Pollutants	Averaging Time	Concentration Limit (µg/m³)⁽¹⁾	Number of Exceedance Allowed
Respirable Suspended Particulates (PM₁₀)⁽²⁾	24-hour	100	9
Respirable Suspended Particulates (PM₁₀)⁽²⁾	Annual	50	N/A
Fine Suspended Particulates (PM_2.5)⁽³⁾	24-hour	75	9
Fine Suspended Particulates (PM_2.5)⁽³⁾	Annual	35	N/A

Notes:

(1) Measured at 293K and 101.325kPa

(2) Suspended particulates in air with a nominal aerodynamic diameter of 10µm or smaller.

(3) Suspended particulates in air with a nominal aerodynamic diameter of 2.5µm or smaller.

3.2.2.2 Apart from AQOs, the limit of hourly Total Suspended Particulates (TSP) concentration should not exceed 500 µg/m³ (measured at 25°C and one atmosphere) for construction dust impact assessment according to Annex 4 of EIAO-TM.

3.2.2.3 In accordance with Annex 4 of EIAO-TM, the limit of 5 odour units based on an averaging time of 5 seconds for odour prediction assessment should not be exceeded at any ASRs.

3.2.3 Air Pollution Control (Construction Dust) Regulation

3.2.3.1 Notifiable and regulatory works are under the control of Air Pollution Control (Construction Dust) Regulation. This Project is expected to include notifiable works (foundation and superstructure construction and demolition) and regulatory works (temporary stockpile, dusty material handling, excavation and blasting). Contractors and site agents are required to inform Environmental Protection Department (EPD) and adopt dust reduction measures to minimize dust emission, while carrying out construction works, to the acceptable level.

3.3 Description of Environment

3.3.1.1 The Project is to construct a new STW at Nui Po Shan of A Kung Kok on the southern side of Shing Mun River to replace the existing STSTW and to demolish the existing STSTW upon full operation of the relocated STSTW. The study area includes Sha Tin area and Ma On Shan area in vicinity of the relocated STSTW and the existing STSTW.

3.3.1.2 The study area in Sha Tin and Ma On Shan area is a new town area with mainly residential buildings and educational institutes. Existing air quality in the study area is affected by emissions from the existing traffic from Tolo Highway and Tate’s Cairn Highway.

3.3.1.3 The nearest EPD fixed air quality monitoring station is located at Sha Tin Government Secondary School. The annual average monitoring data recorded at EPD’s Sha Tin air quality monitoring station has shown steady trend of pollutants’ concentration in the past five years. The recent five years (2010 - 2014) annual average concentrations are summarized in Table 3.2.

Table 3.2 Average Concentrations of Pollutant in the Recent Five Years (Year 2010 – 2014) at Sha Tin EPD Air Quality Monitoring Station

Pollutant	2014	2013	2012	2011	2010	Mean
Maximum Hourly TSP Concentration (µg/m³)	N/A	136	110	161	135	135.5
Annual Average TSP Concentration (µg/m³)	N/A	57	54	66	67	61.0
10th Highest Daily Average PM₁₀ Concentration (µg/m³)	93	107	85	95	96	95.1
Annual Average PM₁₀ Concentration (µg/m³)	39	42	39	47	45	42.4
10th Highest Daily Average PM_2.5 Concentration (µg/m³)	67	85	62	N/A	N/A	71.3
Annual Average Concentration (µg/m³)PM_2.5	25	29	26	N/A	N/A	26.7

Remark:

(1) Monitoring data of TSP in 2014 is not available.

(2) 2^nd highest hourly TSP in 2010 is considered because the highest record is affected by a dust plume originated from northern part of China (Air Quality in Hong Kong 2014, HKEPD)

(3) Monitoring of Fine Suspended Particulates (FSP) commenced since Nov 2011. No monitoring data is available before 2011.

3.4 Identification of Air Sensitive Receivers

3.4.1.1 In accordance with Annex 12 of the EIAO-TM, domestic premises, hotel, hostel, hospital, clinic, nursery, temporary housing accommodation, school, educational institution, office, factory, shop, shopping centre, place of public worship, library, court of law, sports stadium or performing arts centre are considered as ASRs.

3.4.1.2 Potentially affected ASRs by construction dust arisen from the construction of relocated STSTW, emergency outfall and demolition of the existing STSTW are generally identified within 500m study boundary from the Project boundary.

3.4.1.3 Regarding operational odour impact by relocated STSTW, potentially affected ASRs are generally identified within 500m study boundary from the ventilation shaft, portal facilities and relocated STSTW site. Due to major public concern on the odour impact on the local community, ASRs outside the 500m study boundary are also identified to investigate the impact in a longer range.

3.4.1.4 The representative ASRs which would likely be affected by the construction of relocated STSTW, sewage bypass outfall, temporary explosives magazine site, and decommissioning and demolition of the existing STSTW and temporary explosives magazine site are identified and given in Table 3.3 below. Their locations are illustrated in Figure No. 60334056/EIA/3.01 and their coordinates are presented in Appendix 3.01.

Table 3.3 Representative Air Sensitive Receivers affected by Construction of Relocated STSTW and Demolition of Existing STSTW

ASRs	Description	Land Use	Shortest Distance from Project Work Site Boundary	Assessment Height Above Ground (mAG)
ASR1	Chevalier Garden	Residential	225	1.5, 5, 10, up to 80 with 10m interval
ASR2	Wellborn Kindergarten	Education	95	1.5, 5, 10, 20
ASR3	Hay Nien Primary School	Education	140	1.5, 5, 10, 20, 30
ASR4	Ma On Shan Tsung Tsin Secondary School	Education	130	1.5, 5, 10, 20, 30
ASR5	Tai Shui Hang Village	Residential	240	1.5, 5, 10
ASR6	Block H, Kam Tai Court	Residential	95	1.5, 5, 10, up to 120 with 10m interval
ASR7	S.K.H. Ma On Shan Holy Spirit Primary School	Education	110	1.5, 5, 10, 20, 30
ASR8	Ah Kung Kok Fishermen Village	Residential/Retail	170	1.5, 5, 10
ASR9	China Hong Kong Mountaineering and Climbing Union	Societal/Storage	375	1.5, 5, 10
ASR10	Breakthrough Youth Village	Religion/Charity	360	1.5, 5, 10, 20, 30
ASR11	Cheshire Home Sha Tin	Hospital	475	1.5, 5, 10, 20
ASR12	The Neighbourhood Advice-Action Council Harmony Manor	Mental Health Hospital	70	1.5, 5, 10, 20
ASR13	Shing Mun Springs Rehabilitation Centre	Rehabilitation Centre	100	1.5, 5, 10, 20
ASR14	Mui Tsz Lam Village	Residential	1110	1.5, 5, 10
ASR15	Ma On Shan Park / Promenade	Recreational Use	55	1.5
ASR16	Block F, Kam Tai Court	Residential	165	1.5, 5, 10, up to 120 with 10m interval
ASR17	Sausalito	Residential	390	1.5, 5, 10, up to 90 with 10m interval
ASR18	Ocean View	Residential	450	1.5, 5, 10, up to 100 with 10m interval
ASR19	Marine Police Outer Waters District Headquarters and Marine Police North Police Station	Government Office	70	1.5, 5, 10, 20
ASR20	Ah Kung Kok Fishermen Village	Residential/Retail	390	1.5, 5, 10
ASR21	Seaview Villa	Residential	160	1.5, 5, 10
ASR22	Racecourse Gardens	Residential	260	1.5, 5, 10, up to 50 with 10m interval

3.4.1.5 The representative ASRs which would likely be affected by potential operational odour impact from relocated STSTW have been identified and are given in Table 3.4 below. Their locations are illustrated in Figure No. 60334056/EIA/3.02 and their coordinates are presented in Appendix 3.01.

Table 3.4 Representative Air Sensitive Receivers in the vicinity of Relocated STSTW for Operational Odour Impact Assessment

ASRs	Description	Land Use	Shortest Distance from the Ventilation Shaft/Portal /Caverns (m)	Assessment Height Above Ground (mAG)
ASR1	Chevalier Garden	Residential	810	1.5, 5, 10, up to 80 with 10m interval
ASR1a	Chevalier Garden (Block 17)	Residential	800	1.5, 5, 10, up to 80 with 10m interval
ASR1b	Chevalier Garden (Block 6)	Residential	870	1.5, 5, 10, up to 70 with 10m interval
ASR1c	Chevalier Garden (Block 1)	Residential	810	1.5, 5, 10, up to 70 with 10m interval
ASR2	Wellborn Kindergarten	Education	800	1.5, 5, 10, 20
ASR3	Hay Nien Primary School	Education	940	1.5, 5, 10, 20, 30
ASR4	Ma On Shan Tsung Tsin Secondary School	Education	970	1.5, 5, 10, 20, 30
ASR5	Tai Shui Hang Village	Residential	1000	1.5, 5, 10
ASR6	Block H, Kam Tai Court	Residential	1100	1.5, 5, 10, up to 120 with 10m interval
ASR7	S.K.H. Ma On Shan Holy Spirit Primary School	Education	1130	1.5, 5, 10, 20, 30
ASR8	Ah Kung Kok Fishermen Village	Residential/Retail	800	1.5, 5, 10
ASR9	China Hong Kong Mountaineering and Climbing Union	Societal/Storage	800	1.5, 5, 10
ASR10	Breakthrough Youth Village	Religion/Charity	420	1.5, 5, 10, 20, 30
ASR11	Cheshire Home Sha Tin	Hospital	530	1.5, 5, 10, 20
ASR12	The Neighbourhood Advice-Action Council Harmony Manor	Mental Health Hospital	320	1.5, 5, 10, 20
ASR13	Shing Mun Springs Rehabilitation Centre	Rehabilitation Centre	420	1.5, 5, 10, 20
ASR14	Mui Tsz Lam Village	Residential	1360	1.5, 5, 10
ASR15	Ma On Shan Park / Promenade	Recreational Use	1180	1.5
ASR16	Block F, Kam Tai Court	Residential	1200	1.5, 5, 10, up to 120 with 10m interval
ASR17	Sausalito	Residential	1650	1.5, 5, 10, up to 90 with 10m interval
ASR18	Ocean View	Residential	1970	1.5, 5, 10, up to 100 with 10m interval
ASR19	Marine Police Outer Waters District Headquarters and Marine Police North Police Station	Government Office	1720	1.5, 5, 10, 20
ASR20	Ah Kung Kok Fishermen Village	Residential	800	1.5, 5, 10
ASR21	Seaview Villa	Residential	1730	1.5, 5, 10
ASR22	Racecourse Gardens	Residential	1610	1.5, 5, 10, up to 50 with 10m interval
ASR23	Pictoria Garden	Residential	1230	1.5, 5, 10, up to 70 with 10m interval
ASR24	Kam On Garden	Residential	1860	1.5, 5, 10
ASR25	Royal Ascot	Residential	1950	1.5, 5, 10, up to 120 with 10m interval
ASR26	Sha Tin Hospital	Hospital	900	1.5, 5, 10, up to 40 with 10m interval
ASR27	Garden Vista	Residential	1240	1.5, 5, 10, up to 80 with 10m interval
ASR28	Topsail Plaza	Industrial	1020	1.5, 5, 10, up to 50 with 10m interval
ASR29	Hong Kong Baptist University Affiliated School Wong Kam Fai Secondary School	Education	1020	1.5, 5, 10, up to 50 with 10m interval
ASR30	The Castello	Residential	1050	1.5, 5, 10, up to 120 with 10m interval
ASR31	Planned ASR at existing STSTW site	Residential & Recreational	1400	1.5, 5, 10, up to 120 with 10m interval

3.5 Identification of Pollutant Sources

3.5.1 Construction Phase

3.5.1.1 The identified potential air quality impacts during construction phase of the relocation of STSTW (including water reclamation facilities) would arise from fugitive dust emissions generated by various construction activities, including excavation, rock crushing, blasting operation, portal construction, material handling, transportation and removal, construction trucks, stockpiling, wind erosion etc, at all land-based works areas including the existing and relocated STSTW, accesses to and from the relocated STSTW and temporary stockpile area at Area 73. A temporary explosives magazine site would also be provided at A Kung Kok Shan. Potential dust emission would be generated from construction of this temporary explosives magazine including construction of access road from A Kung Kok Shan Road to this temporary magazine site, site formation and construction of explosives compound structures. Once the construction works for the relocated STSTW is completed, the temporary explosives magazine site would be decommissioned but it is expected limited dust impact generated from demolition of the explosives compound structures and the affected period would be last for a week.

