Chapter 1 Introduction: Definitions and Concepts ......................................... 1 1.1 Scope and Definitions ...................................................... 1 1.2 Regulatory Context ......................................................... 3 1.3 Ecorisk Framework .......................................................... 4 1.4 The Remedial Process ....................................................... 6 1.4.1 Preliminary Site Characterization and Scoping Assessment ............. 7 1.4.2 The Problem Formulation Process ...................................... 8 1.4.3 The Analysis Plan .................................................... 8 1.4.4 Baseline Ecological Risk Assessment .................................. 8 1.4.5 Remedial Alternatives Assessment ..................................... 9 1.4.6 Efficacy Assessment ................................................. 10 1.4.7 Damage Assessment ................................................... 10 1.5 Tiers: Scoping, Screening, and Definitive Assessments ..................... 11 1.6 Relationship to Human Health Risk Assessment .............................. 13 1.6.1 Differences in Human Health and Ecological Risk Assessment .......... 14 1.6.2 Why Ecological Entities May Be More Sensitive than Humans ........... 16 1.7 Scale in Human Health and Ecological Risk ................................. 16 1.8 Participants in Ecological Risk Assessments ............................... 17 Chapter 2 Problem Formulation ........................................................... 19 2.1 Risk Managers and Risk Assessors .......................................... 19 2.2 Physical Scope ............................................................ 23 2.2.1 Spatial Extent ...................................................... 23 2.2.2 Spatial Units ....................................................... 24 2.2.2.1 Source Units ................................................ 25 2.2.2.2 Watershed Units ............................................. 26 2.2.2.3 Groundwater Units ........................................... 27 2.2.2.4 Wildlife Units .............................................. 27 2.2.3 Spatial Subunits .................................................... 28 2.3 Site Description .......................................................... 29 2.4 Source Description ........................................................ 31 2.5 Assessment Endpoint Selection ............................................. 31 2.5.1 Selection of Endpoint Entities ...................................... 32 2.5.2 Selection of Assessment Endpoint Properties ......................... 37 2.5.3 Selection of Levels of Effect on Properties of Endpoint Entities .... 40 2.6 Conceptual Models ......................................................... 42 2.6.1 Conceptual Models of Alternative Baseline Scenarios ................ 43 2.6.2 Components of a Conceptual Model ................................... 44 2.6.3 Unit Types and Default Conceptual Models ........................... 45 2.6.4 Sources ............................................................ 45 2.6.5 Routes of Transport ................................................ 47 2.6.6 Exposure Media ..................................................... 49 2.6.7 Routes of Exposure ................................................. 49 2.6.8 Receptors .......................................................... 51 2.6.9 Indirect Exposure and Effects ...................................... 51 2.6.10 Output to Other Units .............................................. 51 2.6.11 Relationship to Other Conceptual Models ............................ 52 2.6.12 Form of the Conceptual Model ....................................... 52 2.7 Analysis Plan ............................................................. 53 2.7.1 Measures of Exposure, Effects, and Environmental Conditions ......... 56 2.7.2 Sampling and Analysis Plan .......................................... 58 2.7.3 Reference Sites and Reference Information ........................... 61 2.7.3.1 Information Concerning the Precontamination State of the Contaminated Site ............................................ 61 2.7.3.2 Model-Derived Information ................................... 61 2.7.3.3 Information Concerning Other Sites .......................... 62 2.7.3.4 Information Concerning the Regional Reference ............... 64 2.7.3.5 Positive Reference Information .............................. 65 2.7.3.6 Background .................................................. 66 2.7.4 Field Verification of the Plan ...................................... 66 2.7.5 Deviations and Contingencies ........................................ 66 Chapter 3 Analysis of Exposure .......................................................... 69 3.1 Components of Analysis of Exposure ....................................... 70 3.1.1 Sampling and Chemical Analysis of Media ............................ 71 3.1.2 Chemical Analysis of Biota and Biomarkers .......................... 73 3.1.3 Bioassay ........................................................... 77 3.1.4 Biosurvey .......................................................... 78 3.1.5 Transport and Fate Models .......................................... 78 3.1.6 Exposure Models .................................................... 79 3.2 Exposure to Contaminants in Surface Water ................................ 79 3.3 Exposure to Contaminants in Sediment ..................................... 82 3.4 Exposure to Contaminants in Soil ......................................... 86 3.4.1 Sampling, Extraction, and Chemical Analysis ........................ 86 3.4.1.1 Partial Chemical Extraction and Normalization .............. 88 3.4.1.2 Nonaqueous-Phase Liquids ................................... 89 3.4.2 Soil Depth Profile ................................................. 90 3.4.3 Future Exposures ................................................... 90 3.5 Exposure of Terrestrial Plants ........................................... 91 3.5.1 Rooting Depth ...................................................... 92 3.5.2 Rhizosphere ........................................................ 93 3.5.3 Wetlands ........................................................... 