4 AIR QUALITY

4.1 Sensitive Receivers

4.1.1 Representative Air Sensitive Receivers (ASRs) have been identified in accordance with criteria set out in the Environmental Impact Assessment Ordinance (EIAO), Technical Memorandum on the Environmental Impact Assessment Process (TMEIA). ASRs has been identified in an area of 500m from the project area. The descriptions and locations of existing sensitive receivers are shown in Table 4.1 and Figures 4.1 to 4.6. Visitors to the country park are also potentially sensitive to impacts but as no permanent facilities, such as camp grounds, are affected and all other visitors being transient in nature, no significant impacts are predicted.

4.1.2 All the sensitive receivers are residential properties with the exception of A1 and A2 which are playgrounds. SR19 is some distance from the main road works and construction works on the new road are not relevant to this ASR. However, SR19 has been selected on the basis of its proximity to the proposed slope remediation works to be undertaken along the obsolete sections of the Tung Chung Road as indicated in Figures 2.12 and 2.13 in Section 2 of this report. Based upon this, impacts associated with SR19 are relevant to the construction phase only.

4.1.3 In addition, the Cheung Sha Layout Plan – Lantau Island, Plan No. L/I-CS/1, has identified several future sales sites in the vicinity of the junction of the new Tung Chung Road with the South Lantau Road. These sites have been allocated for future low rise 2 storey residential development. The layout of the properties is not know at this time but representative locations at the sites which are closest to the proposed road, and at 10m setbacks from the sale site boundary, have been selected in order to assess the potential impacts to any future receivers, as shown on Figure 4.6. The properties will not be constructed and occupied until after the opening of the proposed widened Tung Chung Road and as such ASRs CS1, CS5, CS7, CS10 and CS12 are relevant to the operational phase of the project only.

Table 4.1 Air Sensitive Receivers

SR Ref.	Name of Dwelling	No. of Floors	Description
SR1	8, Ha Ling Pei	3	Residential
SR2	7, Wong Ka Wai	3	Residential
SR3	Village House	3	Residential
SR4	8, Lung Tseng Tau	3	Residential
SR5	Village House	3	Residential
SR6	41, Shek Lau Po	3	Residential
SR7	Village House	3	Residential
SR8	1, Shek Mun Kap	3	Residential
SR9	AFCD Staff Quarters	1	Residential
SR10	74, Leyburn Villas	2	Residential
SR11	12, Cheung Sha Sheung Tsuen	3	Residential
SR12	32, Cheung Sha Sheung Tsuen	3	Residential
SR13	31B, South Lantau Road	2	Residential
SR14	Village House	2	Residential
SR15	YWCA Youth Camp	1	Residential
SR16	Block 1, Acacia Villa	3	Residential
SR17	37, South Lantau Road	3	Residential
SR18	39, South Lantau Road	3	Residential
SR19	Block 17, Butterfly Crest	3	Residential
CS1*	Cheung Sha future sale site	2	Residential
CS5*	Cheung Sha future sale site	2	Residential
CS7*	Cheung Sha future sale site	2	Residential
CS10*	Cheung Sha future sale site	2	Residential
CS12*	Cheung Sha future sale site	2	Residential
A1	-	-	Playground
A2	-	-	Playground

Note: # The Distance between SR19 and the improved Tung Chung Road is more than 500m and it will only be potentially affected by the slope remediation works on the obsolete sections of the existing Tung Chung Road during the construction phase.

* Future sensitive receivers relevant to the operational phase only. Sensitive receiver locations are assumed locations only and site boundaries are indicative.

4.1.4 The Remaining Development in Tung Chung and Tai Ho Comprehensive Feasibility Study has also proposed sensitive development on the fringes of Tung Chung, close to the northern edge of the project and these could be adversely affected by the operation of the improved Tung Chung Road. The impacts on these sensitive receivers are reported separately in Section 12 of this report.

