132

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

(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.

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TABLE OF CONTENTS 
LIST OF ACRONYMS .....................................................................................................vi 
EXECUTIVE SUMMARY ................................................................................................. x 
0 INTRODUCTION .................................................................................................... 1 
0 SCOPE .................................................................................................................. 1 
0 VAPOR INTRUSION EVALUATION ...................................................................... 2 
1 Initial Vapor Intrusion Assessment ...................................................................... 2 
2 Conceptual Site Model ........................................................................................ 4 
3 Data Quality Objective Process and Developing a Sample Plan ........................ 6 
0 SOIL GAS AND SUB-SLAB VAPOR SAMPLING PROCEDURES ........................ 9 
1 Soil Gas and Sub-Slab Vapor Sample Collection and Analysis .......................... 9 
2 Analytical Detection Limits ................................................................................ 11 
3 Soil Gas Sampling ............................................................................................ 11 
4 Soil Gas Probes ................................................................................................ 13 
5 Sub-Slab Vapor Sampling and Data ................................................................. 15 
6 Sampling Basements with Dirt Floors and Crawl Spaces ................................. 17 
7 Leak Testing ..................................................................................................... 18 
8 Passive Soil Gas (Exterior or Sub-Slab) Sampling ........................................... 21 
0 INDOOR AIR SAMPLING .................................................................................... 22 
1 Site Inspection, Product Inventory and Field Screening ................................... 23 
2 Indoor Air Sample Collection and Analysis ....................................................... 23 
0 GROUND WATER MONITORING AND EVALUATION ....................................... 26 
1 Well Placement ................................................................................................. 26 
2 Screen Placement ............................................................................................ 27 
3 Screen Lengths ................................................................................................. 27 
4 Ground Water Sampling ................................................................................... 27 
5 Soil Gas Confirmation of Ground Water Concentration .................................... 28 
6 Other Factors .................................................................................................... 28 
0 BULK SOIL .......................................................................................................... 28 
0 DATA EVALUATION AND ANALYSIS ................................................................. 29 
1 Vapor Intrusion Screening Levels ..................................................................... 29 
2 Bulk Soil Data ................................................................................................... 30 

iv 
 
3 Ground Water Data Screening .......................................................................... 31 
4 Soil Gas and Sub-Slab Vapor Data Screening ................................................. 31 
5 Indoor Air Data Evaluation ................................................................................ 32 
6 Background Source Evaluation ......................................................................... 32 
7 Occupational Exposure Limits .......................................................................... 32 
0 VAPOR INTRUSION FROM PETROLEUM RELEASES ..................................... 33 
1 Petroleum Release Characterization and Phase Partitioning ........................... 34 
2 Lateral Inclusion Zone ...................................................................................... 35 
3 Vertical Separation Distance............................................................................. 35 
4 Ground Water Flow and Dissolved Plumes ...................................................... 36 
5 Compliance with BUSTR .................................................................................. 36 
0 MODELING THE VAPOR INTRUSION PATHWAY ........................................... 36 
1 U.S. EPA Vapor Intrusion Screening Level Calculator .................................... 37 
2 Overview of the Use of Fate and Transport Models in Ohio EPA ................... 38 
3 Overview of U.S. EPA’s Johnson and Ettinger Model ..................................... 38 
4 BioVapor ......................................................................................................... 39 
0 EVALUATION OF IMMINENT HAZARD IN AN EXISTING BUILDING .............. 39 
1 Potential Imminent Hazard Conditions ............................................................ 40 
2 Explosive Hazard ............................................................................................ 40 
0 RISK CHARACTERIZATION ............................................................................. 41 
1 Determining Applicable Risk Goals and the Need for Further Evaluation ....... 41 
2 Use of Maximum Contaminant Levels (MCLs) ................................................ 42 
3 Use of BUSTR Petroleum Standards .............................................................. 42 
0 REMEDY ............................................................................................................ 43 
1 Remedy Selection and Implementation Considerations ................................. 43 
2 Remediation of Environmental Media ............................................................. 46 
3 Institutional Controls ....................................................................................... 46 
4 Engineering Controls ...................................................................................... 46 
5 Active Sub-Slab Depressurization Systems .................................................... 47 
6 Heating, Ventilation, Filtration Units and Air Conditioning (HVAC) Measures . 49 
7 Passive Engineering Controls ......................................................................... 50 
8 Monitoring Requirements for Engineering Controls ........................................ 51 

v 
 
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 ........................................................................................................................ 53 
14.1 Long-Term Management ................................................................................ 53 
14.2 Ground Water, Soil Gas, Sub-Slab Vapor and Differential Pressure 
Monitoring/Sampling ............................................................................................... 54 
14.3 Passive Mitigation System Efficacy Verification .............................................. 54 
14.4 Environmental Covenants and Deed Restrictions ........................................... 55 
14.5 Exit Strategy ................................................................................................... 55 
15.0 CITATIONS AND REFERENCES ...................................................................... 57 
 
LIST OF FIGURES 
Figure 1. Stepwise Approach for Evaluating the Vapor Intrusion Pathway ......................xi 
Figure 2. Examples of Soil Gas Sampling Probes  ........................................................ 13 
Figure 3. Permanent Soil Gas Probe Schematic  .......................................................... 15 
Figure 4. Example of a Sub-Slab Vapor Probe  ............................................................ 17 
Figure 5. Schematic of a Summa Canister  ................................................................... 25 
Figure 6. Petroleum Distillation  .................................................................................... 34 
Figure 7. Schematic of PVI Scenario with LNAPL  ........................................................ 36 
 
LIST OF TABLES 
Table 1. Common Tracers Advantages and Disadvantages ......................................... 20 
Table 2. Comparison of Indoor Air and Sub-Slab Vapor Sampling Conditions to Bias 
Sampling to the Highest Potential Concentrations* ....................................................... 24 
Table 3. Comparison of Mitigation Technologies .......................................................... 45 
 
   

vi 
 
 
LIST OF APPENDICES 
APPENDIX A. Vapor Intrusion Conceptual Site Model Checklist .................................. 61 
APPENDIX B. Special Considerations for Evaluating Residential Properties ............... 63 
APPENDIX C. FSOPs ................................................................................................... 64 
APPENDIX D. Soil Gas Probe Field Data Report Form .............................................. 106 
APPENDIX E. Indoor Air/Sub-Slab Sampling Form .................................................... 107 
APPENDIX F. Soil Gas and Sub-Slab Vapor Analytical Methods and Reporting Limit 
Ranges ........................................................................................................................ 113 
APPENDIX G. Comparison of Tubing Type to Vapor Absorption ................................ 116 
 
LIST OF ACRONYMS  
AC    Alternating Current 
ADS    Active Depressurization System 
AF    Attenuation Factor 
APU    Air Purifying Unit 
AST    Aboveground Storage Tank 
ASTM   American Society of Testing and Materials 
BGS    Below Ground Surface 
BTEX   Benzene Toluene Ethylbenzene Xylene 
BUSTR  Bureau of Underground Storage Tank Regulations 
CERCLA  Comprehensive Environmental Response, Compensation, and Liability  
    Act   
COCs   Chemicals of Concern  
CP    Certified Professional 
CPRG   Closure Plan Review Guidance  
CSM    Conceptual Site Model   
CVAFS  Cold Vapor Atomic Fluorescence Spectrometry 

vii

CV/AA Cold Vapor/Atomic Absorption

DERR Division of Environmental Response and Revitalization

DNAPL Dense Non-Aqueous Phase Liquid

DQOs Data Quality Objectives

EC Environmental Covenant

ECD Electron Capture Detector

ELCR Excess Lifetime Cancer Risk

EPA Environmental Protection Agency

FFS Federal Facilities Section

FID Flame Ionization Detector

FSOP Field Standard Operating Procedure

GC/MS Gas Chromatograph/Mass Spectrometer

HASP Health and Safety Plan

HEPA High-Efficiency Particulate Air

HQ Hazard Quotient

HRV Heat Recovery Ventilation

HVAC Heating, Ventilation and Air Conditioning

IDLH Immediately Dangerous to Life and Health

IRIS Integrated Risk Information System

ITRC Interstate Technology Resource Council

J&E Model Johnson and Ettinger Vapor Intrusion Model

LDPE Low Density Polyethylene

LEL Lower Explosive Limit

LNAPL Light Non-Aqueous Phase Liquid

LPM Liters Per Minute

MIP Male Iron Pipe

NAPL Non-Aqueous Phase Liquid

NCP National Contingency Plan

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NJDEP New Jersey Department of Environmental Protection

O&M Operation and Maintenance

OAC Ohio Administrative Code

OD Outer Diameter

ODH Ohio Department of Health

Ohio EPA Ohio Environmental Protection Agency

ORC Ohio Revised Code

OSHA Occupational Safety and Health Administration

OSI Office of Special Investigation

OSWER Office of Solid Waste and Emergency Response (U.S. EPA)

PCBs Polychlorinated Biphenyls

PCE Tetrachloroethylene

PDS Passive Depressurization System

PEL Permissible Exposure Limit

PHC Petroleum Hydrocarbons

PID Photoionization Detector

PPB Parts per Billion

PPBV Parts per Billion Volume

PPM Parts per Million

PPMV Parts per Million Volume

PTFE Polytetrafluoroethylene

PVI Petroleum Vapor Intrusion

QA Quality Assurance

QC Quality Control

RAGS Risk Assessment Guidance for Superfund

RCRA Resource Conservation and Recovery Act

RI/FS Remedial Investigation/Feasibility Study

RP DERR Remedial Programs (CERCLA and RCRA)

RSL Regional Screening Level

SARA Superfund Amendments and Reauthorization Act

SCIA Source Control Interim Action

SIFU Site Investigation Field Unit (Ohio EPA)

SIM Selected Ion Monitoring

SOP Standard Operating Procedure

SSWP Site-Specific Work Plan

STEL Short-Term Exposure Limits

SVE Soil Vapor Extraction

TCD Thermal Conductivity Detector

TCE Trichloroethylene

TPH Total Petroleum Hydrocarbons

TSCA Toxic Substances Control Act

UPUS Unrestricted Potable Use Standards

U.S. EPA United States Environmental Protection Agency

UST Underground Storage Tank

VAP Voluntary Action Program

VI Vapor Intrusion

VISL Vapor Intrusion Screening Level (U.S. EPA)

VOA Volatile Organic Analysis

VOCs Volatile Organic Compounds

EXECUTIVE SUMMARY

The intrusion of volatile chemicals from the subsurface into buildings is one of many

exposure pathways that must be considered when assessing risk to human health from

contamination. The Ohio EPA Division of Environmental Response and Revitalization

(DERR) recommends a stepwise approach and sampling methodologies for evaluating

vapor intrusion, as described in this document.

Ohio EPA DERR currently administers four environmental media clean-up programs: the

Voluntary Action Program (VAP), the Comprehensive Environmental Response,

Compensation, and Liability Act of 1980 (CERCLA) program, the Federal Facilities

Section (FFS) and the Resource Conservation and Recovery Act (RCRA) program. In

this document sites managed under CERCLA, FFS and RCRA will be characterized as

Remedial Programs (RP).

The VAP is semi-privatized and operates under Ohio Revised Code (ORC) 3746 and

Ohio Administrative Code (OAC) 3745. Site assessments and clean-ups in the VAP are

conducted by Certified Professionals certified by the program. Site clean-ups under the

RP are directed by Ohio EPA staff, and follow the requirements of CERCLA as modified

by the Superfund Amendments and Reauthorization Act, and the National Contingency

Plan. Corrective Actions and Unit Closures are directed by Ohio EPA staff and follow the

requirements of RCRA and subsequent amendments. There are differences between the

programs and their methods of assessment, decision points and remedy selection.

However, this guidance applies to all Ohio EPA DERR clean-up programs unless

explicitly noted.

Stepwise Approach

If volatile chemicals are present in the subsurface at a site, then the vapor intrusion

pathway should be evaluated along with other complete or anticipated exposure

pathways identified through the site assessment. Due to the complexity of vapor intrusion,

many professional disciplines may be needed to evaluate and mitigate the exposure.

Ohio EPA recommends evaluating multiple lines of evidence in a systematic, stepwise

approach depicted in Figure 1 (the flowchart) for the evaluation of the vapor intrusion

pathway. It is not necessary to investigate a site for potential vapor intrusion risk in the

order presented in this guidance. For sites where the environmental release history is

unknown, the stepwise approach should be most useful and effective. However, many

sites in Ohio EPA DERR programs have been assessed in some manner prior to

investigating potential vapor intrusion issues. Therefore, entering the flowchart (Figure 1)

at various steps may be appropriate.

Figure 1. Stepwise Approach for Evaluating the Vapor Intrusion Pathway

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Step 1 Conduct the site assessment.

The site assessment is paramount to determining whether the potential for the vapor

intrusion pathway exists at a site. A site assessment involves examining current and

former activities such as, the types of chemicals used, stored and managed at the site,

as well as the administrative history to determine whether releases occurred or if there

was potential for releases of hazardous substances or petroleum to environmental media

(i.e., soil, ground water, soil gas, sub-slab vapor or indoor air). A site walkover/inspection

is also necessary.

Step 2 Determine if there is the potential for any volatile and toxic chemicals in soil

or ground water.

Chemicals in the subsurface must be both sufficiently volatile and toxic to present a vapor

intrusion risk. If there is no reason to believe that a release of a volatile chemical may

have affected the site, then the information supporting this decision should be

documented and the vapor intrusion pathway does not need further evaluation.

Step 3 Determine if there is a potentially complete vapor intrusion pathway.

If there was a release, or a release of any sufficiently volatile and toxic chemicals was

possible, then develop an investigative workplan that includes a Conceptual Site Model

(CSM) for evaluating the vapor intrusion pathway. The potential for a complete vapor

intrusion pathway depends on factors such as current or future land use, distance

between contamination and existing or proposed buildings, preferential pathways, and

whether contaminant plumes are at steady state. The CSM is not static, but continually

refined and revised based on data and other information collected at the site.

Step 4 Sample environmental media.

After the vapor intrusion pathway is determined to be potentially complete, sample

environmental media (i.e., soil, ground water, soil gas, sub-slab vapor or indoor air) and

determine if concentrations indicate a vapor source is present and/or if vapors have

infiltrated a building. Data from only one environmental medium is generally not sufficient

to fully assess the vapor intrusion exposure pathway. A multiple lines of evidence

approach is preferred to evaluate pathway completeness from all environmental media,

to assess the complete and potentially complete vapor intrusion exposure pathway to

human receptors, and to reduce uncertainties.

Step 5 Evaluate data and determine if data evaluation indicates the possibility of

an imminent hazard.

A number of tools can be used at this stage to determine if the vapor intrusion pathway

poses a potential unacceptable risk for building occupants. Compare ground water, soil

gas, and/or sub-slab vapor concentrations to vapor intrusion screening levels (VISLs) that

correspond to a non-cancer hazard of 1 and an excess lifetime cancer risk (ELCR) of 1E-

5. Update the CSM depending on the outcome of data evaluation. If data indicate the

xiii

possibility of an imminent hazard, which is any condition which poses an immediate risk

of harm to public health, safety, or the environment, Ohio EPA should be contacted as

soon as possible and the volunteer should be prepared to move to Steps 7 and/or 8, as

appropriate, in a timely manner.

Step 6 Evaluate the potential risk and hazard from the vapor intrusion pathway.

For RP sites, if data evaluation indicates that concentrations are below screening values,

those chemicals of concern (COCs) are eliminated from further vapor intrusion

assessment. For VAP properties, if the concentrations are below screening values the

vapor intrusion pathway may not be complete for that COC, however the data and

screening values must be used to calculate incremental site-wide risk.

Step 7 If data evaluation indicates risk or hazard goals are or may be exceeded,

then additional data may be collected, or a remedy may be implemented (see Step

8).

If data evaluation indicates a potential for unacceptable human health risk, then additional

data collection may be necessary to conduct a risk assessment, evaluate lines of

evidence, and/or determine what, if any, remedy is needed. Further investigation may

include the following:

• Collecting data to define physical and chemical parameters for site-specific soil

using recommended test methods.

• Collecting soil gas samples to define the vapor plume at sites where buildings do

not exist.

• Collecting sub-slab vapor samples or crawl space samples at an existing building.

• Collecting indoor air samples in conjunction with sub-slab vapor or soil gas

samples.

• Additional evaluation of the environmental data may be needed to derive an

exposure point concentration for use in a property-specific risk assessment.

Step 8 Remediation, Mitigating Indoor Air Exposure and/or Conducting Long-Term

Monitoring.

If data evaluation indicates the potential for unacceptable human health risk, there are

several remedies that may be considered to mitigate vapor intrusion to indoor air. For

VAP sites, the volunteer selects the remedy. For RP sites, the remedy is selected

following procedures outlined in CERCLA as amended by SARA and the NCP and may

be defined by site-specific orders.

Potential remedies may include:

• Removing vapor-forming chemical contamination through site remediation.

• Installing passive or active vent systems (existing buildings).

xiv

• Installing passive and/or active vent systems/membrane systems (future

buildings).

• Designing ventilation systems to mitigate indoor air concentrations (HVAC).

• Using institutional controls to restrict structures or land use on contaminated

property.

• Implementing and monitoring of appropriate engineered remedies to prevent or

mitigate exposure through vapor intrusion. Monitoring of engineered controls must

continue until risk-based clean-up levels as measured in environmental media

have been met.

For any remedy chosen for a site, long-term monitoring of soil gas and/or indoor air may

be necessary under an Operations and Maintenance (O&M) plan. The frequency of the

monitoring will depend upon site-specific conditions and the degree of vapor-forming

chemical contamination.

1.0 INTRODUCTION

Volatile chemicals in soil or ground water can migrate through the subsurface, enter

buildings, and potentially cause an unacceptable chemical exposure for building

occupants. If volatile chemicals are present at a site, Ohio EPA DERR requires that

potential risk from vapor intrusion be included in the CSM and the potentially complete

pathway investigated. This guidance provides a framework for site characterization and

investigation of the vapor intrusion pathway.

Evaluation of the vapor intrusion to indoor air pathway may involve sampling

environmental media to evaluate and characterize subsurface chemical releases, using

screening models to predict indoor air concentrations, and usually includes conducting

indoor air sampling. This guidance outlines the technical aspects of evaluating the vapor

intrusion pathway and provides recommendations for elements that should be included

in a site investigation. This guidance is not intended to provide detailed information on

conducting a baseline or property specific risk assessment.

Due to the complexity of vapor intrusion, many professionals of varying disciplines may

be needed to evaluate and mitigate exposure, such as geologists, risk assessors,

engineers, HVAC specialists, Certified Industrial Hygienists, and risk communication

specialists. Accordingly, an appropriate project team should be gathered when evaluating

vapor intrusion issues. Ohio EPA DERR anticipates that this guidance will be used by

regulators, responsible parties, environmental consultants, community groups, and

property developers.

Vapor intrusion is a developing field and it is anticipated that some of the procedures and

practices within this guidance will change as understanding of vapor intrusion progresses.

Ohio EPA DERR will update this document as needed to accommodate refinements and

advances in the field of vapor intrusion.

2.0 SCOPE

This guidance provides options of technically defensible and consistent approaches for

evaluating the vapor intrusion to indoor air pathway, but it is not comprehensive, nor does

it impose any requirements or obligations on the regulated community. Other technically

equivalent sampling and engineering procedures exist and those investigating vapor

intrusion may use other technically sound approaches. Furthermore, this guidance does

not alleviate a volunteer or potentially responsible party from any obligations that U.S.

EPA may require.

This guidance document provides procedures to evaluate the vapor intrusion to indoor air

pathway only. All other media characterization and evaluation of complete exposure

pathways at a site must be done in accordance with the rules or procedures of the

appropriate Ohio EPA DERR programs. This guidance is meant to provide information to

fully characterize the potential risk from vapor intrusion at DERR sites.

This guidance assists in addressing, but is not limited to, the following questions:

• What sites are candidates for potential risk from vapor intrusion to indoor air?

• What site-specific data are needed to conduct a vapor intrusion evaluation?

• What methods are recommended for sampling subsurface media and indoor air?

• Should indoor air sampling be conducted?

• What are the data requirements for an evaluation of the vapor intrusion pathway?

• What measures are available to mitigate indoor air exposures?

3.0 VAPOR INTRUSION EVALUATION

The following text describes the stepwise approach for evaluating vapor intrusion found

in Figure 1 (the flowchart). The stepwise approach in this guidance document is meant to

be flexible and may be tailored to site-specific circumstances. Pathway evaluation may

begin at any step in the flowchart provided that the data collection and the CSM clearly

justify entry into that step. However, most vapor intrusion pathway evaluation decisions

and determinations regarding the need for remedial activities and long-term mitigation are

not made using indoor air sampling results alone because a vapor intrusion exposure

pathway is assumed to be complete unless demonstrated otherwise. For this reason, it is

preferred to also have data collected from soil, ground water, soil gas, and/or sub-slab

vapor when making decisions and drawing conclusions about a potential vapor intrusion

pathway from indoor air sampling results.

3.1 Initial Vapor Intrusion Assessment

The steps outlined in the flowchart apply at sites whether or not buildings are currently

present and/or occupied. Current buildings and future building scenarios, as appropriate,

will determine sampling strategy and data evaluation. While the assessment process is

presented in a stepwise fashion, the vapor intrusion pathway is generally evaluated in an

iterative manner and steps may be repeated.

Flowchart Step 1 and Step 2: Conduct the site assessment and determine if there is a

potentially complete vapor intrusion pathway

A comprehensive evaluation of the current and historical operations at a site should be

conducted to identify potential or known releases of volatile chemicals to subsurface

environmental media. A complete compilation of site information is essential for

identifying all potential vapor intrusion exposure pathways. For VAP properties, a

complete Phase I property assessment must be conducted in accordance with the Ohio

Administrative Code (OAC) 3745-300-06. RP sites may use ASTM E1527-13 (or most

recent version) Standard Practice for Environmental Site Assessments: Site assessment

Environmental Site Assessment Process (ASTM, 2013), DERR’s Closure Plan Review

Guidance (CPRG) (Ohio EPA, 2017) or other relevant CERCLA and RCRA guidance.

For simplicity, this guidance will not repeat the requirements necessary to conduct a site

assessment. However, using the site assessment information when developing a CSM is

a necessary component of this guidance. See the discussion in Step 4 for more details

on CSM components for evaluating the vapor intrusion pathway.

U.S. EPA’s June 2015 OSWER Technical Guide for Assessing and Mitigating the Vapor

Intrusion Pathway from Subsurface Vapor Sources to Indoor Air (VI Guidance) (U.S. EPA,

2015b) states that the chemicals in the subsurface must be both sufficiently volatile and

toxic to present a vapor intrusion risk. A chemical is considered “volatile” if its:

• Vapor pressure is greater than 1 millimeter of mercury (mmHg); or

• Henry’s law constant is greater than 10

-5

atmosphere-meter cubed per mole

(atm m

mol

-1

In addition to being sufficiently volatile, a chemical must be potentially toxic to present a

vapor intrusion risk. A volatile chemical may be considered toxic in regard to vapor

intrusion if:

• The vapor concentration of the pure component exceeds the target indoor

air concentration, when the subsurface vapor source is in soil; or

• The saturated vapor concentration exceeds the target indoor air risk level,

when the subsurface vapor source is in ground water.

In addition to researching a chemical’s physical-chemical properties, the most recent

version of the U.S. EPA Vapor Intrusion Screening Level (VISL) calculator can be used

as a tool to help determine if a chemical meets the criteria of sufficiently volatile and toxic

and should be included in a vapor intrusion investigation. Chemicals that are sufficiently

volatile and toxic in regard to vapor intrusion are referred to in this guidance document as

vapor-forming chemicals. For additional information on identifying vapor-forming

chemicals, please refer to Chapter 3 of U.S. EPA’s June 2015 OSWER Technical Guide

for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor

Sources to Indoor Air (U.S. EPA, 2015b).

If any chemicals that meet these criteria were potentially released, then the site should

be evaluated for vapor intrusion. This includes evaluating the history of adjacent

properties for potential releases of vapor-forming chemicals that may have affected the

subject site. If there is no reason to believe that a release of a vapor-forming chemical

may have affected the site, then the information supporting this decision should be

documented and the vapor intrusion pathway does not need further evaluation.

Please note, polychlorinated biphenyls (PCBs) and PCB mixtures (i.e., Aroclors) are

considered sufficiently volatile and toxic in the U.S. EPA VISL calculator. However, only

lighter PCB mixtures and degradants would be expected to volatilize at a site. In most

cases, PCBs do not need to be evaluated in a vapor intrusion (VI) assessment; please

contact Ohio EPA if the site assessment identifies PCBs for vapor intrusion on a site.

Based on the site assessment decide if further investigation and understanding of the

vapor intrusion pathway is warranted. The potential for a complete vapor intrusion

pathway depends on factors such as current or future land use, distance between

contamination and existing or proposed buildings, preferential pathways, and whether

contaminant plumes are at steady state. A potentially complete or complete vapor

intrusion pathway exists if there is: 1) a potential or confirmed source of a sufficiently

volatile and toxic chemical or chemicals; 2) a current or future mechanism to transport the

chemical; and, 3) a current or future human receptor. Please note, future buildings are to

be reasonably anticipated. If a determination is made that there is no complete or

potentially complete vapor intrusion pathway, this determination must be documented. If

the three factors listed above are present at a site, an investigative workplan that includes

a CSM for evaluating the vapor intrusion pathway should be developed. The CSM is not

static, but continually refined and revised based on data collected at the site.

Flowchart Step 3: Develop a conceptual site model and data quality objectives

3.2 Conceptual Site Model

Site investigations should include the development and refinement of a CSM. The

purpose of a CSM is to provide a conceptual understanding of the potential for exposure

to hazardous contaminants based on knowledge of the sources of contamination present,

release mechanisms to the environment, transport mechanisms, exposure pathways, and

potential receptors. The CSM should include a diagrammatic or schematic representation

that relates the source of contamination to human and ecological receptors and identifies

all potential sources of contamination, the potentially contaminated media, and exposure

pathways. The CSM should evolve as site-specific conditions are better understood and

additional data becomes available, thus the CSM should not be static. The CSM

organizes and communicates information about the site characteristics and is not only a

necessary component of any vapor intrusion site investigation, but an essential decision-

making and communication tool for all interested parties.

For vapor intrusion sites the CSM is integral to the development of a sampling plan. The

CSM will focus on the potential receptors and pathways and is updated as additional data

and information is obtained. Ohio EPA recommends that the following items be included

in a CSM for the vapor intrusion pathway. However, in the early stages of investigation,

not all components listed may be available.

• Primary Sources of Contamination. Provide a list of all volatile chemicals for each

potential source. For each potential contaminant source, describe the release and

provide a list of volatile chemicals released into the environment.

• Secondary Sources of Contamination. Include all the environmental media

potentially contaminated by the primary sources, such as surface soil, subsurface

soil, and ground water. Contaminated building materials, such as concrete

foundations, can be a source area for a potential release to an environmental

medium and should be considered.

• Contaminant Transport Mechanisms. For each potentially contaminated

environmental medium, describe the transport mechanism to indoor air, (usually

advection and diffusion through the vadose zone), and describe the characteristics

of the subsurface.

• Exposure Routes. Describe current buildings, potential future building scenarios,

as appropriate, and areas where vapors may accumulate, including smaller

enclosed areas in larger buildings. Discuss any preferential contaminant migration

pathways associated with the buildings, such as foundation cracks, voids, utility

ports, pipes, elevator shafts, sumps, and drain holes.

• Potential Receptors. List all the current and potential future receptors, as

appropriate, that could potentially be exposed to contaminated indoor air from the

vapor intrusion pathway.

