To what extent are EIAs influenced by SEAs?

20th March 2013

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  • Local government



David Hourd and Kate Burrows explore the link between strategic environmental assessment (SEA) and environmental impact assessment (EIA), looking at a sample of EIAs and the barriers to assessments referring to SEAs

The development of EIA theory and practice has been accompanied by a significant amount of literature that identifies weaknesses in its application. These include limited consideration of cumulative impacts and alternatives, and concerns that EIA occurs too late in the planning process. The development of SEA has been cited as a partial solution to these deficiencies, and a means to creating a holistic and tiered system of environmental assessment.

SEA is largely conducted before a corresponding EIA is undertaken. This means that information on the environmental impact of a plan can cascade down through the decision-making process and used in an EIA at a later stage. Theoretically this should reduce the required work to be undertaken, however, experience suggests that link between EIA and corresponding SEAs is not commonplace. Therefore, EIAs may be missing valuable input from relevant SEAs.

Case studies

Identifying EIAs that had been covered in an SEA or sustainability appraisal (SA) was not particularly easy, but four projects where identified and reviewed:

  • The EIA for a bridge replacement in North Wales (assessed in the mid-Wales transport plan SEA ).
  • The EIA for Hinckley Point C (assessed in the nuclear strategic siting assessment (SSA) and national policy statement (NPS) SEA).
  • The EIA for the new Wylfa nuclear power station (scoping stage) (SSA and NPS SEA).
  • The EIA for an eco-town in Oxfordshire (covered in the planned eco-town planning policy statement SA ).

In each, we looked for references to the plan-level SEA/SA, particularly in scoping, impact assessment and mitigation proposals.

The review concluded there was little reference to corresponding SEA/SAs. This was unexpected given that the SEA/SAs provided specific assessments, particularly the nuclear SSAs.

The EIAs for the bridge replacement and the eco-town made no reference to the SEA/SA. Both power station EIAs acknowledged the SSA/SA, but more as a matter of planning context and relevance to the sustainability statements rather than to inform the EIA.

There were, however, consistencies between the assessments and mitigation proposals from the SEA/SAs and the EIAs, although it was hard to identify whether conclusions were formed in the absence of the SEA/SAs or with their direction. It should be noted that other examples identified SEAs drawing from existing project EIAs to assist their assessments showing a bottom-up approach rather than trickle-down.

While only a small sample of projects were considered for this article, broader discussion with experienced EIA practitioners confirms that there seems to be a disconnect between SEA and EIA. Reasons for this include:

  • Timing/sequencing of SEAs and EIAs: a number of local authorities are still in the process of developing their local plans, with many yet to produce their land allocation plans which would cover specific sites and projects, therefore an SEA/SA may not be available.
  • Lack of detail in SEA/SAs: although a project is covered in a particular SEA/SA the level of detail may be insufficient to be useful to inform an EIA, ie it may be too high-level or its findings so apparent any competent EIA would address them anyway.
  • Narrow focus of EIA practitioners: once an EIA practitioner begins work on a new project it is easy to get engrossed in standard procedures for delivering the EIA, so looking for references in an SEA is not a high priority.
  • Lack of mandatory scoping: The scoping stage would be a helpful place for SEA findings to be linked to the EIA, however, at present scoping is not mandatory.

The department for transport’s design manual for roads and bridges (DMRB) is clear about the benefits of linking EIA and SEA, stating : “All projects subject to EIA will need to be aware of any statutory obligations set out in the SEA statement/environmental report prepared for any relevant plans and programmes.”

The DMRB also acknowledges that an SEA can create obligations for projects, such as identifying environmental problems that should be addressed by the project, pinpointing key types of impacts to address or measures for mitigation/monitoring.

The manual recognises that the overseeing organisation has a responsibility to consider these links. In planning for roads/bridges, for example, such responsibility would lie with the relevant highways authority. For non-highways projects, this role could be adopted by the local authority and/or statutory bodies, both of which should be familiar with the relevant completed SEA/SAs.

There is a clear case for the information in an SEA to be carried down to an EIA in a consistent way. This could be part of formal scoping opinion responses from local authorities and statutory consultees, where relevant findings of an SEA/SA could be signposted and/or summarised.

Such an approach could provide more focused scoping responses and identify existing collated data, cumulative effects and generic mitigation/enhancement measures that should be considered.

The forthcoming changes to the EIA Directive may result in a mandatory requirement for scoping which would provide a platform for making the links between SEA and EIA clearer.

There is also scope for EIAs to feedback into future iterations of SEA/SAs or monitoring where more detailed project findings are deemed useful.

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

David Hourd, MIEMA, is a principal environmental consultant and Kate Burrows, AIEMA, is a consultant at Hyder Consulting


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