3.5.1.2 The rock crusher will be situated inside the cavern and is configured as an enclosed system with dust collector. Rocks would be transported from the drill and blast area within the cavern to the rock crusher by trucks. The trucks would unload the rocks to the feed hopper with water spraying. Dust collection will be provided at the exhaust of the enclosed system to suppress the dust emission during rock crushing. Its performance will be assured by regular inspection and adequate stock of spare parts. The crushed rocks will be conveyed via enclosed belt system to temporary stockpile before transferred to trucks. Water spray will be provided at conveyor belt and temporary stockpile to maintain the crushed products in wet condition.

3.5.1.3 The existing STSTW will be decommissioned after the relocated STSTW is in full operation. The demolition of the facilities in the existing STSTW will be started after decommissioning. All the tanks / sludge will be cleaned before demolition. Therefore, odour emission is unlikely arise from construction of the Project.

3.5.1.4 Some of the buildings at the existing STSTW have been built over 40 years. Asbestos containing materials (ACM) may be found in these old buildings. As the existing STSTW is still in operation, asbestos survey on these buildings is not available at the time of this assessment. It is proposed that the asbestos investigations shall be conducted by registered asbestos consultants before the decommissioning of existing STSTW. If any ACM is identified, the asbestos consultant shall formulate overall asbestos management and abatement strategies. The removal and disposal of the ACM shall be conducted by registered asbestos contractor following the Air Pollution Control (Asbestos) (Administration) Regulation.

Identification of Key Air Pollutants of Emission from Construction Activities

3.5.1.5 As mentioned above, major construction activities with significant particulate emission include foundation work, superstructure construction, temporary stockpiling, dust material handling, excavation, rock crushing and concrete production, as well as demolition of existing STSTW facilities. On-site use of diesel powered engines is the potential source for other gaseous pollutants such as nitrogen dioxide (NO₂) and sulphur dioxide (SO₂) and smoke. However, the number of such equipment required on-site will be limited and under normal operation. Equipment with proper maintenance is unlikely to cause significant smoke and gaseous emissions. Thus particulates from construction activities would be the major air pollutant during construction phase. According to Annex 4 of the EIAO-TM, TSP is the criteria pollutant for construction dust impact assessment. Quantitative assessment of TSP emission impact as well as other particulates PM₁₀ and PM_2.5 stipulated in AQOs is conducted for assessing construction dust impact due to the Project.

3.5.2 Operation Phase

3.5.2.1 The potential odour impacts on the neighbour ASRs would be the major air quality concerns during the operation of the relocated STSTW. It is anticipated that the relocation of the existing STSTW into caverns would allow effective control of odour arising from the sewage treatment process and would significantly reduce the potential odour impacts. All treatment units with potential odour emission will be covered and the exhausted air will be conveyed to the deodourizer for treatment before discharge to the environment via ventilation shaft. The potential odour source during the operation phase of the relocated STSTW would therefore be the ventilation shaft.

3.5.2.2 In order to provide proper odour control and treatment before discharge to the ambient, four sets of deodourization unit would be installed at 4 different locations of the relocated STSTW for treating odorous gas collected from preliminary and primary treatment processes, sludge treatment process, UV disinfection process, secondary treatment and liquid-solid separation processes.

3.5.2.3 These deodourization units adopted long proven deodorization technologies, i.e. biotrickling and activate carbon absorption that are commonly adopted in STW including the existing STSTW. The scattered and localized odour treatment provision would minimize the risk of total system failure if only one centralized odour treatment facility is provided. In order to achieve high level of system reliability and redundancy, power source to the deodourization units would be in dual feed and dual ring arrangement from two separate CLP Power Hong Kong Ltd. (CLP) substations. Further, at least one standby of odour extraction fan, biotrickling filter or activated carbon filter would be provided for each set of the deodourization unit.

3.5.2.4 As the relocated STSTW will receive same catchment as the existing STSTW, it is anticipated that influent quality will remain the same. With the alike influent quality and design treatment capacity, similar treatment technologies will be adopted for the relocated STSTW that includes preliminary treatment, primary treatment, biological treatment, solid-liquid separation and UV disinfection.

3.5.2.5 The water reclamation facilities including membrane filtration and/or reverse osmosis as mentioned in Section 2.5.1.2 at the relocated STSTW would not generate any aerial emission in the process, therefore, no air quality impact is anticipated from operation of the water reclamation facilities.

3.5.2.6 It is expected that the proposed relocated STSTW would induce a very slight increase in off-site traffic (about 25 nos. of dewatered sludge tankers per day) near Nui Po Shan. The type of dewatered sludge tankers is proposed to adopt Euro VI type vehicle. In view of minimal traffic flow and lower emissions from the vehicles, negligible off-site road traffic emission impact on the roadside ASRs due to small amount of induced traffic would be expected. In order to minimise the odour impact, the loading and unloading activities will be conducted at the plant in cavern. The loading/unloading bay will be properly vented to deodourization unit for treatment before release to the ambient. The dewatered sludge tankers would be manufactured and fabricated in accordance to the design intends. All the tankers would be required to conduct water test and smoke test to validate its performance.

3.5.2.7 The odour impact from sludge transfer tanks could be controlled by properly design and good cleaning practices of the sludge transfer tanks. The loading of sludge transfer tank is the potential odour source during the transportation when there are gaps between the tank opening and its cover. Sludge tanks with totally enclosed design should be deployed for transporting sludge. With thorough cleaning practice and regular condition test of the sludge tanks, odour emission and leachate leakage during storage and transportation would not pose a concern.

Identification of Key Air Pollutants of Emission from Operation Activities

3.5.2.8 The odour emission releasing via the ventilation shaft would be the major pollutant due to the operation of relocated STSTW, and therefore, quantitative assessment of odour impact is conducted. In view of minor induced traffic from operation of relocated STSTW, vehicular emission due to off-site traffic would be negligible.

3.6 Assessment Methodology

3.6.1 Construction Phase

Emission Inventory

3.6.1.1 According to “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts”, three components of contribution should be considered in evaluating the air quality impact due to the Project upon ASRs, namely primary, secondary and background contributions.

Primary Contributions

3.6.1.2 Primary contributions are the project-induced emission which contributes to the local air quality impact. Thus, construction dust emission associated with the construction works of the Project is the primary contributions during the construction phase.

3.6.1.3 Construction activities with significant particulate emission are identified from the construction method suggested by engineering design. Construction dust emission rate are estimated based on emission factors of US Environmental Protection Agency (USEPA) Compilation of Air Pollution Emission Factors (AP-42), 5th edition and activity data from the engineer design. The major dust emitting construction activities for the Project considered in the modelling assessment include:

(a) Drill & Blast for Cavern, Main Access Tunnel / Secondary Access Tunnel

· Excavation and material handling within the construction site modelled as heavy construction activities;

· Wind erosion of open active area; and

· Rock crusher with loading, crushing and screening.

(b) Construction of Temporary Haul Road / Access Road, Explosives Compound Structures

· Excavation and material handling within the construction site modelled as heavy construction activities; and

· Wind erosion of open active area.

· Stockpiling and material handling within the construction site modelled as heavy construction activities; and

· Wind erosion of open active area.

(d) Demolition of existing STSTW and Explosives Compound Structures

· Concrete breaking and material handling within the construction site modelled as heavy construction activities; and

· Wind erosion of open active area.

3.6.1.4 The dust control measures have been incorporated into the design of rock crusher, as presented Table 3.5. A schematic diagram of a rock crushing plant inside cavern is presented in Appendix 3.02a. These dust control measures of construction activities are taken into account in the estimation of dust emission.

Table 3.5 Rock Crushing Operation with Dust Control Measures

Process	Description	Dust Control Measure
Rock Crusher
Unloading, Screening and Crushing	Unloading from trucks, screening and crushing	· The rock crushing plant is configured as an enclosed system with dust collector. · Dust collector will be provided at the exhaust of the rock during rock crushing. Assume typical dust removal efficiency at 99%. · Watering will be provided to maintain material in wet condition.
Trucks	Vehicle leaving the works area	· Vehicles would be required to pass through the wheel washing facilities provided at site exit.

3.6.1.5 Activity data including excavation rate, material handling rate, percentage active area, moisture content, silt content, number of construction trucks and truck speed are based on the preliminary engineering design. The emission factors for identified dust sources are summarized in Table 3.6. The detailed calculation of dust emission rates and the justification for the percentage active area of construction work sites are presented in Appendix 3.02a, b, c and e.

Table 3.6 Emission Factor for Dust Emitting Construction Activity

Emission Source	Activity	Emission Factor	Remarks
Portal Exhaust from the Cavern and Tunnel	Heavy Construction Activities	E = 2.69 Mg/hectare/month of activity (TSP)	100% area actively operating (for short-term concentration prediction) 10% area actively operating (for annual concentration prediction) AP-42, Section 13.2.3, 1/95 ed.
	Loading Point of Rock Crusher within Cavern	E = 8.00E-06 kg/Mg (PM₁₀)	100% actively operating AP-42, 5th ed. 8/04 ed., Section 11.19.2, Table 11.19.2-1
		TSP-to-RSP factor = 2.1	TSP-to-RSP Factor Response to Comment, February 23, 2004 draft, AP-42 Section 11.19.2
	Crushing by Rock Crusher within Cavern	E = 2.70E-03 kg/Mg (TSP)	100% actively operating AP-42, 5th ed. 8/04 ed., Section 11.19.2, Table 11.19.2-1
		E = 1.20E-03 kg/Mg (PM₁₀)	AP-42, 5th ed. 8/04 ed., Section11.19.2, Table 11.19.2-1
		E = 1.20E-03 kg/Mg (PM_2.5)	Adopt PM₁₀ Emission Factor as upper bound
	Screening by Rock Crusher within Cavern	E = 1.80E-03 kg/Mg (TSP)	100% actively operating AP-42, 5th ed. 8/04 ed., Section11.19.2, Table 11.19.2-1
		E = 1.10E-03 kg/Mg (PM₁₀)	AP-42, 5th ed. 8/04 ed., Section11.19.2, Table 11.19.2-1
		E = 1.10E-03 kg/Mg (PM_2.5)	PM_2.5 Emission Factor Adopt PM₁₀ Emission Factor as upper bound
Construction Sites at Main Portal, Secondary Portal, A Kung Kok Shan Explosives Magazine Site, Area 73 and Unpaved Haul Road Demolition Site at Existing STSTW and Explosives Compound Structures at Magazine Site	Heavy Construction Activities	E = 2.69 Mg/hectare/month of activity (TSP)	100% area actively operating (for short-term concentration prediction) 10% area actively operating (for annual concentration prediction) AP-42, Section 13.2.3, 1/95 ed.
	Wind Erosion	E = 0.85 Mg/hectare/year (TSP)	100% area actively operating (for short-term concentration prediction) 10% area actively operating (for annual concentration prediction) AP-42, 5th ed., Table 11.9-4

3.6.1.6 Construction dust emission factors in AP-42 would be in terms of TSP. Fractions of finer particulates are to be estimated from the TSP emission which requires the size distribution information of the concerned process, in order to compare against the AQOs. The particle size distributions of general construction processes are available in AP-42 by USEPA. Particle size distributions of general construction processes are listed in Table 3.7. Construction dust emission inventory in PM₁₀ and PM_2.5are estimated by applying the factors of associated process to TSP emission. The emission rates in TSP, PM₁₀ and PM_2.5 of each dust source are presented in Appendix 3.02d and e.

