Technical Memorandum
Annex 12
ANNEX 12 : GUIDELINES FOR AIR QUALITY ASSESSMENT
1. General
1.1 This Annex describes the commonly adopted approaches and methodologies for assessment of air quality impact arising from designated projects. The methodologies may vary from case to case, depending on the nature of air quality issues and the latest development in methods and techniques.
2. Determination of Air Sensitive Receiver
2.1 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 shall be considered to be air sensitive receiver. Places/premises in which exposure is transient in nature (for example, cycle track, pedestrian walkway, bus stop, mini-bus stop, and taxi stand) are not considered to be air sensitive receivers.
2.2 Any other premises or place with which, in terms of duration or number of people affected, has a similar sensitivity to the air pollutants as the aforelisted premises and places shall also be considered to be a sensitive receiver.
3. Assessment Methodology
The air quality assessment shall take into consideration the following aspects:
3.1 Identification of Emission Characteristics
It involves the identification of emission characteristics for major sources (including new source(s) proposed in the EIA study, if any) within the study area including, but not limited to, the following elements:
- emission rates, exit velocity and exit temperature as a function of load, time and air pollutants emitted for maximum, average and nominal operating/design conditions;
- location, height of emission, grade level above mean sea level and physical dimensions (areas, volumes and lines) of emission points;
- anticipated growth changes over the time horizon of the EIA study.
3.2 Description of Study Area
The study area for assessing air quality impact may vary from case to case and the EIA study brief may prescribe the study area. It involves the description of the topographical and man-made features which may affect the dispersion characteristics of air pollutants within the study area. This includes terrain height, existing and potential land use within the study area.
3.3 Description of Air Sensitive Receivers
It involves the description of locations, height, and grade level of air sensitive receivers.
3.4 Baseline Study
It involves the description of the existing air quality based on, but not limited to, existing air quality monitoring on-site or quality assured measured data which can be obtained from government agencies, companies or institutions. The baseline study involves a discussion of background air quality value due to other non-project emission sources in the study area and contributions from sources outside the study area.
3.5 Meteorological Conditions
Assessment shall use recent and representative sequential hourly meteorological data obtained from monitoring site or numerical weather simulation. When meteorological data from a monitoring site is adopted, justification is required to demonstrate the representativeness of the monitoring site for the study area. When meteorological data from numerical weather simulation is adopted, it shall refer to EPD Guidelines for Local-Scale Air Quality Assessment Using Models.
3.6 Impact Prediction and Assessment
- Quantitative assessment results shall provide information on the areas of maximum impacts in the study area and cumulative impacts due to background and identified sources.
- Presentation of quantitative assessment results shall be assisted by summary tables and contour map of pollutant concentration.
- Quantitative assessment results shall be compared with acceptable air quality standards as defined according to Annex 4.
- Dust emission from a construction site is controlled under the Air Pollution Control (Construction Dust) Regulation, which sets out effective construction dust control requirements including but not limited to covering the dusty materials and keeping ground surface wet by water spraying to suppress the release of construction dust. Construction dust assessment shall be conducted qualitatively to ensure that the Air Pollution Control (Construction Dust) Regulation is complied with.
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