Table of Contents

3... air quality impact..

3.1.. introduction..

3.2.. environmental legislation, policies, plans, standards and criteria..

3.3.. description of the environment.. 1112

3.4.. Assessment Methodologies.. 2223

3.5.. environmental impact identification, prediction and evaluation.. 5556

3.6.. mitigation of adverse environmental impacts.. 7778

3.7.. Evaluation of residual impacts.. 99910

3.8.. Environmental monitoring and audit.. 99910

3.9.. conclusion.. 10101011

3... air quality impact..

3.1 introduction

3.2 environmental legislation, policies, plans, standards and criteria

3.3 description of the environment

3.4 Assessment Methodologies

3.5 environmental impact identification, prediction and evaluation

3.6 mitigation of adverse environmental impacts

3.7 Evaluation of residual impacts

3.8 conclusion

3... air quality impact.. 3

3.1.. introduction.. 3

3.2.. environmental legislation, policies, plans, standards and criteria.. 3

3.3.. description of the environment.. 4

3.4.. Assessment Methodologies.. 6

3.5.. environmental impact identification, prediction and evaluation.. 8

3.6.. mitigation of adverse environmental impacts.. 11

3.7.. definition and evaluation of residual environmental impacts.. 13

3.8.. conclusion.. 13

List of Tables

Table 3.1 Hong Kong Air Quality Objectives

Table 3.2 Air Pollutant Levels Recorded at EPD’s Air Quality Monitoring Station (Tsuen Wan)

Table 3.3 Description of the Air Sensitive Receivers

Table 3.4 Dust Emission Factors used for Castle Peak Road New Link Assessment

Table 3.5 A Comparison of Combined Effects of Traffic Flow and Emission Factors on Castle Peak Road New Link

Table 3.6 Predicted Cumulative TSP Concentrations at the Representative ASRs at 1.5m above Ground (Unmitigated)

Table 3.7 Predicted Cumulative TSP Concentrations at the Representative ASRs at 10m above Ground (Unmitigated)

Table 3.8 Predicted 1-hour Average NO₂, 24-hour average NO₂ and 24-hour Average RSP Concentrations at the Representative ASRs

Table 3.9 Predicted TSP Concentrations at the Representative ASRs at 1.5 m above Ground (Mitigated)

Table 3.10 Predicted TSP Concentrations at the Representative ASRs at 10m above Ground (Mitigated)

Table 3.1 Hong Kong Air Quality Objectives

Table 3.2 Air Pollutant Levels Recorded at EPD’s Air Quality Monitoring Station (Tsuen Wan)

Table 3.3 Description of the Air Sensitive Receivers

Table 3.4 Dust Emission Factors used in this Assessment

Table 3.5 A Comparison of Combined Effects of Traffic Flow and Emission Factors on Castle Peak Road New Link

Table 3.6 Predicted Cumulative TSP Concentrations at the Representative ASRs at 1.5m above Ground (Unmitigated)

Table 3.7 Predicted Cumulative TSP Concentrations at the Representative ASRs at 10m above Ground (Unmitigated) 998

Table 3.8 Predicted 1-hour Average NO₂, 24-hour average NO₂ and 24-hour Average RSP Concentrations at the Representative ASRs 10109

Table 3.9 Predicted TSP Concentrations at the Representative ASRs at 1.5 m above Ground (Mitigated) 111110

Table 3.10 Predicted TSP Concentrations at the Representative ASRs at 10m above Ground (Mitigated) 111110

Table 3.1 Hong Kong Air Quality Objectives 3

Table 3.2 Air Pollutant Levels Recorded at EPD Air Quality Monitoring Station (Tsuen Wan) 4

Table 3.3 Air Sensitive Receivers 5

Table 3.4 Dust Emission Factors used in this Assessment 6

Table 3.5 Emission Factors for Year 2011 for Different Vehicle Category 7

Table 3.6 Predicted Cumulative TSP Concentrations at the Representative ASRs at 1.5m in Year 2022 (Unmitigated) 9

Table 3.7 Predicted Cumulative TSP Concentrations at the Representative ASRs at 10m in Year 2022 (Unmitigated) 9

Table 3.8 Predicted 1-hour Average NO₂, 24-hour average NO₂ and 24-hour Average RSP Concentrations at the Representative ASRs (With the Proposed Noise Barriers) 10

Table 3.9 Predicted TSP Concentrations at the Representative ASRs at 1.5 m in Year 2022 (Mitigated) 11

Table 3.10 Predicted TSP Concentrations at the Representative ASRs at 10 m in Year 2022 (Mitigated) 12

List of Figures

Figure 3.1 Locations of Representative Airir Sensitive Receivers

Figure 3.2 2022 AM Peak Hour Forecast Traffic Flow

Figure 3.322 Contours of 1-Hour Average Nitrogen Dioxide Concentrations in µgm^-3 at 1.5m above Ground