A preferential contaminant migration pathway is a pathway of less resistance than typical

pathways available for transport through environmental media, taken by chemicals of

concern (COC) while undergoing diffusion or advection. These pathways, which can be

natural or anthropogenic, are a result of disturbance in natural soil layers, (such as

installation of underground utilities or fractures in bedrock), are more porous and

transmissive, and enable more rapid COC transport. Early in the development of a CSM

and sampling plan, preferential pathways need to be considered, located and potentially

sampled for. For example, it has been observed that utility lines are able to influence the

flow of shallow ground water contaminated with vapor-forming chemicals, and either block

the flow of such ground water, or conversely, facilitate flow of soil gas and contaminated

ground water through the porous bedding material or the pipes themselves. Sewer lines

in particular, due to their construction, have been known to convey vapor-forming

chemicals for long distances from a source. Older sewer lines may be composed of clay,

cast iron or Orangeburg pipe, which may have cracks and voids at joints depending upon

their age. Infrastructure present in older cities and towns may be cracked or detached at

joints due to settling. Utility lines are surrounded by bedding material which is typically

more porous than the surrounding native soils. The presence of any preferential pathway

necessitates an examination of whether vapor-forming chemicals can be transmitted

beyond the assumed 100-foot buffer zone. A study by McHugh, et. al. (2017) showed that

concentrations of vapor-forming chemicals were higher in the basement than the sub-

slab vapor concentrations. Therefore, if a sewer line is within the zone of influence (less

than 100 feet) from a source of vapor-forming chemicals, or there is reason to suspect

that a ground water plume contaminated with vapor-forming chemicals above U.S. EPA

VISLs is interacting with the sewer line, then sampling the line and bedding material

should be planned and included in the sub-surface investigation and field sampling plan.

To document current site conditions, the CSM should be supported with maps,

subsurface cross-sections, site diagrams, and any other site-specific details which may

be pertinent, such as building characteristics. The narrative should clearly describe known

site conditions and state what assumptions were made to generate the CSM. The

narrative should include a description of ambient sources and the presence of nearby

potential sources of volatile organic compounds (VOCs) and other volatile chemicals,

such as neighboring dry-cleaning operations. Additional information on the development

of a CSM can be found in guidance published by various entities, including the U.S. EPA

Risk Assessment Guidance for Superfund (U.S. EPA, 1989), Standard Guide for

Developing Conceptual Site Models for Contaminated Sites ASTM E1689 – 95 (ASTM,

2014), Ohio EPA DERR Conceptual Site Models Guidance Document (Ohio EPA, 2015),

and U.S. EPA Guidance on Systematic Planning Using the Data Quality Objectives

Process (U.S. EPA, 2006).

The site evaluation may lead to the conclusion that the vapor intrusion pathway is

incomplete. The following are examples of instances where the vapor intrusion pathway

may be considered incomplete:

• No buildings are present at the site and there is a prohibition on building structures

at the site in the future;

• Absence of sufficiently volatile and toxic chemicals;

• The distance between contamination and existing or proposed buildings is greater

than 100 feet leading to low probability of vapor intrusion, as confirmed with soil

gas data;

• Lack of preferential pathways; or

• Contamination plumes (e.g., ground water, soil gas or sub-slab vapors) are

confirmed to be at steady-state and contaminant concentrations are and will

remain below screening levels.

A checklist of information to assist in the development of a CSM for vapor intrusion and

for planning a soil gas sampling strategy for a site can be found in Appendix A.

3.3 Data Quality Objective Process and Developing a Sample Plan

The scope and objectives of environmental media sampling should be established before

the vapor intrusion investigation is conducted by working through the Data Quality

Objective (DQO) process. For voluntary actions, the DQO process is part of the Phase II

Property Assessment (see OAC 3745-300-07(C)). For RP sites, the CERCLA RI/FS

guidance, RCRA Corrective Action Guidance, Closure Plan Review Guidance and

general U.S. EPA Quality Management documents should be followed when designing a

sampling plan and developing DQOs. The DQOs are qualitative and quantitative

statements that:

• Clarify the study objective.

• Identify the chemicals of concern (COCs).

• Define if the sample will provide qualitative or quantitative information.

• Define the type, quantity, and quality of each piece of data collected in the study.

• Determine required analytical detection limits.

• Define how each sample will be used to assess whether vapors are intruding into

buildings.

• Determine the most appropriate locations, sampling method, and sampling

duration for data collection.

• Specify the amount of acceptable uncertainty in the sampling results.

• Specify how the data will be used to test the exposure hypothesis.

Additional information on the DQO process can be found in U.S. EPA. Guidance on

Systematic Planning Using the Data Quality Objectives Process (February 2006) at

https://www.epa.gov/quality and Ohio EPA, Data Quality Objectives Process Summary,

DERR-00-DI-32, Internal Guidance Document, January 2002 at

https://www.epa.ohio.gov/portals/30/rules/Data%20Quality%20Objectives%20Process%

20Summary.pdf.

The type of environmental media sampled and sampling strategy for the evaluation of the

vapor intrusion pathway is dependent on release history, prior site investigations, the

CSM, and whether the site is being evaluated under the VAP or RP programs.

For RP sites, the sampling strategy is directed by the RI/FS, RFI/CMS or unit closure site

characterization process. For VAP sites, the Phase I will direct the sampling with the

results presented in the Phase II. For RP sites, the sampling strategy should be sufficient

to characterize the complete nature and extent of contamination. For VAP sites the

sampling strategy may be tailored to the remedy selection. During site characterization,

the sampling and analysis plan that was developed during the project planning is

implemented and field data are collected and analyzed to determine if a complete vapor

intrusion pathway exists and to what extent the site poses a threat to human health and

the environment. This is an iterative process and the resulting data and information will

be used for selecting a remedy for the site.

The U.S. EPA OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion

Pathway from Subsurface Vapor Sources to Indoor Air (June 2015) recommends

collecting multiple rounds of sampling at multiple locations to evaluate spatial and

temporal variations of the concentrations of COCs in environmental media. Spatial and

temporal variability factors to consider include depth to ground water, heterogeneity in

subsurface materials, weather conditions, building operations, building construction and

age, interior compartmentalization, preferential contaminant migration pathways (such as

foundation cracks, sumps and utilities), and whether the site is developed or

undeveloped.

In most cases, soil gas data is part of the multiple lines of evidence approach to determine

whether the vapor intrusion pathway is potentially complete from contaminated soil or

ground water. For existing buildings, sub-slab vapor concentrations best reveal the

potential for vapor intrusion directly into the building. The flow chart in Figure 1 does not

require that environmental media be sampled in a linear fashion (i.e., soil and ground

water, then soil gas, then sub-slab vapor, and finally indoor air). However, where

receptors are potentially being exposed, the preference is to determine impacts from soil

gas, soil, and ground water first to determine if a potential for vapor intrusion exists. A

more detailed discussion of the relative importance and iterative sampling of different

media is provided in Sections 4.3, 4.5, and 6.4. If soil gas, soil and/or ground water data

indicate a potential risk to building occupants, then sub-slab vapor and indoor air data

should be collected and used in the risk evaluations. Special considerations are advisable

when evaluating residential properties and/or imminent hazard situations and are

discussed in Appendix B and Section 11.0, respectively.

Ambient air and sub-slab vapor should be collected when sampling indoor air to aid in

data interpretation and determining if vapor intrusion is occurring. Although measuring

indoor air concentration is a direct measurement at the exposure point, many factors can

influence indoor air results, including materials used or stored indoors, disturbance of

sampling equipment during testing, and the possibility of ventilating the building during

the sample event (i.e., opening doors/windows). Additionally, indoor air values can be

influenced by concentrations of volatile chemicals in ambient outdoor air that are

unrelated to releases in soil or ground water.

For all vapor-forming chemical releases, if the data collected during the site investigation

indicates existing or future buildings at a site or near the site are greater than 100 feet

laterally from the known extent of subsurface contamination above screening levels and

there are no preferential pathways (e.g., sewer lines) that can be a direct conduit from a

vapor source to a building, then vapor intrusion is not likely under the current site

conditions, and no further consideration of the exposure pathway should be needed until

such time site conditions change in a way that warrant a vapor intrusion investigation

(e.g., a building is built directly above the source area). For relatively small releases

compromised of only petroleum hydrocarbon (PHC), such as underground storage tank

(UST) sites, a lateral separation distance of 30 feet and a vertical separation distance of

15 feet (above LNAPL) or 6 feet (above dissolved sources) can be applied instead of the

default 100 feet. Sites with a potential for larger petroleum releases, such as bulk plants,

refineries, petrochemical plants, or pipelines, or sites where lead scavengers were used

or stored should use the 100 feet lateral separation distance recommended for non-PHC

VOCs. See Sections 9.2 and 9.3 for additional information regarding PHC lateral and

vertical separation distances.

Evaluations of building distance from contamination should only be conducted if the

movement of subsurface contamination has reached steady-state conditions (i.e., when

the maximum migration potential of the subsurface plumes has been reached). For

ground water, the migration potential can be evaluated with data from routine sampling

of ground water monitoring wells. If COCs in ground water indicate stable or decreasing

contaminant trends, the maximum contaminant migration for ground water has probably

occurred. For soil gas, a similar evaluation can be conducted if routine sampling data is

available from permanent or temporary sampling points. If sufficient time has passed

since the chemical release to allow for diffusional movement to the building in question,

then steady-state conditions have probably occurred. If soil gas or ground water

contaminant plumes are increasing, 100 feet is not an appropriate distance for potential

pathway elimination.

When evaluating the distances between subsurface contaminant plumes and buildings,

it is important to consider whether preferential pathways exist which could allow vapors

to migrate beyond the lateral separation distance. These preferential pathways could be

either natural or anthropogenic. Examples of preferential pathways include fractures,

macropores, gravel base for utility conduits, and subsurface drains, etc.

Flowchart Step 4: Sample environmental media

4.0 SOIL GAS AND SUB-SLAB VAPOR SAMPLING PROCEDURES

The following section provides basic guidelines for conducting soil gas and sub-slab vapor

sampling for assessing the vapor intrusion pathway. Soil gas sampling refers to samples

collected outside of a building footprint and sub-slab vapor sampling refers to samples

collected from directly underneath an existing building. Appendix C contains Ohio EPA

DERR’s standard operating procedures for installing soil gas probes, sub-slab vapor

probes and direct push techniques for collection of soil gas.

Soil gas and sub-slab vapor sampling can be used for a number of purposes including

initial site characterization, delineation of impacts from ground water plumes, identification

of source areas and potential receptors, remediation and post-remediation monitoring,

and for developing and refining a CSM.

4.1 Soil Gas and Sub-Slab Vapor Sample Collection and Analysis

Depending on the scope of the study and the DQOs, samples may be collected using

devices such as gas-tight syringes, Tedlar

bags, passive sorbent samplers or Summa

canisters. Gas tight syringes are appropriate only when an on-site field laboratory is used,

and samples are analyzed immediately following sample collection. Field screening and

use of a mobile lab are acceptable in order to refine DQOs by conducting on-site, real

time field analysis. Alternative soil gas and sub-slab vapor sampling options can be

proposed to Ohio EPA for considerations.

Prior to collecting the sample for analysis, Ohio EPA DERR recommends purging three

tubing volumes or conducting a purge test until parameters (e.g., oxygen, carbon

monoxide, or VOCs) stabilize in order to determine the optimal purge volume for the

location. The purge volume should be consistent for all samples collected from the study

area. An approximate 10-minute delay should occur between purging and sampling.

When purging or collecting samples using a vacuum pump or an evacuated canister, the

vacuum applied to the probe should not exceed ten inches of mercury or 100 inches water

and the flow rate generally should not exceed 200 milliliters per minute. This should limit

the potential for ambient air being drawn into the sample from the ground surface and it

should limit desorbing of vapors from contaminated soils.

To maintain sample integrity:

• The recommended maximum holding times for samples should not be exceeded.

The laboratory should be contacted for holding times and to ensure the sampler

uses the best collection method.

• If stored samples are to be subjected to changes in ambient pressure (such as

shipping by air), canisters are recommended (ITRC, 2007).

• Samples should not be chilled during storage unless specified by the method.

• Tedlar

bag samples should be kept out of direct sunlight.

• All sampling records should be completed and maintained (e.g., chain of custody,

sample data forms).

The appropriate sample method is dependent on the DQOs developed for the project.

The contract laboratory can provide information on appropriate sample volume for

analysis. Samples should be analyzed for the appropriate COCs, including breakdown

products. Syringe samples and Tedlar® bags generally are only acceptable for qualitative

and possibly semi-quantitative analyses. Quantitative analysis by TO-15/8260 or TO-17

should be used for human health risk assessments. The analytical method used should

be able to identify and quantify the target analytes and be capable of meeting program

specific requirements. Sample results submitted to Ohio EPA DERR should be reported

in units of ppbv and/or µg/m

. Lower explosive limit (LEL) percentages should be used

for explosive gas determinations. Soil gas and sub-slab vapor sampling field data should

be recorded on either the Soil Gas Probe Field Data Report Form (Appendix D) or the

Indoor Air/Sub-Slab Vapor Sampling Form (Appendix E) or equivalent forms, as

applicable, and submitted with the results.

Utility and sewer lines should be located prior to conducting sampling for safety and to

aid in locating samples. Contact a local municipal utility authority to obtain accurate layout

of utilities and sewer lines in immediate vicinity of the site before a subsurface

investigation. In Ohio, it is 8-1-1, the Ohio Utilities Protection Service, which coordinates

with local utility contacts. The utilities and sewer lines should be depicted on the cross

section of the CSM, and a determination should be made if there is a potential for utility

or sewer lines to interact with shallow ground water. Utility lines within 100-feet of a known

vapor-forming chemical release should be screened via a Photoionization detector (PID)

or equivalent field screening instrument.

A utility line preferential pathway investigation should take into consideration the type,

depth, diameter and construction specifications of all lines and bedding material, utilizing

historical resources. Screen sewer gas and determine depth of lines through manhole

apertures if possible, using a PID. Sampling in sewer lines and the bedding around utilities

requires caution and expertise given the risks involved if utilities are pierced or damaged.

The following resources discuss techniques which can be utilized to sample for soil gas

in and around utilities:

• Indiana Department of Environmental Management (IDEM): Investigation of

Manmade of Preferential Pathways, Office of Land Quality, August 2015:

https://www.in.gov/idem/cleanups/files/remediation_tech_guidance_investigation

_mpp.pdf

• Massachusetts Department of Environmental Protection (MassDEP) Vapor

Intrusion Guidance, Site Investigation, Mitigation and Closure, October 2016:

https://www.mass.gov/files/documents/2016/10/nu/vapor-intrusion-guidance-10-

14-2016.pdf

4.2 Analytical Detection Limits

Analytical detection or reporting limits for soil gas samples should be sufficiently low to

adequately evaluate the vapor intrusion pathway per the project’s DQOs. For VAP sites,

an estimate of the applicable standard, adjusted for the presence of multiple chemicals,

provides the basis for the minimum detection limits. For screening at Ohio EPA DERR

RP sites, the minimum detection limit is determined by the appropriate screening value.

More information on the analytical methods and reporting limits can be found in Appendix

4.3 Soil Gas Sampling

In many cases, soil gas sampling is essential in evaluating the vapor intrusion pathway.

There are a variety of techniques for obtaining these samples, from placing probes using

boring devices to measuring soil gas using passive-type samplers. Whatever technique

is chosen, the soil lithography and stratigraphy should be determined using on-site data

from previous investigations, data from nearby sites, or based on information from county

soil surveys to aid in characterizing the source and transport mechanisms. Other pertinent

information that should be considered when planning a soil gas investigation include

depth to ground water and the presence of perched impermeable zones. This information

should be used to determine appropriate sampling depths. Ohio EPA generally expects

that initial soil gas samples should be taken above the capillary fringe to determine if a

contamination source is of sufficient concentration to warrant additional soil gas sampling

or to conduct sub-slab vapor sampling. It may be necessary to install probes at multiple

depths to evaluate the vertical distribution of contaminants in soil gas. For vertical

delineation, soil gas samples could be collected at various depths (e.g., 5 feet, 10 feet,

and 20 feet below ground surface (bgs)) to demonstrate attenuation and the likelihood

that the vapor intrusion pathway is complete. Ohio EPA DERR recommends that vadose

zone monitoring points for sample collection be installed to evaluate the temporal

variations in soil gas concentrations. Soil gas sampling should be postponed at least 24-

hours after a major rain event (one-half inch or more) and the sampling area must be free

of ponded water.

Soil gas sample locations should be biased toward the source, if known, or toward highest

expected concentrations. If a property is developed, sub-slab vapor sampling rather than

soil gas sampling is preferred to evaluate the potential vapor intrusion pathway to the

building. If sub-slab vapor sampling is not practical, then soil gas samples should be

collected as close to the building as possible. However, keep in mind that soil gas samples

may exhibit a high degree of spatial and temporal variability (U.S. EPA, 2015b). According

to U.S. EPA (2015b), “…soil gas concentrations measured exterior to a building may not

be representative of sub-slab concentrations measured directly beneath the building

foundation sub-slab. The bias introduced by these factors may be high or low depending

on climatic and building conditions and the extent to which the samples accurately

represent the spatial and temporal variability of concentrations under the building.” If soil

gas samples are being collected in lieu of sub-slab samples, then bias should be given to

preferential pathways, such as utilities and fill materials located at the site to account for

this potential variability. It is important to note that situations may exist where vertical

fractures may provide preferential pathways, in such instances sub-slab vapor sampling

may be necessary to adequately evaluate the indoor air pathway.

Ohio EPA DERR recommends that a minimum of two rounds of soil gas data be collected

to evaluate the vapor intrusion pathway. However, early or interim response actions may

be required following one round of sampling. The two rounds will begin to estimate

temporal and seasonal variations at the site and other site-specific factors which may

influence vapor migration. Since two rounds constitute a limited database, the maximum

concentration detected should be used to evaluate potential risk. Based on these results,

additional samples may be required depending on the source strength, plume movement

and how soil gas concentrations compare to screening levels. If soil gas samples exceed

screening values and buildings are within 100 feet of the sample location for non-

petroleum vapor-forming chemicals and within 30 feet of PHC vapor-forming chemicals,

then sub-slab vapor samples and/or indoor air samples should be collected to further

evaluate the vapor intrusion risk pathway. For further information on evaluating petroleum

releases and their inclusion zones see Section 9.0.

For undeveloped sites with vapor-forming chemical contamination, soil gas samples

should be collected to evaluate the potential for vapor intrusion should the property be

developed in the future. The number and depth of soil gas samples should be sufficient

to evaluate concentrations in soil gas and attenuation of soil gas as it migrates to the

surface. Reassessment of the vapor intrusion pathway may be warranted once structures

are built on the site to evaluate the site-specific situation.

Generally, soil gas samples should not be collected at depths shallower than five feet bgs

due to the potential for atmospheric interference. Ambient air may infiltrate the soil column

and could result in dilution of the soil gas sample near the surface. For sites where the

depth to ground water or the soil source is less than five feet, but sub-slab sampling

beneath an enclosed structure is not an option, an attempt should be made to collect soil

gas samples from beneath existing impermeable surfaces such as outdoor patios, parking

lots, or roads. When shallow (< 5 feet bgs) soil gas sampling is performed, leak testing is

a critical element of the sampling to verify the integrity of the vapor probe seal and the

quality of the data (Section 4.7). If an impermeable surface is not present beneath a

structure or in outdoor areas, then it may be more appropriate to rely on other lines of

evidence such as passive soil gas sampling, ground water sampling, crawl space or

indoor air sampling to evaluate the vapor intrusion pathway.

4.4 Soil Gas Probes

Soil gas sampling probes are either temporary or permanent. Temporary soil gas probes

are only sampled once, and all equipment is removed upon sample completion.

Permanent soil gas probes are sampled over time to evaluate seasonal, temporal or other

variations in concentrations. When possible, permanent soil gas probes should be

installed when collecting soil gas samples for risk assessments. Figure 2 shows several

types of soil gas probes (NJDEP, 2005). Whether installing a temporary or permanent

soil gas probe, it is necessary to prevent ambient air from diluting the soil gas sample. A

leak test should be performed to verify the integrity of the vapor probe seal. For further

information on leak testing refer to Section 4.7.

Figure 2. Examples of Soil Gas Sampling Probes (NJDEP, 2005)

Temporary vapor probes can be installed by a variety of methods. The most common

methods are direct push and manual slide hammer. These methods allow sample tubing

to be placed at the desired depth for sampling then removed once a sample is collected.

Temporary vapor probes use a retractable or removable drive tip. Typically, ¼” nylon,

Teflon or polyethylene tubing is used to collect subsurface vapors for sampling in

temporary applications.

Figure 3 is a schematic of a permanent soil gas probe. Samples from permanent soil gas

probes should be collected over an appropriate seasonal or temporal time frame in order

to adequately evaluate the risk from the contaminants detected. Permanent soil gas

probes typically consist of a screen or sample port installed at the tip or near the bottom

of the tubing. Stainless steel, Teflon or nylon tubing are preferred in permanent

applications. Tubing selections should be based upon duration of sampling, type of

COCs, and how long the sampling point needs to remain in place (see Appendix G for

comparison of sample tubing type to vapor absorption). Common installation methods

include direct push equipment (e.g., Geoprobe®), hollow stem auger and manual slide

hammer (see Appendix C for the standard operating procedure for advancing soil gas

probes). The soil gas probe is installed to a specific depth in a bore hole created with a

slide hammer, direct-push system or a hollow stem auger. Sand is placed in the annulus

around the sampling port screen and the remainder of the bore hole is sealed with

hydrated bentonite. The tubing is usually labeled and capped at the surface. The bore

hole is completed with a protective cover at the surface.

Figure 3. Permanent Soil Gas Probe Schematic

4.5 Sub-Slab Vapor Sampling and Data

Sub-slab vapor data, which is collected from under the foundation floor and is within the

advective envelope of building-driven depressurization, indicate whether contaminants

have accumulated directly under the building. Analytical detection limits should be low

enough to effectively evaluate the indoor air risk posed by the vapor intrusion pathway.

See Section 12.0 for more information on evaluating the indoor air risk from vapor

intrusion by calculating risk levels.

When there is an indication of a potentially complete exposure pathway, proceeding

directly to sub-slab vapor sampling may shorten the investigation. However, if the purpose

of an investigation is to directly link a known or suspected source to vapor intrusion, then

sub-slab vapor sampling is only one step in the process. In this situation, it is important

to also consider collecting soil, ground water, soil gas, sub-slab vapor, utility or sewer

line, and indoor air samples, as applicable, in order to link the source to the exposure

point (i.e., the indoor air). When collecting sub-slab vapor samples, Ohio EPA DERR

recommends the event be paired with indoor air samples and an ambient air sample in

order to compare the chemicals detected in these samples to aid in vapor intrusion

assessment data interpretation and conclusions.

If COCs are detected in sub-slab vapor samples above screening levels, then installation

of permanent sampling ports may be necessary to determine the temporal variability of

the data. However, the collection of sub-slab vapor samples can be inconvenient to

building occupants since it requires the removal of floor coverings and drilling through the

foundation slab, thus clear communication with inhabitants and property owners about

the sampling process is needed.

When sub-slab vapor sampling is conducted, an appropriate number of samples should

be taken to characterize the sub-slab area. The number, type (time-integrated or grab

samples), and locations of the sub-slab samples should be determined based on

information collected during the building survey, an understanding of the building

foundation(s), the COCs (e.g., PHC versus chlorinated), the results from nearby soil gas,

ground water, and/or soil sampling, and the site-specific DQOs. At residential properties,

at least two sub-slab vapor samples should be taken with one sample taken in the center

of the building’s foundation. For foundations greater than 5,000 square feet, at a minimum

sub-slab vapor samples should be collected approximately every 2,000 to 5,000 square

feet from biased locations, such as locations directly over source areas, maximum ground

water concentration areas or near preferential pathways, and one of the sample locations

should be located near the center of the building foundation. If indoor air sampling is not

performed concurrently, but is subsequently needed, the indoor air samples should be

analyzed only for the chemicals detected in the sub-slab vapor (see Section 5.0). By

selecting for the chemicals detected in the sub-slab samples, the chance of inadvertent

inclusion of indoor sources of chemicals can be decreased or eliminated. However,

analyzing indoor air samples for the method’s full analyte list can be necessary when the

full nature and extent of contamination has not yet been determined.

During sub-slab sampling care should be taken to not damage the integrity of the slab or

underground utilities. Sub-slab utilities or tension cables need to be located prior to

selecting sampling locations. Blueprints can assist in locating these features. A private

utility locating service should be contracted to determine the presence of sub-slab utilities

or tension cables if there is no information available from other sources. Since penetrating

the slab creates a preferential pathway, proper sealing of the sampling port is essential

to avoid leaks. Sub-slab sampling should be avoided in areas where ground water might

intersect the slab. Figure 4 is a schematic of a sub-slab vapor probe made with Swagelok

parts. Another alternative is the Cox-Colvin vapor pin

Figure 4. Example of a Sub-Slab Vapor Probe

Multiple sampling rounds may be needed to adequately account for temporal variability

due to the “substantial spatial variability in sub-slab vapor concentrations” (U.S. EPA,

2015b). Generally, if both indoor air and sub-slab vapor samples are collected during the

most desirable sampling conditions to evaluate reasonable maximum exposure and both

are non-detect or below screening values, then one round of sampling may be sufficient.

If, however, COCs are detected in both sub-slab vapor and indoor air, or if indoor air is

non-detect, but COCs are elevated in sub-slab vapor, soil gas or other media, then

multiple rounds of sampling (or preemptive mitigation) are typically required. The number

of additional rounds depends on the chemical concentrations and other site-specific

circumstances. For example, long-term quarterly, semi-annual, or annual sampling may

be necessary in situations where vapor concentrations are variable, or to verify remedy

effectiveness.

4.6 Sampling Basements with Dirt Floors and Crawl Spaces

If a basement or crawl space has a dirt floor, any sampling conducted should be with an

evacuated air canister in the same manner as for sampling indoor air.

4.7 Leak Testing

Atmospheric air drawn into a soil gas or sub-slab vapor sample can result in dilution of

the sample. Negatively biased samples, resulting from the inclusion of atmospheric air

during soil gas or sub-slab vapor sampling, will be unusable to demonstrate that a vapor

intrusion pathway is incomplete. To ensure that valid soil gas and sub-slab vapor samples

are collected, leak tests on the probes should be conducted to demonstrate that dilution

is not a concern. It is often desirable to conduct leak testing with utilization of tracer gases

or a water dam. The water dam can consist of a secondary, larger hole surrounding the

smaller hole that the vapor sampling point is installed through (such as the hole used for

flush mount Vapor Pin® installation) or can be a ring temporarily sealed to the floor with

VOC-free putty. The water dam is filled with water after connecting the tubing to the

Summa canister. Changes in water level or appearance of bubbles during sampling are

indicative of possible leaks.

Soil gas probes should be installed greater than five feet bgs and should be tested for

integrity with a particular emphasis on the sampling train (i.e., the tubing or the

connectors). This testing is usually performed with compounds not found at the site that

enshroud the sampling train. Atmospheric oxygen and CO

may also be considered for

leak tests. As a general rule, shallow soil gas samples (i.e., less than 5 feet bgs), are

discouraged. However, if shallow soil gas sampling is the only option at a site, then leak

testing should be utilized, and sampling must be discussed with Ohio EPA DERR

personnel prior to collection of these samples. Temporary soil gas probes should be

abandoned immediately after the investigation is concluded. Sub-slab vapor sample

collection can also be affected by leaks from surface air and a sub-set of these samples

should also have leak tests performed. In addition to tracer gas leak tests, a mechanical

leakage test of the sampling train should be considered, such as Shut-in Test as proposed

by McAlary et. al. (2009). This test involves pulling a vacuum on the tubing and valves

used to construct the sampling train. Typically, a vacuum of 100 inches of water is applied

to the “closed-off” sampling train and potential leaks are verified with an in-line vacuum

gauge.

Depending on the contaminants of concern a number of different compounds can be used

as a tracer, as shown in Table 1. Sulfur hexafluoride (SF

), perfluorhydrocarbons and

helium are commonly used as tracers because they are readily available, have low

toxicity, and can be monitored with portable measurement devices. Isopropanol can also

be used as a tracer but requires laboratory analysis for the tracer. In all cases the same

tracer should be used for all sampling probes at any given site. The leak test should be

conducted using a tracer that is not expected to be present in the soil gas or sub-slab

vapor being tested. When choosing a liquid tracer, check with the laboratory to determine

the reporting limit for the proposed tracer. Ideally, the reporting limit for the tracer should

be similar to the constituents present in the soil gas or sub-slab vapor.

