ecological risk assessment methodology and problem formulation

DRAFT Tier 1 Technical Memorandum:

Ecological Risk Assessment Methodology and Problem Formulation

Revised Site-Wide Ecological Risk Assessment

University of California Davis Davis, California

July 2005

SEMS-RM DOCID # 1162066

BLASLAND, BOUCK & LEE, INC. 7/12/05 engineers, scientists, economists Tier 1 Tech Memo_Section 3_71205.doc

DRAFT

Table of Contents

Abbreviations and Acronyms

Section 1. Introduction ............................................................................................................... 1-1

1.1 Objectives and Approach ................................................................................................ 1-1 1.2 Site Setting ...................................................................................................................... 1-1

1.2.1 Site History ......................................................................................................... 1-1 1.2.2 Previous Studies................................................................................................. 1-2

1.3 Technical Memorandum Organization ............................................................................ 1-3

Section 2. SWERA Methodology................................................................................................ 2-1

2.1 Tier 1 Assessment........................................................................................................... 2-1 2.1.1 Problem Formulation .......................................................................................... 2-2

2.1.1.1 Environmental Setting......................................................................... 2-2 2.1.1.2 Selection of COPECs.......................................................................... 2-5 2.1.1.3 Development of the Conceptual Site Model ....................................... 2-7 2.1.1.4 Selection of Assessment Endpoints/Measurement Endpoints ......... 2-10 2.1.1.5 Selection of Receptors of Concern ................................................... 2-10

2.2 Tier 2 Assessment......................................................................................................... 2-11 2.2.1 Refined Problem Formulation........................................................................... 2-12 2.2.2 Exposure Assessment...................................................................................... 2-12

2.2.2.1 Statistical Derivation of the EPC....................................................... 2-13 2.2.2.2 Direct Exposures Based on Direct Contact ...................................... 2-15 2.2.2.3 Exposure Estimates Based on Food Web Exposure........................ 2-16 2.2.2.4 Exposure Estimates Based on Inhalation Exposure......................... 2-17

2.2.3 Effects Assessment .......................................................................................... 2-18 2.2.3.1 Direct Contact Toxicity Benchmarks................................................. 2-18 2.2.3.2 Food Web Toxicity Reference Values (TRVs for Wildlife) ................ 2-19 2.2.3.3 Inhalation Effects Values .................................................................. 2-19

2.2.4 Risk Characterization ....................................................................................... 2-19 2.2.4.1 Risk Estimates .................................................................................. 2-20 2.2.4.2 Further Evaluation of List 2 COPECs ............................................... 2-20 2.2.4.3 Uncertainty Analysis ......................................................................... 2-21

2.3 Conclusion and Recommendation................................................................................. 2-21

Section 3. Tier 1 Problem Formulation...................................................................................... 3-1

3.1 DOE Disposal Box ......................................................................................................... 3-1 3.1.1 Previous Investigations ................................................................................... 3-1 3.1.2 Evaluation of the Environmental and Biological Setting ............................. 3-2 3.1.3 Selection of COPECs ....................................................................................... 3-2 3.1.4 Conceptual Site Model ..................................................................................... 3-2 3.1.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................... 3-3

3.2 Domestic Septic Systems............................................................................................. 3-3 3.2.1 Previous Investigations ................................................................................... 3-3 3.2.2 Evaluation of the Environmental and Biological Setting ............................. 3-6


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3.2.3 Selection of COPECS....................................................................................... 3-6 3.2.4 Conceptual Site Model ..................................................................................... 3-7 3.2.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................... 3-7

3.3 Eastern Dog Pens.......................................................................................................... 3-7 3.3.1 Previous Investigations ................................................................................... 3-7 3.3.2 Evaluation of the Environmental and Biological Setting ............................. 3-8 3.3.3 Selection of COPECs ....................................................................................... 3-8 3.3.4 Conceptual Site Model ..................................................................................... 3-9 3.3.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................... 3-9

3.4 Eastern Trenches .......................................................................................................... 3-9 3.4.1 Previous Studies .............................................................................................. 3-9 3.4.2 Evaluation of the Environmental and Biological Setting ........................... 3-10 3.4.3 Selection of COPECs ..................................................................................... 3-10 3.4.4 Conceptual Site Model ................................................................................... 3-11 3.4.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-11

3.5 Landfill Unit No 1 ......................................................................................................... 3-11 3.5.1 Previous Investigations ................................................................................. 3-11 3.5.2 Evaluation of the Environmental and Biological Setting ........................... 3-12 3.5.3 Selection of COPECs ..................................................................................... 3-12 3.5.4 Conceptual Site Model ................................................................................... 3-13 3.5.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-13

3.6 Landfill Unit No. 2 ........................................................................................................ 3-13 3.6.1 Previous Investigations ................................................................................. 3-14 3.6.2 Evaluation of the Environmental and Biological Setting ........................... 3-14 3.6.3 Selection of COPECs ..................................................................................... 3-14 3.6.4 Conceptual Site Model ................................................................................... 3-15 3.6.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-15

3.7 Landfill Unit No 3 ......................................................................................................... 3-15 3.7.1 Previous Investigations ................................................................................. 3-16 3.7.2 Evaluation of the Environmental and Biological Setting ........................... 3-16 3.7.3 Selection of COPECs ..................................................................................... 3-16 3.7.4 Conceptual Site Model ................................................................................... 3-17 3.7.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-17

3.8 Radium/Strontium Treatment System Area .............................................................. 3-17 3.8.1 Previous Investigations ................................................................................. 3-17 3.8.2 Evaluation of the Environmental and Biological Setting ........................... 3-18 3.8.3 Selection of COPECs ..................................................................................... 3-18 3.8.4 Conceptual Site Model ................................................................................... 3-19 3.8.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-19

3.9 Southern Trenches...................................................................................................... 3-19 3.9.1 Previous Investigations ................................................................................. 3-19 3.9.2 Evaluation of the Environmental and Biological Setting ........................... 3-20 3.9.3 Selection of COPECs ..................................................................................... 3-20 3.9.4 Conceptual Site Model ................................................................................... 3-20 3.9.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-21

3.10 Southwest Disposal Trenches ................................................................................... 3-21 3.10.1 Previous Investigations ................................................................................. 3-21


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3.10.2 Evaluation of the Environmental and Biological Setting ........................... 3-22 3.10.3 Selection of COPECs ..................................................................................... 3-22 3.10.4 Conceptual Site Model ................................................................................... 3-22 3.10.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-22

3.11 Waste Burial Holes ...................................................................................................... 3-23 3.11.1 Previous Investigations ................................................................................. 3-23 3.11.2 Evaluation of the Environmental and Biological Setting ........................... 3-24 3.11.3 Selection of COPECs ..................................................................................... 3-24 3.11.4 Conceptual Site Model ................................................................................... 3-24 3.11.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-24

3.12 Western Dog Pens....................................................................................................... 3-25 3.12.1 Previous Investigations ................................................................................. 3-25 3.12.2 Evaluation of the Environmental and Biological Setting ........................... 3-25 3.12.3 Selection of COPECs ..................................................................................... 3-26 3.12.4 Conceptual Site Model ................................................................................... 3-26 3.12.5 Selection of Assessment and Measurement Endpoints (AE and ME) ...... 3-27

3.13 Land Treatment Pilot Study (LTPS) ........................................................................... 3-27 3.13.1 Previous Investigations ................................................................................. 3-27 3.13.2 Evaluation of the Environmental and Biological Setting ........................... 3-27 3.13.3 Selection of COPECs ..................................................................................... 3-27 3.13.4 Conceptual Site Model ................................................................................... 3-28 3.13.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-28

3.14 Non-Operational Unit (OU) Site .................................................................................. 3-28 3.14.1 Evaluation of the Environmental and Biological Setting ........................... 3-28 3.14.2 Previous Investigations ................................................................................. 3-28 3.14.3 Selection of COPECs ..................................................................................... 3-29 3.14.4 Conceptual Site Model ................................................................................... 3-29 3.14.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-29

3.15 Old Davis Road Drainage Ditch.................................................................................. 3-30 3.15.1 Previous Investigations ................................................................................. 3-30 3.15.2 Evaluation of the Environmental and Biological Setting ........................... 3-30 3.15.3 Selection of COPECs ..................................................................................... 3-30 3.15.4 Conceptual Site Model ................................................................................... 3-31 3.15.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern ................................................................................................. 3-31

3.16 Far-Ranging Species................................................................................................... 3-31 3.16.1 Previous Investigations ................................................................................. 3-31 3.16.2 Evaluation of the Environmental and Biological Setting ........................... 3-31 3.16.3 Selection of COPECs ..................................................................................... 3-32 3.16.4 Conceptual Site Model ................................................................................... 3-32 3.16.5 Selection of Assessment and Measurement Endpoints and Receptors of Concern ........................................................................................................................ 3-32

3.17 Putah Creek.................................................................................................................. 3-32

Section 4. References ................................................................................................................. 4-1

