TOW RI REPORT REV. #1 09/JAN/92 ' *»£r, •' ' ft•*-! ;•', • • ENVIRONMENTAL PROTfi<ia?l6N A61NCY liRiNiATfVE RENEWAL CONTRACTING S-WATEGY (ARC! TETRA TECH, INC. O flR30000! TCW 4203 Rl REPORT 09/JAM/9REV. #12 TABLE OF CONTENTS 1.0 IKTRODUCTIOH 1-1 1.1 PURPOSE OF REPORT 1-1 1,2 SITE BACKGROUND 1-2 1.2.1 Site Description 1-2 1.2.2 Site History 1-5 1.2.3 Previous Site Investigations 1-9 2.0 PHYSICAL CHARACTERISTICS OF THE STUDY AREA 2-1 2.1 DEMOGRAPHY 2-1 2.2 METEOROLOGY 2-2 2.3 SURFACE FEATURES 2-2 2.4 SURFACE HYDROLOGY 2-3 2.5 SOILS 2-4 2.6 ECOLOGY 2-5 2.6.1 General Flora 2-5 2.6.2 General Fauna * 2-6 2.6.3 Threatened and Endangered Species 2-6 2.7 REGIONAL GEOLOGY 2-7 2.7.1 Geologic Setting 2-7 2.7.2 Lithologic Description 2-8 2.7.3 Structural Features 2-12 2.8 REGIONAL HYDROGEOLOGY 2-14 2.8.1 Hydrogeologic Setting . 2-14 2.9 ADDITIONAL BACKGROUND INFORMATION 2-20 2.9.1 Historical/Cultural Areas 2-20 2.9.2 Recreational and Other Natural Areas 2-20 2.9.3 Floodplain/Wetland Areas 2-21 2.9.4 Sources of Potable Water 2-21 3.0 STUDY AREA INVESTIGATIONS 3-1 3.1 SITE SURVEY 3-1 3.2 AIR INVESTIGATION . 3-3 3,3 SURFACE WATER AND SEDIMENT INVESTIGATION 3-4 3.4 ECOLOGICAL ASSESSMENT 3-6 3.5 SOIL INVESTIGATION 3-9 flR300002 TON 4208 RI REPORT REV. #1 09/JAN/92 3.5.1 Surface Soil Investigation 3-10 3.5.2 Subsurface Soil Investigation 3-13 3.6 GEOLOGIC AND HYDROGEOLOGIC INVESTIGATIONS 3-16 3.6.1 Geologic Field Characterization 3-16 3.6.2 Monitoring Well Installation 3-16 3.6.3 Monitoring Well Sampling 3-19 3.6.4 Residential Well Sampling 3-20 3.6.5 Groundwater Flow Determination 3-23 3.6.6 Aquifer Testing 3-23 4.0 RESULTS OF INVESTIGATION 4-1 4.1 DATA VALIDATION AND USE _ 4-1 4.2 SITE SURVEY 4-2 4.2.1 Population Survey 4-2 4.2.2 Residential Well Survey 4-3 4.2.3 Solid Waste Fill Volume - 4-3 4.2.4 Validation of Site Geology 4-4 4.3 AIR INVESTIGATION _ 4-4 4.3.1 Particle Monitoring 4-4 4.3.2 Organic Emission Monitoring 4-4 4.4 SURFACE WATER AND SEDIMENT INVESTIGATION 4-6 4.4.1 Surface Water Investigation 4-6 4.4.2 Sediment Investigation 4-17 4.5 ECOLOGICAL INVESTIGATION 4-26 4.5.1 General Description of Study Area 4-32 4.5.2 Threatened and Endangered Species 4-39 4.5.3 Summary of Ecological Investigation 4-40 4.6 SOIL INVESTIGATION RESULTS 4-41 4.6.1 Surface Soils Investigation 4-41 4.6.2 Subsurface Soils Investigation 4-48 4.7 GEOLOGIC/HYDROGEOLOGIC INVESTIGATION 4-56 4.7.1 Site Geologic Characterization 4-56 4.7.2 Ground-Water Flow Direction 4-63 4,7.3 Ground-water Velocity 4-71 4.7.4 Monitoring Well Sampling Results J 4-74 4.7.5 Residential Well Sampling Results 4-87 ii AR300QO"3 TOM 4203 RI REPORT REV. #1 09/JAM/92 4.7.6 General Chemistry Comparison - Residential PW Well / Data vs. Site Monitoring RIW Well Data 4-97'' 5.0 CONTAMINANT FATE AND TRANSPORT 5-1 5.1 CONTAMINANT FATE 5-1 5.1..1 Fate Processes 5-1 5.1.2 Identification of Contaminants 5-2 5.1.3 Fate/Transport Processes Relevant to Site Contaminants 5-4 5.2 POTENTIAL ROUTES OF CONTAMINANT MIGRATION 5-4 5.3 CONTAMINANT TRANSPORT 5-5 5.3.1 Groundwater and Surface Advective Transport of Dissolved Contaminants 5-6 5.3.2 Erosion of Sorbed Contaminants From Waste Areas 5-7 5.3.3 Sediment Transport of Sorbed Contaminants