Table 3.7 Particle Size Distribution of Various Processes

Process	Cumulative % of TSP
Process	RSP	FSP	Reference
Aggregate Handling (equivalent to Heavy Construction Activities)	47.3%	7.2%	Page 13.2.4-4, Section 13.2.4, AP-42, USEPA (Version 11/06 )

3.6.1.7 For the prediction of the highest hourly average TSP, the 10th highest daily average and annual average Respirable Suspended Particulates (RSP) and Fine Suspended Particulates (FSP) concentrations, 12-hour (07:00-19:00) per normal working day is assumed for the construction period in the assessment. Since no construction activity would occur on Sundays and public holidays, only wind erosion would be assumed for these days as well as for other non-working hours (19:00 to 07:00 of the following day) on normal working days.

Secondary Contributions

3.6.1.8 Secondary contributions are the air pollutant emissions immediate neighborhood of the Project Site contributing further to the local air quality impact. Any particulates emission sources within 500m of the project boundary with notable impact shall be identified and considered in the construction phase impact assessment. The secondary contribution in particulates mainly comes from the vehicular emission in the vicinity of the Project, in particular Tolo Highway and Tate’s Cairn Highway. As mentioned in Section 2.10, the construction programme of Proposed Works for Upstream Sewerage Facilities for Relocation of STSTW would be overlapped with construction of CSTW. As reviewed, only the work site of the modification / improvement work of sewage pumping station at A Kung Kok would be located within 500m from work site of CSTW. Since this modification/improvement work would be minor and in small scale, its contribution to cumulative dust impact is anticipated to be insignificant. Sha Tin ISEPS and the rest of concurrent projects would locate more than 500m away from the major construction work of the cavern. Owing to the locality of construction dust impact, no cumulative construction dust impact due to these concurrent projects would be expected.

3.6.1.9 Based on the tentative construction programme presented in Appendix 2.03, the major construction tasks are construction of tunnels and caverns for relocated STSTW and demolition of existing STSTW. These two tasks would be carried out at different work site areas and their construction programme would not be overlapped. The worst-case year scenario of individual construction task would be assessed in this study. The construction of tunnels, caverns and its driveways will be conducted during Year 2019 – 2024. Referring to Table 7.1, the total explosive delivery trips for the tunnel main portal, the maximum number of the delivery trips would occur in Year 2022. It means that maximum rate of spoil generated from drill and blast of cavern and maximum flow of dump trucks for spoil handling from cavern to stockpile would be peak in Year 2022. Fugitive dust impact due to spoil handling and traffic of dump trucks will reach its maximum in Year 2022 together with the construction dust impact due to the cavern construction. Therefore, the worst-case year scenario for construction of tunnel and cavern for relocated STSTW considered in the assessment is Year 2022. For the demolition of existing STSTW, it will be undertaken after the commencement of relocated STSTW as early in Year 2027 and would be completed in Year 2028. Since the majority of excavation works would be conducted in Year 2027, the worst-case year scenario for demolition of existing STSTW considered in the assessment is Year 2027. Year 2022 and Year 2027 traffic forecasts are selected for calculation of vehicular emission which are adopted as the secondary contribution in dust impact during cavern construction and demolition of existing STSTW respectively. The traffic forecasts have been endorsed by Transport Department (TD). The traffic data including 24-hour traffic flow with vehicle percentage, trips, daily vehicle-kilometer-travelled (VKT), speed fraction in 16 types of vehicle for the assessment year are presented in Appendix 3.03.

3.6.1.10 Emission Factors Hong Kong Model (EMFAC-HK) version 2.6 has been adopted to estimate the vehicular emission rates of RSP and FSP for different road types, namely expressway, district distributor and local distributor. This is essential in representing the variation of vehicle emissions for different road types which has different vehicle travel speeds and vehicle compositions in local context.

3.6.1.11 The “2010 Licensed Vehicle by Age and Technology Group Fractions” provided in EPD’s website, is adopted in this assessment. Since the provided exhaust technology fractions are only up to Year 2010, those after Year 2010 are projected in accordance with EPD’s Guideline on Modelling Vehicle Emissions – Appendix 2 “Implementation Schedule of Vehicle Emission Standards in Hong Kong (Updated as at 20 December 2013)” and Appendix 3 “EMFAC-HK V2.6.0 Exhaust Technology Group Indexes”.

3.6.1.12 According to EPD’s Guideline on Modelling Vehicle Emissions - Appendix 2, the implementation schedules of Euro V and Euro VI standards are in the middle of a year for some vehicle classes or fuel types. Since the detailed fraction data is not available after Year 2010, as a conservative approach, the exhaust technology fractions of these vehicle classes or fuel types are assumed to be kept as the previous standards fully for the scheduled year, while upgraded to the higher standards fully at the following year. Evaporative technology fraction in the model is based on the default value.

3.6.1.13 As recommended in the EPD’s Guideline on Modelling Vehicle Emissions, default vehicle populations forecast in EMFAC-HK is used.

3.6.1.14 The default accrual rates in EMFAC-HK are estimated from the local mileage data adjusted to reflect the total VKT for each vehicle class. The default value has been used.

3.6.1.15 For those roads with cold starts, the diurnal variation of daily trips in the study area applied in the EMFAC-HK model is provided by the traffic team.

3.6.1.16 VKT represents the total distance travelled on a weekday. The VKT is calculated by multiplying the number of vehicle which based on the highest predicted hourly traffic flow, and the length of road travelled in the study area. The diurnal variation of VKT in the study area is provided by the traffic team, and the input in the model is by vehicle/fuel/hour.

3.6.1.17 Speed fraction represents the percentage in different speed ranges of each vehicle type weighted by VKT. The speed limits of existing road were made reference to the Traffic Aids (plan marked the road marking, traffic sign and speed limits) from TD.

3.6.1.18 The resulting hourly emissions of RSP and FSP have been divided by the number of vehicles and the distance travelled to obtain the emission factors in gram per miles per vehicle which are to be directly adopted by the air dispersion model.

3.6.1.19 All major roads within 500m study boundary, including Tolo Highway and Tate’s Cairn Highway are incorporated into the assessment as indicated in Appendix 3.04. The calculation of the composite emission rates for each road links are presented as well in the appendix.

Background Contributions

3.6.1.20 As suggested by “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts”, an integrated modelling system, Pollutants in the Atmosphere and their Transport over Hong Kong model (PATH) which is developed and maintained by EPD is applied to estimate the background pollutant concentrations. Mesoscale Model 5 (MM5) meteorological data of the same gird cell should also be adopted to drive local air quality modelling over the grid area as recommended by the guideline.

3.6.1.21 As dataset of PATH consist only the background concentration of PM₁₀, daily and annual average PM_2.5 background concentration are estimated by a factor of 0.75 and 0.71 to PM₁₀ concentration respectively, as suggested by “Guidelines on the Estimate of PM_2.5 for Air Quality Assessment in Hong Kong”.

3.6.1.22 Dataset of PATH has no TSP background either. TSP background concentration will be assumed to constitute of 100% of PM₁₀ concentration. PM₁₀ concentration from PATH is directly adopted as TSP background concentration for the assessment.

3.6.1.23 The study area covers 4 grid cells of PATH, namely grid (31, 35), (32, 34), (32, 35) and (33, 34). PATH dataset (Year 2020) of these four grid cells are adopted as the background concentration for the assessment.

Dispersion Modelling & Modelling Approach

3.6.1.24 Fugitive Dust Model (FDM) (1993 version), approved air dispersion model by EPD, is applied to assess potential primary dust impact from the construction works and secondary ones due to concurrent construction works.

3.6.1.25 California Line Source Dispersion Model, version 4 (CALINE4), the USEPA approved line source air dispersion model developed by the California Department of Transport is used to assess the secondary contribution due to vehicular emission from nearby highways.

3.6.1.26 Within 3km radius of the relocated STSTW, more than 50% of area is Shing Mun River and flat land, the land use of the study area is therefore classified as “Rural”. Sha Tin is a new development town. The surface roughness applied in the FDM model is thus taken as 100 cm according to EPD’s “Guidelines on Choice of Models and Model Parameters”.

3.6.1.27 According to “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts”, MM5 meteorological data extracted from PATH system should be used to drive the local air quality models on an hour-by-hour basis while adopting the air quality data from PATH system as background concentration. Hourly meteorological conditions including wind data, temperature and mixing heights are to be extracted from MM5 data. Hourly pasquill stability class is to be determined by PCRAMMET Meteorological Program (PCRAMMET) with input from MM5 data. No missing meteorological data is expected when adopting MM5 data. Anemometer height is assumed to be 10 metres above ground for the first layer of MM5 data as input.

3.6.1.28 Cumulative dust impact upon ASRs is derived from the sum of predictions by local air quality models and background concentration from PATH system on hour-by-hour basis. Averaging results, namely hourly, daily and annual, are derived from the cumulative hour-by-hour results in accordance with Title 40, Code of Federal Regulations (USEPA 40 CFR) Part 51 “Revision to the Guideline on Air Quality Models, Version 2005”. Cumulative average predictions at each ASR amongst 365 days are ranked in descending concentration and compared with the maximum allowable concentration to determine the number of exceedance throughout a year. The dust impact upon ASRs is evaluated by number of exceedance per annum against the AQO criteria.

3.6.1.29 Active construction activities might be undertaken at multiple works faces spreading across each site. It is not feasible to determine the exact location of individual dust emission source at a specific time. As such, for the purpose of predicting annual concentrations and in conservative approach, it is assumed that dust emissions would be distributed across the whole area of each site with all activities operating at the same time for a complete year. The dust emission rates are estimated based on the annual average percentage active works area of each works site. Based on the preliminary engineering design, the annual average active area is estimated to be 10% as presented in Appendix 3.02b and e and would be assumed for predicting the annual average concentrations. The rock crusher is considered to be working at full capacity throughout the construction period, taken as a worst-case assumption, i.e. 100% emission from the operation of the rock crusher with the dust collector with 99% dust removal efficiency is assumed in the model.

3.6.1.30 Works activities and plant would not be concentrated in certain areas of the site close to ASRs for an extended period of time during the construction period. However, notwithstanding that such a scenario would not be expected to occur, a hypothetical Tier 1 screening test assuming 100% active area of construction site of the Project with mitigation measures in place has been undertaken for predicting hourly and daily average TSP levels. It aims to highlight the hot spot locations where construction dust may potentially become an issue. However, it should be emphasized that Tier 1 screening test is a hypothetical one which is very conservative and does not occurred in reality.

3.6.1.31 The Tier 1 results have allowed a more focused Tier 2 assessment to be undertaken at the specific hot spot locations where TSP non-compliance is predicted under the Tier 1 screening test, a focused Tier 2 assessment is undertaken whereby the percentage of daily maximum active works areas, which is assumed to be 20%, for the Project are positioned closest to the potentially worst affected ASRs. The Tier 2 assessment areas are shown in Appendix 3.02b and e. Same as for predicting annual average TSP levels, 100% emission from the operation of rock crusher with the dust collector with 99% dust removal efficiency is assumed in the model.

3.6.2 Operation Phase – Odour Impact Assessment

Odour Emission Inventory

3.6.2.1 As the relocated STSTW will receive same catchment as the existing STSTW, it is anticipated that influent quality will remain the same. With the alike influent quality and design treatment capacity, similar treatment technologies will be adopted for the relocated STSTW that includes preliminary treatment, primary treatment, biological treatment, solid-liquid separation and UV disinfection. The schematic diagram of the plant layout, is referred to Section 2. The odour emission rates of sewage treatment facilities in the relocated STSTW therefore made reference to the odour emission rates of treatment facilities in the existing STSTW. Several site visits and on-site sampling were conducted in summer 2015 to identify the potential odour emission sources in the existing STSTW. The sources included inlet fine screen, open areas of inlet channel, screening skips, aerated grit channel, primary influent channel, primary sedimentation tanks, primary effluent channel, aeration tanks (anoxic and aerobic zones), final sedimentation tanks, Mixed Liquor Suspended Solid (MLSS) channel, dewatered sludge skips and digested sludge holding tanks at sludge dewatering house, influent and effluent channels of primary sedimentation tanks, Surplus Activated Sludge (SAS) holding tanks, thickened SAS holding tanks and overflow boxes of the digestion tanks.

