7. AIR QUALITY IMPACT

Introduction

7.1 The potential air quality impacts associated with the construction and operation of the proposed Spur Line project are assessed in this section. In view of the fact that the proposed alignment is relatively long (7.4km) and will cover areas where existing and future residential development are clustered, the residents may be prone to potential nuisance due to the construction works, in particular during the site formation of some sections of the alignment. However, the air quality impacts due to the operation of the Spur Line are considered to be minor.

7.2 Construction works associated with the Spur Line include:

· A permanent way of a total route length of 7.4 km between Lok Ma Chau Station and Sheung Shui Station. The alignment of 5 km will be constructed on viaduct and 1.6 km on cut and embankment. The remaining 0.8 km will be at grade. The project includes construction of the viaducts, rock cutting and earth embankment. The permanent way will be completed with traction power supply;

· Construction of Lok Ma Chau Station: The station consists of an island platform with future provision for platform screen doors, two tracks and two concourse levels (one for arriving and one for departing passengers), KCRC public facilities, staff facilities, and plant and support facilities;

· Immigration and customs facilities for Lok Ma Chau Station: Immigration halls for departing and arriving passengers, non-public immigration facilities, immigration and custom staff facilities, non-public custom facilities, security facilities, agricultural and quarantine facilities and Department of Health facilities;

· A two level footbridge linking Lok Ma Chau and Huanggang Stations;

· Landscaping works and noise barriers where required. All other mitigation works as agreed in the EIA; and

· The Dongjiang Raw Water Mains near the existing Sheung Shui Station have to be diverted. Works need to be carried out during the Dongjiang supply shut down in December 2001 and 2002 respectively.

7.3 Among the construction works, the most polluting process from an air quality point of view will be site formation works which involve a significant amount of earth movement. The air quality impacts from other processes will be relatively insignificant when compared with the impacts from site formation. The nuisance from construction vehicle and plant emissions is likely to be negligible because it is anticipated that the number of these vehicles and plant will be small for the areas involved.

Air Quality Assessment Criteria

7.4 The principal legislation regulating air emissions in Hong Kong are the Air Pollution Control Ordinance (APCO) [Cap. 311] and its subsidiary regulations. The whole of the territory has been covered by Air Control Zones. The Hong Kong Air Quality Objectives (AQOs) stipulate maximum acceptable concentration of air pollutants. The AQOs for hourly, daily and annual concentrations of four major pollutants are shown in Table 7.1.

Table 7.1

Hong Kong Air Quality Objectives (AQOs)

Pollutants	Concentration in Micrograms per Cubic Metre (ìng/m^3)
	Average Time
	1 hour ^a	24 hour ^b	1 year ^c
Nitrogen Dioxide (NO2)	300	150	80
Sulphur Dioxide (SO2)	800	350	80
Total Suspended Particulates (TSP)	500 ^e	260	80
Respirable Suspended Particulates (RSP)^d	-	180	55

Notes : Concentrations measured at 298K(25^oC) and 101.325kPa (one atmosphere).

^a Hourly criteria not to be exceeded more than 3 times per year.

^b Daily criteria not to be exceeded more than once per year.

^c Arithmetic means.

^d Respirable suspended particulates means suspended particulates in air with a nominal aerodynamic diameter of 10 micrometer (ìum) or smaller.

^e This control limit has no statutory basis but is used as a target level for limiting fugitive dust emissions generated by construction activities.

The Study Area adjoins the "Special Measures Zone" (SMZ) detailed in the Deep Bay Guideline (DBG) which is more stringent than the AQO. For example, TSP and RSP daily average objectives are 180 ìg/m³ and 110 ìg/m³, while annual average objectives are 80 ìg/m³ and 55 ìg/m³ respectively.

Air Sensitive Receivers

7.5 The representative air sensitive receivers (ASRs) that will be impacted by the Spur Line are mainly rural villages while the remaining are residential estates around the Sheung Shui Station. They are listed in Table 7.2. The location of the ASRs is shown in Figure 3.1 of the Noise Assessment Chapter.

7.6 Sheung Shui is a new town containing a number of residential developments and housing estates such as Choi Po Court, Choi Yuen Estate, Tai Ping Estate, Sheung Shui Centre, Lung Fung Garden and Tin Ping Estate. North of the existing Sheung Shui Station is Shek Wu Hui and Sheung Shui Wai with mainly traditional village houses.