Infiltration of atmospheric air during sampling may also be indirectly evaluated through

the measurement of oxygen and carbon dioxide concentration differences due to the

presence or absence of petroleum hydrocarbon degradation. For example, if oxygen

concentrations at a probe installed within a petroleum hydrocarbon source area are at

atmospheric levels, the soil gas data should not be considered reliable and the probe seal

should be modified and the probe re-sampled, because oxygen levels would be expected

to have been depleted in the biological degradation process. Care should be exercised

using this logic when investigating sub-slab vapor as the absence or presence of a robust

microbial community may be questionable. The Soil Gas Probe Field Data Report Form

in Appendix D is useful for recording data when conducting soil gas evaluations. Table 1

lists advantages and disadvantages of common tracer compounds.

Table 1. Common Tracers Advantages and Disadvantages

Tracer

Advantages

Disadvantages

Helium

Can check for leaks on site

with handheld detector.

Can quantify amount of

leakage accurately.

Does not interfere in TO-15

analysis.

Party-grade helium may have low VOC

contamination. If used, send a QC sample

to lab for analysis.

Process is more cumbersome than some

others.

Cannot be analyzed by TO-15

Can be difficult to apply to sampling train

connections.

Liquid Tracers

Easy to use in identifying

leaks.

Can be detected by VOC

analytical methods.

Easier to apply to sampling

train connections.

Concentration introduced to assess leak is

estimated.

Large leak may lead to VOC analysis

interferences.

No simple field screening method.

May leave residual contamination on

sampling train.

Qualitative.

Sulfur

Hexafluoride

Can check for leaks with

on-site instrument with very

low detection limits.

Very expensive.

Field instrument subject to interference with

chlorinated solvents.

Cannot be analyzed by TO-15.

A greenhouse gas.

Ambient Air

Oxygen

Cost effective, easy.

Check for leaks with on-site

multi-gas meter.

Cannot be used in an environment where

oxygen is expected to be present at

ambient levels.

Qualitative.

If elevated levels of the tracer (greater than 10% in the shroud) are observed in a sample,

the soil gas data should be evaluated for the significance of bias on the results. If the

evaluation provides evidence that the results cannot be considered reliable, then re-

testing should be attempted after determining the cause for the atmospheric or tracer

break through. Portable, tracer gas-specific field monitoring devices with detection limits

in the low part per million (ppm) range are available to screen samples for tracer leak

testing.

4.8 Passive Soil Gas (Exterior or Sub-Slab) Sampling

Most methods for soil gas sampling involve the measurement of volatile constituents in

soil gas after drawing soil gas into evacuated canisters, such as Summa canisters, with

analysis by U.S. EPA method TO-15. Summa canister use is limited by flow regulators

with sampling durations ranging from immediate grab up to 72-hour samples. Scientists

and engineers concerned about impact of temporal variability on the representativeness

of soil gas concentrations may consider longer sampling durations using passive soil gas

sampling techniques. Passive sampling uses adsorbent materials which are placed in the

subsurface and left for a period of time (up to weeks). The sampling devices are then

retrieved and analyzed. Passive soil gas samples therefore may provide longer-term time-

weighted average concentrations.

Passive samplers generally consist of a container with an opening to allow gas to

permeate and be sorbed onto a sorbent. The opening is configured to allow vapors into

the device with a steady uptake rate. The sorbent is selected for the chemicals of concern.

The average concentration over the sampling period can be determined using the

following equation.

C = M/(UR x t)

Where: C = Concentration

M = Mass of sorbed chemical (µg)

UR = Uptake Rate (mL/min)

t = time (min)

Conversion of these parameters into familiar units of µg/m

is usually performed by the

laboratory. The analysis of the sorbent material can determine the mass (M) of the

chemical adsorbed with high accuracy. The duration of sample acquisition (t) is also

known, but the uptake rate (UR) can depend on a variety of factors. These factors include

the geometry of the sampling device, the physical-chemical characteristics of the

chemicals of concern (diffusion coefficient); the humidity of the soil atmosphere and the

permittivity of the chemical through the soil.

Many of these factors for the uptake rate are not known without study, therefore Ohio

EPA DERR considers passive soil sampling to be qualitative. Studies (McAlary et al.,

2014a) suggest that quantitative passive soil gas sampling analysis is possible, but

consultants should consult with Ohio EPA before site work begins to demonstrate the

acceptability of passive soil gas sampling for quantitative purposes.

Passive soil gas sampling methods can be a useful tool for:

• Collecting soil gas from low-permeability and high moisture settings where

conventional active soil gas sampling may be problematic;

• Detecting compounds present at very low concentrations;

• Assessing preferential vapor migration pathways such as utility corridors and

foundation cracks to determine if these pathways are acting as significant VOC

migration pathways into a structure; and

• Providing chemical vapor concentrations if the sampling method meets the project

DQOs.

For additional information on passive sampling techniques, see:

• ITRC guidance, Vapor Intrusion Pathway: A Practical Guideline. January 2007,

Appendix D, page D-16.

• NAVFAC Memorandum (July 2015), Navy Facilities Engineering Command:

Passive Sampling for Vapor Intrusion Assessment. TM-NAVFAC EXWC-EV-1503.

14 pages.

• McAlary, T.A., H. Groenevelt, S. Seethapathy, P. Sacco, D. Crump, M. Tuday, B.

Schumacher, H. Hayes, P. Johnson, and T. Górecki. 2014b. Quantitative passive

soil vapor sampling for VOCs—Part 2: laboratory experiments. Environ. Sci.:

Processes Impacts 16(3): 491–500.

5.0 INDOOR AIR SAMPLING

Indoor air sampling should be conducted when soil, ground water, soil gas, or sub-slab

vapor data indicate the potential for unacceptable risk due to vapor intrusion, or an

imminent hazard is suspected. Indoor air sampling in lieu of other media sampling may

be necessary under circumstances where soil gas or sub-slab vapor sampling is not

viable, such as: contaminated soil or ground water in close proximity to the foundation,

during or after mitigation, or where preferential pathways may exist that would limit the

usefulness of data from other environmental media. As previously noted, indoor air

sampling in conjunction with sampling other media is recommended to prevent the

potential for concentrations of chemicals from indoor sources (not related to vapor

intrusion) inadvertently being included in the vapor intrusion risk evaluation.

Several steps should be considered when conducting indoor air sampling as part of a

vapor intrusion assessment:

• Define the study goals and DQOs;

• Identify the vapor-forming chemicals, including parent and breakdown products;

• Inspect building interiors and product inventory;

• Select the number and location of indoor sample locations;

• Select the number and location of ambient air sample locations;

• Select the duration of samples based on DQOs and risk assessment or risk

management needs;

• Select appropriate sampling methods with acceptable detection limit(s); and,

• Establish QA/QC requirements.

When assessing large plumes that have the potential to affect a significant number of

structures, Ohio EPA DERR recommends a tiered approach to indoor air sampling.

Highest priority for sampling should be given to structures at the greatest risk for indoor

air contamination through an evaluation of nearby ground water concentrations, soil gas

concentrations, sub-slab vapor concentrations, structural characteristics and sensitivity

of receptors. Conduct sampling at the primary structures, i.e., at the greatest risk of indoor

air contamination, first. Conduct sampling at secondary structures if COC concentrations

in or below primary structures are at unacceptable levels. This systematic “step-out

process” should be implemented sequentially until a perimeter of structures with

concentrations at acceptable levels is defined.

5.1 Site Inspection, Product Inventory and Field Screening

Prior to indoor air sampling, a site inspection and inventory of products containing volatile

chemicals should be conducted in the building (see Appendix E). Activities that could

influence indoor air concentration levels should be suspended a minimum of 24-48 hours

prior to and during sampling. Activities that should be suspended include, but are not

limited to, smoking, use of sprays and/or solvents, mowing, painting, and asphalting.

Containers containing products that could confound indoor air vapor intrusion assessment

results should be removed from the building if possible.

Field screening instruments used to assist with identifying indoor air sample locations

should be capable of detecting vapors in the µg/m

range. However, field screening

results are considered qualitative and often are not capable of measuring levels over time

or at low enough concentrations to inform risk management decisions. Therefore,

quantitatively collected indoor air samples are still needed to evaluate receptor exposure

and quantify potential human health risks.

5.2 Indoor Air Sample Collection and Analysis

Ohio EPA DERR recommends that indoor air samples be paired with sub-slab vapor

samples and an ambient air sample in order to compare the chemicals detected in these

three distinct zones when interpreting data and making conclusions about the vapor

intrusion pathway. When conducting paired indoor air and sub-slab vapor sampling, it is

recommended that the samples be collected a minimum of 2 hours after the installation

of sub-slab vapor ports to allow for equilibration of both the indoor air and sub-slab vapor

sampling spaces (U.S. EPA, 2015b).

When collecting indoor air samples, it is preferable to collect samples under conditions

that will result in the highest potential concentrations (see Table 2). Indoor air samples

should not be collected when doors and windows are open frequently or for long periods

of time. Special consideration should be given to areas where sewer lines may provide a

preferential pathway, and it is often beneficial to sample in bathrooms, laundries, and mud

rooms where dry traps or leaking plumbing are present and may be acting as a

preferential pathway. Sampling in the lowest level of a residence or commercial/industrial

building is often needed to evaluate the most likely highest concentrations in indoor air. If

vapor-forming chemicals are detected in the lowest levels above applicable standards,

then additional sampling may be needed from the next higher level of the building to

further assess vapor intrusion exposures.

While sampling under the more conservative conditions specified in Table 2 is

recommended, Ohio EPA DERR acknowledges that it may be difficult to time sampling

to when these conditions are present. The sampling team must decide when to sample

based on site-specific circumstances and each individual project’s DQOs.

Table 2. Comparison of Indoor Air and Sub-Slab Vapor Sampling Conditions to

Bias Sampling to the Highest Potential Concentrations*

*Modified from Mass DEP Vapor Intrusion Guidance Document (2016)

Sampling duration should represent the exposure scenario(s) under consideration.

Typical exposure scenarios include residential and commercial categories. A twenty-four

(24) hour sampling duration is used to represent exposure for a residential setting and an

eight (8) hour sample duration for a commercial or industrial setting. A 24-hour sample in

a commercial or industrial setting is also acceptable.

The number and location of indoor air samples is site-specific and dependent upon the

site conceptual model. Indoor air samples should, at a minimum, be collected from the

lowest level of the structure where vapors are expected to enter such as basements or

crawl spaces, and in areas where preferential pathways, including foundation

penetrations and cracks, have been identified. In some circumstances, it may be

beneficial to collect samples in first or second floor spaces, or necessary when a building

is built slab on grade. However, subsequent risk management decisions based on these

samples are site-specific and should be made in consultation with Ohio EPA DERR.

Multiple indoor air sample locations are typically necessary in the following instances:

when there is significant or unknown spatial variability in subsurface contamination, large

buildings (>1,500 square feet), small rooms such as offices and break rooms present

within larger buildings, buildings with additions, and areas subject to different HVAC

Parameter

More Conservative

Less Conservative

Temperature

Indoors 10°F greater

than outdoors

Indoor temperature less than

outdoor

Wind

Steady greater than 5

mph

Calm

Soil

Dry

Saturated with rain (1/2” of rain or

more within 24 hours)

Doors/Windows

Closed

Open

Mechanical Heating

System

Operating

Off

systems. In larger buildings, samples should both be biased toward known or suspected

subsurface contamination as well as collected from occupied areas of the building.

Multiple rounds of sampling may need to be collected to adequately account for temporal

and seasonal variability. Generally, if both indoor air and sub-slab vapor samples are

collected during more conservative sampling conditions (see Table 2) and both are non-

detect or below screening values, one round of sampling may be sufficient. If, however,

COCs are detected in both sub-slab vapor and indoor air, or if indoor air is non-detect but

COCs are elevated in sub-slab vapor or subsurface media, then multiple rounds of

sampling, or preemptive mitigation, are typically required. The number of additional

rounds of sampling depends on the chemical concentrations and other site-specific

circumstances. For example, long-term quarterly, semi-annual, or annual sampling may

be necessary in situations where vapor concentrations are variable, or to verify remedy

effectiveness.

For details on collecting indoor air, see Figure 5 and the appendices.

Figure 5. Schematic of a Summa Canister (Eurofins Lancaster Laboratories

Environmental, LLC 109)

Indoor air samples are typically collected in Summa canisters. When requesting Summa

canisters from a lab, it is recommended that you request canisters that are dedicated to

indoor air sampling and are certified clean to appropriate levels for indoor air screening.

The canisters from a lab can either be certified clean by "batch" certification or "individual"

certification. Project DQOs as well as a discussion with the lab should help identify the

need for "batch" or "individual" certification of the sample canisters. The analytical method

chosen for the indoor air sample analysis must be able to identify and quantify the target

volatile chemicals and be capable of detection below acceptable indoor air risk evaluation

levels. Ohio EPA DERR recommends that laboratory analysis for VOCs be done using

gas chromatography/mass spectrometry (GC/MS) and where appropriate, using the high-

resolution selected ion monitoring (SIM) mode for low level detection.

Analyzing indoor air samples for the method’s full analyte list is often necessary when the

full nature and extent of contamination has not yet been determined, such as when indoor

air samples are collected prior to or in lieu of sampling other media. However, if

contaminant concentrations in ground water, soil, sub-slab vapor and/or soil gas have

been sufficiently characterized, the analyte list may be limited to only those COCs known

or suspected to be present and the degradation products of the primary VOC

contaminants. By selecting for the chemicals detected in the release, the chance of

inadvertent inclusion of indoor sources of chemicals can be decreased or eliminated.

6.0 GROUND WATER MONITORING AND EVALUATION

Vapor-forming chemical contamination in ground water can be a source of vapors that

may impact an overlying structure. Ideally, soil gas or sub-slab vapor sampling should be

conducted in addition to ground water sampling when a source of vapor-forming

chemicals is present in or on the ground water. However, ground water data alone can

sometimes be used to evaluate the potential for vapor intrusion from ground water

contamination. Proper ground water monitoring well placement and construction,

including screen placement, screen lengths, and sampling protocols, are important for

gathering appropriate ground water data to evaluate the presence and concentrations of

vapor-forming chemicals to assess vapor intrusion potential and the need for additional

media samples. For technical guidance on installing and sampling ground water

monitoring wells, please see the Ohio EPA Division of Drinking and Ground Waters

Technical Guidance Manual in addition to the modifications for the VI assessment

discussed below.

6.1 Well Placement

Sufficient sampling is needed to determine ground water contamination levels,

contamination location, plume movement, and to assess and evaluate the potential vapor

intrusion from ground water contamination. For the purposes of investigating vapor

intrusion, wells should be placed in each area of anticipated maximum concentrations, or

the core of the plume(s). Monitoring wells must also be properly located proximal to areas

of known indoor air receptors to assess the potential impacts to those receptors. A

conceptual site model and DQOs can help evaluate spatial and temporal variability in

ground water concentrations and identify potential well locations.

6.2 Screen Placement

Ground water samples obtained from the uppermost portion of the aquifer

are

recommended to characterize representative vapor source concentrations for vapor

intrusion assessments. Ground water samples from wells screened across the water

table interface are preferred. Ohio EPA recommends that samples representing a flow-

weighted average be collected as close as possible to the top of the water table using

sampling methods designed to minimize loss of volatiles because VOCs volatilize from

the top of the water table. Thus, monitoring wells used to make vapor intrusion evaluations

should not have screens submerged below the top of the water table.

6.3 Screen Lengths

Monitoring wells with long well screens, regardless of screen placement, should not be

used for VI evaluations. When sampling long well screens, clean water entering the well

screen at depth may dilute the contaminated ground water near the top of the screen,

biasing the sampling results and the associated risk determination. Therefore, short

screen lengths are preferred for monitoring wells that will be used to make vapor intrusion

evaluations. Ideally, the saturated thickness at a well screen should always be less than

10 feet.

A flow-weighted averaging of ground water concentrations happens when mixing of water

from different stratigraphic units occurs while purging a well using low-flow methods, such

as low-flow purge and sample. Areas of higher conductivity provide a proportionally higher

volume of water than lower conductivity regions across the screened interval.

6.4 Ground Water Sampling

Ohio EPA recommends low-flow ground water sampling with bladder pumps or

submersible pumps. These pumps minimize the loss of VOCs during sample collection

and handling. Some submersible pumps can cause cavitation of the ground water and

release of volatiles, so care should be taken in selection and operation of the pumps. For

well-characterized sites where the contaminants are known, the appropriate diffusion

bags may be used to sample ground water following the procedures in Interstate

Technology and Regulatory Council (2004) guidance document Technical and

Regulatory Guidance for Using Polyethylene Diffusion Bag Samplers to Monitor Volatile

Organic Compounds in Groundwater. However, if levels of VOCs in ground water

collected using diffusion bags are found to be near screening levels, samples may need

to be verified using bladder or submersible pump sampling techniques.

This may require multiple sampling events conducted quarterly over several years to

represent seasonal variations. The stability of the VOC plume must be demonstrated so

that the risk to receptors would not be expected to increase due to contaminant migration

or degradation to more toxic constituents, such as the degradation of tetrachloroethylene

(PCE) and trichloroethylene (TCE) to vinyl chloride. Plume stability and migration may be

affected by factors as simple as a change in the surface drainage and recharge patterns.

Understanding these changes is important when characterizing the vapor intrusion

potential of a ground water source.

6.5 Soil Gas Confirmation of Ground Water Concentration

Ground water chemical concentrations can be compared to VISLs to evaluate the

potential of VI and the need for further sampling (see Section 8.3). Ohio EPA recommends

applying the appropriate VISLs for any building with receptors within 100 feet of the plume

boundary for non-PHC vapor-forming chemicals and 30 feet for PHC vapor-forming

chemicals.

If ground water concentrations are less than VISL and a determination is made that

additional sources in soil or preferential pathways are not present the investigation may

be discontinued. If there is uncertainty as to whether a complete vapor intrusion pathway

exists, soil gas, sub-slab vapor and/or indoor air data may be needed in addition to ground

water data to determine vapor concentrations in vadose zone soils. Indoor air samples

may be needed to establish whether the vapor intrusion exposure pathway from

environmental media to indoor receptors is complete.

When collecting soil gas samples to measure concentrations of vapor-forming chemicals

emanating from ground water, Ohio EPA recommends that seasonal ground water table

elevation fluctuations be considered. Ground water elevation fluctuation can impact

measured vapor concentrations in the vadose zone. Multiple sampling events may be

needed to adequately address seasonal variations in concentrations from sources in

ground water.

6.6 Other Factors

If the vapor-forming chemicals are present as Light Non-Aqueous Phase Liquid (LNAPL),

then ground water sampling may underestimate soil gas concentrations in the vadose

zone and a soil gas survey should be conducted. For further information on evaluating

petroleum releases see Section 9.0.

7.0 BULK SOIL

Soil data are used to define the type, location and extent of soil contamination when

investigating the potential for vapor intrusion. If a release of a vapor-forming chemical has

been confirmed, a lack of detections in soil should not be interpreted to indicate the

absence of a subsurface vapor source and soil data alone is not recommended to

evaluate vapor intrusion risk or pathway completeness. Rather, a well-developed

conceptual site model along with multiple lines of evidence should be used when

evaluating the potential for vapor intrusion at a site. The uncertainty associated with soil

partitioning equations and the potential for VOC contaminant loss during sample

collection and analysis (Hewitt, 1994; Hewitt, 1999; Liikala et al., 1996; Vitale et al., 1999)

makes using soil data alone unreliable for drawing risk assessment conclusions about a

suspected or confirmed release at a site. Therefore, Ohio EPA DERR recommends soil

vapor sampling when a suspected or known soil source of vapor-forming chemicals has

a potential for vapor intrusion. VOC loss during sampling can be minimized using SW-

846 Method 5035A (U.S. EPA, 2002). U.S. EPA SW-846 Method 5035A (2002) provides

the minimum requirements and standards to prevent loss of VOCs during sample

collection and handling. Specific soil collection requirements for SW-846 Method 5035A

include chemical preservation in the field, using multi-functional sampling devices, or

using empty, tared and labeled Volatile Organic Analysis (VOA) vials with

Polytetrafluoroethylene (PTFE)-lined septum caps. Refer to the method for specific

instructions.

Flowchart Step 5: Evaluate data and determine if data evaluation indicates the possibility

of an imminent hazard

8.0 DATA EVALUATION AND ANALYSIS

For each site, multiple lines of evidence are used to assess the vapor intrusion pathway.

Most of the lines of evidence will be based on empirical data from environmental media

including soil, ground water, soil gas, sub-slab vapor and/or indoor air. Evaluating data

from several environmental media, averaging among different collection times, and

differing environmental conditions, poses a unique set of considerations when evaluating

data for vapor intrusion. Generally, the multiple lines of evidence approach starts with

evaluating soil and/or ground water data from the environmental release for the presence

of volatile chemicals to assess the vapor intrusion pathway. If sufficiently volatile and toxic

chemicals are detected in soil and/or ground water, additional sampling is usually

warranted to further assess the vapor intrusion pathway.

Analytical methods, quantitation limits, qualified and coded data, and blanks should all be

evaluated prior to relying on the data for decision making. Data are evaluated for several

reasons which should be described in DQOs for the site. Generally, data are evaluated

to determine the most logical and efficient next step in the investigation or remedial

process. Initial comparisons to the appropriate risk-based screening levels or applicable

standards may be appropriate and provide evidence for reacting to an imminent hazard

or implementing early or interim response measures. For more information on

comparisons to risk-based screening levels and appropriate responses to imminent

hazards see Section 11.0 and flowchart Step 5.

8.1 Vapor Intrusion Screening Levels

U.S. EPA VISLs (https://www.epa.gov/vaporintrusion/vapor-intrusion-screening-levels-

visls) are media-specific, risk-based screening level concentrations for ground water, sub-

slab vapor and soil gas, and indoor air. VISLs are applied to identify site areas, building

locations, exposure points, and/or concentrations of COCs that are either unlikely to

present a human health concern and can be eliminated from further assessment or where

further evaluation of the VI pathway is needed. Established DQOs should be met, and

exposure assumptions should be consistent with the appropriate exposure scenario (i.e.,

residential or commercial/industrial land use).

For Ohio EPA DERR RP sites, when considering concentrations measured in sub-slab

vapor, soil gas, or ground water, the VISLs should be applied corresponding to an excess

lifetime cancer risk (ELCR) of 1E-5 (i.e., one increased cancer risk in 100,000 people)

and a noncancer hazard quotient (HQ) of 1. Ohio EPA considers the generic application

of the attenuation factor (AF) within the VISL calculation as an appropriate extension of

safety to provide for applying these ELCR and HQ values. If the measured concentrations

in the sampled media are less than the appropriate exposure scenario VISLs set at an

ELCR of 1E-5 and a HQ of 1, Ohio EPA DERR considers the pathway to be ‘incomplete’

and additional investigation or risk estimation of this pathway is not warranted.

For Ohio EPA DERR VAP sites the VISLs should be applied corresponding to an ELCR

of 1E-5 and a HQ of 1. If the measured concentrations in the sampled media are less

than the appropriate VISLs set at an ELCR of 1E-5 and a HQ of 1 for the appropriate

exposure scenario then additional investigation of this pathway is not warranted.

However, the estimation of risk generated from the analysis of the media or indoor air

must be included within the sitewide risk characterization in accordance with VAP rules

OAC 3745-300-08 and OAC 3745-300-09. A sitewide risk characterization must meet the

Ohio EPA cumulative risk goals of an ELCR of 1E-5 and a HQ of 1. In summary, the

removal of detected COCs from the risk assessment using a risk-based approach is not

permitted in the VAP, and the detected COCs must be multiple chemically adjusted and

included in the summation of risk and hazards across the complete exposure pathways.

Ohio EPA considers concentrations in indoor air to be the exposure point concentration

from which risk and hazard levels can be estimated and applicable standards can be

demonstrated. When VISLs or U.S. EPA Regional Screening Levels (RSLs) are being

used for risk and hazard assessment, care should be taken to use the appropriate land

use scenario and an ECLR of 1E-5 and a HQ equal to 1. In some cases, it may be

appropriate to evaluate multiple chemicals within indoor air to ensure Ohio statewide

cumulative risk and hazard goals are met.

8.2 Bulk Soil Data

Soil data are less than ideal for evaluating vapor intrusion risk and the need for early or

interim measures because of the uncertainty associated with using partitioning equations

and the potential loss of VOCs during sample collection (see Section 7.0). In general,

identification of elevated levels of VOCs in soil indicate the need for sub-slab vapor and

indoor air sampling when buildings are present, or soil gas data in areas where buildings

do not exist. Bulk soil detections of VOCs may be used to define the location of a VOC

source and extent of soil contamination, to assess the risk from direct contact with soils,

and to evaluate leaching to ground water.

8.3 Ground Water Data Screening

Ohio EPA recommends comparing ground water concentrations to U.S. EPA screening

values calculated through the U.S. EPA VISL calculator (Section 8.1). Ground water

sample data should be compared to screening values developed for the appropriate

exposure scenario (i.e., residential or commercial/industrial exposures), utilizing a default

or site-specific attenuation factor (AF), and a default or site-specific ground water

temperature.

The U.S. EPA VISL calculator uses AFs to calculate target ground water vapor intrusion

screening levels from toxicity-based target indoor air concentrations. Ground water data

should be compared with the appropriate VISL calculated with the recommended default

ground water AF appropriate to the CSM for the site. A generic ground water AF of 0.001

can be applied for most site scenarios with the exception of shallow water tables less than

five feet below the foundation of a building or when preferential vapor migration routes

are present in vadose zone soils (U.S. EPA, June 2015b). A default ground water AF of

0.0005 can be applied at sites with fine-grained (low permeability) vadose zone soils

when laterally extensive layers are present (U.S. EPA, June 2015b). Site-specific soil and

geologic information are needed to support the use of non-default AFs.

In addition to adjusting the default AF, the ground water temperature in U.S. EPA’s VISL

calculator can be adjusted to Ohio EPA DERR’s default ground water temperature of 11

degrees Celsius, or a verified property-specific value, to generate Ohio or site-specific

target ground water vapor intrusion screening levels.

Areas with ground water COC concentrations exceeding the ground water VISLs warrant

further evaluation of the VI pathway, including sampling of soil gas, sub-slab vapor and

indoor air, depending on the presence and location of buildings. If buildings are not

currently present at the site, it is recommended that a pre-emptive remedy requirement

or future evaluation of potential VI pathway be recorded in an Environmental Covenant to

avoid exposure to future receptors in the form of an institutional control (see Section 13.0,

Remedy).

8.4 Soil Gas and Sub-Slab Vapor Data Screening

Soil gas and sub-slab vapor data for each area of concern should be compared

individually to the VISLs. The recommended generic AF of 0.03 should be used to develop

sub-slab vapor and soil gas VISLs. However, soil gas VISL values should not be used for

VI source areas that are present less than five feet below the ground surface or if

preferential vapor migration routes are present in vadose zone soils (U.S. EPA, 2015b).

Soil gas and sub-slab vapor data that exceed VISLs warrant further VI assessment. If

buildings are not currently present in the area(s), additional assessment is warranted in

the future if buildings are constructed, and an Environmental Covenant with a building

occupancy limitation may be needed depending on the site conditions and reasonably

anticipated future use.

For evaluating the human health risk associated with crawl space air, an attenuation

factor of 1.0 should be used for crawl spaces, consistent with U.S. EPA guidance (2015b).

The use of an attenuation factor of 1.0 indicates the indoor air quality is assumed to be

equal to the crawl space air quality for evaluation purposes.

8.5 Indoor Air Data Evaluation

The indoor air data collected (Section 5.2) provides a time-weighted (e.g., 8 or 24 hours)

average concentration representing the reasonable maximum exposure to a receptor to

be evaluated in a human health risk assessment. The indoor air data is used to determine

whether there is a potential risk to human health posed from vapor intrusion.

