Final Phase Iii Remedial Investigation Report Volume I Text and Appendices

FINAL PHASE III REMEDIAL INVESTIGATION REPORT VOLUME I TEXT AND APPENDICES

For

REMEDIAL INVESTIGATION AND FEASIBILITY STUDY COLD REGIONS RESEARCH AND ENGINEERING LABORATORY (CRREL) HANOVER, NEW HAMPSHIRE

Contract No.: W912WJ-11-D-0005 TASK ORDER 0004

Prepared for:

New England District U.S. Army Corps of Engineers 696 Virginia Road Concord MA 01742-2751

June 29, 2018

U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

TABLE OF CONTENTS

EXECUTIVE SUMMARY ...... ES-1 1.0 INTRODUCTION ...... 1-1

1.1 REGULATORY STATUS ...... 1-1 1.2 ROLES AND RESPONSIBILITIES ...... 1-2 1.3 PURPOSE AND SCOPE OF THE RI REPORT ...... 1-2 1.4 SITE BACKGROUND ...... 1-3 1.4.1 Site Description (From FY 2013 CRREL Army Defense Environmental Restoration Program, Installation Action Plan, US Army Installation Command) ...... 1-4 1.4.2 Operational History ...... 1-4 1.4.3 CRREL Facilities ...... 1-5 1.5 REPORT ORGANIZATION ...... 1-6 2.0 STUDY AREA INVESTIGATIONS AND REMEDIAL ACTIVITIES ...... 2-1

2.1 SUMMARY OF PREVIOUS INVESTIGATIONS...... 2-1 2.2 SUMMARY OF INTERIM ACTIONS AND PILOT TESTS ...... 2-4 2.3 PHASE III REMEDIAL INVESTIGATION ...... 2-6 2.4 SOIL/BEDROCK INVESTIGATIONS – PHASE III RI ...... 2-7 2.4.1 Child Development Center ...... 2-8 2.4.2 AOC 2 ...... 2-9 2.4.3 AOC 9 ...... 2-10 2.4.4 AOC 13 ...... 2-11 2.4.5 AOC 15 ...... 2-11 2.5 GROUNDWATER INVESTIGATIONS – PHASE III ...... 2-12 2.5.1 Overburden Groundwater ...... 2-13 2.5.2 Bedrock Groundwater ...... 2-14 2.5.3 Aquifer Testing ...... 2-15 2.6 VAPOR INTRUSION INVESTIGATIONS ...... 2-16 2.6.1 Onsite Air Investigation ...... 2-18 2.6.2 Off-Post Air Investigation ...... 2-21 2.6.3 Synoptic Soil Gas Sampling Event ...... 2-22 2.7 SOIL VAPOR EXTRACTION PILOT TEST ...... 2-22 2.8 DATA QUALITY OBJECTIVES AND DATA VALIDATION ...... 2-23 3.0 PHYSICAL CHARACTERISTICS OF CRREL AREA AND LAND USE ...... 3-1

3.1 GEOGRAPHY ...... 3-1 3.2 DEMOGRAPHY ...... 3-1 3.3 CLIMATE ...... 3-2 3.4 GEOLOGY ...... 3-2 3.4.1 Overburden Geology ...... 3-3 3.4.2 Bedrock Geology...... 3-4 3.5 SURFACE WATER HYDROLOGY ...... 3-5 3.6 HYDROGEOLOGY ...... 3-5 3.6.1 Overburden Groundwater ...... 3-6 3.6.2 Bedrock Groundwater ...... 3-7 3.7 ECOLOGY ...... 3-7 3.7.1 Onsite Habitats and Ecological Receptors ...... 3-8 3.7.2 Off-Post Habitats and Ecological Receptors ...... 3-8 3.7.3 Threatened and Endangered Species ...... 3-9

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

4.0 NATURE AND EXTENT OF CONTAMINATION ...... 4-1

4.1 SOURCES OF CONTAMINATION ...... 4-1 4.2 SOIL/BEDROCK ...... 4-2 4.2.1 Membrane Interface Probe (MIP) and TCE in Soil Results Comparison ...... 4-3 4.2.2 Child Development Center ...... 4-4 4.2.3 AOC 2 ...... 4-6 4.2.4 AOC 9 ...... 4-9 4.2.5 AOC 13 ...... 4-11 4.2.6 AOC 15 ...... 4-12 4.2.7 Downgradient Bedrock Matrix ...... 4-13 4.2.8 Soils Summary ...... 4-13 4.2.9 Bedrock Matrix Summary ...... 4-14 4.3 GROUNDWATER ...... 4-14 4.3.1 Overburden Groundwater ...... 4-16 4.3.2 Bedrock Groundwater ...... 4-20 4.3.3 Groundwater Summary ...... 4-21 4.4 SURFACE WATER ...... 4-21 4.5 SEDIMENT ...... 4-21 4.6 SOIL GAS ...... 4-22 4.6.1 Onsite Soil Gas Investigation ...... 4-23 4.6.2 Off-Post Soil Gas ...... 4-26 4.6.3 October 2015 Synoptic Sampling Round ...... 4-29 4.7 INDOOR AIR ...... 4-30 4.7.1 Onsite Indoor Air Investigation ...... 4-32 4.7.2 Off-Post Indoor Air Investigations ...... 4-39 4.8 VAPOR MIGRATION PATHWAY SUMMARY ...... 4-47 4.8.1 Brendel & Fisher (64 Lyme Road) ...... 4-49 4.8.2 Hanover Family Chiropractic & Hanover Yoga (68 Lyme Road) ...... 4-50 4.8.3 Dartmouth College Housing, Cedar Drive and Fletcher Circle ...... 4-51 4.8.4 Rivercrest Property (49 Lyme Road) ...... 4-51 4.8.5 Dartmouth Printing (69 Lyme Road) ...... 4-52 4.8.6 Richmond Middle School Property (63 Lyme Road)...... 4-53 4.9 SOIL VAPOR EXTRACTION PILOT TEST ...... 4-55 4.9.1 Controlling Off-Site Migration ...... 4-56 4.9.2 Develop Horizontal and Vertical Profiles ...... 4-56 4.9.3 SVE Effects on Main Laboratory Vapor Mitigation...... 4-57 4.9.4 Additional Data to Support the Remedial Investigation ...... 4-58 4.9.5 Horizontal and Vertical Locations of Contamination ...... 4-58 4.9.6 Effects of SVE on Groundwater Contamination ...... 4-59 5.0 CONCEPTUAL SITE MODEL...... 5-1

5.1 PRIMARY CONTAMINANT SOURCES ...... 5-6 5.2 TCE SOURCES AND RELEASES ...... 5-7 5.2.1 Primary Sources and Releases ...... 5-7 5.2.2 Secondary Sources and Releases...... 5-8 5.3 EXPOSURE MEDIA AND ROUTES ...... 5-9 5.3.1 Onsite Indoor Air/Inhalation ...... 5-9 5.3.2 Outdoor Ambient Air/Outdoor Air Inhalation ...... 5-10 5.3.3 Onsite Soil Vapor/Inhalation in an Excavation ...... 5-10 5.3.4 Rivercrest Soil Vapor/Future Indoor Inhalation at Rivercrest ...... 5-10 5.3.5 Off-Post Sub-Slab Soil Vapor/Future Indoor Inhalation ...... 5-10 5.3.6 Soil/Direct Contact and Inhalation of Particulates ...... 5-10 5.3.7 Groundwater/Ingestion, Dermal Contact, and Inhalation of Volatiles While Showering ...... 5-11

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

5.4 ASPECTS OF THE CONCEPTUAL SITE MODEL THAT MAY INDICATE DATA GAPS ...... 5-11 5.4.1 Extent of Soil Contamination ...... 5-11 5.4.2 Extent of TCE Contamination Beyond the CRREL Boundary ...... 5-12 5.4.3 Extent of TCE Source Areas ...... 5-12 5.4.4 Impacts to Connecticut River Sediments ...... 5-12 5.4.5 Impacts to Ambient Air ...... 5-13 6.0 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS (ARARS) ...... 6-1

6.1 LOCATION SPECIFIC ARARS ...... 6-3 6.2 CHEMICAL SPECIFIC ARARS ...... 6-4 6.3 ACTION SPECIFIC ARARS ...... 6-5 7.0 BASELINE HUMAN HEALTH RISK ASSESSMENT ...... 7-1

7.1 INTRODUCTION ...... 7-1 7.1.1 Summary of Conceptual Site Model for Human Health ...... 7-3 7.1.2 Hazard Identification ...... 7-5 7.1.3 Exposure Assessment ...... 7-8 7.1.4 Toxicity Assessment ...... 7-12 7.1.5 Risk Characterization ...... 7-13 7.1.6 Uncertainty ...... 7-17 7.2 TO-15 NON-BASELINE SUPPLEMENTAL HUMAN HEALTH RISK ASSESSMENT ...... 7-18 7.3 HAPSITE® SUPPLEMENTAL HUMAN HEALTH RISK ASSESSMENT ...... 7-19 7.4 CONCLUSIONS ...... 7-20 7.4.1 Baseline Risk Assessment Conclusions: Current and/or Foreseeable Land Use ...... 7-20 7.4.2 Baseline Risk Assessment Conclusions: Hypothetical Receptors ...... 7-22 7.4.3 TO-15 Non-Baseline Supplemental Human Health Risk Assessment Conclusions ...... 7-22 7.4.4 HAPSITE® Supplemental Human Health Risk Assessment Conclusions ...... 7-22 8.0 ECOLOGICAL RISK ASSESSMENT ...... 8-1

8.1 INTRODUCTION ...... 8-1 8.2 PROBLEM FORMULATION ...... 8-1 8.2.1 Environmental Setting ...... 8-1 8.3 COMPLETE EXPOSURE PATHWAYS ...... 8-2 8.4 ECOLOGICAL RISK CONCLUSIONS & RECOMMENDATIONS ...... 8-3 9.0 PRELIMINARY REMEDIATION GOALS ...... 9-1

9.1 COMPOUNDS OF CONCERN ...... 9-1 9.2 ARAR-BASED PRELIMINARY REMEDIATION GOALS ...... 9-1 9.3 OTHER NHDES CRITERIA ...... 9-1 9.4 RISK-BASED PRELIMINARY REMEDIATION GOALS ...... 9-1 10.0 SUMMARY AND CONCLUSIONS...... 10-1

10.1 SUMMARY ...... 10-1 10.2 CONCLUSIONS ...... 10-4 11.0 REFERENCES ...... 11-1

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

LIST OF APPENDICES - PROVIDED ON SEPARATE CD

Appendix A CRREL Land Title Survey Appendix B Soil Boring Logs Appendix C Surface Soil Sample Field Data Records Appendix D Membrane Interface Logs Appendix E Monitoring Well Completion Diagrams Appendix F Groundwater Sample Field Data Records Appendix G WaterlooAPS Data Report Appendix H Bedrock Boring Logs Appendix I Borehole Geophysical Logs Appendix J Soil gas implant Installation Logs Appendix K Air Sample Field Data Records Appendix L HAPSITE® Standard Operating Procedure Appendix M Soil Chemistry Data and Validation Reports Appendix N Groundwater Chemistry Data and Validation Reports Appendix O Air Chemistry Data and Validation Reports Appendix P Paired Soil Boring and MIP Profiler Comparison Analysis Appendix Q NAPLATOR Mass Output Reports Appendix R Historic Groundwater Sample Results Appendix S Aquifer Pumping Test Results Appendix T HAPSITE® Daily Indoor Air Monitoring Results Appendix U Baseline Human Health Risk Assessment Appendix V Photographs from November 10, 2015 Site Visit

LIST OF FIGURES – VOLUME II

Figure ES-1 Site Map Figure ES-2 Interpreted July 2014 Overburden Groundwater TCE Iso-Concentrations Figure ES-3 Interpreted March and July 2014 Bedrock Groundwater TCE Iso-Concentrations Figure ES-4 Conceptual Site Model and Migration Pathways Figure ES-5 CRREL Conceptual Site Model Flowchart

Figure 1.0-1 Project Location

Figure 1.4-1 Site Map Figure 1.4-2 Site Layout

Figure 2.1-1 Historic Surface Soil Samples Figure 2.1-2 Historic Soil Borings Figure 2.1-3 Historic Extent of TCE Contaminated Soils Figure 2.1-4 Historic Monitoring Wells Figure 2.1-5 Historic Extent of TCE Contaminated Groundwater Figure 2.1-6 Historic Areas of Concern

Figure 2.2-1 Location of Interim Actions and Pilot Tests

Figure 2.3-1 Current Areas of Concern and Area of Study

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Figure 2.4-1 Child Development Center Shallow Soil Boring Locations Figure 2.4-2 Membrane Interface Probe, Soil Boring and Bedrock Matrix Locations Figure 2.4-3 AOC 2 Soil Boring Locations Figure 2.4-4 AOC 9 Soil Boring Locations Figure 2.4-5 AOC 13 Soil Boring Locations Figure 2.4-6 AOC 15 Soil Boring Locations

Figure 2.5-1 Groundwater Profiler Boring Locations Figure 2.5-2 MIP and Groundwater Profiler Locations Figure 2.5-3 Overburden and Bedrock Monitoring Well Locations Figure 2.5-4 Constant Rate Discharge Test

Figure 2.6-1 Onsite Vapor Intrusion Investigation Timeline Figure 2.6-2 Onsite Soil Gas Implant Locations Figure 2.6-3 Indoor Air and Sub-Slab Vapor Sample Locations - Main Laboratory Basement and Lab Addition Figure 2.6-4 Indoor Air Sample Locations - Main Laboratory and Lab Addition First Floor Figure 2.6-5 Indoor Air Sample Locations - Main Laboratory and Lab Addition Second Floor Figure 2.6-6 Indoor Air and Sub-Slab Vapor Sample Locations - Lab Addition Sub Basement Figure 2.6-7 Indoor Air and Sub-Slab Vapor Sample Locations - Child Development Center Figure 2.6-8 Indoor Air and Sub-Slab Vapor Sample Locations - Logistics Management Facility Figure 2.6-9 Indoor Air and Sub-Slab Vapor Sample Locations - Vehicle Storage Figure 2.6-10 Indoor Air Sample Locations - Greenhouse Buildings Figure 2.6-11 Indoor Air Sample Locations - Frost Effects Building Figure 2.6-12 Indoor Air and Sub-Slab Vapor Sample Locations – Technical Information Analysis Center Figure 2.6-13 Indoor Air Sample Locations – DPW Storage Figure 2.6-14 Indoor Air Sample Locations - Asphalt Laboratory Figure 2.9-15 Indoor Air Sample Locations - Project Support Facility Figure 2.6-16 Indoor Air Sample Locations – Ballistics Lab Building Figure 2.6-17 Gate Houses and Ambient Air Sample Locations Figure 2.6-18 Off-Post Vapor Intrusion Investigation Timeline Figure 2.6-19 Off-Post Soil Gas Implant Locations Figure 2.6-20 Richmond Middle School, 63 Lyme Road Vapor Intrusion Sample Locations Figure 2.6-21 Brendel & Fisher, 64 Lyme Road Vapor Intrusion Sample Locations Figure 2.6-22 Hanover Family Chiropractic & Hanover Yoga, 68 Lyme Road, Vapor Intrusion Sample Locations Figure 2.6-23 Dartmouth College Housing Cedar Drive and Fletcher Circle, Vapor Intrusion Sample Locations Figure 2.6-24 Dartmouth Printing, 69 Lyme Road, Vapor Intrusion Sample Locations Figure 2.6-25 October 2015 Synoptic Soil Gas Round Sample Locations

Figure 2.7-1 Soil Vapor Extraction Pilot Test Layout

Figure 3.1-1 Site Regional Surficial Geology Figure 3.1-2 Site Vicinity Topography Figure 3.1-3 South to North Three-Dimensional Representation of CRREL Subsurface Utilities

Figure 3.2-1 Site Map and Adjacent Properties

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Figure 3.3-1 Barometric Pressure by Month, 2004-2014 (Percentile) Figure 3.3-2 Barometric Pressure by Month, 2004-2014 (Min-Max)

Figure 3.4-1 Three-Dimensional View of Esker Surface Figure 3.4-2 Glacial Lake Hitchcock Figure 3.4-3 Lithologic Cross Section Figure 3.4-4 Plan View –Contours for SM (Sand, Silt, Clay) Thickness Figure 3.4-5 Interpreted Bedrock Surface Contour Map Figure 3.4-6 South to North Three-Dimensional Representation of Bedrock Surface Figure 3.4-7 North to South Three-Dimensional Representation of Bedrock Surface Figure 3.4-8 Site Regional Bedrock Geology

Figure 3.6-1 South to North Three-Dimensional Representation of Groundwater Surface Figure 3.6-2 North to South Three-Dimensional Representation of Groundwater Surface Figure 3.6-3 Interpreted July 2014 Overburden Groundwater Potentiometric Surface Figure 3.6-4 Interpreted July 2014 Bedrock Potentiometric Surface and Gradients

Figure 4.2-1 Child Development Center Contaminant Summary Figure 4.2-2 AOC 2 Soil MIP/HPT Profiles Figure 4.2-3 AOC 2 Soil TCE Results and MIP XSD Logs Figure 4.2-4 AOC 2 Estimated Area in Excess of 800 µg/kg of TCE in Soils Figure 4.2-5 AOC 9 MIP/HPT Profiles Figure 4.2-6 AOC 9 Soil TCE Results and MIP XSD Logs Figure 4.2-7 AOC 9 Estimated Area of TCE in Excess of 800 µg/kg in Soils Figure 4.2-8 AOC 13 MIP/HPT Profiles Figure 4.2-9 AOC 13 Soil TCE Results and MIP XSD Logs Figure 4.2.10 AOC 13 Estimated Area of TCE in Excess of 800 µg/kg in Soils

Figure 4.2.11 AOC 15 Soil Contaminant Summary

Figure 4.3.1 Interpreted July 2014 Overburden Groundwater TCE Iso-Concentrations Figure 4.3-2 Groundwater Profiler TCE Results Figure 4.3-3 Interpreted Extent of TCE Contaminated Overburden Groundwater Figure 4.3-4 Groundwater Profiler Sample Results 3-D View Figure 4.3-5 Groundwater Profiler, Monitoring Well Sample Results and MIP Data below the Water Table Figure 4.3-6 Groundwater Profiler Data and Interpreted Vertical Extent of Overburden Groundwater Plume Figure 4.3-7 Interpreted March and July 2014 Bedrock Groundwater TCE Iso-Concentrations

Figure 4.6-1 Onsite May 2012 Soil Gas TCE Results Figure 4.6-2 Onsite May 2012 Soil Gas TCE Results Compared to USEPA Residential Soil Gas Screening Level Figure 4.6-3 Onsite May 2012 Soil Gas TCE Results Compared to NHDES Residential Soil Gas Screening Level Figure 4.6-4 Onsite Perimeter Soil Gas TCE Results – May, July and October 2012 Figure 4.6-5 Onsite July 2012 Soil Gas TCE Results Compared to USEPA Residential Soil Gas Screening Level

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Figure 4.6-6 Onsite July 2012 Soil Gas TCE Results Compared to NHDES Residential Soil Gas Screening Level Figure 4.6-7 Onsite October 2012 Soil Gas TCE Results Compared to USEPA Residential Soil Gas Screening Level Figure 4.6-8 Onsite October 2012 Soil Gas TCE Results Compared to NHDES Residential Soil Gas Screening Level Figure 4.6-9 Onsite November 2012 Soil Gas TCE Results Figure 4.6-10 Onsite November 2012 Soil Gas TCE Results Compared to USEPA Residential Soil Gas Screening Levels Figure 4.6-11 Onsite November 2012 Soil Gas TCE Results Compared to NHDES Residential Soil Gas Screening Level Figure 4.6-12 Dartmouth College Properties May 2013 Soil Gas TCE Results Figure 4.6-13 Dartmouth Rivercrest January 2014Soil Gas TCE Results Figure 4.6-14 Richmond Middle School May 2013 Soil Gas TCE Results Figure 4.6-15 Dartmouth Printing May 2013 Soil Gas TCE Results Figure 4.6-16 Dartmouth Printing November 2013 Soil Gas TCE Results Figure 4.6-17 Dartmouth Printing November 2013 Soil Gas PCE Results Figure 4.6-18 October 2015 Synoptic Sample Round Soil Gas TCE Results Figure 4.6-19 October 2015 Synoptic Sample Round Soil Gas TCE Results Compared to USEPA Residential Soil Gas Screening Levels Figure 4.6-20 October 2015 Synoptic Sample Round Soil Gas TCE Results Compared to NHDES Residential Soil Gas Screening Level Figure 4.6-21 TCE Impacts to Soil Gas in Excess of 100 µg/m3 2010 to 2014 Data Figure 4.6-22 TCE Impacts to Soil Gas in Excess of 100 µg/m3 October 2015 Data

Figure 4.7-1 Event 7 Ambient Air Sample Locations TCE Results Figure 4.7-2 Event 8 Ambient Air Sample Locations TCE Results Figure 4.7-3 Event 9 Ambient Air Sample Locations TCE Results Figure 4.7-4 Event 10 Ambient Air Sample Locations TCE Results Figure 4.7-5 Event 11 Ambient Air Sample Locations TCE Results Figure 4.7-6 Main Laboratory Basement Vapor Intrusion Event 7 TCE Results Figure 4.7-7 Main Laboratory Basement Vapor Intrusion Event 8 TCE Results Figure 4.7-8 Main Laboratory Basement Vapor Intrusion Event 9 TCE Results Figure 4.7-9 Main Laboratory Basement Vapor Intrusion Event 10 TCE Results Figure 4.7-10 Main Laboratory Basement Vapor Intrusion Event 11 TCE Results Figure 4.7-11 Main Laboratory Basement Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-12 Main Laboratory First Floor Vapor Intrusion Event 7 TCE Results Figure 4.7-13 Main Laboratory First Floor Vapor Intrusion Event 8 TCE Results Figure 4.7-14 Main Laboratory First Floor Vapor Intrusion Event 9 TCE Results Figure 4.7-15 Main Laboratory First Floor Vapor Intrusion Event 10 TCE Results Figure 4.7-16 Main Laboratory First Floor Vapor Intrusion Event 11 TCE Results Figure 4.7-17 Main Laboratory First Floor Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-18 Main Laboratory Second Floor Vapor Intrusion Event 7 TCE Results Figure 4.7-19 Main Laboratory Second Floor Vapor Intrusion Event 8 TCE Results Figure 4.7-20 Main Laboratory Second Floor Vapor Intrusion Event 9 TCE Results Figure 4.7-21 Main Laboratory Second Floor Vapor Intrusion Event 10 TCE Results Figure 4.7-22 Main Laboratory Second Floor Vapor Intrusion Event 11 TCE Results

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Figure 4.7-23 Main Laboratory Second Floor Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-24 Main Laboratory Addition Sub-Basement Vapor Intrusion Event 7 TCE Results Figure 4.7-25 Main Laboratory Addition Sub-Basement Vapor Intrusion Event 8 TCE Results Figure 4.7-26 Main Laboratory Addition Sub-Basement Vapor Intrusion Event 9 TCE Results Figure 4.7-27 Main Laboratory Addition Sub-Basement Vapor Intrusion Event 10 TCE Results Figure 4.7-28 Main Laboratory Addition Sub-Basement Vapor Intrusion Event 11 TCE Results Figure 4.7-29 Main Laboratory Addition Sub-Basement Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-30 Child Development Center Vapor Intrusion Event 7 TCE Results Figure 4.7-31 Child Development Center Vapor Intrusion Event 8 TCE Results Figure 4.7-32 Child Development Center Vapor Intrusion Event 9 TCE Results Figure 4.7-33 Child Development Center Vapor Intrusion Event 10 TCE Results Figure 4.7-34 Child Development Center Vapor Intrusion Event 11 TCE Results Figure 4.7-35 Child Development Center Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-36 Logistics Management Facility Vapor Intrusion Event 7 TCE Results Figure 4.7-37 Logistics Management Facility Vapor Intrusion Event 8 TCE Results Figure 4.7-38 Logistics Management Facility Vapor Intrusion Event 9 TCE Results Figure 4.7-39 Logistics Management Facility Vapor Intrusion Event 10 TCE Results Figure 4.7-40 Logistics Management Facility Vapor Intrusion Event 11 TCE Results Figure 4.7-41 Logistics Management Facility Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-42 Vehicle Storage Vapor Intrusion Event 7 TCE Results Figure 4.7-43 Vehicle Storage Vapor Intrusion Event 8 TCE Results, Indoor Air Figure 4.7-44 Vehicle Storage Vapor Intrusion Event 9 TCE Results Figure 4.7-45 Vehicle Storage Vapor Intrusion Event 10 TCE Results Figure 4.7-46 Vehicle Storage Vapor Intrusion Event 11 TCE Results Figure 4.7-47 Vehicle Storage Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-48 Greenhouse Buildings Vapor Intrusion Event 7 TCE Results Figure 4.7-49 Greenhouse Buildings Vapor Intrusion Event 8 TCE Results Figure 4.7-50 Greenhouse Buildings Vapor Intrusion Event 9 TCE Results Figure 4.7-51 Greenhouse Buildings Vapor Intrusion Event 10 TCE Results Figure 4.7-52 Greenhouse Buildings Vapor Intrusion Event 11 TCE Results Figure 4.7-53 Greenhouse Buildings Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-54 Frost Effects Laboratory Vapor Intrusion Event 7 TCE Results Figure 4.7-55 Frost Effects Laboratory Vapor Intrusion Event 8 TCE Results Figure 4.7-56 Frost Effects Laboratory Vapor Intrusion Event 9 TCE Results Figure 4.7-57 Frost Effects Laboratory Vapor Intrusion Event 10 TCE Results Figure 4.7-58 Frost Effects Laboratory Vapor Intrusion Event 11 TCE Results Figure 4.7-59 Frost Effects Laboratory Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-60 DPW Storage Vapor Intrusion Event 7 TCE Results Figure 4.7-61 Ballistics Lab Building Vapor Intrusion Event 7 TCE Results Figure 4.7-62 Project Support Facility Vapor Intrusion Event 7 TCE Results Figure 4.7-63 Asphalt Laboratory Vapor Intrusion Event 7 TCE Results Figure 4.7-64 Exterior Sheds Vapor Intrusion Event 7 TCE Results

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Figure 4.7-65 South Gate House Vapor Intrusion Event 9 TCE Results Figure 4.7-66 South Gate House Vapor Intrusion Event 10 TCE Results Figure 4.7-67 South Gate House Vapor Intrusion Event 11 TCE Results Figure 4.7-68 South Gate House Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-69 North Gate House Vapor Intrusion Event 9 TCE Results TCE Results Figure 4.7-70 North Gate House Vapor Intrusion Event 10 TCE Results TCE Results Figure 4.7-71 North Gate House Vapor Intrusion Event 11 TCE Results TCE Results Figure 4.7-72 North Gate House Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-73 Technical Information Analysis Center Vapor Intrusion Event 9 TCE Results Figure 4.7-74 Technical Information Analysis Center Vapor Intrusion Event 10 TCE Results Figure 4.7-75 Technical Information Analysis Center Vapor Intrusion Event 11 TCE Results Figure 4.7-76 Technical Information Analysis Center Vapor Intrusion Time Series TCE Results Compared to the Interim Action Level Figure 4.7-77 Brendel & Fisher, 64 Lyme Road Vapor Intrusion TCE Results Figure 4.7-78 Hanover Family Chiropractic & Hanover Yoga, 68 Lyme Road Vapor Intrusion TCE Results Figure 4.7-79 Dartmouth College Housing, Cedar Drive and Fletcher Circle Vapor Intrusion TCE Results Figure 4.7-80 Dartmouth Printing, 69 Lyme Road Vapor Intrusion TCE Results Figure 4.7-81 Dartmouth Printing, 69 Lyme Road Vapor Intrusion PCE Results Figure 4.7-82 Richmond Middle School, 63 Lyme Road Vapor Intrusion April 2013 TCE Results Figure 4.7-83 Richmond Middle School, 63 Lyme Road Vapor Intrusion July 2013 TCE Results Figure 4.7-84 Richmond Middle School, 63 Lyme Road Vapor Intrusion January 2014 TCE Results Figure 4.7-85 Richmond Middle School, 63 Lyme Road Vapor Intrusion April 2014 TCE Results Figure 4.7-86 Richmond Middle School, 63 Lyme Road Vapor Intrusion August 2014 TCE Results Figure 4.7-87 Richmond Middle, 63 Lyme Road Vapor Intrusion January 19, 2015 TCE Results Figure 4.7-88 Richmond Middle School, 63 Lyme Road Vapor Intrusion January 24, 2015 TCE Results Figure 4.7-89 Richmond Middle School, 63 Lyme Road Vapor Intrusion April 2015 TCE Results Figure 4.7-90 Richmond Middle School, 63 Lyme Road Vapor Intrusion August 2015 TCE Results

Figure 4.9-1 Soil Vapor Extraction Pilot Test Layout Figure 4.9-2 Rivercrest Property Summary of Soil Gas Results for TCE Figure 4.9-3 Constant Rate Test SVE Influent Concentration Trends Figure 4.9-4 MW-14-107 Overburden Groundwater TCE Results Figure 4.9-5 CECRL08 Overburden Groundwater TCE Results

Figure 5.0-1 Conceptual Site Model and Migration Pathways Figure 5.0-2 CRREL Conceptual Site Model Flowchart Figure 5.0-3 Spatial Relationship Between TCE Contaminated Soil and Soil Gas Figure 5.0-4 Spatial Relationship Between TCE Contaminated Soil Gas and Groundwater Figure 5.0-5 Spatial Relationship Between TCE Contaminated Soil, Soil Gas, and Groundwater

Figure 7.1-1 Off-Post Properties Figure 7.1-2 Onsite Structures and Layout Figure 7.1-3 Human Health Risk Assessment Organization Figure 7.1-4 Baseline Cancer Risk for On-Post Receptors: Construction Worker, Outdoor Worker, Trespasser, and Utility Workers

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Figure 7.1-5 Baseline Hazard Index for On-Post Receptors: Construction Worker, Outdoor Worker, Trespasser, and Utility Workers Figure 7.1-6 Baseline Cancer Risk for: CDC Daycare Child, Indoor Workers, and Off-Post Future Rivercrest Residents Figure 7.1-7 Baseline Hazard Index for: CDC Daycare Child, Indoor Workers, and Off-Post Future Rivercrest Residents Figure 7.2-1 TO‐15 Indoor Air Baseline Cancer Risk vs. TO‐15 Indoor Air Non‐Baseline Cancer Risk: On‐Post Indoor Air Figure 7.2-2 TO‐15 Indoor Air Baseline Hazard Index vs. TO‐15 Indoor Air Non‐Baseline Hazard Indoor: On‐Post Indoor Air Figure 7.3-1 Comparison of HAPSITE® and TO-15 Indoor Air Data and Calculated EPCs- Non- Baseline Figure 7.3-2 Comparison of HAPSITE® and TO-15 Indoor Air Data Calculated Means and Standard Error- Non-Baseline Figure 7.3-3 Comparison of HAPSITE® and TO-15 Indoor Air Non-Baseline Datasets: Main Laboratory Figure 7.3-4 TO-15 Indoor Air Non-Baseline Cancer Risk vs. HAPSITE® Indoor Air Non-Baseline Cancer Risk: On-Post Indoor Worker Figure 7.3-5 TO-15 Indoor Air Non-Baseline Hazard Index vs. HAPSITE® Indoor Air Non-Baseline Hazard Index: On-Post Indoor Worker

Figure 8.2-1 Habitat Observations Figure 8.3-1 Habitat Map

LIST OF TABLES – VOLUME III

Table 2.0-1 Section 2 Table Notes Table 2.1-1 CRREL Previous Investigation Timeline Summary Table 2.1-2 Summary of AOCs

Table 2.4-1 Summary of Soil Sampling and Analytical Program Child Development Center Table 2.4-2 Summary of Soil Sampling and Analytical Program AOC 2 Table 2.4-3 Summary of Soil Sampling and Analytical Program AOC 9 Table 2.4.4 Summary of Bedrock Matrix Samples and Analytical Program Table 2.4-5 Summary of Soil Sampling and Analytical Program AOC 13 Table 2.4-6 Summary of Soil Sampling and Analytical Program AOC 15 Table 2.4-7 Summary of Soil Sampling and Analytical Program MIP and Groundwater Profiler Locations

Table 2.5-1 Overburden Groundwater Analytical Summary Table 2.5-2 Bedrock Groundwater Analytical Summary Table 2.5-3 Overburden and Bedrock Well Installation Summary

Table 2.6-1 Summary of Air Sampling and Analytical Program Onsite Table 2.6-2 Summary of Air Sampling and Analytical Program Background Table 2.6-3 Summary of Air Sampling and Analytical Program Rivercrest Table 2.6-4 Summary of Air Sampling and Analytical Program Richmond Middle School Table 2.6-5 Summary of Air Sampling and Analytical Program Dartmouth Printing Table 2.6-6 Summary of Air Sampling and Analytical Program Brendel and Fisher Table 2.6-7 Summary of Air Sampling and Analytical Program Hanover Chiropractic Table 2.6-8 Summary of Air Sampling and Analytical Program Dartmouth Housing

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Table 2.6-9 Onsite Vapor Intrusion Sampling Events Table 2.6-10 Summary of Air Sampling and Analytical Program October 2015 Synoptic Soil Gas Sampling Event

Table 2.7-1 Timeline of Soil Vapor Extraction Pilot Test Events

Table 3.6-1 Groundwater Elevations Measured During the Month of July (2005 through 2015)

Table 4.0-1 Section 4 Table Notes Table 4.2-1 Child Development Center Soil Results - Hits Only Summary Table 4.2-2 AOC 2 Soil Results - Hits Only Summary Table 4.2-3 Summary of Estimated Mass of TCE in AOC 2 Soils Table 4.2-4 AOC 9 Soil Results - Hits Only Summary Table 4.2-5 Summary of Estimated Mass of TCE in AOC 9 Soils Table 4.2-6 AOC 9 Bedrock Results - Hits Only Summary Table 4.2-7 AOC 13 Soil Results - Hits Only Summary Table 4.2-8 AOC 15 Soil Results - Hits Only Summary Table 4.2-9 Volumes of TCE Contaminated Soil by AOC

Table 4.3-1 Overburden Groundwater Results - Organic Compounds - Hits Only Summary Table 4.3-2 Summary of XSD Values Associated with Selected Measured Groundwater Concentrations Table 4.3-3 Overburden Groundwater Results – Metals - Hits Only Summary Table 4.3-4 Summary of Volume of Overburden Groundwater Impacted by TCE Table 4.3-5 Summary of Mass of TCE in Overburden Groundwater Table 4.3-6 Bedrock Groundwater Results – Hits Only Summary

Table 4.6-1 Summary of Soil Gas Sampling Events Table 4.6-2 May 2012 Onsite Soil Gas Results - Hits Only Summary Table 4.6-3 May 2012 Onsite Soil Gas Results - Frequency of Detection Summary Table 4.6-4 July 2012 Onsite Soil Gas Results - Hits Only Summary Table 4.6-5 July 2012 Onsite Soil Gas Results - Frequency of Detection Summary Table 4.6-6 October 2012 Onsite Soil Gas Results - Hits Only Summary Table 4.6-7 October 2012 Onsite Soil Gas Results - Frequency of Detection Summary Table 4.6-8 November 2012 Onsite Soil Gas Results - Hits Only Summary Table 4.6-9 November 2012 Onsite Soil Gas Results - Frequency of Detection Summary Table 4.6-10 Dartmouth College Housing, Fletcher Circle, and Cedar Drive Soil Gas Results - Hits Only Summary Table 4.6-11 Dartmouth College Housing Properties Soil Gas Results - Hits Only Summary Table 4.6-12 Richmond Middle School, 63 Lyme Road Soil Gas Results - Hits Only Summary Table 4.6-13 Dartmouth Printing, 69 Lyme Road Soil Gas Results - Hits Only Summary Table 4.6-14 Dartmouth Printing, 69 Lyme Road Soil Gas Results - Bottle Vac Summary Table 4.6-15 October 2015 Synoptic Sample Round Soil Gas Results Rivercrest - Hits Only Summary Table 4.6-16 October 2015 Synoptic Soil Gas Sampling Event - TCE Results

Table 4.7-1 Summary of Onsite Indoor Air Sampling Events Table 4.7-2 Event 7 Onsite Ambient Air - Hits Only Summary Table 4.7-3 Event 7 Onsite Indoor Air - Hits Only Summary (Summa Canister) Table 4.7-4 Event 7 Onsite Indoor Air - Hits Only Summary (Radiello Samples)

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Table 4.7-5 Event 7 Onsite Sub-Slab Air - Hits Only Summary (Summa Canister) Table 4.7-6 Event 7 Onsite Radiello-Summa Results Comparison Table 4.7-7 Event 7 TCE Results Compared to Interim Action Level Table 4.7-8 Event 8 Onsite Ambient Air - Hits Only Summary Table 4.7-9 Event 8 Onsite Indoor Air - Hits Only Summary Table 4.7-10 Event 8 Onsite Sub-Slab - Hits Only Summary Table 4.7-11 Event 8 TCE Results Compared to Interim Action Level Table 4.7-12 Event 9 Onsite Ambient Air - Hits Only Summary Table 4.7-13 Event 9 Onsite Indoor Air - Hits Only Summary Table 4.7-14 Event 9 Onsite Sub-Slab - Hits Only Summary Table 4.7-15 Event 9 TCE Results Compared to Interim Action Level Table 4.7-16 Event 10 Onsite Ambient Air - Hits Only Summary Table 4.7-17 Event 10 Onsite Indoor Air - Hits Only Summary Table 4.7-18 Event 10 Onsite Sub-Slab - Hits Only Summary Table 4.7-19 Event 10 TCE Results Compared to Interim Action Level Table 4.7-20 Event 11 Onsite Ambient Air - Hits Only Summary Table 4.7-21 Event 11 Onsite Indoor Air - Hits Only Summary Table 4.7-22 Event 11 Onsite Sub-Slab - Hits Only Summary Table 4.7-23 Event 11 TCE Results Compared to Interim Action Level Table 4.7-24 Summary of Off-Post Indoor Air Sampling Events Table 4.7-25 Brendel & Fisher, 64 Lyme Road 2013 Vapor Intrusion Sampling - TCE Results Table 4.7-26 Brendel & Fisher, 64 Lyme Road 2013 Vapor Intrusion Sampling Results – Indoor Air and Ambient Air - Hits Only Summary Table 4.7-27 Brendel & Fisher, 64 Lyme Road 2013 Vapor Intrusion Sampling Results - Sub-Slab Hits Only Summary Table 4.7-28 Hanover Family Chiropractic & Hanover Yoga, 68 Lyme Road 2013 Vapor Intrusion Sampling Results - TCE Results Table 4.7-29 Hanover Family Chiropractic, Hanover Yoga, 68 Lyme Rd 2013 Vapor Intrusion, Indoor - Ambient Air Hits Only Summary Table 4.7-30 Hanover Family Chiropractic & Hanover Yoga, 68 Lyme Road 2013 Vapor Intrusion - Sub- Slab Hits Only Summary Table 4.7.31 Dartmouth College Housing, 49 Lyme Road, Fletcher Circle, Cedar Drive 2013 Vapor Intrusion Sampling - TCE Results Table 4.7.32 Dartmouth College Housing, 49 Lyme Road, Fletcher Circle and Cedar Drive 2013 Vapor Intrusion - IA and AA Hits Only Summary Table 4.7.33 Dartmouth College Housing, 49 Lyme Road, Fletcher Circle and Cedar Drive 2013 Vapor Intrusion - Sub-Slab Hits Only Summary Table 4.7.34 Dartmouth Printing, 69 Lyme Road, Fletcher Circle and Cedar Drive, 2013 Vapor Intrusion Sampling TCE Results Table 4.7.35 Dartmouth Printing, 69 Lyme Road 2013-2014 Vapor Intrusion Sampling Results - IA and AA Hits Only Summary Table 4.7.36 Dartmouth Printing, 69 Lyme Road 2013-2014 Vapor Intrusion - Sub Slab Hits Only Summary Table 4.7.37 Richmond Middle School, 63 Lyme Road 2013-2015 Vapor Intrusion Sampling - TCE Results Table 4.7.38 Richmond Middle School, 63 Lyme Road 2013-2015 Vapor Intrusion Sampling Results - IA and AA Hits Only Summary Table 4.7.39 Richmond Middle School, 63 Lyme Road 2013-2015 Vapor Intrusion - Sub-Slab Hits Only Summary

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Table 5.1-1 Conceptual Site Model CRREL Primary TCE Release Sources, Migration Mechanisms, Receiving and Exposure Media Table 5.1-2 Conceptual Site Model CRREL Secondary TCE Release Sources, Migration Mechanisms, Receiving and Exposure Media Table 5.1-3 Conceptual Site Model CRREL Tertiary TCE Release, Migration Mechanisms, Receiving and Exposure Media Table 5.1-4 Conceptual Site Model CRREL Quaternary TCE Release, Migration Mechanisms, Receiving and Exposure Media

Table 6.1-1 Potential Location-Specific Applicable or Relevant and Appropriate Requirements (ARARs) and Criteria To Be Considered (TBCs) Table 6.1-2 Potential Chemical-Specific Applicable or Relevant and Appropriate Requirements (ARARs) and Criteria To Be Considered (TBCs)

Table 7.1-1 Selection of Exposure Pathways Table 7.1-2 Summary of Chemicals of Potential Concern by Media – Baseline Table 7.1-3 Summary of Potential Carcinogenic Risk and Hazard Index: Baseline Scenario – All Media and TO-15 Indoor Air Table 7.1-4 Summary of Compounds of Concern: Indoor Air and Excavation Air

Table 7.2-1 Summary of Potential Carcinogenic Risk and Hazard Index for Indoor Air: Non-Baseline Scenario - TO-15 Indoor Air

Table 7.3-1 Comparison of Summary Statistics and Results: HAPSITE® versus TO-15 Table 7.3-2 Summary of Potential Carcinogenic Risk and Hazard Index: Baseline and Non-Baseline Scenario - HAPSITE®

Table 8.2-1 State-Listed Rare, Threatened, and Endangered Species in Hanover, NH

Table 9.1-1 Onsite Indoor Worker Inhalation of Indoor Air: Preliminary Remediation Goals Table 9.1-2 Onsite Construction Worker Inhalation of Excavation Air: Preliminary Remediation Goals Table 9.1-3 Rivercrest Off-Post Future Resident Inhalation of Indoor Air: Preliminary Remediation Goals

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

ACRONYMS AND ABBREVIATIONS

4,4’-DDE 4,4’-Dichlorodiphenyldichlorethylene 4,4’-DDT 4,4;-Dichlordiphenyltrichloroethane AEC Army Environmental Command ADD Average Daily Dose ADE Average Daily Exposure ADR Automatic Data Review Amec Foster Wheeler Amec Foster Wheeler Environment & Infrastructure, Inc. AOC Area of Concern ARAR Applicable Relevant and Appropriate Requirements AST Aboveground Storage Tank bgs Below Ground Surface BHHRA Baseline Human Health Risk Assessment BV Bottle-Vac

CDC Child Development Center CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFR Code of Federal Regulations CFS Cubic Feet per Second cis 1,2-DCE cis 1,2-dichloroethene COC Contaminants of Concern COE Core of Engineers COPC Compound of Potential Concern CRREL Cold Regions Research Engineering Laboratory CSM Conceptual Site Model

DERA Defense Environmental Restoration Account DERP Defense Environmental Restoration Program DoD Department of Defense DNAPL Dense Non-Aqueous Phase Liquid DPW Department of Public Works DRO Diesel Range Organics DQI Data Quality Indicators DQO Data Quality Objective

ELCR Excess Lifetime Cancer Risk EPC Exposure Point Concentration ERDC Engineer Research and Development

FDR Field Data Records FERF Frost Effects Research Facility FS Feasibility Study ft/sec Feet per Second g/cm3 grams per cubic meter

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

GC/MS gas chromatography/mass spectrometry GMP Groundwater Management Present GMZ Groundwater Management Zone gpm gallons per minute GRO Gasoline Range Organic

HAPSITE® Hazardous Air Pollutants on Site Hg Mercury HHRA Human Health Risk Assessment HI Hazard Index HSIA Halogenated Solvents Industry Alliance HQ Hazard Quotient HVAC Heating Ventilation and Air Conditioning

IRP Installation Restoration Program

LMO Logistics Management Facility LOD Limit of Detection

MCL Maximum Contaminant Level mg/kg milligrams per kilogram MIP/HPT Membrane Interface Probe and Hydraulic Profiling Tool µg/m3 micrograms per cubic meter MPR Multi-Purpose Room mV Microvolts NAPL Non-Aqueous Phase Liquid NCP National Contingency Plan NHDES New Hampshire Department of Environmental Services NPDES National Pollutant Discharge Elimination System

PAH Polynuclear Aromatic Hydrocarbon PCB Polychlorinated Biphenyl PCE tetrachloroethylene

QA/QC Quality Assurance/Quality Control QAPP Quality Assurance Program Plan

RAB Restoration Advisory Board RAGS Risk Assessment Guidance for Superfund RAP Remediation Action Plan RCRA Resource Conservation and Recovery Act RI Remedial Investigation RME Reasonable Maximum Exposure RMS Richmond Middle School RQD Rock Quality Designations RSL Regional Screening Level

SARA Superfund Amendments & Reauthorization Act

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

SI Site Investigation SIM Selected Ion Monitoring SL Screening Level SSDS Sub Slab Depressurization System SVE Soil Vapor Extraction SVOC Semi-volatile Organic Compound

TAL Target Analyte List TBC to be considered TCE Trichloroethene or Trichloroethylene TIAC Technical Information Analysis Center TPH Total Petroleum Hydrocarbons trans-1,2-DCE trans-1,2-dichloroethene

USACE-NAE U.S. Army Corps of Engineers, New England District USEPA United States Environmental Protection Agency UFP-QAPP Uniform Federal Policy Quality Assurance Project Plan USC United States Code UST Underground Storage Tank

VDOH Vermont Department of Health VDEQ Virginia Department of Environmental Quality VI Vapor Intrusion VISL Vapor Intrusion Screening Level VOC Volatile Organic Compound VTDEC Vermont Department of Environmental Conservation XSD Halogen Specific Detector

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

EXECUTIVE SUMMARY

Phase III Remedial Investigation Cold Regions Research and Engineering Laboratory (CRREL) Hanover, New Hampshire.

Introduction and Background

Amec Foster Wheeler Environment & Infrastructure, Inc. (Amec Foster Wheeler) has prepared the Phase III Remedial Investigation (RI) Report to document environmental investigation activities conducted at the Cold Regions Research and Engineering Laboratory (CRREL) located in Hanover, New Hampshire. The RI Report has been prepared for the United States Army Corps of Engineers New England District (USACE-NAE) under contract number W912WJ-11-D-0005 Task Order 0004.

The CRREL Phase III RI:

• Provides information on physical characteristics of the CRREL environmental setting and waste characterization. • Draws conclusions regarding types of potential contaminants of concern (COC) present, their sources, nature and extent. • Estimates the quantity of contaminants. • Evaluates COC migration pathways, receptors and exposures. • Characterizes risks posed. • Provides information for development of a Feasibility Study (FS) Report.

The RI identifies data gaps and proposes a supplemental RI for characterization of sediment in the Connecticut River and bedrock groundwater.

Prior environmental investigations have been conducted at the site beginning in 1990. The data and findings from these investigations are referenced in the RI report but are not re-presented.

Overview

• CRREL is an active Army research installation in Hanover, New Hampshire that utilized trichloroethene (TCE) as a secondary heat transfer fluid. Past operations at CRREL have resulted in losses of TCE to the soil and groundwater beneath the installation. • The Army has conducted environmental investigations at CRREL since 1990. Four Areas of Concern (AOCs) are the focus of the Phase III RI. • The RI collected thousands of samples of soil, soil vapor, groundwater, bedrock, outdoor, and indoor air over a four-year period.

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

• TCE is the primary COC. Human health risks are driven by exposure to TCE in indoor air of four onsite buildings, soil vapor in onsite excavations and groundwater onsite if it were to be used for drinking water in the future. Off-Post the human health risks are driven by potential future residents’ exposure to indoor air at the undeveloped property north of the Site which is owned by Dartmouth College Real Estate also called “Rivercrest property”. • Next steps in the CRREL Installation Restoration Program are pilot testing and interim actions to evaluate soil vapor extraction as a remedial technology, the FS, Proposed Plan, and Decision Document. • Supplemental RI work in the Connecticut River is being conducted in the fall of 2016 • Supplemental RI work for bedrock may be conducted in the spring and summer of 2017.

Site Background

The CRREL facility is located on 30 acres of land in Hanover, Grafton County, New Hampshire, and west of and adjacent to State Highway 10 (Lyme Road), 1.5 miles north of the center of Hanover (Figure ES-1).

Dartmouth College housing consisting of approximately 30 units is located immediately south of and adjacent to the CRREL facility. The Hanover Country Club, owned by Dartmouth College, borders the Site to the southwest. Further to the east and northeast are the Richmond Middle School and Dartmouth Printing Company, respectively. The Connecticut River is located west of the CRREL facility.

Regulatory Status

As an active United States Army installation, RI activities at the CRREL facility are conducted under the Defense Environmental Restoration Program (DERP) Installation Restoration Program (IRP). The CRREL facility is not on the United States Environmental Protection Agency’s (USEPA) National Priorities List). Therefore, actions conducted by the Army as the lead agency are coordinated with the New Hampshire Department of Environmental Services (NHDES) as the lead regulatory agency.

In January 1992, the installation was placed on the federal agency hazardous waste compliance docket as a result of a release of TCE into the Connecticut River in 1970. Eighteen AOCs were identified and investigated. Based on these investigations, the Army prepared a Remedial Action Plan (RAP) for CRREL in 2003 to address NHDES remediation and groundwater protection laws. The NHDES concurred that no further action was required at 14 of the identified sites (i.e., AOCs). AOCs 2 (former underground storage tank [UST]), 9 (Ice Well), 13 (Former Drum Storage Area), and 15 (former greenhouse area) needed additional investigation (CRREL, 2003).

In 2010 the Army evaluated the potential for vapor intrusion (VI) into CRREL buildings and found elevated concentrations of TCE in indoor air. A number of VI mitigation measures are in place

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Roles and Responsibilities

The lead agency for the DERP is the Department of Defense (DOD) and the work at CRREL is executed by the USACE Engineer Research and Development Center (ERDC). Funding for the DERP work is provided by the Defense Environmental Restoration Account (DERA) through the Army Environmental Command (AEC), Fort Sam Houston, Texas. The USACE-NAE is supporting ERDC CRREL in implementing the following:

• Phase III RI/FS. • Pilot studies. • Operation of the groundwater treatment system for non-contact cooling water. • Operation of the sub-slab vapor mitigation systems.

Amec Foster Wheeler is implementing the Phase III RI/FS for USACE-NAE as well as several pilot studies. Sovereign Consulting is operating the groundwater treatment system and the sub-slab vapor mitigation systems.

Phase III Remedial Investigation

Environmental investigations have been conducted at CRREL since November 1990. The investigations have included production well sampling for TCE, investigations of the history and use of TCE, groundwater sampling of onsite wells, water supply well sampling in Vermont across the Connecticut River from CRREL, investigation of each AOC and surface water and sediment sampling near CRREL. These prior investigations are described in the Phase III RI Report and the documents are included in the CRREL Administrative Record.