Figure 3.433 Contours of 1-Hour Average Nitrogen Dioxide Concentrations in µgm^-3 at 10m above Ground

Figure 3.544 Contours of 24-hour Average Nitrogen Dioxide Concentrations in µgm^-3 at 1.5m above Ground

Figure 3.655 Contours of 24-hour Average Nitrogen Dioxide Concentrations in µgm^-3 at 10m above Ground

Figure 3.766 Contours of 24-hour Average Respirable Suspended Particulate Concentrations in µgm^-3 at 1.5m above Ground

Figure 3.787 Contours of 24-hour Average Respirable Suspended Particulate Concentrations in µgm^-3 at 10m above Ground

List of Figures (cont’d)

Figure 3.898 Contours of 1-Hour Average Total Suspended Particulate Concentrations in µgm^-3 at 1.5m above Ground (Mitigated)

Figure 3.9109 Contours of 124-Hour Average Total Suspended Particulate Concentrations in µgm^-3 at 10.5m above Ground (Mitigated)

Appendices

Appendix 3.1 Calculations of Dust Emission Factors

Appendix 3.2 Sample Computer Output of FDM Calculations

Appendix 3.33 Calculations of Emission FactorsCalculations of Road Traffic Emission Factors

Appendix 3.44 Sample Computer Outputs of Caline4 CALINE4 Calculations

3. air quality impact

introductionIntroduction

3.1 This section presents an assessment of air quality impacts associated with the construction and operation phases of the Improvement to castle Castle pPeak road Road between ka Ka loon Loon tsuen Tsuen and siu Siu lam Lam. D It is anticipated that Route 10 will be under construction concurrently with the Project. Hence, the accumulative dust impact will be evaluated as well.

3.1

3.1 It is foreseeable that dust is a major potential air quality impact during construction phase while vehicle emissions may pose a potential air quality concern after completion of the Project.impact during operation phase.

3.1

Environmental Legislation, Policies, Plans, Standards And and Criteria

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

3.2

3.3 The Air Pollution Control Ordinance (APCO) provides the statutory authority for controlling air pollutants from a variety of sources. The Oordinance includes a number of Air Quality Objectives (AQOs) which stipulate maximum concentrations for a range of pollutants, of which nitrogen dioxide (NO₂), respirable and total suspended particulates (RSP & TSP) are relevant to this study. The relevant AQOs are listed in Table 3.1.

Table 3.1 Hong Kong Air Quality Objectives

Parameter	Maximum Average Concentration (µgm^-3)^1
	1-Hour^2	24-Hour^3	Annual^4
NO2	300	150	80
RSP	-----	180	55
TSP	-----	260	80

1. Measured at 298 K and 101.325 kPa.

2 Not to be exceeded more than three times per year.

3 NotNot to be exceeded more than once per year.

4. Arithmetic mean.

3.4 The criteria for tunnel quality, which are based on EPD’s Practice Note on Control of Air Pollution in Vehicle Tunnel 1995, are presented in Table 3.2.

Table 3.2 Tunnel Air Quality Criteria

Parameter	Maximum Concentration ^(1)(2)
CO	115,000 mg m^-3	100 ppm
NO2	1,800 mg m^-3	1 ppm
SO2	1,000 mg m^-3	0.4 ppm

1. Average time is 5 minutes

2 Measured at 298 K and 101.325 kPa

3.5 In addition, the visibility in tunnels acts as an indicator of smoke concentration and should be controlled so that extinction coefficient does not exceed 0.005 per meter (over five minutes).

3.6 The EIAO-TM also stipulates that the hourly TSP level should not exceed 500 µgm^-3 TSP (measured at 25°C and one atmosphere) for construction dust impact assessment. Mitigation measures from construction sites have been specified in the Air Pollution Control (Construction Dust) Regulations.

Description Of of The the Environment

Baseline Condition

3.7 The air quality at the Study Area is primarily affected by traffic emissions from the existing Castle Peak Road, Tuen Mun Road and small local access roads.

The nearby construction activities along the sea band of the existing Castle Peak Road may also contribute air quality impact to the surrounding area. Other dust sources may come from a concrete batching plant located at Brothers Point (Tai Lam Kok) and the construction activities from the project “Improvement to Castle Peak Road from Siu Lam to So Kwun Tan” which will be completed in mid 2000.

3.1

3.1

3.8 The annual average concentrations of pollutants measured at the nearby EPD’s air quality monitoring station (Tsuen Wan) was chosen as the background of the Study Area. Table 3.3 summarises the annual average concentrations of the pollutants in Year 1999.As EPD ’s air quality monitoring station has not been established in Tuen Mun, data from Tsuen Wan monitoring station was chosen to use as the background level. Data from EPD’s publication, Air Quality in Hong Kong 1999, was extracted to indicate the relevant background pollutants level.