93 3.5.4 Soil Properties .................................................... 94 3.5.5 Chemical Form ...................................................... 95 3.5.6 Chemical Interactions .............................................. 95 3.5.7 Interspecies Differences ........................................... 95 3.5.8 Air as an Exposure Route ........................................... 96 3.6 Exposure of Soil Invertebrates ........................................... 97 3.6.1 Depth of Exposure and Ingested Material ............................ 97 3.6.2 Soil Properties and Chemical Interactions ......................... 100 3.7 Exposure of Soil Microbial Communities .................................. 100 3.8 Exposure of Wildlife .................................................... 101 3.8.1 Exposure Based on Internal Measures ............................... 101 3.8.2 Exposure Based on External Measures ............................... 103 3.8.2.1 Exposure-Modifying Factors ................................ 108 3.8.2.2 Probabilistic Exposure Estimation ........................ 108 3.8.3 Parameters for Estimation of Exposure ............................. 109 3.8.3.1 Body Weight ............................................... 109 3.8.3.2 Food and Water Consumption Rates .......................... 110 3.8.3.3 Inhalation Rates .......................................... 111 3.8.3.4 Soil Consumption .......................................... 112 3.8.3.5 Home Range and Territory Size ............................. 113 3.9 Uptake Models ........................................................... 115 3.9.1 Aquatic Organism Uptake ........................................... 118 3.9.2 Terrestrial Plant Uptake .......................................... 121 3.9.2.1 Empirical Models for Inorganic Chemicals .................. 122 3.9.2.2 Empirical Models for Organic Chemicals .................... 125 3.9.2.3 Mechanistic Models ........................................ 128 3.9.2.4 Surface Contamination ..................................... 128 3.9.2.5 Plant Tissue Type ......................................... 129 3.9.3 Earthworm Uptake .................................................. 129 3.9.4 Terrestrial Arthropod Uptake ...................................... 134 3.9.5 Terrestrial Vertebrate Uptake ..................................... 135 3.10 Petroleum and Other Chemical Mixtures ................................... 137 3.11 Summary of Exposure Characterization .................................... 140 Chapter 4 Analysis of Effects .......................................................... 141 4.1 Single-Chemical or Single-Material Toxicity Tests ........................ 142 4.1.1 Types of Toxicity Tests ........................................... 143 4.1.2 Aquatic Tests ..................................................... 145 4.1.3 Sediment Tests .................................................... 146 4.1.4 Soil Tests ........................................................ 147 4.1.5 Dietary and Oral Tests ............................................ 148 4.1.6 Body Burdens-Effect Relationships ................................. 149 4.1.7 Criteria and Standards ............................................ 153 4.1.8 Screening Benchmarks .............................................. 154 4.1.8.1 Criteria and Standards as Screening Benchmarks ............ 155 4.1.8.2 Tier II Values ............................................ 155 4.1.8.3 Thresholds for Statistical Significance ................... 155 4.1.8.4 Test Endpoints with Safety Factors ........................ 156 4.1.8.5 Distributions of Effects Levels ........................... 156 4.1.8.6 Other Methods Used for Sediment Benchmarks ................ 157 4.1.8.7 Summary of Screening Benchmarks ........................... 160 4.1.9 Single-Chemical Test Endpoints and Definitive Assessment .......... 161 4.1.9.1 Extrapolation Approaches .................................. 161 4.1.9.2 Extrapolations for Specific Endpoints ..................... 166 4.1.10 Quantitative Structure-Activity Relationships ..................... 173 4.1.11 Mechanistic Models of Effects ..................................... 175 4.1.12 Ecotoxicity Profiles .............................................. 175 4.2 Contaminated Media Toxicity Tests ........................................ 175 4.2.1 Aqueous Toxicity Tests ............................................. 180 4.2.2 Sediment Toxicity Tests ............................................ 180 4.2.3 Soil Toxicity Tests ................................................ 183 4.2.4 Ambient Media Tests with Wildlife .................................. 186 4.3 Biological Surveys ....................................................... 188 4.3.1 Aquatic Biological Surveys ......................................... 190 4.3.1.1 Periphyton ................................................. 191 4.3.1.2 Plankton ................................................... 192 4.3.1.3 Fish ....................................................... 193 4.3.1.4 Benthic Invertebrates ...................................... 194 4.3.2 Soil Biological Surveys ............................................ 196 4.3.3 Wildlife Surveys ................................................... 197 4.3.4 Plant Surveys ...................................................... 197 4.4 Biomarkers of Effects .................................................... 199 4.5 Indirect Effects ......................................................... 200 4.6 Exposure-Response Profile ................................................ 201 Chapter 5 Risk Characterization in Screening Assessments ............................... 203 5.1 Screening Chemicals ...................................................... 204 5.1.1 Screening against Background ....................................... 205 5.1.1.1 Selection of Background Data ............................... 205 5.1.1.2 Quantitative Methods for Comparison to Background .......... 207 5.1.1.3 Treatment of Background in Multimedia Exposures ............ 207 5.1.1.4 What Chemicals Can Be Screened against Background? ................................................ 