Exceedances of indoor air applicable risk and hazard levels require implementation of

remedial activities, and a confirmation of the effectiveness of the remedial activities.

8.6 Background Source Evaluation

Many VOCs are also present in common household and industrial products and may

contribute to VOC detections in indoor air. Sources of background indoor air detections

need to be evaluated and documented to help interpret data when VOCs are detected in

indoor air (see Section 5.1). An inventory of potential background indoor air sources

should be conducted prior to or during indoor air sampling. If background vapor sources

are found to be primarily responsible for indoor air concentrations, then response actions

for vapor intrusion would generally not be warranted. Information on “background”

contributions of site-related VOCs in indoor air are part of the data evaluation because

vapor intrusion mitigation will not address VOCs generated within the building or that are

from natural or anthropogenic background levels. However, it is not appropriate to

subtract background or ambient air concentrations from the quantitative evaluation of

indoor air exposure determinations when it cannot be determined that the concentrations

are not also from a vapor intrusion pathway. Sub-slab volatile chemical levels should be

used to estimate the contribution of sub-slab VI sources to indoor air levels. Confirmation

sampling (i.e., an additional or additional rounds) may need to be conducted in order to

estimate the contribution from the environmental release.

8.7 Occupational Exposure Limits

The Occupational Safety and Health Administration (OSHA) is the primary regulatory

agency tasked with protecting workers while on the job. OSHA regulations and initiatives

encompass many aspects of worker safety, including, among others, fall risks, workplace

violence, heat illness, and chemical safety. Ohio EPA investigates and has jurisdiction

over releases of hazardous chemicals to environmental media, including releases

affecting receptors at OSHA-regulated sites.

When it has been demonstrated that OSHA has jurisdiction at a site or property, OSHA

will regulate using its own indoor air regulatory thresholds. However, changes in

processes or OSHA’s jurisdiction must be considered for future exposure scenarios.

OSHA’s indoor air regulatory thresholds for workers are called Permissible Exposure

Levels (PELs). OSHA also has indoor air regulatory standards called Short-Term

Exposure Limits (STELs) for 15-minute exposures, and ceiling limits above which no

worker should be exposed for any period of time.

9.0 VAPOR INTRUSION FROM PETROLEUM RELEASES

Petroleum Vapor Intrusion (PVI) is the intrusion of vapors from subsurface petroleum

hydrocarbons (PHC) and non-PHC fuel additives into overlying or nearby buildings or

structures. PVI can occur from PHC-contaminated soil or ground water contaminant

plumes with high concentrations of dissolved PHC contaminants, or if the plume is in

contact with a building foundation, basement, or slab. In contrast to chlorinated solvents

that degrade slowly under anaerobic conditions, PHCs generally biodegrade rapidly

under aerobic conditions. The biodegradation intermediates from PHC are also less toxic

than chlorinated compounds. Some petroleum hydrocarbons may also degrade

anaerobically and may produce methane, particularly if the source is from an ethanol-

blended gasoline (U.S. EPA, 2015a).

Due to the effectiveness and speed of aerobic biodegradation in biologically active soils,

Ohio EPA DERR recommends different lateral and vertical separation distances PVI sites

with relatively small petroleum releases, such as underground storage tank (UST) sites,

than VOC release sites to streamline the VI evaluation. Petroleum contamination at sites

with a potential for larger petroleum releases, such as refineries, petrochemical plants,

terminals, aboveground storage tank farms, bulk plants, pipelines, and large scale fueling

and storage operations at federal facilities, sites where lead scavengers were used or

stored, or sites with releases of non-petroleum chemicals including comingled plumes of

petroleum and chlorinated solvents regardless of the source, should be addressed under

more general vapor intrusion guidance such as other chapters of this guidance or U.S.

EPA. (US EPA, 2015b) and should use the 100 feet lateral separation distance

recommended for non-PHC VOCs.

A variety of petroleum products may be present at a site, such as gasoline, diesel,

kerosene, jet fuels, and mineral oils, with varying potential for volatilization. Generally,

less dense petroleum fractions such as benzene, toluene, ethylbenzene, and xylenes

(also known as BTEX) will volatilize more easily than heavier fractions such as lubricating

oils, waxes, asphalts and pitch and thus have a higher potential for vapor intrusion. Figure

6 shows petroleum fractions from light to heavy. Generally, lighter fractions are more

volatile, and heavier fractions are less volatile. Sample analysis should correspond to the

chemicals expected from the release.

Petroleum products are potentially flammable, and investigators should identify if there is

a potential threat of explosion due to the presence of flammable PHCs, non-PHC fuel

additive vapors, or methane. Methane cannot be detected based on odor, taste, or visible

signs, so methane-detecting devices must be used if the presence of methane is

suspected.

Figure 6. Petroleum Distillation (GlobalSpec.com)

9.1 Petroleum Release Characterization and Phase Partitioning

The PVI site characterization should consider the hydrologic and geologic characteristics

of the site, identify potential receptors, and assess the potential for biodegradation of the

PHCs and non-PHC fuel additives. A primary objective of site characterization is

delineation of the lateral and vertical extent of contamination in the subsurface so that

lateral and vertical separation distances can be accurately determined. It is also important

to determine whether preferential transport pathways are present and, if so, delineate

them to determine if they connect vapor sources directly to potential receptors. (U.S. EPA,

2015a)

The site characterization should address the potential for biodegradation of PHCs in soil.

However, care should be taken if the vadose zone is not well-oxygenated as PHC

degradation may be incomplete, thus posing a greater potential for PVI. Additionally,

ethanol-blended gasoline (blends greater than E-20) may degrade anaerobically and may

produce methane, which may result in methane buildup inside buildings and a risk of

explosion (U.S. EPA, 2015a). See Section 11.2 if site conditions indicate the potential of

an imminent explosive threat.

When petroleum fuels are released to soils from a leaking UST, PHCs partition into

several phases: a light non-aqueous phase liquid (LNAPL), an accumulation of mobile

LNAPL on and in the capillary fringe, an immobile residual phase, a phase dissolved in

ground water, a phase dissolved in soil moisture, a phase adhered onto or absorbed into

soil solids, and a phase of vapors in soil gas. While it is important to keep in mind the

various PHC phases potentially present at the site, the vertical and lateral separation

distance described in this document apply to the LNAPL and dissolved phase of PHCs.

The LNAPL phase floats at the water table. However, if a sufficient amount of LNAPL

accumulates the LNAPL can become mobile and flow downgradient. Conversely, if it is a

small release of LNAPL it can become immobile in the capillary fringe or smear zone as

the elevation of the water table fluctuates due to seasonal changes. This is referred to as

residual LNAPL. Residual LNAPL is not free-flowing and can represent a significant

source of contaminants that may persist and generate PHC vapors, as well as a source

of dissolved-phase contaminants, and thus should not be overlooked in a CSM or when

developing DQOs.

Dissolved-phase sources in ground water consist primarily of BTEX, other aromatic

hydrocarbons, and relatively water-soluble PHCs. Vapors emanating from LNAPL

sources contain these petroleum fractions as well as aliphatic and relatively insoluble

hydrocarbons, such as naphthalene, especially if the source is large or unweathered.

(U.S. EPA, 2015a)

9.2 Lateral Inclusion Zone

The Lateral Inclusion Zone is the area surrounding a contaminant mass through which

petroleum vapors may travel, move into buildings, and potentially pose a threat to human

health and the environment. Buildings within 30 feet laterally of relatively small petroleum

contaminated sources, whether as mobile LNAPL, residual LNAPL, or PHCs dissolved in

ground water, are considered to be in the lateral inclusion zone. Buildings outside this

zone generally may be excluded from further assessment unless site conditions change,

preferential transport pathways are present connecting vapor sources to receptors,

impermeable surface cover is so extensive that there is a concern whether sufficient

oxygen is present to support biodegradation, or soil conditions are inhospitable to

microorganisms (i.e., dry soils with less than 2% soil moisture by dry weight).

9.3 Vertical Separation Distance

The vertical separation distance is the thickness of clean, biologically active soil between

the highest vertical extent of a contaminant source and the lowest point of an overlying

building (basement floor, foundation, or crawlspace surface). For a petroleum vapor

intrusion investigation, clean soil does not necessarily mean that it is contaminant-free,

but rather that the level of any contamination present is low enough that the biological

activity of the soil is not diminished, and the subsurface environment will support sufficient

populations of microorganisms to aerobically biodegrade PHC contamination. The

highest vertical extent of contamination for dissolved sources is the historical high-water

table elevation; for LNAPL sources this is the top of the smear zone or residual LNAPL in

the source area.

LNAPL sources are capable of producing higher vapor concentrations than dissolved

sources. Thus, the necessary vertical separation distance between PHC contamination

and an overlying building foundation, basement, or slab is 6 feet for dissolved vapor

sources and 15 feet for LNAPL sources beneath buildings that are less than 66 feet on

the shortest side. Additional investigation, including sampling, is recommended if the

vertical separation distance is less than this minimum. Where the vertical separation

distance between a dissolved contaminant plume and the lowest point of a building is met

or exceeded, no further investigation for PVI is necessary if there are no precluding factors

present.

9.4 Ground Water Flow and Dissolved Plumes

Contaminants dissolved in ground water can migrate with flowing ground water and

create three-dimensional distributions of contaminants called plumes. In aquifers where

the direction and speed of ground water flow are stable, the plumes are usually long and

narrow. Other plumes appear to spread in both the transverse as well as the longitudinal

direction. This apparent transverse dispersion may be the result of changes in the

direction of ground water flow. What may appear to be transverse dispersion is

longitudinal dispersion occurring in different directions and the direction of flow changes.

Plume movement and dispersion must be considered when applying lateral and vertical

separation distances to a site. Figure 7 shows a typical PVI scenario with LNAPL,

dissolved phase petroleum contamination in ground water, LNAPL smear zone, and

vertical separation distances.

Figure 7. Schematic of PVI Scenario with LNAPL (ITRC-PVI, 2014)

9.5 Compliance with BUSTR

The State Fire Marshal, Bureau of Underground Storage Tank Regulations (BUSTR)

program has regulatory primacy for UST petroleum cleanups. Entities undertaking PHC

cleanup must consult with BUSTR in addition to, or instead of, Ohio EPA.

10.0 MODELING THE VAPOR INTRUSION PATHWAY

Predictive modeling has historically been extensively utilized by Ohio EPA DERR

programs as a tool to predict contaminant concentrations and exposures at a site, often

used to estimate the changes in concentrations and future movement of contaminants in

ground water. Predictive models have also been developed to estimate the indoor air or

soil vapor concentration of a contaminant in soil or ground water by using default and

user-input chemical, soil, physical and building construction parameters, such as the U.S.

EPA’s Johnson and Ettinger Model (J&E). Recently, the U.S. EPA created and supports

the Vapor Intrusion Screening Level (VISL) calculator, which uses exposure estimates,

attenuation factors, volatility factors and inhalation toxicity in equations to develop

screening levels below which vapor intrusion is not expected at a site. Lastly, due to the

different nature of PHC vapor intrusion, the American Petroleum Institute created a model

called BioVapor that estimates the potential for vapor intrusion of petroleum constituents

in soil gas and ground water. While all three of these models are fundamentally different

in nature, each is a predictive tool that can be used as part of a vapor intrusion evaluation

and are discussed further in the subsections below.

Generally, Ohio EPA DERR requires that any use of modeling be confirmed with empirical

data. Ohio EPA DERR RP sites can use VISL to make determinations of incomplete

exposure pathways from subsurface contamination of volatile chemicals to indoor air, but

this is a limited application. Ohio EPA DERR considers the use of models as one line of

evidence when evaluating the vapor intrusion pathway, and generally requires that

empirical data be provided at the point of exposure in order to determine that risk and

hazard goals have been, and will continue to be met, and to eliminate the vapor intrusion

pathway as a potentially complete exposure pathway.

10.1 U.S. EPA Vapor Intrusion Screening Level Calculator

Ohio EPA DERR recommends the use of U.S. EPA’s VISL calculator to preliminarily

evaluate the potential for vapor intrusion at remedial sites. While the VISL calculator may

be used as a screening method to determine whether vapor intrusion is likely to occur at

sites, in most situations, Ohio EPA requires empirical data to be used to eliminate vapor

intrusion as a potentially complete exposure pathway. Please refer to Sections 3.0, 8.0

and 10.0 of this guidance for more information on data collection, data screening and

general modelling.

The VISL calculator applies attenuation factors (AF) to toxicity-based indoor air

concentrations to provide screening levels for soil gas and ground water. VISL can also

be utilized to calculate risk and hazard estimates to receptors from chemical

concentrations in ground water, soil vapor, and indoor air. These default attenuation

factors were developed from measured vapor intrusion data. The default ground water to

indoor air exposure pathway AF used by VISL calculator is 0.001, while the soil gas to

indoor air exposure pathway default AF is 0.03. When the AFs are applied with the

appropriate target risk and hazard levels and exposure scenarios, the resulting VISLs are

levels below which soil gas or ground water concentrations are unlikely to provide the

source strength to drive indoor air concentrations above health-based indoor air

standards. While VISL uses default AFs, site-specific AFs may be developed and used

to meet remediation goals at a site.

The VISL calculator allows the user to alter other select parameters in addition to the

attenuation factors, including the target risk or hazard, exposure scenario, and ground

water temperature. If any default VISL parameters are changed when determining site-

specific VISLs for Ohio EPA DERR sites, the changes must be disclosed to Ohio EPA.

Specific factors may result in unattenuated or enhanced transport of vapors towards

receptors and are likely to render the default assumptions of the VISL calculator, and thus

its effectiveness as a predictive modeling tool, inappropriate. These factors include: 1)

very shallow ground water sources, for example less than 5 feet below foundation level;

and 2) buildings with significant openings to the subsurface, for example, sumps, unlined

crawlspaces, earthen floors, or significant preferential pathways. In addition, certain vapor

sources invalidate the recommended attenuation factors and screening levels used in the

VISL: 1) sources originating in landfills where methane is generated in sufficient quantities

to induce advective transport in the vadose zone; 2) sources originating in commercial or

industrial settings where volatile chemicals can be released within an enclosed space and

the density of the chemical’s vapors may result in significant advective transport of the

vapors downward through cracks and openings in floors and into the vadose zone; and

3) leaking vapors from pressurized gas transmission lines. In all of these scenarios the

use of VISL calculator may not accurately predict movement of vapors from the

subsurface to indoor air and indoor air sampling is recommended.

10.2 Overview of the Use of Fate and Transport Models in Ohio EPA

Fate and transport models can assist in evaluating the intrusion of subsurface volatile

contaminants into enclosed spaces. However, models are not intended to serve as the

exclusive approach for evaluating human health risk from vapor intrusion. When used in

combination with site-specific empirical information, the results of modeling will add to the

multiple lines of evidence for the exposure pathway, and to develop risk management

decisions. As stated above, Ohio EPA DERR considers the use of models as one line of

evidence when evaluating the vapor intrusion pathway, and generally requires that

empirical data be provided at the point of exposure in order to determine that risk and

hazard goals have been, and will continue to be, met, and to eliminate the vapor intrusion

pathway as a potentially complete exposure pathway.

10.3 Overview of U.S. EPA’s Johnson and Ettinger Model

The U.S. EPA’s Johnson & Ettinger (J&E) model spreadsheets may be used as a

predictive tool for evaluating subsurface vapor intrusion into buildings. However, the J&E

model should not be used to estimate indoor air values for a demonstration that applicable

standards or that risk and hazard goals have been met. The most current version should

be used for predictive site-specific use only. As of the date of this guidance, the most

current is Version 6.03.1, dated February 2017, updated September 2017.

The current version of the J&E model does not allow for vapor intrusion estimates to be

made from bulk soil concentrations, which is a change from previous versions of the J&E

model. The current version of J&E may be used to predict vapor intrusion to indoor air

from soil gas and ground water concentrations.

This guidance does not provide recommended J&E model input values and uses. Ohio

EPA recommends appropriately applying the model recommendations provided in the

U.S. EPA Johnson and Ettinger Model support documents and user’s guide.

Again, given the uncertainty and variability in the VI pathway and the constraints to the

J&E model, the model has limited use in the characterization of risk and should only be

used as a tool to estimate or predict indoor air concentrations of hazardous constituents

at sites where empirical data has not yet been gathered. Modeling results must be verified

with empirical data.

10.4 BioVapor

The American Petroleum Institute’s model BioVapor estimates the potential for vapor

intrusion of petroleum constituents in soil gas and ground water. Petroleum constituents

differ from chlorinated VOCs in that they degrade relatively rapidly in soil with the

presence of oxygen. BioVapor is a steady-state 1-D analytical model designed to help the

user understand the potential effect of aerobic biodegradation in the vadose zone on the

vapor intrusion pathway. BioVapor does not directly account for spatial or temporal

variations in parameter values.

BioVapor is an algebraic model that incorporates a steady-state vapor source, diffusion-

dominated soil vapor transport in a homogeneous subsurface soil layer with vapor mixing

in a building. The soil is divided into a shallow aerobic layer including first-order

biodegradation and a deeper anaerobic layer where biodegradation does not occur. The

user has three options for specifying the oxygen supply below the building foundation: 1)

concentration below the building foundation; 2) constant oxygen concentration below the

building foundation; or 3) constant flow of atmospheric air below the building foundation.

In the absence of aerobic biodegradation, the BioVapor model is essentially equivalent to

the J&E Model. All model outputs should be verified with empirical data. BioVapor does

not evaluate other potential exposure routes, migration pathways, or risks from fire or

explosion. For more information on the BioVapor model, see the BioVapor User’s Manual

(GSI Environmental, 2012). For more information on other ways to address the potential

for petroleum vapor intrusion, see Section 9.0 of this guidance.

11.0 EVALUATION OF IMMINENT HAZARD IN AN EXISTING BUILDING

For the purposes of this guidance, imminent hazard is defined as any condition which

poses an immediate risk of harm to public health, safety, or the environment. Imminent

hazards require an expeditious response to mitigate or end the exposure. Typically, prior

to sampling, the potential threat level is unknown. There are situations where available

historical sampling data or current conditions indicate that immediate actions are

warranted.

11.1 Potential Imminent Hazard Conditions

Possible imminent hazards due to vapor intrusion include direct exposure to

concentrations of vapors at risk of explosion or immediate danger to life and health, as

well as exposure to chemical concentrations that may cause deleterious effects from short

term exposures. If evaluation of data or current conditions indicate the possibility of an

imminent hazard from a known or suspected nearby source, prompt action is necessary

to verify or abate threats to human health.

The following conditions may indicate a potential imminent hazard and thus warrant

prompt actions and early or interim measures for occupied structures:

• Known spill in a structure that may affect environmental media (e.g., a release from

a heating oil tank);

• Odors, particularly if described as “chemical,” “solvent,” or “gasoline”;

• Reports of physiological effects (e.g., dizziness, nausea, vomiting, confusion);

• Wet basement or sump in areas with known contaminated ground water;

• Free product at the water table under or immediately adjacent to a structure;

• Exceedance of one-tenth (10%) of a lower explosive limit; or,

• Vapor intrusion-caused indoor air concentrations of a chemical with an

unacceptable human health risk for an acute or short-term exposure scenario.

Professional judgment should be applied to these criteria and the timeframe appropriate

to evaluate whether an imminent hazard is present. Please note that spills not affecting

environmental media may pose an imminent hazard or unacceptable human health risk

and, as a result, may be under the jurisdiction of regulatory agencies other than Ohio EPA

(i.e., OSHA or ODH).

Where vapor intrusion is of concern and indoor sources of volatile chemicals are present

(for either occupational use or any other identifiable indoor source), sub-slab vapor or soil

gas data may be utilized to evaluate the relative contribution to the indoor concentrations

from environmental media. The presence of identifiable indoor air sources may alter the

need for or type of early or interim response action taken.

11.2 Explosive Hazard

Commonly encountered chemicals that can exhibit explosive hazard are generally

petroleum hydrocarbons (PHCs) and the landfill gas methane. Prompt action is required

when the concentration of a combustible chemical exceeds 10% of its lower explosive

limit (LEL). If data collected from inside buildings, below buildings, or utility conduits

indicate an exceedance of 10% of the LEL, immediate action may be needed whether the

building is inhabited or not. If concentrations in indoor air indicate the potential for

explosion or imminent danger to life or health, building occupants should be evacuated

and building owners and the fire department should be notified immediately. Also notify,

Ohio EPA DERR immediately via Ohio EPA’s Spill Hotline at 1-800-282-9378. For

BUSTR-regulated releases, notify BUSTR immediately via the BUSTR hotline at 1-800-

589-2728.

Flowchart Step 6: Evaluate the potential risk and hazard from the vapor intrusion pathway

12.0 RISK CHARACTERIZATION

Risk characterization for the vapor intrusion pathway compares measured indoor air

concentrations to chemical-specific target cancer and noncancer concentrations

considered protective for the anticipated land use exposure. The primary scenarios

evaluated are residential and worker/commercial exposures. Additionally, in the VAP, a

characterization of the vapor intrusion risk may be developed by a proportional estimation

of a VISL from media other than indoor air. For example, if carbon tetrachloride is the only

COC that has been measured in sub-slab vapor, and the concentration is half of the VISL

based on a hazard quotient of 1, the VAP volunteer can assume a HQ contribution to the

site-wide non-carcinogenic risk characterization of 0.5 from the vapor intrusion to indoor

air pathway. Please refer to Section 8.1 for further information on vapor intrusion

screening levels. Risk characterization serves to bridge risk assessment and risk

management and therefore assist in the decision-making process. The appropriate media

target concentrations and risk and hazard goals must be utilized. Please refer to Section

8.0 concerning data evaluation.

The investigator should be aware of imminent hazards involving explosive gasses,

unacceptable human health risk from an acute or short-term exposure scenario, and

gasses that may collect and create a deadly environment. Please refer to both Sections

11.0 and 13.0, for more information on evaluation of imminent hazards in an existing

building and remedies, respectively.

12.1 Determining Applicable Risk Goals and the Need for Further Evaluation

For Ohio EPA DERR sites, the excess lifetime cancer risk (ELCR) goal is 1E-5 and the

noncancer hazard quotient or index is 1, accounting for exposure to multiple

contaminants, as appropriate. For all Ohio EPA DERR sites, if the complete pathways,

including direct contact, ingestion and vapor intrusion, from soil and ground water

releases are well-characterized, and meet a cumulative ELCR of 1E-5 and a hazard index

of 1, then no further evaluation of the vapor intrusion pathway may be warranted. If media

other than indoor air are not well characterized or exceed an ELCR of 1E-5 or a hazard

index of 1 on a multiple chemical and multiple pathway (if applicable) basis, then further

sampling or preemptive remediation may be necessary.

In the VAP, all site-related COCs must undergo a multiple chemical adjustment and the

resulting ELCR and hazard values are carried through as a contribution to site-wide risk

and must meet Ohio EPA risk and hazard goals of an ELCR of 1E-5 and a Hazard Index

of 1. Thus, risk and hazard contributions from vapor-forming chemical detections in indoor

air due to vapor intrusion should be calculated in a multiple chemical adjustment and

pathway summation for a complete exposure pathway. If indoor air data was not

collected, the risk and hazard contributions from the vapor-forming chemicals detected in

an alternative media sampled to evaluate vapor intrusion (i.e., either soil gas, sub-slab

vapor or ground water) should be included in a multiple chemical adjustment and pathway

summation. This is because the VAP requires the incremental risk and hazard from all

COCs be aggregated within each complete exposure pathway and then summed across

all complete exposure pathways.

12.2 Use of Maximum Contaminant Levels (MCLs)

Screening and cleanup levels for other exposure pathways are not necessarily protective

of the vapor intrusion pathway. Since the MCLs and VAP risk-based unrestricted potable

use standards (UPUS) address the potable ground water pathway, additional sampling

may be necessary even if ground water concentrations meet MCLs or VAP risk-based

UPUS values.

12.3 Use of BUSTR Petroleum Standards

At VAP sites, a volunteer may use BUSTR action levels, including action levels for soil

and ground water to indoor air contained in look-up tables found in OAC 1301:7-9-

13(J)(3), as the generic numerical standards for petroleum at residential, commercial, and

industrial properties in the VAP. For more information on applying BUSTR action levels

as VAP applicable generic standards, please see VAP Technical Guidance Compendium

Applying Generic Petroleum Standards under the VAP.

At RP sites the potential for using BUSTR action levels for addressing the VI pathway for

petroleum and petroleum constituents is something the responsible party may

contemplate, however coordination with Ohio EPA is recommended.

Flowchart Step 7: If data evaluation indicates risk or hazard goals are or may be

exceeded, then additional data may be collected, or a remedy may be implemented

If data from environmental media other than indoor air exceed risk or hazard goals, then

additional data may need to be collected and/or a remedy may need to be implemented.

If indoor air exceeds risk or hazard goals, then mitigation must be implemented and

maintained to reduce the concentrations of COCs in indoor air to acceptable levels until

the final remedy has rendered the VI pathway incomplete. If indoor air concentrations

meet risk or hazard goals for commercial/industrial land use but not residential land use,

then a land use restriction may be necessary to ensure the site remains protective of

future receptors. Communication with Ohio EPA DERR is recommended when a site does

not contain buildings, but a potential future VI problem is identified, and for sites with

current vapor intrusion problems.

Flowchart Step 8: Remediation, mitigating indoor air exposure and/or conducting long-

term monitoring

13.0 REMEDY

This chapter provides an overview of considerations when selecting and implementing a

remedy to mitigate or eliminate risk from the VI pathway.

Remedies may be short-term interim actions meant to mitigate acute exposures to

receptors over the near term, and long-term actions meant to provide ongoing mitigation

by rendering the VI pathway incomplete until a remedy addressing the source of

contamination is completed. These remedies can be to prevent a potentially complete VI

pathway. A combination of the remedies discussed in the following sub-sections can be

implemented to mitigate or eliminate risks from VI. Please note, additional remedial

actions may be required on a site-specific basis. Confirmatory sampling is often required

to determine if further remedial actions are necessary to protect human health.

13.1 Remedy Selection and Implementation Considerations

Remedy selection should consider the type of risk present at the site, site-specific building

conditions, and the proximity and nature of current and future receptors. The following

site conditions should be considered:

• Sensitivity of receptor;

• Type of contaminant – total petroleum hydrocarbons (TPH) vs. chlorinated

solvents;

• Type of exposure risk (acute vs. chronic);

• Cumulative risk from multiple chemical exposures;

• Time frame or length of exposure (current or future exposure);

• Temporary, interim or permanent mitigation measures;

• Source strength;

• Media contaminated (soil vs. groundwater);

• Foundation type;

• Building age;

• Preferential pathways;

• Agency jurisdiction (U.S. EPA, Ohio EPA, OSHA, health department); and,

• Potential future receptors.

When implementing a remedy several items should be considered such as:

• Immediate response requirements;

• Interim response;

• Short-term mitigation until a more permanent fix is completed;

• Long-term response;

• On-going sampling;

• System installation;

• System monitoring; and,

• Confirmatory sampling after disturbance.

Some examples of available mitigation technologies are provided in Table 3, along with

typical applications and challenges of each (ITRC, 2007).

Table 3. Comparison of Mitigation Technologies

Technology

Typical Applications

Challenges

Passive barrier

New construction.

Crawl spaces (existing homes).

Often combined with passive or active

venting, sealing openings in the slab, drains,

etc.

Preventing tears, holes.

May not suffice as a stand-alone technology.

Ensuring caulking seals cracks in floors and

preferential pathways.

On-going monitoring and maintenance.

Passive venting

New construction.

Low soil gas flux sites.

Should be convertible to active system if

necessary.

Relies on advective flow of air due to wind and

heat stack effects.

Air flows and suctions typically far less than

achieved by fans (active venting).

Passive aerated

floor

New construction or extensive remodeling.

May be useful for large commercial

structures.

Not yet widely used.

May not be suited for all soil types.

Active sub-slab

depressurization

(ADS)

New and existing structures.

