3.                      AIR QUALITY

3.1         Introduction

This section assesses the potential air quality impacts associated with the construction and operation of Tung Chung Cable Car Project.  Dust generation during the construction phase is the major sources of the air pollution.  Following completion of construction works there will be no adverse air quality impact. Operation of the proposed Tung Chung Cable Car system will not generate emissions and thus air pollution is not an issue for the operational phase.

No sensitive uses identified at the proposed Ngong Ping Terminus and Theme Village will be subject to any adverse air quality impacts for instance the odour impact from the proposed Ngong Ping Sewage Treatment Works (NPSTW) and traffic emission impact.

In the approved NPSTW EIA report, the potential odour impact at the nearest boundary of the adjacent proposed Cable Car Terminal Site and the Public Transport Interchange (PTI) was assessed and its findings concluded that exceedance ofthe criteria was not predicted with implementation of the proposed odour control measures such as all major odour sources within the proposed STW will be constructed underground.

The traffic emission impact on the sensitive uses of the proposed Ngong Ping Terminal, Theme Village and Tung Chung Terminal is not considered to be significant as the Hong Kong Planning Standards and Guidelines recommended buffer distances are met.  There would be no major concern of aerial emission from the proposed Theme Village.

The representative Air Sensitive Receivers (ASR's) within 500m of the study area have been identified and worst case impacts on these receivers have been modelled. The findings are presented in this Section. Suitable mitigation measures, where necessary, are recommended to protect the ASRs and to ensure that the legislative criteria and guidelines will be satisfied. 

3.2         Legislation, Standards, Guidelines and Criteria

The criteria for evaluating air quality impacts are laid out in Annexes 4 and 12 of the Technical Memorandum on Environmental Impact Assessment (TMEIA).  The relevant criteria are given below.

The principal legislation for the management of air quality is the Air Pollution Control Ordinance (APCO) (Cap 311).  The whole of the Hong Kong Special Administrative Region (HKSAR) is covered by the Hong Kong Air Quality Objectives (AQOs) which stipulate the statutory limits of some typical air pollutants and the maximum allowable numbers of exceedance over specific periods.  The relevant AQOs for Total Suspended Particulates (TSP) and Respirable Suspended Particulates (RSP) extracted from TMEIA are shown in Table 3.1 below.

Table 3.1        Hong Kong Air Quality Objectives (µg m^-3) ⁽¹⁾

Pollutant	Average Time
	1 Hour (2)	24 Hour (3)	1 Year (4)
Total Suspended Particulates (TSP)	500*	260	80
Respirable Suspended Particulates (RSP)(5)	N.A.	180	55
Note: 1.        Measured at 298K (250C) and 101.325 kPa (one atmosphere). 2.        Not to be exceeded more than three time per year. 3.        Not to be exceeded more than once per year. 4.        Arithmetic means. 5.        Respirable Suspended Particulates means suspended particles in air with a nominal aerodynamic diameter of 10 micrometers and smaller. N.A. Not Available. *      Maximum allowable dust levels at ASRs provided in the TMEIA.

 

The TMEIA also states that the hourly Total Suspended Particulate (TSP) level should not exceed 500mgm^-3 (measured at 25^oC and one atmosphere) for construction dust impact assessment.  Mitigation measures from construction sites have been specified in the Air Pollution Control (Construction Dust) Regulation.

3.3         Baseline Conditions

The existing environment of the proposed Tung Chung Cable Car Project is primarily affected by the traffic in Tung Chung such as North Lantau Highway, Tung Chung Waterfront Road, Tat Tung Road and Shun Tung Road, as well as on Ngong Ping such as Ngong Ping Road. Immediately north of the works site for the proposed Tung Chung Terminal is the bus car parks. No industrial uses are located within the Study Area. As such, the local traffic is considered to be the dominant source affecting the ambient air quality.

There is currently one fixed air quality monitoring station which is located in Tung Chung  operated by Environmental Protection Department (EPD). The background concentration of pollutants reported for the year 2000 at Tung Chung station is included in Table 3.2 below. Dust levels recorded at this station are 71 mgm^-3 for TSP and 45 mgm^-3 for RSP.  The annual average concentration levels of 71 mgm^-3 is used as the background level of TSP in the subsequent assessments.

        Table 3.2   Annual Average of TSP and RSP Monitored at Tung Chung 2000

Air Pollutants	Annual Average Concentration (mgm-3)	Annual AQO
TSP	71	80
RSP	45	55

 

3.4         Air Sensitive Receivers

Representative Air Sensitive Receivers (ASRs) within 500m of the Project limit have been identified according to the criteria set out in the TMEIA and through site inspections and a review of land use plans. ASRs and their horizontal distance to the nearest emission source  have been identified and are summarized in Table 3.3.  Locations of the ASRs are shown in Figures 3.1 and 3.2.

