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Vapor Intrusion

Site Investigation Tools

Figure 1. Example conceptual Site Model (<a href='/download/issues/vi/VI-Tech-Guide-2015.pdf' target='_blank'>EPA, 2015</a>).

Figure 1. Example conceptual Site Model (EPA, 2015).

There are many tools available to environmental practitioners for investigating a site for vapor intrusion. As with any site investigation, an important early step is to develop a conceptual site model (CSM)1. One critical element of the CSM is an understanding of the type of volatile chemical that has been released into the subsurface. Some types of chemicals, such as petroleum hydrocarbons, degrade rapidly under aerobic conditions in the vadose zone, limiting the potential for vapor intrusion. Thus, the type of chemical present should inform the investigation strategy (ITRC, 2014 and EPA, 2015).

EPA's 2015 Vapor Intrusion Technical Guide recommends that the planning and data review team develop an initial CSM for vapor intrusion when the preliminary analysis indicates the presence of subsurface contamination with vapor-forming chemicals underlying or near buildings (Figure 1). This CSM is used to guide planning and scoping of the investigation and is updated and refined as additional information and insights are generated.

The vapor intrusion pathway is generally assessed by collecting, weighing, and evaluating multiple lines of evidence (e.g., hydrogeologic information in addition to soil, groundwater or vapor sampling data). Predictive modeling can be used to develop not only the CSM but also to plan appropriate sampling. Building design should be evaluated to determine how it affects the potential for vapor intrusion and vapor intrusion pathways. Click on the following sections for summaries of different lines of evidence for vapor intrusion and resources for further information:

Figure 2. Trace Atomospheric Gas Analyzer (TAGA) Mobile Laboratory (<a href='https://response.epa.gov/sites/3806/files/EPA Region 5 Vapor Intrusion Handbook.pdf' target='_blank'>U.S. EPA Region 5, 2020</a>).

Figure 2. Trace Atomospheric Gas Analyzer (TAGA) Mobile Laboratory (U.S. EPA Region 5, 2020).

Sample collection for chemical analysis is the primary way in which a CSM is augmented and refined with site-specific data. Sampling may be needed to refine the understanding of the source and extent of contamination, as well as possible receptors and risk levels. The use of real-time analysis can expedite the investigation of vapor intrusion at a site. Figure 2 shows EPA's Trace Atmospheric Gas Analyzer (TAGA) mobile lab deployed in the field. Other commercial available portable gas chromatographs/mass spectrometers also provide the same capabilities (EPA Region V, 2020). Sampling may also help evaluate the amount of contamination present beneath the floor or foundation or inside a particular building. Table G-5 of ITRC's 2014 Petroleum Vapor Intrusion guide provides a matrix of measurement approaches and their appropriateness for evaluating vapor intrusion in different circumstances. The investigation toolbox in Appendix G was developed for both petroleum and non-petroleum vapor intrusion assessments. Table G-6 evaluates the advantages/disadvantages of investigative strategies. The strategies discussed here include:

Groundwater Sampling

Contaminated groundwater may serve as a source for vapor intrusion into commercial and residential buildings. It is important to identify which groundwater contaminants are most likely to partition into a vapor phase that could potentially migrate into overlying structures. Section 6.3.1 of the EPA's 2015 Vapor Intrusion Technical Guide contains recommendations for characterizing groundwater plumes so that representative vapor source concentrations can be determined. Characterizing water table concentrations is key. To that end, the EPA recommends that groundwater samples be obtained from wells with short, screened intervals that span the water table. For additional information on various groundwater sampling methods and their associated pros and cons, see the Interstate Technology & Regulatory Council (ITRC) 's 2014 Petroleum Vapor Intrusion: Fundamentals of Screening, Investigation and Mitigation, Table G-1 Groundwater Sampling Methods for Vapor Intrusion Investigations.

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Soil Gas Sampling

Figure 3. Advancing a Soil Gas Probe (<a href='https://response.epa.gov/sites/3806/files/EPA Region 5 Vapor Intrusion Handbook.pdf' target='_blank'>U.S. EPA Region 5, 2020</a>).

Figure 3. Advancing a Soil Gas Probe (U.S. EPA Region 5, 2020).

Soil gas samples are collected in the area of concern to determine the nature and extent of vapor contamination in the vadose zone. Figure 3 shows a soil gas probe being used to collect data near the foundation of a structure. Soil gas data can also help in the design and performance monitoring of soil vapor extraction systems. Soil gas surveys can employ either active2 or passive3 soil gas sampling techniques. Soil gas sampling methods are available from a variety of sources (e.g., EPA Region 5, 2020, ITRC 2014, and state-specific guidance). If vapor contamination is present, further characterization of nearby buildings might be warranted using approaches such as sub-slab soil gas and indoor air sampling.

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Bulk Soil Sampling

Bulk soil sampling is useful in delineating source areas of VOC contamination (nature and extent) and determining the gross mass of contamination present in a source area. However, it is problematic to use bulk soil sampling to assess the potential for vapor intrusion exposure from VOCs in undisturbed soil or residual soil contamination left in an excavation following a removal action. As described in EPA's Challenges in Bulk Soil Sampling and Analysis for Vapor Intrusion Screening of Soil, (2014), the challenges in using bulk soil samples for vapor intrusion exposure calculations include:

  • Volatilization and degradation losses - Significant losses of VOCs can occur during collection of the bulk samples. Samples must be prepared and preserved quickly in the field to limit losses of VOCs. Preservatives, such as methanol, used to prevent volatilization and degradation of the sample are flammable and can be dangerous to transport. A non-field-preservation method uses sampling devices that minimize VOC loss by containing the soil sample in a sealed zero headspace chamber. The sample can be stored up to 48 hours before analysis.
  • Sensitivity of analytical methods - The method detection limits (MDLs) for bulk soil analytical methods when methanol is used as a preservative are typically higher than the calculated soil screening levels for vapor intrusion. In addition, for some VOCs such as trichloroethylene (TCE) and tetrachloroethylene (PCE), which are common vapor intrusion concerns, the non-methanol preservative method still has MDLs above the screening levels for vapor intrusion.
  • Heterogeneity of soil and contaminant distribution - Soil properties such as fraction of organic carbon, porosity and moisture content can exhibit significant heterogeneities (i.e., vary considerably both laterally and with depth at a site). The scale of the heterogeneities may also vary. Additionally, soil moisture may exhibit temporal variability. These variabilities pose challenges when trying to use VOC vapor concentrations from discrete soil samples to estimate large-scale average VOC concentrations.

Bulk sampling is useful for determining the nature and extent of contamination. Field headspace techniques can be employed on bulk soil samples to rapidly determine the presence and concentrations of VOCs with enough precision to identify areas for excavation/removal. Remaining contamination can then be addressed by subsurface remedies that will achieve concentrations below vapor intrusion concentrations of concern. Bulk sampling is unreliable for predicting whether VOC concentrations detected in the soil or groundwater will migrate as vapor into structures (EPA, 2014).

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Sub-Slab Sampling

Figure 4. Advancing a Sub-Slab Soil Gas Probe (<a href='https://response.epa.gov/sites/3806/files/EPA Region 5 Vapor Intrusion Handbook.pdf' target='_blank'>U.S. EPA Region 5, 2020</a>).

Figure 4. Advancing a Sub-Slab Soil Gas Probe (U.S. EPA Region 5, 2020).

In addition to collecting soil gas data from a potential vapor intrusion source, the investigator may want to assess the soil vapor directly beneath a building where there is a concern about indoor air quality. This is done by collecting sub-slab soil vapor samples. Sub-slab sampling is the collection of a soil vapor sample from beneath a building's slab foundation. Sub-slab sampling is typically employed when the CSM and existing data (e.g., groundwater or soil vapor) suggest that vapor intrusion through the foundation may be a concern. A sub-slab soil gas sample is obtained by coring or drilling through the slab to insert a probe (Figure 4). Placement of the probe is targeted to air spaces that have formed beneath the concrete over time or the pore space within the granular material placed below the slab during construction. Sub-slab data may be useful in determining whether the subsurface vapor migration pathway is complete and poses a potential health concern. Additional considerations regarding sub-slab soil gas sampling can be found in EPA's 2015 Vapor Intrusion Technical Guidance.

