TOW RI REPORT REV. #1 09/JAN/92 '

*»£r, •' ' ft•*-! ;•', • • ENVIRONMENTAL PROTfi

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 (.. .'•*•. " REV. #1 *^~j 09/JAM/92

Table 6-12 Summary of Chemicals of Potential Concern 6-38 Table 6-13 Potential Human Exposure Pathways Under Current Land Use 6-42 Table 6-14 Potential Human Exposure Pathways Under Future Land Use 6-56 Table 6-15 Exposure Point"Concentrations for Chemicals of Potential Concern Detected in Surface Soil 6-50 Table 6-16 Exposure Point Concentrations for Chemicals of Potential Concern Detected in Surface Water 6-51 Table 6-17 Exposure Point Concentrations for Chemicals of Potential Concern Detected in Sediment .6-52 Table 6-18 Exposure Point Concentrations for Chemicals of Potential Concern Detected in Representative Groundwater 6-54 Table 6-19 Exposure Parameter Values Used to Estimate Exposure to Residents via Ingestion of Groundwater 6-56 Table 6-20 Exposure Parameters Used to Estimate.Exposure to Estimate Exposure to Residents via Direct Contact with Groundwater 6-60 Table 6-21 GDIs Estimated for the Ingestion of Groundwater and Dermal Absorption Exposure to Groundwater from Private Wells Downgradient of the Dixie Caverns Landfill Site 6-63 Table 6-22 Exposure Parameters Used to Estimate Exposure to Children via Incidental Ingestion of Surface Soil and Sediments 6-65 Table 6-23 Exposure Parameters Used to Estimate Exposure to Children via Dermal Absorption of Chemicals in Surface Soil and Sediments 6-70 Table 6-24 GDIs Estimated for Direct Contact with Surface Soil by Children Playing at the Dixie Caverns Landfill Site 6-72 Table 6-25 Exposure Parameters Used to Estimate"Exposure to Children via Direct Contact with Surface Water 6-74 Table 6-26 CDIs Estimated for Direct Contact with Surface Water in the Dixie Caverns Landfill Site by Children for the RME Case 6-75 Table 6-27 CDIs Estimated for Direct Contact with Sediments by Children Playing in the Vicinity of the Dixie Caverns Landfill Site 6-77 Table 6-27a Exposure Parameters Used to Estimate Exposure to Hypothetical Residents via Incidental Ingestion of Surface Soil at the Dixie Caverns Landfill Site under Future Land-Use Conditions 6-79 Table 6-27b Exposure Parameters Used to Estimate Exposure to Hypothetical Residents via Dermal Absorption of Chemicals in Surface Soil at the Dixie Caverns Landfill Site under Future Land-Use Conditions 6-79 Table 6-27c Chronic Daily Intakes (CDIs-) Estimated for Direct Contact with Surface SoiV by Hypothetical Residents at the Dixie Caverns Landfill Site for "the RME Case 6-81 Table 6-28 CDIs Estimated for Ingestion of Groundwater and Dermal Absorption Exposure to Groundwater by Hypothetical Residents 6-83 Table 6-29 Carcinogenic Toxicity Criteria (SFs) for Chemicals of Potential Concern at the Dixie Caverns Landfill Site 6-87 Table 6-30 Chronic Non-carcinogenic Toxicity Criteria (RFDs) for Chemicals of Potential Concern 6-89 Table 6-31 Potential Non-carcinogenic Risks Associated with the Use of Groundwater from Residential Wells Downgradient of the Dixie Caverns Landfill Site for the RME Case 6-95 Table 6-32 Potential Carcinogenic Risks Associated with Direct Contact with Surface Soil for Children Playing the Vicinity of

vii SR300008 TON 4208 RI REPORT REV. #1 09/JAM/92

the Dixie Caverns Landfill Site for the RME Case 6-96 Table 6-33 Potential Non-carcinogenic Risks Associated with Direct Contact with Surface Soil for Children Playing at the Dixie Caverns Landfill Site for the RME Case . 6-97 Table 6-34 Potential Carcinogenic Risks Associated with Direct Contact with Surface Hater in the Vicinity of the Dixie Caverns Landfill Site 6-99 Table 6-35 Potential Non-carcinogenic Risks Associated with Direct Contact with Surface Water in the Vicinity of the Dixie Caverns Landfill Site 6-100 Table 6-36 Potential Carcinogenic Risks Associated with Direct Contact with Sediments for Children Playing in the Vicinity of the Dixie Caverns Landfill Site for the RME Case 6-102 Table 6-37 Potential Non-carcinogenic Risks Associated with Direct Contact with Sediments for Children Playing in the Vicinity of the Dixie Caverns Landfill Site for the RME Case 6-103 Table 6-38 Potential Risks from Multiple Exposure Pathways under Current Land-Use Conditions 6-109 Table 6-38a Potential Carcinogenic Risk Associated with Direct Contact with Surface Soil by Hypothetical Residents in the Vicinity of Dixie Caverns Landfill Site for RME Case 6-111 Table 6-38b Potential Noncarcinogenic Risks Associated with Direct Contact with Surface Soil by Hypothetical Residents at the Dixie Caverns Landfill Site for the RME Case 6-112 Table 6-39 Potential Carcinogenic Risks Associated with Use of Groundwater by Hypothetical Residents for the RME Case 6-113 Table 6-40 Potential Non-carcinogenic Risks Associated with Use of Groundwater by Hypothetical Residents for the RME Case 6-115 Table 6-41 Uncertainties Associated with the Baseline Risk Assessment 6-117 Table 6-42 Conclusions for the Baseline Risk Assessment 6-126 Table 6-43 Animals of Special Concern in Virginia 6-137 Table 6-44 Potential Receptors in the Dixie Caverns Study Area 6-141 Table 6-45 Summary of Virginia Water Quality Criteria for Protection of Aquatic Life (VAWQC) 6-165 Table 6-46 Daily Exposure Rate of the Song Sparrow to Ingested Surface Water Contaminants 6-178 Table 6-47 Daily Exposure Rates of the Song Sparrow and Shorttailed Shrew to Ingested Contaminated Food 6-180 Table 7-1 Summary of Ground Water Exceedences of Standards 7-3

viii aR300009 TCN 4208 RI REPORT REV. #1 09/JAN/92 1.0 INTRODUCTION

The United States Environmental Protection Agency (EPA), Region III, utilizing the Alternative Remedial Contracting Strategy (ARCS), authorized Tetra Tech, Inc. to perform a Remedial Investigation/Feasibility Study (RI/FS) at the Dixie Caverns Landfill (DCL). The RI/FS activities were performed under Work Assignment 92-08-3LR9, dated August 17, 1989, and approved September 7, 1989. All RI/FS activities were based on requirements of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) as amended in the Superfund Amendment and Reauthorizatlon Act (SARA), and the regulations and procedures for implementing response actions set forth In the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 CFR Part 300.

1.1 PURPOSE OF REPORT

The primary objectives of the RI/FS, as described in the Work Plan (Tetra Tech, 1990), are as follows:

• to characterize the physical setting of the DCL site;

• to determine the nature, extent, and magnitude of contamination on and adjacent to the site, focusing on three historic waste disposal areas: the solid waste area, the drum disposal area, and the sludge pond;

• to identify and characterize all migration pathways, routes of entry, and receptors for contaminants from the DCL site;

• to determine fully if contaminants related to the DCL site pose a threat to human health or the environment;

• to determine the need for remedial actions at the site to reduce or remove the environmental threat posed by contaminants at the DCL site; and

1-1 fl'R3GOOfO TCN 4208 RI REPORT REV. #1 09/JAN/92 • to Identify, develop, and evaluate remedial action objectives for the DCL site.

Note, as described below, a fourth waste area consisting of a slag or fly ash pile has been identified at the DCL site. Currently, this waste area is considered to be a separate source of waste and as such discussion herein is United. For information regarding the remediation efforts related to the fly ash pile see Proposed Plan - Dixie Caverns Landfill Site (USEPA, 1991) and Supporting Documentation for Fly Ash Remediation Plan (USEPA, 1991). An interim Record-of-Decislons addressing the fly ash pile has been formulated and signed by all affected parties.

1.2 SITE BACKGROUND

1.2.1 Site Description

The DCL site is located north of Interstate 81, along Twine Hollow Road (State Route 778), in southwest Roanoke County, Virginia (37°15'27UN and 80°11132"E) (Figure 1-1). The DCL site covers approximately 63 acres in a steeply-sloped, lightly populated rural area. Roanoke County used the unpermitted DCL site to dispose of unknown amounts of municipal refuse, scrap metal, fly ash (also referred to as slag), sludge and other industrial wastes from 1965 to 1976.

The current status of the DCL site is illustrated in Figure 1-2, Extensive remediation activities by Roanoke County have greatly reduced/removed areas of with obvious contaminants. Currently, two potential sources of contaminants remain on site; 1) solid waste fill area, and 2) a fly ash pile (sometimes referred to as a the slag pile). Mitigation efforts by Roanoke County include the collection and treatment of leachate originating from the solid waste fill area and the Installation of a series of detention ponds to minimize the migration of eroded fly ash. In addition, the County has installed a number of small detention ponds to collect storm water generated by the site and limit the migration of eroded soil. A full description of the site history follows In Section 1.2.2.

flRSOOO TCN 4208 RI REPORT LOCATION MAP 09/JAN/92

VIRGINIA ,'W .HtrHM-i

/ Ck*pl*tti»IK* . f . •

DIXIE CAVERKS LANDFILL SITE

S73 ' Z.LLISTQV 4,5 Vf, 10' APPROXIMATE SCALE 2000 0 2000FEET TETRA TECH, INC.

SOURCE: U.S.G.S 7% MINUTE QUAD GLENVAR, VIRGINIA FIGURE 1-1 LOCATION MAP ' r •VIRGINIA ^' DIXIE CAVERNS LANDFILL SITE QUADRANGLE LOCATION ...... _.._..__._ ...... _. .... I. flR300012 1-3 1-4 TCN 4208 - ' • RI REPORT -v'- REV. #1 ^ - / 09/JAN/93 At this time, the DCL site is not used by County, and public access to the site is limited by topography, bordering properties, and a locked gate at the site entrance.

1,2.2 Site History

The Dixie Caverns Landfill was sited on a series of rolling hills located 1n an area which remained forested area at least as late as 1962 (ERA, 1984). Based on aerial photographs and the information available to date, no significant industrial or resource development (logging, quarrying, etc.) activities predates the County's waste disposal.

Roanoke County first leased the Dixie Caverns site for garbage disposal in January, 1965. An abbreviated chronology of site history from that time forward is provided in Table 1-1. Refuse disposal at the site had begun by June of 1965. Sometime before June 30, 1966, Roanoke County purchased the property, and in 1971 submitted a permit application to operate the DCL site as a solid waste disposal facility. Waste disposal activities were in full operation prior to any quarrying of limestone on adjacent properties. Ravines at the site appear to have been filled with waste during landfill operations. There is no evidence that the site was quarried or excavated prior to any landfill activities.

The permit was denied by the Virginia Health Department Bureau of Solid Waste and Vector Control, which stated that prior to considering issuance of a permit, the County would have to evaluate the soils at the site with respect to their suitability for a landfill operation, and request a field investigation by the State Water Control Board (SWCB). The resulting SWCB report stated that the landfill site could not be approved until suitable modifications were made.

The County attempted to correct the deficiencies by installing drainage improvements, and in November, 1971, the County Executive Officer requested that the State Health Department reinspect the site and issue a permit for operation. This reinspection resulted in additional adverse comments from the State Health Department. After further modifications by the County (tree planting, storm- water cut-off ditch), the State Health Department and SWCB revisited the site in 1-5 ftR3000U TCN 4208 RI REPORT REV. *1 09/JAN/92 TABLE 1-1 ABBREVIATED DIXIE CAVERNS LANDFILL SITE HISTORY CHRONOLOGY

1965 Municipal and industrial wastes first oisposed of at the site. Oct. 1971 Roanoke County Executive Officer submitted an application to the Virginia State Health Department to operate the Dixie Caverns Landfill (DCL) Site as a solid waste disposal facility. After a site inspection by representatives of the State Health Department, the pemit was denied in November, 1971. Jul. 1972 Roanoke County notified by the State that the Dixie Caverns Landfill operation must be phased out by July 1, 1973 (State deadline for jurisdictions to get a solid waste disposal perait). Jul. 1976 Dixie Caverns Landfill closed by Roanoke County. Refuse would now be taken to the new regional landfill in eastern Roanoke County. Jun. 1983 NUS Corporation performed a preliminary assessment of the site for £PA. Four separate waste disposal areas within the site were found, with the 3 largest being the sludge, slag/fly ash, and drum disposal areas. Jun. 1985 NUS Corporation performed another site inspection. Found heavy metal contamination in slag/fly ash, and organic contaminants in the sludge. Feb. 1986 KUS Corporation performed a Hazard Ranking System analysis of the site. Apr. 1986 Roanoke County notified by the EPA that "Dixie Caverns site is a serious candidate for addition to the NPL [National Priorities List]." Jul. 1986 EPA Technical Assistance Team (TAT) found slag/fly ash exceeded cadmium & lead max. allowable concentrations for RCRA EPA Toxicity Test. Sludge organic contamination (phthalates, benzene, pentachlorophenol, naphthalene, dichloroethene) found. Fall 1987 Consent Agreement and Order executed by Roenoke County in September and EPA Region III in October. Dec. 1987 As part of Consent Agreement and Order, Roanoke County had its contractor Giver, Inc. develop a work plan for removal and/or treatment of hazardous wastes at site. Aug. 1988 GSX Services stabilized the sludge and associated soils in the sludge disposal area with cement kiln dust, and covered it with a plastic sheet for later offrsite disposal. Solidified sludge and soil, and some crushed drums, were shipped for disposal to GSX's landfill in South Carolina. Full and partially full drums were stored in a dumpster for later off-site disposal. Spot sampling in the sludge and drum disposal areas was undertaken. Fly ash remediation was scheduled 10/88. Oct. 1988 Roads were cleared and graded to provide access to the fly ash disposal area. Adjacent ravine was filled in, and the. area cleared and graded. A trench was dug for & drainage pipe, which would divert water around the fly ash pile. Jan. 1989 Olver, Inc. prepared a preliminary closure sampling and analysis plan for the sludge disposal area for Roanoke County. Apr. 1939 Maximum contaminant concentration threshold values for three semi-volatiles (fais(2- ethylhexyljphthalate, d1-n-buty1phthalate, and naphthalene) and three volatiles (ethylbenzene, 1,1-dichloroethene, and toluene) were approved by EPA Region III for closure of the sludge disposal and tire staging areas. Hay 1989 Olver, Inc. prepared for Roanoke County a revised closure sampling and analysis plan for the sludge disposal area, and a preliminary closure sampling and analysis plan for the tire staging area. Closure sampling was undertaken at the sludge & drum disposal areas. Preparatory work for slag/fly ash treatment was completed. Treatment startup still to be scheduled with EPA Region III. Oct. 4, 1989 Dixie Caverns Landfill added to NPL by EPA (54 FR 41015). Ranked 619 of 929 NPL sites. based on a Hazard Ranking System (MRS) score of 34.60-35.57. Jan. 1990 Method of treatment and disposal of the fly ash is still awaiting resolution. Cleanup of other disposal areas has been completed. flRSOOOIS - TCN 4208 RI REPORT REV. #1 09/JAN/92 June, 1972. Despite the modifications made by the County, the State expressed additional concerns (e.g., uncontrolled runoff through the fill, uncovered waste, larger holding pond needed) following the inspection, and advised the County to phase out all landfill operations by July 1, 1973.

In 1973, the County hired John McNair and Associates to conduct a study of the site and to make specific recommendations on the proper operation of a sanitary, landfill. The McNair report (McNair and Associates, 1973) contained plans for significant grading, capping, and seeding of the previously landfilled area, and proposed detailed drainage work for two new landfill areas. The State later issued a nonconforming permit for the DCL site until a decision could be made on expanding the landfill. However, no further modifications were made to the site.

In 1973 and 1974, State Water Control Board (SWCB) collected data showing landfill leachate (containing high chemical oxygen demand (COD), ammonia, and total Kjeldahl nitrogen concentrations) to be a problem and expressed concerns about potential impacts upon nearby surface waters. In 1976, the County Board of Supervisors stated that because the County was still having problems with the State in securing a landfill permit, it would not continue landfill operations at DCL site. By 1978, after landfill closure, fill, debris, and possible sludge were evident on-site. Areas of tires, drums, sludge, and slag (fly ash) were identified in the central portion of the site (Figure 1-3), and solid waste disposal areas were seen in the south and southwestern portions of the site. The northeast portion of the landfill was used as a pistol range from 1978 until the early 1980s by the Roanoke County Sheriff's office. Intermittently, the site was also used as an equipment storage area for a nearby quarry.

Since the 1987 Consent Agreement and Order, Roanoke County has made a significant effort regarding removal and/or treatment of hazardous wastes at the site. As of January 1990, large' scale removal/treatment actions were performed at the sludge pond and drum disposal areas. The sludge pond and adjacent soils were stabilized and removed from the sludge disposal area. Full and partially full drums were removed and disposed of off-site. Tires once intermixed with drums in the drum disposal area were collected, cleaned and buried on the DCL site. Spot closure sampling was performed in the sludge and drum disposal areas. As 1-7 SR300016 anotroo L— - TCN 4208 f ' , RI REPORT ' REV. #1 09/JAN/92 of this time, the fly ash pile remains on the DCL site. The various federal, state and county agencies have yet to agree on an acceptable method for treatment or removal of the fly ash pile.

1.2.3 Previous Site Investigations

A preliminary assessment of the DCL site was conducted in mid 1983 by a USEPA contractor, NUS Corporation. This preliminary assessment resulted in a more detailed site inspection in September of 1983, also by NUS on behalf of USEPA Region III. According to the Site Inspection of Dixie Caverns Landfill Report (NUS, 1985), four separate landfilled areas were identified:

1) A large landfill area, with a storage shed and drag-line equipment from a quarry located on State Route 778, (see Solid Waste Disposal Area in Figure 1-3); 2) Northeast of the above area was another landfill plot situated on a small knob. This area contained a sludge pond with partially submerged drums and a major drum disposal area was located on northern slope of the knob; 3) The smallest of the four areas lay directly south of the first area, and contained several trailers; 4) The last area contained a large slag heap of undetermined constituents which covered the entire northeastern slope of a ravine (see Slag/Fly ash pile in Figure 1-3). This ravine was also reported to be an old pistol range used by the Roanoke County Sheriff's office.

Approximately 200 to 300, 55-gallon drums were observed by NUS during a drum inventory conducted at drum piles. The majority of the drums were rusted and empty. NUS also observed a sludge pit at the eastern portion of the site. The pit was approximately 15 feet wide and 25 feet long and contained solidified, crusty, black-white material.

NUS observed orange leachate flowing slowly along the southwest perimeter of the landfill site. The leachate and corresponding sediment were sampled, as was the blue leachate drainage observed leaving the site and entering the perimeter 1-9 AR3000I8 TCN 4208 RI REPORT REV. #1 09/JAN/92 leachate flow. A small ponded area of water, which appeared to be leachate, was observed entering a small unnamed tributary located across the road (Route 778) from the landfill.

A small stream bed, which appeared to flow beneath the drum pile, was dry during the NUS inspection. However, water was observed to occur in the stream downstream of the drum pile, near the slag/fly ash pile. An oily sheen was observed on the surface of the water below the slag heap area. A sediment sample was collected from the dry stream bed near the drum pile, and water and sediment samples were collected downstream of the drum pile. Data from water, sediment, and leachate samples collected by NUS are shown in Table 1-2 and sample locations are shown in Figure 1-4.

Table 1-3 is a compilation of the highest contaminant concentrations observed by NUS during their sample collections, most of which are related to the slag pile (S6). NUS determined that the largest potential threat posed by the contaminants Identified was due to the presence of high concentrations of metals, such as arsenic, cadmium, chromium, lead, and zinc. Metals were detected in off-site surface water samples collected adjacent to the site at levels that could adversely affect aquatic life (Samples A5 and A3). The organic compounds benzene, substituted benzenes, phthalate esters, and chlorinated ethanes/ethenes were also identified on site. PCBs were found at elevated levels in downstream samples, Implying that there could be either localized, highly contaminated areas or widespread PCB contamination on-site (Sample S7). The presence of PCBs in off-site samples (e.g., Samples A2 and S2) also suggests that PCBs may be migrating off site by way of intermittent streams. As part of their 1985 evaluation, NUS estimated the volume of the fly ash pile to be 15,046 cubic yards (Letter Report to EPA Hazardous Site Control Division, from NUS, October 11, 1985).

In February, 1986, an EPA Hazard Ranking System (HRS) score was developed for the site by NUS based upon information obtained from NUS's previous reports. The site obtained a composite score of 34.12 (58.37 for the groundwater route, 8.73 for the surface water route, 0 for the air route, 0 for fire and explosion, and 25.00 for direct contact). In an April 10, 1986 memo from Richard Brunker, USEPA 1-10 flR300019 TCN 4208 RI REPORT REV. n 09/JAN/92

Table 1-2 Contaminants Detected in NUS Samples Collected During September 1983 Site Inspection

Unnamed Trib. Unnamed Trib. Confluence of Ponded Leachate Unnamed Stream Above Access Rd. Below Access Rd. Leachate Flow Seep Below Slag (Al) (A2) (A3) (A4(AS) ) Parameters (Concentration in milligrams/liter) aluminum 0.16 0.16 0.51 l.Z .22 arsenic 0.001 0.001 0.012 0.004 .001 barium 0.30 0.43 1.3 0.38 .18 boron 0.077 0.50 0.69' 0.39 1.0 cadmi urn - - 0.002* 0.003* .14 chromium - - - - .016* copper 0.018* 0.008* 0.065* 0.01* .026* Iron 1.8* 0.60* 94 48 1.1* lead _ - 0.002* - .78 manganese 1.7 0.084* 1.0 3.0 .21 mercury - - - - - ni ckel 0.026 0.024 0.040 - - silver - - 0.11 - - tin 0.075* 0.076* 0.084* 0.029* .023* vanadi urn - - 0.027 0.024 - zinc 0.029* 0.089* 0.21* 0.014* 9.9 cyani de 0.038* 0.022* 0.017* 0.013* .006*

(Concentration in micrograms/liter) methylene chloride 5.7* 3300* 5700* 1100* 110* N-ni trosodi phenyl amine 1.5* 4.6* 12* 2.0* 6.8* PCB-1254 - 0.37 _ - chl orobenzene _ _ 1.2 _ di ethyl phthal ate . — 2.5* -

*Denotes results of questionable qualitative significance based upon quality assurance review of data.

J-ll RR300020 TCN 4208. RI REPOR REV. 09/JAN/92 Table 1-2 (continued) Contaminants Detected in NUS Samples Collected During September, 1983 Site Inspection

SrattonYoungUnnamedTrib.Unnamed~Trib.Sediment et Home Well Home Well Above Access Rd Below Access Rd Confluence (A6) (A7) (SI) (S2) (S3) (Concentration Parameters in milligrams/liter) (Concentration in milligrams/kilogram) tluminua .10* .12 21000 10000 1800 arsenic - 28 7.4 64 barium .038 28 31 -130 boron .049 - 58 9 48 cadmium - - 1.2* .3* .3* chrowiira .007* - 10 6.3 copper .031* .018* 270 12 12 iron - .31* 60000 23000 240000 l«td .003* 44 15 - manganese - - 920 380 430 mercury - - .007* nickel 32 19 - silver - - .... _ . -.44* tin .08* .071* - - vanadium - - 87 37 66 zi nc . 11* .077* 140 ., 48* 74 cyanide - - 1.3* 1.3* 1.7*

(Concentrations in fflicrograms/liter) (Concentrations in micrograms/kilogram) methylene chloride O5 O*"'• 1Z5 OF I55 N-nitrosodiphenylaraine - 2.0* 110* 860* alpha-endosulfan - - - - 1.3* PCB-1242 - , - - 19 PCS-1254 - - - 27 PCB-1260 - • - 4 di ethyl phthal ate - - 44* 2200* 180* phenol 1.4* - - - ...._-_ di-n-butylphthalate - - 33* 410* bis(2-tthylhexyl) phthalate - - - • 250* 190* 2,4-dinitrotoluene - - - — 260* 2,6-dinitrotoluene - - 310* phenanthrene - - - 560 - fluorene - - - 220 - pyrene - - 330 -

*Denotes results of questionable qualitative significance based upon quality assurance review of data.

AR3Q002 L

TCN 4208 RI REPORT REV. #1 09/JAN/92 Table 1-2 (continued) Contaminants Detected in NUS Samples Collected During September, 1983 Site Inspection

Soil at Leachate Pond Stream Sediment Stream Bed Leachate Seep Sediment Slag Below Slag Soil (S4) (55) (S6) (S7) (S8) Parameters (Concentration in mill 1 grams/kilogram) aluminum 8800 5200 2900 350 7200 arsenic 5.9 5.2 76 59 9.6 barium 72 7.2 30 20 5.6. boron 31 10 150 63 - cadmium .2* .1* 1600 1100 1.3* chromium 2.7* 3.1* 420 11 4.6 copper 57* 64* 3000 1400 9.6 iron 93000 15000 240000 160000 20000 lead 2.9* 10 45000 34000 85 manganese 560 200 32000 21000 260 mercury - .072* 3.1 1.5 - ni ckel 13 - 4.6 200 140 6.8 silver _ _ 31 8.6 - tin _ . 300 . 100 2.9* vanadium 62 19 130 100 22 zinc 65* 37* 220000 140000 160 cyanide 3.7 2 1.7 1.5 1*

(Concentration in micrograms/kilogram) methylene chloride 22* 7.3* 21* 7.9* 28* N-ni trosodi phenyl ami ne 130* 190* 120* 140* 43* 4,4'-DDE - _ - ,26* PCB-1248 - 55 75 - PCB-1254 7 _ 320 - PCB-1260 - -130 120 - dieldrin _ _ , - - 2.5* - diethylphthalate - 63* ... . - phenol - 75 - - di -n-butyl phthal ate 47* 41* 20* 36* butyl benzyl phthal ate - 48* - - bis(2-ethylhexyl) phthalate - 64* 670* 67* 38* phenanthrene - 62 45 - fluoranthene - 200 150 - pyrene - - 130 63 - to! uene 36* 5.1* - - benzo (a) anthracene _ 210 110 - benzo (k) f 1 uoranthene - 490 150 benzo (b) f 1 uoranthene - 190 56 - benzo (a) pyrene 36 36 - -

*Denotes results of questionable qualitative significance based upon quality assurance review of data.

flR300022 TCN 4208 RI REPOR' REV. 09/JAN/9

Table 1-2 (continued) Contaminants Detected by NUS in Sludge Pond Sample (S10) Collected During the September 20, 1983 Site Visit

Concentration Parameter milli grams/ki1ogram

aluminum 3300 arsenic 0.9 barium 390 boron 26 cadmium 2.6* chrorai urn 36 cobalt 59 copper 58 iron 3000 lead 21 manganese 100 tin 3.2* zinc 820 mi crograms/ki1ogram methylene chloride 250* 1,1-dichloroethane 320 trichloroethene " 130 tetrachloroethene 130 1,1,1-trichloroethane 29 2-chloroethyl vinyl ether 110* benzene 1100 toluene 2500 tthylbenzene 140 bis(2:-chloroethoxy)methane 28000* ni t robenzene 40000* PCB-1254 4000** diethylphthalate 9400* di-n-butylphthalate 48000 bi s(2-ethylhexylJphthalate 100000* di-n-octylphthalate 80000 naphthalene 110000 phenanthrene 1600 2,6-di cM orophenol 8700 pentachlorophenol 350000

*Denotes results of questionable qualitative significance based upon quality assurance review of data. **Represents large mixtures of PCBs

1-14 flR300023

TCN 4208 RI REPORT REV. #1 09/JAN/92

Table 1-3 Highest Contaminant Concentrations Detected by NUS in Samples Collected During the September 20. 1B83 Site Visit*

Parameter Concentration

bcnzo(k)fluoranthene 490 ppb toluene 2500 ppb PCB-1254,-1260,-1248 130 ppb 1,1-dichloroetnane 320 ppb benzene 1100 ppb aluminum 21000 ppm chromium 420 ppm barium 30 ppm zinc 220000 ppm arsenic 76 ppm antimony 14 ppm mercury 3.1 pom cadmium 1600 ppra lead 45000 ppm cyanide 3.7 ppm

*Predominantly from slag sample (S6),

Source: NUS Site Inspection Report, Part 2 - Waste Information, IV. Hazardous Substances, September 14, 1933

1-16 flR300025 &&*,. TCN 4208 K '*'&/ RI ' 09/JAN/92 Region III Toxlcologist, to Darius Ostrauskas, Environmental Scientist, USEPA Region III, Brunker expressed concerns that the high concentrations of lead (as much as 45,000 ppm or 4.5%) in the unsecured fly ash pile and nearby contaminated soils posed "an imminent and substantial endangerment to the nearby residents and anyone else who must, for any reason, spend any substantial time in the vicinity of this contamination." In July, 1986, the EPA Technical Assistance Team (TAT) investigated the site. Sampling occurred in the sludge disposal area, the fly ash pile, the stream bed below the fly ash pile, and some of the drums. The TAT results Table 1-4 indicated high levels of cadmium (1,600 ppm) and lead (45,000 ppm) in the fly ash pile, and organics in the sludge disposal area. On January 27, 1987, the EPA proposed the sixth update of the National Priorities List (NPL) which included the addition of the DCL site, and on October 4, 1989, the DCL site was added to the NPL by the EPA (54 FR 41015). It ranked 619 of 929 NPL sites, based on a Hazard Ranking System score between 34.60 and 35,57.

Landfill leachate samples were collected by Olver, Inc. (Roanoke County contractor) in 1988, and the data are shown in Table 1-5. These samples collected contained high concentrations of dissolved solids (conductivity 700 pmhos), total iron (85mg/l), manganese (0.76mg/l) , total sodium (93mg/l), and ammonia nitrogen (57 mg/1).

Groundwater data are currently collected by the Virginia State Water Control Board (SWCB) from a 205 foot deep well located just outside the property of the Dixie Caverns landfill site near the entrance, downgradient of the municipal waste fill area. The well has surface casing installed to 21 feet below grade. Water quality in this well was considered by the SWCB to be very poor as exhibited by a high mean concentration of conductivity (1289.6 //mhos), T.D.S. (752 mg/1), chloride (211 mg/1), T.O.C. (23 mg/1), hardness (344 mg/1), iron (24 mg/1), manganese (1.07 mg/1), and ammonia nitrogen (25 mg/1). The similarity in constituents between this groundwater and the Olver leachate samples may indicate the migration of landfill leachate into the groundwater. The SWCB also expressed concerns that the well was not properly constructed (pers. com., Khoa Nguyen, Senior Environmental Engineer, Virginia Department of Waste Management), suggesting a grout contamination problem, which renders the water sample results questionable. ._...... -

1-17 flR300026 TCN 4208 RI REPORT REV. #1 09/JAN/92

Table 1-4 EPA Technical Assistance Team Sampling Results (1986)

Fly Ash Pile and Stream Bed Parameter Ash pile (ppm) Stream Sediment (ppm)

Cadmium 1,600 1,100 Lead 45,000 34,000

Sludge Disposal Area Parameter Disposal Area (ppm)

diethyl phthal ate •' 9,400 di-n-butylphthalate 48,000 bis(2-ethy1hexyl)phthalate 100,000 di-n-octylphthalate 30,000 2,4-di chlorophenol 8,700 pentachlorophenol 350,000 PCB-1254 4,000 benzene 1,100 naphthalene 110,000 bi s(2-chloroethoxy)methane 28,000 nitrobenzene 40,000 1,1-di chloroethane 320

flR300027 1-18 TCN 4208 RI REPORT REV. #1 09/JAN/92 Table 1-5 Conventional and Priority Pollutants Detected in Olver 1988 Leachate Sample Analyses

Sample t Sample t 33896 36879 Parameters Leachate Leachate (4/28/88) (12/12/88)

PH 6.5 alkalinity (mg/1) 506 COD (mg/1) 142 conductivity (//mhos/cm) 700 ammonia as N (mg/1) 57 nitrate as N (mg/1) <.01 nitrite as N (mg/1) <.01 TKN (mg/1) 10 orthophosphate (mg/1) . <.05 tot. phos. as P (mg/1) .05 sulfate (mg/1) 6 susp. solids (mg/1) 50 diss. solids (mg/1) 5010 TOC (mg/1) 22.5

mi 111 grams/11ter

arsenic* .01/<.002 <.001/- cadmi urn* <.002/<.002 .004/- calcium* 68/43 chromium* .03/.01 <.02/- copper* .02/.02 .02/- 1ron* 85/41 lead* .02/.02 <.05/- mangonese* .76/.74 mercury* <.0002/<.0002 <.0002/- nickel* .06/.02 ,02/- selenlum* .007/.006 <.002/- silver* <.01/<.01 ,01/- sodium* 93/87 zinc* .058/.055 ,05/- mi crograms/1i ter 1,4-di chlorobenzene 1.6 naphthalene .71 n-nitroso- diphenylamine 3.6 17 chlorobenzene 10 5

*Total/soluble concentrations

1-19 flR300028 TCN 4208 RI REPORT REV. #1 09/JAN/92 Roanoke County expressed concerns that the SWBC well bore could potentially act as a conduit of groundwater contamination due to its open hole construction between 21 and 205 feet (below ground surface). The combination of this potential with the suspected grout contamination has lead Roanoke County to suggest the SWBC well be grouted and formally abandoned. No action on this request has been taken by the SWCB to date. ,

1-20 fiR30QQ29 TCN 4208 RI REPORT REV. #1 09/JAN/92 '/ 2.0 PHYSICAL CHARACTERISTICS OF THE STUDY AREA v

2.1 DEMOGRAPHY

The Dixie Caverns Landfill site is located in western Roanoke County near the boundary of Roanoke and Montgomery Counties. The Roanoke County region covers approximately 240 square miles and contains two adjacent but independent cities, Roanoke and Salem, and one township, Vinton. The population of the County is 77,200, not including its two cities, and 229,600 including the cities of Roanoke and Salem. The region can be generally characterized as a metropolitan area located within an elongated river valley, surrounded by steep, heavily wooded mountains. In 1989, Roanoke County had.an annual budget of $62 million, part of which was used 1n programs to attract high technology 1ndustrial and manufacturlng compani es to the regi on. The present 1ocal government i s attempting to broaden the County's tax base by augmenting existing railroad-based industries (County of Roanoke 1989 Annual Report). The land immediately surrounding the Dixie Caverns site is rural; however, development is spreading west towards the site from Salem and Roanoke.

A total of 55 structures have been identified within approximately 1-mile of the DCL site, based on current Roanoke County tax maps. The population within a 1- mile radius of the site was estimated using the 1990 Preliminary Census Map of Roanoke County [Tract 303.98, BG (Block Group) 9]. The total 1-mile radius population was estimated at 235 people, 179 of which are 18 years old or older.

The population within a three-mile radius of the Dixie Caverns site includes individuals living in neighboring Montgomery County. Montgomery County comprises 30 percent of the area within the three-mile radius, with the remainder of the area falling in Roanoke County. The vast majority of the residents live to the west and south of the DCL site, and there are no residents located north of the site within a 3-mile radius. The estimated combined 1990 Roanoke and Montgomery County populations within 3 miles of the site is 2497, of which 1909 are 18 years

2-1

flR300030 TCN 4208 RI REPORT REV. #1 09/JAN/92 old or older. Appendix A details the process used to develop the 1- and 3-mile radius population estimates.

2.2 METEOROLOGY

Roanoke County is located 1n a zone of temperate climate, but is subject to seasonal variations in temperatures and precipitation. The climate has been described as "mild" fay the U.S. Weather Bureau (1970) because temperatures rarely exceed 100°F In summer or fall below 0°F in winter. The average yearly temperature for the area 1s approximately ,56°F, with a maximum in the 90's and lows 1n the upper 20's (Waller, 1976).

Regional climate is affected by both subtropical and polar air masses, and frequent and rapid weather changes are associated with frontal movements (Waller, 1976). Events of heavy rainfall are usually associated with thunderstorms in the summer months, tropical hurricanes in the late summer and fall, and subtropical storms in the winter and spring. The average annual precipitation is 44 inches, fairly evenly distributed throughout the year.

2.3 SURFACE FEATURES

The topography In the region of the DCL site is characterized by long, narrow, parallel valleys and mountain ridges. The mountains in this section of the county are rugged and heavily forested, and are traversed by numerous small streams. The slope of the surface grade ranges from a minimum of 20 percent up to 40 percent in undisturbed areas. Ridge tops are typically 500 to 700 feet above adjacent small stream valley floors. The DCL site lies on a relatively steep ridge complex between two steep valleys, each of which contains an Intermittent stream (Figure 1-3). The elevation at the site ranges from approximately 1400 feet above mean sea level (ft. msl) at the site entrance to 1650 ft. msl in the northwest corner of the site.

2-2 flR3QQ03 TON 4208 RI REPORT REV. il 09/JAN/92

Locally, 2,171 feet of relief are traversed between the ridge top of Fort Lewis Mountain (3,251 ft. msl) and the Roanoke River (1,080 ft. msl), which converts to a local surface gradient of approximately 1,500 ft/mile.

2.4 SURFACE HYDROLOGY

Two unnamed intermittent streams are located on or near the DCL site (Figure 1-3). During the periods of time that they contain water, they both flow to the southeast toward the Roanoke River, located approximately 2 miles south-southeast of the site. The first intermittent stream is located south of the southern boundary of the site along Twine Hollow Road (Stream A in Figure 1-3). Surface runoff from the southern and southeastern portions of the site drains toward this intermittent stream. The second intermittent stream is located on the northern portion of the landfill, and drains the central and northern portions of the site, Including the former drum disposal area and the fly ash pile (Stream B in Figure 1-3).

Presently, Stream A flows south of the entrance to the Dixie Caverns landfill site, along State Route 778 (Twine Hollow Road). This stream originates on the property of an explosive factory located at the northern end of Route 778. At one time, runoff and leachate from the DCL site solid waste disposal area could flow into stream A, however action by Roanoke County resulted in the installation of a leachate collection system to collect these flows. Currently, the Landfill site contributes surface runoff to Stream A only on an infrequent basis, by way of an old stream bed which parallels the north side of Route 778. This old stream bed conveys stormwater runoff from the vicinity of the existing leachate collection pond during high rainfall periods. Stream A and the old stream bed join near the entrance to a former limestone quarry southeast of the DCL site. During non-rainfall periods, Stream A disappears approximately 1000 feet below the entrance of the limestone quarry. During and following periods of rainfall, Stream A flows to the Roanoke River.

Stream B, which originates uphill and northwest of the northwest portion of the landfill, traverses the site north of the former drum and tire disposal areas.

2-3

flR300032 TCN 4208 RI REVREPOR. nT 09/JAN/92

Originally, this stream flowed undisturbed in a southeasterly direction near the present fly ash pile. However, in 1988, surface water control measures undertaken by Olver, Inc., under contract with Roanoke County, modified the path of Stream B extensively from above the drum disposal area to the eastern site boundary. A surface water diversion channel was constructed around the base of the drum disposal area. Further to the east, the stream was diverted into a pipe which conveyed 1t under the toe of the fly ash pile. Earth retention dams were constructed immediately upstream (and west) of both the drum disposal area and fly ash pile diversion pipe. An additional detention pond was constructed below the fly ash pile, below the diversion pipe outlet, to capture any eroded fly ash materi al.

Also as part of the County operations, a small tributary to Stream B (Stream C) was also diverted from its original southward path. Near the Roanoke County well, which was installed as a water source for the fly ash treatment system, the County diverted Stream C Into a pipe which discharged into stream B just below the fly ash pile.

2.5 SOILS

The Soil Conservation Service Soil Survey Manual for Roanoke County is in progress, but has not been released for publication. Correspondence between Tetra Tech Inc. and the Soil Conservation Service resulted in the preliminary identification of the major soil types in the vicinity of the DCL site, as described below. No accompanying map is available.

Approximately the southeastern half of the landfill site, as well as the adjacent quarry, belong to the mapping unit Pits and Quarries. This miscellaneous area consists of open excavations from which rock is mined, and their associated spoils piles. The characteristics of these areas are so variable that site- specific investigation is required to determine the potential of an area for any use.

2-4 AR300Q33 TCN 4208 RI REPORT *"V REV. #1 09/JAN/92

The most common soil mapping unit in the vicinity of the landfill is the Wiekert- Berks complex, which consists of shallow and moderately deep, well drained soils on upland side slopes with 15 to 45% slopes. The Wiekert-Rock outcrop complex is also common, which consists of steep to very steep, well drained soils intermingled with outcrops of rock. It occurs along the side slopes of drainageways and streams, and has slopes of 45 to 70 percent. These two complexes occupy the northeastern half of the landfill, and surround the landfill from the southwest to the northeast.

To the south and east of the landfill are small areas of the Tumbling loam, very stony, with 25 to 40% slopes. This very deep, steep, well drained soil occupies upland foot and side slopes, and commonly occurs associated with the Wiekert and Berks soils. ,

With the exception of the Pits and Quarries, the soils in the vicinity of the landfill support woodlands which consist largely of Virginia pine, northern red oak, and black oak.

2.6 ECOLOGY

2.6.1 General Flora

The original flora of the project site is an oak-pine forest, which still covers about 30% of the DCL site. The forest cover type 1s Chestnut Oak-Pitch pine, a variant of the Chestnut Oak forest cover type (see Eyre, 1980). This is a subclimax or climax forest type that occurs on dry sites, particularly rocky outcrops, ridge-tops and southern slopes. The forest is mature, or nearly mature, secondary or tertiary growth, but lacks overmature and windthrown trees characteristic of a true climax forest.

Most of the project site has been recently disturbed (within the last 3 years), and now consists of early successional field vegetation. The species composition of this field vegetation varies in different parts of the landfill, depending upon time since disturbance and highly localized conditions. Disturbed portions

2-5 TCN 4208 RI REPORT REV. #1 09/JAN/92 of the DCL project site are vegetated almost entirely by annual species. Most of the site vegetation consists of various grass species, particularly broomsedge (Andropogon spp.), mixed in places with several composite species, mosses and lichens. Some areas have been planted Into grass. Approximately one- third of the site is barren due to recent remedial activities.

Finally, a young pine stand (pitch, Virginia, and table-mountain) covers about 10% of project site. This area is essentially a southern variant of the pitch pine forest cover type, with a mix of pitch, Virginia and table-mountain pine (see Eyre, 1980). This is an intermediate successional step from the recently disturbed fields back to the original forest cover type.

2.6.2 General Fauna

The fauna expected to populate the project site are typical of those found in the fields and forest-field ecotones with generally open-habitat preferences. Bird species such as northern mockingbird, eastern bluebird, brown thrasher, European starling, common grackle, and slate-colored junco are typical of this habitat. Populations of small mammals and game species, such as deer, are likely to be present. Wildlife on the project site will change with time as the vegetation undergoes successional changes.

The DCL site occurs along a major migratory bird route, which expands the list of birds that may be found in the area to include any species whose migratory route passes through the study area. This includes slate-colored juncos, which winter 1n the area, and the chestnut-sided warbler, which migrate through the area. Many bird species that do not breed in the area could be found on the site during spring or fall migration, or wintering on the site.

2.6.3 Threatened and Endangered Species

Several threatened and endangered species have been identified in the region. Roanoke logperch (listed as "Federal Endangered" on the Endangered Species List) and Orangefin madtom (Federal Candidate) have been recorded as present in the

2-6

flR300035 TCN 4208 : RI REPORT •."-; REV. #1 09/JAN/92

Roanoke River in the vicinity of the Dixie Caverns region. Based on Virginia Department of Game and Inland Fisheries habitat descriptions, neither of these species would be found in the intermittent streams close to the landfill site (streams A through G in Figure 1-3); members of these two species would be limited to the Roanoke River.

The benthic community 1n the streams in the area is dominated by Ephemeropteran, Plecopteran, and Tricopteran (EPT) populations, which are primarily collectors. In March of 1986, a qualitative biological survey (Queisser, 1986) reported leachate effects from the landfill on benthic macroinvertebrate populations in Stream A. Since that time, Roanoke County has installed a leachate collection system at the landfill site to mitigate the effects of landfill leachate on aquatic populations.

The Eastern woodrat (Federal Candidate) has been recorded as present in the Dixie Caverns area (Glenvar quadrangle), particularly in locations near caves or in very rocky terrain with deciduous cover.

A January, 1989, letter from the Department of Interior to USEPA Region III confirmed the potential presence in the region of the DCL site of a federally proposed endangered fish species (Roanoke logperch) and an endangered bat species (Indiana bat), and described the potential use of the area by endangered migratory birds. However, a later, detailed search of the Fish and Wildlife Service BOVA system did not identify the Indiana bat as an ETPC (Endangered/Threatened/Proposed/Candidate) species residing within the area adjacent to the DCL site.

2.7 REGIONAL GEOLOGY

2.7.1 Geologic Setting

Roanoke County, Virginia, straddles two geologic major provinces; approximately the southern third of the county lies within the Blue Ridge province (igneous and metamorphic rocks) of the Appalachian Mountains, while approximately the northern

2-7 4R300036 TCN 4208 RI REPORT REV. #1 09/JAN/92 two-thirds of the county, Including the DCL site, lies within the Valley and Ridge province (sedimentary rocks) (Figure 2-1). Roanoke County is also located at the juncture between the northern and the southern Appalachians, at the "Hinge Line", where a change in regional strike (general direction of rock structures and features) occurs.

Three local physiographic units are identified in Roanoke County (Waller, 1976). They include:

• the Blue Ridge Mountains of the Blue Ridge province along the southeastern third of the county; • the Fort Lewis-Brushy Mountaln-Catawba Valley complex of the Valley and Ridge province along the northwestern third of the county, in which the DCL site is found; and * the Roanoke Valley of the Valley and Ridge province, which is broad and flat and comprises the central portion of the county, in which the residential wells south of the DCL site are found.

2.7.2 Llthologic Description

A listing of the stratigraphy (different rock types and formations) in the DCL region Is given in Table 2-1. The DCL site was mapped by Murphy (1968) as lying within the Devonian-age Chemung and Brallier Formations, which conformably contacts the Devonian-age Millboro Shale along the southeast landfill boundary (Figure 2-2). The Devonian rocks are described by Amato (1968) as consisting mainly of shale and sandstone with lesser amounts of limestone. To the east- southeast of the DCL site lies a biconvex body of rocks that display an Incomplete sequence of early through late Ordovician-age rocks, which have been overturned and thrust faulted over the younger Devonian rocks in this area. The Ordovlclan rocks 1 n this general area consist of carbonates, sandstones, s11tstones, and shales of the Marti nsburg, Bays, Li berty Hal 1, and Knox Formations.

2-8 AR300037 to

o

2-9 flR300038 TCN 4208 RI REPORT REV. #1 09/JAN/92

Table 2-1 Regional Strati graphic Units Dixie Caverns Landfill Site

Age Symbol Formatlon

Hlssissippien Mp Price Formation

Devonian Ds Chemung Formation Brallier Shale Dm Hillboro Shale Needmore Formation Huntersville Formation

Silurian St Tuscarora Sandstone

Ordovician Omfa Hartinsburg Formation Ob Bays Formation Olh Liberty Hall Formation Oe Effna Limestone .1 Ok Knox Dolomite

Cambrian Ge Elbrook Formation 6r Rome Formation

2-10 3R300039

TCN 4208 RI REPORT REV. #1 09/JAN/92

Further to the southeast, the Cambrian age El brook Formation has been thrusted over the younger, biconvex body of rocks and is exposed in the quarry neighboring the site (Salem Stone Company). Amato (1968) described the Elbrook Formation as being composed of thin-to-medium bedded dolomite, with some limestone and shale. Most of the residential areas in the vicinity of the DCL site are underlain by the Elbrook Formation.

2.7.3 Structural Features

Deformation by both folding and faulting characterizes the rocks of the Valley and Ridge province. The major local fold and fault systems of the Roanoke County region are shown on Figure 2-3. Folding has created a series of parallel, northeast-to-southwest trending, anticlinal and synclinal folds. Differential erosion of the exposed, non-resistant formations has resulted in the distinctive parallel topographic ridges which, as in the case of the Fort Lewis Mountain to the northwest of the site, may lie as much as 2,000 feet above their adjacent valleys. The tectonic forces that created the folis have also formed major low- angl e thrust fault systems trendi ng paral1el to the stri ke of the fol ds (northeast-southwest). Numerous northeast-striking thrust faults have been mapped In the vicinity (including the Salem Fault), with massive amounts of older rocks thrusted northwesterly over younger rocks (Waller, 1976). The major thrust faults were accompanied by minor faulting of various types, by increasing deformation (e.g., bed overturn), and by extensive fracturing and brecciation along fault planes. Jointing is also prevalent in the region.

Regionally, the DCL site lies on the Overthrust Belt, which 1n the southern Appalachian chain Includes all of the area between the Pulaski Overthrust to the northwest of the site and the Blue Ridge Overthrust to the southeast (Lowry, 1979), a span of about 10 miles in the vicinity of the site. Locally, the site lies just northwest of the Salem thrust fault within the Catawba Syncline. The Catawba Syncline Is part of the Pulaski Fault block, which has been displaced horizontally at least 8 miles to the northwest. Beds strike to the northeast and dip to the southeast; most bedding exposed in outcrop appears to be overturned to the northwest.

2-12 flRSQQQU TCN 4208 RI REPORT MAJOR GEOLOGIC STRUCTURES IN ROANOKE COUNTY

READ MTN. ANTICLINE

Fauli — — — 4-— Anticline Thrust Fault - 4- — — — Syncline Overthrust Side __-X.— Overturned Anticline — - Overturned Svncline

It TETRA TECH, INC. FIGURE 2-3 REGIONAL GEOLOGIC STRUCTURES DIXIE CAVERNS LANDFILL SITE SOURCE: BREEDINft #U* flWSPfl. 1976

2-13 TCN 4208 RI REPORT REV. #1 09/JAN/92

2.8 REGIONAL HYDROGEOLOGY

A discussion of the regional hydrogeologic setting of the DCL site is presented below based upon published information contained in Waller (1976) and Breeding and Dawson (1976).

2.8.1 Hydrogeologic Setting

By grouping the major 1 Ethologies present in Roanoke County, geohydrologic units were Identified by Waller (1976), and designated as "aquifer systems" by Breeding and Dawson (1976) (Figure 2-4). The DCL site is situated within the Ordovician to Hlssisslpplan elastics Geohydrologic Unit of Waller (1976), which is nearly equivalent to the Hississippian-Devonian-Silurian Aquifer System (MDS-AS) of Breeding and Dawson (1976). The private residential wells to the south of the DCL site are situated within the adjacent Cambrian and Ordovician Carbonates Geohydrologic Unit (Waller, 1976), which is nearly equivalent to the Cambrian- Ordovlcian Aquifer System (CO-AS) of Breeding and Dawson (1976). Ground-water flow In these two geohydrologic units is quite different.

For this RI report, the geohydrologic nomenclature of Breeding and Dawson (MDS-AS and CO-AS) will be used to describe the hydrogeology of the site. These two aquifer systems will be further described from oldest to youngest below (from Breeding and Dawson, 1976).

Cambrian-OrdQvlcian Aoulfer System - This aquifer system is composed primarily of the carbonate limestone and dolomite formations, and to a lesser extent some sandstones, siltstones, and shales, all of which occupy the major valley areas of Roanoke County. Recharge to the system depends upon topography, soil characteristics, and permeability of the aquifer, and upon the degree of development of vertical fractures. Because it is a karst aquifer system, recharge is both diffuse (direct infiltration with little overland flow) and concentrated (capture or diversion of surface streams), with the former more significant than the latter. Although few streams flowing across this system are totally captured, most appear to lose some flow to (discharge to) the ground

2-14 flR3000l»3 2-15 TCN 4208 RI REPORT REV. tl 09/JAN/92 water system. The storage and movement of ground water in this system Is characterized as highly variable and related to the structural geology of the area. Ground water is stored and moves through enlarged solution channels analogous to a series of Interconnected conduits.

Productivity 1s high from this geohydrologic unit, and over 80% of the total groundwater used 1n the Roanoke-Salem Metropolitan area is obtained from this unit (Waller, 1976). Well yields ranged from 15 to 500+ gpm, with the mean yield being 55 gpm. Extensive additional well Information, including pump test data from numerous wells, 1s found in Waller (1976).

Overall water quality in the CO-AS is described as excellent, although moderately hard. Because of the dissolution of calcium and magnesium from carbonate rocks, ground water In the CO-AS system commonly has hardness values ranging from 100 to 175 rag/1. High Iron and sulfate concentrations have been noted in areas where faults and fractures are concentrated. Ranges of observed background water quality constituents for the CO-AS are shown in Table 2-2.

H1s5lss1pp1an-Devon1en-Silurlan Aquifer System - This aquifer system lies predominantly witntn clastic sandstone, si 1tstone, and shale 11thologies. Recharge occurs by the Infiltration of precipitation through the soil profile and into openings (e.g., joints, fractures, bedding planes, and fault zones) in the underlying rock, through which ground water moves to discharge points at springs and along stream valleys. Recharge-discharge regimes are localized in nature. The rate of recharge is relatively rapid because of the thin soil mantle on the ridges. Discharge rates are also indicated to be relatively rapid, due to the steep hydraulic gradient associated with areas of high topographic relief. Although shale has a high porosity, its permeability is generally low, thus shale units tend to act as aquitards unless fractured.

Primary porosity 1s not thought to be an important feature in this aquifer system. Typical primary porosity values for sandstones range between 5-30%, while values for shales typically range between 0-10% (Freeze and Cherry, 1979). The percentage of interconnected voids, i.e., effective porosity, is anticipated

2-16

flRSQOQUS at u in 0) o~ r-« **i—i * o£d IO CO CO . r-t CO •* r- ^ to o o * tvj CO

«J "C 3 i *r o Ot 0 X T-H in "± in o CO (J a • in »M • o Ot CO ft r-t O O IH in 1— 1 e1 •9

g •f •?- CM •-• Ol c *H O 0 o S y £ m co «*• o o ~H o o a.

~i- at a> U) tA at •** M 0) ^J d* 01 fl> ot c *r™ 4J fe c/» c e t. •rt «j 40 • -O C TO o i|- s. a f- o c .^ •^ .P ^C * lO t -< £ o M z

P OJ £ IO ^ CO at in to cy ^* o co >o 1 > • |^ fQ » • • fO r- «-• »-• o o to rH in ^ Ot.

E ^ a c a 3 S. Irt f- •r* to to o. i_ X 10 c D) e a i- 1 u S ^ •a 01 "u 3 br~*^-% i- •F— > eg i-H E 4B o C IO O A in r^ ^. •*-> S •o ,00 • • C « CO Q X IO IO —I O O O e O •r-'O o •D •»* 41 C I £ -j_ c CD 41 at *u o at VI (A at u at at -a at at "5 • 4* CZ •«•» XH- s- E (/) C *3 t. d 41 3 01 • -0 C 5» o it- £ +J i- Q & o e •u 41 C B a4.3 =c . -• s u Crt £ tn -a a> Of 41 -M « at •M « en II) U v> e T- f- L. f^h l*» r~ c 0) f-» CM O IO tO en Ui -P- J- c fc. < to * to o o CM CD to A T fi •*- IO 3 r* «c, a^t en T- a tA 1 * C in -H CM c e X ^^ If V^ tM O *«- o ' e » a O 4A IA l-x * ^ O O m r-t o I/I 4- 4) r— I 41 » 3 O a r— tO •o i « C c £ Ol ^J at * "5. E f". O O O CSJ Ok 3= > eOl a. £ m * 10 o o ^ ^. o 2"! in O M i a i| a-. . ta-t at M ea IA at D-r— a> VI U) at 4) « £ •u H at at •o 4> 4t U 4-> •• gj at c •F- X O at € c/> c « (. ^ ^ UJt— u • -p c o> O t. E o £ p e ^ i 3 o z 40 t a .C 3 .^ * f O o. Q. t— K «-i Z V) 3= -HCJ to

2-17 flR3QQQU6 TCN 4208 RI REPORT REV. #1 09/JAN/92 to be significantly less. Fissile shale (e.g., the Hillboro Fm.) and interbedded sandstone, slltstone, and shale (e.g., the Brallier and Chemung Fms.) are not anticipated to offer significant primary porosity because the depositional environments 1n which these types of interbedded deposits form are typically marginal marine areas with abundant fines which become deposited in the interstices of the granular units.

Overall water-bearing properties of this system include fair to good yields in the valleys, and poor yields on the ridges. Only 5% of the groundwater pumped In the Roanoke-Salem metropolitan area was derived from this geohydrologic unit (Waller, 1976). Wells 1n the clastic aquifer system have a mean yield of 15 gpm and a mean total depth of 333 feet.

Ground water quality within the MOS-AS is classified as poor to fair, especially in the shale units. The MDS-AS generally contains higher amounts of iron, manganese, and sulfate than the other aquifer systems. Rarely, methane from the decomposition of organic matter in the shales has been encountered. Representative concentrations of the common ground water constituents of the MDS- AS are shown on Table 2-2.

Generalized Direction of Ground Water Flow -.Ground water flow is controlled fay both Hthology and geologic structure. The geologic structures in the area which may influence ground-water flow include the apparent northwest trending joints and other associated fracture features (as observed by regional stream reach structural analysis), northeast to southwest trending bedding planes, and several northeast-southwest trending thrust faults (including the Salem Fault) located 1n the region. Stream valleys have formed in these fracture areas (less resistance), and stream reaches usually reflect general ground-water flow paths.

The generalized direction of ground water movement in Roanoke County is shown on Figure 2-5. It can be seen that the regional gradient in the vicinity of the DCL site coincides with surface topography, flowing southeast towards the Roanoke River, then easterly parallelling the river flow direction. Consequently, it follows that the boundaries of ground-water basins are likely to be nearly

2-18 flR30QQl*7 TCN 4208 RI REPORT REV. fl 09/JAN/92

TETRA TECH, INC. •t LEGEND. GENERALIZED GROUNDWATER FLOW DIRECTION FIGURE 2-5 GENERALIZED GROUND WATER FLOW DIRECTION DIXIE CAVERNS LANDFILL SITE SOURCE: BREEDING AND DAWSON, 1976 flR300Qt*8 TCN 4208 RI REPORT REV. #1 Q9/JAN/92

equivalent to the surface-water basins 1n the region, except in areas where pumping has changed natural ground-water gradients.

2.9 ADDITIONAL BACKGROUND INFORMATION

2.9.1 Historical/Cultural Areas

Historic and Archeoloalcal Sites - Two historic sites are located approximately 3 miles northeast of the site (Middleton, 1991). The Pleasant Grove Home and the Fort Lewis Church are located on Main Street in the town of Salem, Virginia. Dixie Caverns are also considered historic (Middleton, 1991). No other historical or archeological sites are in the vicinity of the DCL site.

2.9.2 Recreational and Other Natural Areas

Wild and Scenic Rivers - No Wild and Scenic Rivers are associated with the site. The Roanoke River is designated for recreational use by the Virginia Department of Conservation and Recreation.

