Introduction: Definitions and Concepts Scope and Definitions Regulatory Context Ecorisk Framework The Remedial Process Site Characterization and Scoping Assessment The Assessment Planning Process The Assessment Plan Baseline Ecological Risk Assessment Remedial Alternatives Assessment Efficacy Assessment Damage Assessment Tiers: Scoping, Screening, and Definitive Assessments Relationship to Human Health Risk Assessment Differences in Human Health and Ecological Risk Assessment Why Ecological Endpoints May be More Sensitive than Humans Scale in Human Health and Ecological Risk Participants in Ecological Risk Assessments Problem Formation Risk Managers and Risk Assessors Physical Scope Spatial Extant Spatial Units Source Units Watershed Units Groundwater Units Terrestrial Integrator Units Spatial Subunits Site Description Source Description Assessment Endpoints Selection Selection of Endpoint Properties Selection of Levels of Effect on Properties of Endpoint Entities Conceptual Models Conceptual Models of Alternative Baseline Scenarios Components of a Conceptual Model Unit Types and Default Conceptual Models Sources Routes of Transport Exposure Media Receptors Indirect Exposure and Effects Output to Other Units Relationship to Other Conceptual Models Form of the Conceptual Model Analysis Plan Measures of Exposure, Effects, and Environmental Conditions Sampling and Analysis Plan Reference Sites and Reference Information Field Verification of the Plan Deviations and Contingencies Analysis of Exposure Components of Analysis of Exposure Sampling and Chemical Analysis of Media Chemical Analysis of Biota and Biomarkers Bioassay Biosurvey Transport and Fate Models Exposure Models Exposure to Contaminants in Surface Water Exposure to Contaminants in Soil Sampling, Extraction, and Chemical Analysis Partial Chemical Extraction and Normalization Nonaqueous Phase Liquids Soil Depth Profile Future Exposure Exposure of Aquatic Organisms Exposure of Plants Rooting Depth Rhizosphere Wetlands Soil Properties Chemical Form Chemical Interactions Interspecies Differences Air as an Exposure Route Exposure of Soil Invertebrates Depth of Exposure and Ingested Material Soil Properties and Chemical Interactions Exposure of Soil Microbial Communities Exposure of Wildlife Exposure Based on Internal Measures Exposure Based on External Measures Parameters for Estimation of Exposure Uptake Models Aquatic Organism Uptake Terrestrial Arthropod Uptake Terrestrial Vertebrate Uptake Petroleum and Other Chemical Mixtures Summary of Exposure Characterization Screening Against Ecotoxicological Benchmarks Exposure Concentrations Screening Media Screening Receptors Screening Sites Data Collection and Evaluation Data Adequacy and Uncertainties Presentation of a Screening Assessment Risk Characterization: Definitive Single Chemical Toxicity Aqueous Exposure of Aquatic Organisms Sediment Exposure of Benthic Invertibrate Soil Exposure of Plants, Invertebrates and Microbial Communities Multi-Media Exposure of Wildlife Body Burdens of Endpoint Organisms Ambient Media Toxicity Tests Biological Surveys Biomarkers Weight of Evidence Triad Alternatives Future Risks Interpretation Reporting Ecological Risks Uncertainty Concepts and Definitions Why Analyze Uncertainty? Quantitative Techniques for Analysis of Uncertainty Making Sense of Uncertainty and Probability Methods for Exposure Methods for Effects Methods for Risk Characterization Parameters to Treat as Uncertain Remedial Goals Preliminary Remedial Goals Prigs for Surface Water Sediment Soil Modification of PRGs Land Use Remedial Goal Options Human Health Remedial Decisions Risks From Remediation Problem Formulation Conceptual Models for Alternatives Assessment Assessment Endpoints Exposure and Effects Assessment Case Studies Recovery Time to Recovery Hastening Recovery Balancing Risks Different Risk Metrics Win/Lose Outcomes Land Use Conflicts, Etc. Cost-Benefit Analysis Post-Remedial Assessment Post-Remedial Monitoring Residual Risks Preassessment Screen Phase Assessment Plan Phase Assessment Phase Quantification Phase Damage Determination Post-Assessment Phase Alternative Approaches Conclusions Glossary Appendix References