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Air Quality and Development Control ­ Key Issues Dr Michael Bull, Ove Arup and Partners Ltd, 13 Fitzroy Street, London, W1T 4BQ Paper presented at NSCA Spring Workshop 2004. Introduction Planning has been considered for some years as one of the key means to deliver improvements in air quality in the UK. However, even some seven years following the first Government guidance on the subject1 there still remains considerable confusion over how air quality should be considered in the planning process. In the original DETR guidance, it was stated that air quality could be used as a reason for refusal of a planning application where the impact was `significant'. It is this simple statement that continues to exercise planning authorities as there is no simple definition of significance. More fundamentally, even the process of considering air quality in the planning process has no clear guidance although various parties have attempted to assist authorities by compiling guidance or Good Practice Guides. However, no consistent approach is being applied in the UK at present.

This paper examines some of these issues and notes the key issues that require further exploration and further work.

When do you need an Air Quality Assessment

The first issue that is important for planning authorities is whether a proposed development actually requires an air quality assessment. Although `asking an appropriate expert' might seem to be an obvious response, it is clear that in many authorities this kind of communication is not automatic. In any event, without some kind of guidance one can envisage air quality experts within planning authorities having to consider all kinds of irrelevant or trivial application applications. Recognising this, several of the guides available, for instance the RTPI Good Practice Guide2 and the ALG Guidance3 proposed thresholds based on percentage changes in traffic flows, car parking spaces and particular types of industrial process as simple triggers where planners could ask for an assessment. This approach is simple to apply and can avoid requests for trivial air quality assessments (such as one I was asked to make to discharge a planning condition where the traffic changes were less than 10 vehicles an hour on a quiet suburban road). However, in some cases, even this can lead to debate and it is evident that the significance of change can vary depending on the location. Even in the year between the RTPI Guide and the ALG Technical Note the suggested threshold for road traffic reduced

Air Quality and Land Use Planning, DETR, LAQM.G4(97) Air Quality and Land Use Planning, Good Practice Guide, RTPI, 1997 3 Air Quality Assessment for Planning Applications ­ Technical Guidance Note, ALG Transport and Environment Committee, 2001

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from a 10% change on a road with 20,000 vehicles per day (vpd) to 5% change on a road with 10,000 vpd (this may have also reflected the fact that the RTPI was compiled by a team of consultants whilst the ALG note was largely written by local authority officers).

Ultimately, although simple rules can be applied there are always exceptions to these rules where authorities may be rightly concerned about air quality in a particular location, however, speaking from a consultants point of view, it appears that many more air quality assessments are requested than are strictly required. This judgement is easy to make having the benefit of knowing the results but even at the outset it should be evident that the addition of 10 vpd is not going to significantly change the air quality in a particular location.

Therefore we can anticipate that simple threshold rules will continue to be applied to assess the need for an assessment although these will often be overridden by planning authorities where there is a particular concern.

The Content of an Air Quality Assessment

Having decided that an assessment is required then there should be a basic expectation of what the assessment should provide. Ultimately the planning authority simply needs to know the air quality impacts of a proposed development, arguably these need not consider the significance of these impacts as this is a decision for the planning authority. In arriving at predicted impacts, authorities can rightly expect to be convinced that the assessment has been carried out appropriately and that the results are valid. In principle, this simply requires the selection of an appropriate method and input data and a reasonable application of the selected method.

However, even these simple requirements can lead to constant discussion about the failings of a particular assessment. As I write this paper I have been scanning the results of a recent review of one of my own assessments. This review claims the assessment to be significantly flawed because I have not assessed the impacts of a mixed use development against all the air quality strategy pollutants. This does beg the question whether planning authorities are going to be significantly better informed if, for instance, they know that 1,3, butadiene concentrations are not going to exceed the air quality objective (just where in the country do they exceed the objective!!). Sadly I have to lay the blame for this kind of approach at my own profession where it appear to be difficult for competing companies to accept that another has carried out an appropriate assessment. (just as an aside, can I ask when such reviews are carried out that the reviewer considers whether the addition of the information they consider to be essential will actually inform the planning process one iota!).

Dealing with Planning Applications

Having received a planning application possibly with an accompanying air quality assessment the key question is how air quality will be considered during the decision making process, in particular, how the significance of an impact on air quality will be assessed. In general the guidance available tends to concentrate on how to consider development that results in an increase in pollutant levels and little if any advice is available on how to consider development that is relatively benign, for instance, a few houses located in an AQMA.