Tables


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1 LEHR Areas to be Evaluated in the Revised ERA 2 Observed Onsite and Offsite Primary Producers 3 Observed Onsite Primary, Secondary and Tertiary Consumers 4 Observed Offsite Primary, Secondary and Tertiary Consumers 5 Tier 1 Screening Benchmarks for Terrestrial Soils 6 Tier 1 Screening Benchmarks for Surface Water 7 Tier 1Screening Benchmarks for Sediment 8 Habitat Designation for LEHR Areas under Evaluation 9 Assessment and Measurement Endpoints and Associated Receptors of Concern 10 Tier 2 Receptor Exposure Factors 11 Tier 2 Toxicity Reference Values or Equivalents 12 Summary of COPECs in Soil, DOE Disposal Box 13 Summary of COPECs in Soil, Domestic Septic System 1 14 Summary of COPECs in Soil, Domestic Septic System 3 15 Summary of COPECs in Soil, Domestic Septic System 4 16 Summary of COPECs in Soil, Domestic Septic System 5 17 Summary of COPECs in Soil, Domestic Septic System 6 18 Summary of COPECs in Soil, Domestic Septic System 7 19 Summary of COPECs in Soil, Dry Wells A-E 20 Summary of COPECs in Soil, Eastern Dog Pens 21 Summary of COPECs in Soil, Eastern Trenches 22 Summary of COPECs in Burrow Air, Eastern Trenches 23 Summary of COPECs in Soil, Landfill Unit No. 1 24 Seasonally Ponded Water COPEC Summary, Landfill Unit No. 1 25 Summary of COPECs in Soil, Landfill Unit No. 2 26 Summary of COPECs in Burrow Air, Landfill Unit No. 2 27 Summary of COPECs in Soil, Landfill Unit No. 3 28 Summary of COPECs in Soil, Radium/Strontium Treatment System 29 Summary of COPECs in Soil, Southern Trenches 30 Summary of COPECs in Soil, Southwest Trenches 31 Summary of COPECs in Soil, Waste Burial Holes 32 Summary of COPECs in Soil, Western Dog Pens 33 Seasonally Ponded Water COPEC Summary, Western Dog Pens 34 Summary of COPECs in Soil, LTPS 35 Summary of COPECs in Soil, Non OU Areas 36 Seasonally Ponded Water COPEC Summary, Old Davis Road Ditch 37 Summary of COPECs in Soil, Far-Ranging Receptors Figures 1 Site Location Map 2 LEHR Areas under Evaluation 3 EPA 8-step Ecological Risk Assessment Process 4 Habitat Map 5 Storm Water Flow Pathways and Monitoring Points 6 Terrestrial Food Web 7 Aquatic Food Web 8 Conceptual Site Model for the Terrestrial Habitats 9 Conceptual Site Model for the Seasonally-Ponded Habitats 10 Conceptual Site Model for the Aquatic Habitats 11 DOE Disposal Box Sampling Locations of List 1 COPECs 12 Domestic Septic System #1, #5 and Dry Wells Sampling Locations of List 1 COPECs 13 Domestic Septic System #3 and #4 Sampling Locations of List 1 COPECs 14 Domestic Septic System #6 and #7 Sampling Locations of List 1 COPECs


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15 Eastern Dog Pens Sampling Locations of List 1 COPECs 16 Eastern Trenches Sampling Locations of List 1 COPECs 17 Landfill Unit No. 1 Sampling Locations of List 1 COPECs 18 Soil Sample Locations included in the Ponded Water Evaluations 19 Landfill Unit No. 2 Sampling Locations of List 1 COPECs 20 Landfill Unit. No. 3 Sampling Locations of List 1 COPECs 21 Radium/Strontium Treatment System Sampling Locations of List 1 COPECs 22 Southern Trenches Sampling Locations of List 1 COPECs 23 Southwest Trenches Sampling Locations of List 1 COPECs 24 Waste Burial Holes Sampling Location of List 1 COPECs 25 Western Dog Pens Sampling Location of List 1 COPECs 26 LTPS Sampling Location of List 1 COPECs 27 Non OU Areas Sampling Locations of List 1 COPECs Appendices A Conference Call Notes B Depth Interval Memorandum C Tier 1 COPEC Selection in Soil D Tier 1 General Radionuclude Screening E Example Dermal Contact Exposure and Risk Estimate Calculation F Tier 2 Rationale for Selection of Representative Receptors G Pond Water Partitioning Coefficients H Tier 2 Terrestrial Uptake, Bioaccumulation and Does Calculations By Area I Tier 2 Toxicity Profiles for COPECs J Background Statistical Comparisons


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Abbreviations and Acronyms AEs Assessment Endpoints AOC Administrative Order of Consent ARCS Assessment and Remediation of Contaminated Sediments ATSDR Agency for Toxic Substance Control and Disease Registry BAFs Biota-Sediment Accumulation Factors BCG Biota Concentration Guideline bgs Below Ground Surface BBL Blasland, Bouck & Lee, Inc. BTAG Biological Technical Assistance Group CDFG California Fish and Game CERCLA Comprehensive Environmental Response, Compensation and Liability Act CFR Code of Federal Regulations CHE Center for Health and the Environment Sr-90 Strontium 90 Co-60 Cobalt-60 COPECs Constituents of Potential Ecological Concern CSM Conceptual Site Model DOE Department of Energy DSS Domestic Septic System DST Domestic Septic Tank DTSC Department of Toxic Substance Control EcoSSL Ecological Soil Screening Levels EIR Environmental Impact Report EPA Environmental Protection Agency EPC Exposure Point Concentration ERA Ecological Risk Assessment ERE Ecological Risk Estimate HERD Human and Ecological Risk Division HHRA Human Health Risk Assessment HQs Hazard Quotient LEHR Laboratory for Environmental Health Related Research LOAEL Lowest Observed Adverse Effects Level LS-1 Lift Station One LTPS Land Treatment Pilot Study MEs Measurement Endpoints MWH Montgomery Watson Harza NOAEL No Adverse Effect Level NPL National Priority List ODR Old Davis Road


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ORNL Oak Ridge National Laboratory OU Operable Unit PCB Polychlorinated Biphenyl PNNL Pacific Northwest National Laboratory QC Quality Control Ra-226 Radium-226 Ra/Sr Radium/Strontium RATL Reptile and Amphibian Toxicity Literature RI Remedial Investigation RI/FS Remedial Investigation/Feasibility Study RME Reasonable Maximum Exposure ROC Receptors of Concern RWQCB Regional Water Quality Control Board SCDS South Campus Disposal Site SVOC Semi-Volatile Organic Compounds SWERA Site Wide Ecological Risk Assessment SWRA Site-Wide Risk Assessment TELs Threshold Effects Levels Tier 1 ERA Tier 1 Ecological Risk Assessment TOC Total Organic Carbon TM Technical Memo TRVs Toxicity Reference Values UC Davis University of California Davis UCL Upper Confidence Limit USACE United States Army Corp of Engineers USEPA U.S. Environmental Protection Agency UTL Upper Tolerance Limits VOC Volatile Constituents WA Weiss Associates WBH Waste Burial Hole WET Wastewater Effluent Test WWTP Wastewater Treatment Plant

BLASLAND, BOUCK & LEE, INC. 7/12/05 engineers, scientists, economists sections 1 and 2.doc

Sections 1 and 2 Submitted on June 24, 2005

BLASLAND, BOUCK & LEE, INC. 7/12/05 engineers, scientists, economists 3-1 Tier 1 Tech Memo_Section 3_71205.doc

DRAFT

3. Tier 1 Problem Formulation The following section will present the Tier 1 Problem Formulations for each of the 17 areas under evaluation for the Draft Revised SWERA. The problem formulation defines the goals and objectives of the risk assessment through a formal process to develop and evaluate preliminary hypotheses concerning the likelihood and causes of ecological effects that may have occurred, or may occur, from human activities (USEPA, 1998). The following information will be presented per each area: • evaluation of the environmental setting; • selection of constituents of potential ecological concern (COPECs); • development of the conceptual site model (CSM); • selection of assessment and measurement endpoints (AEs and MEs); and • selection of receptors of concern (ROCs) Additionally, a brief description of each area, any relevant removal actions and previous investigations are also discussed.

3.1 DOE Disposal Box As described in the Ecological Risk Estimate (ERE) (MWH, 2004), the DOE Disposal Box is a 0.03-acre area located between the Western Dog Pens and Landfill Unit No. 2 (Figure 11). The DOE Disposal Box functioned as a small disposal trench with steel reinforced shoring which contained laboratory waste, and approximately 55 cubic yards of low-level radiological waste (WA, 2002).

3.1.1 Previous Investigations In 1996, a time-critical removal action was conducted at the DOE Box area. The waste matrix was encountered at 2 to 3 ft bgs, beneath a layer of gravel/soil overburden. Approximately 110 cubic yards of waste were removed, including soil, gravel, steel runway matting, plywood, syringes, bottles and vials. All of the waste items were removed from the excavation and an additional 6 to 12 inches of native soil were removed beyond the initial excavation limits. The final excavation at the DOE Box area was approximately 40 ft by 12 ft by 10 ft deep. The excavation was lined with a 20-mil high-density polyethylene liner and backfilled with clean fill. Thirty samples and three field duplicates were collected during closure sampling. Nine samples were analyzed for the full suite of parameters and twenty-one for a limited suite of constituents (WA, 2003). These data were collected immediately following excavation in 1996 and in 2002 as part of a data gaps evaluation. These data, reflecting post-removal conditions, were used for COPEC ID in the SWERA. As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the data set for the DOE Disposal Box Area included 2135 analytical results from the aforementioned investigations. Twenty-five of the results, or 1.2%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of six records, or 0.3%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte.


DRAFT

3.1.2 Evaluation of the Environmental and Biological Setting The DOE Disposal Box is characterized as terrestrial habitat. The site currently does not support any vegetation due to the aforementioned remediation activities (MWH, 2004). It is expected that ruderal, annual grassland and/or landscaped vegetation will be present at the site in the future. Once the vegetation returns, traditional terrestrial ecological receptors are also expected to return, therefore it is conservatively assumed that terrestrial receptors may at some point in the future be exposed to COPECs in this area. No threatened or endangered species were observed in this area.

3.1.3 Selection of COPECs The selection of COPECs for chemical constituents, as per the methodology described in Section 2.1.1.2, is presented in Appendix C, Table J-1 and summarized in Table 12. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). Constituents whose reporting limits are consistently above benchmarks or where a benchmark nor a TRV were available, are identified as COPECs, but are not evaluated quantitatively but referred to instead in the uncertainty section since quantitative risk cannot be calculated with the available information. The List 1 COPEC list includes metals and SVOCs in soils. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information. Sampling locations at the DOE Disposal Box can be found on Figure 11. Figure 11 focuses on the sampling locations where List 1 COPECs were sampled (as described in Table 12). Because radionuclides were not identified as List 1 COPECs, locations that were only sampled for radionuclides were not included in the figure. It is also important to note that not all sampling locations had all List 1 COPECs analyzed since analyte lists varied by investigation. Therefore, Figure 11 identifies locations where data is available for some if not all of the List 1 COPECs identified in Table 12. Similar maps were generated for each site and will be referred to as the “List 1 COPEC Sample Location Maps” from here forward.

