Introduction to Assessments

Background and purpose

In some geographic areas, there may be national regulatory requirements to conduct underwater sound disturbance assessments or similar studies, which may be either standalone studies or part of wider Environment Impact Assessments (EIA).

In addition to, or in the absence of, any national requirements, individual companies may also have internal standards and procedures for reviewing project activities, implementing either EIAs or standalone underwater sound assessments.

The purpose of this tool is to provide a high-level overview of the various steps that are commonly undertaken to review and assess potential impacts of underwater sound associated with oil and gas exploration and production related activities. This tool is not intended to replicate existing guides or definitions of existing Environment Impact Assessment processes.

Impact and Risk Assessment

A major difference between environmental impact and risk assessment processes is the approach taken to define and account for uncertainty.

For impact assessment purposes, an impact is assumed to occur and is assessed in terms of significance. Impacts not considered likely to occur will often be removed during the scoping stage of an EIA and therefore not further assessed. The evaluation of the significance of impacts generally combines the magnitude of potential impacts against the sensitivity of the receptor.

Risk, however, is traditionally defined in term of a product of an ‘impact’, or consequence of an event, and the likelihood or probability of the event occurring.

Environmental Impact Assessment (EIA) is a process of evaluating the likely environmental impacts of a proposed project or development, evaluating interrelated socioeconomic, cultural, and human health impacts, both beneficial and adverse. It aims to predict environmental impacts at an early stage in project planning and design, find ways and means to avoid or reduce adverse impacts through the application of the mitigation hierarchy, and present the predictions and options to decision makers.

The magnitude describes the change that the impact of an activity is likely to impact upon the receptor and is a function of severity, duration (temporary to permanent effect), extent (local to global), scale (not distinguishable to major change in) and frequency. The sensitivity of the receptor considers a species (or habitat) conservation or protection status, life stage (juvenile, adult) and functions (reproduction, migration, feeding).

Risk assessment is a tool typically used to assess potential impacts associated with industry activities and manage the identified risks to acceptable levels. Striking a balance between being fit-for-purpose and being excessive in the assessment of environmental risk requires first developing a robust understanding of potential hazards and the probability that such hazards might occur. From this analysis, an estimate of risk is developed.

High risk activities would have both a high consequence level and a high probability of occurrence. Medium risk activities would have a high negative consequence, but negligible probability of occurrence; or high probability of occurrence, but minor negative consequence. Low risk activities would have a minor negative consequence and negligible probability of occurrence.

The higher the potential risk, the more complex a risk assessment becomes and, therefore, the greater the need for a science-based understanding to support the analysis. For higher levels of risk, additional mitigation or prevention controls to reduce risk should be identified, if possible, by either lowering the consequence of the interaction or reducing the probability that the interaction will occur.