Sumps, drain tiles, and block wall foundations

may also be depressurized if present.

Low permeability and wet soils may limit

performance.

Incurs operating cost.

Requires monitoring and fan upkeep.

Passive sub-

membrane

Existing structures.

Crawl spaces.

Sealing to foundation wall, pipe penetrations.

Membranes may be damaged by occupants or

trades people accessing crawl space.

Active sub-slab

pressurization

Same as ADS.

Most applicable to highly permeable soils.

Higher energy costs and less effective than ADS.

Potential for short-circuiting through cracks.

Active building

pressurization

Large commercial structures, new or existing.

Specialized cases only.

Requires regular air balancing and maintenance.

May not maintain positive pressure when building

is unoccupied.

Incurs cost to operate.

Active indoor air

treatment

Indoor air spaces.

Special cases where other remedies cannot

be applied.

May generate waste disposal stream.

May not effectively capture all air contaminants.

May be subject to tampering.

Sealing the

building

envelope

Cracks and holes in existing building.

Access to perforations.

Lack of permanence.

Active heat

recovery

ventilator

Useful in crawl spaces or basements that

cannot be sealed or depressurized.

Incurs higher energy loss.

Higher costs to operate.

13.2 Remediation of Environmental Media

An environmental media source of VI can be addressed through application of a soil or

ground water remedy. Remediation of soil and ground water contamination may include

source removal, technologies to reduce contaminant concentrations in soil and soil gas,

such as soil vapor extraction (SVE), or technologies to reduce concentrations in ground

water such as in-situ bioremediation (chemical oxidation or reductive de-chlorination),

thermal desorption, or air-sparging. In general, source removal and SVE remedies are

likely to be the most successful to reduce or eliminate soil gas migration and this may

prevent the need for institutional or engineering control remedies.

Environmental media should be monitored during the remedial process to assess

breakdown products that may form as a result of natural attenuation or chemical treatment

processes and may pose risks to receptors, and to determine when remediation efforts

can be terminated.

13.3 Institutional Controls

Institutional controls are activity and use limitations that are recorded in an environmental

covenant within the property deed that restricts how a site can be used or what activities

can occur at the site. Examples of institutional controls include:

• Restriction of a property to commercial or industrial uses only;

• Prohibition against constructing habitable structures in areas with VI risk;

• Prohibition of building occupancy unless indoor air concentrations are below

screening levels; and,

• Building-specific conditions, such as prohibitions of basements.

Generally, two rounds of indoor air sampling collected at least 30 days apart are needed

prior to occupancy of a building located within a vapor intrusion activity and use limitation

area.

13.4 Engineering Controls

Engineering controls, also known as building controls for vapor intrusion, can be

considered interim remedial measures as they usually do not address the reduction of the

source contamination. They can be implemented in both new and existing buildings.

Engineering controls can be separated into two groups: active or passive. An active

engineering control usually involves a mechanical system, such as a sub-slab

depressurization system. Engineering controls that do not involve mechanical systems,

such as a floor slab, are known as passive controls. Future conditions must be considered

when choosing an appropriate engineering control. Maintenance, repair, failure

monitoring, and termination criteria should be considered when selecting an engineering

control. These considerations are contained within an operating and maintenance (O&M)

plan and an O&M agreement between Ohio EPA and the property owner. This agreement

identifies and ensures that the responsibility for the engineering control and liability for

the contamination is maintained while vapor intrusion remedial goals are exceeded in the

subsurface.

13.5 Active Sub-Slab Depressurization Systems

Active Sub-Slab Depressurization Systems (ADS) are defined as systems that rely on

motor-driven fans to maintain a negative pressure below the building floor, evacuating

contaminated vapors before they enter the building. ADS can have a variety of

configurations, both designed as standalone systems or as components in a mitigation

engineering system.

There are generally two types of active sub-slab depressurization systems, those for

newly constructed buildings and those installed in existing buildings. Systems for newly

constructed buildings usually consist of a sub-slab layer of granular fill coupled with a

network of slotted pipes that vent to the roof with the aid of a fan. The granular layer is

overlain by an impermeable barrier layer. The motorized fans are used to draw a vacuum

on the sub-slab granular layer, assuring the necessary vacuum differential. The number,

size and spacing of the slotted pipes are building-specific with the performance standard

being an adequate pressure differential generally across the floor of the entire building.

The exhaust points of the discharge pipes should be positioned to avoid ingress to the

surrounding buildings through windows, vents, or HVAC system intakes. Generally, the

granular bed and barrier layers should cover the entire footprint of the building unless the

owner can demonstrate that less coverage is needed.

For existing buildings, the sub-slab system generally consists of pits under the floor, filled

with granular material and connected to the extraction system. The major obstacle to

performance of these systems is low permeability soil, since installation of a granular layer

under the entirety of an existing building is usually impossible. Again, the number and

placement of the suction points is site-specific and performance driven. A lower

permeability soil may require more extraction points. Another concern with preexisting

buildings is the presence of subsurface barriers, such as building footers, that might

impede airflow. The placement of suction points must consider such barriers.

ADS are most effective if the building is isolated from the environmental media. This

condition increases the efficacy of the sub-slab depressurization and removal of vapors

beneath the slab. Therefore, Ohio EPA recommends that sealing of foundation crack and

other conduits into the building be included with the construction of an ADS. The building

floor should be examined for competency and building construction diagrams should be

evaluated for utility and plumbing penetration points. These seals should be identified and

maintained throughout the active life of the ADS. Seals that are a component of an ADS

should be labeled to identify that these seals should be maintained in any operation and

maintenance plan.

In regard to sealing, the following should be considered when reviewing work and design

plans for ADS systems:

• Caulks and sealants should be reviewed thoroughly prior to use for volatile content.

Sealants that are selected should be durable and designed for minimal maintenance

over the expected lifespan of the ADS (ASTM C1193-16).

• Sumps, other pit openings in the slab, and utility corridors that need to maintain their

accessibility should use sealants such as silicone caulks that may easily be re-applied.

Sump covers should remain accessible by utilizing gasket or non-permanent sealants.

Piping emanating from sumps should also be sealed to prevent vapor migration.

• Cracks less than 1/16-inch in width may be sealed using selected sealants or caulks.

• Cracks greater that 1/16-inch in width may require special backing material or

expandable foam sealants.

• Expansion joints.

• Wall/floor junctions.

• Utility lines, drains, and other plumbing features that penetrate the building slab offer

a direct conduit to soil gas. To seal these penetrations, practitioners may have to wrap

these features with membrane material and seal these to competent flooring.

Specialty spray on products, such as Liquid Boot™, may have to be applied if the

penetration points are too difficult to seal via normal means.

• Drains may provide a vapor intrusion pathway that can be prevented using one-way

flow valves that retard or prevent vapor entering buildings. Drains used to draw water

from basement areas to sumps need to be covered, sealed and tied into the ADS to

draw vapors to the outside air.

In some cases, a competent floor is not present or may only cover a portion of the building

footprint. An example of this condition is a home that has an open crawl space. Conditions

such as these require special consideration as an ADS may not be capable of providing

adequate mitigation unless the building floor and walls are sufficiently sealed.

Dug basements with open areas or crawl spaces will require covering to prevent soil gas

migration and to provide a seal for the ADS to depressurize the lower area of the building.

A soil gas barrier can be installed over open soil in a crawl space or dug basement to

prevent vapor migration and provide a plenum that will be evacuated using the ASD. The

membrane should be sealed to competent walls. Seams between membrane sheets

should be overlapped at least 12 inches and sealed with sealant or caulk. Membrane

material should be designed to prevent vapor migration. Common moisture barriers used

in construction may not be adequate as a vapor intrusion membrane. This is especially

true if the space may be used to store heavy objects. Ohio EPA recommends that

membranes be at least 10-mil thick and may range up to 60-mil depending on the

occupancy requirements for the area being covered. Vapor barriers should have a

permeance of at least 0.1 perms as defined by ASTM E96/96M. Pipe penetrations or

drains penetrating the membrane should be sealed as described previously in this

section.

If the floor is generally soil and without rubble, concrete can be poured to provide

adequate cover. This option may be desirable if the floor space is used to store heavy

materials or heavy use would puncture membrane materials.

Ohio EPA has encountered rubble-filled or dug basements that are inaccessible that

prevent the use of membrane or cementitious coverings. In these cases, the open space

itself may need to be ventilated and have fresh air brought in from the outside and stale

air vented (see Section 13.6 for more information).

Water tables that seasonally intersect the building slab, wet basements, or contaminated

pore water infiltrating directly into buildings requires an additional engineering control

before the installation of an ADS. These conditions can be mitigated by foundation

drainage systems and treating surfaces to prevent water infiltration. Consideration of

these conditions should be made before an ADS is installed.

Back drafting from indoor heating sources may be problematic in some basements where

furnaces or water heating equipment is used. The ADS should be checked by local HVAC

personnel and local fire marshals before the initial system demonstration. There may be

some situations where an ADS cannot be installed due to homeowner requirements. Any

site where back drafting could be a problem should have CO

monitors installed as part

of the ADS.

13.6 Heating, Ventilation, Filtration Units and Air Conditioning (HVAC) Measures

Ventilation system modifications can be made in a variety of ways, but the general

approach is to increase the intake of make-up (fresh ambient) air. In commercial

buildings, HVAC systems can be modified to increase the amount of make-up air. These

modifications should be made by experienced HVAC professionals. Systems in

residential properties may be limited in the degree of modification for make-up air. In

these cases, the addition of a Heat Recovery Ventilation (HRV) unit may be necessary to

increase the intake of fresh air. HRV systems can be installed independently of existing

HVAC systems and may be beneficial to residential properties that need to vent

crawlspaces or basements that can’t be incorporated into an ADS. HRVs are designed

with two fans. One fan brings in fresh air from outside the building, the second fan vents

stale air from inside the structure. A heat exchanger equalizes the temperature between

these two independent air streams which are not allowed to physically mix. The net result

in an increased air exchange rate that can significantly reduce concentrations of

contaminants. HRVs can be costly to install and must be powered which can increase the

average cost for heating a home or small business.

Filtering of air can be an option for vapor mitigation. These systems are designed to pass

contaminated air through filtering media, usually granular activated carbon, thereby

removing VOCs from the air. Industrial-sized units can be designed, but generally these

filters are used on a temporary basis before permanent systems can be installed. Filter

use requires regular monitoring to ensure breakthrough of contaminants from the filter

has not occurred. Costs for units vary by size, electrical costs, costs for the filter media

and monitoring.

HVAC systems can sometimes be modified to create a positive pressure within a building

or room to resist vapor ingress from the sub-slab, or to maintain sufficient air flow through

the building to dilute indoor air concentrations to acceptable levels.

The ultimate standard of performance must be the measured indoor air concentrations

rather than analyses based on flow calculations. Indoor air samples should be collected

several times during the year to assess the effects of heating and air conditioning on the

system’s performance. Caution should be exercised choosing these types of methods as

the high air flow rates needed to achieve remedial goals may greatly increase heating

and cooling costs and have the potential to decrease occupant comfort.

13.7 Passive Engineering Controls

Passive Depressurization Systems (PDS) are similar to active systems except the

extraction fans are not motorized. Rather, PDS use wind-driven turbines or venturi

systems to maintain a vacuum on the extraction pipes. The major issue for PDS is

maintenance of an adequate sub-slab vacuum. Passive systems are best used in new

construction with highly permeable granular layers. PDS are not as effective for existing

structures with low permeability soils. The performance standard for passive systems is

consistent maintenance of adequate pressure differentials under the building.

Barrier systems are typically installed during new building construction and consist of an

impermeable barrier between the granular collection bed and the floor of the building. The

barrier can either be laid out in overlapping sheets or sprayed in-place. Some sheet

systems consist of multiple layer laminates to achieve both strength and vapor resistance.

A critical requirement for any vapor barrier is resistance to the chemical contaminants in

the underlying soil. Installation should strictly follow the manufacturer’s directions with

particular attention to adequate joining and sealing of sheet materials and adequate

thickness of sprayed materials. Any penetrations through the barrier, such as plumbing

or utility conduits, must be properly sealed. Typically, the finished system is subject to

smoke testing to locate any breaches in the barrier. Long-term operation and

maintenance plans must require proper sealing of any future breaches through the barrier

layer.

Barrier systems can also include building slabs. Proper sealing of cracks in floors or

around the bases of walls to break ingress routes should be conducted as necessary for

preferential pathways to improve the effectiveness of the passive slab engineering

control. This approach is more applicable for older existing buildings. Such repairs will

require long-term monitoring and maintenance to assure their reliability (Section 14.3),

which may need to be recorded in an operation and maintenance plan. Low permeability

flooring materials have sometimes been installed in existing buildings to reduce vapor

ingress. Such coatings should be durable enough to withstand expected industrial

activities including chemical spills and would also require careful installation and sealing.

13.8 Monitoring Requirements for Engineering Controls

For ADS, Ohio EPA recommends that the depressurization field be mapped to

demonstrate that depressurization is occurring across the building footprint for residential

structures and commercial buildings or is of sufficient aerial extent under a large building

to effectively remove sub-slab vapors. Any sub-slab depressurization systems should be

equipped with sampling ports in the floor to allow measurement of the pressure differential

between the building and the sub-slab space. Differential pressure gauges should be

capable of reading to 1/1000-inch water column or 0.25 pascals with + 25% accuracy.

There should be adequate sample ports to cover the entire floor space of the building. If

it is proposed that only a small portion of the structure needs to be covered by the sub-

slab system, then the owner/operator will have the burden of proving that only limited

coverage is needed. Based on a review of the available guidance and state standards, a

presumptive minimum pressure differential across the slab should be 5 pascals or 0.02

inches of water. That standard should be applied if there is no granular backfill under the

slab or if the soil composition under the slab is unknown. If the slab has been underlain

with a permeable, granular backfill then a lower pressure differential could be considered

based on a demonstration that the flow through the backfill is sufficient to capture vapors

emanating from the underlying soil.

Depressurization field monitoring should be followed with indoor air measurements to

complete the demonstration that the remedy is effective. A sufficient number of indoor air

samples should be taken to demonstrate that indoor air quality meets the standards for a

residential or commercial/industrial setting. The number of indoor air samples will be

dependent on the building size or footprint, the presence of a basement or crawlspace or

occupancy conditions. The typical approach is to sample at the same locations as used

to determine that the vapor intrusion pathway was complete. Ohio EPA DERR

recommends that the number of samples and locations be reviewed and discussed with

agency personnel prior to implementation.

The collection lines for a sub-slab system should be equipped with sampling ports to

analyze the sub-slab vapors. The initial performance evaluation of a sub-slab system

should include indoor air sampling. If the performance evaluation is not being met,

sampling must be repeated until corrective actions have met remedial goals.

13.9 Post-Mitigation and Seasonal Monitoring

Once indoor air sampling shows acceptable COC concentrations and, if applicable,

vacuum ports show adequate depressurization, then the remedy monitoring program may

be reduced to periodic pressure differential measurements at the vacuum sampling ports

and/or indoor air samples to demonstrate system effectiveness through seasonal

variations in temperature, pressure, humidity and building occupancy conditions. Prior to

sampling frequency reduction, vacuum differentials should be measured several times a

year to account for variations caused by seasonal heating and air conditioning.

The effect of seasonal variations should be considered in both the heating and cooling

seasons. This evaluation is especially important if modifications to the HVAC system were

made as a mitigation measure. In addition, in cases where seasonal high-water tables

are present, sub-slab differential pressure measurement should be made to determine if

the sub-slab conditions are present to maintain the depressurization requirements.

The results of these seasonal post-mitigation tests should be carefully evaluated to

determine the degree of variability in results. If the system is functioning adequately to

mitigate vapor intrusion issues, it is possible that only periodic checks will be needed in

the future. If HVAC modifications are not protective in all seasons, additional engineering

measures will need to be installed. Ohio EPA should be consulted if results show break-

through of vapors into indoor air. In these cases, additional indoor air sampling on a

frequent basis may be needed in the post-mitigation period.

13.10 Termination of Engineering Controls

Termination of mitigation systems should only be considered if the contamination source

has been remediated to the point where vapor intrusion is not an on-going concern. Any

request to terminate monitoring should contain a demonstration that sub-slab vapor

concentrations are below VISLs during several sampling events.

Any site with methane should include combustible gas monitors. The combustible gas

monitors should have alarms if safe levels are exceeded.

The precise details of sampling and maintenance of the system should be specified in an

O&M plan whose requirements are included in an environmental covenant.

13.11 Owner Documentation/Notification of Engineering Controls

The building owner should be provided with information on the mitigation system, which

should be passed on to future owners during property transfers. This information should

include, at a minimum:

• The pre-mitigation concentrations of constituents of concern;

• The post-mitigation concentrations of constituent of concern; and,

• The regulatory standards used for each constituent.

The mitigation system installation should be described. This should include:

• System diagram showing the individual components of the system (e.g., slab,

SSDS, vapor barrier);

• As built diagrams, if available; and,

• The operational requirements, such as inches of water vacuum, slab competency,

fan or filter life.

The schedule for replacing system components, such as filters, should be described,

including:

• The schedule for monitoring the system, such as review of manometer readings;

and,

• Any warranty information should be included with the system documentation

package.

The owner, either through O&M agreements or self-initiated investigation, should

describe and document any system disruption and subsequent corrective actions taken

and provide the documentation to Ohio EPA DERR, if required. Information on the

mitigation system (e.g., environmental covenants, remedial design/remedial action

judicial consent decrees, O&M plans and agreements) should be disclosed to future

property owners as required by the RP or VAP (see Section 14.4 for more information).

14.0 LONG-TERM MANAGEMENT AND EXIT STRATEGY AT VAPOR INTRUSION

SITES

Remediation of a vapor intrusion source can take a long time, often months or years.

Therefore, when vapor intrusion has been determined to be a significant risk pathway at

sites, mitigation measures such as ADS systems or institutional controls are needed to

prevent exposure to current occupants and to make sure that future occupants are

protected. Many sites have the long-term goal or requirement to eliminate the source of

the vapor intrusion and termination of the mitigation systems. Therefore, the need to

address long-term management and pathway mitigation should be understood, discussed

with Ohio EPA, and plans formulated to make sure that occupants remain protected.

14.1 Long-Term Management

Long-term management at vapor intrusion sites may consist of the one or more of the

following:

• Ground water or soil gas monitoring;

• Sub-slab vapor or indoor air monitoring;

• Contingency plans if monitoring shows exceedance of indoor air standards;

• Land use restrictions recorded in an environmental covenant;

• Inspections or audits of environmental setting and slab competency if used as an

engineering control;

• Periodic review of the protectiveness and/or efficiency of the remedy or mitigation

system;

• Inspection and corrective action of mitigation systems;

• Notification plan to inform new occupants/potential purchasers of need to maintain

mitigation systems; or,

• Development of an exit strategy for turning off active mitigation.

Ohio EPA DERR does not have a single approach for long-term management because

there are many site-specific variables and unique requirements for each administrative

program, Ohio EPA DERR will work with responsible parties through orders, permits and

the VAP to develop appropriate controls and monitoring strategies and to develop

administrative requirements. Several of the above referenced items will be discussed in

the following sections.

14.2 Ground Water, Soil Gas, Sub-Slab Vapor and Differential Pressure

Monitoring/Sampling

Sites that are undergoing an environmental response for vapor intrusion may require

long-term ground water or soil gas monitoring to verify that new or un-mitigated buildings

within the area of influence of contamination are protected and that mitigation or remedial

systems are functioning properly. In these cases, the type of monitoring (e.g., soil gas or

ground water), frequency of monitoring, applicable screening levels and appropriate

secondary actions if data is above screening levels will need to be recorded in an O&M

Plan and O&M Agreement. Demonstrations of ongoing remediation may also include

statistical analysis for trend monitoring which can help in determining if the contaminated

area is increasing or decreasing.

Where appropriate, sub-slab monitoring ports may be installed and used for routine

monitoring of vapor concentrations and differential pressure. For example, where the slab

of the building has been designated as an engineering control, sub-slab samples can

establish the need for continued maintenance of the slab or indicate when indoor air

sampling should be conducted to determine if risk and hazard goals continue to be met.

Differential pressure monitoring may be considered when facilities have increased the

intake of air to create positive pressure conditions. The monitoring ports can also be used

to monitor differential pressure between the sub-slab and indoors with the use of a

manometer to help determine whether a differential pressure remedy is being maintained.

Once the efficacy of the engineering system is verified by a qualified professional, system

maintenance should be recorded in an O&M plan that details the system’s components,

operation and maintenance schedule and system performance standards. Sub-slab

vapor and/or periodic indoor air monitoring should be considered to demonstrate

continued system efficacy. The plan should also include the corrective measures to be

taken if the system unexpectedly fails and the interim measures to be used to protect

human health while the system is not functional.

14.3 Passive Mitigation System Efficacy Verification

If the mitigation system involves vapor barriers, seals or passive venting, the building

conditions must be carefully checked periodically to determine that these passive

components remain in place and are effective. Building operations change through time

and altering structural components can provide less of a barrier to vapor migration. In

addition, sealants also degrade through time. On-going review of these components must

be made, and it is highly recommended that periodic indoor air monitoring be considered

while volatile chemicals remain above screening levels in the sub-surface.

Data generated during the monitoring period may also provide evidence of favorable

conditions for termination of monitoring and any associated mitigation systems once

sources have been remediated or risk and hazard goals have been met.

14.4 Environmental Covenants and Deed Restrictions

Environmental covenants (EC) and deed restrictions compliment engineering and

institutional controls for addressing vapor intrusion exposure. Ohio’s Environmental

Covenant Law is found in Ohio Revised Code (ORC) 5301.80 - 5301.92. The law states

that an owner of a real property may enter an EC with the State of Ohio if an environmental

response project has occurred on that property. In many cases, vapor intrusion

investigations can be considered an environmental response project. The EC may contain

restrictions for land use or occupancy status, such as restricting a property to

commercial/industrial land use or prohibiting building occupancy until certain conditions

are met. Environmental covenants require the property owner to report compliance with

the restrictions to Ohio EPA once a year. Ohio EPA also reviews sites with ECs at least

every three years to verify compliance. ECs provide information to future occupants that

vapor intrusion is a concern at the site. Deed restrictions are not reviewed or enforced by

Ohio EPA; therefore, even if a site has a deed restriction Ohio EPA requires an EC.

Ohio EPA legal and technical staff can provide more information on how ECs can be

utilized to address vapor intrusion exposure.

14.5 Exit Strategy

The time period for remedial efforts can vary and actions taken to mitigate exposure from

vapor intrusion may continue for some time. Nevertheless, an exit strategy to terminate

active mitigation should be contemplated by site managers. The Ohio EPA expects that

RP sites continue to work on decontamination until sources for vapor intrusion are abated.

RP sites can build exit strategies into orders, records of decision or permits so that

responsible parties can approach the agency to terminate vapor intrusion mitigation when

the source(s) has been reduced to appropriate levels. VAP sites need to plan for how to

determine when remedial activities can be terminated as well; however, the remedial

goals for VAP sites may not include source removal. In these cases, the on-going

mitigation of the vapor intrusion pathway is tied to an operation and maintenance plan.

Specific requirements for termination outlined in the O&M Plan are then followed and

Ohio EPA is notified and provided a demonstration when applicable standards are met

and will continue to be met at the time termination is requested.

The exit strategy should clearly identify what criteria will be used to determine that the

site no longer poses an unacceptable vapor intrusion risk. The exit strategy should be

developed early in a vapor intrusion project so as to provide defined criteria for when risks

at a site have been adequately mitigated or controlled. Factors such as mitigation or

remediation techniques, final cleanup goals, land use, and future building construction,

should be considered when developing the exit strategy. The exit strategy should be

recorded in a decision document with specific, reasonable and achievable outcomes

defined.

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American Society for Testing and Materials (ASTM). 2016a. C1193016: Standard Guide for Use

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Waste  and  Emergency  Response.  Currently  available  online:  https://clu-
in.org/download/contaminantfocus/tce/TCE-compilation-final-2014.pdf 
 
U.S.  Environmental  Protection  Agency  (EPA).  June  2015a.  Technical  Guide  for  Addressing 
Petroleum Vapor Intrusion at Leaking Underground Storage Tank Sites [EPA 510-R-15-
001]. Office of Solid Waste and Emergency Response, Office of Underground Storage 
Tanks.  Currently  available  online:  https://www.epa.gov/sites/production/files/2015-
06/documents/pvi-guide-final-6-10-15.pdf 
 
U.S.  Environmental  Protection  Agency  (EPA).  June  2015b.  OSWER  Technical  Guide  for 
Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to 
Indoor  Air  [OSWER  Publication  9200.2-154].  Office  of  Solid  Waste  and  Emergency 
Response,  Office  of  Underground  Storage  Tanks.  Currently  available  online: 
https://www.epa.gov/sites/production/files/2015-09/documents/oswer-vapor-intrusion-
technical-guide-final.pdf 
Vitale, R. J., R. Forman, and L. Dupes. 1999. Comparison of VOC Results Between Methods 
5030  and  5035  on  a  Large  Multi-State  Hydrocarbon  Investigation.  Environmental 
Testing and Analysis, January 1999, p. 18 – 39. 
 
Wisconsin Department of  Health and Family Services  (DHFS).  February  2003.  Chemical 
Vapor Intrusion and Residential Indoor Air Guidance for Environmental Consultants 
and  Contractors.  Division  of  Public  Health.  Currently  available  online: 
https://www.dhs.wisconsin.gov/publications/p4/p45037.pdf 
 
 
 

APPENDIX A. Vapor Intrusion Conceptual Site Model Checklist

Utilities and Process Piping

Identify on a site plan all underground utilities near the soil or ground water

impacts; pay particular attention to utilities that connect impacted areas to occupied

buildings.

Identify on a site plan all underground process piping near the soil or ground water

impacts.

Buildings

Identify on a site plan all existing and future buildings under investigation.

Identify the occupancy and use of each building (e.g., residential, commercial)

Describe building construction materials (e.g., wood frame, block,), openings (e.g.,

windows, doors), and height (e.g., one-story, two-story, multiple-story); identify if there is

an elevator shaft in the building.

Describe building foundation construction including:

Type (e.g., basement, crawl space, slab on grade)

Floor construction (e.g., concrete, dirt)

Depth below grade.

Describe the building HVAC system including:

Furnace/air conditioning type (e.g., forced air, radiant)

Furnace/air conditioning location (e.g., basement, crawl space, utility closet, attic, roof)

Source of return air (e.g., inside air, outside air, combination)

System design considerations relating to indoor air pressure (e.g., positive pressure is

often the case for commercial buildings).

Identify sub-slab ventilation systems or moisture barriers present on existing

buildings.

Source Area

Identify the COC’s related to the vapor intrusion pathway.

Describe the distribution and composition of any NAPL at the site.

Identify on a site plan all source areas for the COC’s related to the vapor intrusion

pathway.

Identify on a site plan soil and ground water results for the COC’s, between the

source area and the buildings under investigation.

Identify on a geologic cross section soil and ground water results including depth.

Describe the potential migration characteristics (e.g., stable, increasing,

decreasing) for the distribution of COC’s.

Geology/Hydrogeology

Review all boring logs and soil sampling data to understand the locations of:

Sources: NAPL, soil, ground water, suspected vapor leaks.

Soil types:

Finer-grained soil layers

Higher-permeability layers that may facilitate vapor migration.

Identify on a geologic cross section distinct strata (soil type and moisture content,

e.g., “moist,” “wet,” “dry”) and the depth intervals between the vapor source and ground

surface, and include the depth to ground water.

Describe ground water characteristics (e.g., seasonal fluctuation, hydraulic

gradient).

Site Characteristics

Estimate the distance from the ground water concentration contour interval for

each COC to buildings under investigation.

Estimate the distance from vadose zone source area to buildings under

investigation.

Describe the surface cover between the vapor source and buildings under

investigation.