3.1.4 Conceptual Site Model Soils impacted by historic waste disposal and not removed via the aforementioned removal action are the potential media of concern. Soil-associated constituents may impact resident ecological receptors through uptake into plants and soil invertebrates, and incidental ingestion of soil or bioaccumulation via the food web to herbivorous, insectivorous and carnivorous birds and mammals. Potentially complete but minor exposure pathways include dermal contact with impacted soils by birds and mammals and exposure via inhalation to surface dwelling receptors.


DRAFT

The aforementioned chemical migration pathways were assessed at the site to identify complete and insignificant exposure pathways of soil-associated constituents to resident terrestrial ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8.

3.1.5 Selection of Assessment and Measurement Endpoints (AE and ME) and Receptors of Concern

The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the DOE Disposal Box. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.2 Domestic Septic Systems There were 7 domestic septic systems (DSS) historically on the Site. Additionally, a leach field containing five dry wells was also located near DSS 1 and 5. As described in the ERE (MWH 2004), a typical DSS consisted of a domestic septic tank (DST), leach field and interconnecting piping. Liquid wastes and sewage were discharged to six of the seven DSSs from 1958 until the Site's connection to the UC Davis WWTP in 1971. DST 7 was installed adjacent to the Cobalt 60 field to receive waste from the irradiator building. This tank was reportedly never used, since this building was connected to the UC Davis domestic sewer system during construction. It is believed that DST 7 was demolished in place during the installation of the existing sewer line. In 1971, DSS 1 through 6 were reportedly backfilled with sand and the influent/effluent lines for each tank were reportedly cut and capped. DSS 2 and portions of the Dry Wells associated with DSS 1 and 5 were removed in 1999 as part of the Ra/Sr removal action. Each of these areas will be evaluated individually in the Revised SWERA.

3.2.1 Previous Investigations Previous investigations at each DSS are summarized below: DSS 1 Parts of the DSS 1 leach field were removed during the Radium/Strontium (Ra/Sr) Treatment System Removal Action occurring in 1999/2000 described in section 3.8.1. Five soil samples, including one soil field duplicate sample, were collected from the DSS 1 area during 1996 data gaps investigations and the 2001 DSS Investigations performed for the Remedial Investigation (WA 2003). These data, excluding those collected at depths greater than 10 ft bgs, are used to select COPECs for the Revised SWERA. As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the DSS 1 includes 676 analytical results from the aforementioned investigations. Thirty-four of the results, or 5.0%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 172 records, or 25.4%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte.


DRAFT

DSS 2 As mentioned above, DSS 2 was removed during the Ra/Sr Treatment Systems Area I removal action in 1999. Confirmation samples taken during the demolition of the reinforced concrete tank and the soil excavation are reported in the Ra/Sr section. DSS 3 Non-time critical removal actions were conducted at the DSS 3 between April and July of 2002. The distribution box and all of the effluent lines were removed along with the concrete, perforated Orangeburg pipe and leach trench gravel. Approximately one foot of additional soil was removed from the trench floor and sidewalls. The DSS 3 leach trench excavation depth ranged from 11 to 12.5 ft bgs, and was up to 8 ft wide and 50 ft long. As documented in the SWRA HHRA (UC Davis, 2004), approximately 170 cubic yards of piping, concrete, gravel and underlying soil were removed. The overburden soil from the DSS 3 removal action was used as backfill in the excavation. Thirty-six confirmation samples, including four field duplicate samples, were collected between 3.6 feet bgs and 12.5 feet bgs. Three tank contents samples, including one field duplicate and one concrete sample were also collected from the bottom of DST 3 (WA, 2003). Data used for COPEC identification in the SWERA were collected from the post-removal samples or those not impacted by the removal action and collected during the 1997 data gaps investigation. The final data set are reflective of area conditions after soil removal and at depths from 0 to 10 ft bgs. As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the DSS 3 includes 2096 analytical results. One hundred six of the results, or 5.1%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 115 records, or 5.5%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. DSS 4 Nine soil samples, including one field duplicate, were collected from the DSS 4 area during a data gaps investigation in 1997 and the 2001 DSS Investigation conducted as part of the Remediation Investigation (WA, 2003). These data are used for the revised SWERA COPEC selection. The final data set used to estimate risk was evaluated and redacted to exclude samples collected at depths greater than 10 ft bgs. As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the DSS 4 includes 996 analytical results. None of these results were rejected from the total data set (“R”-qualified). Seventy-three of the results, or 7.3%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 98 records, or 9.8%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. DSS 5


DRAFT

Parts of the DSS 5 leach field were removed during the Radium/Strontium (Ra/Sr) Treatment System Removal Action occurring in 1999/2000 as described in section 3.8.1. One soil sample was collected from the DSS 5 area and analyzed for a full suite of analytes. As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the DSS 5 includes 231 analytical results. Seven of the results, or 3.0%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of eight records, or 3.5%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. DSS 6 Removal activities in 2002 also occurred at DSS 6 in addition to DSS 3. All effluent lines, perforated Orangeburg pipe and leach trench gravel were removed from the area between April and June. Approximately one foot of additional soil from the trench floor and sidewalls was also removed. The excavation depth ranged from six feet bgs to seven feet bgs and was 11 feet wide by 105 feet long. Following waste removal and confirmation sampling, the DSS 6 excavation was lined with a geotextile fabric and backfilled to grade with clean fill. The overburden soil from the DSS 6 removal action was also used as backfill in the excavation. Thirty confirmation samples, including three field duplicates and four analyzed exclusively for mercury, were collected from the DSS 6 excavation. Data collected during these removal activities were combined with additional soil data collected in the 1997 data gaps investigation and the 2001 DSS investigation. These data, excluding samples collected at depths greater than 10 ft bgs or those collected in locations that were subsequently excavated, were used for COPEC selection (3.3.3). As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the DSS 6 includes 1083 analytical results. Forty-seven of the results, or 4.3%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 144 records, or 13.3%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. DSS7 There is limited data associated with this area since the tank was reportedly never used. Three soil samples were collected from the suspected former location of DST 7 during the investigations conducted in 1996. Data used for COPEC identification in the SWERA were collected from this one investigation and evaluated and redacted to exclude samples collected at depths greater than 10 ft bgs. As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the DSS 7 includes 332 analytical results. Fourteen of the results, or 4.2%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 70 records, or 21.1%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. Dry Wells A-E


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Five Dry Wells (A through E), a distributor box, and associated piping that served the leach fields for DSS 1 and 5 were investigated and removed in 1999. The upper portions of the Dry Wells A-E were removed to depths ranging from 8 ft to 20 ft bgs. Removal action samples were taken (1999) and the area was backfilled. Soil samples were collected at 10, 20, 30 and 40 ft bgs from a borehole located approximately 2 ft from the axis of each dry well (Weiss, 2005). Eleven investigation samples were collected during the removal action and an additional twenty soil samples were collected from boreholes in 2001 (WA 2003). Those data, in addition to data collected in the 1997 nature and extent/data gaps investigations and the 1999 Radium/Strontium Treatment Systems Area I removal action, excluding samples below 10 ft bgs, were used to select COPECs in Section 3.3.3. As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the Dry Wells includes 1712 analytical results. Ninety-eight of the results, or 5.7%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 161 records, or 9.4%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte.

3.2.2 Evaluation of the Environmental and Biological Setting The DSS areas are comprised of seven domestic septic systems and their leach fields generally placed under or adjacent to buildings. Biological receptors in these areas are extremely limited. Despite the lack of vegetation and receptors, portions of the former septic system areas may support or impact terrestrial vegetation and receptors in the future, therefore they are evaluated as terrestrial habitat. No threatened or endangered receptors were identified in the area.

3.2.3 Selection of COPECS The selection of COPECs for chemical constituents is presented in Appendix C, Tables J-2 through J-8 and summarized in Tables 13-19. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of DSS soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 12 through 14. List 1 COPECs at each of the DSSs include the following: • DSS1: SVOCs and Metals; • DSS3: SVOCs, Pesticides, PCBs and Metals; • DSS4: SVOCs, Pesticides and Metals; • DSS5: Metals; • DSS6: SVOCs and Metals; • DSS7: Metals; and • Drywells: VOCs and Metals.


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Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 13-19 but are not evaluated quantitatively but referred to instead in the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.2.4 Conceptual Site Model Soils impacted by the waste discharged to the Domestic Septic Systems from 1958 to 1971 are the media of concern at each of these areas. Six of seven of the systems received liquid wastes and sewage during this period, the seventh septic system was reportedly never used. Soil-associated constituents for the seventh septic system are also evaluated for risk in the same manner as with sites one through six. The source of DSS constituents are those related to liquid waste and sewage disposal that are still present in the soil matrix following removal actions that have occurred at DSS 3 and 6. The migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8.


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the DSS. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.3 Eastern Dog Pens The Eastern Dog Pens are a 0.8 acre area that were formerly used to house beagles following radiation exposure and a 30-day holding period. Dog feces were removed daily while urine was allowed to disperse into the gravel floor of the pens (WA, 2005). Gravel was removed on occasion and disposed off-site or at the Southwest Trenches. The Eastern Dog Pens are located on tope of the southern portion of Landfill Unit No. 2.

3.3.1 Previous Investigations CERCLA removal actions have not occurred in this area. The chain-link pen partitions and concrete pedestals were removed in 1996 as part of the area decommissioning process. The interior chain-link fencing was shipped off-site for recycling in 1999. The perimeter chain-link fence, concrete curbs, gravel and three asphalt aisles currently remain (WA, 2005).


