Inspector’s Ruling Against Sainsbury’s Store Extension has Implications for Air Quality Assessments
A recent appeal decision against the refusal of planning permission to extend an existing supermarket in Sheffield has important implications for the way in which air quality assessments should be conducted. The Inspector concluded that “the potential harm….. identified with regard to the effect of the proposal on local air quality, and consequently human health, is not outweighed by other considerations” and “it would not be possible …to make the proposal acceptable in planning terms through the imposition of reasonable conditions”.
The decision taken by the Inspector was based largely on the view that the findings of the air quality assessment prepared for the appeal could not be relied upon, and a number of matters were highlighted.
One key assumption for the modelling that was questioned was that emissions from road traffic would reduce year-on-year. The emission factors used were those published by Defra. These emission factors are year-specific, and include projections of how newer vehicles will enter the fleet; newer vehicles are expected to emit less pollution as they conform to increasingly stringent Euro standards. Recently, however, a disparity between these official emission projections and measured concentrations of nitrogen oxides and nitrogen dioxide has been identified, and the reductions expected over the past 6 to 8 years have not been realised at many locations across the UK. There is therefore concern that nitrogen oxides and nitrogen dioxide concentrations may not decline as rapidly in the future as projected by these official emissions factors.
At this stage there are no other emissions factors that can be used. Defra have advised local authorities that where existing forecasting information is used, account should be taken of the performance of different vehicle types and of the Euro standards overall, but no prescriptive guidance is provided.
The air quality assessment carried out on behalf of Sainsbury’s predicted concentrations in the opening year of the scheme (2013) using assumptions on background concentrations and vehicle emissions for that year. The Inspector notes that “the modelled concentrations in 2013 are lower than would otherwise have been the case had 2010/11 emission rates been assumed to continue”. Taking into account the guidance issued by Defra, the Inspector further concluded that “under these circumstances it would be reasonable to expect sensitivity tests to be undertaken on the outcome of the modelling, based on the possibility that the emissions reductions suggested by [the official forecasts] would not be realised”.
It is important to note that this was not the only matter of concern identified by the Inspector. Other issues noted in the Appeal Decision are:
- The short-term (7 month) period of monitoring that was carried out to verify (calibrate) the model was shown to have “significantly overestimated the 12 month concentration”. This will have affected model performance and consequently overestimated concentrations in 2013.
- The approach taken to predict the increase in traffic associated with the proposed scheme was questioned given that the extension was primarily related to goods sales rather than food sales. The Inspector concluded that this would indicate “an increase of traffic…..some 67% higher than was assumed in the modelling” would be a reasonable assumption.
- The assessment failed to take account of the potential cumulative impacts of other committed developments (although at no stage did the Council request that this be done).
- The mitigation measures proposed by the appellant (and suggested by the Council) “would be unlikely to adequately address the adverse effects of the proposal on local air quality”.
What Are The Implications for Air Quality Assessments?
- At this stage there are no other vehicle emissions factors that can be practicably used, other than those published by DfT. Given the considerable uncertainties in these emissions factors, at least until the next set of Euro standards is introduced in 2013/14 and these vehicles make up a significant proportion of the fleet, it is important that air quality assessments should adequately consider the consequences should the forecast emissions reductions over the short term not materialise. There are a number of ways that this can be done – one approach is to ensure that vehicle emissions factors are assumed to remain unchanged from the base (model verification) year, this applying equally to projections of background concentrations and to the scheme traffic. This will produce two sets of results (one based on the “official” forecasts, and the other assuming there is no improvement) – professional judgement will then need to be applied to the interpretation, taking into account other precautionary or worst-case assumptions that may have been included in the assessment.
- It is clear that considerable care needs to be taken with the model verification process, particularly where short-term monitoring data are used. Such approaches should be avoided wherever possible.
- It also needs to be recognised that agreement on issues with the local planning authority does not abrogate the developer from a duty to ensure that the air quality assessment is thorough and robust.In particular, careful consideration needs to be given to the inclusion of conservative assumptions regarding traffic data, while due account needs to be taken of cumulative effects and of the efficacy of mitigation measures.
Air Quality Consultants, in conjunction with the Air Quality Management Resource Centre at the University of the West of England, ran a successful morning workshop on
Planning and Air Quality – appraising air quality assessments in line with the EPUK guidanceThe workshop, held on 13
th September 2011 in Bristol, was organised on behalf of the South-West Division of Environmental Protection UK (EPUK). It provided guidance to local authority officers on how to assess, evaluate and make decisions based on air quality assessments submitted in support of planning applications. Presentations covered planning policy, the 2010 update of the EPUK Planning and Air Quality Guidance, and issues relating to modelling and monitoring that are pertinent to air quality assessments. The event was attended by 20 delegates from across the south of England.
Any local authorities who are interested in attending a similar workshop should contact ClareBeattie@aqconsultants.co.uk