QMark - significance in EIA

16th December 2016

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Patrick Little, senior environmental consultant CBRE, discusses why standardised significance descriptors would be sensible.

A previous EIA QMark article by Hyder Consulting tackled changes in the way the assessment of significance is undertaken in EIA. The piece concludes that guidance and best practice are beginning to move away from the use of a significance matrix standardised across topic areas, towards methods specifically tailored to each topic.

The obvious benefit of the standardised matrix approach is that it provides consistency - not only across topic areas in a single environmental statement but also across environmental statements. However, the weakness of this approach, and the reason it is being abandoned, is that one size does not always fit all. EIA topics can differ widely in nature and in the way they are assessed.

To attempt to provide a consistent approach to the assessment of significance across all topic areas inevitably leads to compromise, which can sacrifice accuracy and ultimately affect the reliability of the EIA.

While an assessment of ecological effects, based on a consideration of the sensitivity of the receptor and the magnitude of the impact may readily lend itself to the use of the standardised matrix approach, a pedestrian wind assessment based on a consideration of anticipated wind conditions against the Lawson Comfort Criteria, for example, does not.

The criteria have been widely adopted by planning authorities and wind practitioners across the UK for the assessment of site suitability in terms of wind conditions for pedestrians and inherently include a consideration of the sensitivity of the receptor. For example, areas where people would be expected to sit would be more sensitive to windier conditions than an area where people would be expected to walk briskly and as a result, the more stringent ‘sitting’ criteria would be applied.

The classification scale employed in the criteria also lends itself to a consideration of the magnitude of the impact. Significance can therefore be assessed against an increase or decrease in this scale, above or below the category considered suitable for the intended use.

For example, a one category increase in the severity of wind conditions above that considered suitable (such as conditions meeting the pedestrian walking criteria identified in a location proposed for sitting) could represent a minor adverse effect. This clearly represents a logical approach to the assessment of significance that is tailored to this assessment and which does not accord with the standardised matrix approach.

Others topics follow a similar vein. Daylight, sunlight and overshadowing assessments, for example, are generally undertaken against standard targets and non-compliance thresholds provided in the BRE guide Site Layout Planning for Daylight and Sunlight. As with wind, these assessments suit bespoke significance assessment methodologies rather than the standardised matrix approach.

So if the standardised matrix is out, where does this leave us? With greater variation in significance assessment methods, regulatory issues can arise as a result of disputes between applicants and regulators over the details of the methods employed. These issues can result in project delays and additional costs to applicants.

Furthermore, variations in significance assessment methods lead to inconsistencies between both the results reported in distinct chapters within an environmental statement and between environmental statements. These inconsistencies have the potential to reduce the effectiveness of an environmental statement as a decision making tool for competent authorities.

One change that could be made to improve consistency is to standardise significance descriptors. Specific guidance regarding significance is not available for most topics and such descriptors used by different practitioners vary; although general standard practice is to use major, moderate, minor, negligible.

However for ecology, for example, the Chartered Institute of Ecology and Environmental Management (CIEEM) guidelines recommend that the descriptor also includes a defined geographical context, for example, minor adverse significance at the national level.

There is also no guidance regarding what constitutes a significant impact. Again, there is what is generally considered standard practice but even so, not all practitioners choose this approach.

A sensible move would be for IEMA to devise national best practice guidance providing standardised significance descriptors and work with other professional institutions to ensure they are included in their future guidance. This measure would be an important step in improving consistency in EIA across the country.


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