Table 3.3        Representative Air Sensitive Receivers

ASRs	Area	Location	Usage	Distance to the nearest Emission Source
ASR1		Scattered Village House	Residential	20
ASR2		Village houses along Ngong Ping Road near bus terminus	Residential	120
ASR3		Scattered Village House	Residential	370
ASR4	Ngong Ping	Scattered Village House	Residential	240
ASR5		Po Lin Monastery	Religious	670
ASR6		Tin Tan Buddha Status	Religious	250
ASR7		SG Davis Youth Hostel	Residential	270
ASR8		Lin Chi Monastery	Religious	390
ASR9		Tung Chung Crescent	Residential	50
ASR10	Tung Chung	Fu Tung Estate	Residential	324
ASR11	Tung Chung	Seaview Crescent	Residential	350
ASR12		Wan Ho Kan Primary School	Institutional	443
ASR13		Tung Chung Post Office	office	24
ASR14		Sunshine House International Pre-school	Institutional	14

3.5         Potential Sources of Impact During Construction

Construction of the proposed cable car system may cause short-term air quality impacts on the surrounding air sensitive land uses at the terminal stations, the tower sites and the proposed emergency rescue trails underneath the route. However, it is expected that the dust generated from the construction works of tower and angle stations; the excavation and laying of utilities in the emergency rescue trails to maintain safe operations would be of small scale, localised and short-term.

For constructing the towers within the Country Park, helicopters will be used rather than a haul road (not permitted within the Country Park) for the import of materials to individual sites.  An alternative suggestion has been made to erect a material ropeway for transport of material to individual sites. As the proposed construction of such a facility would be through staking a tower in the ground and secure it with four anchors (not concrete) driven into rock there would be negligible impact on air quality either in terms of constructing the temporary facility or closed containers to avoid dust and spillage through its use. However for other reasons detailed in the text, this method of construction is not recommended. Construction activities that would generate dusts include:

·           pile driving

·           minimal excavation for the towers;

·           construction of the termini; and

·           earthworks for the construction of the 1.5m wide proposed emergency rescue trails underneath the route.

For tower construction, ready mix or in-situ concrete/grouting will be used. This means that there will be no need for a concrete batching plant to be established on-site. Major worksites have been identified along the route and are shown in Figure 3.3.

The extent of impacts depends on the distances between the work sites and the identified ASRs, the construction methods employed and the number of plant used and vehicle movements. Construction works for Tung Chung Cable Car will primarily be earthworks, excavation and termini construction. Since only a small number of items of construction equipment will be used, the overall exhaust emissions of SO₂ and NO₂ from the diesel-powered mechanical equipment of these plants are expected to be minimal.

3.6         Construction Dust Assessment Methodology

As aforesaid the dust generated from excavation for the towers and earthworks for the construction of emergency rescue trail would be of small scale, localised and short-term and no ASRs have been identified within the study boundary. The quantitative assessment would therefore be carried out on dust impact arising from the construction of the termini at Tung Chung and Ngong Ping.

Potential cumulative dust impacts could be related to the concurrent construction activities associated with the planned development in the vicinity of the Project including the proposed Sewage Treatment Works and Sewerage, and Cable Car associated Theme Village at Ngong Ping.

Dispersion Model

The extent of dust impacts arising from the construction of Cable Car Project have been predicted using the USEPA approved model Fugitive Dust Model (FDM) in conjunction with the construction programme. The Compilation of Air Pollutant Emission Factors, 5th Edition, US Environmental Protection Agency, 1996, (AP-42) was used to determine the various fugitive dust sources.

Meteorological Data Input

Sequential meteorological data for 2001 from Chek Lap Kok and King’s Park weather station, operated by Hong Kong Observatory, were used as input to the model to obtain 1-hour and 24-hour average TSP concentration at the identified ASRs. Data obtained from Chek Lap Kok and King’s Park stations used as input to the model includes, wind direction and speed together with atmospheric Pasquill stability class, and mixing heights together with air temperature.

Emission Factors

Emission factors, for various fugitive dust sources have been determined based on the USEPA Compilation of Air Pollution Emission Factors, 5th Edition (AP-42). Emission factor for typical construction operations given in the USEPA is 1.2 tons per acre of construction per month of activity (269 g/m²/month).  The emission factors used for carrying out the modelling are summarised in Table 3.4.  Detailed c Dust emission factor of 2.87 x 10^-4 g s^-1m^-2 was obtained by converting the above emission factor based on 26 working days per month and 10 operation hours per day. Calculations of the emission factors are given in Annex D.

The dust emission from construction is associated with drilling, ground excavation, earthworks and vehicle movement on unpaved road. The emission factor for general construction is illustrated in Table 3.4 below.

