3.1.1. This section presents the assessment on the potential air impacts that are likely to be generated during the construction phase of the Project. Appropriate mitigation measures have been identified to mitigate the potential air quality impacts as far as practicable.

3.2 Relevant Legislations, Standards & Guidelines

3.2.1. The principal legislation for the management of air quality in Hong Kong is the Air Pollution Control Ordinance (APCO) (Cap. 311). The APCO provides a statutory framework for establishing the Air Quality Objectives (AQOs) and stipulating the control requirements for air pollution sources. The AQOs have been defined for seven pollutants and are given in Table 3-1 below. It stipulates the statutory limits of air pollutants and the maximum allowable numbers of exceedance over the specific periods.

Table 3‑1 Hong Kong New Air Quality Objectives

Pollutant	Averaging time	Concentration limit ⁽¹⁾ (µg/m³)	Number of exceedances allowed
Nitrogen dioxide (NO₂)	1-hour	200	18
Nitrogen dioxide (NO₂)	Annual	40	Not applicable
Sulphur dioxide (SO₂)	10-minute	500	3
Sulphur dioxide (SO₂)	24-hour	125	3
Respirable suspended particulates (PM10) ⁽²⁾	24-hour	100	9
Respirable suspended particulates (PM10) ⁽²⁾	Annual	50	Not applicable
Fine suspended particulates (PM2.5) ⁽³⁾	24-hour	75	9
Fine suspended particulates (PM2.5) ⁽³⁾	Annual	35	Not applicable
Ozone (O₃)	8-hour	160	9
Carbon monoxide (CO)	1-hour	30,000	0
Carbon monoxide (CO)	8-hour	10,000	0
Lead	Annual	0.5	Not applicable

Notes:

(1) All measurements of the concentration of gaseous air pollutants, i.e., sulphur dioxide, nitrogen dioxide, ozone and carbon monoxide, are to be adjusted to a reference temperature of 293Kelvin (K) and a reference pressure of 101.325 kilopascal (kPa).

(2) Respirable suspended particulates means suspended particles in air with a nominal aerodynamic diameter of 10 µm or less.

(3) Fine suspended particulates means suspended particles in air with a nominal aerodynamic diameter of 2.5 µm or less.

3.2.2. Annex 4 of Technical Memorandum on Environment Impact Assessment Process (EIAO-TM) stipulates the hourly Total Suspended Particulates (TSP) concentration of 500 µg/m³ measured at 298 K and 101.25 kPa (one atmosphere) for construction dust impact assessment.

Air Pollution Control (Construction Dust) Regulation

3.2.3. The Air Pollution Control (Construction Dust) Regulation specifies processes that require special dust control. The Contractor is required to inform the Environmental Protection Department (EPD) and adopt proper dust suppression measures while carrying out “Notifiable Works” and “Regulatory Works” to meet the requirements as defined under the regulation.

Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation

3.2.4. The Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation comes into effect on 1 June 2015. Under the Regulation, Non-road mobile machinery (NRMM), except those exempted, are required to comply with the prescribed emission standards. From 1 September 2015, all regulated machines sold or leased for use in Hong Kong must be approved or exempted with a proper label in a prescribed format issued by EPD. Starting from 1 December 2015, only approved or exempted NRMMs with a proper label are allowed to be used in specified activities and locations including construction sites. The Contractor is required to ensure the adopted machines or non-road vehicle under the Project could meet the prescribed emission standards and requirement.

3.3 Baseline Environmental Conditions

3.3.1. There are both highly urbanized and village/rural areas in Yuen Long. The proposed drainage improvement works at the four villages are located in the village/rural areas. The EPD’s Yuen Long Air Quality Monitoring Station is located in the urban areas (at Yuen Long District Office, 269 Castle Peak Road) and is considered nearest to the proposed drainage improvement works at these four villages. The baseline air quality monitoring results for 2015-2019 are shown in Table 3‑2.