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The nature and extent of contamination at the area was evaluated via soil samples collected in 1999. Soils were collected from the upper soil horizon only and did not include material from the landfill underneath the Eastern Dog Pens. Gravel and concrete curbing materials were also sampled (UC Davis, 2004). Data used for COPEC identification in the SWERA were collected from a 1996 study conducted as part of site decommissioning activities (IT Corp, 1997) and a more comprehensive nature and extent evaluation in 1999 (WA, 1999). The final data set used to estimate risk includes data from both the 1996 and the 1999 investigations. The 1996 data, although not collected in keeping with CERCLA guidance, was included at the request of the US EPA since it provides additional data on contaminant distribution at the site (WA, 2005). As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the Eastern Dog Pens includes 2340 analytical results from the aforementioned investigations. One hundred thirty of the results, or 5.6%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of five records, or 0.2%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte.

3.3.2 Evaluation of the Environmental and Biological Setting The Eastern Dog Pens are comprised of a mixture of impervious surfaces (25%) and terrestrial habitat including ruderal, annual grassland and/or landscaped vegetation (UC Davis, 2004). Specific vegetation identified at the site include milk thistle and Italian thistle, plantings of silver maple and Aleppo pine along the borders, and isolated elderberries and almonds scattered across the area. The elderberry longhorn beetle is not expected to be present in the area based on site observations and that contiguous elderberry bushes are generally needed to support new populations of the threatened and endangered insect (MWH, 2004). It is anticipated that this area will have a specifically engineered landfill cap once the Feasibility Study is completed.

3.3.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-10 and summarized in Table 20. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Eastern Dog Pens soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 15. The List 1 COPECs include the metals and pesticides. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 20 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated


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quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.3.4 Conceptual Site Model The area housed beagles that were used to research chronic health effects of exposure to radioactive isotopes. The source of potentially soil-associated constituents at the site today are pesticides formerly used for flea control, and excreta containing residual radionuclides and nitrates. Fencing and concrete pedestals that supported dog beds previously have been removed but dog pen foundations, asphalt walkways and gravel inside the pens are still present. Soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.4, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats.


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Eastern Dog Pens. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.4 Eastern Trenches As described in the UC Davis Remedial Investigation (Geomatrix, 2004), the Eastern Trenches include five to seven north-south trending trenches and four to six east-west trending trenches covering approximately 0.8 acres and holding approximately 426 cubic yards of waste. The trenches were operational from 1957 to 1965 and were used for waste disposal of general laboratory constituents, pesticides and dog pen waste. In general, the trenches are approximately 2 1/5 feet wide and 6 feet deep and range from 45 to 142.5 feet long and are filled with approximately 4 feet of waste and capped with 2 feet of clean soil (Geomatrix 2004).

3.4.1 Previous Studies As described in the SWRA HHRA (UC Davis, 2004), investigations conducted in the Eastern Trenches include two reconnaissance trenching programs (Wahler 1988; Dames & Moore 1991), a soil gas investigation (PNNL 1995), a surface geophysical survey, the drilling of two soil borings (PNNL 1995), a trenching and soil boring program (Dames & Moore 1997a), passive soil gas and surface, subsurface flux sampling (Dames & Moore1999a), and surface soil sample investigation (MWH 2002c). Five trenches, three soil borings and 12 hand auger holes were used to collect 43 samples. Samples were collected from 19 locations at depths ranging from 2.5 to 40 feet bgs. Forty soil gas samples were collected and analyzed for chloroform. Twenty passive soil gas modules measured VOCs, and two surface flux and two down-hole flux measurements were made for VOCs. Metals, VOCs, SVOCs organochlorine pesticides, and radionuclides were typically measured. WET analyses were performed on selected samples.


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Data used for COPEC identification in the SWERA were collected from the investigations described above. Specifically, the SWERA soil dataset includes nature and extent data from investigations conducted in 1995, 1996 and 2002. The final data set used to estimate risk was evaluated and samples collected at depths greater than 10 ft bgs were excluded. Soil gas data collected in the aforementioned investigations were also used to develop List 1 COPECs for potential exposures to burrowing mammals as described in Section 3.4.3 below. The soil data set for the Eastern Trenches includes 5501 analytical results. Ninety-five of the results, or 1.7%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 193 records, or 3.5%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. Seven of the results, or 0.1%, had “U” qualifiers, which indicate that an analyte was not detected above the laboratory reporting limits.

3.4.2 Evaluation of the Environmental and Biological Setting The Eastern Trenches is comprised of terrestrial habit and an access road running over the long and narrow cell. Ruderal vegetation consisting mostly of Italian thistle, pineapple weed, and yellow star thistle is present but controlled by mowing for vehicle access in the past. The area is bordered on the east by mature Canary Island pines. Threatened and endangered species have not been identified at the site. It is anticipated that this area will have a specifically engineered landfill cap once the Feasibility Study is completed.

3.4.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-12 and summarized in Table 21. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Eastern Trenches soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 16. These constituents include SVOCs, pesticides and metals. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 21 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information. Based on soil data, VOCs were not identified as soil COPECs because VOC concentrations were found to be below soil screening numbers. However, VOCs detected in soil gas were identified as List 1 COPECS and will be evaluated as COPECs in burrow air (Table 22). The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated


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quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.4.4 Conceptual Site Model Soils impacted by historic waste disposal are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats. Inhalation of volatile compounds in subsurface air by burrowing mammals is another potential exposure pathway. Evaluating this pathway at the Eastern Trenches is possible at this area is due to the presence of soil gas data. Figure 8 notes a potentially complete exposure pathway to burrowing mammals from inhalation of air in subsurface burrows.


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Eastern Trenches. These AE and MEs are listed in Table 9. All terrestrial receptors with potentially significant exposure pathways as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.5 Landfill Unit No 1 Landfill Unit No. 1 is the oldest of the three landfills units and is reported to have operated in the 1940s and 1950s. It is located 250 yards east of Old Davis Road, immediately north of the north levee of the South Fork of Putah Creek and west of the UC Davis Raptor Center and covers 1.9 acres with two percent impervious surface. General campus wastes, possibly including chemical wastes, are thought to have been disposed at Landfill Unit No. 1. Sludge from the adjacent sewage treatment plant was reportedly disposed in this Landfill (DOE-NNSA, 1998). The eastern portion of Landfill Unit No. 1 is covered by small buildings used to house research animals (X-1, X-2, X-3) (UC Davis, 2004).

3.5.1 Previous Investigations Several soil investigations have been conducted at this area. They include a soil and landfill gas investigation (PNNL 1995), a geophysical program and three soil borings (PNNL 1995), a trenching and soil boring program (Dames & Moore 1996a) and surface soil sample collection (MWH 2002c). According to UC Davis (2004), four soil borings and 30 surface soil samples were collected in conjunction with 13 exploratory trenches (to define landfill limits). The 30 samples were analyzed from 16 locations at depths from surface to 40 feet bgs. Seventy-nine soil gas samples were collected and analyzed for chloroform. Soil samples were analyzed for metals, VOCs, SVOCs, organochlorine pesticides, PCBs and radionuclides and included WET analyses.


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Data used for COPEC identification in the SWERA were collected from the investigations described above. The data were evaluated and all the data collected from below 10 ft bgs were excluded. The soil data set for Landfill Unit No. 1 includes 3720 analytical results. Thirty-eight of the results, or 1.0%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 161 records, or 4.3%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. Fifteen of the results, or 0.4%, had “U” qualifiers, which indicate that an analyte was not detected above laboratory reporting limits.

3.5.2 Evaluation of the Environmental and Biological Setting Two percent of Landfill Unit No. 1 is characterized as impervious surface. Much of the remaining area is characterized as terrestrial habitat which supports ruderal, annual grassland and landscaped vegetation. Vegetation is mostly absent from the eastern portion of the landfill due to a gravel surface and herbicides applied near buildings currently used for climate-controlled animal research. Mature hackberry trees are present along the north and south borders, ruderal vegetation and several elderberry shrubs are found along the fence line dividing the eastern and western portions of the landfill. The western portion of the landfill supports vegetation such as malvella, milk thistle, Italian thistle, charlock, yellow-star thistle, annual rye grass, soft chess and red-stemmed filaree. It is expected that this area will have a specifically engineered landfill cap once the Feasibility Study is completed. During the rainy season, intermittent ponds may periodically form in a small area of the landfill near the stormwater outfall, LF-1. Amphibians may use the seasonally-ponded waters for breeding. Ponded water areas in Landfill Unit No. 1 are planned to be mitigated by backfilling (MWH, 2004).

3.5.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-14 and summarized in Table 23. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Landfill Unit No. 1 soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 17. These constituents include SVOCs, pesticides, PCBs and metals. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 23 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated


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quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs in seasonally-ponded water were based on the soil data collected in the vicinity of the ponding areas since surface water data is not available. Therefore, a ponded water COPEC is a chemical detected at least once at the station/stations within the soil “footprint” of the ponded water. Soil sample locations included in the ERE ponded water evaluation are presented in Figure 18. It is recognized that there may be ongoing discussions on what samples will be included. Based on the ERE soil samples the pond COPECs include 4,4-DDT and metals (Table 24). 1

3.5.4 Conceptual Site Model General campus wastes, construction materials (concrete, paint, metal, rebar), sewage sludge and chemical wastes potentially deposited in the landfill are the source of potential soil-associated constituents. Surface and subsurface soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats. Surface water in seasonal ponds is also considered a media of concern with potential impacts to amphibians. Soil-related constituents may leach from soil into ponded surface water or via runoff from other areas. Direct contact between amphibian eggs laid in these ponds and surface water constituents represent a potentially complete exposure pathway as illustrated in Figure 9, the CSM developed for seasonally ponded habitats. Because ponded, surface water data does not exist, concentrations of potential contaminants in the ponds were estimated via partitioning from soils present in the soil in the ponded area of the Landfill. Partitioning is estimated via the use of literature-derived Kd values and via results from WET tests with subsurface soil data. 2


The AE and ME developed for the general suite of receptors found at terrestrial and seasonally-ponded sites are applicable for the Landfill Unit No. 1. These AE and MEs are listed in Table 9. All terrestrial and seasonally ponded receptors with significant exposure as defined in the CSMs (Figure 8 and 9) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals and amphibians.