3.6.2.2 On-site odour measurement has been conducted at the facilities of existing STSTW on 15 and 17 July 2015 to determine the odour emission rates by odour sampling and olfactometric analysis. The ambient temperature during sampling was ranged from 31 to 36 °C. The report of the odour sampling and analysis including the sampling location plan and sampling procedures is presented in Appendix 3.05. The measured odour emission rates of the sampling locations are summarized in Table 3.8. The odour emission rate adopted at each source in the relocated STSTW is presented in Table 3.9. As the sludge treatment facilities and dewatering treatment in relocated STW is different from the existing STSTW, the odour emission rate of these facilities will follow the odour emission rates from the operation of Stonecutters Island Sewage Treatment Works (SCISTW).

Table 3.8 Summary of Measured Odour Emission Rate in Existing STSTW

Location	Sample ID	Maximum Emission Rate (OU/m²/s)
Screening Skip	F2	3.83
Inlet Channel	F1	5.42
Aerated Grit Channel	F3	2.71
Primary Influent Channel	F4	3.41
Primary Sedimentation Tank	F5	2.90
Primary Effluent Channel	F6	4.82
Aeration Tank (Aerobic Zone)	F7	0.07
Aeration Tank (Anoxic Zone)	F8	0.14
Final Sedimentation Tank	F9	0.03
MLSS Channel	F10	0.02
Dewatered Sludge Skip	F12	1.14
Digester Overflow Box	A4	1.26

Odour Source in Relocated STSTW	No. of Duty Unit	Dimension of Surface (m) per unit	Total Exposed Surface Area (m²)	Corresponding Odour Source in existing STSTW	Odour Emission Rate (OU/m²/s)	Odour Control Method
Primary Treatment
Inlet Chamber	1	6.7 x 16.5	111	Inlet Channel	5.42	Covered Exposed Area + Deodourizer (DO1)
Fine Screen	4	7 x 2	56	Inlet Channel	5.42	Covered Exposed Area + Deodourizer (DO1)
Fine Screen By Pass	1	16.5 x 1.5	25	Inlet Channel	5.42	Covered Exposed Area + Deodourizer (DO1)
Fine Screen Screenings Handling Area	1	6 x 5	30	Screening Skip	3.83	Covered Exposed Area + Deodourizer (DO1)
Fine Screen Outlet Channel	1	14.2 x 4.5	64	Inlet Channel	5.42	Covered Exposed Area + Deodourizer (DO1)
Distribution Channel	1 1	26.25 x 2.5 13.5 x 7	95	Inlet Channel	5.42	Covered Exposed Area + Deodourizer (DO1)
Aerated Grit Channels	5	15 x 4	300	Aerated Grit Channel	2.71	Covered Exposed Area + Deodourizer (DO1)
Grit Handling Area	4	4.5 x 3.5	63	Screening Skip	3.83	Covered Exposed Area + Deodourizer (DO1)
Aerated Grit Channel Outlet Channel	2	17 x 2.25	77	Primary Influent Channel	3.41	Covered Exposed Area + Deodourizer (DO1)
Header Channel to Primary Sedimentation Tank	2	259 x 2	1036	Primary Influent Channel	3.41	Covered Exposed Area + Deodourizer (DO1)
Header Distribution Channel to Primary Sedimentation Tank	8 2	7.4 x 2 28 x 2.5	398	Primary Influent Channel	3.41	Covered Exposed Area + Deodourizer (DO1)
Primary Treatment
Primary Sedimentation Tank	10	51 x 9	4590	Primary Sedimentation Tank	2.90	Covered Exposed Area + Deodourizer (DO1)
Primary Sedimentation Weir	4	28 x 2	224	Primary Sedimentation Tank	2.90	Covered Exposed Area + Deodourizer (DO1)
Primary Sedimentation Tank Outlet Channel	4	15 x 2	120	Primary Effluent Channel	4.82	Covered Exposed Area + Deodourizer (DO1)
Header Channel to Biological	2	227.5 x 2	910	Primary Effluent Channel	4.82	Covered Exposed Area + Deodourizer (DO1)
Sludge Treatment ⁽¹⁾
Thickening Facilities	3	6.5 x 2	39	Stonecutter Island STW	26.42	Covered Exposed Area + Deodourizer (DO2)
Thickened Sludge Holding Tank	2	N/A	354 + 298	Stonecutter Island STW	26.42	Covered Exposed Area + Deodourizer (DO2)
Direct Dewatering Facilities	10	10 x 3.6	360	Stonecutter Island STW	26.42	Covered Exposed Area + Deodourizer (DO2)
Skip Room	10	6 x 2.4	144	Stonecutter Island STW	26.42	Covered Exposed Area + Deodourizer (DO2)
Dewatering Treatment ⁽¹⁾
Primary Sludge Holding Tank	1	18 x 9.4	169	Stonecutter Island STW	26.42	Covered Exposed Area + Deodourizer (DO3)
Thickening Centrate Tank	1	10 x 9.4	94	Stonecutter Island STW	26.42	Covered Exposed Area + Deodourizer (DO3)
Direct Dewatering Facilities	10	10 x 3.6	360	Stonecutter Island STW	26.42	Covered Exposed Area + Deodourizer (DO3)
Thickened Sludge Holding Tank	1	N/A	298	Stonecutter Island STW	26.42	Covered Exposed Area + Deodourizer (DO3)
Skip Room	10	6 x 2.4	144	Stonecutter Island STW	26.42	Covered Exposed Area + Deodourizer (DO3)
Final Treatment
UV Distribution Channel	1	10.5 x 8.1	85	Final Sedimentation Tank / MLSS Channel	0.03	Covered Exposed Area + Deodourizer (DO3)
UV	5	12.4 x 3	186	Final Sedimentation Tank / MLSS Channel	0.03	Covered Exposed Area + Deodourizer (DO3)
UV Outlet Channel	2 1	12.7 x 2.2 34.9 x 1.7	56 59	Final Sedimentation Tank / MLSS Channel	0.03	Covered Exposed Area + Deodourizer (DO3)
Secondary Treatment
Biological Tank
Header Distribution to Biological	5	117.9 x 2	1179	Aeration Tank (Anoxic Zone)	0.14	Covered Exposed Area + Deodourizer (DO4)
Anoxic Zone	35	10.2 x 13.75	4909	Aeration Tank (Anoxic Zone)	0.14	Covered Exposed Area + Deodourizer (DO4)
Aerobic Zone	35	12.1 x 13.75	5823	Aeration Tank (Aerobic Zone)	0.07	Covered Exposed Area + Deodourizer (DO4)
Biological Outlet Channel	5	144.2 x 2	1442	Aeration Tank (Anoxic Zone)	0.14	Covered Exposed Area + Deodourizer (DO4)
Header Channel to Dissolved Air Flotation (DAF)	2	226.3 x 2	905	Aeration Tank (Anoxic Zone)	0.14	Covered Exposed Area + Deodourizer (DO4)
Header Distribution to DAF	4	77.25 x 2	618	Aeration Tank (Anoxic Zone)	0.14	Covered Exposed Area + Deodourizer (DO4)
Final Treatment
DAF Units	20	8 x 11	1760	Final Sedimentation Tank / MLSS Channel	0.03	Covered Exposed Area + Deodourizer (DO4)
DAF Outlet	4	77.75 x 2	622	Final Sedimentation Tank / MLSS Channel	0.03	Covered Exposed Area + Deodourizer (DO4)
Header Channel to UV	2	233.35 x 2	933	Final Sedimentation Tank / MLSS Channel	0.03	Covered Exposed Area + Deodourizer (DO4)
Header Distribution to UV	1	9.8 x 2	20	Final Sedimentation Tank / MLSS Channel	0.03	Covered Exposed Area + Deodourizer (DO4)

3.6.2.3 All odour sources in caverns will be confined and ventilated to the deodorization units for treatment before discharge to the ambient. The odour emission rate was based on the projection of existing STSTW odour sample measurements under several rounds of Odour Survey and Stonecutters Island STW. Appropriate level of odour treatment, i.e. one or two stage(s) deodorization system will be accordingly provided for odour sources.

3.6.2.4 With reference to the “Code of Practice on Assessment and Control of Odour Nuisance from Waste Water Treatment Works, April 2005” published by the Scottish Executive, odour removal efficiency of two common odour abatement technologies, namely bio-filters and dry scrubbing (carbon or impregnated media) are of at least 95%. Therefore, for one-stage and two-stage deodorization system, the combined practicable odour removal efficiency could be up to 95% and 99.75% respectively.

3.6.2.5 However, as a more conservative approach for this assessment, odour removal efficiencies of 80% and 97% are assumed for one-stage and two-stage deodorization system respectively which is practically achievable. Table 3.10 summarizes the performance of proposed treatment technologies to be installed for specific treatment process.

Table 3.10 Summary of Required Odour Removal Efficiency for Deodorization System

Deodorization Unit	Location	Possible Treatment Technology	Odour Removal Efficiency
DO1	· Preliminary Treatment · Primary Treatment	Biotrickling Filter Plus Activated Carbon Filter	97%
DO2	· Thickening Facilities · Dewatering Facilities · Dewatered Sludge Handling Facilities · Thickened Sludge Holding Tanks	Biotrickling Filter Plus Activated Carbon Filter	97%
DO3	· Dewatering Facilities · Dewatered Sludge Handling Facilities · Centrate Holding Tank · Primary Sludge Holding Tank · Thickened Sludge Holding Tank · UV Disinfection Channels	Biotrickling Filter Plus Activated Carbon Filter	97%
DO4	· Biological Treatment · Solid-Liquid Separation	Activated Carbon Filter	80%

3.6.2.6 The processing capacity of relocated STSTW is expected to reach 280,000 m³/day upon commencement up to Year 2036 (hereafter as interim stage) and reach 340,000 m³/day from Year 2036 onward (hereafter as Ultimate Stage). With reference to the findings of odour measurement survey, the potential odour emission after deodorization treatment is estimated to be at 3,530 OU/s at interim stage and 4,420 OU/s at ultimate stage. The calculation of odour emission rates is shown in Appendix 3.06.

3.6.2.7 The ventilation shaft is proposed to be located further south of A Kung Kok Shan Road, as illustrated in Figure No. 60334056/EIA/3.02. The current configuration of the relocated STSTW includes 4 deodorization units plus 1 stand-by each for contingency, which situate close to odour sources for targeted treatment. The odour removal efficiency of three deodorization units would be 97% and one unit would be at 80%. The design parameters of the ventilation shaft are summarized in the Table 3.11. The exit temperature is assumed to be 30°C in this assessment.

Table 3.11 Design Parameter of the Ventilation Shaft

Parameter	Design Value
Base elevation	177 mPD
Height of ventilation outlet above ground surface	5 metres
Dimension (diameter in metres) of ventilation outlet	4.8 metres
Exit velocity	13.51 m/s (interim stage) 15 m/s (ultimate stage)
Operation hour	24 Hours

Dispersion Modelling & Modelling Approach

3.6.2.8 Air quality impacts of odour on the ASRs from the operation of the relocated STSTW are modelled with the air dispersion model, Industrial Sources Complex Short Term 3 (ISCST3), which is approved by EPD.

3.6.2.9 It is assumed that the proposed deodorizing units/system of relocated STSTW operate continuously on a 24-hour-per-day basis with steady state ventilation rate and exhaust gas velocity in the assessment, unless specified in the engineering design. The assessment heights are at predetermined heights above ground level according to the height of the ASRs. The contour plots of the predicted odour levels at the worst affected heights of the ASRs are produced.

3.6.2.10 Odour emission from the exhaust outlet of the deodorizer is modelled as point source in the assessment.

3.6.2.11 Within 3km radius of the relocated STSTW, more than 50% of area is Shing Mun River and flat land, the land use of the study area is therefore classified as “Rural”. Sha Tin is a new development town. The surface roughness applied in the ISCST3 model is thus taken as 100cm in according to EPD’s “Guidelines on Choice of Models and Model Parameters”.