Table 3.3 Air Pollutant Levels Recorded at EPD’s Air Quality Monitoring Station (Tsuen Wan)

Pollutants	Annual Average Concentrations (mgm^-3)
	Tsuen Wan (1999)
NO2	67
RSP	54
TSP	79

Air sensitive receivers

Air sensitive Receivers (ASrsASRs)

3.9 According to the criteria set out in the EIAO-TM, thirteen representative ASRs have been identified. The existing Air Sensitive Receivers (ASRs) including an educational institute, a correctional training school, a hospital, a psychiatric centre, domestic premiseslow density residential area such as Correctional Services Department Staff Quarters, Poseidon Coast and some scattered rural village houses have been identified for air quality impact assessment. A brief description of the representative ASRs and their horizontal distance from the alignment adjacentnearest road source have been identified and are summarised in Table 3.4. Figure 3.1 shows the locations of the identified ASRs.

Table 3.4 Description of the Representative Air Sensitive Receivers

ASR IDs	Description	Distance from the Noise SourceNearestAdjacent Road Source (km)*
A01	CSD Married Staff Quarters	5412.4
A02	CSD Married Staff Quarters	182.2
A03	Poseidon Coast	408.4
A04	CSD Staff Quarters	287
A05	Siu Lam Hospital	5012
A06	Siu Lam Psychiatric Centre Quarters	9031.4
A07	Customs and Excise Training SchoolGodown	1029
A08	Customs and Excise Training SchoolGodown	2816
A09	Vocational Training Council – Seamen’s Training Centre	2614.8
A10	Ka Lueoon Tsuen	1010.4
A11	Wu Uk Tsuen	1114
A12	Customs and Excise Training School	1223.6
A13	Temple	82.6

Note: * Distance measured from the nearest kerb side of the road to the receiver.

3.10 Several elevations were chosen for the assessment: 1.5 metres above local ground level (which is the average height of the human breathing zone), 10.0 metres , 20.0 metres, 30.0 metres and 40.0 metres above local ground level.

Potential Sources of Impact

It is anticipated that impacts arising from the construction of Castle Peak Road New Link mainly relate to dust nuisance and gaseous emissions from construction plant and vehicles, with dust generation being the major concern. The potential air quality impact during construction of the Castle Peak Road New Link may be caused by the following activities:

Piling

Material handling

Excavation

Filling and Backfilling

Retaining wall construction

Vehicle movements on unpaved site area

Vehicle and plant powered by diesel that emit SO₂ and NO₂ can cause some air quality impact, but the amount of such emission would be limited and will be unlikely to breach the AQO.

Assessment Methodologies

Construction Phase

3.11 The major dusty activities for the project include:

· Piling

· Material handling

· Excavation

· Filling and backfilling

· Retaining wall construction

· Vehicle movements on unpaved site area

3.1 Since the construction of Castle Peak Road from Sham Tseng to Ka Loon Tsuen would be undertaken concurrently with the project, cumulative construction dust impact was assessed

3.1

3.12 Cumulative construction dust impact owing to the construction of the road project and the adjacent Route 10 construction works has been assessed.

3.13 Fugitive Dust Model (FDM) was used to assess potential dust impacts from construction activities. Prediction of dust emissions was based on emission factors from USEPA Compilation of Air Pollution Emission Factors (AP-42), 5^th Edition. For a conservative simulation, general construction activities and wind erosion of open sites were considered to be the major dust emission sources from the construction work in this study.

3.1

3.14 The dust emission factors adopted in this assessment are given in Table 3.5. Detailed calculations of the emission factors are provided in Appendix 3.1.

Table 3.5 Dust Emission Factors used for Castle Peak Road New Link in this Assessment

Activities	Dust Emission Factor
General construction activities	2.69 Mg/hectare/month (Section 13.2.3)*
Wind erosion of open site	0.85 Mg/hectare/year (Table 11.9.4)

* Reference to AP-42, 5^th Edition

3.15 Since the works area covers a large section of Castle Peak Road, it is very likely that the improvement works would not be carried out at the full length of the site. For conservatism, construction activity was assumed to be continuous (although night time and evening work is not actually planned). The sites to be developed cover large areas, but only parts of the site will be actively worked at any one time. Taking into account the horizontal extent of a generalthe construction site, it was assumed that a maximum of 70 percent of the construction site area would be actively operated at any one time during the construction period. Wind erosion would occur from all open construction areas. It is also assumed that 50% of dust mitigation measure is applied at Route 10 to predict the cumulative dust impact.

3.15 Fugitive Dust Model (FDM) was used to assess potential dust impacts from construction activities. 1-hour average and 24-hour average of TSP concentrations were predicted at selected air sensitive receivers.