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Conduit/Utilities Sampling

As part of the vapor intrusion investigation, the site should be evaluated to identify the presence of utilities or conduits that may facilitate vapor transport across the site and potentially into buildings or structures that are serviced by the utilities. A search of public and facility records for as-built diagrams, construction specifications and/or locations of the utilities may be warranted (EPA, 2015).

As in the ESTCP Project ER-201505 report, the following sampling methods may be used to assess the contribution to vapor intrusion in buildings/structures via conduits and utility tunnels:

  • Collect vapor samples from sewer or conduit - If the conduit or sewer has liquid in it, collect a vapor sample by lowering the collection device to within 1 foot of the bottom or the liquid in the conduit, whichever is shallower. Connect a small-diameter nylon tubing to a three-way valve to allow purging of the line and sample collection. After at least three line volumes of vapor are purged, a sample container can be attached for collection of a sample.
  • Collect liquid samples from sewer or conduit - Liquid samples should be collected in the appropriate VOA vials provided by the analytical lab. The same sample protocols for handling groundwater samples apply to liquid samples from the sewer or conduit.
  • Tracer Testing - Research conducted by McHugh, T., et al. (2017) at the EPA vapor intrusion research duplex in Indianapolis, Indiana, demonstrated that tracer testing could be used as a tool to determine whether conduits such as sewer lines are contributing to vapor intrusion into a structure.

Tracers such as perfluorocarbon4 tracers (PFTs) are deployed within the sewer or conduit as sources. Each source emits a different perfluorocarbon compound. Passive samplers are stationed within various locations of the structure to collect data for assessing if and when a particular perfluorocarbon compound (tracer) reaches the sampler. In this way, the vapor intrusion contribution can be "mapped" from different sources such as sewer lines, utility conduits, etc. Data from the tracer test, used in conjunction with sewer liquid and vapor samples, sub-slab vapor samples, indoor air samples and soil gas samples can determine whether sewer lines or other utilities act as conduits for intrusion of contaminant vapors into structures.

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Air Sampling

Air samples are collected to assess whether vapors are present in the building at levels that pose a health risk. Indoor air data can also be used to evaluate the performance of vapor mitigation systems. Interpreting indoor air sampling results can be complicated by indoor and outdoor air sources of VOCs unrelated to the subsurface contaminant source (see EPA, 2015 and EPA, 2011).

Sample collection methods include pressurized (active) and unpressurized (passive) evacuated canisters and active and passive sorbent samplers. Canisters provide the benefit of "whole air" samples (i.e., collection of the vapor phase itself), allowing multiple sub-samples and the ability to analyze for a wide variety of compounds. The canisters are typically left in place for a period of 8 hours in commercial settings and 24 hours in residences (EPA, 2015). Passive sorbent samplers provide the ability to collect time-integrated samples over longer periods, as recommended in EPA's Vapor Intrusion Technical Guidance, in part to reduce the likelihood of obtaining false-negative results (Nocetti, D., et al., 2019). Disadvantages of sorbent samplers include the need to pair the sorbent material with the chemicals of interest, and potentially being limited to only one analysis for each individual device. Additional information regarding indoor air sampling can be found in EPA's Vapor Intrusion Technical Guidance.

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Analytical Methods

Analytical methods used in vapor intrusion site assessment should be capable of achieving detection limits below applicable screening criteria such as the levels identified by EPA's Vapor Intrusion Screening Level Calculator. The calculator provides general risk-based target concentrations for groundwater, near source soil gas and sub-slab soil gas, and indoor air. Table G-5 of ITRC's 2014 Petroleum Vapor Intrusion guide provides a list of parameters and the appropriate associated analytical methods.

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Building design will impact the potential for vapor intrusion to be a complete pathway for human exposure and should be considered in developing and refining the CSM. Appendix C of ITRC's 2007 Vapor Intrusion Pathway: A Practical Guide provides a more detailed discussion of the various factors in building design that can affect the potential for vapor intrusion into buildings. These factors include but are not limited to:

  • Building air exchange.
  • The presence or absence of cracks, seams, gaps in basement floors, walls, or foundations.
  • The presence or absence of openings for utilities in basement floors, walls, or foundations.
  • Whether the building is constructed with a crawl space, basement or is built on a slab on grade.

In addition to building factors, recent research has shown that sanitary sewers, land drains, and utility tunnels can act as preferential pathways for vapor intrusion (e.g., Guo et al 2015, McHugh and Beckley 2018). Sites are typically at higher risk for sewer vapor intrusion if the sewer lines directly intersect subsurface VOC sources. Thus, sewer preferential pathways should be considered during development of the CSM and the investigation program.

Vapor intrusion investigation approaches continue to be developed. Ma et al (2020) summarizes a variety of conventional and innovative methods currently in use. These methods include the following:

High Purge Volume Sub-slab Sampling/Pneumatic Conductivity Testing

Sub-slab soil gas sampling is a common line of evidence in vapor intrusion investigations. However, spatial variability is common and can increase the risk of failing to identify elevated chemical concentrations beneath the building. To overcome this problem, high purge volume sampling can be done to spatially average the sub-slab concentrations and obtain an improved understanding of conditions beneath a given building(McAlary, et al., 2010).

This method can also be applied to support design of mitigation systems. It is analogous to pneumatic testing for soil vapor extraction system pilot tests. Application of suction and measuring the vacuum can be used for pneumatic conductivity testing of subsurface geologic layers. Data from pneumatic testing may be used to determine whether a laterally continuous soil layer acts as a barrier to upward soil vapor transport, or of a building's floor slab to optimize the design of sub-slab depressurization or venting systems.

Meteorological Monitoring

Weather conditions can influence both soil gas and indoor air concentrations of contaminants. Meteorological parameters that may affect soil gas and indoor air concentrations include (ITRC, 2007):

  • Rainfall events - Vapor intrusion rates and concentrations of soil gas can be affected by precipitation. Significant rainfall events may skew data collected during or immediately after the event and, therefore, may not be representative of long-term conditions.
  • High wind speed - Pressure differentials can be created around a structure during high wind events. This can cause an advective flow in shallow soil gas around and beneath the structure.
  • Frozen ground or permafrost - When the ground is frozen, the flow of air into the vadose zone and/or the flow of soil gas out of the vadose zone may be restricted.
  • Major storm events - A process known as barometric pumping can occur due to changes in barometric pressure creating movement in the near surface vadose zone.

Because weather can affect soil gas and indoor air concentrations, meteorological monitoring (and monitoring of building differential pressure) during sample collection can provide another line of evidence for interpretation of vapor intrusion investigation data.

Forensic Approaches

Because indoor sources of VOCs are ubiquitous, it can be difficult to distinguish whether VOCs found in indoor air samples are from indoor sources or the subsurface (i.e., vapor intrusion). Several innovative methods are now available to help differentiate the chemical profiles of subsurface sources (i.e., groundwater, soil gas) and indoor air samples. Forensic approaches include hydrocarbon fingerprinting and forensic analysis, CSIA (compound-specific isotope analysis), on-site chemical analysis, and the use of radon as a tracer (NAVFAC, 2013; Ma et al 2020).

Guo, Y., et al., 2015. Identification of Alternative Vapor Intrusion Pathways Using Controlled Pressure Testing, Soil Gas Monitoring, and Screening Model Calculations. Environmental Science &Technology, 49:22, p. 13472-13482, October 12.

Interstate Technology Regulatory Council (ITRC), 2014. Petroleum Vapor Intrusion: Fundamentals of Screening, Investigation, and Management. 388 pp, October.

Interstate Technology Regulatory Council (ITRC), 2007. Vapor Intrusion Pathway: A Practical Guideline. 172 pp, January.

Ma, J., et al., 2020. Vapor Intrusion Investigations and Decision-Making: A Critical Review. Environmental Science & Technology, 54:12, p. 7050-7069, May 8.

McAlary, T., et al., 2010. High Purge Volume Sampling-A New Paradigm for Subslab Soil Gas Monitoring. Groundwater Monitoring & Remediation, 30:2, p. 73-85, May 12.

McHugh, T. et al., 2017. Evidence of a Sewer Vapor Transport Pathway at the USEPA Vapor Intrusion Research Duplex. BLN-113837-2017-JA. 18 pp, April.