3.6.2.12 One year valid meteorological data including wind data, stability class, ambient temperature extracted from Sha Tin meteorological station, which is located at Sha Tin Racecourse and is the nearest meteorological station to STSTW, and the mixing height data recorded at the King’s Park Weather Station are adopted for the assessment. Since the mixing data of year 2012, 2013 and 2014 are less than the EPD’s requirement of 90 percent valid data, the latest available meteorological data of year 2011 is therefore selected for modelling use in the assessment.

3.6.2.13 The modelled hourly odour concentrations at the ASRs are converted into the peak 5-second odour concentrations so as to compare with the odour criteria (5 odour units based on an averaging time of 5 seconds) stipulated in the EIAO-TM. EPD’s “Guidelines on Choice of Models and Model Parameters” recommends the methodology proposed by Duffee et al.[1]and Keddie[2] in performing the conversion from hourly to 5-second average concentration. In addition, Turner[3] has identified that the Pasquill-Gifford vertical dispersion parameter used in the ISCST3 model is around 3 to 10 minutes. As a conservative assumption, the hourly average estimated by ISCST3 model is assumed as 15 minutes, and the conversion factors for the predicted 1-hour averaged concentration of odour at the receivers would be adjusted to 5-second averaging time by the values shown in Table 3.12

Table 3.12 Conversion Factors to 5-second Mean Concentration for Point Source

Pasquill Stability Class	Conversion Factor
Pasquill Stability Class	15 min to 3 min	3 min to 5 sec	Overall
A	2.23	10	22.3
B	2.23	10	22.3
C	1.7	5	8.5
D	1.38	5	6.9
E	1.31	5	6.55
F	1.31	5	6.55

3.7 Prediction and Evaluation of Environmental Impacts

3.7.1 Construction Phase

3.7.1.1 The cumulative dust impacts due to construction of relocated STSTW and demolition of existing STSTW at the representative ASRs have been evaluated. The predicted unmitigated cumulative maximum hourly average TSP, 10^th highest daily and annual average PM₁₀ and PM_2.5 concentrations at the representative ASRs are summarized in Table 3.13 and Table 3.14

Table 3.13 Predicted Cumulative Air Pollutant Concentrations at Representative Air Sensitive Receivers (Construction of Relocated STSTW) (Unmitigated Scenario)

ASR	Assessment Height (mAG)	Cumulative Concentration (µg/m³)
ASR	Assessment Height (mAG)	Maximum Hourly TSP	10th Highest Daily PM₁₀	10th Highest Daily PM_2.5	Annual PM₁₀	Annual PM_2.5
ASR1	1.5	7575	199	64	43	30
	5	7316	201	64	43	30
	10	6233	194	62	43	30
	20	3731	172	60	43	29
	30	1910	132	59	42	29
	40	1487	104	59	41	29
	50	1092	85	58	41	29
	60	760	79	58	40	28
	70	568	77	57	40	28
	80	458	77	57	40	28
ASR2	1.5	2850	112	60	41	29
	5	2856	113	60	41	29
	10	2580	112	59	41	29
	20	1869	105	59	41	29
ASR3	1.5	9480	303	81	47	31
	5	9228	300	79	47	31
	10	7954	277	74	46	31
	20	4991	208	65	44	30
	30	2519	144	60	43	29
ASR4	1.5	14458	274	80	47	31
	5	12920	271	80	47	31
	10	9655	244	77	46	31
	20	4207	183	70	44	30
	30	2020	141	61	42	29
ASR5	1.5	4755	208	63	44	30
	5	4749	210	63	44	30
	10	4282	199	62	44	30
ASR6	1.5	10170	247	76	45	30
	5	9678	247	75	45	30
	10	7976	228	72	44	30
	20	4483	189	63	43	30
	30	1958	147	60	42	29
	40	1451	115	58	41	29
	50	1039	95	58	41	29
	60	712	81	58	40	28
	70	576	78	58	40	28
	80	460	77	57	40	28
	90	378	77	57	40	28
	100	330	77	57	40	28
	110	287	77	57	40	28
	120	248	77	57	40	28
ASR7	1.5	7460	233	73	44	30
	5	7144	233	72	44	30
	10	5910	220	69	44	30
	20	3423	180	63	43	29
	30	1720	141	59	42	29
ASR8	1.5	11785	443	118	55	34
	5	10569	432	117	54	34
	10	7896	396	110	53	34
ASR9	1.5	6587	214	77	46	31
	5	6418	214	77	46	31
	10	5525	205	75	45	31
ASR10	1.5	1968	141	64	39	27
	5	1995	143	63	39	27
	10	1834	141	63	39	27
	20	1413	131	61	39	27
	30	964	119	59	38	27
ASR11	1.5	1334	140	65	39	27
	5	1375	142	65	39	27
	10	1315	139	64	39	27
	20	1146	132	63	39	27
ASR12	1.5	1885	132	58	39	27
	5	1564	121	57	39	27
	10	907	105	57	39	27
	20	760	95	56	38	26
ASR13	1.5	1308	118	57	39	27
	5	1351	118	57	39	27
	10	1275	110	57	39	27
	20	1073	99	56	38	27
ASR14	1.5	294	75	55	38	27
	5	311	75	55	38	27
	10	307	75	55	38	27
ASR15	1.5	4953	243	71	44	30
ASR16	1.5	5992	159	61	42	29
	5	5890	161	61	42	29
	10	5095	154	60	42	29
	20	3314	131	59	42	29
	30	1812	117	58	41	29
	40	1107	100	58	41	29
	50	895	88	58	41	29
	60	701	81	58	40	28
	70	539	79	58	40	28
	80	482	78	57	40	28
	90	433	77	57	40	28
	100	394	77	57	40	28
	110	365	77	57	40	28
	120	346	77	57	40	28
ASR17	1.5	1142	83	57	40	28
	5	1192	83	57	40	28
	10	1123	83	57	40	28
	20	935	83	57	40	28
	30	721	80	57	40	28
	40	517	79	57	40	28
	50	440	79	57	40	28
	60	419	79	57	40	28
	70	398	79	57	40	28
	80	378	79	57	40	28
	90	360	78	57	40	28
ASR18	1.5	829	79	57	40	28
	5	876	79	57	40	28
	10	835	79	57	40	28
	20	725	79	57	40	28
	30	595	79	57	40	28
	40	463	79	57	40	28
	50	347	79	57	40	28
	60	341	79	57	40	28
	70	334	78	57	40	28
	80	327	78	57	40	28
	90	321	77	57	40	28
	100	316	77	57	40	28
ASR19	1.5	1330	89	57	41	29
	5	1346	90	57	41	29
	10	1197	89	57	41	29
	20	995	87	57	41	29
ASR20	1.5	9291	266	85	48	32
	5	8873	267	84	48	32
	10	7368	252	82	47	32
ASR21	1.5	1794	87	59	41	29
	5	1824	89	59	41	29
	10	1632	88	58	41	29
ASR22	1.5	1713	83	57	41	29
	5	1752	84	57	41	29
	10	1571	83	57	41	29
	20	1146	81	57	41	29
	30	736	80	57	40	29
	40	451	79	57	40	29
	50	384	78	56	40	28

Remark:

Boldfaced value represents that the predicted concentration exceeds the respective criterion.

Table 3.14 Predicted Cumulative Air Pollutant Concentrations at Representative Air Sensitive Receivers (Demolition of Existing STSTW) (Unmitigated Scenario)

ASR	Assessment Height (mAG)	Cumulative Concentration (µg/m³)
ASR	Assessment Height (mAG)	Maximum Hourly TSP	10^th Highest Daily PM₁₀	10^th Highest Daily PM_2.5	Annual PM₁₀	Annual PM_2.5
ASR1	1.5	661	83	58	40	28
	5	697	83	58	40	28
	10	684	83	58	40	28
	20	642	83	58	40	28
	30	585	82	58	40	28
	40	518	80	58	40	28
	50	448	80	58	40	28
	60	380	79	57	40	28
	70	346	79	57	40	28
	80	339	79	57	40	28
ASR2	1.5	554	80	58	40	28
	5	586	81	58	40	28
	10	577	81	58	40	28
	20	548	80	58	40	28
ASR3	1.5	819	88	59	40	28
	5	861	89	59	40	28
	10	820	88	59	40	28
	20	745	87	59	40	28
	30	655	85	59	40	28
ASR4	1.5	860	89	59	40	28
	5	902	90	59	40	28
	10	855	90	59	40	28
	20	776	88	59	40	28
	30	674	85	59	40	28
ASR5	1.5	760	84	59	40	28
	5	800	85	59	40	28
	10	765	85	59	40	28
ASR6	1.5	1204	98	60	41	29
	5	1253	99	60	41	29
	10	1169	97	59	41	29
	20	923	94	59	40	28
	30	721	86	59	40	28
	40	549	83	59	40	28
	50	484	80	58	40	28
	60	428	79	58	40	28
	70	379	79	58	40	28
	80	336	79	57	40	28
	90	300	78	57	40	28
	100	272	77	57	40	28
	110	252	77	57	40	28
	120	240	77	57	40	28
ASR7	1.5	1349	103	59	41	29
	5	1400	105	59	41	29
	10	1296	104	59	41	28
	20	995	96	59	41	28
	30	701	88	59	40	28
ASR8	1.5	854	95	60	40	28
	5	890	96	60	40	28
	10	855	95	60	40	28
ASR9	1.5	954	90	60	40	28
	5	999	90	60	40	28
	10	923	89	60	40	28
ASR10	1.5	722	77	56	37	26
	5	769	77	56	37	26
	10	733	77	55	37	26
	20	628	77	55	37	26
	30	499	77	55	37	26
ASR11	1.5	571	81	56	37	26
	5	604	81	56	37	26
	10	574	81	56	37	26
	20	485	80	56	37	26
ASR12	1.5	309	74	55	37	26
	5	330	74	55	37	26
	10	319	74	55	37	26
	20	306	74	55	37	26
ASR13	1.5	360	75	55	37	26
	5	383	76	55	37	26
	10	376	75	55	37	26
	20	356	75	55	37	26
ASR14	1.5	235	74	55	38	27
	5	250	74	55	38	27
	10	248	74	55	38	27
ASR15	1.5	1719	125	59	41	29
ASR16	1.5	1566	108	59	41	29
	5	1616	111	59	41	29
	10	1478	109	59	41	28
	20	1090	100	59	41	28
	30	705	90	59	40	28
	40	597	82	59	40	28
	50	518	79	58	40	28
	60	441	79	58	40	28
	70	368	79	57	40	28
	80	303	78	57	40	28
	90	281	77	57	40	28
	100	262	77	57	40	28
	110	245	77	57	40	28
	120	237	77	57	40	28
ASR17	1.5	555	81	58	40	28
	5	595	84	58	40	28
	10	579	83	58	40	28
	20	532	80	58	40	28
	30	468	79	58	40	28
	40	396	79	58	40	28
	50	373	77	58	40	28
	60	356	77	58	40	28
	70	339	77	58	40	28
	80	323	77	57	40	28
	90	308	77	57	40	28
ASR18	1.5	635	79	58	40	28
	5	680	79	58	40	28
	10	665	79	58	40	28
	20	622	79	58	40	28
	30	564	78	58	40	28
	40	496	78	58	40	28
	50	424	77	58	40	28
	60	353	77	58	40	28
	70	287	77	58	40	28
	80	229	77	57	40	28
	90	228	77	57	40	28
	100	228	77	57	40	28
ASR19	1.5	4567	216	67	44	29
	5	4167	215	67	44	29
	10	2752	197	65	44	29
	20	1275	151	60	43	29
ASR20	1.5	807	93	60	40	28
	5	849	94	60	40	28
	10	810	93	60	40	28
ASR21	1.5	3338	220	65	45	29
	5	3103	221	65	45	29
	10	2117	206	64	44	29
ASR22	1.5	1578	163	68	43	29
	5	1576	166	68	43	29
	10	1425	161	67	43	29
	20	1164	148	66	43	29
	30	894	132	62	42	29
	40	719	118	61	42	29
	50	625	101	60	41	28

Remark:

Boldfaced value represents that the predicted concentration exceeds the respective criterion.