3.1

3.16 1-Hourly average and 24-hour average TSP concentrations were predicted at the representative ASRs. based on the assumption of As a worst-case scenario, 10-tTen-hour working day.

3.16

3.1 As discussed in Section 3.3, a background TSP concentration of 79 mgm^-3 has been added to the maximum 1-hour average and maximum 24-hour average results.

3.1

3.17 The dispersion model was undertaken for 288 predefined separate meterological conditions. The following meteorological conditions have been assumed in the modeling:

· Wind speed : 1m/s and 2 m/s

· Wind direction : worst case

· Resolution : 5^o

· Stability class : B & D (Day time) or D & F (night time)

· Surface roughness : 1m

· Mixing height : 500m

3.18 As discussed in Section 3.8, a background TSP concentration of 79 mgm^-3 has been added to the maximum 1-hour average and maximum 24-hour average results.

3.18

3.19 A sample output file of the FDM model run, which includes all the input information and model parameters for this assessment, is provided in Appendix 3.2 of this report for reference.

Operation Phase

Potential source of Impacts

3.20 Potential air quality impact on the surrounding ASRs during the operation phase of the project New Link includes:

· background pollution

· open road emissions from the existing and planned roads with the incorporation of the proposed noise barriers,

· portal emission from full enclosure at the slip road of the Siu Lam Interchange,

· portal emission from full enclosure at the Castle Peak Road viaduct ; and

· portal emission from full enclosures at the Route 10 NLYLH’s Siu Lam Link Road (SLLR).

Impact from Open Roads

Open Road Emissions

3.21 The US EPA CALINE4 model, which is based on the Gaussian diffusion equations to characterise pollutant dispersion over the roadway, has been used to model air quality at the air sensitive receiverASRs. As Nitrogen Dioxide (NO₂) and Respirable Suspended Particulates (RSP) are the prime concern on air quality associated with road traffic, the model has been used to predict the 1-hour and 24-hour concentrations of these two pollutants. The 1-hour NO₂, 24-hour NO₂ and 24-hour concentrations of NO₂ and RSP concentrations were calculated and compared with the HKAQO.

3.21

3.22 The EPD’s Fleet Average Emission Factor (EURO3) contains emission factors for various types of vehicles in different years of operation. A sensitivity test was conducted to determine the worst air quality scenario in terms of the traffic flow and emission factors on Castle Peak Road New Link between 2007 and 2022, as shown in Table 3.6. Results indicated that the worst scenario in terms of air pollution from vehicle emissions would occur in year 2022.

3.22The traffic forecast at year 2022 is assumed to be the worst year within 15 years of commencement of the operation. The AM peak hour traffic flow and vehicle mix predicted by the traffic consultant for the road network for 2022 was used for the assessment. The most up-to-date vehicular emission factors (Fleet Average Emission Factors – EURO3 Model) available from the EPD are for the year 2011 and these were adopted for the assessment. The composite emission factors for the road links were calculated as the weighted average of the emission factors of different types of vehicles. The vehicular emissions for different vehicle categories are listed in Table 3.5. Details for the calculations of the composite emission factors for each road link are provided in Appendix 3.3.

3.22

3.22Table 3.5 Emission Factors for Year 2011 for Different Vehicle Category

3.22

Pollutant	Emission Factors (gm/km)
	Petrol	HGV	LGV
NOx	6.80	3.84	1.23
RSP	0.69	0.53	0.11

Table 3.6 A Comparison of Combined Effects of Traffic Flow and Emission Factors on Castle Peak Road New Link

Year	Traffic Flow (veh/hr)	NOx Emission (g/mile-veh)	Total NOx Emission (g/mile/hr)
2007	1800	4.53	8158
2022	2410	4.01	9674

3.22

3.23 Projected 2022 peak hour traffic flows and vehicle composition of the roads are shown in Figure 3.2Appendix 2.21. Detailed calculations of the composite emission factors for each road link in year 2022 are given Appendix 3.3.

3.23

3.24 Discrete Parcel Method (i.e. NO₂ option) was used to predict NO₂ concentration for daytime period. . For RSP concentration, the particulate option was used for calculation in CALINE4.

3.24 In order to calculate the cumulative pollutant concentrations from different sources using different models (Caline4 and ISCST3) in the later part of the assessment, the dispersion modeling was undertaken for 360 predetermined meteorological conditions and the highest predicted pollutant concentration amongst the 360 wind directions were identified.