Table 3‑2 Air Quality Monitoring Data (Yuen Long station, Year 2015-2019)

Pollutant	Averaging Time	Pollutants Concentrations (µg/m³)						5-year Average Concentration (µg/m³)
Pollutant	Averaging Time	2015	2016	2017	2018	2019
NO₂	19^th highest 1-hour	162	149	156	150	161	156
NO₂	Annual	45	46	41	43	44	44
SO₂	4^th highest 10-minute	51	58	80	52	42	57
SO₂	4^th highest 24-hour	17	17	20	16	11	16
PM₁₀	10^th highest 24-hour	102	86	87	75	83	87
PM₁₀	Annual	44	37	40	37	37	39
PM_2.5	10^th highest 24-hour	78	63	52	46	45	57
PM_2.5	Annual	30	23	22	20	20	23
O₃	10^th highest 8-hour	161	143	175	162	200	168
CO	1-hour	2460	2080	1450	1720	2150	1972
CO	8-hour	2143	1474	1324	1574	1903	1684

Note:

(1) Data extracted from the EPD’s “Air Quality in Hong Kong” (2015 – 2019).

(2) Monitoring results exceeding the AQO are bolded and underlined.

3.3.2. Monitoring records of SO₂ and CO indicated that these two pollutants were in relatively low level. Both pollutants were well within the AQOs.

3.3.3. Table 3‑2 indicates that the annual average concentration of NO₂ from Year 2015 to 2019 exceed the AQO criteria. The 8-hour average O₃ concentrations from Year 2014 to 2019 also exceed the criterion except Year 2016. The 10^th highest daily PM₁₀ concentration exceeds the criterion in Year 2015 only. Similarly, the 10^th highest daily PM_2.5concentration exceeds the criterion in Year 2015 only. The high levels of PM₁₀ and PM_2.5are possibly due to the regional air quality problem around the Pearl River Delta Regions and local road emission from heavy vehicles also contributes to the high levels of NO₂, PM₁₀ and PM_2.5concentrations.

3.4 Future Air Quality Conditions

3.4.1. With reference to Section 2, the year for commissioning of the Project is in 2022. In order to predict the future ambient air quality taking into account the measures to improve air quality, PATH-2016 (Pollutants in the Atmosphere and their Transport over Hong Kong), a regional air quality model, has been developed by EPD to simulate air quality over Hong Kong. The result of PATH-2016 in Year 2020 is adopted.

3.4.2. The 500m assessment area involves 20 grid cells at these four villages in PATH-2016. The pollutant concentrations prediction by PATH-2016 in Year 2020 are summarized in Table 3‑3 and the location of concerned PATH-2016 grids is illustrated in Appendix 3-1.

3.4.3. It could be seen from Table 3‑3, the background concentrations in the relevant PATH grids in 2020 are well below the relevant AQO criteria, except for an exceedance of the 8-hour O₃ criterion in PATH grids in Ha Che (i.e. (32,47), (32,48), (33,47) and (33,48)).

