Electricity Act 1989 - section 36 applications: guidance for applicants on using the design envelope

5. Assessment and the EIA report

5.1. Applicants should carefully consider the approach to assessing uncertainty and understand how this will influence the complexity of their assessment in the EIA report. If in the course of preparing the EIA report, it becomes clear that it is not possible to specify all the final details of the proposed development, the EIA report must explain how this has been addressed. The EIA report will need to establish the parameters of the proposed development for the purpose of the assessment. Relevant parameters enabling flexibility within an application will be project-specific. Examples include: maximum and minimum number of turbines and blade tip heights associated with wind farms; and maximum and minimum heights or widths of buildings associated with electricity generating development and associated infrastructure.

5.2. Where this approach is adopted, assessments should:

• be undertaken on the basis of the relevant design parameters applicable to the characteristics of the proposed development included in the application documents; and
• for each of the different receptors, establish those parameters likely to result in the maximum adverse effect (the worst case scenario) and be undertaken accordingly to determine significance.

5.3. Where flexibility is being sought, the EIA report should:

• clearly identify the characteristics of the proposed development that are yet to be finalised in the description of the development - the description of the development in the EIA report must not be so wide that it is insufficiently complete to comply with requirements of the EIA Regulations;
• include information relating to where flexibility is sought, taking into account the variations applicable to the proposed development;
• explain the reasons as to why characteristics of the proposed development remain uncertain in order to justify the flexibility sought; and
• ensure that the approach taken in the assessment is not overly complex, as this may impede the understanding of the assessment and the finding of likely significant effects - fewer options and variations make the EIA report easier to understand.

5.4. Where the applicant chooses to use a design envelope approach using a parameters-led assessment to establish the worst case scenario for the EIA report, the applicant should ensure that the applicable parameters are explained and clearly set out in order to:

• ensure that interactions between assessments of the relevant descriptions of the environment (identified in accordance with the EIA Regulations) are taken into account relevant to the worst case scenario(s) established and that careful consideration is given to how these are assessed;
• ensure that the assessment of the worst case scenario(s) addresses impacts which may not be significant on their own but could become significant when they inter-relate with other impacts alone or cumulatively with impacts from other developments (including those identified in other assessments of the relevant descriptions of the environment (identified in accordance with the EIA Regulations)); and
• ensure that the potential cumulative impacts with other developments are carefully identified such that the likely significant effects can be shown to have been identified and assessed against the appropriate baseline.