Previous soil and groundwater sampling investigations at CRREL have narrowed the focus of the Phase III RI to four remaining AOCs including: AOC 2, a former UST that leaked TCE; AOC 9, the location of the former Ice Well and documented TCE release in July 1970; AOC 13, a former disposal area; and AOC 15, the location of a former UST that leaked fuel oil. These AOCs are shown in Figures ES-2 and ES-3. The Child Development Center (CDC) was investigated to evaluate the potential for contaminant migration to or the use of contaminated fill in areas where children may be exposed to surface soils.

For the Phase III RI, the following work was conducted.

1. Thirty-one membrane interface probes and hydraulic profiling tool (MIP/HPT) locations were advanced. 2. Thirty-six hand auger borings were advanced and 38 soil samples were submitted for laboratory analysis. 3. Eleven soil borings were advanced and 246 soil samples were submitted for laboratory

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

analysis. 4. Twenty-two WaterlooAPS profiling locations were advanced and 261 groundwater grab samples were submitted for laboratory analysis. 5. Five overburden monitoring wells were installed. 6. Three piezometers were installed (one nested pair). 7. Five bedrock wells were installed and 35 rock matrix samples were submitted for laboratory analysis. 8. One round of overburden and bedrock monitoring well sampling was conducted and 48 groundwater samples were submitted for laboratory analysis. 9. One overburden aquifer pumping test was performed to evaluate capture and aquifer properties. 10. Onsite VI related samples were collected from sub-surface, sub-slab, ambient and indoor air locations with 1,084 samples submitted for off-site laboratory analysis; over 7,000 air samples were collected for onsite analysis with an Inficon Hazardous Pollutants On Site (HAPSITE®)) gas chromatograph/mass spectrometer (GC/MS) unit in support of characterization of VI indoor air sources and monitoring of indoor air quality. 11. Off-Post VI related samples were collected from indoor air, ambient air, sub-slab, and subsurface locations with 358 samples submitted for laboratory analysis. 12. One soil vapor extraction pilot test and associated testing of subsurface characteristics were performed. 13. Location and elevation surveying for overburden and bedrock monitoring wells

Nature and Extent of Contamination

Sources of Contamination

Potential sources of contamination were identified and investigated during previous investigations. Through these investigations many of the original source areas were designated as no further action. Previous investigations narrowed the focus to four source areas including: AOC 2, a former 10,000-gallon TCE UST that leaked; AOC 9, the former Ice Well; AOC 13, a former disposal pit area; and; AOC 15, a former fuel oil UST that leaked. The CDC is not considered a source of contaminants at the site and is not designated as an AOC, but rather, an area of study. TCE is the primary COC at AOC 2, AOC 9, and AOC 13. Persistent leaks associated with a former 10,000-gallon UST containing TCE at AOC 2 contaminated the varved fine grained sands, silts, and clays. A soil gas plume migrated laterally and vertically from the AOC 2 source area by diffusion.

At AOC 9, TCE was released to the ground surface during experiments associated with the former Ice Well, leaks from a portable refrigeration unit adjacent to the Ice Well, and a nearby rupture of

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I a 10,000 gallon above ground storage tank (AST) containing approximately 6,000 gallons of TCE (Faran, 1991). As a result of the AST rupture, approximately 3,000 gallons were spilled over the parking lot surface and washed into the storm drain system that discharges from an outfall into the Connecticut River.

TCE was reportedly discharged to the ground surface at AOC 13 during waste disposal practices that were common for the period. Episodic releases of TCE in this area have resulted in the chemical adsorbed to soils that continue to be a source of contamination in soil and soil gas.

Investigations and Findings

Soils

Approximately 77,000 cubic yards (59,000 cubic meters) of soil are estimated to be contaminated by TCE in excess of New Hampshire Department of Environmental Services (NHDES, 2013a) screening criteria of 0.8 milligrams per kilogram (mg/kg) (800 µg/kg) at CRREL. Concentrations of TCE in excess of screening criteria extend deep into the soil profile.

The volume of TCE adsorbed to soils in the AOC 2 and AOC 9 source areas was estimated at 1,450 gallons (5,500 liters) and 1,300 gallons (4,900 liters), respectively. Due to the geologic conditions, such as the heterogeneity of soils, percentage of organic carbon, and ability to adsorb TCE these volume estimates may be over or under estimated by orders of magnitude.

Low levels of semi-volatile organic compounds (SVOCs) and pesticides exist in some locations at the Site. Most SVOCs in soils are likely attributable to combustion of hydrocarbons and the presence of trace amounts of asphalt in soils. At AOC 15, SVOCs detected in soils are related to fuel oil releases. Few SVOCs were detected in excess of soil screening criteria. Pesticides were found in site soils, but do not exceed screening criteria.

Arsenic was detected in each soil sample analyzed. Arsenic is a metal common to New Hampshire soils and the concentrations at the Site are comparable to average concentrations calculated for the State (Sanborn, Head & Associates, 1998). No other metals were detected in excess of soil screening criteria.

Herbicides and Polychlorinated Biphenyls (PCBs) were not detected in Site soils.

Based on the results of the soil investigation and historic practices at CRREL, TCE is the primary COC in soils at AOCs 2, 9, and 13 with the bulk of contamination residing adsorbed in AOC 2 and AOC 9 soils. TCE mass may also be immobilized within the soil pore spaces at these locations. Exposure to TCE contaminated soils is further evaluated in the Human Health Risk Assessment (Section 7 of the Phase III RI Report).

Bedrock Matrix Summary

Bedrock matrix sampling did not indicate the presence of TCE in rock. Each of the 35 rock samples collected was non-detect at locations immediately downgradient of the former Ice Well at AOC 9

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I and beyond the terminus of the overburden groundwater TCE plume. The bedrock matrix is not a source of TCE for bedrock groundwater on the CRREL property.

Groundwater

Sixteen overburden groundwater monitoring wells and five overburden production wells are present at the Site. The five overburden production wells were installed to provide non-contact cooling water for CRREL. Groundwater from four of the five production wells has historically contained TCE. Depending on pumping rates, up to 1.8 pounds of TCE can be removed from overburden groundwater each day. It is estimated that over the 23-year operation (1995-2017) of the treatment plant, approximately 15,000 pounds or 6,800 kilograms (~1,250 gallons or 4,700 liters) of TCE have been removed from the overburden aquifer.

Overburden Groundwater

The overburden groundwater TCE plume originates from AOC 2 and AOC 9 source areas. TCE contaminated groundwater migrates from these source areas and moves in a westerly, northwesterly direction towards the line of production wells. The production wells are oriented in a line (north-south), parallel to the Connecticut River, (Figure ES-2).

TCE was detected in 201 of 298 samples collected with concentrations ranging from 0.25J µg/L to 100,000 µg/L. The USEPA maximum contaminant level (MCL) and the NHDES drinking water standard for TCE in groundwater is 5 µg/L (USEPA, 2016a and NHDES, 2013a). TCE in excess of 5 µg/L was detected in eighty-five (85) groundwater profiler samples.

Groundwater profiler and monitoring well sample results at locations west of the production wells and east of the river suggest that the production wells are effectively capturing the overburden groundwater plume. Concentrations of TCE at these locations are either non-detect for TCE, or show very low levels, less than 5 µg/L.

The volume of contaminated overburden groundwater was estimated using MIP data collected below the water table, groundwater profiler data, and conventional monitoring well data. An estimated 50 million gallons (190 million liters) of overburden groundwater below the facility is contaminated by TCE, in excess of 5 µg/L.

Bedrock Groundwater

Two areas of bedrock groundwater contaminated by TCE have been identified at the Site (Figure ES-3). They are located below the AOC 2 and AOC 9 source areas. Bedrock groundwater flow mimics overburden groundwater flow and moves from east to west beneath the Site.

Bedrock groundwater sampling detected TCE in excess of the USEPA MCL (5 µg/L) downgradient of AOC 2, and in the AOC 9 source area. The concentrations in these bedrock wells ranged from 6 µg/L to 12 µg/L, which is three orders of magnitude lower than nearby overburden groundwater wells. Groundwater sampling indicates that high levels of TCE contamination do not exist in the

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I bedrock groundwater beneath the CRREL property. Deep bedrock wells located downgradient beyond the terminus of the overburden groundwater plume had TCE concentrations ranging from non-detect to 0.52J µg/L.

Several other VOCs were detected in bedrock groundwater, including the degradation products of TCE (cis-1,2-dichloroethene (cis-1,2-DCE), trans-1,2-dichloroethene (trans-1,2-DCE), and vinyl chloride) suggesting that reductive dechlorination of TCE occurs in bedrock groundwater in the area of AOC 9. Of these compounds, only cis-1,2-DCE was detected at concentrations in excess of USEPA and NHDES drinking water criteria (70 µg/L). Concentrations of cis-1,2-DCE ranged between 520 µg/L and 610 µg/L.

Surface Water

Connecticut River surface water samples were not collected during Phase III RI activities. Surface water was sampled in the fall of 2016. The results of the sampling will be presented in a supplemental RI report.

Sediment

Connecticut River sediment samples were not collected during Phase III RI activities. Sediment was sampled in the fall of 2016. The results of the sampling will be presented in a supplemental RI report.

Soil Gas

A soil gas investigation was conducted to evaluate the nature and distribution of contaminated soil gas at the CRREL facility and adjacent off-Post locations.

Onsite Soil Gas Investigation

The highest concentrations of TCE in soil gas were detected proximal to the AOC 2 and 9 contaminated soil source areas and were in excess of the USEPA Vapor Intrusion Screening Level (VISL) Calculator residential soil gas screening level of 16 micrograms per cubic meter (µg/m3) and the NHDES residential soil gas screening level of 20 µg/m3 (NHDES, 2013b and 2013c). TCE concentrations on the high end ranged from approximately 1.4M to 2.3M µg/m3 in these source area locations. Along the northern perimeter of the facility abutting the Rivercrest property concentrations of TCE in soil gas ranged from 6.2 µg/m3 to approximately 450,000 µg/m3. Soil gas locations along Lyme Road to the east show concentrations ranging from 513 µg/m3 to 1.5M µg/m3. Along the southern property boundary abutting Dartmouth College Properties, TCE concentrations ranged from 0.83 µg/m3 to 66 µg/m3 at shallow locations (2 to 5 feet below ground surface [bgs]). Deeper values ranged from 1.9 µg/m3 to 8,896 µg/m3.

Off-Post Soil Gas

Based on the elevated concentrations of TCE detected in deep soil gas at several locations along the CRREL Site boundary during the 2012 soil gas investigations, the USACE initiated further

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I investigations to determine if TCE vapors are migrating through soils at properties adjacent to CRREL. Sampling was conducted six times over a two-year period in 2013-2014.

Dartmouth College Properties

In the Dartmouth Cedar/Fletcher Housing area soil gas sampling detected TCE concentrations exceeding screening levels. The highest concentration (548 µg/m3) was measured at 75 feet bgs.

Dartmouth College Housing (Rivercrest) Soil Gas

The highest concentrations of TCE in soil gas on the Rivercrest Property were detected along the southern boundary of the property that abuts CRREL. Concentrations ranged from approximately 30,000 µg/m3 to 150,000 µg/m3 in deep soil gas implants (50 to 75 feet bgs) which exceeds the regulatory criteria by over 10-fold. Shallow samples (less than or equal to 10 feet bgs) across the Rivercrest property ranged from 0.68 µg/m3 to 2,665 µg/m3.

Dartmouth Printing Soil Gas

TCE on the Dartmouth Printing Property ranged in concentration from 0.67 to 2,068 µg/m3 in shallow samples (10 feet bgs). Soil gas TCE concentrations from deeper sample intervals ranged from 0.64 to approximately 450,000 µg/m3. TCE exceeded the USEPA soil gas screening levels at 5 of the 7 locations by over 10 times.

Richmond Middle School Soil Gas

TCE contaminated soil gas is located beneath the Richmond Middle School property; however, it is primarily located at depths greater than 25 feet bgs. TCE was detected at low concentrations in each shallow sample location (less than or equal 10 ft bgs) ranging from non-detect to 80 µg/m3. TCE results from deeper samples (50-75 feet bgs) ranged from non-detect to 23,424 µg/m3.

Indoor Air

Since March 2010, the USACE-NAE has been investigating the VI pathway from soil gas into the indoor air of several buildings at CRREL. Eleven summer and winter sampling events were performed between 2010 and 2015. VI sampling detected TCE and other contaminants in indoor air at several facility buildings. Mitigation of VI impacts to indoor air is currently ongoing at the Site.

Indoor air sampling was also conducted at buildings on properties adjacent to CRREL. Seventeen Off-Post indoor air sampling events were performed between April 2013 and August 2015.

Onsite Ambient Air

Ambient air was collected from outdoor locations during onsite vapor intrusion sampling. TCE was the only compound detected in the ambient samples exceeding the USEPA Industrial Air Regional Screening Level (RSL) and the Interim Action Level which is a risk based adult worker screening

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I value (note that this value was not used for selection of compounds of potential concern in the risk assessment). TCE concentrations in three ambient air samples exceed the Interim Action Level of 8.8 µg/m3 and the Industrial air RSL of 3 µg/m3 was exceeded in six samples. The highest concentrations were in the ambient air near the FERF and AOCs 2 and 9.

Onsite Buildings Indoor Air

Sixteen onsite buildings and rooms were monitored for TCE in indoor air. Seven buildings had rooms and work spaces with concentrations of TCE in air that exceeded the Interim Action Level of 8.8 µg/m3.

Off-Post Indoor Air Investigations

Indoor air and sub-slab soil vapor investigations were conducted to provide an assessment of indoor air quality conditions and sub-slab conditions at properties located east of the CRREL Facility, the five closest Dartmouth College housing units to the south boundary of CRREL, and adjacent properties located to the north east and east of CRREL including the Richmond Middle School. Concentrations of TCE in indoor air did not exceed 8.8 µg/m3.

The only off-Post building that had TCE detections above indoor air residential or commercial screening levels in or sub-slab vapor was the Dartmouth Printing facility. The concentrations of TCE in soil vapor ranged from 0.07 µg/m3 to 350 µg/m3 with several exceeding the USEPA soil gas screening level of 16 µg/m3 and the NHDES commercial soil gas screening level of 100 µg/m3.

Conceptual Site Model

The conceptual site model (CSM) defines the exposure pathways and receptors to define the human health risk assessment. The physical and chemical processes that affect COC migration in soil, groundwater, and air are described.

Figure ES-4 is a pictorial representation of the CSM for TCE related sources, migration pathways and mechanisms and receiving and exposure media. Figure ES-5 shows the CSM in flowchart form.

Baseline Human Health Risk Assessment

The purpose of the Baseline Human Health Risk Assessment (BHHRA) is to characterize the potential human health risk associated with assumed exposure to impacted environmental media in the absence of mitigation or remediation (Baseline Scenario) as described by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) risk assessment guidance.

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Baseline Risk Assessment Conclusions: Current and/or Foreseeable Land Use and Receptors

Baseline risk assessment results for current and/or foreseeable receptors exposed to baseline conditions (pre-mitigation/remediation) are summarized below.

• Each potential cancer risk calculated is within or below the USEPA’s risk range, with the exception of future residents at the Rivercrest Property. • The Indoor Worker Hazard Index (HI) is greater than the threshold hazard index (HI) of 1 for exposure to indoor air in six onsite buildings: 1) CDC, 2) Department of Public Works (DPW) Storage Area, 3) Frost Effects Research Facility (FERF), 4) Groundwater Treatment Facility, 5) Main Laboratory (North Basement, North first floor, South Basement, West Sub-Basement) and, 6) Vehicle Storage Building. • The HI for the future onsite construction worker exposure to soil vapor in an excavation also exceeds the threshold HI of 1. • The potential cancer risk and HI for the hypothetical off-Post resident exposed to indoor air modeled from soil vapor (all depths) at the Rivercrest property are above the upper end of the USEPA risk range and the threshold HI of 1, respectively.

Baseline Risk Assessment Conclusions: Hypothetical Receptors

The potential cancer risk for the hypothetical future onsite resident from combined exposure to soil, groundwater as a drinking water source, and indoor air modeled from sub-slab soil vapor, is above the USEPA risk range and the potential cumulative HI for this receptor is above the non- cancer threshold HI of 1.

• The cancer risk and HI driver is the hypothetical use of groundwater for potable use. • Exposure to surface soil is associated with negligible risk and hazard. • Cancer risk and/or HI is above the cancer risk range or threshold HI of 1 for indoor air (vapor intrusion) for several onsite buildings (based on conservative modeling of sub- slab soil vapor data).

The potential cancer risk for the hypothetical future off-Post resident exposed to indoor air modeled from sub-slab soil vapor is below the USEPA risk range for off-Post properties except for Rivercrest (as discussed previously). The potential HI (indoor air) for the hypothetical future off-Post resident at Brendel & Fisher is above the non-cancer threshold HI of 1. The potential HI is below 1 in off- Post buildings evaluated (except for Rivercrest as discussed above).

Ecological Risk Assessment

A Screening Level Ecological Risk Assessment has been conducted to determine if there are ecological exposure pathways associated with the historical release of TCE at CRREL that require further ecological risk evaluation.

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Considering that land within the secured area is fully developed with a combination of buildings, impervious surfaces (parking lots, roadways, sidewalks), maintained lawn, staging areas, and miscellaneous research infrastructure and does not provide natural habitat for populations or communities of wildlife, there is no complete ecological exposure pathway.

The Ecological Risk Assessment found that there is negligible risk to ecological receptors within the secured, fenced-in area at CRREL because there is no habitat and therefore no complete exposure pathway. No additional ecological risk assessment activities are needed within the secured area.

TCE discharged to the ground surface at the facility was flushed into the Connecticut River through storm drains (Faran, 1991), resulting in a potentially complete exposure pathway for surface water and sediment in the Connecticut River.

The ecological risk assessment did not evaluate potentially complete exposure pathways for ecological receptors (e.g., benthic invertebrates, fish, and other wildlife) present within the Connecticut River adjacent to the facility. Further investigation of the nature and extent of contamination in the Connecticut River was conducted in the fall of 2016. Additional risk assessment activities will be carried out to evaluate potential risk to ecological receptors. Findings will be presented in a supplemental RI report.

Preliminary Remediation Goals

Compounds of Concern

Preliminary Remediation Goals (PRGs) have been developed for COCs, which were defined as compounds exceeding Applicable Relevant and Appropriate Requirements (ARARs), or as defined within the BHHRA in the current and/or foreseeable scenarios. COCs were identified for each exposure medium/area.

ARAR-Based Preliminary Remediation Goals

TCE has been the predominant focus of the investigation, and is expected to be the primary focus for remediation at CRREL. Accordingly, TCE is the primary COC. Section 4.3 of the RI has established that TCE and cis-1,2-DCE have been detected in groundwater above relevant and appropriate requirements (Safe Drinking Water Act MCLs) and applicable requirements (New Hampshire Groundwater Quality Criteria) and are therefore identified as COCs for groundwater. The USEPA MCL and the NHDES standards for TCE in groundwater is 5 µg/L and for cis-1,2- DCE is 70 µg/L.

Risk-Based Preliminary Remediation Goals

Risk-based PRGs were developed for each COC identified within the applicable exposure medium. PRGs have been developed based on a target Excess Lifetime Cancer Risk (ELCR) of 1x10-6, 1x10-5, and 1x10-4 and a target HI of 0.1 and 1. PRGs were developed for an indoor worker

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I exposure scenario since this scenario is consistent with the current use of the facility. PRGs were also calculated for the construction worker, as re-development of the Site is a foreseeable future activity. PRGs were also calculated for an off-site residential scenario at Rivercrest, as residential re-development is a foreseeable future use. Risk-based PRGs for TCE were calculated for the media identified below.

Onsite Indoor Air

The selected risk-based PRGs are listed below for TCE in indoor air.

• TCE-0.80 µg/m3 (HI=0.1); 8.8 µg/m3 (HI=1.0)

Soil Vapor (Excavation Air)

The risk-based PRGs for TCE in soil vapor are listed below.

• TCE-1.2 µg/m3 (HI=0.1); 12 µg/m3 (HI=1.0)

Rivercrest Indoor Air

The risk-based PRGs for TCE in future indoor air (residential scenario) at Rivercrest are listed below.

• TCE- 0.21 µg/m3 (HI=0.1); 2.1 µg/m3 HI=1.0)

The PRGs will be carried forward to the FS for evaluation of remedial alternatives.

Based on the findings of the RI and the risk assessment the FS will evaluate the following migration/exposure pathways:

• Vapor as it pertains to off-site migration and vapor intrusion into existing and future buildings. • Exposures to soil and soil vapor by construction workers. • Overburden groundwater as a source of drinking water.

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

1.0 INTRODUCTION

Amec Foster Wheeler Environment & Infrastructure, Inc. (Amec Foster Wheeler) has prepared this Phase III Remedial Investigation (RI) Report to document environmental investigation activities conducted at the Cold Regions Research and Engineering Laboratory (CRREL) located in Hanover, New Hampshire (Figure 1.0-1). This RI Report has been prepared for the United States Army Corps of Engineers New England District (USACE-NAE) under contract number W912WJ-11-D-0005 Task Order 0004.

1.1 Regulatory Status

As an active United States Army installation, RI activities at the CRREL facility are conducted under the Defense Environmental Restoration Program (DERP) Installation Restoration Program (IRP). IRP is the program element that requires restoration activities be conducted in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) (42 United States Code [USC] Section 9601, et seq.), as amended by the Superfund Amendments and Reauthorization Act (SARA), and to the extent practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) (40 Code of Federal Regulations [CFR] 300.400). The CRREL facility is not on the United States Environmental Protection Agency’s (USEPA) National Priorities List. Therefore, actions conducted by the Army as the lead agency are coordinated with the New Hampshire Department of Environmental Services (NHDES) as the lead regulatory agency.

The Army is investigating potential Areas of Concern (AOC) for detrimental environmental impacts and implementing its response authority under DERP. In January 1992, the installation was placed on the federal agency hazardous waste compliance docket as a result of a release of trichlorethene (TCE) release into the Connecticut River in 1970. TCE was used as secondary heat transfer fluid in refrigeration systems in the Main Laboratory and was used in experiments conducted by CRREL from approximately 1963 to 1987.

Eighteen AOCs were identified and investigated; summary details of these investigations are presented in Section 2. Based on these investigations, the Army prepared a Remedial Action Plan (RAP) for CRREL in 2003 to address NHDES remediation and groundwater protection laws. NHDES concurred that no further action was needed at 14 of the identified sites (i.e., AOCs). AOC 2 (former underground storage tank [UST] containing TCE), AOC 9 (Ice Well), AOC 13 (Former Drum Storage Area), and AOC 15 (former greenhouse area) needed additional investigation. The RAP also described the plan to continue pumping the production wells, which provide non-contact cooling water to the facility, to maintain hydraulic control of the contaminated groundwater plume, preventing direct discharge to the Connecticut River. The plan included treatment of the captured water before discharge through an outfall to the Connecticut River under a USEPA National Pollutant Discharge Elimination System (NPDES) discharge permit (NH0001619).

On July 9, 2004, the NHDES issued a groundwater management discharge permit establishing a Groundwater Management Zone (GMZ) that includes the five production wells, the groundwater treatment system, and 14 onsite monitoring wells. The GMZ requires containment of groundwater

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I contamination within the boundaries of the Site. The NHDES issued CRREL a Groundwater Management Permit (GMP) for the Site (Permit Number GWP-199101025-H-001) on July 9, 2004. The GMP requires quarterly sampling and testing of the five production wells and the outfall that discharges the non-contact cooling water to the Connecticut River. Annual sampling is conducted at the groundwater monitoring wells, CECRL07 through CECRL20. Wells installed during the Phase III RI are not currently required to be sampled as part of sampling under the NHDES discharge permit, however the data was included in the 2014 sampling report (AMEC, 2014j). The groundwater management discharge permit was renewed in January 2011 and is pending regulatory approval anticipated in the fall of 2018.

In 2010 the Army evaluated the potential for vapor intrusion (VI) into CRREL buildings and found elevated levels of TCE in indoor air. A number of VI mitigation measures are in place and further investigation of VI sources and control measures are ongoing.

This RI Report for the Phase III RI/Feasibility Study (FS) is focused on AOCs 2, 9, 13 and 15 and presents data collected between March 2012 and October 2015.

1.2 Roles and Responsibilities

The lead agency for the DERP is the Department of Defense (DoD) and the work at CRREL is executed by the USACE Engineer Research and Development Center (ERDC). Funding for the DERP work is provided by the Defense Environmental Restoration Account (DERA) through the Army Environmental Command (AEC), Fort Sam Houston, Texas. The USACE-NAE is supporting ERDC CRREL in implementing the following:

• Phase III RI/FS. • Pilot studies. • Operation of the groundwater treatment system for non-contact cooling water. • Operation of the sub slab vapor mitigation systems.

Amec Foster Wheeler is implementing the Phase III RI/FS and pilot studies for USACE New England. Sovereign Consulting is operating the groundwater extraction treatment system and the sub slab vapor mitigation systems. The NHDES serves as the lead regulatory agency on the project providing support for environmental restoration and ensuring compliance with applicable state laws.

To meet requirements for community involvement, a Restoration Advisory Board (RAB) was established in January 2014. The RAB is a public forum for sharing information about the environmental restoration program with the community.

1.3 Purpose and Scope of the RI Report

The objectives of the CRREL Phase III RI are:

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

• Provide information on physical characteristics of the CRREL environmental setting and waste characterization. • Draw conclusions regarding types of potential contaminants of concern (COC) present, their sources, nature and extent. • Estimate the quantity of contaminants. • Evaluate COC migration pathways, receptors and exposures. • Characterize risks posed. • Provide sufficient information for development of a FS Report. Prior environmental investigations have been conducted at the Site beginning in 1990. A summary of these reports is presented in Section 2. The data and findings from these investigations are referenced in this report but are not re-presented.

1.4 Site Background

The CRREL facility is located on about 30 acres of land in Hanover, Grafton County, New Hampshire, west of, and adjacent, to State Highway 10 (Lyme Road), 1.5 miles north of the center of Hanover. (Figure 1.0-1 and Figure 1.4-1). The CRREL property is shown on a land title survey included in Appendix A.

Prior to development of the Site by the DoD, the property was primarily used for agriculture, with gravel mining on the western edge of the Site. In 1960, the US Army leased 19.2 acres of land from Dartmouth College for the purpose of constructing a research facility. On June 15, 1960, the cornerstone for the facility's first building was laid. CRREL was officially established on February 1, 1961 and has been active since its inception. In 1982, 11.02 acres of additional land were purchased to accommodate the Frost Effects Research Facility which is located along the western border of the original CRREL tract (Nichols, C [USACE], 1991). The purchase expanded CRREL to its current size of 30.22 acres.

The CRREL facility has been assigned the Federal Facility Identification Number NH157002484700. The daily work population consists of approximately seven military and 240 civilian personnel. There is no residential use of the CRREL facility. The term “facility” under CERCLA means:

(A) “any building, structure, installation, equipment, pipe or pipeline (including any pipe into a sewer or publicly owned treatment works), well, pit, pond, lagoon, impoundment, ditch, landfill, storage container, motor vehicle, rolling stock, or aircraft, or (B) any site or area where a hazardous substance has been deposited, stored, disposed of, or placed, or otherwise come to be located; but does not include any consumer product in consumer use or any vessel. (CERCLA Sec. 9601, Paragraph 9)”

In this Phase III RI, the term “Site” means areas affected by DoD contamination on or off the CRREL facility where investigations have been or will be undertaken. The term “installation”

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I means the CRREL facility buildings and infrastructure. The term “off-Post” means locations and activities outside the CRREL facility boundaries.

The CRREL facility is roughly rectangular in shape and measures approximately 1,360 feet east to west, and 970 feet north to south at its greatest extent (Figure 1.4-1; Appendix A).

Dartmouth College housing consisting of approximately 30 units is located immediately south of and adjacent to the CRREL facility. The Hanover Country Club, owned by Dartmouth College, borders the Site to the southwest. Former Dartmouth College student housing (demolished in 2007) was located immediately north of, and adjacent to the CRREL facility and consisted of approximately 61 units. This property is owned by Dartmouth College Real Estate and is referred to as the “Rivercrest property”. Highway 10 (Lyme Road) forms the eastern boundary of the Site. Further to the east and northeast are the Richmond Middle School (RMS) and Dartmouth Printing Company, respectively.

The Connecticut River is located west of the CRREL facility, separated from the Site by former gravel pits, an unofficial small arms range, a stump dump yard, and a former domestic recycle storage area. The property between the Site and the river is owned by Dartmouth College Real Estate.

1.4.1 Site Description (From FY 2013 CRREL Army Defense Environmental Restoration Program, Installation Action Plan, US Army Installation Command)

CRREL is an active sub-installation of the US Army ERDC of the USACE. As a USACE center of expertise, CRREL performs basic and applied research in snow, ice, and frozen ground. CRREL also provides the US Army with practical engineering research to develop equipment and procedures for application in cold regions. Today, land use within one quarter mile is primarily rural and residential, with zones of light industry, industrial/service, cropland/pasture, and deciduous and mixed forest.

1.4.2 Operational History

CRREL combined the work of two predecessor organizations previously located in other states: The Snow, Ice, and Permafrost Research Establishment (formed on Aug. 27, 1947) and the Arctic Construction and Frost Effects Laboratory (established on Feb. 25, 1953). In late-1963, the Main Laboratory Building became fully operational, and several new buildings have been added since that time. The Facilities Engineering building opened in 1968, the Logistics and Supply building (referred to also as the Logistics Management Facility) opened in 1976, the Laboratory Addition opened in 1977, the Frost Effects Research Facility completed in 1985 and the Ice Engineering building opened in 1978. More recent construction also includes: The Child Development Center (CDC) (1990); the new Sea Ice Pond (Winter 1992); the Remote Sensing Facility (July 1993); the Technical Information Analysis Center (November 1993); and the Groundwater Treatment Plant (February 1994).

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

1.4.3 CRREL Facilities

CRREL consists of eleven primary buildings and other smaller support structures, including pump houses for five groundwater extraction wells (Figure 1.4-2). Primary buildings include the following:

1. Main Laboratory Building – offices and laboratory space. 2. Main Laboratory Addition. 3. Technical Information Analysis Center (TIAC) – offices and library. 4. Ice Engineering Facility – ice research, large pool. 5. Logistics Management Office (LMO) – equipment and supply warehouse. 6. Directorate of Public Works (formerly Facility Engineering) – offices. 7. Remote Sensing Facility – offices and conference rooms. 8. Greenhouse Research Facility – offices and laboratory space. 9. Frost Effects Research Facility (FERF) – offices and laboratory space. 10. Geophysical Research Facility. 11. Groundwater Treatment Plant (including extraction wells). 12. CDC.

A small storm water detention pond (100 feet by 50 feet) is located at the southwest corner of the Site.

CRREL has extensive refrigeration capacity in the Main Laboratory building, the Ice Engineering Facility, and the FERF. Starting in the early 1960s, until the late 1987, the laboratories in the Main Laboratory Building utilized TCE as a secondary heat transfer fluid and groundwater as a non- contact coolant. While TCE is no longer being utilized as a secondary heat transfer fluid at CRREL, and has been replaced by ethylene glycol since the late-1980s, the use of groundwater as a non- contact coolant in the laboratories continues to the present day.

Five production wells (CECRL-01 through CECRL-05) are located on the western portion of the CRREL property (Figure 1.4-2). These wells draw groundwater from an esker that parallels the Connecticut River and which is likely hydraulically connected to the river. Operation of CRREL’s industrial water supply and storm water discharge system prior to 1994 is unknown; however, as a result of surface water samples collected in the vicinity of the Site in 1991, the system was redesigned to include a treatment system to remove volatile organic compounds (VOCs) and metals. Treated water is contained in a subsurface storage reservoir located west of the Main Lab until it is needed by the facility laboratories. After use, the non-contact cooling water is discharged to the Connecticut River under a USEPA NPDES discharge permit (NH0001619) (Arthur D. Little, 1994).

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

1.5 Report Organization

The RI is a three-volume set. Volume 1 presents the text of the RI. In addition to the Executive Summary and background information contained in Section 1, the remainder of this document has been organized into the following sections, consistent with USEPA guidance (USEPA, 1988).

Section 2: provides a summary of previous investigation activities and interim actions performed at the CRREL facility and a summary of the scope of recent investigation work. Section 3: describes the physical characteristics of the Site. Section 4: describes the nature and extent of contamination. Section 5: presents the Conceptual Site Model (CSM) and fate and transport of contamination. Section 6: identifies and discusses Applicable, Relevant and Appropriate Requirements (ARARs). Section 7: presents the results of the baseline human health risk assessment. Section 8: presents the baseline ecological risk assessment. Section 9: presents Preliminary Remediation Goals (PRGs). Section 10: provides summary statements and conclusions of the RI.

Volumes II and III contain the RI figures and tables, respectively. Appendices are contained in Volume I on a CD.

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

2.0 STUDY AREA INVESTIGATIONS AND REMEDIAL ACTIVITIES

The following subsections provide a summary of investigations and remedial activities performed to date at CRREL including a summary of historical documents and a description of the Phase III RI activities.

Previous investigation reports summarized below were reviewed as part of the Final Historical Review and Data Gaps Analysis Report (AMEC, 2012a). The report provided an assessment of previous environmental data and presented a revised CSM as a planning tool for the Phase III RI. The report identified data gaps that were addressed in the Final Remedial Investigation/Field Sampling Plan (AMEC, 2012d).

Phase III RI work was conducted in accordance with the NHDES approved Final Remedial Investigation/Field Sampling Plan (AMEC 2012d) and the Draft Quality Assurance Project Plan Remedial Investigation/Feasibility Study/Pilot Study and Decision Document Work Plan (AMEC, 2012b). Work was performed under the Accident Prevention Plan and Site Safety and Health Plan (AMEC, 2013c) and the Site-Specific Health and Safety Plan (2013d).

Two early documents discuss the use and handling of TCE at CRREL. In 1968, a CRREL research chemist, John Sayward described issues with TCE in his white paper entitled “Troubles and Safety with Trichloroethylene (TCE) System,” in which he notes an ever-present TCE odor throughout the facility, especially in the areas of the Cold Rooms in the Main Laboratory. Leaks were noted in the systems, due to corrosion and the presence of water in piping and tanks. Sayward (1968) also describes releases to the Cold Pit in the Main Laboratory, and noted increased purchasing of TCE to restore system losses due to leakage. Anecdotal information suggests that up to 3,000 gallons of TCE may have been purchased each year over an undocumented number of years.

The second document is entitled “History of TCE Use and Handling at CRREL” (Faran, 1991). The Faran report describes that TCE was used as a secondary refrigerant in the cooling system in the Main Laboratory. TCE was lost due to leaks in pumps, machinery, and piping. TCE also was lost to the ground during experiments with the former Ice Well (AOC 9), and by the explosion of an aboveground storage tank (AST) containing thousands of gallons of TCE in 1970. Leaks were observed in the Mechanical Room below the Cold Rooms and in the Cold Rooms themselves. The Faran Report describes the explosion of the 10,000-gallon AST, leaks from the 10,000-gallon UST (AOC 2), and disposal practices exercised in former borrow pit areas (AOC 13). In addition, the Faran Report notes two locations in the esker deposits where TCE may have been discharged to the ground surface in historic gravel pit excavations. These two areas were reportedly mined and no longer exist.

2.1 Summary of Previous Investigations

A listing of investigations conducted at CRREL prior to the Phase III RI and a summary of the findings is presented in Table 2.1-1. Figures 2.1-1 through 2.1-5 show the location of surface soil samples, soil borings, TCE concentrations in contaminated soils, the RI monitoring well network, and TCE concentrations in contaminated groundwater for the pre-Phase III RI investigations. The

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I sampling locations and concentrations of TCE contamination in soil and groundwater are summarized from previous reports (AMEC, 2012a).

The eighteen AOCs are currently identified as follows (Figure 2.1-6): 1. AOC 1 - Former TCE Storage Area. 2. AOC 2 - Former TCE and Fuel Oil Underground Storage Tank (UST) Area. 3. AOC 3 – Facility Engineering’s (Department of Public Works [DPW)] Former Fuel Oil UST. 4. AOC 4 – Facility Engineering’s (DPW) Current Fuel Oil UST. 5. AOC 5 – Diesel Fuel and Gasoline ASTs. 6. AOC 6 – Former Gasoline UST Area. 7. AOC 7 – Fuel Oil UST. 8. AOC 8 – Waste Oil AST. 9. AOC 9 – Ice Well. 10. AOC 10 – Former Open Storage Area. 11. AOC 11 – Concrete Storage Pad Area. 12. AOC 12 – Exterior Test Pond Area. 13. AOC 13 – Former Gravel Pad. 14. AOC 14 – Main Laboratory Machine Room. 15. AOC 15 – Former Greenhouse Fuel Oil UST Area. 16. AOC 16 – Former Open Storage Area. 17. AOC 17 – Ice Engineering Pond. 18. AOC 18 –Groundwater Treatment and Discharge.

Of these AOCs, only AOCs 2, 9, 13, and 15 are open. The others have been closed and are no further action AOCs. AOC 18 is active as it is the groundwater treatment plant for the overburden groundwater plume.

The following paragraphs present a summary of documents that provide a description of prior investigation work conducted at the Site, followed by a brief summary of the document’s contents. Each final document referenced is contained in the CRREL Administrative Record.

1. CRREL Site Investigations/Operation Sweetwater (November 1990). In November 1990, the first groundwater samples were collected from CRREL production wells and the Hanover supply well. Analytical results indicated VOC contamination in several wells prompting CRREL to initiate Operation Sweetwater which used CRREL’s in- house capabilities to test the water supplies of concerned citizens in the vicinity of the

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Site (Arthur D. Little, 1994). Additional internal publications during this time period include: History of TCE Use and Handling at CRREL (Faran, 1991); CRREL’s Site Investigation and Analysis for Trichloroethylene (Perry, et al., 1991); and Geology and Geohydrology at CRREL: A Preliminary Site Investigation (Gatto and Shoop, 1991) [Arthur D. Little, 1994]. 2. Monthly Monitoring of Residential and Municipal Wells in Vermont (Vermont Department of Health (VDOH)). Beginning in December 1990, VDOH conducted monthly groundwater sampling of 13 residential wells and the Town of Norwich municipal supply well located across the river from the facility. In response to findings, three residences were connected to a municipal water supply (Arthur D. Little, 1994). 3. USATHAMA Groundwater Sampling (March 1991). In March 1991, samples collected from the sewer outfall, the five production wells, the Ice Well and two residential wells were analyzed for VOCs and metals. TCE and tetrachloroethylene (PCE) were the most commonly occurring VOCs detected (Arthur D. Little, 1994). 4. Groundwater Investigation near Norwich, Vermont (Wehran Engineering, 1991). Based on results from the March 1991 sampling, the Vermont Department of Environmental Conservation (VTDEC) retained Wehran Engineering Corporation to conduct a groundwater investigation in the town of Norwich, Vermont. The investigation involved the design of a groundwater monitoring network to assess the hydrology, contaminant distribution, and identification of possible local sources of TCE on the west side of the Connecticut River (Arthur D. Little, 1994). 5. New Hampshire Department of Environmental Services Sampling (1991). As a result of the TCE contamination identified at CRREL, NHDES conducted surface water sampling at five locations at and near CRREL. TCE was detected at four surface water locations (Arthur D. Little, 1994). 6. Site Analysis of the Cold Regions Research and Engineering Laboratory (USEPA, September 1991). In September 1991, the Environmental Photographic Interpretation Center conducted an imagery analysis of CRREL through an interagency agreement between USEPA and USAEC (then USACE). The objective of the study was to interpret aerial photographs of the region taken between 1942 and 1982 focusing on activities and features that may have resulted in groundwater contamination within a 2-mile radius of CRREL (Arthur D. Little, 1994). 7. Remedial Investigation Report for Cold Regions Research and Engineering Laboratory (Ecology and Environment, 1992). From August 1991 through April 1992, Ecology and Environment conducted the Phase I field investigation at the Site. The purpose of the investigation was to collect sufficient data to prioritize AOCs, define physical characteristics of CRREL, and assess the nature and extent of contamination at the AOCs (Arthur D. Little, 1994). 8. Bedrock Groundwater Investigation near Norwich, Vermont (Johnson Company, 1993 and Wheran, 1991). In late spring 1993, VTDEC requested Johnson Company to

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conduct a bedrock aquifer investigation at three residential water supply wells identified in previous investigations. The investigation included evaluation of groundwater flow in the bedrock aquifer, determination of potential sources of TCE found in the wells, and identification of other water supply wells at risk of contamination (Arthur D. Little, 1994). 9. Phase II Remedial Investigation for Cold Regions Research and Engineering Laboratory (Arthur D. Little, 1994). In 1993, Arthur D. Little performed a Phase II RI to close the data gaps remaining from the Phase I RI. The investigation included soil gas surveys, geophysical investigations, soil and sediment/surface water sampling, bedrock and overburden monitoring well installation, and sampling of groundwater from the production wells, monitoring wells, and the Ice Well. The objectives were to determine the nature and extent of contamination throughout the CRREL facility and to evaluate the risk posed to human health and the environment (Arthur D. Little, 1994). The human health and ecological risk assessments conducted were qualitative and based on standards used in the early 1990s. 10. Innovative Technology Demonstration at the US Army CRREL (ENSR, 1996). In 1996 USACE CRREL conducted a feasibility study including groundwater direction analysis, in-well discrete depth groundwater contamination profiles, TCE soil vapor survey, cone penetrometer testing, unsaturated zone air distribution numerical modeling, a bench-scale TCE bioremediation treatability study, soil and groundwater sampling, pilot-scale soil vapor extraction tests, and in-situ air stripping pilot tests. The purpose of this work was to determine the most applicable technology for remediation of TCE in AOCs 2, 9, and 13 (Stanley Consultants, 2006). 11. CRREL Site Investigation, AOC 2 and AOC 9 (Stanley Consultants, 2006). In 2006, Stanley Consultants conducted a Site Investigation (SI) to review historic studies and conduct field activities at two previously identified source areas (AOCs 2 and 9). The objective of the investigation was to evaluate the post treatment extent and distribution of TCE-related contamination and to propose remedial alternatives. The SI focused on soil contamination and removing vadose-zone sources (Stanley Consultants, 2006). 12. CRREL Direct Push Optical Screening Tool Pilot Demonstration (Haley and Aldrich and Dakota Technologies, November 2012). Haley and Aldrich and Dakota Technologies conducted a pilot demonstration of a direct push optical screening tool at AOC 2 and AOC 9 to determine the presence or absence of TCE in Non-Aqueous Phase Liquid (NAPL) form in shallow overburden soils. Work was conducted in support of Environmental Security Technology Certification Program Project ER- 201121 (Haley and Aldrich and Dakota Technologies, 2016). The pilot test showed no evidence of NAPL at AOC 2 or 9 at the locations profiled.

2.2 Summary of Interim Actions and Pilot Tests

This subsection describes interim actions conducted at CRREL in order to mitigate exposure to TCE in soils, soil gas, and air. Figure 2.2-1 shows the location of the interim removal actions

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1. Response Action to TCE Explosion (July 1970). In response to the July 2, 1970 TCE tank explosion in AOC 1, an internal investigation was initiated to determine the topography of the river basin and to determine the extent of TCE contamination in sediment in the vicinity of the CRREL storm sewer outfall and downstream locations (Faran, 1991 and Arthur D. Little, 1994). 2. Limited Soil Removal Action at AOC 15 (1997). Little documentation exists regarding the removal of a UST containing fuel oil and associated contaminated soil. Reportedly, approximately 200 cubic yards of soil were removed from the former Greenhouse area and stockpiled onsite in covered concrete basins as passive bioremediation cells. 3. In-situ Pilot Study at AOC 2 and AOC 9 (Nobis Engineering, 2003). Between November 2002 and May 2003, Nobis Engineering, Inc. conducted a pilot study at AOC 2 and AOC 9 consisting of in-situ injection of potassium permanganate at concentrations ranging from 1 percent to 3 percent to reduce TCE concentrations that were initially as high as 55,000 parts per million (Nobis Engineering, 2003). 4. Limited Soil Removal Action at AOC 2 in 2001. Little documentation exists for this removal event. Reportedly, up to 100 cubic yards of soil were removed and stockpiled onsite in an uncovered concrete basin and allowed to passively aerate. The soil was determined to be non-hazardous however the NHDES requested that it be disposed of at a licensed solid waste facility (letter dated October 31, 2005 from J. Dulcos NHDES to J. Gagnon GZA and Environmental) The soil was transferred to a permitted facility in late Fall 2005 (email correspondence dated May 17, 2006 from B. Young [CRREL] to B. Minicucci [NHDES]). The concrete pad which held down the former UST was also removed; however, its disposition is unknown. 5. Final Action Memorandum Child Development Center for Time Critical Removal Action (AMEC, 2013g). The removal action was conducted between October 2011 and June 2012. The objective of the response action was to install a sub-slab depressurization system in the basement of the CDC building to mitigate the potential intrusion of vapor phase contamination into the building from the subsurface.

6. Final Action Memorandum for the Technical Information Analysis Center (AMEC, 2013h). The removal action was conducted between December 2011 and February 2012 in accordance with the Work Plan for Communication Testing and Extraction Well Installation (AMEC, 2011a). The objective of the response action was to install sub- slab vapor extraction wells and associated interior piping to allow potential future sub- slab depressurization of the Technical Information Analysis Center to allow the proposed renovation/construction activities to proceed. The system will be activated as needed to control intrusive vapors.

7. Final Action Memorandum Deployment of Portable Room Air Cleaner Units at Multiple Locations for Time Critical Removal Action (AMEC, 2014g). The deployment portion

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of the removal action was conducted between July 2012 and February 2014. Operation of the air cleaner units (Healthmate™ Plus equipped with approximately 13.6 pounds of granular activated carbon) is ongoing at the facility. The objective of the removal action was to deploy portable air cleaner units at multiple locations in facility buildings to mitigate concentrations of TCE in excess of the action level in indoor air in occupied areas of the Main Laboratory Building (Basement, First Floor, and Second Floor), CDC (Basement; occupied by adults only), Directorate of Public Works, Logistic Management Office, Project Support Building, Technical Information Analysis Center, and Greenhouse Buildings.

8. Action Memorandum Main Laboratory Building for Time Critical Removal Action (AMEC, 2014b). The removal action was conducted between April 2012 and August 2014. The objective of the removal action was to mitigate the concentrations of TCE in excess of the action level in indoor air in occupied areas of the Main Laboratory. This included installation of a sub-slab mitigation system in the Multi-Purpose Room, the Main Laboratory, and the Main Lab Sub Addition.

9. Final Soil Vapor Extraction Pilot Test Report for AOC 2 (Amec Foster Wheeler, 2016b). SVE was piloted in the shallow and deep zones of the vadose zone. The pilot system ran from June 2015 to August 2016, approximately 450 gallons (5,490 pounds) of TCE were removed from the soil gas in the area of AOC 2.

Additional SVE pilot testing is also slated for AOC 9 in early 2017. Other types of pilot testing are being considered for soil, soil gas, and groundwater supplemental to the FS.

2.3 Phase III Remedial Investigation

The following section describes the investigations that were conducted during Phase III RI activities. Previous soil and groundwater sampling investigations at CRREL have narrowed the focus of environmental investigations to four remaining AOCs: AOC 2, a former UST that leaked TCE; AOC 9, the location of the former Ice Well; AOC 13, a former disposal area; and AOC 15 the location of a former UST that leaked fuel oil (Figure 2.3-1). As a result of a vapor intrusion study of indoor air at the CDC in 2011, additional sampling of soils was conducted. The CDC is not identified as an AOC in the RI as there are no reports of historical chemical handling in this area of CRREL; this area was investigated to evaluate the potential for contaminant migration to, or use of, contaminated fill in areas where children may be exposed to surface soils.

A summary of the AOCs and the CDC area of study prior to the Phase III RI is provided in Table 2.1-2.

For the Phase III RI, the following work was conducted:

1. Thirty-one membrane interface probes and hydraulic profiling tool (MIP/HPT) locations were advanced.

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2. Thirty-six hand auger borings were advanced and 38 soil samples were submitted for laboratory analysis. 3. Eleven soil borings were advanced and 246 soil samples were submitted for laboratory analysis. 4. Twenty-two WaterlooAPS profiling locations were advanced and 261 groundwater grab samples were submitted for laboratory analysis. 5. Five overburden monitoring wells were installed. 6. Three piezometers were installed (one nested pair). 7. Five bedrock wells were installed and 35 bedrock matrix samples were submitted for laboratory analysis. 8. One round of overburden and bedrock monitoring well sampling was conducted and 48 groundwater samples were submitted for laboratory analysis. 9. One overburden aquifer pumping test was conducted to evaluate capture and aquifer properties. 10. Onsite vapor intrusion related samples were collected from sub-surface, sub-slab, ambient and indoor air locations, with 1,084 samples submitted for offsite laboratory analysis; over 7,000 air samples were collected for onsite analysis in support of characterization of vapor intrusion indoor air sources and monitoring of indoor air quality. 11. Off-Post vapor intrusion related samples were collected from indoor air, ambient air, sub-slab, and subsurface locations with 358 samples submitted for laboratory analysis. 12. One soil vapor extraction pilot test and associated testing of subsurface characteristics. 13. Location and elevation surveying for overburden and bedrock monitoring wells (New Hampshire State Planar NAD83 NAVD88, US survey feet).

The scope of the soil, groundwater, and vapor intrusion investigations are described in the sections that follow.

Sampling and analysis was conducted as described in the NHDES approved Final Remedial Investigation/Field Sampling Plan (AMEC 2012d) and the Draft Quality Assurance Project Plan Remedial Investigation/Feasibility Study/Pilot Study and Decision Document Work Plan (AMEC, 2013b) unless otherwise noted below.

2.4 Soil/Bedrock Investigations – Phase III RI

The following subsections describe soil investigations conducted as part of the Phase III RI. Soil samples were collected at the CDC, AOC 2, AOC 9, AOC 13, and AOC 15 (Figures 2.4-1 through 2.4-6).

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Tables 2.4-1 through 2.4-6 provide summaries of the surface soil, subsurface soil and bedrock matrix sampling and analytical program conducted at each area of study or AOC. These tables provide sample, location identification, sample date, and chemical analyses performed. Appendix B contains the soil boring logs and Appendix C contains soil sampling field data records (FDRs).

Soil investigations consisted of hand auger sampling of shallow soils at the CDC and AOC 15. Soil samples collected at AOC 2, AOC 9, and AOC 13 were collected by direct push and sonic methods.

Soil investigations at AOC 2, AOC 9, and AOC 13 were conducted in a phased approach. Thirty- one MIP/HPT profiling locations were advanced at each AOC between November 13, 2012 and February 6, 2013 (Figure 2.4-2). Bedrock matrix locations are also shown on Figure 2.4-2. Table 2.4-7 provides a summary of the MIP and groundwater profiler soil sample locations.

The MIP is a field screening tool routinely used in high resolution soil characterization studies to profile subsurface impacts (Geoprobe Systems, 2015, USEPA, 2017, ERDC, 2002). The MIP provides continuous measurement of VOCs in soil and groundwater as it is advanced. The HPT profile provides a continuous measurement of electrical conductivity and hydraulic pressure. The purpose of the profiling was to evaluate the vertical and lateral distribution of TCE as represented by elevated detector response. Appendix D contains the MIP/HPT log results for each location.

Following analysis of MIP/HPT data, recommendations were made to strategically locate soil borings to confirm and quantify the presence (or absence) of TCE in selected soil profiles. Comparison of MIP detector response and the concentration of TCE detected in co-located soil samples is discussed further in Section 4 (ERDC, 2002).