7.7 The areas between Sheung Shui Station and Lok Ma Chau, are mainly agricultural uses with villages scattered around Kwu Tung, Ho Sheung Heung and Pak Shek Au. Within the vicinity of the Study Area are ranges of enterprises including several timber mills, a small scale chemical plant, several car repair shops, rattan factory, pottery factory, umbrella factory, as well as food and sauce factories.

7.8 Lok Ma Chau is a boundary control area with restricted access. Most of the land is for agriculture and fish ponds use with a few scattered villages.

Table 7.2

Representative Air Sensitive Receivers

ASRs	Description	mPD	No. of Floor
1	Hong Kong Taoist Association Tang Hin Memorial Secondary School at Sheung Shui	9.7	6
2	Sheung Shui Centre (Block 1) at Sheung Shui	7.7	30
3	Tong Wu Mansion at Sheung Shui	8.8	30
6	Low rise commercial / residential building at San Fung Avenue at Sheung Shui	7.6	4
7	Choi Po Court at Sheung Shui	9.2	30
11	Village house at Tsung Pak Long Village	6.1	3
13	Village house at Ho Sheung Heung	5.9	1
17	Village house at Tong Kok	7.9	3
22	Village house at Kwu Tung	18	1
23	Village house at Kwu Tung	23.1	1
25	Village house at Pak Shek Au	12	1
27	Village house at Pak Shek Au	6.7	1
28	Village house at Chau Tau	5.3	1
31	Village house at Ha Wan Tsuen	3.2	1

Baseline Air Quality

Meteorology and Topography

7.9 The Study Area is situated in the northwest corner of Hong Kong and falls within the Deep Bay Airshed. There are several hills higher than 400 m in the Shenzhen area to the northeast (Wutong Mountain and Jigong Tou Mountain) and two hills to the east (Kai Kung Leng and Tai To Yan) (Figure 7.1).

7.10 Figure 7.2 illustrates the wind conditions at Lau Fau Shan Station of Hong Kong Observatory which is close to the Study Area and will be taken as an indication of the conditions that prevail at the western end of the alignment. During the winter season, the dominant wind direction is northeasterly. For the rest of the season, 45-50% of the winds are from the east while about 15-20% come from the southwest direction[1]. The wind pattern characteristic is the result of the blocking effect of hills over the western part of the New Territories. Topographic barriers also create eddies that change the direction and speed of the air.

7.11 In addition to these wind patterns, the Study Area generally exhibits a limited dispersive capacity because of the occurrence of an inversion layer in the morning and evening over this area[2]. In other words, the stable layer associated with the inversion layer acts as a lid thereby trapping the pollutants[3]. Thus the occurrences of frequent and extensive inversions make it very difficult for the air pollutants to disperse from the Deep Bay area.

7.12 Figure 7.3 illustrates wind conditions at the Hong Kong Observatory's Ta Kwu Ling Station, which is representative to the eastern part of the Study Area. The prevailing wind direction in the Study Area is southeasterly, due to the channelling effects of nearby mountain ridges.

Existing Air Conditions

7.13 There is no baseline air quality data available for the entire site. EPD's latest data from the air quality monitoring station at Yuen Long has been used to estimate the ambient air quality over the western part of the Study Area. According to Air Quality in Hong Kong (1997), the concentration levels of the NO₂, SO₂, TSP and RSP for Yuen Long Station during 1997 are shown in Table 7.3[4].

Table 7.3

Air Pollutants Concentrations at Yuen Long EPD Station (1997)

Pollutant	Concentration in Micrograms per Cubic Metre (ìg/m^3)
	1 hour		24 hour		Annual
	Maximum	AQOs	Maximum	AQOs	Maximum	AQOs
TSP	N/A	500	232	260	103	80
RSP	N/A	N/A	164	180	64	55
NO2	202	300	134	150	61	80
SO2	310	800	87	350	21	80

Note : N/A means Not Applicable.

7.14 Table 7.3 indicates that the concentrations of NO₂ and SO₂ are below the AQOs. The short term maximum concentrations of TSP and RSP are close to the AQOs while the annual average TSP and RSP concentrations exceed the AQOs.