Table 3.4        Emission Factors for Various Construction Activities

Activities	Emission Factors	Remarks
Material Handling	3.17.56 x 10-4 g/s	Based on USEPA AP-42 Vol. 1 5th Edition, Section 13.2.4.3
Bulldozing	0.499 g/s	Based on USEPA AP-42 Vol. 1 5th Edition, Table 11.9-2
Vehicle Movements on Unpaved Site Roads	0.096288 g/s	Based on USEPA AP-42 Vol. 1 5th Edition, Section 13.2.2
Wind Erosion	2.695 x 10-6 gs-1 m-2	Based on USEPA AP-42 Vol. 1 5th Edition, Table 11.9-4

1-hour TSP Levels    

It was assumed that construction would take place over ten hours per day.  The corresponding meteorological data has thus been used as input to the FDM. The highest predicted TSP levels were obtainedand the background TSP were added together and compared with the recommended 1-hour limit of 500 mgm^-3.

24-hour TSP Levels  

The 24-hour TSP level was estimated by taking the average of 10 hours with worst-case daytime 1-hour average concentration and 14 hours with worst-case night time 1-hour average concentration. The predicted 24-hour TSP levels and the background daily TSP level were added together and compared with the AQO of 260 mgm^-3.

3.7         Evaluation of Impact

Construction dust impacts were modelled using the Fugitive Dust Model (FDM) with worst case assumptions as input data and at ground level.  Since construction of proposed Sewage Treatment Works and Sewerage, and Cable Car associated Theme Village at Ngong Ping Route will take place in parallel with this project, cumulative dust impacts have therefore been assessed.  Predicted net and cumulative hourly and daily TSP levels at 1.5m above local ground level at the identified ASRs are shown in Table 3.5 below. The background annual average TSP levels of 71 mgm^-3 measured at Tung Chung monitoring station has been added to the predicted hourly and daily results to provide the cumulative impact.

               Table 3.5     Predicted Hourly and Daily TSP Levels ( mgm^-3) ⁽¹⁾ at 1.5m above local ground level

ASRs	Area	Location	Net Dust Impacts		Cumulative Dusts Impacts
			Maximum Hourly Average TSP Level	Maximum Daily Average TSP Level	Maximum Hourly Average TSP Level	Maximum Daily Average TSP Level
ASR1		Scattered Village House	591427280	29085160	15931443874	725192425
ASR2		Village houses along Ngong Ping Road near bus terminus	222174132	1347597	713594409	346100219
ASR3		Scattered Village House	153127104	1057485	359328252	19584150
ASR4	Ngong Ping	Scattered Village House	13411496	977382	278275228	16082139
ASR5		Po Lin Monastery	13711698	997382	286243215	16383134
ASR6		Tin Tan Buddha Status	172140112	1137488	358358357	19590195
ASR7		SG Davis Youth Hostel	1059485	857277	192168160	12377110
ASR8		Lin Chi MonasteryLin Chi Monastery	257146198	14910376	359270316	19515887
ASR9		Tung Chung CrescentTung Chung Crescent	12375501313	573149287	12371313550	573149287
ASR10	Tung Chung	Fu Tung Estate	231299137	14079101	231299137	14079101
ASR11		Seaview Crescent	200266124	1278095	200266124	1278095
ASR12	Tung Chung	Wan Ho Kan Primary Sch	207248127	1307696	207248127	1307696
ASR13		Tung Chung Post Office	1696739	771372	1696739	771372
ASR14		Sunshine House International Pre-school	1849801	837400	1849801	837400
		Dust Criteria	500	260	500	260
Notes: (1)    Background TSP levels included in the results of hourly and daily average TSP (2)    Bold figure exceeds dust criteria (3)    N.A. denotes Not Applicable

 

The measured annual average TSP level at Tung Chung monitoring station is 71 mgm^-3. From the results obtained the unmitigated construction activities are likely to contribute significantly to the cumulative dust impact at the identified ASRs.  Construction is expected to be completed within 2 years.

As indicated in Table 3.5, all the predicted 1-hour and 24-hour TSP levels at the ASRs will comply with the AQO dust acceptable criteria of 500mgm^-3 and 260 mgm^-3 respectively during earthworks and termini construction except ASRs 1 and 2 at Ngong Ping and ASRs 9, 13 and 14 at Tung Chung due . However, due to in theirclose proximity to the works site. of ASRs 1 and 2 the scattered Village House at Ngong Ping and ASR 9 Tung Chung Crescent,  The cumulative dust impacts predicted at these ASRs 1, 2, 9, 13 and 14 indicate maximum hourly dust levels of 87415931443 mgm^-3, 713 mgm^-3, 594501237 mgm^-3, 7391696mgm^-3and 80118491313 mgm^-3 and maximum daily dust levels of 425725mgm^-3, 346 mgm^-3, 287573mgm^-3,372771mgm^-3 and400837mgm^-3,(hourly average), which would exceed the recommended hourly TSP guideline level of 500 mgm^-3 by 75219189%, 10439%, 147%, 48239%  and 1602703%, and daily TSP guideline level of 260mgm^-3, by 63179%, 33%, 10120%, 43197% and 54222%  respectively. 

