3                    Air Quality

3.1                 Introduction

3.1.1.1           This section provides an evaluation of the potential air quality impacts associated with the construction and operation of the Proposed Helipad of the New Block of QMH.  A review of the site environs and construction works suggests that the key source of air pollution during construction will be fugitive dust, while operational impacts might arise from helicopter exhaust emissions.

3.1.1.2           The assessment of air quality addresses Clause 3.4.3 of the EIA Study Brief and refers to the assessment guidelines and evaluation criteria of air quality stipulated in Annex 12 and Annex 4 (Section 1) of the TM-EIAO, respectively.

3.2                 Criteria and Guidelines

3.2.1.1           The Air Pollution Control Ordinance (Cap. 311) (APCO) provides the statutory authority for controlling air pollutants from a variety of stationary and mobile sources, including fugitive dust emissions from construction sites.  It encompasses Air Quality Objectives (AQOs) for 7 air pollutants which are presented in Table 3.1.

Table 3.1       Air Quality Objectives

Note:

1.     Not to be exceeded more than 18 times per year

2.     Not to be exceeded more than 9 times per year

3.     Not to be exceeded more than 3 times per year

4.     No exceedance allowed

5.     All measurements of the concentration of gaseous air pollutants are to be adjusted to a reference temperature of 293K and a reference pressure of 101.325kPa.

3.2.1.2           Section 1, Annex 4 of TM-EIAO stipulates the hourly average Total Suspended Particulate (TSP) concentration of 500 mg/m³ measured at 298 K and 101.325 kPa for construction dust impacts.  Mitigation measures for construction sites specified in the Air Pollution Control (Construction Dust) Regulation should be followed.

3.2.1.3           The Air Pollution Control (Construction Dust) Regulation defines notifiable and regulatory works activities that are subject to construction dust control, as follows:

Notifiable Works

·         Site formation;

·         Reclamation;

·         Demolition of a building;

·         Work carried out in any part of a tunnel that is within 100 m of any exit to the open air;

·         Construction of the foundation of a building;

·         Construction of the superstructure of a building; or

·         Road construction work.

Regulatory Works

·         Renovation carried out on the outer surface of the external wall or the upper surface of the roof of a building;

·         Road opening or resurfacing work;

·         Slope stabilisation work; or

·         Any work involving any of the following activities:

o    Stockpiling of dusty materials;

o    Loading, unloading or transfer of dusty materials;

o    Transfer of dusty materials using a belt conveyor system;

o    Use of vehicles;

o    Pneumatic or power-driven drilling, cutting and polishing;

o    Debris handling;

o    Excavation or earth moving;

o    Concrete production;

o    Site clearance; or

o    Blasting.

3.2.1.4           Notifiable works require that advance notice of activities be given to EPD.  The Regulation also requires the works contractor to ensure that both notifiable works and regulatory works will be conducted in accordance with the Schedule of the Regulation, which provides dust control and suppression measures.

3.3                 Description of the Environment

3.3.1                Baseline Air Quality

3.3.1.1           There is no EPD’s monitoring station located in the vicinity of the Site.  As such, the nearest general monitoring station, Central/Western which is approximately 2 km from the Site is selected.  The monitoring concentrations between 2011 and 2015 are summarised in Table 3.2 below.

Table 3.2      Air Quality Monitoring Concentrations (μg/m³) at Central/Western (2011 to 2015)

Note:

1.     Daily maximum running 8-hr average.

2.     Bold value indicates the exceedance of the AQO.

3.3.1.2           Exceedances of annual average NO₂ were found in the last 5 years.  Exceedances were also observed for 1-hr average NO₂ at 2013, 24-hr average for PM₁₀ at 2011, 2013 and 2014 and 24-hr average PM_2.5 at 2013.

3.3.1.3           It should be noted that the Central/Western monitoring station is located within a more densely populated urban area where the pollutant concentration is considered to be higher due to stagnation and more influence of vehicular emissions.  It is also located 2km away from the Site.  Hence, the monitoring concentrations at the Central/Western station is not considered as representative of the Site.

3.3.1.4           There is a monitoring station which is more representative of the Site than the Central/Western monitoring station which is operated by Hong Kong Electric Company (HKEC).  The monitoring station was once installed at the roof of the Senior Staff Quarter (Station - SSQ) of QMH and was located approximately 340m south of the Site.  However, it was suspended after October 2013.  A new one was started to operate from January 2015 at the roof top of Caritas Wu Cheng-chung Secondary School (Station - CWCSS).  It is 360m south-west of the Site.  Hence, there was no monitoring of pollutants in the year 2014. Table 3.3 below summarised the latest 5 years of monitoring results for the pollutants of both of the monitoring stations.