7.15 The high TSP and RSP levels recorded at EPD's Yuen Long Station were probably attributed to the intensive construction activities in the vicinity of the station including works for the Route 3 (Country Part Section), Village Flood Protection for Yuen Long, Kam Tin & Ngau Tam Mei (30CD), Drainage Channels for Yuen Long & Kam Tin (43CD and 60CD), infrastructure provision for Yuen Long South development and the heavy industrial activities near Shenzhen. In the long term, TSP and RSP levels in the Yuen Long area are likely to remain high as construction and industrial activities continue.

7.16 There is no EPD air quality monitoring station within the eastern part of the Study Area. The closest station is at Tai Po. Although there are only a small number of industrial establishments, in comparison to the Tai Po Area, scattered around Sheung Shui, pollutants associated with heavy industrial activities in Shenzhen are believed to significantly influence air quality in the Sheung Shui basin. Thus the air quality data from Tai Po Station is used only as a reference to the general air quality for the eastern section of the Study Area. According to Environment Hong Kong (1998), the averaged concentration levels of the NO₂, SO₂, TSP and RSP during 1997 at Tai Po Station are tabulated below.

Table 7.4

Air Pollutants Concentrations at Tai Po EPD Station (1997)

Pollutant	Concentration in Micrograms per Cubic Metre (ìg/m^3)
	1 hour		24 hour		Annual
	Maximum	AQOs	Maximum	AQOs	Maximum	AQOs
TSP	N/A	500	204	260	80	80
RSP	N/A	N/A	153	180	55	55
NO2	244	300	138	150	50	80
SO2	178	800	54	350	13	80

Note : N/A means Not Applicable.

7.17 The data indicates that the concentrations of NO₂ and SO₂ were well below AQO. However, long-term and mid-term averages of TSP and RSP were closed to and just exceeded the AQO respectively. The high RSP levels were probably due to emissions from traffic utilising the Fanling Highway and heavy industrial activities on Tai Po Industrial Estate. These trends are expected to be continued in the short and medium term.

Southern China

7.18 According to the Air Pollution Index (API) in major Chinese cities (27th March to 2nd April, 1998; source: China Environmental Monitoring Centre), Guangzhou was one of the fifteen cities that have moderate air quality (with API below 100) whereas Beijing, the most polluted city during the week, registered 259 API points. The dominant pollutant in the Guangzhou, Shenzhen and Zhuhai areas was found to be nitrogen oxides which are due to the emission from increased traffic.

Future Air Quality

7.19 Due to rapid development near the Deep Bay area, both from the Hong Kong side and the Shenzhen side, it is likely that the air quality of the area will deteriorate further, particularly if emissions to the atmosphere from future developments are not properly controlled.

7.20 The proposed development of the Kwu Tung SGA close to the current Study Area may impact air quality. The findings and recommendations of the current study should be considered in the evaluation of overall impacts of the area and the development of suitable mitigation measures in other studies.

Construction Impact Assessment

7.21 The principal potential source of air quality impact arising from the construction of the Spur Line will be fugitive dust. The temporary dust nuisance, measurable as TSP (Total Suspended Particulates) and RSP (Respirable Suspended Particulates) would be generated as a result of construction activities, especially from site formation works where large quantity of silty material movement will be involved. However, the nuisance from emission of construction vehicles and plants is likely to be negligible because it is anticipated that the number of these vehicles and plant will be relatively small for the area involved.

7.22 The tentative construction programme of the project is scheduled to be commenced in late 2000 and will be completed in late 2003. Thus the construction period is about three years. However, it is expected that the major construction activities that will result in major dust generation will take place during the site formation of the Lok Ma Chau Station and the cut slope at Pak Shek Au. Prior to the commencement of the Spur Line construction, there will be a six months advanced water mains diversion works in early 2000.

7.23 Construction of the line will be fairly straightforward along the majority of the length of the alignment. The Spur Line will be constructed on 5 km of viaduct structure, 1.6 km on cut and embankment and the remaining 0.8 km will be at grade. The proposed Lok Ma Chau Station will be on elevated structure.