207 5.1.1.5 When Is a Concentration Not Comparable to Background? ................................................ 208 5.1.1.6 Screening Biota Contamination Using Background Concentations for Abiotic Media ............................ 208 5.1.1.7 Screening Future Exposure Concentrations against Background ................................................. 208 5.1.2 Screening against Detection Limits ................................. 208 5.1.3 Screening against Waste Constituents ............................... 209 5.1.4 Screening against Physicochemical Properties ....................... 209 5.1.5 Screening against Ecotoxicological Benchmarks ...................... 209 5.1.6 Exposure Concentrations ............................................ 211 5.2 Screening Media .......................................................... 212 5.3 Screening Receptors ...................................................... 212 5.4 Screening Sites .......................................................... 213 5.5 Data Collection and Evaluation ........................................... 213 5.6 Data Adequacy and Uncertainties .......................................... 213 5.7 Presentation of a Screening Assessment ................................... 214 Chapter 6 Risk Characterization in Definitive Assessments .............................. 215 6.1 Single-Chemical Toxicity ................................................ 215 6.1.1 Aquatic Organisms ................................................. 219 6.1.2 Benthic Invertebrates ............................................. 222 6.1.3 Soil Exposure of Plants, Invertebrates, and Microbial Communities ....................................................... 224 6.1.4 Multimedia Exposure of Wildlife ................................... 226 6.1.4.1 Comparison of Exposure to Toxicity ........................ 226 6.1.4.2 Individual vs. Population Effects ......................... 228 6.1.5 Body Burdens of Endpoint Organisms ................................ 231 6.2 Ambient Media Toxicity Tests ............................................ 233 6.3 Biological Surveys ...................................................... 236 6.4 Biomarkers and Pathologies .............................................. 239 6.5 Weight of Evidence ...................................................... 241 6.6 Triad Alternatives ...................................................... 250 6.7 Risk Estimation ......................................................... 252 6.8 Future Risks ............................................................ 252 6.9 Interpretation .......................................................... 253 6.10 Reporting Ecological Risks .............................................. 254 Chapter 7 Uncertainty .................................................................. 257 7.1 Concepts and Definitions ................................................. 257 7.2 Why Analyze Uncertainty? ................................................. 260 7.2.1 Desire to Ensure Safety ............................................ 261 7.2.2 Desire to Avoid Excessive Conservatism ............................. 262 7.2.3 Desire to Acknowledge and Present Uncertainty ...................... 262 7.2.4 Need to Estimate a Probabilistic Endpoint .......................... 263 7.2.5 Planning Remedial Investigations ................................... 263 7.2.6 Aiding Decision Making ............................................. 263 7.2.7 Summary of Reasons ................................................. 264 7.3 Quantitative Techniques for Analysis of Uncertainty ...................... 264 7.3.1 Uncertainty Factors ................................................ 264 7.3.2 Data Distribution .................................................. 265 7.3.3 Monte Carlo Analysis and Uncertainty Propagation ................... 267 7.3.4 Nested Monte Carlo Analysis ........................................ 267 7.3.5 Sensitivity Analysis ............................................... 268 7.3.6 Analysis of Model Uncertainty ...................................... 269 7.4 Making Sense of Uncertainty and Probability .............................. 270 7.4.1 Defining Exposure Distributions .................................... 270 7.4.2 Defining Effects Distributions ..................................... 271 7.4.3 Defining Risk Distributions ........................................ 273 7.4.4 Data Distributions and Risk ........................................ 273 7.5 Methods for Exposure ..................................................... 274 7.5.1 Distributions of Measured Concentrations ........................... 274 7.5.2 Multimedia Exposure Models ......................................... 276 7.5.3 Transport and Fate Models .......................................... 278 7.6 Methods for Effects ...................................................... 279 7.6.1 Screening Benchmark Values ......................................... 279 7.6.2 Species Sensitivity Distributions .................................. 270 7.6.3 Sediment Effects Distributions ..................................... 282 7.6.4 Biological Surveys ................................................. 282 7.6.5 Media Toxicity Tests ............................................... 283 7.7 Methods for Risk Characterization ........................................ 283 7.7.1 Simple Quotient Methods ............................................ 283 7.7.2 Joint Probabilities ................................................ 284 7.8 Parameters to Treat as Uncertain ......................................... 285 7.9 Quality Assurance ........................................................ 286 Chapter 8 Remedial Goals ............................................................... 291 8.1 Preliminary Remedial Goals ............................................... 292 8.1.1 PRGs for Surface Water ............................................. 293 8.1.2 Sediment ........................................................... 294 8.1.3 Soil ............................................................... 294 8.1.4 Modification of PRGs ............................................... 295 8.1.5 Land Use ........................................................... 297 8.2 Remedial Goal Options .................................................... 