3.25 Peak hour traffic flow of the study area will occur during daytime. With reference to the Screening Procedures for Estimating the Air Quality Impact of Stationary Source (EPA-454/R-92-019), a conversion factor of 0.4 is used to convert the 1-hour average concentrations to 24-hour average concentrations.The following summarises the meteorological conditions adopted in the air quality modeling using the CALINE4 model:

·

· The following summarises the meteorological conditions adopted in the air quality modelling using the CALINE4 model to determine the worst case scenario:

· Wind speed : 1 m/s

· Wind direction : 360 wind directions

· Resolution : 1^o

· Wind variability : 18^o

· Surface roughness : 1 m

· Mixing height : 500 m

· Ozone concentration : 57 mgm^-3 (concentration is extracted fromAccording to the modeling guidelines or the urban rural/new development area provided by EPD)

· Photodissociation rate : 0.004 s^-1

3.26 With reference to the Screening Procedures for Estimating the Air Quality Impact of Stationary Source (EPA-454/R-92-019), a conversion factor of 0.4 was used to convert the 1-hour average concentrations to 24-hour average concentrations.

3.26

3.27 As described in Sections 4.60-4.61, an extensive noise mitigation measures were proposed for T Castle Peak Road, including New Link. two full enclosures and three cantilevered barriers. Noise mitigation measures such as full enclosures, semi-enclosures, and 3- and 5-meter high vertical barriers were also proposed at the Route 10 NLYLH’s SLLR for the Route 10 project. Potential air quality impacts from the barriers/enclosures at the proposed Castle Peak Road and the Route 10 NLYLH’s SLLR have been taken into account in the air quality model. Figure 4.5 shows the locations of the proposed noise barriers/enclosures for the project New Link and the Route 10 NLYLH’s SLLR.

3.27

3.28 It was assumed that with the installation of noise barriers, all the traffic pollutants would be emitted from the top of the noise barriers. For the cantilevered barriers and semi-enclosures, the source of the emissions was adjusted by shifting the road section by a distance equal to the width of the road section covered by the cantileverenclosures. In the air quality model, the road type was set to ‘fill’ and the relative height was set to the effective height of the barrier.

3.29 Appendix 3.44 provides sample computer outputs of the CALINE4 model which was adopted for the vehicle emissions impact assessment.

Portal Emissions from Full Enclosures

3.30 The Industrial Source Complex Short-term (ISCST3) dispersion model was used to predict the portal emissions from full enclosures.

3.31 The followings are the portal emissions in and around the study area:

· Portal emissions from the full enclosure at the Castle Peak Road viaduct,

· Portal emissions from the full enclosure at the slip road to the Siu Lam Interchange,

· Portal emissions from the full enclosures at the Route 10 NLYLH’s SLLR

3.32 Portal emissions from the full enclosures were assessed based on the procedures stated in Section III of the Permanent International Association of Road Congresses (PIARC), 1991. Pollutants were assumed to eject from the portal as a portal jet such that 2/3 of the total emissions was dispersed within the first 50m of the portal and 1/3 of the total missions within the second 50m.

3.33 As mentioned in Section 3.25, 360 wind angles were used. The following summarises the meteorological conditions adopted in the air quality modeling using the ISCST3 model:

· Wind Speed : 1m/s

· Wind direction : 360 wind directions

· Resolution : 1^o

· Stability class : D

3.34 The total mass of pollutants is presented in Appendix 3.5. A sample of the computer output is provided in Appendix 3.6.

Cumulative Impacts

3.35 Cumulative impacts will arise from vehicle emissions from open sections of the existing and planned road networks and portal emissions from the proposed full enclosures at the slip road of the Siu Lam Interchange, Castle Peak Road viaduct and the Route 10 NLYLH’s SLLR.

3.36 The pollutant concentrations at the ASRs at different wind directions (1 degree resolution) were predicted by both CALINE4 and ISCST3 models, where

· the CALINE4 model was adopted to predict the open road emissions from the existing and planned road networks; and

· the ISCST3 model was adopted to predict all the portal emissions from the full enclosures.

3.37 The cumulative pollutant concentrations at the ASRs at each specific wind direction were calculated by summing the results angle by angle from the two models.

3.38 The highest pollutant concentrations at the ASRs amongst the 360 wind directions were identified as the worst predicted cumulative pollution concentrations.

3.39 The background concentrations of NO₂ and RSP, as mentioned in Section 3.8, were taken as 67 mgm^-3 and 54 mgm^-3 respectively. Such background concentrations were added to the corresponding predicted hourly and daily concentrations.

Air Quality inside Full Enclosures

3.40 According to the findings in Section 4, two full enclosures of approximately 175m and 76m respectively have been proposed for the improved Castle Peak Road in order to alleviate the traffic noise impact. The air quality inside these full enclosures was assessed using the theory developed by Ohashi and Koso⁽¹⁾.

3.41 Two scenarios were considered for these two full enclosures, i.e. normal traffic flow condition and congested traffic flow condition. The detailed calculation is presented in Appendix 3.7.

Environmental Impact Identification, Prediction And and Evaluation

Construction phase

3.42 The cumulative maximum 1-hour average and 24-hour average TSP concentrations at the representative ASRs in 2022at 1.5m and 10m above ground have been predicted and are tabulated in Tables 3.67 and 3.87. These results are for the unmitigated scenario, that is without any dust suppression measures.

