Environmental Impact Assessment Ordinance

Technical Memorandum

Annex 12


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 a sensitive receiver.

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:

  1. 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;
  2. location, height of emission, grade level above mean sea level and physical dimensions of emission points, areas, volumes and lines;
  3. 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, locations and dimensions of physical obstruction, existing and potential land use, existing and potential building downwash, building wake, street canyon or cavity effects within the study area.

3.3 Description of Sensitive Receivers

It involves the description of locations, height, grade level, dimension of sensitive receivers and impact area.

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 instructions. The baseline study involves a discussion of background air quality value due to uninventoried sources and contributions from outside the study area and description of the method used for determining this value.

3.5 Meteorological Conditions

Assessment shall use the recent representative sequential hourly meteorological data obtained from on-site observation, government agencies, companies or institutions. It also involves a discussion of meteorological variations due to difference between the monitoring site and the study area as well as within the study area. Meteorological conditions due to topographic / land use influences shall be identified and discussed.

3.6 Impact Prediction and Assessment

  1. Assessment results shall provide information on the worst case meteorology; areas of maximum impacts in the study area and cumulative impacts due to background and identified sources.
  2. Presentation of assessment results shall be assisted by summary tables and contour map of pollutant concentration.
  3. Assessment results shall be compared with acceptable air quality standards as defined according to Annex 4.