APPENDIX B. Special Considerations for Evaluating Residential Properties

Ohio EPA generally recommends evaluating the vapor intrusion pathway using the

prescribed stepwise approach listed in Figure 1. Sub-slab vapor and indoor air samples

should be collected to assess the vapor intrusion pathway if site ground water or soil gas

data indicates hazard and risk goals may be exceeded. If available data indicates there

may currently be unacceptable risk to residential receptors, Ohio EPA should be

contacted promptly and potential exposures to residential receptors evaluated in an

expedited manner. If it is determined that no current unacceptable risk exists to residential

receptors, the stepwise approach shown in Figure 1 may resume.

Prior to conducting residential sampling, the person undertaking the vapor intrusion

investigation should consider how the potentially impacted community and local

government should be notified. Proper community involvement efforts are critical to the

effective implementation of sample collection, evaluation, and risk communication. Ohio

EPA should be involved early in the risk communication planning process to ensure

proper interagency notification and coordination with the U.S. EPA, Ohio Department of

Health, and local health departments, as appropriate.

Public meetings may be necessary, including a pre-sampling meeting to explain results

from previous sampling and the vapor intrusion sampling workplan, and a post-sampling

meeting to explain any findings. Meetings may also be necessary to discuss additional

and/or follow-up air sampling or the determined remedy. Please contact Ohio EPA DERR

for assistance or additional guidance on informing property owners and/or tenants about

sampling results and possible next steps.

The quality of outdoor air is important to consider in the CSM and remedy selection. Thus,

collecting outdoor ambient vapor samples concurrently with indoor air sampling is

required. Additionally, the indoor air/sub-slab sampling form found in Appendix E should

be completed prior to indoor air or sub-slab vapor sampling at residential properties. Ohio

EPA DERR’s FSOP for indoor air sampling also includes instructions for building

occupants prior to indoor air sampling.

For further guidance on community outreach, please see Appendix A (Community

Stakeholder Concerns) of ITRC’s Vapor Intrusion Pathway: A Practical Guide 2007, and

Chapter 9 (Planning for Community Involvement) in U.S. EPA’s June 2015 VI Guidance.

APPENDIX C. FSOPs

Procedure for Active Soil Gas Sampling Using Direct Push Systems

FSOP 2.4.1 (March 9, 2017)

Ohio EPA Division of Environmental Response and Revitalization

1.0 Scope and Applicability

1.1 Vapor intrusion (VI) is defined as vapor phase migration of volatile organic

compounds (VOCs) into occupied buildings from underlying contaminated

ground water and/or soil. Soil gas surveys provide information on the soil

atmosphere in the vadose zone that can aid in assessing the presence,

composition, source, and distribution of contaminants. The purpose of this

document is to provide guidance for conducting soil gas sampling, and shall

pertain to active soil gas surveys, whereby a volume of soil gas is pumped

out of the vadose zone into a sample collection device for analysis.

1.2 U.S. EPA’s OSWER Technical Guide for Assessing and Mitigating the

Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air (U.S.

EPA June 2015) states that the chemicals in the subsurface must be both

sufficiently volatile and toxic to present a vapor intrusion risk. A chemical is

considered volatile if its vapor pressure is greater than 1 millimeter of

mercury (mmHg) or if its Henry’s Law constant is greater than 10

-5

atmosphere-meter cubed per mole (atm M

mol

-1

). Please refer to the Vapor

Intrusion Screening Level (VISL) calculator to determine whether to include

a chemical in a vapor intrusion investigation. For additional information refer

to Chapter 3 of U.S. EPA June 2015. A volatile organic chemical may

present a vapor intrusion risk if:

• The vapor concentration of the pure compound exceeds the target

indoor air concentration when the subsurface vapor is in soil, or

• The maximum ground water vapor concentration (i.e., the vapor

concentration above the ground water from the Henry’s Law constant

and water solubility) exceeds the target indoor air concentration for a

ground water vapor source.

1.3 Results from soil gas surveys are used in both qualitative and quantitative

evaluations. The quality and application of the data is dependent upon many

factors, including but not limited to: the DQO’s used to develop the sampling

plan, the number of sample locations and data points, the selection of the

sample locations, the soil characteristics of the site, the distribution of the

contaminants in both the vadose and saturated zones, the equipment and

personnel used to gather the data, etc. The work plan should be finalized

before any sampling is conducted. The work plan will provide specific

information on the type and quality of data gathered during the soil gas

sampling event. Any questions regarding data needs and usage should be

resolved prior to sampling.

1.4 The evaluation of the indoor inhalation pathway at contaminated sites is a

significant concern at sites/properties where contamination is known or

expected to exist. As a result, procedures and technology related to

evaluating the pathway continue to evolve. This procedure pertains to the

active collection of soil gas using direct-push techniques (i.e., driven probe

rods/tooling). With respect to the use of other appropriate methods,

procedures, and equipment for measuring concentrations of chemicals of

concern in soil gas, please refer to Appendix D, Section 4 of the Vapor

Intrusion Guidance: A Practical Guide (ITRC, January 2007).

2.0 Definitions

Terms specific to soil gas sampling using direct-push systems are defined

throughout this FSOP.

3.0 Health and Safety Considerations

3.1 Follow the site-specific health and safety plan (HASP). If a site-specific

HASP is not available, follow the health and safety procedures in FSOP 1.1,

Initial Site Entry.

3.2 The use of direct push systems on a site within the vicinity of electrical

power lines and other utilities requires that special precautions be taken by

the operators. Underground electrical utilities are as dangerous as

overhead electricity. Be aware and always suspect the existence of

underground utilities (water, natural gas, cable and phone lines, fiber optic

cables, storm water and sewer lines, etc.).

REMEMBER....Call B-4-U Dig:

Ohio Utilities Protection Service (OUPS): 800-362-2764

Oil & Gas Producers Underground Protection Service (OGPUPS):

800-925-0988

4.0 Procedure Cautions

A soil gas survey is only applicable to volatile contaminants. Geological barriers

may exist that interfere with vapor migration such as perched water, clay or man-

made structures. Interference from these geological barriers can lead to non-

representative sampling with low or false negative readings or may produce

localized areas of high concentrations. In addition, heavy precipitation, 24 to 48

hours prior to sampling can result in a significant reduction in volatile

concentrations.

5.0 Personnel Qualifications

Ohio EPA personnel working at sites that fall under the scope of OSHA’s

hazardous waste operations and emergency response standard (29 CFR

1910.120) must meet the training requirements described in that standard.

6.0 Equipment and Supplies

Personal Protective Equipment (PPE):

6.1 Hearing protection

6.2 Safety glasses

6.3 Nitrile (or similar) disposable gloves

6.4 Steel-toed boots

Equipment/Tooling/Supplies for Probe Installation:

6.5 Direct push rig

6.6 4-foot probe rods

6.7 2-foot probe rods

6.8 Inner Extension Rods (48")

6.8 Rod Grip Pull System

6.10 Drive Cap

6.11 Miscellaneous tools

6.12 Log book/Data sheets

6.13 Bentonite granules

Soil Gas Sampling:

6.14 Expendable Point Holder

6.15 Implant Expendable Point Holder

6.16 Expendable Drive Points (w/ O-ring)

6.17 6.25 Expendable Point Popper

6.18 PRT Adapter for ¼“ tubing w/ O-ring

6.19 ¼“ OD x 3/16” ID tubing (Teflon

or Nylon)

6.20 20/40 grade sand (#5 quartz silica sand, or equivalent)

6.21 1L Evacuated canisters (i.e., Summa canisters), with grab flow-choke

regulators

6.22 Implants (stainless steel, aluminum, ceramic, or plastic)

6.23 Funnel

6.24 Tubing cutter

6.25 Polycarbonate 2- & 3-way valves

6.26 Disposable 60cc Syringe

6.27 Photoionization detector (FSOP 3.1.1, Photoionization Detector), ppb

capable

6.28 Multi-gas meter (FSOP 3.1.2, Multiple Gas Detection Meters)

6.29 Field documentation equipment and supplies, including pens, markers, field

logbook and data sheets, chain-of-custody forms, camera, etc.

7.0 Procedures: Summary of Probe Installation Methods

7.1 Using the Post-Run Tubing System for Grab Sample Collection

This is a temporary, single use application for collecting a soil gas grab

sample. Using the post-run tubing system (PRT), probe rods are driven to

the desired depth, and then internal tubing, with PRT fitting attached, is

inserted and seated for soil gas sampling. Using the inner tubing for soil gas

collection has many advantages - potential for leakage is reduced, dead air

volume that must be purged is reduced, and decontamination problems are

reduced as the sample does not contact the rod bore.

7.1.1 Clean all parts prior to use. Inspect all probe rods and clear them

of obstructions. Install O-ring on the PRT expendable point holder

and the PRT adapter.

7.1.2 Test fit the adapter with the PRT fitting on the expendable point

holder to assure that the threads are compatible and fit together

smoothly. Ensure the threads are clean of debris.

NOTE: PRT fittings are left-hand threaded and must be rotated

counter-clockwise to engage the point holder threads.

7.1.3 Push the PRT adapter into the end of the selected tubing. Tape

may be used on the outside of the adapter and tubing to prevent

the tubing from spinning freely around the adapter during

connection - especially when using Teflon

tubing.

NOTE: The sample will not come into contact with the outside of

the tubing or adapter.

7.1.4 Attach the PRT expendable point holder (with O-ring) to the female

end of the leading probe rod.

7.1.5 Attach an O-ring to an expendable soil vapor drive point and insert

into the expendable point holder. Attach the drive cap to the male

end of the drive rod and position rod under probe.

7.1.6 Drive the PRT rod configuration into the ground, connecting probe

rods as necessary to reach the desired depth.

7.1.7 After desired depth has been achieved, disengage the expendable

drive point. Using the inner extension rods, insert the expendable

point popper to the bottom of the rod string and then slowly pull up

on the probe rods using the rod grip pull system. Retract the rods

approximately 4"- 6" up to create a void from which to sample the

soil gas. Position the probe unit to allow room to work around the

sample location.

7.1.8 Insert the PRT adapter end of the tubing down the inside diameter

of the probe rods.

7.1.9 Feed the tubing down the rod bore until it hits bottom on the

expendable point holder. Allow approximately 4-6 ft. of tubing to

extend out of the hole before cutting it. Grasp the excess tubing

end and lightly apply downward pressure while turning it in a

counter-clockwise motion to engage the adapter threads with the

expendable point holder. Continue turning until the PRT adapter O-

ring bottoms out in the expendable point holder.

7.1.10 Pull up lightly on the tubing to test the engagement of the threads.

Failure of the PRT adapter to thread could mean that intrusion of

soil may have occurred during driving of the rods or disengagement

of the expendable drive point. Once tubing has been connected,

finish the surface end with a 2-way valve in the closed position.

7.1.11 Sampling at the location can commence following an equilibrium

period (minimum of 15 minutes). Connect the sampling tubing and

follow appropriate purging and sampling procedures. Refer to

“Procedures for Collection of Indoor Air, FSOP 2.4.3” for reference

for use of evacuated canisters for sample collection; and refer to

Section 7.3.1 below, for sampling procedures using the bag

sampler (e.g., Lung Box).

7.1.12 Prior to sample collection and screening, ensure that the implant is

in a porous soil zone that will freely give up soil gas. Connect a 60

cc syringe to the implant tubing, open the 2-way tubing valve, and

gently pull the plunger out to fill the syringe with gas. Let go of the

plunger and observe whether it holds position where released, or if

it can be observed moving back due to an induced vacuum. Should

a vacuum be present, the soil zone at the end of the probe rods

may be too tight to get a representative soil gas sample. Should

this occur, the probe rods can be pulled up 1 to 2 feet at a time,

retesting each interval until soil gas can be freely obtained. If not,

abandon the location, seal the borehole with bentonite, and

reposition the probe; or relocate to another position.

7.2 Installation of Soil Gas Implants

For long-term soil gas monitoring applications (multiple sampling events

from the same location), a stainless steel, aluminum, polycarbonate or

ceramic implant can be installed at any depth by direct push. Implants are

inserted down inside the probe rods when the appropriate sampling depth

has been achieved. When installing soil gas implants, knowledge of the

local geology and soil types is paramount to the success of any soil gas

survey. For sites where geology or soil characteristic information is not

available, the collection of soil borings to target depth may be helpful in

identifying zones or soil horizons in which to set soil gas implants.

7.2.1 Drive probe rods to the desired depth using the implant expendable

point holder and an expendable drive point. Disengage the drive

point using the point popper. Using the inner extension rods, insert

the expendable point popper to the bottom of the rod string and

then slowly pull up on the probe rods using the rod grip pull system.

Retract the rods approximately 1”- 2” to push the expendable point

out with the point popper. Remove all extension rods and point

popper. Check end of last inner rod or point popper for evidence of

moisture. Implants should not be installed in moist zones as these

can inhibit vapor migration as well as, given enough time for water

to accumulate, may result in water being drawn up and into sample

containers (evacuated canister or Tedlar

bag).

7.2.2 Attach implant to one end of appropriate sample tubing (Teflon

or nylon). Depending on implant type and diameter of sample

tubing, a very short length of silicone tubing of appropriate size may

be used to securely connect the implant to the sample tubing.

7.2.3 Lower the implant and tubing down the inside of the probe rods

until the implant hits the top of the anchor/drive point. Note the

length of the tubing to assure that proper depth has been reached.

Cut the tubing flush with the top of the probe rod.

7.2.4 Using an inner extension rod, place one end of the rod on top of

the fresh cut tubing. While holding the rod in place, slowly retract

the rods, 4 feet at a time, and remove the drive rod. Continue this

action of using the extension rod to hold the tubing in place until all

the drive rods have been removed from the borehole.

7.2.5 Slowly pour sand (20/40 grade or #5) down the borehole around

the outside of the tubing so that the sand extends several inches

above the implant. Use the tubing to “stir” the sands into place

around the implant. Do not lift up on the tubing. It should take less

than 250 mL of sand to fill the space around the implant. The sand

therefore will act as a grout barrier, inhibiting the grout from

impacting the implant. Slowly pouring sand and bentonite will

lessen the chance for the materials to bridge in the borehole.

NOTE: Implants come in various sizes and the drive rods can vary

in diameter, so it is best to calculate the necessary volume of sand

for each implant installation. Placement of the grout barrier by

backfilling the borehole can only be performed in the vadose zone,

not below the water table.

7.2.6 Once the sand is in place, slowly add the bentonite granules on top

of the sand. After approximately 0.5 L of bentonite has been added,

hydrate the bentonite in the hole. Hydration can be accomplished

using a pump sprayer, or by using a section of tubing connected to

the 60 cc syringe filled with water. Depending on borehole depth,

the bentonite should be hydrated at a minimum of 3-5 intervals.

Allow bentonite to come to ground surface, saturate the bentonite

with water to create a bentonite “mud” and, using a finger, push this

mix around the tube and back down the hole to enhance the

closure. This results in a tight seal preventing gas migration down

the column.

NOTE: Use caution not to over hydrate, as the water may flow out

into the soil formation and travel down to the implant, causing it to

become wet and potentially loose diffusivity

7.2.7 After sealing the borehole, cut the tubing to a manageable length

(~12” - 18”), attach a 2-way valve connector (in the OFF position)

or air tight (e.g., Swagelok

) plug, and mark the location with a pin

flag or stake. Attach a label or tag to the tubing indicating the

sample location identifier and depth at which the implant was set

for future reference when sampling. Example: SG-3-18, meaning a

soil gas point at location #3 with an implant set at 18 feet bgs.

7.2.8 Check the viability of the sample point just installed following the

procedures outlined in Section 7.1.12 using a 60 cc syringe. A

multi-gas meter with a PID is also a very good way to purge and

check the sample point’s viability and usefulness. Stable field

screening measurements for VOC’s, oxygen, and hydrogen sulfide

can be good indicators on a well-sealed and sampling-ready

implant. Should the meter’s pump motor labor, or if the syringe

plunger recedes back into syringe after pulling, a vacuum has been

induced and the point is not viable for sample collection. The

induced vacuum would be too much to overcome to obtain a gas

sample using either an evacuated canister or a bag sampler.

7.2.9 A minimum equilibrium time should be established prior to

sampling the implant (preferably stated in the work plan). While a

24-hour equilibrium period will ensure adequate equilibration, four

to eight hours is generally sufficient. After equilibration, the implant

is ready for sampling. Refer to Section 7.3 for sampling procedures

using a vacuum canister (e.g., Summa or Silco).

7.2.10 To provide long term security to the sampling port, the installation

of a flush mount or above ground protective casing with a cap can

be installed and finished with a concrete pad. For temporary, short-

term finishing of a sampling port, 4-6” (ID) PVC pipe sections with

associated caps can be installed.

7.3 Sample Collection Methods

Two common methods of sample collection for vapor intrusion

contaminants of concern (COCs) are discussed in this FSOP. The lung box

sampler uses Tedlar

bags as sample containers. Collection of samples on

adsorbents is performed by using a small external pump to pull air through

adsorbent media cartridges and/or tubes. Data Quality Objectives (DQOs)

for the project will determine which sample collection method to use. Field

data should be recorded on the Soil Gas Sampling Data Sheet (attached)

or in a field notebook.

7.3.1 The Lung Box Sampler (Bag Samplers)

The Lung Box allows direct filling of a Tedlar

air sample bag using negative

pressure without passing gas through the pump. This eliminates the risk of

contaminating the pump or the sample. The Lung Box, pictured below,

includes an in-line pump. Other types of bag samplers may require the use

of a separate air pump or hand pump.

The recommended holding time for samples collected into Tedlar

bags is

24 to 48 hours. Therefore, soil gas samples collected in Tedlar

bags should

be analyzed as quickly as practical or samples can be transferred to another

container with longer holding times (i.e., Summa canister). If this method of

sampling is performed, ensure that the laboratory can accept Tedlar

bags,

and can meet the holding time requirements.

Semi-permanent soil gas probe location with multi-depth implants. The lung

box sampler is used to collect soil gas samples using 1-liter Tedlar bags.

Note that each tube is labeled with the sampling depth; the PVC pipe is

used to protect the soil gas tubing.

7.3.1.1 Prior to sampling, and after an appropriate equilibrium

period (typically 8 – 24 hrs. depending on DQOs), ambient

air needs to be removed from the sample train by purging.

Purging of the filter pack is required if sampling occurs within

24 hours of installation. At least three volumes should be

removed. For example, the sample tubing can be purged

using a 60 cc syringe with an attached 3-way valve (~4 cc/ft

for ¼” ID tubing/volume). Other methods may be used as

long as a minimum of 3 volumes are purged from the tubing.

Once purging is complete, the sample may be collected.

Field screening may be performed using a direct reading

instrument after sample collection.

7.3.1.2 Install new tubing in the bag sampler before collecting each

sample. Place a new Tedlar

sample bag (already labeled)

inside the bag sampler. Attach the inside portion of the

tubing to the inlet valve on the sample bag. Open the sample

valve on the sample bag following the manufacturer’s

instructions. Close sampler lid and secure. (DO NOT use

any type of permanent marker, i.e., “Sharpie” pens)

7.3.1.3 Attach external part of the inlet tubing to the sample tubing.

Make sure that the purge valve on the side of the box is

closed (closed for fastest fill rate, open for slower fill rate).

7.3.1.4 Turn on the sample pump or initiate hand pumping. While

filling, watch through the observation window of the Bag

sampler as the Tedlar

bag fills with gas. Avoid filling bag

more than 80% of its maximum volume. Turn the pump off

when the bag has filled to the desired volume. Do not over

fill sample bags. The vacuum pump may be strong enough

to break a sample bag.

NOTE: Be sure to watch the sample line for the first sign of

water coming up the line. Pulling water up the line is not

uncommon, especially in cases where the position of the

water table is unknown. This is a good reason why ample

lengths of tubing should be used for the sample line. If water

is drawn up the tubing, the tubing can be cut before the

water reaches the sampling equipment.

NOTE: Exercise extreme caution if filling sample bags with

explosive gases.

7.3.1.5 Once filling of the sample bag is complete, turn off the pump,

open the purge valve to equalize the pressures, unlatch the

bag sampler lid and open. Close the sample bag inlet valve

by holding the side stem and turning the entire upper portion

of the fitting clockwise until snug. Remove the filled sample

bag from the internal inlet tubing.

NOTE: In an effort avoid any photochemical reactions, keep

filled Tedlar

bags out of sunlight. Store and ship bag

samples in a protective box at room temperature. Do not

chill to avoid condensation.

7.3.1.6 If measurements with a portable meter are to be made (e.g.,

oxygen), conduct measurements after collecting the soil gas

sample(s).

7.3.2 Collection of Samples on Adsorbents

7.3.2.1 An alternative approach to collecting soil gas in a sample

container is to concentrate the soil gas on an adsorbent

media. This type of method is required for SVOCs and is

often used for mercury (generally compounds heavier than

naphthalene). Typically, a pump is used to draw soil gas

through the adsorbent matrix, and the adsorbent is then

analyzed by a laboratory.

7.3.2.2 A variety of adsorbent cartridges and pumping systems are

available from commercial vendors. In addition, it is

essential that the soil gas be drawn through the adsorbent

by the pump, not pumped through the adsorbent to eliminate

the chance for cross-contamination by the pump. It is often

recommended that two tubes be used in series to avoid

breakthrough losses in areas of suspected higher

concentrations. The adsorbent, purge rate, and sample

volume must be determined by discussion with the analytical

laboratory.

7.4 Soil Gas Sample Field Screening

7.4.1 Following sample collection, field-screen the borehole or soil gas

probe atmosphere with a PID in accordance with FSOP 3.1.1,

Photoionization Detector, to estimate the bulk concentration of

VOCs present in the soil gas sample. The PID field screening data

should be recorded with the sample information on the chain-of-

custody form. The analytical laboratory needs to be aware of any

samples potentially containing high concentrations of VOCs that

may need to be diluted prior to analysis.

7.4.2 If desired, to perform the field-screening, attach an appropriate

length of tubing to the PID sampling tip with a small piece of silicon

tubing and extend it at least halfway into the boring or attach PID

directly to tubing on a soil gas probe to obtain readings.

7.4.3 The PID field screening data may also be collected for sampler

health and safety concerns or to use as real-time screening

information to help evaluate the need for additional sampling or

other site assessment activities while in the field.

 
75 
 
7.4.4  In addition to a PID, a multi-gas meter (FSOP 3.1.2, Multiple Gas 
Detection Meters) may be used to field screen the borehole or soil 
gas probe atmosphere to collect gas concentration field screening 
data. This information may be provided to the analytical laboratory, 
used to monitor health and safety concerns, or used as real-time 
screening  information  to  help  evaluate  the  need  for  additional 
sampling  or  other  site  assessment  activities  while  in  the  field. 
Parameters  often  include  VOCs  (ppb),  Oxygen  (%  O
2
),  Lower 
Explosive  Level  (%  LEL),  Carbon  monoxide  (ppm  CO),  and 
Hydrogen sulfide (ppm H
2
S)   
 
8.0  Data and Records Management 
 
Refer to FSOP 1.3, Field Documentation. 
 
9.0  Quality Assurance and Quality Control 
 
Refer to the Site-Specific Work Plan 
 
10.0  Attachments 
 
Soil Gas Sampling Data Sheet  
 
11.0  References 
 
FSOP 1.1, Initial Site Entry 
 
FSOP 1.3, Field Documentation 
 
FSOP 3.1.1, Photoionization Detector 
 
FSOP 3.1.2, Multiple Gas Detection Meters 
 
Interstate Technology & Regulatory Council (ITRC) Vapor Intrusion Team, January 
2007, Vapor Intrusion Pathway: A Practical Guideline 
 
U.S. EPA, June 2015, OSWER Technical Guide for Assessing and Mitigating the 
Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air: OSWER 
Publication 9200.2-154 

SOIL GAS SAMPLING DATA SHEET

GENERAL INFORMATION

Site Name:____________________________________

Site Address:_________________________________

City:_________________________________________

County/District_________________________________

Contact Name:_________________________________

Phone #:______________________________________

Sampling Address:_____________________________

(if other than site address)

Grab Sample:________ Canister Sample:_________

Sample ID #: __________________________________

If canister used, complete info below:

Canister ID #:_________________________________

Regulator ID #:________________________________

SAMPLING INFORMATION

(mm/dd/yy) (military)

Soil Gas port installed: Date:_______Time:_______

Depth :_______

If canister used for sample collection, complete

following info:

Sample Collection Start: Date:_______Time:_______

Sample Collection End: Date:________ Time:_______

Regulator Calibrated for:

_____ 8-hr _____ 12-hr _____ 24-hr _____ grab (no

regulator)

Laboratory & Analytical Method: _________________

Sample Delivered: Date_________ Time:__________

Method of Delivery: ____________________________

(ex. Lab courier, UPS, delivered by sampler, etc.)

Canister Info:

Initial canister vacuum:

_______ “Hg or mm Hg

Final canister vacuum:

________”Hg or mm Hg

Temperature:

____________

Field Screening Info:

PID (ppm):__________

% O

:______________

(%LEL):_________

:_______________

CO:________________

S:_______________

List instrument (and ID#)

used to collect parameters:

_________________________

NOTES: (include any information on the installation of the soil gas port, or problems with

sampling/canister etc.)

Signature of Sampler: ___________________________________________ Date:________________

Note: If a diagram of the sample location(s) is sketched on the back of this data sheet, check here

Construction, Installation and Decommissioning of Sub-Slab Vapor Ports

FSOP 2.4.2 (May 2, 2018)

Ohio EPA Division of Environmental Response and Revitalization

1.0 Scope and Applicability

Sub-slab vapor ports are used to sample the vapor contained in the interstitial spaces

beneath the floor slab of dwellings and other structures for volatile organic compounds

(VOCs) and other volatile chemicals. Sub-Slab vapor ports may be constructed using a

custom fit stainless steel implant with Swagelok

fittings or a custom pre-manufactured

Vapor Pin

2.0 Definitions

Summa Canister: Genericized trademark that refers to electro-polished, passivated

stainless steel vacuum sampling devices (i.e., evacuated canister). Sizes of canisters will

vary with the most commonly used sizes being 6L and 1L. Canister size will depend on

the pre-determined time-frame for sampling (e.g., 24-hour vs. “grab”). A “Silco” canister

is another name for a Summa canister.

3.0

Health and Safety Considerations

3.1

This activity involves accessing private residences and spaces in commercial

buildings. Follow Ohio EPA Standard Safety Operating Procedure Number

SP11-19 (Working Alone) to determine if working alone is appropriate given the

site conditions and circumstances.

3.2

Never enter an OSHA-defined confined space for any reason. Only Ohio EPA

Office of Special Investigation (OSI) staff or other appropriately trained staff are

qualified to enter confined spaces for reconnaissance or sampling activities and

will perform such work as necessary in accordance with Ohio EPA Standard

Safety Operating Procedure Number SP14-4 (Confined Space Entry).

3.3

Follow the site-specific health and safety plan (HASP), which should identify the

potential presence of asbestos-containing materials and other building-specific

health and safety concerns. If a site-specific HASP is not available, follow the

health and safety procedures in FSOP 1.1, Initial Site Entry.

3.4

This activity may result in the creation of silica dust when drilling through

concrete. To prevent exposure to silica, a HEPA vacuum with an associated

dust containment system must be used when drilling through concrete. Staff

must be trained in the proper use of the silica dust collection equipment before

installing sub-slab vapor probes.

3.5

When using electricity, be cautious of wet areas or areas with standing water,

e.g., wet basement floors, sump pumps, etc.

3.6

Be aware of potential vermin (fleas, rats, etc.)

3.7

Hearing protection should be worn while using a hammer drill.

3.8

A dust mask may be worn during drilling if desired.

3.9

Use a photoionization detector (PID) to evaluate VOC concentrations during

vapor port installation in accordance with FSOP 3.1.1, Photoionization Detector.

3.10

Review available plans or documents before selecting sampling locations.

Ensure that all sub-slab utilities (public and private or building specific) have

been located and marked prior to installation.

3.11

Do not attempt to drill through steel-reinforcement (e.g., rebar) within a concrete

slab.

4.0

Procedure Cautions

4.1

Review the site-specific work plan (SSWP), which should include a description of

the building’s size and use. In certain emergency circumstances a SSWP may not

be available, and all necessary information for sub-slab vapor port installation and

sampling will need to be obtained during the pre-sampling visit as described below.