Soil borings were advanced by direct push and sonic methods. Direct push soil borings were advanced using a Geoprobe® (Model 7844 or 8040). Soil samples were collected continuously to refusal using a four-foot long, two-inch diameter core sampler equipped with acrylic sample liners. Sonic soil borings were advanced with an LS™250 MiniSonic™ drill rig. Soil samples were collected continuously until refusal or up to the prescribed depth.

Open bedrock borings (6-inch diameter) were advanced by dual rotary/air hammer methods using a Foremost DR12 drilling rig. Continuous rock core was collected (NX core) with a Davey Kent 525 track drill rig.

2.4.1 Child Development Center

The CDC is a child care facility for CRREL employees located in the southeast corner of the Site (Figure 1.4-2). Chemical handling is believed not to have occurred in the area of the CDC; however, analysis of historic photos and aerial photography indicated that the area of the CDC formerly served as a staging area for Site construction activities (specifically the construction of the Ice Engineering Facility) and that soils in the vicinity of the CDC may be comprised of fill material or reworked soils. Given the nature of the current use of the CDC facility grounds by children as a recreational area, investigation of soils was warranted to characterize potential

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The ground surface of the CDC consists of a mix of grassy cover and un-vegetated sandy cover. Twenty-four surface soil samples were collected on November 11th, 2012 from 0 to 2 feet below ground surface (bgs) in the immediate vicinity of the CDC; 22 of which were collected in the playground area. If the surface soil sample was in a grass covered area the first two inches of vegetative cover was removed prior to sampling. Six deeper soil samples were collected from the 2- to 6-foot depth range.

Soil samples were collected utilizing hand tools (e.g. trowel, shovel, or sample spoon) and hand augers. Soil samples were composited in stainless steel bowls prior to transfer to sample containers.

Figure 2.4-1 identifies the location of each soil sample collected at the CDC. Table 2.4-1 summarizes the sampling and analysis for surface soils and subsurface soils. Soil samples were sent off-site for analysis of VOCs, semi-volatile organic compounds (SVOCs), Target Analyte List (TAL) metals, pesticides/ Polychlorinated Biphenyls (PCBs), and herbicides.

2.4.2 AOC 2

AOC 2 is the site of a former UST which was located northeast of the Main Laboratory building (Figure 1.4-2). Two USTs were installed at this location in 1960; one was used for TCE storage (10,000 gallon) and the second was used for fuel oil (12,000 gallon). The TCE UST was reportedly removed in 1972 after it was determined to be leaking. The TCE tank was replaced with a 10,000- gallon fuel oil tank. The two fuel oil USTs were removed in 1989 (Faran, 1991). The area consists of a combination of grassy and paved surfaces.

Previous investigations detected the highest levels of TCE in soil between 20 and 40 feet bgs with TCE concentrations observed in excess of 20,000 mg/kg. One soil boring analyzed in 1996 showed elevated TCE concentrations as deep as 140 feet. A review of previously collected sample data indicated the extent of soil contamination associated with AOC 2 was unbounded to the north, northeast, and to the south (AMEC, 2012a).

AOC 2 soil sampling was conducted between November 2012 and April 2013, and included the following:

1. Ten MIP/HPT Probes located, in or adjacent to, the AOC 2 source area. 2. Nine MIP/HPT probes located downgradient of the AOC 2 source area. 3. Seven soil borings, 3 co-located with MIP/HPT probes, 4 located in the Multi-purpose room inside the Main Laboratory building. 4. One hundred and forty-nine onsite VOC samples.

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5. Five surface soil samples 4 of which were analyzed for full suite analysis of VOCs, SVOCs, TAL metals, pesticides/PCBs, and herbicides to evaluate direct exposure and construction worker risk scenarios for the HHRA.

Figure 2.4-3 shows the location of explorations advanced at AOC 2 (from a 3D perspective) used to evaluate the extent of unbounded soil contamination during the Phase III RI. Figure 2.4-3 is a snapshot from TecPlot360 which was used evaluate the data visually and to develop the conceptual site model. Soil borings SB-101, 102, and 107 are located adjacent to the Main Laboratory Building and soil borings SB-108, 109, 110, and 111 are located underneath the Multi- Purpose Room in the Main Laboratory building.

Table 2.4-2 provides a summary of sampling and analysis of surface and subsurface soil. Soil samples were analyzed for VOCs by an onsite field laboratory and selected soil samples were sent off-site for analysis of VOCs, SVOCs, TAL metals, pesticides/PCBs, and herbicides.

2.4.3 AOC 9

AOC 9 is the location of the former Ice Well and a former AST that had contained TCE. The area is located on the northern side of the Main Laboratory Addition and west of the Main Laboratory building. (Faran, 1991) (Figure 1.4-2). The area is typified by grassy open space and paved surfaces. Elevated levels of TCE in soil have been observed from the near surface to as deep as 142 feet. Historic data indicate that the contamination is unbounded to the south, east, and with depth. The highest concentration detected in 2006 was 2,100 mg/kg at 19 feet bgs. Analytical results from soil samples collected in 1996 showed contamination extending to the water table (AMEC, 2012a).

AOC 9 soil samples were collected in February 2013 to evaluate the extent of unbounded soil contamination. Samples were analyzed by an onsite field laboratory for VOCs and selected samples were sent off-site for analysis of VOCs, SVOCs, TAL metals, pesticides/PCBs, and herbicides.

Bedrock matrix samples were also collected in AOC 9. Samples were collected for VOCs to evaluate potential presence of Dense Non-Aqueous Phase Liquid (DNAPL), and the potential for the bedrock matrix to be an ongoing source of TCE contamination to the groundwater. Samples were collected from location BR-14-101 immediately downgradient of the former Ice Well to assess potential impacts to the bedrock matrix and bedrock groundwater.

The soil investigation associated with defining the nature and extent of soil contamination at AOC 9 included the following:

1. Two MIP/HPT Probes located in the AOC 9 source area. 2. Nine MIP/HPT probes located downgradient of the AOC 9 source area. 3. Two soil borings co-located with MIP/HPT probes. 4. Fifty-one onsite VOC samples.

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5. Two surface soil samples were analyzed for full suite analysis to evaluate direct exposure and construction worker risk scenarios for the HHRA. 6. Thirty-five bedrock matrix samples were submitted for laboratory analysis.

Sample locations are included on Figure 2.4-2. Figure 2.4-4 shows the AOC 9 location of the soil borings from a 3D perspective.

Table 2.4-3 provides a summary of samples and analyses of surface and subsurface soil collected in AOC 9. Table 2.4-4 provides a listing of the samples and analyses of bedrock matrix samples.

2.4.4 AOC 13

AOC 13 is located between the Logistics and Supply Office (LMO) and the Vehicle Storage building (Figure 1.4-2). This was the location of a former gravel pad used for the storage of drums and potential disposal of spent TCE (Faran, 1991). The AOC 13 area is currently paved.

The highest concentration detected at AOC 13 from previous sampling was 37.5 mg/kg in soil, which is approximately two orders of magnitude lower than concentrations detected in soils from AOCs 2 and 9. During the Phase III RI sampling was conducted in AOC 13 to further characterize and delineate soil contamination.

The soil investigation associated with defining the nature and extent of soil contamination at AOC 13 included the following:

1. Five MIP/HPT Probes located in, or adjacent to, the reported AOC 13 source area. 2. Two soil borings co-located with MIP/HPT probes. 3. Forty-six onsite VOC samples.

4. One shallow soil sample was analyzed for full suite analysis for evaluation of the construction worker risk scenario for the HHRA.

Figure 2.4-2 includes the explorations advanced at AOC 13 to determine the extent of unbounded soil contamination during the Phase III RI. Figure 2.4-5 shows the location of the soil borings from a 3D perspective.

Table 2.4-5 provides a summary of samples and analyses of surface and subsurface soil which were collected in AOC 13. Soil samples were analyzed by an onsite field laboratory and selected soil samples were sent off-site for analysis of VOCs, SVOCs, TAL metals, pesticides/PCBs, and herbicides.

2.4.5 AOC 15

AOC 15 is the location of a fuel oil UST that served the former Greenhouse (Figure 1.4.-2). The area consists of grassy and paved surfaces. The 2003 CRREL RAP indicated that fuel oil

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I contamination most likely remained in the utility trench located adjacent to the fuel oil contaminated area to the west. The RAP recommended that shallow soil sampling be conducted within the utility trenches that may serve as a migration pathway for fuels. Based on the objective of targeting the utility trenches and the care needed to avoid damaging the utility lines, hand auger sampling was conducted in lieu of direct push methods.

Soil samples were collected on September 19, 2014 to evaluate the extent of soil contamination along the sanitary and storm drain line excavation. Soil samples were collected utilizing hand augers. Soil samples were composited in stainless steel bowls prior to transfer to sample containers.

A total of eight shallow soil samples from six locations were sent off-site for analysis of VOCs, SVOCs, diesel range organics (DRO), gasoline range organics (GRO), TAL metals, and pesticides/PCBs.

Figure 2.4-2 and Figure 2.4-6 shows the location of explorations advanced at AOC 15. Table 2.4- 6 provides a summary of samples and analyses of surface soil and subsurface soil collected at AOC 15.

2.5 Groundwater Investigations – Phase III

The Phase III RI groundwater investigation was conducted in a phased approach which included WaterlooAPS profiling, monitoring well installation, groundwater sampling, and aquifer testing.

The objectives of the groundwater investigation were:

1. Evaluate contaminant distribution using WaterlooAPS profiler and MIP/HPT data to provide a basis for monitoring well installation. 2. Supplement the existing monitoring well network. 3. Evaluate the effectiveness of the facility extraction wells in capturing TCE contaminated groundwater to prevent off-site migration. 4. Define the contaminant front migrating from fine sands and silts to sands and gravels in the esker to evaluate mass flux. 5. Determine hydrogeologic properties (transmissivity and specific yield) of the overburden aquifer to aid in optimization of CRREL’s groundwater extraction system. 6. Determine if bedrock is a source of TCE contaminated groundwater discharging to the esker and a potential pathway for off-site bedrock impacts. 7. Determine the potential presence of TCE in bedrock. Tables 2.5-1 and 2.5-2 provide summaries of the overburden and bedrock groundwater sampling and analytical program conducted. These tables provide sample, location identification, sample

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I date, and chemical analyses performed. Appendix E contains the well installation logs and Appendix F contains groundwater sampling FDRs.

2.5.1 Overburden Groundwater

Overburden groundwater investigations for the Phase III RI included WaterlooAPS profiling, installation of monitoring wells and sampling existing and new monitoring wells.

The following was conducted in support of the Phase III RI overburden groundwater program.

1. Twenty-two WaterlooAPS profiling locations were advanced with a direct push drill rig and 261 groundwater grab samples were submitted for laboratory analysis, samples were collected each 5 feet until refusal. 2. Five overburden monitoring wells were installed using dual rotary rig drilling methods. 3. Three piezometers were installed (one of which is a nested pair). 4. One round of overburden and bedrock monitoring well sampling was conducted and 37 groundwater samples were submitted for laboratory analysis. 5. An overburden aquifer pumping test was conducted to evaluate groundwater plume capture and aquifer properties.

Between March and April 2013, WaterlooAPS profiling locations were advanced to:

1. Gain a better understanding the impacts of source areas to groundwater. 2. Provide quantitative data for comparison to MIP data. 3. Assess the relationship of contaminant flux between the esker and lacustrine deposits. 4. Assess the relationship between overburden and bedrock groundwater. 5. Select monitoring well locations.

Figure 2.5-1 shows the profiler locations. Documentation of field activities for the WaterlooAPS profiling are included in Appendix G, the WaterlooAPS groundwater data report. Figure 2.5-2 shows MIP and groundwater profiler locations from a 3-D perspective. MIP locations are shown in black and groundwater profiler locations are shown in orange. Previously installed bedrock and overburden monitoring wells are shown in blue and groundwater supply wells nested in the esker are shown in light blue.

Between March and May 2014, overburden monitoring wells were installed to supplement the existing well network both laterally and vertically. Well locations were selected based on the results of MIP/HPT and WaterlooAPS profiling. MW-14-107 was installed to evaluate source area of contamination from AOC 2 that migrated to the water table. Monitoring wells MW-14-104 and MW-14-106 were installed in the central portions of the two lobes of a groundwater plume downgradient of and originating from AOC 2 and AOC 9, respectively to evaluate contaminant

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I concentrations. MW-14-105 was installed as a deep overburden location to further define the vertical nature of contamination at the CECRL19 well location. Monitoring wells MW-14-103 A and B were located along the terminus of the long axis of the overburden groundwater plume to provide monitoring points between the extraction wells and the Connecticut River.

Figure 2.5-3 shows the location of each well installed at the Site. Appendix E contains well construction detail forms installed for the Phase III RI work.

Table 2.5-1 provides a listing of the sampling and analysis of overburden groundwater. Overburden groundwater was analyzed for one or more of the following: TCL VOCs, SVOCs, pesticides, PCBs and metals.

Table 2.5-3 provides a summary of the well installation details for the monitoring wells installed at CRREL including existing wells and the wells installed during the Phase III RI.

2.5.2 Bedrock Groundwater

Bedrock groundwater investigations for the Phase III RI included installation of monitoring wells, geophysical logging and sampling existing and new monitoring wells.

The following was conducted in support of the Phase III RI bedrock groundwater program.

1. Five bedrock wells were installed. 2. Optical Televiewer, acoustic televiewer, caliper, fluid temperature/conductivity, single point resistance, spontaneous potential, and heat-pulse flowmeter logging was conducted in each borehole. 3. Packer testing of open bedrock boreholes. 4. One round of overburden and bedrock monitoring well sampling was conducted and 21 total bedrock groundwater samples were submitted for laboratory analysis.

In April 2014, four bedrock borings were conducted to supplement the existing well bedrock well network, evaluate TCE concentrations in the bedrock aquifer and provide monitoring location between the Site and the Connecticut River. BR-14-101 was installed in the AOC 9 source area immediately downgradient of the former Ice Well to assess potential impacts to the bedrock groundwater. BR-14-104 and BR-14-105 were installed at locations central to the overburden groundwater plume and paired with either existing overburden or new overburden monitoring wells to evaluate vertical migration in those areas. BR-14-102 and BR-14-103 were installed to serve as monitoring locations beyond the terminus of the overburden groundwater plume and as boundary points between the facility and the Connecticut River. Bedrock monitoring wells were installed by dual rotary and air hammer methods and were conducted as a 6-inch diameter open borehole between 100 and 105 feet into competent bedrock.

Following installation of each bedrock boring, a suite of standard geophysical logging was conducted to evaluate the nature of the fracture network and the vertical groundwater flow regime.

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Bedrock boring logs are presented in Appendix H; borehole logging results are presented in Appendix I.

Figure 2.5-3 shows the location of each Phase III RI bedrock well installed at the Site. The groundwater extraction wells and overburden monitoring wells are also shown for reference. Table 2.5-2 provides a listing of the samples and analyses of the bedrock groundwater.

2.5.3 Aquifer Testing

Aquifer testing was conducted to evaluate hydrogeologic properties (transmissivity and specific yield) of the overburden aquifer. This information was gathered to assist in optimizing CRREL’s groundwater extraction system. Tests consisted of a step test and a constant rate pumping test and were conducted between June 17, 2014 and June 30, 2014. Figure 2.5-4 shows the location of the constant rate discharge test.

Step Test

A step test was performed on June 23, 2014 to determine the optimal extraction rate for conducting a constant rate discharge test at MW-14-104. The step test consisted of pumping at rates of 5, 10, 15, and 19 gallons per minute (gpm). Nineteen gpm was the highest extraction rate and was at the upper limit of theoretical entrance velocity of 0.1 feet per second (ft/sec) (Driscoll, 1986). Additionally, pumping capacity, well screen size, and screen length were chosen based on historical observations of the aquifer materials and hydraulic conductivity. During the drilling of MW-14-104 a coarse-grained sand interval was encountered that was not previously identified outside of the esker.

Monitoring well MW-14-107, located approximately 580 feet upgradient of MW-14-104, was instrumented with a data logger to monitor background/antecedent trends. Trend monitoring started on June 17, 2014 (one week prior to the constant rate test) and continued until the completion of the recovery phase on June 30, 2014. Barometric data were logged at the test location over this same time frame.

Analysis of the step test results indicated that MW-14-104 could sustain pumping at a discharge rate of 19 gpm.

Constant Rate Discharge Test

A three-day constant rate discharge test was conducted at MW-14-104 starting at 09:30 on June 24, 2015. A pumping rate of 19.25 gpm was sustained for 72 hours, followed by a 72-hour recovery period. In addition to the extraction well, MW-14-104, seven monitoring wells and/or piezometers were instrumented with transducers and monitored during the drawdown and recovery phases; MW-14-104*, PZ-14-101A, PZ-14-101B, PZ-14-102, MW-14-106, CECRL-10, and MW-14-105 (Figure 2.5-4). The initial location selected for conducting the constant rate test was MW-14-104*,

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I located approximately 7 feet south of MW-14-104. However, the riser pipe at this well was crimped preventing installation of a submersible pump.

2.6 Vapor Intrusion Investigations

The following subsections describe the scope of VI investigations conducted during the Phase III RI. VI studies were initiated in 2010 and were conducted following DoD Vapor Intrusion Guidance (DoD, 2009) and NHDES guidance (NHDES, 2013a).

In 2009, TSC Group, in their Draft Focused Feasibility Study (TSC, 2009), identified AOCs 2, 9, and 13 source areas as possible contributors of VOCs to indoor air. This study recommended that a VI investigation be conducted in the Main Laboratory and the LMO to evaluate if the potential migration pathway was complete from source area soils to human receptors.

Shortly thereafter in early spring 2010, the NAE Core of Engineers (COE) acted upon this recommendation and directed AECOM to sample sub-slab vapor and indoor air at the Main Laboratory and LMO (AECOM, 2010). Indoor air and sub-slab vapor were sampled in March 2010 and June 2010. TCE was detected at concentrations in excess of NHDES screening levels (2006, Revised June 2009) for industrial indoor air and industrial soil vapor during each sample event. The findings of this sampling were documented in AECOM’s Vapor Intrusion Data Report for CRREL (AECOM, 2012). Sample results prompted expansion of the air sampling program to other buildings at CRREL including the CDC. In addition, the NAE COE determined that further characterization of the nature and extent of the soil gas plume was warranted in order to evaluate potential impacts to off-Post buildings and to evaluate if the migration pathway was complete to off-Post receptors.

Air investigations conducted as part of the Phase III RI included soil gas onsite and off-Post. These investigations were conducted concurrently because of potential human health concerns.

Air sampling has been conducted for the following purposes at the Site:

1. Investigation of migration pathways within buildings. 2. Regular monitoring of TCE concentrations in indoor air. 3. Sampling of soil gas to map the extent of the subsurface vapor plume. 4. Real-time indoor air monitoring of TCE concentrations to be protective of human health in the work place environment.

Indoor air and sub-slab soil vapor sampling and related field work was conducted in accordance with the Indoor Air Assessment Work Plan (AMEC 2012e), the project Quality Assurance Program Plan (QAPP) (AMEC, 2012b), the Accident Prevention Plan and Site Safety and Health Plan (AMEC, 2013cb), and the Event 10 (Summer 2014) Indoor Air and Sub-Slab Sampling and Assessment Work Plan (AMEC, 2014i). Additional work plans approved by the NHDES for the off- Post air investigations include:

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1. Final Off-Site Indoor Air Assessment Work Plan for Cold Regions Research and Engineering Laboratory, (AMEC, 2013a). 2. Final Off-Site Vapor Intrusion Pathway Assessment Work Plan for Cold Regions Research and Engineering Laboratory, (AMEC, 2013b). 3. Final Dartmouth Printing Off-Site Vapor Intrusion Pathway Assessment Work Plan for Cold Regions Research and Engineering Laboratory, (AMEC, 2013e). 4. Final Off-Site Vapor Intrusion Pathway Assessment Work Plan Addendum for Dartmouth College Rivercrest Property for Cold Regions Research and Engineering Laboratory (AMEC, 2013f).

Tables 2.6-1 through 2.6-8 provide a summary of the air sampling and analytical program conducted. These tables provide sample, location identification, sample date, and chemical analyses performed. Appendix J contains the soil gas implant installation logs and Appendix K contains air sampling FDRs.

During the RI soil vapor intrusion samples were collected using a variety of containers and methods. Indoor air samples and sub-slab vapor samples from residential properties were collected in Suma canisters equipped with 24-hour flow controllers. Indoor air samples onsite were collected with Summa canisters with 8-hour flow controllers; sub-slab grab samples were collected either with Summa canisters, BottlevacTM samplers or tedlar bags. Indoor air samples from non-residential locations were collected in either a Summa canister or BottlevacTM samplers equipped with 8-hour flow controllers. Off-site sub-slab grab samples were collected either in Summa canisters, or BottlevacTM samplers with 8-hour flow controllers. Summa canisters were shipped to an off-site accredited laboratory for analysis of VOCs by USEPA method TO-15 (USEPA, 1999). BottlevacTM and tedlar bag samples were analyzed with an Inficon Hazardous Pollutants Onsite (HAPSITE®)) gas chromatograph/mass spectrometer (GC/MS). The HAPSITE® is owned by the USACE-NAE and is operated and maintained at the facility by an Amec Foster Wheeler chemist. The standard operating procedure for the HAPSITE® is provided in Appendix E of the QAPP (AMEC, 2012b). The HAPSITE® is used for the investigation of vapor migration pathways and interior sources at the facility. Additionally, the HAPSITE® is used to collect definitive indoor air quality data in support of daily monitoring for protection of human health for personnel at CRREL (AMEC, 2013j).

Ongoing indoor air monitoring is conducted daily onsite during work hours at the facility to evaluate TCE concentrations in real time. This monitoring consists of grab samples collected over approximately one-minute which are analyzed with the HAPSITE®. This methodology allows for a higher frequency of sampling resulting in greater spatial and temporal coverage, when compared to the standard, static 8-hour time-weighted (TO-15 analysis) samples collected with Summa

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I canisters. The HAPSITE® analysis time is 10 to 12 minutes per sample which allows for five to six samples collected in one hour during routine monitoring activities within a building.

2.6.1 Onsite Air Investigation

Onsite air investigations conducted as part of the Phase III RI included soil gas and VI. Soil gas investigation are for evaluation of the nature and extent of the soil gas plume. VI investigations are to evaluate migration and potential migration of TCE into buildings in the vicinity of the soil gas plume. The work was conducted in accordance with the Final Supplemental Soil Vapor Investigation Work Plan (AMEC, 2012f). Figure 2.6-1 shows the onsite air investigation timeline.

The onsite soil gas investigation consisted of the following tasks:

• Reviewed existing utility maps. • Conducted ground-penetrating radar and pipe and cable location surveys. • Established 43 soil vapor sample locations with 98 soil vapor implants which were installed via air knife and direct push methods. • Collected 191 soil vapor samples from shallow soils and deep soils for analysis of VOCs by USEPA Method TO-15. • Collected 247 soil vapor samples from shallow soils and deep soils for analysis of TCE by HAPSITE®. • Conducted a GPS location survey (sub-meter horizontal accuracy).

The onsite VI investigation consisted of the following tasks: • Review utility maps and construction as built drawings. • Conducted ground-penetrating radar surveys. • Established 44 sub-slab monitoring points in the Main Laboratory, TIAC, LMO, Vehicle Maintenance Building, Remote Sensing Geographic Information Systems building, and the FERF. • Established over 100 indoor air monitoring locations in facility buildings. • Established over 20 ambient air sampling locations. • Collected over 750 indoor air, ambient air, and sub-slab samples in facility buildings over five sampling events from August 2012 to August 2015 for analysis to VOCs by USEPA Method TO-15. • Analyzed over 15,000 indoor air, ambient air, and sub-slab samples for TCE by HAPSITE® for protection of human health and VI characterization.

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2.6.1.1 Onsite Soil Gas Investigation

Approximately 191 soil gas samples were collected during the Phase III RI both onsite and off- Post to evaluate the extent of the TCE plume and the potential for vapors to affect the indoor air quality of nearby buildings.

Soil gas samples were collected from implants which were installed using air knife and direct push methods during three mobilizations: May 18-23, 2012, November 5-9, 2012 and November 14- 15, 2012. Soil gas implant installation logs are presented in Appendix J. Implants were installed to targeted utility trenches and more permeable deeper soils underlying the Site. Soil gas implant locations are shown on Figure 2.6-2 with underground utility locations depicted for reference.

Four rounds of soil gas samples were collected during the Phase III RI. A full round was conducted during the week of May 23-25, 2012. Subsequent sampling rounds were conducted from July 18- 19, 2012, and October 17, 2012 from sample locations at the perimeter of the Site. A review of data from these sample rounds revealed data gaps in the soil gas implant network and additional implants were installed and sampled from November 14-16, 2012. Table 2.6-1 lists the samples and analyses of air samples collected onsite.

2.6.1.2 Onsite Vapor Intrusion Investigation

Between 2012 and 2015, approximately 853 VI samples (indoor air, sub-slab vapor and ambient air) were collected to evaluate migration pathways and indoor air concentrations of TCE. Primary routes of entry were thought to be from vapor intrusion through cracks or penetrations through building foundations or diffusion through foundations.

VI sampling has been conducted periodically onsite beginning in March 2010, following the initial recommendations to investigate the vapor intrusion migration pathway (TSC 2009), and is currently conducted biannually. Ten VI sampling events have been conducted to date onsite as part of the Phase III RI.

Potential sources of air contamination at CRREL include:

• Vapor Intrusion: . Enters through foundation cracks. . Enters via diffusion through foundation. . Enters from ambient air through doors and windows. • Indoor Air Sources: . Contaminated building materials. . Legacy piping containing TCE. . Concrete floors and insulation subjected to spills and leaks. . Ongoing operational sources used in labs.

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Indoor sampling events were conducted on the dates presented in Table 2.6-9.

Indoor air sampling has been conducted at the following onsite buildings: CDC, the Main Laboratory Building, the Greenhouse, the FERF, the LMO, the South Gate House, the North Gate House, the TIAC, Project Support Lab, Ballistics Lab, Vehicle Maintenance, and sheds and other outbuildings. Table 2.6-1 includes the samples and analyses of VI samples collected. Each sample was analyzed for VOCs by USEPA method TO-15. Indoor and ambient air samples were collected with Summa canisters equipped with 8-hour flow controllers. Sub slab samples were collected as grab samples. Figures 2.6-3 through 2.6-16 show the location of indoor, sub slab, and ambient air samples in each building sampled. The figures also show the location of HealthMate™ air purifier units deployed as part of an interim action to mitigate indoor air concentrations of TCE. Figure 2.6-17 shows the location of security guard Gate Houses and ambient air samples locations. Table 2.6-2 lists the VI ambient air location samples and analyses.

2.6.1.3 Twenty-four Day Study

A 24-day study of air sample collection and testing procedures was completed at the Main Laboratory facility during June and July 2013. A variety of sample collection and testing procedures were completed simultaneously to evaluate comparability of results from methods that are being used to monitor concentrations of TCE.

Samples were collected and analyzed using the following procedures:

• 8-hour Summa Canister sampling with TO-15 analysis. • 8-hour Bottle-Vac (BV) sampling with transfer to Tedlar bags and HAPSITE® analysis. • Direct grab samples analyzed by HAPSITE® (snapshot analysis). • 5-day Radiello and weekend Radiello passive diffusion samples.

The objectives of the study were to:

1. Evaluate the comparability of results obtained from the 8-hour Summa/Method TO-15 procedure and the 8-hour BV HAPSITE®. Obtain a multiplication factor for BV HAPSITE® results to obtain data that can be used for decision making relative to results obtained from Method TO-15. 2. Evaluate the comparability of results obtained from the 8-hour Summa/Method TO-15 procedure and the grab samples analyzed by HAPSITE®. 3. Evaluate the comparability of the 5-day Radiello results with 8-hour Summa/Method TO-15 procedure. 4. Evaluate the variability of TCE concentrations reported over the 24-day sampling period for Method TO-15 and HAPSITE® data. This information was used to evaluate overall exposure and risk scenarios relative to a risk based value of 8.8 µg/m3.

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Sampling was conducted as described in the Final Main Laboratory Twenty-Four Day TCE Variability Sampling Work Plan (AMEC, 2013i). A list of samples and analyses collected for the 24-hour test are presented in Tables 2.6-1 and 2.6-2.

2.6.1.4 Onsite Indoor Air Monitoring

Ongoing indoor air is monitored using an Inficon HAPSITE® GC/MS and is conducted in onsite buildings daily to evaluate TCE concentrations in real time. The data generated is used for decision making relative to protection of human health, identifying vapor intrusion pathways and/or indoor air sources, and monitoring ambient air quality. Over 15,000 samples have been collected at the Site. The utility of the HAPSITE® GC/MS was presented in the Technical Memorandum Main Laboratory 24-Day Study Results and Interpretation (AMEC, 2013j). The 24-Day Study results and the standard operating procedure for the HAPSITE® is provided in Appendix L.

2.6.2 Off-Post Air Investigation

Off-Post air investigations conducted as part of the Phase III RI included soil gas and VI. Figure 2.6-18 shows the timeline for the off-Post air investigation. Investigations off-Post were initiated as a result of elevated concentrations of TCE detected at several soil gas sampling locations along the CRREL Site boundary (AMEC, 2013a). Based on these findings, the USACE-NAE initiated further investigation to evaluate if TCE vapors are migrating through soils to properties adjacent to CRREL (AMEC, 2013b).

The off-Post air investigation was conducted at the following properties adjacent to the CRREL facility (see Figure 1.4-1):

1. 63 Lyme Road (current location of Richmond Middle School). 2. 64 Lyme Road (current location of Brendel & Fisher Wealth Management). 3. 68 Lyme Road (current location of Hanover Chiropractic and Hanover Yoga). 4. Five Dartmouth Housing Properties on Fletcher Circle and Cedar Drive (Dartmouth Properties). 5. Rivercrest Housing Development (Dartmouth Properties), currently an undeveloped property. 6. 69 Lyme Road (current location of Dartmouth Printing).

2.6.2.1 Off-Post Soil Gas Investigation

Approximately 92 soil gas samples have been collected from locations on off-Post properties to evaluate the potential for VI into nearby buildings or potential future developments.

Thirty-two soil vapor sample locations were established during the Phase III RI, each with multiple depths ranging from 5 to 75 feet bgs resulting in 108 individual implants. Figure 2.6-19 shows the location of off-Post soil gas implants; Tables 2.6-3 through 2.6-5 show the samples and analyses

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I of soil gas locations at each of the off-post properties. Each sample was analyzed for VOCs either by USEPA TO-15 or using the HAPSITE®. Soil gas samples were collected as grab samples in Summa canisters.

2.6.2.2 Off-Post Indoor Air Investigation

Between 2012 and 2015 approximately 376 VI samples (indoor air, sub-slab vapor and ambient air) have been collected at locations at off-Post properties to evaluate TCE plume migration pathways and indoor air quality. Eight rounds of sampling have been conducted at the Richmond Middle School. Two rounds of sampling have been conducted at each of the following properties: Dartmouth College Properties, Brendel and Fisher. Hanover Chiropractic & Hannover Yoga, and Dartmouth Printing.

Figures 2.6-20 through 2.6-24 show the VI sample locations at each off-Post property. Tables 2.6- 6 through 2.6-8 list the samples and analyses of indoor air and sub-slab vapor locations at each of the off-Post properties. Sample were analyzed for VOCs either by USEPA TO-15 or using the HAPSITE®. Indoor air samples were either collected with Summa canisters equipped with 8-hour flow controllers or bottlevacs equipped with 8-hour flow controllers.

2.6.3 Synoptic Soil Gas Sampling Event

In October 2015, a synoptic round of soil gas samples was collected from both onsite and off-Post soil gas sample points to evaluate the current condition of the soil gas plume (Amec Foster Wheeler, 2016a).

Table 2.6-10 provides a summary of the samples collected; sample locations are presented on Figure 2.6-25. Each soil gas sample was collected as a grab sample and analyzed by HAPSITE® GC/MS. Shallow soil gas samples collected at the Rivercrest property north of the facility were analyzed by both HAPSITE® GC/MS and by USEPA analytical method TO-15.

2.7 Soil Vapor Extraction Pilot Test

Data was collected at the Site relative to a soil vapor extraction (SVE) pilot test (Amec Foster Wheeler 2016c) that was conducted in the AOC 2 source area between October 2014 and January 2016. The results of the report are presented in the Final Soil Vapor Extraction Pilot Test Report for Area of Concern 2 (Amec Foster Wheeler, 2017). The findings of the pilot test will be summarized in the FS, however, some of the data and findings are relevant to this RI and help refine the conceptual site model. Therefore, some results from the SVE pilot test are presented. The layout of the SVE pilot test is shown in Figure 2.7-1.

The SVE pilot test was intended to achieve the following objectives:

1. Determine the efficacy and requirements for controlling off-site migration of TCE contaminated soil vapor to the north, including collection of data in support of

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determining whether migration of onsite shallow, deep, or both shallow and deep soil vapor contribute to off-site soil vapor contamination to the north.

2. Determine the horizontal air permeability and vertical soil vapor concentration profiles at the northern property boundary and in AOC 2.

3. Determine if SVE can affect mitigation of vapor intrusion into the Main Laboratory.

4. Collect data for the full-scale design of an SVE system for AOC 2 including vapor extraction well spacing, optimum vapor extraction rate and applied vacuum, moisture removal rates, and initial contaminant removal rates.

5. Collect post-SVE soil vapor concentration rebound data to identify locations where adsorbed and dissolved contamination is acting as a continual source of contamination to soil gas and indoor air.

The SVE pilot test consisted of the following steps:

1. Installation of SVE Wells and Soil Monitoring Points (Figure 2.7-1).

2. Soil Vapor Baseline Sampling and Vertical Permeability and Concentration Profiling.

3. SVE Step Rate Test.

4. SVE Constant Rate Test.

5. Post-SVE Soil Vapor Sampling and Vertical Permeability and Concentration Profiling.

6. Rebound Testing.

A timeline of the events associated with the SVE pilot test is shown in Table 2-7.1. During the pilot test, soil vapor samples were collected from SVE wells and vapor monitoring wells. Each soil gas and SVE system vapor sample was analyzed by HAPSITE® GC/MS.

2.8 Data Quality Objectives and Data Validation

The primary objectives of the RI were presented in Section 1.3. The types of data needed to meet the data quality objectives (DQO’s) as required by CERCLA are detailed in the QAPP (AMEC, 2012c) presented in Appendix L. The DQO’s for the RI include the following:

• Collect soil data of sufficient quality to evaluate the presence or absence of VOCs, SVOCs, Pesticides, PCBs, DRO/GRO, and metals compared to the USEPA regional screening levels (USEPA, 2015a) and the NHDES soil screening levels (2013). • Collect overburden and bedrock groundwater data of sufficient quality to evaluate the presence or absence of VOCs compared to the USEPA Maximum Contaminant

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Levels (as described in the Safe Drinking Water Act promulgated in July 1st, 2010 CFR Title 40 Part 1 to 49) and the NHDES Groundwater Standards (NHDES, 2013). • Collect soil vapor data of sufficient quality to evaluate the presence or absence of VOCs compared to the Site Specific Interim Action Level for TCE calculated by the USACE-NAE (88 µg/m3 or ten times the interim action level for indoor air of 8.8 µg/m3) used for comparison to onsite soil gas and sub-slab vapor samples, the USEPA VISL Calculator screening level for soil gas (USEPA, 2015a), and the NHDES Residential Soil Gas Screening Levels, (NHDES, 2013a). • Collect real time indoor air data (using the HAPSITE®) to monitor worker indoor air quality for protection of human health compared to the Site Specific Interim Action Level for TCE. The quality of the data needed to achieve the DQO’s include the following data quality indicators (DQI): • Method Selectivity/Specificity is defined as the compound type or class that can be detected by the instrument or detector. • Method Sensitivity, the effectiveness of the reporting limits compared to the action levels for the Site. • Precision, addresses analytical variability (field duplicates). • Accuracy, compares measured values to the true value (percent recoveries). • Representativeness, evaluates how well the samples represent the system under study. • Comparability, evaluates how well data from one study compares to data from previous studies. • Completeness, evaluates the percentage of usable data.

Evaluations of the DQI’s are presented in each data validation report associated with indoor air sampling, soil sampling, groundwater sampling, and bedrock matrix sampling.

Data validation was conducted using the Staged Electronic Data Deliverable/Automated Data review (ADR) process. The data were also validated manually by the Amec Foster Wheeler project chemist following the Region I USEPA-New England data Validation Functional Guidelines, Tier II procedures (USEPA, 1996). Quality control (QC) limits established in the QAPP were used during data validation. Data validation actions from the chemist review were compared to the ADR actions prior to preparing the final data set.

Analytical laboratory data including air samples analyzed by HAPSITE® in support of air monitoring sampling events were validated for the Phase III RI. Waste characterization data for disposal of soil and carbon were not validated. Based on the data validation reviews of the Site air, soil gas, groundwater, soil data, and bedrock matrix data no data quality issues were identified regarding

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I the primary Site contaminant TCE or other organic compounds and inorganics. Other target compound results reported are qualified as estimated values as described in the validation reports, but the qualification actions for these compounds are not interpreted to have a significant impact on the matrix testing project objectives. Data presented in this report is considered usable and defensible.

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3.0 PHYSICAL CHARACTERISTICS OF CRREL AREA AND LAND USE

This Section discusses the physical characteristics of CRREL and vicinity. The physical features of the installation, the Site and surrounding off-Post properties and land uses are components of the conceptual site model and are directly related to the location of TCE sources, migration routes, receptors and exposures. The movement and fate and transport of TCE at CRREL and off-Post are impacted by the local climate, surface and subsurface features. The physical characteristics form the basis for the conceptual site model (See Section 5.0) to explain the distribution of TCE and its ultimate fate.

3.1 Geography

CRREL is located in the upper Connecticut River Valley on terraced, unconsolidated glacial, glaciofluvial and glaciolacustrine deposits (see kame moraine description in Figure 3.1-1). Despite modification of the topography by development, CRREL has three main terraces at elevations ranging from 520 feet to 460 feet. The eastern third of CRREL is located on the upper terrace, which slopes gently down to the west, and contains AOCs 2 and 9 (Figure 3.1-2). The middle terrace containing AOC 13 is very narrow (generally less than 100 feet) and covered by asphalt. The lower terrace containing AOC 15 is located at an elevation of 460 feet. This terrace is flat and extends to the western border of CRREL. A steep escarpment drops approximately 80 feet to the Connecticut River 50 to 100 feet west of the CRREL property line (Arthur D. Little, 1994).

As an active research facility, CRREL is served by a series of utilities including sanitary, storm water, non-contact cooling water, municipal potable water, and electrical (Figure 2.6-2 and Figure 3.1-3). The utility corridors are potentially significant features relative to movement of contaminants of concern within the CRREL Site where source areas are adjacent to buildings.

3.2 Demography

CRREL is in the town of Hanover in Grafton County, New Hampshire. The population of Hanover was 11,260 at the time of the 2010 US census. The CRREL installation is an active research facility occupied by civilian employees working in offices and laboratories and the CDC. Approximately 240 people work at CRREL and are comprised of 110 technical staff and 130 support and administrative staff. The CDC employs approximately 16 adult staff members overseeing the care of approximately 50 children from six months to six years of age.

The RMS is located across Lyme Road from the CRREL southern entrance gate. Approximately 400 sixth through eighth grade students attend the RMS from the communities of Hanover, New Hampshire and Norwich, Vermont. Dartmouth Printing Company (owned by the Sheridan Group) is across Lyme Road to the northeast (Figure 3.2-1) and employs approximately 250 people. Two smaller businesses border CRREL to the east along Lyme Road and collectively employ approximately 7 to 10 people. Dartmouth Housing located on the southern boundary of the Site consists of 32 ranch style rental homes that house approximately 100 to 125 people at a given time.

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3.3 Climate

The climate in New Hampshire is characterized as humid and continental, with four distinct seasons and wide temperature fluctuations. The variable conditions are caused by the influence of marine and continental air flows from polar and tropical air masses. The prevailing wind direction and annual mean wind speed is southeast at 7 miles per hour. The 30-year 1981-2010 normal for the average daily high temperature is 56.3°F and the average daily low temperature is 35.4°F for Hanover, New Hampshire (Station 3755). The average annual temperature is 45.8°F. Average annual rainfall is 40.1 inches and average annual snowfall is 61-inches (http://www.usclimatedata.com/climate/hanover/new-hampshire/united-states/usnh0102).

Barometric pressure varies considerably in the CRREL vicinity on a daily, monthly and annual basis. Data from the time period 2004 through 2014 reveal:

• Daily variations can range from 28.52 inches of mercury (in Hg) to 29.76 in Hg.

• Average monthly minimum pressure for the period was 28.378 in Hg; average monthly maximum pressure for the period was 30.091 in Hg. Data shown in Figures 3.3-1 and 3.3-2 are from the Lebanon, New Hampshire Municipal Airport, approximately 12 miles southeast of the CRREL facilities.

• The minimum pressure was 28.30 in Hg. and the maximum was 30.179 in Hg.

• Months with the greatest variations were January through April and September through December. (Figures 3.3-1 and 3.3-2).

3.4 Geology

This Section is a summary of the geology of CRREL and vicinity which was derived from previous investigations, summaries of published papers, and information collected during the Phase III RI.

The geology of CRREL consists of two main geologic units, the overburden sequence and the bedrock. The overburden consists of glaciofluvial and glaciolacustrine sediments. To date, investigations have not indicated the presence of basal till or ablation till. Glaciofluvial deposition at the Site occurred during the glacial advance approximately 20,000 years ago. Glaciofluvial sediments were deposited in a sub-glacial stream resulting in the formation of an esker. Esker deposits, originating from streams or rivers located within or beneath a glacier, result in deposits with a distinctive sedimentary composition and geomorphic expression. Glacial fluvial systems are typically high-energy environments so that finer detrital material is washed from the stream channel, leaving a relatively coarse-grained and chemically immature (i.e., diverse mineralogy) sand component in the channel. The map pattern geometry of eskers is typically sinuous, similar to typical non-glacial fluvial systems, but can cross topographic boundaries such as hills and valleys (Arthur D. Little, 1994).

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An esker passes through the western border of CRREL (interpreted surface shown in Figure 3.4- 1) which is approximately 50 miles long, extending from Bradford, Vermont, north of CRREL to White River Junction, Vermont, south of CRREL. Based on topographic expression and geologic logs, the esker is approximately 400 feet wide at CRREL, approximately 60 feet thick and, where present, rests directly on bedrock. Immediately southwest of the Site boundary, the esker is exposed and forms a ridge. Within the property boundaries, the esker deposits are buried beneath younger glaciolacustrine silt and clay. The esker deposits consist of densely packed fine to coarse sand. Esker deposits are documented as far east as CECRL 03, CECRL 17, and CECRL 19 (Arthur D. Little, 1994).

The glacial retreat, which occurred approximately 13,000 to 11,000 years ago, was associated with glaciolacustrine deposition, in conjunction with the local deposition of ice-contact till during intermittent re-advances of the ice sheet.

3.4.1 Overburden Geology

Glaciolacustrine sediments were deposited during the formation of a glacial lake (Lake Hitchcock) that formed during the glacial retreat as melt water was dammed by a moraine in the Connecticut River Valley. This process occurred approximately 18,000 years ago as the Laurentide ice sheet retreated northward and a mass of sediments at Rocky Hill, CT formed a natural dam across the Connecticut River Valley. Water impounded behind the dam created Lake Hitchcock which extended north to St. Johnsbury, VT (Figure 3.4-2). Within Lake Hitchcock, the erosive grinding action of the glacial ice reduced rocks to fine powder which eventually was deposited as lake sediment. Annual layering of these sediments produced varves of fine sands, silts and clays. (T. M. Rittenour, 2000). These layered fine materials influence the routes of contaminant migration from the ground surface, through the overburden, between AOCs and to off-site receptors. Sediment deposits of glaciolacustrine origin were observed at sample locations throughout the Site. West of the lower terrace access road, the lacustrine deposits overlie the esker. At the remainder of the Site, the lacustrine deposits comprise the overburden stratigraphy. A lithologic cross section is provided in Figure 3.4-3. The stratigraphy of the lacustrine sediment consists of three main units: a fine silty sand, a silt, and a silty clay. The fine silty sand is the basal lacustrine unit for the eastern two-thirds of the Site; it has an observed thickness of at least 160 feet. The silt overlies the fine silty sand unit and esker deposits at the Site. Boring logs suggest the thickness of the silt unit varies between 20 feet and 110 feet; in general, the thickness increases from east to west across the Site. The greatest observed thickness is in the vicinity of the lower terrace access road, where it directly overlies esker deposits. Silty clay to clay units occur within the fine silty sand and silt deposits. Within the fine silty sand unit, the layers of silty clay are thin (approximately 1 to 2 feet). Within the silt unit, the silty clay lithologies occur frequently and range in thickness between 10 and 40 feet (Arthur D. Little, 1994). Included as an inset on Figure 3.4-3 is a representative profile of grain size through the lacustrine and fine sand units collected in the area of AOC 9. The grain size profile shows the fining up sequence of particle size that typifies the former glacial Lake Hitchcock depositional environment. Higher energy environments were in place closer to the retreating ice front. As the ice front retreated further north, lower energy environments deposited more silt and clay (lacustrine deposits).

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Aquifer testing work conducted at the Site (Figure 2.5-4) revealed the presence of a coarse sand unit in the area of MW-14-104, MW-14-105, and MW-14-106. The top of this unit was encountered at depths ranging from approximately 110 (PZ-17-104 near EW-17-01) to 135 (EW-17-102) feet bgs and appears to have hydraulic connection to the esker that makes up the western portion of the facility.

Glacial till lithologies have not been observed overlying bedrock at the Site. Such deposits, if they existed, were most likely eroded away by higher energy glacial melt waters.

Amec Foster Wheeler completed six deep borings in the vicinities of AOCs 2, 9, 13 and 15. Fine sands, silt and clay layers were encountered from 17 feet to 96 feet bgs from east to west. Thicknesses of these layers ranged from 20 feet to 60 feet at the east portion of CRREL to 75 feet to 120 feet along the west property boundary. This is consistent with prior investigations findings for the overburden in borings from the upper terrace, eastern third of CRREL property to the lower terrace and the western border of CRREL (Figure 3.4-4).

3.4.2 Bedrock Geology

Five bedrock borings were completed during this Phase III RI. The top of bedrock elevations in these borings ranged from 345 feet in the northeast portion of CRREL to 278 feet to 300 feet at the south side of CRREL adjacent to the property line (Figures 3.4-5 and 3.4-7). The bedrock beneath the Site consists of metasedimentary rock of the Cambro-Ordovician-age Post Pond volcanic member of the Orfordville Formation. These rocks were formed from volcanic detritus that was subsequently metamorphosed during the Taconic Orogeny, and occur at the Site as amphibolite’s and paragneiss. Rock core retrieved from beneath the area of the esker and AOC 9 during the Phase III RI shows that the bedrock is a greenstone; a chlorite schist with garnet inclusions and calcite veins. The bedrock was observed to be very competent exhibiting rock quality designations (RQD) in excess of 85% (Appendix I). The RQD is a measure of jointing and fracturing of the rock mass sampled. RQD values in excess of 75% indicate hard to fresh rock that is not exceedingly weathered.

CRREL is located immediately east of a major normal fault, the Ammonoosic Fault (Figure 3.4-8). The bedrock in the vicinity of CRREL is characterized by a series of faults and fault splays with varied lineaments. The majority of CRREL is located on top of a buried asymmetric bedrock valley that rests at an elevation between 290 and 270 feet (Arthur D. Little, 1994).

Bedrock drilling at CRREL shows the bedrock is discretely fractured. Geophysical logs show two primary fracture sets, one is a set of north, north easterly trending fractures that dip to the south- southeast between 30 and 60 degrees. The second set trends north-north easterly and dips to the west-northwest between 30 and 40 degrees (Appendix I). The rock matrix was measured to have very low porosity (0.01 to 0.02). Organic carbon ranged from 0.075 to 0.2%

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3.5 Surface Water Hydrology

The Connecticut River drainage basin encompasses an area of 4,092 square miles, with a discharge that ranges from 82 cubic feet per second (cfs) to 136,000 cfs. At the West Lebanon gauging station, located 5.6 miles downstream of CRREL and below the point of confluence with the White River, the average discharge of the river is calculated at 7,121 cfs. The average discharge approximately five miles upstream of CRREL is estimated to be 4,900 cfs (Arthur D. Little, 1994).

The water level of the Connecticut River near CRREL is controlled by TransCanada Hydro Northeast dam at Wilder, Vermont located 4.5 miles downstream of CRREL. The reservoir produced by the Wilder Dam extends 30 miles upstream to the Piermont-Haverhill, New Hampshire area. The normal residence time of water in the reservoir ranges from two to five days, depending on discharge rates at the dam. Under the company’s operating permit, the reservoir elevation is maintained between 380 and 385 feet. The water level in the reservoir normally does not fluctuate more than 1 foot a day, with drawdown occurring during peak power usage (Arthur D. Little, 1994). Surface water elevation measurements were not made in the Connecticut River during the Phase III RI. The United States Geological Survey maintains a staff gauge station below the Wilder Dam and does not maintain a staff gauge upriver on proximal to the Site. Flow data and historic groundwater modeling (USACE, 2010a, 2010b) indicate that the operation of the extractions wells and the direct connection of the esker to the river result in water contribution from the river to the esker.

Surface water drainage at CRREL is generally from east to west. Most of the surface water runoff is collected by CRREL’s storm sewer system which is discharged to the Connecticut River at a NPDES permitted outfall. This system is augmented by drainage culverts and swales. The storm sewer system also conveys spent refrigeration and cooling water from the various engineering laboratories. CRREL has estimated that on average, 365 million gallons of cooling water and 23 million gallons of storm water are discharged through the storm sewer to the Connecticut River annually.

Near production well CECRL03, drainage is to the south through a ravine that runs parallel to the east side of the esker ridge. Other wastewater is discharged to the municipal sewer system operated by the Hanover Water Company.

3.6 Hydrogeology

Groundwater movement at CRREL is influenced by the overburden, the bedrock and the esker that is located beneath the western border. The water table is in both the glaciolacustrine units and the bedrock. Pumping of production wells influences groundwater movement in the overburden (USACE 2010a and 2010b). The hydrogeologic relationship between the lacustrine deposits and the bedrock and the esker and the bedrock is not well defined.

Across most of the Site, the water table is located within the glaciolacustrine units that range between approximately 80 feet bgs and 235 feet bgs. (Figures 3.6-1 and 3.6-2). The

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I hydrostratigraphic units fall into two main categories, unconsolidated deposits and bedrock. Although the unconsolidated and bedrock units are hydraulically connected, there is a significant difference in the manner and rate at which groundwater moves in each unit. Groundwater movement through the unconsolidated deposits is most likely isotropic over short distances. Groundwater movement through the bedrock occurs within a discrete fracture network with the net groundwater movement determined by aquifer potential. Groundwater occurs in the bedrock throughout the Site (Arthur D. Little, 1994).

3.6.1 Overburden Groundwater

The lacustrine clay unit is located above the groundwater table that ranges between approximately 95 feet bgs and 160 feet bgs, but locally contains perched water, especially on the lower terrace near the northern boundary of the Site. Similarly, perched water is also documented in the sandy to clayey silt at the center of the Site along the lower terrace access road. The occurrence of perched water may be due to a combination of factors, including the presence of a drainage swale along the access road, and/or the residual effects of an intermittent stream that was buried during construction (Arthur D. Little, 1994).