3.6 Landfill Unit No. 2

1 This approach will be evaluated more closely in response to recent comments on the first portion of the Technical Memorandum. Uncertainty regarding where the ponds form each year in relation to the available soil data needs to be addressed. 2 The application of partitioning coefficients and WET values to model from soil to water is currently under discussion in response to comments received on the first portion of the Technical Memorandum.


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The Landfill Unit No 2 consist of 12 east west disposal pits and two “geriatrics” buildings that have been built on top of the landfill (MWH, 2004). It is approximately 2.1 acres in size with two percent impervious surface, excluding the portion of the Landfill that lies directly under the Eastern Dog Pens (approximately 50%). Waste disposal at the landfill occurred from 1956 to 1967 and consisted of general refuse, animal parts, and laboratory constituents. Debris piles and stockpiled materials indicate that ground disturbing activities have occurred in this area (UC Davis, 2004).

3.6.1 Previous Investigations The investigations conducted to date at Landfill Unit No. 2, as reported in the SWRA Volume 1 HHRA (UC Davis 2004), have consisted of a soil and landfill gas investigation (PNNL 1995), a geophysical survey and three soil borings (PNNL 1995), a trenching and soil boring program (Dames & Moore 1996b), surface flux and downhole flux soil gas sample collection in 1999 (Dames & Moore 1999b) and surface soil sampling via the data gaps investigation (MWH 2002c). Thirteen exploratory trenches (to define landfill limits), three soil borings and surface sample collection yielded 42 samples. The 42 samples were analyzed from 18 locations at depths ranging from 0.3 to 30 feet bgs. In 1996, 105 soil gas samples were collected and analyzed for chloroform. An additional soil gas investigation was performed in 1999 consisting of surface modules and surface and subsurface flux testing. Similar to Landfill Unit No. 1, the analytes identified for Landfill Unit No. 2 were metals, VOCs, SVOCs, organochlorine, pesticides, PCBs, radionuclides and included WET analyses. Soil and soil gas data used for COPEC identification in the SWERA were collected from the investigations described above. The data were evaluated and all the data collected from below 10 ft bgs were excluded. The soil data set for Landfill No. 2 includes 3836 analytical results. Fifty-eight of the results, or 1.5%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 157 records, or 4.1%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. Four of the results, or 0.1%, had “U” qualifiers, which indicate that an analyte was not detected above laboratory reporting limits.

3.6.2 Evaluation of the Environmental and Biological Setting As mentioned above, approximately 50% of Landfill No. 2 is located under the Eastern Dog Pens. The remaining portion of the landfill covers approximately 2.1 acres with approximate 2% of the site characterized as impervious surface. The remaining area is considered terrestrial habitat. It supports variable densities of vegetation such as milk thistle, Italian thistle, plantings of silver maple and Aleppo pine along the borders and isolated elderberries and almonds scattered across the site. It is anticipated that this area will have a specifically engineered landfill cap once the Feasibility Study is completed. No threatened or endangered species were identified at the site.

3.6.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-16 and summarized in Table 25. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in


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the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Landfill Unit No. 2 soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 19. These constituents include VOCs, SVOCs, pesticides, PCBs, and metals. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 25 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information. VOCs were initially eliminated as COPEC because VOC concentrations were found to be below soil screening numbers. Subsequently, VOCs were re-introduced as COPEC for the burrowing mammal due to the availability of soil gas data for this area. All constituents detected in soil gas were identified as burrow air COPEC (Table 26).

3.6.4 Conceptual Site Model Wastes consisting of general refuse, animal parts and laboratory constituents are the source of soil-associated constituents at the site. Surface and subsurface soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats.


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Landfill Unit No. 2. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.7 Landfill Unit No 3 Landfill Unit No. 3 was operated from 1963 to 1967. Waste, such as general municipal and campus waste, construction debris and potentially minor quantities of laboratory waste, was placed in two large, pit-like excavations and covered with a soil cap. The Landfill Unit No. 3 area covers 1.1 acres and the volume of waste is approximately 331 cubic yards (Geomatrix, 2004). . Currently, this area is comprised of raptor research


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enclosures and a concrete lined drainage channel. The drainage channel is bordered by bare ground, a condition maintained by routine herbicide application.

3.7.1 Previous Investigations Previous soil investigations conducted at Landfill Unit No. 3 include a soil gas and landfill gas investigation and a geophysics program (PNNL 1995), five soil borings and eight exploration trenches (PNNL 1995), a trenching and soil boring program (Dames & Moore 1996c) and an additional soil gas investigation in 1999 (Dames & Moore 1999b). As reported in the SWRA HHRA (UC Davis, 2004), this landfill was investigated with ten exploratory trenches and two soil borings. Forty-one soil samples were analyzed from 17 locations at depths from the surface to 35 feet bgs. Thirty-nine soil gas samples were collected and analyzed for chloroform in 1996 and 21 passive soil gas modules were measured in 1999. The analytes were the same as the analytes for Landfill Unit Nos. 1 and 2. The data used for COPEC identification in the SWERA were collected from the investigations described above. The data were evaluated and all the data collected from below 10 ft bgs were excluded. The data set for Landfill No. 3 includes 3483 analytical results from the above investigations. Twelve of the results, or 0.3%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates.

3.7.2 Evaluation of the Environmental and Biological Setting As mentioned above, two percent of Landfill Unit No. 3 is covered by an impervious surface. The remaining area is comprised of a vacant lot, with raptor research enclosures and a concrete-lined drainage channel. Dense ruderal vegetation is present in portions of the site not maintained by mowing such as Milk thistle, Italian thistle, Bermuda grass, annual rye, wild oat, ripgut, yellow star thistle and charlock. It is expected that the area will support ruderal, annual grassland and/or landscaped vegetation in the future. A burrowing owl program was present at the site in the early 1990s. The program has ceased since this time and no burrowing owls are expected at the site. No threatened or endangered species were identified at the site.

3.7.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-18 and summarized in Table 27. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Landfill Unit No. 3 soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 20. These constituents include SVOCs, pesticides, PCBs, and metals. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 27 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information.


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The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.7.4 Conceptual Site Model These wastes disposed into Landfill Unit No. 3 are identified as the source of potential soil-associated contaminants at the site. Surface and subsurface soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats.


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Landfill Unit No. 3. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.8 Radium/Strontium Treatment System Area The Ra/Sr Treatment System area was generally used to treat animal wastes containing radioactive material, primarily strontium-90 (Sr-90) and radium-226 (Ra-226) using two separate systems for each radioactive material. The Radium-226 Treatment System consisted of a single subsurface concrete tank with a distribution tank feeding three, 40-foot deep dry wells and two leach trenches (UC Davis, 2004). The Strontium-90 Treatment System consisted of a series of nine interconnected “Imhoff” tanks and a leach field (WA 2003).

3.8.1 Previous Investigations Numerous removal actions have occurred at this site. Approximately 40,000 gallons of low-level radioactive liquid and sludge waste were removed from the Ra-226 septic tank and Sr-90 “Imhoff” tanks in 1992. This waste was solidified on-site, properly packed in 55-gallon drums, and shipped to the DOE Hanford site for disposal. This occurred prior to the LEHR Federal Facility’s listing on the NPL, and is not considered part of the CERCLA Removal Actions (RAs) (UC Davis, 2004). Following waste removal, the Ra/Sr Treatment Systems were divided into two areas to facilitate clean up. Ra/Sr Treatment Systems Area I consisted of a distribution box, piping, three dry wells, and the two leach trenches. In addition, given the close proximity and connectivity of domestic septic tank (DST) 2 to the Ra-226 Treatment System, it was also included in the Area I RA. Area I RA activities began in May 1999 and were completed by


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November 1999. Confirmation samples were collected at the completion of the excavation activities. The lower portions of the dry wells were filled with controlled low strength material to 8 ft bgs and backfilled and compacted to grade with clean fill. Area II consisted of the Ra-226 Tank, the Sr-90 Tank, the Sr-90 Tank Leach Field and the influent tank piping. The Area II RA occurred from July to November 2000. Following removal of the subsurface structures and the surrounding soil, confirmation samples were collected. The area was then backfilled and compacted to grade with clean fill. Seventy confirmation samples and eight field duplicate samples were collected from the Ra/Sr Treatment System removal action excavation areas (WA 2003). Samples were collected between one foot bgs and 42.5 feet bgs. Data used for COPEC identification in the SWERA include the confirmation sample data collected during the aforementioned removal actions. These data were evaluated such that all samples taken below 10 ft bgs were excluded. None of the prior characterization sample results were used since they represented removed soil. As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the Ra/Sr Treatment Systems area included 13,880 results. Five-hundred eleven of the results, or 3.7%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 889 records, or 6.4%, had “UJ” qualifiers, which means that an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte.

3.8.2 Evaluation of the Environmental and Biological Setting The Ra/Sr area includes the former tank area which is bordered on three sides by single story structures and on the other by a parking lot and the former leach filed and dry well area. Ruderal vegetation, such as a variety of thistles are present at the area. The site is expected to be paved in the future, but if this does not occur, it is expected that the area will support more ruderal, annual grassland and/or landscaped vegetation. No threatened or endangered species were identified at the site.

3.8.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-19 and summarized in Table 28. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Radium/Strontium Treatment Systems soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 21. These constituents include VOCs, SVOCs, pesticides and metals. Note that DSS No. 2 is a part of the Radium/Strontium Treatment System and the DSS No. 2 data were included in EPC calculations. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 28 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information.