Table 3.67 Predicted Cumulative TSP Concentrations at the Representative ASRs at 1.5m in Year 2022above Ground (Unmitigated)

ASRs	CPR^1		STKLT^2		Background Level	Cumulative
	1-hr	24-hr	1-hr	24-hr		1-hr	24-hr
A01	333	150	2	1	79	414	230
A02	481	216	2	1	79	561	296
A03	145	66	2	1	79	226	145
A04	188	84	2	1	79	269	164
A05	364	162	2	1	79	444	242
A06	119	54	2	1	79	200	134
A07	342	155	2	1	79	423	235
A08	87	39	2	1	79	169	119
A09	120	53	3	1	79	201	134
A10	73	34	140	63	79	292	175
A11	211	95	3	1	79	293	175
A12	103	46	3	2	79	185	127
A13	357	159	3	1	79	439	240

Value in bold type indicates the TSP concentration exceeds the guideline level or AQO limit

Improvement works of the Castle Peak Road

Improvement works From Sham Tseng to Ka Loon Tsuen, with 50% dust suppress measures

Table 3.78 Predicted Cumulative TSP Concentrations at the Representative ASRs at 10m in Year 2022above Ground (Unmitigated)

ASRs	CPR^1		STKLT^2		Background Level	Cumulative
	1-hr	24-hr	1-hr	24-hr		1-hr	24-hr
A01	184	80	2	1	79	265	159
A02	201	87	2	1	79	282	167
A03	135	59	2	1	79	215	139
A04	159	69	2	1	79	240	149
A05	161	69	2	1	79	242	149
A06	95	42	2	1	79	176	122
A07	142	62	3	1	79	224	142
A08	78	34	3	1	79	159	114
A09	89	39	3	1	79	171	119
A10	69	31	60	24	79	204	134
A11	122	53	3	1	79	204	134
A12	86	37	4	2	79	168	118
A13	110	48	3	1	79	192	128

Value in bold type indicates the TSP concentration exceeds the guideline level or AQO limit

1 Improvement works of the Castle Peak Road

2 Improvement works From Sham Tseng to Ka Loon Tsuen, with 50% dust suppress measures

*Mitigated scenario (50% mitigation measure) was incorporated for assessment.

3.43 From the rThe highest predicted 1-hour average TSP concentration is was 689 561 mgm^-3 predicted at A02 (CSD Married Staff Quarters), which was about 12% higher than the TSP guideline level in air quality objectives. It is also predicted that 24-hour TSP concentration at ASR A02 at 1.5m above ground would may be likely to be exceed the AQO. All ASRs at the receiver height 10m above ground would comply with the TSP guideline level and the AQO.

3.43

3.43

3.44 Since the predicted TSP concentration would exceed the guideline and AQO at one of the representative ASRs, mitigation measures are required.

Operation Phase

Impact from Open Roads

3.45 Taking into account of vehicle emissions from open road networks and portal emissions from the proposed full enclosures on the slip road at Siu Lam Interchange, Castle Peak Road viaduct and the Route 10 NLYLH’s SLLR, the cumulative 1-hour and 24-hour NO₂ and RSP concentrations were predicted. The highest pollutant concentrations at 360 wind directions at each ASRs under the worst wind directions have been calculated.

3.46 The pollutant concentrations at various levels (1.5m, 10m, 20m, 30m and 40m above ground) have been predicted and the results are presented in Tables 3.9 to 3.11. The results indicate that the maximum pollutant concentrations are predicted at the level of 1.5m above ground.

3.46

3.47 As indicated in Tables 3.9-3.11, the predicted 1-hour average NO₂, 24-hour average NO₂ and 24-hour average RSP concentrations at 1.5m above ground are in the range of 139 to 262 mgm^-3, 131 - 22596 to 145 mgm^-3 and 90 - 17171 to 113 mgm^-3, respectively. No exceedance of the AQO is expected. Hence, mitigation measures are not required.

3.48 The predicted 1-hour average NO₂, 24-hour average NO₂ and 24-hour average RSP concentrations contour plots at 1.5m above ground have been plotted and are shown in Figures 3.2, 3.4 and 3.6.

3.49 The predicted 1-hour average NO₂, 24-hour average NO₂ and 24-hour average RSP concentrations contour plots at 10m above ground are also presented in Figures 3.3, 3.5 and 3.7.

From Table 3.88, the predicted 1-hour average NO₂, 24-hour average NO₂ and 24-hour average RSP concentrations at 1.5m high above ground range between 131 -263 mgm^-3, 131 - 225 mgm^-3 and 90 - 171 mgm^-3, respectively. No exceedance of the AQO limit is expected and it would not be necessary to impose any mitigation measures.