Across the Site, overburden extends up to 235 feet bgs. Groundwater flow is in the fine-medium grained sand, silty sand, and clay units of the lake sediment deposits, and the medium-coarse grained sand of the esker. Groundwater flow in the former lake sediment deposits is to the west with progressively decreasing horizontal hydraulic gradients to the west decreasing from 0.006 feet per foot (ft/ft) to 0.003 ft/ft. Within the esker, groundwater flow is less defined, but evidence suggests radial flow to the production wells (USACE, 2010a) is produced by pumping (Figure 2.5- 3 and Figure 3.6-3). These production wells draw groundwater from the esker that parallels the Connecticut River and is likely hydraulically connected to the river. TCE-contaminated overburden groundwater migrating from AOC 2 and AOC 9 is captured by the facility’s five supply wells located within esker materials bordering the Connecticut River (USACE, 2010a). The esker materials are the most permeable soils at the Site. The average river elevation adjacent to the Site is estimated at 384 feet.

Recharge to the overburden aquifer has not been estimated nor has it been quantified. Recharge is expected to be very low based on the depth of the vadose zone (up to 130 feet bgs) and the presence of developed and paved surfaces found on the facility.

Overburden wells (CECRL series wells) screened in the fine sand deposits displayed hydraulic conductivity values ranging from 1.37 x 10-4 ft/sec and 1.91 x 10-6 ft/sec. Overburden wells spanning the silts, silty sand showed hydraulic conductivity values ranging from 1.46 x 10-5 ft/sec to 3.67 x 10-7 ft/sec (Arthur D. Little, 1994). Horizontal groundwater flow velocities were estimated to range between 0.1 ft/day to 0.001 ft/day (Arthur D. Little, 1994). Porosity has been assumed to range between 0.25 and 0.3 (Freeze and Cherry, 1979).

The vertical hydraulic gradients at CRREL are subtle, but small negative (recharge conditions) gradients exist west of CECRL15, and small positive (discharge conditions) gradients exist east of CECRL15 (Arthur D. Little, 1994). Table 3.6-1 provides groundwater elevations for the month of

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

July including historical measurements beginning in 2005 through 2015. Table 3.6-1 also lists well screen intervals.

AOC 2, AOC 9 and AOC 13 are in the low permeability silty-clay units of the overburden portion of the unconfined water table aquifer and are located near the transition between positive and negative vertical gradients that occurs near wells CECRL 08/15. Data indicates that depth to water is approximately 132 feet bgs in AOC 2 and has a subtle positive vertical gradient while depth to water in AOC 9 is approximately 127 feet bgs and has a subtle negative vertical gradient (Arthur D. Little, 1994).

3.6.2 Bedrock Groundwater

Groundwater flow in metamorphic bedrock is heterogeneous and is determined by paths of least resistance through a complex network of fractures. Measurements at the Site indicate the net direction of groundwater movement in bedrock is toward the west-southwest (Figure 3.6-4). Previous reports identified the horizontal gradient is steepest at the northeast part of the Site and progressively decreases toward the west, consistent with the overburden (Arthur D. Little, 1994).

Figure 3.6-4 shows the interpreted groundwater elevation contours for bedrock groundwater in July 2014. Vertical gradients between the overburden groundwater varied. At the background overburden/bedrock pair (CECRL 07 and 13) the vertical gradient was downward at -0.05 feet. In the area of AOC 2 the gradient was upward from bedrock at 0.29 feet. Neutral gradients were observed immediately downgradient of AOC 2 at CECRL 09 and 14. Gradients in the central portion of the facility mixed and ranged between -0.78 and 0.09 feet. At overburden/bedrock well pairs adjacent to the Connecticut River gradients were slightly upward (0.04 and 0.1 feet) to neutral. The gradient between overburden and bedrock was greatest between the CECRL 17 and 16 pair at 8.75 feet. It is not known why such a large gradient is observed in this area as measuring points and survey elevations appear to be correct. It may be that local mounding of the overburden water table is due to a leaking storm drain in the area.

The bedrock is discretely fractured. Geophysical logs show two primary fracture sets; one is a set north-northeasterly trending fractures that dip (30 to 60 degrees) to the south-southeast. The second set trends north-northeasterly and dips (30 to 40 degrees) to the west-northwest. Bedrock groundwater migrates through fractures from areas of higher hydraulic head to the east to areas of lower head towards the river in the west.

Physical measurements of the bedrock matrix were conducted on rock core retrieved from BR-14- 101 and BR-14-103. Appendix I presents the results. Matrix porosity is low at both locations and averaged to 0.015 or 1.5%. Bulk density averaged 2.82 g/cm3. Total organic carbon averaged 0.138%.

3.7 Ecology

The ecology of the Site and vicinity has been examined to document local ecological resources for evaluation of potential adverse ecological impacts to onsite and off-site habitats from TCE in

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3.7.1 Onsite Habitats and Ecological Receptors

In general, the Site contains very little terrestrial, wetland, or aquatic wildlife habitat because it is an extensively developed property (Figure 1.4-2).

Onsite terrestrial habitat is comprised of maintained lawns, foundation plantings including flower beds and shrubs and trees.

Onsite wetland and aquatic habitat consists of a storm water detention pond located in the southwest corner of the property. A small palustrine wetland has become established in the pond (Figure 1.4-2). Storm water and process water discharges are periodically pumped from the northwest corner of this pond through a closed pipe system into the Connecticut River. The pond is a low-quality wetland unlikely to provide significant food or habitat resources for wildlife because it is used for ice experiments and receives overland runoff from paved surfaces.

Onsite ecological receptors have not been surveyed at CRREL. Given the developed nature of the property, the receptors might include:

• Terrestrial and wetland plants and fauna. • Soil invertebrates and small birds and mammals that feed on soil organisms. • Invertebrates inhabiting the sediments and surface water of the storm water detention pond. • Resident amphibians, birds, waterfowl or mammals that may use or feed in the pond. • Similar fauna residing in off-site receptor habitats could be onsite receptors if they visit the CRREL property occasionally. • Deer, fox, rabbit, and predatory birds are often observed onsite.

3.7.2 Off-Post Habitats and Ecological Receptors

Off-Post habitats and ecological receptors that would be found on properties immediately adjacent to CRREL include:

• Developed land with lawn, gardens, and plantings, which are the dominant habitat type on three sides of the CRREL property. • Open fields with seasonal grasses and leafy plants. • Areas of mixed hardwood dominant forest. • Freshwater aquatic habitats of the Connecticut River.

The fields and forest areas adjacent to the CRREL property and Connecticut River offer the best

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Off-Post wetland habitats do not exist adjacent to CRREL or along the off-Post areas of the Connecticut River in the vicinity of the Site. The Connecticut River is the only aquatic habitat of significance proximal to the Site. The benthic habitat consists mostly of a sandy bottom near shore and a gravel/cobble bottom in the deeper channel areas. Off-Post ecological receptors near CRREL are similar to those onsite for exposures to soil, sediment and/or surface water. The only off-Post aquatic ecological receptors of site–derived contaminants would be the habitats and biota of the nearby Connecticut River.

Based on observations from the prior investigative activities at the CRREL property no visible stress symptoms were observed in the vegetation of potentially affected onsite or off-site habitats. Even the off-site grassy swale, which originally drained the southwest quarter of the Site and was a likely contaminant migration route from CRREL to the Connecticut River before construction of the detention pond in the 1980s , exhibited no visible symptoms of vegetation stress.

Based on comments and reports on past field observations, the health of the resident bird and mammal fauna appears to be normal. No obvious symptoms of vegetation stress were evident on the berms or in the bottom of the stormwater detention pond.

3.7.3 Threatened and Endangered Species

The New Hampshire Natural Heritage Inventory reported to Arthur D. Little in 1994 that no federal or state listed rare, threatened, or endangered species of flora or fauna are known to occur within the CRREL property or in nearby locations. However, a later publication by the New Hampshire Natural Heritage Bureau titled Rare Plants, Rare Animals, and Exemplary Natural Communities in New Hampshire Towns (July 2013) listed several threatened and endangered plant species in the town of Hanover. Threatened vertebrates included the bald eagle. Endangered invertebrates included the tule bluet (damselfly), brook floater (mollusk), and the dwarf wedge mussel (mollusk).

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4.0 NATURE AND EXTENT OF CONTAMINATION

The testing and laboratory analytical data from the CRREL Phase III RI have been compiled, reviewed and evaluated to characterize the nature and extent of contamination in soil, groundwater, air, and bedrock. Analytical chemistry data was reviewed in accordance with the CRREL Site RI/FS/PP and Decision Document Work Plan and Uniform Federal Policy Quality Assurance Project Plan (UFP-QAPP) (AMEC, 2012c). Data validation reports for soil, groundwater and air samples are included in Appendices M, N and O respectively. Analytical chemistry data results from sampling activities conducted during the Phase III RI are interpreted to be usable.

The results of sampling and testing of these environmental media are presented in the following subsections.

4.1 Sources of Contamination

As described in Section 2.1of this report, potential sources of contamination were identified and investigated during previous investigations. Through these investigations many of the original source areas were designated as no further action (Figure 2.1-6). Previous investigations narrowed the focus to four source areas including: AOC 2, a former 10,000-gallon UST containing free phase TCE that leaked; AOC 9, the former Ice Well; AOC 13, a former disposal pit area; and AOC 15, a former fuel oil UST that leaked (Figure 2.3-1). The Phase III RI was conducted (Section 2.3) to further characterize these AOCs. The CDC is not considered a source of contaminants at the Site and is not designated as an AOC, but rather an area of study. The Phase III investigation at the CDC was conducted to evaluate potential migration of Site related contaminants to or use of contaminated fill in outdoor recreation areas where children may come in contact with soils.

TCE is the primary COC at AOC 2, AOC 9, and AOC 13. Leaks associated with a former 10,000- gallon UST containing TCE at AOC 2 contaminated the varved fine-grained sands, silts, and clays. TCE appears to have migrated partially through the soil column profile to depths ranging up to 50 to 60 feet bgs. DNAPL in these soils was not observed during the collection of subsurface samples during the Phase III RI, however, its presence was noted in previous investigations (ENSR, 1996). TCE remains adsorbed to the silts and clays and fine sands in the upper lacustrine soil unit. TCE may be immobilized in the soil pore space. TCE migrated to the water table dissolved in precipitation and runoff water percolating through the TCE contaminated soil and from soil gas ultimately entering groundwater. A soil gas plume migrated laterally from the AOC 2 source area by diffusion and to some degree by advection due to barometric pressure changes. TCE in soil gas is also denser than non-contaminated soil gas and will migrate as a result of density differences by gravity. The TCE vapor is most likely in equilibrium with TCE adsorbed to fine grained materials in the soil column, acting as a continuous secondary source of soil gas contamination. TCE contaminated soil gas moves by advection in the subsurface when a vacuum stress is placed on the vadose zone. TCE moved vertically and laterally away from TCE contaminated soils by diffusion in soil gas in the vadose zone. Because soil gas concentrations are sufficiently high (upwards of 1,000,000 µg/m3) in AOC 2, TCE likely partitions out of the vapor

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I phase and into groundwater. Once dissolved in groundwater, the TCE moves by advection to the west towards the Connecticut River. TCE contaminated groundwater in the overburden is captured before discharging to the river by a series of five production wells that pump from the eastern flank of the esker deposit.

At AOC 9, TCE was released to the ground surface during experiments associated with the former Ice Well, leaks from a portable refrigeration unit adjacent to the Ice Well, and a nearby explosion of a 10,000-gallon AST containing TCE (Faran, 1991). Breaches in the 3-foot diameter, 200-foot deep casing of the former Ice Well are not known to have occurred; however, TCE was lost from heat transfer piping within the borehole. Historic water level measurements in the Ice Well suggest that the structure held fluid well above the water table without levels changing over time. It is uncertain whether the Ice Well introduced TCE or TCE contaminated fluids to deep vadose zone soils; however, historic information suggests that this was an unlikely scenario. Overland flow of TCE from the AST explosion may have sorbed to shallow soils in grassy surfaces and penetrated cracks in pavement and entered nearby storm drains in July 1970. The AST was alleged to be half full at the time of the explosion (approximately 5,000 to 6,000 gallons). An unknown volume of TCE was washed into the storm drain system and discharged from an outfall in the Connecticut River. TCE remains adsorbed to the varved, fine sand, silts, and clays that underlie the AOC 9 area. The mechanisms for TCE present in soil, soil gas, and groundwater at AOC 9 are the same as those previously discussed for AOC 2.

TCE was reportedly discharged to the ground surface at AOC 13 during waste disposal practices that were common for the period. Concentrations of TCE in soil are not as great as observed at AOCs 2 and 9. Episodic releases of TCE in this area have resulted in its being adsorbed to soils in the area that continue to be a source of contamination in soil and soil gas.

Fuel oils remain adsorbed to shallow soils in the area of AOC 15, the site of the former Greenhouse. Fuel oil leaked from piping and the former UST impacting shallow soils. A limited soil removal action occurred in the late 1990s, and some fuel contaminated shallow soils were left in place due to their proximity to sanitary and storm sewer utilities. Fuel oil constituents are relatively immobile and persist in soils adjacent to these utilities. Natural attenuation of these compounds is expected to occur under aerobic conditions in shallow soils. These constituents are not expected to impact groundwater, as the unsaturated zone is approximately 80 feet thick beneath AOC 15.

4.2 Soil/Bedrock

Soil sample results collected during the Phase III RI are presented in the following subsections. Tables identify each detected analytical parameter and the frequency of detection. Analyte concentrations are compared to the following soil screening criteria.

• Regional Screening Levels (RSLs) – USEPA RSLs –Generic Tables November 2015: o Residential RSL – Residential RSL (TCE 0.41 mg/kg). o Industrial RSL – Composite Worker RSL (TCE 1.9 mg/kg).

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

• NHDES soil screening values. Values are provided in the NHDES Risk Characterization and Management Policy (Section 7.4(4), Appendix E) (updated February 2013) (NHDES, 2013a): o NHS-1 –Soil Category Direct Contact Risk-based Concentrations based upon sensitive uses of property and accessible soils, either currently or in the reasonably foreseeable future (TCE 0.8 mg/kg). o NH Leach - Leaching-based Soil Values consider the potential of chemicals to leach from soil and contaminate the underlying groundwater (TCE 0.8 mg/kg).

Compounds or metals concentrations detected in excess of the screening criteria are highlighted in each subsequent table. Each subsequent figure depicting the location of soil samples lists each compound or metal detected in excess of screening criteria. Each compound detected in excess of the aforementioned criteria will be carried through to the risk assessment for further evaluation (Section 7).

Arsenic was detected in soils at each AOC. Arsenic is a metal common to New Hampshire soils and these values fall within the range of established NHDES background concentrations. The background concentration is 11 mg/kg (Sanborn, Head & Associates, 1998). Arsenic is not a Site- related contaminant associated with releases at CRREL as it naturally occurs in Site soils. Arsenic concentrations in Site soils are discussed in subsections below.

The bedrock matrix sample results are discussed in subsection 4.2.4 and 4.2.9.

4.2.1 Membrane Interface Probe (MIP) and TCE in Soil Results Comparison

Soil investigations at AOC 2, AOC 9, and AOC 13 were conducted in a phased approach. A series of 31 MIP/HPT locations were advanced to refusal, generally along transects oriented perpendicular to groundwater flow. The MIP heats the soil, and provides a continuous measurement of VOCs in soil and groundwater as it is advanced. The purpose for conducting MIP logging was to create a soil profile to determine the vertical and lateral distribution of TCE or other VOC contaminants as represented by elevated detector response. Appendix D contains MIP/HPT logs.

The MIP is a field screening tool for the detection of volatile and SVOCs. The accuracy of the MIP is typically assessed by comparing the relative agreement between MIP response and corresponding confirmatory laboratory samples (ERDC, 2002). In the Phase III RI, the MIP XSD response data was compared to soil sample results from AOC 2, AOC 9, and AOC 13. The results of this analysis are presented in Appendix P and summarized below.

The MIP sensor detection system used during Phase III RI soil and groundwater investigations was equipped with three laboratory grade detectors. These detectors consisted of a photo ionization detector, a flame ionization detector, and a halogen specific detector (XSD). The XSD can detect a wide range of halogenated compounds including TCE and its associated daughter

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I products. The detector response is not calibrated to TCE but correlated to TCE based on soil sampling results. The units of the XSD response are microvolts (mV).

Seven soil boring locations were paired/co-located with MIP profile locations (Figure 2.4-2). These pairs include:

1. SB-101 and MP-06 (AOC 2). 2. SB-102 and MP-07 (AOC 2). 3. SB-107 and MP-01 (AOC 2). 4. SB-103 and MP-15 (AOC 9). 5. SB-104 and MP-18 (AOC 9). 6. SB-105 and MP-17 (AOC 13). 7. SB-106 and MP-26 (AOC 13).

One hundred and thirty-three (133) soil sample results for TCE collected from the vadose zone were compared to their corresponding XSD response profile. The XSD response was averaged over a one-foot vertical profile of the soil column where the soil sample was collected. For example, a soil sample collected at SB-107 from the 70-foot depth interval was compared to the average of the MIP XSD response results (n=20 records) obtained over the 69.5 to 70.5-foot zone in MP- 01. The comparison analysis is provided in Appendix P for each paired soil boring and MIP profile location.

Correlation coefficients associated with each comparison between TCE soil concentrations and XSD response in each paired location did not show strong linear relationships as R2 values ranged between 0.22 and 0.76 (weak to moderate). Accordingly, p-values associated with each comparison were less than 0.05 indicating that the difference of the means is significant and the null hypothesis is rejected. In other words, predicting that a certain XSD response value will result in a certain soil concentration value is not probable based on the data set.

MIP logs typically show elevated response in soils impacted by TCE (Appendix D). Areas of elevated MIP response are generally associated with elevated detections of TCE in soil and high concentrations of TCE in the soil gas or vapor phase. For the purposes of this report, MIP response values of more than 85,000 µV are assumed to likely represent the presence of TCE contaminated soils more than the NHDES soil clean up criteria of 0.8 mg/kg (or 800 µg/kg). The NHDES soil clean up criteria is used in this report as a guide for delineation.

4.2.2 Child Development Center

The soil investigation included surface soil and shallow soil sampling to provide spatial coverage of the recreational grounds surrounding the CDC. Sampling was conducted to evaluate the presence or absence of potential contamination by VOCs, SVOCs, pesticides/PCBs, herbicides, or metals.

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Figure 4.2-1 shows the location of each sample collected and a summary of analytes detected in excess of the soil screening criteria. The analytical data associated with the Phase III RI soil sampling are presented in Table 4.2-1 which provides a hits-only summary (“hits only” indicates that only the analyte/compounds detected in the samples are listed in the table) of the analytical parameters detected.

VOCs. Surface soils and shallow soils collected at the CDC were non-detect for the presence of TCE and other solvent related contaminants. Acetone, a common lab contaminant, was detected in one sample at low concentration. The compound 4-iso-propyltoluene was detected in four samples at low concentrations, the presence of this chemical may be attributable to the presence of tree sap or wood chips contained in mulch. Site related VOC contaminants of concern were non-detect in shallow soils at the CDC.

SVOCs. Several polynuclear aromatic hydrocarbons (PAHs) were detected in soils at the CDC. Benzo(a)anthracene, benzo(a)pyrene, and benzo(b)fluoranthene were detected in excess of the USEPA Residential RSLs at two locations, SS-405 and SS-423. Indeno(1,2,3-cd) pyrene was detected in excess of the USEPA Residential RSL at surface soil sample location SS-423. The PAHs detected are not associated with operations at the facility. These compounds are typical by-products of incomplete combustion of carbon containing materials (e.g., wood or fuels) and are also common constituents in asphalt. Each surface soil sample that exceeds screening criteria is located less than 10 feet from paved parking surfaces. These PAHs exhibit exceedingly low solubility, are not mobile in groundwater, and partition strongly to soils. Their presence in soils is considered to be related to common anthropogenic sources. The nature and extent of these compounds is considered to be defined at the CDC.

Pesticides and PCBs. PCBs were not detected in soil samples collected from the CDC. Pesticides were detected at very low concentrations in 4 of the 18 samples collected from shallow soils at the CDC. The compounds 4,4;-Dichlordiphenyltrichloroethane (4,4’-DDT), 4,4’- Dichlorodiphenyldichlorethylene (4,4’-DDE), dieldrin, and heptachlor epoxide were detected but did not exceed USEPA or NHDES soil screening criteria. These pesticides have a low water solubility and will remain strongly adsorbed to soils. The nature and extent of these classes of compounds has been defined.

Herbicides. Surface soils were non-detect for the presence of herbicides.

Metals. Several metals were detected in surface soils at the Site. Arsenic and chromium were detected in excess of screening criteria in each of the 17 soil samples collected. Arsenic was detected at concentrations in excess of USEPA residential and industrial RSLs. One sample result (SS-412) exceeded the NHDES soil screening value. The concentration of arsenic in CDC surface soils ranged between 6.5J to 14.8 mg/kg with an average concentration of 8.8 mg/kg.

Chromium concentrations at the CDC ranged from 16.8 to 45.3 mg/kg with an average concentration of 33 mg/kg. Chromium analysis was conducted for total chromium and did not speciate trivalent and hexavalent chromium. Therefore, the lowest applicable standard for the chromium ions was applied for comparison. Seventeen of the 17 samples collected exceeded the

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I residential and industrial RSLs; none of the results exceed the NHS-1 criteria. The average concentration for chromium detected at the CDC is consistent with the NHDES background concentration of 33 mg/kg, therefore, the chromium detected at the CDC is likely naturally occurring.

Arsenic and chromium are not Site-related contaminants associated with a release at the CDC as they naturally occur in Site soils.

Based on these data and comparison to soil screening criteria, it is concluded that the nature and extent of contamination of surface soils at the CDC has been defined, and no further sampling of soil is needed. These findings will be further evaluated in the human health risk assessment.

4.2.3 AOC 2

AOC 2 is the location of a former 10,000-gallon UST that contained TCE for use as a heat transfer agent in the Main Laboratory. Two USTs were installed at this location in 1960; one was used for TCE storage and the second was used for fuel oil. The USTs were reportedly removed sometime between 1969 and 1972 after the TCE tank was determined to be leaking. The USTs were replaced by two fuel oil USTs that were removed in 1989 (Faran, 1991). The UST leaked and an unknown quantity of TCE was released to fine grained varved soils. Records documenting the quantity of TCE released at AOC 2 or how much TCE was purchased by CRREL are not available prior to 1987. However, there is anecdotal evidence that the facility ordered up to 3,000 gallons per year of TCE over a period of several years (Sayward, 1968).

Soil sampling conducted in support of an SVE Air Sparging Pilot Test (ENSR, 1996) reported the presence of residual phase DNAPL resting above dense silty clay layers interspersed through the soil column from 23 to 33 feet bgs. This observation was based on pungent solvent odors and visible sheens on dense silt soil samples; mobile DNAPL was not observed. Residual phase DNAPL was not observed in Phase III drilling and sampling activities. Immobile DNAPL may exist in pore spaces in the silt clay layers.

As discussed in Section 2.4, the soil investigation at AOC 2 was conducted in a phased approach. A series of MIP/HPT profiles were completed to guide the location of soil borings to ground truth results and define the nature and extent of soil contamination. Figure 4.2-2 shows the location of MIP/HPT profiles in relation to the location of the former UST that contained TCE. MIP results show elevated XSD response in an area northeast of the former UST location. It appears that free phase TCE once moved laterally to the northeast at AOC 2, the highest MIP response extends from 10 to 45 feet bgs, where the highest results range from 29 to 39 feet bgs. MIP XSD response decreases with depth towards the water table. These data, as well as data collected previously at AOC 2 (ENSR, 1996 and AD Little, 1992), suggest that the primary mass of TCE resides adsorbed to varved fine grained soils. Based on historical and recent Phase III RI soil sampling the data suggests that residual/free phase TCE did not migrate through the underlying fine sands and enter into the capillary fringe (approximately 130 feet bgs). The free phase TCE migrated laterally along silt and clay layers in the more shallow lacustrine deposits impeding migration deeper towards the water table. Additionally, four soil borings were advanced in the multipurpose room of the Main

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

Laboratory immediately adjacent to AOC 2. Each boring was advanced to 75 feet below the floor surface, very little TCE was detected in soils beneath this area of the building.

Figure 4.2-2 shows the location of MIP profiles in relation to the former UST. Elevated MIP response values are shown in excess of 85,000 µV or an approximate equivalent soil concentration in excess of 800 µg/kg. Elevated MIP response were identified to the northeast of the former UST location. This suggests that a preferential pathway for the migration of TCE in soils in this area.

Three soil borings were advanced at AOC 2 to confirm and quantify TCE in the subsurface. Three soil borings were co-located with three MIP locations to compare MIP XSD response with the concentration of TCE at similar depths and include the following pairs:

1. MP-01 and SB-107. 2. MP-06 and SB-101. 3. MP-07 and SB-102.

The soil investigation included surface soil and deep soil sampling to provide spatial coverage to define the extent of TCE contamination in soils associated with AOC 2. Soil samples were collected from SB-101, SB-107 through SB-111. Additional sampling was conducted while advancing casing at MIP locations MP-01 and MP-09. Soil samples were analyzed by an onsite laboratory for a select list of Site related VOCs. Full suite analytical samples were collected to determine the presence or absence of VOCs, SVOCs, pesticides/PCBs, TPHs, Herbicides or metals.

Figure 4.2-3 shows the location of each sample collected and a summary of analytes detected in excess of the soil screening criteria. The analytical data associated with the Phase III RI soil sampling are presented in Table 4.2-2 which provides a hits-only summary of the analytical parameters detected. The results of the analytical sampling are discussed further below.

VOCs. TCE was not detected in surface soils collected at SB-101 and SB-108 through SB-111. TCE was detected at elevated concentrations in AOC 2 subsurface soils. In 44 of 144 soil samples TCE was detected in excess of the NHDES screening criteria for protection of groundwater (800 µg/kg or 0.8 mg/kg). Concentrations of TCE in subsurface soils detected in excess of screening criteria ranged from 0.87 mg/kg to 120 mg/kg.

At SB-101 TCE was detected in soils exceeding 800 µg/kg from 48 feet bgs to the groundwater table at 132 feet bgs. In SB-102 soils exceeded 800 µg/kg from 9 to 12 feet bgs, and from 30 to 57 feet bgs and from 75 feet bgs to the water table at approximately 130 feet bgs. At SB-107, soils exceeding 800 µg/kg were detected in each sample extending from 4 to 70 feet bgs (Figure 4.2-4).

Comparison of MIP XSD results and analytical soil results show a moderate linear relationship. A cut-off value of 85,000 uV (interpreted equivalent soil concentration in excess of 800 µg/kg) was applied to the MIP data collected at AOC 2. These XSD data, Phase III RI soil data, and historic

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I sample data collected at AOC 2 were used to estimate a soil volume estimated to exhibit TCE concentrations in excess of 800 µg/kg (or 0.8 mg/kg). The estimated volume of soils at AOC 2 exceeding 800 µg/kg is approximately 28,480 cubic yards. Soil volume estimates are presented in Appendix Q. Figure 4.2-5 shows the extent of TCE in soils interpreted to exceed 800 µg/kg.

Soil vapor data, MIP XSD, and soil data were used to estimate the mass of TCE in AOC 2 soils. This will be discussed further in Section 5 of this report. An inverse distance interpolation was conducted in TecPlot where the mass of TCE was calculated within each 10-foot grid node. Table 4.2-3 presents a summary of the mass for a given soil gas concentration range, and the corresponding total TCE concentration (sum of vapor, soil, and pore water) most likely associated with that range (estimated using NAPLATOR [ESTS, 2004]). Based on these calculations, total TCE equivalent to approximately 1,450 gallons (~17,700 lbs) of TCE mass may be adsorbed in AOC 2 soils. Mass estimate calculations are presented in Appendix Q.

SVOCs. Chrysene was detected at a very low concentration in one surface sample located under the floor slab of the multi-purpose room (MPR) within the Main Laboratory basement. Chrysene did not exceed the USEPA or NHDES screening criteria. Chrysene is a by-product created during the burning or distillation of coal, crude oil, and plant material. PAHs detected below RSLs may be associated with the supply line trench that was used to provide fuel oil from the former UST, previously located within AOC 2, to the boilers located in the adjacent mechanical room in the basement. Total petroleum hydrocarbons (TPH) were detected at a low concentration in one subsurface sample located under the floor slab of the MPR within the Main Laboratory basement. The detection of TPH did not exceed the NHDES screening criteria. TPH detected may be associated with the supply line trench that was used to provide fuel oil from the former UST, previously located within AOC 2, to the boilers located in the adjacent mechanical room in the basement.

Pesticides and PCBs. AOC 2 samples were non-detect for the presence of PCBs. Methoxychlor was detected in one shallow soil sample located in the grassy area to the northwest of the Main Laboratory building. The compound did not exceed USEPA or NHDES soil screening criteria. This pesticide has a low solubility and will remain strongly adsorbed to soils. The nature and extent of those classes of compounds has been defined.

Herbicides. Surface soils were non-detect for the presence of herbicides.

Metals. Several metals were detected in AOC 2 soils, but only arsenic exceeded screening criteria. Arsenic was detected in each of the 6 soil samples collected at AOC 2 at concentrations in excess of USEPA residential and industrial RSLs. The concentration of arsenic in AOC 2 soils ranged from 4.2 mg/kg to 16 mg/kg. Three of the samples exceeded the NHDES soil screening value at locations SB-101, SB-102, and SB-110. As stated previously, arsenic is a metal common to New Hampshire soils and these values fall within the range of established NHDES background concentrations (Sanborn, Head & Associates, 1998). The nature and extent of arsenic in surface soils exceeding NHDES screening criteria has been defined. The presence of arsenic in CDC soils is considered representative of background conditions and is not associated with Site related releases at AOC 2.

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I

4.2.4 AOC 9

Contamination at AOC 9 originated from the former Ice Well and a former AST containing TCE. Releases at this AOC were from leaking piping associated with the Ice Well, handling of chemicals and discharged to the ground as the result of an explosion of the nearby AST. Emergency response to the explosion spread the TCE as it was washed over paved and grassy surfaces.

Soil and bedrock samples were collected at AOC 9. Soil samples were analyzed for VOCs, pesticide/PCB, SVOCs and metals; bedrock matrix samples were analyzed for VOCs.

4.2.4.1 AOC 9 Soil

The soil investigation at AOC 9 was conducted in a phased approach (see Section 2.4). A series of MIP/HPT profiles were completed to guide the location of soil borings to ground truth results and define the nature and extent of soil contamination. Figure 4.2-5 shows the location of MIP/HPT profiles in relation to AOC 9 the location of the former Ice Well.

Elevated MIP response values are shown in excess of 85,000 µV.

Two soil borings were advanced at AOC 9 to confirm and quantify TCE in the subsurface along the MIP transect located immediately downgradient of AOC 9. Two soil borings were collocated with two MIP locations to compare MIP XSD response with the concentration of TCE at similar depths and include the following pairs:

• SB-103 and MP-15. • SB-104 and MP-18.

The soil investigation included surface soil and deeper vadose zone soil sampling to provide spatial coverage to define the extent of TCE contamination in soils associated with AOC 9. Soil samples were collected from SB-103 and SB-104 and were analyzed by an onsite laboratory for a select list of Site related VOCs. Samples were also collected and analyzed at an off-site laboratory for a full suite of target analytes to determine the presence or absence of VOCs, SVOCs, pesticides/PCBs, TPH, herbicides, and metals.

Figure 4.2-6 shows the location of each sample point and a summary of the TCE results compared to the MIPs XSD logs. The analytical data associated with the Phase III RI soil sampling are presented in Table 4.2-4, which provides a hits-only summary of the analytical parameters detected. The results of the analytical sampling are discussed below.

VOCs. TCE was not detected in surface soils collected at SB-103 or SB-104. TCE was detected in AOC 9 subsurface soils, in 30 of 51 samples. In 4 of 51 soil samples, TCE was detected in excess of the NHDES soil screening value for protection of groundwater (0.8 mg/kg). One sample result exceeded the USEPA Industrial RSL. Concentrations of TCE in subsurface soils detected

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Comparison of MIP XSD results and analytical soil results show a moderate linear relationship. A cut off value of 85,000 µV was applied to the MIP data collected at AOC 9. As discussed previously, these XSD data, Phase III RI soil data, and historic sample data collected at AOC 9 were used to calculate a soil volume estimated to exhibit TCE concentrations in excess of 800 µg/kg (or 0.8 mg/kg). The estimated volume of these TCE contaminated vadose zone soils at AOC 9 is approximately 46,795 cubic yards (Figure 4.2-7).

Soil vapor data, MIP XSD, and soil data were used to estimate the mass of TCE in AOC 9 soils. An inverse distance interpolation was conducted in TecPlot where the mass of TCE was calculated within each 10-foot grid node. Table 4.2-5 presents a summary of the mass over a given soil gas concentration range and the corresponding predicted soil concentration most likely associated with that range (estimated using NAPLATOR). Based on these calculations, TCE vapor equivalent to approximately 1,350 gallons (~15,900 lbs) of TCE may be adsorbed in AOC 9 soils. Mass estimate calculations are presented in Appendix Q.

SVOCs. Two surface soil samples were collected in the area of AOC 9 for SVOC analysis. Both surface soil samples were non-detect for the presence of SVOCs.

Pesticides and PCBs. Heptachlor epoxide was detected in one of two surface soil locations and did not exceed screening criteria.

Herbicides. Surface soils were non-detect for the presence of herbicides.

Metals. Several metals were detected in AOC 9 soils. One sample exceeded screening criteria. Arsenic was detected in the two soil samples collected at AOC 9 at concentrations in excess of USEPA Residential and Industrial RSLs. The concentration of arsenic in AOC 9 soils ranged from 4.6 to 6.7 mg/kg. Neither sample exceeded the NHDES screening criteria. Arsenic is not a Site- related contaminant associated with releases at AOC 9 as it naturally occurs in Site soils.

4.2.4.2 AOC 9 Bedrock Matrix

Samples of the bedrock matrix within AOC 9 were collected at BR-14-101 (Figure 2-4.2) located immediately downgradient of the former Ice Well. Table 4.2-6 provides a hits-only summary of the VOCs detected in bedrock matrix samples. Bedrock matrix samples were collected to determine if TCE concentrations in bedrock fractures and the bedrock mass were sufficient to cause matrix diffusion into bedrock groundwater. Bedrock samples were collected from 240.5 to 264 feet bgs. TCE was not detected in the bedrock matrix below AOC 9. Carbon disulfide was detected in two rock samples in BR-14-101. Concentrations were 0.081 mg/kg and 0.0247J mg/kg in samples collected from 241 and 243 feet bgs. Toluene was detected in the bedrock matrix at low concentrations ranging from 0.00941J mg/kg to 0.0215 mg/kg through 240 to 262 feet bgs.

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4.2.5 AOC 13

AOC 13 is a former open pit where waste TCE was potentially discharged to the ground surface. The soil investigation at AOC 13 was conducted in a phased approach (see Section 2.4). A series of MIP/HPT profiles were completed to guide the location of soil borings where TCE is present to define the nature and extent of soil contamination. Figure 4.2-8 shows the location of MIP/HPT profiles in relation to the location of the former disposal area. Elevated MIP response values are shown in excess of 85,000 µV.

Two soil borings were advanced at AOC 13 to confirm and quantify TCE in the subsurface along the MIP transect. Two soil borings were co-located with two MIP locations to compare MIP XSD response with the concentration of TCE at similar depths and include the following pairs:

• SB-105 and MP-17. • SB-106 and MP-26.

The soil investigation included shallow and deep soil sampling to provide spatial coverage to define the extent of TCE contamination in soils associated with AOC 13. Soil samples were collected from SB-105 and SB-106. Soil samples were analyzed by an onsite laboratory for a select list of Site related VOCs. Full suite analytical samples were collected to determine the presence or absence of VOCs, SVOCs, pesticides/PCBs, Herbicides, or metals.

Figure 4.2-9 shows the location of each sample collected and analytes detected in excess of the soil screening criteria. The analytical data associated with the Phase III RI soil sampling are presented in Table 4.2-7 which provides a hits-only summary of the analytical parameters detected. The results of the analytical sampling are discussed further in the following paragraphs.

VOCs. TCE was detected at elevated concentrations in AOC 13 subsurface soils. TCE was detected in 25 of 46 samples at concentrations, ranging from 0.028 mg/kg to 1.1 mg/kg. In 2 of 46 soil samples, TCE was detected in excess of the NHDES screening criteria for protection of groundwater (800 µg/kg or 0.8 mg/kg). One sample result exceeded the USEPA Industrial RSL. Concentrations of TCE in subsurface soils detected in excess of screening criteria ranged from 0.84 mg/kg to 1.1 mg/kg in SB-106, extending from approximately 43 to 45 feet bgs.

Comparison of MIP XSD results and analytical soil results show a moderate linear relationship. A cut-off value of 85,000 µV was applied to the MIP data collected at AOC 13. As discussed previously, these XSD data, Phase III RI, soil data and historic sample data collected at AOC 13 were used to calculate a soil volume estimated to exhibit TCE concentrations in excess of 800 µg/kg (or 0.8 mg/kg). The estimated volume of those TCE contaminated vadose zone soils in AOC 13 is approximately 1,463 cubic yards (Figure 4.2-10).

Low levels of cis-1,2-dichloroethene (cis 1,2-DCE) were detected in 10 of 46 soil samples at AOC 13, but they did not exceed soil screening criteria. Detected concentrations ranged from 0.042J mg/kg to 0.49 mg/kg in SB-106, extending from approximately 29 to 63 feet bgs.

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SVOCs. Flouranthene, phenanthrene, and pyrene were detected at low concentrations in shallow soils (3 feet bgs) at SB-106. Analytical results did not exceed soil screening criteria.

Pesticides and PCBs. The compounds 4,4’-DDE, alpha-chlordane, and gamma-chlordane were detected at low concentrations in shallow soils (3 to 4 feet bgs) at SB-105 and SB106. These pesticides did not exceed soil screening criteria.

Herbicides. Soils were non-detect for the presence of herbicides.

Metals. Several metals were detected in AOC 13 soils. Only one exceeded screening criteria. Arsenic was detected in each of the 2 soil samples collected at AOC 13 at concentrations in excess of USEPA residential and industrial RSLs. The concentration of arsenic in AOC 9 soils ranged from 7.7mg/kg to 8.3 mg/kg.

4.2.6 AOC 15

AOC 15 is the location of a former UST containing fuel oil. Releases occurred through breaches or slow/steady leaks from the tank and associated piping. The soil investigation at AOC 15 included shallow sub surface soil sampling along the course of sanitary sewer and storm drain lines located immediately to the west of the former greenhouse. Sampling was conducted to determine the presence or absence of potential contamination by VOCs, SVOCs, pesticides/PCBs, DRO/GRO, and metals.

Figure 4.2-11 shows the location of each sample collected and analytical testing results for fuel related compounds. The analytical data associated with the Phase III RI soil sampling at AOC 15 is presented in Table 4.2-8 which provides a hits-only summary of the analytical parameters detected.

VOCs. Very low concentrations of TCE were detected in shallow soils at AOC 15 on the north side of the sanitary sewer at HA-103 and 105, at depths of 7 and 10 feet, respectively. Concentrations of TCE in soils at these locations did not exceed screening criteria. Several other VOCs were detected at low concentrations. The solvent-related compound 1,2,3-trichloropropane was detected at two sample locations (HA-101 and 102 at 10 feet bgs) at concentrations exceeding the USEPA residential RSLs, but they were an order of magnitude lower than the NHDES leaching to groundwater standard.

SVOCs. A number of SVOCs were detected in shallow soils. Most of the compounds are related to fuels. The compounds n-nitrosodi-n-propylamine and naphthalene were the only SVOCs detected at concentrations in excess of screening criteria. N-nitrosodi-n-propylamine was detected at sample location HA-102, from 10 feet bgs at 0.37J mg/kg, slightly above the USEPA Industrial RSL of 0.33 mg/kg. Napthalene was detected in excess of the NHDES screening criteria and the USEPA industrial RSL, at a concentration of 6.5 mg/kg.

Total Petroleum Hydrocarbons DRO/GRO. Diesel range organics (DRO) ranged from 7.3 to 1,900 mg/kg. GRO ranged from non-detect to 230 mg/kg. The sum of the DRO and GRO concentrations

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I range between 7.3 mg/kg to 2,130 mg/kg. The highest concentrations were located at HA-101 and 102, and did not exceed the NHDES TPH screening level of 10,000 mg/kg. Based on these data, the nature and extent of TPH contamination in soils is completed and no further sampling is needed.

Pesticides and PCBs. PCBs were not detected in AOC 9 soils. The pesticides 4,4’-DDD, 4,4’- DDE, and 4,4’-DDT were detected at very low levels in soils collected from HA-103 and 105 at depths of 7 and 10 feet, respectively. These compounds did not exceed USEPA or NHDES screening criteria.

Metals. Several metals were detected in shallow soils at AOC15. Only one metal was detected in excess of screening criteria. Arsenic was detected in each of the eight soil samples collected at concentrations in excess of USEPA Residential and Industrial RSLs. None of the sample results exceeded NHDES screening criteria. The concentration of arsenic in AOC15 soils ranged between 3.75 mg/kg to 7.5 mg/kg. Arsenic is a metal common to New Hampshire soils.

4.2.7 Downgradient Bedrock Matrix

Bedrock matrix samples were collected from BR-14-103 located at the downgradient edge of the Site from 196.9 to 214.2 feet bgs. Rock samples were non-detect for VOCs in each sample collected (Table 4.2-6).

4.2.8 Soils Summary

The volume of soils contaminated by TCE in excess of screening criteria at the Site amounts to an estimated total of 77,000 cubic yards of material; See Table 4.2-9. Concentrations of TCE in excess of screening criteria extend deep into the soil profile at the Site. At each AOC, TCE daughter products were detected at low levels, suggesting that limited anaerobic degradation is occurring in the form of reductive dechlorination.

The volume of TCE adsorbed to soils in the AOC 2 and AOC 9 source areas was estimated at 1,450 gallons and 1,300 gallons respectively. These estimates were calculated based on the current understanding of the geologic conditions and could potentially be an order of magnitude greater if there is significant variability of fractional organic carbon in the Site soils. TCE was used at CRREL from 1963 to 1987 and limited records exist related to purchases and disposal practices. Existing records (Sayward, 1968) indicate that the facility may have ordered up to 3,000 gallons per year spanning a period from at least 1961 to 1968 as operations and experiments used TCE and refrigeration systems leaked.

Contaminated soils will continue to act as a source of soil gas and groundwater contamination at the Site as TCE adsorbed to soils partitions into gas and dissolved phases.

Low levels of SVOCs and pesticides exist in some locations at the Site. These compounds are expected to remain adsorbed to soils and persist in the environment. Most SVOCs in soils are likely attributable to incomplete combustion of organic materials and the presence of trace

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I amounts of asphalt in soils. At AOC 15 SVOCs detected are related to fuel oil releases. Few SVOCs were detected in excess of soil screening criteria. Pesticides were found in Site soils, but do not exceed screening criteria.

Arsenic was detected in each soil sample analyzed. As stated previously, arsenic is a metal common to New Hampshire soils and the concentrations at the Site are comparable to average concentrations calculated for the State (Sanborn, Head & Associates, 1998). No other metals were detected in excess of soil screening criteria.

Herbicides and PCB’s were not detected in Site soils.

Based on the results of the soil investigation and historic practices at CRREL, TCE is the primary contaminant of concern in soils at AOCs 2, 9, and 13 with the bulk of contamination residing in AOC 2 and AOC 9 soils. Exposure to TCE contaminated soils are further evaluated in the HHRA (Section 7). Additionally, each compound detected in excess of the regulatory criteria will be carried through to HHRA for further evaluation.

4.2.9 Bedrock Matrix Summary

Bedrock matrix sampling did not indicate the presence of TCE, as each of the 35 bedrock samples collected was non-detect at locations immediately downgradient of the former Ice Well (BR-14- 101) and between the FERF and the Connecticut River (BR-14-103). (Table 4.2-6). The bedrock matrix is not a source of TCE for bedrock groundwater on the property. The bedrock core matrix sampling and analysis report is located in Appendix I.

4.3 Groundwater

Sixteen overburden groundwater monitoring wells and five overburden production wells are present at the Site. Groundwater from four of the five production wells (CECRL01, CECRL02, CECRL04, and CECRL05) has historically contained TCE. Water extracted from these four production wells is treated onsite using air stripping towers prior to its use in the non-contact cooling water process in the research facility and then ultimately discharged to the Connecticut River. VOC results of discharge water collected at the outfall are presented on Table 4.3-1. TCE was non-detect in the four samples collected between October 2014 and October 2015. Based on reported production well pumping rates (USACE, 2010b) and measured concentrations of TCE influent to the groundwater treatment plant up to 1.8 to 2.3 pounds of TCE can be removed from overburden groundwater each day. It is estimated that over the 25-year operation (1990-2015) of the treatment plant that approximately 16,000 pounds (~1,350 gallons) of TCE have been removed from the overburden aquifer. These estimates are based on numerous monthly status reports detailing the performance of the waste water treatment plant (Sovereign Consulting, 2017).

Ten bedrock wells are present at the Site. Five are shallow bedrock wells that penetrate up to 20 feet into the bedrock surface. Five are deeper wells that were advanced during Phase III RI activities approximately 100 feet into bedrock.

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The pre-2013 monitoring well network (consisting of 10 wells) was installed between 1992 and 1993. The wells were sampled 5 times between 1992 and 2004. Since 2004 the wells have been sampled annually. Annual groundwater reports can be found on the NHDES OneStop data and report retrieval website.

As part of the Phase III Remedial Investigation, six additional overburden monitoring wells (MW-14-103A, MW-14-103B, MW-14-104 through MW-14-107) were installed in May and June of 2014 (total of 16 wells). In addition, five bedrock wells (BR-14-101 through BR-14-105) were installed to supplement the bedrock groundwater monitoring network. These wells were located based on the results of MIP response data and groundwater profiler data that better defined the lateral and vertical extent of the TCE contaminated overburden groundwater plume.

Tables in the following subsections identify each analytical parameter detected in groundwater, the frequency of detection, the concentration compared to the following criteria:

• Maximum Containment Limit (MCL) - USEPA Maximum Contaminant Level (as described in the Safe Drinking Water Act promulgated in July 1st, 2010 CFR Title 40 Part 1 to 49).

• NHDES Groundwater Standards - screening values are provided in the NHDES Risk Characterization and Management Policy (Section 7.4(4)) Table 2 (updated February 2013).

. NH GW1 - values are equivalent to the Ambient Ground Water Quality Standards

. NH GW2 - groundwater is considered to be a potential source of vapors to indoor air

Compounds or metals detected in excess of these standards will be further evaluated in the HHRA (Section 7).

Membrane Interface Probe Response and TCE in Groundwater Results Comparison. A series of 31 MIP/HPT locations were advanced to refusal, generally along transects oriented perpendicular to groundwater flow (Figures 2.4-2 through 2.4-4, and Figures 2.5-1 through 2.5-1). Some of the MIP profiles penetrated through the groundwater table and were co-located with existing and newly installed monitoring wells and groundwater profiler locations. These locations include the following pairs:

1. MP-01 and MW-14-107. 2. MP-04 and CECRL-8. 3. MP-14 and CECRL-9. 4. MP-24 and CECRL-10. 5. MP-14 and SB/GW-103.

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6. MP-18 and SB/GW-104.

The following paragraphs provide a discussion on the comparison of MIP response data to groundwater sampling results for the purpose of defining the nature and extent of TCE contaminated groundwater associated with AOC 2, AOC 9, and AOC 13.

Four overburden groundwater sample results for TCE were compared to their corresponding XSD response profile averaged over the length of the well screen interval. For example, for a MIP boring that penetrated through the water table, a groundwater sample was compared to the average XSD response over an approximate 2-foot interval bracketing the groundwater sample interval (approximately 20 records). The comparison analysis is provided in Appendix P for each paired location.

The MIP XSD data related to overburden groundwater will be evaluated in the following manner in regard to the contamination assessment. MIP XSD response values measured in excess of 70,000 µV are assumed to be due to the presence of TCE in overburden groundwater at concentrations in excess of 100 µg/L. These XSD response values and groundwater concentration results were used to estimate the volume of TCE contaminated overburden groundwater.

4.3.1 Overburden Groundwater

Overburden groundwater was analyzed for VOCs, SVOCs, and metals during the Phase III RI.

VOCs: The overburden groundwater TCE plume originates from AOC 2 and AOC 9 source areas. TCE contaminated groundwater migrates from these source areas and moves in a westerly, northwesterly direction towards the line of production wells (CECRL01 through CECRL05). These production wells are oriented in a line (north-south), parallel to the Connecticut River. The overburden wells and an interpreted overburden potentiometric surface are shown on Figure 3.6- 3.

Figure 4.3-1 shows the interpreted extent of overburden groundwater contaminated by TCE in excess of 5 µg/L. The analytical data associated with the Phase III RI overburden groundwater sampling is presented in Tables 4.3-1 and 4.3-3, which provides a summary of the VOCs and metals detected. Groundwater profiler data collected as part of the 2013 field program is included on Table 4.3-1. Historical groundwater data collected from overburden monitoring wells is included in Appendix R.

TCE was detected in 203 of 306 samples collected with concentrations ranging from 0.25J µg/L to 100,000 µg/L as depicted on Figure 4.3-2. TCE in excess of 5 µg/L was detected in eighty-five (85) groundwater profiler samples.

The overburden groundwater plume is characterized by two distinct cores that have their origins beneath TCE source areas (AOC 2 and AOC 9). The width of the overburden groundwater plume is approximately 600 feet. The longest core axis extends approximately 950 feet from AOC 2 to

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Groundwater profiler results show that the two cores of the TCE plume range between 101 and 140 feet bgs, where concentrations exceed 10,000 µg/L. Further inspection of the groundwater profiler data shows that the concentrations of TCE below 140 feet bgs and with increasing depth towards the bedrock surface trend to lower concentrations (shown in Figure 4.3-2 and Figure 4.3- 4). For example, note the TCE concentration profile located in the AOC 2 source area in SB-101 (Figure 4.3-2). TCE at a concentration of 65,000 µg/L was detected at the water table. Deeper into the water table TCE concentrations decrease by over three orders of magnitude. Similar trends are observed at groundwater profiler locations downgradient of AOCs 2 and 9. Groundwater profiling at SB-103 shows the highest concentration in core of the AOC 9 plume of 100,000 µg/L at 135 feet bgs. Deeper in the profile at SB-103 (160 and 180 feet), TCE concentrations are two to three orders of magnitude less. Groundwater profiler data collected from GW-105, GW-107, and GW-108 show that the highest concentrations of TCE in groundwater span the 106-foot to 150-foot depth interval where concentrations ranged from 1,300 µg/L to 23,000 µg/L. TCE concentrations in the deeper portion of the overburden groundwater in the area of profiles range between two to three orders of magnitude less than in the shallower portion of the groundwater plume. Similar observations were made by CRREL when conducting discrete groundwater profile sampling in CECRL series wells (CRREL, 1997).

MIP data collected below the water table also show a comparable relationship as shown in Figure 4.3-5, where response values decrease towards the bedrock surface. These data suggest that if a DNAPL source (see Section 4.3.3) ever existed, it did not penetrate deep enough into the overburden aquifer to migrate to or into the bedrock (Figure 4.3-6). Figure 4.3-6 shows two highly concentrated overburden plume cores.