Currently in Intermittent Streams 5-9 5.3.4 Transport of Contaminants Dissolved in Surface Streams 5-13 6.0 BASELINE RISK ASSESSMENT 6-1 6.1 HUMAN HEALTH EVALUATION 6-2 6.1.1 Introduction to the Human Health Evaluation 6-3 6.1.2 Selection of Contaminants Under Review 6-5 6.1.3 Exposure Assessment 6-39 6.1.4 Toxicity Assessment 6-84 6.1.5 Human Health Risk Assessment 6-91 6.1.6 Uncertainties Associated with the Human Health Risk Assessment 6-116 6.1.7 Summary and Conclusions of the Human Health Risk Assessment 6-122 6.2 ECOLOGICAL ASSESSMENT 6-133 6.2.1 General Description of Study Area 6-134 6.2.2 Identification of Potential Receptors 6-136 6.2,3 Characterization of Contaminants 6-140 6.2.4 Toxicity Assessment 6-161 6.2.5 Exposure Assessment 6-174 6.2.6 Assessment of Risk 6-188 6.2.7 Conclusions of Ecologic Assessment 6-187 iii SR3000014 TON 4208 RI REPORT REV. #1 09/JAM/92 7.0 SUMMARY AND CONCLUSIONS 7-1 7.1 SUMMARY 7-1 7.1.1 Nature and Extent of Contamination 7-1 7.1.2 Data Limitations and Recommendations for Additional Work 7-6 7.2 FATE AND TRANSPORT 7-7 7.3 RISK ASSESSMENT 7-8 7.4 RECOMMENDED REMEDIAL OBJECTIVES 7-17 8.0 REFERENCES 8-1 8.1 REFERENCES FOR SECTIONS 1-5 AND SECTION 7 8-1 8.2 REFERENCES FOR SECTION 6.0 8-3 9.0 APPENDICES (submitted under separate cover), includes: APPENDIX A SITE SURVEY INFORMATION APPENDIX B SEDIMENT/SURFACE WATER INVESTIGATION INFORMATION APPENDIX C ECOLOGICAL ASSESSMENT INFORMATION APPENDIX D SOIL INVESTIGATION INFORMATION APPENDIX E GEOLOGIC/HYDROGEOLOGIC INVESTIGATION INFORMATION APPENDIX F RISK ASSESSMENT INFORMATION iv SR300005 row 4zos Rt REPORT - REV. fl 6 V 09/JAN/92 "j *, i."• -•- : V/- LIST OF FIGURES ... ................I..___.. - - -----^ Figure 1-1 Location Map 1-3 Figure 1-2 Current Waste Disposal Features 1-4 Figure 1-3 Historic Waste Disposal Areas 1-8 Figure 1-4 NUS Sample Locations 1-15 Figure 2-1 Virginia Physiographic Province Map 2-9 Figure 2-2 Regional Geologic Map 2-11 Figure 2-3 Regional Geologic Structures 2-13 Figure 2-4 Regional Geohydrologic Units 2-15 Figure 2-5 Generalized Ground-Water Flow Direction 2-19 Figure 2-6 Wetlands and Floodplains Areas 2-22 Figure 3-1 Surface Water and Sediment Sample Locations 3-5 Figure 3-2 Ecological Sampling Locations 3-7 Figure 3-3 Surface Soil Sample Locations 3-11 Figure 3-4 Subsurface Soil Sample Locations 3-14 Figure 3-5 Remedial Investigation Well Locations 3-17 Figure 3-6 Residential Well Location Map 3-21 Figure 4-1 Solid Waste Isopach Map 4-5 Figure 4-2 Stream Sediment Concentrations 4-25 Figure 4-3 Schematic Illustration of NX Cores 4-59 Figure 4-4a Line of Cross-Section *• 4-60 Figure 4-4b Cross-Section A to A' 4-61 Figure 4-4c Cross-Section B to B' 4-62 Figure 4-5 Regional Ground-Water Flow Direction 4-66 Figure 4-6 Potentiometric Surface and Groundwater Flow Direction 4-68 Figure 4-7 Local Ground-Water Flow Directions 4-69 Figure 4-8 Hydrogeochemistry Comparison Summary 4-96 Figure 5-1 Relationship Between Stream Velocity, Particle Size, and Regimes of Erosion, Transport, and Deposition 5-10 Figure 5-2 Lead Levels in Sediment and Surface Water - High Flow Conditions 5-11 Figure 5-3 Lead Levels in Sediment and Surface Water - Low Flow Conditions 