Recreational Areas - Three recreational areas are located within the general region of the Dixie Caverns Landfill site, but at considerable distances from the site proper. The Havens Wildlife Management Area is located approximately 3.5 miles north-northeast of the site. The Jefferson National Forest is approximately 6 miles to the north. The Appalachian Trail runs along the ridge of Catawba Mountain, approximately 6.5 miles to the north-northeast, but turns north over Sandstone Ridge into the Jefferson National Forest. All of these sites are considered regionally upgradient and too distant to be potentially impacted by the site.

Dixie Caverns, which are privately-owned caverns that are open to the public 364 days a year, are located approximately 5,000 feet southeast of the Dixie Caverns Landfill site. Surface water occasionally flows In an intermittent stream along Twine Hollow Road past Dixie Caverns and into the Roanoke River.

2-20

flR300Ql*9 TCN 4208 RI REPORT REV. #1 09/JAN/92

Other Natural Areas - Woodlands in the area are used by migratory birds during spring and fall migration. Some birds winter in the area.

2.9.3 Floodplain/Wetland Areas

Floodplalns - No floodplalns are mapped to occur on the DCL site, according to mapping by the Flood Insurance Rate Map for Roanoke County, Virginia (page 75 of 150). The closest mapped floodplain 1s located approximately 1.5 miles south- southeast of the site, along the Roanoke River (Figure 2-6).

Wetlands - No wetlands are mapped on the DCL site according to the National Wetlands Inventory mapping oTthe Glenvar quadrangle, Virginia. However, four small Palustrine, Unconsolidated Bottom, Permanently Flooded wetlands are mapped within 1200 feet of the site (Figure 2-6). Three of these wetlands appear to be less than one acre in size and occur along the intermittent stream channel, while the other wetland is larger and is described as excavated and diked/impounded, apparently corresponding to the ponded water in the former limestone quarry located along Twine Hollow Road.

2.9.4 Sources of Potable Water

A combination of surface water, community wells and private wells are used in the vicinity of the DCL site. The City of Roanoke currently collects part of its water from the Roanoke River, downstream of the DCL site. The specific location of the water treatment plant Inlet is unknown, but it is several miles downstream of the site.

Currently, only one active community well is known to be near the DCL site. This well is located over 2 miles to the northwest of the site and serves a total of 30 residences. Based on the regional groundwater flow direction, this small community well is not downgradient of the site.

In the immediate vicinity of the site (within 1 mile), residents use private wells for potable water. Specific information regarding data collected during the RI on these wells is provided later in Section 3.1 (Site Survey).

2-21 ftR3QGQ5Q 2-22 flR30005 TCN 4208 RI REPORT REV. #1 09/JAN/92 3.0 STUDY AREA INVESTIGATIONS

This portion of the report describes the field investigation performed for the Dixie Caverns Landfill (DCL) RI/FS. There were four major elements to this field investigation which was performed between November 1st, 1990 and June 15th, 1991, as follows:

• soils investigation in on-site areas with a history of waste disposal activities, • groundwater investigation on-site and in the vicinity of the site, • investigation of surface water and sediments from water bodies above, across and below the site, and • ecologic investigation of benthic and terrestrial communities on-site and in the vicinity of the site.

Each field investigation element is described in detail in the following section.

All sample collection, sample handling, and equipment decontamination procedures have been previously described in detail in Tetra Tech's Field Sampling Plan and Quality Assurance Plans submitted and approved by USEPA. Text in this chapter only presents a summary of the procedures and methodologies used during field investigation activities.

3.1 SITE SURVEY

Purpose and Scope - The purpose of this effort was to update base information on the site and surrounding area. The primary goals were to obtain current site maps (illustrating topography and stressed vegetation areas), to survey the population near the site, to estimate the volume of solid waste fill, and to obtain detailed information on the site geology. The nature of activities performed to fulfil these goals are described below.

3-1 &R3QQ052 TCN 4208 RI REPORT REV. #1 09/JAN/92 Methodology

Site Aerial Survey - The aerial survey to update site topographic information utilized control points established on site with a ground survey. The ground survey originated from a beachmark at the intersection of Dow Hollow Road (Route 647) and Interstate 81. Control points were established at the site entrance (the lowest on-site elevation) and high elevation points on site and were used to develop a site specific grid system, based in feet and oriented north-south and east-west.

As a contingency, another aerial survey was tentatively planned to collect, using infrared photographs, to investigate whether contaminants originating from the site were causing stressed vegetation in the site vicinity. This second aerial survey was not performed because field assessment of terrestrial habitat was sufficient to delineate areas of distressed vegetation.

Population Survey - The population survey was utilized to estimate the population within 1- and 3-ndles of the site. A detailed description of the methodology is given in Appendix A. In summary, the methodology relied on an estimate of the average number of residents per structure (based on the 1990 Census) and the number and placement of structures.

In addition, a door-to-door survey was performed of residences in the immediate (1 mile) vicinity of the site. This surveying was also served to identify the location and use of structures (e.g., were they inhabited) and to acquire Information on residential well construction. Information on residential well construction was also acquired collected from the Roanoke County Department of Health.

Solid Haste Fill Volume - The thickness and extent of the solid waste fill deposited at the DCL site was determined from a comparison of the original and present ground surface elevations at the site. The original ground surface was determined from a 1963 USGS topographic map, and compared to the site topography developed from the aerial survey described above.

3-2 AR300053 TCN 4208 RI REPORT REV. #1 09/JAN/92 Validation of Map Site Geology - Site geology was validated through a combination of field activities and literature review. Field surveys were performed by geologists to find, locate, and examine any springs, surface seeps, or other manifestations of the groundwater elevation and character. In addition, major geological surface features and structures were examined, including the nearby Inactive limestone quarry. Historical and current aerial photographs were examined for evidence of fracture traces or other surface evidence of geological structures that could influence groundwater movement. This information was used to refine the locations of monitoring wells installed at the site, and, in conjunction with the door-to-door survey/to identify the residential wells to be sampled.

3.2 AIR INVESTIGATION

Purpose and Scone - The objectives of the limited air investigation were to screen historic waste areas for emissions and to assess the potential for emissions from the site. The nature and scope of activities were not explicitly specified in the Work Plan to permit the flexibility to respond to conditions encountered in the field. Activities were developed in the field in coordination with USEPA based on conditions encountered.

Methodology - Both HNu and OVA monitoring devices were extensively used at site to perform real-time air monitoring for volatiles from the ground level to the breathing zone level. Air monitor screening was initially performed to characterize the current status of historic waste disposal areas, and subsequently during intrusive site activities (e.g., well drilling).

A Mini-Ram particulate air sampler was also used at the site, particularly 1n the vicinity of the fly ash pile. Eight hour average particulate levels were collected for two full days, and numerous short-term measurements were also taken. Eight hour averages were performed approximately 5-feet above the ground surface in very open and large (greater than 5 acres in area) clearings. In general, conditions were favorable for air monitoring and the activity was aided by the absence of leaves on the trees.

3-3 RR30005U TCN 4208 RI REPORT REV. #1 09/JAN/92 3.3 SURFACE WATER AND SEDIMENT INVESTIGATION

Purpose and Scope - Extensive surface water and sediment sampling was performed in Intermittent streams on-site and adjacent to the DCL site. The goal was to Investigate the movement of contaminants from the site along the two major surface drainage pathways of the site. In all, two rounds of surface water sampling, under dry- and wet-weather conditions respectively, were performed at 27 locations. Only one round of sediment sampling was performed (concurrent with the first or dry-weather stream water sampling effort) at 28 locations. Figure 3-1 indicates the nature of sampling performed at surface water and sediment sampling sites.

The DCL site Work Plan called for aqueous sampling above and below the activated carbon filter operated by the County. During preliminary field investigation activities, It was discovered that the County had modified the leachate collection system, making It Impossible to sample above the filter. Accordingly, sampling locations were shifted slightly from those proposed in the Work Plan. SL-1 was taken in the leachate pond, below the filter. The sample labeled SL-2 was taken just upstream of the OS-1 location, in the old stream channel just downhill of the leachate pond and adjacent to a seep originating from the leachate pond embankment.

Hethodologv - At each sampling location in Figure 3-1, the surface water sample was collected first, followed by the collection of the sediment sample. This was done 1n order to minimize agitation of the sediment and re-suspension into the water column. Sampl1ng occurred from downstream to upstream i n areas characterized by a steady, non-turbulent, flow of water. Surface water samplings were collected using a decontaminated, 32-ounce, stainless-steel pitcher. All surface water samples collected from stream locations were analyzed in the field for temperature, dissolved oxygen, Eh, pH, and specific conductance. Laboratory analysis of surface water samples included the parameters on the CLP Target Analyte and Compound Lists (TCL and TAL) along with water quality parameters (total suspended solids, alkalinity, biological and chemical oxygen demand, total dissolved solids, and total organic carbon).

3-4 flR300055 3-5 TCN 4208 RI REPORT REV. #1 09/JAN/92 Sediment samples were collected from the biologically active zone (0 to 2 inches below grade) in areas of natural sediment deposition. An effort was made to collect the finest-grained sediments at each location. A stainless -steel scoop was used to collect the sediment sample, and the scoop was decontaminated between each sample location. Sediment samples were analyzed for the TCL and TAL parameters as well as total organic carbon, grain size, and percent moisture.

3.4 ECOLOGICAL ASSESSMENT

Purpose and Scope

The objective of the ecological investigation was to identify and evaluate the quality of the aquatic and terrestrial communities in the vicinity of the DCL site. Identification of flora and fauna population constituents provides a means to evaluate potential environmental impacts from direct and/or indirect sources of contamination.

Vegetative data were taken from a total of 22 quadrats (Figure 3-2). Nine of the quadrats were located in riparian (streamside) areas along the designated tributaries In the study area. Six of the riparian quadrats were located in areas where potential site related impacts were expected to be found. The remaining three riparian quadrats were located in areas that were expected to be unaffected by the DCL site, and were used as reference quadrats. Each of the riparian quadrats were designated with a "S" followed by a number (e.g., SI). Each riparian quadrat was bisected by one of the tributaries. Five of the 22 quadrats were located in emergent (field) areas on-site. Each of the emergent quadrats were designated with an "E" followed by a number (e.g., El). There were no known areas in the vicinity of the study area that could be considered an appropriate reference. The remaining eight quadrats were located in upland forested areas on and surrounding the DCL site. Five of the forested quadrats were located In areas where potential site related impacts were expected to be found. The remaining three forested quadrats were located in areas that were expected to be unaffected by the DCL site, and were used as reference quadrats. Each of the forested quadrats were designated with a "F" followed by a number

3-6 flR300057

TCN 4208 RI REPORT REV. #1 09/JAN/92 (e.g., Fl). If a quadrat was used as a reference, a letter "B" was added to the quadrat designation (e.g., S2B).

Six stations were sampled for the aquatic phase of the investigation. These stations correspond with six of the surface water and sediment sampling locations (Figure 3-1). Benthic macroinvertebrate samples were collected at each of the six stations along unnamed tributaries to the Roanoke River, and were designated with an *S," plus the letter assigned to the tributary, and a number (e.g., SD- 1). In addition to the invertebrate collection, aquatic and riparian habitat evaluations were performed at each station. SG-1 was used as the reference station. Each of the six sample stations were located in the center of one of the riparian quadrats (SG-1 = S2B, SF-1 = S6, SA-5 = S5, SE-1 - SI, SD-1 = S2, and SB-6 s S4; Figure 3-2).

Surface water and sediment samples were collected from SG-1, SF-1, SA-5, and SB-7 for bloassay testing using USEPA protocols. Samples were shipped overnight to an EPA contract laboratory. Static, chronic bioassays using Ceriodaphnia dubia and 7 day chronic bioassays using Pimephales promelas were conducted using the surface water samples. Ten day chronic bioassays using Hyallela azteca were conducted using the sediment samples.

Terrestrial Investigation Methodology

Terrestrial sample stations consisted of 40' X 401 quadrats delineated by flagging. The sample stations were laid out so that the east and west boundary of the quadrangle lay on a north-south axis. The NW corner of the quadrat was labeled "Ql,11 NE corner labeled "Q2," SE corner labeled "Q3," and SW corner labeled *Q4.H The plot center was flagged and labeled with the station Identification code (e.g., DC-EA-F5).

The following terrestrial vegetation identification methodology was utilized, based on methods from the Federal Interagency Committee for Wetland Delineation (1989). Within the quadrat, all plants in the tree, sapling, shrub and woody vine layers, and a subsample of plants in the herbaceous layer, were identified and recorded on vegetation sample sheets. For all layers, the dominant plant 3-8 . flR300059 TCN 4208 RI REPORT REV. #1 09/JAN/92 species and its wetland indicator status (USFWS, 1988) were determined for each station. For shrubs, saplings and woody vines, percent areal cover and cover class were determined. For trees, average tree diameter and basal area for each species were determined. For the herbaceous layer, four 40" x 40" subsamples were taken.- The average abundances of each individual plant species were determined from the subsamples for each station. Additional details on the sampling methodology, including calculations used to determine plant dominance and tree basal area, are given in Appendix C.

In addition to collecting data on the vegetation, all animal sightings, scat, tracks and other related observations were recorded on the field sheets.

Aouatic Investigation Methodology

Aquatic invertebrates were collected by a two-person Tetra Tech sampling team to gain information on the benthic macroinvertebrate community. Riffle/Runs and Coarse Particulate Organic Matter (CPOM) areas were sampled separately.

The substrate in the riffle/run and CPOM areas were sampled using a D-Frame net or a drift net (1 m2). Approximately one square meter of substrate was sampled at each station. An effort was made to maintain consistency in techniques and collection area between stations, and to obtain representative organisms from all Riffle/Run and CPOM types.

Supplemental observations regarding climatological data, stream characteristics and aquatic vegetation Were recorded on data sheets (Appendix C). All sample 1ocatlons were photo-documented. Samp!e i nterpretati ons and taxonomi c identifications were made in the lab by Tetra Tech biologists. More detailed methodologies for all ecological assessment investigation activities are included in Appendix C.

3.5 SOIL INVESTIGATION

The soil investigation consisted of both surface and subsurface soil evaluation and sampling. The subsurface soil investigation employed drilled test borings. 3-9 aR300060 TCN 4208 RI REPORT REV. n 09/JAN/92 3.5,1 Surface Soil Investigation

Purpose and Scope - The objectives of the surface soil investigation were: to determine the magnitude and extent, if any, of surface soil contamination; to determine whether wind-blown transport of fly ash to nearby areas had occurred, to evaluate the characteristics of the material used to cover the solid waste disposal area, and to determine whether any environmental or human health risk were associated with contact with the soil.

A total of 13 surface soil samples were collected in the DCL site study area (Figure 3-3). Three background surface soil samples (Bl, B2, and B3) were collected in undisturbed areas on or near the site to establish a baseline for comparison with soil samples obtained from areas of suspected contamination. These samples were submitted for analysis of TCL organic compounds, TAL inorganic analytes, pH, total organic carbon, cation exchange capacity, percent moisture, percent solids, and grain size.

The solid waste disposal area (southwestern portion) of the landfill area was divided into five zones. In each of the five zones, four surface soil samples were collected and composited together. These five composite samples (SWD-1 through SWO-5) were also submitted for analysis of TCL organic compounds and TAL inorganic analytes. In addition, these 5 surface soils samples were also analyzed for grain size, Atterburg limits, standard Proctor (optimum moisture/maximum density ratio), and permeability.

Five surface soil samples. (FAP-1 through FAP-5) were collected from areas surrounding the fly ash pile to assess the potential for transport of contamination by the wind. These samples were submitted for analysis of TAL analytes, pH, total organic carbon, cation exchange capacity, percent moisture, percent solids, and grain size.

In addition to the 13 surface soil samples described above, four samples were collected directly from the Fly Ash Pile (FAP-10 through FAP-13). These samples were submitted for analysis of cadmium, chromium, lead, nickel, and zinc. Table 3-1 lists the specific analyses performed on the various surface soil samples. 3-10 flR30006l

TCN 4208 RI REPORT REV. #1 09/JAN/9? TABLE 3-1 < Surface Soil Sample Analyses Dixie Caverns Site

V % Atterburg Grain Std. TCL TAL pH TOC CEC Hoi sture Sol i ds U mi ts Si ze Proctor Permeabi 1 i ty SI X X XXX X X 82 X X X X X X X S3 X X XXX X X SWD1 X X * X XX X X 3WD2 X X X XX X X SW03 X X X XX X X SUD4 X X X XX X X SHD5 X X X XX X X FAP1 X XXX X X FAP2 X X X X X X FAP3 X XXX X X FAP4 X XXX X X i FAP5 X X X. X X X FAP10 X* FAP1I X' FAP12 X' FAP13 X* * Cd, Cr, Pb, Hi, and Zn only.

3-12 flR300063 TCN 4208 RI REPORT REV. #1 09/JAN/92

Methodology - The surface soil samples were collected with stainless steel scoops from an approximate depth of 0-6 Inches below grade and placed into a stainless steel bowl for compositing. Vegetative matter was removed from the soil prior to placing the soils into the sample containers. Note, TCL volatile samples were not composited but were collected from one of the five areas in each zone. Areas were selected at random.

All samples were analyzed by assigned CLP laboratories. Standard CLP protocol was followed for analysis of TCL organic compounds and TAL inorganic analytes. The geotechnfcal samples were analyzed according to the following ASTM standards: grain size by ASTM D422-63; Atterburg Limits by ASTM D4318-84; standard Proctor by ASTM D698-78/Method C; and moisture content by ASTM 02216-80. Permeability testing was performed using a falling head permeability method. There is no ASTM standard for falling head permeability.

3.5.2 Subsurface Soil Investigation

Purpose and Scope - The objectives of ttre surface soil investigation were to: determine the magnitude and extent, if any, of subsurface soil contamination; to confirm that cleanup of contamination in the drum and sludge disposal areas had been completed as part of the emergency removal action; and to determine whether any environmental or human health risk were associated with contact with the soil.

A total of twenty-nine subsurface soil samples were collected from 14 test borings at the DCL site study area (Figure 3-4). Subsurface soil samples were collected from most of the borings completed as part of the on-site monitoring well installation and from borings completed in areas where hazardous contaminants were known to be stored or disposed. Two subsurface soil samples were collected from 10 of the 12 monitoring well locations. No samples were collected from the borings for wells RIW-3 and RIW-4 because saturated conditions were encountered prior to reaching the original ground surface (both RIW locations were sited on man-made earthen dams). Well RIW-5 appeared to be unwarranted, and was not installed. Three subsurface samples were collected at 3-13 flR30006U

TCW 4208 RI REPORT REV. #1 09/JAN/92 each of the two drum disposal (DD-1 and DD-2) areas. Three subsurface samples were collected from the sludge disposal area; two from location SD-1 and one from location SD-2.

Methodology - A hollow_stem__auger drilling rig was used to drill through the overburden soils during monitoring well installation. Subsurface soil samples were collected using a standard 24-inch long split spoon sampler. Continuous samples of subsurface soils were collected at 2-foot intervals until bedrock was reached. Bedrock was indicated when the split spoon sampler could not be driven more than 6 inches by 50 blows from a 140 Ib. hammer dropped from a height of 30 inches.

As each sample was extruded from the split spoon sampler, it was visually inspected and described by the field geologists and then quickly transferred to a 32-oz. wide mouth jar. Aluminum foil was then placed over the top of the 32- oz. jar to seal the opening. Upon reaching the bedrock surface, all the 32-oz. sample jars from the borehole were subjected to headspace screening for volatile organic compound emissions by means of a HNu meter and OVA. The results of the headspace screening was used as a criteria to select the horizons to be sampled for full laboratory analysis; samples were collected from horizons with the highest volatile organic readings.

After the two horizons of interest were identified at a borehole location, the drilling rig was moved a few feet away from the first location and a second boring was advanced. Laboratory samples were then collected from the desired soil horizons at this second boring. The portion of the sample to be analyzed for volatile organic compounds was placed in 40-ml sample vials first. Other fractions were then placed in their appropriate sample containers.

During the subsurface sample activity, the drilling rig and the hollow stem augers were cleaned prior to drilling each boring. Additionally, all split spoon samplers were thoroughly decontaminated before collection of each sample from successive depths.

3-15 AR3QQ066 TCN 4208 RI REPORT REV. #1 09/JAN/92 3.6 GEOLOGIC AND HYDROGEOLOGIC INVESTIGATIONS

3.6.1 Geologic Field Characterization

Purpose and Scope - Geological field observations and measurements were conducted at the DCL site during field activities from November, 1990, to March, 1991. The scope of work consisted of locating outcrops and measuring the attitude of planar features such as bedding planes, faults, and joints. Other observations consisted of noting the weathering of the bedrock, geomorphological features, and determining whether bedding was upright or overturned. This last function was accomplished using the relationship of features such as fossil shell layers, sole marks and ripple marks to the attitude of the bedding.

Methodology - Field traverses were performed by Tetra Tech geologists. Rock outcrops were Identified and planar features were measured using a Brunton compass/clinometer. The locations of the features were triangulated from visible site features, e.g., buildings and power line transmission towers.

3.6.2 Monitoring Well Installation

Purpose and Scope - Twelve ground water monitoring wells were Installed at the DCL site during the period November 19, 1990 to December 18, 1990 (Figure 3-5). All wells were installed in rock and were intended to serve several purposes. Primarily, the wells were used to collect ground water quality information, in order to determine the nature and extent of ground water contamination. Additionally, through measurement of water levels in the wells, interpretations have been made as to the direction of ground water flow direction. Slug tests were performed on the newly installed monitoring wells to determine aquifer characteristics. Finally the test borings, in which the monitoring wells were installed, were used to gain further knowledge regarding the geologic setting of the site.

Methodologv - Three drilling methods were us_ed to drill the monitoring wells. The boreholes for RIW-1 and RIW-2 were advanced through the overburden using a track mounted hollow stem auger drilling rig. At the point the auger could not 3-16 flR300067 3-17 TCN 4208 RI REPORT REV. #1 09/JAN/92 be advanced further (considered the top of bedrock) the borehole was advanced using NX rock coring. The borehole for monitoring well RIW-3 was advanced through the overburden using a hollow stem auger drilling rig and then advanced through the rock using an air rotary drilling rig. The remainder of the boreholes were advanced solely by an air rotary drilling rig. All borings were terminated within 10 to 20 feet after the first sign of water was encountered in the borehole.

Eight-Inch diameter steel surface casing was installed into the bedrock in all of the boreholes drilled with an air rotary drilling rig. The steel casing was used to isolate the overburden materials from the bedrock. In wells RIW-1, RIW- 2, RIW-3, RIW-4, and RIW-11, 2B diameter, schedule 40, flush threaded, PVC well casing and screen were used to construct the monitoring wells. Four (4) inch diameter, schedule 40, flush threaded PVC well casing and screen were used in all of the other wells. Either 10 or 20 feet of screen was used in the wells. Generally the longer section of screen was used in the deeper wells. In all cases, the height of the slot opening in the screen was 0.010 inches.

After the well was placed in the borehole, an equivalent to #2 Morie Sand was placed In the annular space to approximately 2 feet above the top of the screen to act as a filter pack. A 2 to 3 foot thick bentonite seal was then placed above the filter pack material. The annular space above the bentonite seal was then pressure grouted to the surface through a trenrie pipe using Type I Portland cement grout.

An exception to this procedure occurred at wells RIW-1 and RIW-2. In these wells, the 2W diameter well screen was placed exactly into the 2" borehole created by the NX coring process; no filter pack or bentonite were placed in the annulus due to lack of space. The remainder of the annular space above the screen was grouted to the surface.

After well construction was completed, the wells were developed to ensure the free flow of water from the aquifer into the wells. The wells were developed through a combination of mechanical surging with a surge block, and pumping using a Waterra or Water Wizard pump. Well development of NX cored wells included 3-18 flR300069 TCN 4208 RI REPORT REV. #1 09/JAN/92 purging of a volume equivalent to that injected during NX coring activities or until sustained yield was obtained.

Complete drilling logs are included in Appendix E.

3.6.3 Monitoring Well Sampling i> Purpose.and Scope - Ground-water samples were collected in two rounds of sampling (January, 1991, and February, 1991) from the 12 monitoring wells installed as part of this investigation. The purpose of the sampling was to define the nature and extent of contaminants in the ground water. The wells are screened in bedrock.

Methodology - The following procedures were followed to perform the sampling: First the volume of water in the well was calculated using well depth, well diameter, and water level. A dedicated positive displacement pump was used to purge each well prior to sampling. During well' purging, measurements of pH, specific conductance, temperature, and turbidity were measured periodically. Well purging continued until all parameters became stable and at least three well volumes were purged.

Ground water samples were collected using dedicated bailers. All samples were collected immediately after well purging. Sample bottles were filled directly from the bailer with as little agitation as possible. All samples were submitted to CLP laboratories for analysis of organic compounds listed on the Target Compound List (TCL) and inorganic analytes on the Target Analyte List (TAL). Samples were collected and submitted for analysis of total (unfiltered) metals and dissolved (filtered) metals. Ground water samples to be analyzed for volatile organic compounds were collected first and preserved with hydrochloric acid. Samples to be analyzed for cyanide were preserved with sodium hydroxide and samples to be analyzed for metals were preserved with nitric acid. Samples were collected for both total and dissolved metals. .Samples destined for dissolved metals analysis were filtered (using a 0.45 micron filter) to remove suspended metals/materials.

3-19 SR300070 TCN 4208 RI REPORT REV. #1 09/JAN/92 3.6.4 Residential Well Sampling

Purpose and Scope - Sixteen residential wells were sampled at the DCL site (Figure 3-6) during January, 1991. The purpose of the well sampling was to gain further information regarding the ground water quality in the area. Of the sixteen locations, eight of the wells sampled are located at residences along Twine Hollow Road; three are located along Kelly Lane; .and five are located along Meacham Road.

In addition to the residential well sampling described above, a second round of residential well sampling was performed in July, 1991. The intent was to further evaluate the presence and extent of semi-volatile compounds and eight heavy metals detected in some of the residential wells during the first round of sampling. A total of 4 residential wells were sampled; two of these wells had been previously sampled In January, 1991, and 2 wells were sampled for the first time. A table listing the residential well numbers, the street address, and the date(s) sampled is found in Table 3-2.

Methodology - Well owners were first interviewed to gain as much information regarding their wells as possible. Information requested included well completion date, total well depth, the availability of boring logs, and whether any chemical or particle filters were in use. The process used to select the residences to be sampled was described in detailed in Section 3.1.

A clean garden hose was then connected to an outside spigot downstream of any filters. Water was then purged from the system until 10 minutes after the well pump was activated. Where possible, temperature, pH, and conductivity were measured during the purging. After purging was completed, the hose was removed and water samples were collected directly from the spigot. Water samples were submitted to assigned CLP laboratories for analysis of TCL/TAL parameters. Samples collected from the residential wells were submitted for total metals (unfiltered) only.

3-20 flR30007 3-21 TCN 4208 RI REPORT REV. #1 09/JAN/92

TABLE 3-2 Residential Well Locations By Street Address Dixie Caverns Landfill Site

Well Number Street Address Date(s) Sampled PH-1 5828 1/91 PW-2 5842 1/91 PW-3 5981 1/91 PW-4 5982 1/91 PW-5 6032 1/91 PW-6 6038 1/91 PH-7 6048 1/91 PW-8 6111 1/91 PH-9 6210 1/91, 7/91 PW-10 6233 1/91, 7/91 PW-11 6331 1/91 PW-12 6347 1/91 PW-13 6406 1/91 PH-14 6443 . 1/91 PW-15 6444 1/91 PW-16 6300 1/91 PW-2Q 6191 7/91 PW-21/22 6224 7/91

3-22 flR300073 TCN 4208 RI REPORT REV. #1 09/JAN/92 3.6.5 Groundwater Flow Determination

Purpose and Scope - A determination of the horizontal flow gradient for the ground water in the bedrock was made for a four month period between December, 1990 to March, 1991. The purpose of determining the horizontal flow gradient is to gain information that will aid in the evaluation of contaminant fate and transport.

Methodology - In order to determine horizontal flow gradient, the elevation and the depth to water of each well must be known. The elevation of each well, referenced from the top of the well casing, was measured as part of the topographic survey. The depth to water in each well was measured once in each of the four months and later converted to an elevation. Groundwater elevations were then used to determine horizontal hydraulic gradients.

3.6.6 Aquifer Testing

Purpose and Scope - Slug tests, were performed during the week of March 11, 1991. The purpose of the slug tests were to determine the hydraulic conductivity (K) and the transmissivity (T) of the bedrock aquifer. These parameters provide insight into the rate at which water recharges, moves through, and discharges through soils and other subsurface materials beneath the site. It should be noted that slug tests are widely considered to describe aquifer conditions only very near to the borehole.

Methodoloov - The static water level in each well was initially recorded. One and two gallon distilled water slugs (for 2-inch and 4-inch diameter wells, respectively) were then instantaneously injected into each well. A pressure transducer and a data logger were used to record the changes in water levels with time. The data logger was started several seconds before the slug was introduced into each well. Each test was allowed to run for at least one hour and was then checked to determine progress. If the test was not completed, more time was allowed for the test.

3-23 SR30007U TCN 4208 RI REPORT REV. #1 09/JAN/92 Two methods were used to evaluate the slug test data. The first method Is applicable for unconfined aquifers using either fully or partially-penetrating wells (Bouwer and Rtce, 1976). _This method allows for direct determination of aquifer hydraulic conductivity. The second method is applicable for confined aquifers (Cooper et. al., 1967). The second method yields aquifer transmissivity which can be translated to aquifer hydraulic conductivity by dividing the transmisslvity by the length of saturated intake in the monitoring well. The aquifer test analysis program AQTESOLV (Geraghty & Miller, 1991) was used to evaluate the field data in terms of a solution for both of these methods. The two methods were applied to this data for comparison purposes.

3-24 flR300075 TCN 4208 RI REPORT REV. #1 09/JAN/92 4.0 RESULTS OF INVESTIGATION

4.1 DATA VALIDATION AND USE

All laboratory analyses performed during this Remedial Investigation have been fully validated. Analyses performed at the USEPA Region III Central Regional Laboratory (CRL) were validated by CRL personnel prior to release of the data to Tetra Tech. Analyses performed by laboratories in the Contract Laboratory Program (CLP) or a Tetra Tech subcontractor were validated by Tetra Tech personnel. All data validation that was performed by Tetra Tech was reviewed by CRL prior to final release of the data by USEPA CRL.

All available data have been used in this RI. Some of these data are qualified with a qualifier code. A list of all qualifier codes that may apply to the laboratory data 1s included 1n Appendix B. The most common qualifier code that appears in the data is "J". A "J" qualifier associated with the concentration of a given compound means the compound was detected but its reported value may not be accurate or precise. Other qualifiers that appear in data summary tables include "K" and "L". A "K" qualifier indicates that the reported value for an analyte is expected to be lower, while an "L" qualifier indicates that the reported value for an analyte 1s expected to be higher.

In the discussion that follows, emphasis is placed on chemicals that have been found above quantisation or detection limits. Quantitation limits apply to organic data and detection limits apply to inorganic data. It is important to note that quantitation and detection limits may vary both from sample to sample and from chemical to chemical. For example, the quantitation limit for trichloroethene, a volatile organic compound, may be 5jug/l in one sample and 10 //g/1 in another sample. Similarly, the quantitation limit for benzene, another volatile organic compound, may be 10 pg/1 In one sample and 12 pg/1 in another sample. Because of the range of variation, quantitation and detection limits are not included in the data summary tables in the text of the RI. * Another important point with regard to data use is associated with evaluation of inorganic elements. Unlike the organic compounds which are not naturally

4-1 flR300076 TCM 4208 RI REPORT REV. #1 09/JAK/92 occurring, the inorganic elements may be derived from natural weathering of earth materia1 as well as anthropogenic sources. In the discussion of chemical results, focus is placed on the inorganic elements indicated to be present above background levels and/or at concentrations that may be of potential concern to human health or to the environment.

Background levels have been established from upgradient locations for the media of surface water, sediment, and surface soil. Background samples were unavailable for ground water or subsurface soil media because organic contaminants were identified in a subsurface soil sample collected at the background location (RIW-1). Accordingly, available published data from Roanoke County were used to establish background levels for ground water. Selected organics in subsurface soil samples were compared against cleanup levels used by Roanoke County In remedial activities and determined by USEPA to be protective of human health.

4.2 SITE SURVEY

The result of the work element designed to obtain current topographic information on the DCL site Is illustrated in Plate 1 (Appendix A). Superimposed on the current topograp is the site boundary as it is given on the Roanoke County Property Identification Map Also given In Appendix A are coordinates of key sampling locations in terms of the site specific grid system.

4.2.1 Population Survey

Using the 1990 Preliminary Census map .of Roanoke County [Tract 303.98, BG (Block Group) 9] the entire population within a one mile radius of the Dixie Caverns Landfill was found to be:

Total Population = 235 people and Population, 18 years and over » 179 people

The population within 3-miles of the site,*which includes Roanoke and Montgomery counties, was estimated to be:

flR300077 TCN 4208 RI REPORT REV. #1 09/JAH/92

Total Population = 2497 people and Population, 18 years & over - 1909 people

These population estimates are dependent upon the accuracy of the 1990 Census data, and do not reflect possible population shifts since the census was taken.

4.2.2 Residential Well Survey

A total of 51 homes were visited in the door-to-door survey, and 49 were found to be occupied. Well log information was available from the County Department of Health and/or the residents for 11 residences. Information collected indicate that residential wells range in depth from 105 to 455 feet below ground surface. Detailed Information collected during the residential well survey is provided in Appendix £. Based on information collected during the door-to-door survey, 16 residences were identified for residential well sampling (two other residences were added at a later date). Table 3-2 and Figure 3-6 illustrate the position of sampled residences relative to the site. The factors used to identify residential wells to be sampled (in order of priority) were;

• availability of well construction information * number of residences served by well • geologic and spatial relationship to the site • spatial relationship of well to other nearby wells

The results of the residential well sampling effort are discussed later in Section 4.7.5.

4.2.3 Solid Waste Fill Volume

As part of the Dixie Caverns Landfill RI/FS, an estimate of the volume of solid waste disposed at the site was prepared. The volume process is described in

4-3 AR300078 TCM 4208 RI REPORT REV. #1 Q9/JAN/92 detail in Appendix A. The fill volume was estimated to be approximately 440,000 y_$i3 or 272 acre-feet. The approximate distribution of this volume relative to the landfill site entrance is illustrated In Figure 4-1. » 4.2.4 Validation of Site Geology

The findings of the geologic surveying performed at the DCL site are described 1n Section 4.7.1.

4.3 AIR INVESTIGATION

4.3.1 Particulate Monitoring

The M1n1-Ram particulate monitoring apparatus was used to measure 8-hr average particulate levels on two different days. Measured particulate levels were found to be undetectable on the first day and 0.01 mg/m3 (the lowest reading possible on the Mini-Ram device) on the second day. The monitoring event which resulted in below detection levels was performed on a relatively windy day (average wind speed approximately 10 mph) and the Mini-Ram meter was placed in a clearing in a generally downwind directly from the fly ash pile. For the second monitoring event, the meter was placed at the end of a very large (greater than 10 acres) and completely unvegetated area adjacent to RIW-7. Due to the extensive area of exposed crushed sandstone and shale upwind of this monitoring location, obtaining an 8-hr average particulate reading of 0.01 mg/m3 does not appear to be unwarranted or to represent a cause for concern.

4.3.2 Organic Emission Monitoring

Real-time monitoring of air and bottle headspace analysis of excavated soils for volatile emissions did not reveal any localities with high emission levels. These results are consistent with the site history. Two factors which greatly reduce emission potential are the site age (more than 15 years since last disposal operations) and the extensive remediation efforts performed by Roanoke County at the drum disposal and sludge pond areas.

flR300079

TCH 4208 RI REPORT REV. #1 09/JAH/92 Historic site conditions and current air monitoring indicate that potential or real organic emissions from the DCL site appear to be negligible. In addition, fly ash particulate mobility appears to be low. As "detailed later, soil sampling adjacent to the fly ash indicate very low levels of fly ash deposits. Based on a stream sediment containing approximately 60% fly ash, the fly ash appears to have an average diameter similar to sand (between 2.0 and 0.85 microns). Accordingly, the potential for air dispersal of fly ash appears to be very low. Based on a qualitative assessment of contaminants encountered at the DCL site, mathematical modeling of airborne dispersal is not warranted.

4.4 SURFACE WATER AND SEDIMENT INVESTIGATION '

Two rounds of surface water samples were collected, one during a season of low flow (November) and one during a season of higher flow (March). In general, sediment samples were collected at the same locations used for surface water sampling except for locations along the old stream bed (OS-1 and OS-2). Sampling locations are Illustrated In Figure 3-1.

4.4.1 Surface Water Investigation

4.4.1.1 Water Quality and Field Parameters

Water quality and field parameters varied between the two rounds of sampling (See Table 4-1). In general, Eh, Dissolved Oxygen (DO), Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), Total Dissolved Solids (TDS) and Alkalinity were higher during low-water conditions (November, 1990). Temperature, and pH were both higher during high-water conditions (March, 1991). These trends are Interpreted to reflect seasonal variations in water parameters.

Samples of leachate collected during the first round of sampling (SL-1 and SL-2) are significantly different from those measured in nearby streams and lakes. These samples contained significantly higher levels of conductivity, COD, TSS, and alkalinity than any other (Round 1 or 2) sample taken. These samples were collected to provide a reference of leachate composition for comparison with upstream and downstream surface water samples.

flR30008l TCN 4208 RI REPORT REV. *1 09/JAN/92

Table 4-1 Surface Water Field and Water Quality Paranatars

Temperature Eh DO Conductl v1 ty BOD COO TOC TSS TDS Al leal 1 nlty Loeatl on deg C ^H^ my. mg/1 uahos mg/1. mg/1 nq71 inq/1 mg/1 jng/1

Round 1 (low-water conditions) Q-l 13.0 8.09 31.0 5.4 0.460 <1.0 NA MR NA MA NA SA-1 7.0 6.91 79.0 >15 0.058 NR 16.5 1.8+0.1 <4 62 18.6 SA-2 10.0 7.80 185.0 13.6 0.045 NR 7.7 3.2+0.8 <4 79 34.9 SA-3 11.0 7.23 190.0 11.0 0.122 NR 5.6 2.6+0.1 10 96 45.3 SA-4 9.5 6.42 102.0 11.3 0.142 NR 14.5 4.2+0.5 4 143 94.2 SA-5 11.0 6.83 134.0 11.2 0.100 NR 8.5 3.9+0.1 <4 138 84.9 SB-1 10.0 7.38 180.0 13.0 0.060 15 0.050 2.4 13 4.7+0.3 <4 58 17.0 SB-4 NA 6.62 111.0 12.1 0.140 2.2 9.7 5.2+0.2 <4 97 52.1 SB-5 10.5 6.76 91.0 13.6 0.260 5.0 13.4 23.8+0.5 <4 208 81.5 SB-6 9.0 6.31 54.0 14.6 0.240 1.1 14.2 5.6+0.4 4 206 94.5 SB-7 8.5 6.30 96.0 14.2 0.270 1.0 12.1 5.0+0.2 <4 202 92.8 SC-1 NANANANANANANANA NANA NA SD-1 , 10.0 6.52 142.0 13.5 0.065 2.4 <4 2.4+0.3 <4 90 19.2 SE-1 9.5 5.85 158.0 >15 ••.- 0.120 1.7 5.7 3.2+0.1 <4 88 41.9 SF-1 NANANANANANANANA NANA NA SG-1 10.0 7.50 131.0 11.6 0.100 NR <4 2.0+0.1 <4 72 44.8 SL-1 12.0 6.83 -35.0 13.8 1.300 NR 74 38.1+1 36 176 644 SL-2 9.0 6.90 -73.0 14.6 1.000 NR 52 30.1+ 46+0 138 486 SR-1 13.0 8.42 120.0 11.2 0.140 NR 27.4 11.5+0 24 65 55.2 SR-2 NA 7.76 54.0 10.6 0.190 NR 14.5 6.8+0.6 14 74 90.2 Round 2 (high-water conditions) SA-1 12.0 8.10 24.0 9.0 0.082 2.2 <4 2.0 <4 42 8.9 SA-2 12.0 8.05 25.0 8.4 0.092 2.2 <4 3.0 <4 56 7.7 SA-3 11.0 8.11 33.0 10.0 0.100 1.1 <4 2.0 <4 54 14.4 SA-4 10.0 8.17 40.0 9.8 0.108 1.1 <4 2.0 <4 51 14.4 SA-5 9.6 7.14 70.0 10.0 0.166 1.5 <4 2.5 <4 36 33.2 SB-1 13.0 8.18 5.0 9.0 0.062 1.1 <4 2.1 <4 83 4.4 SB-2 NA NA NA NA NA <1.0 5.5 2.2 <4 75 4.4 SB-3 NA NA NA NA NA <1.0 4.7 2.3 <4 36 3.3 SB-3 (dup) N/A N/A N/A N/A N/A

Note: N/A " not applicable; NA • valut not available due to fltld conditions; NR - no laboratory analysis ptrforMd.

4-7 flR300082 TCN 4203 RI REPORT REV. #1 09/JAM/92

In general, BOD and COO values were low, and DO was at or near saturation levels. The lowest DO measured was in the limestone quarry, which contained a appeared to be oligotrophic in nature and to have a low reoxygenation potential. The pH measured at all stations ranged from a low of 5.85 to a high of 8.66. In general, surface water pH values were +0.5 from neutral . Eh ranged from -73 (SL~ 2) to 192 mv (SB-2) in Round 1, and from 4.0 (SG-1) to 70.0 mv (SA-5) in Round 2. Conductivity ranged from to 0.045 to 1.30 /mhos in Round 1, and from 0.038 to 0.166 in Round 2. The highest conductivity values obtained, an order of magnitude higher than any others, were in the leachate samples.

4.4.1.2 Results of Chemical Sampling

The surface water sampling effort entailed collecting samples from 27 locations on-site and in the vicinity of the DCL site. Fifteen (15) and twelve (12) locations, respectively, were located in the northern and southern drainage pathways of the site. Two rounds of aqueous samples were collected from intermittent stream, man-made ponds and lakes. Table 4-2 and Table 4-3 lists the chemicals/contaminants detected by laboratory analysis in collected samples. A complete report of all validated data available from the laboratory analysis of surface water samples can be found in Appendix B.

Volatile Organic Compounds - There were no volatile organics detected at elevated levels In the surface water of the streams during either of the sampling rounds.

Semi -Volatile Organic Compounds - For the most part, there were no semi-volatile organics or pesticides detected at elevated levels in the surface water during either of the sampling rounds. The only exception is the detection of bis(2-ethylhexyl)phthalate at Station SB-6 during high flow conditions (210

Inorganic Compounds - As indicated in Table 4-2, a wide range of inorganic analytes were found In surface water samples collected in and around the DCL site. A description of the contaminant levels and the spatial distribution of some Inorganic analytes follows for some of these metals.

flR300083 r-l O -3 -3 "» 1 1— 1 €^ i c^ C3 o c^ c^ o o cd i O O i j i c^ co e3 * o C3 e^ O I <*•> O O ^ O «= O O T^ O Ol ' O O O CO i • • i i i *ro ni o 10 O O • 01 CM in CO o" CM in eg CM CM t~i FH a O U ^3 ^> f^ 1 -r- i i OO t t OOOO I O O O O O o o o o o o o i "a i t en o i > o «—< o o i oo I-H^TO CM OCM c Q ^ fo O O FH O<0 OlOOCO *M* r— cs C3 •—i co ot to o S m 01 >H in m ^* CM ^ co o co f* CM Ol to O f— O CO CO ^ CO CMP- CM

I-l ~* O "3 "3 T3 I C ^- 1 lOOlOOOOO I O C5 C^ 1 C3 3 t i i i-i o t t*- o *r o o 1 rH O GO 1 O 1— O ^ O O O CM O OS to mo CM o co O O CMC3CM ^ ^^ O ^t 01 O O r-- CO C3 C^ ^H in CM to oen o CO CO IO C3 O CM 1 .^ CO *r COCM * * * * t. ^ CO CM IO Cs) CM -H CM +J M «3 C T-l o *^ F^ "^ '^ ^3 41 1 at > I 1 O O O 1 O 1 O O I OO I I 1 1 i «r O i i i 1 O O 1 OOO e o 1t 1 I C..M OO. 1 O . 1 O.O . t *.iii **- 35 r— O OO O OO CMO O ^ O O Ot i- ci ^f *"** to en ^" CM ^T Cw CM f— tO« 3 'r— en CM co m co r*tife r- •» to v? x • • * A « •h * * to to T-*(O to in T-I to

T-l ^'S O ^ ^ ^. 1 "3 •* CM i i a o i o o i o o 1091 i i 091 I99O 1 i i OO i •>» o i o O I r-l O 1 - 1 1CM O 1 1 O O Ol at T- -l a u ^ CO ^ i •a CM*TO bj o oo • CM tno M O OOfO «*- c co CO PO ^ co K co eg m coot CM o « CM CO CMC* O co CM en *• «• en CM -HTH 1 en CM T-l TH

i •— 1 *» o 3 o i 5 */» 1 1 1 O O O 1 O 1 I 1 r-1 i— 1'iroOcnioiii o i co O i i i i o i i a o i 1 « i i ... i . i i i i **iit 1 .11 . . t o- 4* OO P- O 1 co o o o o O mo <••) o i mo o o o f- r— tn i o CO CM Ol i 01 r— 10 r— m in 1 « Csl CM --"

"o u I G"« ^ 5S<. iSJsL a*1-— J-—^ 3 3 3 _j a~a^U 0 tn-—,a > 3--j—— s-3-2^2.^^*. >— 3 at 3 _i.^ a> _i at ot—i •*- 3—— -*O^ • 0) • 3 *^ 3*^ 3-—.•*—, • « = • 3*^. • v^ en 01 3 w 3>— —— •*— 0 as 3 «*— 3— in U • 3 3^-3* T «- eU r— —tn •*—3 • -—"c "T- a) « wi § T- • 3-T- t->—— 0> tg U .j- o c -o e 01 « •— = |-| * w = IA i-r- t- a. c e we u **T3 c 5—^sxa!« QJ lO K) T— O O br—

4-9 o "3 1 OOO I i i O O O 1 O OO 1 1 O O O 1 1 r OOO 1 i tocOO i i t ty O SS i ooO i i toesio i i !o8§ i OO O LU 1 ... 1 ii ... i i to *"» tft o to oto 0 O »H. OO 0»

•HJ O "3 -^ ~> .•H 1 O 1 O 1 t OOO i 1 O O 1 1 1 O 1 O 1 t 1 I O 1 i 9 0 O". 1 O 1 O t 1 SOTH O 1 1 O O 1 i i in i o i i i i O i i O O CO O 1 . 1 . 1 ii • i * i i 1 1 • 1 tn •H O con-to 0 O CO O o o o" eo CM to rH tn *K rH &l or COoT CM *H m or o ^* lO Co CM * ft r--. rH TH"« r^. TH rH CO

TH o ~> -5 r, * 1 O OO O i OO o g I 1 OOO O O > 0 0 O aa1 1 O O O i i CMOO «r eo ; §s§ 1 O O O OOO CO *^ ^p C$ ^^ ^H ttl o o •§ CO»t O tf> T4 ^3 ^3 to (O or r^. ^ to *^ ^o in *t too «* « r-» en CM TH ORj en«\i rHO CS| c CM CM TH CM CM ^M£ 13 rH ^na CD •-3 ,, •-3 j^ T-3 ^3 i ca o. to i OOOO 1 I O O OO 1 O O 9 g Q_ ... OO 1 . I % % o §orS§§ 1 I fO «H O to 1O tn i i O O O O ia oo o i 99 O OO u « i ea »*oo ! §§§ e? *w e3 C9 S: Z OO io eta ! el^iS i • - • . 1 •*--S to o\o ^ OOO 01 »H o to en Oo o OOO ^ V COOT i- a) l^» TMl (^ TH Cfi Ojf 50 Q^ OO"-! to o^ c^ TH to en 4 <-> "T TH O <*| -^ W> X tn r11. cvj co en ^4 m r^ ^ O to *>« c CO T-l Csl TH rH CM CM i«: > or 1 O t O O i §S°§ 1 O O IOO 1 OOOO 1 O O O CL T- 90 StVJ- t i cs] t Q tn 1 CSI !•-. 1 O CO 1 0«0§ 1 O O "* a£ t— OO CM 100 1f— 1» *) tf• c C9 U 1 « »S« CMU* i* f*^ CO T>^ CM IO CM V* > i-i ta c\j CM «r in to N CM or T— • • rH i TH * € -Gt i o tr* *« -H ^»* i •M •*• 4*1 O IE •^ "3 r^ «"3 1 IV «C M Je (O >» I O i 9 I i o«a o o 1 O O I i— CD .L O 1 O 1 1 1 100 1 OO 1 m c O O •*»• i (J 1 Csl 1 O 1 1 t^ Vr| C? ^-1 t CD ^3 1 ^t Ol 1 CM 1 O 1 1 1 I O CSI 1 OO 1 i >P— es ^^ £j ea 1 . [ .1 1 ....1 . • 1 4J .1 • 1 *11 III. 1 • * 1 caof . . -a co o oo i I-- CO O O CM o o i*- e CM csi to in co CM CM rH (rj CM CM ^~ i O ft CSI CM CO en TH «r CM o o i M P- CM TH<0 S tO CM CM to * »*• ^ 2 <• -H *» "o O -M 4* 8 O It T^ *^ M i >a 9 I ^£ M < Ml pB V) CM O O 1 Q 1 i OO i t> 1 1 O 1 O 1 1 i IOO 1 OOO TH e 0 99 1 p- O OO 1 O i :§g§§ I OO I O i i ift i O i i 1 1 O CO 1 OO CM S»> OO M . . 1 . 1 1 . . > . 1 « • 1 1 1 • 1 .11 — J CC (A ** Q CO 9 o <« o ** OO -1 or o o r-. 0000 VJ'— 1 OC tO fs* cOO to in i CM CO o 01 to CM 1 v— eo or VI CO *^ en TH i men 1 * "-* * * j - CO «V? CM TH tO CO CM THCM 1

DI ^ _ s T—— U u 4J ^-v-r^i ^ ~- crtj 3- i 5? "*^.^ _-.: 1 —— ••-. jmuftflBt, '^^^^ 1 ^J ^~___~- **"* * ^^J^x >*n^. JX O> O O ^^V^rf^^-J - * ^•"fcfc __I O) B) *"Hnfc____J -^ J ^-J^1^^'^ en 01.**•*, |j]_j u g^ — t *^- _•**-. _— ..i-^ 33 tj"3*^J |3)i***B.t.—J "^^^''-^..i.J ^J 3 XJ—1 3—1 '•^"•C 3-^l3»0^^ OL _i ,^i_i^i_i^**^**^^^^*^ ?j Q>X^~O3 En^^J^^<^^*--^— u rj> oi-J •^—- 9 O» .3 ^ O» O_J_J 4^^^^^^h%^^pD3 en_^ j "** 's*-^3- §*— -~-O^B 91 ^-* 3x--*^^ 3 3 3 • 3-^, e« en En 3 M S1*^ ^^^-* CB 01 3 ui*— 3—- 01 33 3 S T- - 3 ^i •— vt g*— S^.33** t Or- tv~ 3 f *j— r~*^ C9 c •r— £ 3 T- *r- r^ ffl dj IB O tfl 9 S— • u e j^ a t- o e-a = g -^ « ^- O ' oh j>: I--8 — ja IS S B OlS ti+j-a c 3 tn t. ~o ^ .aO a v & C U +J "O C >sl- V « « -r- O O •*— -e 03 * TH O 1 1 1091 TH Q 1 1 I 1 1 O 1 1 1 1 1 i i i a i ^5 1 VI i 1 i O O I 1 U) 1 1 1 1 1 rH 1 1 1 1 | t i i i LU C 111 • . 1 -J c 1 1 1 I 1 'Illll i i i i i i i i i . i { l O tO 1- m to V) •— CM i i i i i IN j 1 f*x i i i > 1 • as OS m TH

*« T-3 *aT CO -w ^ 1 O to -i- or co tO 'r- 1 "CM C™M i! i' i' i'C ™M 1 5*4 qQ 1 ^" o: Q£ P** ^ CM

rH TH O o 1-3 -3 1 1 CM i i i i i i CM O IQOOOOO IOO i i i i i i 1 o iwoocoor*. 100 1 i i i i i i oc ' ! ! ' ' ' ' i 1 | to to O OOOCMOO OO i ! ! ' 1 ] 1 r-. oroo OCM coor I'll ' CM 10 *n co into • 0 ft ft * • rH rH TM Ot CSI rH CO rH rH TH O o •-3 -^ "3 -a 1 1 e rH i i i i i i rH c5 i ^3 cs ^P ^5 ^5 e^ i o o .IO l — 0 0 1 i i i i i i 1 1 CM O | o 1 gino1 o 1 I o t i i i i t 1 ' (^^ 1 «O 1 ' 1 1 ae S5 to O ^^ o m co c> r*v czt c^ «f^ •« 1 1 in CMOrH f-)CM CMCO CMO ' *r ' XCMOCM i or CM r«» un to IO o 2 o»m ft ft ft * « rH .to- i. or en eo mrn » V rH CO co ^^ rH a c TH rH o F"3 *^ O r^ *^ at 1 1 F-3, at > CM O i 9 i t i CM IO09OOOO IOO u O CM Lft ^r e? cS t3'To x- °1 CO • "^ m K m CM*O " . * CSj ^0 p™ CO i in CM «*» ^" , 1— 1 O O 1 1 1 O rH • 1 IOOOOOO900 CM 0*» 1 OO 1 I I O 1 •O i iaoOO*oooOo ! ! 3g i . §$ 1 5 -T- ."111 . °^0^ 1 CO •** c y> en to *—i to C COO O<*t Oi toi*».o to «g in ^ O^ ^» ^T CJ m *o >* coft coo* r* • . * *" ^ * r— at •— > •a in CM co in CM i CM «H h- 49 O -4J SrH 1 m -H « SrH 0-C rH (J TH 44 1 O U 1 o a *^ ^£ 1 T- 1 M M rH T— 1 1 1 1 1 1 1 1—— 1 1 O O 1 1OIIO9 T—— , i oo i i i S 9 J oS 1 o •c-5 i a. 1 1 1 1 1 1 1 r— •J 1 1 op o 1 I O 1 1 O C3 M i i-* (j ta 3 • 1 1 1 1 1 1 ta a. 4* ||.. II. ii.. +t 1 I « ^^ ''f^t^ 1 ^^ * toes tO 3 ft fS)O O OO ft CM® ' ' ' *» ,,. a £ CMO TH COtO X S °§ ' 0 4* co o r— o• o•r C•M e*o ^ rH ""* S^l ^ ^ « OT or -HrH • » ^ *»H t O 4* TH > >*^ 40 3-* O F- <-• BJ TH rH *• -^ s T-J E o o ^ *• 3 I I 1 1 *» i-l I t I I i I I TH 1 1 1 O O O O O 1 lOO •*• O ' nO 1 I i l l i l I 1 1 1 1 O ^ r> »H O t lOO O i I I i I I S» iiS • g^ !* !* !* i0 J §=>1 1 to to CSIOCM*>«O O O i W ^x • l • 1 1 (M o CM co en TH i CO CV,g CM , CM rH CO ' i §§ O« rH fO TH

at 3 a -J *^5 u u *nL_4S s •S^X S ~ CTG1 ta ^ t czrtr ^ -C •—•H--. Ol O*— • -c _j ^** ^** ^^^r^**^- - *^** 4^ ^^ ^——\ **ta*-*^11*-."****-. ^J _J_] Ol 3>— _l Ol— ->_*— ^, 3 3— 1 3_1 ~or^3'1^j"j 3 3 3*COt O HJt W QJ O> 3 EJV^^. o>-^>^^«— **^ 3 3 N • 3 — 3 Hi 3 cn tn_j _l a ««»«_1 ^* 3 ^^ 3 3 -*Ox 03 O C • ^^ CT> Ol 3 irt •—— 3 '— • S-s- <—* — 01 a-"§ v> §*— SOI CD Q? 4 l|— 4) fl> 3U •33-r-OI •— U • 33-r- tl> T- 3 C S 0 O— C C T- • 3 '-^1—— U1 C T— M • M e M • o o £ u at a) •r> c Si- a) c --*T3 e E Coi Crat— ^z«* r—£ -fcir at— o r— t- « « s. a» aa-r-oo £*3 o a <

CO TH TH TH tO TH -J rH

i CM 10 1 tO 1 9O 1 OO 1 OOO 19 I O 1 1 O i OO 1 O O t OCMO 1 O 93 1 . t 1 . 1 . . O OOO O o r-«. o O 01 o com O!"«. COO rH 1t0 o CiMn * A K A CM rH THrH CO rH rH TH

g o- 1 TH 1 0 O t 0 |O0 i O O O9 i O ( O 1 1IO .O . 1t o. 1IO .O . i o o t«o i o i a vCOt. o to o o o o too 90 co P*»» co r11** 5 CM in o CO Ot O Co ^ O or ^~ CM TH TH i-l CM TH rH TH CM oCM o- e to O O i r O O O O Q O O O O O O iC3 3 •i do i i o ^ O o GOOochOeno 10 M to if) O O Ol O O rH O O O Ift O O co O to TH en CM «O«3 r^-HrHeh OT 1 tn co TH tn o is r*» ^ *i. O to CMIO ot eo ^4 to -J M 3K fe- O i o- es > or OO 1 O O 1 OO o 09 i o i o 19 i to a o i O i o i o OO i O O IOO ... i • t .1 » tn t. CtOM tOo *CrM « O• tocO Qo CMO tOo Oo mC O COM 3 *^ CM CM CO THO» oo CM en en to X • m ft * A ft ft e iQ~ !•«. CSI rHTH tO CM rH u^ 0 >- O* *» >v *o OO 1 1 O l O O OOO l O 19 1 O i to O i t o i o o en o o t o 10 i s . . 1 t « 1 . . . « . i «i .1 . I*-* £ to oro o 90 CM9 OOO & •*•* i CMO * eocrj CM O CO TH CM O O 1 to O Of-* *r en o r-. ifl 3-» *O CSI TH rH tO TH rH >-l t 10 d •& L U.E CM I v* 4-9 O e O" l 9 £ CM X OQ t t 0 1 90 .-^ O O 0 1 O to 10 1 U Oi O 1 1 €3 1 OO 4tf CM OO 1 O 1 O 1 O 0"~ ^c ..II .1 . . _|j ... 1 * 1 .1 • •*- VI •eB CCMM COM Ot a COmcOo i CTMH nO O ' oOr oOr o * TH r^ en or 0* r** a\ in •S in TH TH ?•> M tO rH rH > 3« •t OJ *> "3 o- i l w trt TH O O t t O t O O O O 0 O 9 l O 19 1 T«— to•o . iI t1 o. t1 o.o . S CO £9 €3 •$ Cw 1 C? J C3 to ** HTO O OO i •H (3 O O Ol O O CM to -H I^.CM i CM o -H eo ip o r— CM ^ rH^- i rH

1 o —i\_j 3 3 aC7 G'ci.^i. i1 i" M1"^^ E313 »_J Er> O* 5 3 -J •— • DI 3"—*^-'^^ M SJ » 3 •^'"'-B.'wl % S3 ^^ O Z? w* 3 B *•— •* • 63 3 T- O) T- § 3 •— T— OJ ^ U> 3 ~v o ^ c cz en ^ *r— — W CT3 ^ CB id 5-r- t-^-^ a o*e:*J-o j«5tj'JJ1Jj>ciS 4.12 5R300087 •

I O 10 ' O O 9 O

00 O . . _ _ __ _ mO cCOo CtMo rH f-or^ IOm r He Ool CM CM or rn CM CM

t«O»O T H <^-O TH *TrH MeOnO CM esi en eo co csi

t--o ut— o ouiou-- - i 1*o1 (Too C M oesri CMOOOCMOitor-oOr <» «r f\ at CM TH w

9 _.=.______ooor-o

O tOr»*WOCO9iOT«tOO— -• — -• cMm^ivrorO CMC^T MO cnotinrH 3 fc.« to ot csj m 10 .£ tO X

m+ ttf T- or ^ = •» O rH m « i-

w 1 1 1 1 Ol SO i ao j O O 1 1 OO I O O O O 1 1 1 i oor "•» 1 OO r O O O O 1 1 O 1 0 1 O O 1 +» ' ' Oo in co l co CM Ot l*~ CM o in m 1 en o o m

§£*2i-=-_. OlJ> ft«n 0s—1 T<-A •>•—3 at « o w> 3 0c1 cn^e wc +j-a -ra -c o BR300088 4-13 SI——t CM Og *Mi Ot -3-0. • SE UJ ?* *C uae s Ua.--*J ^.>

® .b) S£ e ca QT « UJ C i i i i i O i 1 I i |ii' iiitii 1111 i i i i T- iiiti r*- i i i i \ i i i i i i i i i 1 1 1 1 i i i i i i i i i >iii i i i i i i i i i i i i i i i B£ eo 1 II 1 ' CM JM: u: c §"B m aSQ. a T-3 "3 ST SOo 1t oO tOn 1111 i 1111 i i i i i i 1 1 1 1 tiii . . i . . i i i i i i i i i i i i i * i 1111 i i i i '-* tn rH tn 1111 i i i i i i i i i i i 1 1 1 1 i i i i j* rca CM esea u_ r-g •a e *•• i i i O t 1 1 i t i i i i i t i i i i i i t 1 1 1 1 iiii 3 o» 1 J 1 O 1 1 1 i i i i i i i t i t i i i i i 1 1 1 1 iiii Q I 1 1 . 1 1 1 1111 i i i i i i i i i i i 1111 i i i i

g = rH i i i i t i • l l IOI 1 i 1011 1 1 O 1 O 1 1 IOI 1011 S 1 C\l 1 1 i toil 1 1 O 1 toti 1 i i i f i r- 1 ( i i O i O i o d • i i i i r f 1 1 I'll i I'll II • t • 1 i i • r I'll to 1— 4* -a CM o o o o o **- — X CM r-. TH m CO o 4> r- i s CM in rH CM « O A fr w in rH rH rH CsJ 5 i j O 1 i tn I 1 ii«i I'll

_i _j a O* Ot 3 3 -ae cCT s O "— ^^^. 01 3 >, ^H^S ___1 ^C dj^> ^^»^- Q> *-w-%G" _j M .e '— C » K ^-- X ^J ^^*—s *^, *"> ^— — "***^~. ^.— » u — J 5 « 3 O ^^.*^^^J *— N a>vj — j i***x''^<-^_J OtOJ« .Of**,f '• *• - »^^^**-. ^-=_ -?C ot ot^^—i 3"-O-^Ot-J ^~^, _3_.~^-=J 3 O>«-J ^ o> c Cft O * O 3 3 01^ Ol OS 3^ -^.^-3 3 fc 3_ N -^_ ^——— 3 Ol 3 3-^ 01 3 at -^134 av*-"— — -c c C^: Si *— 3 —— 3 • 3 3 «J u s O u -u «>)•—•|git..* •—' O> Ol 3 U!« 3 • a i- .a**- o WU1 3 C 0 C-EJ 0 O • C OT- • o o i- i- S OCsI 55-S- •-> • o o t- !«**—• • T- Q) -r- 9 Or— r— J3 C tn £"-i£ (-.§ t~ 0 *>»— — -a e t u t-.e.e -r- o_ •3— *cJ ien- at-at «j o ^ o£e o"« aic ea OO o O OU*— *XX XZ o.ts> (0 VJI— > flR300089 4-14 CO >— rH«SJ

E ^£ C 55 ea-a Q —— — 1 V 1 1 1 1 1 1 I 1 O UJ -T- ii l 1 1 t 1 1 O u.-— 1 1 1 1 1 1 1 1 or. to rH

CM I "^ E 1 1 1 1 1 1 1 1 1 3 in 1 t 1 1 1 1 t 1 1 O E o-e.5 1 I 1 1 1 t I 1 1 « t. 01 s-3 . . at a -r- CM 3 X O l 01 Q CM OO OO OO IOO ^^ U a1. oooomo i o oo "5S3 •S'•*•S o co O 0 o in «? o om t^O OU^rHO O CO E = >» ^~ \& in f^ r^^ ot ~ to +* A A A A Tc^ s>T e— tCM0 1wO rmH CuOs CM 1 ^01 >5 O1 rH 1 oooateoooocsf' *7 « « Q- ^" "M 4J .« SE OOOf-.rHO O CO ft ft A A fi "^ O ifl O Csl i tO«r in to >- "o 1 u esj 1 o 1 n 1 s rH «— I cp 9 l l 0 1 O l f^ 1 M I O ^ 1 1 O 1 O 1 u 40 4* | . . | | . i . i ^ to • OO O O <*- X OJ CO CM CO H- o •a OtA * T. C3> CO& 2 £• • <• rH rH rH a r". "3" ^» CM O S r^rj i w Ul | to —• 0091 19191 1 OO l Q r-.e> cp i i o i o > cc'* 1 OO U. to l uft O O O O LU-—— CSI CO i1 CMcOo CtoM *r- - Oeol A A 'ft A 10 in rH CM

_J "c u U *"^ •- -. - - — . i O^J "-t i 03 _) - * .£= ^**^**?*~* ***^ .E •r- O> -- ; (J i — _ 1 O3 C71* *v Of* i .^ h U **- 3 ^^ ^-t^ 3 S •*- J 3 — J ^J ***^ Jl ^^ ^^f^^*.^^**^'^sfc^*N *3 99 DI O»O)-J *»" C 3N-- • 0 3 | 3 3^, a o BT- 0) -r- 3 S3 MI c ^- tn t. •*— • E O ^- T(-j a ct 01^a *« «t n> o >•* -3 o a0 ot~ S-r— O>E CJ *ir- TJ E ^ 0 ^9 fl3 *r— O T- O T— •TS j; COUEEZO-tOtOFsl oo

4-15 flR300090 TCN 4208 RI REPORT REV. #1 09/JAM/92

The greatest levels of manganese were grouped 1n the northern drainage path between SB-4 and SB-7. For example in the first round, total manganese ranged from 2,450 jug/1 (SB-7) to 2,730 jjg/1 (SB-6), an order of magnitude higher than any other water samples collected. With the exception of SB-2, SE-1 and SP-2, the total manganese concentrations in surface water was below 100jug/l. Detected levels of dissolved manganese ranged from 4.6 to 2,620 pg/1 and the highest levels are also found between SB-4 and SB-7.