Table 3.3      Air Quality Monitoring Concentrations (μg/m³) at the Monitoring Stations – SSQ & CWSS (2011 to 2015)

Note:

1.     Station - SSQ was suspended after October 2013. Data for 2013 in the Table above was up to October and is for reference only.

2.     No monitoring station was operated at 2014.

3.3.1.5           According to the above monitoring records, there was no exceedance found for both of NO₂ and SO₂.

3.3.2                Future Air Quality

3.3.2.1           Hour-by-hour estimated background concentrations for PM₁₀, SO₂, NO₂, CO and O₃ were provided from the EPD’s PATH-2016 model.  The model covers the whole Hong Kong area in numbers of grids with spacing of 1km x 1km for each of the grid.  Five years, 2016 to 2020 background concentrations can be obtained from EPD’s website and it is observed that the air quality would be improving year by year according to the model results of PATH model.  Refer to EPD’s “Guidelines on Assessing the ‘Total’ Air Quality Impacts’ prescribes a study area of 500m from the project boundary which covers 3 grids (35, 28), (36, 28) and (36, 29) in the PATH model. Table 3.4 below summarised the future background concentrations of the 3 grids at the nearest year to the commencing year (i.e. 2020).

Table 3. 4      The PATH Background Concentrations at Concerned Grids (μg/m³) (2020)

Note:

1.     For annual average PM₁₀, adjustment concentration of 15.6mg/m³ is added as per EPD’s Guidelines on Choice of Models and Model Parameters.

2.     For 24-hr average PM₁₀, adjustment concentration of 26.5mg/m³ is added as per EPD’s Guidelines on Choice of Models and Model Parameters.

3.     As no annual average PM_2.5 provided, a conversion factor of 0.71 is multiplied to the annual average of PM₁₀ as per EPD’s Guideline on Estimation of PM_2.5 for Air Quality Assessment in Hong Kong.

4.     As no 24-hr average PM_2.5 provided, a conversion factor of 0.75 is multiplied to the 24-hr average of PM₁₀ as per EPD’s Guideline on Estimation of PM_2.5 for Air Quality Assessment in Hong Kong.

5.     Conversion factors for corresponding stability classes are multiplied to the 1-hr average of SO₂ as per EPD’s Guideline Estimation of 10-min average SO₂ Concentration for Air Quality Assessment in Hong Kong.

6.     Daily maximum running 8-hr average.

3.3.2.2           No exceedance of AQOs was predicted from the PATH background concentrations at year 2020.

3.3.3                Air Sensitivity Receivers

3.3.3.1           In accordance with the Annex 12 of Technical Memorandum on Environmental Impact Assessment Process (TM-EIAO), any 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 Air Sensitive Receivers (ASRs).

3.3.3.2           Based on Clause 3.4.3.2 and Appendix A – 2(i) of the EIA study brief, existing and planned ASRs within the 500m study area are considered in the assessment.  Representative ASRs are chosen in terms of the shortest distances to the proposed helipad and/or the tallest in different directions around the proposed helipad.  The locations of the representative ASRs are shown in Figure 3.1 and details are summarised in Table 3.5 below.

Table 3.5      Summary of Representative Air Sensitivity Receivers (ASRs)

Note:

1.     The location of fresh air intake would be within that range and subject to the future detail design under D&C contract.

3.3.3.3           For the impact during operation stage, the major pollutant emissions will be generated from the helicopter when it arrives, idles or departs the helipad.  Representative assessment points were selected at the worst affected ASRs, New Block (ASR1) and Block K (ASR 2) of QMH, due to the shortest distance to the emissions of helicopter operation modes.

3.4                 Construction Stage

3.4.1                Identification of Impact

3.4.1.1           The Proposed Helipad will be built on the rooftop at 299.4mPD height of the New Block.  The proposed construction period would be a year between 2022 and 2024.  Referring to Section 2.5 of the proposed construction method, the main structure of the helipad is likely to be constructed by in-situ concrete and prefabricated steel members.  The construction time for the proposed construction method would be shorten comparing to the in-situ concrete method.  No piling of materials would be stored and gaseous emission from construction plant would be limited.  It is also anticipated that only limited amount of C&D materials would be generated from its construction activities and there will be about 1 truck per week for transportation of the C&D materials only.  The construction impact of the New Block is not applicable in this assessment. 

