and good site practices, the predicted dust impact at ASRs would comply with the TSP criterion in EIAO-TM and AQO.

Environmental Monitoring and Audit Requirements

11.44    Environmental monitoring and audit for dust emission should be conducted during the construction phase of the Project so as to check compliance with legislative requirements.  Details of the monitoring and audit programme are contained in a stand-alone EM&A Manual.

Conclusions

11.45    Air quality impacts from the construction works for the Project would mainly be related to construction dust from excavation, materials handling, spoil removal and wind erosion, as well as operation of crushing plants, temporary magazine site, stockpiles and barging facilities.  With the implementation of mitigation measures specified in the Air Pollution Control (Construction Dust) Regulation, proposed dust suppression measures, good site practices and dust control measures for the Specified Process (crushing plant) checked by an EM&A programme, no adverse dust impact on the ASRs in the vicinity of the construction sites would be anticipated.