Table 3‑3 Air Pollutants Concentrations in 2020 Predicted from PATH-2016 Model

Location	PATH Grid	Concentration Pollutants (µg/m³)
		NO₂		SO₂		PM₁₀		PM_2.5		O₃	CO
		19^th highest 1-hour	Annual	4^th highest 24-hour	4^th highest 10-mins	10^th highest 24-hour	Annual	10^th highest 24-hour	Annual	10^th highest Daily Max. 8-hour	Daily Max 1-hour	Daily Max 8-hour
Sung Shan New Village	(26,44)	106.5	16.9	24.8	202.1	81.1	35.1	60.8	24.9	154.1	1000.8	892.3
	(26,45)	103.3	16.6	25.0	203.4	81.5	34.9	61.1	24.8	155.9	1004.7	899.3
	(27,44)	103.1	15.3	24.7	202.1	83.5	36	62.6	25.6	155.3	999.9	863.4
	(27,45)	93.8	14.8	24.8	204.1	83.2	35.3	62.4	25.1	155.6	1003.6	884.1
Tai Wo	(29,43)	85.3	13.3	24.7	199.9	81.5	35.1	61.1	24.9	154.3	985.7	818.6
	(29,44)	84.0	13.3	24.7	199.2	82.8	35.4	62.1	25.1	152.6	987.9	818.9
	(30,43)	84.3	12.7	24.8	200.2	79.7	34.7	59.8	24.6	154.9	980.5	816.9
	(30,44)	82.0	12.9	24.8	198.2	80.8	34.5	60.6	24.5	151.9	978.7	813.7
	(31,44)	81.7	12.2	24.5	213.2	79.1	33.7	59.3	23.9	153.3	978.2	815.4
Lin Fa Tei	(30,45)	81.5	13.2	24.8	199.2	79.7	34.4	59.8	24.4	153.9	987.2	819.4
	(31,44)	81.7	12.2	24.5	213.2	79.1	33.7	59.3	23.9	153.3	978.2	815.4
	(31,45)	81.4	12.4	24.0	196.7	77.8	33.5	58.4	23.8	153.2	979.8	814.7
	(31,46)	82.4	12.0	23.9	191.1	78.6	33.4	59.0	23.7	155.6	988.3	824.0
	(32,44)	84.4	11.7	23.3	202.9	76.2	32.3	57.2	22.9	153.1	988.8	824.4
	(32,45)	78.0	11.3	22.7	201.1	75.5	32.3	56.6	22.9	156.5	981.3	818.7
	(32,46)	66.3	11.3	22.8	201.1	78.2	32.5	58.7	23.1	158.5	985.4	819.1
Ha Che	(32,47)	63.0	11.1	22.8	203.1	79.38	33.3	59.5	23.6	161.8	995.4	826.6
	(32,48)	61.4	11.1	22.7	205.8	83	35	62.3	24.9	160.5	1006.1	837.9
	(33,47)	57.4	11.0	22.9	200.9	79.5	33.5	59.6	23.8	160.7	988.54	817.7
	(33,48)	59.4	11.2	22.9	204.1	78.4	33.7	58.8	23.9	161.3	1002.8	831.2
AQOs (µg/m³)		200 (18)	40	125(3)	500(3)	100(9)	50	75(9)	35	160(9)	30,000	10,000

Notes:

(1) Values in ( ) mean the number of exceedances allowed per year.

(2) Underlined values indicate an exceedance of the HKAQO.

(3) PM_2.5is not available from PATH model outputs, 24-hour average PM_2.5and annual average PM_2.5 estimated by 0.75 x PM₁₀ and 0.71 x PM₁₀ respectively with reference to Guidelines on the Estimation of PM_2.5 for Air Quality Assessment in Hong Kong.

(4) With reference to EPD’s Guidelines on Choice of Models and Model Parameters, PATH-2016’s output of RSP concentration are adjusted by adding 26.5µg/m3 for 10th highest daily RSP concentration and adding 15.6µg/m3 for annual RSP concentration.

(5) The most conservative conversion factor of 2.45 (Stability A class) was applied to SO₂ concentration to estimate 10-minute SO₂ concentrations.

Sung Shan New Village

3.4.4. The proposed works area is located within Sung Shan New Village and Tong Tau Po Tsuen. The surrounding land uses comprise village houses, temporary structures, open storage areas, vehicle repairing areas, offices and workshops. A soy sauce factory is located on the northern part of the proposed works area. The existing air quality in the proposed works area is primarily influenced by the vehicular emissions from village access road and Tai Shu Ha Road East, chimney emission from the soy sauce factory and construction dust emission from the nearby construction sites.

Tai Wo

3.4.5. The proposed works area is located within Cheung Po and Tai Wo. The surrounding land uses comprise village houses, open car parking areas, playground and agricultural lands. MTR Corporation Pat Heung Depot and Kam Ho Road (classified as a “rural road” according to the Annual Average Daily Traffic (AADT) Census 2017) are located in close proximity to the proposed drainage improvement works alignment at Cheung Po. The existing air quality in the proposed works area is primarily influenced by the vehicular emissions from Kam Ho Road and construction dust emissions from the nearby construction sites.

Lin Fa Tei

3.4.6. The land uses in the vicinity of the proposed works area at this village are low rise residential buildings, car parking area, open storage areas and car scrapyard. Kam Sheung Road (classified as a “rural road” according to the AADT Census 2017) runs to the northern portion of the proposed works area. The existing air quality in the proposed works area is primarily influenced by the vehicular emissions from Kam Sheung Road, Kam Shui Road and village access road and construction dust emissions from the nearby construction sites.