4.2 Background Air Quality

4.2.1 The Study area for the project is generally situated in a rural undisturbed area with the major source of air quality pollution traffic on the existing Tung Chung Road. Based upon this, prevailing air quality is expected to typical of rural areas in Hong Kong. Since there is no on-site monitoring records available, background level of TSP, NO₂ and RSP levels of 87 mg/m³, 39 mg/m³ and 51 mg/m³ respectively have been assumed as extracted from the EPD’s “Guidelines on Assessing the ‘Total’ Air Quality Impacts”.

4.3 Construction Phase Assessment

4.3.1 Assessment Methodology

4.3.1.1 The key impact arising from the construction phase will be the generation of dust. SO₂ and NO₂ will be emitted from the diesel-powered equipment used. Also, a very small amount of smoke could be expected to be emitted during ignition of diesel-powered mechanical equipment. However, as the numbers of such plant required on-site will be limited and under normal operation, equipment with proper maintenance is unlikely cause significant dark smoke emissions, such gaseous emissions are expected to be minor and the Air Quality Objectives (AQOs) are not expected to be exceeded.

4.3.1.2 The principal source of dust during the construction phase will be from exposed site areas, stockpiling, movement of vehicles along unpaved roads, excavation and handling of construction materials, all of which will be particularly relevant during the dry seasons.

4.3.1.3 The Fugitive Dust Model (FDM) will be adopted to predict dust emissions from the contruction activities. This model is based on Gaussian dispersion formulation, which incorporates an improved gradient-transfer deposition algorithm. Particulate emission rates for the identified potential dust sources would be determined as “heavy construction operations” in accordance with the Compilation of Air Pollution Emission Factors (AP-42) (USEPA, 5th edition, 1995). The emission factor is 2.69 Mg/ hectare/ month of activity (AP-42, Section 13.2.3.3) and a 26 day working month has been assumed. Dust emissions from a maximum length of 50m of the road works at any time has been assumed. Table 4.2 shows the particle size distribution used for this assessment based on AP-42 with an average dust density of 1600 kg/m³:

Table 4.2 Particle Size Distribution

Particle diameter (mm)	Mass fraction (in %)
0-1	4
1-2	7
2-2.5	4
2.5-3	3
3-4	7
4-5	5
5-6	4
6-10	17
10-30	49

4.3.1.4 Meteorological data for 1999 has been obtained from the Hong Kong Observatory for the weather station at Chek Lap Kok, while mixing height information for 1999 used in the Study being obtained from the weather station at King’s Park.

4.1.5 Both 1-hour and 24-hour TSP concentrations at representative ASRs along the study area have been determined, based upon the worst case scenario that construction activities would be carried out continuously for 12 hours per day. 1-hour concentration levels are read directly from the model output and 24-hour average dust levels are calculated by multiplying a factor of 0.6 [1] from the 1-hour dust levels. The concentration at 1.5m above ground of each ASR has been determined.

4.3.2 Construction Air Quality Assessment

4.3.2.1 The maximum predicted unmitigated 1-hour and 24-hour TSP concentrations at representative ASRs in the study area is shown in Table 4.3. The predicted TSP levels in Table 4.3 show that, at some ASRs, exceedances of both the 1-hour (500 µg/m³) and 24-hour (260 µg/m³) criteria will occur. Thus mitigation measures at these locations will be required.

Table 4.3 1-hour and 24-hour maximum TSP concentrations (µg/m³) at ASRs (including background level)

	Receiver Reference	Maximum (1-hour) Concentration (Standard 500 µg/m^3)		Maximum (24-hour) Concentration (Standard 260 µg/m^3)
		Unmitigated	Mitigated	Unmitigated	Mitigated
	SR1	214	150	163	125
	SR2	585	336	386	236
	SR3	198	143	154	120
	SR4	759	255**	490	188*
	SR5	235	161	176	131
	SR6	190	138	149	118
	SR7	247	167	183	135
	SR8	256	172	188	138
	SR9	308	198	220	153
	SR10	94	90	91	89
	SR11	144	116	121	104
	SR12	208	147	159	123
	SR13	857	280**	549	203*
	SR14	246	166	182	135
	SR15	391	163***	270	133***
	SR16	178	132	142	114
	SR17	141	114	120	103
	SR18	121	105	108	98
	SR19	247	167	183	135
	A1	362	224	252	169
	A2	98	93	94	90
Note		denotes TSP level in excess of criteria

* Adopted 75 % dust reduction. All other mitigated levels based upon 50% dust reduction.