5-12 Figure 6-1 Probability Density Plot of Blood-Lead Levels in Six-Year- Old Children Playing near Station SB-7 in Stream B 6-105 Figure 6-2 Probability Density Plot of Blood-Lead Levels in Six-Year- Old Children Playing near Station SE-13-in Stream E 6-107 Figure 6-3 Probability Density Plot of Blood-Lead Levels in Six-Year- Old Children Playing near Station SE-10 in Stream E 6-108 Figure 6-4 Ecological Sample Locations/Quadrants 6-188 flR300006 TON 4208 RI REPORT REV. f1 09/JAN/92 LIST OF TABLES Table 1-1 Abbreviated Dixie Caverns Landfill Site History Chronology 1-6 Table 1-2 NUS Data Summary (September, 1983) 1-11 Table 1-3 NUS High Concentration Summary (September, 1983) 1-16 Table 1-4 TAT Data Summary (1986) 1-18 Table 1-5 Olver Leachate Data Summary (1988) 1-19 Table 2-1 Regional Stratigraphic Units 2-10 Table 2-2 Groundwater Quality Background in Roanoke County 2-17 Table 3-1 Surface Soil Sample Analyses 3-12 Table 3-2 Residential Well Locations by Street Address 3-22 Table 4-1 Surface Water Field and Water Quality Parameters - 4-7 Table 4-2 Summary of Chemicals Detected in Surface Water - Round 1 4-9 Table 4-3 Summary of Chemicals Detected in Surface Water - Round 2 4-12 Table 4-4 Stream Sediment Characteristics 4-18 Table 4-5 Summary of Chemicals Detected in Sediment 4-21 Table 4-6 Benthic Macroinvertebrate Collection Summary 4-27 Table 4-7 Metric Values for the Benthic Investigation 4-29 Table 4-8 Plants Observed in the Dixie Caverns Landfill Study Area 4-30 Table 4-9 Geotechnical Parameters for Solid Waste Area Surface Soils 4-42 Table 4-10 Summary of Chemicals Detected in Surface Soil Samples 4-43 Table 4-11 Surface Soil Characteristics ' 4-45 Table 4-12 Summary of Chemicals Detected in Subsurface Soil 4-49 Table 4-13 Subsurface Soil Characteristics at RIW Locations 4-54 Table 4-14 Remedial Investigation Well Installation Specifications 4-58 Table 4-15 Remedial Investigation Well Groundwater Elevation Data 4-64 Table 4-16 Results of Slug Test Analysis 4-72 Table 4-17 Field Parameters - Remedial Investigation Wells 4-75 Table 4-18 Summary of Chemicals Detected in Ground Water - Round 1 4-76 Table 4-19 Summary of Chemicals Detected in Ground Water - Round 2 4-79 Table 4-20 Field Parameters Summary - Residential Wells 4-88 Table 4-21 Summary of Chemicals Detected in Ground Water - Private Wells 4-89 Table 4-22 Summary of Chemicals Detected in Ground Water Private Wells (7/91) 4-91 Table 6-1 Relative Toxicity Equivalency Factors Derived for Carcinogenic PAHs 6-8 Table 6-2 Summary of Chemicals Detected in Groundwater 6-15 Table 6-3 Tentatively Identified Compounds (TICs) in Groundwater 6-17 Table 6-4 Summary of Chemicals Detected in Private Wells 6-19 Table 6-5 Summary of Chemicals Detected in Surface Soil 6-22 Table 6-6 Tentatively Identified Compounds (TICs) in Surface Soil 6-24 Table 6-7 Summary of Chemicals Detected in Subsurface Soil 6-26 Table 6-8 Tentatively Identified Compounds (TICs) in Subsurface Soil 6-28 Table 6-9 Summary of Chemicals Detected in Surface Water 6-29 Table 6-10 Tentatively Identified Compounds (TICs)'in Surface Water 6-33 Table 6-11 Summary of Chemicals Detected in Sediment 6-34 vi flR300007 TON 4208 „;; •"•' RI REPORT (.