Technical Papers

Ecological risk assessment can be a critical part of the site remediation process, with the potential to fundamentally influence the cost and scope of site clean-up. The initial phase of an ecological risk assessment is screening, in which site contaminant concentrations are compared to published ecological screening levels (ESLs) in order to identify contaminants for further evaluation. Risk assessments in most State and Federal programs follow a process in which the identification of one or more contaminants in any sample above respective ESLs may trigger the requirement for a full baseline ecological risk assessment. Full baseline assessments are costly and time consuming, often adding months or years to the project schedule. However, many of screening levels that trigger baseline assessments are not environmentally meaningful and only serve to create unnecessary evaluation. Screening levels are also often misused at later stages of the risk process to draw inappropriate conclusions about ecological hazard. Common problems with the development and application of screening levels are described below, followed by suggestions to improve the screening and risk management processes.