** recommended 75% dust reduction in this area to ensure all ASRs are protected, although no exceedance of the 1 hour criteria at ASR4 with 50% dust reduction is predicted.

*** while a 50% dust reduction is sufficient to reduce levels to within the 24 hour criteria at the designated ASR location, due to a marginal exceedance at the football field, a 75% reduction is recommended in this area.

4.3.3 Mitigation Measures During Construction

4.3.3.1 It is predicted that the construction work would cause dust impacts in excess of both the 1-hour (500 µg/m³) and 24-hour (260 µg/m³) criteria at SRs 2, 4 and 13 and in excess of the 24-hour (260 µg/m³) criteria at SR15 and its associated football pitch. Thus, mitigation measures as follows are recommended:

(i) all unpaved roads/exposed area shall be watered which results in dust suppression by forming moist cohesive films among the discrete grains of road surface material. An effective watering programme of twice daily watering with complete coverage, is estimated to reduce by 50%. This is recommended for all areas in order to reduce dust levels to a minimum; and

(ii) watering of the construction area every 1.5 hours is estimated to reduce dust emissions by 75% and shall be undertaken in the vicinity of SRs 4, 13 and 15.

4.3.3.2 Predicted dust concentrations at the representative sensitive receivers with these measures implemented are provided in Table 4.3 above and mitigated 1 hour and 24 hour dust contours are provided in Figures 4.8 to 4.21. The construction dust concentration calculations are given in Appendix D. It can be seen that the above measures are sufficient to reduce dust levels to within the relevant criteria at all ASRs. These measures are also summarised in the Environmental Mitigation Implementation Schedule in Appendix C.

4.3.3.3 However, in addition to these measures, under the auspices of the Air Pollution Control (Construction Dust) Regulation, the Contractor will be required to ensure that dust control measures stipulated in the Regulation should be implemented to control dust emissions. The dust control measures detailed below shall be incorporated into the Contract Specification as an integral part of good construction practice. These measures are also summarised in the Environmental Mitigation Implementation Schedule in Appendix C.

(i) The Contractor shall, to the satisfaction of the Engineer, install effective dust suppression measures and take such other measures as may be necessary to ensure that at the Site boundary and any nearby sensitive receiver, dust levels are kept to acceptable levels;

(ii) The Contractor shall not burn debris or other materials on the works areas;

(iii) in hot, dry or windy weather, the watering programme shall maintain all exposed road surfaces and dust sources wet;

(iv) where breaking of oversize rock/concrete is required, watering shall be implemented to control dust. Water spray shall be used during the handling of fill material at the site and at active cuts, excavation and fill sites where dust is likely to be created;

(v) open dropping heights for excavated materials shall be controlled to a maximum height of 2m to minimise the fugitive dust arising from unloading;

(vi) during transportation by truck, materials shall not be loaded to a level higher than the side and tail boards, and shall be dampened or covered before transport. Materials having the potential to create dust shall not be loaded to a level higher than the side and tail boards, and shall be covered by a clean tarpaulin. The tarpaulin shall be properly secured and shall extend at least 300mm over the edges of the side and tail boards;

(vii) no earth, mud, debris, dust and the like shall be deposited on public roads. Wheel washing facility shall be usable prior to any earthworks excavation activity on the site;

(viii) areas of exposed soil shall be minimised to areas in which works have been completed shall be restored as soon as is practicable; and

(ix) all stockpiles of aggregate or spoil shall be enclosed or covered and water applied in dry or windy condition.

4.3.4 Slope Stabilisation and Detailed Ground Investigation

4.3.4.1 The Natural Terrain Hazard Assessment (NTHA) has identified that some measures to protect against landslip/rockfall from the natural terrain above the road link will be required. The work will include the stabilisation of unstable boulders. In addition, a detailed ground investigation will also be required during the design phase of the detailed project. This will comprise trial pit and boreholes along the length of the alignment, particularly at foundation locations. Details on the scope and extent of these proposed works are provided in Section 2 of this report.