3.4.1.2           Therefore, the construction work for the construction of the proposed helipad is not considered to be dusty and should not cause any adverse dust nuisance.  With the implementation of dust control measures stipulated under Air Pollution Control (Construction Dust) Regulation, no adverse dust impact is anticipated.  Quantitative assessment is not necessary. 

3.4.2                Cumulative Impact

3.4.2.1           At the time of construction of the Proposed Helipad, there will be only one concurrent construction work within 500m of the Site which is the finishing works and building services installation works at the New Block.  These works will not generate significant amount of fugitive dust.  Therefore, no adverse cumulative construction impact is anticipated.

3.4.3                Recommended Mitigation Measures

3.4.3.1           The use of in-situ concrete and prefabricated steel members method would shorten the construction time, thus reduces dust generation comparing to in-situ concrete method.

3.4.3.2           Although there is no significant fugitive dust impact, relevant dust control measures as recommended in the Air Pollution Control (Construction Dust) Regulation shall also be implemented.  These shall include:

·         Restricting heights from which materials are to be dropped, as far as practicable to minimise the fugitive dust arising from unloading/ loading;

·         Immediately before leaving a construction site, all vehicles shall be washed to remove any dusty materials from its body and wheels;

·         All spraying of materials and surfaces should avoid excessive water usage;

·         Where a vehicle leaving a construction site is carrying a load of dusty materials, the load shall be covered entirely by clean impervious sheeting to ensure that the dusty materials do not leak from the vehicle;

·         Travelling speeds should be controlled to reduce traffic induced dust dispersion and re-suspension within the site from the operating haul trucks;

·         All dusty materials shall be sprayed with water immediately prior to any loading, unloading or transfer operation so as to maintain the dusty materials wet.

3.4.4                Residual Impact

3.4.4.1           No exceedance of relevant AQOs and TM-EIAO is anticipated in consideration of the low dust emission with implementation of dust control measures.  Therefore no residual impact during construction phase of the proposed development is anticipated.

3.4.5                Environmental Monitoring and Audit Requirements

3.4.5.1           It is necessary to ensure proper implementation of the dust control measures as required under the Air Pollution Control (Construction Dust) Regulation.  No specific construction dust monitoring is necessary.  Site environmental audits are recommended to ensure proper implementation of dust control measures.

3.5                 Operation Stage

3.5.1                Air Quality Impact – Helicopter Operation

3.5.1.1           The engine exhaust from the helicopter is the only air pollution source for the proposed development.  No odour emission is considered to be generated from the engine exhaust of the operation of helicopter.

3.5.1.2           The proposed flight sectors will be at North-to-west and South.  The emissions from the operation modes of the Landing and Take-off cycle (LTO) of the helicopter within the study area as described below are included in the assessment.  The emission from the Cruise / Flyover mode is ignored as it is outside the study area and the typical flight height of the mode is more than 450mPD that is more than 150m above of the highest ASR (New Block).  Hence, it is considered to have negligible impact to the ASRs from the Cruise / Flyover mode.  The operation duration of the LTO of the helicopter is short and the duration of each of the operation modes of the LTO for the assessment is listed below.  The total time is approximately 7 minutes only.

·         Approach: within 60 sec.;

·         Hovering (Approach): within 5 sec.;

·         Touchdown: within 3 sec.;

·         Idling: 5 minutes;

·         Lift-off: within 3 sec.;

·         Hovering (Departure): within 5 sec.;

·         Take-off: within 60 sec.

3.5.1.3           The proposed new helipad in QMH is for medical emergencies only.  According to the past record of the number of emergency helicopter operation in PYNEH between 2010 and 2015, the average daily emergency helicopter operation was less than one.

          Identification of Key Pollutant of Concern

3.5.1.4           In consideration of such short duration of the LTO (~ 7 minutes) and low frequency of the emergency helicopter operation (< 1 helicopter per day in average), the impact of the helicopter emission is short-term only.  The emission impact for longer term, e.g. 1 hour or longer is considered to be minimal as pollutants will be further dispersed and diluted with the ambient air.  Referring to the AQOs, 10-min average SO₂ is the appropriate AQO in assessing the operation impact upon the ASRs.  The AQOs for the other pollutants are in longer time averaging periods, the impacts for the pollutants are considered to be minimal.