Ha Che

3.4.7. The proposed works area is located within Sheung Che Tsuen, Chuk Hang and A Kung Tin. The major land uses in the vicinity of the proposed works area are low rise residential buildings, temporary structures, open storage areas and workshops. Fan Kam Road (classified as a “rural road” according to the AADT Census 2017) runs crossing the proposed works area. The existing air quality in the proposed works area is primarily influenced by the vehicular emissions from Fan Kam Road and construction dust emissions from the nearby construction sites.

3.5 Study Area and Air Sensitive Receivers

3.5.1. The Study Area for air quality assessment covers all areas within 500 m from the proposed drainage improvement works site boundary. Representative air sensitive receivers (ASRs) within 500 m Study Area have been identified according to the criteria set out in Annex 12 of the EIAO-TM, observations from site visits and review of the latest approved Outline Zoning Plans (OZPs) including OZP No. S/YL-TT/17 (Tai Tong), S/YL-KTS/15 (Kam Tin South), S/YL-SK/9 (Skek Kong) and S/YL-PH/11 (Pat Heung) and information available in the Statutory Planning Portal of Town Planning Board. The representative ASRs are summarized in Table 3‑4 and their locations are shown in Figures 3.1 to 3.5.

Table 3‑4 Representative Air Sensitive Receivers

ASR ID	Description of ASRs	Nature of Use	Approximate Shortest Horizontal Distance from Proposed Works Area (m)	Approximate ground level of ASRs (mPD)
Sung Shan New Village
SSNV 1	#88A, Yau Cha Po	Residential	12	13.6
SSNV 2	Village house next to a nullah in Tong Tai Po Tsuen (near DD118 1720 S.A)	Residential	2	13.3
SSNV 3	Village house near a soy sauce factory in Sung Shan New Village (near DD118 1712)	Residential	2	13.4
SSNV 4	#25, Sung Shan New Village	Residential	30	14.4
SSNV 5	#43, Sung Shan New Village	Residential	19	14.4
SSNV 6	Village house next to a track in Sung Shan New Village (DD118 Lot. 1767)	Residential	36	17.5
Tai Wo
TW 1	Temporary structure near footbridge in Cheung Po (DD113 Lot. 1542)	Residential	15	15.4
TW 2	#200, Cheung Po	Residential	36	17.3
TW 3	#3H, Kai Yip Garden, Tai Wo	Residential	50	20.6
TW 4	#40B Tai Wo	Residential	37	21.8
Lin Fa Tei
LFT 1	#2G, Lin Fa Tei	Residential	6	23.7
LFT 2	Temporary building next to a nullah in Lin Fa Tei (DD112 Lot. 964)	Residential	3	25.2
LFT 3	#125, Lin Fa Tei	Residential	<1	19.4
LFT 4	#156A, Lin Fa Tei	Residential	4	19.2
LFT 5	#47, Shui Tsan Tin	Residential	6	18.0
LFT 6	Village house near a nullah and Kam Sheung Road (DD112 Lot. 679 S.C.)	Residential	1	18.2
LFT 7	Moon Wo Grand Houses, #510, Lin Fa Tei	Residential	14	18.6
LFT 8	#210, Ngau Keng	Residential	4	20.1
LFT 9	#231C, Lin Fa Tei	Residential	2	19.3
LFT10	Shui Tsan Tin Village Office	Office	3	16.9
Ha Che
HC 1	#149, Chuk Hang	Residential	10	23.4
HC 2	Block N, Fu Hing Garden, #88, Sheung Che	Residential	1	21.5
HC 3	#1C, Chuk Hang	Residential	1	23.2
HC 4	#300 Sheung Che	Residential	3	23.6
HC 5	The Arbutus House 1, #51, Shui Kan Shek	Residential	25	25.4
HC 6	The Arbutus House 12, #51, Shui Kan Shek	Residential	4	27.1
HC 7	Sheung Ha Che Sport Association	Recreational	<1	23.6

3.6 Assessment Methodology

3.6.1. An air quality impact assessment has been undertaken in accordance with the criteria and guidelines as stated in Annexes 4 and 12 of the Technical Memorandum on Environmental Impact Assessment Process (TM-EIAO). With consideration of the small and limited scale of the project (mainly small scale drainage channel widening and new drainage culverts), adverse construction dust impacts with incorporation of dust control measures are not anticipated. Thus, a quantitative assessment is not proposed. The relevant justifications and assessment results are presented in below sections.