McHugh, T. and L. Beckley, 2018. Sewers and Utility Tunnels as Preferential Pathways for Volatile Organic Compound Migration into Buildings: Risk Factors and Investigation Protocol. ESTCP Project ER-201505. 791 pp, November.

Naval Facilities Engineering Command (NAVFAC), 2013. Innovative Vapor Intrusion Site Characterization Methods. 8 pp, February.

Nocetti, D., et al., 2019. Sampling Strategies in the Assessment of Long-term Exposures to Toxic Substances in Air. Remediation Journal, 30:1, p. 5-13, December.

U.S. EPA Region V, 2020. Vapor Intrusion Handbook. Superfund and Emergency Management Division. 150 pp, March.

U.S. EPA, 2015. OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air. OSWER Publication 9200.2-154. 267 pp, June.

U.S. EPA, 2014. Challenges in Bulk Soil Sampling and Analysis for Vapor Intrusion Screening of Soil. Office of Research and Development. EPA/600/R-14-277. 14 pp, December.

U.S. EPA, 2011. Background Indoor Air Concentrations of Volatile Organic Compounds in North American Residences (1990-2005): A Compilation of Statistics for Assessing Vapor Intrusion. EPA 530-R-10-001. EPA, 67 pp, June 2011.



Underground Storage Tanks (USTs) Petroleum Vapor Intrusion 2021 U.S. Environmental Protection Agency, February 1, 2021. EPA website provides an overview of petroleum vapor intrusion sampling and characterization, modeling, mitigation and remediation, and guidance. Groundwater Sampling Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling Analytical Methods Predictive Modeling Building Design Meteorological Monitoring Forensic Approaches
Vapor Intrusion Investigations and Decision-Making: A Critical Review 2020 Jie Ma, Thomas McHugh, Lila Beckley, Matthew Lahvis, George DeVaull, and Lin Jiang, Environmental Science & Technology 2020 54 (12), 7050-7069, DOI: 10.1021/acs.est.0c00225. Paper provides a detailed review of the vapor intrusion conceptual site model including biological and hydrogeologic factors that may affect the potential for vapor intrusion. Key elements to vapor intrusion characterization are summarized and a review of innovative investigation tools is provided. Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling Analytical Methods Predictive Modeling Building Design High Purge Volume Sub-slab Sampling/Pneumatic Conductivity Testing Meteorological Monitoring Forensic Approaches
Passive Sampling for Vapor Intrusion: Let Diffusion Do the Work for You! 2020 Pautler, B., H. Hayes, and T. McAlary. Midwestern States Environmental Consultants Association Virtual Environmental Conference, 2-3 and 9-10 December, 68 minutes, 2020. Webinar discusses passive sampling for soil vapor, indoor air, and outdoor air to support subsurface vapor intrusion to indoor air assessments. The presentation includes theoretical considerations for sampler selection, sorbent selection, sample duration, and uptake rate verification; laboratory considerations for high-quality data; a patented method to quantify soil vapor concentration using the Waterloo Membrane Samplerâ„¢; and benefits relative to conventional summa canister/TO-15 methods of sampling and analysis. Soil Gas Sampling (Passive/Active) Indoor Air Sampling Analytical Methods
Vapor Intrusion Handbook 2020 U.S. Environmental Protection Agency, 150 pp. March 2020. This handbook was developed for On-Scene Coordinators and Remedial Project Managers in the EPA's Superfund and Emergency Management Division. The document focuses on hazardous substances other than petroleum hydrocarbons. It provides an overview of vapor intrusion, development of a conceptual site model, sampling strategies and data quality objectives and mitigation. It includes a discussion regarding community engagement in the assessment and remedial decision-making process. Groundwater Sampling Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling Analytical Methods Building Design
Vapor Intrusion Mitigation Model: VIM Model V2.2 2020 McAlary, T., ESTCP Project ER-201322, Model/Software, 2020. This spreadsheet tool was developed to help users: 1) interpret the results of sub-slab venting pilot tests, 2) calculate building-specific attenuation factors from flow and vacuum data, 3) assess the mass removal rate of a vapor mitigation system, and 4) interpret high volume sampling testing programs. Stepwise instructions to use the spreadsheet are provided. Predictive Modeling
Demonstration Of A Long-Term Sampling And Novel Analysis Approach For Distinguishing Sources Of Volatile Organic Compounds In Indoor Air 2020 Rossner, A., ESTCP Project ER-201504, 16 pp, 2020. The recently commercialized Aura™ capillary canister sampling method captures both canisters and sorbent samplers' advantages without their limitation by allowing for longer-term (1-3 weeks) sample collection and characterization of average VOCs in buildings at risk for vapor intrusion. The approach is robust, comparable in cost or is less expensive than current methods, allows for long-term sample collection, and requires one sample to capture the full range of analytes and concentrations of interest. Sampling does not require a power source, and analysis does not require solvent desorption. Indoor Air Sampling
Vapor Intrusion: Modeling Tools and Cost Effective Mitigation 2019 Suuberg, E. and T. McAlary. | SERDP & ESTCP Webinar Series, Webinar #93, July 2019. SERDP and ESTCP sponsored two presentations on new vapor intrusion modeling projects. The first examined the factors responsible for reports of large, several-order-of-magnitude variations in indoor air contaminant concentrations resulting from vapor intrusion processes. A case study of the Arizona State University site adjacent to Hill AFB was presented where modeling was used to characterize VI preferential pathways. The second presentation demonstrated new tools to reduce the cost of mitigating VOC vapor and radon intrusion to buildings. This research demonstrated several new ways to assess the radius of influence of soil gas extraction wells, including vacuum, velocity, travel time, vertical flow across the floor slab, and mass removal rates to design, operate and maintain optimal systems. A summary of the testing methods and four case studies were provided. Predictive Modeling
Key Design Elements of Building Pressure Cycling for Evaluating Vapor Intrusion - A Literature Review 2019 Schumacher, B., John H Zimmerman, C. Lutes, R. Truesdale, AND C. Holton. Key Design Elements of Building Pressure Cycling for Evaluating Vapor Intrusion—A Literature Review. Groundwater Monitoring & Remediation. Wiley-Blackwell Publishing, Hoboken, NJ, 39(1):66-72, (2019). Building pressure cycling is a tool used to distinguish between the contribution of subslab vapor and indoor sources of vapor intrusion. Protocols and outcomes from applications of the technology are reviewed in this paper. Lessons learned, testing protocols and research gaps are discussed. Building Design
Sewer and Utility Tunnels as Preferential Pathways for Volatile Organic Compound Migration into Buildings: Risk Factors and Investigation Protocol 2018 McHugh, T., L. Beckley. ESTCP Project ER-201505, 793 pp, November 2018. Report on investigation of sewer/utility tunnel vapor intrusion as a pathway in the conceptual site model for vapor intrusion. Risk factors and investigation protocols were identified. The project was divided into three tasks: Task 1 included field demonstrations of investigation protocols, Task 2 refined and validated the protocols based on the results of Task 1, Task 3 incorporated the results of Task 1 and 2 into the development of the conceptual site model and evaluation of risk factors. Sub-Slab Soil Gas Sampling
Use of Tracers, Surrogates, and Indicator Parameters in Vapor Intrusion Assessment, Fact Sheet Update No. 005 2017 Tri-Service Environmental Risk Assessment Workgroup. 13 pp. September 2017. Fact sheet suggests that VI assessments can be improved using tracers, surrogates, and indicator parameters. Tracers are substances that migrate similarly to the VOCs of interest for VI. Indicators are parameters or variables that are associated with the potential for VOC exposures through VI. Surrogates are variables with a quantitative relationship to the target VOCs for a VI study, sufficient to be useful as a substitute for directly measuring the target compounds. Sub-Slab Soil Gas Sampling
EPA Spreadsheet for Modeling Subsurface Vapor Intrusion 2017 U.S. Environmental Protection Agency, September 2017. Spreadsheet tool that implements the steady-state solution to vapor transport described by Johnson and Ettinger in 1991. Predictive Modeling
Use of Building Pressure Cycling in Vapor Intrusion Assessment 2017 Department of Defense, Vapor Intrusion Handbook Fact Sheet Update No:004, August 2017. Building pressure cycling (BPC) offers an alternative approach to the methods for indoor air sampling and determining the influence of background sources described in the Handbook. Building Design
High Volume Soil Gas Sampling for Vapor Intrusion Assessment, Fact Sheet Update No. 003 2017 Tri-Service Environmental Risk Assessment Workgroup. 14 pp. February 2017. This fact sheet summarizes high volume sampling as a method for assessing vapor concentrations and distributions in the subsurface, and is particularly well suited to sub-slab soil vapor sampling as part of a VI assessment. Sub-Slab Soil Gas Sampling
