The RI report (URS Greiner, Inc. and CH2M Hill 2001a) was prepared by contractors for EPA Region 10 based on EPA’s guidance document for conducting RI/FS studies (EPA 1988) through the RI process set forth in the National Oil and Hazardous Substances Pollution Contingency Plan (NCP, 40 CFR Part 300) (URS Greiner, Inc. and CH2M Hill 2001b, p. 1-2). The information in the RI report is used to evaluate risks to human health and the environment and potential remedial alternatives.
In this chapter, the RI of the Coeur d’Alene River basin (URS Greiner, Inc. and CH2M Hill 2001a) is assessed with respect to the following:
Adequacy and application of EPA’s own Superfund guidance for RIs
Consistency with best scientific practices
Validity of conclusions
Additionally, this chapter evaluates the scientific and technical aspects of the following:
EPA’s determination of the geographic extent of areas contaminated by waste-site sources
Types of data and analyses used to assess the extent of contamination
Approaches used to collect and analyze the data that resulted in conclusions
Considerations of contaminant chemical speciation and transport
Human health aspects of the RI are primarily evaluated in Chapter 5, “Human Health Risk Assessment in the Coeur d’Alene Basin.” The Human Health Risk Assessment (HHRA), undertaken concurrent with the RI, characterizes heavy-metal contamination in relation to potential human health risks.
The Coeur d’Alene River basin is a large-scale, complex system with extensive anthropogenic overprints that have increased the multiple complexities and interacting processes at work throughout the basin. This vast, mountainous river system has a long history of mining, logging, fishing, trading, and tourism (see Chapters 2 and 3). The high precipitation and high-flow events, which are characteristic of the Coeur d’Alene basin, have distributed mining wastes over many miles. The size and complexity of the basin combined with the highly variable nature of the mine wastes render site characterization a formidable task.