3.6.2. For operational phase, no air pollution source from the Project is identified. Thus, adverse air quality impact is not anticipated. No mitigation measures are required.

3.7 Air Quality Impact Assessment

3.7.1. The project will involve drainage channel widening and construction of new drainage culverts only. Potential sources of air quality impact associated with the proposed construction activities at Sung Shan New Village, Tai Wo, Lin Fa Tei and Ha Che have been identified and these include:

· Site clearance and excavation;

· Formwork and reinforcement works;

· Handling of construction materials; and

· Wind erosion of open sites and stockpiling areas.

3.7.2. Potential impacts associated with the construction of the Project mainly include vehicular emissions (i.e. NO₂, PM₁₀ and PM_2.5) from on-site vehicles/PMEs and the fugitive dust (i.e. TSP, PM₁₀ and PM_2.5) emissions from the excavation, formwork and reinforcement, storage and handling of materials and the movements of on-site vehicles on haul roads.

3.7.3. The proposed drainage improvement works will be carried out in sections and each section is taken to be approximately 15 - 30 m. No concurrent excavation sections will be conducted within the same channel.

3.7.4. With considerations of the scale of active works areas, the proposed drainage improvement works at each active works area (each approximately 15-30m) which is programmed to take only about 3-5 weeks to complete, thus the short-term fugitive dust impacts are localized. With the implementation of the good site practices stipulated in the Air Pollution Control (Construction Dust) Regulation, fugitive dust impacts during the construction phase are expected to be controlled to acceptable level.

3.7.5. Fuel combustion from the use of on-site vehicles/Powered Mechanical Equipment (PME) during construction work would be a source of NO₂, SO₂ and CO. The air quality impacts are expected to be small and localized because it is anticipated that the scale of the proposed drainage improvement works would be small, and the number of construction equipment employed would be limited given the small work space available. According to the Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation, starting from 1 December 2015, only approved or exempted NRMMs with a proper label are allowed to be used for construction activities in construction sites. Under the Regulation, NRMMs, except those exempted, are required to comply with the prescribed emission standard. Based on the above, potential dust and gaseous impact from those construction equipment and NRMMs during the construction phase of the Project are anticipated to be minor.

3.8 Recommendation of Mitigation Measures

3.8.1. Good house-keeping and dust suppression measures should be incorporated to ensure that dust emissions are minimized during the construction phase of the Project. Relevant dust control requirements stipulated in Air Pollution Control (Construction Dust) Regulation should be implemented. These include the following:

Excavated Material and Stockpiling Areas

· Proper and regular watering should be provided for all exposed and excavated work sites.

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

· All excavated or stockpile of dusty materials should be entirely covered by impervious sheeting or sprayed with water to ensure that the entire surface is wet. They should be sprayed with water immediately prior to any loading or transfer activities. These materials should be removed, backfilled or reinstated where practicable.

· After the removal of stockpiles, the remaining dusty material should be sprayed with water and cleared from the surface of roads. Stockpiling areas of dusty materials should not be extended beyond the pedestrian barriers, fencing or traffic cones.

· At locations with proposed open excavation and reinstatement works, hoarding of not less than 2.4m from ground level should be provided along the entire length of that portion of the site boundary except for a site entrance or exit or works on public road. The Contractor should ensure that the hoardings are well maintained throughout the entire construction period.

Transport and Removal of Materials

· Vehicles used for the transportation of dusty materials/spoils should be covered with tarpaulin or similar material. The cover should extend over the edges of the sides and tailboards.