7.24 Potential fugitive dust sources from the construction of the Spur Line are expected from the following activities:

- vehicular movement at the haul roads within the works area and along the track alignment;

- material handling and stockpiling;

- precasting and concrete batching plants;

- wind erosion of unpaved works areas;

- earthworks in cutting and embankment (Kwu Tung to Pak Shek Au); and

- earthworks in excavation and filling for the foundations and platforms of the Lok Ma Chau Station.

7.25 Since details of the engineering design and the amount of cut and fill to be generated within the alignment and station sites are not available in this preliminary design stage, a rough estimate of material volumes is provided in the following table.

Table 7.5

Material Quantities for the Spur Line

Construction Activities	Disposal Quantity (m^3)	Import Quantity (m^3)
Lok Ma Chau Station	307,000	595,000
Lok Ma Chau Infrastructure	6,000	4,000
Rail Alignment	119,000*	267,000

* Approximately half of this material is reusable and can be utilized in the imported quantity volume.

7.26 During the foundation cutting works associated with the Lok Ma Chau Station, the dust impacts is expected to be relatively insignificant as the excavated material of that area will be mainly from fish ponds which is of high moisture content. Material may be exported transferred to other areas of the site by road or by barge on Shenzhen River. Given the high moisture content of the fish pond mud, the dust impacts are likely to be small if recommended mitigation measures are implemented. As shown in Table 7.5 about 600,000 m³ of fill material will need to be impactedimported, which is likely to be hydraulic fill from the Pearl River. The river will probably be used as the route for transportation, thus minimizing the distance for movement of materials, and also minimizing dust generation. Implementation of appropriate mitigation measures will help minimize dust generation. If road transportation is required for import of material, mitigation measures described in this report will be used to minimize dust impacts. Thus the dust impacts due to the foundation works on the villages at Lok Ma Chau (ASR 31) will be very limited.

7.27 For the construction of other superstructure of the station, a relatively small amount of disposal and filling material will be involved, estimated to be 6,000 m³ and 4,000 m³ respectively. Construction of various government control offices such as Immigration and Customs facilities, security facilities, agricultural and quarantine facilities and Department of Health facilities involve only minor cutting and filling of materials. It is anticipated that the dust impacts to the sensitive receivers will not be significant. Any materials dropped on sealed roads will need to be cleaned up immediately to prevent any dust nuisance.

7.28 Widening the Boundary Patrol/Control Road to serve as emergency vehicle access for Lok Ma Chau Station is required. The major potential construction impact due to this road widening including the associated drains, sewers and water distribution mains in the Lok Ma Chau Boundary Crossing Area is the dust arising from breaking up the existing road surface. Construction of drains, culverts, sewers and water distribution mains will require excavation of trenches. Laying this new infrastructure will be conducted section by section; thus the quantity of the excavated material will only be stockpiled at each local works area. The duration of stockpiling will be as short as possible as most of the material will be used as backfill material for the open cut trenches. Leveling, compacting and resurfacing of the new roads will not involve significant movement of materials; hence dust impacts will be insignificant. However, proper watering of exposed dirt should be undertaken throughout the construction phase to ensure that the cumulative impacts of these and other concurrent works such as Shenzhen River Regulation Phase III and San Tin MDC East Channel, comply with the AQO at all times.

7.29 A foot bridge connecting the Huanggang Station and Lok Ma Chau Station will accommodate the smooth passenger flow upon the commissioning of Spur Line. Percussive piling will be required to provide foundations for the foot bridge. As the construction activities involve minor cutting and filling of materials, it is anticipated that the dust impacts to the sensitive receivers will not be significant.

7.29Lok Ma Chau falls within the area bordered by the "Special Measures Zone" (SMZ) of the Deep Bay Guideline (DBG) which is more stringent than AQOs. Therefore, strict dust mitigation measures must be implemented. If human sensitive receivers are adequately protected, other wildlife species, such as birds, will also be protected.

7.30 For the construction of the rail alignment, the disposal volume of excavated material is estimated to be about 162,000 58,500 m³ while the imported filling materials will be 126,000 208,500 m³, which is expected to be hydraulic fill from the Pearl River. Construction activities for viaduct sections involve excavation during site preparation, construction of foundations by bored piling and construction of the viaduct deck. The dust levels associated with the viaduct construction will be relatively small as the viaduct deck is likely to be pre-cast. It is likely that excavated materials will be disposed off-site by dump truck and hence haul road dust is anticipated. Proper watering of exposed dirt will be undertaken throughout the construction phase so that dust generation is minimised and compliance with the AQOs can be achieved at the representative air sensitive receivers at all times.

