Companies may own a number of sites, which are potentially a risk to the environment from ground contamination. The company may be at risk of prosecution Under Part IIA of the Environmental Protection Act 1990, or the Water Resources Act 1991.

Benefits

In order to prioritise expenditure on remedial measures a company would benefit from a tool to aid decision-making by ranking the sites in terms of risk.

Analysis

We have applied the Multi-Attribute Analysis Technique to the problem of risk ranking of contaminated sites for a private UK company. The Environment Agency who participated in the refinement of the model has approved the approach and risk-ranking model developed.

Multi-Attribute Techniques provide a means for aggregating disparate information on impacts into a single measure of impact, in this case risk. The method decomposes the risk into factors (attributes) which contribute to risk, thus forming a risk hierarchy. Adopting the terminology used in Part IIA of the legislation to define a contaminated site, the first level factors used in the model are source (contamination), pathway, and receptor. These factors are further dis-aggregated into contributors to risk.

Scores are assigned for a site under each of the factors according to defined criteria, which represent the potential for causing harm to the environment. Weights are assigned between factors according to their relative importance in contributing to harm to the environment.

How can we help

We will work with companies to define the risk model (hierarchy) by using a structured approach to facilitate an expert group. The objective is to define a model, which fully accounts for the contributors to risk and best suits the contaminated site data collected available to the company. Once the model has been defined sites can be readily rank ordered.

Sensitivity analysis can also be carried out to determine the effect of data uncertainties on the rank order.