· Vehicle wheel washing facilities will be provided at exit of the works site. The areas where vehicle wheel washing activities are carried out and the section of the construction site between the vehicle washing facilities and the exit should be paved with concrete or bituminous materials.

Construction Works within Work Areas

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

· All demolished materials that may generate dust should be covered entirely by impervious sheeting or placed in a covered area with the top and three sides enclosed within a day of demolition.

· At construction works areas where demolition takes place, water or dust suppression chemicals should be sprayed prior to, during and immediately after the demolition activities to ensure that the top surface remains wet.

Site Cleanliness and Tidiness

· The requirements stipulated in the Works Branch Development Bureau Technical Circular No. 08/2010 Enhanced Specification for Site Cleanliness and Tidiness should be followed as far as practicable to enhance the cleanliness and tidiness of construction sites.

Control on NRMMs

· NRMMs should be approved or exempted with a label issued by EPD. The label should be displayed at a conspicuous position of the machine or vehicle. Non-road vehicles are required to meet the Euro V emission standards and smoke requirements as stipulated under the Air Pollution Control (Vehicle Design Standards) (Emission) Regulations.

Potential Concurrent Project

· In order to prevent potential cumulative construction air quality impacts to ASR at Fan Kam Road, the works at overlapping section are recommended to be scheduled to avoid works at the areas near Fan Kam Road.

· The Contractor shall liaise with the contractors of Agreement No. CE 61/2012 (HY) – Improvement to Fan Kam Road – Investigation so as to avoid undertaking works concurrently with the works from Agreement No. CE 61/2012 (HY) project when they are in the close proximity. As a conservative approach, proposed drainage improvement works shall be carried out when the works from the Agreement No. CE 61/2012 (HY) project is over 500m away.

3.9 Residual Impact

3.9.1. With consideration of the background environmental conditions, and the scale and nature of the Project, with the implementation of the recommended mitigation measures, adverse air quality impact is not anticipated. Therefore, no adverse residual air quality impact is anticipated.

3.10 Potential Cumulative Impact

3.10.1. As discussed in Section 2.6.1, the construction of drainage improvement works is scheduled from 2022 to 2025. In order to assess the cumulative impacts for the concurrent project as discussed in Section 2.7.1, the tentative construction program for each project site is listed in Table 3‑5.

Table 3‑5 Identified Potential Interface Project within Proximity of the Project.

Project

Name of Project

Remarks

No.1

Agreement No. CE 61/2012 (HY) - Improvement to Fan Kam Road – Investigation

(Tentative construction period: 2021 to 2025)

Project would overlap with the construction of this Project. Physical conflict identified in Ha Che Section.

Project No.1: Agreement No. CE 61/2012 (HY) – Improvement to Fan Kam Road – Investigation

3.10.2. Under Agreement No. CE 61/2012 (HY), a road improvement work is proposed to be constructed along Fan Kam Road and the certain sections will be within the 500m study area of the Project. Based on information from the website, construction works will commence in 2021 and scheduled for completion in 2025. With reference to Agreement No. CE 61/2012 (HY), the alignment of the road improvement has physical conflict with the proposed drainage improvement works (nearest works under Ha Che section). It is recommended that the Contractor for the Project shall coordinate and liaise with the contractor of the Fan Kam Road improvement project and schedule the construction works in order to minimize concurrent works at interfacing locations to be carried out under the two projects. With this arrangement in place and implementation of mitigation measure, adverse cumulative air quality impact is not anticipated.

3.11 Summary

3.11.1. Potential impacts arising from the construction of the Project are expected to be related to the dust nuisance from construction works and gaseous emissions from the construction plant and vehicles. The air quality impacts are expected to be localized because it is anticipated that the scale of the proposed drainage improvement works would be small and the number of construction equipment employed would be limited given the small work space available. With proper implementation of good site practices stipulated in the Air Pollution Control (Construction Dust) Regulation, and with the adoption of construction machineries and non-road vehicles meeting the prescribed emission standards and requirements specified in the Air Pollution Control (Non-road Mobile Machinery) (Emission) Regulation, no adverse air quality associated with the proposed drainage improvement works is anticipated. It is also anticipated that there would be no adverse impact during the operation phase.