Passive Sampling for Vapor Intrusion Assessment, Fact Sheet Update No. 001 2017 Tri-Service Environmental Risk Assessment Workgroup. 7 pp. Revised February 2017. This fact sheet is intended to provide a high level overview and offer reference to resources that detail the application and analysis of passive sampling for VI. Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling
Real-Time Monitoring for Vapor Intrusion Assessment, Fact Sheet Update No. 002 2017 Tri-Service Environmental Risk Assessment Workgroup. 9 pp. February 2017. This fact sheet summarizes the rationale for using real-time monitoring in VI investigations as well as potential advantages and limitations. Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling
Petroleum Vapor Intrusion Modeling Assessment with PVIScreen 2016 U.S. EPA, National Risk Management Research Laboratory, Ada, OK. EPA 600-R-16-175, 53 pp, August 2016. To better understand the behavior of petroleum compounds, the PVIScreen model was developed that applies the theory developed for the BioVapor model to a lens of petroleum hydrocarbons in the subsurface that is capable of acting as a source of petroleum vapors. The PVIScreen model automatically conducts an uncertainty analysis using Monte Carlo simulations and is intended to make uncertainty analysis practical for application at petroleum vapor intrusion sites. The model can be run in either a batch mode, using Microsoft Excel files for both input and model outputs, and an interactive mode using a graphical user interface. Each of these is described, along with required inputs, example problems and the theoretical background of the model. Model simulations agree with an EPA-sponsored analysis of field data that illustrate and document the attenuation of concentrations of petroleum compounds in soil gas with distance above the source of the vapors. Predictive Modeling
Integrated Field-Scale, Lab-Scale, and Modeling Studies for Improving Our Ability to Assess the Groundwater to Indoor Air Pathway at Chlorinated Solvent-Impacted Groundwater Sites 2016 Johnson, P.C., C. Holton, Y. Guo, P. Dahlen, H. Luo, K. Gorder, E. Dettenmaier, and R.E. Hinchee. SERDP Project ER-1686, 248 pp, 2016. This project was conducted mainly at a house overlying a dilute chlorinated hydrocarbon (TCE) groundwater plume. The house was outfitted with sensors and automated systems to facilitate monitoring of indoor air and ambient and building conditions as well as groundwater and soil gas. Monitoring was conducted under both natural and controlled building conditions for about 2.5 yr, and both TCE and radon were quantified in indoor air and soil gas. Two recurring behaviors were observed with the indoor air data. The temporal behavior prevalent in fall, winter, and spring involved time-varying impacts intermixed with sporadic periods of inactivity. In summer, VI showed long periods of inactivity with sporadic VI impacts. Predictive Modeling
Vapor Intrusion Estimation Tool for Unsaturated-Zone Contaminant Sources: User's Guide 2016 Johnson, C.D., M.J. Truex, M. Oostrom, K.C. Carroll, and A.K. Rice. ESTCP Project ER-201125, 50 pp, 2016 This guide presents a tool for estimating vapor intrusion into buildings from unsaturated (vadose) zone contaminant sources. The tool builds on and is related to guidance for evaluation of SVE performance relative to the impact of a vadose zone source on groundwater concentrations. This user guide is available with several tools for estimating vapor intrusion at the bottom of the project web page. Predictive Modeling
Vapor Intrusion Screening Level (VISL) Calculator 2015 U.S. EPA Office of Superfund Remediation and Technology Innovation (OSRTI). The U.S. EPA Office of Superfund Remediation and Technology Innovation developed a tool that: (1) lists chemicals considered to be volatile and sufficiently toxic through the inhalation pathway; and (2) provides VISLs for groundwater, soil gas and indoor air, which are generally recommended, media-specific, risk-based screening-level concentrations. The primary purpose of the VISL calculator is to assist Superfund site managers and risk assessors in determining, based on an initial comparison of site data against the VISLs, whether chemicals found in groundwater or soil gas can pose a significant risk through vapor intrusion and, if so, whether a site-specific vapor intrusion investigation is warranted. Other Agency cleanup programs may also find it helpful to consider the VISLs for their own specific needs. Predictive Modeling
Identification of Alternative Vapor Intrusion Pathways Using Controlled Pressure Testing, Soil Gas Monitoring, and Screening Model Calculations 2015 Yuanming Guo, Chase Holton, Hong Luo, Paul Dahlen, Kyle Gorder, Erik Dettenmaier, and Paul C. Johnson, Environmental Science & Technology 2015 49 (22), 13472-13482, DOI: 10.1021/acs.est.5b03564. Alternative vapor intrusion pathways such as neighborhood sewers, land drains, and other major underground piping can be significant contributors to vapor intrusion into buildings, even those beyond the footprint of the soil and groundwater contamination. Controlled-pressure-method testing (CPM), soil gas sampling and screening level emissions calculations were used to identify alternate vapor intrusion pathways that might have been overlooked using conventional sampling methods. Groundwater Sampling Soil Gas Sampling (Passive/Active) Indoor Air Sampling Analytical Methods
NAVFAC Technical Memorandum on Vapor Intrusion Passive Sampling 2015 Dawson, H., T. McAlary, and H. Groenevelt. NAVFAC Technical Memorandum TM-NAVFAC EXWC-EV-1503, 20 pp, 2015. This technical memorandum describes the basics of passive sampler theory and design, available types of passive samplers, advantages and limitations of passive samplers, and important considerations when implementing a passive sampling program. Results from two vapor intrusion case studies at DoD sites are highlighted. Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling
OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air 2015 U.S. Environmental Protection Agency, 214 pp, June 2015. This Technical Guidance presents current technical recommendations of the EPA based on our current understanding of vapor intrusion into indoor air from subsurface vapor sources. One of its main purposes is to promote national consistency in assessing the vapor intrusion pathway. At the same time, it provides a flexible science-based approach to assessment that accommodates the different circumstances (e.g., stage of the cleanup process) in which vapor intrusion is first considered at a site and differences among pertinent EPA programs. Groundwater Sampling, Soil Gas Sampling (Passive/Active), Sub-Slab Soil Gas Sampling, Indoor Air Sampling, Analytical Methods, Predictive Modeling, Building Design, Meteorological Monitoring, Forensic Approaches,
Petroleum Vapor Intrusion: Fundamentals of Screening, Investigation and Management 2014 Interstate Technology & Regulatory Council, 388 pp, October 2014. A reference document designed to support the screening, investigation, and management of petroleum vapor intrusion (PVI) sites that is protective of human health. The document builds off of the 2007 Vapor Intrusion Pathway: A Practical Guideline (VI-1) which addressed both PVI sites and sites with chlorinated volatile organic compounds. Groundwater Sampling Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling Analytical Methods Predictive Modeling Building Design High Purge Volume Sub-slab Sampling/Pneumatic Conductivity Testing Meteorological Monitoring Forensic Approaches
Development of More Cost-Effective Methods for Long-Term Monitoring of Soil Vapor Intrusion to Indoor Air Using Quantitative Passive Diffusive-Adsorptive Sampling 2014 T. McAlary, 358 pp, July 2014. Five passive samplers — the SKC Ultra and Ultra II, Radiello®, Waterloo Membrane Sampler, Automated Thermal Desorption tubes, and 3M OVM 3500 — were tested in lab and field conditions for VOCs (e.g., chlorinated ethenes, ethanes, and methanes, and aromatic and aliphatic hydrocarbons). All provided data that met the success criteria under some or most conditions, and most provided highly reproducible results throughout the demonstrations at costs comparable to or lower than monitoring with conventional methods. Soil Gas Sampling (Passive/Active) Indoor Air Sampling