Groundwater profiler and monitoring well sample results at locations west of the production wells and east of the river suggest that the production wells are effectively capturing the overburden groundwater plume. Groundwater concentrations for TCE at groundwater profiler locations GW- 101, GW-111, GW-112, GW-113 were non-detect through the overburden saturated zone (Figure 4.3-2). The MW-14-103A well screen was placed from 95 to 105 feet bgs to monitor groundwater at an elevation where contaminated groundwater would discharge to the Connecticut River. The well screen for MW-14-103B was placed on top of bedrock spanning the 174 to 189-foot interval. TCE in each of these wells was non-detect (Figure 4.3-1). Additionally, concentrations of TCE at GW-104 and GW-115 within the area of the production wells are two to three orders of magnitude lower than TCE concentrations GW-105, GW-105, and GW-110 located immediately upgradient (Figure 4.3-2).

Other VOCs were detected in overburden groundwater in excess of screening criteria. These compounds are each collocated with elevated concentrations of TCE, and include carbon tetrachloride, cis-1,2-DCE, methyl tert-butyl ether and methylene chloride. The presence of cis- 1,2-DCE is most likely due to limited reductive dechlorination of TCE. Methylene chloride is most likely an analytical laboratory contaminant.

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Metals: Samples for TAL metals were collected from six monitoring wells. Metals were detected in each of the wells; however, concentrations did not exceed the USEPA or New Hampshire criteria.

Volume of Contaminated Groundwater and Mass Estimates

The volume of contaminated overburden groundwater was estimated using MIP data collected below the water table, groundwater profiler data, and conventional monitoring well data. Volume estimates were calculated in TecPlot 360 using an inverse distance interpolation. Based on this analysis, an estimated 50 million gallons of overburden groundwater contaminated by TCE, in excess of 10 µg/L exists below the facility. Table 4.3-4 summarizes the estimated volume of contaminated groundwater (assumes a range of porosity values of from 0.25 to 0.3 [Freeze and Cherry, 1979]).

The mass of TCE dissolved in overburden groundwater was estimated using two approaches, each assuming a porosity of 0.30. One approach assumed a midpoint concentration for a range of groundwater concentrations and a certain range of contaminated groundwater volumes. For example, for the groundwater concentration range 10 µg/L to 100 µg/L, a concentration of 50 µg/L was chosen. TCE mass was estimated from the volume of impacted groundwater between the 10 µg/L to 100 µg/L interval. The second method used an inverse distance interpolation, where the mass of each node in the grid was summed. The mass of TCE dissolved in the overburden groundwater plume was estimated at approximately 1,525 lbs (125 gallons) using either approach. Estimates of the mass of TCE in overburden groundwater are summarized in Table 4.3-5. Mass calculations are provided in Appendix Q using each approach.

4.3.1.1 Aquifer Testing

Aquifer testing was conducted to evaluate hydrogeologic properties (transmissivity and specific yield) of the overburden aquifer. This information was gathered to assist in optimizing CRREL’s groundwater extraction system. Tests consisted of a step test and a constant rate pumping and were conducted between June 17, 2014 and June 30, 2014. These results are summarized below.

Step Test

A step test was performed to determine the optimal extraction rate for conducting a constant rate discharge test. The step test was performed on June 23, 2014 and consisted of pumping rates of 5, 10, 15, and 19 gallons per minute (gpm). Nineteen gpm was the highest extraction rate possible given the existing pump setup and was at the upper limit of the theoretical entrance velocity of 0.1 ft/sec (Driscoll, 1986). Qualitative analysis of the step test results indicated that MW-14-104 could sustain pumping at the discharge rate of 19 gpm.

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Constant Rate Discharge Test

A three-day constant rate discharge test was conducted at MW-14-104 starting at 09:30 on June 24, 2015. A pumping rate of 19.25 gpm was sustained for 72 hours, followed by a 72-hour recovery period. In addition to the extraction well, MW-14-104, seven monitoring wells and/or piezometers were instrumented with transducers and monitored during the drawdown and recovery phases; MW-14-104*, PZ-14-101A, PZ-14-101B, PZ-14-102, MW-14-106, CECRL-10, and MW-14-105. Figure 2.5-4 shows the layout of the constant rate discharge test. The initial location selected for conducting the constant rate test was MW-14-104*, located approximately 7 feet south of MW-14- 104. However, the riser pipe at this well was crimped, preventing installation of a submersible pump.

Prior to analysis of the test data observed antecedent trends were removed from the data followed by correction for barometric efficiency. A relationship to barometric changes was observed in each well with the exception of MW-14-107, PZ-14-102A, and CECRL-10. The lack of barometric effects suggests that the aquifer is unconfined at these locations. A mean barometric efficiency of 0.8 was calculated for the aquifer indicating semi-confined to confined conditions within the overburden aquifer.

Analysis of the trend and barometric corrected data showed that drawdown was observed at the following monitoring wells/piezometers:

• MW-14-104 (pumping well): drawdown of 1.3 ft. • MW-14-104*: drawdown of 0.5 ft at 7 ft radial. • PZ-14-10A: drawdown of 0.1 ft at 25 ft radial. • PZ-14-10B: drawdown of 0.1 ft at 25 ft radial.

While no drawdown was observed in PZ-14-102A, a pressure spike was observed at the time of pump shutdown.

Sustained yield from MW-14-104 was significantly larger, and drawdowns were less than predicted prior to the aquifer text. A coarse sand and gravel unit approximately 2 feet thick was observed at 124-126 feet bgs in MW-14-104. This previously unobserved feature is believed to be responsible for the increased yield and relatively small observed drawdown in MW-14-104. The lateral extent of this high hydraulic conductivity feature is unknown. Additional aquifer testing may be needed to determine the storativity of this feature. Constant rate drawdown data from the observation well MW-14-104 were analyzed by the Theis confined solution in Aqtesolv (Appendix S). The Theis solution yielded an estimated transmissivity of 9,700 square feet per day and a storativity (assuming confined conditions) of 0.019.

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Water level data from MW-14-105 showed a distinct pattern of spikes in groundwater elevation of approximately 0.25 ft within a 60 to 70-minute cycle. MW-14-105 is located downgradient of MW- 14-104, adjacent to the esker. The changes in water levels are believed to be due to the cycling of the production wells within the esker. This same effect was observed to a lesser degree in each of the monitored wells, with the exception of CECRL-10 and MW-14-107. It is unclear if the pumping response is observed in PZ-14-101A and PZ-14-102A.

Based on the results of this aquifer testing, a more robust aquifer pilot test will be conducted in summer of 2017. The results of the 2017 aquifer pilot test will be presented under separate cover in a supplemental RI report. The supplemental RI report will include the results of the aquifer test presented in this report.

4.3.2 Bedrock Groundwater

Two areas of bedrock groundwater impacted by TCE have been identified at the Site and are shown in Figure 4.3-7. Each area is coincident with the AOC 2 and 9 source areas. The bedrock groundwater potentiometric surface is shown in Figure 3.6-4. Bedrock groundwater flow mimics overburden groundwater flow and moves from east to west beneath the Site.

Bedrock groundwater sampling consisted of sampling existing bedrock wells completed as conventional monitoring wells and packer sampling of open bedrock wells. Packer sampling targeted water bearing fractures identified from borehole geophysical logs (Appendix I). Table 4.3-6 provides a hits-only summary of the analytical parameters detected for bedrock groundwater. Historical groundwater data collected from bedrock monitoring wells are included in Appendix R.

Bedrock groundwater sampling detected TCE in excess of the USEPA MCL (5 µg/L) in CECRL- 15 (spans the upper 25 feet of the bedrock), located downgradient of AOC 2, and from packer samples collected from BR-14-101 (spans the upper 106 feet of the bedrock) located in the AOC 9 source area. The detected concentrations in these bedrock wells ranged from 6 µg/L to 12 µg/L, which is three orders of magnitude lower than nearby overburden wells. Two areas of interpreted bedrock groundwater impact are depicted in Figure 4.3-8 encompassing these two wells. Groundwater sampling indicates that high concentrations of TCE like those detected in overburden contaminated groundwater do not exist in the bedrock beneath the CRREL property. Deep bedrock wells BR-14-102 and BR-14-103 were located downgradient beyond the terminus of the overburden groundwater plume to serve as boundary wells. Bedrock groundwater TCE concentrations at these locations ranged from non-detect to 0.52J µg/L.

Several other VOCs were detected in bedrock groundwater, including the degradation products of TCE (cis-1,2-DCE, trans-1,2-DCE, and vinyl chloride) suggesting that abiotic reductive dechlorination of TCE (Butler and Hayes, 2001) occurs in bedrock groundwater in AOC 9. Of these compounds, only cis-1,2-DCE was detected at concentrations in excess of USEPA and NHDES drinking water criteria (70 µg/L). Concentrations of cis-1,2-DCE ranged between 520 µg/L and 610 µg/L in BR-14-101.

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4.3.3 Groundwater Summary

Overburden and bedrock groundwater flows from the east to the west consistent with natural gradients. Vertical gradients between the overburden groundwater and bedrock groundwater vary from slightly upward to slightly downward across the Site. In previous studies, vertical gradients were measured as primarily downward indicating a recharged condition to the bedrock (Arthur D. Little, 1994). The results of Phase III groundwater studies show that the overburden groundwater TCE plume is defined by two highly contaminated lobes associated with vapor phase and soil contaminant sources below AOC 2 and AOC 9. The depth of these two lobes is greater than identified in previous RI studies, and the contaminant front is wider. The overburden groundwater plume is captured by the series of production wells located in the esker parallel to the Connecticut River. As a result, contaminated overburden groundwater does not discharge to the river. The overburden groundwater plume does not appear to be a significant source of bedrock groundwater contamination. Groundwater profiler data show that concentrations decrease towards the bedrock surface. The results of bedrock groundwater sampling and bedrock matrix sampling indicate that free phase TCE did not migrate through the overburden and into the bedrock. Bedrock groundwater concentrations are orders of magnitude lower than overburden groundwater concentrations and bedrock matrix sampling was non-detect for the presence of TCE. Bedrock monitoring wells located between the Connecticut River and the supply wells located in the esker were either non-detect or slightly in excess of the detection limit for TCE in groundwater.

TCE is the primary COC in overburden and bedrock groundwater at the Site based on the results of groundwater sampling and historic chemical use at the Site. The overburden groundwater TCE plume originates from two highly contaminated cores and is captured by the groundwater supply wells located in the esker. TCE in bedrock groundwater is limited to areas below AOC 2 and 9 at concentrations slightly in excess of the federal MCL (5 µg/L).

4.4 Surface Water

Surface water samples were not collected during Phase III RI activities. Surface water samples will be collected from the Connecticut River during supplemental RI activities scheduled for the fall of 2016. These data will be presented in a supplemental RI report.

4.5 Sediment

Sediment samples were not collected during Phase III RI activities. Sediment samples will be collected from the Connecticut River during supplemental RI activities scheduled for the fall of 2016. These data will be presented in a supplemental RI report.

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4.6 Soil Gas

Two areas of highly contaminated soil gas have been identified at the Site which have resulted from high concentrations of TCE adsorbed to soil in the AOC 2 and 9 source areas (see Section 4.2.3 and 4.2.4). TCE adsorbed to soil particles moves into the soil gas by volatilization and chemical diffusion and occupies n the space between soil particles in the vadose zone, which is up to 130 feet deep at the Site. The shallow fine grained lacustrine soil unit, located generally greater than 50 feet in depth, acts as a cap and creates a confined to semi-confined condition in the deep vadose zone. Atmospheric barometric changes result in dynamic pressure gradients between ground surface and the underlying lacustrine unit.

Concentrations of TCE in soil gas in immediate vicinity of AOC 2 and AOC 9 range from 1,000,000 µg/m3 to greater than 10,000,000 µg/m3. Sampling of the soil gas at CRREL and off-Post shows that the areal footprint of the soil gas plume in excess of 100 µg/m3 is approximately 52 acres and impact over 4,000,000 cubic yards of soil in the vadose zone. Because there have been no new inputs of TCE into the soil since the 1980s, the soil gas plume is assumed to be in equilibrium in the vadose zone and has reached its most areal extent.

Soil gas contaminated with TCE is in contact with the capillary fringe and is partitioning into groundwater. Soil gas is most likely the source of groundwater contamination at the Site.

As described in Section 2.6 of this report, a soil gas investigation was conducted to evaluate the nature and distribution of contaminated soil gas at the CRREL facility and adjacent off-Post locations. These investigation events are summarized in Table 4.6-1.

Soil gas vapor data collected during these events are evaluated by comparison to the following criteria:

• Interim Action Level – Site specific action level for TCE calculated by the USACE-NAE (88 µg/m3 or ten times the interim action level for indoor air of 8.8 µg/m3) used for comparison to onsite soil gas and sub-slab vapor samples.

• Soil Gas RSL - USEPA RSL for residential ambient air in which an attenuation factor (α) of 0.03 is applied. The residential screening level is 0.48 µg/m3 for TCE in indoor air; the soil gas vapor concentration calculated to potentially impact indoor air is 16 µg/m3. The USEPA recommends using the same attenuation factor for shallow and deep soil gas. In other words, an attenuation factor of 0.03 is recommended as the conservative screening- level attenuation factor for soil gas samples, whether sub-slab vapor or exterior soil vapor (USEPA, 2015a). This criterion is used for comparison to off-site soil gas and sub-slab vapor samples.

• Soil Gas Screening Level – NHDES Residential Soil Gas Screening Levels, (NHDES, 2013a). This residential value is used based on a potential future use scenario. These criteria are used for comparison to soil gas and sub-slab vapor samples both onsite and Off-Post.

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Compounds detected in excess of these action and screening levels will be further evaluated in the HHRA (Section 7).

The following subsections describe the soil gas investigation results.

4.6.1 Onsite Soil Gas Investigation

As discussed previously in Section 2.6, three reports document the results of the soil gas investigation conducted at CRREL. These reports include:

1. Final Soil Vapor Investigation Results for Cold Regions Research and Engineering Laboratory (AMEC, 2014e)

2. Final Soil Vapor Investigation Results – Addendum for Cold Regions Research and Engineering Laboratory (AMEC, 2014f).

Onsite soil gas data sampling results are presented in Tables 4.6-2 through 4.6-9 and Figures 4.6.-1 through 4.6.-11. The results of these sampling events are summarized in the following subsections.

4.6.1.1 May 2012 Soil Gas Sampling

In May 2012 soil gas samples were collected from vapor sampling points located throughout the CRREL facility using Summa canisters. This sampling effort is described in the Final Soil Vapor Investigation Results for Cold Regions Research and Engineering Laboratory (AMEC, 2014e).

A hits-only summary of analytical results from the May 2012 soil gas sampling are provided on Table 4.6-2 and TCE results shown on Figure 4.6-1. Table 4.6-3 provides a frequency of detection summary of compounds detected compared to the USEPA RSLs for residential indoor and corresponding soil gas screening levels. In addition to TCE, the most frequently detected compounds in excess of these RSLs include: 1,4-dichlorobenzene, benzene, chloroform, and ethyl benzene.

As shown on Figure 4.6-1 TCE concentrations in soil gas are highest in shallow soils beneath the parking lots adjacent to AOC 2. Concentrations of TCE at vapor sample locations SV-12-28 and SV-12-29 range from 28,000 µg/m3 to 200,000 µg/m3.

The highest concentrations of TCE in soil gas at the perimeter of the CRREL property were detected in the northeast corner from the deeper soil sampling interval (approximately 50 feet bgs) at locations SV-12-18 (1,900 µg/m3) and SV-12-20 (2,100 µg/m3) (Figure 4.6-1).

Figures 4.6-2 and 4.6-3 show the TCE soil gas concentrations of TCE compared to the soil gas RSLs and the soil gas Screening Levels, respectively. Each figure shows that TCE exceeds screening criteria at two locations along the northern perimeter (SV-12-20 and SV-12-21), one location along the eastern boundary (SV-12-18), and at one location along the southern boundary (SV-12-25). Within the facility, concentrations of TCE in soil gas exceed screening criteria at two

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During this sampling event utility trenches were targeted as potential preferential pathways (SV- 12-12 water line, SV-12-13 electrical, and SV-12-25 electrical). TCE concentrations in shallow trench locations exceed the interim action level for soil gas at SV-12-12 and SV-13 located adjacent to the CDC and at SV-12-36 located north of the Storage Building. Shallow soil gas at SV-12-25 located along the southern boundary also showed the presence of TCE in excess of the interim action level.

4.6.1.2 Supplemental Perimeter Soil Gas Sampling

Supplemental soil gas sampling rounds were conducted in July, October and November 2012 to evaluate TCE concentrations at the Site boundary. This sampling is documented in the Final Soil Vapor Investigation Results – Addendum for Cold Regions Research and Engineering Laboratory (AMEC, 2014f). Samples were collected using Summa canisters.

July 2012 Supplemental Soil Gas Sampling

In July 2012, supplemental soil gas sampling was completed along the perimeter of the CRREL property (northern, eastern, and southern boundaries). A hits-only summary of analytical results is presented on Table 4.6.-4. Soil gas concentrations for TCE are shown on Figure 4.6-4. Table 4.6-5 provides a frequency of detection summary compared to the USEPA RSLs for residential indoor air and soil gas. In addition to TCE, compounds frequently detected at concentrations in excess of these RSLs include carbon tetrachloride and chloroform.

May sample results the highest concentrations of TCE in soil gas were detected in the northeast corner of the property at sample locations SV-12-20 (23,000 µg/m3) and SV-12-18 (21,000 µg/m3) from the deeper sample interval (approximately 50 feet bgs). Most shallow soil gas sample (<10 feet bgs) analytical results for TCE were either non-detect, or detected at low concentrations.

Figure 4.6-5 and Figure 4.6-6 show the TCE soil gas results compared to the soil gas RSL and soil gas Screening Levels, respectively. TCE exceeds screening criteria at one location along the northern perimeter (SV-12-20), at four locations along the eastern boundary (SV-12-18, SV-12- 02, SV-12-27, and SV-12-08), and at one location along the southern boundary (SV-12-24).

TCE concentrations in shallow trench locations exceed preferential pathway screening criteria at perimeter location SV-12-17 along the northeastern corner of the Site.

As shown on Figure 4.6-4, the concentrations of TCE at deep soil gas sample locations (>10 feet bgs) generally increased by an order of magnitude from May to July. Shallow soil gas (<10 feet bgs) concentrations for TCE were typically non-detect, or detected at lower concentrations during both the May and July sampling events.

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October 2012 Supplemental Soil Gas Sampling

A second supplemental soil gas sampling round was conducted in October 2012 for perimeter sample locations. A hits-only summary of analytical results are presented on Table 4.6-6; TCE soil gas results are shown on Figure 4.6-4. Table 4.6-7 provides a frequency of detection summary compared to the USEPA RSLs for residential indoor air and soil gas. In addition to TCE, compounds frequently detected at concentrations in excess of these RSLs include: carbon tetrachloride, chloroform, and toluene.

Consistent with the May and July sample results, TCE concentrations in soil gas were highest at the northeastern corner of the CRREL property. TCE soil gas was detected at sample locations SV-12-20 (10,000 µg/m3) and SV-12-18 (1,900 µg/m3) (Figure 4.6-4).

Figure 4.6-7 and Figure 4.6-8 show soil gas locations in excess of the soil gas RSLs and soil gas Screening Levels, respectively. TCE exceeds screening criteria at 5 locations along the northern, eastern and southern boundary of the facility, and one location along the southern boundary

Concentrations of TCE are generally lower than those observed in the July sampling event as shown in Figure 4.6-4.

November 2012 Supplemental Soil Gas Sampling

In November 2012, additional vapor implants were installed at existing locations to evaluate deeper intervals for further characterization of soil gas at the perimeter of the CRREL property (northern, eastern, and southern boundaries). In addition to the perimeter samples, select locations associated with AOCs were sampled to evaluate the source concentrations concurrent with the perimeter samples. A hits-only summary of the analytical data results are presented in Table 4.6-8. Soil gas concentrations for TCE are presented in Figure 4.6-9. Table 4.6-9 provides a frequency of detection summary for the November 2012 supplemental sampling event compared to the RSLs for residential indoor air and soil gas. In addition to TCE, compounds frequently detected at concentrations in excess these RSLs include: carbon tetrachloride, chloroform, ethyl benzene, and trichlorofluoromethane.

Soil gas sample locations along the northern and eastern perimeter of the facility show TCE concentrations ranging from 0.48 µg/m3 to 2,300,000 µg/m3. The highest concentrations of TCE were detected in deep soil gas implant locations (~46 to 75 feet bgs) along the Site boundary at soil gas locations SV-12-18, SV-12-20, SV-12-02, SV-12-38, SV-12-27, and SV-12-08 (Figure 4.6- 9). Concentrations of TCE in the deeper soil gas implants in November were an order of magnitude greater than those observed in previous sampling events.

Figure 4.6-10 and Figure 4.6-11 show soil gas locations compared to the soil gas RSL and soil gas Screening Levels, respectively. TCE exceeds screening criteria at 10 locations along the northern, eastern and southern boundary of the facility.

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4.6.2 Off-Post Soil Gas

Based on the elevated concentrations of TCE detected in deep soil gas at several locations along the CRREL Site boundary during the 2012 investigations the USACE initiated further investigations to determine if TCE vapors are migrating through soils properties adjacent to CRREL (AMEC, 2013a; AMEC, 2013b).

As discussed in Section 2.6, off-Post soil gas sampling has been documented in the following reports.

1. Final Soil Vapor Investigation Results Frances C. Richmond Middle School Property (AMEC, 2014k). 2. Soil Vapor Investigation Results Rivercrest – Dartmouth College Property (AMEC, 2014l). 3. Final Soil Vapor Investigation Results Dartmouth College Properties (AMEC, 2014m). 4. Final Indoor Air and Sub-Slab Vapor Investigation Results Dartmouth Printing Property (AMEC, 2014n). 5. October 2015 Soil Gas Monitoring Data Report For Remedial Investigation and Feasibility Study, Cold Regions Research and Engineering Laboratory (CRREL) (AMEC, 2016a).

The following subsections summarize the results of these reports.

Off-post soil gas results are presented in Tables 4.6-10 through 4.6-14 and on Figures 4.6-12 through 4.6-17.

4.6.2.1 Dartmouth College Properties

Soil gas sample locations for the Dartmouth College Properties are presented on Figure 2.6-19. Tables 4.6-10 through 4.6-11 provide hits only summaries of compounds detected in soil gas sampling at the Dartmouth College property compared to the soil gas RSLs and Screening Levels. The data are also presented on Figure 4.6-12. This sampling is documented in the Soil Vapor Investigation Results Rivercrest – Dartmouth College Property (AMEC, 2014l) and the Final Soil Vapor Investigation Results Dartmouth College Properties (AMEC, 2014m). Samples were collected using Summa canisters.

4.6.2.1.1 Cedar/Fletcher Housing May 2013

In May 2013 soil gas samples were collected at three locations in the Dartmouth College housing complex on Cedar Drive and Fletcher Circle. TCE was detected at concentrations ranging from non-detect to 14 µg/m3, which is below the soil gas RSL.

4.6.2.1.2 Rivercrest Property May 2013

In May 2013, 14 samples were collected from five locations on the Dartmouth College Rivercrest property along the north side of the CRREL property. TCE was detected at concentrations ranging

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4.6.2.1.3 Rivercrest Property –January 2014 Supplemental Sampling

In January 2014, samples were collected from the five existing and seven new soil gas sample locations on the Dartmouth College Rivercrest property. TCE concentrations from the five existing wells ranged from 24 µg/m3 91,183 µg/m3 (Figure 4.6-13). Similar to the previous sample results TCE concentrations were highest nearest the CRREL Site boundary at depth of 50 to 75 feet bgs.

The results from the seven additional locations ranged in concentration from non-detect to 180 µg/m3. Similar to the existing location samples the majority of these samples had detected concentrations in the deeper (i.e., 50 feet bgs and 75 feet bgs) intervals and non-detects or estimated values in the shallower samples. The detected concentrations in the 75-foot bgs samples ranged from non-detect to 55 µg/m3. The highest detected concentration was measured in sample SV49-13-08 from the 10-foot bgs interval, which was somewhat inconsistent with other samples collected.

4.6.2.2 Richmond Middle School Property May 2013

In May 2013, soil gas samples were collected in 10 locations west and south of the school building as shown on Figure 2.6-19. This sampling is documented in the Final Soil Vapor Investigation Results Frances C. Richmond Middle School Property (AMEC, 2014k). Samples were collected using Summa canisters.

Sample results are presented on Table 4.6-12 and are compared to the soil gas RSLs and soil gas Screening Levels. TCE concentrations in these samples ranged from non-detect to 53,000 µg/m3 (Figure 4.6-14). TCE for samples collected from 50 feet bgs and above generally showed very low concentrations. Except for one location (farthest northwest near Lyme Road), sampled values at 50 feet or above were non-detect or well below the sub-slab soil vapor screening value of 88 µg/m3. For samples collected at 75 feet bgs, the locations nearest to the CRREL boundary had TCE concentrations ranging from 1,600 µg/m3 to 53,000 µg/m3. In the playing field area, TCE concentrations in samples from 50 feet bgs or above were non-detect or well below the screening value for sub-slab soil vapor. The 75-foot bgs samples in the three locations south of the school ranged from 2.9 µg/m3 to 180 µg/m3.

4.6.2.3 Dartmouth Printing

Soil gas samples were collected at the Dartmouth Printing property in May 2013. Based on the levels of TCE detected in soil gas, further characterization of the Dartmouth Printing property was warranted. In late October 2013, four soil gas implants at 10, 25, 50, and 75 feet bgs were installed at three locations (SV69-13-04, SV69-13-05, and SV69-13-07) and two soil gas implants were installed at location SV69-13-06 (10 feet bgs and 75 feet bgs). Soil gas sample locations for Dartmouth Printing are shown on Figure 2.6-19. This sampling was documented in the Final

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Indoor Air and Sub-Slab Vapor Investigation Results Dartmouth Printing Property (AMEC, 2014n). Samples were collected sing Summa canisters.

Table 4.6-13 contains a hits-only summary of compounds detected in soil gas samples at the Dartmouth Printing property compared to the soil gas RSLs and soil gas Screening Levels.

4.6.2.3.1 Dartmouth Printing May 2013

In May 2013, soil gas samples were collected from three locations on the Dartmouth Printing property west of facility near Lyme Road. Samples were collected from three intervals at each location using Summa canisters.

TCE concentrations ranged from 37 µg/m3 to 1,200,000 µg/m3; concentrations increased with depth at each location. TCE detected in eight of the nine samples exceeded both the soil gas RSL and the Screening Levels. Results for TCE detected in soil gas in the initial sampling at the property is shown in Figure 4.6-15. PCE was also detected in five soil gas samples ranging from non-detect to 40 µg/m3; concentrations did not exceed either the soil gas RSL or Screening Level. Results for PCE are shown in Figure 4.6-16.

4.6.2.3.2 Dartmouth Printing November 2013

On November 7, 2013, the four new soil gas locations and three existing locations were sampled. The samples were analyzed using two methods: off-site analytical laboratory (by Method TO-15) and onsite analysis using BV samplers and a HAPSITE® GC/MS. Samples from the 10 ft bgs soil gas points were collected in SUMMA canisters. Samples from the soil gas points at 25 ft bgs, 50 ft bgs, and 75 ft bgs were collected in Bottle-vacs and analyzed onsite for TCE using the HAPSITE® field GC/MS. these data are presented Table 4.6-14.

TCE was detected at the three existing soil gas points at concentrations ranging from 250 µg/m3 to 7,200 µg/m3 (Figure 4.6-16), which are on the same order of magnitude as the samples collected in May 2013 at these locations. Four of the seven samples from the 10 ft bgs interval exceeded the soil gas RSL of 16 µg/m3.

TCE was detected in each of the 19 samples analyzed using the HAPSITE® field GC/MS at concentrations ranging from 6.4 µg/m3 to 659,758 µg/m3 (Table 4.6-14). The samples collected from the soil gas points at locations SV69-13-01 through SV69-04 had the highest detected concentrations, each in excess of the residential and industrial screening levels. However, the samples collected from the soil gas points at locations SV69-13-05 through SV69-13-07 had much lower concentrations, with six out of seven samples detected at concentrations below the industrial screening value. The one sample with a detected concentration in excess of the industrial screening value was from the 75 ft bgs soil gas point at location SV69-13-07. Only one sample was detected at concentrations below the residential and industrial screening level.

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4.6.3 October 2015 Synoptic Sampling Round

A synoptic round of soil gas sampling was conducted between October 12th and October 14th, 2015 which included both onsite and off-Post sample locations (Figure 2.6-25). This synoptic round is described in the October 2015 Soil Gas Monitoring Data Report for Remedial Investigation and Feasibility Study, Cold Regions Research and Engineering Laboratory. Samples were collected with tedlar bags and analyzed onsite with the HAPSITE® GC/MS. In addition to the tedlar bags samples from the Rivercrest property were collected in Summa canisters and submitted to an off-site laboratory for TO-15 analysis. Results for TCE in soil gas are presented in Tables 4.6- 15 and 4.6-16 and are compared to soil gas RSLs and Screening Level. Figure 4.6-18 show the TCE results for the October 2015 synoptic sample round. Sample results in excess of soil gas RSLs and soil gas Screening Level are shown on Figure 4.6-19 and 4.6-20 respectively.

4.6.3.1 Onsite Soil Gas

The highest concentrations of TCE in soil gas were detected proximal to the AOC 2 and 9 contaminated soil source areas. TCE concentrations on the high end ranged from approximately 1.4M µg/m3 to 2.3M µg/m3 in these source area locations (Figure 4.6-18). Along the northern perimeter of the facility abutting the Rivercrest property concentrations of TCE in soil gas ranged from 6.2 µg/m3 to approximately 450,000 µg/m3. Soil gas locations along Lyme road to the east show concentrations ranging from 513 µg/m3 to 1.5M µg/m3. Along the southern property boundary abutting Dartmouth College Properties TCE concentrations ranged from 0.83 µg/m3 to 66 µg/m3 at shallow locations (2 to 5 feet bgs). Deeper values ranged from 1.9 µg/m3 to 8,896 µg/m3.

4.6.3.2 Dartmouth College Housing, Rivercrest Soil Gas

The highest concentrations of TCE in soil gas on the Rivercrest property were detected along the southern boundary of the property that abuts CRREL (Figure 4.6-18). Concentrations ranged from approximately 30,000 µg/m3 to 150,000 µg/m3 in deep soil gas implants (50 to 75 feet bgs) at SV49-13-01, SV49-13-02, and SV49-13-03, which exceeds the regulatory criteria by over 10-fold. These location are due north of the AOC 2 source area. Shallow samples (less than or equal to 10 feet bgs) across the Rivercrest property ranged from 0.68 µg/m3 to 2,665 µg/m3. The highest shallow soil gas concentration was detected at SV49-13-03 along the facility boundary. Shallow Rivercrest soil gas samples were also analyzed for TCE by USEPA method TO-15. Concentrations of TCE in shallow gas ranged from non-detect to 3,700 µg/m3 in these samples which is consistent with data from the HAPSITE® GC/MS.

4.6.3.3 Dartmouth Housing, Cedar Drive and Fletcher Circle Soil Gas

TCE was detected at very low concentrations in shallow sample location with concentrations ranging from 0.88 µg/m3 to 1.1 µg/m3. The highest concentration was detected at the 75-foot depth in SV25-13-01 at 548 µg/m3. TCE exceeded the USEPA soil gas RSL by over 10-fold at SV25- 13-01. Two locations did not exceed the soil gas Screening Level.

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4.6.3.4 Dartmouth Printing Soil Gas

TCE on the Dartmouth Printing Property ranged in concentration from 0.67 µg/m3 to 2,068 µg/m3 in shallow samples (10 feet bgs); the highest detected concentration was along Lyme Road at SV69-13-03 (Figure 4.6-18). Soil gas TCE concentrations from deeper sample intervals ranged from 0.64 µg/m3 to approximately 450,000 µg/m3. The highest concentrations were detected in the deepest samples (75 feet bgs) along Lyme Road. These locations are the closest to the AOC 2 source area. TCE exceeded the USEPA soil gas RSL at 5 of the 7 locations by over 10 times. TCE exceeded the NHDES residential level of 67 µg/m3 by 10 times the value at three locations along Lyme Road.

4.6.3.5 Richmond Middle School Soil Gas

TCE was detected at low concentrations in each shallow sample location ranging from non-detect to 80 µg/m3. The highest concentrations in shallow soils were detected along Lyme Road. TCE results from deeper samples (50-75 feet bgs) ranged from non-detect to 23,424 µg/m3; the highest concentrations were detected along Lyme Road in the 50- to 75-foot depth range the most proximal to sample locations to the CRREL property boundary. TCE exceeded the USEPA soil gas RSL by over 10-fold at 5 soil gas implant locations. Two locations exceeded the NHDES residential level by over 10 times the value.

4.6.3.6 October 2015 Soil Gas Summary

The highest TCE soil gas concentrations detected during this round of sampling are located on the CRREL facility in the areas of AOC 2 and 9. The highest off-site TCE soil gas samples are located along Lyme Road in the area of SV69-13-01, SV69-13-02, SV69-13-03, and SV63-13-01.

Figures 4.6-21 shows the interpolated footprint of the TCE impacts to soil gas in excess of 100 µg/m3 based on the October 2015 data. For comparison, Figure 4.6-22 presents the interpolated footprint of TCE impacted soil gas from previous sampling events. Comparison of these data show that the footprint of TCE impacted soil gas has remained relatively unchanged over a 5-year period. However, concentrations in this sampling round at the core of the TCE impacted areas are lowers but at the Rivercrest development are slightly higher, which may be a result of the soil vapor extraction pilot test (see Section 4.8).

4.7 Indoor Air

Since March 2010, the USACE-NAE has been investigating the VI pathway from soil gas into the indoor air of several buildings at CRREL. VI samples detected TCE and other contaminants in indoor air at several facility buildings. Mitigation of VI impacts to indoor air is currently ongoing at the Site. Assessments and monitoring of indoor air quality have been completed at the facility and indoor air monitoring is ongoing to understand the extent of TCE impacts and protect receptors within the buildings. (AECOM, 2012 and AMEC 2012).

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The purpose of the indoor air and sub-slab vapor sampling program is to determine existing conditions of indoor air quality within designated CRREL buildings, to assess the effectiveness of mitigation, and to assess the potential need for operational modifications to mitigation systems for protection of human health.

A summary of sampling events conducted at CRREL are presented in Table 4.7-1.

It is recognized that although the indoor air data were collected to investigate the potential vapor intrusion pathway, some compounds detected in indoor air are not associated with vapor intrusion. Volatiles detected in indoor air could also be associated with use of the compounds in the buildings, with contaminated building materials that release vapors, or with the outdoor air that is entering the buildings. This possibility has been investigated as part of the evaluation performed in Appendix U.

Indoor air sampling was also conducted at buildings on properties adjacent to CRREL. Based on the findings of the onsite soil gas investigation initiated in May 2012 and the subsequent off-Post soil gas investigations the COE-NAE initiated further investigation to determine if TCE vapors are migrating through soils to buildings on properties adjacent to CRREL (AMEC, 2013b).

The off-Post air investigation was conducted at the following properties adjacent to the CRREL facility (Figure 1.4-1):

1. 63 Lyme Road current location of Richmond Middle School. 2. 64 Lyme Road current location of Brendel & Fisher Wealth Management. 3. 68 Lyme Road current location of Hanover Chiropractic. 4. Five Dartmouth Housing residences on Fletcher Circle and Cedar Drive (Dartmouth College Properties). 5. Rivercrest Housing Development (Dartmouth College Properties), currently an undeveloped property. 6. 69 Lyme Road, current location of Dartmouth Printing.

The Site and off-Post indoor air and sub-slab sampling investigation results are presented in the following sub sections.

Ambient air samples were collected during each sampling event. These samples were collected to evaluate vapor encroachment (vapors entering structures via outdoor ambient air) which may potentially impact indoor air quality within the structures. Ambient air sample results are discussed in more detail below.

Indoor Air results are compared to the following criteria:

• Interim Action Level – Site specific action level for TCE calculated by the USACE-NAE; this is used for comparison to onsite indoor air samples.

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3 o Adult Interim Action Level - 8.8 µg/m compared to areas used by only adults.

3 o CDC Interim Action Level -7 µg/m for the first floor (not the basement) of the CDC. • USEPA RSLs – This criteria is used for comparison to off-Post indoor air samples.

o Residential RSL - Resident Ambient Air.

o Industrial RSL - Composite Worker Ambient Air Table. • Soil Gas Screening Levels – NHDES Vapor Intrusion Screening Levels (revised February 2013) for comparison to both onsite and off-Post indoor air.

4.7.1 Onsite Indoor Air Investigation

As stated previously in Section 2.6, the results of onsite indoor air and sub slab soil gas sampling at CRREL has been documented in the following reports:

1. Addendum to the Project Work Plan for the Vapor Intrusion Investigation at the Cold Regions Research and Engineering Laboratory (AECOM, 2011). 2. Interim Vapor Intrusion Data Report for the Cold Regions Research and Engineering Laboratory (AECOM, 2012). 3. Final Indoor Air Assessment Investigation Event 7 Results for Cold Regions Research and Engineering Laboratory, (AMEC, 2014c). 4. Final Indoor Air Assessment Investigation Event 8 Results for Cold Regions Research and Engineering Laboratory, (AMEC, 2014d). 5. Final Indoor Air Assessment Investigation Event 9 Results for Cold Regions Research and Engineering Laboratory, (AMEC, 2014h). 6. Final Indoor Air Assessment Investigation Event 10 Results for Cold Regions Research and Engineering Laboratory, (AMEC, 2014i). 7. Final Indoor Air Assessment Investigation Event 11 for Cold Regions Research and Engineering Laboratory, (AMEC, 2015).

Data from Events 7 through 11 are presented in this report. Refer to the AECOM reports (AECOM, 2011 and 2012) listed above for Events 1 through 6.

The following sub-sections provide a summary of data presented in the Event 7 through 11 reports. Figures referenced in the following subsections present nature and extent of known TCE contamination in indoor air and sub slab vapor. Where sufficient indoor air data exist, figures showing a time series summary of TCE concentrations are presented. Time series figures show where TCE was detected in indoor air and sub-slab samples from sampling Events 1 through 11.

Tables 4.7.-2 through 4.7-7 show the results of vapor intrusion sampling and Radiello samples collected during indoor air sampling Event 7.

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Tables 4.7.-8 through 4.7-11 show the results of vapor intrusion samples collected during air sampling Event 8.

Tables 4.7-12 through 4.7-15 show the results of vapor intrusion samples collected during air sampling Event 9.

Tables 4.7-16 through 4.7-19 show the results of vapor intrusion samples collected during air sampling Event 10.

Tables 4.7-20 through 4.7-23 show the results of vapor intrusion samples collected during air sampling Event 11.

Ongoing monitoring of indoor air at CRREL buildings is conducted using a HAPSITE® gas chromatograph. Data generated is used to evaluate the potential risk to human health from TCE vapor. HAPSITE® monitoring of TCE concentrations in indoor air was initiated in late October 2012 and occurs daily in the Main Lab building, once weekly in the LMO, and once monthly in the TIAC and CDC. HAPSITE® data are presented in Appendix T.

4.7.1.1 Radiello and Summa Comparison

As part of the indoor air investigation, in order to evaluate the accuracy of the Radiello passive- diffusion sample method compared to Summa canisters, twenty-six co-located indoor air and three ambient air samples were collected during characterization activities. Results from the Radiello samplers were compared to the Summa canister results (AMEC, 2014a) (Table 4.7-6). Eighty- four sets of detections in both the TO-15 results and co-located Radiello results were observed in the overall data set. Thirteen sets of detections for TCE only were observed. A linear regression of the paired data was performed for the overall and TCE only paired data sets. The ideal distribution of data are described by a slope of one and an intercept of zero, (USACE EM 200-1- 16 [USACE, 2013]). The correlation coefficient demonstrates the degree of association between the TO-15-Summa canister method and the 8240-Radiello method. A perfect correlation is demonstrated by a correlation coefficient of one.

Summary data from this evaluation is provided in Appendix L. For the data set overall, which includes the target analytes reported, the regression slope (0.65) is statistically significant at the 95 percent probability level and indicates fair agreement of the data, while the correlation coefficient (0.98) indicates good agreement of the data. For the subset of TCE only data, the regression slope (0.94) is statistically significant at the 95 percent probability level indicates good agreement of the data and the correlation coefficient (1.0) also indicates good agreement of the data.

This Site-specific study indicates the Radiello samplers provided reliable results for TCE and suggests that Radiello samplers can be used in place of Summa canisters for monitoring of indoor air locations for the primary Site contaminant.

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4.7.1.2 Onsite Ambient Air

Ambient air samples were collected from outdoor locations during onsite vapor intrusion sampling Events 7 through 11.

TCE ambient air concentrations for Event 7 ranged from non-detect to 1.5 µg/m3 (Table 4.7-2; Figure 4.7-1). The highest concentrations were located at AOC 2 and AOC 9.

TCE was detected in each of the 20 ambient air samples collected over the two-week period during Event 8 with concentrations ranging from 0.15 µg/m3 to 77 µg/m3 (Table 4.7-8; Figure 4.7-2). Consistent with the previous event, the highest concentrations of TCE in ambient air were from samples collected in the vicinity of AOC 2 and AOC 9.

Event 9 ambient air samples were collected over a two-week period (Table 4.7-12; Figure 4.7-3). TCE was not detected in ambient air samples during the week 1 sampling program. TCE was detected in four of the eight ambient locations during the week 2 sampling program. Detected concentrations of TCE ranged from 0.086J µg/m3 to 0.44J µg/m3. Consistent with the previous events, the highest concentrations of TCE in ambient air were from samples collected in the vicinity of AOC 2 and AOC 9.

Event 10 ambient air samples were collected over a two-week period (Table 4.7-16; Figure 4.7-4). TCE was detected in five of the eight ambient air samples during the week 1 sampling Program. Detected concentrations of TCE ranged from 0.075J µg/m3 to 0.50J µg/m3. TCE was detected in nine of the twelve ambient air locations during the week 2 sampling program. Detected concentrations of TCE ranged from 0.10J µg/m3 to 0.64 µg/m3. The highest concentration of TCE in ambient air for this event was from a location on the east side of the FERF.

TCE was detected in two of the thirteen ambient air locations sampled during Event 11 (Table 4.7- 20; Figure 4.7-5). Detected concentrations of TCE ranged from 0.064J µg/m3 to 0.13J µg/m3. The highest concentration of TCE in ambient air was from the location on the west side of the FERF.

TCE was the only compound detected in the ambient air samples exceeding the USEPA Industrial RSL and the Interim Action Level. During Event 8 TCE concentrations in three ambient air samples exceed the Interim Action Level of 8.8 µg/m3 and the Industrial RSL of 3 µg/m3 was exceeded in six samples.

4.7.1.3 Main Laboratory Basement

Figures 4.7-6 through 4.7-10 show the results for TCE of indoor air, Heating Ventilation and Air Conditioning (HVAC), and sub-slab samples collected in the Main Laboratory Basement for Events 7 thru 11. Areas sampled include the Lab Addition, Machine Room, Mechanical Room, and Northeast Basement. Fourteen indoor air samples and a duplicate sample were collected. Twelve sub-slab samples and two duplicate samples were collected; most were paired with indoor air samples. Two HVAC system samples were collected; one within the building and one exterior to the building.

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Figure 4.7-11 shows a time series summary of TCE concentrations from samples collected during Events 1 through 11 compared to the indoor air interim action level. Eleven of the 16 indoor air samples and 13 of 13 sub-slab samples have periodically exceeded the interim action level. Ambient air samples collected from two HVAC intakes have also periodically exceeded the interim action level. Indoor air concentrations of TCE did not exceed the interim action level during the last two sample events.

Other compounds detected at concentrations above USEPA Industrial RSLs include 1,2-dichloroethane, 1,3-butadiene, chloroform, and ethyl benzene.

4.7.1.4 Main Laboratory First Floor

Figure 4.7-12 through 4.7-16 shows the TCE results from indoor air and HVAC samples collected in the Main Laboratory 1st floor for each sampling event.

Nine indoor air samples were collected throughout the floor. Two HVAC system samples were collected exterior to the 1st floor.

Figure 4.7-17 shows a time series summary of TCE concentrations from samples collected during Events 1 through 11 compared to the indoor air interim action level. Eight of the 9 indoor air samples have periodically exceeded the interim action level. However, indoor air TCE concentrations have been below the interim action level for the last three sample events.

Other compounds detected at concentrations greater than USEPA Industrial RSLs include 1,2-dichloroethane, benzyl chloride, chloroform, hexachlorobutadiene, and tetrachloroethene.

4.7.1.5 Main Laboratory Second Floor

Figure 4.7-18 through 4.7-22 shows the TCE results from indoor air and HVAC samples collected in the Main Laboratory 2nd floor for Event 7 through 11.

Figure 4.7-23 shows a time series summary of TCE concentrations from samples collected in the Main Lab second floor during Events 1 through 11 compared to the indoor air interim action level. Five of the 6 indoor air samples have periodically exceeded the interim action level. However, indoor air TCE concentrations have been below the interim action level for the last three sample events.

Other compounds detected at concentrations greater than USEPA Industrial RSLs include 1,4- dichlorobenzene and chloroform.

4.7.1.6 Main Laboratory Addition Sub-Basement

Figures 4.7-24 through 4.7-28 shows the TCE results for indoor air, HVAC, and sub-slab samples collected in the Main Laboratory Addition Sub-Basement for Events 7 through 11.

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Nine indoor air samples were collected in the Sub-Basement. Seven sub-slab samples were collected and paired with indoor air samples. Three HVAC system samples were collected; HV-01 and 02 are intake and outtake structures, respectively. Sample HV-03 is an HVAC intake sample.

Figure 4.7-29 shows a time series summary of TCE concentrations from Event 1 through Event 11 for TCE in indoor air and sub-slab vapor in the Main Lab Addition Sub-Basement. Indoor air and sub-slab samples have periodically exceeded the interim action level; however, indoor air TCE concentrations have been below the interim action level for the last two sampling events.

Other compounds detected at concentrations greater than USEPA Industrial RSLs include 1,2-dichloroethane, chloroform, and dichlorodifluoromethane.

4.7.1.7 Child Development Center

Figures 4.7-30 through 4.7-34 shows the TCE results for indoor air and sub-slab samples collected in the CDC for Event 7 through 11. A sub-slab mitigation system is currently in place and operating at the CDC.

Four indoor air samples were collected on the first floor of the CDC and four were collected in the basement area (one duplicate). Six sub-slab samples were collected in the basement.

Figure 4.7-35 shows a time series summary of TCE concentrations from samples collected at the CDC during Events 1 through 11 compared to the interim action levels. TCE concentrations in indoor air continue to be below risk-based concentrations over eight rounds of sampling.

4.7.1.8 Logistics Management Facility

Figures 4.7-36 through 4.7-40 shows the TCE results for indoor air, HVAC, and sub-slab samples collected at the LMO for Events 7 through 11.

Seven indoor air and seven sub-slab samples were collected in the LMO. One duplicate sub-slab sample and one HVAC system sample were also collected.

Figure 4.7-41 shows a time series summary of TCE concentrations from samples collected during Events 1 through 11 compared to the interim action level at the LMO. TCE concentrations in the indoor air and sub-slab samples have periodically exceeded the interim action level; however, indoor air concentrations have been below the interim action level for the last seven sampling events.

Other compounds detected at concentrations greater than USEPA Industrial RSLs include ethyl benzene, xylene (m&p), benzene and bromomethane.

4.7.1.9 Vehicle Storage Area

Two indoor air and one sub slab sample were collected in the Vehicle Storage Area Building. Figure 4.7-42 through 4.7-46 show the results of TCE concentrations from Events 7 through 11.

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Figure 4.7-47 shows a time series summary of TCE concentrations from samples collected during Events 1 through 11 compared to the interim action levels at the Vehicle Storage. Results did not exceed the interim action level for TCE.

Other compounds detected at concentrations greater than USEPA Industrial RSLs include ethyl benzene, xylene (o), and xylene (m&p),

4.7.1.10 Greenhouse

Figures 4.7-48 through 4.7-52 show the TCE results for indoor air collected in Events 7 through 11. TCE has not been detected in excess of the interim action levels in the Greenhouse.

Figure 4.7-53 shows a time series summary of TCE concentrations from samples collected during Events 1 through 11 concentrations compared to the interim action level at the Greenhouse. Results did not exceed the interim action level for TCE.

Other chemicals detected at least once at concentrations above USEPA industrial RSLs in indoor air include benzene, bromodichloromethane, and chloroform.

4.7.1.11 Frost Effects Research Facility

Figures 4.7-54 through 4.7-58 show the TCE results for indoor air collected in Events 7 through 11. Four indoor air samples were collected in the FERF as well as one duplicate. TCE was detected at concentrations ranging from 1.3 µg/m3 to 26 µg/m3.

Figure 4.7-59 shows a time series summary of TCE concentrations from samples collected during Events 1 through 11 compared to the interim action levels at the FERF. In two of the four samples collected during Event 7 had concentrations of TCE detected at concentrations exceeding the interim action level. Concentrations have been below the interim action level for the last four sampling events.

Other compounds detected at concentrations greater than USEPA Industrial RSLs include chloroform, dichlorodifluoromethane, benzene, and tetrachloroethene.

4.7.1.12 DPW Storage

Figure 4.7-60 shows the TCE results for indoor air collected in Event 7. Two indoor air samples were collected in the DPW Storage area. TCE concentrations in indoor air were low (0.21 µg/m3 and 0.26 µg/m3), and below the interim action level.

No other chemicals were detected at concentrations above USEPA industrial RSLs in indoor air.

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4.7.1.13 Ballistics Laboratory

Figure 4.7-61 shows the TCE results for indoor air collected in Event 7. One indoor air sample was collected in the Ballistics Lab. TCE was detected at a concentration of 0.7 µg/m3, and below the interim action level.

Only 1,3-butadiene was detected at a concentration above the USEPA industrial RSLs in indoor air.

4.7.1.14 Project Support Facility

Figure 4.7-62 shows the TCE results for indoor air collected in Event 7. Two indoor air samples were collected in the Project Support Facility. TCE concentrations in indoor air were low (0.28 µg/m3 and 0.39 µg/m3), and below the interim action level.

No other chemicals were detected at concentrations above USEPA industrial RSLs in indoor air.

4.7.1.15 Asphalt Laboratory

Figure 4.7-63 shows the TCE results for indoor air collected in Event 7. One indoor air sample was collected at the Asphalt Lab during Event 7. TCE was detected at a concentration of 0.97 µg/m3, and below the interim action level.

No other chemicals were detected at concentrations above USEPA industrial RSLs in indoor air.

4.7.1.16 Exterior Sheds

Figure 4.7-64 shows the TCE results for indoor air collected in Event 7. Indoor air in three exterior sheds was sampled. Each shed sampled was built on a concrete slab. TCE concentrations in the sheds were low and ranged from 0.3 µg/m3 to 1.7 µg/m3. These concentrations are below the interim action level.

Ethylbenzene and xylene (m&p) were detected at location EX03 exceeding the USEPA industrial RSL.

4.7.1.17 South Gate House

Figures 4.7-65 through 4.7-67 shows the TCE results for indoor air collected in Events 9 through Event 11.

TCE was not detected in the indoor air samples.

Figure 4.7-68 shows a time series summary of TCE concentrations from samples collected during Events 1 through 11 compared to the interim action levels.

No other chemicals were detected at concentrations above USEPA industrial RSLs in indoor air.

