SAMPLE COLLECTION AND EVALUATION OF VAPOR INTRUSION TO INDOOR AIR FOR REMEDIAL RESPONSE, RESOURCE CONSERVATION AND RECOVERY ACT AND VOLUNTARY ACTION PROGRAMS Division of Environmental Response and Revitalization March 2020 Acknowledgements This updated guidance was developed by a workgroup of Ohio Environmental Protection Agency (EPA) staff. Workgroup members included: Michael Allen Gavin Armstrong Sarah Beal Chris Bulinski Dawn Busalacchi Corin Fogle Erik Hagen Melissa Langton Chuck Mellon Chris Osborne Carrie Rasik Lisa Shook Vanessa Steigerwald-Dick Brian Tucker Katie Weyrauch The following guidance document represents an update to the May 2010 Ohio EPA document of the same title and supersedes any and all previous vapor intrusion guidance documents presented by the agency. This update reflects the Ohio EPA Division of Environmental Response and Revitalization’s (DERR) latest understanding of appropriate policies regarding vapor intrusion. The document was developed using established guidance from the United States (U.S.) Environmental Protection Agency (EPA), the Interstate Technology Resource Council (ITRC), American Society of Testing and Materials (ASTM), and other states, modified for the purposes of complying with remedial response, resource conservation and recovery act and voluntary actions in Ohio. Special thanks to the California Environmental Protection Agency, Department of Toxic Substances Control, for permission to use the Interim Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air, December 2004, as a template. In some instances, exact phrasing from California’s guidance was used. Disclaimer This guidance was developed solely for sites under the oversight of Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), the Resource Conservation and Recovery Act program (RCRA), and the Voluntary Action Program (VAP), carried out under the supervision of Ohio EPA DERR. In this document sites managed under CERCLA and RCRA will be characterized as remedial programs i (RP). Use of this guidance for other Ohio EPA programs or other state agency programs may not be appropriate. The guidance serves as an instructional tool for the investigation and evaluation of vapor intrusion at sites in Ohio. It is not meant to be a regulatory document and any statements provided herein are not legally binding. ii TABLE OF CONTENTS LIST OF ACRONYMS .....................................................................................................vi EXECUTIVE SUMMARY ................................................................................................. x 1.0 INTRODUCTION .................................................................................................... 1 2.0 SCOPE .................................................................................................................. 1 3.0 VAPOR INTRUSION EVALUATION ...................................................................... 2 3.1 Initial Vapor Intrusion Assessment ...................................................................... 2 3.2 Conceptual Site Model ........................................................................................ 4 3.3 Data Quality Objective Process and Developing a Sample Plan ........................ 6 4.0 SOIL GAS AND SUB-SLAB VAPOR SAMPLING PROCEDURES ........................ 9 4.1 Soil Gas and Sub-Slab Vapor Sample Collection and Analysis .......................... 9 4.2 Analytical Detection Limits ................................................................................ 11 4.3 Soil Gas Sampling ............................................................................................ 11 4.4 Soil Gas Probes ................................................................................................ 13 4.5 Sub-Slab Vapor Sampling and Data ................................................................. 15 4.6 Sampling Basements with Dirt Floors and Crawl Spaces ................................. 17 4.7 Leak Testing ..................................................................................................... 18 4.8 Passive Soil Gas (Exterior or Sub-Slab) Sampling ........................................... 21 5.0 INDOOR AIR SAMPLING .................................................................................... 22 5.1 Site Inspection, Product Inventory and Field Screening ................................... 23 5.2 Indoor Air Sample Collection and Analysis ....................................................... 23 6.0 GROUND WATER MONITORING AND EVALUATION ....................................... 26 6.1 Well Placement ................................................................................................. 26 6.2 Screen Placement ............................................................................................ 27 6.3 Screen Lengths ................................................................................................. 27 6.4 Ground Water Sampling ................................................................................... 27 6.5 Soil Gas Confirmation of Ground Water Concentration .................................... 28 6.6 Other Factors .................................................................................................... 28 7.0 BULK SOIL .......................................................................................................... 28 8.0 DATA EVALUATION AND ANALYSIS ................................................................. 29 8.1 Vapor Intrusion Screening Levels ..................................................................... 29 8.2 Bulk Soil Data ................................................................................................... 30 iii 8.3 Ground Water Data Screening .......................................................................... 31 8.4 Soil Gas and Sub-Slab Vapor Data Screening ................................................. 31 8.5 Indoor Air Data Evaluation ................................................................................ 32 8.6 Background Source Evaluation ......................................................................... 32 8.7 Occupational Exposure Limits .......................................................................... 32 9.0 VAPOR INTRUSION FROM PETROLEUM RELEASES ..................................... 33 9.1 Petroleum Release Characterization and Phase Partitioning ........................... 34 9.2 Lateral Inclusion Zone ...................................................................................... 35 9.3 Vertical Separation Distance............................................................................. 35 9.4 Ground Water Flow and Dissolved Plumes ...................................................... 36 9.5 Compliance with BUSTR .................................................................................. 36 10.0 MODELING THE VAPOR INTRUSION PATHWAY ........................................... 36 10.1 U.S. EPA Vapor Intrusion Screening Level Calculator .................................... 37 10.2 Overview of the Use of Fate and Transport Models in Ohio EPA ................... 38 10.3 Overview of U.S. EPA’s Johnson and Ettinger Model ..................................... 38 10.4 BioVapor ......................................................................................................... 39 11.0 EVALUATION OF IMMINENT HAZARD IN AN EXISTING BUILDING .............. 39 11.1 Potential Imminent Hazard Conditions ............................................................ 40 11.2 Explosive Hazard ............................................................................................ 40 12.0 RISK CHARACTERIZATION ............................................................................. 41 12.1 Determining Applicable Risk Goals and the Need for Further Evaluation ....... 41 12.2 Use of Maximum Contaminant Levels (MCLs) ................................................ 42 12.3 Use of BUSTR Petroleum Standards .............................................................. 42 13.0 REMEDY ............................................................................................................ 43 13.1 Remedy Selection and Implementation Considerations ................................. 43 13.2 Remediation of Environmental Media ............................................................. 46 13.3 Institutional Controls ....................................................................................... 46 13.4 Engineering Controls ...................................................................................... 46 13.5 Active Sub-Slab Depressurization Systems .................................................... 47 13.6 Heating, Ventilation, Filtration Units and Air Conditioning (HVAC) Measures . 49 13.7 Passive Engineering Controls ......................................................................... 50 13.8 Monitoring Requirements for Engineering Controls ........................................ 51 iv 13.9 Post-Mitigation and Seasonal Monitoring ....................................................... 51 13.10 Termination of Engineering Controls ............................................................ 52 13.11 Owner Documentation/Notification of Engineering Controls ......................... 52 14.0 LONG-TERM MANAGEMENT AND EXIT STRATEGY AT VAPOR INTRUSION SITES .......................................................................................................................