Comparison of Similarities and Differences Among Risk Assessment and Risk-Based Cleanup Goals Guidances. K. Zhang, C. Susiene, M. Garry, M. G. Norman, and C. M. Velicer, Foster Wheeler Environmental, 10900 NE 8th St., Suite 1300, Bellevue, WA 98004-4405
Many risk assessment paradigms have been published. Many of these result in risk-based clean-up goals. Examples are U.S. EPA’s Risk Assessment Guidance Standards (RAGS), U.S. EPA’s Soil Screening Guidance (SSG), ASTM’s Risk-Based Corrective Action Standard (RBCA), and EPA Region IX’s Preliminary Remediation Goals (PRGs). Superficially, the guidances appear very similar. They utilize the same databases to evaluate chemical toxicity information, and they calculate risk using equations similar to those presented in RAGS. However, the similarities may be misleading. Subtle differences in the guidance’s requirements for collecting samples, defining exposure parameters, assessing exposure pathways, and identifying target risk levels can result in substantially different results thereby causing likely schedule delays and increased corrective action costs. This paper addresses key similarities and differences among several guidances currently utilized to either perform risk assessments or to derive risk-based cleanup goals. A site-specific comparison is made utilizing several risk-based approaches.