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4.7.1.18 North Gate House

Figures 4.7-69 through 4.7-71 shows the location of and TCE results for indoor air samples collected at the North Gate House in Events9 through 11.

TCE was detected in indoor air samples at concentrations of 0.059 µg/m3 and 0.086J µg/m3, which were less than the interim action level.

Figure 4.7-72 shows a time series summary of TCE concentrations from samples collected during Events 9 through 11 compared to the interim action levels.

No other chemicals were detected at concentrations above USEPA industrial RSLs in indoor air.

4.7.1.19 Technical Information Analysis Center

Figures 4.7.-73 through 4.7-75 shows the location of and TCE results for indoor air, HVAC, and sub-slab vapor samples collected at the TIAC in Events 9 through 11.

Four indoor air samples, four sub-slab samples, and one HVAC system sample were collected in the TIAC. TCE has not been detected at concentrations exceeding the interim action level in indoor or ambient air (HVAC) samples. Sub-slab samples have periodically exceeded the interim action level.

Figure 4.7-76 shows a time series summary of TCE concentrations from samples collected during Events 9 through Event 11 compared to the interim action levels.

Other compounds detected at concentrations greater than USEPA Industrial RSLs include 1,3- butadiene, benzene, ethyl benzene, and xylene (o).

4.7.2 Off-Post Indoor Air Investigations

Indoor air and sub-slab soil vapor investigations were conducted to provide an assessment of indoor air quality conditions and sub-slab conditions at properties located east of the CRREL Facility, the five closest Dartmouth College housing units to the south boundary of CRREL, and adjacent properties located to the north east and east of CRREL (Figure 1.4-1) including the Richmond Middle School.

In March 2013, USACE-NAE representatives contacted neighboring property owners to inform them of the presence of deep soil vapor contamination at the facility boundary. Each of the parties contacted agreed that sampling of indoor air and sub-slab soil vapor was warranted in nearby buildings to determine if TCE is present.

A summary of off-Post sampling events is presented in Table 4.7-24.

The results of these sampling events have been documented in the following reports.

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Extensive indoor air sampling has been conducted at off-Post property locations. Six rounds of sampling have been conducted at the Richmond Middle School. Two rounds of sampling have been conducted at Dartmouth Properties, 64 Lyme Road, 68 Lyme Road, and 69 Lyme Road (Figure 1.4-1). The results of these sampling efforts are documented in the following reports.

1. Final Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, April 1, 2013 Sampling Event. (AMEC, 2014o). 2. Final Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, July 31, 2013 Sampling Event. (AMEC, 2014p). 3. Final Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, January 3, 2014 Sampling Event. (AMEC, 2014q). 4. Final Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, April 15, 2014 Sampling Event. (AMEC, 2014r). 5. Final Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, August 12, 2014 Sampling Event. (AMEC, 2014s). 6. Final Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, January 19 and 24, 2015 Sampling Event. (AMEC, 2015b). 7. Final Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, August 13, 2015 Sampling Event. (AMEC, 2015c). 8. Final Indoor Air and Sub-Slab Investigation Results 64 Lyme Road, Hanover, NH (AMEC, 2014t). 9. Final Indoor Air and Sub-Slab Investigation Results Round #2 64 Lyme Road, Hanover, NH (AMEC, 2014u). 10. Final Indoor Air and Sub-Slab Investigation Results 68 Lyme Road, Hanover, NH (AMEC, 2014v). 11. Final Indoor Air and Sub-Slab Investigation Results Round #2 68 Lyme Road, Hanover, NH (AMEC, 2014w). 12. Final Indoor Air and Sub-Slab Investigation Results for Five Dartmouth College Housing Units (AMEC, 2014x). 13. Final Indoor Air and Sub-Slab Investigation Results for Five Dartmouth College Housing Units Round #2 (AMEC, 2014y). 14. Final Indoor Air and Sub-Slab Investigation Results Dartmouth Printing Property (AMEC, 2014z). 15. Final Vapor Intrusion and Soil Vapor Investigation Results Dartmouth Printing Property (AMEC, 2014aa).

The following subsections provide a summary of the results from these reports.

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For ease of assessment, two tables are provided for each off-Post property that was investigated. The first table presents results for TCE only, the second presents a hits-only summary of the full TO-15 analysis.

Brendel & Fisher is located at 64 Lyme Road abutting the eastern boundary of CRREL. Table 4.7-25 through Table 4.7-27 and Figure 4.7-77 present the vapor intrusion sampling results.

Hanover Family Chiropractic & Hanover Yoga occupy a building at 68 Lyme Road abutting the eastern boundary of CRREL Tables 4.7-28 through Table 4.7-30 and Figure 4.7-78 present the vapor intrusion sampling results.

Dartmouth College Housing consists of five residences abutting the southern boundary of CRREL. Table 4.7-31 through, Table 4.7-33 and Figure 4.7-79 present the vapor intrusion sampling results.

Dartmouth Printing is located at 69 Lyme Road to the northeast of the CRREL Facility. Table 4.7-34 through Table 4.7-36 and Figures 4.7-80 and 4.7-81 present the vapor intrusion sampling results.

Richmond Middle School is located at 63 Lyme Road to the east of the CRREL Facility. Table 4.7-37 through Table 4.7-39 and Figures 4.7-82 through 4.7-90 present the vapor intrusion sampling results.

4.7.2.1 Brendel & Fisher, 64 Lyme Road April 2013

In April 2013, TCE was detected in four indoor air samples collected at 64 Lyme Road, however, three of the four results are estimated values that are below the LOD (i.e., J-qualified). The concentration of TCE in indoor air ranged from 0.16J µg/m3 to 0.75 µg/m3. The highest TCE concentrations were detected in two air samples on the first floor and TCE was not detected in either of the two sub-slab vapor samples. These results indicate that the indoor air concentrations are possibly from ambient air rather than soil vapor intrusion.

Trans-1,2-dichloroethene (trans-1,2-DCE) was also detected in the April 2013 vapor intrusion samples at concentrations in excess of NHDES residential and industrial indoor screening levels (12 µg/m3 and 53µg/m3 respectively). Concentrations of trans-1,2-DCE ranged from 190 µg/m3 to 420 µg/m3 in indoor air. Concentrations in sub-slab samples were 7.9 µg/m3 and 5,700 µg/m3. Although trans-1,2 DCE has been detected in samples collected at the CRREL Facility, the levels detected in vapor intrusion samples collected at 64 Lyme Road are several orders of magnitude higher.

The highest sub-slab trans-1,2 DCE concentration was detected in the recently renovated area of the building. Blue foam insulation was observed immediately below the concrete slab during the installation of vapor point 64RM01. A materials safety data sheet for a commonly used foam insulation that shows trans-1,2-DCE as a component. The presence of this foam beneath the concrete slab may be the source of trans-1,2-DCE detected in sub-slab and indoor air.

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One ambient air sample was collected outside on April 2, 2013 to the northwest of the building at 68 Lyme Road. Winds were primarily from the west at the time of sample deployment. TCE was not detected in that sample.

4.7.2.2 Brendel & Fisher, 64 Lyme Road November 2013

In November 2013, TCE was detected in three indoor air samples collected from 64 Lyme Road at low levels. Two of the three are estimated values below the LOQ (i.e., J-qualified). The concentration of TCE in indoor air ranged from 0.19J µg/m3 to 0.54 µg/m3. The results for TCE detected in indoor air are similar to sample results collected in the April round of sampling.

The highest TCE concentration was detected in an indoor air sample collected in the basement which does not exceed the USEPA indoor air industrial RSL of 3 µg/m3. TCE was detected in one sub-slab vapor sample at 2.8 µg/m3 at location 64RM-02 which is below the USEPA soil gas RSL and the NHDES soil gas screening level.

Trans-1,2-DCE was detected in indoor air at concentrations in excess of NHDES indoor air residential and industrial Preliminary Action Levels (PALs). Concentrations of trans-1,2-DCE ranged from 210 µg/m3 to 1,400 µg/m3 in indoor air. Sub-slab vapor samples showed trans-1,2- DCE at concentrations of 22 µg/m3 and 16,000 µg/m3. As discussed previously the presence of a foam insulation beneath the concrete slab may be the source of trans-1,2-DCE detected in sub- slab and indoor air.

One ambient air sample was collected outside on November 7, 2013 to the west side of the building at 64 Lyme Road. Winds were primarily from the west at the time of sample deployment. TCE was not detected in the ambient air sample.

4.7.2.3 Hanover Family Chiropractic & Hanover Yoga, 68 Lyme Road April 2013

In April 2013, TCE was detected in two of the five indoor air samples collected at 68 Lyme Road; however, both detections are estimated values below the Limit of Quantitation (LOQ) (i.e., J- qualified). The concentration of TCE in indoor air ranged from non-detect to 0.2J µg/m3, which is below the USEPA indoor air industrial RSL and the NHDES residential screening levels.

TCE was detected in three sub-slab vapor samples, ranging from 0.64J µg/m3 to 1.8 µg/m3, with two of the three as J estimated values that are below the LOQ. These concentrations are below the USEPA soil gas RSL and the NHDES soil gas screening level

One ambient air sample was collected outside on April 2, 2013 to the northwest of the building at the CRREL fence. Winds were primarily from the west at the time of sample deployment. TCE was not detected in the sample.

4.7.2.4 Hanover Family Chiropractic and Hanover Yoga, 68 Lyme Road November 2013

In November 2013, TCE was detected in four of the five indoor air samples collected at 68 Lyme Road. The detected concentrations in indoor air ranged from 1.3 µg/m3 to 3.2 µg/m3. TCE was

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One ambient air sample was collected outside on November 7, 2013; winds were primarily from the west at the time of sample deployment. The sample was located between the building and the CRREL facility at the perimeter fence. TCE was not detected in the ambient air sample.

4.7.2.5 Dartmouth College Housing, Cedar Drive and Fletcher Circle April 2013

In April 2013, TCE was detected in eight of eleven indoor air samples collected from the Dartmouth College Housing, however, the detections were J estimated values. The concentration of TCE in indoor air samples ranged from non-detect to 0.31J µg/m3 which is below the USEPA indoor air residential RSL and the NHDES residential screening levels.

TCE was detected in four of five sub-slab vapor samples, but again the values were estimated and below the LOQ (i.e., J estimated). The concentration of TCE in sub-slab samples ranged from non-detect to 0.64J µg/m3; below the USEPA soil gas RSL and the NHDES soil gas screening level.

One ambient air sample was collected on April 2, 2013 to the north of the building at 19 Fletcher Circle. Winds were primarily from the west at the time of sample deployment. TCE was not detected in the sample.

4.7.2.6 Dartmouth College Housing, Cedar Drive and Fletcher Circle October 2013

In October 2013, TCE was detected in the 1st floor and basement indoor air samples at 23 Fletcher Circle at 0.44J µg/m3 and 0.22J µg/m3, respectively, both detections were estimated values that are below the LOQ. TCE was also detected in the 1st floor indoor air sample at 25 Fletcher Circle at 0.086J µg/m3, also an estimated value. These concentrations detected in indoor air are below the USEPA indoor air residential RSL and the NHDES residential screening levels for TCE.

TCE was detected in sub-slab samples at 12 Cedar Drive, 19 Fletcher Circle and 24 Fletcher Circle at 0.18J µg/m3, 1.4 µg/m3, and 0.15J µg/m3, respectively. Two of the detected concentrations are estimated values and are well below the USEPA soil gas RSL and the NHDES soil gas screening level.

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Five ambient air samples were collected on October 24, 2013; winds were primarily from the west at the time of sample deployment. TCE was not detected in ambient air samples.

4.7.2.7 Dartmouth Printing, 69 Lyme Road September 2013

In September 2013, TCE was detected at low concentrations in 3 of 11 indoor air samples collected from 69 Lyme Road. Concentrations in indoor air samples ranged from non-detect to 0.38J µg/m3. Concentrations of TCE in indoor air did not exceed the USEPA indoor air industrial RSL of 3 µg/m3.

TCE was detected in sub-slab vapor samples at each location. Concentrations of TCE in soil vapor ranged from non-detect to 22 µg/m3. Concentrations of TCE in soil vapor beneath the slab exceed the USEPA soil gas RSL and the NHDES soil gas screening level.

PCE was detected at low concentrations in 10 of 11 indoor air samples. Concentrations in indoor air samples ranged from non-detect to 1.1 µg/m3, which is less than the USEPA indoor air industrial RSL of 47 µg/m3. The presence of PCE in indoor air may be attributable to Brakleen® which is used as a machine parts cleaner.

Sub-slab samples showed the presence of PCE in each sample ranging from 6.6 µg/m3 to 460 µg/m3. PCE was detected in 2 of 10 samples in excess of the NHDES industrial soil gas screening level of 100 µg/m3. Previous sampling of soil vapor (AMEC, 2013c) outside the building footprint showed the presence of PCE in 2 of 3 samples collected at the 10-foot depth interval. Detected concentrations were 3.9 µg/m3 and 30 µg/m3 in shallow soil vapor.

Four ambient air samples were collected on September 26, 2013. TCE was not detected in ambient air samples.

4.7.2.8 Dartmouth Printing, 69 Lyme Road February 2014

In February 2014, TCE was detected at low concentrations in 8 of 11 indoor air samples collected at 69 Lyme Road. Concentrations in indoor air samples ranged from non-detect to 0.34J (estimated) µg/m3. Concentrations of TCE detected in indoor air were more than an order of magnitude lower than the indoor air action level of 8.8 µg/m3.

TCE was detected in 9 of 10 sub-slab samples at concentrations ranging from 0.07J µg/m3 to 1.5 µg/m3. Concentrations of TCE in soil vapor beneath the slab do not exceed the USEPA soil gas RSL and the NHDES soil gas screening levels.

PCE was detected at each indoor air sample location. Concentrations in indoor air samples ranged from 0.095J µg/m3 to 45 µg/m3. The presence of PCE in indoor air may be attributable to the legacy use of Brakleen® as a machine parts cleaner.

Sub-slab samples showed the presence of PCE in each sample ranging from 1.6 µg/m3 to 350 µg/m3. PCE was detected in 1 of 10 samples in excess of the NHDES industrial soil gas screening level of 100 µg/m3.

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Four ambient air samples were collected on February 27, 2014. TCE was detected in 4 of 4 ambient air sample locations at estimated concentrations ranging from 0.17J µg/m3 to 0.19J µg/m3. PCE was not detected in ambient air samples.

4.7.2.9 Richmond Middle School, 63 Lyme Road April 2013

In April 2013, TCE was detected in 11 of 14 indoor air samples collected from the Richmond Middle School. The concentration of TCE in indoor air ranged from non-detect to 1.2 µg/m3. The highest TCE concentrations were detected in Room 715 and 717, the Woodworking and Living Arts rooms, respectively.

TCE was detected in 8 of 10 sub-slab vapor samples. The concentration of TCE in sub-slab samples ranged from non-detect to 0.86 µg/m3. The highest TCE concentrations were detected in samples below Room 800 and 807, the science room and the social studies room, respectively. TCE concentrations were below the USEPA soil gas RSL and the NHDES soil gas screening levels.

Four ambient air samples were collected on April 1, 2013; winds were primarily from the west- southwest. TCE was detected in 3 of 4 samples. The highest concentration of TCE in ambient air was detected at the northern-most location at 0.91 µg/m3, which is not dissimilar to the indoor air concentrations. Wind was primarily from the west-southwest at the time of sample deployment.

4.7.2.10 Richmond Middle School, 63 Lyme Road July 2013

In July 2013, TCE was not detected in the 15 indoor air samples which were collected.

TCE was detected in five of ten sub-slab vapor samples; however, four of the five detections at J estimated levels. The single sample with a non-estimated concentration of TCE in sub-slab soil vapor was measured at 5.9 µg/m3 (beneath Room 721). TCE concentrations were below the USEPA soil gas RSL and the NHDES soil gas screening levels.

Four ambient air samples were collected on July 31, 2013; winds were light. TCE was not detected.

4.7.2.11 Richmond Middle School, 63 Lyme Road January 2014

In January 2014, TCE was not detected in the 15 indoor air samples which were collected.

TCE was detected at low concentrations in six of ten sub-slab vapor samples, only one of the six detections was not a J estimated value. The single sample with a non-estimated concentration of TCE in sub-slab soil vapor was measured at 2 µg/m3 (beneath Room 80). TCE concentrations were below the USEPA soil gas RSL and the NHDES soil gas screening levels.

Five ambient air samples were collected on January 3, 2014; winds were light from the west. TCE was detected in both samples collected to the west of the RMS at concentrations of 0.086 µg/m3 and 0.1 µg/m3. Samples collected to the north, east, and south were non-detect for the presence of TCE.

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4.7.2.12 Richmond Middle School, 63 Lyme Road April 2014

In April 2014, TCE was detected at a low concentration in one of 15 indoor air samples and was detected below the LOQ and reported as a J estimated value Limits of Detection (LOD). TCE was detected at low concentrations in three of ten sub-slab vapor samples.

Four ambient air samples were collected on April 15, 2014; wind was gusting from the south. TCE was not detected in these samples.

4.7.2.13 Richmond Middle School, 63 Lyme Road August 2014

In August 2014 TCE was not detected in the 15 indoor air samples which were collected. TCE was detected in 3 of 10 sub-slab vapor samples at low concentrations ranging from 0.11J µg/m3 to 0.97 µg/m3.

None of the samples collected showed values approaching the interim action levels for TCE. No sub-slab or indoor air concentration exceeded the USEPA indoor air industrial RSL or the NHDES residential screening levels for TCE.

Four ambient air samples were collected on August 12, 2014 winds were gusting from the southeast. TCE was detected in 3 of 4 samples. Ambient air samples collected outside the school were non-detect for the presence of TCE.

4.7.2.14 Richmond Middle School, 63 Lyme Road January 2015

TCE was detected the 15 indoor air samples which were collected January 19, 2015. With the exception of the indoor air sample collected in the cafeteria, concentrations of TCE in indoor air were below the USEPA indoor air industrial RSL and the NHDES residential screening levels ranging from 0.28J µg/m3 to 2.1 µg/m3. The TCE result in the Cafeteria was 2,600 µg/m3. Based on this result, additional indoor air sampling was conducted on January 24, 2015.

TCE was detected 14 of the 15 indoor air samples which were collected January 24, 2015. TCE was detected at low concentrations ranging from 0.086J µg/m3 to 0.24J µg/m3, and were below the USEPA indoor air industrial RSL and the NHDES residential screening levels. TCE was detected in 9 of 11 sub-slab vapor samples at low concentrations ranging from 0.27J µg/m3 to 7.5 µg/m3.

For the January 24th sampling, there was no sub-slab or indoor air concentration exceeding interim action levels for TCE.

Four ambient air samples were collected on January 19th, winds were intermittingly gusting from the southwest. With the exception of the ambient air sample collected at the south end of the building, concentrations of TCE in ambient air were below the USEPA indoor air industrial RSL and the NHDES residential screening levels ranging from 0.35J µg/m3 to 1.2 µg/m3. The ambient air TCE result at the south end of the building was 58 µg/m3.

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Four ambient air samples were collected on January 24th; winds were mostly calm with light winds occasionally from the southeast. TCE was detected in 3 of 4 ambient air samples at low concentrations ranging from 0.10J µg/m3 to 0.44J µg/m3.

4.7.2.15 Richmond Middle School April 2015

In April 2015, TCE was detected in 1 of the 16 indoor air samples collected at a 0.57 µg/m3 in room 717, which is below USEPA indoor air industrial RSL and the NHDES residential screening levels. TCE was not detected in the sub-slab vapor samples.

4.7.2.16 Richmond Middle School August 2015

TCE was not detected in the 15 indoor air samples collected in August 2015. TCE was detected in 4 of the 11 sub-slab vapor samples collected. Concentrations were low, ranging from 0.55 µg/m3 to 0.97 µg/m3. These detections were below the USEPA indoor air industrial RSL and the NHDES residential screening levels.

Four ambient air samples were collected associated with this sampling event. Wind direction was generally variable with a period in the afternoon from the west-southwest. TCE was not detected in these samples.

4.8 Vapor Migration Pathway Summary

Sections 4.6 and 4.7 present the subsurface soil gas and indoor air sampling and analytical results for onsite and off-Post properties. Section 4.8 presents the outdoor air sampling and analytical results for outdoor air. Information from sections 4.6 and 4.7 have been considered in a weight of evidence approach for determining: 1) if there is a complete Site-related vapor intrusion pathway for each of the onsite and off-Post properties investigated; and 2) if there is a complete outdoor air migration pathway from onsite locations to each of the off-Post properties investigated.

USEPA released OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air, OSWER Publication 9200.2-154 in June 2015.

The 2015 guidance identifies five current conditions for a complete vapor intrusion pathway:

• A subsurface source of vapor-forming chemicals is present underneath or near buildings; • Vapors form and have a route along which to migrate toward the building; • The building(s) are susceptible to soil gas entry (openings exist and air pressure differences exist to draw vapors from subsurface through openings into the building(s); • One or more vapor-forming chemicals comprising the subsurface vapor source(s) is (are) present indoors; and

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• The building(s) is (are) occupied by one or more individuals when the vapor-forming chemical(s) is (are) present indoors.

The 2015 guidance states that a “complete vapor intrusion pathway indicates that there is an opportunity for human exposure, which warrants further analysis to determine whether there is a basis for undertaking a response action(s).”

The 2015 guidance states that the vapor intrusion pathway is considered “incomplete” if one or more of the conditions identified above is currently absent and is reasonably expected to be absent in the future. The guidance recommends that a finding of an “incomplete” vapor intrusion pathway be supported by Site-specific information demonstrating that the nature and extent of vapor- forming contamination in the subsurface is well characterized and the vapor sources and vadose zone conditions do not present opportunities for “unattenuated or enhanced transport of vapors… toward and into any building.” The guidance indicates “Incomplete” vapor intrusion pathways generally do not warrant mitigation.

The 2015 USEPA guidance includes the following statement. “Generally, vapor-forming chemicals with concentrations that consistently fall below screening levels (see Section 6.5) through multiple sampling events (see Section 6.4) warrant no further action or study, so long as the exposure assumptions match those taken into account by the calculations and the Site fulfills the conditions and assumptions of the generic conceptual model underlying the screening levels (see Section 6.5.2).” The onsite vapor intrusion pathway has been presented in Section 4.6.1 and 4.7.1. The onsite vapor intrusion pathway is complete and is currently being mitigated in the Main Laboratory, the CDC, and the TIAC by sub-slab depressurization systems. The evaluation of the vapor intrusion pathway for off-Post properties includes the comparison of sub-slab vapor and indoor air data to corresponding screening levels and draws conclusions based on the 2015 USEPA vapor intrusion guidance.

The September 2015 USEPA Vapor Intrusion Screening Level (VISL) Calculator has been used to derive indoor air screening levels and sub-slab vapor screening levels for an industrial/commercial scenario and a residential scenario. The indoor air screening levels were set at the lower of the concentration associated with cancer risk of 1 x 10-6 and the concentration associated with a Hazard Quotient of 1. The industrial/commercial and residential indoor air screening levels are 3 µg/m3 and 0.48 µg/m3, respectively. These screening levels are associated with a de minimus cancer risk of 1 x 10-6 for a long-term exposure scenario. The concentrations associated with a noncancer Hazard Quotient (HQ) of 1 are higher than the screening levels and they are 8.8 µg/m3 and 2.1 µg/m3 for the industrial/commercial scenario and the residential scenario, respectively.

NHDES has also identified indoor air and sub-slab vapor screening concentrations in the February 7, 2013 Revised Vapor Intrusion Screening Levels and TCE Update. The screening levels are based on the same inhalation unit risk value and the inhalation Reference Concentration used by USEPA to derive the VISL Calculator-based screening levels that are discussed above. The NHDES based its screening levels on concentrations associated with an HQ of 0.2 (to account for

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The sub-slab vapor screening levels were calculated from the indoor air screening levels and dividing by the default attenuation factor (indoor air concentration: sub-slab soil vapor concentration) of 0.03 obtained from the VISL Calculator. NHDES uses a sub-slab vapor to indoor air attenuation factor of 0.02 (less conservative) to calculate the sub-slab vapor screening levels from the indoor air screening levels. Therefore, the sub-slab vapor screening levels derived from the USEPA VISL Calculator are used as the point of comparison for this off-Post vapor intrusion evaluation. The use of the VISL calculator is the current USEPA approach for evaluating VI. The EPA approach is appropriate for screening VI in a CERCLA-compliant RI and risk assessment screening. The attenuation factor of 0.03 is a conservative estimate for residential scenarios from the USEPA VI database. At least 90% of the residences in the EPA database have attenuation factors that are less conservative (ranging to 0.001 or more). The 33% – 50% attenuation factors may suggest that the VOCs in indoor air are not related to subsurface conditions. These four data points are a small sample set, and should not be considered more representative of future conditions than the EPA VI database (USEPA, 2012).

The industrial/commercial and residential sub-slab vapor screening levels are 100 µg/m3 and 16 µg/m3, respectively. As was the case for indoor air, the sub-slab screening levels are associated with the de minimus cancer risk of 1 x 10-6 for a long-term exposure scenario. The corresponding industrial/commercial and residential sub-slab vapor screening levels based on the noncancer HQ of 1 are 293 µg/m3 and 70 µg/m3.

4.8.1 Brendel & Fisher (64 Lyme Road)

The vapor intrusion pathway is incomplete for the Brendel & Fisher Wealth Management property. At the Brendel & Fisher Wealth Management property, the vapor intrusion pathway is considered incomplete for the following reasons, which support the conclusion that vapor intrusion is not evident.

Sub-slab Vapor – Concentrations below screening levels and lack of a typical vapor intrusion gradient:

• The sole TCE detection in soil vapor samples (2.8 µg/m3) is well below the industrial/commercial sub-slab soil vapor screening concentration of 100 µg/m3. • TCE was not detected in three of the four sub-slab vapor samples, indicating there is no vapor intrusion gradient from sub-slab vapor to indoor air. This suggests there is no TCE immediately below the slab acting as a source of vapor intrusion.

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• TCE was not detected in the paired indoor air sample for the single sub-slab vapor sample with detected TCE, again showing no relationship between these values, and indicating there is no complete vapor intrusion pathway.

Indoor Air – Concentrations below screening levels and likely from ambient air:

• TCE was detected in seven of eight indoor air samples at concentrations ranging from 0.16 J µg/m3 to 0.75 µg/m3. TCE detections in indoor air samples were below the industrial/commercial indoor air screening levels (concentration of 3 µg/m3 at 10-6 cancer risk and 8.8 µg/m3 at Hazard Quotient of 1). Detected concentrations were below 1 µg/m3. • Detectable TCE concentrations in indoor air and only one detection of TCE in sub-slab vapor samples (well below the sub-slab vapor screening levels) indicates that indoor sources of TCE are likely (TCE was not detected in associated outdoor air samples).

4.8.2 Hanover Family Chiropractic & Hanover Yoga (68 Lyme Road)

The vapor intrusion pathway is incomplete for the Hanover Chiropractic property. At the Hanover Chiropractic property, the vapor intrusion pathway is considered incomplete for the following reasons, which support the conclusion that vapor intrusion is not evident.

Sub-slab Vapor – Concentrations below screening levels and lack of a typical vapor intrusion gradient.

• The TCE concentrations detected in sub-slab soil vapor samples (highest of 1.9 µg/m3) are well below the industrial/commercial sub-slab soil vapor screening concentration of 100 µg/m3. • In two of the six collocated sub-slab vapor and indoor air sample pairs, the indoor air concentrations are higher than the sub-slab vapor concentrations (the opposite of a typical vapor intrusion gradient). • In three of the remaining four co-located pairs, TCE was not detected in the indoor air sample (indicating there is no complete vapor intrusion pathway).

Indoor Air – Most concentrations below screening levels and potential impact from ambient air.

• TCE was detected in six of the ten indoor air samples; however, only one of the TCE detections (3.2 µg/m3) in indoor air samples are below the industrial/commercial indoor air screening levels (concentration of 3 µg/m3 at 10-6 cancer risk and 8.8 µg/m3 at Hazard Quotient of 1). • The one indoor air concentration exceeding the indoor screening level is 1.7 times higher than the collocated sub-slab vapor sample, indicating that this indoor air concentration is not the result of a typical vapor intrusion gradient, and is more likely indicative of an indoor air source. Alternatively, the higher concentration in indoor air

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may be a result of higher sub-slab concentrations elsewhere beneath the building floor slab.

4.8.3 Dartmouth College Housing, Cedar Drive and Fletcher Circle

The vapor intrusion pathway is incomplete for the tested Dartmouth Housing properties on Cedar Drive and Fletcher Circle. At the Dartmouth Housing residences at 12 Cedar Drive, 15 Cedar Drive, 19 Fletcher Circle, 23 Fletcher Circle, and 25 Fletcher Circle, the vapor intrusion pathway is considered incomplete for the following reasons, which support the conclusion that vapor intrusion is not evident.

Sub-slab Vapor – Concentrations below screening levels and lack of a typical vapor intrusion gradient:

• TCE was detected in eight of nine sub-slab vapor samples at concentrations ranging from 0.15 µg/m3 to 1.4 µg/m3. These sub-slab concentrations are not indicative of a subsurface vapor intrusion source. Detected concentrations are well below the residential sub-slab vapor screening levels of 16 µ/m3 (at de minimus cancer risk of 1 x 10-6) and 70 µg/m3 (HQ equal to 1). • For the eight sub-slab vapor samples with detected TCE, there are four corresponding co-located indoor air samples in which TCE was not detected (there is no vapor intrusion gradient, indicating the vapor intrusion pathway is not complete). For the other four sub-slab samples with detectable TCE, there are four corresponding co-located indoor air samples with TCE concentrations that are approximately 33% - 50% of the sub-slab concentrations (0.44 µg/m3 or lower). These low TCE concentrations in both sub-slab vapor samples and indoor air samples are not indicative of a complete vapor intrusion pathway.

Indoor Air – Concentrations below screening levels:

• TCE was detected in half of the indoor air samples (ten of twenty indoor air samples) at concentrations ranging from 0.086 µg/m3 to 0.44 µg/m3. Detected indoor air concentrations are below the residential indoor air screening levels of 0.48 µg/m3 (at de minimus cancer risk of 1 x 10-6) and 2.1 µg/m3 (HQ equal to 1). • TCE was not detected in outdoor air samples collected from these properties (no indication of a complete migration pathway from the facility to these properties). Sub-slab depressurization systems have been installed in each property by Dartmouth College Real Estate.

4.8.4 Rivercrest Property (49 Lyme Road)

There is no current complete vapor intrusion pathway for the Rivercrest property because there are currently no occupied buildings. A potential future vapor intrusion pathway should be

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During the vapor intrusion investigation at the Rivercrest property, substantial concentrations of TCE (well above sub-slab and exterior vapor screening levels) were detected in soil vapor samples collected on the property (from 10 ft bgs to 75 ft bgs). TCE concentrations were highest in the samples collected from locations near the border of CRREL and the Rivercrest property (SV49- 13-04, SV49-13-03, and SV49-13-02). TCE was either not detected or detected at substantially lower concentrations in samples collected further to the north and northwest of those three sample locations. The TCE concentrations reported at locations SV49-13-04, SV49-13-03, and SV49-13- 02 represent a potential subsurface vapor source and as such should be considered when assessing the potential for a complete vapor intrusion pathway in the future (if construction of occupied buildings is planned). If occupied buildings are planned in the future, additional soil vapor sampling and analysis and engineered vapor mitigation systems or building designs (such as open-air ground level parking structures and occupied spaces on higher floors) and/or institutional controls (do not construct occupied buildings in specific areas) should be considered to eliminate or control vapor intrusion potential for the future buildings.

4.8.5 Dartmouth Printing (69 Lyme Road)

The vapor intrusion pathway is currently incomplete for the Dartmouth Printing property. A potential future vapor intrusion pathway should be addressed by additional monitoring in the future. At the Dartmouth Printing property, the vapor intrusion pathway is considered incomplete for the following reasons, which support the conclusion that vapor intrusion is not evident.

Sub-slab Vapor – Concentrations below screening levels:

• Although TCE was detected in most of the 20 sub-slab vapor samples, detected concentrations of TCE in sub-slab vapor samples were below the industrial/commercial sub-slab soil vapor screening concentration of 100 µg/m3. • Fifteen of the nineteen detected concentrations of TCE were below 1 µg/m3. Those concentrations, which are below both the sub-slab screening level (100 µg/m3) and the indoor air screening levels (concentration of 3 µg/m3 at 10-6 cancer risk and 8.8 µg/m3 at Hazard Quotient of 1).

Indoor Air – Concentrations below screening levels:

• TCE was detected in 12 of 22 indoor air samples below the industrial/commercial indoor air screening concentration of 3 µg/m3 (in fact detected concentrations were below 1 µg/m3).

Gradient – Lack of a typical vapor intrusion gradient:

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• There were nine instances where TCE was detected in both the sub-slab vapor sample and the co-located indoor air sample. In five of those instances, the indoor air concentrations were higher than the sub-slab vapor TCE concentrations. • In three of the remaining four instances, the TCE sub-slab vapor concentrations are only slightly higher than the corresponding indoor air concentrations. • In the final instance, the sub-slab TCE concentration (22 µg/m3) is higher than the indoor air concentration (0.38 µg/m3), but the indoor air concentration is very similar to the other detected TCE concentrations in indoor air (suggesting no current complete vapor intrusion pathway).

Outdoor Air – Concentrations similar to indoor air:

• TCE was detected in each outdoor air samples collected in February 2014 and it was not detected in the four outdoor air samples collected in September 2013. Most of the indoor air samples collected in February 2014 had TCE detections at concentrations consistent with concentrations detected in the February 2014 outdoor air samples. Most of the indoor air samples collected in September 2013 did not have detectable TCE, which is consistent with the outdoor air samples collected at the same time. This indicates the TCE detected in indoor air samples may be associated with an outdoor source.

During the vapor intrusion investigation at 69 Lyme Road, contrary to the findings in the sub-slab soil vapor samples, substantial concentrations of TCE, trichlorofluoromethane and dichlorodifluoromethane were detected in soil vapor samples collected outside the Dartmouth Printing building footprint at depth (10 ft bgs to 75 ft bgs). TCE concentrations were highest in the deepest samples. These concentrations represent a potential subsurface vapor source that should be considered when assessing the potential for a complete vapor intrusion pathway in the future. Therefore, periodic monitoring of sub-slab soil vapor concentrations beneath the building would be appropriate to confirm that sub-slab VOC concentrations have not increased (which could suggest greater potential for a complete vapor intrusion pathway).

4.8.6 Richmond Middle School Property (63 Lyme Road)

The vapor intrusion pathway is incomplete for the Richmond Middle School Property. A potential future vapor intrusion pathway should be addressed by additional monitoring in the future. At the Richmond Middle School property, the vapor intrusion pathway is considered incomplete for the following reasons, which support the conclusion that vapor intrusion is not evident.

Sub-slab Vapor – Concentrations below screening levels

• TCE was detected in 34 of 59 sub-slab vapor samples at concentrations ranging from 0.059 µg/m3 to 5.9 µg/m3. These levels of TCE are not indicative of a substantial source of volatiles immediately beneath the building slab. These results for the school are conservatively screened using residential sub-slab vapor screening levels of 16 µg/m3

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(at de minimus cancer risk of 1 x 10-6) and 70 µg/m3 (HQ equal to 1). TCE concentrations in sub-slab vapor samples are below these residential sub-slab screening levels, indicating that vapor intrusion is not a concern.

Indoor Air – Most concentrations below screening levels and potential impact from outdoor air:

• TCE was detected in 38 of 109 indoor air samples from the Richmond Middle School. However, on January 19, 2015, a release of TCE to the interior of the school associated with maintenance activities was identified. - One TCE concentration of 2,600 µg/m3 was detected. - TCE was detected in each of the 15 indoor air samples collected from within the school. - Air within the school was impacted by the TCE release (not associated with the CRREL facility). - Therefore, the TCE indoor air data associated with samples collected on January 19, 2015 are not considered further. • Excluding indoor air samples collected on January 19, 2015, TCE was detected in 23 of 94 indoor air samples from the school. Indoor air TCE concentrations in those samples ranged from 0.086 µg/m3 to 1.2 µg/m3. • For indoor air samples in the school, there were only five TCE detections above the residential screening level of 0.48 µg/m3. Each TCE detection were from samples collected on April 1, 2013. The detections were at concentrations of 0.49 µg/m3, 0.64 µg/m3, 0.75 µg/m3, 1.1 µg/m3, and 1.2 µg/m3. On April 1, 2013, there were four outdoor air samples collected from the school property (63Lyme-01, 63LYME-02, 63LYME-03, and 63LYME-04). TCE was detected in three of those four ambient air samples at concentrations of 0.18 J µg/m3, 0.21 J µg/m3, and 0.91 µg/m3. It is reasonable to conclude that the only TCE concentrations above the residential screening level of 0.48 µg/m3 detected in indoor air samples from the school are associated with outdoor sources as evidenced by the outdoor TCE concentrations recorded on April 1, 2013 and the release from maintenance activities on January 19, 2015. As indicated in the USEPA 2015 vapor intrusion guidance, the mere presence of VOCs associated with the vapor source (TCE) is not definitive proof of a Site-related complete vapor intrusion pathway.

Gradient – Lack of a typical vapor intrusion gradient:

• The TCE sub-slab soil vapor concentrations in each of the samples collected from the school are below the residential sub-slab vapor screening values, and only five indoor air concentrations among 94 indoor air samples were above residential indoor air screening levels (collected on a day when three of the four ambient air samples had detectable TCE), therefore, no typical vapor intrusion gradient exists between the sub- slab vapor and indoor air.

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• The majority of co-located sub-slab and indoor air samples indicated that concentrations were below the detection limit in either the sub-slab vapor or indoor air concentration, supporting the conclusion that a typical vapor intrusion gradient is not evident.

During the vapor intrusion investigation at 63 Lyme Road, contrary to the findings in the sub-slab soil vapor samples, substantial concentrations of TCE (well above sub-slab and exterior vapor screening levels) were detected in soil vapor samples collected on the Middle School property. TCE concentrations were highest in the deepest samples (75 ft bgs) located west (along Lyme Road) and north of the school. These concentrations represent a potential subsurface vapor source and should be considered when assessing the potential for a complete vapor intrusion pathway in the future. Therefore, periodic monitoring of sub-slab soil vapor concentrations beneath the building would be appropriate to confirm that sub-slab VOC concentrations have not increased (which could suggest greater potential for a complete vapor intrusion pathway).

4.9 Soil Vapor Extraction Pilot Test

As a result of the off-site detections of TCE in soil gas, Amec Foster Wheeler was tasked by the USACE to conduct an SVE Pilot test at AOC 2. The results of the SVE report are presented in the Final Soil Vapor Extraction Pilot Test Report for Area of Concern 2 (Amec Foster Wheeler, 2017). The findings of the pilot test will be summarized in the FS.

The SVE pilot test consisted of the following steps:

1. Installation of SVE Wells and Soil Monitoring Points.

2. Soil Vapor Baseline Sampling and Vertical Permeability and Concentration Profiling.

3. SVE Step Rate Test.

4. SVE Constant Rate Test.

5. Post SVE Soil Vapor Sampling and Vertical Permeability and Concentration Profiling.

6. Rebound Testing.

The following results are from the SVE report are provided below as there are several findings that are important in the context of the RI. The findings provide refinements to the conceptual site model (Section 5).

The SVE pilot test was conducted to evaluate the following:

1. The efficacy and requirements for controlling off-site migration of TCE contaminated soil gas to the north. This included collection of data to evaluate if migration of shallow soil gas, deep soil gas or both contribute to this off-site soil vapor contamination.

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2. The permeability of soil for air flow and the soil vapor concentration profiles at the northern property boundary and in AOC 2.

3. The ability of an SVE system to enhance or replace the mitigation system at the Main Laboratory.

4. Data needed to design an SVE system for AOC 2.

5. Potential for post-SVE soil vapor rebound.

The SVE layout at AOC 2 is shown on Figure 4.9-1.

Additionally, the SVE Pilot test was intended to add to the body of knowledge gained from site investigation regarding the nature and extent of contamination in the subsurface.

4.9.1 Controlling Off-Site Migration

Pilot test data was evaluated to determine if SVE has the potential to control vapor migration to the north, toward the Rivercrest property. Data collected during a vacuum step test indicates that there is an influence on migration of the northern plume during SVE operation. Vacuum can be measured at distances of at least 55 feet in the deep sandy soils (>40 feet bgs), and at least 40 feet in the shallow silty unit (<40 feet bgs). Measurable vacuum is generally assumed to indicate that advective flow can be developed, and that vapors will be drawn toward the SVE well.

As shown on Figure 4.9-2, TCE soil gas concentrations on the Rivercrest property generally decreased during the pilot test even though vapor monitoring points are outside the radius of measurable vacuum influence of the pilot test conducted at AOC 2. This is likely a result of the upper silty unit acting as a confining unit between the deeper sand unit and the atmosphere. Amec Foster Wheeler assumes that soil gas flow in the deep unit during the SVE operation was horizontal. Additionally, reductions in soil gas concentrations outside the area of advective flow, may be a result of the SVE preventing diffusion of TCE from AOC 2 toward the Rivercrest property.

4.9.2 Develop Horizontal and Vertical Profiles

Pneulog® vertical permeability and TCE concentration profiling was performed both before and after pilot test activities. Praxis concluded that “the shallow vadose zone to depths of 50 to 60 feet below the surface is dominated by relatively low permeability material suggestive silts or a high moisture content,” which is consistent with historical boring logs and Site observations (Amec Foster Wheeler, 2017). The middle vadose zone permeability increases with depth and the highest permeability zone is within the deep sandy layers. Praxis reports that TCE infiltration from the shallow vadose zone recharges the more permeable zones beneath more slowly than to groundwater below the vadose zone, resulting in a non-uniform TCE concentration across the deep vadose zone, with higher concentrations toward the top of the deep vadose zone.

The Praxis Report concluded that constant rate test caused a reduction of the volume of the vapor plume in the deep vadose zone by at least an order of magnitude. However, the highest

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4.9.3 SVE Effects on Main Laboratory Vapor Mitigation

Monitoring of the existing Sub Slab Depressurization System (SSDS) at the Main Laboratory Building provided insight on the ability to utilize SVE as a method for reducing vapor intrusion in the building. Routine samples collected from various locations related to the SSDS system were analyzed to determine the amount of TCE that the system is removing during the SVE pilot test. The SSDS system layout is provided in Appendix U.

Routine samples collected from various locations related to the SSDS system were analyzed to determine the amount of TCE that the system is removing. Because the SVE pilot test also is designed to remove subsurface soil vapors using an extraction system, some effect on influent SSDS soil vapors was expected. Samples were collected from the MPR SSDS vents located approximately 30 and 65 ft. from the vapor extraction points (VEW-3 and VEW-4. Samples were also collected from the lab addition sub-basement (located on the opposite side of the Main Laboratory building approximately 200 to 350 feet. from VEW-3 and VEW-4); locations are shown in Figure 4.9-1.

Due to its proximity to the MPR, it is likely that AOC 2 is the major contributor to the TCE vapors beneath the MPR. The data collected from the MPR sampling location shows a reduction of approximately 97% in TCE vapor concentration from the start of the constant rate test in June 2015 (4,822 µg/m3) to test shutdown in December 2015 (130 µg/m3). After shutdown in December, concentrations rose to 761 µg/m3 shortly after system restart in January 2016, a rebound of approximately 13% of initial (pre-pilot test) concentration, and 5.8 times the pre-shutdown (end of pilot test) concentration TCE vapor concentration. The data collected in the MPR shows a direct relationship between sub-slab TCE vapor concentration and the operation of SVE wells VEW-3 and VEW-4.

The data collected from the lab addition subbasement show a reduction of approximately 61% in TCE vapor concentration from the start of the constant rate test in June 2015 (7,309 µg/m3) to test shutdown in December 2015 (2,862 µg/m3). After shutdown in December, concentrations rose to 5,365 µg/m3 shortly after system restart in January 2016, a rebound of approximately 1.9 times the pre-shut down TCE vapor concentration. Because the data generally tracks with the operation of the SVE pilot test (reductions during operation and increases during shutdown periods), this suggests that there may be some influence on the sub-slab vapor concentrations from the operation of the SVE pilot test. However, due to the distance of this sampling location from the operating SVE wells, VEW-3 and VEW-4, and the small difference between starting concentration and final concentration when compared to natural variability in historical data, it is unclear whether the reduction in TCE vapor concentration is due to the operation of the SVE pilot test or natural variability in analytical data.

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Data from the SSDS in the central portion of the main lab building shows little change in influent concentration during the constant rate test and rebound. This suggests that the source of contamination affecting this system was not influenced by the SVE system. This may be partially due to both the SSDS and SVE systems drawing contamination from the area of AOC 9. Because this SSDS is in a direct line between AOC 9 and the SVE system at AOC 2, the effect of the SVE system could have been masked by an increase in contaminant contribution from AOC 9. It is also possible that the SVE system resulted in advective flow beneath the central portion of the main lab but the flow was not sufficient to substantially impact contaminant concentrations in that area.

Data collected from the MPR SSDS influent shows that the operation of a nearby soil vapor extraction well can have a significant impact on sub-slab vapors in the Main Laboratory building. Results from the other SSDS systems in the Main Lab and Lab Addition sub-basement do not show conclusive evidence of SVE pilot operation influence.

4.9.4 Additional Data to Support the Remedial Investigation

Data collected during the SVE pilot also provides additional support for the Phase III RI. Data evaluated for this purpose include:

• Identification of vertical and horizontal locations of contamination.

• Effects of SVE on groundwater contamination.

4.9.5 Horizontal and Vertical Locations of Contamination

Data collected during the SVE pilot test confirms conclusions derived from soil and soil vapor data gathered during the RI. The SVE data shows that a majority of the TCE mass in the subsurface of AOC 2 exists adsorbed to soils. Further, data suggests that residual separate phase TCE is not present at AOC 2. Because the TCE exists as a vapor, it is mobile and naturally migrates through diffusion and pressure gradients that has created a vapor plume. The plume has higher concentrations in the vicinity of AOC 2 and AOC 9, and lower concentrations as distance increases from these source areas.

During the SVE pilot test influent concentrations and the soil vapor concentrations in close proximity to the SVE wells decreased continually. The rate of concentration decrease was initially high, then leveled off following the removal of the first pore-volume of vapor around the SVE well, and as diffusion limited dynamic equilibrium was established between adsorbed, dissolved, and vapor phase contamination. Following extended shut downs, the vapor phase concentration rebounded back to the higher static equilibrium concentration. This pattern can be seen in the influent vapor concentration graph (Figure 4.9-3).

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4.9.6 Effects of SVE on Groundwater Contamination

The effects of the SVE pilot on groundwater concentrations were evaluated at monitoring well MW- 14-107 located in the AOC 2 source area and at CERCL 08 located between AOC 2 and AOC 9.

Groundwater baseline data at MW-14-107 was collected approximately one year before the start of the pilot test (July 2014) with TCE detected at a concentration of 23,000 µg/L. Annual monitoring of the groundwater wells conducted in July of 2015 showed a three order of magnitude reduction in the TCE concentration (83 µg/L). Additional groundwater sampling has been conducted at MW- 14-107, the results are plotted graphically on Figure 4.9-4. Groundwater concentrations have remained low since the SVE pilot began in June 2015. Concentrations appear to respond directly to the operation of the SVE pilot as shown by the increase in TCE concentrations observed during the SVE pilot rebound period.

TCE in groundwater at monitoring well CERCL 08 was also evaluated as part of the SVE pilot. This well is located between AOC 2 (where the SVE is operating) and AOC 9 which is also considered a TCE soil gas source area. As shown on Figure 4.9-5 TCE concentrations in CECRL 08 remained within a range of 32 to 620 µg/L for the 10 years prior to initiation of the SVE pilot. Following start-up of the SVE pilot TCE concentrations spiked at 4,800 µg/L and have continued to increase. This is likely a result of contaminated soil vapor movement by advective flow from AOC 9 toward AOC 2 which is causing higher contaminated soil gas to come in contact with the capillary fringe upgradient of CECRL 08 and the TCE is partitioning into groundwater.

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5.0 CONCEPTUAL SITE MODEL

This section describes the current CSM that defines the exposure pathways and receptors to define the human health risk assessment. Preparation and analysis of the CSM leads to identification of potential data gaps that may need to be filled to address areas of uncertainty in the risk assessment and the FS.

The physical and chemical processes that affect COC migration in soil, groundwater, and air are described. Estimates of contaminant mass present in each medium were presented in Section 4.2. The primary COC at the facility is TCE and is the focus of this CSM discussion.

Figure 5.0-1 is a pictorial representation of the CSM for TCE related sources, migration pathways and mechanisms and receiving and exposure media. The CSM will also be described through identification of primary and secondary release and migration mechanisms to receiving media to exposure routes and receptors. These elements are shown in the form of a flowchart in Figure 5.0- 2.

TCE was used as secondary heat transfer agent in refrigeration systems in the Main Laboratory and was used in experiments conducted by CRREL from approximately 1963 to 1987. TCE leaked from piping in the Main Laboratory and from piping and other appurtenances associated with a 10,000 gallon UST located in AOC 2 (Sayward, 1968 and Faran, 1990). TCE was also lost to the ground surface in support of experiments associated with a former Ice Well at AOC 9 and from an explosion of an AST in 1970. Although each was designed as a closed system, the facility reportedly ordered up to 3,000 gallons per year of TCE over a period of several years. Over 30 years have elapsed since TCE was used in large quantities at the Site. The largest known releases of TCE to soils occurred over 47 years ago. There have been no known releases of TCE at the Site for over 30 years, therefore, it is assumed that TCE is in equilibrium in soil, soil gas, and groundwater. Migration of TCE occurs in the unsaturated subsurface primarily by chemical diffusion. Contaminant transport in the saturated zone is primarily by advective flow in groundwater.

The spatial relationship between observed TCE contamination in soil vapor and soil in AOCs 2 and 9 are presented in Figure 5.0-3. Soil sample results, MIP profiling, and soil gas results show that the two cores of soil gas with concentrations greater than 2.5M µg/m3 of TCE are co-located with soils that are interpreted to show TCE in excess of 800 µg/kg. TCE is adsorbed to soil, therefore, TCE contained in the vapor phase in the surrounding soil gas are most likely in equilibrium with each other.