Dust suppression measures are therefore recommended to reduce emissions from the site to ensure the criteria would not be exceeded.

3.8         Recommended Mitigation Measures

It is expected that dust levels would exceed the specified criteria and thus dust control measures are required to minimise the nuisance to acceptable levels.  In addition to this, the dust control requirements of the Air Pollution Control (Construction Dust) Regulation shall be followed to control the dust emission.  Dust control measures for construction activities associated with the earthworks for Tung Chung Cable Car are outlined below.

Material Handling

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

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

·           water spray should be used during the handling of excavated and fill material where dust is likely to be created; and

·           all dusty materials should be sprayed with water immediately prior to any loading, unloading or transfer operation so as to maintain moisture content of the dusty materials.

Vehicle Movements on Unpaved Site Road

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

·           the load on the vehicles should be covered entirely by clean impervious sheeting to ensure that the dusty materials do not leak from the vehicle; and

·           vehicle speeds limited to 20 8 kph to reduce the traffic induced dust dispersion and re-suspension within the site; and

·           damping of unpaved roads.

Earthworks

 

·           the amount of exposed soil should be kept in minimal by re-vegetation of completed earthworks.

Through the implementation of the above mitigation measures, dust levels can be reduced. Based on section 11.2.4.4 of the AP42 4th edition, the effectiveness of the mitigation measures has been evaluated. It is estimated that a 7850% reduction in dust levels would be achieved for material handling, road construction and vehicle movements with the introduction of frequent surface watering by at least every four two times hours daily and compacting on active areas on the site. The predicted mitigated hourly and daily TSP levels at 1.5m above local ground level are shown in Table 3.6.

             Table 3.6       Mitigated Hourly and Daily TSP Levels ( mgm^-3) ⁽¹⁾ at 1.5m above local ground level

ASRs	Area	Location	Net Dust Impacts		Cumulative Dusts Impacts
			Maximum Hourly Average TSP Level	Maximum Daily Average TSP Level	Maximum Hourly Average TSP Level	Maximum Daily Average TSP Level
ASR1		Scattered Village House	175160176	11675117	375407384	218102221
ASR2		Village houses along Ngong Ping Road near bus terminus	10197101	847284	199202203	13278133
ASR3		Scattered Village House	878587	787278	129130130	997499
ASR4	Ngong Ping	Scattered Village House	848284	767177	113117114	927492
ASR5		Po Lin Monastery	848284	777277	114111115	917492
ASR6		Tin Tan Buddha Status	918891	807280	131131131	10076100
ASR7		SG Davis Youth Hostel	787778	747174	959496	837383
ASR8		Lin Chi Monastery	108103108	877287	130127131	10075100
ASR9		Tung Chung Crescent	304382310	18591187	304382310	18591187
ASR10	Tung Chung	Fu Tung Estate	103128104	877387	103128104	877387
ASR11	Tung Chung	Seaview Crescent	9712098	847384	9712098	847384
ASR12		Wan Ho Kan Primary Sch	9811599	847285	9811599	847285
ASR13		Tung Chung Post Office	396405	229233	396405	229233
ASR14		Sunshine House International Pre-school	427436	244248	427436	244248
		Dust Criteria	500	260	500	260
Notes: (1)  Background TSP levels included in the results of hourly and daily average TSP (2)    Bold figure exceeds dust criteria (3)    N.A. denotes Not Applicable

The predicted results show that with the inclusion of mitigation measures dust levels at all ASRs will comply with both the hourly and daily dust criteria.

 

3.9         Residual Impacts

No adverse residual impacts are predicted for the construction of Tung Chung Cable Car.

3.10       EM&A Requirement

Full compliance with the dust criteria will be achieved at all ASRs with the implementation of mitigation measures.  Dust monitoring is recommended to ensure that the dust levels do not exceed the criteria during the construction phase at Ngong Ping and Tung Chung.  Monitoring requirements are discussed in the EM&A Manual.

3.11       Conclusions

The construction of Tung Chung Cable Car will inevitably lead to dust generation. It is predicted that various construction activities associated with the earthworks, excavation and construction of termini would give rise to high hourly TSP levels. Mitigation measures are therefore necessary to suppress dust emissions from construction activities through good site practice. In order to ensure full compliance of the dust levels with the criteria, it is recommended that baseline dust monitoring and dust impact monitoring is carried out prior to and during the construction works.