The measured levels and distribution of zinc in surface water samples matches those described above for manganese. Total zinc encountered in the first round of sampling ranged from 2,210 to 2,680 (jug/1) between Stations SB-4 and SB-7. The concentration of zinc (total and dissolved) in all other surface water samples typically was less than 50 (pg/1).

The majority of data available for assessment of lead levels in surface water samples originates from the first round of sampling. Many of the lead levels detected in the second round, of sampling were similar to those found in the laboratory blanks and are unusable for assessment. However, low flow data available from the first round provides information on the highest possible lead concentrations because of lesser dilution. Lead was detected in surface water at Stations SA-1, SA-2, SB-3, SB-4, SB-5, SB-6, SB-7, SD-1, and SE-1 at total concentrations between 1.1/jg/1 and 55.7pg/l. The average total concentration was 11.5;/g/l. The highest lead concentrations were found between Stations SB-5 and SB-7 1n the northern drainage pathway.

Summary - Generally water quality parameters in the study area appear to be within acceptable ranges. Between the two sampling rounds, high-flow water quality appears to be more consistent and of better quality than low-water conditions. Generally, elevated levels of TDS correspond with sections of Streams A and B containing high contaminant levels in surface water. Elevated TDS and alkalinity also corresponded with high levels of contaminants found in surface water samples taken from the leachate pond located near the site entrance.

4-16 AR30Q09I s s TCN 4208 RI REPORT REV. #1 Q9/JAN/92 Inorganic analytes appear to the most common surface water contaminant at the DCL site. Aluminum, cadmium, copper, iron, lead, manganese, nickel, and zinc were detected above Virginia Water Quality Criteria (VAWQC) or were at levels above background, where no criteria exists. In the stream surface water samples the levels of many inorganics (e.g., cadmium, lead, zinc, and manganese) are distributed in a similar pattern - the highest concentrations are grouped between Stations SB-4 and SE-1. High levels of inorganics were also found in leachate samples comprised of drainage originating from the solid waste area.

4.4.2 Sediment Investigation

4.4.2.1 Geotechnical and Physical Parameters

Table 4-4 summarizes the geotechnical and physical characteristics of sediments collected at the DCL site. Two parameters of particular interest are the Cation Exchange Capacity and the Total Organic Carbon. Respectively, these parameters measure the capacity for sediments to sorb cations (e.g., lead and zinc), and organic contaminants (e.g., PAHs).

In general, sediment TOC in the northern and southern drainage paths appear to be approximately equal. Generally, TOC was found to increase in the downstream direction, although the background sediment sample (SG-1) collected in a relatively large stream contains one of the lower TOC values. CEC appears to be greatest in the northern drainage path; values are approximately three times those in Stream A.

4.4.2.2 Results of Chemical Sampling

Qualities of sediments collected in Stream C (SC-1) appear to be significantly different than other sediments. In particular, CEC and TOC values are significantly higher at this sample location, and percent solid is significantly lower. It is believed that very high levels of organic matter in the SC-1 sediment sample is the cause of this behavior. At the sampling location Stream C is essentially buried under layers of leaf matter, and the sediment sample probably contained significant quantities of organic matter.

4-17 AR3QQQ92 TCN 4206 RI REPORT REV. II 09/JAN/92 Table 4-4 Strcu Sedintnt Characteristics Dixie Caverns Landfill Site

Depth of SM^tlt Total EPA telow Orgule Melsturt Ptrcext S«?U S«Dlt 6 round Carbon Conttnt Solid CEC So41w I location HiW)tr (ft) (*9Ag) (Percent) (Nrctnt) PH Mcq/lSOg (•9/1) SA-1 5386C-07 0-0.2 845 12.8 87.1 * 2.3 530 SA-2 5336C-06 0-0.2 959 11.0 80.8 * 5.3 1,220 SA-3 5336C-05 0-0.2 1,432 17.4 33.4 * 5.5 1.257 * SA-4 5886C-Q4 0-0.2 4.404 20.2 32.6 4.4 1.02* • wfc*.*01 ag

SA-5 5S86C-03 0-0.2 3,923 21.2 84.3 * 5.9 i,J3I 3S£2 BH

SA-5 5SS6C-01 0-0.2 20,446 20.5 84.0 * 5.1 1,10t tnc3 IMI SB-1 5S86C-016 0-0.2 2,664 8.0 92.5 * 8.5 1.953 1 SB-2 5386C-015 0-0.2 11,598 28.9 74.0 * 7.1 1,637 J SB-3 58S6C-018 0-0.2 1,348 21.1 78.7 * 11.8 2,720 1 SB-4 5886C-014 0-0.2 3.680 21. S 78.3 * 16.6 3.823 J SB-5 5SS6C-G13 0-0.2 5.418 27.6 72.7 * 10.5 2.41-fl SB-6 5S86C-Q11 0-0.2 1,264 28.2 71.8 * 11.9 2,738^ SB-7 58S6C-012 , 0-0.2 7,933 34.6 69.7 * 13.6 3.138 SC-1 58S6C-017 0-0.2 106,944 53.4 49.9 * 34.7 7,988 SD-1 5836C-010 0-0.2 8.111 41.6 68.4 * 6.2 1,425 SE-1 5S86C-09 0-0.2 20,050 37.7 58.4 * 12.2 2,810 SI-1 5S36C-08 0-0.2 20,953 39.1 59.9 * 13.8 3.152 SF-1 S836C-023 0-0.2 14,900 21.8 31.6 * 12.7 2,925 SG-1 S88SC-02 0-0.2 2,932 21.2 77.2 * 4.6 1.062 SR-1 5336C-021 0-0.2 5,570 36.3 70.9 * 13.8 3,173 SR-2 5886C-Q22 0-0.2 5.580 30.8 69.6 * 10.7 2.463 OS-1 5SS6C-019 0-0.2 2.020 12.7 85.7 * 4.1 935 OS-2 53S6C-020 0-0.2 1.321 15.1 83.5 * 4.0 923 | Analysis not p«rfon-td.

4-18 flR300093 TCN 4208 RI REPORT REV. #1 09/JAH/92

Volatile Organic Compounds - In the sediment samples collected, only one location contained detectable levels of a single volatile; Station SB-5 sediment contained 44.0 mg/Kg of Acetone. As this sample location is somewhat distant from the site and none of the other sediment samples collected contained any volatiles, the source of this contaminant is unclear.

Semi-Volatile Compounds - The.semi-volatile contaminants encountered in sediments at the DCL site fall into two classes, Polycyclic Aromatic Hydrocarbons (PAHs) and Phthalate Esters. The predominant PAHs encountered in sediments are compounds similar to Benzo(a)pyrene and Benzo(b)fluoranthene. The predominate phthalate compounds found in sediment are bis(2-Ethylhexyl)phthalate and di-n- octyl phthal ate. Information on the levels and distribution of these contaminants is presented below in terms of the total PAH and phthalate concentrations. At background sampling locations the total PAH and phthalate concentrations are essentially below laboratory detection limits.

The most significant levels; of phthalate compounds occurs in Stream A in the southern drainage path. Bis(2-ethylhexyl)phthalate and di-n-octylphthalate were detected at SA-4 at total concentration of 1,520 mg/kg. Just downstream of SA-4, bis(2-ethylhexyl)phthalate was detected in two sediment samples collected at SA-5 400 and 1,900 mg/kg, respectively. Sediment samples in the old stream channel (OS-1) also contained phthalate compounds which totaled 253 mg/Kg

PAHs are the predominate semi-volatile compounds found in the Stream B sediments. In particular, PAHs were detected with frequency at SB-4, SB-5, SB-6 and SB-7. Respectively, these sediments at stations contained total PAH levels of 659, 273, 47, and 304 mg/Kg. Just downstream of SB-7i in Stream E, the total PAH concentration is 870 and 2,330 mg/Kg in two duplicate sample. PAH compounds are also found in the Stream F sediments, at a total concentration of 803 mg/Kg.

A unique semi-volatile compound, Benzoic Acid was found in the sediments collected in Stream C. Benzoic Acid (not a PAH or a phthalate compound) was only detected at the one sampling station in Stream C (SC-1) at 2,000 mg/Kg. This was only occurrence of this compound in sediments at the DCL site and is found at a

flR30009U TCN 4208 RI REPORT REV. #1 09/JAH/92 location relatively removed from waste disposal activities at the site. It is unclear from where this compound originates.

Inorganic Compounds - As indicated in Table 4-5, heavy metals are a major contaminant associated with the sediments. Lead, manganese, and zinc are among the heavy metals found above background levels. A discussion of the levels and distribution of these metals follows.

Detected lead in stream sediments ranged from 4.6 mg/kg (SA-1) to 30,800 mg/kg (SB-7), and averaged 5,410 mg/kg. Naturally occurring lead levels detected at the reference station were 27.7 mg/kg. Figure 4-2 indicates the spatial distribution of the lead concentration found in stream sediments in and around the site. It appears that lead concentrations in Streams A and D, and Stream B, upstream of SB-4, appear to be at background levels. Downstream of Station SB-4 lead levels increase by orders of magnitude. Peak concentration occur at Station SB-7 and then decrease in the downstream direction along Stream E.

Detected manganese in stream sediments ranged from 184 mg/kg (SD-1) to 21,000 mg/kg (SB-7), with the average being 4,280 mg/kg. The reference station had a manganese concentration of 536 mg/kg. The highest manganese concentrations were found in Streams B and E, however, slightly elevated levels were also found in Stream A and in the old stream channel. The distribution of manganese is similar to that of zinc.

The spatial pattern of zinc in stream sediments matches that of lead (Figure 4- 2). Concentrations detected ranged from 22.7 mg/kg (SA-1) to 129,000 mg/kg (SE- 2), and averaged 24,400 mg/kg. The reference station had a zinc concentration of 19.7 mg/kg.

In addition to the metals discussed above, Chromium, Silver, Cadmium, Antimony and Barium all increase dramatically at the toe of the fly ash pile, peak near the confluence of Streams B and E, and then decrease as Stream B moves southeastward.

4-20 flR300095 -3 -3 rs— i -3 -5 "3 m I 1 O OOOtOOOOOOOOOOOOQ rH 1 1 1 1 1 O 1 1 i i i i i 1 1 O O^m^o^totPOrHoocMomcM 1 1 t 1 1 1 & t 1 1 1 1 i < 1 1 . U 1 1 1 1 1 * 1 1 1 1 t 1 i §2S iS*>Si2|S'*i-£ § * -H in tmo <«s <•*m? CM

-3 O -3 T l 1 O 1 ilOOlQlliiO i i i O ssislsigssigssss 1 1 1 O O 1 O 1 1 1 i O t 1 • QD ( 1 1 * • 1 f t 1 1 1 . (rt a 0000 O o 01 r- o — o *r IM ov -*• r- o m co >H o rH m in eo * •-• rH 9 in r*OCMOmrHOVCMlO ^- rv• o • v • to* m CM CM

O i O ooof*-oooogooooooo to i 1 1 O 1 1 1 1 1 1 1 1 i O 1 0 OrH^-mooooaOOGioOOotnoi 1 i t i O i i i i i i < i • 1 . OQ 1 1 1 « 1 1 1 1 1 1 t 1 5 CD O Otoir5 oco m0 O O oo com m rH •21 T -3T -3 c m 1 1 1 O O O >£> O O'O OOOOOOOOO in 9 liOOlOitiii "^ i 1 1 1 o(r>aolnoo1CMt-*Olo6omo^^*H i O IIOOIOIIIII 1 1 1 aa . ll'.l'lllll •r- 3> C9 f) r*^ O- rH co tn o co ^^ LO CM tn ot ep (/» V O O f> -* rH rH ^$ O *H ^H ^3 rH eO *^ rH O% rH ^f ^F rH r^ Ot rH

J rH CM

CSI 1 1 1 OOO 1 OOOO OO 00 OOOO 1 OOOOlOOOOOi C < 1 1 1 otno ' O^CM« oe oo^-O o » 1 OOOO IOOOOO 1 0> 1 1 1 ca V* o m rH o v o CM o to o V1 "> o ^ o v> CM rH ^ O rH rH rH O TH O Ot rH m rH in rH rH (^ rH &t ^f rH r^K tn* ao» m * rHK tn 2 CM CM fH «1r -c3 £ r^ ^3 *^ ^3 *3 ^3 ^T 5 *^ ^^ 1 1 t oogooooooooooogo f^ 1 1 I 1 1 1 1 1 1 1 1 1 i I 1 1 oinomorHotmaioootooisi^* t 1 1 1 I 1 1 1 1 1 1 1 1 fl y .** 1 1 1 CD 1 1 1 t 1 1 1 1 1 1 1 1 *- ,ga O * o> o tn m « o ^ o o *o * <•*« CM V) to i A oo • o rH ^ o 01 in CM Ol ^^ i CM o c^ m rH in i * • A K « 0 CM ot eo co In 41 CM to ^T 1 •o **H 1 1 1 U "e rj rj ^ r-3 r-g 1 1 1 1 CM • III OOOCVIOOOOOOgOOOOO CM 1 1 • 1 1 1 1 1 1 1 1 1 1 1 l ^ III 5 1 1 r- 1 1 1 1 1 1 1 1 1 1 1 1 ca • 1 H- 1 1 1 1 1 1 1 1 1 1 1 u t/S — III o to *>« o to m m o tn e o in o in rH O 4* m CM o r** rH CM O CM o rH ^ m m o V* = -B 1 P*. *4 (•» rH t»* OlfS> O r^ 4* r- o i m o 2? "5 W S m 5*^ *"* 3 * • 1 ,,-3-3 ^3 —J J ' "3 "3 i 1 (A 3 rH OOO ^3 O O^ T*^ ^3 ^3 *— * ^D O ^3 *— * ^3 tS ^3 C9 ^3 ^H 1 1 1 1 1 1 1 1 1 1 1 1 1 1 < ooe O^O*OOCM^Olo5o*O.HO 1 1 1 1 t 1 1 1 t 1 1 1 1 1 1 l/t CO 1 1 1 t 1 1 1 1 1 1 1 1 1 O 4* o «r IA o o> «t to o m o o n o r^> CM

"5 Ol

"3f ^ Ol • ,O> 3 *-* *"""* o» o* -^ _ « a f^ ^£ ££ OJ w -—. e ^ O) Ol v-« a ^"^ 3 3 r— •O5l iJ—: oa^^^^"^^ df Q •w 3 °* m § ^ 70 » .C e ^S.E E*St "0*2 Ol -E u •-> a. V Ol 47 43 ^£ ^£ ^>^£ ^L *i *^ *"*S _r-|i_in^ ^^ -^ E 3 -C JS ~^. "^. fl.^-s — * i la ">. ^^ W ^^ O* O* O**11* S «-«, u e e a 013-0 3 x -c J£^^ X 2^ Ot^1^41111^. Ok^^ ^^^'^ ^>wi>>^iii^^I^^«^£ -e ^Ot f^eui-*^.l 0 Q *J s ^^j;^.^ i^J *^^r'0^1 Xa) u 3=2.c "5^.2 'S^ai22*~<*-» m m£ ?"»--<. u -^"oV^, -S M^"* S-i'w'CT5S^^— "~aT*-£'£ 3 E >*— •— W*^ CO CM W Ol >i u ui 5«— 3 • VM O)OI3 Uf— ' 3 • pi « o «J3J^ u e c — 1-> LU C£ «^ § J*. (.Ai'S Cr-'SJ J5 1 = CM "r» f^ 3 ^— *r> • r* m Q <0 0 V) ^O d ooooowt-ssoeeM B ffl>— 1 b M S M k U ^- U JD O, P IB OlE O *J E E f^ ^. ir» u flj ffl d/ ctf o jz r— £• .c ^L >i a&ifl r^^eocofjootj*"— W 0 0 Q -^ OO^®0— Jixact^4 *^ O 4M *T" < caeDeo.

4-21 &R300096 i i i I i i ii I I I I I I II i i i i i i i i

i i i i i i t i i i i i

§9 i OO O i ' O O I 9 O O 1 I O e9O 9m eQO O^ OCM Ooo

•"3—I -3 O 9 9 99 O0< • i o c? i i r- I O O < I I . . I I iOn Oco

§1 999 i l O OCM I ir-»O CM

•o ot. •rt-^- a- O

— rl I U** ii * .1 3*

flR300097 >•" ' 1 •

9 rH O 9 CD O O 1 ii i i ttoioiii i ioi i i m i ii i i 10 UJ Illll • 1 .1111 .111 .111111 . t/) ii i i icMiOti i icoiiimi ii i i 10 rH m Hf CM 0

CM

-3 "3—J -3 <~3 CM 9 1 OO CM 1OOO9 IO0OO I9O l l 1 lOO 1 oiinp4^»ioinmwioe*iooioai ' i i « » O -• *o a ^ m o> aoov i-< o r*v P*« rHiO m rH rH .-* OCOOIf"* rH rH CM 00 f* CM 80 CM CM n* • B • * • Ol 80 rH in «H CM

-3 -3-J -3 -3 rH Ol99in IOO99 l O

V) 9 in co 9 f ft o 9 at 9 to CMO cMm Gl rH f*» 04 rH rH CM O PO <*> 01 —H Ot CM P1^ CM 99 Ol *-*

-3 -3—» -3 -3 rH OiO9fOiO0OO CMr-t m* at* wf+-r« « * CM• to* f* CM CM CO >H -H rH CM

_[ -3 ^--^ -3-3-3 m a rH OOO9rHOOOO9 i O C» 0 0 i O O O O O lOO rH o o O oo ocMCooto^oomo tooOO i o o O ^* ^3 i ^3 ^^ tn O r^< o co CM rH ^^ ct ^3 ^3 oi CD oi ^^ in O. i co ot O r* 10 i CM CM ^ 01 eo oi o in co o rnto i~* o/ 1 -H CM Ol " 1 « CM 9 in rH IT IO IO rH r4 Ok rH in • rH rH CO CM rH CM CM • rH ^ rH rH •a

CM rH >, O999 IO9CDO9 IQOO9 IOO9O9 1 OO rH 1 99gO§ 1 U O (-1 OO 1 OOOrHCD 1 OOOO 1 OO O* *T O «• *r m rH OCMIOCM g> * CO rm— rH j! « -J -rs-» 4> rH rH O 1 OOO 1 O 199 l OOO 0 lOOm i O lOO rH o oo o o a1 r- O 1 f-OO IO 1 rHr- 1 OHT O C3 IVOCO 19 ICMO 1 p- 0 O O OO 4* O O rH rH O CM r-. O CO CD «. rH O O VCM

u u .^wot ^oi^- « ^O—t -—.*« 01i ^-, ^O£l a^^O* ^ ^O>* —o' i ^^.-oi oi ^ — ^*o> 1 ^ ^e o^-.-^ at oiM •——•-. at "•^.'^^ oio'K'-x^c ^^^-.^ ^ •^ov^tf o> 01^ ie-~^ 01 01^ g> o>^ oi g1^*^ °* a>*N^*^> u 3 B OP"'*.1^* oi Oi • "^Ox- Ot Oi o» •"'••• or^*.1"— • B "-O^ B B en Ol B 0)**** Ol

SEU •— B B 5 a) B B-— ® >i — 3 . *3B CO— »— 33-r---* -.T3-—— • trt E t.— «»— fc •^.^-—• •r- • c 3 — — -r- * — , t- 4)«a$-r-o 01— o.c B— • &R3G0098 o f— rH

"e "o « •N*

1- -£ « "H 9 H^ T£

J< "3 u < ei T- CO £3. Q. -r- * 0 *t •4o-

t— *——

a u

1

• BC as3—

4-24 flR300099 4-25 TCN 4203 RI REPORT REV. #1 09/JAN/92 Summary - Polycyclic Aromatic Hydrocarbons (PAHs) and Phthalate Esters are the predominate organic compounds found In sediments at the DCL site. In the southern drainage path, phthalate compounds are more common, and include bis(2- ethylhexyl)phthalate and di-n-octylphthalate. Phthalate compounds are first identified in Stream A starting at Station SA-4 which is downstream of the site entrance. PAHs are the predominate semi-volatile compounds found in the Stream B sediments and include, Benzo(a)pyrene and Benzo(b)fluoranthene. PAHs are first identified in sediments just downstream of a historic waste area i.e., the drum disposal area.

A range of inorganic metals appear to originate from the DCL site. The major concentration of metals in sediments are found in the northern drainage path and are found in an easily recognized pattern. Metals, including Lead, Manganese, Zinc, Chromium, Silver, Cadmium, Antimony and Barium all increase dramatically above background levels starting at the toe of the fly ash pile. Metal concentrations in sediment then reach their peak concentration at or near the confluence of Streams B and E, and then decrease as Stream B moves southeastward.

4.5 ECOLOGICAL ASSESSMENT • --

An ecological investigation was performed along the streams and stream banks in the vicinity of Dixie Caverns Landfill (DCL) site to evaluate the potential environmental impacts of the site. Six (6) sample stations were designated for the ecological evaluation, including one reference station. Each sample station is described below, and then compared to the reference station. Summaries of the benthic macroinvertebrates collected and stream community evaluations are found in Table 4-6, and Table 4-7, respectively. Measurements taken at all sampling locations and detailed site descriptions are given on the stream data sheets (Appendix C). Bioassays were performed on surface water and sediments taken from the streams. Additional stations were designated for terrestrial vegetation analysis in both the landfill and the adjacent forest. A summary of the vegetation analysis, including the scientific names of all plants identified on the site, is given in Table 4-8. Details of the vegetation analysis are given in the vegetation data sheets (Appendix C). Photodocumentation for all sampling stations 1s found in Appendix C.

4-26 flR300!OI ot-r-Cr >•• (7M» o ^- 0. • Z OSUJ O

rH m CM rH CMrHiO — t CM Ol -HCM CM

(0 O (« ee rH r—— rH

rH trtt* , rH rH ITjrHrHrH rH F^. rH rH

rH U. wo: * rH -H rH rH CM rH rH f-> rH rH t«» C-J rH

rH UJ ' tn •» P^in rH rH CM V »/*fc> *

V) «-« •, LU o V3 fiC *O E a3 o CM CO CMrH rH CM .0 <-> ' a s 1 wo: «• CMin CM •H CM .3 &

i. rH CM —" «• -

to See CM « rH m rH Sample ; 3e s co fr rH rH m m to to m ^ r-

1 O Oi 3«* „. rH «T rH

« o> , at : , , S o »' '• ' S ^; • . ft ft C1 « • .'>»« —— ( • , * ' ao < Cevt 0»3*, &« u *«*a 0i .d < —C o 1 CUf r7j|3 f=«r.—— ?-s'r*3S1'Ctrl* CtrC'fli.v- •£«> cKJ £a »

• I Siiinthupi d J Corfxlda e -c v «tl» ':' • ' -C-O. *••

C'l : derrida e — o :^T c 1 «S-J : O'g & , : '3-r-''. '• " a _,*,. .' . • , ,-: .0 • i J '*e 1 <— «8 S U) W .

Isopod * -•: . tntwwbry f tkm »...--« '>v, PUnorblda e ta*W>". \ , WV> undetermine d P«»p(«J« - : S S Collentiol a - t— (rt K S«s t rope d -E-- . IHeufpter a IHollusc a Icruatace * 1lns«ct a

AR3QO 4*27 o ae-—* r— «-H 0» QC O

<•—s I rH -H .-4 in 9> rH CM V

O toac rH rH CM »M rH rH rH rH

rH U. LOO iO »* rH CM CM CM ' *"*

rH wee in te CM rH rH rH « IO n wo «"1 rH rH CM rH rHtO

rH UJ r* woe CM rH CM rH rH

rH O t/JO -H rH rH rH ^ rH rH

t- ^^ o Wl fl£ rH CM rH CM o 3n so (n «J o 1/1

s« rH rH rH g e. i? VJO rH rH CM *H

r> *- lac » rH X 1 • * «f 3£ * •3-3-3 -3 .4 * * _*^ ^J "* £r ^™ ^™ ' r^ « ' V ' « a \ T> * «l •W r-" 3.r^S If fe^ S2 5 fe ^ « V «S "§ •s t> •*r» *O ^-< C ' V ' '^ f— U M M Je g e* £ 5 5 5| s* 3 3 UJ t-** SI ! II Ills 1 **_* sS *» o « "SLU *Bi— . Y»V>U b- UJ a, x 4* j=Zj HJ Q.U. « O o. « g a> ;* ft* O !H g- « « ' *° •S 5 S »* u « •M ' JC, * u o a u -a r. M 0.0 By O « m *o S i i 1 I I J= Ol i 11 S« j| « 1 fl "• i? t •£ \S O u

4_28 flRSOOIOS -M H-> !••. o tn rH 9 w Wt U 4. O w w UJ m O O rH ^ u. * o ^ VI- X rH 1 Jj O 9O o o o « U T- rH Ol a B o o o o V 9 9 N en OOt * CM *r CM rH IO 4. rH CM S IM » m N « 9 m m to to 44 O rH I - £ t in » 9 ^•^ ^o O W « f- e r* M o o •w 1. O s 1 CM o in r*. m f^. ut rH K S 10 O m iO o m m o m IO »."« fl « *rt 1 «r ^ Ot «r M rH S • t. « e• u -MH>>^> £O 9 to E* 9 CM >*. O4<-r- JS O ^ ^a u» C— >, CO 9 « 5 .r> « 4d " LA O) O co' CO CM m >H 9 Si e u o E e S3 « 3 O IO m 9m 9m iO CM ?•> u a w M 1 IO rH S S rH *0 m rH o Ol o «i. ea.fi m f tn •H OH- §a- 5l —c CO ^-f o 5 u « o m ar <•- B w a. 0 •• •H- b T> T3 9 •H rH T^ « o v w > « 9 e! §* O •aW 3• ab> 5 o O • tn rH g g. in 1 Sao 5 m •H 9 S rH • in ca Ot CM « » rH o g o 1 o « o M r^ *%^ e e o 44 BHrf *w ^w E—«— ' •^^— — *j « « a . 4* a ** in V* V :** "5 e .i# V 1 w *J— 3*J i. » a; M M J-r--r. « *e* >« 3B eIrt |;:. (-* r* W u o w 8 o M •a e w ••- V w E ! « in o +* 1 I* •». ii » UM w u fl 4* S *> 4> i "x i «J C 3 r- •o i •a ' i o O o- i*j TJ ** , a •c a K e •' « W fl « U (- rM ,.,, Individua l i 09 I 1 -• o 1 t- I_ > t-r- e I i M' ' *•* i r* W *. — fl »l s. r- M *^ ^1^ fl U ft t* * IA w •» 4* M -5 •M *J in i i M. i •VI O'B «-r-^ |I1 I £ I 3 1 * V i 1 i * M u. U. •— a 01 i (. i. U. S K H *j *j e e *j *t JC (A S I tn o. U- •e i S 4* e ** 1- M £ •a «l I •o e e, K 5 B 3 cc B •a i i i i i V I C i • u >H 1 r— X s: X 5 E a. 1 i U I w i? U) v> 2 kH ^m | STATION S | Scrtper. / | % Cohtri b I P«rc«n t C llReferenc d \ C«MUit1t y I CPT/CMro i | % ConiH b H % Contrl b

HR300 4-29 TCM 4208 RI REVREPOR. nT 09/JAN/92

TABLE 4-8 Plants Observed in the Dixie Caverns Study Area

CoM»n Xuc Scientific N*M Station No.

ASH, GREEK Frsxinus pannsylvanica SA5.SE1.SG1 AZALEA Rhododendron spjT SB1.SE1 BEOSTRAW SalTtu" spp7 E1.F1.S61 BEECH, AMERICAN SEI BEECH-DROPS Epjfagus vlrginlajia SEI BIRCH. BLACK gjtlula "nlgra SIB, SEI BITTER-CRESS, PENNSYLVANIA Cardajilne gensyT van1! ca E4.E5.SA5 BLUEBERRY Vacclm'ui spp. Fl,FlB,(:2B,F3,F3B,F4i F5.SB5, SOI CHICKWEED Stall aria SOB. SA2 CLOVER, HOP Trlfoiliiii agrarlu« E2 COLTSFOOT Tussl aqo farfara SEI DANDELION Taraxacum oTHcinale SA5 DOGWOOD Cornus spp. S3B.SB5 DOGWOOD, ALTERNATE-LEAF Cornus a j ternj fol la SIB DOGWOOD, FLOWERING Cornus fl orlda F1,F3B,F4.F5,S3,SB5, SD1,SE1,SS1 FERH. CHRISTMAS PolystlchiM aertistlchoides S38,S3 FORfiET-HE-NOT Hvosotls scorploides S3B GALAX Ga ax aph^lla S3B.SB1 GARLIC, WILD Al ilk vine's la SA5.SF1 SILL-OH-THE-GROUND G' ecoaia fitdaracaa SG1 6RAPE V-t1s spp. S1B.SGI SREEH BRIER SBllax spp. F1,F1B,F2B,F4,F5,S1B, SB5.SD1.S3.S3B.SE1, SS1 HAZEL, WITCH HajajieHs yirglnlana F3,F4,S1B,S3,S3B,SB5. SD1.SE1.S61 HEMLOCK, CAROLINA Tsuga caroTinensIs FI.SB5 HICKORY Carya spp. S3B,SI6,F5.S3 HICKORY, BITTERNUT Carva cordl fgnl s S61 HONEYSUCKLE, JAPANESE LonTcera Tabon f ca SA5.SG1 HOPS, WILD Huiulus luoulus SF1 IRIS Iris spp. F2B IROKUOOD Ostrva vlrginjjinfl SOI IVY. POISON Toxicodtndron radl cans SA5.5S1 LAUREL, MOUNTAIN KalBia lati folia F1,F1B,F2,F2B,F3,F3B. F4,F5.S1B,S3B,SB5, SD1.SE1 MAPLE. RED Acer rubrm E5,Fl.F2B,F3B,F4rF5. S1B,S3.S3B,SB5,SD1. SEI KAYaOHER Eplggaa rapgns F2B OAK Quarcus spp. F1B.F2.F3B.F4.S1B S3B.SB5.SD1 OAK. BLACK Quarcus valutlna S3B OAK. BLACKJACK Qua rejis larlland 1 ea F2 OAK. CHESTNUT Quarcys rprfrjus F1B.F2.F2B.F3.F3B F4,S1B,S38,S65.SD1 OAK, RED Quercus ntbra F1,F3B,F4,SB3,SB5 OAK, SCARLET i(uerc(is cocc' nea F1B.F2B.F5 OAK, SWAKP WHITE Cuercus blco or SG1 OAK, WHITE (tieVcus aTba F1,F2,F4,F5,S3, S3B.SB5.SE1 ONION. WILD AllftiM canadansa SA5,SF1,SG1

flR300!05 TCN 4206 RI REPORT REV. #1 09/JAN/92

TABLE 4-8 (continued) Plants Observed in the Dixie Caverns Study Area

CoMon Nue Scientific N«M Station No.

PARSLEY, HEMLOCK ConlgselinuB chlnense SGI PINE. PITCH PjjiuV riglda E5.F1.FIB.F2.F2B, F3.F5 PINE. TABLE-MOUNTAIN Pinus pungens £5 PINE. VIRGINIA Plnus Virginia E5.F2.F3B PINE. WHITE Pfriiis str'oDtis SEI RASPBERRY, BLACK Rjjb_a_s_Qc'.ci dental Is SA5 REDCEDAR, EASTERN junTparus_yi'rg1 niana SGI SASSAFRAS Sassafras^! bidiw F1,F2,F2B,F3,F3B, F5 SERVICEBERRY Aielanchier SOP, F3,F4,S1B,S3,S3B SORREL. WOOD SxaHs stHcta E4 SPEEDWELL . Veronica spp. SGI SPEEDWELL, CORN Veronica arvensis E1.E3 SPICEBUSH Lfndera benzoin S38.SE1.SG1 STRAWBERRY Fraoarla canadense S3B.SG1 SYCAMORE Plstanus occiidentaHs SB1.SS1 TREFOIL, BIRDSFOOT Lotus cornUuVatus SA5- TUPELO, BLACK Nvssa sylvatie'a F1.F1B.F2.F2B,F3. F3B.F5 TULIP-TREE Ll rlodendrgn _ tul lolfera F1,S3,SBI,SB5,SD1 VETCH Vicla spp. El VIOLET, ROUNDLEAF SIB WALNUT, BLACK Jug.la.ns nigrja SA5 WATERCRESS NasturtiuB officinale El W1NTERGREEN. STRIPED Chiiaphlla waculata F1.F2.F2B,F4,S3B.

4-31 SR300 TCN 4203 RI REPORT REV. m 09/JAM/92 4.5.1 General Description of Study Area

The following is a summary of the results obtained during the ecological investigation. Detailed descriptions of the investigation results are found in Appendix C.

4.5.1.1 Terrestrial Ecology

Terrestrial Vegetation - The terrestrial vegetation was subdivided into three groups; forest vegetation, riparian (stream-side) vegetation, and emergent (field) growth on the site. The forested areas outside the site boundaries are of a Chestnut Oak-Pitch Pine forest cover type (see Eyre, 1980). Undisturbed streamside vegetation has a slightly different species composition then adjacent upland sites, both in the forest and in open areas.

Most of the landfill is recently disturbed, and has a successional field community (see PNDI, 1983; Reschke, 1990). A "successional field" or "succes- sional ol d fi eld" is a di sturbed ecologi cal communi ty where the origi nal vegetation was removed and repopulated by fast growing, opportunistic species. The composition of the herbaceous plant species over various parts of the landfill is a response to the amount of time that has passed since the last major disturbance, but is also partly influenced by micro-site characteristics. The emergent vegetation found on the site proper consist of seven subtypes. The approximate percentages of each type follows. Approximately 22 acres (34% of the site) is barren due to recent remedial activities. Approximately 19 acres (30% of the site) consists of the previously mentioned forest type. Approximately 3 acres (5% of the site) is a field type dominated by grasses (Poaceae) and another approximately 3 acres (5% of the site) is an emergent field type dominated by broomsedge fAndropogon spp.). Approximately 5 acres (8% of the site) is an emergent field type dominated by various composites and to a lesser degree grasses, and another approximately 5 acres (8% of the site) is dominated by broomsedge and mix of bryophytes. Approximately 6 acres (10% of the site) is dominated by broomsedge and composites on the ground layer, pitch pine and Virginia pine saplings, and table mountain pine'as mature trees. The emergent areas represent various stages of successional growth influenced by soil type and

4-32 AR300I07 TCN 4208 RI REPORT REV. #1 09/JAN/92 variations in the times and degrees of past disturbances. The percent riparian vegetation is not further subdivided because "riparian vegetation" represents several community types on the study site that represent only a small area and are contiguous with the aforementioned types. There is poor surface soil present at many areas on the landfill, resulting in xeric conditions and relatively sparse vegetative growth. Detailed information on the observed vegetation is found in Appendix C.

Comparison of Vegetation to Reference - The abundance, distribution, and diversity of the forest and riparian sample quadrats were statistically compared to the reference quadrats. The average values obtained from the three reference stations (XR) will be used for the statistical comparisons. Each of the five vegetative subgroups (trees, shrubs, saplings, vines, and herbs) had the following three tests performed: species diversity, community loss index, and the Chi-square Goodness-of-Fit test. The emergent quadrats were not statistically analyzed against background because there was no appropriate reference vegetation in the vicinity of the study area. Accordingly, the emergent areas, created by remedial actions or landfill operations, were qualitatively assessed to identify obvious distortions of natural successional growth.

Results of Forested Vegetation Comparison: All forest quadrats were found to be minimally comparable (60-70% comparability) to the average of the reference quadrats. The primary difference among forest quadrats was related to the distribution of the vegetation in the middle and lower vegetative layers (herb, woody vine and shrub layers). This difference can be attributed to the location and the stage of succession of the forest quadrats. The reference quadrats appear to be at or approaching the climax stage of the forest type earlier described. The forest quadrats of comparison appear to be in a slightly earlier stage. Differences do not appear to be related to site contamination, but may be related to human disturbance in the vicinity of the quadrats of comparison.

Results of Riparian Vegetation Comparison: Quadrats SI and S4 were found to be slightly comparable to the average of the reference quadrats. Quadrats S2, S3, 55, and S6 were found to be non-comparable (<59% comparability) to the average of the reference quadrats. Differences between quadrats SI and S4 and the

4-33 3R300i08 TCN 4208 RI REPORT REV. #1 09/JAM/92 reference quadrats were primarily related to the distribution in the middle and lower vegetative layers. There was greater canopy cover at the reference quadrats. Quadrats S5 and S6 lacked a shrub, sapling and tree layer, which accounts for the non- comparability. Quadrats S2 and S3 were at slightly higher elevations and appeared to be undisturbed areas. The differences may also be related to the lower quality soils found at this location. "Lower quality soils" refers to the dry, thin layer of soils that are low in nutrients, typical of that found in the present forest type. Although differences were found among the vegetative quadrats, there does not appear to be any site related stress.

Qualitative Assessment of Emerging Vegetation Areas: As stressed above, the emergent quadrats were not statistically analyzed against background because there was no appropriate reference vegetation in the vicinity of the study area. However, a qualitative assessment was performed to identify obvious distortions of natural growth. In general, emerging areas were found to be developing naturally, with no obvious distortions. Only one location was found with atypical growth - a hillside covered with stunted pine growth located uphill (north) of the solid waste disposal area. Apparently, these pines were added relatively recently to prevent erosion of the hillside which was left exposed by borrowing of top soil for landfill use. Accordingly, naturally occurring conditions on the hillside, including rocky/shallow soils and arid conditions, could strongly influence growth. Due to the location of this hillside and the naturally poor growing conditions it appears unlikely that site- related contaminants are strongly influencing the pine growth.

Terrestrial Wildlife - Wildlife found on the landfill is typical of that found in the habitats described. The birds observed have habitat preferences that range from open (i.e., bluebirds) to forested (i.e., plicated woodpecker). Birds observed are typical of those found in the habitat described and season of the visit. Populations of small mammals and game species, such as deer, were present. "Wildlife population utilizing the landfill will change with time as the vegetation succeeds back into forest.

4.5.1.2 Aquatic Ecology

All of the stations were located on first-order mountain streams that appear to be representative of the area. Lower reaches of the tributaries have characteristics

flR300i09 TCN 4208 RJ REPORT REV. #1 09/JAN/92 of second order streams and often have limited canopy cover which may influence the aquatic community. Estimated stream flow ranged from 1.15 ft3/s to 23 fa/s. Detritus was the dominant organic substrate at all stations. Cobble was the dominant inorganic substrate, except at SA-5 where bedrock was present and SB-6 where sand and silt were dominant. Evidence of detritus decomposition was observed at all stations except SB-6, where little decomposition appeared to be taking place. Canopy cover was absent at SA-5 and SF-1, but was found to be 50% or greater at all other stations (average canopy cover was 60%). More detailed information is found in the stream sampling data sheets (Appendix C).

Aquatic Vegetation - The .aquatic plant community varied considerably between stations. Periphyton was common at SG-1, present (but rare) at stations SF-1, SE-1, and SA-5, but absent at SB-6 and SD-1. Slime was only observed at SB-6, where it was dominant. Filamentous algae was common at SF-1 and SE-1, rare at SA-5 and SD-1, and absent at SB-6 and SG-1.

Aquatic Macroinvertebrate Community - The aquatic investigation indicated a healthy overall aquatic community and habitat. The reference station stream characteristics and community were very good and appeared to be representative of the area. Sensitive organisms were usually dominant in the benthic collections. Diversity was good, and the number of organisms collected was generally good. Community structure was generally good, although the shredder abundance was quite low in most of the CPOM samples and the dominant families in the riffle/run samples were more abundant than expected.

Stream Community Evaluations

Stream community evaluations for the each of the ecological sampling stations were made by comparing eight community parameters at the sampling stations of comparison against those of the reference station, as summarized below. Detailed information on the benthic macroinvertebrate evaluation has been provided as Table 4-6.

1. The stream sampling stations had taxa richness ranging from 8 at station SB- 6 to 14 at station SF-1. The presence of ten family taxa or greater is

SR300MO TCN 4208 RI REPORT REV. #1 09/JAM/92 indicative of good diversity. The reference station (SG-1) had a diversity of 13 taxa. At station SB-6, very few organisms (11) were collected, indicating potentially impaired conditions. Many of the families of macroinvertebrates in the riffle/run samples were, sensitive to poor water quality.

2. The Family Biotic Index metric, modified from Hilsenhoff (1982), is indicative of the sensitivity of the aquatic community, with a value of zero (0) being most sensitive and a value of ten (10) being most tolerant. The FBI ranged from 3.40 at station SF-1 to 4.57 at station SA-5. Stations SA- 5 and SE-1 had moderately tolerant communities. The modified FBI at station SB-6 had a value of 3.89, which indicates a moderately sensitive aquatic community, but in this case, this metric may be misleading due to the low number of organisms collected. The FBI value at the reference station was 4.17.

3. The ratio of scraper and fi1tering col 1ector functional feeding groups ("scrapers" and "filterers," respectively) reflects the riffle/run community food base. This ratio value varies with region and habitat, therefore, comparisons should be made relative to the reference station. The 'scraper/collector ratio value ranged from 0.00 at stations SE-1 and SB-6 to 0.147 at station SD-1. The reference station had one (1) scraper and 140 filterers (value - 0.007). Scraper populations were lower than expected at all stations, with station SD-1 being the only station with more than one scraper.

4. The ratio of EPT to Chironomid abundance is a metric of community structure. Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) are sensitive to water quality. Typically the greater the ratio value the better, however, when there is no chironomid population observed, results may be misleading. The EPT to Chironomid ratio ranged from 4.2 at station SF-1 to 80.0 at station SA-5, with no chironomids collected at station SD-1 (Value - oo). The reference station had a ratio of 134/1 (value - 134.0). Generally chironomids were uncommon at all stations.

4-36 . AR300I I I TCN 4208 RI REPORT REV. #1 09/JAN/92 The percent contribution of the dominant family is a metric that indicates community balance. In many cases a community with few dominant taxa is indicative of environmental stress. A low percent contribution of the dominant family (< 30%) typically suggests a healthy community. Most stations had a relatively high percent contribution of the dominant family, ranging from 30% at station SB-6 where Nemouridae, a stonefly family, to 55% at station SA-5 where Heptageniidae, a mayfly family. The relatively good percent contribution of the dominate family at station SB-6 is deceiving because so few organisms were collected. Nemouridae was also the dominant family at station SF-1 (41%). At all other stations, Heptageniidae was dominate. Heptageniidae also was dominant at the reference station, and comprised 64% of the total number of organisms.

The EPT index is a metric that increases as water quality improves. The EPT index values ranged from 5 at station SB-6 to 9 at station SD-1. An index value of 7 or more is usually indicative of a healthy community. The relatively low values at stations SB-6 and SE-1 (Value = 6) indicates potential stress. The reference station has an EPT index value of nine (9), which is good.

The Community Loss Index (CLI) is a measure of dissimilarity that assesses the loss of benthic taxa between the reference and the station of compari- son. Increased dissimilarity reflects a community shift that could potentially be brought on by the loss of sensitive taxa due to ecological stress. A higher CLI value indicates greater dissimilarity. A CLI value less than 0.5 indicates good community similarity. CLI values ranged from 0.29 at station SF-1, to 0.88 at station SB-6. The value at station SF-1 indicates an aquatic community similar to the reference station. The CLI values at station SA-5 (value <= 0.54) and SE-1 (value » 0.57) indicate a moderately similar community, where SD-1 (value - 0.60) has a moderately different community, and the CLI value at station SB-6 indicates a community shift. For station SA-5, dissimilarity appears to be caused by seasonal fluctuations in flow and habitat shifts (i.e., large amounts of bedrock, etc.). For station SD-1, the community difference may be caused by a difference in food sources. This range in CLI values indicates that there

4-37 flR300H2 TCN 4208 RI REPORT REV. #1 09/JAN/92 is a wide range of ecological communities in the streams in this watershed. A CLI value for the reference station alone can not be calculated because it is a relative value.

8. The ratio of individuals in the shredder functional feeding group ("shred- ders") versus total individuals collected in the CPOM sample is a metric used to measure impairment of the CPOM shredder community. This ratio value varies with region and habitat, therefore, comparisons should be made relative to the reference station. The values at the sample stations ranged from 0.14 at station SE-1, to 0.71 at station SA-5. The reference station had a ratio of 18/118 (value - 0.15).

The overall ecological assessment of the aquatic community indicates healthy conditions at stations SG-1, SF-1, SA-5, and SD-1. The number of individuals collected at station SD1 was reduced compared to the reference, however, the stream flow is affected by seasonal changes which could account for the lower numbers. The overall ecological assessment of the aquatic community at station SE-1 indicates a stressed community. The overall ecological assessment of the aquatic community at station SB-6 indicates that significant impairment exists when compared to the reference station, based on the low diversity and especially the low numbers which were collected. The metrics at the reference station are indicative of a healthy aquatic community. Much of the population observed is considered sensitive to poor water quality.

Toxicity Test Results - Three toxicity tests were performed at the DCL site study area. The tests were performed using samples collected from SG-1, SF-1, SA-5, and SB-7.

Surface Water

Two toxicity tests were performed using surface water samples. The first test performed was a static, chronic bioassay using Ceriodaphnia dubia. Results on the surface water taken from SG-1 indicated 20% survival rate when exposed to a 100% concentration of solution. 100% concentration from surface water taken from SF-1 resulted in 0% survival. There were no data received on any possible

4-38 flRSOOi 13 TCN 4208 RI REPORT REV. #1 09/JAH/92 dilutions involving surface water from SG-1 or SF-1. Dilution series factor of 0.5 was performed on surface water collected from SA-5 and SB-7. Results involving SA-5 surface water indicated a lowest observable effect concentration (LOEC) at 100% sample concentration, and a no observable effect concentration (NOEC) at 50% sample concentration. Results from the surface water collected from SB-7 indicated the survival and reproduction LOEC to be 6.25% and the NOEC to be 3.1% concentration. However, 100% mortality was reported at 1.5% which was reported to be non-site related by the laboratory. While this test was being performed, laboratory equipment malfunctions occurred resulting in multiple restarts of tests. Additionally, the sample locations which have been reported to be uncontaminated through chemical sampling and benthic investigation were reported toxic to the test organism. Possible explanations may be that poor laboratory procedures were employed or that the test organism was not compatible with the medium. Due to these uncertainties, the results of this test will not be used in the risk assessment.

The second surface water test was a 7 day chronic bioassay using Pimephales promelas (fathead minnow). During these tests, surface water samples collected from SA-5 and SB-7 were tested using 0.5.dilution factor. Results from surface water collected from SG-1, SF-1, and SA-5 indicated no statistically significant toxicity. Results from surface water collected at SB-7 indicated a LOEC of 50% concentration and a NOEC at 25% concentration.

Sediments _ ._,_.___ , .. . . ., . - ---- = •• -,~-

One test was performed to evaluate the ten day chronic toxicity of the sediments using Hvalella azteca. No toxicity was reported related to the surface water taken from stations SG-1 and SF-1. Survival was slightly decreased at SA-5 (statistically insignificant). A 100% mortality was resulted from the test using the sediments collected at SB-7.

4.5.2 Threatened and Endangered Species

Of the threatened or endangered species that occur in Virginia, only fish species (orangefin madtom and the Roanoke logperch) are known to occur in the general

4-39 TCN 4208 RI REPORT REV. #1 09/JAW/92 vicinity of the study site. Both have been collected from the Roanoke River according to data provided by the VDGIF. There are no plants of special concern known to be in the study area (per. com.: Likins, May/29/91).

There were no Federal or State threatened, endangered, or species of special concern observed within the DCL site study area. This does not eliminate the possibility that they may exist on the site, but since none were observed or suspected to be on the site, these species will not be directly addressed in the risk assessment.

4.5.3 Summary of Ecological Investigation

4.5.3.1 Summary of Terrestrial Investigation

Most of the DCL site has been recently disturbed and as a result supports a successional field ecological community (see PNDI, 1983; Reschke, 1990). Five subcommunities of emergent vegetation were Identified. About 34% of the landfill was barren, the majority of which apparently was due to recent earth-moving activities. The forest surrounding the disturbed portions of the landfill was of a Chestnut Oak-Pitch Pine forest cover type (Eyre, 1980). The site overall has xeric conditions and relatively poor soil conditions resulting in somewhat sparse vegetative growth on some areas of the landfill. No site related gross toxicity to the flora or fauna was observed during the site visit. Habitat variation is predominantly a result of vegetative successional growth and human disturbances, such as past lumbering activities, and remedial activities.

4.5.3.2 Summary of Aquatic Investigation

Benthic Hacroinvertebrate Investigation

The aquatic investigation indicated a good overall aquatic community and habitat. The reference stati on stream character!sti cs and commun i ty appeared to be representative of the area. Sensitive organisms were usually dominate in the benthic collections. Diversity was good, and the numbers of organisms collected was generally good. Exceptions were observed at SE-1 and SB-6 where ecological

4-40 flR300JI5 TCN 4208 RI REPORT REV. #1 09/JAN/92 stress was evident. SB-6 appears to have significant impairment, while SE-1 appears to be under stress. The streams in the area of DCL site are diverse in the types of habitat that they offer, making the interpretation of the metrics more challenging. In addition, differential geologic conditions (e.g. carbonate verse clastic) may influence hardness levels, and vary toxicity responses to concentrations of inorganics in surface water.

Summary of Bioassavs ...... - --

Significant toxicity was reported during each bioassay involving surface water and sediments taken from SB-7. Aside from the bioassay involving SB-7, no significant toxicity was reported during the 7-day chronic bioassay using P. promelas or the 10- day chronic bioassay using H. azteca. A statistically insignificant decrease in survival of H. azteca was reported in sediments collected at SA-5. The chronic bioassay using C. dubia indicated toxicity associated with all surface water sample locations, however, these results are in question.

4.6 SOIL INVESTIGATION RESULTS,

4.6.1 Surface Soil Investigation t Surface soil sampling was performed at total of seventeen (17) locations. Thirteen surface soil samples background and 10 site locations were collected in late November/early December, 1990. Four additional samples of fly ash material were collected directly from the surface of the fly ash pile in July, 1991. The sample locations are depicted in Figure 3-3. Surface soil data are summarized on Table 4-9, Table 4-10, and Table 4-11. Complete laboratory results are included in Appendix D.