If a pre-sampling meeting cannot be held due to time constraints, please collect

as much of the information as possible as listed below. This information can be

obtained during a telephone call or in person.

4.2

A pre-sampling site visit should be conducted to meet with the building’s owner

and/or tenant and inspect the proposed vapor port sampling locations. During the

pre-sampling visit, discuss sample location access and associated logistical

concerns, including, but not limited to, lighting and electrical power, the need to

temporarily move furnishings, the need to remove floor coverings (e.g., carpet or

tile), the location of floor drains and/or other sub-slab utilities, and whether or not

the sampling areas are occupied or unoccupied spaces.

4.3

The thickness of concrete slabs varies from structure to structure. A single

structure may also have a slab with variable thickness. Drill bits of various sizes

and cutting ability may be required to penetrate slabs of variable thicknesses. If

a slab contains steel reinforcement (e.g., rebar), a sub-slab vapor port can only

be installed if SIFU can find a location where steel reinforcement is not present.

SIFU cannot drill through the steel reinforcement within a concrete slab.

4.4

There is a potential for high concentrations of VOC vapors to exist under the

slab. Perform work quickly to ensure minimal exposure to VOCs.

4.5

When installing sub-slab vapor ports in commercial or industrial buildings, there

is the potential to encounter sub-slab utility conduits (e.g., floor drains or electric,

gas or water lines). Follow the procedures provided in Section 7.1 for sub-slab

utility clearance before installing vapor ports.

4.6

Unless approved by Ohio EPA management and the building owner, sub-slab

vapor ports should never be installed in the floor of a building with an existing

sub-slab vapor barrier that is a component of a vapor mitigation system because

vapor port installation could penetrate the barrier. However, sub-slab vapor ports

may be installed through sub-slab moisture barriers that are typically not

components of vapor mitigation systems, providing that the vapor port is

decommissioned when it is no longer needed for sampling purposes.

4.7

When using the drill and HEPA vacuum, you will exceed 15 amps which is the

standard for most household outlets. Therefore, be prepared to connect the drill

and the HEPA vacuum to separate outlets.

5.0 Personnel Qualifications

Ohio EPA personnel working at sites that fall under the scope of OSHA’s hazardous

waste operations and emergency response standard (29 CFR 1910.120) must meet the

training requirements described in that standard. Prior knowledge, training and

experience with this sampling technique is strongly recommended before collecting

samples.

6.0

Equipment and Supplies

General

6.1

Hammer drill or rotary hammer drill

6.2

Alternating current (AC) extension cord

6.3

AC generator, if AC power is not available on site

6.4

Hammer or rotary hammer drill bit, ⅜” diameter

6.5

Hammer or rotary hammer drill bit, 1” diameter

6.6

1 – ¾” open end wrench or 1 – medium adjustable wrench

6.7

2 –

” open end wrench or 2 – small adjustable wrenches

6.8

Disposable cups, 5 ounces (oz.)

6.9

Disposable mixing implement (i.e., popsicle stick, tongue depressor, etc.)

6.10

Vapor Sampling Data Sheet, Sub-Slab and Indoor Air (attached) or log book

6.11

Pens and markers

6.12

Flashlight or equivalent head lamp

6.13

Utility knife

6.14

Disposable syringe (60 cc)

6.15

Personal protective equipment appropriate for site-specific work activities\

6.16

Disposable mixing implement (i.e., popsicle stick, tongue depressor, etc.)

6.17

Tap water, for mixing anchoring cement/grout

6.18

Hand broom and dust pan

6.19

Small bottle brush to remove loose debris clean side walls of borehole

6.20

Portable HEPA vacuum

6.21

Dust collector

Swagelok

Equipment and Supplies

6.22

Hex head wrench, ¼”

6.23

Tubing cutter and pipe cutter

6.24

Swagelok

SS-400-7-4 female connector, ¼” national pipe thread (NPT) to ¼”

Swagelok

connector

6.25

Swagelok

SS-400-1-4 male connector, ¼” NPT to ¼” Swagelok

connector

6.26

Hose barb adapter, brass, 3/16” barb x ¼” male iron pipe (MIP)

6.27

¼” NPT flush mount hex socket plug

6.28

¼” outer diameter (OD) stainless steel tubing, pre-cleaned, instrument grade

6.29

¼” OD Teflon™ or nylon tubing

6.30

Teflon™ or nylon washer ID ¼”, OD ¾”

6.31

¼” OD stainless welded tubing, 12” to 24” length

6.32

Swagelok

tee, optional (SS-400-3-4TMT or SS-400-3-4TTM)

6.33

Appropriate size tubing

Vapor Pin

Equipment and Supplies

6.34

Cox-Colvin Vapor Pin

Kit

6.35

Dead blow hammer

6.36

Appropriate silicon tubing

6.37

Vapor Pin

protective cap to prevent vapor loss prior to sampling

6.38

Standard Operating Procedure Installation and Extraction of the Vapor Pin

https://www.vaporpin.com/resources/#SOP

7.0

Procedures

7.1

Review the SSWP, which should include a description of the building’s size and

use. In certain emergency circumstances a SSWP may not be available, and all

necessary information for sub-slab vapor port installation and sampling will need

to be obtained during the pre-sampling visit as described below. If a pre- sampling

visit is not feasible, call the owner and/or tenant prior to sampling to obtain the

information.

7.2

A pre-sampling site visit should be conducted to meet with the building’s owner

and/or tenant and inspect the proposed vapor port sampling locations. During the

pre-sampling visit, discuss sample location access and associated logistical

concerns, including but not limited to lighting and electrical power, the need to

temporarily move furnishings, the need to remove floor coverings (e.g., carpet or

tile), the location of floor drains and/or other sub-slab utilities and whether or not

the sampling areas are occupied or unoccupied spaces.

7.3

Before installing sub-slab vapor ports in a commercial or industrial building, use

the following procedures for sub-slab utility clearance:

7.3.1 Perform a visual inspection of the area(s) of the building where vapor

ports are to be located for potential sub-slab utility lines.

7.3.2 Discuss the presence and location(s) of sub-slab utility lines with the

building owner and/or operator and review any available building

construction plans that may show the location of sub-slab utility lines.

7.3.3 If the presence or location(s) of sub-slab utility lines cannot be verified

following the procedures in Sections 7. 1 and 7. 2, contract a private utility

locating company to locate potential sub-slab utility lines before installing

vapor ports.

7.4

Preparation and Drilling of the Vapor Port

7.4.1 Connect the dust collector to the HEPA vacuum. Ensure that all

connections are tight.

7.4.2 Plug the HEPA vacuum into the outlet and place the dust collector on the

floor. Turn on the HEPA vacuum and ensure that the dust collector has

created a tight seal with the floor. If a tight seal is not present, turn off the

vacuum and check to ensure that all of the connections between the

vacuum and the dust collector are tight. If the connections are tight, check

the filter. It may be full, and need replaced. Also make sure the rubber

gasket on the dust collector is in good condition. Finally, reposition the dust

collector to a smoother floor surface. Retest the seal between the dust

collector and the floor.

7.4.3 After ensuring that there is a good seal between the floor and the dust

collector, set-up the drill and make sure the dust collector is positioned

over the location selected for the vapor port. Turn on the vacuum and

then the drill.

7.5

Swagelok

Probe Assembly and Installation for Multiple Sampling Events

7.5.1 Drill a ⅜” diameter pilot hole to a depth of approximately 2” (Figure 1).

7.5.2 Using the ⅜” pilot hole as your center, drill a 1” diameter outer hole to a

depth of approximately 1 ⅜” (Figure 1). Vacuum cuttings out of the hole.

Figure 1: Assembled sub-slab port ready for installation

7.5.3 Continue drilling the ⅜” inner or pilot hole through the slab and a few

inches into the sub-slab material.

7.5.4 Determine the length of stainless steel tubing required to reach from the

bottom of the outer hole, through the slab and into the open cavity below

the slab. To avoid obstruction of the probe tube, ensure that it does not

contact the sub-slab material. Using a tube cutter, cut the tubing to the

desired length.

7.5.5 Attach a measured length (typically 3”-4”) of ¼” OD stainless tubing to the

female connector (SS-400-7-4) with the Swagelok

nut. Make sure that

the tubing rests firmly in the fitting body and that the nut is finger tight.

While holding the fitting body firmly, tighten the nut 1¼ turns.

7.5.6 Insert the ¼” hex socket plug into the female connector. If using a stainless

steel socket plug, wrap one layer of Teflon™ thread tape around the

threads to prevent binding. If using a brass socket plug, Teflon™ tape is

not needed. Tighten the plug slightly. Do not over tighten. If excessive force

is required to remove the plug during the sample set up phase, the probe

may break loose from the anchoring cement.

7.5.7 Place the completed probe into the outer hole to check fit and to ensure

that stainless steel tubing is not in contact with the sub-slab material.

Make necessary adjustments to the hole or probe assembly.

7.5.8 In a disposable cup or other container, mix a small amount of the

anchoring cement or grout. Add water sparingly to create a mixture that

is fairly stiff and moldable. Place a spoonful or two of the cement/grout

around the stainless steel tubing adjacent to the female connector nut.

Mold the cement/grout into a mass around the connector nut and up

around the main body of the probe assembly. Slide the Teflon™ washer

onto the stainless steel tube so that it rests next to the cement/grout

mixture. The washer will prevent any anchoring cement/grout from flowing

into the inner hole during the final step of probe installation.

7.5.9 Carefully place the probe assembly into the drilled hole, applying light

pressure to seat the assembly. While inserting the probe assembly, work

the concrete/grout mixture to fill voids. Clean up cement/grout that

discharged out of the hole during placement; avoid getting any of the

concrete/grout into fittings or on fitting threads. Allow the cement/grout to

cure according to manufacturer’s instructions before sampling (typically 24

hours). This elapsed time also allows for subsurface conditions to

equilibrate prior to sampling.

7.6

Swagelok

Sample Set-Up and Collection

7.6.1 Conduct a leak test prior to sampling. Follow project-specific DQO’s

and/or the SSWP to determine which of the following method(s) are

appropriate:

7.6.1.1 The water dam that is included in the Cox-Colvin Vapor Pin

kit

is a simple means of determining if there are any leaks (see

Cox-Colvin instructions, Figure 6). To use the water dam, simply

attach the water dam to the floor using putty ensuring that there

are no holes between the putty and the floor. Then add water to

the dam and observe whether there are any air bubbles. If there

are no air bubbles, the seal is tight. If there are air bubbles, refer

to Section 7.7.

7.6.1.2 Another option is to evaluate the oxygen concentration by

attaching an oxygen sensor (Multi-RAE Pro meter) to the vapor

. If the percent oxygen drops, it can be inferred that there is a

tight seal. However, since this method draws in sub-slab vapor, a

longer waiting period may be required before collecting the

sample to allow for the sub-slab air to re-equilibrate.

7.6.1.3 A tracer gas can be used during sample collection to evaluate

whether the connections between the vapor pin

and the sample

container have any leaks. A tracer gas is very lightly sprayed on

a paper towel and the paper towel is briefly laid around the fittings.

As an alternative, the tracer gas can be lightly sprayed into the

atmosphere near the sample train. Do NOT spray directly on the

fittings. Note: you will not know if there were any leaks until after

the sample has been analyzed. The recommended tracer gas is

1,1-Difluoroethane, which is present in some brands of dust

cleaner for electronics.

7.6.2 Wrap one layer of Teflon™ thread tape onto the NPT end of the male

connector OR wrap one layer of Teflon™ tape onto the threaded end of

the hose barb adapter (3/16” barb x ¼” MIP).

7.6.3 Carefully remove the ¼” hex socket plug from the female connector.

Refer to Section 7.7 if the probe breaks loose from the anchoring

cement/grout during this step.

7.6.4 To ensure that the sub-slab port has not been blocked by the collapse of

the inner hole below the end of the stainless steel tubing, a stainless steel

rod, ⅛” diameter, may be passed through the female connector and the

stainless steel tubing. The rod should pass freely to a depth greater than

the length of the stainless steel tubing, indicating an open space or loosely

packed soil below the end of the stainless steel tubing. Either condition

should allow a soil gas sample to be collected. If the port appears blocked,

the stainless steel rod may be used as a ramrod to open the port. If the

port cannot be cleared, the probe should be reinstalled, or a new probe

installed in an alternate location.

7.6.5 Screw and tighten the Teflon™ taped male connector into the female

connector, or screw and tighten the hose barb adapter (3/16” barb x ¼”

MIP) into the female connector. Do not over tighten. This may cause the

probe assembly to break loose from the anchoring cement/grout during

this step or when the male connector/hose barb adapter is removed upon

completion of the sampling event. Refer to Section 7.7 if the probe breaks

loose from the anchoring compound during this step.

7.6.6 If a co-located sub-slab sample or split sample is desired, a stainless

steel Swagelok

T, may be used in place of the male connector.

7.6.7 Using a short piece of silicon tubing, attach a length of ¼” tubing (Teflon™

or nylon) to the sampling container (e.g., Summa

canister) or system

(e.g., lung box for Tedlar

bag) to be used for sample collection. Connect

the other end of the tubing to the male connector with a Swagelok

nut

or connect directly to the barbed hose adapter.

7.6.8 Refer to site-specific work plan for canister size and type of sample

required (e.g., 6-liter canister with regulator for either 8-hour or 24-hour

sample collection or a 1-liter evacuated canister for a grab sample). After

sampling, use a PID to measure the VOC concentrations to provide the

laboratory with an indication of how concentrated the VOCs may be in the

sample. Provide this information to the laboratory. Note: PID readings are

not contaminant-specific quantifications. Do not assume that the PID

reading equates (or approximates) the concentration of the contaminant of

concern.

7.6.9 After sample collection, remove the male connector or barbed hose

adapter from the probe assembly and reinstall the ¼” hex socket plug.

Make sure the plug threads are wrapped with Teflon tape. Do not over

tighten the hex socket plug. If excessive force is required to remove the

plug during the next sampling event, the probe may break loose from the

anchoring compound. Refer to Section 7.7 if the probe breaks loose from

the anchoring compound during this step.

7.7

Repairing a Loose Swagelok

Probe Assembly

7.7.1 If the probe assembly breaks loose from the anchoring compound while

removing or installing the hex socket plug, the Swagelok

male

connector, or the barbed hose adapter, lift the probe assembly slightly

above the surface of the concrete slab.

7.7.2 Hold the female connector with the ¾“open-ended wrench.

7.7.3 Complete the step being taken during which the probe broke loose,

following the instructions contained in this SOP (i.e., do not over tighten

the hex socket plug, the male connector, or the barbed hose adapter).

7.7.4 Push the probe assembly back down into place and reapply the

anchoring cement/grout.

Figure 2: Swagelok

port connected to canister and ready for sampling

7.8

Vapor Pin

Probe Installation

7.8.1 Refer to attached Cox-Colvin Vapor Pin

Standard Operating Procedure

for proper vapor pin installation and removal.

7.8.2 After installing a Vapor Pin

place the small rubber cap over the barbed

inlet to prevent and gas from escaping.

7.8.3 Conduct a leak test. The project specific DQO’s or SSWP may dictate

which of the following method(s) may be followed. Note: There are other

techniques beyond those listed that may be used.

7.8.3.1 The water dam that is included in the Cox-Colvin Vapor Pin

kit is

a simple means of determining if there are any leaks (see

Cox-Colvin instructions, Fig 6). To use the water dam, attach the

water dam to the floor using putty ensuring that there are no holes

between the putty and the floor. Then add water to the dam and

observe whether there are any air bubbles. If there are no bubbles,

the seal is tight. If there are air bubbles, remove the water and

reset the vapor point. Test with the water dam again to see if the

seal is now tight. Remove the water and dam once test is

complete.

7.8.3.2 Another option is to attach an oxygen sensor (Multi-RAE Pro

meter) to the vapor pin

and evaluate the oxygen concentration.

If the percent oxygen drops, it can be inferred that there is a tight

seal. However, since this method draws in sub-slab vapor, a

longer waiting period may be required before collecting the

sample to allow for the sub-slab air to re-equilibrate.

7.8.3.3 A tracer gas can be used during sample collection to evaluate

whether the connections between the vapor pin

and the sample

container have any leaks. A tracer gas is very lightly sprayed on a

paper towel and the paper towel is briefly laid around the fittings.

As an alternative, the tracer gas can be lightly sprayed into the

atmosphere near the sample train. Do NOT spray directly on the

fittings. Note: you will not know if there were any leaks until after

the sample has been analyzed. The recommended tracer gas is

1,1-Difluoroethane, which is present in some brands of dust

cleaner for electronics.

7.8.3.4 Allow 2 hours for the sub-slab vapor conditions to re-

equilibrate prior to sample collection unless site-specific work

plan requires a different equilibration time.

Figure 3: Vapor Pin

installed and ready for sampling

7.9

Vapor Pin

Sample Collection

7.9.1 Remove the rubber cap and attach a piece of ¼” tubing (Teflon™ or

nylon) to the barbed hose adapter. The tubing must be long enough to

span from the sample port to the sample container (e.g., Summa

canister) or system (e.g., lung box for Tedlar

bag).

7.9.2 Refer to site-specific work plan for canister size and type of sample required

(e.g., 6-liter canister with regulator for either 8-hour or 24-hour sample

collection or a 1-liter evacuated canister for a grab sample). After sampling,

use a PID to measure the VOC concentrations to provide the laboratory with

an indication of how concentrated the VOCs may be in the sample. Provide

this information to the laboratory. Note: this number is not contaminant

specific. Do not assume that your contaminant of concern equates to the

reading from the PID.

7.10

Vapor Port Decommissioning

Remove the vapor pin

according to the attached Cox-Colvin Vapor Pin

Standard Operating Procedure for proper vapor pin

installation and removal.

7.10.1 Prior to filling the vapor port hole, measure the slab thickness. One method

is to use a “hole hook”, a section of rigid wire (such as a stiff-wire coat

hanger) with a small (0.25-inch) 90-degree crimp at one end. Insert the

hole hook inside the drilled hole and catch the hooked end on the underside

of the concrete slab. Mark the wire where it meets the top of the slab,

remove the hole hook, and measure the distance between the hooked end

and marked end of the wire to determine the slab thickness. Record the

measured slab thickness on the log sheet or in a field note book. This

information is necessary if a sub-slab treatment system is ever installed.

7.10.2 Gently pour dry granular bentonite into the hole to fill any void space in the

gravel or soil below the underside of the slab that may have been created

during the drilling of the slab or installation of the vapor port. Continue

adding bentonite until the level is approximately one inch below the top of

the slab.

7.10.3 Slowly add a small amount of water to hydrate the bentonite without

creating a column of standing water in the hole. Use of a flashlight when

adding water helps to visually determine when the bentonite stops

absorbing water. If too much water is added, use a syringe or absorbent

material (e.g., paper towels) to remove the standing water. While adding

water, try to wet the hole side walls to help create good contact with the

floor tile grout that will be used to fill and seal the hole as described below.

7.10.4 Mix approximately ¼ cup of floor tile grout with a small amount of water

using a disposable spoon. Add water until the consistency of the grout

mixture is a little stiffer than drywall or spackling compound.

7.10.5 Use a plastic knife, putty knife, tongue depressor or similar tool to add the

tile grout mixture to the hole until it is completely full. Use a concrete trowel

or similar tool to remove any excess grout and finish the top of the seal so

that it is smooth and even with the surrounding floor.

7.10.6 Clean up the area around the sealed hole and complete any needed field

documentation, including photographs if required.

8.0 Data and Records Management

Refer to FSOP 1.3, Field Documentation.

9.0

Quality Assurance and Quality Control

9.1

Clean Vapor Pins

and sampling ports prior to installation by washing in warm

water with laboratory-grade detergent, followed by rinsing with hot water and then

rinsing with deionized water. Always inspect equipment before use.

9.2

Leak testing should be conducted to document the quality of the sample.

9.3

Photographs of the sampling location and equipment may be required for project

documentation.

9.4

Refer to the data quality objectives (DQOs) provided in the work plan.

10.0 Attachments

Cox-Colvin Standard Operating Procedure, Installation and Extraction of the

Vapor Pin

Vapor Sampling Data Sheet, Sub-Slab and Indoor Air (revised May 2018)

11.0 References

FSOP 1.1, Initial Site Entry

FSOP 1.3, Field Documentation

FSOP 3.1.1, Photoionization Detector

Ohio EPA Standard Safety Operating Procedure SP11-19 (Working Alone)

Ohio EPA Standard Safety Operating Procedure SP14-4 (Confined Space Entry)

Standard Operating Procedure

Installation and Extraction

of the Vapor Pin™

Updated February 27, 2015

Scope:

This standard operating procedure describes

the installation and extraction of the Vapor

Pin™ for use in sub

-slab soil-gas sampling.

Purpose:

The purpose of this procedure is to assure good

quality control in field operations and uniformity

between field personnel in the use

of the

Vapor Pin™ for the collecti

on of sub- slab

soil-gas samples or pressure readings.

Equipment Needed:

•

Assemble

d Vapor Pin™ [Vapor Pin™ and

silicone sleeve(Figure 1)]; Because of sharp

edges, gloves are recommended for sleeve

installation;

•

Hammer drill;

•

5/8-inch (16mm) diameter hammer bit

(Hilti™ TE

-YX 5/8" x 22" (400 mm)

#00206514 or equivalent);

•

1½-inch (38mm) diameter hammer bit

(Hilti™ TE

-YX 1½" x 23" #00293032 or

equivalent) for flush mount applications;

•

¾-inch (19mm) diameter bottle brush;

•

Wet/Dry vacuum with

HEPA

filter

(optional);

• Vapor Pin™ installation/extraction tool;

•

Dead blow hammer;

•

Vapor Pin™ flu

sh mount cover, if desired;

• Vapor Pin™ drilling guide, if desired;

• Vapor Pin™ protective cap; and

•

VOC-free hole patching

material

(hydraulic cement) and putty knife or

trowel for repairing the hole following the

extraction of the Vapo

r Pin™.

Figure 1.

Assembled Vapor Pin

Installation Procedure:

Check for buried obstacles (pipes,

electrical lines, etc.) prior to proceeding.

Set up wet/dry vacuum to collect drill

cuttings.

If a flush mount installation is required, drill

a 1½-inch (38mm) diameter hole at least

1¾-inches (45mm) into the slab.

Use of a

Vapor Pin™ drilling guide is

recommended.

Drill a 5/8-inch (16mm) diameter hole

through the slab and approximately 1-

inch (25mm) into the underlying soil to

form a void.

Remove the drill bit, brush the hole with

the bottle brush, and remove the loose

cuttings with the vacuum.

Vapor Pin

protected under US Patent # 8,220,347 B2

Cox-Colvin & Associates, Inc. • 7750 Corporate Blvd., Plain City, Ohio 43064 • (614) 526-2040 • VaporPin.CoxColvin.com

Standard Operating Procedure

Installation and Removal of the Vapor Pin™

Updated February 27, 2015

Page

ace the lower end of Vapor Pin™

assembly into the drilled hole. Place the

small hole located in the handle of the

installation/extraction tool over the Vapor

Pin™ to protect the barb fitting,

and tap

the Vapor Pin™ into place using a dead

blow hammer (Figure 2). Make sure the

installation/extraction tool is aligned

parallel to the Vapor Pin™ to avoid

damaging the barb fitting.

Figure 2.

Installing the Vapor Pin

During installation, the silicone sleeve will form

a slight bulge between the slab and the

Vapor

Pin™ shoulder. Place the

protective cap on

Vapor Pin™ to prevent vapor

loss prior to

sampling (Figure 3).

Figure 3

. Installed Vapor Pin

For flush mount installations, cover the

Vapo

r Pin™ with a flush mount cover,

using either the plastic cover or the optional

stainless-steel Secure Cover (Figure 4).

Figure 4

. Secure Cover Installed

Allow 20 minutes or more (consult

applicable guidance for your situation)

for the sub-slab soil-gas conditions to re-

equilibrate prior to sampling.

Remove protective cap and connect

sample tubing to the barb fitting of the

Vapor Pin™

. This connection can be made

using a short piece of Tygon

tubing to join

the Vapor Pin

with the Nylaflow tubing

(Figure 5). Put the Nylaflow tubing as

close to the Vapor Pin as possible to

minimize contact between soil gas and

Tygon

tubing.

Vapor Pin

protected under US Patent # 8,220,347 B2

Cox-Colvin & Associates, Inc. • 7750 Corporate Blvd., Plain City, Ohio 43064 • (614) 526-2040 • VaporPin.CoxColvin.com

Standard Operating Procedure

Installation and Removal of the Vapor Pin™

Updated February 27, 2015

Page

Figure 5.

Vapor Pin

sample connection.

10)

Conduct leak tests in accordance with

applicable guidance. If the method of leak

testing is not specified, an alternative can

be the use of a water dam and vacuum

pump, as described in SOP Leak Testing

the Vapor Pin

via Mechanical Means

(Figure 6). For flush-mount installations,

distilled water can be poured directly into

the 1 1/2 inch (38mm) hole.

Figure 6.

Water dam used for leak detection

11)

Collect sub-slab soil gas sample or

pressure reading. When finished, replace

the protective cap and flush mount cover

until the next event. If the sampling is

complete, extract the Vapor Pin™.

Extraction Procedure:

Remove the protective cap, and thread the

installation/extraction tool onto the barrel

the Vapor Pin™ (Figure 7

). Continue

turning the tool clockwise to pull the Vapo

Pin™ from the hole

into the

installation/extraction tool.

Fill the void with hydraulic cement and

smooth with a trowel or putty knife.

Figure 7.

Removing the Vapor Pin

Prior to reuse, remove the silicone sleeve

and protective cap and discard.

Decontaminate the Vapor Pin™ in a hot

water and Alconox® wash, then heat in an

oven to a temperature of 265

F (130

C) for 15 to 30 minutes.

The Vapor Pin™

to designed be used

repeatedly, however, replacement parts and

supplies will be required periodically. These

parts are available on-line at

VaporPin.CoxColvin.com.

Vapor Pin

protected under US Patent # 8,220,347 B2

Cox-Colvin & Associates, Inc. • 7750 Corporate Blvd., Plain City, Ohio 43064 • (614) 526-2040 • VaporPin.CoxColvin.com

VAPOR SAMPLING DATA SHEET: SUB-SLAB AND INDOOR AIR

General Information

Site Name / Address:

Sampling Location / Address:

(if other than site address)

Contact Name: Phone:

Laboratory & Analytical Method: Method of Delivery: _

(Courier, UPS, delivered by sampler, etc.)

Sampling Team Members:

Met with resident/business on (date) to provide information on VOC inventory and sampling

cross-contamination concerns. If not, explain why:

Indoor Air Samples

Sample ID #: Canister ID #: Regulator ID #

Start: Date: Time: Initial canister vacuum: mm Hg

End: Date: Time: Final canister vacuum: mm Hg

Regulator Calibrated for: 8 hr 24 hr grab (no regulator)

Canister/ Regulator Leak Checked: Yes No

Sub-Slab Samples

Sample ID #: Canister ID #: Regulator ID # Size of

canister: Thickness of sub-slab (inches) Port install time:

Sampling Start: Date: Time: Initial canister vacuum: mm Hg

Sampling End: Date: Time: Final canister vacuum: mm Hg

Regulator Calibrated for: 8 hr 24 hr grab (no regulator)

Canister/ Regulator Leak Checked: Yes No Sub-Slab Port Leak Checked: Yes No

Type of sub-slab port: Swagelok Vapor Pin

Sub-Slab Port Installed by: _ Sub-Slab Port Sealed: Yes No

PID Reading: VOC ppb % 02 PID ID#:

NOTES: (sampler/canister problems, other significant sampling details, or FSOP deviations)

Note: If a diagram of the sample location(s) is sketched on the back of this data sheet, check here

Procedures for Collection of Indoor Air FSOP 2.4.3

(March 9, 2017)

Ohio EPA Division of Environmental Response and Revitalization

1.0 Scope and Applicability

Indoor air samples investigate air quality within buildings for possible vapor intrusion of

volatile organic compounds (VOCs) and other volatile chemicals. Samples are collected

from locations within buildings and structures that are occupied on a regular and on- going

basis to evaluate potential exposure to VOCs. Analysis of the air samples are typically

performed using U.S. EPA Method TO-15.

