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Air Quality Assessments

An air quality assessment is a detailed study of the effects of a development on air quality. Certain development applications will need to be accompanied by an Environmental Statement (ES) under the requirements of the Town and Country Planning Regulations 1999. For these applications, air quality should form part of the ES. Developers will normally be required to submit an air quality assessment for an application where the impact on air quality is likely to be significant.

If required, developers should submit the air quality assessment with or preferably before the planning application. Types of development which may need air quality assessments are:

  • proposals that will generate or increase traffic congestion, where ‘congestion’ manifests itself as an increase in periods with stop start driving
  • proposals that will give rise to a significant change in either traffic volumes, typically a change in annual average daily traffic (AADT) or peak traffic flows greater than ±5% or ±10%, depending on local circumstances (a change of ±5% will be appropriate for traffic flows within an AQMA), or in vehicle speed (typically of more than ±10kph), or both, usually on a road with more than 10,000 AADT (5,000 if ‘narrow and congested’)
  • proposals that would significantly alter the traffic composition on local roads, for instance, increase the number of HDVs by say 200 movements or more per day, due to the development of a bus station or an HGV park
  • proposals that include significant new car parking, which may be taken to be more than 100 spaces outside an AQMA or 50 spaces inside an AQMA
  • developments which may significantly affect nitrogen deposition to sensitive habitats
  • introduction of new exposure close to existing sources of air pollutants, including road traffic, industrial operations, agricultural operations etc
  • proposals that include biomass boilers or biomass-fuelled CHP plant
  • consideration should be given to the impacts of centralised boilers or CHP plant burning other fuels (e.g. gas or oil) within or close to an AQMA
  • proposals that could give rise to potentially significant impacts during construction for nearby sensitive locations, e.g. residential areas, areas with parked cars and commercial operations that may be sensitive to dust
  • large, long-term construction sites that would generate large HGV flows (>200 movements per day) over a period of a year or more.

Guidance on undertaking an quality assessment

The following guidance should be taken into account:

Kent and Medway Air Quality Partnership: Air Quality and Planning Guidance and DEFRA's Local Air Quality Management Technical Guidance LAQM.TG(09) found on Defra's Air Quality page (http://ww2.defra.gov.uk/environment/quality/air/air-quality) under guidance notes.

Assessing an air quality assessment

Once an air quality assessment has been received, it is reviewed for adequacy. The council will review whether the assessment report contains all the information required, if an appropriate assessment has been undertaken and if the conclusions are consistent with the assessment results. Where relevant expertise is not available within the council, an external peer review may be needed. The council, as the planning authority, is then informed of the significance of the air quality effects of the development and recommendations on their acceptability and the level of mitigation needed are made.

In the event that mitigation cannot resolve all air quality concerns, the council will decide whether any remaining adverse effects are sufficiently outweighed by the social, economic or other benefits of the development to the area. In doing this, it will consider national, regional and local development and environmental policies and priorities as set out in planning policy guidance, regional planning guidance, the Local Plan and any relevant supplementary planning guidance.

When a development is not expected to meet the objectives set out in the UK National Air Quality Strategy, the council will consider all the issues set out above. It will also consider factors such as the scale and nature of any breach of the objective air quality levels, whether any initial breach is expected to improve over time and when that might happen and the sensitivity of new uses proposed in areas of existing poor air quality.