OTHER FEDERAL RISK ASSESSMENT METHODS
As this report has emphasized, the task of assessing risks at UXO sites is complicated for both technical and political reasons. Technically, the difficulties stem from the presence of multiple hazards, the lack of effective technologies for locating UXO, the many sources of uncertainty associated with UXO and its environmental setting, and the uncertainties associated with future human behavior. The risk assessor must consider hazards with very different natures: explosions of ordnance items with unknown stability at discrete points in the environment, and migration of contaminants from the ordnance area to dispersed receptors. The heterogeneous distribution of UXO, with respect to both depth and area and the lack of technology capable of quantifying this distribution complicate this task. Adding further complexity are questions about which types of human behavior will occur in the future. If the site is designated as a nature preserve, for example, will people wander off the path and dig holes? Will the land use change and the site be developed in the future? Adding to these technical challenges is a lack of trust in risk assessment among many federal and state environmental regulators and concerned community groups. Many stakeholders have expressed concern that the very use of risk assessment implies that some degree of risk above zero is acceptable.
Although the technical and political challenges associated with risk assessment at UXO sites are daunting, they are not insurmountable. Many other agencies have successfully addressed similar challenges in risk assessment and prioritization. In this chapter, we present a sampling of approaches that other agencies have used to handle common problems in risk assessment. Table 4.1 summarizes the agency methods and guidelines we reviewed in developing this