Significance is the key issue for planning, but there is no accepted definition of this term in the context of air quality assessment. Many environmental assessments use significance criteria for each topic to determine the level of impact (whether positive or negative) from a development. Generally speaking for air quality assessments these have been difficult to apply but in certain cases the authors have developed criteria to allow this approach to me made. One example used on some projects is shown in Appendix A. This type of approach has usually followed the principle of using numerical or percentage change to determine significance. However, there are difficulties with this type of approach. For instance, it has normally been the case that impacts are not considered to be significant unless an air quality standard or objective is exceeded. Thus the situation could arise where there was a substantial predicted increase in pollutant concentrations but this would not be considered significant because the final resulting concentrations were below the relevant air quality standard. Conversely, developments could result in a very marginal change that results in an exceedance of standards that would be considered significant. The significance criteria detailed in Appendix A do attempt to avoid this situation by adding in a percentage change criteria but there remain limitations with this approach although it can provide a valuable approach to this problem.

Although this type of approach does attempt to provide some scale of the potential impact current thinking amongst the NSCA working panel on this issue is to move away from numerical criteria and look to how the development would affect local policy, in particular the Air Quality Action Plan and any local air quality strategy. In the RTPI Good Practice Guide conflict with the Action Plan was regarded as one the most important indicators of when air quality would be a material issue and the guide's proposals have been incorporated into the present consultation draft of PPG 23. Thus, conflict with the Action Plan is, at present, considered proposed to be an overriding material consideration.

In terms of other considerations and suggestions of priority some initial suggestions have been as follows:

·

Development that leads to a breach or worsening of a breach of an EU limit value (High priority)

·

Development that results in the declaration of a new AQMA (High priority)

·

Development that will interfere with the implementation of a local air quality strategy (Medium Priority)

·

Development that would lead to an increase in exposure to a sensitive group or location (Medium Priority)

·

Development that will lead to a degradation in air quality or increase in exposure (below the level of the air quality objective) (Medium Priority)

Although these criteria are still being discussed and developed there remains an element of professional judgement that will remain in several of these proposals which will continue to result in a debate about the level of significance of many proposals. Although such judgements will be made by competent people it is evident from experience that two competent people may not have the same opinion!

However, this type of approach can be applied to a wide range of proposals and is equally applicable to situations where non polluting developments are located within AQMAs. For this kind of proposal the issue of exposure will be important but there will remain a judgement to be made whether an increase in exposure even from the construction of one house can be considered acceptable. In such situations sensible compromises need to be made but it is likely to be the case that different judgements will be made depending on the planning authority's position and other benefits likely to arise from the proposal.

Conclusions The approach to the inclusion of air quality within the planning process is moving from one based on numerical indicators to policy based significance criteria.

Appendix A ­ Example of Numerically Based Significance Criteria

Major Adverse Effect

Major detrimental effect on local air quality, in relation to short-term and long-term local air quality standards (national objectives and EC limit values). Predicted environmental concentrations (i.e. scheme contribution plus background) exceed the standard with an increase in concentration between no-scheme and with scheme scenarios of greater than 10%. Where there is no suitable no-scheme scenario, predicted environmental concentrations exceed the standard by greater than 10%. Moderate detrimental effect on local air quality, in relation to short-term and long-term local air quality standards (national objectives and EC limit values). Predicted environmental concentrations (i.e. scheme contribution plus background) exceed the standard with an increase in concentration between no-scheme and with scheme scenarios of between 2.5% and 10%. Where there is no suitable no-scheme scenario, predicted environmental concentrations exceed the standard by 5-10%. Slight detrimental effect on local air quality, in relation to short-term and long-term local air quality standards (national objectives and EC limit values). Predicted environmental concentrations (i.e. scheme contribution plus background) exceed the standard with an increase in concentration between no-scheme and with scheme scenarios of less than 2.5%; or predicted environmental concentrations below the standard with an increase in concentration between no-scheme and with scheme scenarios of greater than 2.5%. Where there is no suitable noscheme scenario, predicted environmental concentrations exceed the standard by less than 5%. No appreciable impact on local air quality. Predicted environmental concentrations below the standard with an increase or decrease in concentration between no-scheme and with scheme scenarios of less than 2.5%. Slight beneficial effect on local air quality, in relation to short-term and long-term local air quality standards (national objectives and EC limit values). Predicted environmental concentrations (i.e. scheme contribution plus background) exceed the standard with a decrease in concentration between no-scheme and with scheme scenarios of less than 2.5%; or predicted environmental concentrations below the standard with a decrease in concentration between no-scheme and with scheme scenarios of between 2.5% and 10%. Moderate beneficial effect on local air quality, in relation to short-term and long-term local air quality standards (national objectives and EC limit values). Predicted environmental concentrations (i.e. scheme contribution plus background) exceed the standard with a decrease in concentration between no-scheme and with scheme scenarios of greater than 2.5%; or predicted environmental concentrations below the standard with a decrease in concentration between no-scheme and with scheme scenarios of between 10% and 25%. Substantial beneficial effect on local air quality, in relation to short-term and long-term local air quality standards (national objectives and EC limit values). Predicted environmental concentrations below the standard with a decrease in concentration between no-scheme and with scheme scenarios of greater than 25%.

Moderate Adverse Effect

Slight Adverse Effect

Negligible Effect

Slight Beneficial Effect

Moderate Beneficial Effect

Substantial Beneficial Effect

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