Table 3.9 Predicted 1-hour Average NO₂ Concentrations at the Representative ASRs at various levels above ground

ASRs	Predicted Concentration (mgm^-3)*
	Receiver height (m)
	1.5	10	20	30	40
A01	185	166	146	135	127
A02	262	224	180	156	140
A03	236	220	189	164	146
A04	245	215	184	161	140
A05	262	216	164	142	128
A06	181	154	126	114	104
A07	200	172	150	142	132
A08	198	194	182	173	157
A09	192	185	172	156	141
A10	217	206	184	161	142
A11	156	149	137	129	120
A12	139	137	132	126	119
A13	196	149	143	136	128

* Background NO₂ concentration of 67 mgm^-3.

Table 3.10 Predicted 24-hour average NO₂ Concentrations at the Representative ASRs at various levels above ground

ASRs	Predicted Concentration (mgm^-3)*
	Receiver height (m)
	1.5	10	20	30	40
A01	114	106	99	94	91
A02	145	130	112	103	96
A03	135	128	116	106	99
A04	138	126	114	105	96
A05	145	127	106	97	91
A06	113	102	91	86	82
A07	120	109	100	97	93
A08	119	118	113	109	103
A09	117	114	109	103	97
A10	127	123	114	105	97
A11	103	100	95	92	88
A12	96	95	93	91	88
A13	119	100	97	95	91

* Background NO₂ concentration of 67 mgm^-3

Table 3.11 Predicted 24-hour Average RSP Concentrations at the Representative ASRs at various levels above ground

ASRs	Predicted Concentration (mgm^-3)*
	Receiver height (m)
	1.5	10	20	30	40
A01	85	82	78	75	72
A02	104	96	87	80	76
A03	107	101	90	82	77
A04	113	100	89	81	75
A05	101	94	82	76	72
A06	77	73	70	68	65
A07	80	76	73	71	69
A08	88	86	83	80	76
A09	101	95	87	80	75
A10	105	100	92	84	78
A11	72	71	69	68	66
A12	71	70	69	68	66
A13	84	76	74	72	70

* Background RSP concentration of 54 mgm^-3 are included.

Air Quality inside Full Enclosures

3.50 The predicted NO₂ concentration inside the full enclosures has been calculated and the results are shown in Table 3.12. Appendix 3.7 shows the detailed calculation.

Table 3.12 Predicted NO₂ Concentration inside the full enclosure

	Normal Condition, mgm^-3	Worst Condition (Congested), mgm^-3
Full enclosure on the slip road at the Siu Lam Interchange	435	522
Full enclosure on the Castle Peak Road viaduct	433	662

Note: Bold value indicates exceedance of Tunnel Air Quality Criteria.

3.51 From Table 3.12, no exceedance of the Tunnel Air Quality Guideline is expected and thus mitigation measures are not required.

Mitigation Of of Adverse Environmental Impacts

Construction Phase

3.52 As mentioned in Section 3.543, exceedance of both TSP guideline level and AQO is predicted at A02. Hence, mitigation measures are considered necessary in order to suppress the potential dust impact.

3.52

3.53 According to AP-42, a 50 percent reduction of the dust generated from wind erosion and general construction activities could be achieved by watering of the site areas twice per day.

3.53

3.1 The dust suppression measures set out in the Air Pollution Control (Construction Dust) Regulation are, in fact, are more extensive. Therefore, it is expected that with watering the construction site twice a day together with strict implementation of dust suppression measures as stipulated in the Air Pollution Control (Construction Dust) Regulation, the dust level is expected to be reduced by over 50%.

3.1

3.54 Calculations of the dust emissions after implementation of recommended dust suppression measures are given in Appendix 3.1 Tables 3.13 and 3.14 present the predicted TSP concentrations after the implementation of the recommended dust suppression measure.. The contours of cumulative hourly average and 24-hour average TSP concentrations at 1.5 m in 2022above ground are presented in Figures 3.8 8 and 3.99.

Table 3.913 Predicted TSP Concentrations at Representative ASRs at 1.5 m in Year 2022above Ground (Mitigated)

ASRs	CPR^1		STKLT^2		Background Level	Cumulative
	1-hr	24-hr	1-hr	24-hr		1-hr	24-hr
A01	167	81	2	1	79	247	160
A02	240	116	2	1	79	321	196
A03	73	35	2	1	79	153	115
A04	94	45	2	1	79	175	125
A05	182	86	2	1	79	263	166
A06	60	29	2	1	79	141	109
A07	171	83	2	1	79	252	163
A08	44	21	2	1	79	125	101
A09	60	28	3	1	79	142	109
A10	37	19	140	63	79	256	160
A11	106	51	3	1	79	188	131
A12	51	25	3	2	79	134	105
A13	179	85	3	1	79	261	165

Value in bold type indicates the TSP concentration exceeds the guideline level or AQO limit