7.31 The cutting at Pak Shek Au is likely to be carried out with a bulldozer with ripper. Dust problems are unlikely, providing mitigation measures are implemented to suppress dust.

7.32 According to the preliminary design information, precast yard and concrete batching plants will be required for the construction of the Spur Line. Storage of the raw materials and material handling at the precast yard and concrete batching plants are identified as potential fugitive dust sources. The locations of precast yard and concrete batching plants are proposed at Kwu Tung. According to the Air Pollution Control (Specified Processes) Regulations, concrete crushing/batching plants with an annual output exceeding 5000a site capacity greater than 50 tonnes will be considered a specified process and require a licence to be operated. Under this regulation, an Air Pollution Control Plan for the batching plant will be prepared in an effort to control the fugitive dust. Thus, operation of concrete batching plant must comply with the strict dust controls so as to reduce the potential dust impact on the nearby sensitive receivers at Kwu Tung and Pak Shek Au.

7.33 The remaining construction activities are not expected to produce any dust nuisance to the air sensitive receivers. Landscaping areas within the Spur Line alignment will not involve significant movement of earth materials; hence dust impacts are expected to be insignificant.

7.34 Proper dust suppression measures, as stipulated by Air Pollution Control (Construction Dust) Regulation, are always required when handling exposed dirt throughout the construction phase to ensure that the compliance of AQOs is achieved at the ASRs. For example, proper watering of exposed dirt will need to be undertaken throughout the construction phase so that dust generation is minimised and compliance with the AQOs can be achieved at the representative ASRs.

7.35 Despite the three years construction period of the Spur Line, the cumulative dust impacts as a result of concurrent construction activities both within the Study Area and surrounding areas are not expected to be significant provided that proper dust suppression measures are implemented. They are highlighted below.

Dust Mitigation Measures

7.36 The following dust control measures as part of good construction practice should be incorporated in the Contract Specification and implemented to minimise dust nuisance to within acceptable levels arising from the works:

(i) The Contractor shall undertake at all times to prevent dust nuisance as a result of his activities. Effective dust suppression measures as are necessary should be installed to minimize air quality impacts, at the boundary of the site and at any sensitive receivers.

(ii) The Contractor shall frequently clean and water the site to minimise fugitive dust emissions.

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

(iv) Watering of exposed surfaces shall be conducted as often as possible depending on the circumstances.

(v) Areas within the site where there is a regular movement of vehicles shall have an approved hard surface, be kept clear of loose surface materials and / or regularly watered.

(vi) Where dusty materials are being discharged to vehicle from a conveying system at fixed transfer point, a three-sided roofed enclosure with a flexible curtain across the entry shall be provided. Exhaust fans shall be provided for this enclosure and vented to a suitable fabric filter system.

(vii) The Contractor shall confine haulage and delivery vehicles to designated roadways inside the Site. If in the opinion of the Engineer, any motorised vehicle is causing dust nuisance, the Engineer may require that the vehicle be restricted to a maximum speed of 15 km per hour while within the Site.

(viii) Wheel washing facilities shall be installed and used by all vehicles leaving the Site. No earth, mud, debris, dust and the like shall be deposited on public roads. Water in the wheel cleaning facility shall be changed at frequent intervals and sediments shall be removed regularly. The Contractor shall submit details of proposals for the wheel cleaning facilities to the Engineer prior to construction of the facility. Such wheel washing facilities shall be usable prior to any earthworks excavation activity on the Site. The Contractor shall provide a hard-surfaced road between any washing facility and the public road.

(ix) Stockpiles of sand and aggregate greater than 20 m³ shall be enclosed on three sides, with walls extending above the pile and 2 m beyond the front of the pile.

(x) Chemical wetting agents shall only be used on completed cuts and fills to reduce wind erosion.

(xi) All site vehicular exhausts should be directed vertically upwards or directed away from ground.