Air Pollutant Emission Rates

3.5.1.5           The proposed type of helicopter will be Airbus H175 and the fuel to be used will be Jet A-1 kerosene as advised by GFS.  The total sulphur content of the fuel is 0.3% in weight and the technical specification of H175 are summarised in Appendix 3.1.  The emission rates of different operation modes of the LTO of helicopter were referred to ‘Guidance on the Determination of Helicopter Emissions’ by Swiss Confederation 2015.  Detailed calculations of emission rates for each operation mode are presented in Appendix 3.2.

            Representative Air Quality Impact Assessment Points

3.5.1.6           As discussed in Section 3.3.3.3, the New Block (ASR 1) and Block K (ASR 2) of QMH are in close proximity to the proposed helipad and flight path which are expected to have the highest air quality impact from the operation of the Project.  Therefore, the ASR 1 and ASR 2 are selected as the representative ASRs for the assessment. 

3.5.1.7           As the exact locations of fresh air intakes for the New Block are not confirmed yet, assessment points along the building facades at lowest, middle and highest levels were considered.  The nearest locations at the building facades to the engine exhaust of the operation of helicopter when it arrives, idles or departs the helipad were selected as the worst affected assessment points (i.e. A1a to A1d) for the assessment.

3.5.1.8           The locations of fresh air intake of Block K were provided by HA.  The worst affected fresh air intake locations (A2a to A2d) were then chosen in the assessment at the lowest, middle and highest levels.  The representative assessment points are shown in Figure 3.2 and the details of assessment levels including floor levels and heights are presented in Appendix 3.3.

            Meteorological Conditions

3.5.1.9           The WRF meteorological data at the latest year 2010 extracted from the PATH model for grids covered the study area as above, i.e. (35, 28), (36, 28) and (36, 29) was processed by AERMET modelling into the format that was employed for the dispersion model.  The mixing heights of WRF that is lower than the minimum mixing height measured at King’s Park meteorological station in year 2010 (i.e. 121.3m) were replaced with the minimum height of the King’s Park weather station.

3.5.1.10         Surface characteristics parameters, i.e. albedo, Bowen ratio and surface roughness for the 3 grids are presented in Appendix 3.2.

            Assessment Methodology and Assumptions

3.5.1.11         Pollutant concentrations were assessed based on “Guidelines on Choice of Models and Model Parameters” issued by EPD.  AERMOD was used for assessing the pollutant concentration for non-road type sources.

3.5.1.12         In accordance with “Guidelines on the Estimation of 10-minute Average SO₂ Concentration for Air Quality Assessment in Hong Kong”, the stability-dependent multiplicative factors for converting 1-hr average concentration to 10-min average SO₂ concentration are extracted and provided in Table 3.6 below.

Table 3.6      Conversion Factors for 1-hour average SO₂ to 10-min Average SO₂ Concentration

3.5.1.13         As per the flight sectors as presented in Figure 2.6, flight paths nearest to the representative assessment points (N90ºW and S8^ºW) were considered to have highest emission impact from the helicopter operation and selected in the quantitative assessment as conservative case.  The locations of selected flight paths and emission of the operation of helicopter within the study area are shown in Figure 3.3.

3.5.1.14         The exhaust from the helicopter should readily be dissipated sideways and downwards by the main rotor blades of the helicopter and then reflected upwards by the helipad.  Therefore, the downwash effect of emission from helicopter is not considered to be significant.

3.5.1.15         Noise barriers are recommended to be installed at west and south-east roof edges of New Block as part of the noise mitigation measures.  Details of the barriers are provided in Section 4.6.  The top level of the barriers is at 286.4mPD which is lower than the proposed helipad and the highest assessment level of New Block (i.e. Level 27, 289.2mPD), hence there is no effect of noise barriers to the highest assessment level of New Block.  For the rest of the representative assessment points at the lower levels, effect of barriers was not assessed for conservative case.

3.5.1.16         As the helicopter operation is not scheduled, the modelling of emission of a helicopter throughout each hour of a year is adopted in order to obtain the worst concentration.

            Assessment Results – Helicopter Emission Only

3.5.1.17         The maximum of predicted 4^th highest 10-min average SO₂ concentrations at the representative assessment points are summarised in Table 3.7 below.  The predicted concentrations at other levels of the representative assessment points are shown in Appendix 3.3.