4.3.4.2 The quantity of equipment required to undertake these works will be minimal and all but a few boreholes for the detailed ground investigation will be undertaken a large distance from the closest residential sensitive receivers. As such, air quality impacts from gaseous emissions from construction plant is expected to be negligible. Drilling of boreholes is a ‘wet’ operation and as such will not generate any dust. Trial pits will expose small area of earth but any dust can be controlled through proper site practices. Drilling undertaken for the rock dowelling activities could create some dust. However, as the stabilisation activities are minor works in comparison to the works in general and will be undertaken some distance from the sensitive receivers, no dust impacts are predicted. Notwithstanding, as the proposed stabilisation works will be carried out as part of the Project, all dust control measures in the Contract, including those detailed in Section 4.3.3 above, will be imposed on these works as well.

4.4 Operational Air Quality Assessment

4.4.1 Assessment Methodology

4.4.1.1 Impacts on air quality during operation of the Tung Chung Road will be due to the vehicular emissions from traffic using the road. The worst case year for the operational air quality assessment has been determined by using a combination of the emissions factors and peak traffic flows within 15 years after the opening of the road. The worst case year has been determined to be 2021, 15 years after the proposed opening of the road, as shown in Figure 4.7.

4.4.1.2 The total emissions in Figure 4.7 are estimated by the summation of emissions (in g/km) associated with different vehicles types using Tung Chung Road. While the emission of each kind of vehicle is calculated by multiplying the amount of such kind of vehicle and its EURO 3 emission factor. A sample of the emission factor calculation is provided in Appendix E. Morning peak hour traffic flows and vehicle mixes for 2021 have been obtained from the transportation modelling study for use in the assessment, as detailed in Section 2.8 of this report, and approved for use by Transport Department. All roads, including Tung Chung Road, existing and planned roads within 500m radius of the studying area have been included in the modelling exercise, as shown in Figure 2.19. A map showing the individual road links which have been input into the model is provided in Appendix E.

4.4.1.3 Vehicular emission factors of nitrogen oxides (NOx) and respirable suspended particulates (RSP) for each vehicle type will be based on EURO III fleet average emission factors for 2011. These are summarised in Table 4.4. The NO₂ will be assumed to be 20% of total NOx emissions. Background levels assumed for the operational assessment are provided in Section 4.2 above. Impacts of carbon monoxide are expected to be insignificant as most vehicles will be fitted with catalyst converters in future. Based upon this, the high statutory limit is not predicted to be exceeded and accordingly this parameter is not included in the operational phase assessment.

Table 4.4 EURO III Emission Factors (g/km-veh.) in 2011

Pollutant	Vehicle
	Car	Taxi	Coach	LGV	HGV	Bus
NOx	0.71	0.73	5.54	1.23	3.84	6.80
RSP	0.03	0.01	0.50	0.11	0.53	0.69

4.4.1.4 In order to provide a full assessment of the operational air pollution impacts from vehicles, scenarios for both with and without noise mitigation have been assessed as follows:

(i) the air pollution concentrations in the year 2021 with the new road in place but without the presence of the noise mitigation measures detailed in Section 5.0 of this report. For this scenario, the existing roads and the whole length of the new road as open sections have been modelled; and

(ii) the air pollution concentrations in the year 2021 with the new road in place and including the recommended direct noise mitigation measures. This scenario requires the modelling of vehicular air pollutants from the existing roads, open sections of the new road and side openings of barriers on the new road. In Tung Chung, the air quality modelling has assumed barriers will be in place between Lung Tseng Tau and Ha Ling Pei. Section 5 of this EIA, however, recommends barriers in Lung Tseng Tau only. The longer length of barrier used for air quality modelling purposes will provide a conservative assessment and in reality the levels will be lower.