4.6.1.1 Samples Collected in November, 1990

Geotechnical Results - Five composite samples collected from the solid waste disposal area were analyzed for moisture content, Atterburg Limits (liquid and plastic limits), Standard Proctor (maximum density/optimum moisture), grain size, and recompacted permeability. Sample results are presented in Table 4-9, except grain size data which are in Appendix D. Grain size distribution indicate U.S.C.S. classifications

4-41 flR300l16 TCN 4208 A RI REPORT • REV. #1 ^ 09/JAH/92

Table 4-9 Geotechnical Parameters for Solid Waste Area Surface Soils Dixie Caverns Landfill Site

Moisture Maximum Optimum Sample SAS Content Liquid Plastic Densi ty Moisture Permeability Location Sample (%) Limit Limit (pcf) (%) (cm/sec) SWD-1 592QC-100 8.8 26.4 19.5 124.7 11.6 1.4 x 10-7 SUD-2 5920C-101 10. 1 30.0 22.2 122.7 11.8 3.3 x 10-8 S140-3 5920C-102 13.3 30.8 23.7 118.0 13.1 8.1 x 10-10 SHO-4 592X-103 10.3 41.9 27.1 119.3 13.3 2.3 x 10-8 SWO-5 592QC-1Q* 16.9 31.6 21.9 113.8 14.0 2.4 x 10-7

4-42 flR300U7 i i i < i i i i i i i i i i < i i i 9 i i i i i i i i i i i i ii i ti i i i o . (M O CO M »H ^ OrHCO M rH f> O «V « r- CO

iI il il il il il il iI iI il iI il iI iI il il iI O I I I I I 1 t I I I I 1 1 t I 1 I •

I I I II I I I I I O ' I I I I I I I I I I I • I I

o V)

I i i i i I i O t i i i i 'i i

o 3 *5 o «j •£ — fi-5 o '•»• 4i *

If I I I I I I I I I O I I I I t t I I I I I l I I t I I I l l I 1 I l l l I I I I o

S

I I I I I

4-43 AR300M8 SH- — CVJ Of •% O^ CSJ«*• aO. «"-- z . UJ »• «;

r— J-J OJ CSI

z IIII OO 1 1 J O 1 O 1 1 1 O 1 1 I f . . t 1 1 • 1 *ll 1 . LL. 1 l l lOOl l lOiF^.1 i IO CMO en csi o * • Ik A r^«— *T CO 9 rH CM rM 80 O 0 O O 1 I i O I O I I I O U. 1 1 r t O O i 1 lOICMI 1 IO tcsien on iOn CM Oo rH rH S> O CSI o 1 §o ^ o ^ O 1 1 I^IOI 1 t & u. I. 1 1 l r^O > O.- 4 t I 1 Oo l CoO l l 1 Oo CMO •* Csl O — IrH (SJ CO •«• 0 CM _j r^ r^ r-j J£ Ul 1A a 1 §OOta OOOO OO OOO tOQ "a. S irtt-ne vineocDOO 010 o 100 1 P*( r^ &l rH rH CM O O Csi O rH W c: If) V cn If) CSI CM rH

ii OOOCslOOOOOOOOO 1 O O I* i o^«a I-IVEOCSIOOOIOO en o *-A ® in rH (r) M •— 1 rH O CO O r-l LO r^ BO ** r^ O rH S7> & rH fSf — X o ^ — C7t tO rHI rH r*4 £3 csi 1 __ —I -3-3 ^ « —1 « — ° OOOO1 Op OOOO OO I(->OO Z Jj i ff O *o ffi Si r^. 01 o o !" fM ^ CM O r™ t? E 1 1 COMEO rH CSI -H ^ S en CE) rH (M CM 1 *0 t1 &t• C*•» (O (0 L•O 1 *~ Si- J 0 •S w -S e 8^ est "g — J -9-3 *3 _1 0^ ^ OOOid r OOO OOOO I rHOO d U- o tO«4€Q rH •• O rH CO rH CM ^ | 0 O rH i^* » CSI Lf) M •M * _l -S-3 "3 ^ —I (0 •e •-* rH X OO O OO 1 55oSS i Q. _ « o o o t** o Lk. *• o m eo rH rH m rH o «O o oo o ift tn 5§ •r* rHO SrH 5 O SCM^& CSI CM (si O *f & -H in t**- o v> oesi £a ^- *• fv, rH CO rH rH«(D rH It-1 kS rH 1 V O 1 rH *r i csi 1 1

•f f> U u -ie "o--. 5^*3 5 ^3*« 1 —s en U H^'IHfM^I^H^^ O^*^**1^ 17a^T*' ^^^>^ ***>^^*^-i !tf %s^ o fists

T-'eS-^ — '••— « a*® w "c5 • 9 -r- >v • 5 • §, g -o ot^t e e « p •5S O-O.it. at u u c <<54tJU«Jt3«j£iEs2(rt3tM

4-44 flR300i19 TCN 4206 RI REPORT REV. #1 09/JAN/92

Table 4-11 Surface Soil Characteristics Dixie Caverns Landfill Site

Depth of Sttrplt Total EPA Below Organic Moisture Percent Swplt SjMplt Ground Carbon Content Solid CEC SodlM Location NiMfa«r (ft) (•g/kg) (Percent) (Percent) PH Meq/lSOg (•B/D 8-1 5886C-100 0-1 17,430 19.3 80.7 4.51 11.8 2.710 B-2 5886C-101 0-1 14.670 19.1 79.2 4.57 11.5 2,653 B-3 5886C-102 0-1 16,307 19.5 80.0 4.55 12.4 2.853 FAP-l 5886C-103 0-1 5,051 14.2 86.1 5.38 19.8 4,570 FAP-2 5386C-104 0-1 20,075 21.6 79,2 5.06 11.8 2,725 FAP-3 5886C-105 0-1 36,072 18.8 82.2 6.73 13.3 3,653 FAP-4 5S86C-106 0-1 22.890 17.9 83.6 5.71 12.2 2,808 FAP-5 5886C-107 0-1 30.330 20.3 80.8 7.88 12.2 2.803

4-45 flRSOO TCN 4208 RI REPORT REV. #1 09/JAH/92 (Casagrande, 1948} for SWD-1, 2, 3, and 7 as coarse grained soils. The gravel fraction comprised over half of the coarse fraction in samples SWD-1, 3, and 4, indicating classifications as GM/GC to GC soils (plasticity indices of 6.9, 6.3, and 14.8, respectively). Sample SWD-2 is classified as SC (plasticity index of 7.8). Sample SWD-5 is indicated to be a fine-grained soil with low plasticity, classified as CL/ML. - - - ..__..._...

Typically, low permeability values such as those reported by the laboratory would indicate that relatively little precipitation will infiltrate into the solid waste disposal area. However, these permeability values are not consistent with the soil textural analyses and U.S.C.S. classification.

Chemical Results - .Thirteen surface soil samples received chemical analysis. Samples B-l, B-2, and B-3 were collected as background samples. Five composite samples were collected from the solid waste disposal area, and five samples were collected adjacent to the Fly Ash Pile (FAP-1 through FAP-5). Additionally, four samples were collected directly from the fly ash pile. The laboratory results from the analyses of these 17, samples are presented in Table 4-10.

Acetone was the only volatile organic compound detected in any of the surface soil samples. It was detected in background sample B-3 in a concentration of 130 jug/kg and was detected in sample SWD-2 in a concentration of 7 (J) /Aj/kg.

The majority of the semi-volatile organic compounds detected in the surface soils were detected at location SWD-2, with seventeen semi-volatile organic compounds accounting for a total concentration of 10,635pg/kg. Bis(2-ethylhexyl)phthalate was detected above background in samples SWD-1 and SWD-2 in concentrations of 110 and 150 j/g/kg, respectively.

No pesticides or PCB's were detected in any of the surface soil samples.

Most of the heavy metals are present in the surface soils above background concentrations. The metals lead, manganese, nickel, and zinc appear to be distinctively elevated above background concentrations.

4-46 AR3QQ12J TCN 4203 RI REPORT REV. #1 09/JAH/92 Barium was present in all surface soil samples at concentrations ranging from 1.5 to 4 times background levels. Beryllium was present in all samples from the solid waste disposal area samples, and in samples FAP-1, FAP-3, and FAP-4 at slightly elevated levels. Cadmium was elevated above background in samples FAP-3 through FAP-5. Chromium was slightly elevated in samples SWD-2, SWD-4, SWD-5, FAP-1, and FAP-3. Cobalt was elevated in all samples except for FAP-2. Copper was elevated above background in all surface soil samples and was a maximum of 4 times above background in sample FAP-3. Lead was elevated above background in all samples with highly elevated levels in SWD-5 (290 mg/kg), FAP-3 (395 mg/kg), and FAP-5 (304 mg/kg). Manganese was elevated in all samples with a maximum concentration of 1080 mg/kg observed in SWD-4. Nickel was also elevated above background in all samples with values ranging from 9.6 mg/kg to 44.0 mg/kg. Finally, zinc was also elevated above background in all samples in concentrations ranging from 2 to 100 times background levels.

Besides analysis for TCL organic compounds and TAL inorganic analytes, analyses of percent moisture, total organic carbon, pH, and cation exchange capacity were also performed on samples B-l .through B-3 and FAP-1 through FAP-5 (Table 4-11). The percent moisture for the background samples averaged 19%. Moisture contents in samples FAP-1 through FAP-5 bracketed those values ranging from 14 to 21.6%. The total organic carbon content of the surface background soil samples averaged 16,136 mg/kg. Only the sample from FAP-1 had lower TOC (5,051 mg/kg), while the other FAP samples had distinctively higher TOC values (20,075-36,072 mg/kg). The pH of the FAP soil samples was also distinctively higher (5.06-6.73) than the average pH of the background soils (4.5). The low pH of the background samples is most likely related to the influence of natural tannic acids in the soils as the samples were collected from an area dominated by Pine (species) trees. The cation exchange capacity (CEC) was also lower in background soils (average 11.9 Meg/180g) as compared to values of CEC (11.8 to 19.8 Meg/180g) for FAP samples.

4.6.1,2 Chemical Results for Fly Ash Samples (July, 1991)

Only cadmium, chromium, lead, nickel, and zinc analyses were performed on the 4 samples collected directly from the Fly Ash Pile. Similar values of these 5 metals were detected in all 4 samples (Table 4-10). Lead and zinc compose the

4-47 flR300!22 TCN 4208 RI REPORT REV. #1 09/JAH/92 greatest proportion of the samples accounting for an average of 4.5% (45,000 mg/kg) and 21% (210,000 mg/kg) of the samples, respectively. The cadmium concentration averages 1368 mg/kg; the chromium concentration averages 1055 mg/kg; and the nickel concentration averages 214 mg/kg. All together, these 5 metals account for approximately 25% of the sample composition of a given sample.

4.6.2 Subsurface Soil Investigation

Twenty-nine subsurface soil samples were collected during late November/early December, 1990 (Figure 3-4) from 14 soil borings. Geologic descriptions of the material encountered in the soil borings are given in the boring logs in Appendix D. The complete results of the laboratory analysis of the soil samples are given in Appendix D. A summary of the compounds detected in the subsurface soil samples is given in Table 4-12.

4.6.2.1 Chemical Results

Only 4 volatile organic compounds were detected in the subsurface soil samples. Benzene was detected in RIW-2, at 16-18 feet below ground surface (bgs), at a concentration of 40 (L) ;/g/kg. Toluene was also detected in RIW-2, at 14-16 feet (bgs), at a concentration of 24 (L) pg/kg. 2-Butanone was detected at RIW-1, at 5-7 feet, at a concentration of 73 /Aj/kg and 4-methyl-2 pentanone was detected at RIW-11, at 3-5 feet, at a concentration of 42 jig/kg.

The highest concentration of semi-volatile organic compounds were detected in the Drum Disposal area. In sample DD-1/4-6 feet (bgs), 8 semi-volatile organic compounds were detected totalling 740 jjg/kg (all 8 were qualified with a J). In sample DD-1/6-8 feet (bgs), bis(2-ethylhexyl)phthalate and di-n-octylphthalate were both detected at a concentration of 100 (J) iug/kg. Bis (2-ethylhexyl) phthalate was detected at a total of 13 of the 29 samples in concentrations ranging from 44 to 4,800pg/kg at various depths ranging from 0 to 16 feet below the ground surface. Nitroaniline was detected at DD-2 at 8-10 feet (bgs), at a concentration of 1,800 (J) pg/kg. Of all the samples collected from the monitoring well test borings, only RIW-13 contained any semi-volatile organic compounds. Nitrosodiphenylamine was detected at RIW-13/3-5 feet (bgs), at a

4-48 flR300!23 CM 1 O -J_J -3 --i CM ^ CM 1 1 1 1 1 1 1 I I i oo o a o o OCM o o oo oo o . i O 1 1 1 1 1 1 1 1 1 1 i o ijp ^ M ui o o .oootOcrtio 1 1 O O 1 1 1 1 1 1 1 1 1 CM SV CSI rH 1C r^. O Ol rH (r) O ^ -H o O^ vH ^J O "^H OO fr^ <5\ rH r*» 1 CM O CM rn 3 •csi rH C-l 1 • o m — J — J *? *^ r -^ rH 1 1 1 1 1 1 1 1 1 i oooiooor>.ooaooo 1 1 1 1 1 1 1 1 1 i o«0en<- I O O a 1 1 1 1 1 1 1 1 1 I1 O• O. M CM O >-lr-l«f rMrHO mCOrHCftrHCM i ^ m O d rH ^ ;• _ ft ft ft ae o tsi f~4 1 _ eo r^ ^J «J ^5 ^^ »^ fr) o 1 CM 1 1 1 l l l l l O i ooo i oo o CM e? o o ooo i i i i i i i i i i i O i i i 1 1 1 1 1 1 1 1 . rH t i i s CO o o^ in n o 10 O1l0 rH ^^ rH CM Cc3o eOn Or o CrOo rH ^* 1 4 * ft 2 ** m ~* .eo ifl i Or1 (O ^J •_! *^3 *^ m ^ tfl ex CM 11 11 1 t1 11 1 1 1 1I i °°§ i OOOCO gO Og OO 1 1 1 O S 1 1 1 1 1 1 1 1 1 <*» ii1 l. *O in O O o r-. rH r- 1 rH CSI O CM 1 in MM v> CM M wt CO « e u £• (0 0 -3 •fl 0 *^ r-t i i I i O ' i I O 1 OOOiQOOOOOOOOOO i l 0 1 1 1 1 1 O 1 1 1 O 1 O rH (M t f-.^- O • O C7* Lfl O r-* tO i 1 1 0 f J IIII .III . rH i i . M § 0 0 O f^ en t0 co o c\j o cp m o m in o J3 9 0 0 C? r*4 r^> rH ep rH 10 rH CP *H ^ o" en 3 T- rH rH CO * ("1 vO rH * V» X ft ft ft ft 1 O » r^ r^ •^ = 3 « ^^ i—1 10 41 ae 14- 1 -W -a o » a r^ J-J'? ^ T •^ *""•* LJ ' f.' o ••5* >^* 1 1 1 O 1 1 1 1 t j oQO'Oooinoooooo O l O u *J *7r^ 1 1 1 O 1 1 1 1 1 i O 'en CM i <^^ CM O * ^s co O cy **i ^o O 1 O 1 1 1 . 1 1 1 1 1 i * 1 • •aUi *£~= a 3 m PT) v*^ S CO 1 CM rH « rH O CO CO rH rH rH CO 75" C* *0 Q U i 1 0 Ol ^2 i fl CD ^3 i •s ae 1 U _^ 1 1 W 1 'F- .4-1 «r 1 1 3 o "^ I |rH = 1 1 1 • 1 r- OOOO IOOOO o u o tf) en i co *o o • & o en o en ^»in _ t 1 r- 1 o"" i • 1 1 w 1 a -** rHcg«ro ooor— g o 'Tf o f^ ok CM in o rH r* ^ ^» o ^ en(-1 **- f^ £f t^ rH *O rH -^ O^ Cfl t^ ir*4 rH CM o ,— rH rH r-lrH ) 3- • w r-. en rH •j ^ • • -a ~ a^^e 1 1 *u i CM * i 5 -J-l T -D V» 3* 1 VI trt rH 1 1 1 1 1 1 1 1 1 If O OOO i OOO«rOOO9OO • 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 • O r— OrHCM 1 CC t-l O • O O C71 O rH rH V 1 II I 1 i i i i i i i i i i a. II 1 1 ^ i O 4* O ^f rH ^ tfi Q iM &l CO rH O <0 00 CSI i O Q) r*rHI0 rH r-t O O CO rH \O rH CM , i M r— CM n OJCM

Ol Mo> <5> Ol 3 3 W Ol —— . MDI a «£* 01 tO "**«. •** Ol Ol -^ fl Ol fl 3 3 Ol •— 3 r^ —— fl 01 *— .C J± ^> ^^ a *j ^f ""•»* B; c e} oi ot Js Ot e .C O ^»* •— • o o. 3 ". *^^«^ lit jn_j D| g| p*» DI ^^ Olr"^ DI Ot Ol^^ u ^tf fl r"* 1 t= e O) e a 3 >« 3 O»-s ^ Ol ^*£ M Ot •«-^*J >i -^ at fl fl M .ei— ^— -* x ^^ ^^ m_i IL ^^^ -^*^ *^^r^^h^^^*i^4£ o> e x tj e *- I.-.*.** oi o ^^^^f Ot QT**^. Of Ol DI Ot D)4*11** a v a. j: 0f}c O3 C3? OIJ3 O.E^ 47: Q}&£^ e-^^£— 3.V——r-s-.r- O » Ol >> ^ ' ^^ • Ot ^^ 9^ ^ DI ^ r"M* d) CS] >, GL>*r» Sn* >^_f" •» 3 ^3 rH ^^ tt H B ^>>^h4li>>^ B 41 H 9 4il%l« e i j= 1 • *<^ 3 • ^^ DI Ot 3 (/I ^^ 3 • DI 4 ^ *M CUC -^ UJ U 3 O -r- 3 • • •— 09 •£ S S (= >> UJ •* i~ _i r"" ^ QJ O fl C! 09 1 O E-r- «r- -r-**^-«— u> Cr- «rt—— ^-< O O O at i Uaecsi r- T- e 3r— »— « 10 at wo u ««-r->,o0e-ac oi oc e « u •S-3 Sff l ^— eccN N N bX Ci ±OJ Ca M£ —i 'n eo X M 1 1 T- CBCOttUC3U-E^Ck^3 < < < tf CD U U •• — J X X Z EU > Kl CM **• ^ 4-49 AR300I2U S K? ** as o£ ^ ""3 CM M*9 —1 —1-9 u o£ "*•• 1 r- -H. OJ P goOio i o i oooooea C£. 0 II II II II 1 Otr,&> gi ' wotntoootn ^B 10 r-l ——O CMCM ee ^- CO -H

i MO -9-. -.-9 II 11 CM II II OOC9CMOOOOQOOOO j — ' *9 -9^9 to II II eSOtoenoootcMoenoo O O »*• *V O CM CM »s tn 1 OCMtO i u"iOn G o ino 1 1 CMf*- at Cfl ^ m 10 rH rH O rH r^ O rH O CM Ol f*.rH Q ocor- §O«M QC •"•i^ CM 10 rH OCM rH^T rHI ^T r-. ift CM O rHrH £^ CM ft ft 1 CO e» O LTt „ at CM CM rH esj M -3—1 -J-9 t a: O _> II 1II1 OOO COOOOOOOOOO "3 M-9-1 -9 -9 to II II OOO i goo I 1 OOOOOO 1 1 OO in l 1 OiOOOOO 1 1 CSJrH gSS S^SSgSKSS t 1— 1 en omo Oastsl ^r*v ce * ft ^•^fc &t ."^co OrHroi^rHCO rH Ift CO *"^ rH CM rH « ft • « ft eo 1 eo esi ^ CM rH rH * csi 1 —1 _J-J -9 v< a: rH SI 1 1 §OO > OOO 1 OOOOO -j r. M-9-J 0 r, 1 1 1 r-.o i OCM co i OOOOU3 CM • 1 II "s. ooo 1 OOO i i OOOOOO 1 1 O 1 1 o **» 1 Ot0r-< i i O voomOi i m i at i ii.i *" IT* S1^ ^M""* f/3 O**i» omeo §' ' <->e» 2 **i **! ^** ***•*, IO*HP*. rHP1^ rH IO O r— .•4 ^n eel"* rH tOCSI O • CM IT" *•* A ft • ft vO O 1 p* •IBt O\ r'H rH rH (A at rH I ^J F^ -J.J -9 y* oe •HI OOO l OOO l OOOOO _i_l -, r-j ;s is Of- 10 i OCM to loeeooen * « CM t" * §OO i I OOOOOO 1 l OO 1 oencM ocno o^fflcoo — . u • t^-O :ss°. 1 1 O<0OOtMC3 1 I rHIO 's 's CnrHtTl »-ti—Ir H O^CSlCOrH i rH IO ^ tO M • si OrHOI §-H6O 1 ' oenococnO <">V S ft ft 3 *Q a ***^ r** rH-ed CSI ^? rH ^p rH ^H en CM 10 r«* rH B H — o <•> 4^ eo ^d e? CM i- t/ax r-t * ft • « * • ** •"• 1 en en t0 F11^ rH in € eo SI M CSI rn i M -3—1 -J-9 e — ^3*9 ^o ^*g 3C *"*^ 1 l OO C9 O1 o^ ^^ ^5 es e3 e3 ^5 o ej? o ^? —4 Stf-3— 1 -3 l l SO ot0O«»>orHinin^enepe3O rH II . • 04 *» >> OOO l l OO I OOOOOO9 1 1 O 1 1 OO Sco*-4 O o csi esi o en o *-> co HI U-KI 1 t EM 1 00 rH 10 CM rH *r o ininio CM ' ^"* 1 1 1 « 1 ChCO f rHi 10 O mrn ac ft 4 * ft •«• •*> e in §ror** L^A esj«e 1 otMOtrtincs 3*^" **x^ | CMrM O rH CO (Jl *-l CO ^•4 ^^ i CM rH t*t rH rHi o 1 *p f * csi 1 I "9 a O O'^3 '^ ^^ ^^ ^^ ^3 ^^ ^? ^P ^^ O (2 *•• ec 9 rH 1 •e £3or«.(^.oioe6rHOcooo^ ii 1 i O _j •3 M-9-1 -9 •9 1 11 • 1 O Sen * o eg) 10 o rH o r- o o r*. "i*^ i rH 1 1 1 r— 1 • •T 10 rH rH CM O rH f^ ^p rH OOO i i OOOOOQ 1 THOO I J~ tn !§SS i flOtneo 4* O i r-i • fl cn CM en ri Ol0ffi ' ^r*-o ' ' OrHOtnieO rf>^ S£ •e •H CSI **- r^ *O rH o rH 1 rHi 1^, n ^to ci § 1 fHl >1 tt eo

Ol M "3a M*— *34— Jfl a e ^. ex: S"*~J5 « u Q. U •— * Ol -— . otot a ,n^r-. ">r— f+t Ol ^^ Ol Ol TT Ol-*^ O) O) i ^ato -_irt ^ ef g^^ 7m. *£"**0» **** § *"«^^ e "sS^JSToi CKM OtOlOlfJ *a£<^. u -^^ atOr^^^CTOl O>D-O» ^^ gr-^M jp^^^aa^ ^~^^_. — i_i~, ^ B ^£ 9^^ cn OT^*N —c*v, a-e 5l^**^.Ml S*****^ O1^*" h£"" j^*> M B ^ft1 ^^ • DT^11^"•^ Q* S ""•**."^th^Oen mi D^I Dr^^^^^^fejv^ DI.•^.m m ot DI DI *r>^» • LM"1**^11"* Ok »"^^-"^*^ Ql u>^ » ^ •- -? rrr^ ^2. "i^*""''Sff B'5'^S'.pyS.B |r.9« M-r-05.e fl-r- r-U*»fl^OCSt-»Ba —— <*;A &UCJU uu-M— iKxaeo.VJr-»fsl 6OI— K rH O OrH CM r-l rH CD l * 1 > > at to CM fn «* en 4) at O i m CM T3 « • Q. en >0 3 CM CM * g r-l 10 ^ M -9— < —1 -9 _1 —I rH i t 1 Csl §£SS§g?g ;§S§S§g "p -9 1 n CM veo tn •s^ §O O eio o ^ r^ m 10 * o o P> o ^-^ O of^ m en CM 1 O CO (•••. ^r tor-* (n cs rM ijp CM r-i 09 COrHV 4) e • 1 • • at in rH f^i tn f—. fl 4) at o i *m 3 •4- » CO CO rH f^ t- fl 3 rH CJ 3C_) ft "45) ut rH 3 -a a in CM af -9 ^ .^ -9 _t e 3-r- i 1 V> X P 1 o-^tnetocsiearOOOrHOOOOH lOOOOOi o r^. o ^^O o l oO 0 O e CO •9-J CO 1 *S* 1 l 0 r-l OOOO at O to ^*rH rH O —* fn CM CM CO 10 rHin <£ •o o at1 O OCM O -H v co en >0 ' at O O Oi 10 3 f O rH rH CM Of 1 CM CO 10 M CM rH u •*•> 1 CSI rH CS1 I 1 ft « •»- rH 4) 0 U .5 * 1 i •*• ^3 ^— CM t J tn » rH 1 i fl- 1 OOOO -9-9 -9 —J —1 -9 -9—1 fl 4) rH 1 OOOCMOO 10 lOOOOOO I I OO U J= 1 0*22^ at rS | oesicor»-HrH i 10 lOooeo^o at 3 Tl i i mco •o CMr-^10 O (*• CM O O» l/» 10 O CO fO rH tn O om I*' as fl « 1 (n CM CO "Hi rH O rH CM m rH rH U ' rH ^ to I 4_ ~ p_ csi*|IJ 1 *"* 2 *"" o * 1 -S •o CM 4* S S-s M-9 — 1 — ) -9 -9—1 a csi ta M rH 1 1 1 1 ooom ica 10 1000000l IOO *fl IIII -£!• I , 1 1 <0rH I at *• IIII 4* to 1 ' ovoio O m O<*>«nm<»io co en 3 ,2 ^s CM rH rH rH O Om 10 tO • 00 rH -H | *• P- 10 . rH 4* 1 • O

l 1

Ol M

a ,_ fl e u *« u ** o. i —^ 1 ^ -^— — -C Ol •— «. ^^ r^ •*•** Ok -**•* Ot Of O ^•^ ^^ u M Ot ^» Dir->« M^-*t» — ^ MM M Ot Ol ** %t^**ltf X ^£ ^"H^^ 01 W-*. "^s,^ Ot BIM *~^ Ol DIM D» CB Ot D ****** OV1*111^ J CT!--*_M S"1^. Ol^ ^*^»»-%*—t ftl HM • DIM OV-. *"— **^»*», M O* • cn44*^^^ DI M ^i|h«4>>^« at at oi^^^^****^^• "•^.K Ol or— M ^^ • Ol 5^^ DI DI II 3£ M Owt fft—— M Is•hi? S>"'5§^* • J-A*"''15t'pt 1 S^-S UJ *lrt «T-S__ 1 0 -r- • 3 . ffl JUS"1" "r-*ifl" l Vt 3-0 CM -r-*C§,3.r-j|f— OT- SflffiWI "c §•£ > fl — fl O flt *rr ^ U M a « s- £*— t- J2 a. e pa en e or - w-H C C O Q fl •— oj a a *r« o_(/j;»»isj A «eaeSuw(jt3cjr-._ lixaco.VlV)>r*J 4.S1 flR300!26 s ia. v» ^

0 p

'-o t. fl ^1 Si O aI .VaI a •r- Wl X JM: e eo M fl ^ """g jg < CO , -9M M -9 -9 aacM o. CM "J >» CM VI O 1 IOI l O i 1 1 lOOQOi l O l O O > 1 1 O i l O 1 1 rH 0 ** 1 £ 911 ! ^ 1 1 O 1 1 1 lOVOOl 1 O 1 CMO 1 1 I * l l O 1 1 1 « —— "** >^ •il .11*1111 *«««ll .1 ..til .11. QC ^U h« 1 1 •*• ** e c-) ^ o in (n O GO O *V O rH ss i ^ csi o en co CM v en 1— U^- « 63*5 t1 tn* rH rH> rH• en• • ^* |rt ^fe __ r^ rH M in ^ •*a CM -H M fl hi -gj < eo ^ -9 -9-9 M — J -9 -9 -9 1 -9-9 •e « ea o. 1 K «-« UI X Ol IOI 1 O O i O i OO t O 1 I I I IOI IO O I i O Q- to •*- i OO o oi iEE9i iomi^rioinir-41 i i i 101 ict ^- 1 I O VM <^ ^ a "" .11. *H S ^ to ^ tn r*. ^- p^cn CM in, co rH >*• sc^^ E t** vn CM to —4 ^* ^f £S^ o 4* t* c M fl "S* *• -» -9 4«* o o i i i 101 t iioooi i i i tot i >o 5 ea i 3C CMO i i i ioi i i (Oeooi i i i iOi i i tn *9-9 eoecj o. •9*9 tsi si • •iiii .iiii . .111111 .iii . i O O i i OO *— fnm to .CMnin CM r*. 1 O O 1 1 OO oee fl 10 -H f% f-) rH m rH 1 « • 1 OEuJt— *• ^ rH in in t— 1 1 1

O) ot ~3? 3 3

u "a U —— « •••••* ^1 OITJ -2-2 B« -^ DIOI "3— s -—— - * ___r ^« M-r- i » O-—*^i»: r——— . O» ^s MM-—. M Ol OlOt -^.t- (^ 1 • DI O ^^•v^^^^ Ol QI1MS ^MC "^x Ol Ol&tf Ol Ol^£ Ol Dl^^v Ol Ot4***!*11**! ^,*3!S^, w —3 _ —e °J g^y..*-*5r ^ ?-^-^ "Si'^Ti''^ j*. 1*1 *r5^ *" S*3^2f 5 ?*n DI ^J Ot ^— —— • • oi • Si *~* 9 « • M M • DI •—' en Of" " - ' ^«c S a-S B" I>. *— ' 3 « of a ui v S • -._-3- • M BI o e: 0 S _ su — • m 3 « ff ff— S >, •-- l^^l S * a **- S a H- V 2x • — a ••• ^t • u !« S. c E -a gienu^ft « (B *-r-r— oo N OJS 3 0 JS a *^ a o fr— *Ja eo CJ XH* <->X 4.52 TCN 4208 RI REPORT REV. #1 09/JAH/92 concentration of 900 (J) pg/kg.

No pesticides were detected in any of the subsurface soil samples. However, the PCB compound Aroclor 1254 was present in sample DD-1/2-4 feet (bgs} and sample DD-1/4-6 feet (bgs) at concentrations of 300 and 370 //g/kg, respectively.

Using the analytical results obtained for background samples B-l through B-3 as a basis for comparison, the metals barium, beryllium, chromium, cobalt, copper, lead, manganese, nickel, and zinc were above background in at least one subsurface soil sample. Barium was elevated above background in 14 samples with the highest concentration of 310 mg/kg observed in RIW-2/16-18 feet (bgs). Beryllium was above background in 4 samples with the highest concentration of 1.3 mg/kg observed in sample SD-2/0-2 feet (bgs). Chromium was also elevated in only 4 samples with the highest concentration observed at RIW-11/3-5 feet (bgs). Cobalt was elevated above background in 13 samples with the highest concentration of 31.2 mg/kg observed in RIW-6/0-2 feet (bgs). Copper was elevated above background in 9 samples with the highest concentration of 42.5 (L) mg/kg observed in RIW-13/3-5 feet (bgs). Lead was also highest in RIW-13/3-5 feet (bgs).in a concentration of 59.9 mg/kg, but was also present in 11 other samples. Manganese was elevated above background in 11 samples with the highest concentration of 982 mg/kg observed in RIW-_2/16-18 feet (bgs). Nickel was elevated above background in every subsurface sample, again as compared to surface background samples B-l through B-3, and ranged from 1.4 to 33.9 mg/kg. Zinc was elevated above background in 15 samples. The highest concentration of zinc was again observed in RIW-13/3-5 feet (bgs). Besides RIW-13/3-5 feet, samples RIW-6/0-2 feet, RIW- 10/1-3 feet, and SD-2/0-.2 feet (bgs) all contained six or more heavy metals elevated above background.

4.6.2.2 Analyses of Additional Parameters

Besides analysis for TCL organic compounds and TAL inorganic analytes, analyses of percent moisture, total organic carbon, pH, and cation exchange capacity were also performed on samples the three DD-1 samples, the three DD-2 samples, the two SD-1 samples, one SD-2 sample, and the 20 RIW samples (Table 4-13). The moisture content for the subsurface soils exhibited a range from 6.5 to 21.6% but were

. flR3-OOI28 TCN 4208 RI REPORT REV. /I 09/JAN/9; Table 4-13 Subsurface Soil Characteristics at Remedial Investigation • Well Locations Dixie Caverns Landfill Site

Depth of SMple Total EPA Btlow Organic Moisture Pare en t Saeple SMplt firound Carbon Content Solid CEC $0411* Location Nurter (ft) (•Q/kfl) (Ptrctnt) (Percent) PH Keq/180g ta/D RIW-1 5SS6C-83 3-5 5,300 13.5 86.2 5.70 9.2 2.130 RIW-1 5S86C-S4 5-7 3.030 22.9 79.3 5.87 8.1 1.875 RIW-10 5836C-53 1-3 762 11.1 89.0 7.30 12.5 2,883 RIW-I1 5S36C-35 1-3 13.500 14.4 85.2 6.53 13.1 3.013 RIW-I1 5S86C-36 3-5 9,800 13.5 86.3 7.14 12.6 2,910 RIU-12 55S6C-62 0-2 4.400 10.5 89.0 7.51 8.5 1.950 RIW-13 5SS6C-55 1-3 1.900 11.4 88.6 6.90 10.0 2,313 RIW-13 58S6C-56 3-5 18.300 23.5 78.9 7.12 16.5 3,795 RIW-7 5886C-6Q 0-2 846 12.7 88.9 5.15 13.9 3.203 | RIW-2 5SS6C-82 16-18 ' 380 15.9 85.3 6.69 8.7 2,008 RIW-2 5886C-S7 14-16 5.360 20.6 79.2 6.14 9.6 2,210 RIW-6 5S86C-53 2-4 779 9.1 90.8 6.08 10.7 2,473 RIW-6 5SS6C-52 0-2 1.260 11.5 88.4 5.45 11.6 2.663 1 RIW-7 5886C-61 2-4 212 10.0 90.8 5.39 11.2 2.570 RIW-7 5886C-59 0-2 600 11.9 89.3 5.11 12.9 2,965 j RIW-3 5S86C-50 0-2 777 10.4 90.0 5.07 14.7 3,380 RIW-8 S886C-51 2-4 840 11.3 89.0 4.95 15.4 3.548 RIW-9 5S86C-66 0-2 1.730 14.2 87.3 4.83 12.0 2,755 RIW-9 5836C-64 2-4 569 9.9 90.3 5.32 9.6 2,218 SD-1 5886C-65 2-4 142 10.5 90.2 5.35 11.7 2,693 SD-1 5636C-63 0-2 304 10.1 90.2 5.45 9.4 2.158 SD-2 5S86C-74 0-2 264 6.5 93.9 5.70 10.7 2.473 DO-1 5836C-76 4-6 1.510 13.9 85.2 5.80 10.3 2.378 DO- 1 5SS6C-S1 6-3 220 10.0 89.5 5.51 12.2 2,805 DD-1 5S36C-75 2-4 3.060 15.6 84.4 5.40 8.9 2.060 00-2 5S86C-71 8-10 790 13.4 86.7 5.71 9.6 2,203 DO-2 58S6C-80 6-8 290 14.0 86.0 5.44 9.5 2.183 DO-2 5886C-70 12-14 1.400 10.2 89.8 5.23 9.3 2,145 DO-3 5886C-77 4-6 3.320 14.9 85.5 5.01 9.6 2.220 AR3QOi29 4-54 TCN 4208 RI REPORT REV. #1 09/JAM/92 generally on the order of 10 %* . The TOC. of Fthe subsurface soils generally was less in the subsurface soils than in the surface soils. The TOC of the SD samples averaged 236 mg/kg, the TOC of the DD samples averaged 1211 mg/kg, and the TOC of the RIW samples averaged 3702 mg/kg. The pH of the subsurface soils was fairly uniform for the SD and the DD samples ranging from 5.01 to 5.83. The RIW .subsurface samples exhibited greater variation ranging from 4.83 to 7.51. The same consistency was observed for cation exchange capacity with SD and DD samples all ranging between 9 and 12 Heo/180g but the RIW samples ranging between 8.1 to 16.5 Meg/180g.

4.6.2.3 Contamination of Attainment of Cleanup Criteria

Threshold levels of selected organics in soils were determined by USEPA as being protective of human health (USEPA Internal Memorandum, 1989). Threshold concentrations of the semivolatiles bis(2-ethylhexyl) phthalate di-n- butylphtlate, and napthalene were established at 19800 pg/ kg dry weight, while threshold concentrations for the volatile organics ethylbenzene, toluene, and 1,1-dichloroethene were established to be 625 /*j/kg for the first two and 300 for the, latter.

AH subsurface soil samples were well below the established threshold criteria. Maximum semivolatiles detected in samples from the drum disposal area (DD samples) were 104 J jug/kg, and no volatiles were detected. NO volatiles or semivolatiles were reported for the Sludge Disposal area (SD) samples. The maximum levels of semivolatiles in subsurface soils were from the RIW soil borings was 1,300 j/g/kg and 4,800 jig/kg of bis(2-ethylhexyl)phthalate from 1 to 3 feet and 3 to 5 feet, respectively.

4-55 flR300!30 TCN 4208 RI REPORT REV. #1 09/JAV/92 4.7 GEOLOGIC AND HYDROGEOLOGIC INVESTIGATIONS

4.7.1 Site Geologic Characterization

4.7.1.1 Surficial Geology - Field Observations

The rock formations identified during the field traverses in outcrop at the DCL site are the Hillboro Shale of Middle Devonian age and the Late Devonian age Brallier and Chemung Formations. The Millboro is described as a black fissile shale with some siltstone and sandstone layers present, which becomes more sandy upwards and grades into the Brallier Formation. The Brallier and Chemung consist of interbedded greenish gray, brown, and reddish brown marine sandstones, siltstones, and shales. Because these formations are lithologically similar and have a gradational contact, they are not differentiated on the geologic map (Figure 2-2).

Outcrops of the bedrock are highly fractured and weathered. The fractures are partially a result of the intense deformation that the rocks underwent as they were folded and overturned, in some cases more than 180°. As erosion removed the overlying rocks, pressure on the rocks was released allowing them to expand, creating additional fractures. These fractures expose greater surface area of the rocks to both mechanical and chemical weathering which, in turn, enlarges the fractures and weakens the rocks, accelerating the rate of erosion. Several rockfalls were observed to have occurred along roadcuts within the DCL site during the winter of 1990-91 due to the highly fractured nature of the bedrock and oversteepening of the slope.

The overturned attitude of the rocks under and near the landfill site, as shown in the cross-section in Figure 2-2, was verified by field work at the DCL site, In the valley to the north of the site, the bedding of exposed formations dips to the southeast, but the age of the various formations becomes younger to the northwest. If the site were on the southern side of a normal syncline, the rocks would occur in the same sequence but the dip direction would be reversed. Also exposed at the site are contacts between shale and sandstone showing ripple marks that have been rotated more than 90° from horizontal.

fiR300i3I TCN 4208 RI REPORT • REV. #1 09/JAN/92 Several geological structures were encountered at outcrops within the site. The axis of an overturned syncline is exposed at an outcrop near the northeastern corner of the site. Several normal faults are prominently exposed in the roadcut wall at RIW-8. These faults all trend to the northeast and range in dip from near vertical to 65° to the southeast. These faults are filled with a clayey material (fault gouge) associated with fault movement, which may limit groundwater flow along them. Confirmation of the fault locations by fracture trace analysis using aerial photographs was attempted, but no discernible features were noted.

4.7.1.2 Subsurface Geology

Twelve Remedial Investigation Wells (RIWs) were installed during the field portion of this RI/FS. The specifications for the RIWs are shown in Table 4-14.

Deep wells installed on the eastern margin of the site were completed in the Millboro Shale, while those west of the main property road and all of the shallow wells were completed in the Brailier/Chemung Formations. Soft zones, potentially representing fractured intervals, were noted during drilling, although no site- wide patterns in the depth or orientation of these zones could be determined. Test boring/well construction logs are located in Appendix E.

NX Rock Coring - NX rock coring was performed in wells RIW-1 and RIW-2. A schematic illustration of the extruded cores is shown as Figure 4-3; heavier lines indicate wider fractures. The rock cores consist of fine sandstone and siltstone, with varying amounts of shale. Horizontal fractures occur within the shale beds. Other low-angle fractures are evident in both cores. Most fractures in RIW-1 occur from approximate elevations of 1552 msl to 1560 msl, while those in RIW-2 correspond to approximate elevations of 1505 msl to 1510 msl.

Geologic Cross-Sections - Two cross-sections were constructed at oblique angles across the DCL site to illustrate site stratigraphy as encountered 1n the well boreholes and its relationship to the landfilled solid waste material. The lines of cross-section are shown on Figure 4-4a, and the cross-sections themselves constitute Figure 4-4b and Figure 4-4c. The depth of the solid waste landfill

4-57 AR3QQI32 TCN 4208 RI REPORT REV. « 09/JAN/92

Table 4-14 Remedial Investigation Wells Installation Specifications Dixie Caverns Site •

Screened Well Diameter Well Total Depth* Interval* (inches) Well Material RIW-1 15.5 5.1 to 15.1 2' Sen. 40 PVC RIW-2 29.05 18.6 to 28.6 2- Sch . 40 PVC RIW-3 42.0 27.0 to 37.0 2" Sch . 40 PVC RIW-4 30.0 15.0 to 25.0 2' Sch . 40 PVC RIW-6 65.0 40.0 to 60.0 4- Sch . 40 PVC RIW-7 110. 0 95.0 to 105.0 4" Sch . 40 PVC RIW-8 95.0 70.0 to 90.0 4- Sch . 40 PVC RIW-9 75.0 53.0 to 73.0 4" Sch. 40 PVC RIW- 10 65.0 20.0 to 50.0 4" Sch. 40 PVC RIW- 11 35.1 20.9 to 30.9 2' Sch. 40 PVC RIW- 12 40.0 19.0 to 38.0 4" Sch. 40 PVC RIW-13 75.0 50.0 to 70.0 4- Sch. 40 PVC

in ftct below grade at tine of well installation

flR300i33 L .-^^ ". - TCN 4208 RI REPORT RIW-2 REV* *l m" * 09/JAN/92 19.5

20.5 RIW-1 5.5 21.5

6.5 22.5

7.5 23.5

8.5 24.5 Z

25.5 h- Q. LL UJ 10,5 26.5 °

11.5 H 27.5 0. 12.5 28.5

13.5 29.5 RIW-2 LUhologic Nature •(4,5 ____Depth Descrlptiort 19.5-20.5 Greenish gray fine sandstone

20.5-21.4 Dark gray siitstoine and fine sandstone with 15.5 thin shala partings

21.4-21.6 Dark gray interbeddal sandstone and shale RIW-1 llthologic Nature Depth Description 21.6-21.8 Dark gray siltstone and fine sandstone with 5.5-9.7 Dark gray to block fine sandstone thin shala partings 9.7-9.9 Same ea 5.5-9.7 with calcita vsin 21,8-21.9 Dark gray sandstone with fracture perpendicular to bedding 21.9-29.5 Dark gray tiltstone and fine sandstone with 9.9-12.1 Dark gray to black siltstone and fine shale partings sandstone with thin shale partings

12.1-12.3 Dark gray fine to medium sandstone with TETRA TECH, INC. fractures it 12,3-15.5 Dark gray siltstone and fine sandstone with thin shale partings FIGURE 4-3 SCHEMATIC ILLUSTRATION t OF NX CORES DIXIE CAVERNS LANDFILL SITE flR300i3if 4-60 -- '^. O*

CO CO

C/) UJ I i-l ae 1/1 3:i t-uii w aeS as x Q

X C 11

CM

X wO: O > > !r-? L—Ji L_Jj .H a: ^So -dg LJ ^ce ^ce" ^ < < < _l X ^5 i— -. " Q Q.

—— O fi ° ° X >

(|SA9| Dss UD8UJ SAoqo ;o9;)- NOLLVA313

4-61 8SC "s*sF " T a

CO

*OS

zo en op a CO CO CO CM O aOS CO ' — ao.: .J J, J, co b•^ g_ > > S Q i— 2 a

« o «n Fs « CVJ ______flR30QI37 4-62 , ... TCN 4208 •-L- RI REPORT j REV. #1 09/JAM/92 material was transferred from the landfill isopach map shown previously in Section 4.2.

No borings were performed in the solid waste disposal area, thus the exact maximum thickness of solid waste material is unknown. An assessment of pre-fill surface topography indicates a maximum thickness between 60 and 70 feet. The minimum and maximum groundwater elevations measured at the DCL site (12/90 and 3/91, Table 4-15) were included on the cross sections to illustrate the relationship of the groundwater table to the landfilled solid waste material. If the water table surface is projected as a planar feature, the solid waste material does not appear to lie below the water table in Figure 4-4b, but may lie below the water table in Figure 4-4c. From the data collected in the RI, it is unclear what portion, if any, of the solid waste fill resides below the water table aquifer. Two possible conditions may exist; 1) ground water mimics the original contours and predominately flows below the fill material; or 2) the fill influences the water table aquifer and cause the groundwater to reside within the fill.

4.7.2 Groundwater Flow Direction

4.7.2.1 Local Aquifer Systems and Groundwater Flow Directions

As discussed previously in the background hydrogeology section of this RI report, groundwater flow in _the vicinity of the DCL site is controlled primarily by stratigraphy (rock type) and geologic structure in the area. In general, groundwater flow in the two aquifers at the site (the clastic MDS-AS and the carbonate CO-AS) is quite different.

Specific observations regarding the groundwater flow in the clastic MDS-Aquifer System (from Waller, 1976) that are applicable to the DCL site include:

• The movement of ground water (in the area) is along fracture paths from areas of recharge in the interstream and drainage divide areas to areas of discharge at springs and along stream valleys where the surface-water baseflow is drainage from the groundwater reservoir.

4-63 flR300138 £ .2: UJ > U4 ec LU W o O in T- fM M •-. o> CM • • . • • « e—e Kot g g § CM in EO S CM K CJ S rg ff CM Kt • • ^^ • *4* * "*4" • **T * **J" • ifcj- *— T* O "^ ^~ "* *~ "* *~ *" "~ in T- 1A »-

g RCM eg o CM 60 K> eo tn • (M F-- S * S CM 3 f^ p> . 2 °^ ?t ^ R! ca >*• xf CM •* K> •* O -t ^- ^- Kt »* -O

f> 03 K) K N. 00• ^-o "• «c>. •*• S S CM CO si

CM T- ^) C\l CK KI 00 O* in i_ - • S" CM • CM • *f • in * K» rsi S . in • in "in • in * in o *^ *o ^ ^" o ^" ^ KI «- KI *- KI «- Ki ^ K> r-

^ •O ffl in ^_ ^., ^^ •- 'O _ Kl w IA * IA * **» JQ o f^ 00 FO O* f^J *^" C^ '•'J* OJ -r •r- f— r^- * • PJ • CN* * rM CM in .r- o> •- *~ »- •- m *• m "~ •" *~ .A -

eo Kl N- >O IA O •* in Kt e5 ^O • eg •f- • CM • Kt • eo « O *- in .^ ^ . *O • ^3 * IA *"I S • ^ in so ^ o *— « ^ 03 w- «} «- « ^~ _

O CM 0 in ,2 e » Offi -o ^ s . S ** in tA H M. 2 ^ fe ^ S 0 | |2 S i r5— TS- gg - N- *— o I *— f> " °* " " *" ^" *~

h- 0 -0 K. o. T ll 1 fXI »- o5 _ oo o * • KI • in • O • SB ••* *™ ,2 i CM ^ LU K e8 00 oo cy M. CM «-^ u • 9 * •> in u\ ^^ in *o ^^ ^O tn irt 1/1 GO Lft o -r- vj- •- IA »- in — ui «- •i i « ^ "° 0 *~ "* ^ -? I •O *- — KI KI i«f s" [x - -" o ^ 1 « s 1 1 * 1 5 S • 2

O SJ Jn " 3 § K>3o o f x^ *o • in 03 . O « CVJ o 8: "^ . £ "1 K in O »2 ^ CM S 5 2 5 s 2 g S 5 S tn t^i FO • CM • *- • T- . r— • T* in tn Kt IA «o tA «o in «O tn tn m CM tN O

Soo in O ^ -* s- T- ^> IA N. e $ «g 0 ^ g ~ « Jg 3 5 S S o• tn in « in • tn • in • IA > in

f *« s Ot- 01 _j w O O 3 ** s « 84— CJ v ' i_ w- o Q! o^ O O* -g cj^ 4-> ^J —* ^ 03 OJ ^ ^^ r-* 1>^*r« ^« 4J "^i* EO r- 43 O *f ^0 CO *s. OS N^ 0* **j « W O> K? •8 r- ** S- %o ^ co v- CM-» O ^ B "5 CM ^ U §C •m. 4-1 a. ^~ 3 r" IO ^ O W o —— \S H- C M- *n o *^ € «) 8-« o t3 ra — • u « ** —• a —• e — * CJ 9 -M f3 V- *-• > go >^ »£ > SO >>r- I f |_ g V g « V O ^k O at <• _< ^~. O — ' ««*-—**" S t- — ' *• 41 -• o § »ri , , 9 4-1 « s « t- V. t- 1 t.^ t-Sl i--. t:! U s^ t, ^ ™ If 0) ai a eo m eo vt> fl* V U V *) «* W «* « u OB W W 4-> 5 —' «». 1 fll U OIH- nx., a^>, «J *J ffl '*• x ON* So LU v UI 3 CQ ^fftrtfir J /•• 39 TCN 4208 RI REPORT REV. #1 09/JAH/92

• Most valley segments, which trend generally northwest-southeast, are predominant groundwater discharge areas and generally reflect groundwater flow paths, and were initially localized (formed) by joints and zones of fracture concentrations.

• Thrust faults, which are oriented northeast-southwest, exert...control on regional permeability and localize groundwater flow.

• Groundwater gradients are significantly less than surface gradients.

• The groundwater surface is generally a subdued reflection of surface topography.

• The fracture system in the rocks in the Upper Roanoke River Basin is interconnected over considerable distances.

Specific observations regarding the groundwater flow in the carbonate CO-Aquifer System (Waller, 1976) that are applicable to areas southeast and southwest of the DCL site include:

• The movement and storage of groundwater in this aquifer is highly variable, as groundwater is stored and transmitted in enlarged solution channels and other void features.

• The majority of groundwater recharge to this system is accomplished by diffuse infiltration and is largely dependent on the topography. Recharge to this aquifer system also occurs from losing streams in the outcrop area. Therefore, surface water quality and quantity directly influences the quality of recharge to this aquifer. Recharge from adjacent aquifers is also important.

General regional groundwater flow directions, as described and measured by Breeding and Dawson (1976) and Waller (1976) and based on stratigraphic and structural considerations, are illustrated in Figure 4-5. As shown on this

4-65 - AR300UO o o x u»-.* UoIc —— u1. r- (o

flROQQU 4-66 TCN 4208 R! REPORT REV. #1 09/JAN/92 figure, the general regional groundwater flow direction in the area of the DCL site is in a southeasterly direction toward the Roanoke River, and then in a general northeasterly direction along the Roanoke River. The Roanoke River is the regional groundwater discharge point; tributaries of the Roanoke River are localized groundwater discharge points. The Roanoke River and its local tributaries generally represent general natural groundwater flow path directions in any given area.

4.7.2.2 Site Specific Groundwater Flow Direction

The groundwater flow direction in the bedrock aquifer in the immediate vicinity of the DCL site, as determined based on water level measurements from on-site Remedial Investigation Wells (Table 4-15), coincides with the general regional groundwater flow direction. A potentiometric map of water level elevations (3/91) is shown in Figure 4-6* Groundwater flow in the vicinity of the site is generally to the southeast, although a minor component of localized groundwater flow is toward the streams which drain the site: . .

General groundwater flow directions in the DCL site area, as determined by the evaluation of local and regional information from residential wells and site RIWs, are depicted on Figure 4-7. On the basis of these data, the majority of the residential wells do not appear to be situated hydrologically downgradient of the DCL site, and consequently would not be impacted by contaminants originating from the site. In addition, it should be noted that most of the residential well areas are hot in the same local surface drainage system as the DCL site. Therefore, surface water runoff from the site is not available for direct recharge to the CO-Aquifer System in the vicinity of most of the residential areas.

Regional structural features are likely to influence directions of groundwater flow. Numerous northeast-southwest trending thrust faults, including the Salem Fault (previously shown on Figure 2-3), are mapped to-be present southeast of the

4-67 AR300U2 4-68 =3 U LU I cOe oUrJ <> r-< O

4-69 TCN 4208 RI REPORT REV. #1 09/JAH/92 site and the geologic cross-section (upper left corner of Figure 2-2) illustrates that sedimentary bedding planes similarly trend northeast-southwest. Surface water features which typically follow fractures and joints trending northwest- southeast (orthogonal to the regional strike) do. not appear to lose significant flow to these fault/bedding plane features. Many minor streams crossing the Salem Fault disappear shortly thereafter in response to the lithologic change to carbonate bedrock. Preferential groundwater flow along these fault/bedding plane features is likely to be in the northeast direction, as this is the direction of the regional topographic and hydrologic gradient in the vicinity.

Groundwater pumping in the area, for example, any dewatering activities conducted at the neighboring limestone quarry, would substantially alter the natural gradients and groundwater flow paths in the vicinity of the site. During dewatering activities, the quarry would be a local groundwater sink, and all groundwater from the site would likely flow toward the quarry. It is likely this situation existed during previous quarry activities. On the contrary, residential pumping of private home wells is not likely to have a substantial effect on local groundwater flow directions given that a considerable amount of water is stored in the average residential well casing (1^ gallons per foot of 6" casing), and that daily residential water usage is relatively low (300 gallons per day). Typical residential well pumping is not of sufficient magnitude nor duration to induce changes in groundwater flow directions to any major extent. However, should the groundwater use in the area change (e.g., from basic residential use to some type of continuous pumping), natural flow directions could be altered.

Site-specific vertical groundwater flow was not assessed during this investigation because no cluster wells were installed at the site. However, vertical flow gradients are anticipated to be downward in the upland recharge areas of the clastic MDS-Aquifer System and carbonate CO-Aquifer System and upward in stream valleys (groundwater discharge areas) as per Waller (1976).

4-70 AR300U5 TCN 4208 Rl REPORT REV. #1 09/JAH/92 4.7.3 Groundwater Flow Velocity

A calculation of groundwater flow velocity for the site is not straight forward. As previously described, the majority of the ground water exists and moves through fractures and cavities in the sandstones, shales, and limestones in the vicinity of the site. Prediction of flow velocity in fractured rock is difficult because the density and interconnection of the fractures is generally unknown. However, the one recourse is to assume that the fractures within the consolidated rocks are of sufficient density and are sufficiently interconnected to approximate a porous medium. To calculate the average linear groundwater flow velocity for a porous medium, Darcy's Law is applied:

v = -k(dh/dl)/n where "v" is the average linear velocity, "k" is the hydraulic conductivity, "dh/dl" is the hydraulic gradient, and "n" is the porosity of the rock. A discussion of the source of the values for hydraulic conductivity, hydraulic gradient, and porosity follows.

Values for hydraulic conductivity were calculated from slug tests performed in the monitoring wells on site. Two different methods were used to evaluate the slug test data to obtain values of hydraulic conductivity for the aquifer. The hydraulic conductivities derived from the slug tests are presented in Table 4-16. The raw slug test data is Included in Appendix E. . For this discussion, values of hydraulic conductivity derived from the method applicable for unconfined aquifers (Bouwer and Rice, 1976) will be used.

The hydraulic conductivities calculated from the slug test data range from 0.03 to 19.30 ft/day. The values of hydraulic conductivity obtained for RIW-2 and RIW-4 are much higher than the results obtained from all other wells. These wells are both located along Stream "B". However, wells RIW-1 and RIW-3 are also located along this stream but slug tests performed in these wells indicate much lower hydraulic conductivities. Evaluation of the Test,Boring/Well Construction Logs for these two wells (RIW-2 and RIW-4) indicates no apparent reason for the higher hydraulic conductivities. It is possible that wells RIW-2 and RIW-4

flR300U6 TCN 4206 RI REPORT REV. #1 09/JAN/92 Table 4-16 Results of Slug Test Analysis Dixie Caverns Landfill Site

Cooper, Bredthoeft, Bcuwer and Rice and Papadopolous Length of (1976) Hydraulic (1967) Transaissivity, Saturated Well Hydraulic Conductivity, K Intake Conductivity Well (ft/dty) (ft'/day) (ft) (ft/day) RIW-1 0.29 5.76 8.46 0.68 RIW-2 8.14 207.0 12.67 16.34 RIW-3 0.95 15.20 15.44 0.98 RIW-4 19.30 267.0 15.77 16.93 RIW-6 0.63 2. 88 1.69 1.70 RIW-7 0.099 3.30 4.40 0.86 RIW-3 0.19 8.36 9.12 0.92 RIW-9 0.17 2.00 19.27 0.10 RIW-10 0.20 3.61 16.85 0.15 RIW-11 a. 73 3.80 17.56 0.22 RIW-12 1.49 12.50 24.3 0.51 RIW-13 1.93 18.50 64.22 0.29

MaxlMJK 19.30 267.0 64.22 16.93 Minium* 0.17 2.00 1.69 0.10 Average 2.79 45.78 17.48 3.31

4-72 flR300U7 '-•••,, TCN 4208 RI REPORT REV. #1 09/JAN/92 intercept a greater density of water-bearing fractures than encountered by other wells, resulting in higher hydraulic conductivities.

In either case, the hydraulic conductivities measured 1n RIW-2 and RIW-4 do not appear to be representative of the hydraulic conductivity for the site. The mean of hydraulic conductivities for all wells, excluding RIW-2 and RIW-4, is 0.66 ft/day. The median hydraulic conductivity for all wells, including wells RIW-2 and RIW-4, is 0.73 ft/day. The close agreement between those 2 values suggests that the value of 0.66 ft/day for hydraulic conductivity can be considered representative for the site.

The horizontal hydraulic gradient has been calculated for three areas of the site. The hydraulic gradient between wells RIW-6 and RIW-10, RIW-9 and RIW-12, and RIW-6 and RIW-4, is 0.09, 0.14, and 0.10, respectively. Using these three values, an average hydraulic gradient of 0.11 was obtained.

A value for porosity of the consolidated rock was not measured at the site. Porosity in consolidated rocks is associated .with fractures and cavities. Typical porosity values range from 5-30% for sandstone and 0-10% for shale (Freeze and Cherry, 1979). The value of 10% was chosen to represent both rock types. — -...-.

Using a value of 0.66 ft/day for the hydraulic conductivity, a value of 0.11 feet per foot for the horizontal hydraulic gradient, and a value of 10% for the porosity, the average linear velocity of groundwater flow across the site is 0.71 feet per day. .

It should again be emphasized that the calculation of flow velocity rests on the assumption that the sandstones and shales are fractured to the extent that they are equivalent to a porous medium. However, the observed range in hydraulic conductivity values, from a low of 0.03 ft/day to a high of 19.30 ft/day, most likely indicate both anisotropy and a limited degree of interconnection in the fractured rock. Substituting these hydraulic conductivity values into the flow velocity equation yields a groundwater flow velocity which may actually range between 0.03 feet per day and 20.84 feet per day.

4-73 BR300U8 TCN 4208 RI REPORT REV. #1 09/JAH/92 4.7.4 Monitoring Well Sampling Results

The results of groundwater quality analyses of samples collected in Rounds 1 and 2 from the 12 monitoring wells during this RI are summarized below. The complete laboratory results are included in Appendix E.

4.7.4.1 Field Parameters

The results of the general water quality field measurements made during well purging (Table 4-17) show a wide range of values for Ph, temperature, conductivity, and turbidity in samples collected from different monitoring wells in the two rounds of sample collection. Possible explanations for some of the observed anomalies follow:

RIW-11 High Ph Value - High pH values can be indicative of grout in the filter pack. Unusually high concentrations of calcium and magnesium (components of grout) detected in this well support this interpretation. Consequently, data for this well may be considered sttspect.