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The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.8.4 Conceptual Site Model Sources of potential soil-associated contaminants include those soils not removed during remediation actions that were impacted by the Radium Strontium Treatment Systems. Remediation at the site occurred in 1992 to remove low-level radioactive liquid and sludge waste from inside the tanks. More removal actions occurred in 1999 and 2000 to remove piping, infiltration trenches and other waste. Surface and subsurface soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.4, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats.


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Ra/Sr Treatment System Area. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.9 Southern Trenches The Southern Trenches consists of two east west trending 250-foot-long trenches that were operated from 1957 to 1965. The trenches occupy 0.16 acres and contain 111 cubic yards of waste (Geomatrix, 2004). The waste disposed in these trenches consisted of animal bones, laboratory waste, manure and gravel.

3.9.1 Previous Investigations Previous investigations collected at the the trenches include two reconnaissance trenching programs (Wahler 1988; Dames & Moore 1991), a soil gas investigation and a geophysical survey (PNNL 1995), trenching and soil boring program (Dames & Moore 1998) and surface soil sample collection (MWH 2002c). Four trenches, three soil borings and eight hand auger locations were used to gather 29 samples. The samples were collected from 15 locations at depths of 1.5 to 30 feet bgs and analyzed for a comprehensive list of site constituents. Twenty-one soil gas samples were collected and analyzed for chloroform. Data used for COPEC identification in the SWERA were collected from the investigations described above. Specifically, substantial soil samples were collected as a part of the field investigations in 1995/1996 and in the data gap evaluation conducted in 2002 (MWH 2002c).


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The data set for the Southern Trenches includes 3602 analytical results. Fifty-four of the results, or 1.5%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 317 records, or 8.8%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. Eight of the results, or 0.2%, had “U” qualifiers, which indicate that an analyte was not detected above laboratory reporting limits.

3.9.2 Evaluation of the Environmental and Biological Setting The area is characterized as terrestrial habitat. It is bordered by mature tree plantings of Aleppo pine to the south and the Western Dog Pens to the north. The soil present at the site is completely contained under the Aleppo pine canopy and is devoid of vegetation, based on site observations. Vegetation may be present at the site in the future, therefore risks to terrestrial receptors are evaluated in the ERA. No threatened or endangered species were identified at the site.

3.9.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-21 and summarized in Table 29. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Southern Disposal Trenches soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 22. These constituents include pesticides and metals. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 29 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.9.4 Conceptual Site Model Sources contributing to soil-associated constituents include the wastes disposed at the site from 1957 to 1965. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in


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Figure 8, the CSM developed for sites with terrestrial habitats. Selection of Assessment and Measurement Endpoints


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Southern Trenches. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.10 Southwest Disposal Trenches As described in the ERE (MWH 2004), the Southwest Trenches are an approximately 0.6 acre area located at the corner of Old Davis Road and the north levee of the South Fork of Putah Creek. Between the late 1950s and early 1970s, LEHR-generated low-level radioactive waste, fecal material, and laboratory wastes were reportedly disposed in shallow pits and trenches at the Southwest Trenches Area. Disposal practices consisted of excavating a trench and placing laboratory waste along with dog pens gravel and soil in the trenches. The trenches were then backfilled with native soil. In addition, part of the area was used for treating dogs with chlordane as flea control. Chlordane was apparently either used or stored in the southwest corner of the Area.

3.10.1 Previous Investigations The Southwest Trenches removal action activities were conducted in 1998. The removal action removed chlordane-impacted surface and subsurface soil. A total of 450 cubic yards of chlordane-impacted soil were excavated and shipped off site for disposal. Following the chlordane-impacted soil removal, waste disposal cells were located and 217 cubic yards of waste were removed from the northern excavation area, 466 cubic yards of waste was removed from the western excavation area and 190 cubic yards of waste were removed from the southern excavation area. Following completion of the waste removal activities and confirmation sampling, the excavations were lined with geotextile fabric, backfilled and compacted to grade with clean fill. A total of sixty-three samples and seven duplicates were collected from the excavation sidewalls and floor between two and thirteen feet bgs. They were analyzed for a full suite of constituents. Data used for COPEC identification in the SWERA include samples taken in nature and extent studies in 1996 that were not impacted by removal action and removal action confirmation samples taken in 1998 and 1999. As described in the Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the final data set for the Southwest Trenches includes 12589 analytical results. Five hundred fifty-one of the results, or 4.4%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 1473 records, or 11.7%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte.


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3.10.2 Evaluation of the Environmental and Biological Setting The Southwest Disposal Trenches cover approximately 0.6 acres. Black plastic lining generally prevents vegetation from this site. At the margins of the site, vegetation such as Italian thistle, black mustard, yellow sweet clover, ripgut and soft chess are present, therefore the site is characterized as supporting terrestrial habitat. Aleppo pine also is present along two of the fence lines. Ecological receptors, nor threatened or endangered species were observed on the site due to recent remedial activity.

3.10.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-23 and summarized in Table 30. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Southwest Trenches soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 23. These constituents include VOCs, SVOCs, pesticides and metals.. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 30 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.10.4 Conceptual Site Model Potential sources of soil-associated constituents include those soils not removed by remediation actions that were impacted by laboratory waste or dog pen gravel which was disposed of in the trenches. Dogs were also treated at the site with chlordane as flea control which is another potential source for soil-associated contaminants. Surface and subsurface soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats.



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The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Southwest Disposal Trenches. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.11 Waste Burial Holes As described in the ERE (MWH 2004), the Waste Burial Hole (WBH) area is a long, narrow area approximately 0.2 acres in size located along the southern border of Landfill Unit No.2 and the Eastern Trenches, immediately north of the north levee of the South Fork of Putah Creek. The WBH Area was used to dispose of low-level radioactive materials, animal remains, and laboratory chemical waste from 1956 to 1974. According to records, the base of each burial pit was approximately 10 ft bgs, and was covered by 1 to 4 ft of clean soil (Geomatrix, 2004). After disposal, the holes were covered with a layer of native silty fill material.

3.11.1 Previous Investigations Two reconnaissance trenching programs (Wahler 1988; Dames & Moore 1991), a soil boring and soil gas investigation (PNNL 1995) and a trenching and soil sampling program (Dames & Moore 1997b) were completed in the Waste Burial Holes area. Between 1988 and 1998, approximately 15 soil and 15 waste samples were submitted for a full range of analytes including metals, radionuclides, VOCs, SVOCs and organochlorine pesticides. Eleven soil gas samples were also tested for VOCs. A removal action was performed at this site in 1999 to remove all waste material in the entire area to 12 feet bgs. The waste and soil were sorted and the sorted soil was replaced in the excavation and covered with clean fill (Geomatrix 2004). Confirmation samples were collected from the excavation areas prior to backfilling and sorted soils were tested prior to their replacement in the excavation. In addition, samples were collected from the area post removal action to confirm the effectiveness of the action. In 2001, following the removal action, 55 soil samples were collected from two to 20 feet bgs, and five in-situ groundwater samples were collected at approximately 40 feet bgs (MWH 2002c). The 55 soil samples were analyzed for metals, VOCs, SVOCs, organochlorine pesticides, PCBs, and radionuclides. The five groundwater samples were analyzed for VOCs, TDS, nitrate, chromium, tritium, and carbon-14. In 2002, six soil samples were collected from two to six feet bgs, and each sample was analyzed for nickel, tritium and carbon-14. Data used for COPEC identification in the SWERA were collected from the investigations described above. These data were evaluated such that all samples taken below 10 ft bgs or before removal actions were excluded. The resulting SWERA dataset contains data from 1995, 1996, 1999, and 2001. Some of these data were taken from soil tested prior to excavation, removed for waste removal and returned to the area. The original sample locations therefore are no longer accurate. The data set for the Waste Burial Holes includes 2426 analytical results. Eighty-five of the results, or 3.5%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 112 records, or 4.6%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. Eleven of the results, or 0.5%, had “U” qualifiers, which indicate that an analyte was not detected above laboratory reporting limits.


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3.11.2 Evaluation of the Environmental and Biological Setting The Waste Burial Holes cover a 0.2 acre area along the southern border of Landfill Unit No. 2 and the Eastern Trenches. The area currently supports sparse to dense patches of ruderal vegetation composed of Italian thistle, pineapple weed and yellow star thistle. The vegetation at the site ranges from spares to dense, although vegetation in the area may have been historically disked. It is anticipated that this area will have a specifically engineered landfill cap once the Feasibility Study is completed.

3.11.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-25 and summarized in Table 31. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Waste Burial Hole soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 24. These constituents include VOCs, SVOCs, pesticides and metals. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 31 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. The WBH Area initially failed the general terrestrial screening for radionuclides, but passed the Area-specific screening using 95% UCL exposure point concentrations. All radionuclides were eliminated as COPECs in this Tier 1 step and will not be advanced to the Tier 2 evaluation.

3.11.4 Conceptual Site Model Potential sources of soil-associated contaminants include the low level radioactive materials, animal remains, and laboratory constituents that were disposed of in these holes from 1956 to 1974 and remain following removal actions in 1999. Surface and subsurface soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats.


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Waste Burial Holes. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure


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as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.12 Western Dog Pens As described in the ERE (MWH 2004), the Western Dog Pens are an approximately 2.0 acre site located between the research buildings on Old Davis Road, and Landfill Unit No.2, immediately north of the Southern Trenches. The Western and Eastern Dog Pens were used from 1958 through the mid-1980s to house beagles that were subjects of research on the chronic health effects of exposure to radioactive isotopes, primarily Sr-90 and Ra-226 exposure. The Western Dog Pens were also used until the mid-1990s to house dogs in non-radiological research studies. Pesticides used for flea control and excreta containing residual radionuclides and nitrates (from urination) may have been released in the dog pen areas.

