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 TOC-i 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 ...................................................................................................................................