Hloh Conductivity Values: RIW-11, 12 and 13 - RIW,-13 is Jocated near the leachate collection system. In addition, these three wells lie along Stream A downstream of the Atlas Powder Company, and appear to lie within a different groundwater drainage as compared to other site monitoring wells.

High Turbidity Values - High turbidity values are likely to be related to the presence of fractured shale zones within the screened interval. The wells which have higher turbidity generally are deeper and screened in "soft" shales. Inadequate well development may also be indicated.

4.7.4.2 Organic Compounds

A tabular summary of organic analytical results for the monitoring wells are given for Round 1 and Round 2 in Table 4-18 and Table 4-19, respectively .

4-74 . fiR3QQU9 TCK 420fl RI REPORT REV. fl 09/JAH/92

Table 4-17 Field Parameters Remedial Investigation Wells Dixie Caverns Landfill S1t«

Temperature Conductivity Turbidity (°c) pH (umhos) fntu) Well Location 1/91 2/91 1/91 2/91 1/91 2/91 1/91 2/91 RIW-1 9.8 10.1 8.6 7.3 118 420 24.5 157.2 RIW-2 12.5 12.3 6.5 6.7 128 367 56.0 30.5 RIW-3 11.2 8.7 7.0 6.7 88 193 40.7 62.2 RIW-4 13.9 12.6 7-9 6.7 214 450 40.7 61.1 RIW-6 13,8 14.2 6.6 5.9 167 263 200.0* 111.6 RIW-7 14,6 14.4 6.6 6.1 114 169 111.1 117.7 RIW-8 15.3 15.2 6.9 5.6 131 131 181.0 200.0* RIW-9 14.5 13.7 6.8 % 6.0 55 90 109.0 182.3 RIW-10 13.5 13.0 6.8 6.5 211 487 123.5 110.0 RIW-11 13.3 11.3 11.9 10.7 436 1333 65.1 152.9 RIW- 12 15.0 13.5 (7.0 6.8 787 1300 158.7 109.7 RIW-13 16.5 14.5 6.8 6.3 455 1307 21.3 8.3 * Off turbidity scale

SR300I50 4-75 UJ ^B ^* 3E c£ LL! ^3 •^ r— HH Q> rH QC O O -i « -? CM < «n 1 191 §O O Q i i 190991991 IO i ' OO i i 1019991 'P'9 i > O I ^ o o i i i oio a o i o o i i o l lOOl < lOiOOOti l O l r-» 3 1 I.I rH cr> ^r Q Q O 9 O 9 O O O C3 O 9. 9 fl9 C3 ^* ac r-.. CIO >-* »« O "T O rH d rH ^3 (r) O^ PH £A fO ^r eg rH eo mo esi <*» CM Ot ift to O *^ CM <») krt rH -H ^ -H CM IO-^ -H •» M ") rH rH O _l ^^ 2 csf***i 00 O Ol CMCO CMCM too i*. o co 10 •» « ^ (r) IS* (*> «M *O d ^ fr) (M rH *J rH Cn ' I9O9O199I 19 1 33 i ill iooi i i oeo oo i o o i 10 S— i ill o esi o o rH o CM op g« esi 9 o o f*. is o 9 ~* J l« 1AO f** -H ^ rM M4 ft (Si CMO rH O^.vHr-1 O Cl QO ^^ IO €h kA Ot €0 O ^ CO ^1" CO €0 Ot O 1 K * .. B * rH t-« t^ \O CM rH po ^ to CM m t- eo CM o tO CM 0 • ui rH — • IP O * C 1 3 5 tsl PesIi « -9 -9 i o i i 9IOOI lOO999i99OOO ' '99* ' i p i p p o p i p i o •5 * 3 1 lOOl 1 lOlOOCMOlOlr-l JIU i * i i (K mo o ou^rHO 9 le rH$ in OlOr^tM 9 **> -^ O ^ tft ^ f*- Cfl GO O r i O I O t p r O O Cfl i iii SSSS^SSSSSSSSS ! $3 VOOOI 1 ICMir^lOlOCO «• i I? i i iii S ,O^irtpr-.r-.i©pmoooop ' eo ffl 1- t rH rH tO ^~ CM r*4 ^H C9 ^T CSI ^^ ^H CM C3 rH ^0 §rH C3 C3 PO ^* CJ i 0t CV1 C5 ^s *4 ^^ lA (*) tf^t m in i i 4 « !•**•• • • ft i &t &t en mv «re rH mo J££ i • esi — • 9 rH »-i i rH .^ ^E O 2 i 1 T * T „ •9 1** rH i ^ iii >» SlOOl 1 109991991 1 O »— I 1991 I99I99O99999 «^J —— 3 <1 ^ ii1 1 i1 U l Ot O i J l 0 10 O *O 1 O O I l OOUtOCMOCMCiK Vfc. ^ O rH rH O ^ CM O Ot >A O I * 1 *f rH Ot Ot ^» O ft ft ft ft fl rH rH (O • (r> rH CM (O £ rH » rH O ±2 •= r» 1 o s -S 5 M: T-a 3 -^ rH « •*• X tl? —a 1i *• IIt iI i P— I t O p 1 I tOlOOOOOplO i 3.» t ^ lit m oiooi i loOoaioOimot a i lOo i i i O lOomoiAO ico ac o mo oeopo 9O CMO i t i O SuTl O O Ca &l CO C\J ft t SS S §S"eiNg v 1 1 r- CM * r^ ef> *•» (M xO i rHfs. CQ Ot * S* -* 1 1 1 CM CM CM r-»rH ^> »• CM Ot SM »H rH pg -^

.7 _fe * -7 a u 1 *H~ •— "x • — . *->. ^j.7 ^ —*^« . r«* ———» ^CT ^ —— * — Ir-, *—_J **C^ -*» ^ U a -g.1 •^V^-H.^*^^-^«-S 9 OL— , a-r-s-^,-^. ->. r-UJ-g gr**»_j ^.. a— i -J __ »?_3.-J 3 -J at a* d^Zr-s.ai—i —i^ ^ sj^1 3 -JJ w 1* e t- o •-* m o — *-» a st S^r at ot_j.^ 9 5* —* "-" —J "•^^'"'liXlE^rsi § s-iCiXir'ii'gi « e• i3— .Bo

4"76 SR300I5I •ocf~*-^H -9 -9 s. a i 0 i 9 O £r- 1 Ol. 1 O •f *. * c 3 co ^ a. *"3 "s *? • 0 OO O «H H 1 CO ^* C3 IO QC ^~ 1 • .u n• • -. c 3 co — J U.TJ Si 00 1 1 IOI 1 O 1 10 i i 9 i • i i i i i O i i ' l l O .1 O 1 1-9OO9 i Or*. ( 1 1 IA 1 1 O 1 1 O < i o i i i i i i i eo i i ' 1 1 eg l r>s l i o O rnS "H *r> i • i . . C 1 1 .11 .11 . i i * i i i i i i i . i i i ll *i .(I • . . > Q£ I*- *H ^ CM r% «r tn 10 O O lACStrHCO O Ol 10 ifi m ot rH

rH rH O 1 -J •» ^^ Ot *O C 1 SI 1 1 1 Si i o i i go oo lOOOOlOOl IOI t —, i O999OOO i 99 3 IIII i lOi I O r-. ao ^ lOf^ooiesioi i o > t 2 i atoooooo i om « 1 1 1 1 at O •r g oun CMca OtnOCO rH O O ^ SO O O tfl f> <3 Q0| CM o m r» in *HJ ot coo CO rH IO rH p* CM rH Ot *** 1 • » ft ft k CM ft «T CM "T esi—*^- CM 10 O rH «£ O —1 3 n CO ^ ** "3 *^ ^ -o g 1 SI 1 1 1 §i o o ' i o * a F199001 19 i i o > 9 A 3 IIII i en o > i o i ot i loeoooi 101 i o i *n S CMOOOOO IO l O CM • 1 1 1 1 .1 ..II .1 .1 1 «...| | .11 .| .» 3 o com o m IOMOO9«^ P OCO 1 is rH ^P ^9 ** CM ^-O •»• **• S tn o ot co gp*. eg *o u — <*• o — "go 1 *^ ** ^ -3 1 1 1 1 1 1 o i i ca i i o i o i 100901 i O i i P i i« 109999 19 i O O 2 "i1 3 1 1 1 1 1 ' o " rH rH PS. IO CM « tn 1 • • «o ^* rH IO tn o t1* 9 >O O r-. o rH — 1 •H rH 0 "« ffl rH -3 o S O 1 •9 "5 ** vO * -.., I l 1! O« 1 1 1 1 »5» O 1 OO I 1 p p O O I Op 199 i O i99 2 O > t i i O i SSSS ! S3 1 ! 3 i S§ J!100 too i o i a o o- • >iiii 'os p mo gmcor- 90*90 *ro P r^to £ •W Q p IO O O IO 4- = * 1 t-» o o 10 in a eg o •** * •>•<&> ot co co 10 co co fu IE rnr— «» 10 O at ft * ft ft • KM —— ft ft 4 ft r— W i« tn »* ot «r -a r-4 tn m »»• <-? ^ rH eO CM rH • ^H rH rH a rH O 1 1 *i .it "^ ** "^ 3 •^ 1 i i i i i i 81 i O i 1 p 1 I I l p OO P I I P l I P I I o M 3 1 t 1 1 1 1 r— > i oi i o i i i iCPCMOOl IOI lOi t S ™* V°SSS9 O O O OS O 'I O9 lOO ' t2^ 1 1 1 1 1 • *it .11 * i i i i... 'ii.ii. ii, O at •*• Ot « at a — > LO o ot p co un o en CM r« CM >43 Ot I rH rH Ot Q rH Ot ITt • • * • » i ft ft « ft 1 fo CO ^O rH O ^p rH •I1 (M 1

_( J _J

* * ce S I?-,! 1 "o-S^."* — «-. tj — . CT-7 G1—. -*— . J^" ^ u GS'o 5* 8 ^,C..C7»-* "oiG^^i-*«— *J '5>'oiuJ*-i,'nt^ir-u-.gl^l ^—— S^" Qt Oti—X gV-1 r-1. -^_ 3 3 -— ^.J 3 O>-J -J Ol O> 3 3 CS^*— Ot EJt 3 -NS.*^. CSk^^Nt IJ|j^lL"llJ 1 Hr 1^. H^ ^ ^JI"H §*— i • — '——*-* 3 p» 3 3Xr»o>Ol 3 o> 3 — l en o> w— * •— 'JS C9 Cf <»*• 3*—--^« 0) 3 • 3 3-^. Or-^ V e-5 E p I JJIII^fl J~J ll -r-«3u*~ m —3- 'ifle- S**— —mi <—>-. (v' 3^ *o* oid o oC C5 S-2 is -r- >» • uoa& «C •3— "r u> c B9 oi^n 4c )a V>I —9 o3 s si. — .« ** yt fc I.-B— £2 o. vi fc— o ac o -MI— -a e CJ *• ftj ^5 -^ •*• C ^ 4 Cjt • • «e O O W a • fe ft fl—— O—— O-r- •£ QQ (j ^j pr» ^ ^ ^ A tt O O U tJ CU*-J- J £ J J X Ck t/! M M r^ » M 4-77 flR300!52

O h- r-e£l Oo\

act a. iiiti a-5

ju in •r——JB

4-78 SR300I53 J?

or-el (Jo* 3 ssssss isss ;s ; :§ss issss issg 0£ j» CM PS, Q O» O OOQ O CMCO1 Oi CM at PS, o»^s 10 eg i

909009190019 ' 1000100901990 OGOOCMOIOQOlO I lOOOimcSoOlOOrH «-fiO a? OOfr; ('J ^^ Ot I rH rH in PS. in m rH *H I

i i i 1009010091lOOotoioooi9o i i iooi P pi iloooiao i O 9 O i 9m O O

Ot S CM I I CM 3 1 I lOOiOO'OOOiO P—LniOOCMiAOOOWO « ctrHOmQovO o coot'^romtnooeocbooco ' at ps. 1ps,0 CMO COM ps.coOrHpmg O ii>CM n»IOO>m « CMmc" o *r o ^ <£ CM Ot CM «T-» CM' CO o co eg i

•. E *? 1 -9 §2229 a0.0.0.0. ' 2 522 ' 22°. ' '9' ' 22°. ££ 3 ...... iOQQceocMOoQio. c>•? en !i ...t o o

= O -» ^ -? O«5oei.....> o. '•icoioomioooioSc' ...i«..i ..o. «-? g O at O. ^ f^ 9 Y 9 9

w-e — ... m9 Xj | -1H0 PSPS., o p 10 ^OOC< o 9M o itn_ i S **" ?H § ^ o»>«*H * GOS X —«r HPS ^. eS ommco^§OCM ft * or -HO * O fSI TI -5 r- Csl-HrH " 5 i 2 * - - 3 5 i o •— SiSovoiooS'S 5 imiSoioaooSegoSo* 2 ** o >opiop ooo Q i m ps,oiomopo*'9(' 3 <0 O PSI . '

SrH PS,rHCM Ot r* rH

£5

ii u.-g f* O ^^ 3 PI 3~ Ql^ ^ ______

?sJ § <**** •""I*!?-— S'r-*"^"' I C*o''™'« l"""?-*- S*"*-P-**1 1 •C— —e •3-*. 9«.e « M M fcI .9 • 3 e• -Os •- e • S ST >— .• —•-»*-'t *«*M3n £—« B-T^.

4-79 <3 S-* CM OOv«!9 !l r-~

ca OOO t • a to O tn i sa — ... i p-

€3-s.

*3 •H ui t i < i i i 1 S rsO . li 1i li li liil | i I i I i l i I i l i i i i i i i sZM e*^ • lit i ii ( i i i t i i i i i i i

rH at (M r-j CM a,t "3 -3 i iiii i ii $99900 1 90090 l O O O IO99 1 0 i CM 3 iiii l ll O O O O (*• O 1 O OO OtO S i oato i r-OSssss i O i ee CM rH o m a CM o I CMCO« «*O 3 Ot rH M S2^W ^vt g IO rH IO CO Ps.ft^«H CM o * rsi CM rs, «r al m —i r0H* V eVg r*« ^in •>• FH in 1 « § • 9 i iiii i it 990000 19099 i t l OOO l i P l a o i o 3 i i t i i it o o o o m o i Sooo i i i OO..O. i i O• . ii . « i .ISS ac ot*r rs.aino o — o o moo 9 9*r o •n OCM ^f ^f tA CD U^ IO Cr^ c^ «• is ie ia eo CM Ol 1 1-2 ^n rH 9^ IO co to ^r c9 rHOt in ^ in ^p m ^™ 3 Ml • ft • « • * m » » 4^ 9 T^ eo m PS, CM"s rs CM r«» CM rs. A a ^^ * «-» SO i •3 -3 \ "s, 1119 i ' ii 9I9OO9 1 999 9 ' o<9 i99999 t l OO S tj.;? 1 1 1 IO 1 II O 1 O O rH O i OOOO i CEIL ssss i O in •r »* e at CM 100 *ro CM*•> ooco*r O §dO €% O § o * 00 rH 1^ Ps.C * So 1 rH rHOt 9 rH rH CM f-t ^ cSS"* O eo r** m 1 ft ft ft ft ft -^ • i** co mot lA •* IO O^ CM ! rH tn PS, r— tn-•e eov . i -,-, 4 "* i rH r— ** i i i hnm « •3 •J M *^ U S i i till • i H Op X* OQQOOO l 1 OO l 1 l 1 1 29 lilt *— l M OO <•> OOOOtOOissss : •38 f1 IOOt I 1 i 1 €§ ! S1 OCO ee O IOO O Sot o OCM r —— « 1 Ot —— lS -H is o rs. u *• r— -B B rH *»CM P*. IO kO «•• rH rH IT) IO I4> ft ft ft m m*o CM CM CM o 3 " —— rH rH rH 1 rH rH (.4 g 135 £• J -• S 2 1 -3 -3 -a i iiii p UL i i pi OOOO — o i 3 1 IIII 1 O*- II r— O 1 OOrHO issss : SS ! S: ss GO ee i m • 4. * * « rHCM « • * t i CM m IO rH rH rH rH 10 i""4«M i

rot —i s-. s* ^* SOr-o v "3 B— J M .!—*Ji"a t ^ * -.•.j** m -s» v i<— > 1 SGC1 ^^-^ ,-s — ^ Cj f "^.*Ss^S. __ j -J I ? s ut a 4^*3 ^J^1 ^ -J« ^"s^ 0> 0>-s, 04 S*^£ * gtto ?*^~' **s,-J 3 3 3—1 ^ 33—13 _i_i a 3 3 or>s.a s-ssrf^w. -s.^s.3 — P— • E >—— ^ s— 3 Ot 3 O»-J-j at— i ^^"s* 3 gi a*— a— i— i 9 •e&^jft* • • s_ as-. 3-s^ s^ 3 «-» 3 -^s-^..• * 3 f "Si * i^-*at X "— ' •"-» ot o3 ««— 3«3— ••* 3- flAl 3s- *— 3 !e w • I 33.*. • -r. "s— i* es in •«— S— • 3— *js-n-. u 1 3 g E a*— «* iui w^S^-p~ £§•*••'— a « • H)® 3-e? S*— ^-3 e, ftr-rj i M U— ^ c"2 &c "^ C 1 elf^S-5-i = aUQr- 2 HTUJ <<2oO-H j53<£ «rtr«g «c ««i < 3 5 § <3 -H -zalzo.Vt

0£ O

or>H CM

CM e i fCl .,1 £VI eo e « a *•» > — . fl a §22CD O °^ •g =»5 mi— 3 -a » p-— - e oe t2o5 a o >»- CQ s— CO a "3-3-3 at »•> in -— i OOC9 rH -B *J tfih- «» *< "c (— s— a i *w -^ 3 a > c 18 m fl ^5 CO a i •^"3 w e i l OO l eap1 U- • !"* {

u •"*! u- Je* 5 o a "o a m —a i t. I IOOl S3r- 1 I COO 1 4/1 *-*—

9 Ctt B C

1

I*— '•'—

Ifll <

The Round 2 sample results were not consistent with those of Round 1. Acetone was not detected in any RIW. Xylene was detected at a very low concentration (below Ipg/1) in RIW-7, which is located near the former sludge area. Several other volatiles (including chloroform and dibromochloromethane) were detected in trip and field blanks, although none of these compounds were detected in groundwater samples, suggesting a potential problem with trip blank and field blank source water.

Other Organic Compounds - Only one semivolatvle compound, Naphthalene, was detected at one location (RIW-4, located east of the Fly Ash Pile) in the sample collected in Round 2. Very low concentrations (below 0.01 //g/1) of the pesticides endosulfan II, heptachlor epoxide, gamma-chlordane, alpha chlordane, endosulfan sulfate, and 4-4 ODD were also detected in RIW-2, RIW-3, and RIW-12 in Round 1, and in RIW-6 and RIW-10 in Round 2. Only heptachlor epoxide was detected in the same well (RIW-3) in both rounds.

In summary, only very few organic compounds were detected at extremely low concentrations in site monitoring wells. Although these organic compounds are not naturally occurring and indicate some low level of groundwater contamination at the site, the detections reported are not consistent between the two sampling rounds, nor do they demonstrate a definitive spacial relationship to historic site disposal areas.

4.7.4.3 Inorganic Compounds . . .

The results of the TAL inorganic analyses for the groundwater samples from site monitoring wells are summarized for Round 1 and Round 2 in Table 4-18 and Table

4-82 flR300157 TCN 4208 RI REPORT REV. #1 09/JAN/92 4-19, respectively. Both a Total Metals plus cyanides and a Dissolved Metals analysis were performed at each site RIW.

Total metals values reported for any particular analyte were generally inconsistent from Round 1 as compared to Round 2. The presence of abundant particulates in the sampled ground water (as indicated by the high turbidity values) is believed to be the cause of the observed wide variation in total metal results from one sampling round to the other. The dissolved metals analysis is considered to be more representative of the actual groundwater chemistry than the total metals analysis, and exhibits more consistency in reported concentrations between sampling rounds for any particular analyte.

Comparison to "Background" __.. ,_.. , . ,_ ...... _. ,

Remedial Investigation Well RIW-1 was designated as the background groundwater quality location. Although the detection of one volatile organic compound and one semivolatile organic compound in the soil boring sample collected from 5 to 7 feet below grade (Table 4-12) causes the assignment of "background" to be questionable, RIW-1 represents the most upgradient site well location and is used as a basis for comparison to other site RIWs.

Dissolved metals appear to be distinctly elevated at the following locations as compared to "background" conditions at RIW-1. In both rounds of sampling, barium is elevated at RIW-12 and 13; calcium is elevated at RIW-11, 12, and 13; iron is elevated at all locations except RIW-11 and 6; magnesium is high at all locations except RIW-2, 3, 9, and 11; manganese is elevated at RIW-2, 3, 10, 12 and 13; and sodium is high at RIW-4, 6, 12, and 13.

Slightly elevated levels of aluminum and chromium were seen in both rounds at RIW-11, and of sodium at RIW-7. Slightly elevated levels of chromium were noted in Round 1 at RIW-12 and RIW-13, and of lead at RIW-9 (Round 1) and RIW-11 (Round 2).

Comparison to Local Published Values

4-83 flR300158 TCN 4203 RI REPORT REV. #1 09/JAW/92 Because groundwater chemistry at RIW-1 may not be indicative of background conditions, site ground water quality was compared against local published values. Two publications provide a limited reference for comparison to RIW chemical data: Roanoke County Groundwater (Breeding and Dawson, 1976) and Geohvdroloav of the Roanoke River Basin (Waller, 1976). The former contains minimum, maximum, and average concentrations for selected inorganics based upon an unspecified number of wells by aquifer system, and also contains water quality data from two "background" wells located at the Atlas Powder Company which are mapped as lying within the same hydrologic unit as the site RIWs (the clastic Mississippian/Devonian/Silurian Aquifer System). In Waller (1976), the number of wells used to describe the groundwater chemistry for each system is provided (e.g., 4 wells lie within the hydrologic unit containing the Dixie Caverns site), but the locations of the wells are not given. The DCL site is mapped as lying within the "Ordovician to Hississippian elastics" system by Waller (1976). The Waller (1976) local well data are included in this RI Report as Table 2-2 (background water quality) for reference.

Selected inorganics parameters provided in the published literature are compared against the site RIW data below.

Iron - Published iron values range from 90 to 300 pg/1 ? with an average ^alue of 270pg/l, and the Atlas wells each reported 300/*g/l (Breeding and Dawson, 1976). Waller (1976) reports iron ranges of 20 to 80pg/l, with an average of 30 jyg/1 and a "near a fault" value of 140//g/1. Dissolved iron values at the site were higher than published values, ranging from 113 pg/1 to 8,170pg/l.

Calcium - The published calcium values are 41,000 and 6,000 /jg/1 for the Atlas wells (Breeding and Dawson, 1976), and a range of from 36,000 to 61,000 jug/1 (average 52,000pg/l), with values near a fault given as 109,000pg/l (Waller, 1976). Dissolved calcium in site RIWs ranged from 2,700 to 121,000^/1, with RIW-11, 12, and 13 having values similar to the "near a fault" value and the remainder of the RIWs having values approximately equivalent to the published ranges for the clastic HDS hydrogeologic unit.

4-84 flR300i59 TCN 4208 RI REPORT REV. #1 09/JAN/92 Magnesium - The published magnesium values are 11,300 and 3,900pg/l in the Atlas wells (Breeding and Dawson, 1976), and a range of from 5,800 to 10,000 pg/1 (19,000 near a fault) (Waller, 1976). Dissolved magnesium in site RIWs ranged from 779 to 37,000 pg/1, with approximately half of the values exceeding the published ranges.

Manganese - The published manganese values are 10 to 150 pg/1 (average 70//g/l) and Atlas well values both are reported as 10 pg/1 (Breeding and Dawson, 1976). Site RIW dissolved values ranged from 2.7 to 1,780/yg/l, which generally exceed the published values.

Sodium plus Potassium - Atlas wells are reported to contain 4,300 and 6,300//g/l (Breeding and Dawson, 1976). Waller (1976) reported higher values of 2,200 to 10,000 pg/1 (14,000 near a fault). The sum of dissolved sodium plus potassium values for site RIWs ranged from 4,840 to 112,660 pg/1. The high sodium values for site RIWs causes the sum of sodium plus potassium to consistently exceed the published ranges.

Percent Ca+Mq versus Percent Na+ K - Waller (1976) reported percentages for Ca+Mg as compared to the percent Na+K for the Ordovician to Mississippian elastics hydrologic group. The percent Ca+Mg ranged from 86 to 97% (average 92%), while the percent Na+K ranged from 3 to 14% (average 8%). A calculation of these ratios for the dissolved metals values from site RIWs shows a much greater range in both values: the percent Ca+Mg ranges from 48 to 90% (average 66.3%), and the percent Na+K ranges from 52 to 10% (average 33.6%). As indicated above, both magnesium and sodium are present in site RIWs in greater concentrations than the published ranges.

Although published data on only a few selected inorganics are available, the comparison of site groundwater against selected published groundwater values supports the findings of the previous evaluation made using RIW-1 as the standard of reference for comparison of site RIW data. No published reference concentrations are available for inorganics such as arsenic, barium, or chromium in the clastic MDS hydrologic unit.

4-85 3R300I60 TCN 4208 RI REPORT REV. #1 09/JAH/92 Patterns In Monitoring Well Data: Relationship to Geologic Structure

Remedial Investigation Wells RIW-11, RIW-12, and RIW-13 consistently have among the highest dissolved (and total) reported concentrations of most inorganic analytes. The strike of a line connecting these wells is oriented generally perpendicular to geologic strike. Although situated in the same clastic hydrogeologic unit as the other monitoring wells, these locations may intercept joints or fracture zones orthogonal to the regional strike. Published data support the occurrence of elevated levels of inorganics in groundwater along fault zones as compared to locations not along faults (Waller, 1976).

A piper ternary diagram of dissolved concentrations of calcium, sodium, and magnesium was constructed as an attempt to identify any population groupings among site groundwater data. The reported concentrations of those three dissolved metals were normalized and plotted as a percentage of their sum. The resulting piper diagram (shown as Figure 4-8 in Section 4.7.6.3) illustrates two clusters; one cluster consists of wells RIW-6, 7, 8, 9, and 10, and the other cluster consists of RIW-1, 2* 3, 4, and 13. RIW-12 and RIW-13 lie near one another, but RIW-11 plots away from 12 and 13 as an outlier.

These apparent chemical groupings do not appear to be derived from major lithologic variations, because all RIW monitoring wells reportedly are completed in Devonian-age clastic formations. However, the groupings may be related to regional geologic structure. The east-southeast orientation of the local streams again suggest a structural control, such as joints or minor faulting orthogonal to regional strike. Wells RIW-1, 2, 3, and 4, which comprise one cluster, lie along this same orientation, as do wells RIW-6, 7, and 8, wells RIW-9 and 10, and wells RIW-12 and 13, which also each cluster. These wells may be interconnected to some degree along fractures or faults oriented orthogonal to regional strike. The possible influence of lithologic variations (e.g., bedding) within the Devonian clastic units has not been eliminated as a potential source of chemical groundwater variability, but such an influence would more likely be manifested in groupings of locations which parallel the strike of the beds rather than run perpendicular to it.

4-86 flR300!6 TCN 4208 RI REPORT REV. #1 09/JAN/92 Summary of Inorganic Evaluation

The ground water from site RIWs contains generally higher concentrations than the range of limited published values for iron, magnesium, manganese, and sodium. Calcium values generally correspond to published values except for RIW-11, RIW-12 and RIW-13, which are higher than the published values. Although reference concentrations are not available for several of the inorganics, these findings are generally similar to those of the comparison of the RIW data against RIW-1 concentrations.

The extent of inorganic contamination of the ground water at the DCL site associated with past disposal practices at DCL site is difficult to quantify because of the statistically small published reference population, the wide variability in RIW sample results, and the lack of upgradient background sample locations. Typically, concentrations of constituents in site RIWs which greatly exceed the published ranges would be interpreted to reflect groundwater contamination associated with the landfill. However, many of the highest reported concentrations of inorganic analytes were detected in RIW-11, which is only marginally, if at all, downgradient of a very small area of the southwestern tip of the DCL site. The apparent geochemical differences in the published concentrations of groundwater constituents for two adjacent Atlas Powder Company wells drilled in the same geologic unit only three months apart support the contention that some variability in water quality is naturally occurring. Finally, the geochemical patterns in the RlW'data suggest that wells lying in a northwest-southeast orientation perpendicular to- regional strike may be interconnected along joints and fractures.

4.7.5 Residential Well Sampling Results

Two residential well sampling events were performed for this study. In January, 1991 private well locations PW-1 through PW-16 were sampled. In July of 1991, PW-9 and PW-10 were resampled to verify the reported presence of contaminants, and two additional locations in the vicinity of PW-9 (PW-20 and PW-21 and field duplicate designated PW-22) were sampled. The field water quality parameters are summarized on Table 4-20, and analytical results for the two sampling events are

4-87 SR300I62 TCN 4208 RI REPORT REV. #1 Q9/JAN/92

TABLE 4 -HO FIELD PARAMETERS SUMMARY RESIDENTIAL WELLS DIXIE CAVERNS LANDFILL SITE

Temperature Conductivity <°C) pH (pmhos}

U*U w/FHter1 Well and/or Round 1 Round 2 Round 1 Round 2 Round 1 Round 2 Location Water Treatment 1/91 7/911/91 7/91 1/91 7/91 PW-1 H 15.7 7.5 157 py-2 U 16.2 7.0 190 PW-3 U 16.3 7.2 292 PW-4 N 13.5 7.9 248 PU-5 Y 15.7 7.5 357 PU-6 Y 14.5 7.6 333 PU-7 U 16.3 6.9 283 PU-8 U 16.0 6.8 328 PW-9 U 16.3 15,4 6.7 7.2 370 643 PU-10 Y 17.2 6.9 590 a,. 2 2 PU-11 H PW-1 2 U 15.5 7.5 303 - PU-13 U 14.7 6.7 493 PU-14 U 15.7 6.5 387 PV-15 u 16.0 7.0 322 PU-16 u 19.7 6.4 135 PU-20 u 17.9 7.0 943 PU-21/22 u 14,8 7.3 580

1 Y - Yw; H - So; U « Unknown 3 Mo measurements taken at this location. - Location not sampled during this round of residential well sampling.

4-88 SR300I63 _T J t-~+Cpem,oM* k£ -3 B•: oU£J L U= -»3 < ^ ^^ r— •-ac» OOf* 1 1 1 1 1 1 1 1 1 1 1 i O OO 1OOOOQ ) rH 1 II 1 1 1 1 1 1 1 ^3 CD CO 1 rH ^3 f^ ^3 O 1 1 1 1 1 1 1 1 1 2 CM O CM fO O rH O O -4 CM r*. \fltfi ft . • • CM r- f-.

1 1 —1 ^ 1 II 1 1 1 1 1 I S 1 II > 1 1 1 1 1 0 i 0 i • i 0 I I Q i 1 1 1 1 1 1 1 li•t 1< O • 1 1 1IO I.1 1 1 O• 11 2 •"TO O O 9 (^ O tCMn "O CM 1-3 • IIII i O O i i i OO O O O rH IIII loo i i i o tn o O <•"> 1 1 1 « 1 1 1 1 §9 O «e cno csi Q O r* Ps 10 IO ^ CM a >o eoo (A en in «n rH ^ rH £ 't*+ Ot 1 g CM rH A CM 'OOO l O O iQQO •£ rH i in i i . . i i rHom *2 ooo -i 2 tn C3 co ^9 tn to PH o. en CM a CM f. 0 CM 1 M in CM •- S 2 9 PM i i l 11 i i i i i i i O Q i OOO i OOO i ii i i i i i i |S i i i i i i i i < OO i OOO i Oom 2 39 ^ *^ S S *"* *S . - ^2 *^* CM rH «6 StC ^ CM 50 ^•*, <-> t^l CM am ' •ew 1 I 5"S u r-j i O " i i i i I ( O O ' O O O O * 1 If 1t Ol « 1 1I l1 11 11 l1 11 1 ^3 * CO C9 1 C3 *^ ^9 C3 1 Pn. 1 1 |*i U 2I . I CM • in in eo rH *"n *^ 1 1 *» •JJ4: 1 Or— ll O 1 l 1 OO U • • H- II -H .iii.. -JS 5 2 * 1 I u 2 & in CM rH CM O *M tn ll "3 H * 4 ft ft ft ft I*. ft* Ol rHin o 3r.- »> ••* -M2 eo

a rH i i •i i i it o* i a. o. i V) 2 • [ II ft. 1 , 1 t 1 I • r».g g *ro •ro o mca 1 r- rH CD tn to ^* 1 • * • 1 Cft CM rH 1 esi ^ 1 -7

a—- C7 Oa BI ^C^f "O^l fc— — .» 3—^ &• -J 3 •—— -J e l£l ^.^^1^S""*^ ^t j^^ 1 •— , ui Sa —-Jt *j 9 o^-^*x ^-e ec • U —i *N j. ^*>»S,gi'r» « S— *-7*-. '»*»''»--* ^5 ^? ?^ -o-^-7 ^^J"^,J 3 3 3«4 1? . — --> — '-S (."^ ** o 3 Bl 3 OIJ.Il Ot^ >— 3*— 3 •>*.->»• • » 3*^s ^^ ' £ ^C r^ TC 3? ^S •— •— » » 3 u» S'— e* e o £ L c u i i i •U— • •9 -.«—•—33*-*-r• M e M> •"3—' 1 ** .'S 2 T 5 5 3 2 «-r.'u S.C-Q S 5 •»—— U oO ^J4 ^iE *»0• ^ c3 ^oL - ^^t < •3 •9 M w r— a. p • ai c *J^ c -c CMX QUJ3; * ate» •CnUw^^iJXX^^Ifc A) M CJ1 W • V 4 O NO *r>

4-89 uj ^- -—- ^^q x S^. i—, t_H en Qg O a "* S OOO IOO i

2 Ste CM T) C3 flQ ^| ^^ m f^ O •»• CM CM* ua tn« eo —*ft IS — 1 00 *•>

g < OO 1 1 IOO r O Q 1 1 00 1 1 1 OtO IOO < 2 1 . . 1 1 l §<-• >• 1 o> o• l eo o eo P- CM >n* • ' ^ p^. CO S "*rt

o 1 O O 1 1 10 i OOOO 1 1 91 O 1 1 i o i n o o *r 2 <">-So ' ' 1 g ' «««g* CM 1^- 10 O

M IV 1 rH •a3 "g* • : sg; i IS! !§g ! 2 i to. g• i i 1 g.1 1 .o * o 1

i J s £ -CM *2 in •^ ^L d i o |? > i 1 iO CO l O O n o o ot eo 4* S •> • ed (^ CM-/ r- M O i ._ 3 CM "S * £ "m -J I . i ggg. rH i x o o o oo go | i OO i OO i 1 1 l in OOrnO OO 1 O • « « soio CM 1 r^ ft^ rH CSI 1 rH 1 •* rH 1 1

i.

5 9 u

tTC C" ^-7O I 1 r* i * -*.-!--;. u 0 f 3J fS < CT<3fi*-j' 1» *^» B*^1-..^! O 93 01— 1^ »'""^«O * 3 • • ^"^ w-e ^— M^—S• a 9 • •*• • w 3 i • 9 s-'— e • 9 M B M «•— CM 3 •— « """*» «*• M S"*" & 9 — o m M 5 -«—« ' -..»— U— ^.§.g S•«e> Pe Ee« jo* **- • e— eu -** •-*.- —u oie.w-s; ai «ia • —e o

4-90 flR300!65 uca ^ a

w ^ (M o ir> sf K» ru in OJ "o i 3 ^ fl) ^> t-l I— CD O

O. CM .1 o 4^ O CM CD OC 1 7 Is o. 0 t. cf-a» >O i CO

|| O

QJ O 2

U) 4-> y03 '—E Is -C - >l o L. 2

(rt

uCO

.c u

4'91 9R300I66 TCN 4203 RI REPORT REV. #1 09/JM/92 summarized in Table 4-21 and Table 4-22, respectively. A general discussion of the data follows.

4.7.5.1 Field Parameters

The results of the field water quality parameter'measurements (Table 4-20) show a relatively narrow range of values for pH, temperature, and conductivity. The only apparent anomaly was encountered at location PW-16, which exhibited the lowest pH, lowest conductivity, and highest temperature of all the wells measured. PW-16 is located at the Atlas Powder Company site immediately south of the DCL site, upstream of RIW-12 and RIW-11 along surface Stream A.

4.7.5.2 Organic Compounds

The results of the organic analyses of the groundwater from the residential wells are summarized in Table 4-21 (Round 1) and Table 4-22 (Round 2).

A total of el even organi c compound detecti ons were reported at very 1ow concentrations in samples collected from five residential wells in Round 1. Six of the detections had reported values of less than IO"2 pg/1, most of which were 0-qualified as not being accurate or precise. The volatile compound acetone was detected in PW-10 and in the field blank (PW-18) at concentrations of 13 and 22 pg/1 respectively, both of which, were L-qualified. (biased low). Well PW-10 additionally contained three low level detections of pesticides, all reported at concentrations of below IO"2 pg/1 (J). Two other pesticides'were reported at below IO"2 pg/1 (0) concentrations in wells PW-12 and PW-13. A single semivolatile compound, n-nitro-di-n-propylamine, was detected in PW-12 at a level of 5(J) pg/1. One other single semivolatile compound, bis(2-chloroethyl)ether, was detected in PW-9 at a level of 9.0 pg/1, while the duplicate of PW-09 (designated PW-17) contained a single semi-volatile compound, 2-2-oxybis(l- chloropropane) at 7(0) pg/1.

The detection of semi-volatile compounds in the two PW-9 samples motivated a second sampling round of residential wells in the vicinity of PW-9 in July 1991. 4-92 flR300!67 TCN 4208 RI REPORT REV. #1 09/JAH/92 As indicated in Table 4-22, no above detection limit levels of semi-volatile compounds were observed in the second sampling round.

4.7.5.3 Inorganics

Results of the inorganic groundwater analyses for the residential well locations are summarized in Table 4-21 (Round 1) and Table 4-22 (Round 2).

A wide range of total metals values was reported for the ground water collected from the residential wells. In all private wells except for PW-14 and PW-15, calcium and magnesium were the primary inorganic constituents, which is typical of groundwater in carbonate bedrock. Total calcium was low at PW-16 (18,100 ug/1) and very low at PW-14 (850J ug/1); for all other locations, it ranged from 29,800J to 119,OOOJ ug/1. Total magnesium was also low at those same locations, reported as 6,960 and 350 ug/1, respectively. The inorganic present in the greatest concentration in PW-14 and PW-15 was sodium. Total sodium was extremely high at PW-14 (152,000 ug/1) and PW-15 (76,500 ug/1); at all other locations it ranged from 1,120 to 10,000 ug/1.

The distribution of the more variable constituents detected in the residential wells is discussed below.

Arsenic - Total arsenic was detected only in PW-14 at 4.5 pg/1, qualified as biased low.

Barium - In the first round of sampling, total b'arium was detected in all residential wells except PW-14, at reported concentrations ranging from 31.9 (PW- 7) to 388 (PW-10) pg/1. In the second residential well sampling round, barium levels were found to be slightly higher in PW-10 (468 pg/1).

Copper - Total copper was detected only in PW-2, 3, 9, 10, 12, and 15. Reported concentrations ranged from 28.7 to 85.1 pg/1.

Iron - Total iron was detected only in wells PW-9 (and PW-9 dup), 10, and 11 at reported concentrations of 672 (565), 4,220, and 166 pg/1, respectively.

4-93 flR300J68 TCN 4208 RI REPORT REV. *1 09/J/W92 Legd - Total lead was detected in five wells; PW-9, 10, 11, 12, and 15. The detected concentrations ranged from 3.0 to 26.0pg/l, with the two highest values qualified as biased high. The residential well with the highest lead level in the first round of sampling (26 pg/L at PW-10) was one of four neighboring wells resampled. Of the four closely spaced residential wells sampled in the second round, only PW-10 contained elevated lead levels (16pg/L).

Manganese - Total manganese was detected in ten of the sixteen residential wells. The maximum reported value of 239 ug/1 occurred at PW-10; elsewhere, reported concentrations ranged from 2.1 (PW-3) to 17.1 (PW-16) pg/1. Total manganese was not detected in PW-1, 6, 7, 11, 12, and 14.

Zinc - Total zinc was detected in eight of the sixteen residential wells: PW-4, 5, 7, 10, 11, 12, 13, and 16. It ranged in concentration from 34.5 J (PW-11) to 536 0 (PW-10) pg/1. Total zinc was reported at 10.1 pg/1 in the field blank.

Comparison of Inorganics in Residential Wells to local Published Data

The table below summarizes the comparison of residential wells sampled for this RI to the available published data for wells in the Cambrian-Ordovlcian carbonate unit.

METAL CARBONATE CARBONATES- CARBONATE PRIVATE WELLS CONCENTRATION COMPOSITION NEAR A FAULT COMPOSITION (Tetra Tech, 1991; Cw/D (Waller, 1976; (Waller, 1976; (Breeding and 17 samples) 17 samples} 8 samples) Dawson, 1976)

IRON 0-180 0-1,500 10-1.400 166-4,220 CALCIUM 23,000-62,000 54,000-137,000 _ 850-119,000 MAGNESIUM 8,500-29,000 22,000-54,000 - 350-45,600 SQOIUH-r POTASSIUM 0-7,900 0-7,600 - 1.774-154,460

The range of concentration values for these four metals in residential wells generally coincides with published ranges for wells located near a fault. Two very high sodium values skew the sodium + potassium range, however most reported sodium concentrations lie within the published ranges. Similarly, one unusually

4-94 flR30Qj69 TCN 4208 RI REPORT REV. #1 Q9/JAN/92 high iron concentration was observed, with the remainder reported as below 700

Percent Ca. pi us Mq versus Percent Na plus K - Waller (1976) reported percentages for Ca+Mg as compared to the percent Na+K for the hydrologic grouping of Cambrian to Ordovician Carbonates. The published %Ca+Mg ranged from 92% to 100% (average 97%), while the %Na+K ranged from 0 to 8% (average 3%). To compare the private wells sampled for this investigation to the published data, these same ratios were calculated for the residential wells (omitting the anomalous data points at PW-14, PW-15, and PW-16). The results show a slightly greater range in both values: the %Ca+Mg ranges from 90% to 98% (average 94.5%), and the %Na+K ranges from 3% to 10% (average 5.5%). This degree of agreement between the sampled residential wells and published local values indicates that the primary constituents of the ground water in the sampled private wells are chemically similar to those of background wells that are not impacted by the DCL site.

Patterns 1n Inorganics Data from Residential Wells

An analysis of the distribution of reported chemical data among the residential wells reveals no trend or pattern regarding organic compounds, however several anomalies regarding inorganics, namely at PW-14, PW-15, and PW-16, are apparent. PW-14 and PW-15 appear to lie within a different surface water divide from the other private wells along the west end of Kelley Drive (Figure 4-7). The anomalous chemical data reported for PW-16 are attributed to the geologic setting of the well in the Devonian clastic unit rather than in the Cambrian carbonate as are the other private wells. Compared to the site RIWs, also situated in the clastic unit, the groundwater from well PW-16 contained relatively high levels of magnesium and zinc, relatively low (for silicate rock) levels of sodium and potassium, and no reported total aluminum.

A ternary piper diagram was constructed using the total metal values of calcium, sodium, and magnesium to compare the groundwater from the private wells to that from DCL site monitoring wells (Figure 4-8). The reported concentrations were normalized and plotted as a percentage of the sum of the three cation concentrations. The piper diagram illustrates the close clustering of nearly all

4-95 flR3QOI70 oc I

=O»B oOc a<. I-UJH X J-H >- I-l U. 3S(J

o _

3 3 ai a u 5 * «2o o lo !S *-. vX^fb ;^,r _^ )i |£| a S B:

4-96 /I TCN 4208 RI REPORT * '-:->M REV. #1 , ,, ' 09/JAN/92 .1 PW locations with regard to these major cation concentrations, indicating geochemical homogeneity in the concentrations of these groundwater constituents, Well PW-10 is an outlier because of the very high calcium values reported for that location, while PW-14 and PW-15 are outliers near the high sodium corner of the piper diagram.

4.7.6 General Chemistry Comparison - Residential PW Well Data vs. Site Monitoring RIW Well Data

4.7.6.1. Field Parameters

A plot of the field parameters measured at the monitoring wells and the residential wells is shown on Figure 4-8. Clusters of data points are formed by each of the two well types, identifying two distinct groundwater populations in the two different aquifer systems. The ternary piper plot of the cation concentrations similarly identifies the two hydrologic groupings.

4.7.6.2 Organic Compounds

Very few organic were detected in either the private wells or the site RIWs at extremely low concentrations. The only volatile organic, acetone, was detected in one private well, one private well field blank, four site RIWs, and one RIW trip blank. The lack of a consistent pattern suggests some degree of laboratory cross-contamination as indicated by the detects in the QA/QC samples. Of the few, low levels of semivolatiles and pesticides detected in the PW residential wells, only heptachlor epoxide and gamma chlordane were detected in the on-site RIW monitoring wells. It should be noted that none of the pesticides or semivolatiles found in the residential wells were detected 1n the soils, surface water, or sediment at the DCL site. These data suggest that the organic compounds detected in the residential wells have not originated from the DCL site.

4-97 SR300I72 TOt 4208 RI REPORT REV. #1 09/JAN/92 4.7.6.3 Inorganic Compounds

With regard to inorganics, the comparison between data from residential private wells and that from site RIW monitoring well data is more complex. The total i norgani c concentrati ons detected i n residenti al we!1s cannot be di rectly compared against those detected in monitoring wells because of the high turbidity of the groundwater in the monitoring wells, which are largely screened in shale formations. The occurrence of particulates causes the total inorganics analysis to be biased high as compared to the actual inorganic concentrations in the ground water itself. Accordingly, the total inorganics data collected from the residential wells have been compared to the dissolved inorganics data collected from the site monitoring wells to assess the actual groundwater chemistry and the presence of site contaminants in the residential wells.

The following trends were noted in the reported inorganic concentrations. The on-s1te RIW wells generally contain proportionally higher amounts of aluminum, potassium, sodium, arsenic, chromium, cobalt, iron, and manganese. The residential wells generally contain proportionally higher amounts of calcium and magnesium. The two populations have roughly equivalent proportions of barium, copper, lead, and zinc.

The general population trends are a direct reflection of the hydrogeologic setting of the two well groupings. The site RIW monitoring wells situated in the Devonian Chemung and Brallier Formations (consisting of interbedded marine sandstone, siltstones, and shales) show greater proportions of aluminosilicate metals, those expected to weather from clastic units. All of the residential wells except PW-16 are situated in the Cambrian Elbrook Formation (which consists of a thin-to-medium bedded dolomite with some limestone and shale) which would be expected to weather to leach greater amounts of carbonate minerals enriched in calcium and magnesium.

The comparison of site RIW data to those from RIW-1 and to published selected local inorganic reference concentrations indicate that RIW-11, 12, and 13 are chemically anomalous. Attempts to identify site-wide or localized groundwater contamination arising from past disposal practices has resulted in the

4-98 8R3QQi73 TCN 4208 RI REPORT REV. #1 09/JAN/92 recognition of widely distributed elevated levels of iron, magnesium, and manganese, and selected locations with elevated sodium, arsenic, and perhaps chromium, and dispersed detections of very low concentrations of a few organic compounds (largely pesticides) at the DCL site.

These constituents are not found in elevated concentrations in the groundwater from the residential wells. Barium levels in the residential wells have not been detected in on-site RIWs, thus the DCL site is not indicated to be the source of the barium in the private wells. Further, both regional and site-specific groundwater flow direction data, supported by topographic data, indicate that the majority of residential wells along Meacham, Road (PW-9 through PW-15) are not hydrologically connected to the DCL site.

Further discussion of groundwater contaminant fate and transport is presented in Section 5.0.

4-99 3R3QOI71* ... TCN 4204 RI REPORT REV. #1 09/JAN/92 5.0 CONTAMINANT FATE AND TRANSPORT

In this section of the report, the goals are to:

• Characterize the contaminants present at the Dixie Caverns Landfill (DCL) site and describe the particular fate processes that are applicable to the contaminants. • Describe the potential routes of migration and attempt to quantify the transport of these contaminants.

5.1 CONTAMINANT FATE

5.1.1 Fate Processes

The migration and transport of any organic or inorganic contaminant can be affected by numerous fate processes. The dominant processes are partitioning, speciation, transformation, and bioaccumulation.

Partitioning processes Include dissolution/precipitation, volatilization, and sorption. Properties of the contaminant that may be associated with partitioning include its density, solubility, the octanol water coefficient, and vapor pressure. Properties of the medium (in which the contaminant is present) that may affect its partitioning include soil type, porosity, pH, geologic setting, grain size, and moisture content.

Speciation processes Include acid-base^^quilibria and organic and inorganic complexation. These processes may be affected by the acid or base equilibrium constant, (pk^/pl^) and the pH of the medium.

Transformation processes include biodegradation, photolysis, hydrolysis, and reduction-oxidation. The chemical parameters of importance 1n these processes include the light absorption coefficient, and the hydrolysis rate constant. Environmental factors include the temperature, oxygen content, size of bacteria population, amount of sunlight, and pH.

5-1

- flR300(75 TCN 4204 RI REPORT REV. #1 09/JAN/92 Bioaccumulation refers to the processes of either the passive Intake of contaminants through such means of absorption, or the uptake of contaminants through consumption of contaminated food sources.

5.1.2 Identification of Contaminants

Over 170 samples were collected in this investigation to determine the nature (and extent) of the organic and inorganic contaminants associated with the DCL site. Samples were collected from surface and subsurface soils, surface water and sediments in streams and seeps, and groundwater on-site and in the vicinity of the site.

It Is possible to identify classes of contaminants located at the DCL site and to use the classifications to assess the fate and transport mechanisms applicable to the site. (Contaminants within the same classification share the same basic behavior patterns in the environment.) Classes of contaminants encountered at the site are described below. A full description of all chemicals of concern detected at the DCL site follows in Section 6.1.2.8.

The primary class of contaminants Identified in the groundwater in the vicinity of the DCL site is inorganics. Among the metals detected in groundwater collected in on-site wells were arsenic, manganese, and antimony. Although the extent to which these metals originate from natural sources is unquantified, for the assessment of fate/transport processes it is as'sumed that all metals originate from wastes disposed of"at the DCL site. Herein, the fate/transport of inorganic metals will be evaluated as group.

Three classes of contaminants have been identified 1n surface and subsurface soils and in sediments. These classes are Inorganics, organic polycycllc aromatic hydrocarbons (PAHs), and organic phthalate esters. Specific inorganic metals of concern are silver, lead, zinc, and cadmium. Because these metals behave 1n similar fashion 1n the environment, fate/transport mechanisms will be evaluated collectively for the metals class of contaminants.

5-2

ftR3QQI76 L

TCN 4204 RI REPORT REV. #1 09/JAN/92 A range of PAH and phthalate contaminants were detected at the DCL site. Because organic PAHs and phthalate compounds behave in a similar manner, a prevalent PAH, benzo(a) pyrene, will be used to assess the fate/transport of these contaminant classes. ..__._.._——^— ..-••.... -

5.1.2.1 Characterization of PAHs and Phthalate Esters using Benzo(a)pyrene

Partitioning - The octanol water coefficient of benzo(a)pyrene is 1 x IO6, indicating a high tendency to sorb to sediment or soil particles. The sorption of benzo(a)pyrene onto soil and sediments is an important fate process.

The solubility of benzo(a)pyrene is 0.0038 mg/1 in water. This indicates why benzo(a)pyrene is not generally present in surface water or groundwater.

The vapor pressure of benzo(a)pyrene is 5 x IO"9 torr. Volatilization of this compound is not an important fate process.

Transformation - As__a group, polycyclic aromatic hydrocarbons and phthalate esters are not amenable to hydrolysis; therefore hydrolysis is not an important fate process (Callahan and others, 1979).

Photolysis of dissolved benzo (a) pyrene may be rapid in the solar spectral region with a half life of only several hours (Smith and others, 1978). However, the rate of photolysis of benzo(a) pyrene may be highly restricted when benzo (a) pyrene is sorbed onto sediments.

Oxidation appears only to be an important fate process if chlorine and ozone are present in the environment as oxidizing agents; these reagents do not appear to be found at above normal levels at the DCL site.

Biodegradation of PAHs with 4 or more carbon rings does not appear to be a rapid process. It may however, be the ultimate fate for PAHs and 1s therefore considered an important fate process (Callahan and others, 1979).

5-3 AR3QQI77 TCN 4204 RI REPORT REV. #1 09/JAN/92 Bloaccumulatlon - Bio-uptake of PAHs by multicellular organisms does apparently take place. However, the PAHs are metabolized and excreted and therefore, bioaccumulation 1s not considered an important fate process (Callahan and others, 1979).

5.1.2.2 Characterization of Inorganic Metals

Metals are generally unreactive and are not subject to fate processes such as volatilization, photolysis, biodegradation and speciation. They may be best treated as a "conservative" contaminant. The dominant fate processes important for metals are the dilution and advective transport of dissolved metals in water, and the transport of metals sorbed onto sediment. Bioaccumulation may also be an important fate process for some metals, such as mercury, but it is not an Important process for the metals encountered at the DCL site.

5.1.3 Fate/Transport Processes Relevant to Site Contaminants

Based on field investigation results, fate/transport processes should be considered for organic PAH and phthalate contaminant classes and the inorganic (metals) contaminant class. Accordingly, processes associated with Benzo(a)pyrene and the inorganic metals group will be assessed.

Benzo (a) pyrene and similar PAHs are known to favor sorption to soil and sediment. PAHs are susceptible to biodegradation, however this fate is not considered to be a significant process because it results 1n no net reduction in contaminant concentration. Inorganic contaminants (metals) are conservative in nature, and the Important fate processes controlling their distribution are dilution and advective transport in groundwater and surface water, and sediment transport.

5.2 POTENTIAL ROUTES OF CONTAMINANT MIGRATION

To evaluate routes of contaminant migration, it must assumed that all contaminants of concern present in various media on and adjacent to the DCL site were introduced as a result of disposal practices at the landfill. This 1s a 5-4 flR300!78 •"*•••-,, TCN 4ZQ4 '- RI REPORT REV. n 09/JAN/92 conservative assumption given the fact that a number of the contaminants found at the site occur naturally in soils, surface water, and ground water.

In general, the semi-volatile contaminants detected at the DCL site have relatively low mobility in groundwater. However, extremely low levels of organic and various levels of Inorganic contaminants were found in monitoring wells installed on-site. A limited potential exists for the transport of contaminants downgradient. Advective transport by groundwater will be evaluated below with an emphasis on concentrations of inorganics.

PAHs, phthalate esters, and metals are present in the soil covering and, at some locations, just beneath the landfill surface. Because of their strong tendency to sorb to soil, these compounds are unlikely to leach into the groundwater. However, erosion of soils/sediments with sorbed contaminants is a potential pathway for migration. Currently, approximately 34% percent of the landfill has little or no soil covering due to recent efforts to remediate historic waste disposal areas. This increases the potential for erosion and overland transport of soils from the steeply sloped site into intermittent streams.

Prior to County efforts to remediate historic waste areas at the DCL site, surface water and soils were free to move from the site into Intermittent streams. In the late 1980s, Roanoke County installed a number of detention ponds designed to intercept natural drainage and collect eroded soils. Some eroded material is treated by the County through Its leachate collection system. However, sediment which migrated off-site into intermittent streams prior to the County efforts to limit erosion and sediment movement are free to continue to move away from the site. Based on field investigation activities, these sediments contain contaminants and sediment erosion constitutes a plausible transportation mechanism for contaminants.

5.3 CONTAMINANT TRANSPORT

To understand the ultimate fate of contaminants associated with the DCL site, the physical setting of the site must be defined. To summarize information presented in previous sections: "5-5

flR300!79 TCN 4204 RI REPORT REV. #1 09/JAN/92 * Significant remedial actions on the part of the County have removed visible contaminants from two of the four known waste areas - the drum disposal area and sludge disposal pond. In addition, the County has installed a drainage system which currently collects for treatment the leachate originating from the solid waste area. In addition, the County has installed a small detention pond on-site below the fly ash pile which appears to collect fly ash material eroded from the fly ash pile. • The surface topography slopes steeply to the southeast. Surface water drainage follows topography, such that most surface water flows to the southeast. • In general, there is a thin layer of well drained soil (0-2 feet) covering fractured bedrock. The fractured bedrock consists of interbedded sandstone, si 1tstone, and shale. Recovered NX Cores indicate that fracturing occurs In all lithologic units. • The horizontal groundwater flow direction in the bedrock aquifer is generally to the southeast, mimicking surface water flow direction. Groundwater flow in the bedrock appears to be primarily controlled by structural rather than stratigraphic characteristics.

5.3.1 Groundwater and Surface Advective Transport of Dissolved Contaminants

Section 4.7.3 presents calculations from slug test data which suggest groundwater moves through the DCL site at an average rate of approximately 0.66 ft/day. However, the range of calculated groundwater flow rates in the vicinity of the RIW locations varied between 0.03 and 19.3 ft/day. Accordingly, the potential rate of migration 1n the downgradient direction is difficult to quantify without complex numerical models.

Typically, major groundwater contaminants are diluted and sorbed with increased distance from a source. This suggests the levels of dissolved metals should decrease with distance from the DCL site. It is possible to use a simple dilution model to estimate the reduction of dissolved metals between the site and the nearest downgradient residential wells. The area of the DCL site used in disposal activities constitutes approximately 1 percent of the combined southern and northern drainage areas in which the site is located (20 of 2000 acres). Accordingly, by way of a simple ratio of contributing areas, the approximate level of dissolved metals in groundwater at the nearest residential wells should be approximately 1% of those observed on site. While this approach neglects

5-6

flRSOOiSO ...... TCN 4204 RI REPORT REV. #1 09/JAN/92 naturally occurring levels of dissolved metals it strongly suggests extensive dilution of any site related contaminants.

A review of groundwater monitoring data seems to indicate a high level of dilution occurs. For example, levels of four metals commonly found in site RIWs (aluminum, arsenic, chromium, and manganese) are either undetectable or two orders of magnitude lower 1n residential wells near the confluence of Streams A and E (PW-1 through PW-6). Of course, more than dilution influences the concentration of these metals. Natural geochemical changes also occur as groundwater moves from the clastic into carbonate geohydrologic unit.

5.3.2 Erosion of Sorbed Contaminants from Waste Areas

The Universal Soil Loss Equation (USLE) is useful for estimating the quantity of soil/sediment likely to erode. The USLE equation was developed from more than 40 years of data collected from small plots located in many states (Schwab, 1981). Despite its simplification of the many variables Involved, the USLE is the most widely accepted method for estimating sediment loss (Equation 1).