Improvement works of the Castle Peak Road

2. Improvement works From Sham Tseng to Ka Loon Tsuen, with 50% dust suppress measures

Table 3.1014 Predicted TSP Concentrations at Representative ASRs at 10 m in Year 2022above Ground (Mitigated)

ASRs	CPR^1		STKLT^2		Background Level	Cumulative
	1-hr	24-hr	1-hr	24-hr		1-hr	24-hr
A01	92	41	2	1	79	173	121
A02	101	45	2	1	79	181	125
A03	67	31	2	1	79	148	111
A04	80	36	2	1	79	160	116
A05	80	36	2	1	79	161	116
A06	48	22	2	1	79	129	102
A07	71	32	3	1	79	153	112
A08	39	18	3	1	79	120	98
A09	44	20	3	1	79	126	100
A10	35	16	60	24	79	169	120
A11	61	28	3	1	79	143	108
A12	43	19	4	2	79	125	100
A13	55	25	3	1	79	137	105

Value in bold type indicates the TSP concentration exceeds the guideline level or AQO limit

1 Improvement works of the Castle Peak Road

2 Improvement works From Sham Tseng to Ka Loon Tsuen, with 50% dust suppress measures

3.55 With the implementation of the proposed mitigation measures, dust would be suppressed and the dust level at all ASRs are expected to be within the 1-hour and 24-hour average TSP guideline level / HKAand AQO.

3.56 To further ensure compliance with the guideline and AQO limit at the ASRs at all time, it is recommend to implement of the Air Pollution Control (Construction Dust) Regulation and include good site practice in the contract clauses to minimize cumulative dust impact. In addition, a comprehensive dust monitoring and audit programme is recommended to ensure proper implementation of the identified mitigation measures. Details of the monitoring and audit requirements are provided in a separate EM&A Manual.

Operation Phase

3.57 The results show that no exceedance of 1-hour average NO₂, 24-hour average NO₂ and 24-hour average RSP guideline concentrations is predicted at all the representative ASRs. Thus, mitigation measures are not required.

3.58 As discussed in Section 3.51, the predicted NO₂ concentration inside the two proposed full enclosures would comply with the Tunnel Air Quality Criteria. Hence, no mitigation measure is required.

Evaluation of Residual Impacts

Construction Phase

3.59 With the implementation of the proposed dust suppression measures, good site practice and a comprehensive dust monitoring and audit programme, no adverse residual impact is expected.

Operation Phase

3.60 The cumulative air quality at the nearby air sensitive receivers and the air quality inside the full enclosure are predicted to comply with the relevant limits and guidelines. No adverse residual impact is expected.

Environmental Monitoring Aand Audit

Construction Phase

3.61 In view of the potential changes in the air quality during construction phase, a comprehensive dust monitoring and audit programme has been recommended to verify the effectiveness of the proposed measures. 1-hour and 24-hour TSP levels should be measured to indicate the impacts of the construction dust on local air quality. Details of the monitoring requirements such as frequency of baseline and impact monitoring are presented in the EM&A Manual.

Operation Phase

3.62 Since no exceedance of AQOs is predicted at all representative ASRs during operation phase, environmental monitoring and audit is not required.

3.63 For the air quality within the two proposed full enclosures at Castle Peak Road, no exceedance of Tunnel Air Quality Criteria is expected. Hence, no environmental monitoring and audit is required.

Conclusion

Construction Phase

3.64 Without mitigation measures, the 1-hour1-hour and 24-hour average TSP AQO limitconcentrations would may exceedexceed the TSP guideline level and AQO at some representative receivers. Hence, dust suppression measures are considered necessary.

3.65 By watering the actively worked areas twice per day to ensure the work site and dust materials in a wet condition, no adversever cumulative dust impact is predicted at the representative ASRs.

the exposed construction area entirely, it would be effectively reduced the fugitive dust generated from wind erosion.

3.65

3.1 Implementation of the suggested dust suppression measures in the proposed Air Pollution Control (Construction Dust) Regulation, good site practices and a comprehensive dust monitoring and audit programme are essential to minimize dust impact.

3.66 A comprehensive dust monitoring dust monitoring and audit programme is also recommended in order to maintain a satisfactory air quality throughout the construction period.

Operation Phase

3.67 No exceedance of the AQOs is predicted at all representative ASRs during the operation phase. Therefore, no mitigation measures are required.

3.68 The tunnel air quality within the two full enclosures recommended for the proposed Castle Peak Road would comply with the Tunnel Air Quality Criteria. Hence, no mitigation measures are required.

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⁽1⁾ Ohashi H. and T. Koso, Longitudinal Diffusion of Exhaust Pollutants in Two-way Automobile Tunnels, International Symposium on the Aerodynamics & Ventilation of Vehicle Tunnels, 1995