3.7.1.2 Based on the predictions presented in Table 3.13 and Table 3.14, the predicted cumulative maximum hourly average TSP, 10^th highest daily and annual average PM₁₀ and PM_2.5 concentrations at some representative ASRs would exceed the criteria stipulated in EIAO-TM and AQOs under unmitigated scenario. The contour plots of cumulative maximum hourly average TSP, 10^th highest daily and annual average PM₁₀ and PM_2.5 concentrations at 1.5 metres above ground are presented in Figure Nos. 60334056/EIA/3.03 to 3.07 and Figure Nos. 60334056/EIA/3.16 to 3.20 for the construction of relocated STSTW and the demolition of existing STSTW respectively. As the predicted dust impact exceeds the criteria, proper dust mitigation measures should be implemented.

3.7.2 Operation Phase

3.7.2.1 In response to the public concern on the potential odour impact during operation of the relocated STSTW, the following appropriate odour control measures would be implemented.

(i) Adopting the advantage of caverns as natural barriers for odour control;

(ii) Covering up of odour sources;

(iii) Preventing odour leakage through the access tunnels by applying negative pressure inside caverns;

(iv) Installing deodourizing units to clean up the collected foul air;

(v) Discharging exhausted air at height to further enhance the dilution effect; and

(vi) Enhancing the odour management of the sludge transportation.

3.7.2.2 The ventilation shaft for the relocated STSTW would be sit at a remote location on the hill, The odour emission from the ventilation shaft exhaust is to be treated by deodourizers at 80% - 97% odour removal efficiency (three deodourizers at 97% and one at 80%) before venting to the ambient. The proposed deodourization technologies include activated carbon and biotrickling filter. Subject to the detailed design, a combination of both technologies may be utilized for enhanced odour removal performance. To minimize the involvement of the handling of chemicals, chemical scrubbers are not considered. The odour impacts on representative ASRs in interim and ultimate stages are predicted and the assessment results are summarized in Table 3.15 and Table 3.16, respectively. The maximum 5-second average odour concentration among representative ASRs in the interim and ultimate stages are 0.9 OU/m³ and 0.8 OU/m³, respectively. The odour concentration at each representative ASR is well below the criterion of 5 OU/m³.

3.7.2.3 According to Table 3.15 and Table 3.16, the maximum odour concentration would likely occur at 30 meters above ground (mAG) for low-rise building, and 100 mAG and 120 mAG for high-rise building. Therefore ambient odour concentrations at these levels, as well as the lowest assessment level 1.5 mAG are predicted. The contour plots of 5-second average odour concentration at 1.5 mAG, 30 mAG, 100 mAG and 120 mAG are presented respectively in Figure Nos. 60334056/EIA/3.27, 3.28, 3.29 and 3.30 for interim stage and Figure Nos. 60334056/EIA/3.31, 3.32, 3.33 and 3.34 for ultimate stage. The prediction odour impacts on ASRs with sensitive uses at these levels are well below the criterion of 5 OU/m³. No adverse odour impact due to the operation of the relocated STSTW would be expected.

Table 3.15 Predicted Operational Odour Impact on Representative Air Sensitive Receivers (Interim Stage)

	5-second Average Odour Concentrations in OU/m³ at Different Heights (Height in mAG)
ASR ID	1.5	5	10	20	30	40	50	60	70	80	90	100	110	120
ASR1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	-	-	-	-
ASR1a	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.3	-	-	-	-
ASR1b	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	-	-	-	-	-
ASR1c	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	-	-	-	-	-
ASR2	0.1	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-	-
ASR3	0.1	0.1	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-
ASR4	0.1	0.1	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-
ASR5	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-	-	-
ASR6	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2
ASR7	0.1	0.1	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-
ASR8	0.2	0.2	0.2	-	-	-	-	-	-	-	-	-	-	-
ASR9	0.2	0.2	0.2	-	-	-	-	-	-	-	-	-	-	-
ASR10	0.3	0.3	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-
ASR11	0.3	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-
ASR12	0.0	0.0	0.1	0.1	-	-	-	-	-	-	-	-	-	-
ASR13	0.0	0.0	0.0	0.1	-	-	-	-	-	-	-	-	-	-
ASR14	0.2	0.2	0.2	-	-	-	-	-	-	-	-	-	-	-
ASR15	0.2	-	-	-	-	-	-	-	-	-	-	-	-	-
ASR16	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.3
ASR17	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	-	-	-
ASR18	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	-	-
ASR19	0.3	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-
ASR20	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-	-
ASR21	0.2	0.2	0.2	-	-	-	-	-	-	-	-	-	-	-
ASR22	0.3	0.3	0.3	0.3	0.3	0.3	0.3	-	-	-	-	-	-	-
ASR23	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.3	0.4	-	-	-	-	-
ASR24	0.2	0.2	0.2	-	-	-	-	-	-	-	-	-	-	-
ASR25	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.2
ASR26	0.2	0.2	0.2	0.2	0.2	0.2	-	-	-	-	-	-	-	-
ASR27	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	-	-	-	-
ASR28	0.2	0.2	0.2	0.2	0.2	0.2	0.3	-	-	-	-	-	-	-
ASR29	0.3	0.3	0.3	0.3	0.3	0.3	0.3	-	-	-	-	-	-	-
ASR30	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.6
ASR31	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.3	0.3	0.4	0.5

Table 3.16 Predicted Operational Odour Impact on Representative Air Sensitive Receivers (Ultimate Stage)

	5-second Average Odour Concentrations in OU/m³ at Different Heights (Height in mAG)
ASR ID	1.5	5	10	20	30	40	50	60	70	80	90	100	110	120
ASR1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	-	-	-	-
ASR1a	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.3	0.4	-	-	-	-
ASR1b	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	-	-	-	-	-
ASR1c	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.3	-	-	-	-	-
ASR2	0.1	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-	-
ASR3	0.1	0.1	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-
ASR4	0.1	0.1	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-
ASR5	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-	-	-
ASR6	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.3
ASR7	0.1	0.1	0.1	0.1	0.1	-	-	-	-	-	-	-	-	-
ASR8	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-	-
ASR9	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-	-
ASR10	0.4	0.4	0.4	0.4	0.4	-	-	-	-	-	-	-	-	-
ASR11	0.3	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-
ASR12	0.0	0.0	0.0	0.1	-	-	-	-	-	-	-	-	-	-
ASR13	0.0	0.0	0.0	0.1	-	-	-	-	-	-	-	-	-	-
ASR14	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-	-
ASR15	0.2	-	-	-	-	-	-	-	-	-	-	-	-	-
ASR16	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.3	0.4
ASR17	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	-	-	-
ASR18	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	-	-
ASR19	0.3	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-
ASR20	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-	-
ASR21	0.2	0.2	0.2	-	-	-	-	-	-	-	-	-	-	-
ASR22	0.4	0.4	0.4	0.4	0.4	0.4	0.4	-	-	-	-	-	-	-
ASR23	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.4	0.5	-	-	-	-	-
ASR24	0.3	0.3	0.3	-	-	-	-	-	-	-	-	-	-	-
ASR25	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3
ASR26	0.2	0.2	0.2	0.2	0.2	0.2	-	-	-	-	-	-	-	-
ASR27	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	-	-	-	-
ASR28	0.3	0.3	0.3	0.3	0.3	0.3	0.3	-	-	-	-	-	-	-
ASR29	0.4	0.4	0.4	0.4	0.4	0.4	0.4	-	-	-	-	-	-	-
ASR30	0.7	0.7	0.7	0.7	0.7	0.7	0.7	0.7	0.7	0.7	0.8	0.8	0.8	0.8
ASR31	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.4	0.5	0.6

3.8 Mitigation of Adverse Environmental Impacts

· Watering eight times a day on active works areas, exposed areas and unpaved haul roads to reduce dust emission by 87.5%. The calculation for the proposed dust suppression efficiency by watering is presented in Appendix 3.02f. Any potential dust impact and watering mitigation would be subject to the actual site condition. For example, a construction activity that produces inherently wet conditions or in cases under rainy weather, the above water application intensity may not be unreservedly applied. While the above watering frequency is to be followed, the extent of watering may vary depending on actual site conditions but should be sufficient to achieve the removal efficiency. The dust levels would be monitored and managed under an EM&A programme as specified in the EM&A Manual.

3.8.1.2 With the implementation of the above measures, the predicted cumulative maximum hourly average TSP, 10^th highest daily and annual average PM₁₀ and PM_2.5 concentrations at the representative ASRs are summarized in Table 3.17 and Table 3.18 for construction of Sha Tin CSTW and demolition of existing STSTW respectively. The contour plots of cumulative maximum hourly average TSP, 10^th highest daily and annual average PM₁₀ and PM_2.5 concentrations at 1.5 mAG are presented in Figure Nos. 60334056/EIA/3.08 to 3.10 and 3.14 to 3.15 and Figure Nos. 60334056/EIA/3.21 to 3.23 and 3.25 to 3.26 for construction of relocated STSTW and demolition of existing STSTW respectively.

Table 3.17 Predicted Cumulative Air Pollutant Concentrations at Representative Air Sensitive Receivers (Construction of Relocated STSTW) (Tier 1, Mitigated Scenario)

ASR	Assessment Height (mAG)	Cumulative Concentration (µg/m³)
ASR	Assessment Height (mAG)	Maximum Hourly TSP	10^th Highest Daily PM₁₀	10^th Highest Daily PM_2.5	Annual PM₁₀	Annual PM_2.5
ASR1	1.5	979	79	58	40	28
	5	948	79	58	40	28
	10	820	79	58	40	28
	20	523	79	58	40	28
	30	285	79	58	40	28
	40	211	78	57	40	28
	50	184	77	57	40	28
	60	162	76	57	40	28
	70	145	76	57	40	28
	80	138	76	57	40	28
ASR2	1.5	395	79	58	40	28
	5	395	79	58	40	28
	10	363	79	57	40	28
	20	278	79	57	40	28
ASR3	1.5	1148	82	58	40	28
	5	1118	82	58	40	28
	10	967	81	58	40	28
	20	614	79	58	40	28
	30	321	77	57	40	28
ASR4	1.5	1786	84	58	40	28
	5	1602	84	58	40	28
	10	1213	82	58	40	28
	20	523	80	58	40	28
	30	292	77	57	40	28
ASR5	1.5	587	79	58	40	28
	5	586	79	58	40	28
	10	531	78	58	40	28
ASR6	1.5	1273	80	57	41	29
	5	1214	80	57	40	29
	10	1011	80	57	40	28
	20	596	77	57	40	28
	30	296	77	57	40	28
	40	210	77	57	40	28
	50	162	76	57	40	28
	60	138	76	57	40	28
	70	138	76	57	40	28
	80	138	76	57	40	28
	90	138	76	57	40	28
	100	138	76	57	40	28
	110	138	76	57	40	28
	120	138	76	57	40	28
ASR7	1.5	953	79	57	40	28
	5	916	79	57	40	28
	10	768	79	57	40	28
	20	471	77	57	40	28
	30	255	77	57	40	28
ASR8	1.5	1441	105	60	41	29
	5	1294	104	60	41	29
	10	973	100	59	41	29
ASR9	1.5	813	87	59	40	28
	5	793	87	59	40	28
	10	687	86	59	40	28
ASR10	1.5	302	75	54	37	26
	5	305	75	54	37	26
	10	286	75	54	37	26
	20	236	75	54	37	26
	30	182	74	54	37	26
ASR11	1.5	196	75	55	37	26
	5	201	75	55	37	26
	10	195	75	55	37	26
	20	179	75	54	37	26
ASR12	1.5	280	74	53	37	26
	5	239	74	53	37	26
	10	174	72	53	37	26
	20	157	72	53	37	26
ASR13	1.5	223	74	53	37	26
	5	228	74	53	37	26
	10	219	74	53	37	26
	20	195	73	53	37	26
ASR14	1.5	132	73	55	38	27
	5	132	73	55	38	27
	10	132	73	55	38	27
ASR15	1.5	619	80	58	40	28
ASR16	1.5	777	77	57	40	28
	5	765	77	57	40	28
	10	671	77	57	40	28
	20	458	77	57	40	28
	30	279	77	57	40	28
	40	173	77	57	40	28
	50	148	76	57	40	28
	60	138	76	57	40	28
	70	138	76	57	40	28
	80	138	76	57	40	28
	90	138	76	57	40	28
	100	138	76	57	40	28
	110	138	76	57	40	28
	120	138	76	57	40	28
ASR17	1.5	188	76	57	40	28
	5	194	76	57	40	28
	10	186	76	57	40	28
	20	163	76	57	40	28
	30	138	76	57	40	28
	40	138	76	57	40	28
	50	138	76	57	40	28
	60	138	76	57	40	28
	70	138	76	57	40	28
	80	138	76	57	40	28
	90	138	76	57	40	28
ASR18	1.5	150	76	57	40	28
	5	156	76	57	40	28
	10	151	76	57	40	28
	20	138	76	57	40	28
	30	138	76	57	40	28
	40	138	76	57	40	28
	50	138	76	57	40	28
	60	138	76	57	40	28
	70	138	76	57	40	28
	80	138	76	57	40	28
	90	138	76	57	40	28
	100	138	76	57	40	28
ASR19	1.5	205	76	57	40	28
	5	213	76	57	40	28
	10	205	76	56	40	28
	20	182	76	56	40	28
ASR20	1.5	1136	90	59	41	29
	5	1087	90	59	41	29
	10	908	88	59	41	28
ASR21	1.5	272	76	57	40	29
	5	276	76	57	40	29
	10	253	76	57	40	29
ASR22	1.5	227	75	57	40	28
	5	231	75	57	40	28
	10	210	75	56	40	28
	20	159	75	56	40	28
	30	142	75	56	40	28
	40	142	75	56	40	28
	50	141	75	56	40	28