3.12.1 Previous Investigations The Dog Pens and associated structures were removed from 1975 -1999. In 2001, approximately, 1,725 cubic yards of gravel, 650 cu yd of asphalt, 800 cu yd of concrete curbing, and 45 cubic yards of metal grating and fence posts were also removed as part of a non-time critical removal action. Following waste removal and confirmation sampling, the southern portion of the Western Dog Pens was then backfilled and compacted to grade, but the northern portion of the Western Dog Pens was left below grade. Currently, waste and material stockpiles are stored within the backfilled area of the Western Dog Pens, pending characterization sampling results. The northern portion of the Western Dog Pens will be backfilled in the near future. Thirty-eight confirmation samples, including five field duplicates, were collected from the Western Dog Pens excavation (UC Davis, 2004). Soil data used for COPEC identification in the SWERA were collected during various investigations and sampling events that were conducted at the Western Dog Pens. Confirmation sample data were combined with prior characterization data that were determined to be representative of post-removal conditions. As described in The Draft SWRA Volume 1 HHRA, Part B (WA, 2005), the data set for the Western Dog Pens includes 10248 analytical results. Four hundred sixty-four of the results, or 4.5%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 254 records, or 2.5%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte.

3.12.2 Evaluation of the Environmental and Biological Setting The Western Dog Pens are characterized as supporting both terrestrial habitat and seasonally-ponded areas. Vegetation at the site exists in variable densities. Elderberry shrubs are found in this area, along with ruderal vegetation, dominated by Italian thistle, black mustard, yellow sweet clover, ripgut, and soft chess in areas not impacted by remediation activities.


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During the rainy season, intermittent ponds may periodically form in small areas (approximately 10 feet by 5 feet) along the northeastern corner of the site. Amphibians may use the seasonally-ponded waters for breeding. The area is planned to be mitigated by backfilling in the near future.

3.12.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-27 and summarized in Table 32. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Western Dog Pens soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 25. These constituents include pesticides and metals. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 32 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information. Seasonally ponded water periodically pools in the northeast corner of the Western Dog Pens. The ponded water COPEC lists consists of constituents detected in the soil “foot-print” of the ponded water. Ponded water COPECs are listed in Table 33. This list consists of pesticides and metals. 3

3.12.4 Conceptual Site Model Potential sources for soil-associated and surface water contaminants include soils impacted by pesticides used for flea control and excrete containing residual radionuclide and nitrates that were not previously removed in clean up actions. Surface and subsurface soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats. Surface water in seasonal ponds is also considered a media of concern with potential impacts to amphibians. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 1.5.3 and illustrated in Figure 9, the CSM for seasonally ponded habitats.

3 It is recognized that there are currently outstanding comments received from Weiss and PEA concerning the seasonal pond evaluation for Western Dog Pens. Modifications to this approach will be made as deemed necessary.


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3.12.5 Selection of Assessment and Measurement Endpoints (AE and ME) The AE and ME developed for the general suite of receptors found at terrestrial and seasonally-ponded sites are applicable for the Western Dog Pens. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals and amphibians.

3.13 Land Treatment Pilot Study (LTPS) The LTPS area, outlined in Figure 2, refers to pasture lands that are currently irrigated by extracted and treated groundwater. This program was initiated in the fall of 2000 to allow the Treatment System to operate within reduced effluent injection requirements and to provide irrigation water to the pasture lands.

3.13.1 Previous Investigations A background set of soil samples was collected in 2000 prior to the initiation of the Pilot Study. Six composite soil samples were 1, 3 and 5 feet below ground surface (bgs) and analyzed for metals, pH, salts, and total organic carbon (TOC) (Figure 26). These same stations were resampled in 2003 and 2004 and analyzed for the same set of constituents to determine if changes were occurring as a result of the LTPS program. These data were used for COPEC identification at the LTPS Site for the Revised SWERA as described in Section 3.13.3.

3.13.2 Evaluation of the Environmental and Biological Setting The groundwater treatment extraction well, the building that houses the air stripper and a few monitoring wells initially were the only major features present at the LTPS. The land to the north was used for horse pens and the land to the south possessed sheep and goat barns. The University decided to make the remaining land available at the LTPS into horse pens. Grass was planted, the pens were built and a road was constructed allowing access to the pens. The vegetation at the Site today is predominantly annual grasses and ruderal vegetation and is therefore characterized as a terrestrial site.

3.13.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-31 and summarized in Table 34. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of LTPS soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 26. These constituents include metals.


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Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 34 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.13.4 Conceptual Site Model Potential sources for site-related impacts include constituents potentially present in treated groundwater that is used to irrigate the area. Soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats.


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the LTPS. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.14 Non-Operational Unit (OU) Area The Non-OU area includes the 16 acres of land between buildings and structures that are not associated with any of the previously described OUs. Non-OU area is included in this assessment at the request of USEPA and to provide perspective. The areas between buildings and investigated areas consist of dirt access roads and undeveloped and/or landscaped land.

3.14.1 Evaluation of the Environmental and Biological Setting These areas are mostly comprised of dirt access roads, and undeveloped ruderal/non-native grassland/landscaped habitat. They are therefore assessed in the SWERA as terrestrial habitat.

3.14.2 Previous Investigations Sampling of the Non-OU Areas was conducted as part of the 2002 data gaps investigation (MWH 2003b). The purpose of this sampling was to provide surface soil chemical and radiological data for the SWRA. Ten surface (0 to 0.5 feet bgs) soil samples were collected at locations outside DOE-NNSA and UC Davis areas. The samples were analyzed for radionuclides, metals, organochlorine pesticides, SVOCs and general chemical parameters. These data were used for COPEC identification in the Draft SWERA. The data set for the Non OU Area includes 2815 analytical results. One hundred seventy-four of the results, or 6.2%, had “J” qualifiers, which indicate that an analyte was positively identified in the sample, but the analytical


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result is an approximation of the analyte concentration in the sample. Data with “J” qualifiers were used in developing risk estimates. A total of 151 records, or 5.4%, had “UJ” qualifiers, which mean than an analyte was not detected, but the detection limit is approximate. Data with “UJ” qualifiers were included in the risk estimate and were treated as a non-detection of an analyte. Sixteen of the results, or 0.6%, had “U” qualifiers, which indicate that an analyte was not detected above laboratory reporting limits.

3.14.3 Selection of COPECs The selection of COPECs for chemical constituents is presented in Appendix C, Table J-28 and summarized in Table 35. Those constituents whose maximum concentration in the 0 to 10 feet bgs soil interval exceeds the conservative benchmarks are identified as List 1 COPECs and are carried forward for quantitative evaluation in the Tier 2 analysis. Constituents are also carried forward as List 1 COPECs in cases where a benchmark was not identified in order to conduct Tier 1 COPEC screening, but a TRV is available enabling a Tier 2 analysis (TRV documented in Table 11). The locations of Non-OUs soil samples analyzed for constituents considered List 1 COPECs are presented in Figure 27. These constituents include metals and SVOCs. Constituents whose reporting limits are consistently above benchmarks or where a benchmark was not available, are identified as COPECs in Table 35 but are not evaluated quantitatively. These constituents are instead referred to the uncertainty section since quantitative risk cannot be calculated with the available information. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.14.4 Conceptual Site Model Historic air borne dust from the Site is identified as a potential source of soil-associated constituents. Historic dust is evaluated in particular since a majority of the OU surface areas are not regegetated or covered by clean fill. Soils are the media of concern with potential impacts to terrestrial receptors. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats.


The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Non-OU Site. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.


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3.15 Old Davis Road Drainage Ditch The Old Davis Road (ODR) Drainage Ditch is an off-site area located just to the west of Old Davis Road. Stormwater runoff from building gutters and parking lots on the western half of the Site drains into the lift station (LS-1, Figure 5), where stormwater runoff is pumped into a culvert under Old Davis Road (MWH, 2004). It then mixes with stormwater from other sources and accumulates in the ditch.

3.15.1 Previous Investigations Stormwater runoff from LS-1 has been monitored since 1994 because this water potentially could reach Putah Creek. The likelihood of this is low given that the elevation of the culvert through the levee to the Creek is above LS-1 and the drainage ditch (WA, 2003) Soil samples from the ODR ditch were collected in three phases by Weiss Associates. In the first phase in 1996, 4 samples were collected for a broad range of constituents. The second investigation was conducted in 1997. 16 additional samples were collected and analyzed for Cs-137 only in 1998. There are gaps in the numbering for this set due to the collection of samples for in-house uncertified analytes (Weiss, 2005). The soil data collected by Weiss were used for COPEC identification in the SWERA.4 The soil sample locations included in the ponded water evaluation are presented in Figure 18.

3.15.2 Evaluation of the Environmental and Biological Setting The ODR Drainage Ditch is characterized as seasonally-ponded habitat. Water ponds in the ditch during the rainy season. Vegetation is not present in the ditch itself, but shrubs are present on its sides. Western toad and Pacific chorus frog may reproduce in the temporary water during the rainy season. Local wildlife has not been observed using the drainage ditch but it may serve as an occasional travel route for mammals and birds for a short period of time (MWH, 2004).

3.15.3 Selection of COPECs The Old Davis Road Ditch accounts for site-related constituents impacting the area via fate and transport processes. Surface water has not been sampled at the site, therefore the aforementioned soil samples are used for the COPEC evaluation. Soil sample locations included in the ponded water evaluation are presented in Figure 18. It is recognized that there may be ongoing discussions on what samples will be included in the evaluation therefore this figure may be modified based on these discussions. List 1 COPECS are identified at the ODR ditch as those constituents detected in the ditch soil samples that are also identified on the comprehensive site-wide soil COPEC list in order to link the samples back to site-related impacts. The resulting COPEC list is summarized in Table 36. These constituents include pesticides and metals.

4 It is recognized that there are currently outstanding comments received from Weiss and EPA concerning the ponded water evaluation for ODR ditch. Modifications to this approach will be made as deemed necessary by the team.