Vapor Intrusion from Entrapped NAPL Sources and Groundwater Plumes: Process Understanding and Improved Modeling Tools for Pathway Assessment 2014 Illangasekare, T., B. Petri, R. Fucik, C. Sauck, L. Shannon, T. Sakaki, K. Smits, A. Cihan, J. Christ, P. Schulte, B. Putman, and Y. Li. SERDP Project ER-1687, 206 pp, 2014. Mechanisms controlling vapor generation and subsequent migration through the subsurface in naturally heterogeneous subsurface under different physical and climatic conditions were investigated using lab and modeling studies alongside the development of improved modeling tools. Dynamic and complex subsurface vapor pathways sometimes contribute to counterintuitive cause-effect relationships. Infiltration affects vapor signals in indoor air, with the time scales and the strength of the vapor signals depending on the interplay of the intensity, duration of rainfall, and subsurface heterogeneity. Water table fluctuation imparts very complex transport behavior within the capillary fringe, which has significant effects on vapor loading from the groundwater plumes. Trapped sources in the unsaturated zone are capable of loading significant mass into the unsaturated zone, but the loading rate is a strong function of the moisture distribution in the vicinity of the source. Indoor sampling strategies need to factor in the transients associated with climate and weather. Predictive Modeling
User's Guide for CSIA Protocol 2014 Beckley, L., T. McHugh, T. Kuder, and P. Philip. ESTCP Project ER-201025, 16 pp, 2014. This document i) describes the applicability of CSIA for vapor intrusion investigations (Section 2.0), ii) provides a step-by-step procedure for sample collection (Section 3.0), and iii) includes guidelines for data interpretation (Section 4.0). Additional background information on this investigation approach is available in the ESTCP Project ER-201025 Final Report (GSI, 2013a). Forensic Approaches
Passive Samplers for Investigations of Air Quality: Method Description, Implementation, and Comparison to Alternative Sampling Methods 2014 U.S. EPA, Engineering Technical Support Center. EPA 600-R-14-434, 44 pp, 2014. This paper covers the basics of passive sampler design and compares passive samplers to conventional methods of air sampling; discusses considerations for implementing a passive sampling program; and addresses field sampling and sample analysis considerations to ensure adequate data quality and supportable interpretations of the passive sample data. The reader is expected to have a basic technical background on the VI exposure pathway and the use and interpretation of indoor air sampling data. Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling
Innovative Vapor Intrusion Site Characterization Methods 2013 TDS-NAVFAC EXWC-EV-1301, 8 pp, 2013. This fact sheet provides an overview of the following emerging and innovative methods for the characterization of indoor air at potential vapor intrusion sites: passive sampling, use of a portable gas chromatography/mass spectrometry instrument, use of building pressure control techniques, hydrocarbon fingerprinting, compound-specific isotope analysis, and radon sampling. Three brief case studies are included. Sub-Slab Soil Gas Sampling Indoor Air Sampling Analytical Methods Building Design
Conceptual Model Scenarios for the Vapor Intrusion Pathway 2012 Abreu, L. and H. Schuver. EPA 530-R-10-003, 154 pp, 2012. The simulation results presented in this document illustrate how different site and building conditions may influence both the distribution of VOCs in the subsurface and the indoor air quality of the structures in the vicinity of a soil or groundwater VOC source. This information can help practitioners develop more accurate conceptual site models about soil and vapor intrusion, design better sampling plans, and better interpret the results of site investigations. Predictive Modeling Building Design
Vapor Intrusion Database: Evaluation and Characterization of Attenuation Factors for Chlorinated Volatile Organic Compounds and Residential Buildings 2012 Dawson, H.E. and R.B. Kapuscinski. EPA 530-R-10-002, 188 pp, 2012. This report provides updated information about the design, structure, and content of EPA's vapor intrusion databases, which supersedes EPA's 2008 preliminary report on the database. Technical information is presented about sites in the United States that have been investigated for vapor intrusion. The primary focus is the evaluation of concentrations of chlorinated VOC's in and beneath residential buildings based on EPA's vapor intrusion data as of 2010. This report was peer reviewed under a different working title: U.S. EPA's Vapor Intrusion Database: Preliminary Evaluation of Attenuation Factors. Building Design
Simulation Program i-SVOC User's Guide 2012 Guo, Z. EPA 600-R-13-212, 92 pp, 2013 . The i-SVOC simulation program estimates the emissions, transport, and sorption of semivolatile organic compounds in the indoor environment as functions of time when a series of initial conditions is given. This program implements a framework for dynamic modeling of indoor SVOCs and covers six types of indoor compartments: air (gas phase), air (particle phase), sources, sinks (i.e., sorption by interior surfaces), contaminant barriers, and settled dust. Potential applications of this program include (1) use as a stand-alone simulation program to obtain information that the current equilibrium models cannot provide, including evaluation of the effectiveness of pollution mitigation methods such as variable ventilation rates, source removal, and source encapsulation; (2) reducing the uncertainties in the existing multimedia models; and (3) use as a front-end component for stochastic exposure models to provide information about the SVOC distribution in indoor media in the absence of experimental data. This program is intended for advanced users who are involved in and familiar with indoor environmental quality modeling or indoor exposure assessment. i-SVOC model setup. Predictive Modeling
Ground Water Issue: An Approach for Developing Site-Specific Lateral and Vertical Inclusion Zones within Which Structures Should Be Evaluated for Petroleum Vapor Intrusion Due to Releases of Motor Fuel from Underground Storage Tanks 2012 Wilson , J.T., J.W. Weaver, and H. White. EPA 600-R-13-047, 35 pp, 2012. Definition of subsurface lateral and vertical inclusion zones in combination makes the best use of site characterization data for assessing the risk of PVI to structures at a leaking underground storage tank site. The procedures outlined in this issue paper provide a realistic data-driven approach to screen buildings for vulnerability to PVI . Predictive Modeling
Use of Compound Specific Stable Isotope Analysis to Distinguish Between Vapor Intrusion and Indoor Sources of VOCs: Laboratory Validation Report 2012 McHugh, T., T. Kuder, M. Klisch, and R.P. Philp. ESTCP Project ER-201025, 59 pp, 2012. The objective of this study was an empirical validation of selected adsorbents for preconcentration of TCE, PCE, and benzene in air samples containing low concentrations of these VOCs. For validation of adsorbent tube performance, the investigators selected adsorbent-analyte pairings likely to offer good quantitative recovery of the target VOCs. Results demonstrate fractionation-free performance for Carboxen 1016, which allows precise isotope ratio analysis into vapor intrusion site assessment protocols and other applications where VOCs of interest are present at low microgram-per-cubic-meter concentrations. Forensic Approaches
Guidance for Environmental Background Analysis, Volume IV: Vapor Intrusion Pathway 2011 Naval Facilities Engineering Command (NAVFAC), UG-2091-ENV, 153 pp, April 2011. This guidance document provides instructions for evaluating background conditions in vapor intrusion investigations. The background analysis techniques presented in this document are based on exploratory, forensic, and statistical methods. The guidance recognizes the unique features of vapor intrusion investigations and treats the recommended methods as "multiple lines of evidence" that should be considered when determining whether volatile chemicals measured in indoor air should be attributed to subsurface releases, indoor air background, or possibly both. Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling Analytical Methods Forensic Approaches
Pneumatic Testing, Mathematical Modeling and Flux Monitoring to Assess and Optimize the Performance and Establish Termination Criteria for Sub-Slab Depressurization Systems (PowerPoint presentation) 2011 Todd McAlary, David Bertrand, Paul Nicholson, Sharon Wadley, Danielle Rowlands, Gordon Thrupp and Robert Ettinger, Geosyntec Consultants, Inc., Presented at the U.S. EPA workshop, “Addressing Regulatory Challenges in Vapor Intrusion: A State-of-the-Science Update Focusing on Chlorinated VOCs,� held at the Association for Environmental Health and Sciences 21st Annual Meeting and West Coast Conference on Soils, Sediments, and Water - Workshop: Addressing Regulatory Challenges in Vapor Intrusion, San Diego, California March 15, 2011. Presentation slides include explanation of how to calculate the pneumatic conductivity of a building’s floor slab. High Purge Volume Sub-slab Sampling/Pneumatic Conductivity Testing
Vapor Intrusion in Urban Settings: Effect of Foundation Features and Source Location 2011 Yijun Yao, Kelly G. Pennell, Eric Suuberg, in Procedia Environmental Sciences, Vol. 4, pp 245–250, 2011. A 3-D computational fluid dynamics model is used to investigate how the presence of impervious surfaces affects vapor intrusion rates. To complement modeling efforts, the investigators are in the initial stages of conducting a field study in a neighborhood where vapor intrusion is occurring. Predictive Modeling Building Design