Remark:

Boldfaced value represents that the predicted concentration exceeds the respective criterion.

Table 3.18 Predicted Cumulative Air Pollutant Concentrations at Representative Air Sensitive Receivers (Demolition of Existing STSTW) (Tier 1, Mitigated Scenario)

ASR	Assessment Height (mAG)	Cumulative Concentration (µg/m³)
ASR	Assessment Height (mAG)	Maximum Hourly TSP	10^th Highest Daily PM₁₀	10^th Highest Daily PM_2.5	Annual PM₁₀	Annual PM_2.5
ASR1	1.5	167	78	57	40	28
	5	172	78	57	40	28
	10	170	78	57	40	28
	20	165	77	57	40	28
	30	157	77	57	40	28
	40	149	77	57	40	28
	50	145	76	57	40	28
	60	144	76	57	40	28
	70	143	76	57	40	28
	80	142	76	57	40	28
ASR2	1.5	153	77	57	40	28
	5	157	77	57	40	28
	10	156	77	57	40	28
	20	153	77	57	40	28
ASR3	1.5	185	79	58	40	28
	5	190	79	58	40	28
	10	187	79	58	40	28
	20	178	78	57	40	28
	30	166	78	57	40	28
ASR4	1.5	191	79	58	40	28
	5	196	79	58	40	28
	10	192	79	58	40	28
	20	182	78	57	40	28
	30	169	78	57	40	28
ASR5	1.5	168	79	58	40	28
	5	172	79	58	40	28
	10	170	79	58	40	28
ASR6	1.5	231	79	58	40	29
	5	237	79	58	40	28
	10	226	79	58	40	28
	20	198	79	58	40	28
	30	174	78	57	40	28
	40	167	78	57	40	28
	50	160	77	57	40	28
	60	154	77	57	40	28
	70	147	76	57	40	28
	80	142	76	57	40	28
	90	138	76	57	40	28
	100	138	76	57	40	28
	110	138	76	57	40	28
	120	138	76	57	40	28
ASR7	1.5	249	79	58	40	28
	5	255	79	58	40	28
	10	242	79	58	40	28
	20	204	79	58	40	28
	30	175	78	57	40	28
ASR8	1.5	193	79	58	40	28
	5	197	79	58	40	28
	10	192	79	58	40	28
ASR9	1.5	168	79	58	40	28
	5	171	79	58	40	28
	10	168	79	58	40	28
ASR10	1.5	150	74	54	37	28
	5	156	74	54	37	28
	10	151	74	54	37	28
	20	143	73	54	37	28
	30	143	73	53	37	28
ASR11	1.5	143	74	54	37	28
	5	143	74	54	37	28
	10	143	74	54	37	28
	20	143	73	54	37	28
ASR12	1.5	143	73	53	37	28
	5	143	73	53	37	28
	10	143	73	53	37	28
	20	143	72	53	37	28
ASR13	1.5	143	73	53	37	28
	5	143	73	53	37	28
	10	143	73	53	37	28
	20	143	72	53	37	28
ASR14	1.5	132	73	55	38	27
	5	132	73	55	38	27
	10	132	73	55	38	27
ASR15	1.5	295	81	58	40	28
ASR16	1.5	276	79	58	40	28
	5	282	79	58	40	28
	10	265	79	58	40	28
	20	216	79	58	40	28
	30	172	78	57	40	28
	40	155	77	57	40	28
	50	149	77	57	40	28
	60	146	76	57	40	28
	70	143	76	57	40	28
	80	140	76	57	40	28
	90	138	76	57	40	28
	100	138	76	57	40	28
	110	138	76	57	40	28
	120	138	76	57	40	28
ASR17	1.5	161	77	57	40	28
	5	164	77	57	40	28
	10	163	77	57	40	28
	20	160	77	57	40	28
	30	157	77	57	40	28
	40	152	77	57	40	28
	50	147	77	57	40	28
	60	143	77	57	40	28
	70	139	76	57	40	28
	80	138	76	57	40	28
	90	138	76	57	40	28
ASR18	1.5	151	77	57	40	28
	5	154	77	57	40	28
	10	153	77	57	40	28
	20	152	77	57	40	28
	30	149	77	57	40	28
	40	147	77	57	40	28
	50	144	77	57	40	28
	60	141	76	57	40	28
	70	138	76	57	40	28
	80	138	76	57	40	28
	90	138	76	57	40	28
	100	138	76	57	40	28
ASR19	1.5	640	82	58	41	29
	5	590	82	58	41	29
	10	413	81	57	41	29
	20	206	79	57	40	28
ASR20	1.5	185	79	59	40	28
	5	189	79	58	40	28
	10	185	79	58	40	28
ASR21	1.5	491	81	57	41	29
	5	461	81	57	41	29
	10	337	80	57	41	29
ASR22	1.5	230	85	57	40	28
	5	237	85	57	40	28
	10	221	84	57	40	28
	20	196	81	57	40	28
	30	166	80	57	40	28
	40	143	78	57	40	28
	50	142	78	57	40	28

Remark:

Boldfaced value represents that the predicted concentration exceeds the respective criterion.

3.8.1.3 Based on the prediction of Tier 1 screening, the predicted hourly TSP levels and daily RSP levels would still exceed the criterion stipulated in EIAO-TM while the predicted annual RSP levels, daily and annual FSP levels at all representative ASRs would comply with the criteria of AQOs. During construction of relocated STSTW, the predicted hourly TSP would exceed the criterion at A Kung Kok Fisherman Village (ASR8, ASR9 and ASR20), and area of Chevalier Garden (ASR1), Tai Shui Hang (ASR3, ASR4 and ASR5), and Kam Tai Court (ASR6, ASR7, ASR15 and ASR16). During demolition of existing STSTW, the predicted hourly TSP would exceed the criterion at Marine Police Outer Waters District Headquarters and Marine Police North Police Station (ASR19).

3.8.1.4 Those ASRs with non-compliance in hourly TSP levels under Tier 1 screening during the construction of relocated STSTW are selected to undergo Tier 2 assessment. Two hot spot areas have been identified by Tier 1 screening, which are A Kung Kok Fishermen Village and Kam Tai Court. Two scenarios of Tier 2 assessment, namely Tier 2a and 2b, are therefore conducted for these two areas accordingly by considering maximum percentage active area of 20% for heavy construction activity and positioning the dust sources closest to the hot spot area. In fact, the assumption of 20% active area for Tier 2 assessment is a conservative approach as the estimation of maximum active work area is 4.7% for CSTW. The crusher within the cavern and haul roads are assumed to be working in full capacity in both scenarios. In particular, dust sources of Main Portal and Area 73 are positioned next and opposite to A Kung Kok Fishermen Village in Tier 2a while they are positioned opposite to Chevalier Garden, Tai Shui Hang and Kam Tai Court in Tier 2b. Dust sources of A Kung Kok Shan explosives magazine site and Secondary Portal are positioned towards these two areas. The allocation of dust source in both Tier 2a and 2b is illustrated in Appendix 3.02d. The predicted results of Tier 2a and 2b are summarized in Table 3.19 and Table 3.20. The tier 2 contours plots of cumulative maximum hourly average TSP and 10^th highest daily average RSP concentrations at 1.5 mAG are presented in Figure Nos. 60334056/EIA/3.11, 3.12 and 3.13. According to these contour plots, the exceedance zone at 1.5mAG would confine to the construction work areas of main portal area, temporary road and Area 73, and would also appear in hill area southeast of A Kung Kok Fishermen Village. To confirm that no land lots with air sensitive uses within the exceedance zone at 1.5mAG, a site survey was conducted on 30 December 2015. Site photos are shown in Appendix 3.07.

Table 3.19 Predicted Cumulative Air Pollutant Concentrations at Representative Air Sensitive Receivers (Construction of Relocated STSTW) (Tier 2a, Mitigated Scenario)

ASR	Assessment Height (mAG)	Cumulative Concentration (µg/m³)
ASR	Assessment Height (mAG)	Maximum Hourly TSP	10^th Highest Daily PM₁₀
ASR8	1.5	426	83
	5	358	81
	10	242	79
ASR9	1.5	199	78
	5	194	78
	10	172	78
ASR20	1.5	283	78
	5	271	78
	10	227	78

Remark:

Boldfaced value represents that the predicted concentration exceeds the respective criterion.

Table 3.20 Predicted Cumulative Air Pollutant Concentrations at Representative Air Sensitive Receivers (Construction of Relocated STSTW) (Tier 2b, Mitigated Scenario)

ASR	Assessment Height (mAG)	Cumulative Concentration (µg/m³)
ASR	Assessment Height (mAG)	Maximum Hourly TSP
ASR1	1.5	262
	5	255
	10	230
	20	173
	30	144
	40	138
	50	138
	60	138
	70	138
	80	138
ASR3	1.5	263
	5	256
	10	222
	20	155
	30	139
ASR4	1.5	448
	5	400
	10	310
	20	162
	30	138
ASR5	1.5	159
	5	159
	10	157
ASR6	1.5	346
	5	329
	10	277
	20	180
	30	138
	40	138
	50	138
	60	138
	70	138
	80	138
	90	138
	100	138
	110	138
	120	138
ASR7	1.5	298
	5	283
	10	236
	20	156
	30	138
ASR15	1.5	219
ASR16	1.5	245
	5	242
	10	216
	20	159
	30	138
	40	138
	50	138
	60	138
	70	138
	80	138
	90	138
	100	138
	110	138
	120	138

Remark:

Boldfaced value represents that the predicted concentration exceeds the respective criterion.

3.8.1.5 Marine Police Outer Waters District Headquarters and Marine Police North Police Station (ASR19) which would be non-compliance in hourly TSP level under Tier 1 screening during demolition of existing STSTW also undergoes a Tier 2 assessment. The allocation of dust source in Tier 2 is illustrated in Appendix 3.02e. The predicted results of Tier 2 are presented in Table 3.21. The Tier 2 contour plot of cumulative maximum hourly TSP concentration is shown in Figure No. 60334056/EIA/3.24. According to the contour plot, the exceedance area would confine to the area of the demolition work areas and appear at Sha Tin Seafront Salt Water Pumping Station and cycling track outside the existing STSTW. To confirm that no land lots with air sensitive uses within the exceedance zone at 1.5mAG, a site survey was conducted on 30 December 2015. Site photos are shown in Appendix 3.07.

