EIA and the search for significance

1st May 2012

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Hyder's Andrew Saunders explores how the evaluation of the significant effects in environmental impact assessment (EIA) needs to evolve

Is it true that combining the value of a receptor with the magnitude of impact determines the level of significance? Or that effects considered to be “moderate or above” are significant in the context of the EIA Regulations?

Schedule 4 of the Regulations requires an environmental statement to include: “a description of the likely significant effects of the development on the environment”, but tellingly it gives no advice as to how to derive significance or what level of significance is significant.

Deriving significance

EIA practitioners are used to combining the value of the receptor with the magnitude of impact in order to derive levels of significance and over the years have witnessed attempts to standardise this approach across topic areas with varying degrees of success (see below).

Significance Value of receptor
High Medium Low
Major Major Major Moderate
Moderate Major Moderate Minor
Minor Moderate Minor Negligible

However, it now appears that certain guidance and best practice is moving away from this traditional “one size fits all” formulaic approach. Examples include IEMA’s own advice on climate change mitigation and EIA which states: “GHG emissions have a combined environmental effect that is approaching a scientifically defined environmental limit, as such any GHG emissions or reductions from a project might be considered to be significant.”

Interim advice notes from the Highways Agency also recognise that the standard approach to applying significance criteria may not be applicable to the assessment of particular topics, such as air quality, noise and material resources.

Recent guidance has also pointed out that matrices are not prescriptive and that EIA professionals need to be able to demonstrate a consistent and justifiable argument in making judgements on the significance of effects.

Paul Maile, from Eversheds, argues: “What is important is that the assessor sets out a transparent methodology which explains how they approach the assessment, and that they then demonstrably apply that methodology in their assessment.

“The methodology should explain how the assessor deems whether or not a significant effect will occur and as a matter of good practice it should take into account all appropriate guidance in reaching those judgements.”

The EIA Regulations and significance

Many environmental statements contain the assertion that an effect considered to be “moderate or above” is significant in the context of the EIA Regulations. As identified in IEMA’s special report into EIA practice in the UK, this is most frequently occurs in the assessment of infrastructure developments, particularly wind farms.

This view is also apparent with certain decision makers. For example, I was recently informed by one local planning authority that the council would automatically object to a project on the basis that a visual assessment had concluded that a limited number of receptors would be moderately adversely affected.

This assertion is flawed for a number of reasons:

  • It can ignore a project’s merits, including any positive environmental effects.
  • It doesn’t accord with the EIA Regulations or any other well known guidance.
  • It can lead to nervousness among assessors about concluding an effect may be of moderate adverse significance, thereby compromising objectivity.
  • It could mean that, in an attempt to reduce a moderate environmental effect to slight, other effects may worsen.
  • It may cloud the decision making and assessment process.

Tim Smith, from Berwin Leighton Paisner, warns: “Drawing a line under ‘moderate’ and excluding anything lower would tend to lead to errors in assessing cumulative effects properly. Very limited impacts when taken cumulatively can become significant.”
Furthermore, he notes: “Construing ‘significance’ is always more important at the screening stage than when drafting the environmental statement. The history of judicial reviews in this area has shown that getting the screening decision wrong always makes permissions more vulnerable than criticisms about the content of the environmental statement.”
In summary, the traditional matrix-based approach to assessing the significance of effects may no longer be applicable to many topic areas. More bespoke significance criteria are emerging and an effect of “moderate significance or above” does not necessarily mean it is significant in the context of the EIA Regulations.

Given that the EIA Regulations require an environmental statement to include “a description of the likely significant effects of the development on the environment”, if only moderate adverse effects are deemed significant they would be very short documents indeed.

This article was written as a contribution to the EIA Quality Mark’s commitment to improving EIA practice.

Andrew Saunders is a technical director at Hyder


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