| Tier-3 Evaluation: |
A risk-based analysis (risk-based assessment) that involves a significant incremental effort over the Tier-2 evaluation to develop site-specific corrective action goals. The Tier-3 evaluation for human exposures pathways typically use advanced exposure assessment, toxicity and risk assessment screening techniques, for example, probable and most likely exposure assessment methods, use of bio-availability data, use of advanced fate and transportation models, allowing maximum flexibility of the site-specific target levels (SSTL) for potential direct and indirect exposure pathways at the point(s) of exposure based on site-specific conditions. Tier-3 requires statistical models before, during and after corrective action of the source and exposure pathways, along with clearance methods and analysis. See Phase III, IV and V |