Because of past nuclear production operations along the Columbia River, there is intense public and tribal interest in assessing any residual Hanford Site related contamination along the river from the Hanford Reach to the Pacific Ocean. The Columbia River Comprehensive Impact Assessment was proposed to address these concerns. The assessment of the Columbia River is being conducted in phases. The initial phase is a screening assessment of the risk, which addresses current environmental conditions for a range of potential uses. One component of the screening assessment estimates the risk from contaminants in the Columbia River to the environment. The objective of the ecological risk assessment is to determine whether contaminants from the Columbia River pose a significant threat to selected receptor species that exist in the river and riparian communities of the study area. This report (1) identifies the receptor species selected for the screening assessment of ecological risk and (2) describes the selection process. The species selection process consisted of two tiers. In Tier 1, a master species list was developed that included many plant and animal species known to occur in the aquatic and riparian systems of the Columbia River between Priest Rapids Dam and the Columbia River estuary. This master list was reduced to 368 species that occur in the study area (Priest Rapids Dam to McNary Dam). In Tier 2, the 181 Tier 1 species were qualitatively ranked based on a scoring of their potential exposure and sensitivity to contaminants using a conceptual exposure model for the study area.
