Technical challenges in the qualitative ecological risk assessments performed on the Hanford Site operable units

Qualitative Risk Assessments (QRAS) have been selected as the method for providing the risk-driver indications for interim, remedial, and cleanup actions for the Hanford Site operable units' ecological risk assessments. This expedited response action path has been developed for the Hanford Site to facilitate time-critical decisions and generate immediate emergency cleanup actions. Tight budgets and aggressive time schedules are a major factor in the development of the QRA process. The QRA is a quick way to find immediate threats and a good precursor to a full risk assessment. However, numerous technical challenges have been identified with the QRA approach. The QRA approach differs from a baseline risk assessment in several ways. The main differences involve the use of data that have previously been gathered from the site, and the development of a ''bias-for-action'' document that would reveal qualitative risks from the contaminants identified at the operable units. Technical challenges concerning the ecological portion of these QRAs have raised questions about using the ORA for decision-making and may have weakened the validity of its use in the established procedural framework. Challenges involving such issues as the extrapolation of the contaminant data, data validation and screening techniques, receptor selections, and the final risk characterization outcome threaten the feasibility of the QRA as a decision-making tool. This discussion provides insight into resolving technical challenges and may be a ''lessons-learned'' device for those interested in the QRA approach. Ultimately, these challenges are proving to be learning tools for scientists, regulators, and ecologists and are identifying the data gaps and research direction for future ecological baseline risk assessments