Temporal Variation of VOCs in Soils from Groundwater to the Surface/Subslab: APM 349 2010 Elliot, J., G. Swanson, and B. Hartman. EPA 600-R-10-118, 143 pp, October 2010. This report presents the activities, results, findings, and recommendations associated with monitoring the variations in active soil vapor sample results near and under a slab adjacent to Building 170 at Naval Air Station Lemoore from November 2008 through October 2009. The work described in this report follows up on EPA's 2009 report, Vertical Distribution of VOCs in Soils from Groundwater to the Surface/Subslab. Groundwater Sampling Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling
Household Products Database 2010 U.S. National Library of Medicine. Determine what's in consumer products before sampling indoor air. Indoor Air Sampling
The Use of Tracer Gas in Soil Vapor Intrusion Studies 2010 Peter Reynolds, in Proceedings of the Annual International Conference on Soils, Sediments, Water, and Energy, Vol. 12, Issue 1, Article 39, 7 pp, January 15, 2010. Discusses the use of tracer gas to verify that sub-slab samples do not contain ambient air. Sub-Slab Soil Gas Sampling
HVAC Influence on Vapor Intrusion in Commercial and Industrial Buildings 2010 David Shea, Claire Lund, and Bradley Green, in Proceedings of the Air & Waste Management Association’s Vapor Intrusion 2010 Conference, 12 pp, 2010. This paper presents an overview of common HVAC components and how they influence indoor air quality. Several case studies are presented describing the role of HVAC operations in vapor intrusion assessment and mitigation. Favorable and unfavorable effects of HVAC operations on vapor intrusion also provided. Sub-Slab Soil Gas Sampling Building Design
Vertical Distribution of VOCs in Soils from Groundwater to the Surface/Subslab 2009 U.S. Environmental Protection Agency, 326 pp, August 2009. Field study conducted at Installation Restoration Program Site 14 on Naval Air Station Lemoore, California to assess the vertical and horizontal distribution of volatile organic compounds in the subsurface and to develop a database of paired macro-purge and micro-purge soil gas sample measurements. In addition, sampling was conducted to evaluate the performance of a variety of soil gas probe construction materials (tubing types) and to test passive diffusion samplers. Soil Gas Sampling (Passive/Active)
Review of Best Practices, Knowledge and Data Gaps, and Research Opportunities, for the U.S. Department of Navy Vapor Intrusion Focus Areas 2009 T. McAlary et al, 86 pp, May 2009. Provides a review by a team of subject-matter experts of current best practices, opinions on the current state of knowledge and data gaps, and offers suggestions for research directions for the following three Navy-identified VI focus areas: Sub-surface sampling for complete determination of VI pathway to minimize the need for intrusive sub-slab sampling; Passive indoor air sampling methods to improve VI exposure estimates; and Indoor air source separation to determine if indoor air contamination is from VI or indoor sources. Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling Predictive Modeling
DOD Vapor Intrusion Handbook, The Tri-Service Environmental Risk Assessment Workgroup 2009 Department of Defense, 172 pp, January 2009. Guidance from the Department of Defense includes discussion of sampling soil, groundwater, soil gas, sub-slab, and indoor air for vapor intrusion sites as well as the influence of building design parameters. Groundwater Sampling Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling Analytical Methods Predictive Modeling Building Design
Vapor Intrusion Sampling Options: Performance Data for Canisters, Badges, and Sorbent Tubes for VOCs 2009 Linda S. Coyne, George Havalias, and Maria C. Echarte, in Proceedings of the Air & Waste Management Association’s Vapor Intrusion 2009 Conference, 9 pp, San Diego, California, January 27-30, 2009. Discusses results of two field studies comparing Summa canisters, passive sampling badges, and sorbent tubes. The study found good correlation between the canisters and the other two methods and concluded that sorbent-based sampling devices can be used effectively in vapor intrusion studies as a reliable alternative to canister sampling. Indoor Air Sampling
A Guide for Assessing Biodegradation and Source Identification of Organic Ground Water Contaminants Using Compound Specific Isotopes Analysis (CSIA) 2008 EPA 600/R-08/148, U.S. Environmental Protection Agency, 82 pp, December 2008. Intended for managers of hazardous waste sites who design sampling plans that will include CSIA and specify data quality objectives for CSIA analyses, for analytical chemists who carry out the analyses, and for staff of regulatory agencies who review and approve the sampling plans and data quality objectives, and review the data provided from the analyses. Forensic Approaches
Canisters v. Sorbent Tubes: Vapor Intrusion Test Method Comparison 2008 Joseph Odencrantz, Harry O`Neill, and James Kirkland, in Proceedings of the Sixth International Battelle Conference: Remediation of Chlorinated and Recalcitrant Compounds, 7 pp, May 2008. The results from each method revealed a linear relationship between molecular weight and the difference in concentration between the two methods. The TO-17 results were generally lower than the TO-15 results for PCE. Sub-Slab Soil Gas Sampling
Recommendations for the Investigation of Vapor Intrusion (ESTCP Project ER-0423) 2008 Thomas McHugh, 23 pp, April 2008. Recommends approaches to collecting groundwater and soil gas samples to generate data suitable for pathway screening and a field investigation program to provide a cost-effective and timely evaluation of the presence or absence of vapor intrusion impacts. Groundwater Sampling Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling
Evaluation of Spatial and Temporal Variability in VOC Concentrations at Vapor Intrusion Investigation Sites 2007 Thomas McHugh, Tim Nickels, and Samuel Brock, in Proceedings of Air & Waste Management Association’s Vapor Intrusion: Learning from the Challenges, 14 pp, September 2007. Discusses the representativeness of sub-slab samples given temporal and spatial concentration variability. Sub-Slab Soil Gas Sampling
Vapor Intrusion Pathway: A Practical Guide (VI-1) 2007 Interstate Technology & Regulatory Council, 172 pp, January 2007. A reference document that provides a flexible framework for developing an investigative strategy at vapor intrusion sites. Various tools for investigation, data evaluation and mitigation are described. Groundwater Sampling Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling Analytical Methods Predictive Modeling Building Design High Purge Volume Sub-slab Sampling/Pneumatic Conductivity Testing Meteorological Monitoring Forensic Approaches
Vapor Intrusion Pathway: A Practical Guide, Interstate Technology & Regulatory Council 2007 ITRC, 72 pp, January 2007. Includes discussion of the utility of and how to conduct pneumatic tests for the investigation of vapor intrusion. Groundwater Sampling Soil Gas Sampling (Passive/Active) Sub-Slab Soil Gas Sampling Indoor Air Sampling Analytical Methods Predictive Modeling Building Design High Purge Volume Sub-slab Sampling/Pneumatic Conductivity Testing
Comparison of Geoprobe® PRT and AMS GVP Soil-Gas Sampling Systems with Dedicated Vapor Probes in Sandy Soils at the Raymark Superfund Site 2006 EPA/600/R-06/111, U.S. Environmental Protection Agency, 79 pp, November 2006. Documents study conducted near the Raymark Superfund Site in Stratford, Connecticut to compare results of soil-gas sampling using dedicated vapor probes, a truck-mounted direct-push technique - the Geoprobe Post-Run-Tubing (PRT) system, and a hand-held rotary hammer technique - the AMS Gas Vapor Probe kit. Soil Gas Sampling (Passive/Active)
Groundwater Sampling and Monitoring Using Direct Push Technologies 2005 U.S. Environmental Protection Agency, 78 pp, August 2005. Explains groundwater sampling issues related to use of direct push technology, in particular those regarding the quality and usability of the groundwater data. Groundwater Sampling Indoor Air Sampling
A Review Of Recent Vapor Intrusion Modeling Work 2021 Verginelli, I. and Y. Yao. | Groundwater Monitoring & Remediation 41(2):138-144(2021) This paper reviews vapor intrusion modeling studies published from 2010-2020. Predictive Modeling
Modeling Fate and Transport of Volatile Organic Compounds (VOCs) Inside Sewer Systems 2021 Verginelli, I. and Y. Yao. | Groundwater Monitoring & Remediation 41(2):138-144(2021) A new numerical model simulates the VOC concentrations in sewer gas in different stages throughout the sewer lines. The model considers temperature, sewer liquid depth, groundwater depth, and sewer construction characteristics to incorporate local and operational conditions. The output was verified using field data from a sewer system constructed near a Superfund site. A sensitivity analysis was conducted to evaluate the model's response to variation of the external input parameters. The model can be used as a numerical tool to support the development of sewer assessment guidelines, risk assessment studies, and mitigation strategies. Predictive Modeling



