The benefits of assessing risk in EIA

27th September 2012

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Atkins' Daniel Parsons and Andrew Croft examine how risk assessment is being used in environmental impact assessment (EIA) and suggests they could be of value on sites where there may be archaeological remains

In creating an EIA, practitioners assemble a detailed baseline establishing the nature and the environmental value of a site to provide a sound basis on which to determine the potential impacts of a project.

As a project will occur in the future, and we can never have complete understanding of an environment, identified impacts are derived from predictions based on imperfect knowledge.

The methods for determining impacts vary considerably between environment disciplines and different projects; from detailed computer models to qualified professional judgement.

The availability of accurate information is important in all forms of impact assessment and is critical to the usefulness of the outcome. The scanter the information, the less predictable the impact.

Risk assessments quantify the likely outcome of an unknown event by assessing the likelihood of the event occurring and the severity of the consequences of the event occurring. In this respect all impact assessments are a form of risk assessment since they are based on imperfect knowledge, although most are not recognised as such.

Some sectors go a step further in their approach, embracing a more formal and recognised risk assessment method. For instance, risk assessments relating to contamination of land are common in environmental statements, and the Highways Agency’s Design manual for roads and bridges uses the agency’s water risk assessment tool to identify potential impacts to controlled waters from traffic accidents.

Using risk assessments

A risk assessment is particularly useful when there is a substantial degree of uncertainty in the occurrence of an impact or the existence of a receptor, and where an impact is likely to result in a significant environmental effect.

By using a risk-assessment approach this uncertainty is included in the EIA process and is clearly expressed in the determination of whether significant effects would result.

For most EIAs, however, this may not be a useful approach as the likelihood of an impact occurring, or the presence of a receptor, is a virtual certainty. The demolition of a listed building, for example, would not be best described in terms of risk assessment since the presence of the building is easy to determine definitively and the impact is straightforward to predict.

On the other hand, it can be more difficult to identify and assess potential impacts on other receptors with the same level of confidence. For example, it is often difficult to ascertain accurately whether there are important below-ground archaeological remains present at a site.

Standard approaches, such as desk-based assessment, can help us identify known features or readily identifiable remains, but they struggle to provide certainty for less physically substantial archaeology.

To address this, various forms of archaeological prospection can be employed, but these are often costly and can fail to determine conclusively the presence or absence of remains. For example, trenching often misses the scattered remains of Saxon period activity.

Archaeologists, therefore, have to interpret contextual evidence to predict the risk that archaeological remains survive on the site and the likely nature and importance of such remains.

The latter aspect is critical to risk assessment as the purpose of EIA is to identify significant environmental effects. In the case of archaeology, to be considered “significant” the remains would have to be of some importance. Such remains are unusual; the majority of archaeology is of local interest and can be addressed through standard post-consent planning conditions without the need for detailed consideration in an environmental statement. Only more important remains require detailed consideration, including pre-submission investigation and post-consent investigation.

Archaeologists practising EIA often undertake informal risk assessments but do not tend to focus on the likely importance of archaeological remains.

A wider approach

The adoption of a more formal risk-assessment model for determining potential impacts to archaeology, as demonstrated above, could benefit archaeological EIA practice.

The EIA process would not need to change a great deal as it is already informally risk-assessment based. Practitioners would, however, need to apply a more structured approach and think about the way risks and impacts are reported within the environmental statement.

Such a model could certainly benefit developers as significant risks could be identified earlier in the process and managed accordingly. It may also help focus attention on locations where our understanding of the past may be furthered by archaeological investigation – rather than expending our efforts exploring areas of minimal archaeological potential.

Another benefit of using risk assessments is that they provide practitioners with a more structured framework on which to base decisions of professional judgement. In turn, this could aid competent authorities by providing a more consistent and less subjective approach to assessment.

A more formal, risk-based approach that addresses presence and importance may benefit archaeological EIA practice and could provide pointers for other disciplines.

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

Daniel Parsons, AIEMA, is a senior environmental consultant and Andrew Croft is an associate heritage consultant at Atkins


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