7.37 In addition, based on the Air Pollution Control (Construction Dust) Regulation, any works involved regulatory work, such as stockpiling, loading and unloading of dusty materials, shall take precautions to suppress dust nuisance. Examples of dust suppression methods are:

- the working area of any excavation or earth moving operation shall spray with water or a dust suppression chemical immediately before, during and immediately after the operation so as to maintain the entire surface wet;

- exposed earth shall be properly treated by compaction, turfing, hydroseeding, vegetation planting or sealing with latex, vinyl, bitumen or other suitable surface stabiliser within six months after the last construction activity on the construction site or part of the construction site where the exposed earth lies; and

- any stockpile of dusty materials shall be either covered entirely by impervious sheeting or placed in an area sheltered on the top and 3 sides; and sprayed with water or a dust suppression chemical so as to maintain the entire surface wet.

Concurrent Construction Activities

7.38 The major concurrent construction activities are shown in Table 6.14 of the water chapter. In brief, the construction activities include Shenzhen River Training Phase III, San Tin Eastern Main Drainage Channels; Fanling, Sheung Shui & Hinterland Main Drainage Channels, Lok Ma Chau Control Point Expansion Project. As each construction project must and will implement the adequate dust mitigation measures, the cumulative impacts of these projects together with Spurline project are expected to be within the acceptable levels.

Operational Impact Assessment

Vehicular Emission

7.39 There are no major air quality impacts associated with the operation of the Spur Line as only Electric Multiple Units (EMU), which would not emit atmospheric pollutants, are to be used. It is proposed that used air inside the station will be removed through ventilation facilities which are expected to be limited and no adverse air quality impacts to nearby ASRs are expected.

7.40 Ventilation fans and air ventilation systems should be provided to ensure sufficient local air movement within the station concourse. Smoke extraction vents should also be provided in the event of fire. The vents for all ventilation systems should be directed away from nearby sensitive receivers.

7.41 As such, none of the areas will likely be subject to adverse air quality due to the operation of the Spur Line.

7.42 The additional traffic flow around the station at Sheung Shui Station as a result of the Spur Line is expected to be minimal as passengers will generally reach the station on foot or by public transport. No more trains than at present will pass through Sheung Shui Station; some trains will simply be diverted onto Spur Line. Works vehicles are not expected to increase significantly above present traffic flows.

7.43 The road leading to Lok Ma Chau station is a restricted access road, for which a permit is required to cross into the Closed Border area. The road will be widened within the Closed Border Area for use as an Emergency Vehicle Access (EVA) route. Vehicles will therefore continue to be restricted in this area, and the additional traffic due to the presence of the station will be minimal. No public access to the station will be permitted.

Summary and Recommendations

Construction Dust Impact

7.44 The construction dust impact assessment has identified Air Sensitive Receivers (ASRs) within the Study Area. It has also identified those works that have potential to generate substantial dust impact to the nearby ASRs.

7.45 The transportation of earth material by trucks over haul road is likely to be the dominant dust generation during the site formation of the construction stage. With the implementation of the recommended dust suppression measures and backed up by a proper designed EM&A programme, the construction of Spur Line should comply with the Air Quality Objectives.

Operational Air Quality Impact

7.46 Air quality impacts arising from the operational phase of the Spur Line are not considered to be of concern as limited potential sources have been identified. No adverse residual impacts due to the Spur Line are anticipated.

Environmental Monitoring & Audit (EM&A) Requirements

7.47 Dust impacts during the construction phase can be easily mitigated through implementation of standard mitigation measures and good house keeping practices.

7.48 However, if the proposed mitigation measures for dust during construction are not fully implemented, it is likely that some nearest sensitive receivers would suffer unacceptable impact. It is therefore recommended that an EM&A programme in respect of dust issues is carried out at two locations. The first location is at Lok Ma Chau due to the proximity to the “Special Strategic Measures Zone” of Deep Bay. The second location is Pak Shek Au where some sensitive receivers are very close to the construction areas.

---

[1] Royal Observatory Hong Kong, 1981: A Preliminary Report on the Meteorological Conditions in the Deep Bay Area.

^[2] Royal Observatory Hong Kong, 1984: Meteorological Assessment of Atmospheric Transport Condition in the Deep Bay Airshed.

^[3] Roland, B.S. (1988): An Introduction to Boundary Layer Meteorology, Kluwer Academic Publishers, p.666.

^[4] EPD 1998 : Environment Hong Kong 1998, Hong Kong Government