O'Neill Groundwater Superfund Site, O'Neill, Nebraska 2018 U.S. EPA webpage The U.S. EPA is supporting the Nebraska Department of Environmental Quality in a groundwater and VI investigation at the O’Neill Superfund site (O'Neill, Neb). Groundwater TCE contamination is associated with former industrial use of the property, including manufacturing, dry cleaning, and degreasers used for parts cleaning. Groundwater Sampling Soil Gas Sampling
Evidence of a Sewer Vapor Transport Pathway at the U.S. EPA Vapor Intrusion Research Duplex 2017 McHugh, T., L. Beckley, T. Sullivan, C. Lutes, R. Truesdale, R. Uppencamp, B. Cosky, J.H. Zimmerman, and B. Schumacher. Results from the tracer study at the U.S. EPA VI research duplex (Indianapolis, Ind.) demonstrated the migration of gas from the sewer main line into the duplex. The migration pathway appears to be complex and may include leakage from the sewer lateral at a location below the building foundation. These results combined with those from a prior multi-year study suggest sewer lines should be routinely evaluated as part of VI investigations.
Vapor Intrusion Investigation and Mitigation Report - Holley Automotive/Coltec Industries Facility, Water Valley, Mississippi 2017 First Environment This report describes a VI investigation at a former automotive manufacturing plant including sampling of ambient air, indoor air, and sub-slab soil gas sampling for chlorinated solvents trichloroethene and cis-1,2-dichloroethene. An ambient air extraction system and sub-slab depressurization system were installed to mitigate vapors. Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling Analytical Methods
Vapor Intrusion Remediation Project Naval Base Point Loma, San Diego, California 2016 Chief of Naval Operations: Environmental Award Competition This narrative describes the successful environmental restoration and installation of a remediation system to address VOC contaminated groundwater, soil gas, and indoor air at the Naval Base Point Loma, a former aircraft manufacturing facility. Storage of solvents at the base resulted in TCE contamination in groundwater, soil gas, and indoor air. TCE levels were reduced below EPA exposure limits as a result of a horizontal well SVE system and sub-slab ventilation system. Vapor entry points were identified and sealed to eliminate migration of remaining vapors and supplement the sub-slab ventilation system. Groundwater Sampling Soil Gas Sampling Indoor Air Sampling
Simple, Efficient, and Rapid Methods to Determine the Potential for Vapor Intrusion into the Home: Temporal Trends, Vapor Intrusion Forecasting, Sampling Strategies, and Contaminant Migration Routes 2015 Truesdale, R., C. Lutes, B. Cosky, N. Weinberg, M. Bartee, B. Munoz, R. Norberg, and H. Hayes. An investigation began in 2011 into the general principles of how vapors enter a single residence, a highly instrumented pre-1920 residential duplex located in Indianapolis. This report, the third in a series of reports based on that research, examines the use of radon and other variables, such as weather data, changes in temperature and differential pressure between indoors and outdoors, as potential low-cost, easily monitored indicators of when to sample for VI events and when to turn on the mitigation system to reduce VI exposure to residents. Select data trends through the years of study at this site are also presented. Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling Analytical Methods Building Design Meteorological Monitoring Forensic Approaches
Use of Compound-Specific Stable Isotope Analysis to Distinguish Between Vapor Intrusion and Indoor Sources of VOCs 2013 Beckley, L., T. McHugh, T. Kuder, and R.P. Philp This demonstration was conducted to validate use of CSIA to distinguish between VI and indoor sources of VOCs. As part of the project, a step-by-step protocol was developed that can be used to provide an independent line of evidence to determine whether or not buildings are affected by VI. Results from concurrent conventional VI and onsite GC/MS investigations were compared with the CSIA results to evaluate the relative effectiveness of the different investigation approaches. Forensic Approaches
Use of On-Site GC/MS Analysis to Distinguish Between Vapor Intrusion and Indoor Sources of VOCs 2013 Beckley, L., T. McHugh, K. Gorder, E. Dettenmaier, and I. Rivera-Duarte Rapid onsite analysis of indoor air samples using a portable GC/MS allows the user to understand the distribution of VOCs in real time, supporting identification of the source while in the field. A step-wise investigation procedure was developed and validated using commercially available off-the-shelf onsite GC/MS analysis (a portable HAPSITE unit) with real-time decision-making as a tool to distinguish between VI and indoor sources of VOCs. Results from concurrent conventional VI and CSIA investigations were compared with the GC/MS results to evaluate the relative effectiveness of the different investigation approaches. Analytical Methods Forensic Approaches
Fluctuation of Indoor Radon and VOC Concentrations Due to Seasonal Variations 2012 RTI International and Arcadis on behalf of U.S. EPA, National Exposure Research Laboratory During the course of a full year of weekly measurements of sub-slab soil gas, external soil gas, and indoor air in a single house impacted by radon and halogenated VOCs VI, investigators studied seasonal concentration variations and evaluated the long-term performance of sorbent-based sampling devices for time-integrated measurement of indoor air levels of VOCs. Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling Meteorological Monitoring
Grand Prairie Vapor Intrusion Investigation, Grand Prairie, Dallas County, Texas 2012 Texas Department of State Health Services This report describes the VI investigation of the former Delfasco Forge facility (Grand Prairie, Texas), added to the NPL list in 2018 based solely on subsurface VI. The Delfasco facility performed steel and iron forging, using TCE as a degreaser, resulting in chlorinated solvent contamination in soil and groundwater. An investigation of TCE vapors migrating into the main building on the site and into nearby residential properties included sub-slab, crawl space, and indoor air sampling. Groundwater, soil vapor, indoor air, and biological tissue samples were tested during an exposure investigation. Sub-slab depressurization and crawlspace ventilation systems have been installed in approximately 35 residences; cleanup activities are ongoing. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling Analytical Methods
Soil Gas Survey Oakland, CA (U.S. EPA Brownfields Assessment Grant) 2012 Baseline Environmental Consulting This report describes the methodology and results of a soil gas survey conducted at a former metal plating facility to determine whether VOCs in soil gas are present at levels to cause an indoor VI concern. Soil Gas Sampling Analytical Methods
Understanding Soil Gas at Former Fort Ord 2011 U.S. Army This Frequently Asked Questions document explains how chlorinated VOCs, including TCE and PCE, found in groundwater at Fort Ord U.S. Army Base in Marina, California, resulted in contaminated soil gas. Mitigation efforts included capping the landfill and removal and treatment of landfill gas, and the installation of an SVE system to remove VOCs within the vadose zone above the chlorinated solvent groundwater plume. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling
Characterizing TCE Exposure Distribution for Occupants of Houses with Basements 2010 Wanyu Chan, Gregory Brorby, and Brian Murphy Describes how a two-compartment modeling approach was applied to a group of 13 single-family houses situated above a trichloroethene (TCE) groundwater plume to estimate the exposure distribution for occupants residing in houses with a basement. Exposure predictions were compared to the conservative assumption that the measured TCE concentrations in the basement are representative throughout the whole house. This analysis characterizes two important parameters used to evaluate exposure to elevated TCE concentrations in the basement. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling Analytical Methods Predictive Modeling Building Design Meteorological Monitoring
Innovations in Site Characterization: Streamlining Cleanup at Vapor Intrusion and Product Removal Sites Using the Triad Approach: Hartford Plume Site, Hartford, Illinois 2010 Tetra Tech, EMI on behalf of EPA VI from widespread hydrocarbon plumes at the site resulted in numerous fires and forced residents to move from their homes. The EPA Region 5 Emergency Response Team's OSCs worked with area oil companies to address the public concerns at the site quickly. The project team used the Triad approach best management practices to expedite investigation, mitigation, and cleanup processes. The extent of contamination was defined in roughly two years, and an existing mitigation system was augmented and optimized. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling
Vertical Distribution of VOCs in Soils from Groundwater to the Surface/Subslab 2009 Tetra Tech EMI on behalf of U.S. EPA, National Exposure Research Laboratory Field study conducted at Installation Restoration Program Site 14 on Naval Air Station Lemoore, California to assess the vertical and horizontal distribution of VOCs in the subsurface and to develop a database of paired macro-purge and micro-purge soil gas sample measurements. In addition, sampling was conducted to evaluate the performance of a variety of soil gas probe construction materials (tubing types) and to test passive diffusion samplers. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling
Detailed Field Investigation of Vapor Intrusion Processes (ESTCP Project ER-0423) 2008 GSI Environmental Demonstration study by Department of Defense to identify a cost effective and accurate protocol for investigation of VI into buildings overlying contaminated groundwater. Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling
JV Task 86-Identifying The Source of Benzene In Indoor Air Using Different Compound Classes From TO-15 Data 2007 Steven B. Hawthorne This DOE document evaluates VOC data collected using EPA method TO-15 at four different sites to determine whether the source of indoor air benzene was caused by outdoor air or VI. Results indicated the indoor air contamination was likely from outdoor air and not the contaminated soils. Forensic Approaches
Evaluation of Vapor Intrusion from a Subsurface Diesel Plume Using Multiple Lines of Evidence 2006 John Connor, Farrukh Ahmad, and Thomas E. McHugh A series of investigations were conducted near a railway facility in Mandan, North Dakota, where organic vapors had been detected in both the subsurface and in indoor air. The results of this investigation demonstrate how multiple lines of evidence, including statistical cluster analysis, can be employed to distinguish between background indoor air quality and organic vapors associated with actual subsurface VI. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling Analytical Methods Meteorological Monitoring Forensic Approaches
Results and Lessons Learned Interim Report: Altus AFB Site 2005 Groundwater Services, Inc. for the Department of Defense ESTCP Demonstration study to identify and validate site investigation scope. The study provides the most accurate and reliable evaluation of VI at corrective action sites by: collecting a high density of data related to VI; analyzing the data to obtain a thorough understanding of VI processes; and evaluating data subsets that reflect various options for conducting a limited scope VI investigation to determine which subset provides the most accurate indication of the actual VI at the site. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling
An Evaluation of Vapor Intrusion into Buildings Through a Study of Field Data 1996 Nancy Fitzpatrick and John J. Fitzgerald, Systematic examination of cases on file with the Massachusetts Department of Environmental Protection undertaken to identify a universe of VOC contaminated sites in close proximity to buildings. Locations were grouped according to site variables, such as contaminants of concern and concentrations in various media; soil type; depth to groundwater; distance to buildings; and building construction. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling
Rockwell International Wheel & Trim Superfund Site, Grenada, Mississippi   U.S. EPA webpage This Superfund NPL site page describes how the operation of a former wheel cover manufacturer and chrome plating facility in Grenada, Miss. from 1966 to the early 2000's resulted in TCE contamination of groundwater, surface water, soil and indoor air. TCE vapors present in the subsurface soil and groundwater entered the building through cracks, joints, and other openings in the concrete floor. A sub-slab depressurization system was installed to reduce high TCE levels inside the manufacturing building and periodic indoor air sampling was conducted to ensure proper operation of the system. For additional information see the site webpage:https://www.epa.gov/grenadacleanup Groundwater Sampling Sub-Slab Sampling Indoor Air Sampling
Soil Vapor Investigation and Remediation, Omaha, Nebraska   Seneca Companies Profile of a soil vapor investigation and remediation project following the removal of three USTs. A subsurface VI assessment included sub-slab sampling in the basement of a daycare facility. Following SVE pilot testing, and the operation of a full-scale SVE system for eight months, vapor concentrations reached acceptable levels and the system was decommissioned. Groundwater Sampling Sub-Slab Sampling Indoor Air Sampling
Highway 7 and Wooddale Avenue Vapor Intrusion Investigation, St. Louis Park, Minnesota   U.S. EPA webpage The U.S. EPA supported the Minnesota Pollution Control Authority’s investigation of VI at an estimated 300 properties in St. Louis Park, Minnesota. Sub-slab sampling and indoor air sampling found PCE and TCE in soil vapor. Mitigation measures included the design and installation of vapor abatement systems for residences. Groundwater Sampling Sub-Slab Sampling Indoor Air Sampling
Vapor Intrusion Investigation - Amphenol/Franklin Power Products, Franklin, Indiana   U.S. EPA webpage Amphenol Corporation completed a VI investigation under EPA oversight in a residential area located south of the former Amphenol facility. Contaminated process water was poured into a floor drain connected to the city’s sanitary sewer system, resulting in soil and groundwater contamination. Sampling of VOC sewer gas, sewer backfill gas, groundwater, indoor and ambient air sampling was conducted to determine whether vapors from groundwater VOC contamination or from sewer lines were migrating to the indoor air of residences. Mitigation efforts included the installation of a sub-slab depressurization system in the facility building and in several residential homes, sewer relining and remediation of contaminated soil and groundwater. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling
Behr Dayton Thermal System VOC Plume (Vapor Intrusion Investigation). Dayton, Ohio   U.S. EPA webpage Superfund NPL site; U.S. EPA issued an Interim Record of Decision in 2019 to cleanup groundwater contaminated with TCE and reduce exposure from soil vapor at the Behr Dayton, Ohio site. Past cleanup activities included the installation of vapor removal systems in over 200 residential properties. Following a recent VI investigation, an air sparging and SVE system, considered an interim remedial action, began operation in 2018. A long-term cleanup plan to address remaining portions of the groundwater TCE plume and soil contamination is being developed. Groundwater Sampling Soil Gas Sampling Sub-Slab Sampling Indoor Air Sampling