Equation 1. A=R*K*LS*C*P where A = average annual soil loss in tons/acre, R - rainfall and runoff erosivity Index by geographic location, K = soil-credibility factor, which is the average soil loss per unit of erosion index for a particular soil in cultivated continuous fallow with an arbitrarily selected slope length 1 of 22 m (73 ft) and slope steepness S, of 9 percent, LS = topographic factor, C = cropping management factor, which is the ratio of soil loss for gi ven condi t1 ons to sol 1 1 oss from cul ti vated continuous fallow, and P - conservation practice factor, which is the ratio of soil loss for a given practice to that for up and down slope fanning.

5-7

flRSOOIS TCN 4204 RI REPORT REV. #1 09/JAN/92 To estimate the level of erosion possible from currently exposed zones on the DCL site the following parameter values were selected: R « 150 based on rainfall and erosion characteristics for the region K s 0.27 based on a predominately gravelly silt loam and gravelly clay loam soil classification. Factor used is for sandy loam with 0.5% organic matter. LS = 2.4 based on a flow length of 600 feet and an average slope of 8% in exposed area. C » 1.0 little surface coyer exists so this value most duplicates actual field conditions P - 1.0 because there are no soil conservation practices currently in place to stabilize soils.

Using the parameter values given above, the annual eroded soil from the USLE is,

A = (150) (2.4) (0.27) (1.0) (1.0) = 97 tons/acre

As a reference value, the Soil Conservation Service recommends that soil erosion levels from agricultural areas should be less than 5 tons/year. Ninety-seven (97) tons per acre equals an annual loss of 0.5 inches of soil per unit area of surface. This suggests that a very large quantity of sediment will be moved from Its original location over the solid waste fill zone and be deposited in swales and in the stormwater collection system below the exposed area.

The USLE erosion estimate can be used to estimate the amount of PAHs which can be eroded from the surface of the solid waste fill area. Specifically, surface soils 1n the SWD-2 zone contain the only significant levels of PAHs in the surface sol 1 samples col1ected at the DCL site. The SWD-2 area covers approximately 5 acres and the total PAH level detected in a composite surface soil sample was 9,920 ug/kg. Assuming a uniform distribution of PAHs in the SWD- 2 area, the amount of PAHs moved from SWD-2 1s approximately 1.9 Ibs/year.

5-8 flR300!82 TCN 4204 RI REPORT REV. ^l 09/JAN/92 5.3.3 Sediment Transport of Sorbed Contaminants Currently 1n Intermittent Streams

Contaminant migration via transport of sediments in intermittent streams will predominantly depend on the average grain size of the sediments and average stream flow velocities. The Hjulstrom diagram (Figure 5-1; Blatt and others, 1980) can be applied to evaluate whether sediment is being eroded, transported, or deposited under a certain flow condition.

The greatest concentration of contaminated sediment is located in the northern drainage path just downstream of the fly ash pile. Stream velocities in the affected area were estimated to range from 1.2 fps at Station SE-1 to 2.3 fps at Station SB-6 (See Appendix C) during spring or high water conditions. Of the sediment samples collected, sample SB-7 was found to contain the highest fraction of fly ash: approximately 60% by weight based on a comparison of zinc concentrations. Accordingly, this sample was used to assess the transport of fly ash material currently found off-site. The median diameter (D50) of the SB-7 sediment sample was found to be that of a large sand grain - between 2.0 and 0.85 mm in diameter (Appendix B). Figure 5-1 illustrates probable sediment behavior between Station SB-6 and SE-1 for this range of grain sizes under the range of flow velocities measured. It appears that the SB-7 sediment is likely to erode under the flows measured under high flow conditions. This conclusion is supported fay the results of the field investigation, as illustrated 1n Figures 5-2 and 5-3, which show movement of sediment downstream away from the site. (Note, these figures will be discussed in detail in the next subsection below).

It should be noted that the goal of the sediment sampling effort was to obtain fine grain sediment to facilitate laboratory analysis, i.e., larger than gravel- size stone was present in the stream but was avoided during sampling. Based on field observations (Appendix C), a significant portion of the stream bed in Stream B and E consists of cobble and boulder (between 20 and 65%). These larger particle sizes integrate to armor the stream bottom and limit bed erosion. The sand-size sediment sampled in Stream B and E will erode, but at a lesser rate than 1f the stream consisted of only sand-size sediment.

5-9 flR30Qi83 TCN 4206 RI REPORT REV. #1 09/JAN/

Zone of Sediment Behavior between Stations SB-6 and SE-1 Note: EROSION , , , ,n . 30 cm/sec -Ifps

TRANSPORTATION

SEDIMENTATION

SILT SAND PARTICLE DIAMETER, mm

-•L. TETRA TECH, INC. T* FIGURE 5-1 ^ RELATIONSHIP BETWEEN STREAM M VELOCITY, PARTICLE SIZE, AND V REGIMES OF EROSION, TRANSPORT, SOURCE: BUTT AND OTHERS, 1980 AND DEPOSITION ——— _ ——— _ — ...... —————————————————— 5-10 flR300i8l* en o o: LhU- UJ r-H

LU OO HH O< Zo Lau UI U. HH Z =a) i-i—t «Jc —CO spuesnoifx oo Q in o 10 o >o

5-11 flR3TOOT85 S UJ P OLU 00 LL. LL<. oZ aQe (S^/Stu) juauiipag ur C£ PS § 00 t-t a oo spuesnoqx IS a z z: oo z o ce: »o CO _J < O UJ >0 I LU > IT) r»- h- 3B < LU Z O O LU —1 LU —J I CC E Li. LU 2 Q t—I r-l U) < O X X IS r—; LU LU O •—i U_ _1 OO -J Q

5"12 3R300I86 TCN 4204 RI REPORT REV. #1 09/JAN/92 Field investigation efforts suggest a plume or slug of sediments with high metal concentrations is slowly moving away from the site in Stream E. Based on laboratory analysis of sediment samples, the slug has not reached the Roanoke River. Sampling along Stream E suggests the front of this slug is somewhere between 800 and 1600 feet upstream of the confluence of Streams E and G. Based on current information, the slug front has moved downstream between 100 and 200 feet per year, assuming movement started when the waste disposal ceased in 1976.

5.3.4 Transport of Contaminants Dissolved in Surface Streams

As discussed in Section 5.3.3, fly ash has become incorporated with natural sediment in Streams B and E. The heavy metals found in the fly ash are very slightly soluble in water, and dissolution of metals into stream water can occur. It is possible to estimate the magnitude of metals partitioning using the results of chemical analysis of water and sediment samples collected concurrently in the affected streams. For this effort, the lead concentration (total for sediment and dissolved for aqueous samples) is used as an indicator of the heavy metal class of contamination.

Figures 5-2 and 5-3 illustrate the results from two rounds of stream water sampling (high and low water conditions) and one round of sediment sampling. These figures clearly demonstrate a correlation between water column and sediment lead levels. Prior to discussing details, two general observations are worth noting. First, surface water lead concentrations (dissolved) exceed the proposed EPA Action Level (15 ug/1) only at locations with the highest sediment concentrations (above 17,000 mg/kg). One exception to this observation does exist; an apparent outlier value occurs in Station SB-1 high flow data. Secondly, given the data in hand, the relatively moderate variation in stream water pH do not seem to significantly affect the movement of lead from sediment to the water column.

The movement of lead from the source (the sediment) to the sink (the water column) can be demonstrated using a ratio. During high flow conditions (when most sediment transport occurs) the ratio of water column lead to sediment lead is relatively low, ranging between 1:1,500 to 1:2,000 (i_g/L to mg/kg) in the most 5-13

flR300!87 TCN 4204 RI REPORT REV. #1 09/JAN/92 contaminated stream sections. Under low flow conditions this ratio increases, and ranges from 1:3,300 to 1:12,000, i.e., the dissolution of lead decreases. For both flow conditions, the highest potential for lead to move into the water column (a ratio of 1:300) was observed in a detention pond containing standing water and obvious fly ash contamination (SB-5). Although the detention pond produced the lowest ratio the actual dissolved levels of lead in the water column remains below the proposed EPA action level (15 jig/L).

Little is known about the sorption of heavy metals in Stream B and E; sorption from the water column and onto natural sediment. As illustrated in Figures 5-2 and 5-3, the lead concentration in the water column is known to decrease in the downstream direction. It is reasonable to assume that both dilution and sorption processes are responsible for this reduction. The dissolved lead levels in Stream F (SF-1) were found to be at background concentrations.

5-14 4R300I88 6.0 BASELINE RISK ASSESSMENT

The draft baseline risk assessment report for the Dixie Caverns Landfill (DCL) site quantifies potehtTal human heaTth risks and environmental impacts associated with the site. The RI baseline risk assessment determines whether contaminants at the DCL site pose a current or future risk to human health and the environment under the no-action alternative (i.e., in the absence of remediation of the site). According to the NCP (USEPA 1990), the baseline risk assessment ",..provides a basis for determining whether remedial action is necessary and the justification for=performing remedial actions." This baseline risk assessment was prepared i n keepi ng wi th avai1able Federal EPA guidance for conducting Superfund risk assessments, including Risk Assessment Guidance for Superfund (USEPA 1990, 19893,5,0). In addition, the baseline risk assessment was prepared using EPA Region Ill-specific guidance (USEPA 1991a).

The baseline "risk assessment consists of two assessments: human health evaluation and ecological evaluation. The evaluation of the potential carcinogenic human health risks and noncarcinogenic hazards from exposure to contaminants released from the site is presented in Section 6.1. The evaluation of the potential terrestrial and aquatic ecological impacts due to contaminant releases from the site is presented in Section 6.2.

flR30QI89 TCN 4208 RI REPORT REV ffl 9/JAN/92

. Section 6.1

HUMAN HEALTH EVALUATION

AR3GOI9Q TCN 4208 RI REPORT REV #1 9/JAN/9 2 6.1.1 Introduction .to the Human Health Evaluation

The human health evaluation for the DCL site quantifies potential human health risks associated with the site. The human health risk assessment process consists of four basic steps which form the basis of this report,

STEP 1. Selection of Chemicals of Potential Concern. (Section 6.1.2) Monitoring data collected as part of the Remedial Investigation (RI) are analyzed and chemicals of potential concern are selected. Of the compounds detected at the site, chemicals of potential concern are selected based on an evaluation of risk factors (which quantify the relative percent contribution of each chemical to the overall risk), frequency of detection, low toxicity to humans (i.e., essential human nutrients), and background concentrations. Selected chemicals of potential concern are evaluated further in the report.

STEP 2. Exposure Assessment. (Section 6.1.3) Exposure pathways are identified based on an evaluation of the environmental setting of the site and the environmental fate and transport of chemicals of potential concern. Exposure pathways are selected for both current and future land-uses of the site. Exposure point concentrations and exposures are estimated for each chemical of potential concern for the exposure pathways quantitatively evaluated ,in this report.

STEP 3. Toxicitv Assessment. (Secti on 6\1.4) Toxi city cri teri a for assessing carcinogenic risks and noncarcinogenic hazards for the selected chemicals of potential concern are presented and evaluated.

STEP 4. Risk Characterization. (Section 6..1.5) The exposure estimates presented in Section 5.1.3 and the toxicity criteria presented in Section 6.1.4 are combined to estimate potential carcinogenic risks and noncarcinogenic hazards for the exposure pathways quantitatively

6-3 ftR3QOI9l TCN 4208 RI REPORT REV 9\ 9/JAN/92 evaluated in this report. These risks characterize the potential human health impact associated with the DCL site.

In addition, the uncertainties associated with the human health risk assessment process and the conclusions of the report are presented in Section 6.1.6 and Section 6.1.7, respectively.

6-4

flR300!92 TCN RI REPORT REV AM 9/JAN/9 2

6.1.2 Selection of-Chemicals of .-Potential Concern

This section selects chemicals of potential concern to be evaluated further in the human health risk assessment for the DCL site. Chemicals of potential concern were selected for groundwater sampled from monitoring wells and nearby residential wells, surface and subsurface soils at the landfill, and surface water and sediment from groundwater seeps and streams in the vicinity of the DCL site. The methods used' to analyze monitoring data and select chemicals of potential concern for the DCL site are presented in Section 6.1.2.1 and Section 6.1.2.2, respectively. Chemicals selected for groundwater monitoring wells, residential wells, soils, surface water, and sediment are presented in Sections 6.1.2.3, 6.1.2.4, 6.1.2.5, 6.1.2.6, and 6.1.2.7, respectively. A summary of chemicals selected for all media is presented in Section 6.1.2.8.

6.1.2.1 Methods for Evaluating and Analyzing Data

The RI monitoring data were analyzed using several screening procedures in order to derive a database suitable for risk assessment purposes (USEPA 1989a). Differences between the data presented in Section 6 and other portions of the RI are reflective of the modifications in the database which must be made in order to perform the human health risk assessment. Factors considered when evaluating the RI monitoring data included possible blank contamination, data validation procedures and usability codes, elevated detection limits, combined data from field duplicate samples, and the summation of chemical mixtures. The screening procedures used to analyze RI monitoring data collected for the DCL site are discussed below.

• For the DCL site, both total and dissolved inorganic monitoring data were available for evaluating groundwater and surface water quality. All monitoring well samples appeared silty; therefore, dissolved (i.e., fi 1 tered) moni toring data were used in this report. 6-5 flR300i93 TCN 4.208 RI REPORT REV *1 9/JAN/9 2 Residential well samples were relatively clearl "therefore, total (i.e., unfiltered) monitoring data were used in this report to evaluate potential exposure. With respect to surface water data, the primary exposure route of concern was dermal absorption of chemicals dissolved in water. Therefore, surface water dissolved concentrations were used in this report.

• Pursuant to USEPA (1989a), common laboratory contaminants (i.e., acetone, 2-butanone, methylene chloride, certain phthalate esters, and toluene) detected in on-site samples that were within ten times the highest concentration detected in associated laboratory, field or trip blanks had been flagged as unreliable with a "B" qualifier by the data validator and were not included in the analysis. Likewise, "uncommon" laboratory contaminants (i.e., those organic contami nants not 1i sted above and any i norgan i c contami nants) detected in on-s,1te samples that were within five times the highest concentration detected in laboratory, field or trip blanks had been flagged by the data validator and were not included in the analysis (USEPA 1989a).

• Monitoring data qualified with an "R" (unreliable or rejected) by the data validator based on quality control problems due to the sample matrix or on poor laboratory performance were deleted from the RI monitoring database.

• Sample Quantitation Limits (SQLs) that exceeded two times the maximum detected concentration of a compound in a particular medium were not Included when estimating mean concentrations for the site, but were counted when estimating the frequency of detection. For example, if a compound was not detected in one sample and the SQL was 100 ug/L and the maximum detected concentration at the site was

6-6

flR300i9U TCN 4208 RI REPORT REV KI 9/JAN/92 10 ug/L, then the SQL was not included when calculating various statistics since the high SQL would bias the results.

• One-half the reported SQL was used as the sample concentration for monitoring data qualified with a "U," "UJ," or "UL" (i.e., a non- detect).

• Compounds which were never detected in a given medium were deleted from the RI monitoring database.

• Laboratory variance tends to be normally distributed; therefore, the arithmetic mean was used to combine the results from field duplicate samples. If a compound not detected in one sample was detected in the duplicate sample, then the compound was considered to be detected in the combined data point for the purpose of calculating frequency of detection. One-half of the SQL was used when determining the average concentration in the duplicate analyses.

• Toxicity criteria were not available for all carcinogenic PAHs detected at the DCL site. The total concentration of carcinogenic PAHs for each sample was calculated using a weighted sum by applying toxicity equivalency factors (TEFs) (Clement 1988). TEFs quantify the cancer potency'of carcinogenic PAHs relative to benzo(a)pyrene. For eacli sample, TEFs were multiplied by the chemical concentration . . and then summed to derive the concentration of benzo(a)pyrene (equivalent). Available TEFs for carcinogenic PAHs are presented in Table 6-1.

6-7 flR300i95 6-1 RtUttvt Toxicity Equival«ncy Factors (TSFs) OtMvtd for Carcinogtntc PAHs (a)

Carcinogenic PAH TEF

Anthanthr«n* 0.3tQ (b) 3«nza(i}pyr«rit l.fl atnzo(tjpyr«n« O.OC4 (bj Stnzo ( 4 ) anthrtctnt 0.145 (c) Stnjo { b ) f luaranthcnt 0.140 (b) S«PJ:O( j J f 1 uortntfwnt 0.061 (d) 8t nzo [ It J f 1 uortnth«n« — 0.066 (b) Itnzotg.h. t)p«ryl«n« 0.022 (b) Chrystn« 0.0044 (t) Cyc1o5tnt*di*no(c,dJpyr«Ti« 0.023 (d) Oibtnz(i,h)»nthricin« i.ll (•) Ind«no [1,2,2-c.dJ pyr«n« 0.232 (bj Pyr«nt 0.081 (f)

{«) Adopted froa ICF - Clmnt (1988). (b) Otutsch-VMztl *t *1. (19S3). (c) Singhw and F«lk (1969). (d) Htbs tt ai, (1980). (i) Wyndcr and Hcffmann (1959). (f) Wl*lodci «t *1. (1986).

6-8 AR300I96 TCN 4208 RI REPORT REV #1 9/JAN/9 2 • Various summary statistics were calculated for each compound detected in a given medium, including frequency of detection, geometric means, and range of detected concentrations (minimum and maximum values). Most chemical distributions in nature tend to be log-normally distributed, with the exception of abundant metals such as aluminum and iron (Connor and Shacklette 1975, Dean 1981, Esmen and Hammad 1977, and Ott 1988). Theoretically, the geometric mean represents the median (i.e., 50th percentile) of the chemical distribution. Other statistics from the chemical distribution were used to estimate exposure point concentrations for the purpose of estimating exposure. The methods used to estimate these statistics (e.g., the 95th upper confidence limit on the arithmetic mean) are presented in Section 6.1..3-.2.

6.1.2.2 Methods for Selecting Chemicals of Potential Concern

A subset of the compounds detected at the site was selected as chemicals of potential concern for further evaluation in this report. Generally, chemicals of potential concern "are selected based on a comparison with background concentrations; risk factors which quantify the relative percent contribution of each chemical to the total risk; low human toxicity (i.e., essential human nutrients); and, to some extent, frequency of detection. In addition, organic tentatively identified compounds (TICs) were not evaluated as chemicals of potential concern since both their qualitative and quantitative identifications are highly uncertain. However, available monitoring data on TICs were evaluated qualitatively'in this report. In order to be conservative, compounds appearing to be elevated above background levels that are not essential human nutrients, but do not have available toxicity criteria, were selected as chemicals of potenti al concern. The uncertai nty associ ated wi th the i nabi1i ty to 6-9

AR300I97 TCN 4208 RI REPORT REV #1 9/JAN/92 quantitatively evaluate these compounds in the risk assessment will be discussed in the sections to follow.

The methods used to select chemicals of potential concern for the DCL site are discussed below.

• Background Comparison. Comparing chemical concentrations detected at the site with background concentrations is important in order to properly delineate whether certain compounds are associated with site activities or from natural background. The presence of certain inorganic compounds detected at the site may be due to natural background, while certain organic compounds such as PAHs may be due to anthropogenic activities (e.g., incomplete combustion of alkanes in automobiles may form PAHs) or natural background.

For groundwater, one monitoring well (RIW-1) was thought to be located upgradient from the site and was intended for use to assess background concentrations in groundwater for the monitoring and residential wells. The sampling team had reason to believe, however, that this well"might actually have been affected by site activities. To. be conservative, the analytical results from this well were not used for comparison. Because of this, there are no site-specific groundwater background data, and sample data will be evaluated based on the other criteria described below.

For soil, surface soil samples B-l, B-2, and B-3, which are located upgradient of the known disposal areas at the site, were used to determine background concentrations in soil. Cochran's approximation to the Behrans-Fisher Student t-test using an alpha level of 0.05 was used to statistically compare site-specific background chemical concentrations with on-site surface soil and subsurface soil chemical concentrations.

6-10

fiR3GQI98 TCN 4208 RI REPORT REV *1 9/JAW92 For surface water and sediment, Stations SA-1, S8-1, SD-1, and SG-1, which are located -along intermittent streams in locations considered to be unaffected by the landfill, were used to determine background concentrations. Samples collected from these streams were used to assess site-specific background for evaluating potential contamination of surface water and sediment from runoff and/or seeps in the vicinity of the DCL site. The statistical test previously mentioned was used to perform the .statistical comparison with background.

Risk Factors. Of_those__contaminants considered to be elevated above background, only those which may significantly contribute to carcinogenic risk and noncarcinogenic hazards were selected for further evaluation in this report. Contaminants which would significantly contribute to estimated risk were identified by calculating the percent contribution of these compounds to the total carcinogenic risk and noncarcinogenic hazard (USEPA 1989a). Contaminants which contributed greater than 1 percent of the total carcinogenic risk or noncarcinogenic hazard were selected as chemicals of potential concern. This method can be used for any exposure pathway, since the same exposure parameters would be applied to all compounds.1 As previously discussed, detected compounds without available toxicity criteria were selected as chemicals of potential concern in order to be conservative.

Slope factors and reference doses (RfDs) used to calculate risk factors were obtained from the Integrated Risk Information System (IRIS) (USEPA 1991b) and the Heal'th Effects Assessment Summary Tables (HEAST) (USEPA 1991c). These sources are discussed further in Section 6..1.4 of this report.

The only exception to this rule is when the exposure estimate is dependent on the physicochemical properties of each chemical (e.g., dermal absorption). 6-11 flR300I99 TCN 4208 RI REPORT REV (M 9 /JAN/9 2 The percent contribution to total carcinogenic risk for each' detected compound was calculated using the following equation:

EPC± * SF, n -* 100 S EPC, * J=l

where:

%CCRj - Percent contribution to carcinogenic risk for compound^ EPCj - Exposure Point Concentration for compound,, (see Section 6.1.3.3 for discussion of the derivation of exposure point concentrations); and SFj « Slope Factor for compoundj.

The denominator of the equation sums the risk scores (i.e., exposure point concentration for compoundj multiplied by the slope factor for compoundj) for all compounds with available toxicity criteria.

The percent contribution to noncarcinogenic risk for each detected compound was calculated using the following equation:

* 100 n S BPCi/RfDi J=l

6-12 flR300200 TCN 4208 RI REPORT REV f 1 9/JAN/92 where: %CNR| = Percent contribution to noncarcinogenic risk for compound^

= Exposure Point Concentration for compoundj (see Section 6.1.3.3 for discussion of the derivation of exposure point concentrations); and = Reference Dose for compoundj.

The denominator of the equation sums the noncarcinogenic risk scores (i.e., exposure point concentration for compoundj divided by the RfD for compoundj) for all compounds with available toxicity criteria.

• As recommended in USEPA (1989a), organic TICs (tentatively identified compounds) were not 'selected as chemicals of potential concern for quantitative evaluation, but were evaluated qualitatively in this report.

• Inorganic compounds considered to be essential human macronutrients (i.e., calcium, iron,, magnesium, potassium, and sodium) have low toxicity to humans and thus were not selected as chemi cals of potenti al concern. Since micronutrient inorganics such as cobalt, copper, manganese, and zinc have slightly higher toxicity than do the macronutrient compounds, they were evaluated in a similar manner to other compounds detected at the site.

Chemicals of potential concern were selected for groundwater monitoring wells, residential wells, surface soils, subsurface soils '(soil boring samples), and surface water and sediment from nearby groundwater seeps and streams and are presented in the following sections.

6-13

fiR3Q02QI TCN 4208 RI REPORT

9/JAN/92 6.1.2.3 Groundwater Monitoring Wells

Table 6-2 presents the compounds detected in the groundwater monitoring wells at the DCL site. Chemicals of potential concern identified in Table 6-2 were selected based on the criteria presented in Section 6.1.2.2, with the exception of the comparison to background since no site-specific data were available. Groundwater samples were collected from twelve monitoring wells at the site (see Figure 3-5 for monitoring wells locations). However, one of the monitoring wells, RIW-11, was not evaluated because of problems associated with the installation of the well . Seven of these monitoring wells are located within the boundaries of the landfill and five are located in the area south of the landfill. Since the groundwater samples were silty, much higher levels of many of the inorganics were found in the unfiltered samples than in the filtered samples. Table 6-2 presents the results of the filtered samples, since the samples were rather silty. Groundwater samples were collected from monitoring wells during two rounds of sampling, which were approximately one month apart. For the purpose of selecting chemicals of potential concern, the two sampling rounds .were combined by averaging the two data sets by sample location and compound.

The geological formations in the area of the DCL are such that would allow infiltration from the surface of either direct precipitation or runoff. Shallow groundwater in the site region moves along bedding and fracture and solution channels from recharge areas to discharge areas at springs and along stream valleys. Natural groundwater recharge is rapid because of the thin soil mantel. Precise groundwater conditions under the entire site are not known; however, based on the elevation of a spring which is now contained in one of the retention ponds, groundwater may be present at depths of less than 75 feet under the high ground at the site. In this region, groundwater flow is typically southeast toward the Roanoke River; however, groundwater can also move along the formation strikes, parallel to the mountain chains, as well as down toward the Roanoke River. 6-14 flR3002Q2 Table 6-2 Summary of Chemicals Detected in Groundwater at the Dixie Cavern*' Landfill Site

Concentration Data (Units: ug/L) SF Risk RfD Risk Hunan Frequency of Minimua Geometric Max i nun Compound Factor (a) Factor Cb) Hutrient (c) Detection (d) Detected Mean Detected

Organics: - —- Acetone -- <1X Ho 4/4 8.0 13.0 20.0 ganma-Chlordane (total.) <1X <1X No 1/11 .0012 .00053 .0012 4,4'-DOO <1X <1X HO 1/11 .0015 .0096 .0015 Endosulfan Sulfate -- -- Ho 1/11 .0013 NC .0013 Heptachlor Epoxide <1X <1X Ho 1/11 .0014 NC .0014 •naphthalene -- 1.!X Ho 1/11 2.8 2.4 2.3 Xylenes

NC Not calculated • Chemicals of Potential Concern Mo toxicity criteria (a) Percent contribution of carcinogenic ritic bated on the expoturt point concentration and the slop* factor (see text for further discussion). (b) Percent contribution of noncarcinogenic ri»k based on the exposure point concentration and the RfO (see text for further di SCUM ion). (c) Compound is an essential human nutrient. (d) The number of detected concentrations divided by the number of samples. 6-is /JR300203 TCN" 4203 RI REPORT REV *1 9/JAN/92

Few organic compounds were detected in the monitoring wells in the vicinity of the DCL site. Acetone was detected in only four wells at levels significantly above laboratory or field blank contamination. Chlordane, 4,4'-DDD, endosulfan sulfate, heptachlor epoxide, naphthalene, and xylenes (total) were each detected in only one well at very low levels. All of the organic chemicals with available toxicity criteria detected In monitoring wells had risk factors below 1 percent with the exception of naphthalene. Naphthalene, which was detected in RIW-4 southeast of the fly ash pile, was the only organic compound selected as a chemical of potential concern.

All of the inorganic compounds with risk factors in excess of 1 percent were selected as chemicals of potential concern, since no groundwater background data were available. It is uncertain whether levels of antimony, arsenic, barium, chromium, cobalt, manganese, and silver can be attributed to site-related activities or natural background. Lead was detected at less than 5 ug/L (dissolved concentration), which is lower than the current Action Level of 15 ug/L. When comparing filtered and unfiltered levels, the marjority of the lead appeared to be bound to silt in the groundwater samples (the maximum concentration of lead in unfiltered samples was 60 ug/1 found in RIW-4, during round 2). Virtually all of the carcinogenic risk (>99%) was due to arsenic, which was found in wells sunk near the fly ash pile and between the solid waste disposal area and Twine Hollow Road to the south. The wells to the south of the solid waste disposal area, RIW-9 and RIW-12, contained the highest levels of antimony, barium, and chromium. The highest levels of cobalt and manganese were found near the drum disposal area and fly ash pile. Organic TICs detected in the groundwater at the DCL site are presented in Table 6-3. These include several alcohols and phenols.

6-16 Table 6-3 Tentatively Identified Compounds (TICs) Detected in Groundwiter at the Oixia Caverns Landfill Site

TIC Range of Concentrations (ug/L) Alkylpcntanediol 3 Ch loromethy Igentano 1 SO 2.3-Qichloro-2-methylbutane 22-42

Dimethyl ester of sulfurfc acid 2 bis (I,l-01ir»thy1tthy1)phsflol 21 2,4-bis(l.l-OimethylJphenol 18-19 Unknown 1-290 Unknown alcohol 540-830

6-17

AR30Q205 TCN 4208 RI REPORT REV tft 9/JAN/9 2 6.1.2.4 Private Residential Wells

As part of the remedial investigation, groundwater samples were collected from 18 private residential wells in the vicinity of the DCL site (see Figure 3-6 for private wells locations). Compounds detected in these residential wells are presented in Table 6-4. Chemicals of potential concern identified in Table 6-4 were selected based on criteria presented in Section 6.1.2.2, with the exception of comparison to background since no site-specific data were available. The samples were taken as close to the residential well-head as possible, but before any in-line filters or treatment. The results from total metals analysis were used to determine chemicals of potential concern since the samples where relatively clear.

Nine of the residential wells (i.e., PW-9 through PW-15, PW-2Q, PW-21) lie to the south/southwest and are totally hydrogeologically isolated from the site. Organic chemicals were detected in four of these residential wells including PW- 9, PW-10, PW-12, and PW-13. The organic chemicals detected in these residential wells which include acetone, bis(2-chloroethylJether, gamma-chlordane, dieldrin, endrin aldehyde, alpha-BHC, gamma-BHC, and heptachlor epoxide. None of these chemicals were detected at the DCL site, which further indicates that the site is not the source of these chemicals. Arsenic (4.5 ug/L), which is a known human carcinogen, and elevated levels of lead (16-26 ug/L) also were detected in residential wells PW-14 and PW-10, resepectively. None of the chemicals detected in these wells were selected as chemicals of potential concern, since these wells are totally hydrogeologically isolated from the site and the organic chemicals detected in these wells were not detected at the site. It should be noted, however, that the potential risks associated with use of groundwater from certain residential wells may be of concern. Specifically, the potential carcinogenic risks associated with use of groundwater (i.e., ingestion and bathing) from PW-9 and PW-14 were estimated to be approximately 2xlO"4, which slightly exceeds the upper-bound of the NCP acceptable risk range (i.e., IO"4). However, the chemical

6-18 flR300206 Table 6-4 Summary "ofChemicals. Detected in Private Wells Sampled in the Vicinity of the Dixie Caverns Landfill Site

Detected Detected Concentrat ion Concentrat ion Private We! Is (PW)/Chemical "~(ug/lj" "" Private Wells (PW) /Chemical (ug/L)

PW-I PW-9 (a)(b) • Sariun -" - - U7.00 Organics: Ci ICJUITI 29800.00' bls(2r"ChTor.oe.thy1)ether 8.00 ' Maones ium -— --— • • 12500.00 3otassiurr • - - - - 554 _QO. Inorganics: s Odium ------_•• - —— 1780. OQ Barium 274.00 • i jnc------——— ' ' - : . __1 "2U'.50 Calcium 83550.00 Copper 60.40 'PW-2 - - : — .-• - . .:-••-----•--•:- -.._.. Iron 619.00 • Barium. ." 151.00 Lead 3.60 Calcium : " .4J70OO" Magnesium 36500.00 Copper .- - • - - . ...«, :::^8_70 Manganese 7.10 Magnesium ... -.__._, .. -_,_-_. ± --14800.00 Potassium 854.00 » Manganese . „...-...-...... ;. --"ZTBQ Sodium 1140.00 Potassium • 1040.00 Sodium 2430.00 PW-10 (a)(b) • Zinc: - . ._ ..::. -~~ .._.._ ... .___20.40 Organics: Acetone 13.00 PW-3 . -": .'. ..^..__ Oieldrin 0.002 • Barium - - 46.20 gamma -8HC 0.002 Calcium ----_..------68300,00 gamma-Chlordane 0.002 Copper ... __ ...... B5:1Q Magnesium ... . ._...._.____ - , 28500.. 00 Inorganics: • Manganese .2.10. • Barium 468.00 Potass ium , ...... ;,_ 2460:00 Calcium 87500.00 Sodium ...... 4400.00 Copper 40.90 • Zinc . ...„.._. -• :M.::"1S.30 ' Iron 4220.00 Lead 26.00 PW-4 Magnesium 9140.00 • Barium ••-.-..-:—- . -- - --" 68710 Manganese 239.00 Ca Ic ium ...... 55lOO;00 Potassium 1090.00 Magnes ium - - ——— 1S6QQ.QO Si Iver 33.00 • Manganese ....:_^. ____:j..__.__ ---.--4.20 Sodium 5110.00 Potassium --'-'-— -' "^—^1760.00 Zinc 536.00 Sodium . .: -:• -•-:.._...... -5610.00 • L mc.= _ -.;. -:.--—- :. • :-:•• 159.00 PW-11 (a) ...... _.._. .-„.. . .. ——— ._ Barium 84.00 PW-5 " " Calcium 73200.00 * Barium - - .- "•" r"82770 Iron 166.00 Calcium 73500.66 Lead 3.00 Magnesium . . .- 31700.00 Magnesium 33600.00 • Manganese 5,30 Potassium 883.00 Potassium 1770.00 Sodium 2650.00 Sodium . ..-._-.. - -loooo.oo Zinc 34.50 * Zinc .." .. .::.._ ------—-——-:- gg^Q PW-12 (a) PW-5 . . . — . _ ...... Organics: • Barium ^T7OO = Heptachlor Epoxide 0.003 Ca.1ci.um ••••--• "69300.00 alpha-8HC 0.002 Ma g n es i urn ...... -_36700.QO Potassium " """ •" 1590. 00_ Inorganics: Sodium - 29,10:00 Barium 51.80 Calcium 57900.00 PW-/ - ~"~ ------' ----- Copper 35.80 • Bar-ium - - 31.9Lead0 4.00 Ca Icium ..-- - 54200.00 .Magnesium 23200.00 Magnesium . ._. ...._. _ -19700,00 Potassium 850.00 • Nickel 8 .i JnU Sodium 2230.00 Potassium -- - 1630.00 Z.inc • 73.10 Sodium • "- -' 3070.00 • Zinc : : . -=-::_..,- :.. - .7..,_56.40 rPU-l W~1*^J fx^a \f Organics: PW-8 Endrin Aldehyde 0.004 • Barium .'.._. 283 . 00 Calcium...... _. : .. :.__. •_- 78500.00 Inorganics: Magnes ium .. ._._ .... _.__._., -,. 35100_OQ Barium 208.00 • Manganese 3.60 Calcium 119000.00 Potass ium "- Tn430.00 Magnesium 45600.00 Sodium 3770.00 Manganese 16.50 Potassium 879.00 Sodium 5060.00 Zinc ————— ^^_ , 62.30 6-19 48300207 Table 6-4 (cont.) Summary of Chemicals Detected in Private Wells Sampled in the Vicinity of the Dixie Caverns Landfill Site

Detected Concentration ff'waia Ufetls [JWChemical (ug/l) Private Wells (PW)/Chemical

PW-14 U) PW-16 Arsenic 4.50 * Barium Calcium 850.00 Calcium Hagnes lure 350.00 Magnesium Sodium 152000.00 • Manganese Zinc 17.60 Potassium , Sodium PW-15 (a) • Zinc 84 r luta 142.00 Calcium 26200,0.0 PW-20 (a)(c) Copper 32 . 80" Barium Leao 3,10 Chromium Magnesium 14700.00 Lead Manganese 11.30 Silver Potassium 1530.00 Sodium 75500.00 PW-21 (a)(c) Zinc 41.20 Barium Chromium Silver

• Chemical of Potential Concern (a) Residential wells are not hydrogeologically connected to site groundwater (see text for further discussion). Therefore, the chemicals detected In these wells (i.e.. PW-9 through PW-15, PW-20, PW-21) were not selected as chemicals of potential concern. . (b) A second round of well sampling was performed at these locations. Results indicate below detection levels of bis(2-chloroethyl)ether m PU-9. and total lead levels of 16 ug/L of lead in PW-10. In addition, silver in PW-10 was detected only during the second round of sampling' in July of 1991. (c) PV-20 and PW-21 were sampled only in the second round of data collection in July of 1991.

6-20 flR300208 TCN 4208 R! REPORT REV *1 9/JAN/92 of concern found in PW-9, bis(2-chloroethyl)ether,"was not detected during the second round of sampl ing "TrorrPthis well. In addition, the chemical of concern found in PW-14, arsenic, was detected at a concentration 10 times below the current MCL of 50 ug/L. The low detected concentrations of pesticides found in PW-10 and PW-12 resulted in carcino"genTc risks "of TxlO'6, which equals the NCP point-of-departure. In addition, the level of lead in PW-10 (Round 1: 26 ug/L, Round 2: 16 ug/L) exceeds the current Action Level of 15 ug/L.

No organic chemicals were detected.in the other 9 residential wells sampled which 1 ie to the southeast. Barium, manganese, nickel, and zinc were the only chemicals of potential concern selected for these residential wells. It is unlikely that these chemicals are linked to the site given the distance from these wells to the site and" the general low mobility of inorganics in groundwater. However, to. be conservative, these chemicals were selected as chemicals of potential concern, since background levels' of inorganics in the region were not ayailable.for these chemicals and.these wells are downgradient of the site. .._-..

No organic TICs were identified in the residential wells near the DCL site.

6.1.2.5 Soils at the DCL Site

Surfac.e.-_£QTTs. Table 6-5 presents the compounds detected in the surface soil at the DCL site. Chemicals of potential concern identified in Table 6-5 were selected based on the criteria presented in Section 6.1.2.2. Thirteen surface soil samples were collected including five in the solid waste disposal area; five around the perimeter of the fly .ash pile within the boundaries of the DCL site;

6-21

36300209 Tab It 5-5 iarmary af Chemicals Qtttcttd m Surfact Soi 4t tnt Qixi« Cav«rns Landfill Sitt

Conctntrat'on Data (Qrgamcj: ug/kg. Inorganics: SF RUk HfQ Risk Human Within Frtquency o? *1nimu» (Jtonxtnc :=

Ac*ton« —

NC Nat c«lcul*ttd • ChMtcaU of PottntUl Concarn No toxicity critirl* (a) Ptrctnt contribution af carefnogwlc rick bas«d on th* txposun point eoncwitratlon tnd tha slept factor (at* ttxt for further diicutsion). (b) ?irctnt contribution of noocirelnoatnle risk band on th* txposurt point conccntntlon and th* ftfC (st* ttxt for furthtr discuss ion). (c) Compound Is tn tsstfltUl huwn nutrient. (tj) Th* nufiotr of d*tact*d conctrt rat lexis dlvictod by th* nuvb«r of unplts. (t) Th* chtMicil was not d*t*et*d in background i*»?1«s; thirafar*. th* ch*«lcal was consioarwd to b* abovt background. (f) No • raxinji on-iitt MS grutar than 2 tliaas th* maxlnui In background (not tnough lanplts to pcrfern a t-t«st) Yts • mixiflui on-sit* wa« Itss than 2 t1**s th* maxiaui \n background (not tnough uapl*s to p*rform a t-t»t). (g) No • Qn-iitt concantratlon significantly graatar than background baitd on rasult* of t t-tast. Yts • On-sit* canctntritJon is not significantly grtattr than background basad on rtsults of a t-ttst. (h) 3«nzo(a}pyrtn* (tquivaltnt} rtprcscnts th* »*igntad >ut of th* concentrations of th* carcinogenic PAHs listtd abov* using 6-22 flR3002lO TCN 4208 RI REPORT REV 31 9AJAN/92 and three located topographically upgradient of the 1andfi11 to serve as background samples (see Figure 3-3 for surface soil sampling locations). Since the samples adjacent to the fly ash pile were intended to assess potential dispersion of wind-blown dust, these samples were analyzed only for TAL inorganics. Only five of the on-site surface soil samples (those taken at the solid waste fill area) were analyzed for TCL organics.

The detected organic compounds were found at SWD-2 toward the western side of the solid waste "..disposal" area. Carcinogenic PAHs (i.e., benzo(a)pyrene [equivalents]), acenaphthene, dibenzofuran, and phenanthrene were selected as chemicals of potential concern for the surface soil samples. Carcinogenic PAHs were the primary organic chemicals of potential concern in surface soil (carcinogenic risk factor of 39 %).

Inorganic compounds selected as chemicals of potential concern included arsenic, barium, beryllium, cadmium, cobalt, manganese, nickel, and zinc. Arsenic appeared to be the primary chemical of potential concern. The concentrations of arsenic, beryllium, and'cobalt were greater near the solid waste disposal area, while the levels of the remaining metals were higher near the fly ash pile. The maximum detected concentration of lead was below the soil cleanup criterion of 500 mg/kg (USEPA 1989d); therefore, lead was not selected as a chemical of potential concern. This indicates that wind-dispersion from the fly ash pile is not a significant route of transport (as compared to. surface water runoff). It should be noted, however, that elevated levels of several inorganic compounds were found in the fly ash pile. Lead and zinc comprise the largest fraction of the fly ash, 4.5 and 21 percent, respectively. The fly ash pile, however, was considered a separate operable unit and thus was not within the scope of this baseline risk assessment.

Organic TICs detected in the surface soil samples from the solid waste disposal area at the DCL site are presented in Table 6-6. These include numerous hydrocarbons, carboxylic acids, and acid derivatives.

6-23 /5R3002N Tablt 6-6 T«ntativ«ly Identified Compoundi (TICs) Dvttctid in Surfact Sail at th* Qixi« Cav«rns Landfill Site

Rangt of Concentrations TIC (ug/kg) Aliphatic hydrocarbons 140-74,000 Alkyl substituted compound 140-300 Carbaxylic acid methyl tsttr 400 4-Heptadecane 180 Hexadtcane 140-320 Htxadecanoic Acid 180-17.000 Hydrocarbons 150-5.400 4-Hydroxy-*-(ntthyl-2-pentanone 4.100-19.000 Long chain compounds 2.100-4.400 Kcnadecane 210 Octadecane 130 Ptntadecanolc acid 5,700 Phenanthrenc derivative 960 Phthalate 240-730 Flntne derivative 36 Proptnyl btnzodioxol* 750 Sitosteral 1,400 Ttrpene derivative ' 13 Tetradecanoic acid 4.500 Unknown ISO-35,000 Unknown benzene 10 Unknown hydrocarbon 3-600

6-24 flft3002!2 I V

TCN 4208 RI REPORT REV ffl 9/JAN/92 Subsurface Soils. Subsurface .aoll samples were collected during the installation of 12 monitoring wells at the site. Five of these borings are located within the boundaries of the landfill and five are located in the area to the south between the landfill and Twfrie HbTTow Road. Subsurface soil samples were also collected from the~dr.um disposal and the sludge pond areas (two samples from each site). In each boring, samples were collected at multiple depths across the site. Table 6-7 presents the compounds detected in the 30 subsurface soil boring samples collected at-the DCL site. Chemicals of potential concern identified in. Table 6-7 were selected based on the criteria presented in Section 6.1.2.2.

Several organic compounds were detected in subsurface soil samples including PAHs, PCBs, and phthalates. The organic chemicals were detected infrequently, generally in only one or two "sampTes (typically less 5 %). The majority of the detected concentartions were found in the drum disposal area (DD-1 at a depth of' 4 to 6 feet) and/or at RIW-13 near the entrance of the landfill site. Benzo(a)pyrene (equivalents} and aroclor-1254 were the only chemicals selected as chemicals of potential concern, which were both detected at sample location DD-1 at a depth of 4 to 6 feet.

Arsenic, nickel, thallium were the only inorganic compounds selected as chemicals of potential concern in subsurface soil samples. Arsenic and nickel were found at all 27 sampTe locations, whereas thallium was detected only at RIW-1 at the western boundary of the landfill site. Arsenic was the primary chemical of potential concern. Although noncarcinogenic risk factors greater than one were derived for barium, chromium, manganese, and vanadium, these inorganic compounds were considered to be within natural background levels. In addition, the maximum detected concentration of lead of 60 mg/kg was within natural background levels and was well below the interim soil clean-up level of 500 mg/kg (USEPA 1989d); therefore, lead was not selected as a chemical of potential concern.

6-25 AR3002I3 Table 6-7 Sumnary of Chemicals Ottected in Subeurfacs soil at the Oixit Cavtrns landfill Sfti

Concimrition Dtte COrganic*: ug/kg. Inorganics: ag/kg) Sf Risk RfO Risk Hunan Within Frequency of Minimum Geometric Kaxiaui Compound factor (a) Factor (b) Nutritnt (c) Background Detection (d) Detected Mean Detected

Organic*: iApoclor-1254 4.4X 5.0X No No (e) 2/30 227.5 150.0 232.5 lenzene <1X - No No (e) 1/30 40.0 1.2 40.0 Di-n-octylphthslate — -- No No (e) 1/30 100.0 NC 100.0 bis(2-ithylhexyUphthaUte <1X <1X No Ho (g) 13/30 44.0 270.0 4,800.0 4-Methyl-2-pentanone -- -- No No 1/29 188.1 NC 188.1 Fluorenthene — <1X No Ho 1/30 140.0 NC 140.0 Toluene — <1X Ho No Ce) 1/30 24.0 3.2 24.0 Inorganic*: Aluminum -- — Mo Yee (a) 27/27 6,290.0 8,500.0 12,800.0 •Arsenic 70.7X 34.4X Mo Mo (s) 27/27 2.8 9.6 20.0 Barium -- 4.9X Mo Yee (3) 27/27 19.6 58.0 310.0 Beryllium 17.9X <1X Mo Yee Ca) 9/12 .3 .5 Calcium — -- Yee Mo (e) 14/14 39.1 920.0 39,0 Chromium -- 9.§X Mo Yee (g) 27/27 7.8 15.0 Cobelt -- -- No Yee (g) 23/25 4.3 9.5 31.2 Copper -- *- Yes Mo (g) 8/8 10.2 20.0 42.5 Cyanide — <1X No Mo Ce) 3/27 .7 .4 1.5 Iron -- - Yee Yee (g) 27/27 19,100.0 27,000.0 43,000.0 Ltad — -- No Yee Cg) 27/27 3.0 14.0 59.9 Magnesium -- — Yes No (e) 27/27 111.0 720.0 17,800.0 Manganese -- 18.7X Mo Yee (8) 27/27 12.1 140.0 982.0 •Nickel -- 2.4X No Ho (e) 27/27 2.5 12.0 33.9 Potassium -- -- Yee No Ce) 27/27 914.0 1,300.0 1,790.0 Selenium -- <1X No Yes Cg) 1/27 .5 .3 .5 Sodium -- -- Yee NO Ce> 4/4 68.4 100.0 180.0 •Thallium - 14.8X No No

NC Hot calculated • Chemicals of Potential Concern No toxieity erittria (a) Percent contribution of carcinogenic risk besed on the exposure point concentration and the slope factor (see text for further discussion). (b) Percent contribution of nonesrcinogenic risk beeed on the exposure point concentration and the RfD (see text for further discussion). CO Compound is en essentiel huaan nutrient. (d) The number of detected concent ret i one divided by the number of samples. (e) The chemical use not detected in background samples; therefore, the chemicil we* considered to be above background. (f) No - maximum on-sit* wee greeter than 2 times the maximum in background (not enough temples to perform a t-test). Yts * maximum on-site wee less than 2 times the maximum in background Cnot enough samples to perform a t-test). (3) Mo « On-site concentration significantly greater than background baaed on results of a t-test. Yes « on-site concentration is not significantly greater than background besed on results of e t-teet. (h) lenzoCa)pyrene (equivalent) represents the. weighted sum of the concentrations of the carcinogenic PAHs listed above1 TEFs. 6-26 SR3QQ2U TCN 4208 RI REPORT REV *1 9/JAW92

Organic TICs detected In the subsurface soil samples from the DCL site are presented in Table._6-8. These include numerous hydrocarbons, polynuclear aromatic hydrocarbons (PAHs), and acids.

6.1.2.6 Surface Water in the Vicinity of the DCL Site

Surface water samples were collected from 24 locations to determine the presence and extent of contamination originating from the DCL site (see Figure 3-1 for surface water sampTfng"locations).' fable 6-9 lists the compounds detected in samples taken from the various surface water stations located in the vicinity of the DCL site. These stations have been separated into three areas: northern drainage area (Streams B, C, D, and E), and southern drainage area (Stream A), and Stream F.

The northern drainage area includes surface water samples collected from Streams B, C, D, and E. Stream B flows across the northern side of the landfill from west to southeast through the drum disposal area and the lower portion of the fly ash pile. Stream C also crosses the northern part of the landfill and joins Stream B near the fl^y ash pile. Stream D cuts across the northeast corner of the landfiTT anrf Joins Stream B off the eastern edge of the landfill to form Stream E. This combined,Stream E flows to the southeast, where it is joined by Stream G flowing from the north. Eight surface water samples" were collected from these streams which may be impacted primarily by surface water runoff from the fly ash pile. . .

The southern drainage area includes surface water samples collected from Stream A and the quarry. Stream A runs south of the landfill to the southeast along Twine Hollow Road. It receives stormwater runoff from a culvert leading from an adjacent explosives factory, as well as runoff from the solid waste disposal area of the landfill and drainage from leachate ponds and seeps. Ten surface water samples were collected in the southern drainage area which may impact Stream A.

6-27 AR3002I5 Table 6-8 Tentatively Identified Compounds (TICs) Detected In Subsurface Soil at the Dixie Caverns Landfill Sits

Range of Concentrations TIC______(ug/kg)______Alkanes 600-4,000 2.4-01metnyl-3-penwncnt 20 Z.4-bis(l,I-Q1raetnyl)phenol 20 •t-Etbany1-1.4-0-cyclohaxene 800 Heptadecane 400 Kexacosane 3,000 Hexadecane 300 Hexadecanoic acid 300 Molecular sulfur 300 Naphthalene compounds 500-900 Pentacosane 2,000 2,S.6,9-Tetriff*thyl-(E.E.E)-l.4,a-cyc1ounoecatr1ene 300-400 Tetrametnylphenantnrane •' 5,000 2.3.S-Trimtthylhexane 200-300 Unknown 6-4,000 Unknown acid 300 Unknown alkane 900-2.000 Unknown chlorinated compound 700 Unknown hydrocarbon 400-600 Unknown PAH 4-3,000

6-28 Table 6-9 Sumnary of Chemicals Detected in Surface Water at the Dixie Caverns Landfill Site

Concentration Data (Units: ug/L) SF Risk RfD Risk Hunan Within Frequency of Minimum Geometric Maximum Compound Factor (a) Factor {b) Nutrient (c) Background Detection (d) Detected Mean detected

Northern -D_rainaqa_ Area ...... Organics: " - - - — Acetone — <1X No Mo (e) 2/8 6.0 5.0 6.0 Carbon Disulfide -- - <1X No Yes (g) 1/8 27.3 3.4 27.3 •bis(2-Ethylhexyl)phtnalate 27.9X 3.8X Ho Ho (e) 1/8 107.5 7.1 LQ7.S Inorganics: Aluminum ™ - --— No Yes (g) 2/8 27.9 17.0 47.4 Arsenic 72.IX 1.6X Ho Yes (g) 1/8 1.6 1.0 1.5 •Barium ~ 7.3X Ho Ho (g) 7/7 24.5 55.0 369.0 •CachHum -- 52.1% Ho Ho (e) 5/8 1.6 3.7 41.3 Calcium — — yes Yes (g) 8/8 946.0 6,500.0 17,400.0 •Cobalt — — Yes Ho (e) 4/8 4.7 3.0 11.4 Copper . -- — Yes Ho (e) 1/7 3.8 1.6 3.3 Iron -- -- Yes Yes (g) 4/5 96.2 120.0 600.0 Lead -- ---• —No Yes (3) 6/8 2-8 4.6 14.0 Magnesium — — Yes Yes (g) 8/8 841.0 2.800.0 6.270.0 •Manganese -- 18.« YM No (g) 7/7 12.3 310.0 1.459.5 Nickel -- <1% Ho Mo (e) 1/7 6.9 3.5 3,9 Potassium — -•* " Ye» Mo {gj 8/8 1.320.0 4.000.0 14,025.0 Selenium -- <1X Mo Mo (e) 1/8 2.1 1.6 2.1 Sodium — " Yes No (g) 3/8 1,290.0 4.800.0 14.865.0 •Zinc — 15.5X Yes No (g) 6/6 28.2 510.0 2,460.0 Sgutherri Drainage Area . . _...... _.___._.... __...__._ Organics: ...... - Acetone -- <1X No No (e) 2/9 9.0 5.5 9.0 •Benzene 1.5X - No No (e) 1/tl 3.0 2.5 3.0 Benzoic add -- <1X No No (e) 1/11 . 2.0 NC 2.0 Chlorobenzene -- <1X No No (e) 2/11 .5 2.2 4.0 *bis(2-Ethylhexyl)phtha]ate 1.1X <1X No No (e) 1/11 4.0 MC 4.0 Toluene - <1X . No _____No (e) 1/11 11.0 2.3 11.0 Inorganics: Arsenic 97.3X 10.OX No Yea (s) 1/10 7.2 1.3 7.2 •Barium. -- 40.OX No No (g) 10/10 27.2 100.0 558.0 Calcium — — Yes No (g) 10/10 10,015.0 30.000.0 66,000.0 •Chromium —. ll.SX No «o (e) 1/10 44.7 2.8 44.7 •Cobalt - "" Yes Mo {e) 1/8 4.6 1.8 4.6 Capper ~ - Yes No (e) 4/8 2.5 2.3 4.6 Iron -- -- Yes No {e) 3/3 278.0 4,600.0 25,400.0 Lead -- -- Ho Ye« (g) 5/10 .9 1.2 ' 5.7 Magnesium -- - Yes No (g) 10/10 3,070.0 14,000.0 46.500.0 •Manganese - -- 27.3X Yes No (g) 8/10 4.2 28.0 761.0 Nickel -- 5.9X No No (e) 3/10 14.5 5.6 64.1 Potassium - " Yes No (g) 10/10 1,125.0 7,300.0 57,100.0 •Silver -- 1.9X No No (e) 1/10 2.0 1.1 2.0 Sodium -- « Yes (to (g) 10/10 1,520.0 13,000.0 120,000.0 •Vanadium -- l.OX No No (e) 1/10 3.9 1.4 3.9 Zinc -- <1X Yes Yes {g) 8/8 16.9 28.0 45.1

6-29 AR3QQ2I7 fable 6-9 (cont.) Summary of Chemicals Detected in Surface Water at the Dixie Caverns Landfill Site

Concentration Data (Units: ug/L) SF Risk RfD Risk Human Within ' Frequency of Minimum Geometric Maximum Compound Factor (a) Factor {b) Nutrient (c) Background Detection (d) Detected Mean Detected

Inorganics: Barium - 100,OX No Yes (f) 1/1 25.7 NC 25.7 Calcium - - Yes Yes (f) 1/1 16,300.0 NC 16,300.0 Lead -- — No Yes (f) 1/1 9.0 NC 9.0 Magnesium -- — - - Yes Yes (f) 1/1 5.S20.0 NC 5,620.0 Potassium -- - Yes Yes (f) 1/1 1,740.0 NC 1.740.0 Sodium -- — Yes Yes (f) 1/1 2,890.0 NC 2.890.0

NC Not calculated • Chemicals of Potential Concern No toxicity Criteria. (a) Percent contribution of carcinogenic risk based on the exposure point concentration and the slope factor (see text for further discussion). (b) Percent contribution of noncarcinogenic risk based on the exposure point concentretlon and the RfO (see text for further discussion). (c) Compound is an essential human nutrient. (d) The number of detected concentrations divided by the number of samples. (o) The chemical was not detected tn background saeejles; therefore, the cnest leal was considered to be above background. if) NO • maxima on-site was greater than 2 tltees the? maxieui In background (not enough samples to perform a t-test). Yes • maxim* on-site was less than 2 times the maxieui In background (not enough samples to perform a t-test}. (g) No • On-site concentration significantly greater than background based on results of'a t-test. Yes - On-s1te concentration is not significantly greater than background based on results of a t-test.

6-30 /JR3002I8 TCN" 4208 R! REPORT REV ff1 9/JAN/9 2 An additional surface water sample collected from a nearby abandoned limestone quarry also was grouped with Stream A.

Streams A and E join after flowing under Interstate 81 to form Stream F. Sample SF-1 was taken slightly upstream of the location whether Stream F empties into the Roanoke River. Stream F was evaluated separately from the northern drainage area and southern drainage area.

Since. Stations SA-1, SB-1, SD-1, and SG-1 were considered to be unaffected by the site, these samples were used collectively to represent background concentrations for all other surface water stations. Although these samples were collected from different portions of unaffected streams in the vicinity of the site, evaluation of the chemistry of these streams indicated that these samples could be used. collectively to represent background. The advantage of pooling this data set was that a statistical test could be used to evaluate background.

Northern Drainage Area. ,Bis(2-ethylhexyl)phthalate was selected as the only organic chemical of potential concern. It was detected only at SB-6 southeast of the landfill at a level above laboratory blank contamination. The dissolved concentrations of aluminum, arsenic, copper, iron, lead, and nickel were within natural background levels. Barium, cadmium, cobalt, manganese, and zinc were selected as the inorganic chemicals of potential concern. The highest levels of these contaminants were found in Streams B and C in the vicinity of the fly ash pile. - - .:__...__.._._. . "" "". .' __ —---

Southern Drainage Area. Benzene and bis(2-ethylhexyl)phthalate were selected as the organic chemicals of potential concern. Barium, chromium, cobalt, manganese, silver, and vanadium were selected as the inorganic chemicals of potential concern. The highest levels of these contaminants, with the exception of chromium, were found in samples of the leachate and seeps. The maximum concentration of chromium was found at SA-4.

6-31 SR3002I9 TCfi~4~2'C58 RI REPORT REV #1 9/JAN/9 2 Stream F. No organic contaminants were detected in the__sample taken from Stream F. All of the inorganic contaminants were detected within background levels. Thus, no chemicals of potential concern were selected for surface water from Stream F.

TICs in Surface Water. Low levels of dimethyl ethyl phenol isomers and a secondary amine were detected in surface water in the vicinity of the DCL site, as shown in Table 6-10.

6.1.2.7 Sediments in the Vicinity of the DCL Site

Sediment samples were collected concurrently with the surface water samples, at the same locations, as described in the previous section (see Figure 3-1 for sediment sampling locations). In addition, two samples were collected in a dry stream bed at the southeast corner of the site that would empty into Stream A. Table 6-11 lists the compounds detected in the sediment samples collected from the streams and groundwater seeps in the vicinity of the DCL site. Chemicals of potential concern identified in Table 6-11 were selected based on the criteria presented in Section 6.1.2.2. Overall, sediment samples were collected from 25 locations to determine the presence and extent of contamination originating from the DCL site.