Table 3.21 Predicted Cumulative Air Pollutant Concentrations at Representative Air Sensitive Receivers (Demolition of Existing STSTW) (Tier 2, Mitigated Scenario)

ASR	Assessment Height (mAG)	Cumulative Concentration (µg/m³)
ASR	Assessment Height (mAG)	Maximum Hourly TSP
ASR19	1.5	282
	5	270
	10	213
	20	141

Remark:

Boldfaced value represents that the predicted concentration exceeds the respective criterion.

3.8.1.6 Based on the contour plots presented above, localized exceedances of particulates concentration are predicted in the vicinity of the Project. However, no existing or planned ASR is identified within these predicted exceedance areas during the construction phase of the project, which has been confirmed with site survey conducted on 30December 2015. The modeling results indicate that the predicted cumulative particulate concentrations at all representative ASRs would comply with the respective AQOs and criteria stipulated in EIAO-TM.

3.8.1.7 In addition to the dust control measures described above, dust suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation and good site practices listed below shall be carried out to further minimize construction dust impact:

· Use of regular watering to reduce dust emissions from exposed site surfaces and unpaved roads, particularly during dry weather.

· Use of frequent watering for particularly dusty construction areas and areas close to ASRs.

· Side enclosure and covering of any aggregate or dusty material storage piles to reduce emissions. Where this is not practicable owing to frequent usage, watering shall be applied to aggregate fines.

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

· Tarpaulin covering of all dusty vehicle loads transported to, from and between site locations.

· Establishment and use of vehicle wheel and body washing facilities at the exit points of the site.

· Provision of wind shield and dust extraction units or similar dust mitigation measures at the loading area of barging point, and use of water sprinklers at the loading area where dust generation is likely during the loading process of loose material, particularly in dry seasons/ periods.

· Provision of not less than 2.4m high hoarding from ground level along site boundary where adjoins a road, streets or other accessible to the public except for a site entrance or exit.

· Imposition of speed controls for vehicles on site haul roads.

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

· Every stock of more than 20 bags of cement or dry pulverized fuel ash (PFA) should be covered entirely by impervious sheeting or placed in an area sheltered on the top and the 3 sides.

· Instigation of an EM&A program to monitor the construction process in order to enforce controls and modify method of work if dusty conditions arise.

3.8.2 Operational Odour Impact

3.8.2.1 With the implementation of proposed odour control measures as mentioned in Section 3.7.2.1 and Section 3.7.2.2, the predicted odour concentrations at the representative ASRs are well below the criterion of 5 OU/m³ and would comply with the EIAO-TM. No further mitigation measure would be required during the operation phase.

3.9 Evaluation of Residual Impacts

3.9.1 Construction Phase

3.9.1.1 With the implementation of the mitigation measures as stipulated in the Air Pollution Control (Construction Dust) Regulation together with the recommended dust control measures and good site practices on the work sites, no adverse residual impact would be expected from construction of relocated STSTW and demolition of existing STSTW and temporary explosives magazine.

3.9.2 Operation Phase

3.9.2.1 During operation phase of the Project, the predicted 5-second average odour concentration at the representative ASRs would comply with the EIAO-TM. No adverse residual impact is expected.

3.10 Environmental Monitoring and Audit

3.10.1 Construction Phase

3.10.1.1 EM&A for potential dust impacts should be conducted during the construction phase of the Project so as to check compliance with legislative requirements. Details of the monitoring and audit programme are contained in a stand-alone EM&A Manual.

3.10.2 Operation Phase

3.10.2.1 No adverse impact would be generated during the operation phase of CSTW. Therefore, odour monitoring at the inlet and outlet of the deodourizing units is proposed to be conducted for first three years of the operation of CSTW, quarterly in the first year, and once every 6 months in the second and third years if monitoring results remain below the limit levels. An Odour Complaint Registration System is also proposed in the EM&A programme to check whether the deodorizing units can fulfill the recommended odour removal performance.

3.10.2.2 Any unexpected leakage from tanks could be observed with monitoring equipment. Monitoring equipment would be installed in the CSTW to monitor the concentration of H₂S, carbon monoxide (CO) and carbon dioxide (CO₂)and methane. Investigation and repair works would be carried out immediately if abrupt increase of these concentrations are reported. Emergency Plan would be established for these upset conditions.

3.11 Conclusion

3.11.1 Construction Phase

3.11.1.1 The potential air quality impacts from the construction works of the Project including decommissioning and demolition of existing STSTW and temporary explosives magazine would mainly be related to construction dust from excavation, materials handling, spoil removal and wind erosion. With the implementation of mitigation measures specified in the Air Pollution Control (Construction Dust) Regulation together with the recommended dust suppression measures, good site practices, and EM&A programme, the predicted dust impact at ASRs would comply with the hourly, daily and annual particulate criteria stipulated in the AQOs and EIAO-TM.

3.11.2 Operation Phase

3.11.2.1 The relocated STSTW is fully enclosed in the cavern and the potential odour emission from the sewage treatment facilities would all be treated in the deodourizing units before discharge into atmosphere from the ventilation shaft which is located at a remote area on the hill. With further implementation of odour control measures as mentioned in Section 3.7.2, the assessment results show that the predicted 5-second average odour concentration at the representative ASRs and within the Study Area would comply with the criterion in EIAO-TM. The Project is considered to have considerable improvement on the air quality condition at the study area as comparing with the operation of existing STSTW.

3.11.2.2 No air quality impact is anticipated with the operation of the water reclamation facilities inside cavern.

<End of Section 3>

[1] Richard A. Duffee, Martha A. O”Brien and Ned Ostojic (1991). Odor Modeling – Why and How, Recent Developments and Current Practices in Odor Regulation, Controls and Technology, Air & Waste Management Association

[2] Keddie, A. W. C (1980). Dispersion of Odours, Odour Control – A Concise Guide, Warren Spring Laboratory

[3] Turner, D. (1994). Workbook of Atmosphere Dispersion Estimates, 2nd Edition, Lewis Publishers

3.2.1.1 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 EIAO-TM as well as the requirements set out under Clause 3.4.1 of the EIA Study Brief.

Pollutants

Averaging Time

Concentration Limit (µg/m3)(1)

Number of Exceedance Allowed

Respirable Suspended Particulates (PM10)(2)

24-hour

100

9

Annual

50

N/A

Fine Suspended Particulates (PM2.5)(3)

24-hour

75

9

Annual

35

N/A

Notes:

(1) Measured at 293K and 101.325kPa

(2) Suspended particulates in air with a nominal aerodynamic diameter of 10µm or smaller.

(3) Suspended particulates in air with a nominal aerodynamic diameter of 2.5µm or smaller.

3.2.2.2 Apart from AQOs, the limit of hourly Total Suspended Particulates (TSP) concentration should not exceed 500 µg/m3 (measured at 25°C and one atmosphere) for construction dust impact assessment according to Annex 4 of EIAO-TM.

3.2.2.3 In accordance with Annex 4 of EIAO-TM, the limit of 5 odour units based on an averaging time of 5 seconds for odour prediction assessment should not be exceeded at any ASRs.

3.3.1.2 The study area in Sha Tin and Ma On Shan area is a new town area with mainly residential buildings and educational institutes. Existing air quality in the study area is affected by emissions from the existing traffic from Tolo Highway and Tate’s Cairn Highway.

3.4.1.2 Potentially affected ASRs by construction dust arisen from the construction of relocated STSTW, emergency outfall and demolition of the existing STSTW are generally identified within 500m study boundary from the Project boundary.

3.4.1.5 The representative ASRs which would likely be affected by potential operational odour impact from relocated STSTW have been identified and are given in Table 3.4 below. Their locations are illustrated in Figure No. 60334056/EIA/3.02 and their coordinates are presented in Appendix 3.01.

3.6.1.1 According to “Guidelines on Assessing the ‘TOTAL’ Air Quality Impacts”, three components of contribution should be considered in evaluating the air quality impact due to the Project upon ASRs, namely primary, secondary and background contributions.

3.6.1.2 Primary contributions are the project-induced emission which contributes to the local air quality impact. Thus, construction dust emission associated with the construction works of the Project is the primary contributions during the construction phase.

3.6.1.13 As recommended in the EPD’s Guideline on Modelling Vehicle Emissions, default vehicle populations forecast in EMFAC-HK is used.

3.6.1.14 The default accrual rates in EMFAC-HK are estimated from the local mileage data adjusted to reflect the total VKT for each vehicle class. The default value has been used.

3.6.1.15 For those roads with cold starts, the diurnal variation of daily trips in the study area applied in the EMFAC-HK model is provided by the traffic team.

3.6.1.17 Speed fraction represents the percentage in different speed ranges of each vehicle type weighted by VKT. The speed limits of existing road were made reference to the Traffic Aids (plan marked the road marking, traffic sign and speed limits) from TD.

3.6.1.18 The resulting hourly emissions of RSP and FSP have been divided by the number of vehicles and the distance travelled to obtain the emission factors in gram per miles per vehicle which are to be directly adopted by the air dispersion model.

3.6.1.19 All major roads within 500m study boundary, including Tolo Highway and Tate’s Cairn Highway are incorporated into the assessment as indicated in Appendix 3.04. The calculation of the composite emission rates for each road links are presented as well in the appendix.

3.6.1.22 Dataset of PATH has no TSP background either. TSP background concentration will be assumed to constitute of 100% of PM10 concentration. PM10 concentration from PATH is directly adopted as TSP background concentration for the assessment.

3.6.1.23 The study area covers 4 grid cells of PATH, namely grid (31, 35), (32, 34), (32, 35) and (33, 34). PATH dataset (Year 2020) of these four grid cells are adopted as the background concentration for the assessment.

3.6.1.24 Fugitive Dust Model (FDM) (1993 version), approved air dispersion model by EPD, is applied to assess potential primary dust impact from the construction works and secondary ones due to concurrent construction works.

3.6.1.25 California Line Source Dispersion Model, version 4 (CALINE4), the USEPA approved line source air dispersion model developed by the California Department of Transport is used to assess the secondary contribution due to vehicular emission from nearby highways.

Note:

(1) The odour emission rates for sludge treatment and dewatering treatment facilities are made reference to Appendix 3.4 of the approved EIA Report for Harbour Area Treatment Scheme (HATS) Stage 2A (EIA-148/2008).

3.6.2.8 Air quality impacts of odour on the ASRs from the operation of the relocated STSTW are modelled with the air dispersion model, Industrial Sources Complex Short Term 3 (ISCST3), which is approved by EPD.

3.6.2.10 Odour emission from the exhaust outlet of the deodorizer is modelled as point source in the assessment.

3.8.1.1 In order to minimize the construction dust impact, the following dust mitigation measures shall be implemented:

3.8.1.7 In addition to the dust control measures described above, dust suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation and good site practices listed below shall be carried out to further minimize construction dust impact:

3.9 Evaluation of Residual Impacts

3.9.2.1 During operation phase of the Project, the predicted 5-second average odour concentration at the representative ASRs would comply with the EIAO-TM. No adverse residual impact is expected.

3.10 Environmental Monitoring and Audit

3.11.2.2 No air quality impact is anticipated with the operation of the water reclamation facilities inside cavern.

Concentration Limit (µg/m³)⁽¹⁾

Respirable Suspended Particulates (PM₁₀)⁽²⁾

Fine Suspended Particulates (PM_2.5)⁽³⁾

3.2.2.2 Apart from AQOs, the limit of hourly Total Suspended Particulates (TSP) concentration should not exceed 500 µg/m³ (measured at 25°C and one atmosphere) for construction dust impact assessment according to Annex 4 of EIAO-TM.

3.6.1.22 Dataset of PATH has no TSP background either. TSP background concentration will be assumed to constitute of 100% of PM₁₀ concentration. PM₁₀ concentration from PATH is directly adopted as TSP background concentration for the assessment.