Table 3. 7      Predicted 4^th Highest 10-min Average SO₂ Concentration at Worst Affected Assessment Points (Emission from the Helicopter Operation only)

3.5.2                Cumulative Air Quality Impact

            Emissions from nearby chimneys

3.5.2.1           Five chimneys were identified within the study area.  All of them are located on the roof of Block K.  Based on information provided by HA, three chimneys are connected to three boilers which are operated continuously while the remaining two are connected to two incinerators which are no longer in use.  Towngas is the primary fuel and diesel is used as backup fuel for emergency only.

3.5.2.2           There will be three new chimneys to be installed on the roof of the New Block which will be connected to three proposed boilers.  Towngas will also be used as the primary fuel and diesel will be the emergency backup fuel for the proposed boilers.  The final design of the boilers and chimneys will be carried out by the future D&C contractor in the later stage.

3.5.2.3           As Towngas is classified as clean fuel with ultra-low sulphur content.  Therefore, the impact of chimney emission for SO₂ is considered to be negligible.

            Vehicular Emissions

3.5.2.4           The only air emission during the operation of the Project is the engine exhausts from the helicopters.  There is large vertical separation distance between the helipad and road vehicles (over 160m).  In addition, ultra-low sulphur fuel is used for all vehicles in Hong Kong, the vehicular emission of SO₂ is considered to be negligible. 

            Background Air Quality

3.5.2.5           EPD’s PATH background hourly SO₂ concentration at 2020, i.e. the nearest year to the commencing year of the helipad were employed for the assessment.  The representative assessment points are located within PATH grid (36, 28).  The conversion factor as described in the Table 3.6 was used to estimate the 10-min average background SO₂ concentrations from the hourly concentrations. Table 3.8 below summarised the 4^th highest 10-min average SO₂ background concentrations of the grid (36, 28) at the year 2020.

Table 3.8      The 4^th Highest 10-min Average SO₂ Background Concentrations (μg/m³) (2020)

Note:

1.     Conversion factors for corresponding stability classes are multiplied to the 1-hr average of SO₂ as per EPD’s Guideline Estimation of 10-min average SO₂ Concentration for Air Quality Assessment in Hong Kong.

            Cumulative Impact

3.5.2.6           In order to evaluate the total air quality impact on the representative assessment points, the cumulative air quality impacts for the emissions from the operation of the proposed helipad of 10-min average SO₂ and the background concentrations extracted from the EPD’s PATH model were considered in this assessment.

3.5.2.7           The predicted maximum 4^th highest 10-min average SO₂ concentrations of representative assessment points are presented in Table 3.9 below.  The contour for the 4^th highest 10-min average SO₂ concentration at the worst affected height, 289.2mPD of the assessment points is presented in Figure 3.4.

Table 3.9      Predicted 4^th Highest 10-min Average SO₂ Concentration at Worst Affected Assessment Points (Cumulative Impact)

3.5.2.8           Refer to the results above, no exceedance of the 10-min average SO₂ is predicted.  The background concentrations contribute the most of the cumulative SO₂ concentration.  Detail results of the predicted concentrations are shown in Appendix 3.3.

3.5.2.9           The cumulative impact at the worst assessment points is predicted to be far below the AQO, therefore the cumulative impact of the operation of the Proposed Helipad is minimal.

3.5.3                Recommended Mitigation Measures

3.5.3.1           No adverse air quality impact is expected during the operation of the Proposed Helipad as no exceedance of the AQO.  Therefore, no mitigation measure is required.

3.5.4                Residual Impact

3.5.4.1           As the predicted concentrations at ASRs comply with the AQO, there is no residual impact.

3.5.5                Environmental Monitoring and Audit Requirements

3.5.5.1           Based on the findings above, the air quality impact of the Proposed Helipad operation will comply with the AQO.  Environmental monitoring and audit programme will not be required.

3.6                 Conclusion

3.6.1.1           This Section has identified potential sources of air quality impact during Project construction and operation.

3.6.1.2           The Project does not include works that may generate fugitive dust but further construction dust control as stipulated under the Air Pollution Control (Construction Dust) Regulation shall be implemented in order to minimise the impact.  Therefore, no specific construction dust monitoring is necessary, although regular environmental audits are recommended to ensure proper implementation of the dust control measures.

3.6.1.3           Regarding Project operation, the helipad will be used for medical emergencies only and the duration of landing and take-off of a helicopter would be less than 10 minutes.  According to the modelling results, the air quality impact of the operation of the Proposed Helipad will comply with the AQO.  Hence, no adverse impact is anticipated. 

3.6.1.4           Overall, no adverse air quality impacts are anticipated from Project construction or operation.