Northern Drainage Area. Benzo(a)pyrene (equivalents) and phenanthrene were identified as organic-chemicals of potential concern. Both compounds were detected at. SB-4, whereas benzo(a)pyrene (equivalents) were also found at SE-1. Arsenic, which had the highest estimated carcinogenic risk factor (87%), was within natural background concentrations and, therefore, was not selected as a chemical of potential concern. The highest concentrations of the selected inorganic chemicals of potential concern, antimony, cadmium, chromium, lead, manganese, silver, and zinc, were detected at SB-7, SE-1, and SB-4. Cadmium, lead, manganese, and zinc appeared to be the primary chemicals of potential concern in sediments. In fact, the highest detected concentration of lead 6-32 4*300220 Table 6-10 Tentatively Identified Compounds (TICs} Detected In Surface Water at the Dixie Caverns landfill Site

TIC Range of Concentrations (uo/L) N,N-01ethy1-3-fliethylbenzajnine 9 3-(l,l-01methyletnyl)phenol 9 bis(l,l-Q1methylethyl)phenol 20 2,4-bis(l,l-Dtmethyl)phenol 10-20 Unknown 7-9

6-33 SR3G022I Table 6-11 Summary of Chemicels Detected in Sediment at the Dixie Caverns Landfill Site

Concentration date (Organic*: ug/kg. Inorganics: mg/itg) Sf Risk RfD Risk Human Within Frequency of Minimum Geometric Maxim* Compound Factor Ca) Factor (b) Nutrient (c) Background Detection (d) Detected Mean Detected

Northern Or»Jnaoe Area Organics: Acetone -- <1X Ho No (e) 1/8 44.0 9.4 44.0 Senzoic acid -- <1% HO No Ce) 1/8 2,000.0 1,200.0 2,000.0 bisc2-lthylhexyOphth«late <1X <1X NO No Ce) 2/8 31.0 210.0 337.5 PoiycycAlc Aroffletlc Hydrocarbons 8enzoCa)snthracene NO No (e) 1/8 67.0 NC 67.0 SenzoCe)pyrene No No (e) 2/8 64.0 210.0 365.0 Benzo 5/8 190.2 490.0 1,231.5 Flooranthtne -- <1X . HO NO 8/8 636.0 4,600.0 18,200.0 •Chromium -- 9. IX No No Cg) 12/12 9.9 98.0 822.0 Cobalt Yee Yes Cg) 8/8 8.3 15.0 38.9 Copper Yee Ho (g) 3/8 8.1 110,0 1,720.0 Iron Yee Yee Cg) 3/8 19,300.0 45,000.0 166,000.0 •Lead NO Ho eg) 12/12 16.9 1,400.0 30,800.0 Magnesium Yee Yes Cs) 8/8 804.0 3,900,0 16,600.0 •Mtngenese •- 11. OX Yes HO Cs) 8/8 202.0 2,500.0 20,000.0 Nickel -- <1X HO Ho (9) 12/12 12.4 51.0 186.0 Potassium Yee Yes (9) 8/8 349.0 1,300.0 1,760.0 Selenium -- <1X Ho No Cg) 4/8 1.3 1.3 6.1 •Silver - 1.3X HO Ho Cg) 5/8 1.7 6.6 72.9 Sodium Yee HO 2/2 574.5 HC 594.0 Vanadium -- <1X NO Yes 8/8 13.1 24.0 43.8 •Zinc -• 35.0X Yes No (g) 12/12 42.8 5,200.0 127,000.0 Southern OreineaeiA'te Organic* j *oi-n-octylphthalate No He (e) 2/8 63.0 160.0 220.0 bis(2-ithylhexyl)phthalate <1X <1X No Ho Ce) 5/8 57.0 250.0 1,300.0 PolvcvcHc Araatfe Hydrocarbons. Pyrene HO No ce) 1/8 49.0 MC 49.0 §«nzo

6-34 flR300222 Ubl« 6-U (cone.)

Sunnary of Chemicals D«e*ct«d in Sediment at the Dixie Caverns landfill Site

Concentrition Data COrganics: ug/kg, Inorganics: mg/kg) SF Risk RfD Risk Huran Within Frequency of Minimum Geometric Maximum Compound Factor (a) Factor Cb) Nutrient

SojJthe£n___Drs_inaqe Area (cont. j . ______._ ..._._._. Calciun -- _..—.-... YM Yes (g) 8/8 5,090.0 33,000.0 157,000.0 Chronii* -- 53. 6X Ho Yes Cg) 8/8 11.9 46.0 509 0 Cebelt . . -• -- Yes Yes Cg) 8/3 3.8 8,3 13.4 Copper .... yti Ytt (g) 8/8 12_3 20>0 w>7 Iron " " Yes Yes Cg) 8/8 17,800.0 26,000.0 32,800.0 Lead -- -- NO Yes Cg) 8/8 13.6 23.0 39.9 Magnesium -- -- Yes Yes Cg) 8/8 3,930.0 18,000.0 54,900.0 Manganese -- 32. 3X Yes Y«s Cg)_ 8/8 196.0 840.0 6,140.0 Nicktl -- <1X No Yes Cg) 8/8 8.0 12.0 15,4 Potassium -- .._.___. Yet Yes Cg) 8/8 570.0 1,000.0 1,710.0 Vanadiuo -- 3.5X No Yes Cg) 8/8 14.0 25.0 77 1 Zinc -- - <1X Yes Yes Cg) 8/8 48.1 75.0 152.0 Stream F . _.__. .. _ ...... _ ... __ __ _ . ... Organ ics: Polycyciic AromaticL 8enzoCa)anthracene -- - -- No Mo Ce) 1/1 80.0 NC 80.0 8enzo 1/1 76.5 NC 76.5 Beryllium 15.3X <1X No Yee (f) 1/1 .7 NC .7 •Cadmium - 20.5X No Ho Ce) 1/1 8.9 NC 8.9 Calcius - -, Yea Ytt (f) 171 12,900.0 NC 12,900.0 Chromium -- 11. OX No Yee Cf) 1/1 24.0 NC 24.0 Cobelt -- -- Yes Yes Cf) 1/1 10.7 NC 10.7 Copper -- •• Yes Yes Cf) 1/1 37.3 NC 37.3 Iron - -- Yes Yes Cf) 1/1 22,400.0 NC 22,400.0 Lead -- -• No Ho Ce> 1/1 457.0 NC 457.0 Magnesium -- -- Yes Yes Cf) 1/1 8,700.0 NC 8,700.0 Manganese -- 17.4X Yes Yes Cf) 1/1 754.0 HC 754.0 Nickel -- 2.2X No Yes (f) 1/1 19.4 HC 19.4 Potassiun — -- Yes Yee Cf) 1/1 1,290.0 HC 1,290.0 vanadiun -- 7.2X No Yes Cf) 1/1 22.0 NC 22.0 •Zinc - 13.5X' Yes No Ce> 1/1 1,610.0 NC 1,610.0

NC Not calculated * Chemicals of Potential Concern No toxicity criteria (a) Percent contribution of carcinogenic risk besed on the exposure point concentration and the slope factor Csee text for further discussion). Cb) Percent contribution of noncarcinogenic risk besed on the exposure point concentration end the RfD Csee text for further discussion). Cc) Coopound is en essential hunen nutrient. Cd) The number of detected concentrations divided by the nwfeer of samples. Ce) The chemical uee not detected in background samples; therefore, the chemical was considered to be above beckgromi. Cf) No « maximum on-site wee greeter then 2 times the nexliue in background Cnot enough samples to perform e t-test). Yes « mexinu* on-site was Less then 2 tines the maxima-, in background Cnot enough samples to perform e t-test). Cg) No « On-site concentration significantly greater then background besed on results of e t-test. Yes - On-site concentration is not significantly greeter then background based on results of e t-test. Ch) BenzoCe) pyrene C equivalent) represents the weighted sue of the concentrations of the carcinogenic PAHs listed above using TEF"- ' 6-35 fiR300223 TCN 4208 RI REPORT REV #1 9/JAN/92 (30,800 mg/kg) was over 60 times higher than the interim soil clean-up criteria of 500 mg/kg. In addition, the geometric mean concentration of lead (1,400 mg/kg), which represents the 50th percentile of the chemical distribution, exceeded the interim soil clean-up criteria by nearly a factor of 3. Therefore, U appears that surface water runoff from the fly ash pile is significantly impacting nearby streams.

Southern Drainage Area. The only chemical selected as a chemical of potential concern in the southern drainage area was di-n-octylphthalate. The highest concentration of this contaminant was found in the samples from the old stream bed and stormwater runoff ditches at the extreme southeast corner of the site. None of the detected inorganics significantly exceed background concentrations; therefore, these chemicals were not selected as chemicals of potential concern. The maximum concentrations of lead detected in sediments was only 40 mg/kg in the southern drainage area, indicating that the DCL site does not impact this stream.

Stream F. ____PAHs were the only organic compounds detected in Stream F. Benzo(a)pyrene (equivalents) and phenanthrene were the only organic chemicals selected as chemicals of potential concern in Stream F. The concentration of benzo(a)pyrene (equivalents) was approximately 5 times lower in Stream F, than in upstream samples collected from the northern disposal area. The concentrations of cadmium, lead, and zinc were elevated above background levels; therefore, they were selected as chemicals of potential concern in Stream F. These results indicate that the site {specifically the fly ash pile) has impacted the chemistry of Stream F. The concentrations of these inorganic chemicals, however, were orders of magnitude below those found further upstream in the northern disposal area.

6-36 TCN 4208 RI REPORT REV #1 9/JAN/92 TlCs._lo_SfidJ.menJL_ ...... -„-.-..-...,.-,,., . ,,_,...._-.-...,._,_.. .-,-..

No organic TICs were identified in the sediments collected at the DCL site.

6.1.2.8 Summary of Chemicals of Potential Concern

Table 6-12 presents a summary of the selected chemicals of potential concern for all media sampled at the DCL site. Over 20 compounds were selected as chemicals of potential concern at the DCL site, including carcinogenic and noncarcinogenic PAHs, phthalate esters, and several heavy metal compounds such as cadmium, lead, and zinc. From the groundwater monitoring results, arsenic and manganese appeared to be the primary contaminants of concern; however, the concentrations of these inorganics did not appear to be elevated. Inorganics that may have been released from the fly ash pile, such as cadmium, lead, and zinc did not appear to have significantly impacted groundwater at the site. Residential wells in the area also did not appear impacted by the site based on a comparison of water chemistry. In surface water, barium, cadmium, manganese, and zinc were the primary chemicals of potential concern. Lead released from the site did not appear to significantly impact groundwater, surface water, or soil (beyond the influence of storm water runoff from the fly ash pile) at the DCL site. Both carcinogenic and'noncarcinogenic PAHs were found in sediment, surface soil, and subsurface soil. .The southern drainage area does not appear to be impacted by the site. Sediments in the northern drainage area, however, appear to be significantly impacted from storm water runoff from the fly ash pile. Highly elevated levels of cadmium, lead, and zinc were found in sediment samples collected near the fly ash pile. Slightly elevated levels of cadmium, lead, and zinc also were found as far downstream as the Stream F sample location.

6-37

flR.300225 Table 6-12 Summary of Chenicals of Potential Concern for the Dixie Caverns Landfill Site

Soil Groundwater Surf ice Compound Water Sediment Surface Subsurface Site Residents Organics: Aroc lor- 1254 * Semen e * 3enzo(a)pyrene (Equivalent) * * r Oibenzofuran * Oi-n-octylphthalate f bis(2-Ethy1hexy1.phtha1ate * Kanhthalene * Phenanthrene » * Inorganics: Antimony * * Arsenic * * » Barium * * * * Beryl . i w 1 » CaciniuB. * * » Chrc-B.ut * * * Cobalt * * * Lead * Manganese * * * * * Nickel * * » Silver * * * Thalltue * Vanadium * Zinc * * * *

6-38

3R3QQ226 TCN 4208 RI REPORT REV (M 9/JAN/92 6.1.3 Exposure As_s_&SLS.ment

This section quantifies the magnitude, frequency, and duration of exposure from contaminants released to groundwater, soil, surface water, and sediment from the OCL site. The exposure assessment for the DCL site was conducted in accordance with available USEPA guidance (1988; 1989a,b,c; 1990; 1991a,d).

The first step in the exposure assessment process is to characterize the environmental setting of the site. The environmental setting consists of the physical environment and potentially exposed populations. The physical environment for the DCL site wa.s discussed in Section 2 of this RI report. The environmental setting of the DCL site will be further discussed in Section 6.1.3.1. - —----

The second step of the exposure assessment process is the identification of exposure pathways, which includes: 1) evaluating contaminant sources and release and transport mechanisms; 2) identifying possible exposure points; and 3) identifying the exposure routes. Contaminant sources and release and transport mechanisms were discussed in Section 5 of this RI report. Section 6.1.3.1 reviews possible exposure routes and identifies the exposure pathways of concern.

The final step in the"exposure assessment process is the quantitation of exposure for the identified exposure routes for the reasonable maximum exposure (RME) case, as specified in the NCP (USEPA 1990). Exposures are quantified in Sections 6.1-3.2 and 6.1.3.3 for~~the exposure pathways of concern. Section 6.1.3.2 describes the methods used to estimate exposure point concentrations and quantifies exposure point concentrations for the chemicals of potential concern identified in Section 6.1.2. Section 6.1.3.3 .describes the methods used to estimate exposure (i.e., chronic daily intakes [CDIs]) for the exposure pathways evaluated in this report. The CDIs will be used in conjunction with toxicity criteria (identified in Section 6.1.4) to characterize the potential risk associated with the DCL site under current and future land-use conditions.

6-39

AR300227 TCN 4208 RI REPORT REV *! 9/JAN/92 6.1.3.1 Exposure Pathway Assessment

This section identifies "complete" exposure pathways which will be quantitatively evaluated in the DCL baseline risk assessment. A potentially "complete" exposure pathway has the following four characteristics:

1) mechanism of release (e.g., release of chemicals of potential concern from subsurface soil to groundwater); 2) transport media (e.g., transport of chemicals of potential concern in groundwater along a gradient); 3) point of exposure (e.g., chemicals of potential concern present in residential wells); and 4) route of exposure (e.g., resident ingests groundwater from a private well).

Only "complete" exposure pathways which__are both quantifiable and potentially significant are quantitatively evaluated in the baseline risk assessment. The environmental setting and pathway selection are discussed below.

Env1ronmental Sett1nt.. The DCl site is located just north of Interstate 81, directly off State Route 778, in southwest Roanoke County, Virginia. The surrounding land is rural; however, development is spreading west towards the site from the cities of Salem and Roanoke. Within a 3-mile radius of the landfill site, the population is <2,500; within a 1-mile radius are <250 residents. The vast majority of the population within 1 mile is located to the south-southeast (downhill) of the site. A total of 51 occupied residences have been identified within approximately 1 mile of the site. There are no residents located north of the site within a 3-mile radius. Approximately .2 miles to the south-southeast of the landfill site are the Dixie Caverns, a tourist attraction located directly off Interstate 81.

6-40 flR300228 TCN 4208 RI REPORT REV #1 9/JAN/92 The DCL site__lies on a relatively steep ridge complex between two steep valleys with intermittent streams. Relief of up to 200 feet above the valley floors occurs within 500 feet of horizontal distance. Land slope ranges from a minimum of 20 percent up to 40 percent on undisturbed areas. The topography of this area of the County is characterized by long, narrow, parallel valleys and mountain ridges. The mountains in this part of the County are rugged and heavily forested, with numerous small streams traversing them. Streams in the northern .and southern drainage areas eventually discharge to the Roanoke River.

In this region, groundwater flow is.typically southeast toward the Roanoke River, however, groundwater can also move along the formation strikes and parallel to the mountain chains. Hydrogeolbgically, there is no connection between the site and residential wells located to the south/southwest of the site.

Exposure^Pathways under Current Land-Use. The media of concern in this study include groundwater, soil, surface water, and sediment. The exposure pathways of concern under current land-use of-the DCL site and surrounding area are discussed below by medium. Complete exposure pathways evaluated under current land-use conditions of the DCL site are summarized in Table 6-13.

Groundwater. Residents located in the vicinity of the DCL site may use groundwater from their wells as a source of water for drinking, cooking, showering, and bathing. Possible exposure routes include ingestion and dermal absorption of chemicals of potential concern. No VOCs were selected as chemicals of potential concern in groundwater; therefore, inhalation exposure while showering is not a complete exposure route. Exposure" to contaminants in residential wells will be calculated assuming the absence of any corrective measures in order to evaluate the "no-action alternative." Monitoring data from the inlet (prior to treatment) were us.ed to characterize potential exposure to residents from use of groundwater from their wells.

6-41

38300229 U SU_ - - . -^- - aU) *mJ ^_ Q at — c O ^ CT *^ ^ *•» w ^Z S~2J ~ •a 3 >9 3 J3 u- 3 £ ••— . *•" L. iQ M M w * •oS o& ex1 . ia o > a? 3) QJ O I- •— X Q. (_ U4 •as Q. w 09 *~

(- c: e 01 -n 09 w f— c o> V o — rn eo Q 10 3 ns o ••- >> a» E C i^ f- 0) 4J JE "C 4-1 M U 3 4J X ^-^* £ 3 ^^ rd C rO C '^ ^~' **™ c -i M 4-> J2 W 3 ^ O C O fB 43 O pi a. — tl 41 -fe g cn O * -^ Ol d) rQ <_ ^— ' c 3 £ — o u fc- 4J O O Q — «J *•* ic ^ -C >» O>J ^f~O E^;3 r tC i*- O^ *^C- ^0j9 E c^- ai n- u -* "^ a) o -^ aj co w o x > u. o w _Q <9 - x ai £ ^ O t- —— OT 4-1 a> >> j-i u _c u— ai IB aj aj ~3 W •*-> aj 4_> " ^ v "~ ——— - O4-ie.ca>£ — 09 "g. - fj Ot *^ ^ ra -i- 4-> (- -w 3 *"* ml g "~* 1 W S C 3 Q to ^ S U ^""c jr a) w o) E •«- o B _ _ «^— w o *J >^ -4-J -*^ (Q o p_ t* . * ^1 -- -'- *™ ^ I- U 3 r^ oj *o cu "^ x |+— aj i^ E C — — >*i-;c ai 4i — - « J-> ITS C 0) J- 4-J 4-> TJ —— | n U C 3 s- 3 y oj ij Q. C -M ffl « a) >~ 50 C -J £ -u 1 QJ 4-1 Q. t- —— '!_ 09 W 4J —i O *«- (- ta S *J ifc.- £3 M • d) ^ " • m it— • 0) • C 3 Q.^ — *J fir? Q> > 01 4-> KI O> U OJ T3 W 1J IV* C x OJ n i^ w ft *~ ai n U— Q OJ'*-'D 3.C 0 2 UJ >- 3 O >- O « >- X >-«ocoo'O'a4J

Q Q g -o « « — 5. 8) 03 ng 0 W Bee £ - ^ •hJ ^fc "Q •O 43 C t. n> fc 4-1 -M -3 3 r-4 *Q = C 0) c c c a OJ U- Q U- • • O §ci 03 a o W J3 O g 4-> U-. Q "^ 3 — ^ —— E 4J HJ n a.~a p o a Q G 4-* "^ ^^- i^ CJ ij c c t- c **- ^£> aj — o u- 09 M *•* t_ "O ^& "~ " 07 3 — a o o 3 ^ la X — coa. ^ 3 4J Ol M j-i o» w m ta 4J 4J — O en -U 14- Q» Q. e U- t- C fO a) Q-^ j^ 3 O **"* ^9 nj 4-1 — rg 4J •— S »— — - --*-5j £ 4-1 ^-> *** £j ^^ •^ •** -£S C fO C n) t H3 *J OJ = -^ t- .E .... Q) ^ *J Q. ^— (U o i — (U (J JM O B u (a g K c -M *O >- 0) BJ -D ••— "O -" t- •— « 01 • .3 « — t. 4> O •-" S "° 'S .-^ > 4-1 a. O -^ ^ c ^* *c aj E ^ 'a 0) c _c e ^ — w— "os^St. X LLJ c 1 M ^ ^ M cu c: M .*• Q L. 4_) CO 0) c 4-J .^j -^- O C1 EO t- oj a c e +J +J g) fll "Q c- e= a. C 13. ^3 O- — -D — - a_l 05 €J •*• ta -^" p— ^^ 2 o *^ O n 0) -C -^ m w o o flj I- O -c — cu Q. a. >y oe: o a. cc

c 4-1 "o F——— — (U 1*- ^— - - - O- Q 4J ^ c a « 4J V) "~ >i 0) 4-> £ ^ §4-1 -M c 3 ai U U 0) u -o » *o ^ C C/l •Q W O a) -^ s. U '^ t- t- O 03 n a> X 5) (0 3 4-1 d9 w UJ

i- •5 ^ (U I- 4-1 4J (S 3 jcjn 39 o» e 1 O u Sj 1 JQ a} £ So 3 t^_ a. O f- t -5 t- x L. 3 3 01 •^ l_J t£J e/5 VI t/» < flR300230 TCN 4208 RI REPORT REV #1 9/JAN/92 Soil. There is___no, .fence surrounding the ,pCL_site to prevent access. Children from nearby residential areas may trespass on the landfill property and come in direct contact with topsoil while playing at the site. Contact with surface soil may result in exposures through dermal absorption and incidental ingestion.

Surface Water/Sediments. Exposure pathways involving the surface water and sediment could manifest in several ways. One route of exposure is direct contact with the surface water from various streams and groundwater seeps in the vicinity of the DCL site (see Section 6.1.2 for further description of these areas). Children and teenagers wading or playing in the water may come into direct contact with contaminants in surface water. Exposure from incidental _..jj_ngest ion of surface water is considered negligible durjng playing activities. In addition, individuals may come into direct contact with contaminated sediments from various .streams and groundwater seeps. Contact with the sediments may result in exposures through dermal absorption or incidental ingestion.

Air. Benzene was the only VOC selected as a chemical of potential concern at the DCL site. Benzene was detected in surface water at a concentration of only 3 ug/L. After release to the air, this VOC would be significantly diluted at potential downwind exposure points (i.e., nearby residents). Therefore, this exposure pathway is not of concern. With respect to wind- borne dust, the fly ash pile may be a significant exposure pathway which would warrant quantitative evaluation. However, the fly ash pile is being evaluated as a seperate operable unit and, therefore, was not evaluated in this pathway. Surface soil at the DCL site (with the exception of soils impacted by storm water runoff from the f 1 y ash pile) did not have significant levels of chemicals which would warrant quantitative evaluation of this pathway. Direct contact with surface soil which will

6-43

flR30023l TCN 4208 RI REPORT REV ffl 9/JAN/92 be evaluated in this report also would result in much higher exposures than those estimated from inhalation. Therefore, the inhalation exposure route will not be evaluated in this report.

Biota. The natural habitats of the intermittent streams draining the DCL site are not of the nature which supports harvestable fish; therefore, this does not represent a complete exposure pathway. Surface water and sediment data collected from the farthest downstream sample (Stream F) indicates that significant levels of contaminants have not reached this location. Therefore, the DCL site does not appear to have any current impact on the Roanoke River (particularly given the potential dilution).

Exposure Pathways under Future Land-Use. Complete exposure pathways evaluated under future land-use conditions of the DCL site are summarized in Table 6-14. Exposure pathways related to surface water, sediments, air, and biota are not expected to change in the future. The exposure pathways evaluated under current land-use conditions for these media should be representative and sufficiently protective of future land use of the DCL site. Exposure pathways related to future contact with surface soil and to future use of groundwater at the Dixie Caverns Landfill site are the only additional pathways evaluated in the baseline risk assessment.

Soil. It is highly unlikely that excavation of soil as a result of construction activities would occur under future land-use of the DCL site. Institutional controls regulate the construction of buildings on former landfill sites. Therefore, exposure to subsurface soil was not considered a complete exposure pathway of concern. If hypothetical residents at the. DCL site come into contact with surface soil they may be exposed to contaminants through dermal absorption and incidental ingestion.

6-44

/5R300232 TCN 4208 RI REPORT REV ffl 9/JAN/92 Groundwater. If groundwater at the site were used as a source of water in the future, then residents may be exposed to contaminants via ingestion. In addition, use of groundwater for bathing or showering would result in exposure via dermal absorption (no VOCs were selected as chemicals of potential concern). It should be emphasized that it is highly unlikely that residents would actually use groundwater at the DCL site as a source of drinking water in the future. Future use of groundwater was evaluated quantitatively in this report primarily to justify further restrictions on groundwater use and in 'order to provide the basis for making risk management decisions concerning remediation of groundwater at the DCL site. : -.

Summary of Exposure Pathwav.s_to__b_e_Quantitat1velv Evaluated. The following current land-use exposure pathways will be quantitatively evaluated in this report: • ingestion and dermal »absorption of chemicals of potential concern in groundwater from private wells by off-site residents (assuming no treatment of groundwater); • direct contact with surface soil by trespassers (i.e., children) playing at the DCL; and • direct contact with surface water and sediments by children playing in various streams and groundwater seeps in the vicinity of the DCL site.

The followin.g'future land-use exposure pathways will be quantitatively evaluated in this report: • direct contact With surface soil by hypothetical future residents; and

• ingestion and dermal absorption of chemicals of potential concern in groundwater at the DCL site by hypothetical future residents.

6-45 AR3QQ233 •aaj >i 09 Q- <— 10 >-

CF- *aJ §^J 09 fl U 01 v S fl 4-9 ta Cg) •*f-l « C 3 -D <- >a t_ fl — 3 P" n o fl M M a) 09 b-i ^* «. ^ QC f 09 £_*— * 4-9 o f_ • fIl Ca (3- • "a — — — u v> >v E- M U >i *-> CJ —— Q. 0 — ufl *— >• fl a? 09 >i fl 4-1 * ' ra o £ j= g —o oe z. j-» -u U ^s 1 a. c - ta • U fQ « £ -- 09 4J 1. J= 4-1 -J a. *g* -q *—* Cfl 40J9 4-o1 aUj • ai CL 39 w c fl 0. !- .— -—o 4- —1 W i ^ fl i (3 C•—. M ^ w d 4-1 4>1 4-9 3 O Q. n n CO W 4J 49 « £ X di c -v> o t- - — - •— 4J S3 *-> c_ u a. •o to 4-9 - _ c •— fl 93 1- » o ^3 at __J g •a en 09 •— fl >. 3 Ol 4-9 M •o «- o> C Q. 1- "9 IS e o = ~- " S >- aQ. .a -^ a J»BJ f3* x C J= •— u> fl 3 UJ c o *J fl -Q O — - fl 4-1 fl a. u- >. — 4.. .a ai b t- 4-t Q. aW> (oT —09 Is 3 ^3 o E O* «i3 U e ^a !c a B- —— IB S ^€ X UJ t: 1 4-9 4-> 39 2= ^J5t •Q , _ (O M fl r~- «i a> •a s- ce O£ 4^ — O 0) aa £3 E 13. t- & at 3 3 O *J U ^j 4-1 a. O 63 3 3 Q- se U. U.

*» = "o «.• +a a. fl tff tQn (B «. JJ to 09 i_ c 9) t. 4J 3 U 3 — W US-. TS3 fl a> m 3 — —— 4-t (0 r— t- S. 0} IX" 3 <0 03 3 X J= UJ u. oe S WI UJ 4-1

•a L. _g 09 4J iS_I fl 3 -i M e * —— g. o X t.- O UJ *o t/1 6-46 J TCN 4208 RI REPORT REV # 1 9/JAN/92 6.1.3,2 Estimation of Exposure Point Concentrations

Methodology for Estimating Exposure_Poln.t.Concentrations. To calculate exposure and ultimately risk, chemical-specific concentrations that a receptor could contact over the duration of the exposure period (i.e., exposure point concentrations) must be estimated. The exposure point concentration is defined as the average concentration contacted over the duration of the exposure period.

This section describes the methods used to estimate exposure point concentrations for the exposure pathways quantitatively evaluated in this report.

In general, USEPA (1989a) recommends calculating the 95th upper confidence limit (UCL) on the arithmetic mean as the exposure point concentration using available monitoring data provided by the RI. .USEPA (1989a) recommends applying a 95th UCL on the arithmetic mean concentration because of the uncertainty associated with available monitoring data.. Two alternative methods for calculating the 95th UCL on the arithmetic mean have been recommended by USEPA in Risk Assessment Guidance for Superfund" (Gilbert '1987, 'as cited in USEPA 1989a). One of the methods assumes that the individual chemical concentrations are normally distributed and calculates a 95th UCL on the arithmetic mean from the t-distribution (Gilbert 1987). The other method, based on Land (1971, 1975), is used for chemical concentration data that are log-normally distributed (Gilbert 1987).

The equation for calculating the 95th UCL on the arithmetic mean assuming a normal distribution (Gilbert 1987) is presented below:

UCL(normal) n q, = Y

6-47

flR3Q0235 TCN 4"208 RI REPORT REV *l 9/JAN/9 2 where:

UCL(normal)09S = The 95th UCL on the arithmetic mean assuming a normal distribution; Yn * arithmetic mean of the untransformed data; Sn - standard deviation of the untransformed data; ^0.95 " t-statistic for a one-tailed confidence limit test with an alpha - 0.05; and N « sample size.

In general, most chemical distributions in nature tend to be -log-normally distributed, except for abundant metals such as aluminum and iron (Connor and Shacklette 1975, Dean 1981, Esmen and Hammad 1977, Ott 1988). Therefore, of the two methods recommended by USEPA, the method developed by Land (1971, 1975) should be used in most cases to calculate the 95th UCL on the arithmetic mean. Based on the frequency distributions for the contaminants at the DCL site, the log-normal method for estimating the 95th UCL on the arithmetic mean appeared to be the most appropriate method.

USEPA (1989a) recommends the use of the maximum detected concentration as the exposure point concentration if the 95th UCL on the arithmetic mean exceeds the maximum detected concentration. The maximum concentration is often lower than the 95th UCL on the arithmetic mean calculated using the Land (1971, 1975) method when the sample size is small (e.g., less than 10 samples) and/or the chemical concentration distribution is highly positively skewed.

Estimation of Exposure Point Concentrations for Current Land-Use Pathways

Use of GroyndwaterJErom Residential Wells. Monitoring results presented in Table 6-4 were used directly as the exposure point concentrations for estimating exposure from use of groundwater from private wells. The monitoring data from these residential wells sampled at the inlet pipe were used to estimate exposure.

6-48

AR300236 TCN 4208 RI REPORT REV #1 9/J AN/92 Children Playing in Surface .Sol7._ , It was assumed that children may contact surface soil at DCL while playing, over an exposure period of 10 years. Surface soil data collecteeL.during the RI were used collectively to estimate exposure point concentrations. Distribution statistics for chemicals of potential concern in surface soil are presented in Table 6-15.

Children Playing in"Nearby Streams and Seeps. It was assumed that children may contact different streams and seeps in the vicinity of the DCL site while playing over an exposure duration of 10 years. Monitoring data collected from different drainage areas were evaluated ..separately. Surface water exposure point concentrations used to estimate exposure to children from dermal absorption of contaminants while playing in surface water are presented in Table 6-16. Sediment exposure point concentrations used to estimate exposure to children from dermal absorption and incidental ingestion of contaminants in sediments are presented in Table 6-17.

Estimation of.iExposure Point Concentrations for Future Land-Use Pathways

Direct-Contact with Surface Soil. It was assumed for future land-use of surface soil that residents may be exposed to surface soil over a period of 30 years (6 years as a child; 24 years as an adult). Surface soil data collected during the RI were used collectively to estimate exposure point concentrations. Distribution statistics for chemicals of potential concern in surface soil are presented in Table 6-15.

Use o.f .Groundwater from Hypothetical Residential Wells. For the future land-use groundwater pathway, it was assumed that a hypothetical resident may install a well anywhere at the site. In order that potential exposure will not be underestimated, USEPA Region III (1991a) recommends the selection of three wells with groundwater contamination which is indicative of overall site contamination. USEPA recommends the use of several sampling rounds from these wells in order that the seasonal influence on contamination levels may be characterized. The 6-49 AR300237 Table 6-15 Exposure Point Concentrations for Chemicals of Potential Concern Detected in Surface Soil at tht Oixi* Caverns Landfill Site (Units; Organtcs: ug/kg. Inorganics: mg/ltg)

95th UCL on tht Arithmetic Mean Exposure Average ——————————————— Maximum Point Compound Concentration Normal Log-normal Concentration Concentration

Organics: Dibenzofuran 153.0 NC . NC 150.0 150.0 (b) Benzo(a)pyrene (Equivalent) 1.400.0 2.QQO.Q 2,300.0 Z.500.7 2.300.0 (a) Acenaphthene 19C.3 NC NC 190.0 190.0 (b) Phenanthrene 640.3 1,200.0 2,200.0 1.700.0 1.700.0 (b) Inorganics: Arsenic 13.0 21.0 22.0 27.6 22.0 (a) 3

NC Not calculated (a) Exposure point concentration based on th* 95th UCL on tht arlttvttlc mean concentration derived using land (1971, 1975} which assumes that tht distribution Is lognormal. (b) The 35th UCL on tht arUtmttic mean concentration exceeded tht maxlRUi detected concentration, or there were not enough sa<»p]" (i.e., < 3) available for estimating tht 95th UCL on tht arithmetic mean. Therefore, the Mx.nue concentration was used as tht exposure point concentration.

6-50

flR300238 Table 6-16 Exposure Point Concentrations for Chemicals of Potential Concern Detected in Surface Water at the Dixie Caverne Landfill Site (Units; ug/L)

95th UCL on the Arithmetic Mean Exposure Avenge --- —— --• — -••-——— Mexfirui Point Compound Concentration Mormel Log-normal Concentration Concentration

Northern Drainage _Area ...... _...... ------.— —-—— Organics: b.sc2-Ethylh*xyl)phthaUte 18,0 42.0 61.0 107.5 61.0 (a) Inorganics: Bariin 89.0 180.0 290.0 369.0 290.0 (a) Cadmium 9.6 19.0 120.0 41.3 41.3 Cb) CobeLt **2 6-7 u-° 11-* 'I-* Manganese 820.0 1,300.0 >1,000,000.0 1,459.5 1,459.5 Cb> Zinc 1,200.0 2,100.0 >1,000,000.0 2.460.0 2,460.0 Cb)

Southern Drainage Area Organics: Senzen* 2.5 2.6 2.6 3.0 2.6 Ce) bisc2-Ethylh*xyl)phthalate 3.2 NC NC 4.0 4.0 Cb) Inorganics: r Saritn 220.0 350.0 1,400.0 558.0 558.0 Cb) Chromiue 6.5 14.0 16.0 44.7 16.0 Ca) Cobalt 2.0 2.7 2.9 4.6 2.9 Ca> Manganese 190.0 360.0 140,000.0 761.0 761.0 Cb) Silver 1.2 1.5 1.6 2.0 1.6 Ce) Vanadiue 1.5 2.0 2.0 3.9 2.0 Ca)

Stream F .-...-- Ha chemicals of potential concern were selected in surface water.

NC Hot calculated Ca) Exposure point concentration btsed on the,95th UCL on the arithmetic ween concentration derived using Land (1971, 1975) which assumes that the distribution i* lognorml. Cb) The 95th UCL on the arithmetic mean concentration exceeded th* maxinua detected concentration, or there were not enough samples (i.e., < 3) available for estimating the 95th UCL on the arithmetic mean. Therefore, th* maximum concentration was used as th* exposure point concentration.

6-51

AR300239 Table 6-17 Exposure Point Concentration* for Chemicals of Potential Concern Detected in Sediment at the Dixie Caverns Landfill Sit* (Units: Organics: ug/kg, Inorganics: mg/kg)

95th UCL on th* Arithmetic Mean Exposure Average ...... -.-,,-. ———— Maximum Point Compound Concentration Normal Log-normal Concentration Concentration

H9C.tftjt.fn. Organics: BcnzoCa)pyren* (Equivalent) 570.0 800.0 1,000.0 1,231.5 1,000.0 (a) Phenanthrene 62.0 NC MC 62.0 62.0 Cb) Inorganics: Antimony 14.0 24.0 75.0 39,3 39.3 Cb) Cacmius 170.0 230.0 780,000.0 605.0 605.0 Cb) Chromium 260.0 400.0 4,000.0 S22.0 822.0 Cb) Lead 9,500.0 15,000.0 >1, 000, 000.0 30,300.0 30,800.0 Cb) Manganese 6,800.0 12,000.0 540,000.0 20,000.0 20,000.0 Cb) Silver 25.0 46.0 6,200.0 72.9 72.9 (b) Zinc 42,000.0 66,000.0 >1, 000,000.0 127,000.0 127,000.0 Cb)

Southern Driimg* Arte Organics: D.-n-octylphthelate '170.0 220.0 300.0 220.0 220.0 Cb)

Organics: 8«nzoCa)pyr*n* (Equivalent) NC NC HC 220.4 220.4 Cb) Phenanthrtn* NC NC NC 45.0 45.0 (b) Inorganics: Cacfcium * NC NC HC 8.9 8.9 Cb) Zinc NC NC NC 1,610.0 1,610.0 Cb)

HC Not calculated Ca) Exposure point concentration besed on th* 95th UCL on th* arithmetic mean concentration derived using Land (1971, 1975) which assumes that tht distribution is lognonul. Cb) Th* 95th UCL on th* arithmetic m**n concentration exceeded th* maximum detected conetntration, or th*r* w*r* not enough samples (i.*., < 3} available for estimating th* 95th UCL on th* arithmetic mean. Therefore, th* Maximum concentration wss used as th* exposure point concentration.

6-52 TCN 4208 RI REPORT REV #1 9/JAN/92 95th UCL on the arithmetic mean is estimated using all of the data collected from the three representative wells.

Two rounds of monitoring data from the three most contaminated monitoring wells (i.e., RIW-2, RIW-7, and RIW-12) were used to estimate exposure point concentrations for the chemicals of potential concern. Distribution statistics for these groundwater data are presented in Table 6-18. The 95th UCL on the arithmetic mean exceeded the maximum detected concentration for all chemicals of potential concern. Therefore, according to USEPA (1989a) guidance, the maximum concentrations were used as the exposure point concentrations.

6.1.3.3 Estimation of Chronic Daily Intakes

This section describes the methods used to estimate exposure for the pathways quantitatively evaluated under both current and future land-use conditions. According to the National Contingency Plan (NCP) (USEPA 1990), the exposure estimates should be based on a reasonable maximum exposure case. Exposure is referred to as the chronic daily intake (CDI), which is expressed in terms of milligrams of contaminant contacted per kilogram of body weight per day (i.e., nig/kg/day). The CDI is calculated by combining exposure point concentrations and exposure parameter estimates using a chemical intake equation.

The following sections "describe the methodology used to estimate CDIs for the pathways quantitatively evaluated in this report. In addition, CDIs for the chemicals of potential concern with available toxicity criteria are estimated for these exposure pathways.

Current.Land-Use: Use of Groundwater from Residential Wells. Exposure routes evaluated for current land-use of residential wells includes ingestion and dermal absorption while bathing. Ingestion and dermal absorption CDIs were summed since oral toxicity criteria were used to evaluate the combined exposure via these routes. 6-53 Table 6-18 Exposure Point Concentrations for Chemicals of Potential Concern Detected in Representative Grounduatcr Wells at th* Dixie Caverns Landfill Site (Units: ug/L)

95th UCL on th* Arithmetic Mean Exposure Average ------——...——,.. Meximum Point Compound Concentration Normal Log-normal Concentration Concentration

Qrganici! Naphthalene Ca) 2.4 2.6 2.7 2.8 2.7 CO Inorganics: Antimony 13.0 24.0 500.0 18.6 18.6 Ce) Arsenic 2.3 6.3 140,000.0 5.1 5.1 CO garium 390.0 820.0 >1,000,000.0 567.0 567.0 (c) Chromium 5^ 12.0 8,300.0 9.7 9.7 CO Cobalt 5.3 8.5 15.0 7.5 7.5 (c) Manganese 1,000.0 1,300.0 11,000.0 1,575.0 1,575.0 Co) Silver t-4 1.7 1.9 2.5 1.9 Cb)

NC Mot calculated Ca) tiaphthelen* uas not detected in th* three representative monitoring veils at th* site; therefore, data from all monitoring wells w*r* used to estimate exposure point concentration* for thfs chemical.

6-54

flR3002l*2 TCN 4208 RI REPORT REV ai 9/JAN/92 Ingestion of Groundwater from Residential Wells. Residents in the vicinity of the DCL s_ite7presumably use groundwater from their private wells as a source of drinking water. Potential exposures to the chemicals of potential concern via ingestion of,groundwater for the RME case were calculated using the following equation:

where: CDI = Chronic Daily Intake (mg/kg/day); EPC = Exposure Point Concentration (ug/L); CF = IO'3 mg/ug; IR = Ingestion Rate (L/day); EF = Exposure Frequency (days/year); ED = Exposure Duration (years); BW = Body Weight (kg); and AT = Averaging Time.(days).

Exposure parameter values used to estimate exposure via ingestion of groundwater are discussed below and summarized in Table 6-19.

EPC: The methods for estimating exposure point concentrations are presented in Section 6.1.3.2.

CF: A conversion factor of IO"3 mg/ug was used to convert mass units.

IR: Gillies and Paulin (1983) estimated the 90th percentile of daily water consumption to be 1.9 L/day. Studies conducted by Cantor et al. (1987) suggested that an ingestion rate of 2.0 L/day represented the 90th percentile of the ingestion rate distribution. USEPA (1989a)5 after reviewing available data, concluded that a groundwater ingestion rate of 2.0 L/day represents a reasonable maximum ingestion rate. Using this value in the risk assessment, 6-55 .,:...... - flR3QQ2if3 Table 6-19 Exposure Parameter Values Uied to Estimate Exposure to Residents via Ingestion of Groundwater

Parameter Value Reference

CF 1CT3 mg/ug - - - IR 2 L/day (EPA 1985, 199U) EF 365 days/year (EPA 1939a, L991a) EO 30 years ' (EPA 1939a. 199U) By 70 kg f=PA 1985, 199ia) AT Carcinogens 25.550 days (EPA L989a. 199U) Non-carcinogens 10,950 days . (EPA i989a. 199La)

6-56 TCN 4203 RI REPORT REV #1 9/JAN/92 however, assumes that the individual ingests water only from one's own tap during the course of the day. Data presented in USEPA (1989b) suggest that individuals may receive approximately 30 percent of their drinking water from sources other than their own wel1s.

EF: For the RME it is assumed that a resident ingests groundwater from the private residential well 350 days per year (USEPA 1991a).

ED: An. exposure duration of 30 years was assumed for estimating exposure (USEPA 1989a, 1991d) since approximately 90 percent of the population lives in the same residence for 30 years.

BW: USEPA (1985a) calculated an average body weight for males • and females of 71.8 kg. This value is approximately equal to the consensus value .pf 70 kg which is typically used as the average body weight (USEPA 1989a, 1991a).

AT: The averaging time is 30 years (exposure duration) x 365 days/year for noncarcinogens and 70 years (lifetime) x 365 days/year for carcinogens.

An example calculation of the RME CDI for the chemicals of potential concern for ingestion of groundwater assuming an exposure point concentration of 1 ug/L is presented .below: ... .. _ _

-U_yg/£i (IP"1 fflg/gg) (2J./.c.ay)_.(350 daya/yggr) (301 years) {70 kg) (25,550 days)

6-57

flR3002l*5 TCN 4208 RI REPORT REV ffl 9/JAN/92

CDJ « 1.2 x 10's mg/kg/day

Thus, the CDI for ingestion of groundwater for carcinogens is 1.2 x IO"5 nig/kg/day, assuming an exposure point concentration of 1 ug/L. The CDI for ingestion of groundwater for noncarcinogens is 2.7 x 10"s, assuming an exposure point concentration of 1 ug/L.

Dermal Absorption of Chemicals of Potential Concern in Residential Wells while Showering. Residents in the vicinity of the DCL site may be exposed to chemicals via dermal absorption while bathing or showering. In this assessment, it is assumed that the resident is exposed via dermal absorption while showering since adults typically take showers more regularly than baths. The estimated exposure to a chemical is based on the amount absorbed through the skin.

Potential exposures to chemicals of potential concern in groundwater via dermal absorption were calculated using the following equation:

CDI » (w/*»/day) where: CDI = Chronic Daily Intake (mg/kg/d); EPC * Exposure Point Concentration (ug/L); CF - Conversion Factor (IO"3 mg/ug); PC - Dermal Permeability Constant (L/cm2-hr); SA = Skin Surface Area available for contact (cm2); ET = Exposure Time (hr/d); EF - Exposure Frequency (d/yr); ED - Exposure Duration (yr); BW = Body Weight (kg); and AT = Averaging Time (d).

6-58 flR3002l46 TCN 4208 RI REPORT REV SI 9/JAN/92 Exposure parameter* values used to estimate exposure to residents via direct contact with groundwater are discussed below and summarized in Table 6-20.

EPC: The methods for estimating exposure point concentrations are presented in Section 6.1.3.2.

CF: This conversion factor adjusts the mass units. .

PC: The permeabi1ity constant reflects the movement of the chemical across the skin to the stratum corneum and into the bloodstream. Factors Influencing dermal absorption from water include the nature of the compound and the presence of other agents which might facilitate the permeability of a compound, as well as the properties of the skin itself (USEPA 1988). Chemical-specific permeability constant values are currently under review, as presented in the Superfund Exposure Assessment Manual (SEAM) (USEPA 1988), and are • not recommended for use in baseline risk assessments at this time (USEPA 1989a). Currently, USEPA (1989a) has recommended using the permeability in water of 8.4 x IO"4 L/cm2-hr for chemicals of potential concern (USEPA 1989a, Blank et al. 1984). However, this method may underestimate skin permeability properties for some organic compounds (USEPA 1989a), while overestimating the permeability of certain inorganic compounds.

SA: The average total body surface area assumed to come into direct contact with the groundwater over the duration of the shower is 18,000 cm2. The 50th percentile of the total body surface area was used, rather than an upper-bound percentile, because it reflects the best estimate of the surface area for the individual with the 50th percentile body weight (USEPA 1989a).

6-59

flR3002tf7 Table 6-20 Exposure Parameters Used to Estimate Sxposur* to Residents via Direct Contact with Groundwater while Showering

Parameter Value Reference

CF 1CT3 mg/ug * - . — SA •a. ooo cm2 (EPA 1989a) PC 8.4 x 1(T* L/cmVhrs (Blank et al , 1984; EPA 1989a) £T 0.2 hrs/day (EPA 1939a) EO 30 yrs (EPA 1989a, 199 la) £F 350 days/yr ' (EPA 1989a, 199la) BW 70 kg (EPA 1985a, 199ia) AT Carcinogens 25.550 days (EPA 1989a, 199U) Noncarcinogens 10,350 days (EPA 1339i, 1991*}

6-60

AR3002U8 TCN'4208 RI REPORT REV *1 9/JAN/9 2 ET: For the exposure time, it was assumed that the duration of direct contact with groundwater while showering would be 12 minutes per day, which represents the 90th percentile of the time people spend showering (USEPA 1989a).

EF: ~For the exposure frequency, it was assumed that residents would shower 350 days per year (USEPA 1989a).

ED: The 90th percentile of the time individuals live in the same location (i.e., 30 years) was used as the exposure duration (USEPA 1989a).

BW: USEPA (1985a) calculated an average body weight of 71.8 kg. This value is approximately equal to the consensus value of 70 kg, which is generally used as the average body weight.

AT: The averaging time is 365 days/year x 70 years for evaluating carcinogenic effects and 365 days/year x 30 years for evaluating noncarcinogenic effects.

An example calculation of the CDI for carcinogens assuming an exposure point concentration of 1 ug/L is presented below:

(IP'1 JHff/ug> (ia,ooa_gn'> [8.4 x 1Q-* £/giBJ/Ar) (8,2 Jus/day) [30 yrg? (350 cJays/yrl . (2SS50 dtya} (70 Jt?)

1.3 x lirs

The CDI for noncarcinogens, using 10,950 days for the averaging time and substituted into the above equation, is 4.1 x IO"5 mg/kg/day. 6-61

flR30Q2i*9 TCN 4208 R/ REPORT REV JM 9/JAN/9 2 Total CDIs estimated for dermal absorption and ingestion of chemicals of potential concern in groundwater from private residential wells in the vicinity of the DCL site are presented in Table 6-21.

Current land-Use: Direct Contact with Surface Soil by Trespassers Children.ma^y be exposed to the chemicals of potential concern in surface soil while playing at the DCL. The following sections describe the two potential routes of exposure from direct contact with soils: incidental ingestion and dermal absorption.

Exposure to Soils via Ingestion The ingestion of soil by children is considered to be a normal phase of childhood development (Baltrop et al. 1963, Robinson 1971, Ziai 1983). Usually temporary, this behavior may result from normal mouthing, incidental hand-to-mouth activity, and/or dermal absorption (USEPA 1989a). Ingestion of soil past the ages of 6 or 7 has been termed "abnormal" and is frequently the result of developmental problems (Lourie et al. 1963, Paustenbach et al. 1986). This behavior is known as pica-abnormal ingestion of a non-food substance (USEPA 1989b).

Potential exposures to chemicals of potential concern in surface soil via incidental ingestion for the RME case were calculated using the following equation:

CDI ^/kg/day) - (flM

6-62 flR300250 Table 6-21 Total Chronic Daily Intakes (GDIs) Estimated for the Ingestion of Groundwater and Dermal Absorption Exposure to Groundwater from Private Wells Downgradient of the Dixie Caverns Landfill Site fofnrr r*nthet duRMeE PJI«Case«

RME Total Exposure RME CDIs Point (mg/kg/day) Concentration Well /Chemical (ug/L) Carcinogens Noncarcmogens

PW-1 Barium 147.0 ___ - - - l.OE-02 Zinc 20.5 - -- 1.4E-Q3 PW-2 Barium 151. 0 l.OE-02 Manganese 2.6 1.8E-04 Zinc 20.4 1.4E-03 PW-3 Barium 46.2 3.2E-03 Manganese 2.1 1.4E-04 Zinc 15.3 1. IE-03 PW-4 Barium 68.1 4.7E-03 Manganese 4.2 2.9E-04 Zinc 159 * 1. IE-02 Ptf-5 Barium 82.7 5.7E-03 Manganese 5.3 3.6E-04 Zinc 59.4 4. IE-03 PV-6 Sarium 175.0 1.2E-02 PW-7 Sarlum 31.9 2.2E-03 Nickel 3.3 5.7E-04 Zinc 56.4 " - - - 3.9E-03 PW-8 Barium 283 .'a 1.9E-02 Manganese 3.6 2.5E-04 PW-16 Barium • 60.5 - - - 4.2E-03 Manganese 17.1 1.2E-03 Zinc 356.0 - - - ' 2.5E-02

6-63

AR30025 TCNT42O8 RI REPORT REV #1 9/JAN/92 where: CDI = Chronic Daily Intake (mg/kg/day); EPC = Exposure Point Concentration (mg/kg for inorganics, ug/kg for organics}; CF = Conversion Factor (IO"8 kg/mg for inorganics, IO"9 kg/ug for organics); IR « Ingestion Rate (mg/day); Fl « Fraction Ingested from Contaminated Source (unitless); £F = Exposure Frequency (days/year); ED s Exposure Duration (years); RBF - Relative Bioavailability Factor (unitless); BW * Body Weight (kg); and AT = Averaging Time (days).

Exposure parameter values used to estimate exposure to children via incidental ingestion of surface sails are discussed below and summarized in Table 6-22.

EPC: The methods for estimating exposure point concentrations are presented in Section 6.1.3.2.

CF: The conversion factor of IO"6 kg/mg was used to convert mass units for inorganics. The conversion factor of IO"9 kg/ug was used to convert mass units for organics.

IR: Several studies have been performed to estimate the amount of soil ingested by children. Recent studies have used tracer elements in feces and soil to estimate the amount of ingested soil (USEPA 1989b). Calabrese et al. (1987) estimated that the average 95th percentile of soil ingestion rates for the three best tracers evaluated was approximately 200 mg/day. Problems with the analytical results for the Calabrese study, however, were found. Binder et al. (1986) used three tracer elements to estimate soil ingestion. The results for the three tracer elements were averaged for an estimated average soil ingestion of 108-mg/day with a range from 100 mg/day to 200 mg/day (USEPA 1989b). Van Wijnen et al. 6-64

flR300252 Table 6-22 Exposure Parameters Used to Estimate Exposure to Children via Incidental Ingestion of Surface Soil and Sediments at the Dixie Caverns Landfill Site

Parameter Value Reference

CF . Organics 10"* kg/mg - - - Inorganics 10** kg/mg - - - [R ' 140 mg/day (EPA 19896) fl 1 (EPA 1989a) EF 125 days/year (EPA 1989a) £0 10 years (EPA 1989a) RBF Semivolatne 0-5 (Poiger and Organic Compounds ' " " - - Schlatter, 1980 McConnell et al., 1984. Lucier et al. 1986, Wending et al. 1989, and van den Berg et al., 198o, 1987) Volatile Organics and 1 Assumed' value Inorganics BW 25 kg . (EPA 1985a) AT Carcinogens 25,550 days {EPA 1989a) Noncarcinogens , 3,650 (EPA 1989a)

6-65

flR300253 RI REPORT REV *1 9/JAN/9 2 (1990) reported that the estimated range of 90th percentiles of ingestion rates ranged from 190 mg/day during normal activities to 300 mg/day during vacationing at campgrounds. The interim final guidance for soil ingestion rates released by the Office of Solid Waste and Emergency Response (OSWER) recommended using 200 mg/day as an upper-bound soil ingestion rate for children under the age of 6 (USEPA 1989d). The 200 mg/day ingestion rate appears to be a reasonable upper-bound value given the supporting research discussed above. A soil ingestion rate of 100 mg/day was recommended for children over the age of 6 and adults (USEPA 1989a,d). For the age group evaluated for this pathway (i.e., 2 to 12), a weighted average ingestion rate of 140 mg/day was calculated using the USEPA (1989a,d) recommended ingestion rates (i.e., 200 mg/day for children between the ages of 2 to 6, and 100 mg/day for children between the ages of 6 to 12).

Fl: The fraction ingested from the contaminated source was conservatively assumed to be one (1).

EF: For the exposure frequency, it was conservatively assumed that children would play in surface soil at the site three times per week for 10 weeks in the spring and fall when the temperature is above freezing (total of 60 days). In the summer months, to account for warmer weather and schools being closed, children's exposure is considered to be up to five times per week for approximately thirteen weeks. Therefore, the exposure frequency would be 65 days during the summer. The total number of days exposed per year for the RME case was estimated to be 125 days/year.

ED: Children were assumed to play in the area between the ages of 2 and 12, giving an exposure duration of 10 years. Children in this age group are more likely to engage in the activity outlined in this

6-66

SR30025U TCN 4208 RI REPORT REV #1 9/JAN/9 2 pathway than at other ages. In addition, children in this age group may have relatively higher exposure (mg/kg/day) because of their lower body weights (kg) than older children that would have higher body weights.

RBF: The relative bioavailability factor is used to adjust exposure to chemicals of potential concern which tightly bind to a soil/sediment matrix (e.g., PCBs). Many contaminants which adsorb to soil particles may be less bioavaliable when the contaminant is administered in water or oil, which is the typical vehicle used in laboratory toxicity tests. Experimental data on the relative bioavailability of the chemicals of potential concern are limited. Several studies have been conducted on dioxin which show the relative bioavailability to range from 7% to 50% (Poiger and Schlatter 1980, McConnell et al. 1984, Lucier et al. 1986, Wendling et al. 1989, .and Van den Berg et al. 1986, 1987). To be conservative, all semivolatile organic compounds (e.g., PAHs) are assumed to have a relative bioavailability factor of 50 percent. Other volatile organic compounds and inorganics are assumed to have a relative bioavailability factor of one (1). This is a conservative assumption which would tend to overestimate the bioavailability for some compounds.

BW: The mean body weight for both male and female children between the ages of 2 to 12 is approximately 25 kg (USEPA 1985b).

AT: The averaging time is 10 years (exposure duration) x 365 days/year for noncarcinogens and 70 years (lifetime) x 365 days/year for carcinogens.

An example calculation of the RME CDI for semivolatile carcinogens assuming an exposure point concentration of 1 ug/kg is presented below: 6-67

flR300255 TCN 42Q8 RI REPORT REV *l 9/JAN/9 2

(I tig/Jegl CIO'* fcg/ag) (140 «g/'day. (11 (125 days/yearT'do yaara) (.5) (25 fcg-) (25550 days)

L* x ID'

For semivolatile organic compounds (1 ug/kg exposure point concentration), the RME CDI is estimated to be 1.4.x IO"10 mg/kg/day and 9.6 x 10"10 mg/kg/day for carcinogenic and noncarcinogenic effects, respectively. For inorganic compounds (1 mg/kg exposure point concentration), the RME CDI is estimated to be 2.7 x IO'7 mg/kg/day and 1.9 x IO"8 mg/kg/day for carcinogenic and noncarcinogenic effects, respectively.

Exposure to Surface Soils via Dermal Absorption This assessment will focus on the dermal absorption of organic contaminants since laboratory studies (Skog and Wahlberg 1964, Wahlberg 1968a,b) have shown that dermal absorption of inorganic compounds bound in a soil/sediment matrix is negligible. Potential .exposures to organic chemicals of potential concern in surface soil via dermal absorption for the RME case were calculated using the following equation:

CDI MBS) (gF> .a?) where:

EPC - Exposure Point Concentration (ug/kg); CF - Conversion Factor (IO"9 kg/ug); SA = Skin Surface Area available for contact (cm2/day); AF - Soil-to-Skin Adherence Factor (mg/cm2); ABS - Dermal Absorption Factor (unitless); EF - Exposure Frequency (days/year); ED » Exposure Duration (years); BW - Body Weight (kg); and AT - Averaging Time (days).

6-68 flR300256 TCN 4208 RI REPORT REV tfl 9/JAN/9 2

Exposure parameter values used to estimate exposure to children via dermal absorption of chemicals of potential concern in surface soil are discussed below and summarized in Table 6-23. The exposure frequency (EF), exposure duration (ED), body weight (BW), and averaging time (AT) previously discussed for the surface soil ingestion exposure route were also used to estimate exposure for the dermal absorption exposure route.

EPC: The methods for estimating exposure point concentrations are presented in Section 6.1.3.2.

CF: The conversion factor of IO"9 kg/ug is used to convert mass units.

SA: Approximately one-third of the total surface area of the hands, arms, and legs was assumed to directly contact surface soil. Thus, approximately JOOO cm2 of the body surface would contact contaminated surface soil based on data presented in USEPA (1985a, 1989b) for children ages 2 to 12. The 50th percentile of the surface area of the hands, arms, and legs was used, rather than an upper-bound percentile, because it reflects the best estimate of the surface area for.the individual with the 50th percentile body weight (USEPA 1989a).

AF: A 'soil-to-skin adherence factor of 1.45 mg/cm has been calculated using commercial potting soil (USEPA 1989a).