2.0 Definitions

“Summa

Canister”, a genericized trademark that refers to electropolished, passivated

stainless steel vacuum sampling devices (i.e., evacuated canister). Sizes of canisters will

vary with the most commonly used sizes being 6L and 1L. Canister size will depend on

the predetermined time-frame for sampling (e.g., 24-hour v. “grab” sampling). A “Silco”

canister is another name for a Summa canister.

3.0

Health and Safety Considerations

3.1

This activity involves accessing private residences and spaces in commercial

buildings. Follow Ohio EPA Standard Safety Operating Procedure Number

SP11-19 (Working Alone) to determine if working alone is appropriate given the

site conditions and circumstances.

3.2

Never enter an OSHA-defined confined space for any reason. Only Ohio EPA

Office of Special Investigation (OSI) staff or other appropriately trained staff are

qualified to enter confined spaces for reconnaissance or sampling activities, and

will perform such work as necessary in accordance with Ohio EPA Standard

Safety Operating Procedure Number SP14-4 (Confined Space Entry).

3.3

Follow the site-specific health and safety plan (HASP), which should identify the

potential presence of asbestos-containing materials and other building-specific

health and safety concerns. If a site-specific HASP is not available, follow the

health and safety procedures in FSOP 1.1, Initial Site Entry.

3.4

Be aware of potential vermin (fleas, rats, etc.)

3.5

Review available plans or documents before selecting sampling locations.

4.0

Procedure Cautions

4.1

Review the site-specific work plan (SSWP), which should include a description of

the building’s size and use. In certain emergency circumstances a SSWP may

not be available, and all necessary information for indoor air sampling will need to

be obtained during the pre-sampling visit as described below.

4.2

A pre-sampling site visit should be conducted to meet with the building’s owner

and/or tenant and inspect the proposed indoor air sampling locations. During the

pre-sampling visit, address arrangements for sampling location access and

associated logistical concerns. Also, determine if the sampling areas are

occupied or unoccupied spaces. Obtain property access agreements prior to

sampling.

4.3

Sampling personnel should not handle hazardous substances (such as gasoline),

permanent marking pens, wear/apply fragrances, or smoke before and/or during

the sampling event.

4.4

Care should be taken to ensure that the flow regulator is pre-calibrated to the

appropriate sample collection time (8 hours, 24 hours, etc.). Eight (8) hour

sample collection is utilized for commercial/industrial settings. Twenty-four (24)

hour sample collection is used for residential and/or sensitive receptor settings

(e.g., day care facilities).

4.5

The flow regulator must be correctly connected to the sample canister to

eliminate the potential for leaks.

4.6

The regulator should be closed shortly before the actual sampling time is

completed so that a small amount of vacuum remains. If it isn’t closed and no

vacuum remains in the canister, extracting a sample for analysis may be very

difficult. In addition, sample integrity may be compromised if the canister reaches

atmospheric pressure.

4.7

An interview of the building occupants should be conducted before sampling to

determine if there are any potential chemicals present that could cause false

positives during sample collection. For example, paints, woodworking products,

household solvents and various chemicals used in hobbies may all contain VOCs

that could be detected. If possible, the building occupants should remove such

products several days before sampling takes place. A copy of Instructions for

Building Occupants Prior to Indoor Air Sampling Form (attached) should be

provided to the resident during the interview.

4.8

If sub-slab samples are to be collected from the same building that indoor air

samples are being collected, it is preferable to complete the indoor air sampling

prior to installing a sub-slab vapor port (FSOP 2.4.2, Construction, Installation

and Decommissioning of Sub-Slab Vapor Ports). However, if site-specific

reasons (e.g., access or emergency conditions, etc.) dictate the need to collect

both samples at the same time, care needs to be taken to install the sub-slab

vapor port before beginning the indoor air sampling. In addition, the indoor air

sample should be taken as far as possible from the location where the sub-slab

vapor point is installed.

4.9

Indoor air samples should only be collected from the first floor/ground-level floor

of the structure.

5.0 Personnel Qualifications

Ohio EPA personnel working at sites that fall under the scope of OSHA’s hazardous waste

operations and emergency response standard (29 CFR 1910.120) must meet the

training requirements described in that standard. Prior knowledge, training and

experience with this sampling technique is strongly recommended before collecting

samples.

6.0

Equipment and Supplies

6.1

Stainless steel canister(s) (request at least one additional canister as a backup).

A 6L canister will be required for this sampling activity. A 1L “grab sample”

canister will not provide enough volume to sample for a timed (8 hr. or 24 hr.)

sample period, refer to Section 2.0 (Definitions).

6.2

Flow regulator(s) properly calibrated for the specific sample collection duration –

8 hr. or 24 hr. (request at least one extra regulator as a back-up)

6.3

In-line filters, if needed (e.g., for SVOC volatile compounds)

6.4

Open-end wrenches, typically 9/16” (two wrenches are recommended to tighten

the fitting in two directions at the same time)

6.5

PID (refer to FSOP 3.1.1, Photoionization Detector)

6.6

Indoor Air Building Survey and Sampling Form (attached)

6.7

Instructions for Building Occupants Prior to Indoor Air Sampling Form (attached)

6.8

Vapor Sampling Data Sheet (attached)

6.9

Field documentation supplies and equipment, including pens, markers, field log

book and additional data sheets, chain-of-custody forms, camera

7.0

Procedures

7.1

Sample Location Determination

7.1.1

Conduct a building/structure survey using the Indoor Air Building Survey

and Sampling Form to determine potential target receptors and identify

potential interferences to sample collection. PID screening may also help

to identify VOC sampling interferences. In addition, provide the

Instructions for Building Occupants Prior to Indoor Air Sampling Form to

the building residents or worker for completion at this time. Potential

sampling interferences need to be recognized and eliminated before

sample collection begins. This should be completed at least 48 to 72 hours

prior to sample collection.

7.1.2

Select indoor air sampling locations that are in inhabited or frequently

used.

7.1.3

Do not place sample canisters in locations near primary-use doors or

open windows.

7.1.4

Do not place sample canisters in the pathway of indoor fans.

7.1.5

If ceiling fans are in use, request that they be turned off for the duration of

the sample period.

7.1.6

Note any obvious odors from scented candles, mothballs, cleaning

products, gas or oils.

7.1.7

If the building has a dirt basement or crawl space, evaluate whether or not

an indoor air canister should be placed in this area.

7.2

Sample Set-up

7.2.1

Place the sampling canisters at breathing-zone height.

7.2.2

Remove the brass plug from the canister and connect the flow regulator

(with in-line particulate filter and vacuum gauge, if needed) to the canister.

7.2.3

Gently tighten the connection between the flow regulator and the canister

using the open-end 9/16” wrenches. Do not over-tighten this connection.

Before continuing, record the canister number and the associated flow

regulator number on the “Vapor Sampling Data Sheet”. The canister

number can be used for sample identification on the COC form.

7.2.4

Open the canister/regulator valve. Record the sample start time and the

canister pressure.

7.2.5

Photograph the canister and the surrounding area.

Example of a canister with a regulator attached and placed in the breathing zone.

7.3

Termination of Sample Collection

7.3.1

Return to the sample collection site a minimum of 15 minutes before the

end of the sample collection interval. Examine the flow regulator to

ensure that some vacuum is left on the gauge (preferably 2” to 10” of

mercury on the regulator flow dial).

7.3.2

Record the vacuum pressure and stop sample collection by closing the

flow regulator.

7.3.3

Remove the flow regulator from the canister using the 9/16” open-end

wrenches. Re-install the brass plug on the canister fitting, and tighten it

with an open-ended wrench.

7.3.4

Package the canister and the flow regulator into the shipping container

provided by the lab. Note: the canister does not require preservation.

7.3.5

Complete the appropriate forms and sample labels as directed by the

laboratory. Use the sample start time when completing the laboratory

chain of custody and double check canister identification numbers for

accuracy.

7.3.6

Ship the canisters to the laboratory for analysis.

8.0 Data and Records Management

Refer to FSOP 1.3, Field Documentation.

9.0 Quality Assurance and Quality Control

Usually, an ambient air sample is collected outside of the building where the indoor air is

being sampled. The ambient air sample is collected at the same time as the indoor air

sample and provides quality assurance/quality control (QA/QC) to help evaluate outdoor

air quality. In addition, the work plan may specify co-located indoor air samples.

Typically, the co-located QA/QC samples are collected at a frequency of 10 percent of

the total samples collected.

10.0 Attachments

Indoor Air Building Survey and Sampling Form

Instructions for Building Occupants Prior to Indoor Air Sampling Vapor

Sampling Data Sheet

11.0 References

FSOP 1.1, Initial Site Entry

FSOP 1.3, Field Documentation

FSOP 2.4.2, Construction, Installation and Decommissioning of Sub-Slab Vapor Ports

FSOP 3.1.1, Photoionization Detector

Ohio EPA Standard Safety Operating Procedure SP11-19 (Working Alone)

Ohio EPA Standard Safety Operating Procedure SP14-4 (Confined Space Entry)

INDOOR AIR BUILDING SURVEY

and SAMPLING FORM

Preparer’s name:

Preparer’s affiliation:

Date:

Phone #:

Site Name:

Part I - Occupants

Case #:

Building Address:

Property Contact: Owner / Renter / other:

Contact’s Phone: home ( ) work ( ) cell ( )

# of Building occupants: Children under age 13

Part II – Building Characteristics

Children age 13-18 Adults

Building type: residential / multi-family residential / office / strip mall / commercial / industrial

Describe building: Year constructed:

Sensitive population: day care / nursing home / hospital / school / other (specify):

Number of floors below grade: (full basement / crawl space / slab on grade)

Number of floors at or above grade:

Depth of basement below grade surface: ft. Basement size: ft

Basement floor construction: concrete / dirt / floating / stone / other (specify):

Foundation walls: poured concrete / cinder blocks / stone / other (specify)

Basement sump present? Yes / No Sump pump? Yes / No Water in sump? Yes / No

Type of heating system (circle all that apply):

hot air circulation hot air radiation wood steam radiation

heat pump hot water radiation kerosene heater electric baseboard

other (specify):

Type of ventilation system (circle all that apply):

I-1

100

central air conditioning mechanical fans bathroom ventilation fans individual air

conditioning units kitchen range hood fan outside air intake

other (specify):

Type of fuel utilized (circle all that apply):

Natural gas / electric / fuel oil / wood / coal / solar / kerosene

Are the basement walls or floor sealed with waterproof paint or epoxy coatings? Yes / No

Is there a whole house fan? Yes / No

Septic system? Yes / Yes (but not used) / No

Irrigation/private well? Yes / Yes (but not used) / No

Type of ground cover outside of building: grass / concrete / asphalt / other (specify)

Existing subsurface depressurization (radon) system in place? Yes / No active / passive

Sub-slab vapor/moisture barrier in place? Yes / No

Type of barrier:

Part III - Outside Contaminant Sources

Potential contaminated site (1000-ft. radius):

Other stationary sources nearby (gas stations, emission stacks, etc.):

Heavy vehicular traffic nearby (or other mobile sources):

Part IV – Indoor Contaminant Sources

Identify all potential indoor sources found in the building (including attached garages), the location of the source (floor

and room), and whether the item was removed from the building 48 hours prior to indoor air sampling event. Any

ventilation implemented after removal of the items should be completed at least 24 hours prior to the commencement of

the indoor air sampling event.

Potential Sources

Location(s)

Removed

(Yes / No / NA)

Gasoline storage cans

Gas-powered equipment

Kerosene storage cans

Paints / thinners / strippers

Cleaning solvents

Oven cleaners

Carpet / upholstery cleaners

Other house cleaning products

Moth balls

Polishes / waxes

Insecticides

Furniture / floor polish

Nail polish / polish remover

Hairspray

Cologne / perfume

Air fresheners

Fuel tank (inside building)

I-2

101

Wood stove or fireplace

New furniture / upholstery

New carpeting / flooring

Hobbies - glues, paints, etc.

Part V – Miscellaneous Items

Do any occupants of the building smoke? Yes / No How often?

Last time someone smoked in the building? hours / days ago

Does the building have an attached garage directly connected to living space? Yes / No

If so, is a car usually parked in the garage? Yes / No

Are gas-powered equipment or cans of gasoline/fuels stored in the garage? Yes / No

Do the occupants of the building have their clothes dry cleaned? Yes / No

If yes, how often? weekly / monthly / 3-4 times a year

Do any of the occupants use solvents in work? Yes / No

If yes, what types of solvents are used?

If yes, are their clothes washed at work? Yes / No

Have any pesticides/herbicides been applied around the building or in the yard? Yes / No

If so, when and which chemicals?

Has there ever been a fire in the building? Yes / No If yes, when?

Has painting or staining been done in the building in the last 6 months? Yes / No

If yes, when and where?

Has there been any remodeling done (flooring/carpeting) in the building in the last 6 months? Yes / No

If yes, when

Part VI – Sampling Information

and where?

Sample Technician: Phone number: ( ) -

Sample Source: Indoor Air / Sub-Slab / Soil Gas

Sampler Type: Tedlar bag / Sorbent / Stainless Steel Canister / Other (specify):

Analytical Method: TO-15 / TO-17 / other: Cert. Laboratory:

Sample locations (floor, room):

Field ID # -

I-3

102

Field ID # - Field ID # -

Were “Instructions for Occupants” followed? Yes / No

If not, describe modifications:

Additional Comments:

I-4

103

Provide Drawing of Sample Location(s) in Building

Part VII - Meteorological Conditions

Was there significant precipitation within 12 hours prior to (or during) the sampling event? Yes / No

Describe the general weather conditions:

Part VIII – General Observations

Provide any information that may be pertinent to the sampling event and may assist in the data interpretation process.

(NJDEP 1997; NHDES 1998; VDOH 1993; MassDEP 2002; NYSDOH 2005; CalEPA 2005; Ohio EPA 2015)

I-5

104

Instructions for Building Occupants Prior to Indoor Air Sampling

Representatives from the Ohio EPA – Division of Environmental Response and Revitalization (DERR) - will be

collecting one or more indoor air samples from your building on - beginning @ and ending

@ . Your assistance is requested during the sampling program in order to collect an indoor air sample

that is both representative of indoor conditions and avoids the common background indoor air sources

associated with occupant activities and consumer products.

Please follow the instructions below starting at least 48 hours (2 days) prior to and during the indoor air sampling

event:

❑

Do operate your furnace and whole house air ❑ Do not open windows or keep doors

conditioner as appropriate for the current open

weather conditions ❑ Do not smoke in the building

❑

Do not use wood stoves, fireplaces or ❑ Do not apply pesticides

auxiliary heating equipment

❑

Do not use window air conditioners, fans ❑ Do not use air fresheners or odor or

vents eliminators

❑

Do not use paints or varnishes (up to a week ❑ Do not engage in indoor hobbies that in

advance, if possible) use solvents (e.g. gun cleaning)

❑

Do not use cleaning products (e.g., bathroom ❑ Do not operate gasoline powered

cleaners, furniture polish, appliance cleaners, equipment within the building,

all-purpose cleaners, floor cleaners) attached garage or around the

❑

Do not use hair spray, nail immediate perimeter of the building

polish remover, perfume, etc. ❑ Do not bring freshly dry cleaned

❑

Do not store containers of gasoline, oil or solvents clothes into the building

within an attached garage.

❑

Do not operate or store automobiles within an attached garage

You will be asked a series of questions about the structure, consumer products you store in your building, and occupant

activities typically occurring in the building. These questions are designed to identify “background” sources of indoor air

contamination. While this investigation is looking for a select number of chemicals related to the known or suspected

subsurface contamination, the laboratory will be analyzing the indoor air samples for a wide variety of chemicals. As a result,

chemicals such as tetrachloroethene that is commonly used in dry cleaning or acetone, which is found in nail polish remover

might be detected in your sample results.

Your cooperation is greatly appreciated. If you have any questions about these instructions, please feel free to

contact at .

105

SUB-SLAB VAPOR SAMPLING AND

INDOOR AIR DATA SHEET

General Information

Site Name / Address:

Sampling Location / Address:

(if other than site address)

Contact Name: Phone:

Laboratory & Analytical Method: Method of Delivery:

(Courier, UPS, delivered by sampler, etc.)

Sampling Team Members:

Met with resident/business on (date) to provide information on VOC inventory and sampling

cross-contamination concerns. If not, explain why:

Indoor Air Samples

Sample ID #: Canister ID #: Regulator ID #

Start: Date: Time: Initial canister vacuum: mm Hg

End: Date: Time: Final canister vacuum: mm Hg

Regulator Calibrated for: 8 hr 24 hr grab (no regulator)

Canister/ Regulator Leak Checked: Yes No

Sub-Slab Samples

Sample ID #: Canister ID #: Regulator ID # Size of

canister: Thickness of sub-slab (inches) Port install time:

Sampling Start: Date: Time: Initial canister vacuum: mm Hg

Sampling End: Date: Time: Final canister vacuum: mm Hg

Regulator Calibrated for: 8 hr 24 hr grab (no regulator)

Canister/ Regulator Leak Checked: Yes No Sub-Slab Port Leak Checked: Yes No

Type of sub-slab port: Swagelok Vapor Pin

Sub-Slab Port Installed by: Sub-Slab Port Sealed: Yes No

PID Reading: VOC ppb % 02 PID ID#:

NOTES: (sampler/canister problems, other significant sampling details, or FSOP deviations)

Note: If a diagram of the sample location(s) is sketched on the back of this data sheet, check here

106

APPENDIX D. Soil Gas Probe Field Data Report Form

Ohio Environmental Protection Agency

Division of Emergency and Remedial Response

Soil Gas Probe Field Data Report Form

Soil Gas Probe Field Data Report

Site:

Date:

Instrument(s) used:

Tracer used:

Weather:

Technician:

Soil

Gas

Probe

Number

Probe

Depth

(ft.)

Probe

Volume

(l)

Purge

Rate

(lpm)

Volume

Purged

(l)

Tracer

Field

Analysis

(ppmv or

ppbv)

%CO

Other

indicators

ND=Non-Detect

NM=Not Measured

107

APPENDIX E. Indoor Air/Sub-Slab Sampling Form

Ohio Environmental Protection Agency

Division of Emergency and Remedial Response

Indoor Air/Sub-slab Sampling Form

OHIO EPA DERR Site #______________________________________

Site Name_____________________________________________________________

Address_______________________________________________________________

_______________________________________________________________

Occupant Information

Name_________________________________________________________________

Address_______________________________________________________________

_______________________________________________________________

Telephone No:

(H) (____)_______________________________________________

(W) (____)_______________________________________________

Number and Age(s) of Occupant(s)

______________________________________________________________________

Does anyone smoke inside the building?

Building Characteristics

Type of building (circle):

Residential / Industrial / School / Commercial / Multi-use / Other?

108

If residential, what type (circle):

Single family / Condo / Multi-family / Other?

If commercial, what is the business?

How many floors does the building have?

Does the building have a (circle):

Basement / Crawl space / Slab-on-grade / Other?

Is the basement used as a living / workspace area?

What type of foundation does the building have (circle):

Field stone / Poured concrete / Concrete block / Other?_____________

Describe the heating system and type of fuel used.

Is there an attached garage?

Spill / Contaminant Source Information

Type of petroleum / VOC release?

When did the release occur?

What areas of the building have been impacted by the release?

Are there any odors? ___________ If so, describe the odors:

Where are the release odors found?

Sampling Information

Sampling Date

Sampler Type (circle):

Sorbent Canister Tedlar

Other__________

Analysis Method ____________________

109

Consulting Firm _________________________________________________________

Contact Person Name___________________________________________________

Contact Person Telephone No (____)_______________________________________

Laboratory Name ______________________________________________________

Laboratory Telephone No (____)___________________________________________

Table 1: Sorbent Tube Sample Information

Sample

ID#

Floor

Room

Tube

ID #

Pump

ID #

Volume

(liters)

Duration

(minutes)

Comments

110

Table 2: Canister Sample Information

Sample

ID #

Floor

Room

Canister

ID #

Initial On-

site

Pressure*

Pressure* On-

site Following

Sample

Collection

Pressure

Received at

the Laboratory

* Indicate pressure in units of inches of mercury.

Please provide a sketch of area and location of sampler unit(s), include all pertinent

structures.

Pre-Sampling Inspection and Product Inventory

List products or items which may be considered potential sources of VOCs such as

paint cans, gasoline cans, gasoline powered equipment, cleaning solvents, furniture

polish, moth balls, fuel tank, woodstove, fireplace, etc.

Date and time of pre-sampling inspection

111

Table 3: Pre-sampling Inspection Product Inventory

Potential VOC

Source

Present

(Y / N)

Location

Field screening

Results (ppm)

Product

Condition

Paints or paint

thinners

Gas powered

equipment

Gasoline storage

cans

Furniture polish

Moth balls

Fuel tank

Wood stove

Fireplace

Perfumes/colognes

Other:

112

Table 4: Potential vapor migration entry point information

Potential Vapor entry points

Present

(Yes/No)

Field screening results

(ppm)

Comments

Foundation penetrations in

floor or walls

Cracks in foundation floor or

walls

Sump

Floor drain

Other

Was the building aired out prior to sample collection?

How long was the airing out process?

Were vapor control methods in effect while the samples were being collected?

Windows open? Yes / No Ventilation fans? Yes / No

Vapor barriers? Yes / No

Vapor phase carbon treatment system? Yes / No

Other site control measures_________________________________

Weather Conditions during Sampling

Outside temperature (

F) __________ Inside temperature (

F)_____________

Prevailing wind speed and direction

Describe the general weather conditions (e.g., sunny, cloudy, rainy)

Significant precipitation (0.1 inches or more) within 12 hours of the sampling event?

General Comments

Is there any information you feel is important related to this site and the samples

collected which would facilitate an accurate interpretation of the indoor air quality?

113

APPENDIX F. Soil Gas and Sub-Slab Vapor Analytical Methods and Reporting Limit

Ranges

A list of several analytical methods and reporting limit ranges for soil gas and

sub-slab vapor samples.

NOTE: The laboratory should be consulted prior to choosing the analytical

method. The laboratory can advise sampler on holding times and any method

specific requirements.

Method

No.

Examples of Collection

Device

and Methodology

Type of

Compounds

Reporting Limit

Range**

TO-1

Tenax solid sorbent

GC/MS or GC/FID

VOC

0.02 – 200 µg/m

(0.01-100 ppbv)

TO-2

Molecular sieve sorbent

GC/MS

VOC

0.2 – 400 µg/m

(0.1-200 ppbv)

TO-3

Tedlar

bag or canister

GC/FID

BTEX, MTBE,

TPH

1-3 µg/m

TO-4A*

Filter media

GC/ECD

Pesticides

PCBs

Pesticides (0.5 - 1

µg/sample)

PCBs (1 – 2

µg/sample)

TO9A

Filters designed for

PCB collection

High resolution GC/MS

Mono/Di-PCBs

Contact lab

TO-10A*

Filter media

GC/ECD

Pesticides

PCBs

Pesticides (0.5 - 1

µg/sample)

PCBs (1 – 2

µg/sample)

TO-13A*

Polyurethane foam

(PUF)

GC/MS

SVOCs

5-10 µg/ sample

TO-13A

SIM*

PUF or XAD-2 resin

media

GC/MS

Low Level

SVOCs

0.5-1 µg/sample

TO-14A

Canister / Tedlar

bag

GC/ECD/FID or GC/MS

Non-polar

VOCs

1-3 µg/m

TO14A

Silica lined

canisters/Tedlar

bag/sorbent media

Contact lab

114

A list of several analytical methods and reporting limit ranges for soil gas and

sub-slab vapor samples.

NOTE: The laboratory should be consulted prior to choosing the analytical

method. The laboratory can advise sampler on holding times and any method

specific requirements.

Method

No.

Examples of Collection

Device

and Methodology

Type of

Compounds

Reporting Limit

Range**

TO-15

Canister / Tedlar® Bags

GC/MS

VOC

(polar/nonpolar)

0.4 – 20 µg/m

(0.2-

2.5 ppbv)

TO-15

Silica lined

canisters/Tedlar

bag/sorbent media

Contact lab

TO-15

Canister / Tedlar

bag

GC/FID

TPH – Alkanes

(C4-C12)

0.1 ppmv

TO-15

SIM

Canister / Tedlar

bag

GC/MS

Low level

VOCs

0.011-0.5 µg/m

TO-17*

Sorbent tube (chilled)

GC/MS

VOCs

1-3 µg/m

8021B

modified

Syringe / Tedlar

bag /

Canister/ glass vial

GC/PID

VOC

1 – 60 µg/m

8260D

modified

Syringe / Tedlar

bag /

Canister / glass vial

GC/MS

VOC

50 – 100 µg/m

8270E

Tedlar

bag / Canister

GC/MS

SVOC

1000 µg/m

(20,000

ppbv to 100,000

ppbv)

8015

modified

Tedlar bag / canister

GC/FID

TPH – alkanes

(C4-C24)

10 ppmv

Air Toxics

IO-5

Gold trap

Dual amalgamation

cold vapor atomic

fluorescence

spectrometry (CVAFS)

Contact lab

NIOSH

6009

Hopcalite

cold vapor / Atomic

Absorption (CV/AA)

Contact lab

9056

Silica lined canisters /

Tedlar® Bag / sorbent

media

Contact lab

115

A list of several analytical methods and reporting limit ranges for soil gas and

sub-slab vapor samples.

NOTE: The laboratory should be consulted prior to choosing the analytical

method. The laboratory can advise sampler on holding times and any method

specific requirements.

Method

No.

Examples of Collection

Device

and Methodology

Type of

Compounds

Reporting Limit

Range**

1668A

Filters designed for

PCB collection

High resolution GC/MS

Mono/Di-PCBs

Contact lab

U.S. EPA

Tedlar

bag / Canister

GC / FID

Methane

nitrogen,

oxygen, carbon

dioxide, carbon

monoxide

10 ppmv

0.1% (1,000 ppmv)

ASTM D-

1946

Tedlar

bag/ canister

GC / TCD / FID

Methane,

nitrogen,

oxygen carbon

dioxide, carbon

monoxide

1000 – 2000 µg/m

ASTM D-

1945

Tedlar

bag / canister

GC / FID

Natural gases

1000-2000 µg/m

NOTE: the laboratory should be consulted prior to choosing the analytical method. The

laboratory can advise sampler on holding times and any method specific requirements.

* The indicated methods use a sorbent-based sampling technique. The detection limits

will depend on the amount of air passed through the media.

** Reporting limits are compound specific and can depend upon the sample collection

and the nature of the sample. Detection limits shown are for the range of compounds.

Consult laboratory for specific information.

ECD – electron capture detector; FID – flame ionization detector; GS – gas

chromatography; MS – mass spectrometry; PID – Photoionization detector; TCD –

thermal conductivity detector

High volume collection (may require large sample volume; e.g., 300 m

)/ chilled 4

116

APPENDIX G. Comparison of Tubing Type to Vapor Absorption

Researcher

Tubing

Ouellette

(2004)

Hayes,

et. al.

(2006)

Nicholson, et.

al. (2007)

Hartman

(2008)

LDPE

Sorption of

hexane and

pentane

Sorption of

numerous

compounds

N/A*

Sorption of

TCE and PCE

Tygon

Sorption of

hexane,

butane, and

pentane

N/A

Acceptable for

TCE

Nylaflow

Acceptable

Sorption of

naphthalene

and 1,2,4-

TCB

Sorption of

aromatic

hydrocarbons

Acceptable for

TCE

Teflon

Acceptable

N/A

Acceptable for

TCE

Vinyl

Sorption of

hexane and

pentane

N/A

PEEK

N/A

Acceptable

N/A

Acceptable for

TCE

Copper

N/A

Sorption of

TCE and PCE

*N/A – not analyzed