Figure 5.0-4 shows the spatial relationship of soil gas and groundwater at AOCs 2 and 9. The two cores of soil gas contaminated by TCE in excess of 2.5M µg/m3 and the two cores of the groundwater plume emanating from beneath the AOC 2 and AOC 9 source areas. As discussed in Section 4.9, SVE resulted in reduction of TCE mass in the soil gas phase which has had a direct effect on groundwater concentrations (Figure 4.9-4). TCE in soil gas partitions into groundwater at these locations and is most likely the source of TCE dissolved in groundwater. In the absence of a stress to the soil gas (e.g., SVE), TCE in soil gas and TCE dissolved in groundwater are most

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The key components of the current CSM are summarized below (Figure 5.0-1):

Overburden Soils

• Overburden soil is thick at the Site extending between 195 to 235 feet bgs. • Shallow overburden soils consist of the Hanover silt which is made up of fine-grained varved sediments with alternating layers of silts, clays, and very fine sands deposited in former Glacial Lake Hitchcock. • Shallow overburden soils range up to 50 feet thick at AOC 2 and up to 90 feet thick at AOC 9 and AOC 13. • Deeper overburden soils consist predominately of silty sand and fine sand deposited in the glacial meltwater of Glacial Lake Hitchcock. • The unsaturated zone is extensive, extending up to 130 feet below the Site. • Interlayered fine to coarse sands rest directly on slightly weathered bedrock. Till deposits do not appear to underlie the Site. • Overburden soils contain TCE adsorbed to soil particles, primarily silts and clays, due to spills, leaks, and releases at AOCs 2, 9, and 13. • Mobile DNAPL has not been observed in overburden soils during the Phase III RI Field Investigations at AOCs 2, 9 and 13. However, TCE mass may be immobilized within the soil pore spaces at these locations. • Residual phase, immobile DNAPL was reported in the 23- to 33-foot zone at AOC 2 (ENSR, 1996), it was not observed in recent Phase III work at AOC 2. • TCE in NAPL form was not detected in direct push optical screening profiling at AOC 2 (Haley and Aldrich and Dakota Technologies, 2016). • At AOC 2, most of the TCE contaminant mass is adsorbed to shallow soils extending from 10 to 39 feet bgs as shown by high MIP response and soil sampling. Soil concentrations and MIP response in the vadose zone are lower from 39 to 130 feet bgs. • Residual phase DNAPL was reported in the 16.5- to 30.5-foot zone at AOC 9 (ENSR, 1996); it was not observed during in recent Phase III RI Field Investigations work at AOC 9. • TCE in NAPL form was not detected in direct push optical screening profiling at AOC 9 (Haley and Aldrich and Dakota Technologies, 2016).

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• At AOC 9, the most elevated MIP response extends from 6 to 55 feet bgs. Soil sampling conducted based on MIP response showed the highest soil concentrations extending from 25 to 38 feet bgs. • It does not appear that DNAPL (mobile or residual phase) has migrated through the deep vadose zone, entered the capillary fringe, or penetrated into the groundwater table.

Bedrock

• Observed top of bedrock ranges from 195 to 235 feet bgs. • The bedrock consists of a greenstone, chlorite schist containing garnet inclusions and calcite in healed fractures. The bedrock is competent (RQD’s in excess of 85%) and a weathered bedrock zone is thin to non-existent where borings penetrated bedrock at the Site. • The top of the bedrock surface appears to have been well scoured by glacial meltwaters. • The bedrock is discretely fractured. Geophysical logs show two primary fracture sets, one is a set north-northeasterly trending fractures that dip to the south-southeast. The second set trends north-northeasterly and dips to the west-northwest. • Sampling of the bedrock matrix during the Phase III RI shows it is not contaminated by TCE in the area of AOC 9 nor west of the FERF.

Overburden Groundwater

• Overburden groundwater occurs in response to areal recharge from precipitation, runoff, topographic controls, and to some degree by discharge from bedrock groundwater. • Perched groundwater can exist locally in shallow varved soils. • The groundwater table is deep at the Site. In the areas of AOC 2 and AOC 9 it is encountered at approximately 130 feet bgs. • The flow of overburden groundwater is from the Site to the west-southwest towards the Connecticut River. • Overburden groundwater is recharged by the Connecticut River west of the supply wells under pumping conditions. • The overburden aquifer becomes more permeable with depth below the water table. Coarse grained soils extend from the esker to the east up to at least the area of AOC 13. This unit is hydraulically connected to the esker and shares similar hydrogeologic properties. Hydraulic conductivities for the deeper fine to coarse sands have been estimated by aquifer testing to be 100 feet/day.

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• The lacustrine (very fine to coarse sand) overburden aquifer is semi-confined while the esker portion is unconfined. • Recharge water percolates through TCE contaminated soils and soil gas at AOC 2 and AOC 9 dissolving TCE as it migrates to the water table. • Soil gas, contaminated with TCE, is in contact with the capillary fringe, where it partitions into groundwater and is a source of TCE contamination. • The highest concentrations of TCE in groundwater are located at or near the water table, and decrease with depth through the saturated zone. • TCE-contaminated overburden groundwater in excess of 5 µg/L is present in the form of two highly concentrated cores which originate from AOC 2 and AOC 9. Overburden groundwater TCE concentrations decrease with depth towards the top of the bedrock surface. • TCE-contaminated overburden groundwater migrating from AOC 2 and AOC 9 is captured by the facility’s five supply wells located within esker materials beneath the western portion of the facility and bordering the Connecticut River (USACE, 2010a). • Degradation products of TCE (cis-1,2-DCE, trans-1,2-DCE, and vinyl chloride) suggests that limited reductive dechlorination of TCE occurs in the overburden groundwater.

Bedrock Groundwater

• Bedrock groundwater occurs primarily in open fractures. Bedrock groundwater is recharged from infiltrating overburden groundwater and in areas where bedrock is exposed at ground surface. Bedrock is not exposed in immediate proximity to the facility. • The flow of bedrock groundwater generally mimics the flow of overburden groundwater moving from the Site west-northwest towards the Connecticut River. • Deep bedrock wells installed at the facility show the presence of low-yielding bedrock fractures. • Vertical gradients between bedrock and the overburden vary beneath the facility from neutral to slightly upward and slightly downward. • Geophysical logs show two primary fracture sets, one is a set north, northeasterly trending fractures that dip to the south-southeast. The second set trends north- northeasterly and dips to the west-northwest. • Observed concentrations of TCE in bedrock groundwater are relatively low (only slightly in excess of the federal MCL) and are within the areas of AOC 2 and AOC 9. • Degradation products of TCE (cis-1,2-dichloroethene, trans-1,2-dichloroethene, and vinyl chloride) suggesting that limited abiotic reductive dechlorination of TCE occurs in

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bedrock groundwater in the area of AOC 9. Only cis-1,2-dichloroethene was detected at concentrations in excess of USEPA and NHDES drinking water criteria (70 µg/L). Due to the presence of calcite and calcite healed fractures of low transmissivity, pH increases upwards of 11 as little flushing of calcium carbonate occurs. High pH and negative redox potential make for a reductive bedrock groundwater environment.

Soil Gas

• Soil gas occurs in the space between soil particles in the vadose zone. • Concentration and pressure gradients cause movement of air and volatile contaminants in the vadose zone. • TCE adsorbed to soil particles moves into the soil gas by volatilization and diffusion. • TCE contaminated soil gas moves by advection when a pumping stress is applied to the vadose zone, such as with an SVE system. • The area impacted by TCE-contaminated soil gas is most likely stable and at or near equilibrium as there have been no further known inputs of TCE to the vadose zone since the 1980s. • The two cores of TCE contaminated soil gas are co-located with the highest levels of soil contamination at AOC 2 and AOC 9. • The area impacted by TCE-contaminated soil gas is confined or semi-confined. Atmospheric barometric changes are observed to result in dynamic pressure gradients between ground surface and the underlying lacustrine very fine sands (generally greater than 50 feet in depth). • Soil gas contaminated with TCE is in contact with the capillary fringe and partitions into groundwater.

Indoor Air

• Indoor air can be affected by vapor intrusion where TCE-contaminated vapors migrate through foundation cracks, and by diffusion through concrete into buildings from the AOC 2 and AOC 9 source areas. • TCE-contaminated vapors can enter buildings by migration through sub-surface utility trenches, piping such as roof drains and sanitary sewers, and other penetrations through foundations. • Vapor intrusion is more likely to occur during rapid atmospheric barometric changes where the barometric pressure drops over a relatively short period of time. • TCE-contaminated ambient air can enter buildings via open windows, doors, and air exchange duct work.

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Ambient Air

• Ambient air can become contaminated by the discharge of TCE contaminated vapor by volatilization and diffusion from contaminated soils. It most likely occurs during barometric low periods and low wind conditions. • Migration pathways affecting ambient air may include off gassing from subsurface utilities such as manways and drain structures and from penetrations into the soil column such as monitoring wells and utility trenches.

5.1 Primary Contaminant Sources

Sources of TCE contamination at CRREL are related to former Site operations, primarily the use of TCE as a heat transfer agent as part of the facilities infrastructure and legacy waste disposal practices (Faran, 1990). Sources of fuel-related compounds are due to leaks and breaches of containment systems. Contaminant sources have been investigated as part of the Phase III RI work and have been addressed in a series of removal actions designed to be protective of human health (see Section 2). Source areas were contaminated through releases of contamination which likely occurred as described below:

• Releases from brine (refrigerant fluid) pumps, piping and appurtenances containing TCE in the Main Laboratory (Mechanical Room, Cold Rooms, and former labs in the Multi-purpose Room). • Leaks from a former UST and associated appurtenances containing TCE at AOC 2. TCE was most likely slowly released from small breaches and seeped into and through underlying soils. • Large volume release of TCE from an AST explosion in the area of AOC 9 where TCE was washed into the storm drain system. • Release of TCE in relation to experiments conducted at AOC 9 in and around the former Ice Well. Releases may have been from leaking infrastructure used to support experiments (above ground and below ground piping, temporary storage containers, etc.) and disposal directly to the ground surface and storm sewers. • Disposal of TCE to the ground surface in the area of AOC 13, a former gravel borrow area. • Legacy piping in the laboratory and lab addition, including glycol. • Contaminated building materials, primarily concrete floors and insulation associated with the Cold Rooms in the Main Lab. • Operations instances of TCE usage in lab experiments and maintenance and construction activities.

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TCE from these releases has migrated to primary receiving media soils, building materials, and plumbing.

5.2 TCE Sources and Releases

The following subsections describe contaminant migration pathways for TCE through soil, building materials, infrastructure, and operations.

5.2.1 Primary Sources and Releases

Soils Receiving Media

Spills and releases of TCE to soils resulted in:

• Volatilization to the atmosphere from surface soils. • Movement of TCE through the unsaturated zone and laterally along silt and clay laminae in varved soils. • TCE may have collected in soil pore space at residual saturation (DNAPL). • TCE adsorbed to soil particles (e.g. silts, clays, and organic carbon).

Building Materials Receiving Media

Building materials that have become contaminated with TCE include:

• Legacy piping - Past TCE spills and disposal in sinks and drains has led to accumulations of TCE in piping that has not been flushed or replaced since TCE use was stopped in the mid-1980s. Also, when TCE was replaced with ethylene glycol as a secondary heat transfer fluid the existing piping was used or generally abandoned in place. As a result, spills and leaks from the glycol system could result in further TCE contamination. • Concrete Floors and Insulation - TCE used within the Main Laboratory has contacted floors via spills and leaks which seeped into voids and pore spaces in these materials and remains a source of TCE to indoor air as it volatilizes. • Operations - CRREL is an active ERDC research facility with ongoing projects. Containers of TCE and products containing TCE have been identified in the laboratory and could be used in research projects which may result in losses of TCE to indoor air.

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5.2.2 Secondary Sources and Releases

TCE released as a primary source may then become a subsequent contributor (secondary source) via a variety of release mechanisms. Secondary sources and release mechanisms include:

• Vadose zone soil contaminated with TCE transfers. TCE to groundwater through infiltration and percolation of overburden groundwater. Soil with TCE adsorbed to particles transfers TCE through leaching as water percolates through the vadose zone to overburden groundwater.

• Vapor migration originates from AOC 2 and AOC 9 where TCE vapors have migrated radially outward through diffusion, to establish a vapor cloud. As TCE continues to migrate outward through diffusion, concentrations decrease due to dilution, mass is lost to the atmosphere, and through degradation. The vapor cloud is sustained through continual replenishment from source area soils at AOC 2 and AOC 9. The SVE pilot test, through established an advective transport zone around the source area and appears to have cut off the continual source of vapor to the surrounding area. Since diffusion/dilution continued outside the advective zone, concentrations decreased in those areas, with the greatest effects closest to the advective zone.

• TCE discharged to the ground surface from a ruptured storage tank in 1970 was washed from pavement into the storm drain system that discharge to the Connecticut River. This migration pathway was evaluated in 2016 and 2017. The results will be presented in a supplemental RI report.

• Secondary source building materials and infrastructure release TCE directly to indoor air by evaporation and volatilization, diffusion through foundation materials and migration via utility corridors and foundation wall fissures. TCE released into indoor air is circulated throughout buildings via the HVAC systems.

• Secondary receiving media for the TCE flushed to storm drains could include surface water and river sediment in the Connecticut River.

The nature of the CRREL Site is such that sequential release and migration of TCE as dissolved vapor and TCE product move from one type of release to others as described as follows:

• Vapor intrusion into indoor air results from TCE in groundwater volatilizing or diffusing to soil vapor which then moves to indoor and outdoor air. TCE soil vapor migrates and diffuses horizontally and vertically and follows preferential pathways such as subsurface utility corridors.

• Within the groundwater treatment plant, water from wells CECRL 1, 2, 4, and 5 is treated to remove TCE. As the production water used for non-contact cooling undergoes treatment processes (pre-treatment, filtration, air stripping and carbon polishing) TCE vapors have the potential to migrate to indoor air and outdoor air at the treatment plant.

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• Once TCE (as vapor) is mixed with indoor air at CRREL buildings, it circulates and migrates as air flows in and throughout different rooms. Similarly, as TCE vapor reaches outdoor ambient air, it moves through advection and dispersion to locations on CRREL and beyond.

5.3 Exposure Media and Routes

The following media and routes expose employees, workers, and visitors at CRREL. As described previously in Section 2.2, indoor air and sub-slab concentrations of TCE were elevated enough to warrant the installation of sub-slab depressurizations systems in the Main Lab, Main Lab Addition, and the CDC as interim measures to mitigate indoor air concentrations. A sub-slab system was installed in the TIAC as a pre-cautionary measure when the TIAC basement was under renovation. In addition, carbon air filters are installed in offices and working areas in the Main Lab and other buildings throughout the facility.

TCE and petroleum hydrocarbons were primarily released to soil (surface and subsurface). The TCE partitioned from the separate phase into the soil solid phase, soil moisture, and soil vapor. TCE in soil vapor may have further partitioned into groundwater. A sizable subsurface soil vapor plume or cloud was created as a result of the soil partitioning and that plume migrated horizontally and vertically from TCE release locations. TCE in soil moisture may also have been transported downward towards groundwater by leaching associated with infiltration of rain water and snow melt. TCE reaching groundwater is transported within the groundwater by diffusion and advection (with groundwater flow). The active production wells (non-contact cooling water) contain the groundwater plume within the downgradient (western) portion of the Installation.

Where the soil vapor plume is present beneath existing buildings, soil vapors have the potential to migrate through diffusion and advection through floor slabs into the buildings (vapor intrusion). TCE vapors within indoor air may also be transported throughout some buildings by HVAC systems and preferential pathways associated with the building features (elevator shafts, utility chases, etc.). In areas without buildings and other covered areas such as asphalt pavement, soil vapors migrate via diffusion and advection to the land surface and into outdoor air. Outdoor air is also transported into buildings through diffusion and also advective flow driven by pressure differential from wind, stack effects, and active HVAC systems (vapor encroachment). It is also likely that TCE spilled or otherwise released within buildings has contaminated building materials and is off-gassing into the vapor phase from contaminated building materials. This is a confounding factor with respect to investigation of the vapor intrusion pathway at the facility.

5.3.1 Onsite Indoor Air/Inhalation

The Phase III RI has included sub-slab vapor and indoor air sampling beginning in March 2010 and continuing to the present, both onsite at CRREL and at buildings in the vicinity. Indoor air sampling has detected TCE in the breathing zone within the Main Lab basement, first and second floors, and the Main Lab Addition Sub-basement. TCE has also been detected in the breathing zone in the CDC, Logistics Management, Greenhouse and FERF buildings. Direct measurements of indoor air have been used to evaluate current receptors within the onsite buildings.

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Sub-slab sampling of soil gas has detected TCE beneath the basement of the Main Lab, Lab Addition, CDC, Logistics Management Building, Vehicle Storage and the TIAC. Sub-slab soil vapor has been used to evaluate hypothetical future receptors onsite.

The inhalation of indoor air pathway for both the current and hypothetical future scenario has been addressed in the Baseline Human Health Risk Assessment (BHHRA) and is further discussed in Section 7.

5.3.2 Outdoor Ambient Air/Outdoor Air Inhalation

Ambient air was sampled in the vicinity of AOCs 2, 9, 13 and 15 and in the CDC, Ice Engineering, Project Support and the FERF. The highest concentrations were detected in the area of the former Ice Well (AOC 9) and in the area of AOC 2. This pathway was not carried through the full BHHRA process, and will be further characterized in supplemental RI activities.

5.3.3 Onsite Soil Vapor/Inhalation in an Excavation

There is a soil vapor cloud under the Site and extensive soil vapor sampling has been conducted to characterize its extent. Soil vapor collected between 0 and 20 ft bgs has been evaluated for future inhalation by construction workers during an excavation. This pathway has been addressed in the BHHRA and is further discussed in Section 7.

5.3.4 Rivercrest Soil Vapor/Future Indoor Inhalation at Rivercrest

The soil vapor cloud under the Site extends off-Post to Rivercrest. There are no current buildings on the Rivercrest property, so no sub-slab soil vapor samples were collected. Soil vapor collected at each depth on the Rivercrest property has conservatively been evaluated for potential future migration into new buildings and inhalation by residents. This pathway has been addressed in the BHHRA and is further discussed in Section 7.

5.3.5 Off-Post Sub-Slab Soil Vapor/Future Indoor Inhalation

The soil vapor cloud under the Site also extends off-Post to properties other than Rivercrest. Sub- slab soil vapor collected under existing off-Post buildings has conservatively been evaluated for future migration into newly constructed buildings and inhalation by residents. This pathway has been addressed in the BHHRA and is further discussed in Section 7.

5.3.6 Soil/Direct Contact and Inhalation of Particulates

TCE from primary sources, which has not volatilized or adsorbed onto materials or surfaces, may enter the surficial and subsurface soils. Upon entering soils, it may adsorb to soil particles, and move through the unsaturated zone to the water table. Given the low levels of TCE detected in shallow soils during site investigations, direct contact with contaminated soil is likely to be limited to small pockets of TCE not yet detected. Ingestion, dermal contact, and inhalation of particulates have been evaluated for the 0-2 ft interval for the majority of receptors, the 0-6 ft interval for utility

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5.3.7 Groundwater/Ingestion, Dermal Contact, and Inhalation of Volatiles While Showering

TCE is present in overburden groundwater and bedrock groundwater which is encountered at depths as shallow of 80 feet bgs. Since there is no general use of groundwater from CRREL, exposure due to direct contact, vapor inhalation from groundwater used as tap water, and consumption of groundwater are not occurring. Minimal contact may occur during maintenance of the water treatment plant, but this has not been quantitatively assessed. Hypothetical future groundwater use as tap water has been addressed in the BHHRA. This exposure scenario includes ingestion as drinking water, and dermal contact and inhalation during showering. This pathway is further discussed in Section 7.

5.4 Aspects of The Conceptual Site Model That May Indicate Data Gaps

As explained in the introduction to this Section, the CSM defines exposure pathways and receptors for assessing potential risks from TCE at CRREL. The analysis of sources, release and migration mechanisms indicates potential data gaps that may need to be filled to address areas of uncertainty for the risk assessment.

There are several aspects of the CSM that may indicate data gaps. These potential data gaps are outlined in the following subsections.

5.4.1 Extent of Soil Contamination

The extent of TCE contamination in soil has been largely bounded in AOCs 2, 9, and 13. MIP profiles and soil borings have shown that the highest TCE concentrations, and most of the TCE mass adsorbed to soils resides in the upper 55 feet of varved soils at the Site. Soils with lower concentrations of TCE (< 800 µg/kg [NHDES soil concentration protective of groundwater]) may exist beyond the defined extent of these AOCs based on the likely migration pathway.

Vertical migration of TCE through onsite soils was most likely hampered by silt and clay layers as there are hundreds of dense silt and silty clay layers throughout the upper 30- to 50-foot soil profile at each AOC. If mobile DNAPL was ever present it most likely sank downward until it either reached residual saturation (formed ganglia) or a less permeable unit and pooled. DNAPL may have accumulated on less permeable units and migrated laterally and downward again until it reached another less permeable unit in a cascading effect. This appears to have been the migration route of the TCE at AOC 2 and AOC 9 as indicated by MIP profile data and soil sampling. Contaminant mass in soil appears to be focused in the shallow silt and clay layered soils. The Phase III investigations did not detect TCE at concentrations representative of separate phase TCE; however, the continued presence of isolated, immobile, residual phase TCE cannot be conclusively ruled out. TCE remains adsorbed to the shallow silt and soils deposits at AOCs 2, 9, and 13.

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Lower concentrations of contamination (TCE < 800 µg/kg) may have migrated along silt and clay layered soil in the shallow lacustrine unit outside the edges each source area and may be widely dispersed. Areas of low level soil contamination may preclude certain remedial strategies.

5.4.2 Extent of TCE Contamination Beyond the CRREL Boundary

TCE in contaminated soil gas has been detected in overburden at depths from 10 to 75 feet bgs at a number of off-Post locations. The locations with the highest levels detected are to the east and northeast of the CRREL property. The extent of TCE vapor in off-Post soil in this direction has not been fully defined laterally or vertically to date. However, the TCE soil gas plume extent may be stable due to the age of the spills and there have been no recent inputs of TCE to the vadose zone soils. This is a data gap for evaluating the long-term fate and pathway for TCE vapor in soil in this vicinity and for design of remediation for TCE in soil.

Recent results from a SVE pilot test at AOC 2 have shown a reduction in the concentration of TCE at the northern boundary by up to 90% (Amec Foster Wheeler, 2017). Based on these results, further actions related to off-Post soil gas migration may not be needed.

5.4.3 Extent of TCE Source Areas

Buildings on the CRREL installation may contain sources of TCE within walls, floors, plumbing systems, HVAC systems, storm water drainage systems and the secondary heat transfer system. Presence or absence of these infrastructure sources should be confirmed as part of the RI process supporting removal and/or remediation of TCE. Abandoned piping and concealed pipe chases may also act as migration pathways for indoor air. Several sources of TCE in building materials were identified during the RI and include: legacy cold rooms piping in the Main Laboratory (-73 line) containing TCE and TCE vapors; contaminated blueboard insulation and concrete in the cold rooms; and TCE contaminated glycol in the FERF.

At AOC 9, high concentrations of TCE in soil vapor extend to the groundwater table; however, the limits have not been defined to the north and west.

It is not clear as to why concentrations of TCE have increased.

As with the potential disposal area noted above, the utility trenches that are located within and adjacent to AOC 2 and AOC 9 may also act as sources or migration pathways for TCE into onsite buildings. Utilities may be conveying TCE as vapor or dissolved in water along their route. The extent to which this has occurred is a data gap that may need to be addressed prior to remediation.

5.4.4 Impacts to Connecticut River Sediments

TCE was detected in the sediments of Connecticut River following the release of TCE from an AST explosion in 1970, which was subsequently flushed into the storm drain system which

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5.4.5 Impacts to Ambient Air

Ambient air sampling indicates that impacts occur due to diffusion and volatilization of TCE from contaminated soils. This migration pathway and its role in vapor intrusion may be characterized further as part of supplemental RI activities.

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6.0 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS (ARARS)

ARARs are used to guide investigation and sampling activities in the RI. The ARAR concept was developed to govern compliance with environmental and public health statutes. Applicable requirements include cleanup standards, other environmental protection requirements, criteria or limitations that specifically address a hazardous substance or contaminant, remedial action or location at a site where remediation is being implemented under the CERCLA process.

CERCLA and the NCP require that remedial actions must attain federal standards, requirements, limitations, or more stringent state standards determined to be legally applicable or relevant and appropriate to the circumstances at a given site. ARARs are federal environmental and state environmental and facility siting requirements used to: (1) evaluate the appropriate extent of site cleanup; (2) define and formulate remedial action alternatives; and (3) govern implementation and operation of the selected action. Inherent in the interpretation of ARARs is the assumption that protection of human health and the environment is ensured.

To properly consider ARARs and to clarify their function in the remedy selection process, the NCP defines two ARAR components: (1) applicable requirements; and (2) relevant and appropriate requirements. These definitions are discussed in the following paragraphs:

Applicable Requirements. Applicable requirements are those cleanup standards, standards of control, and other substantive environmental protection requirements, criteria, or limitations promulgated under federal or state law that specifically address a hazardous substance, pollutant, contaminant, remedial action, location, or other circumstance at a CERCLA site (40 CFR 300.400(g)). Basically, to be applicable, a requirement must directly and fully address a CERCLA activity. For example, Resource Conservation and Recovery Act (RCRA) regulations contain air pollution emission standards for process vents associated with operations that manage hazardous wastes. (40 CFR Part 264, Subpart AA). To be considered applicable, state standards must be of general applicability and legally enforceable (i.e., promulgated), identified by the state in a timely manner, and more stringent than federal requirements (40 CFR 300.400(g)(4)).

Relevant and Appropriate Requirements. Relevant and appropriate requirements are those cleanup standards, standards of control, and other substantive environmental protection requirements, criteria, or limitations that, while not applicable to a hazardous substance, pollutant, contaminant, remedial action, location or other circumstance at a CERCLA site, address problems or situations sufficiently similar to those encountered at the Site that their use is well-suited to the particular site (40 CFR 300.400(g)(2)). For example, RCRA Subtitle C regulations establish standards for treatment, storage, transport and disposal of hazardous waste that are relevant and appropriate for a CERCLA site.

Requirements under federal or state law may be either applicable or relevant and appropriate to CERCLA cleanup actions, but not both. However, requirements must be both relevant and appropriate for compliance to be needed. In the case where both a federal and a state ARAR are available, or where two potential ARARs address the same issue, the more stringent regulation

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The NCP at 40 CFR 300.430(f)(1)(ii)(C) provides several ARAR waiver options that may be invoked, providing that the basic premise of protection of human health and the environment is not ignored:

1. The alternative is an interim measure and will become part of a total remedial action that will attain the applicable or relevant and appropriate federal or state requirement.

2. Compliance with the requirement will result in greater risk to human health and the environment than other alternatives.

3. Compliance with the requirement is technically impracticable from an engineering perspective.

4. The alternative will attain a standard of performance that is equivalent to that required under the otherwise applicable standard, requirements, or limitation through use of another method or approach.

5. With respect to a state requirement, the state has not consistently applied, or demonstrated the intention to consistently apply, the promulgated requirement in similar circumstances at other remedial actions within the state.

Substantive requirements pertain directly to the actions or conditions at a site, while administrative requirements facilitate their implementation. CERCLA onsite remedial response actions must only comply with substantive requirements that are “applicable” or “relevant and appropriate,” but not the administrative requirements, such as requirements to obtain federal, state, or local permits (CERCLA §121(e)). The NCP defines onsite as “the areal extent of contamination and suitable areas in very close proximity to the contamination necessary for implementation of the response action.” Off-site response actions must comply with both the substantive and administrative requirements of an applicable (but not a relevant and appropriate) regulation, but such regulations pertaining to off-site actions are not classified as ARARs (OSWER 9347.1-0; USEPA, 1998b).

As noted in the ARARs guidance (USEPA, 1988a):

“The CERCLA program has its own set of administrative procedures, which assure proper implementation of CERCLA. The application of additional or conflicting administrative requirements could result in delay or confusion.”

To ensure that CERCLA response actions proceed as rapidly as possible, USEPA has reaffirmed this position in the final NCP. The USEPA recognizes that certain administrative requirements, such as consultation with state agencies and reporting, are accomplished through the state involvement and public participation requirements of the NCP.

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In the absence of federal- or state-promulgated regulations, there are many criteria, advisories, and guidance values that are not legally binding, but may serve as useful guidance for response actions. These are “to-be-considered” (TBC) guidance (USEPA, 1988a). These guidelines or advisory criteria should be identified if used to develop clean-up goals or if they provide important information needed to properly design or perform a remedial action. Three categories of TBC information are: (1) health effects information with a high degree of certainty (e.g., RfDs); (2) technical information on how to perform or evaluate site investigations or response actions; and (3) regulatory policy or proposed regulations (53 Federal Register [FR] 51436).

This Phase III RI is being conducted in accordance with CERCLA. Potential ARARs are used in planning field investigation activities and will be used in the FS process to evaluate how each remedial alternative being considered attains federal and state ARARs. ARARs are divided in the three categories listed below.

1. Location specific ARARs relate to the geographical and physical location of CRREL. They include restrictions or requirements placed on the concentrations of hazardous substances or conduct of remediation and related activities (USEPA, 1998) because of CRREL’s location. They could also affect the selection of or implementation of the cleanup technology due to culturally or environmentally sensitive areas that may be impacted. The jurisdictional prerequisites of each regulation will be considered for selected remedial actions. 2. Chemical specific ARARs are laws and regulations that identify health or risk based numerical values that, when applied to CRREL, provide cleanup limits for specific hazardous substances such as TCE. The limits will establish the acceptable amount or concentration that may remain in air (indoor and outdoor) and in soil and groundwater or discharged to the environment. (USEPA, 1998). 3. Action specific ARARs define acceptable performance, design or similar controls or restrictions imposed on particular remediation activities. They are usually technology or activity based requirements (USEPA, 1998). Selection of a particular response action at the Site will invoke the appropriate action-specific ARARs that may specify particular performance standards or technologies, as well as specific environmental levels for discharged or residual chemicals. These ARARs will be discussed in the FS for CRREL as remedial alternatives are screened and evaluated.

6.1 Location Specific ARARs

Location-specific ARARs are triggered by the presence of specific natural or manmade features or potentially affected resources at a disposal or cleanup site. Features and resources that can trigger location-specific ARARs include the following:

• Faults. • caves, salt domes, salt beds, and underground mines. • floodplains, wetlands, and water bodies.

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• sensitive ecosystems. • wilderness areas, wildlife refuges, wildlife resources, and scenic rivers. • rare, threatened, or endangered species. • archaeological resources and historic sites.

Of these, wetlands, water bodies, endangered species, facility siting, and wildlife resources may affect response actions at the CRREL.

Potential Location-Specific ARARs and Criteria TBC are listed in Table 6.1-1. Under NHDES regulations the CRREL Site is a designated Groundwater Management Zone (GMZ). CRREL has been issued Groundwater Management Permit (GMP) for the Site (Permit Number GWP- 199101025-H-001). The GMZ designation includes requirements to implement a Remedial Action Plan to maintain groundwater capture and treatment or implement remedial actions to prevent discharges to surface waters that would cause violation of surface water quality standards. The nearest surface water to CRREL is the Connecticut River which now receives discharges of treated and untreated (from CECRL 03) non-contact cooling water from CRREL (NPDES discharge permit NH0001619. In developing remedial alternatives for groundwater at CRREL that may involve continuing or modifying discharges to the Connecticut River, the requirements of the Clean Water Act and Fish & Wildlife Coordination Act will be evaluated and addressed.

6.2 Chemical Specific ARARS

Potential Chemical-Specific ARARs and TBCs are listed in Table 6.1-2. Chemicals of Concern at CRREL are primarily TCE which is the predominant focus for remediation. Under both Federal and New Hampshire statutes and regulations it is a requirement to use Safe Drinking Water MCLs and New Hampshire Groundwater Quality Criteria for developing remedial alternatives for groundwater. NHDES regulations allow establishment of Groundwater Management Zones where a regulated contaminant (TCE) has caused and continues to cause concentrations in excess of groundwater quality criteria.

In addition to TCE, the chemical cis-1,2-dichloroethene is present in groundwater at CRREL at concentrations above MCLs. Cis-1,2,DCE is considered to be a by-product of the degradation of TCE within the aquifer at CRREL. As such this chemical will potentially fall below MCLs as a TCE remedial alternative is implemented.

The Phase III RI for CRREL includes completion of a CERCLA based human health risk assessment. In completing this risk assessment, USEPA Health Advisories, Risk Reference Doses (RfDs) and Carcinogen Assessment Group Potency Factors will be considered in computing risks and in selecting groundwater and soil vapor cleanup goals.

NHDES Revised Vapor Intrusion Screening Levels for TCE will be considered in developing and evaluating groundwater and soil vapor cleanup goals for remedial alternative evaluation. Within the CRREL Site, the groundwater is considered to be Category GW-2. Category GW-2

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6.3 Action Specific ARARs

As discussed previously, action specific ARARs will be addressed in the FS.

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7.0 BASELINE HUMAN HEALTH RISK ASSESSMENT

This Section provides a summary of the BHHRA for the Site (Figure 7.1-1 and Figure 7.1-2). The full BHHRA is included in Appendix U. The BHHRA relies on data collected and discussed within Section 4.0 of this report, and previous Site investigations, to assess risks to human receptors at the Site and vicinity as identified in the conceptual site model included in Section 5.0. The BHHRA will provide information to be used in the FS, which will be presented under separate cover.

The BHHRA has been conducted in accordance with CERCLA requirements and consistent with USEPA risk assessment guidance (including, but not limited to Risk Assessment Guidance for Superfund (RAGS). Volume 1: Human Health Evaluation Manual (Parts A, D, E and F) (USEPA, 1989; 2001; 2004; 2009a)). USEPA national and regional guidance, and state regulations and guidance from New Hampshire (NHDES, 2013a: 2013b) have been used as required and deemed appropriate. A complete list of supporting documents used to complete the BHHRA is included in the references section of the BHHRA. The BHHRA has been performed according to the risk assessment work plan (Amec Foster Wheeler, 2016).

The BHHRA has been conducted using a four-step process, consistent with the framework for risk assessment described in RAGS (USEPA, 1989). The four steps include:

1. Hazard Identification. 2. Exposure Assessment. 3. Toxicity Assessment. 4. Risk Characterization.

The BHHRA and supporting documentation of the risk assessment methods, inputs, and results are provided in Appendix U.

7.1 Introduction

The purpose of the BHHRA is to characterize the potential human health risk associated with assumed exposure to impacted environmental media in the absence of mitigation or remediation (Baseline Scenario) as described by the CERCLA risk assessment guidance. The organization of the BHHRA showing each of the separate components that were evaluated is illustrated in the flowchart on Figure 7.1-3.

The primary environmental impacts evaluated are due to historical use, disposal, and environmental releases of TCE and other chemicals used onsite. Due to TCE’s ability to impact indoor air, one of the fundamental goals of the BHHRA is to evaluate cumulative risk to current indoor receptors onsite in the absence of mitigation and/or remediation. This goal is accomplished by evaluating analytical data for indoor air collected by summa canisters representing baseline conditions, combined with analytical data for other media.

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Current and Reasonably Foreseeable Receptors

Risks are addressed onsite for current and/or foreseeable receptors (daycare children, workers, trespassers, utility/construction workers) from: soil (each receptor), indoor air collected by summa canisters and potentially associated with vapor intrusion (daycare children and indoor workers), and soil vapor migrating into air of an excavation (construction workers). Risks have not been calculated for exposure to outdoor air, although available outdoor air data have been summarized and a preliminary evaluation has been performed to identify compounds that could warrant further evaluation. The purpose of the current and/or foreseeable scenario evaluation is to determine if there is a risk-based requirement to evaluate remedial alternatives and to identify preliminary remediation goals (PRGs) to be considered in the FS.

The off-Post vapor intrusion pathway for current land use is considered incomplete as documented in the Phase III RI vapor intrusion evaluation, which was conducted pursuant to recent USEPA vapor intrusion guidance. Because there are no other exposure pathways identified for off-Post properties under current land use, there is no quantitative human health risk assessment for current land use for off-Post properties in the BHHRA. Risks for two foreseeable future off-Post receptors are addressed in the BHHRA (off-Post resident at Rivercrest, and off-Post construction worker). Both receptors are assumed to be exposed to soil vapor migrating off-Post, either migrating into indoor air through vapor intrusion, or into an excavation, respectively.

Hypothetical Residential Receptors

In addition to the BHHRA assessment of baseline conditions for receptors associated with current and/or foreseeable land use, the BHHRA has also separately considered a hypothetical future onsite and off-Post land use (residential – properties other than Rivercrest). This conservative assessment is intended to represent potential future risks, should existing structures be re- configured with different foundation slab conditions or, removed and new buildings constructed within the existing footprints for future residential use.

Risks for hypothetical future receptors (residents) onsite are assessed from exposure to: surface soil, groundwater used for potable purposes, and indoor air as modeled from sub-slab soil vapor (presumed vapor intrusion). The onsite hypothetical future residential scenario has been evaluated to assist Army decision making regarding the need for institutional controls.

Risks for hypothetical residential receptors off-Post (at properties other than Rivercrest) are assessed only for potential future indoor air migrating from sub-slab soil vapor (associated with vapor intrusion). The off-Post hypothetical future residential scenario has been evaluated to assess potential future impacts beyond the boundary of Army property. The purpose of the hypothetical residential onsite and the off-Post scenarios is to provide information to the Army in evaluating the need for institutional controls. The hypothetical residential scenarios will not be included in the identification and evaluation of remedial alternatives in the FS.

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Supplemental Risk Assessments

In addition to the BHHRA, a supplemental risk assessment for indoor air has been conducted to characterize risks for non-baseline conditions (after mitigation/remedial actions have been implemented in some buildings). The supplemental risk assessment, therefore, provides an assessment of risks associated with “current conditions” rather than “baseline conditions” with respect to indoor air. This risk assessment is not required for the BHHRA, but is informative and is therefore referred to as a supplemental risk assessment. This supplemental risk assessment for “current conditions” is not intended to give the impression that indoor air conditions have permanently changed, since some of the on-going mitigation activities are temporary (deployment of HealthMate® air filtration units) and others may or may not be permanent (sub-slab depressurization systems). Indoor air quality has been characterized subsequent to implementation of mitigation and/or remediation during semi-annual vapor intrusion sampling events (Summa canister sample collection and laboratory analysis via Method TO-15) and during daily indoor air sampling and analysis in multiple buildings using the HAPSITE®.

Health risks associated with indoor air data collected with summa canisters and analyzed by Method TO-15 after mitigation and/or remediation are evaluated in the first portion of a supplemental risk assessment (not part of the BHHRA) referred to as the TO-15 Non-Baseline HHRA.

The second portion of the supplemental risk assessment, referred to as the HAPSITE® HHRA evaluates HAPSITE® data for TCE in indoor air only. The evaluation of HAPSITE® data is not a CERCLA requirement for the baseline risk assessment. The HAPSITE® HHRA evaluates indoor air data for four buildings (CDC, LMO, the Main Laboratory, and the TIAC where non-baseline (post-mitigation) HAPSITE® data are available. In addition, the HAPSITE® HHRA evaluates baseline (not post-mitigation data) HAPSITE® air data for the LMO. The LMO indoor air baseline risk is also evaluated in the BHHRA using summa canister data for that building. HAPSITE® data collected off-Post (primarily from the RMS) have not been evaluated in the supplemental risk assessment, as the vapor intrusion pathway off-Post was already evaluated in the Phase III RI vapor intrusion evaluation and the pathway was found to be incomplete.

The supplemental risk assessment (both the TO-15 Non-Baseline HHRA and the HAPSITE® HHRA) have been voluntarily performed for informational purposes to evaluate the effectiveness of mitigation measures and to evaluate the utility of HAPSITE® data within the risk assessment process. The supplemental risk assessment calculations do not evaluate baseline conditions, and are therefore not a CERCLA requirement.

7.1.1 Summary of Conceptual Site Model for Human Health

The CSM has been developed in Section 5. The purpose of the CSM is to identify source areas, potential migration pathways along which chemicals can move, and to identify potential receptors associated with relevant exposure pathways. The BHHRA considers only potentially complete pathways, where a source-pathway-receptor linkage may exist. The CSM in Section 5 has been used as a basis to select Compounds of Potential Concern (COPCs) for each medium. The

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I selected exposure pathways for the BHHRA are summarized in Table 7.1-1. The potential human receptors, exposure pathways and receptors considered for the BHHRA are listed below.

7.1.1.1 Sources

Historical use of the property as a research facility has resulted in the following sources:

• USTs (AOC 2 and AOC 15) and ASTs (AOC 1): TCE and petroleum hydrocarbons released to soil.

• Use of TCE as a secondary heat transfer medium piped into the Main Laboratory. Use of TCE and other compounds during experiments (AOC 9), and the disposal of TCE and other compounds in former borrow pit areas (AOC 13). TCE and other compounds used in research that were released to soil.

Due to the historical use of the Site, TCE is the primary compound that was analyzed and detected; however, other VOCs were identified. SVOCs, PAHs, and metals were also detected in one or more environmental media onsite.

Six media have been identified that may be impacted either directly from the releases (soil and groundwater) or by migration from one of the primary receiving media. The media evaluated are: 1) Soil, 2) Groundwater, 3) Indoor Air, 4) Sub-Slab Soil Vapor, 5) Exterior Soil Vapor, and 6) Outdoor Air (outdoor air data are not evaluated quantitatively in the BHHRA).

7.1.1.2 Migration Pathways and Exposure Pathways

A migration pathway is the route that a compound takes when it moves from the point of release to the point of exposure. TCE and petroleum hydrocarbons were primarily released to soil (surface and subsurface).

An exposure pathway describes the course a chemical takes from the source media to the exposed individual. The following pathways are considered:

• Current and/or foreseeable future human receptors may contact exposure medium through the following exposure pathways:

1. inhalation of directly measured indoor air.

2. direct contact with soil (ingestion and dermal contact).

3. inhalation of fugitive dust from soil.

4. onsite and off-Post inhalation of excavation air (from soil vapor) during construction.

5. inhalation of future indoor air modeled from soil vapor (future residents at Rivercrest, where there currently are no buildings).

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• Hypothetical receptors (residents) may contact exposure media through the following exposure pathways:

1. ingestion of groundwater as drinking water.

2. contact with groundwater during showering (dermal contact and inhalation).

3. direct contact with soil (ingestion and dermal contact).

4. inhalation of fugitive dust from soil.

5. inhalation of future indoor air modeled from sub-slab soil vapor (used instead of directly measured indoor air concentrations as hypothetical residential buildings are expected to be very different than the existing buildings).

7.1.1.3 Receptors

Receptors are chosen in order to cover the foreseeable range of potential exposures (exposure media and exposure routes) and to identify the exposure parameters for a theoretical reasonably maximally exposed individual in the receptor group. The following receptors are considered:

• Current and foreseeable receptors include: 1) daycare child (CDC area only), 2) indoor daycare worker (CDC area only), 3) indoor worker in non-CDC buildings onsite, 4) outdoor worker, and 5) utility worker.

• Future foreseeable receptors (not evaluated as current) include: 1) trespasser, 2) resident at Rivercrest, and 3) onsite and off-Post construction worker.

• Hypothetical receptors include: 1) onsite resident, 2) off-Post resident (at properties other than Rivercrest).

7.1.2 Hazard Identification

The purpose of the hazard identification process is two-fold:

1. to compile available data collected to evaluate the nature and extent of chemicals released at the Site. 2. to select a subset of these chemicals for quantitative evaluation in the risk assessment.

The risk assessment considered: soil, groundwater, soil vapor, indoor air, and outdoor air data from field activities conducted between 1991 and 2015 and summarized in the following reports:

• Remedial Investigation Report, CRREL, Hanover, New Hampshire, Final (Ecology & Environment, Inc., 1992).

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• The Phase II Remedial Investigation for CRREL, Hanover, New Hampshire (Arthur D. Little, 1994). • The CRREL Site Investigation AOC 2 and AOC 9 (Stanley Consultants, Inc., 2006). • This Phase III Remedial Investigation Report.

Data for samples collected prior to 1995 pre-date the use of methanol extraction and various remedial efforts onsite. Therefore, data from 1992 and 1993, which included both VOC and petroleum hydrocarbon analysis, have not been used.

In addition to data generated by fixed laboratory, there are field-derived data and data generated by mobile analytical instrumentation. The analytical data were generally considered usable based on validation performed according to the project-specific QAPP. However, an evaluation of detection limits was also performed to determine the usability of the data. In general, most values reported are appropriate and are interpreted as acceptable for use throughout the risk assessment.

The data were processed prior to summarizing the analytical data, eliminating duplication in cases where compounds have been reported by more than one analytical method in a given sample and for field sample/field duplicate pairs. This process identifies a single result for each parameter for each method within each sampling location/event for use in the data summary. Following this processing step, summary statistics were compiled for each medium and exposure area, by chemical, including: minimum and maximum detected concentrations, frequency of detection, range of reporting limits for non-detects, and arithmetic mean concentrations. Analytes/compounds that were not detected within a medium/area are not retained for further quantitative evaluation.

COPCs were selected for evaluation in the quantitative risk assessment per USEPA protocol (USEPA, 1989). Screening based on toxicity is done by comparing the maximum detected concentrations in each exposure area to appropriate risk-based screening levels. If the maximum detected concentrations are lower than these criteria, then they are unlikely to pose unacceptable risks through Site-specific exposure pathways. Risk-based screening levels were generally selected as the minimum of the USEPA RSLs (USEPA, 2016a) and the NHDES risk-based standards (NHDES, 2013a; 2013b). The USEPA MCLs (USEPA, 2016b) were also considered for groundwater ingestion, and the Vapor Intrusion Screening Levels (VISL) (USEPA, 2015a) were considered for evaluation of sub-slab soil vapor and exterior soil vapor (at Rivercrest) migration into indoor air. The selected RSLs for each exposure pathway have been derived as the lower of the concentration associated with a cancer risk of 1 in 1 million (1x10-6) and the concentration associated with a non-cancer hazard quotient (HQ) of 0.1.

If risk-based screening levels are not available, a surrogate compound was identified based on structural similarity, if available. If an appropriate surrogate could not be identified and there were no human health toxicity data available, the compound was not selected as a COPC (this was only applicable for ethanol, which is not generally considered toxic in small quantities). Chemicals that are considered essential nutrients and do not have screening levels (calcium, magnesium, sodium, potassium, and phosphorous) have not been included as COPCs (USEPA, 1989).

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Analytical data for petroleum hydrocarbon compounds are available for multiple hydrocarbon fractions and individual compounds detected within each fraction. Appropriate carbon ranges have been selected to represent each analytical result based on the analytical method. These surrogate carbon ranges have been used within the risk-based screening of these compounds as documented in the screening level selection tables in the BHHRA. The standard USEPA approach has been followed, which is to assess exposure to both indicator and non-indicator compounds separately from the hydrocarbon fractions when appropriate analytical data are available (USEPA, 2009b). This may cause double-counting in some cases as the mass of these compounds has not been removed from the hydrocarbon fraction it was associated with in cases where analysis was performed for both the individual compounds and petroleum hydrocarbon fractions.

COPCs were selected for soil, groundwater, indoor air (17 buildings), sub-slab soil vapor (14 buildings), soil vapor, and outdoor air. A summary of COPCs selected per area/medium is shown on Table 7.1-2.

The results of the COPC selection are identified below, by medium.

• COPCs in soil include: arsenic, benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, diesel range organics, gasoline range organics, indeno(1,2,3- cd)pyrene, n-nitrosodi-n-propylamine, naphthalene, and TCE.

• COPCs in groundwater include: antimony, arsenic, carbon tetrachloride, chloroform, cobalt, cis-1,2-Dichloroethene, iron, manganese, methylene chloride, thallium, and TCE.

• COPCs in indoor air include: 1,1,1-trichloroethane, 1,2,4-trichlorobenzene, 1,2,4- trimethylbenzene, 1,2-dichloroethane, 1,3,5-trimethylbenzene, 1,3-butadiene, benzene, bromodichloromethane, C5-C8 aliphatic hydrocarbons, C9-C10 aromatic hydrocarbons, C9-C12 aliphatic hydrocarbons, carbon tetrachloride, chloroform, dichlorodifluoromethane, ethylbenzene, hexachlorobutadiene, hexane, naphthalene, tetrachloroethene, TCE, trichlorofluoromethane, xylene (o), and xylenes (m&p).

• COPCs in onsite sub-slab soil vapor include: 1,1,1-trichloroethane, C5-C8 aliphatic hydrocarbons, C9-C10 aromatic hydrocarbons, C9-C12 aliphatic hydrocarbons, carbon tetrachloride, cis-1,2-dichloroethene, dichlorodifluoromethane, tetrachloroethene, TCE, trichlorofluoromethane, and xylenes (m&p).

• COPCs in off-Post sub-slab soil vapor include: chloroform, dichlorodifluoromethane, ethylbenzene, tetrachloroethene, trans-1,2-dichloroethene, TCE, and trichlorofluoromethane.

• COPCs in off-Post soil vapor at Rivercrest (where soil vapor is used as a surrogate for sub- slab soil vapor due to the lack of buildings at Rivercrest) include: 1,2,4-trichlorobenzene, 1,4-dichlorobenzene, carbon tetrachloride, chloroform, dichlorodifluoromethane, hexachlorobutadiene, TCE, and trichlorofluoromethane.

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• COPCs in onsite soil vapor (0-20 ft) include: 1,1,2,2-tetrachloroethane, 1,2,4- trichlorobenzene, 1,2-dibromoethane, 1,4-dichlorobenzene, C5-C8 aliphatic hydrocarbons, carbon tetrachloride, chloroform, hexachlorobutadiene, TCE, and trichlorofluoromethane.

• COPCs in off-Post soil vapor (0-20 ft) include: carbon tetrachloride, chloroform, tetrachloroethene, TCE, and trichlorofluoromethane.

• COPCs in outdoor air include: 1,1,2,2-tetrachloroethane, 1,2,4-trichlorobenzene, 1,2,4- trimethylbenzene, 1,3,5-trimethylbenzene, benzene, benzyl chloride, C9-C12 aliphatic hydrocarbons, carbon tetrachloride, chloroform, ethylbenzene, hexachlorobutadiene, tetrachloroethene, TCE, and xylenes (m&p).

Although twenty-three (23) compounds were selected as COPCs for indoor air in onsite buildings, it is noted that some compounds detected in indoor air samples are not associated with vapor intrusion. Volatiles detected in indoor air could also be associated with use of the compounds in the buildings during the regular course of facility operations, with contaminated building materials that release vapors, or with outdoor air that is entering the buildings. To evaluate whether selected COPCs in indoor air samples may be the result of vapor intrusion, concentrations of sub-slab soil vapor data collected onsite have been compared to concentrations of indoor air data in Attachment E of the BHHRA. Where concentrations are higher in indoor air than sub-slab soil vapor, the COPC is unlikely to be related to vapor intrusion. This evaluation indicates that indoor air in several onsite buildings may be affected by vapor intrusion. A total of twenty compounds detected in indoor air samples were considered likely to originate from sub-slab soil vapor in at least one building. Due to the uncertainty involved in this evaluation and the desire to provide an accurate portrayal of current risks, each of the 23 potential COPCs has been carried through the assessment.

7.1.3 Exposure Assessment

The purpose of the exposure assessment is to estimate the magnitude and frequency of potential human exposure to COPCs present in release-impacted media at each exposure area. The first step in the process is identifying potential receptors (i.e., people who may contact the impacted environmental media). This step was accomplished previously in the CSM. The second step is to develop potential exposure scenarios identifying appropriate environmental media, exposure points and exposure pathways considering a Reasonable Maximum Exposure (RME) scenario. The third step is to quantify the exposure (including identification of exposure point concentrations) for potentially complete pathways where COPCs are identified.