ABS: The absorption factor reflects the percentage of a compound contacting the skin which will pass.through the skin to the stratum corneum and into the bloodstream. Factors influencing dermal absorption from a soil matrix include the affinity of the compound for the soil matrix and the presence of other agents that might facilitate the permeability of a compound, as well as the properties 6-69

SR300257 Table 6-23 Exposure Parameters Used to Estimate Exposure to Children via Dermal Absorption of Chemicals in Surface Soil and Sediments at the Dixie Caverns Landfill Site

Parameter Value Reference

CF 101* kg/ug ^ . ^ -- - - SA 1000 cmVday {EPA 1989a) AF 1.45 mg/cffl2 (EPA 1989a) ASS (EPA 1989a) SemlvolatUe 0.05 (rang et al., 1986a,b Organic Compounds Wester et al., 1997, Volatile Organic 0.1 Poiger & Schlatter. Compounds -- 1980} inorganics 0 (SJcog 1 Wahlberg, 1964, Uahlberg, 1963a,b) EF •-- - —— ~ 125 days/year (EPA 1939*) EO 10 years (EPA 1939.1) aw 25 kg (EPA 1985a) AT Care inogens 25,550 days (EPA 1939a) Honcarcinogcns 3,550 days (EPA 1989aJ

6-70

AR300258 TCN 4208 RI REPORT REV *1 9/J AN/92 of the skin itself (USEPA 1988). Based on results from Yang et al. (1986a,b), Wester et al. (1987), and Poiger and Schlatter (1980), it is assumed that 5 percent of the semivolatile compounds (e.g., PAHs) in surface soil are absorbed through the skin. There is insufficient experimental evidence, to derive dermal absorption factors for other chemicals of potential concern. Based on laboratory studies (Skog and Wahlberg 1964, Wahlberg 1968a,b), inorganic compounds are not considered to be absorbed and thus exposure to inorganics from dermal contact is assumed to be zero.

An example calculation of the RME CDI for semivolatile carcinogens assuming an exposure point concentration of 1 ug/kg is presented below:

CDT - (J- ug/kg) (10"* kg/up) {logo cg.Vgay)_fl.45 mg/cm3) (_.Q5? (12S days/year} (10 years) . . . . - (25 kg) (25550 days)

1-4 x 10"" flJff/kff/ day

For semivolatile organic compounds (1 ug/kg exposure point concentration), the RME CDI is estimated to be 1,4 x IO*10 mg/kg/day and 9.9 x 10'10 mg/kg/day for carcinogenic and noncarcinogenic effects, respectively.

CDIs estimated for ingestion and dermal absorption of chemicals of potential concern in surface soil at the DCL site are presented in Table 6-24.

Current Land-Use: ..Direct Contact with Surface Water by Children Playing in Streams and Gmundwater Seeps Children mav be exposed to chemicals of potential concern in surface water from streams and groundwater seeps in the vicinity of the DCL site. The estimated exposure to a contaminant is based on the amount absorbed through the skin. Since the amount of surface water ingested during

6-71

SR3QQ259 "dole 6-24 Chrome Oa.i'y Intakes (CDIs] Estimated" for Direct Contact •nth1"™" iu«"ace loil by Children Playing at tne Dixie Caverns Landfill Site for the" RME Case

RHE RME CDIs. .-.RME CO Is Exposure Point for Incidental Ingestion __ for Dermal Absorotion Concentration (mg/kg/day} (mg/kg/day] (Organics: ug/kg) —————————————————- —————---*———-———-*-*———- Chemical [Inorganics: mg/kg) Carcinogens Noncarcinogens Carcinogens Noncarci.nogens

Organics: StnzoUJpyrene (Equivalent) 2300.Q 3.2E-07 - - - 3,3£-07 - - --

Inorganics (b): - ,-—.-.. - - - Arsenic 22.0 - 6.0E-0.6 4.2E-05 - - - -- Barium 160.0 ' - ———— 3.IE-04 .------fiery Ilium 1.1 3.0E-07 2.IE-06 ' ------Cadnium 11.0 --- 2.IE-OS —------Manganese 1080.0 - - - 2.IE-03 - - - •- - — Kldctl 34.0 - - - 6.5E-OS - - - Zinc - 2100.0 - - — 4.0E-03 - - -

(a) No toxicity criteria were available for difaenzofuran, phenanthrene, acenaphthene, and cobalt; therefore, no CDIs or risks were estimated for these chemicals. (b) Dermal absorption of inorganics in a soil matrix is negligible.

6-72 flR300260 TCN 4208 RI REPORT REV 31 9/JAN/9 2 play activities .is negligible, such exposure was not considered in this assessment. ' - '

Possible exposure to chemicals of potential concern in surface water via dermal absorption were calculated using the same equation presented for dermal absorption while showering. Exposure parameter values used to estimate exposure to children via contact with surface water are summarized in Table 6-25. The same skin surface area (SA), exposure frequency (EF), exposure duration (ED), body weight (BW), and averaging time (AT) previously discussed for the surface soil ingestion exposure route were used to estimate exposure for the dermal absorption of contaminants In surface water. The same permeability constant (PC) used to estimate exposure via dermal absorption while showering, also was used to estimate dermal absorption while playing in surface water. For the exposure time (ET), it was assumed that contact with surface water during play activities would be similar to the national average of time spent swimming, or 2.6 hrs/day (USEPA 1988, 1989a).

An example calculation of the CDI for carcinogens assuming an exposure point concentration of 1 ug/L is presented below:

(1 ug/L) (1Q-* jng/'ugrU'ood '.taii1'. (8.4 xlO"4 L/cm*/hr) (2.6 his/day) (IQ yrs) [125 days/yr) (25550 days) (25 Jcj?)

4.3 X 10-*

The COI for noncarcinogens, using 3,650 days for the averaging time substituted into the above equation, is 3.0 x IO'5 mg/kg/day. CDIs estimated for dermal absorption of chemicals of potential concern in surface water from streams and groundwater seeps in the vicinity of the DCL site are presented in Table 6-26.

6-73

flR30026 Table 6-2S Exposure Parameters Used to Estimate Exposure to Children via Direct Contact with Surface Water

Parameter Value Reference

CF IO"3 mg/ug . .-•_ 5A 1000 cm2 (EPA 19aSa) PC 8.4 x IO* L/cmVhr [9 lank at al. 1984; EPA 1989a) ET 2.6 hrs/day Assumed value EO 10 yrs (EPA 1989t) EF 125 days/yr (EPA 1989a) BU 25 kg (EPA 1985a) AT Carcinogens 25.550 days (EPA 1939*) Noncarcinogens 3. 650 days (EPA 1989a)

6-74

AR300262 Table 6-26 Chronic Daily Intake*

Northern Drainage Area Organic*: bis<2-£thylhexyt)phthaUte 61.0 2.66-04 1.36-03 Inorganics: BariiM 290.0 - - - 8.7E-03 Cadmiu* 41.3 - - - 1.2E-03 Manganese 1459.5 - - - 4.46-02 Zinc 2460.0 - - - 7.46-02 Southern Oreinege Area Organics: Benzene 2.6 1.16-05 bii<2-£thylh«xyl)phthelat* 4.0 1.71-05 1.2E-04 Inorganics: Bariue 55*.0 - - - 1.76-02 Chroeiije 16.0. - - - 4.8C-04 Kangancse 761.0 - • • 2.36-02 Silver 1.6 - - - 4.8E-05 Vanadiun 3.9 - - - 1.2S-04 Streeei f No cheeiicalt of potential concern Mere selected for surface water.

(a) No toxicity criteria were available for eobelt; therefore. CDU and risks were not estiMted for this cheeriest.

6-75 AR30026-3 TCN 4208 RI REPORT REV #1 9/JAN/9 2 Current land-Use: Direct Contact with Sediments by Children Playing in.Streams and Groundwater Seeps CDIs for direct contact with contaminants present in sediments were estimated using the same methods (i.e., exposure parameter values [Tables 6-22 and 6-23] and COT equation) outlined for direct contact with surface soil. Although play activities along the banks of streams may result in the incidental ingestion of sediments, studies have not been performed specifically on the ingestion rate of sediments. USEPA (1989a) recommends using the soil dermal contact equation for sediments, although due to their textures, most sediments are probably less likely to adhere to the skin than soil. CDIs estimated for incidental ingestion and dermal contact with sediments are presented in Table 6-27.

Estimating Exposure to Lead Using Pharmacokinetic Modeling. A pharmacokinetic model, known as the Integrated Uptake/Biokinetic (IU/BK), was used to estimate exposure to children from lead present in sediment at the northern drainage area of the DCL site. The ILf/BK model is a computerized pharmacokinetic model that analyzes the effects of lead poisoning because, unlike most chemicals (which have a threshold for noncarcinogenic effects), lead may impact development of neurological function at any dose level (i.e., no threshold level).

The IU/BK model quantifies the distribution of possible lead concentrations in the blood using a multimedia approach. The IU/BK model consists of two basic modules: 1) the uptake of lead, and 2) the biokinetics of lead in the body. Uptake of lead is defined as the amount of lead that is absorbed into the body's blood-plasma system from various sources (i.e., ingestion, inhalation, and dermal absorption). Using absorption factors calculated from the above uptakes, the biokinetic model calculates the amount of lead that will occur in a number of "body compartments." In the body, lead is exchanged among body compartments such as plasma and the extracellular fluid (ECF) pool, red blood cell (RBC) pool, kidneys, liver, trabecular bone, cortical bone, and other soft tissue pools. The important factor of the biokinetic model is the transition time for the movement of lead between compartments (which includes removal by feces and urine). The 6-76 AR300264 t> Ii f ,...,. •» 1 1 fi u /N 5 $ £ OS O > -E « S < •£

m*» HIC ?• c E? .•.iii « i > a U ** w O O "SI-d2 u Q 9 UI UJ O ^F t * • i i i v* 1 i t_ £ —Qi uC o — 841 i ^ u — « ^ 4t mL. ^ ^ -*C- - u t. « -MC t. Q •- 0 **" 9 •i u'— • £ 0 ws i«*• • SSSSS5 ' S9 j-p u 3 I U LU UJ IU ^J U LU ^J * *- i UtfM ««•*•* i ^^ g I ^. -— •- K. •- CM ^M _2 jj (. k — o — v §Q ^i 0 > u ^* c B C X u O *— 5 2 ts s f- •4. V M tV A )~ CM *4 ^rf ^3 e1 uX •i "B — 8 S~9 41 m £< fl'S ii? p N- i i > l l i a 1 r 1 0 , , , , . ** tA i* g- 1 iu uj Is LU ** **'c u ••• *- ni (0 — 0 U •i* **• Sm 1-s is oa

-M .- * ffl C e"" w ** *» O M O O O &> O «* OO ii • H— A e c5^ S 3t£(%fSKS S 0O l]| Q a S (M "" £g fl!! •*• • • s ^ e 8-S V ^ v iw *-«* M J* i 6 ^3 ^L o -C— H U s !L IB «•* ^3 U £ ^L • £ p ^^ ^ u * u ? a «• ** W i S3 • • B) * i 2 c W ' M i 6 S *to ?3 . 1 •£ » ? .1 1 V « • V 3 3 t 8- fr —— -^ Bt < IU UI w ^ ** 1 a x€^ i £ I — * •" .S5S u « ^ * g£t 1 *c N»Wl —3£-«l 5 5*r iC t- ^ . ..«• ^I* —"5« b u 5•^ t* uo S ""S 8 ™ S « wo 5*« .«•«O. O.MC o (_ g*w *OTN *; , gu^* < m O — «i o — 5.

6-77 flR3Q0265 TCN 4208 RI REPORT REV *1 9 /JAN/9 2 transition time fs the rate-determining factor for the rate at which lead enters, resides in, and then leaves each compartment during a monthly iteration. The transition time is calculated on a monthly basis and is dependent upon the body weight and individual compartment weight at that monthly age.

In this assessment, potential exposure to lead in the sediments collected from the northern drainage area was evaluated. The exposure point concentration for lead in these sediments of 30,800 mg/kg (the maximum concentration exceeded the 95th UCL on the arithmetic mean) was used as the soil concentration in the IU/BK model. Default values for other parameters in the model were used to estimate exposure from other sources such as drinking water, air, maternal sources, etc.

In accordance with EPA Region III guidance (USEPA 1991b), the default geometric standard deviation (GSD) of 1.42 was changed to 1.7, based on more recent data on the GSD of blood lead levels in children at hazardous waste sites (e.g., Baltimore Lead Abatement and Cincinnati Lead Abatement studies, as cited in USEPA

Future Land-Use: Direct Contact with Surface Soil. If hypothetical residents at the DCL site come into contact with surface soil they may be exposed to contaminants through dermal absorption and incidental ingestion. The equations used to estimate CDIs for these exposure routes were presented previously for direct contact with surface soil by trespassers under current land-use of the DCL site. Exposure parameter val ues used to estimate exposure vi a i ncidental ingestion and dermal absorption for this pathway are presented in Tables 6-27a and 6-27b, respectively. It was assumed that a hypothetical resident would be exposed over a 30 year period (6 years as a child and 24 years as an adult). CDIs estimated for ingestion and dermal absorption of chemicals of potential concern in surface soil under future land-use conditions at the DCL site are presented in Table 6-27c.

6-78 fiR3Q0266 Table 6-27a Exposure Parameters .Used to Estimate Exposure to Hypothetical Residents.via Incidental Ingestion of Surface Soil at the Dixie Caverns Landfill Site Under Future Land-Use Conditions

Parameter - Value Reference

CF "" ———— ...... Organics . „...... —. - -— --— • IO"9 kg/mg - - - Inorganics IO"8 kg/mg . ,_.._,__ -- . .. . . - - - IR / ~ " " children: 200 mg/day. (EPA 1989b) adults: 100 mg/day; [weighted average: 120 mg/day] Fl .1 . {EPA 1989a) EF .... 350 days/year. . . ..__...___.._-... . (EPA 1989a) £0 8 years as a child. (EPA 1989a) 24 years as an adult RBF Semivolatile _. _ 0.5 . {Poiger and Organic Compounds ' - • ..... Schlatter, 1980 HcConnell et a.'., Lucier et al, 1986, Wending et al 1989, and van den Berg et al., 1986, ' - - - 1987} Volatile .Organ'ics and 1 . _ ..... Assumed value Inorganics - - BU children: 15 kg, [EPA 1985a) adults: 70 kg; ' " [weighted average: 59 kg] AT ...... Carcinogens . ------.- : "25,550 days [EPA 1989a) Noncarcinogens " " 10,950 days (EPA 19S.9a)

6-79 flR300267 Table 6-27b Exposure Parameters Used to Estimate Exposure to Hypothetical Residents via Dermal Absorption of Chemicals in Surface Soil at the Dixie Caverns Landfill.Site Under Future Land-Use Conditions

Parameter Value Reference

CF ' ' 10'9 kg/ug SA children: 1000 cm2, {EPA 1989a) adults: 3000 cm2; [weighted average: 2600 cm2/day] "~

AF ' ~~" 1.45 mg/cm2 (EPA 1989a) ASS (£PA 1989a) Seraivolatne 0.05 (Yang et al., 1986a,b Organic Compounds Wester et al., 1987, VolatiIt Organic 0.1 . - Poiger & Schlatter, Compounds 1380) Inorganics 0 (Skog & Uahlberg, 1964, Wahlberg. 1968a,b) EF 350 days/year _ [EPA 1989a) £0 6 years as a child, (EPA 1989a) 24 years as an adult BU children: 15 kg, (EPA 1985a) adults: 70 kg; [weighted average: 59 kg] " AT Carcinogens 25,550 days (EPA 1989a) Moncarcinogans 10,950 days (EPA 1989a)

6-80 AR30Q268 Table 6-27c . '. - - Chronic _Daily Intalces.._(CDl5.J. Estimated for Direct Contact with Surface Soil by Hypothetical .Residents at trie-Dixie Caverns Landfill Site for the RME Case

RME _. .__._ .. .;:_._.._.__._.__~_RME CDIs .. RME CDIs Exposure Point ... for Incidental Ingestion for Dermal Absorption Concentration .... (mg/kg/day) (mg/kg/dayj (Organics:. ug/kg) ---——————-~^-.-.-_.-————— —————•——————————————— Chemical (Inorganics: mg/kg) Carcinogens Noncarcinogens Carcinogens Noncarcinogens

Organ ics:_.,--=-——=-.-=------" ------• - — 8enzo{a)pyrene (Equivalent) " " "2300.0. - - 9.6E-07 - - - 3.0E-06 - - -

Inorganics (b): - " -.---. . ... _ ...... ,==,.. .. Arsenic .. - ---— ----- ..22.0 .. : . l.'SE-OS I'.tt-QS Barium - 160.0 - - - 3,IE-04 Beryllium 1.1 9.2E-07 2.IE-06 Cadmium - ...--- -n_0 ..... 2.1^-05 Manganese - - • ••• • •-• -IQflO.O ' - - - 2-IE-03 Nickel . - -34.0 - - - • 6.6E-05 Zinc - . .. . 2100.0 .- - -- 4.IE-03

(a) No toxicity criteria were available for dibenzofuran, phenanthrene. acenaphthene, and cobalt; therefore, no ,COIs or risks were estimated for these chemicals. (b) Dermal absorption of inorganics in a sail matrix is .negligifale.

6-81 flR300269 TCN 42.08 R! REPORT REV *1 9/JAN/92 Future Land-Use: Use of Groundwater at the DCL Site. For"the future use of groundwater, It was assumed that a resident may install a well in the vicinity of the most contaminated monitoring wells at the site. It should be emphasized that it is highly unlikely that residents would actually use groundwater directly from the DCL as a source of drinking water in the future. The future land-use pathway was quantitatively evaluated in this report in order to justify further restrictions of groundwater use and in order to provide the basis for making risk management decisions concerning groundwater contamination at the DCL site. Exposure routes evaluated for future use of groundwater include ingestion and dermal absorption while showering. The methods used to estimate CDIs for these exposure routes were presented previously for current land-use of residential well groundwater. CDIs estimated for ingestion and dermal absorption of chemicals of potential concern in groundwater under future land-use conditions at the DCL site are presented in Table 6-28. Inhalation exposure was not evaluated because no VOCs were detected in the monitoring well samples.

6-82 AR300270 Table 6-28 Chronic Daily Intakes (CDIs) Estimated for Ingtstion of Groundwater and Otrmal Absorption Exposure "to Groundwater from the Dixie Caverns Landfill Sitt by Hypothetical Residents for tht RH£ Cast

RM£ . Total RME COls Exposure Point (mg/kg/day) Concentration Chemical (ug/L) Care inogtns Noncarc i nogens

Organics: Naphthalene 2.7 - - - 1.9E-04 Inorganics: - Antimony 18.6 1.3E-03 Arsenic 5.1 1.5E-04 3.5E-04 Barium 567.0 3.9E-GZ Chromium 9.7 - - - 6.7E-04 Manganese 1575.0 - - - 1. IE-01 Silver 1.9 1.3E-04

6-83 flR30027l TCN 4208 RI REPORT REV *1 9/JAN/92 6.1.4 Toxicitv Assessment

This section evaluates the carcinogenic "and noncarcinogenic toxicity of chemicals of potential concern selected in Section 6.1.2 for quantitative evaluation in this report. Toxicity assessment is the process of evaluating the potential for a contaminant to cause an adverse health effect in humans and, if possible, to quantify the relationship between exposure levels (i.e., dose) and the adverse health effect. Hazard identification, the first step in conducting a toxicity assessment, involves the evaluation of the potential for a contaminant to cause an adverse health effect. Dose-response evaluation, the second step in the toxicity assessment process, attempts to quantify the relationship between the dose of the administered contaminant and increased incidence of the adverse health effect.

The slope factor is used to evaluate the potential carcinogenic risks associated with exposure to a contaminant. The reference do.se (i.e., RfD) is used to evaluate the potential noncarcinogenic' hazards associated with exposure to a contaminant. Toxicity criteria and supporting toxicity data used in the baseline risk assessment were obtained from the Integrated Risk Information System (IRIS) (USEPA 1991a), FY91 Health Effects Assessment Summary Tables (HEAST) (USEPA 1991b), Health Effects Assessment documents, Toxicity Profiles developed by the Agency for Toxic Substances and Disease Registry (ATSDR), and other sources. This report evaluates both chronic oral exposure for all chemicals of potential concern and inhalation exposure for volatile organics in groundwater. Dermal absorption of contaminants in surface soil, surface water, and sediments were evaluated even though dermal absorption toxicity criteria were not available. In this report, oral toxicity criteria were used to estimate impacts from the dermal absorption route.

6-84 flR300272 TCN 4208 RI REPORT REV #1 9/JAN/9 2 6.1.4.1 Toxicity Criteria for Evaluating Potential Carcinogenic Effects

The slope factor, expressed in (mg/kg/day)"1, quantifies the potential cancer potency of a conTaminant in order to evaluate the carcinogenic risks associated with exposure. Unlike noncarcinogenic effects, a small number of molecular events may alter a cell in such a way as to cause uncontrolled cellular proliferation, thereby resulting in disease (i.e., carcinogenic effect). Therefore, since any exposure may result in the manifestation of a carcinogenic effect, no exposure is considered to be risk-free.

To evaluate the potential carcinogenic toxicity of a contaminant, USEPA first determines the likelihood that the contaminant is a human carcinogen. USEPA uses a classification system (i.e., weight-of-evidence classification) for the characterization of the potential carcinogenicity of a contaminant based on the evidence resulting from animal and human studies. The weight-of-evidence classification scheme is presented below:

A - Human Carcinogen; 81 - Probable Humain Carcinogen, based on limited human data; B2 - Probable Human Carcinogen, based on sufficient evidence in animals and inadequate or no evidence in humans; C - Possible Human Carcinogen; D - Not classifiable as to human carcinogenicity; and E - Evidence of noncarcinogenicity for humans.

If the contaminant is a human carcinogen (Group A) or a probable human carcinogen (Group Bl or Group 82), a slope factor "is. calculated for the contaminant which quantifies its cancer potency. In certain cases, slope factors are derived for possible human carcinogens (Group C compounds). Slope factors are derived by extrapolating dose-response relationships measured under high dose conditions in laboratory animal studies or epidemiological studies to low dose conditions typically encountered at Superfund sites. The first step in deriving a slope 6-85 flR300273 TCN 4208 R! REPORT REV #1 9/JAN/9 2 factor involves fitting a mathematical model to the experimental data (USEPA 1986a). Of the available low dose extrapolation models (i.e., Weibull, probit, logit, one-hit, and gamma multihit models), the more conservative linearized multistage model is typically used to derive a slope factor from animal data. This model assumes that the dose-response relationship at low doses is linear. Once the data are fit using the linearized multistage model, the 95th upper confidence limit on the slope of the line represents the slope factor. Slope factors are then verified and validated by the Carcinogen Risk Assessment Verification Endeavor (CRAVE) Workgroup before being placed on IRIS. Slope factors based on epidemiological data are fit on an ad hoc basis.

Slope factors and supporting toxicity data for chemicals of potential concern are summarized in Table 6-29.

6.1.4.2 Toxicity Criteria for Evaluating Potential Noncarcinogenic Effects

The reference dose (RfD), expressed in mg/kg/day, is used to evaluate the potential noncarcinogenic hazards associated with exposure to a contaminant at a Superfund site. A chronic RfD is defined as an estimate of a daily exposure level for the human population, including sensitive subpopulations, that is 1 ikely to be without an appreciable risk of deleterious effects during a lifetime based on an administered dose (USEPA 1989a). It is assumed that a protective mechanism in the body must be overcome in order for a noncarcinogenic effect to occur (I.e., threshold effect). For example, numerous cells in an organ must be damaged before an effect may be manifested.

In general, RfDs are derived from animal laboratory studies or human epidemiological studies. These studies are reviewed to derive a no-observable- adverse-effeet level (NOAEL) for the contaminant. The lowest-observable-adverse- effect level (LOAEL) is used when a NOAEL cannot be derived from the study. In this case, an additional uncertainty factor is applied to estimate the RfD.

6-86 AR3QQ27** Table 6-29 Carcinogenic Toxicity Criteria (SFs) for Chemicals of Potential Concern at the Dixie Caverns Landfill Site

Slope Factor. (SF) Weight-of-£vidence Type of Route/Chemical (.15 A 9/ day)"1 _ _ Classification (a) Cancer 5F Source

Oral Route ..---,.. --— - - - - -—--•— -- Organics: - - - - - ..... -..-

Benzene 2.9E-2 A Leukemia [RIS* 3enzo(a)pyrene (Equivalent) 1.2E+1 92 Stomach ^€ffi^• bis(2-Ethylnexyl)phtnalata 1.4E-2 '82 Liver IRIS Inorganics: Arsenic 1.7E+0 A Lung IRIS Beryllium 4.3E*0 82 Total Tumors IRIS

IRIS data obtained March 1991. ** First Quarter HEAST data used (January, 1991). (a) Se« text for weight-of-evidence classification description.

6-87

flR300275 TCN 4208 RI REPORT REV *\ 9/JAN/9 2 Uncertainty factors (UFs) are applied to the NOAEL (or LOAEL) to account for various types of uncertainty, including:

• variation in the human population (UF = 10); « extrapolation from animal to human studies (UF - 10); • derivation of a chronic RfD from a subchronic NOAEL (UF = 10); and • derivation of a chronic RfD from a chronic LOAEL (UF = 10).

An additional safety factor, referred to as the modifying factor (MF), may be applied when deriving the RfD to account for other sources of uncertainty in the study. The modifying factor is a value that ranges from 1 to 10 which is assigned based on a qualitative evaluation of the study. RfDs are developed by the intra-agency RfD Workgroup in accordance with USEPA guidelines (USEPA 1986b, 1989f,g).

The approach discussed abovexan be used to evaluate the noncarcinogenic effects associated with chemicals at the DCL site, with the exception of lead. Recent studies on the noncarcinogenic effects of lead suggest that developing a RfD would not be appropriate given that the effects may not have a threshold. EPA recommends the use of a pharmacokinetic model known as the Integrated Uptake/Biokinetic (IU/BK) model to estimate blood levels in children (see Section 6.1.3.4 for more information concerning the IU/BK model). This model is used to predict the proportion of the population above the interim criterion of 10 ug/dL of lead in blood. Blood lead levels in children above 10 ug/dL show indications of peripheral nerve dysfunction, indexed by slowed nerve conduction velocities (NCV) based on collective neurobehavioral studies of central nervous system (CNS) cognitive effects. These results may be indicative of a likely association between neuropsychological defects and exposure to low levels of lead.

RfDs and supporting toxicity data for chemicals of potential concern are summarized in Table 6-30. Toxicity profiles for the primary chemicals of

6-88 AR300276 Table 6-30 Chronic Noncarcinogtnic Toxicity Criteria (RfOs) far Chemicals of Potential Concern at tht Dixie Cavtrna Landfill Site

(Chronic RfO (mg/kg/day) Confidence Critical RfD Uncertainty (c) and Chemical (a) (oral route) Level (b) Effect Source Modifying Factors

Organics: _...._.. -.-:---— - ""---- .. .: — ~- -"-- -

bisU-EtnylhexylJphthalate 2.0E-2 Medium Increased relative IRIS UF - 1000 for H.A.S;

Naphthalene 4.0E-3 ------Ocular and internal lesions HEAST UF - 10,000 far H.A.S. I Inorganics: .....,- ... .._

Antimony 4.0E-4 Low Blood glucose. IRIS UF - 1000 for H.A.L; cholesterol MF » L

Arsenic I.OE-3 - - - -

Barium 7.0E-2 Medium Increased blood . IRIS UF - 3 for H; pressure MF - 1 Cadmium 5.0E-4 High Significant prottinuria IRIS UF - 10 for H; MF - 1 • Chromium (hexavalent) 5.0E-3 """- - - None observed IRIS UF » 500 for H.A.S

Manganese l.OE-1 Medium Central ntrvous IRIS UF - L; system effects MF - 1 Nickel 2.QE-2 Medium Decreased body IRIS UF - 300 for H.A.S; and organ weights MF « 3 1 Silver 3.0E-3 Medium Argyrit IRIS UF - 2 MF - 1 Vanadium 7.0E-3 None observed HEAST UF « 100 for H.A Zinc 2.0E-1 Anemia HEAST UF .10 for H

- - - - -No data available " HEAST data used from January, 1991 ** IRIS data obtained March, 1991 (a) No toxicity criteria wtre available for tht following chtmicals of potential concern: aluminum. cobalt, lead, dibenzofura acenaphthtnt, phenanthtnt, di-n-octylphth«l«tt. N-nttroiodlphtnylamint. and 4-nitroanilint. (b) Confidence level as given by IRIS (c) Uncertainty idjustmtnts represent tht following combined txtripoUflont: H * variation in human sensitivity; A * animal to human extrapolation; S - extrapolation from subchronic to chronic NOAEL; and L - extrapolation froM a LOAEL to a NOAEL.

6-89 flR300277 TCN 4208 RI REPORT REV *1 9/JAN/92 potential concern at the DCL site (i.e., antimony, arsenic, cadmium, bis(2- ethylhexyljphthalate, benzo(a}pyrene, silver, and zinc) are presented in Appendix F. .. . .

6-90 AR300Z78 TCN 4208 RI REPORT REV ft 9/JAN/92 6.1.5 Human Health_.-Risk Assessment

The final step in the baseline risk assessment process is risk characterization. In this section, toxicity criteria identified in Section 6.1.4 are combined with exposure estimates presented in Section 6.1.3 to quantify potential noncarcinogenic and carcinogenic effects associated with chemicals of potential concern at the DCL site. Section 6.1.5.1 presents an overview of the methods for the quantitation of potential carcinogenic risks and noncarcinogenic hazards. Potential risks associated with exposure pathways evaluated under current and future land-use of the DCL site are discussed in Section 6.1.5.2 and Section 6.1.5.3, respectively.

6.1.5.1 Methods for Estimating Carcinogenic Risks and Noncarcinogenic Hazards

Potential carcinogenic risks are expressed as an increased probability of developing cancer over a lifetime (i.e., excess individual lifetime cancer risk) (USEPA 1989a). For example, a 10~6- excess lifetime cancer risk can be interpreted as an increased risk of 1 in 1,000,000 for developing cancer over a lifetime if an individual is exposed as defined by the pathways presented in this report. A IO"6 excess lifetime cancer risk is the point of departure established in the NCP (USEPA 1990). In addition, the NCP (USEPA 1990) states that "for known or suspected carcinogens, acceptable exposure levels are generally concentration levels that represent an excess upper bound lifetime cancer risk to an individual' of between IO"4 and IO"6."

Since the excess lifetime cancer risks are below IO"2 for the DCL site, carcinogenic risks for chemicals of potential concern are quantified using the equation below:

6-91

SR300279 TCN 4208 RI REPORT REV tfl 9/J AN/92

Cancer where:

Cancer Riskj - The potential carcinogenic risks associated with exposure to contaminant (unitless); CDI. « Chronic daily intake for contami nan tj (mg/kg/day); and SFj = Slope Factor for contaminant (mg/kg/day)"1.

Contaminant-specific cancer risks are summed in accordance with USEPA (1989a, 1986a,b) guidance in order to quantify the combined cancer risk associated with exposure to a chemical mixture. The slope factor is the 95th UCL on the linear slope that describes the cancer potency of the contaminant. Use of the 95th UCL on the linear slope is a conservative approach adopted by the USEPA in order that the true risks will not be underestimated.

Noncarcinogenic effects are not quantified as a probability of exhibiting a particular effect. Rather, noncarcinogenic effects are evaluated by comparing the estimated dose (i.e., CDI) with a reference dose (RfD). The hazard quotient is used to quantify the potential for an adverse noncarcinogenic effect to occur and is calculated using the following equation:

where: HQ, • Hazard quotient for contaminant (unitless); CDI, - Chronic Daily Intake for contaminant (mg/kg/day); and RfD; - Reference Dose for contaminants (mg/kg/day).

6-92 SR30G280 TCN 4208 RI REPORT REV #1 9/JAN/92 If the hazard quotient exceeds unity (i.e., 1), then an adverse health effect may occur. The. higher the hazard quotient, the more likely that an adverse noncarcinogenic effect Will occur as a result of exposure to the contaminant. The relationship is not, however, linear. If the estimated hazard quotient is less than unity, then an adverse noncarcinogenic effect is unlikely to occur.

USEPA (1989a, 1986b) recommends summing contaminant-specific hazard quotients to evaluate, the combined noncarcinogenic hazard from exposure to a chemical mixture. The sum of the contaminant-specific hazard quotients is called the hazard index. Using this approach assumes that contaminant-specific noncarcinogenic hazards are additive. Limited data are available for actually quantifying the potential synergistic_a.nd/or antagonistic relationships between contaminants in a chemical mixture. In addition, it is assumed that the target organs and toxicological mechanisms that may result in the effect are the same for all contaminants evaluated in the chemical mixture. If the latter assumption is not valid and the hazard index exceeds unity,,then hazard indices should be calculated by target organ and mechanism, as recommended by USEPA (1989a).

The following sections present carcinogenic risks and hazard quotients for chemicals of potential concern for the RME case for pathways under current land- use and future land-use conditions.

6.1.5.2 Potential Risk under Current Land-Use Conditions

Use of Grp-undwater from Residential Wells Downgradient of the PCI Site. No potential carcinogenic chemicals were detected in the 10 residential wells detected downgradient of the DCL site. Potential carcinogenic risks associated with use of groundwater from residential wells located to the south/southwest of the site were discussed in Section 6.1.2.4 of this report. As previously discussed, these wells are not hydrogeologically connected to the site.

6-93

flR30Q28 TCN 4208 RI REPORT REV #1 9/JAN/9 2 Potential noncarcinogenic hazards associated with ingestion and dermal absorption of groundwater from private residential wells downgradient of the DCL site are presented in Table 6-31. The hazard indices for all of the private residential wells were below unity. The highest hazard index of 0.3 was estimated for use of groundwater from PW-8. Therefore, noncarcinogenic effects associated with ingestion and dermal absorption of contaminants from these residential wells are unlikely to occur.

Direct Contact with Surface Soil bv Children Playing at the DCL. potential carcinogenic risks to children playing in surface soil at the DCL due to dermal absorption and incidental ingestion are presented in Table 6-32. Benzo(a)pyrene (equivalents) and beryllium, which are considered probable human carcinogens (Group 82), and arsenic which is a known human carcinogen (Group A), were the only potential carcinogenic contaminants identified for evaluation in this report. The total excess cancer risk associated with incidental ingestion and dermal absorption (i.e., 2xlO*5) exceeded the NCP point of departure (i.e., IO"6), but was below the upper-bound of the'NCP acceptable risk range (i.e., IO"4) (USEPA 1990). The only detected concentration of benzo(a)pyrene (equivalents) was found in sample SWD-2 which was collected in the solid waste disposal area. Similar levels of arsenic and beryllium were found in both the solid waste disposal area and in the vicinity of the fly ash pile.

The potential noncarcinogenic hazards to children playing in surface soil at the DCL due to dermal absorption and incidental ingestion of chemicals of potential concern are presented in Table 6-33. All of the contaminant-specific hazard quotients, as well as the hazard index, were below unity. Therefore, noncarcinogenic effects associated with direct contact with surface soil while playing at the DCL are unlikely to occur.

Direct Contact with Surface Water bv Children Playing in Streams and Seeps. Potential carcinogenic risks to children playing in streams and groundwater seeps in the vicinity of the DCL site due to dermal contact with surface water are 6-94

flR3QQ282 Table 6-31 Potential Noncarcinogenic Siska Associated with the Use of Groundwiter from Residential Wells Oowngradient of the Dixie Caverns Landfill Site for tht RHE Case (a)

RHE Chronic RfD Daily Intake RfD Uncertainty Hazard Well/Chemical (b) {mg/kg/day) (mg/kg/ day) factor Quotient

PW-1 Barium l.OE-OZ 7.0E-OZ 3 1.4E-01 Zinc 1.4E-03 2.0E-01 10 7. IE-03 Total Hazard Index:, 2E-01 PV-2 Barium l.OE-02 7.0E-02 3 1.5E-01 Manganese 1.8E-04 1.0E-Q1 1 I.8E-03 Zinc 1.4E-03 2.0E-Q1 10 7.0E-03 Total Hazard Index: 2E-01 PW-3 Barium 3.2E-03 7.QE-Q2 3 4.5E-Q2 Manganese 1.4E-04 1.0E-Q1 1 1.4E-03 Zinc 1. IE-03 2.0E-01 10 5.3E-03 Total Hazard Index: 5E-02 PW-4 Barium 4,7E-Q3 7.0E-02 3 6.7E-02 Manganese 2.9E-04 l.OE-Ql 1 2.9E-03 Zinc 1. IE-02 2.0E-01 10 5.5E-Q2 Total Hazard Indtx: IE-01 PW-S Barium S'.7E-03 7.0E-02 3 3. IE-02 Manganese 3.6E-Q4 l.OE-01 1 3.6E-03 Zinc 4, .IE-03 2.QE-01 10 2.0E-02 Total Hazard Index: IE-01 PU-6 Barium 1.2E-02 7.0E-02 3 2E-01 PU-7 ' Barium 2.2E-03. 7.0E-02 3 3. IE-02 Nickel S.7E-04 2.0E-02 300 2.9E-02 Zinc 3.9E-03 2.QE-01 10 1.9E-02 Total Hazard Index: 8E-02 PW-8 Barium 1.9E-02 7.0E-02 3 2.SE-01 Manganese- 2.5E-04 l.OE-01 . 1 2.5E-03 Total Hazard Index: 3E-01 PW-1S Barium 4.2E-03 7.0E-02 3 5.9E-02 Manganese 1.2E-03 l.OE-01 1 1.2E-02 Zinc 2.5E-OZ 2.QE-01 10 1.2E-01 Total Hazard Index: 2E-01

(aj Exposure routes includt ingtstion and dtmtl absorption whtlt bathing.

6-95 ftR300283 —— Ji—— = (£3 I I to §O C3 ^3 "^ 1 til '• • uj c - ej c. CO i i 03 —a• au> i-Q M ro ro a_ e o J3

t& m co u") u^ "**S* £U gU o ea o o o -—. t_ 1^ ^ i i i i i *J o «Jt c y j< n tLoU U«3J «•UJ» UBRJ Uesji to e* c: « e> 01 •-<

J= O "* ai 'o

uv! OJ IS <1> ** u §~ g^i S •* UJ t- OJ W >. o u . J2 U- a £ oi 01 £ 41 •£ oo 5« 10 O €3 O O O t* f3 4* * 4* ^~ "^ "n (if ei a "a tjj LU UJ C C m — ' x S" O oi to — ca t/J Ll_ -^. £ £Z u cn >^- »,— OJ Qb_ B U 0 ja m f t- t- us < X o o

— o o o h- 1— u C — Q» o O i 1 i 5) ~> o — • >. U o^ c ii_ ea. « e*l i i G-— J^^. to -"• c* (J CSl .*; SJ >, ^-- i1 na oe g —

|| e O ^~ o r-* tor- rt »«• O C3 O L. *J— ^ 1 ' 11 ^J a « >. UJ UJ LU ib> aj

C

3 UJ

CJ

-- 0. 0 g *———— M ——- —— 3 "3 O -3 C U •— U CO 01 E —— P* aa IM t. 03 >i ? eC O M 1- o 0) C S-

4-1 C esj fO ^f CO Csl i-i (M C O O O O O O O O ' l tu UJ UJ TjJ UJ UJ UJ UJ V) 4-t CO CM •-< CM (M ^^ CO O ro O 4) Cj o3- cOl ^ CA ^" ^ CSJ fO CSJ UJ •a X t- t-- «3 O 01 NJ <+-

*** 0- •*-> u ai c on a •g1

4->- a '5 ° 00-, 0 _ rti T1 t*™ *J fl — .0 0 °—< 0 2 t- C •~i — i m"

3

••- I-

aj o _ ro r-i rn ^r ^H (sj ^^ *-> o o o o o o o fl flj ro i i i i i i i a -a UJ UJ UJ UJ UJ UJ UJ a O a a o o o o(J —X ce 01 -* inm LO --* esj tsj M **^ rf (U J= EOl W JJ r —IO J-ftl CT . o c- C " ~^~" ~~ -^ •*— - •-: a C >i — - -- - ai re 4_j ci^— " " u ex— « i i i i i i i a a- o i- >> C " " M- O OS i i i i i i i >^ C" " in "D u oi ^^ _Q ^-^ i i > i i i i i- S- ^3 >. O (3 C? £5 C? C3 ^9 CJ ^4— C -fl 1 i 1 1 1 ' 1 T3 ta— *o • . r uj uj uj uj uj uj ™ - "i:,- CM _-i -- -H — < in a , U O fl -^ •^- co «sj «M CM ca «• 01 •U ^«« UJ C 01 «-a — u c:

•

^f^l M U E CU ^~ " — ^l ca fl c u •— E^ai u re — e i— 3 c: " o* c 3 •— — to a> t- ai — >I_E 01 j^ u j13 a w u t--O cue u —C «*cam-oa:zrvt. IO d) IB Jfl -^ i•—

6-97 SR300285 4208 RI REPORT REV #1 9/JAN/92 presented in Table 6-34. Bis(2-ethylhexyl)phthalate, a probable human carcinogens (Group B2), was identified as a chemical of potential concern in the northern drainage area in only one surface water sample near the fly ash pile. The potential carcinogenic risk associated with exposure to bis(2- ethylhexylJphthalate detected in surface water at the northern drainage area was 4xlO'8, which is above the IO"8 NCP point of departure, but well below the upper- bound of the NCP acceptable risk range (i.e., 10"*) (USEPA 1990). Arsenic, a known (Group A) human carcinogen would contribute the majority of the excess cancer risk identified for this'scenario; however, the levels at which it was detected in surface" water were below the levels measured in the background samples. Therefore, background presents a higher carcinogenic risk. The site- re! atedness of bis(2-ethylhexyl)phthalate is questionable since it is a laboratory contaminant and is found in plastic materials and was not identified as a chemical of concern in other media at the site. The total potential carcinogenic risks associated with direct contact with surface water in the southern drainage area was below the NCP point of departure (i.e., IO"8) (USEPA 1990). No potential carcinogenic chemicals were detected in surface water in Stream F. "~

Potential noncarcinogenic hazards to children playing in streams and groundwater seeps in the vicinity of the DCL site due to dermal contact with surface water are presented in Table 6-35. For the northern drainage area, cadmium presents a hazard quotient of 3. The highest detected concentrations of cadmium were found at Stations SB-5 and SB-6 which are located near the fly ash pile. The fly ash pile itself consisted of approximately 0.1% cadmium. Thus, noncarcinogenic effects associated with direct contact with surface water directly downstream of the fly ash pile may occur. Individual contaminant-specific hazard quotients and the hazard index for all chemicals of potential concern in the southern drainage area were below unity. Therefore, noncarcinogenic effects associated with direct contact with surface water while playing in streams and seeps in the southern

6-98 flR300286 Tablt 6-34 Potential Carcinogenic Bisk Associated with Direct Contact with Surface Water in the vicinity of the Dixie Caverns landfiUSite for the RHE Case

RHE Chronic Slop* Oai Ly tntakt factor Utight' Pottritial Area/ Chemical (ms/lcg/day) Cmg/k8/day)-1 of-Evidtnct Canctr Risk

Korthtrn orainag* Arta Organics: bU(2-Echyth*xyl)phthalatt 2.6E-M 1.4€-02 12 3.6E-06

Southern Drainagt Arta Organics: Btnztnt 1.TE-05 2.96-02 A 3.2E-07 fais(2-E£hylh*xyDphthatat* 1.7E-OS 1.4E-02 82 2.4E-07 Total Carcinogenic Risk: 6E-07

6-99

RR300287 Table 6-35 Potential Hoocarcinogenic Risks Associated yith Direct Contact with Surface Water in the Vicinity of tht Dixie Caverns Landfill Site for the M46 Case

HMC Chronic RtD Daily Intake RfO Uncertainty Hazard Ar fa/ Chemical (ntg/kg/day) CmgAB/day) factor Quotient

Northern Drainage Area Organic*: bii(2-lH)ylhexyOpnth«Ut« 1m• foe~w - rt^* 2.01-02 1000 9.18-02 Inorganics: Barium 8.7E-03 7.0€-OZ 3 1.28-01 OdnliM 1.28-03 5.0E-04 10 2.5E+QQ Manganese 4.4E-02 1.0E-01 1 4.46-01 Zinc 7.41-02 2.01-01 10 3.71-01 Total Hazard Index: 3E*00 Southern Drainage Area Organics: bisC2-fthylhexyl)phthalat* 1.21-04 2.0E-02 1000 6.06-03 Inorganics: Barium 1.78-02 7.01-02 3 2.41-01 Chromium 4.81-04 5.01-03 500 9.61-02 Manganese 2.31-02 1.01-01 1 2.31-01 Silver 4.81-05 3.01-03 2 1 .6E-02 Vanadium 1.2E-04 7.0E-03 100 1.71-02 Total Hazard Index: 6E-01

6-100 flR300288 TCN 4208 RI REPORT REV JT1 9/JAN/9 2 drainage area of the DCL site are unlikely to occur. No chemicals of potential concern were selected for Stream F.

Direct...Contact with Sediments for Children Playing in Streams and Seeps. Potential carcinogenic risks to children playing in sediments in streams and groundwater seeps due to dermal absorption and incidental ingestion are presented in Table 6-36. Benzo(a)pyrene (equivalent), which is a probable human carcinogen (Group B2), was the only potential carcinogenic chemical identified as a chemical of potential concern in sediments at the DCL site. The potential carcinogenic risk associated with dermal absorption and incidental ingestion of sediments in the northern drainage area slightly exceeded the NCP point of departure (i.e., IO"6), but was within the upper-bound of the NCP acceptable risk range (i.e., IO"4) (USEPA 1990). The potential carcinogenic risk associated with dermal absorption and incidental ingestion of sediments in Stream F was below the NCP point of departure (10"a). No potential carcinogenic compounds were selected as chemicals of potential concern in the southern drainage area.

Arsenic, a known human carcinogen (Group A), and beryllium, a probable human carcinogen (Group 82), account for the greatest carcinogenic risk associated with sediment (see section 6.1.2). However, the levels at which they were, detected were within measured background levels. Thus, background levels in sediment may present a higher carcinogenic risk. In addition, it is unclear whether the PAHs detected in sediments are actually associated with site-related disposal activities. PAHs are commonly found in sediments in seeps and streams.

Potential noncarcinogenic hazards to children playing in sediments in streams and seeps due to dermal absorption and incidental ingestion are presented in Table 6-37. Since inorganics were the only compounds identified as chemicals of potential concern and dermal absorption of inorganics is considered to be negligible, incidental ingestion is the only route of exposure considered. For the northern drainage area, hazard quotients for cadmium, silver, and zinc

6-101

SR300289 •»|I S o 1* Ii. IU UI

£ C^J|

— u*.— S 5 w r\UIi iUn H 0 (JlS C U a. ••

o JS o

*•• (A iij CM M

- 8 »" 0 O || S-,— ^^ ** w^i • ue *o. ' *° * >* D ^ ** f

1— *» U g W » fe1*^** *- 6 u « O & 7* o 3 tu ui

o 2 ill S| * — a. - c - B tl_ oIN. , e3 21 --! UI ^J

I ill 1 1

I I S» 1s- 1s- < UI UI 1 i i * || | e • ** u. n ^ |W U 9 U O 1 II 1 ll « at o tn o

flR300290 J-3 ll-8 {trit u 33 3 !l KS A "S•u o

i

X w oo *E ** M ! • *a* A 3ss5 ^«J N- a ? -p* •O « K _tj «a 5o .a3 j *s - « «- • 9 «! J* X ^5 • • 3 W w • • *S *!i 3 U *0 1 m \ ss 1 KS o M -^M

« U 1

"go j S •i y 2 «- C * ! *•— Q*

6'103 flR30029l TCN 4203 m REPORT REV *i 9/J AN/92 exceeded unity. Therefore, noncarcinogenic effects associated with direct contact with sediments while playing in streams and seeps in the northern drainage area of the DCL site may occur. The origin of these chemicals is probably due to surface water runoff from the fly ash pile.

Di-n-octylphthalate was the only chemical selected as a chemical of potential concern in sediments in the southern drainage area. Toxicity criteria were not available, however, for evaluating the potential noncarcinogenic hazard associated with this chemical. ' Background levels of other inorganic chemicals detected in this stream (e.g., arsenic, barium, chromium, manganese, and vanadium) probably present more of a noncarcinogenic hazard.

In Stream F, individual hazard quotients for the chemicals of potential concern and the hazard index were below unity by nearly 2 orders of magnitude. Therefore, noncarcinogenic effects associated with direct contact with sediments while playing in Stream F near the DCL site are unlikely to occur.

As discussed in Section 6.1.3, the potential noncarcinogenic hazards associated with exposure to lead in sediments was evaluated using a pharmacokinetic approach. The exposure point concentration for lead in the sediments in the fly ash drainage area was used in the soil ingestion module to estimate increased blood-lead levels due to exposure to sediments. Lead was not a chemical of potential concern in other media; therefore, default parameter values were used to estimate exposure to lead from other media (i.e., drinking water, air, etc.). Figure .6-1 presents a probability density function versus blood lead concentrations for six year old children who may play in sediments. The cut-off value of 10 ug/dL (vertical line) is the interim criterion for evaluating the potential risk to children from elevated blood lead levels (USEPA 1991b). Children with blood lead levels in excess of 10 ug/dL may experience adverse effects associated with neurou^ical development (see Section 6.1.4.2 for further discussion). As shown in Figure 6-1, there is a 96% chance that a six year old child regularly playing in sediments near the fly ash pile (sample location SB-7) 6-104 AR3QQ29e ——i——i——i——, Cut.ff: !•.• x *tav«: 9C.34 X »•!•«: 3.C* G. M»*n: 29.43

a •* «•*• h eM D9 5JS 3a

a. u.

•LOOD LCAJ* COHCCMTMITION 71 *• «

Figure 6-1. Probability density plot of blood-ltad levels in six year old children playing near station SB-7 In streaa B (located near the fly ash pile).

6-105 AR300293 TCN 3208 RI REPORT REV *1 9/JAN/32 would have a blood-lead level above 10 ug/dL. The maximum detected concentration of lead (30,800 ug/kg) also exceeds the interim soil cleanup level for lead at Superfund sites by a factor of 60, which is considered sufficiently protective for direct contact in residential settings (i.e., 500 mg/kg) (USEPA 1989d).

As shown in Figure 6-2, there is a 64% chance that a six year old child who regularly plays farther downstream near sample location SE-13 (lead concentration of 11,900 mg/kg) also would have elevated blood-lead levels. Based on a review of lead monitoring data for Stream E, it appears that significant contamination of sediments exist from the fly ash pile at least to Station SE-13. The next downstream sample location is SE-10 which is located almost to the confluence with Stream E and Stream A. The concentration of lead at this location (SE-10: 648 mg/kg) is nearly 20 times lower than SE-13. As shown in Figure 6-3, there is only a 1% chance that a six year old child who regularly plays near Station SE-13 would have elevated blood-lead levels. By simple interpolation, it is estimated that levels of "lead in sediments that may be of concern (a concentration which would result in a S% chance that a six year old would have elevated blood-lead levels) would be found slightly upstream of the confluence between Streams E and G.

Multlmedii Assessment of Risk under Current Land-Use Conditions. Potential carcinogenic risks and noncarcinogenic hazards from exposure to all current land- use exposure pathways quantitatively evaluated in the risk assessment are presented in Table 6-38. It was conservatively assumed that an individual is exposed via all exposure routes evaluated, as well as the highest risk estimated for any given location according to the RME case (i.e., highest risk estimated for direct contact with surface water and sediment, and use of untreated groundwater from PW-8). The total carcinogenic risk was 3xlO"5 and the hazard index was 9. The highest carcinogenic risks were associated with direct contact with surface soil, while the highest noncarcinogenic hazards, were estimated for direct contact with sediments and surface water in the northern drainage area. The most significant risk estimates associated with direct contact with streams 6-106 RR3QQ29E* ew -aa si ^ •-« 9e

IB 29 99 1* 3« «• ?• •• jBLOOD LCAO CONCCHTIMT t OM T* te> «4

Figure 6-2. Probability density plot of blood-lead levels 1n six year old children playing near station SE-13 In streaa E.

6-107 : AR300295 Cuteiff: !•.• x AJMW*: 1.13 x »•!•«: 9*.as C. H*WI: 3.«3

a wi ** a. e s I £

- e 3* *1» 4 9 SB 3 ft. U.

4 t • !• 11 14 It !• 2e> BLOO» LC*» COMCENTJMTIOH 71 t* *4

Figure 6-3. Probability density plot of blood-lead levels 1n six year old children playing near station SE-10 1n strew E.

6-108 AR300296 Table 6-3S Potential Risks from Multiple Exposure Pathways under Current" Land-Use Conditions

Potential Carcinogenic R.isk . .. . Hazard Index Pathway .._ ...... for the RME Case for RME Case

Use of GrbundwaTer'fronf " Untreated Residential Wells (a): -- - -— — - • 0.3 Children Playing In Surface Soil

Ingestion of soil 2E-5 Q.I Dermal absorption from soil 4E-6 — Subtotal "Tor "Pathway : 2E-5 0.1 Children Playing in Northern Drainage Area: Ingestion of sediments 2E-6 5 dermal absorption from sediments ZE-6 Dermal absorption from surface water 4£-6 ' 3 Subtotal for Pathway: 8E-6 8

Total for all Routes (b): 3E-5 , 9

(a) Total risks associated with ingestion and bathing using groundwater from PW-8. (b) It should be noted that these risk estimates are conservative upper-bound estimates that assume that an individual is exposed according to the RME scenario outlined in this'report for all exposure pathways evaluated; and.thus, represents the maximum plausible risk under current land-use conditions.

6-109 AR300297 TCN 4208 R! REPORT REV JM 9/J AN/92 in the northern drainage area are probably associated with surface water runoff from the fly ash pile,

6.1.5.3 Potential Risk under Future Land-Use Conditions

Direct Contact with Surface Soils by Hypothetical Residents at the DCL Site. Potential carcinogenic risks to hypothetical residents at the DCL site from contact with surface soils are presented in Table 6-38a. The potential carcinogenic risk from incidental ingestion of surface soils was 5xlO"5. This risk exceeded the NCP point of departure (i.e., IO"6) but did not exceed the upper-bound of the NCP acceptable risk range (i.e., IO*4) (USEPA 1990). The potential carcinogenic risk from dermal absorption of surface soils was 4xlO"5 which was also between the NCP point of departure and the upper-bound of the NCP acceptable risk range. The total carcinogenic risk for this exposure route of 8xlO"5 also was within the NCP acceptable risk range.

The potential noncarcinogenic hazards to hypothetical residents due to contact with surface soils are presented in Table 6-38b. The hazard index associated with incidental ingestion of surface soils at the DCL site was 0.1 and therefore, is below unity (1). The selected chemicals of potential concern were all inorganics which are not expected to be dermally absorbed; therefore, no hazard quotient for dermal absorption was calculated.

Use of Groundwater fay Hypothetical Residents at the DCL Site. ..Potential carcinogenic risks to hypothetical residents at the DCL site from use of groundwater are presented in Table 6-39. Since the only potential carcinogenic chemical of potential concern detected in groundwater samples is inorganic (arsenic, a known human carcinogen [Group A)]), volatilization was not evaluated. The potential carcinogenic risk from ingestion of groundwater and bathing was 3xlO'4. This risk exceeded the NCP point of departure (i.e., IO"6) and the upper- bound of the NCP acceptable risk range (i.e., 10"*) (USEPA 1990). Arsenic was -Jfek

6-110 SR300298 — .*— C tn i i un rtl ifl 5 o o o c 41 a. UJ ai t. a i_ tn • ' o u <- vi C*l ff> a. c o J3

O — u u- — u UJ UJ UJ UJ UJ C U Ji irt — 1—1 C3 CO .CO UJ 01 C vi 01 x: 4-* us "^ Ol —^ ?o ^r ^^ ee o u a; c a. — tU

o

UJ s — o 1 — to g 14- tu . 0 <- > J2 i*- a o j: ^ in in j=. d) .*— — 4-1 •*-- -- - ae ce — X <,•«. •••« ^? ^? s — ^ o a O o o a i— fll -f -t- +• t— ™- •a flj O TS UJ UJ UJ c c 01 14— C^4-^ ^^ AJ **** ro QJ Q) *J O O U O) ai en -a ^4 *-4 ^f a 5 V) i*-- 'H^fc c- e u 4- o — u u V) C 1 -- - . , -«. L. w — n fl fl <: u CJ (J JS ^ " "re "re ^-- — - d a c~ i i > aj w a -w >i LU «_ a. fl O 1 1 a c <- T3 c &> fO — T3 a M 01 t- .u> (J 42 -* re 09 1 1 i rn 0 CC ^"s — "re"re 1 '^ U a> 4-1 —— o C w 0) OJ -i -C c f% 10 r^ QO- *gJ O o a o a. - I- *-»— > t i i >x O W >!' i*j LU uj 2^"- ~~ 14- u re LD OO CM >% i— i C ^ O) — Ol J2 O— Ol _. ._... CJ ^ o i 5 i* as c — • -33 u T3 ^ U

to

c --- 01

3 V UJ

c(U (U --a. u e ^~ V, — . — 3 fl U fl C CJ — U CO C> E — e^n cN oU . - u O en — ^ tn AR300299 ' a a a. or O v n •o

4J V•a) U C O C3 O O O O O O o o 33 - t i J i i 1 i 1 1 •^ f* I^J UJ UJ UJ UJ UJ W^l UJ UJ '^^ »J J* tn f\i en en -^ m ^ «• — « J5 "• * ** * ~ «•» ~ — ^1 1 •a w ^ a O

* -

re--

re S *• O ^^ ffl ® ^_ ^* ^_ to u .^r _^ *"* •^ ^^ ^3 ^^ .m ^n ^ V in *JT T_ tj JH T*l ^^ !^£ "*^ cu t- C ** rr ^Q n u Q^ -.-. re Q S JC S ^ 3 3 M (J O t/l X QJ (_ •a * >« O So ~ O o O a o ^ O X. X —re a* *? i i i i i i i -a-(U sQJ * - * QJ LiJ UJ UJ UJ L^ c c jft* ^1 m -»£ «-^ ^n in ^n ^^ en c*j ,o 'S'E QO g re re ft rt M •*•** M N |fcf .-• F to re iO rt C s x 11 _ as "S . — — *— - re fl O u tn S 4-a1 4-o1 **r*e co— s; O i— t— a^__ AJ Q re ot. C^^t- >*. 1 I 1 I > 1 1 c u **~ S -S 1 i 1 i 1 1 1 u sJ if J

II ce C — ZT- re >. - S c — g 09 — — a «rf o v> G. t. M "• in v ta tft rt tn t»i O QS ^ o aa oo o o O *^ C fl3 i i i. i i i i re — ~5, £f ^ iti — Si ^ iii 3 8jl

Ui U € 3) ^~ — 3 W ^ §0} O C *"~ -*™ ^ C 3 ^~ *^" ^ 3} u aj — xs ?^ o g W t_ t. "3 c j c 6 —

Table 6-39 Potential Carcinogenic Risks Associated with ust of Groundwater at the Dixie Caverns landfill Site by Hypothetical Residents for tne RM£ Case (a)

Total RM£ Chronic Slope Weight- Potential Dai 1y Intake Factor of- Cancer Chemical (mgAg/day) (mg/kg/d*y)-L Evidence Risk

Arsenic ----- t.S£-04 1.7E*QO A 3E-Q4

(a) Exposure routes include ingestlon and dermal absorption while bathing. Inorganics do not volatilize; therefore, exposure via inhalation while showering would not occur.

6-113

AR30030I