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3.15.4 Conceptual Site Model Soil-associated constituents may be a potential source of contamination to seasonally-ponded areas. Surface water ponded at the site are the media of concern, which are modeled based on soil-associated constituents. Direct contact between amphibian eggs laid in these ponds and surface water constituents represent a potentially complete exposure pathway as illustrated in Figure 9. Chemical migration and exposure pathways are consistent with those presented in Figure 9. Insignificant exposure pathways include ingestion of vegetation by terrestrial mammals since there is very limited vegetation at the site and Ingestion of surface water for drinking by terrestrial mammals. This is considered to be insignificant due to the short exposure time.


The AE and ME developed for the general suite of receptors found at seasonally-ponded sites are applicable for the ODR Drainage Ditch. These AE and MEs are listed in Table 9. Receptors considered susceptible to seasonally ponded surface water exposures will be evaluated for risk in the Revised SWERA. These include amphibians.

3.16 Far-Ranging Species The entire LEHR/SCDS encompasses an area of 14.5 hectares (36 acres). Far-ranging species defined as those species with home ranges as large or larger than the area and are theoretically anticipated to visit at several of the areas (MWH, 2004). The area use factor (AUF) presented in Table 10 provides a realistic estimate of the contact rate on an Area-by-Area basis. Since the coyote, red-tailed hawk, rock dove and Northern harrier have home range areas greater than the Site area, site-wide AUFs were calculated for each species as follows: • Coyote (mammalian predator) with a home range of approximately 1000 hectares and an AUF of 0.0145; • Red-tailed hawk (avian predator) with a home range of approximately 160 hectares and an AUF of 0.09; • Rock dove (avian herbivore) with a home range of approximately 259 hectares and an AUF of 0.06; and • Northern harrier (avian predator) with a home range of approximately 260 hectares and an AUF of 0.06. Exposure will then be estimated by calculating an upper confidence limit on the mean (UCL) for all sampling locations at LEHR (0-10 ft bgs). The UCL for the whole site will then be used to develop a HQ for receptors that might be exposed to more than 1 area.

3.16.1 Previous Investigations This section does not apply for the Far-Ranging Species evaluation.

3.16.2 Evaluation of the Environmental and Biological Setting This risk evaluation does not focus on one particular site at the LEHR. In contrast, it takes into account soil-related risks that species may encounter with home ranges that are as large or larger than the entire site. The overall setting, as described previously is predominantly terrestrial with a mixture of 20% covered by structures


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or paved, 65% unpaved with limited vegetation, 10% occupied with former dog pens and 5% vegetated with trees.

3.16.3 Selection of COPECs Selection of COPECs was performed for each individual LEHR/SCDS area and reported in previous sections. Accordingly, all List 1 COPECs that may be contacted by these far-ranging species at these areas were included as COPECs for this cumulative assessment as summarized in Table 37. The COPEC list consists of SVOCs, pesticides, PCBs, and metals present at this area regardless of naturally-occurring concentrations of inorganic compounds. The selection of COPECs for radionuclide constituents was conducted in accordance with DOE Guidance (DOE, 2002), as explained in Section 2.1.1.2. The results of this evaluation are presented in Appendix D. All radionuclides that could be evaluated quantitatively did not fail this screen, thus no radionuclides were identified as List 1 COPECs requiring further quantitative evaluation. Some radionuclides could not be evaluated quantitatively in Tier 1 and are referred to the uncertainty section since quantitative risk cannot be calculated with the available information.

3.16.4 Conceptual Site Model The source of soil-associated contaminants at the various areas under evaluation have been described in the previous sections. Soils are the media of concern. Similar exposure pathways exist for these receptors as with all of the other receptors, however the exposure duration differs since these species will have a lower contact rate on an area-by-area basis due to their propensity to roam across a greater acreage. The chemical migration pathways, exposure pathways, and receptors of concern are consistent with those presented in Section 3.1.3, and all other sections assessing ecological risks from soil-associated constituents on local ecological receptors. Potentially complete exposure pathways to terrestrial receptors are illustrated in Figure 8, the CSM developed for sites with terrestrial habitats.

3.16.5 Selection of Assessment and Measurement Endpoints and Receptors of Concern The AE and ME developed for the general suite of receptors found at terrestrial sites are applicable for the Non-OU Site. These AE and MEs are listed in Table 9. All terrestrial receptors with significant exposure as defined in the CSM (Figure 8) will evaluated for risk in the Revised SWERA. These include plants, soil invertebrates, herbivorous, insectivorous, and carnivorous birds and mammals.

3.17 Putah Creek To be developed with the Review Team.

4-1 BLASLAND, BOUCK & LEE, INC. 7/12/05 engineers, scientists, economists 4-1 Tier 1 Tech Memo_Section 3_71205.doc

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4. References Blasland, Bouck and Lee, Inc (BBL Inc). 2005. Revised Evaluation of depth intervals for Ecological Risk Assessment. Submitted to Christine Judal and Brian Oatman, UC Davis, June 2, 2005. Bechtel Jacobs Company LLC. 1998a. Empirical Models for the Uptake of Inorganic Constituents from Soil by Plants. Prepared for Oak Ridge National Laboratory, Oak Ridge, TN. Bechtel Jacobs Company LLC. 1998b. Biota Sediment Accumulation Factors for Invertebrates: Review and Recommendations for the Oak Ridge Reservation. Prepared for Oak Ridge National Laboratory, Oak Ridge, TN. California Department of Water Resources (DWR) , 1978. Evaluation of Groundwater Resources, Sacramento Valley, Bulletin 118-6, 136 pp. California Department of Toxic Substances Control (DTSC). 1996. Guidance for Ecological Risk Assessment at Hazardous Waste Sites and Permitted Facilities. California Environmental Protection Agency. Sacramento, CA. California DTSC, Human and Ecological Risk Division (HERD). 1998. HERD Ecological Risk assessment (ERA) Note 1. Dames & Moore. 1991. Summary Report Waste Burial Trench Investigation LEHR Facility. May. Dames & Moore. 1996a Landfill Unit #1 Data Transmittal, Data Gaps Limited Field Investigation, South Campus Disposal Site, UC Davis. October. Dames & Moore. 1996b.. Landfill Unit #2 Data Transmittal, Data Gaps Limited Field Investigation, South Campus Disposal Site, UC Davis. November. Dames & Moore. 1996c.. Landfill Unit #3 Data Transmittal, Data Gaps Limited Field Investigation, South Campus Disposal Site, UC Davis. November. Dames & Moore. 1997a. . Eastern Trenches Data Transmittal, Data Gaps Limited Field Investigation, South Campus Disposal Site, UC Davis. February. Dames & Moore. 1997b Waste Burial Holes Data Transmittal, Data Gaps Limited Field Investigation, South Campus Disposal Site, UC Davis. April. Dames & Moore. 1998. Southern Trenches Data Transmittal, Data Gaps Limited Field Investigation, South Campus Disposal Site, UC Davis. April. Dames & Moore. 1999a.Groundwater Source Investigation and Data Evaluation Report, SCDS/LEHR Environmental Restoration, UC Davis. March. Dames & Moore. 1999b. 1998 Water Monitoring Report for LEHR/SCDS, UC Davis. April.


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Devillers, J., and J.M. Exbrayat. 1992. Ecotoxicity of Constituents to Amphibians. Gordon and Breach Science Publishers. Efroymson, R.A., M.E. Will, G.W. Suter II, and A.C. Wooten. 1997a (ORNL 1997a). Toxicological Benchmarks for Screening Contaminants of Potential Concern for Effects on Terrestrial Plants: 1997 Revision. Oak Ridge National Laboratory, Oak Ridge, TN. Efroymson, R.A., M.E. Will, and G.W. Suter II. 1997b (ORNL 1997b). Toxicological Benchmarks for Contaminants of Potential Concern for Effects on Soil and Litter Invertebrates and Heterotrophic Processes: 1997 Revision. Oak Ridge National Laboratory, Oak Ridge TN. ES/ER/TM-126/R2. Geomatrix Consultants. 2004 (2004) Final Remedial Investigation report, LEHR/SCDS Environmental Restoration. Prepared for the University of California at Davis. Gilbert, R.O., 1987. Statistical Methods for Environmental Pollution Monitoring. Van Nostrand Reinhold, New York, New York. IT Corporation, 1997, DOE Disposal Box Area Closure Report, Laboratory for Energy-Related Health Research, University of California, Davis, California Jones and Stokes. 1996. Draft Environmental Impact Report: Wastewater Treatment Plant Replacement Project. University of California, Davis, Appendix H, Biological Resources, October. Kabata-Pendias, A., and H. Pendias. 1984. Trace Elements in Soils and Plants. CRC Press, Ann Arbor, MI. Kabata-Pendias, A., and H. Pendias 1992 Trace Elements in Soils and Plants. 2nd edition. CRC Press, Ann Arbor, MI. MacDonald, D.D., C.G. Ingersoll, and T.A. Berger. 2000. Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Arch. Environ. Contam. Toxicol. 39: 20-31. Mann, J.F. Jr., 1992. Hydrology of Lower Putah Creek—Preliminary Discussion for Solano County Agency. January. Marchetti, Michael P. and Peter B. Moyle. 1995, Conflicting Values complicate Stream Protection. California Agriculture, November-December, 1995, pp. 73-78. Montgomery Watson Harza (MWH). 2002a. Draft Tier 1 Ecological Risk Assessment. Prepared for the University of California at Davis. MWH 2002b. Site-Wide Risk Assessment Work Plan. Draft. Prepared for the University of California at Davis. MWH. 2002c. Data Summary and Data Gaps Report, Remedial Investigation/Feasibility Study Work Plan Addendum. Prepared for the University of California at Davis. MWH. 2003. Draft UC Davis Remedial Investigation Report. Prepared for the University of California at Davis. MWH. 2004. Draft Final Site-Wide Risk Assessment, Ecological Risk Estimate. October 2004.


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