7.1.3.1 Exposure Scenarios

Receptors are identified based on the current and foreseeable future land uses, as well as hypothetical future land uses (not necessarily foreseeable, but considered to support the Army in evaluating the need for institutional controls). Based on current and potential future land use, the BHHRA considers the following receptors and exposure pathways for the Baseline scenario:

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Onsite – Current and/or Future Foreseeable Current and Future onsite Daycare Child at the CDC: • Dermal contact and incidental ingestion of surface soil (0-2 ft.) at the CDC and inhalation of airborne dust particles in outdoor air. • Inhalation of indoor air vapors at one exposure point (the CDC first floor). Current and Future onsite Indoor Worker at the CDC: • Dermal contact and incidental ingestion of surface soil (0-2 ft.) at the CDC and inhalation of airborne particles in outdoor air. • Inhalation of indoor air vapors in the whole CDC (first floor and basement). Current and Future onsite Indoor Worker at various onsite buildings: • Dermal contact and incidental ingestion of onsite surface soil (0-2 ft.) and inhalation of airborne particles in outdoor air. • Inhalation of indoor air inside onsite buildings. Current and Future onsite Outdoor Worker: • Dermal contact and incidental ingestion of onsite surface soil (0-2 ft.) and inhalation of airborne particles in outdoor air. Future onsite Trespasser: • Dermal contact and incidental ingestion of onsite surface soil (0-2 ft.) and inhalation of airborne particles in outdoor air. Current and Future onsite Utility Worker: • Dermal contact and incidental ingestion of onsite surface soil (0-6 ft.) and inhalation of airborne particles in outdoor air. Future onsite Construction Worker: • Dermal contact and incidental ingestion of onsite surface soil (0-10 ft.) and inhalation of airborne particles in outdoor air. • Inhalation of excavation air from soil vapor (0-20 ft.). Off-site – Current and/or Future Foreseeable Hypothetical Future Onsite Resident at Rivercrest: • Inhalation of hypothetical future indoor air, calculated from soil vapor data (all depths) using a default attenuation factor (USEPA, 2015a) to produce an estimated future indoor air concentration.

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Future Off-Post Construction Worker: • Inhalation of excavation air from off-Post soil vapor (0-20 ft.). Hypothetical Onsite and Off-Post Hypothetical Future Onsite Resident: • Dermal contact and incidental ingestion of onsite surface soil (0-2 ft.) and inhalation of airborne particles in outdoor air. • Ingestion of groundwater as drinking water, and dermal contact, and inhalation of volatiles from groundwater during showering. • Inhalation of hypothetical future indoor air, calculated from sub-slab soil vapor data using a default attenuation factor (USEPA, 2015a) to produce an estimated future indoor air concentration.

Hypothetical Future Off-Post Resident:

• Inhalation of hypothetical future indoor air, calculated from sub-slab soil vapor data off-Post using a default attenuation factor (USEPA, 2015a) to produce an estimated indoor air concentration.

Table 7.1-1 shows the exposure pathways evaluated.

Exposure points were identified for each receptor and exposure medium. Exposure points are:

• Measured Indoor air onsite: Main Laboratory (ten exposure points), CDC (one for adults, one for children), Greenhouse, LMO, TIAC, Asphalt Laboratory, Ballistics Laboratory, DPW Storage Building, FERF, Groundwater Treatment Facility, Ice Engineering Facility, North Gate House, Project Support Facility, Remote Sensing Facility, South Gate House, Storage Shed, and the Vehicle Storage Building.

• Future Residential Indoor air off-Post at Rivercrest (no existing buildings)

• Surface soil (0–2 ft bgs) CDC Area onsite, soil in depth interval, immediate area of the CDC

• Surface soil (0–2 ft bgs) onsite, soil from the property (including the CDC) in the depth interval

• Shallow subsurface soil (0-6 ft bgs), onsite, soil from the property in the depth interval

• Combined surface and subsurface soil (0-10 ft bgs), onsite, soil from the property in the depth interval

• Soil vapor (0-20 ft bgs) onsite, includes soil vapor data collected onsite

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• Soil vapor (0-20 ft bgs) off-Post, includes soil vapor data collected at Dartmouth Housing (DH), Dartmouth Printing (DP), RMS, and Rivercrest.

• Groundwater – no current exposure points. Exposure Point Concentrations (EPCs) were derived for five monitoring wells within the core of the groundwater plume. This EPC represents a hypothetical future exposure point that has been evaluated for the purpose of supporting Army decision-making with regard to institutional controls.

• Hypothetical Future Residential Indoor air onsite: CDC, DPW Storage Building, Groundwater Treatment Facility, Ice Engineering Facility, LMO, Main Laboratory Building (ten exposure points), Remote Sensing Facility, TIAC, and Vehicle Storage Building. These scenarios represent hypothetical future exposure points that have been evaluated for the purpose of supporting Army decision-making with regard to institutional controls.

• Hypothetical Future Residential Indoor air off-Post: Brendel & Fisher, Dartmouth Housing, Dartmouth Printing, RMS, and Hanover Chiropractic and Yoga.

7.1.3.2 Exposure Parameters

Receptor-specific exposure parameters were used to evaluate each receptor for an RME scenario in the BHHRA. These values are used to calculate the Daily Intakes and/or Average Daily Exposures for each of the receptors and exposure pathways. Where possible, exposure parameters were obtained from the USEPA Recommended Default Exposure Factors (USEPA, 2014a). Additional sources were used consistent with USEPA guidance (as referenced in BHHRA) and Post-specific information.

7.1.3.3 Quantification of Exposure

The EPCs were generally expressed as the lower of the 95 percent upper confidence limit (95% UCL) on the arithmetic mean of the measured concentration, and the maximum detected concentration, unless an alternative calculation is selected and defended. The majority of EPCs are calculated based on direct measurements using USEPA ProUCL software (ProUCL 5.0: USEPA, 2013) to develop and select the 95% UCL. Modeling is required to calculate some EPCs as discussed below:

• Soil to outdoor air pathway: The dust concentration in air used in the evaluation of outdoor air pathways for non-excavation and excavation scenarios is the product of the soil EPC and the inverse of the Particulate Emission Factors derived in accordance with USEPA guidance (USEPA, 2002).

• Tapwater (groundwater) into indoor air while showering: modeling was accomplished using a model developed by Andelman and modified by Schaum (Schaum et.al., 1994) is required to calculate the volatilization of COPCs in tap water while showering.

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• Future vapor intrusion from sub-slab soil vapor and soil vapor: EPCs for the future vapor intrusion to indoor air pathway to evaluate a future resident at Rivercrest and a hypothetical future resident have been approximated by first selecting the lower of the 95% UCL and the maximum detected soil vapor concentration or the sub-slab soil vapor concentration for each COPC in each exposure area, and multiplying that concentration by the USEPA default VISL attenuation factor of 0.03 (USEPA, 2015a).

• Soil vapor into an excavation: EPCs have been modeled using a method developed by Virginia Department of Environmental Quality (VDEQ) (VDEQ, 2014), and modified by Meridian in CSAP Technical Review #18 (Meridian, 2012) to estimate excavation air concentrations from a soil vapor source instead of a groundwater source.

In order to estimate the potential hazard or risk posed by oral and dermal exposure, the exposure dose is calculated. This value estimates a receptor's daily intake of each compound and is defined as the amount of a given COPC taken into the receptor, normalized to bodyweight. This value is expressed in units of milligrams of COPC per kilogram of body weight per day (mg/kg-day). The exposure dose for the oral and dermal pathway is termed the Average Daily Dose (ADD). It takes into account the identified exposure assumptions, and averages exposure over the specified period of time exposure is assumed to occur.

In order to estimate the potential carcinogenic risk and hazard posed by the inhalation route of exposure from volatile compounds and particulates, a simplified equation is used that calculates an average air concentration inhaled over the exposure period, rather than a dose per body weight. This value is termed the Average Daily Exposure (ADE).

The ADDs and ADEs have been calculated separately for each compound and receptor at each exposure point, and are presented separately in Appendix U.

7.1.4 Toxicity Assessment

The purpose of the toxicity assessment is to identify the adverse health effects a compound could potentially cause, and then define the relationship between the dose or level of exposure of a compound and the likelihood and magnitude of an adverse effect (response) (USEPA, 1989), and are often termed “dose-response” relationships. Adverse health effects are classified by USEPA as noncarcinogenic (i.e., effects other than cancer), or potentially carcinogenic. Dose-response relationships per COPC are identified for oral and inhalation exposure. The combination of the results of the toxicity assessment and exposure information calculating the magnitude of potential exposure provides an estimate of potential risk. USEPA’s guidance (USEPA, 2003) was followed to identify toxicity values. Age-dependent adjustment factors were applied to each COPC that has a potential mutagenic mode of action, in accordance with USEPA guidance (2005).

USEPA supports a position that assessment of exposures using the chronic Reference Concentration (RfC) for TCE is protective of chronic as well as acute and sub-chronic exposures. The TCE RfC value and its application in managing indoor air exposures has been, and continues to be, a subject of debate among the regulated community and some state environmental

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In 2014 USEPA Region 9 prepared the document Interim Action Levels and Response Recommendations to Address Potential Developmental Hazards Arising from Inhalation Exposures to TCE in Indoor Air from Subsurface Vapor Intrusion (USEPA, 2014b). This document utilizes the TCE RfC and multiples of the RfC in recommending Accelerated Response Action Levels and Urgent Response Action Levels for TCE in indoor air. State regulator response to the Region 9 document has been mixed, and this document is not applicable within Region 1, in the state of New Hampshire. Given the lack of an appropriate and accepted acute standard for TCE, using a chronic RfC to evaluate data collected over an acute or sub-chronic duration, is considered to provide a conservative estimate of risks.

7.1.5 Risk Characterization

Two general types of health risk are characterized for each potential exposure pathway considered: potential carcinogenic risk and potential non-carcinogenic risk.

Firstly, the purpose of carcinogenic risk characterization is to estimate the upper-bound likelihood that a receptor will develop cancer in his or her lifetime as a result of exposure to a COPC in environmental media at the Site. The Excess Lifetime Cancer Risk (ELCR) is the likelihood over and above the background cancer rate. The risk value is expressed as a probability (e.g., 10-6, or one in one million). The potential carcinogenic risk for each exposure pathway is calculated for each receptor. It is assumed that cancer risks are additive. Risk from different exposure pathways are summed to estimate the total Site potential cancer risk for each receptor. The sum of the cancer risk estimates for each receptor is compared to the USEPA’s risk range of 1×10-6 to 1×10-4, which provides the criteria for selection of compounds and provides target levels for remediation goals.

Secondly, the potential for exposure to a COPC to result in adverse non-carcinogenic health effects is evaluated using a ratio, which is unitless, known as the Hazard Quotient (HQ). The total Hazard Index (HI) is calculated for each exposure pathway by summing the HQs for each individual COPC. Where the total Site HI is greater than 1 for a given receptor, a more detailed evaluation of potential non-carcinogenic effects based on specific health or target endpoints (e.g., liver effects, neurotoxicity) is performed (USEPA, 1989). The HI is compared to the HI = 1 on a per target endpoint basis. The risks are calculated and documented in the BHHRA in risk calculation spreadsheets and in risk summary tables.

7.1.5.1 Baseline Results and Conclusions: Current and/or Foreseeable Receptors

Results for current and/or foreseeable receptors exposed to baseline conditions (pre- mitigation/remediation) are shown in Table 7.1-3 and are summarized in Figure 7.1-4 through Figure 7.1-7. The HI is compared to the HI = 1 on a per target endpoint basis. In each scenario

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• Current and Future Onsite Outdoor Worker, Utility Worker, and Future Trespasser

o No cancer risks or HIs were above USEPA thresholds for ingestion and dermal contact with soil or inhalation of soil-derived dust for the current and foreseeable receptors evaluated. Risks were calculated for the Outdoor Worker, Trespasser, and Utility Worker based on soil exposures only. Therefore, risks for these three receptors were acceptable.

• Current and Future Onsite Daycare Child

o No cancer risks or HIs were above USEPA thresholds for the Daycare Child at the CDC from soil (as above), or from inhalation of indoor air at the CDC (first floor).

• Future Onsite and Off-Post Construction Worker

o Potential cancer risks calculated are within or below the USEPA’s cancer risk range for the future Onsite Construction Worker.

o The HI (47) is above the USEPA threshold of 1 for the Construction Worker primarily due to inhalation of soil vapor in an excavation. C5 – C8 aliphatic hydrocarbons and TCE in soil vapor are the predominant contributors to the HI.

• Current and Future Onsite Indoor Worker

o The HI is above the USEPA threshold of 1 for the current and future onsite Indoor Worker for inhalation of indoor air in six onsite buildings (total of 9 indoor air exposure points). The screening HI is above 1 for the LMO and the Storage Shed, but the HIs for specific target organs are equal to or below 1.

. The Indoor Worker HI is greater than the USEPA threshold HI of 1 for at least one target organ or system for exposure to indoor air in the following: DPW Storage Area, FERF, Groundwater Treatment Facility, Main Laboratory (North Basement, North first floor, South Basement, West Sub- Basement), the CDC and, Vehicle Storage Building.

. The HI for Indoor Worker ranged from 1.6 to 24.

. TCE is the predominant contributor to indoor air HI greater than 1 in the three buildings: CDC, the Main Laboratory (North Basement, North first floor, South Basement, West Sub-Basement), and the Groundwater Treatment Facility.

. Fuel-related analytes are the predominant contributors to indoor air HI greater than 1 in two buildings: DPW Storage Area (trimethylbenzenes and C9-C10 aromatic hydrocarbons) and the Vehicle Storage

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(trimethylbenzenes and xylenes). These compounds are considered to be from non-vapor intrusion sources.

. Dichlorodifluoromethane is the predominant contributor to indoor air HI greater than 1 in one building: FERF.

o The Indoor Worker HI is less than the USEPA threshold HI of 1 for exposure to indoor air in nine onsite buildings (total of 9 indoor air exposure points): 1) Asphalt Laboratory, 2) Ballistics Laboratory, 3) Greenhouse, 4) Ice Engineering Facility, 5) Logistics Management Office, 6) Main Laboratory (West – Level 1), 7) Remote Sensing Facility, 8) Storage Shed and 9) TIAC.

• Potential cancer risks calculated are within or below the USEPA’s cancer risk range for each of the onsite current and foreseeable receptors.

• Future Off-Post Resident at Rivercrest

o Potential cancer risk is above the upper end of the USEPA cancer risk range and HI is above 1 for potential indoor air exposure in future residences based on modeling of soil vapor data to approximate future indoor air concentrations (there are currently no buildings on this property)

7.1.5.2 Compounds of Concern

COPCs that substantially contribute to HIs greater than 1 for indoor air or COPCs that substantially contribute to cancer risk greater than the 1x10-4 risk level are identified as COCs. A summary of the total ELCR, HI, along with the exposure medium, pathway, and target endpoint for COCs identified based on cancer risk and/or HI greater than USEPA threshold risk/HI levels are presented for each area, and receptor on Table 7.1-4.

COCs were identified for each exposure medium. They were selected per area/medium using the following criteria:

• Carcinogens: If the total cumulative ELCR is greater than 1x10-4 per exposure pathway, COCs were identified in this area/medium as compounds with an individual ELCR above 1x10-6.

• Non-Carcinogens: If the total HI is greater than 1, COCs were identified as compounds in this area/medium with HQ > 1.0, and HQ > 0.1 if the noncancer effects were additive.

Onsite Indoor Air

Fourteen compounds were selected as potential COCs for indoor air onsite among 9 exposure areas with HIs greater than 1 in onsite buildings. As shown in Attachment E of the BHHRA, an analysis has been performed comparing indoor air concentrations to sub-slab soil vapor to identify whether compounds may be detected in indoor air as the result of vapor intrusion. This analysis has been used to identify whether the potential COCs are likely to be the result of vapor intrusion.

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After comparison with this analysis, the majority of potential COCs were eliminated as not likely to be caused by vapor migration, leaving five remaining COCs in a total of seven exposure areas (within four buildings). Only three COCs remained after considering whether the noncancer effects were additive. Although the HI was above 1 for the DPW Storage Building and the Vehicle Storage Building, the HI is driven by COPCs that are related to indoor air sources, not vapor intrusion. Those COPCs associated with indoor air sources will not be addressed in the FS. The selected COCs are listed below for indoor air.

• Dichlorodifluoromethane. • TCE. • Trichlorofluoromethane.

Soil Vapor (Excavation Air)

One COC was selected for soil vapor (construction worker inhalation of vapors released into an excavation) onsite. The COC in soil vapor is listed below.

• TCE.

Rivercrest Indoor Air

Five COCs were selected for future residential indoor air off-Post at Rivercrest with cancer risk above the USEPA risk range, and HIs greater than 1. The COCs for indoor air are listed below.

• Carbon Tetrachloride. • Chloroform. • Hexachlorobutadiene. • TCE. • Trichlorofluoromethane.

PRGs have been developed for COCs in the current and/or foreseeable scenarios as discussed in Section 9 of this RI. PRGs were developed for a current and future indoor worker exposure scenario, a future construction worker scenario, and future residential use of Rivercrest, as these scenarios have calculated HIs greater than 1 or risks greater than the USEPA risk range for current and/or foreseeable future land use.

7.1.5.3 Baseline Results and Conclusions: Hypothetical Receptors

The risk assessment results for the hypothetical future residential scenarios are also shown in Table 7.1-3. As shown, the potential cancer risk for the hypothetical onsite resident from combined exposure to soil, groundwater as a drinking water source, and indoor air modeled from sub-slab soil vapor, is above the USEPA risk range for each onsite building and the potential HI for this receptor is above the non-cancer threshold HI of 1 in each onsite building. The cancer risk and HI for the potable use of groundwater is well above the USEPA risk range and the threshold HI of 1 respectively. The cancer risk and/or HI is greater than the upper end of the USEPA risk range and

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I the threshold HI of 1 for exposure to modeled indoor air at seven existing onsite buildings. The cancer risk and HI is below the upper end of the USEPA risk range and the threshold HI of 1 for residential exposure to surface soil.

The potential cancer risk for the hypothetical future off-Post resident exposed to indoor air modeled from sub-slab soil vapor is below the USEPA risk range for each off-Post property evaluated (with the exception of Rivercrest, which was discussed previously as a foreseeable future scenario). The potential HI (indoor air) for the hypothetical future off-Post resident at Brendel & Fisher is above the non-cancer threshold HI of 1. The potential HI is below 1 in the other off-Post buildings evaluated (except for Rivercrest as discussed above). PRGs were not calculated for hypothetical residential receptors as these were evaluated for the purpose of assisting the Army by informing institutional controls.

7.1.6 Uncertainty

Risk assessments rely on measured data, and also on assumptions, estimates, and policy decisions. Within the risk assessment process, assumptions are made due to a lack of absolute scientific knowledge. This section identifies and discusses uncertainties in the risk assessment to provide perspective on the quantitative risk estimates. It important to evaluate the assumptions and choices made in the risk assessment to evaluate their impact on the results and conclusions, as each assumption introduces some degree of uncertainty into the process. They are discussed in qualitative terms, because for most of the assumptions there is not enough information to assign a numerical value to the uncertainty that can be factored into the calculation of risk.

In keeping with CERCLA guidance, conservative assumptions are made throughout the risk assessment so that the assessment is overall health protective. When the assumptions are considered collectively, it is much more likely that actual risks are over-estimated rather than under-estimated.

Uncertainties involve assumptions and/or calculations to address unknown values for input parameters for the risk calculations. These include, but are not limited to:

• The use of the conservative estimate of mean concentrations (temporal average) of TCE in air as EPCs is consistent with the chronic RfC, but it may underestimate hazard for developmental effects such as fetal heart malformations that potentially could occur subsequent to brief exposures.

• The measured concentrations of TCE in indoor air may not be sourced exclusively from vapor intrusion. There may be other sources such as contaminated building materials, ongoing experiments, and outdoor air. The measured concentrations may, therefore, overestimate risk or hazard associated with vapor intrusion.

• The approximation of future indoor air concentrations in future residential structures at Rivercrest and other off-Post properties by applying a default attenuation factor to sub-slab soil vapor concentrations or exterior soil vapor concentrations is highly uncertain.

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However, the default USEPA attenuation factor is orders of magnitude more conservative than Site-specific attenuation factors calculated for onsite buildings using actual sub-slab data and co-located indoor air data.

• The estimation of future outdoor air concentrations of VOCs during excavation activities is also uncertain. The model estimates outdoor air concentrations based on release of vapors from the subsurface into the excavation. Whether the model might overestimate or underestimate exposure concentrations for construction workers is unknown.

• The indoor air exposure points were actually exposure areas that included multiple workspaces, offices, labs, hallways, etc. There were no baseline TO-15 data for each of the smaller spaces, so the EPCs for each exposure point were not necessarily representative of concentrations over time in each of those smaller spaces. The EPCs are considered representative of the exposure areas.

• The selected groundwater EPC for TCE from the core of the plume for ingestion and dermal contact is 15 mg/L, which is approximately 3000 times larger than the USEPA MCL (0.005 mg/L). This value is very conservative estimate, and due to the groundwater management zone that encompasses the plume, it is very unlikely that anyone would install a drinking water well within this area.

7.2 TO-15 Non-Baseline Supplemental Human Health Risk Assessment

The supplemental risk assessment has been performed for informational purposes to evaluate the effectiveness of mitigation measures that have been implemented. The supplemental risk assessment follows the same basic process as the BHHRA, but is not a CERCLA requirement.

Several mitigation measures have been implemented onsite including SSDS within the CDC and the Main Laboratory, and deployment of HealthMate® air filtration systems in the CDC, Main Laboratory, Greenhouse, LMO, and TIAC. The TO-15 data collected following implementation of these measures were used in this supplemental risk assessment.

Results for the non-baseline scenario (TO-15 data) are shown in Table 7.2-1. Each potential cancer risk calculated for the inhalation of indoor air pathway post-mitigation, is within or below the USEPA’s risk range of 1x10-6 to 1x10-4 and each HI is below the USEPA threshold HQ of 1, with the exception of the TIAC, which has an HI of 2 that is driven by 1,3-butadiene. This compound was not detected in sub-slab soil vapor, and is therefore considered unrelated to vapor intrusion. The compound was detected in the TIAC during the winter sampling events and may be due to combustion of fuels such as propane (forklifts) and gasoline (vehicles). Fumes may enter the TIAC though an air intake located adjacent to the Lab Addition loading dock.

A comparison of TO-15 baseline and TO-15 non-baseline (post-mitigation) risk and HI for indoor air is shown in Figure 7.2-1 and Figure 7.2-2, respectively. Each of the potential cancer risks calculated for the inhalation of indoor air pathway for baseline and non-baseline (post-remediation) conditions, are within or below the USEPA’s risk range of 1x10-6 to 1x10-4. Baseline conditions

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7.3 HAPSITE® Supplemental Human Health Risk Assessment

The supplemental HAPSITE® risk assessment has been performed for informational purposes to evaluate the effectiveness of mitigation measures and to explore the use of HAPSITE® data within the risk assessment process. The supplemental risk assessment follows the same basic process as the BHHRA, but is not a CERCLA-requirement.

HAPSITE® indoor air samples were collected and analyzed with the field-based portable GC/MS in the selected ion monitoring (SIM) mode for TCE only. The majority of HAPSITE® samples were collected using grab methodology, over one-minute intervals. The one-minute grab samples can be collected with the HAPSITE® at higher frequency resulting in greater spatial and temporal coverage, when compared to the standard, static 8-hour time-weighted (TO-15 analysis) samples collected with Summa canisters. The HAPSITE® analysis time is 10 to 12 minutes per sample which results in five to 6 samples collected in one hour during routine monitoring activities within a building. The remaining samples were collected using BottlevacTM samplers equipped with flow controllers, which were not evaluated in this risk assessment as combining data collected using grab sample methodology with time-weighted methodology is generally considered inappropriate. The grab samples analyzed with HAPSITE® produce real-time indoor air data collected to monitor TCE concentrations. Monitoring is conducted to assist in the protection of human health in the work place environment during the regular course of each work day. Other HAPSITE® data collected to investigate sources and migration pathways that are not representative of breathing zone air have not been considered in the BHHRA. The majority of HAPSITE® indoor air data were collected after some mitigation and/or remedial actions. HAPSITE® indoor air samples have been collected from four buildings onsite. These building include the Main Laboratory, TIAC, CDC, and the LMO.

Summary statistics have been calculated independently for both 8-hour TO-15 data and HAPSITE® samples. The results of the independent statistical analysis have been compared to evaluated differences in TCE concentration distributions and selected EPCs for non-baseline conditions (post-mitigation). As shown in Table 7.3-1, which provides a comparison of the independent summary statistics calculated, and illustrated in Figure 7.3-1, the EPCs are quite similar (but overall slightly higher for HAPSITE® data). The range of concentrations is greater for the HAPSITE® data than for the TO-15 data.

As illustrated in Figure 7.3-2, the independently calculated standard error (which is a statistical term that measures the accuracy with which samples represent a population) is generally much larger for the TO-15 data, indicating that the TO-15 means (though similar to the HAPSITE® means) provide a much less accurate representation of the mean. Figure 7.3-3 shows both sets of non-baseline conditions (post-mitigation) data for the Main Laboratory building. This figure is

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As an example of the variability in the HAPSITE® data, in the Main Laboratory South 1 area, which had a TCE indoor air EPC less than 8.8 µg/m3 (concentration associated HQ = 1 for chronic exposure), also had the highest detected concentration of TCE in indoor air (64.8 µg/m3), approximately 10% of the detected concentrations (63 out of 667 samples) were above 8.8 µg/m3. As multiple samples may be collected within one area over the course of a day, the information does not indicate that 63 days were above the level associated with an HQ of 1. Further evaluation of the data shows that individual concentrations were above 8.8 µg/m3 for 45 days out of the total exposure period. The maximum detected result is about 7 times higher than the level associated with an HQ of 1. The maximum TCE concentrations and the range of TCE concentrations were less in the Main Laboratory North Area and West Area where fully operational SSDSs are installed.

Results for the HAPSITE® scenarios are shown in Table 7.3-2, Figure 7.3-4 and Figure 7.3-5. Each potential cancer risk calculated for the inhalation of indoor air pathway post-remediation (non- baseline), is within or below the USEPA’s risk range of 1x10-6 to 1x10-4 and each hazard is below the USEPA threshold HQ of 1. The CDC worker scenario is not shown, as TCE indoor air concentrations were below the industrial screening level and was therefore not selected as a COPC in the CDC building for the CDC worker, indicating that the potential non-baseline risks for this receptor are negligible.

7.4 Conclusions

The purpose of this BHHRA is to characterize the potential human health risk associated with assumed exposure to impacted environmental media in the absence of mitigation or remediation (Baseline Scenario) as required by the CERCLA risk assessment guidance. The primary environmental impacts are due to historical use, disposal, and loss of TCE and other chemicals used onsite. The BHHRA evaluates onsite indoor air risks using indoor air data collected by Summa canisters with associated laboratory analysis. Supplemental risk assessments have been performed using non-baseline (post-mitigation) indoor air data collected with Summa canisters and analyzed by method TO-15 and also for primarily non-baseline indoor air data collected and analyzed by HAPSITE®. The supplemental risk assessment calculations are not a CERCLA requirement, but have been performed to assess the current Post-mitigation condition of several buildings/exposure points.

7.4.1 Baseline Risk Assessment Conclusions: Current and/or Foreseeable Land Use

Baseline risk assessment results for current and/or foreseeable receptors exposed to baseline conditions (pre-mitigation/remediation) are summarized below.

• No cancer risks or HIs were above USEPA thresholds levels for ingestion and dermal contact with soil or inhalation of soil-derived dust for the current and foreseeable receptors evaluated. Risks were calculated for the Outdoor Worker, Trespasser, and Utility Worker based on soil exposures only. Therefore, risks for these three receptors were acceptable.

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• Each potential cancer risk calculated is within or below the USEPA’s risk range, with the exception of future residents at the Rivercrest Property.

• The Indoor Worker HI is less than the threshold HI of 1 for exposure to indoor air in nine onsite buildings (total of 9 indoor air exposure points): 1) Asphalt Laboratory, 2) Ballistics Laboratory, 3) Greenhouse, 4) Ice Engineering Facility, 5) Logistics Management Office, 6) Main Laboratory (West – Level 1), 7) Remote Sensing Facility, 8) Storage Shed and 9) TIAC.

• The Indoor Worker HI is greater than the threshold HI of 1 for exposure to indoor air in six onsite buildings: 1) CDC, 2) DPW Storage Area, 3) FERF, 4) Groundwater Treatment Facility, 5) Main Laboratory (North Basement, North first floor, South Basement, West Sub- Basement) and, 6) Vehicle Storage Building.

• The HI for the future onsite construction worker exposure to soil vapor in an excavation also exceeds the threshold HI of 1. The potential cancer risk and HI for the future off-Post construction worker are below the USEPA risk range and the threshold HI of 1 at each off- Post property

• The potential cancer risk and HI for the hypothetical off-Post resident exposed to indoor air modeled from soil vapor (all depths) at the Rivercrest property are above the upper end of the USEPA risk range and the threshold HI of 1, respectively.

COCs were identified for each exposure medium. They were selected per area/medium based on whether the total cumulative ELCR is greater than 1x10-4 per exposure pathway; if so COCs were identified in this area/medium as a compound with an individual ELCR above 1x10-6. Or for non- carcinogens: If the total HI is greater than 1, COCs were identified as a compound in this area/medium with HQ > 0.1 if the effects were additive.

Three COCs were selected for indoor air:

• Dichlorodifluoromethane. • TCE. • Trichlorofluoromethane.

One COC was selected for soil vapor (inhalation of vapors released into an excavation) onsite.

• TCE.

Five COCs were selected for future residential indoor air off-Post at Rivercrest:

• Carbon Tetrachloride. • Chloroform. • Hexachlorobutadiene. • TCE.

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• Trichlorofluoromethane.

7.4.2 Baseline Risk Assessment Conclusions: Hypothetical Receptors

• The cancer risk and HI driver is the hypothetical use of groundwater for potable use.

• Exposure to surface soil is associated with negligible risk and hazard.

• Cancer risk and/or HI is above the cancer risk range or threshold HI of 1 for indoor air (vapor intrusion) for several onsite buildings (based on conservative modeling of sub-slab soil vapor data).

The potential cancer risk for the hypothetical future off-Post resident exposed to indoor air modeled from sub-slab soil vapor is below the USEPA risk range for off-Post properties except Rivercrest (as discussed previously). The potential HI (indoor air) for the hypothetical future off-Post resident at Brendel & Fisher is above the non-cancer threshold HI of 1. The potential HI is below 1 in off- Post buildings evaluated (except for Rivercrest as discussed above). The hypothetical scenarios have been run for the purpose of informing institutional controls only.

7.4.3 TO-15 Non-Baseline Supplemental Human Health Risk Assessment Conclusions

Supplemental risk assessment has been performed for informational purposes to evaluate the effectiveness of mitigation measures. The supplemental risk assessment follows the same basic process as the BHHRA, but is not a CERCLA requirement.

Each potential risk calculated for the inhalation of indoor air pathway post-remediation, is within or below the USEPA’s risk range of 1x10-6 to 1x10-4 and each HI is below the USEPA threshold HI of 1, with the exception of the TIAC, which is driven by a 1,3-butadiene. This compound was not found in sub-slab soil vapor in the TIAC, and is therefore considered unrelated to vapor intrusion. This risk information reflects the successful on-going efforts to minimize indoor air concentrations with the use of SSDS and HealthMate® filters in the onsite buildings.

7.4.4 HAPSITE® Supplemental Human Health Risk Assessment Conclusions

The supplemental HAPSITE® risk assessment has been performed for informational purposes to evaluate the effectiveness of mitigation measures and to explore the use of HAPSITE® data within

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HAPSITE® indoor air samples were collected and analyzed with the field-based portable GC/MS in the SIM mode for TCE only. These grab samples represent real-time indoor air data collected to monitor human health exposure to TCE in the work place environment during the course of a typical work day for the purpose of worker safety. The majority of HAPSITE® indoor air data were collected after some mitigation and/or remedial actions. HAPSITE® non-baseline (post-mitigation) indoor air samples have been collected from four buildings onsite: CDC, Main Laboratory, LMO, and TIAC.

Each potential risk calculated for the inhalation of indoor air pathway post-remediation, is within or below the USEPA’s risk range of 1x10-6 to 1x10-4 and each HQ is below the USEPA threshold HI of 1. The conclusions are the same for both HAPSITE® and TO-15 sampling and analysis methods with respect to TCE detections, which supports the overall conclusions of the risk assessment.

The HAPSITE® dataset provides information about day-to-day variability in indoor air TCE presence and concentrations based on large numbers of samples that it would not be practical to obtain using traditional Summa canisters. The fact that the conclusions are the same for both HAPSITE® and TO-15 sampling and analysis methods with respect to TCE detections provides confidence in the overall conclusions of the risk assessment. The fact that the HAPSITE® dataset and the Summa dataset agree provides support for the use of either method to calculate human health risks when TCE is the primary driver.

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8.0 ECOLOGICAL RISK ASSESSMENT

This Section provides a summary of the ecological risk assessment activities undertaken for this Phase III RI for the Site.

8.1 Introduction

A Screening Level Ecological Risk Assessment has been conducted in accordance with the approved work plan (Amec Foster Wheeler, 2016b) to determine if there are ecological exposure pathways associated with the historical release of TCE at CRREL that require further ecological risk evaluation. The risk assessment follows Ecological Risk Assessment Guidance for Superfund (USEPA, 1997), USEPA’s Eco-update entitled Role of Screening-Level Risk Assessments and Refining Contaminants of Concern in Baseline Ecological Risk Assessments (USEPA, 2001), and the Guide to Screening Level Ecological Risk Assessment (TSERAWG, 2008).

8.2 Problem Formulation

8.2.1 Environmental Setting

On 10 November 2015, an Amec Foster Wheeler Senior Ecological Risk Assessor visited the CRREL facility to conduct a qualitative reconnaissance level habitat assessment. A summary of the findings is presented in the following sections, and serves to document information requested in the Checklist for Ecological Assessment (USEPA, 1997 Appendix A). Photographs taken during the habitat assessment are presented in Appendix V.

CRREL is a secured facility protected by a chain link and barbed wire fence. New Hampshire Route 10 runs along the eastern boundary of the fence line. North of the fence line is an open field owned by Dartmouth College, referred to as the Rivercrest development area.

South of the fence line a residential development known as the Dartmouth Housing area. East of the fence line is are developed properties consisting of Dartmouth Printing and Richmond Middle School located immediately east of Lyme Road, (New Hampshire Route 10). Also located adjacent to and east of CRREL property is property owned by Brendel and Fisher and Hanover Chiropractic. West of the fence line is a steep wooded embankment that meets the Connecticut River. Topography within the fenced area of CRREL slopes downward from Route 10 toward the Connecticut River.

Land within the fenced area is fully developed with a combination of buildings, impervious surfaces (parking lots, roadways, and sidewalks), maintained lawn, staging areas, and miscellaneous research infrastructure (Figure 8.2-1). The fully developed area does not provide natural habitat for populations or communities of wildlife. Burrows in the hillside and under the fence, as well as observations made by Site personnel indicate that a fox, groundhogs, skunks, and other animals may inhabit the fenced area, but these animals are likely attracted by the maintained lawns and numerous outbuildings that provide protection and shelter and are not considered wild populations.

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The only surface water body observed within the fenced area is a research pond (approximately 120 feet by 70 feet) which is a clay-lined artificial impoundment located 75 feet above the natural water table. It is part of the research infrastructure and therefore is not considered aquatic habitat. Water levels in the experimental pond are manually controlled. Overflow appears to drain through a surface channel located at its southern end. The surface channel runs toward the south and underneath the fence line off the property. A catch basin in one of the parking lots to the north also appears to discharge storm runoff into the research pond through a corrugated steel pipe.

A flat, wooded area inhabited by birch, white pines, and early successional ground cover (golden rod, mullein, staghorn sumac, grasses) extends approximately 40 feet from the western fence line to the top of the river embankment. Deer runs were encountered in this area. A walking path/former dirt road, stump dump, and former bicycle recycling were also observed here. The embankment is very steep (greater than 30% grade). Vegetation on the embankment is predominantly mature eastern hemlock trees. Substrate in the Connecticut River along the embankment was observed from the shoreline to consist of cobbles, gravel, and sand; the steep and uneven bank, and depth of water at the shoreline prevented access to survey benthic invertebrates in-water.

The U.S. Fish and Wildlife Service (USFWS) has identified the northern long-ear bat as a statewide threatened species (USFWS, 2016). The New Hampshire Natural Heritage Bureau (NHNHB, 2016) has identified several species categorized as threatened or endangered occurring in Hanover (NHNHB) (Table 8.2-1). However, none are known to occur within the secured area of the facility.

8.3 Complete Exposure Pathways

TCE discharged to the ground surface at the facility may have been flushed into the Connecticut River through storm drains, resulting in a potentially complete exposure pathway for surface water and sediment in the Connecticut River.

As explained in Section 5 of the RI, there does not appear to be a mechanism for historical releases of TCE to migrate to surface soil in the wooded area between the facility fence line and the Connecticut River. An incomplete transport pathway results in an incomplete exposure pathway, thus risk to ecological receptors in adjacent woodlands is expected to be negligible.

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8.4 Ecological Risk Conclusions & Recommendations

This Ecological Risk Assessment finds that there is negligible risk to ecological receptors within the secured, fenced-in area at CRREL because there is no habitat and therefore no complete exposure pathway. No additional ecological risk assessment activities are needed within the secured area.

This ecological risk assessment did not evaluate potentially complete exposure pathways for ecological receptors (e.g., benthic invertebrates, fish, and other wildlife) present within the Connecticut River adjacent to the facility. Further investigation of the nature and extent of contamination in the Connecticut River is planned, including the collection of approximately six (6) surface water samples and twenty (20) sediment samples (Amec Foster Wheeler, 2016b). Additional risk assessment activities will be carried out to evaluate potential risk to ecological receptors upon completion of the field sampling.

Because there is an incomplete exposure pathway for soils in the adjacent woodland, risk is considered negligible and no further ecological risk assessment activities are needed.

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9.0 PRELIMINARY REMEDIATION GOALS

This Section provides a summary of the Preliminary Remediation Goals (PRGs) developed in this Phase III RI for the Site. This section relies on ARARs discussed in Section 6.0 and on COCs identified in the BHHRA in Section 7.0. This section provides information to be used in the FS, which will be presented under separate cover.

9.1 Compounds of Concern

PRGs have been developed for COCs, which were defined as compounds exceeding ARARs, or as defined within the BHHRA in the current and/or foreseeable scenarios. COCs were identified for each exposure medium/area.

9.2 ARAR-Based Preliminary Remediation Goals

TCE has been the predominant focus of the investigation, and is expected to be the primary focus for remediation at CRREL. Accordingly, TCE is the primary COC. Under both Federal and New Hampshire statutes and regulations it is a requirement to use Safe Drinking MCLs and New Hampshire Groundwater Quality Criteria for developing remedial alternatives for groundwater. NHDES regulations allow establishment of Groundwater Management Zones where a regulated contaminant (TCE) has caused and continues to cause concentrations in excess of groundwater quality criteria. Section 4.3 of this RI has established that TCE and cis-1,2-DCE have been detected in groundwater above relevant and appropriate requirements (Safe Drinking Water Act MCLs) and applicable requirements (New Hampshire Groundwater Quality Criteria) and are therefore identified as COCs for groundwater. The USEPA MCL and the NHDES standard for TCE in groundwater is 5 µg/L and for cis-1,2-DCE is 70 µg/L.

9.3 Other NHDES Criteria

As discussed in Section 6.0, indoor air and soil vapor screening levels from NHDES, 2013 WMD, Revised Vapor Intrusion Screening Levels and TCE Update has established that concentrations of TCE have been detected in indoor air samples at concentrations greater than corresponding indoor air screening levels.

9.4 Risk-Based Preliminary Remediation Goals

Risk-based PRGs were developed for each COC identified within the applicable exposure medium. PRGs have been developed based on a target ELCR of 1x10-6, 1x10-5, and 1x10-4 and a target HI of 0.1 and 1, and presented in Table 9.1-1 through Table 9.1-3, using the following equation:

Target ELCR or HQ × EPC PRG = Total Estimated ELCR or HQ

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The units for the PRG calculated using this equation are equal to those for the EPC. PRGs were developed for an indoor worker exposure scenario since this scenario is consistent with the current use of the facility. PRGs were also calculated for the construction worker, as re-development of the Site is a foreseeable future activity. PRGs were also calculated for an off-Post residential scenario at Rivercrest, as residential re-development of Rivercrest is a foreseeable future use. PRGs have not been calculated for the hypothetical residential scenarios, as these were calculated for the purpose of identifying institutional controls, not the need to set remediation objectives. Risk- based PRGs were calculated for the media and COCs identified below.

Onsite Indoor Air

The selected risk-based COCs are listed below for indoor air.

• Dichlorodifluoromethane. • TCE. • Trichlorofluoromethane.

Soil Vapor (Excavation Air)

The risk-based COCs in soil vapor are listed below.

• TCE.

Rivercrest Indoor Air

The risk-based COCs for future indoor air at Rivercrest are listed below.

• Carbon Tetrachloride. • Chloroform. • Hexachlorobutadiene. • TCE. • Trichlorofluoromethane.

The PRGs presented in Tables 9.1.1 through 9.1.3 will be carried forward to the FS for evaluation of remedial alternatives.

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10.0 SUMMARY AND CONCLUSIONS

10.1 Summary

Nature and Extent of Contamination

The nature and extent of soil, overburden groundwater, and soil gas contamination has been characterized as part of Phase III RI activities at AOCs 2, 9, 13, and 15.

TCE has been identified as the primary COC at the Site based on the results of the Phase III RI investigation and historic practices at CRREL. TCE was used as a secondary refrigerant in the cooling system in the Main Laboratory as well as for various experiments throughout the Site. TCE was released to the environment due to leaks in pumps, machinery, and piping; during experiments with the former Ice Well and by the explosion of an aboveground storage tank (AST) containing thousands of gallons of TCE in 1970 (AOC 9); leaks and/or overfills of a former UST (AOC 2); and disposal practices exercised in former borrow pit areas (AOC 13).

An estimated 77,000 cubic yards of soil contaminated with TCE in excess of the screening criteria is located at the Site; primarily in AOCs 2 and 9. The volume of TCE adsorbed to soils in the AOC 2 and AOC 9 source areas was estimated at 17,560 pounds (1,450 gallons) and 15,740 pounds (1,300 gallons) respectively1. These estimates were calculated based on our current understanding of the geologic conditions and could potentially be an order of magnitude greater if there is significant variability of fractional organic carbon in the Site soils.

TCE has been detected in overburden and bedrock groundwater at concentrations exceeding the federal MCL (5 µg/L). Overburden and bedrock groundwater flows from the east to the west across the Site toward the Connecticut River. Vertical gradients between the overburden groundwater and bedrock groundwater vary from slightly upward to slightly downward across the Site. The results of Phase III groundwater studies show that the overburden groundwater TCE plume is defined by two highly contaminated lobes associated with contaminant sources below AOC 2 and AOC 9. The depth of these two lobes is greater than identified in previous RI studies, and the contaminant front is wider. The overburden groundwater plume is captured by the series of production wells located in the esker parallel to the Connecticut River. As a result, contaminated overburden groundwater is contained onsite and does not discharge to the Connecticut River. The overburden groundwater plume does not appear to be a significant source of bedrock groundwater contamination. Groundwater profiler data show that concentrations decrease towards the bedrock surface. The results of bedrock groundwater sampling and bedrock matrix sampling indicate that free phase TCE did not migrate through the overburden and into the bedrock. Bedrock groundwater concentrations are orders of magnitude lower than overburden groundwater concentrations and bedrock matrix sampling was non-detect for the presence of TCE. Bedrock

1 Estimates of the mass of TCE present in AOCs 2 and 9 were performed prior to commencement of the soil vapor extraction pilot test in October 2014 and include the mass removed by that system.

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I monitoring wells located between the Connecticut River and the supply wells located in the esker were either non-detect or slightly in excess of the detection limit for TCE in groundwater.

Contamination of groundwater is expected to persist as long as source material exists in the form of highly contaminated soil gas and soils at AOC 2 and AOC 9. Approximately 50 million gallons of TCE contaminated groundwater, in excess of 10 µg/L, are present in the groundwater plume extending from the source areas to the capture area of the supply wells. The mass of TCE dissolved in groundwater is estimated at 1,525 lbs (125 gallons or 475 liters). This estimate could potentially be greater if the cores of the two TCE plumes contain groundwater concentrations that are greater than those determined during investigation activities.

The presence of TCE in soils at AOC 2 and AOC 9 has resulted in a large soil gas plume. The most contaminated soil gas is located coincident with the upgradient terminus of each core of the groundwater plumes. The soil gas plume encompasses an approximate 30-acre area where approximately 4 million cubic yards of soil contains TCE at concentration in excess of 100 µg/m3. The mass of TCE in the vapor phase is estimated to be approximately 1,200 lbs (98 gallons or 370 liters). This estimate was calculated based on our current understanding of the geologic conditions and could potentially be an order of magnitude greater if there is significant variability of fractional organic carbon in the Site soils. Concentrations of TCE in soil gas in AOCs 2 and 9 have been measured ranging from 1 to 10 million µg/m3. This highly contaminated soil gas is partitioning into the groundwater at the capillary fringe and is the primary source of contamination to the overburden groundwater.

Surface water and sediment in the Connecticut River were not characterized as part of Phase III RI activities. These media will be sampled in the fall of 2016. Results will be presented in a supplemental report to the RI.

Conceptual Site Model and Fate and Transport

TCE at the Site is adsorbed to shallow lacustrine soils. TCE was primarily released to soil (surface and subsurface). TCE has partitioned from a separate phase into the soil solid phase, soil moisture, and soil vapor. TCE in soil vapor has further partitioned into groundwater. A sizable subsurface soil vapor plume or cloud was created as a result of the soil partitioning and that plume has migrated horizontally and vertically from TCE release locations. TCE in soil moisture has also been transported downward towards groundwater by leaching associated with infiltration of rain water and snow melt. TCE reaching groundwater is transported within the groundwater by diffusion and advection (with groundwater flow). The active production wells (non-contact cooling water) contain the groundwater plume within the downgradient (western) portion of the Installation.

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U.S. Army Corps of Engineers - New England District Cold Regions Research and Engineering Laboratory Hanover, New Hampshire Final Phase III Remedial Investigation Report – Volume I air is also transported into buildings through diffusion and also advective flow driven by pressure differential from wind, stack effects, and active HVAC systems (vapor encroachment). It is also likely that TCE spilled or otherwise released within buildings has contaminated building materials and is off-gassing into the vapor phase from contaminated building materials. This is a confounding factor with respect to investigation of the vapor intrusion pathway at the facility.

Risk Assessment

A BHHRA and a screening level ecological risk assessment were performed.

The human health risk assessment evaluated risk for current and foreseeable receptors and hypothetical receptors. The primary environmental impacts evaluated are due to historical use, disposal, and environmental releases of TCE and other chemicals used onsite (i.e. COCs). Due to TCE’s ability to impact indoor air, one of the fundamental goals of the BHHRA was to evaluate cumulative risk to current indoor receptors onsite in the absence of mitigation and/or remediation.

Baseline risk assessment results for current and/or foreseeable receptors exposed to baseline conditions (pre-mitigation/remediation) are summarized below.

• Each potential cancer risk calculated is within or below the USEPA’s risk range, with the exception of future residents at the Rivercrest Property.

• The HI for the future onsite construction worker exposure to soil vapor in an excavation also exceeds the threshold HI of 1.

The potential cancer risk and HI for the potential future off-Post resident exposed to indoor air modeled from soil vapor (all depths) at the Rivercrest property are above the upper end of the USEPA risk range and the threshold HI of 1, respectively.

• The cancer risk and HI driver is the hypothetical use of groundwater for potable use.

• Exposure to surface soil is associated with negligible risk and hazard.

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The potential cancer risk for the hypothetical future off-Post resident exposed to indoor air modeled from sub-slab soil vapor is below the USEPA risk range for off-Post properties except for Rivercrest (as discussed previously). The potential HI (indoor air) for the hypothetical future off-Post resident at Brendel & Fisher is above the non-cancer threshold HI of 1. The potential HI is below 1 in other off-Post buildings evaluated (except for Rivercrest as discussed above).

The ecological risk assessment did not evaluate potentially complete exposure pathways for ecological receptors (e.g., benthic invertebrates, fish, and other wildlife) present within the Connecticut River adjacent to the facility. Further investigation of the nature and extent of contamination in the Connecticut River is planned for fall 2016. Additional risk assessment activities will be carried out to evaluate potential risk to ecological receptors upon completion of the field sampling.

10.2 Conclusions

An FS will be prepared to evaluate remedial alternatives to address COCs/complete exposure pathways identified in the risk assessment or as ARARs. PRGs have been developed for COCs, identified for each exposure medium/area.

Based on the findings of the RI and the risk assessment the FS will evaluate the following migration/exposure pathways:

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ARAR-Based PRGs have been identified for TCE and cis-1,2-DCE in groundwater. These contaminants were detected above relevant and appropriate requirements (Safe Drinking Water Act MCLs) and applicable requirements (New Hampshire Groundwater Quality Criteria).

Risk-Based PRGs have also been developed for each COC identified within the applicable exposure medium. Risk based PRGs were developed based on a target Excess Lifetime Cancer Risk (ELCR) of 1x10-6, 1x10-5, and 1x10-4 and a target HI of 0.1 and 1. PRGs were developed for an indoor worker exposure scenario since this scenario is consistent with the current use of the facility. PRGs were also calculated for the construction worker, as re-development of the Site is a foreseeable future activity. PRGs were also calculated for an off-site residential scenario at Rivercrest, as residential re-development is a foreseeable future use. Risk-based PRGs for TCE were calculated and are identified by media below:

• Onsite Indoor Air - TCE-0.80 µg/m3 (HI=0.1); 8.8 µg/m3 (HI=1.0). • Soil Vapor (Excavation Air) - TCE-1.2 µg/m3 (HI=0.1); 12 µg/m3 (HI=1.0). • Rivercrest Indoor Air - TCE-0.21 µg/m3 (HI=0.1); 2.1 µg/m3 HI=1.0).

The PRGs (ARAR and risk based) will be carried forward to the FS for evaluation of remedial alternatives.

The Connecticut River was not investigated as part of the Phase III RI. The nature and extent of potential TCE contaminated sediment and surface water in the Connecticut River are data gaps and will be evaluated in a supplemental RI and presented under a separate cover. Sediment and surface water data will be used to update and refine the CSM.

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11.0 REFERENCES

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AMEC, 2013e. Final Dartmouth Printing Off-Site Vapor Intrusion Pathway Assessment Work Plan for Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire. August 13, 2013.

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AMEC, 2014d. Final Indoor Air Assessment Investigation Event 8 Results for Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire. January 29, 2014.

AMEC, 2014e. Final Soil Vapor Investigation Results for Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire. January 31, 2014.

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AMEC, 2014h. Final Event 9 (Winter 2014) Indoor Air and Sub-Slab Sampling and Assessment Work Plan, Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire. United States Army Corps of Engineers, New England Division.

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AMEC, 2014r. Final Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, April 15, 2014 Sampling Event. 2014.

AMEC, 2014s. Final Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, August 12, 2014 Sampling Event. 2014.

AMEC, 2014t. Final Indoor Air and Sub-Slab Investigation Results 64 Lyme Road, Hanover, NH. 2014.

AMEC, 2014u. Final Indoor Air and Sub-Slab Investigation Results Round #2 64 Lyme Road, Hanover, NH. 2014.

AMEC, 2014v. Final Indoor Air and Sub-Slab Investigation Results 68 Lyme Road, Hanover, NH. 2014.

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AMEC, 2014w. Final Indoor Air and Sub-Slab Investigation Results Round #2 68 Lyme Road, Hanover, NH. 2014.

AMEC, 2014x. Final Indoor Air and Sub-Slab Investigation Results for Five Dartmouth College Housing Units. 2014.

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AMEC, 2015c. Frances C. Richmond Middle School Indoor Air and Sub-Slab Investigation Results, January 19 and 24, 2015 Sampling Event. 2015.

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FIGURES

TABLES

APPENDICES

A THROUGH V

(PROVIDED ON SEPARATE CD)