4.4.1.5 Traffic emissions have been modelled using the line source dispersion model CALINE4. The settling velocity of RSP has been calculated using the equation extracted from FDM User’s Manual Section 4.3 and the deposition velocity is assumed to have the same value. Because the peak hour traffic occurs during daytime, a neutral stability condition of the atmosphere will be assumed. The input parameters for the CALINE4 model will be as follows:

Wind Speed 1 metre per second

Wind Direction worst case for each receiver

Standard Deviation 12 Degree

Stability Class D

Mixing Height 500 metres

Temperature 25 Deg. C

Surface Roughness Height 1 metre

Deposition and Settling Velocity 0.48 cm/s

4.4.1.6 As CALINE4 is a screening model, it is not possible to obtain results over an averaged 24 hour period. However, 24-hour average pollutants levels have been calculated by multiplying a factor of 0.6^[1] from the 1-hour pollutants levels.

4.4.2 Operational Air Quality Assessment

4.4.2.1 The maximum predicted 1-hour and 24-hour NO₂ and RSP concentrations at 1.5 m above ground of the representative ASRs in the study area both with and without the noise mitigation are shown in Table 4.5. A full set of modelling results are provided in Appendix E. These results are also expressed as contour plots which can be seen in Figures 4.22a to 4.22e for 1 hour NO₂ and 4.23a to 4.23e for 24 hour RSP. The results show that both pollutants levels are well within the AQOs.

4.4.2.2 In respect of the proposed bus-bay facilities in Cheung Sha, the vehicles using this facility will be slow moving or parked with their engines turned off. As the facility in not enclosed, the impacts are considered negligible.

4.5 Residual Impacts

4.5.1 Adverse residual impacts are not predicted during the construction and operational phases provided that the recommended mitigation measures are implemented.

4.6 Environmental Monitoring and Audit

4.6.1 The assessment has concluded that mitigated construction dust impacts are within the acceptable levels and no adverse residual impacts will occur. However, it is recommended that construction phase environmental monitoring and audit is undertaken to ensure that there are no adverse impact during the implementation of the construction activities and ensure that recommended mitigation measures are implemented. EM&A during the operational phase is not required. Further details of the specific EM&A requirements are detailed in Section 13 of this report and in the EM&A Manual.

4.7 References

[1] Screening Procedures for Estimating the Air Quality Impact of Stationary Sources, Revised, USEPA, EPA-454/R-92-019.

Table 4.5 1-hour and 24-hour maximum RSP and NO₂ concentrations (µg/m³) at ASRs (including background level) (with and without noise barriers)

Receiver Reference	NO2(µg/m^3)				RSP(µg/m^3)
	1-hour (criteria 300 (µg/m^3)		24-hour (criteria 150 (µg/m^3)		1-hour		24-hour (criteria 180 (µg/m^3)
	Without barriers	With barriers^*	Without barriers	With barriers*	Without barriers	With barriers*	Without barriers	With barriers*
SR1	95	125	73	90	67	76	61	66
SR2	89	104	69	78	65	70	60	62
SR3	60	67	52	56	57	59	54	56
SR4	71	86	58	67	60	64	56	59
SR5	61	68	52	56	57	59	55	56
SR6	53	57	47	50	55	56	53	54
SR7	51	58	46	50	54	56	53	54
SR8	52	56	47	49	55	56	53	54
SR9	52	-	47	-	55	-	53	-
SR10	45	-	43	-	53	-	52	-
SR11	57	-	50	-	56	-	54	-
SR12	60	-	51	-	58	-	55	-
SR13	88	-	68	-	74	-	65	-
SR14	57	-	52	-	56	-	54	-
SR15	61	-	61	-	65	-	60	-
SR16	118	-	87	-	77	-	66	-
SR17	62	-	53	-	57	-	55	-
SR18	67	-	56	-	59	-	56	-
CS1	64	-	54	-	58	-	55	-
CS5	71	-	58	-	60	-	57	-
CS7	106	-	79	-	71	-	63	-
CS10	123	-	90	-	76	-	66	-
CS12	117	-	86	-	75	-	65	-
A1	52	-	47	-	55	-	53	-
A2	46	-	43	-	53	-	52	-

‘-‘ means not applicable, no noise barriers proposed in these areas.

* The air quality modelling has assumed barriers will be in place between Lung Tseng Tau and Ha Ling Pei. Section 5 of this EIA, however, recommends barriers in Lung Tseng Tau only. The longer length of barrier used for air quality modelling purposes will provide a conservative assessment and in reality the levels will be lower.