298 8.3 Spatial Considerations ................................................... 301 8.4 Human Health ............................................................. 302 Chapter 9 Remedial Decisions ........................................................... 303 9.1 Remedial Alternative Analysis ............................................ 304 9.1.1 Risks Associated with Remedial Alternatives ........................ 306 9.1.2 Problem Formulation ................................................ 307 9.1.2.1 The Nature of Stressors .................................... 307 9.1.2.2 Conceptual Models for Alternatives Assessments ............. 307 9.1.2.3 Assessment Endpoints ....................................... 310 9.1.2.4 Reference .................................................. 311 9.1.3 Exposure Assessment ................................................ 312 9.1.4 Effects Assessment ................................................. 313 9.1.5 Risk Characterization .............................................. 313 9.1.5.1 Spatial Considerations ..................................... 314 9.1.5.2 Recovery ................................................... 315 9.2 Risk Balancing ........................................................... 318 9.2.1 Different Risk Metrics ............................................. 319 9.2.2 Land-Use Conflicts ................................................. 320 9.2.3 An Approach to Balancing Risk ...................................... 320 9.2.3.1 A Common Scale ............................................. 321 9.2.3.2 Human Health Categories .................................... 321 9.2.3.3 Ecological Categories ...................................... 322 9.2.3.4 Risk Balancing Based on a Common Scale ..................... 323 9.2.3.5 Remedial Units ............................................. 325 9.2.3.6 Summary of Risk Balancing .................................. 325 9.3 Life-Cycle Assessment .................................................... 326 9.4 Cost-Benefit Analysis .................................................... 326 9.5 Prioritization of Sites for Remediation .................................. 326 Chapter 10 Post-Remedial Assessments .................................................... 329 10.1 Remedial Efficacy ....................................................... 329 10.2 Residual Risks .......................................................... 330 10.2.1 Preassessment Screen Phase ....................................... 334 10.2.2 Assessment Plan Phase ............................................ 334 10.2.3 Assessment Phase ................................................. 335 10.2.3.1 Injury Determination Phase .............................. 335 10.2.3.2 Quantification Phase .................................... 337 10.2.3.3 Damage Determination .................................... 338 10.2.4 Post-Assessment Phase ............................................ 339 10.2.5 Alternative Approaches ........................................... 340 10.2.6 Conclusions ...................................................... 340 Appendix Biota Sampling and Survey Methods ............................................ 343 A.1 Fishes .................................................................. 343 A.2 Periphyton .............................................................. 344 A.3 Plankton ................................................................ 345 A.4 Benthic Invertebrates ................................................... 345 A.5 Terrestrial Plants ...................................................... 347 A.6 Terrestrial Mollusks .................................................... 347 A.7 Earthworms .............................................................. 348 A.8 Terrestrial Arthropods .................................................. 348 A.9 Birds ................................................................... 349 A.9.1 Sampling Birds .................................................... 349 A.9.2 Avian Population Survey Methods ................................... 350 A.9.2.1 Territory Mapping ......................................... 350 A.9.2.2 Transects ................................................. 351 A.9.2.3 Point Counts .............................................. 352 A.9.2.4 Mark-Recapture ............................................ 352 A.9.2.5 Song Tapes ................................................ 352 A.9.2.6 Aerial Counts ............................................. 352 A.9.2.7 Habitat-Focused Surveys ................................... 353 A.9.2.8 Additional Information .................................... 353 A.9.3 Avian Nest Study Methods .......................................... 353 A.9.4 Avian Food Habit Study Methods .................................... 354 A.10 Mammals ................................................................. 354 A.10.1 Sampling Mammals ................................................. 354 A.10.2 Surveying Mammals ................................................ 356 A.10.2.1 Direct Observation ...................................... 356 A.10.2.2 Indirect Observation .................................... 358 A.10.2.3 Additional Information .................................. 359 A.11 Reptiles and Amphibians ................................................. 359 A.12 Vegetation Analysis to Identify Habitat Suitable for Wildlife Species ... 360 A.13 Sampling Considerations ................................................. 361 A.13.1 Spatial Components of Biota Sampling ............................. 361 A.13.2 Sample Handling .................................................. 362 A.13.3 Tissues to Analyze ............................................... 363 A.13.4 Permits .......................................................... 364 A.13.5 Euthanasia ....................................................... 364 A.13.6 Health Concerns .................................................. 365 Glossary ..................................................................... 369 References ................................................................... 377 Index ........................................................................ 423