Helpful Definitions

  1. Conceptual site model (CSM): A CSM is a picture and narrative of the site contamination: how it got there, whether or not it is migrating or degrading, its distribution across the site, who might be exposed to it, and what risk-reduction strategies are most feasible.  ↩

  2. Conceptual site model (CSM): A CSM is a picture and narrative of the site contamination: how it got there, whether or not it is migrating or degrading, its distribution across the site, who might be exposed to it, and what risk-reduction strategies are most feasible.  ↩

  3. Active Gas Soil Sampling: Active soil gas sampling involves the collection of soil gas by pumping a volume of soil gas from the target zone. Samples can be analyzed immediately. Active soil gas sampling facilitates rapid assessment/expedited characterization if volatile organic compounds are primary constituents of concern for vapor intrusion. Soil gas samples can be collected with temporary or permanent sampling probes. Probes can be installed either using augered soil borings or a direct push method such as the Geoprobe®. The sampling tubing typically has a small diameter (<1/4 inch inside diameter) and made of copper, stainless steel or nylon. The tubing runs from the ground surface to the target depth. Sampling can be done at a single target depth or done in clusters where more than one sampling probe is installed at several target depths to define a vertical profile of soil gas concentrations (EPA, 2015 and EPA Region 5, 2020). ↩

  4. Active Gas Soil Sampling: Active soil gas sampling involves the collection of soil gas by pumping a volume of soil gas from the target zone. Samples can be analyzed immediately. Active soil gas sampling facilitates rapid assessment/expedited characterization if volatile organic compounds are primary constituents of concern for vapor intrusion. Soil gas samples can be collected with temporary or permanent sampling probes. Probes can be installed either using augered soil borings or a direct push method such as the Geoprobe®. The sampling tubing typically has a small diameter (<1/4 inch inside diameter) and made of copper, stainless steel or nylon. The tubing runs from the ground surface to the target depth. Sampling can be done at a single target depth or done in clusters where more than one sampling probe is installed at several target depths to define a vertical profile of soil gas concentrations (EPA, 2015 and EPA Region 5, 2020). ↩

  5. Passive Gas Soil Sampling: Passive soil gas surveys deploy absorbent materials in the ground and left for days or weeks. Contaminant vapors are collected on the absorbent material via the ambient flow of soil gas. An advantage to passive sampling is that the samplers can be placed in locations where power is unavailable and can be left unattended for long periods of time (EPA, 2015 and EPA Region 5, 2020). ↩

  6. Passive Gas Soil Sampling: Passive soil gas surveys deploy absorbent materials in the ground and left for days or weeks. Contaminant vapors are collected on the absorbent material via the ambient flow of soil gas. An advantage to passive sampling is that the samplers can be placed in locations where power is unavailable and can be left unattended for long periods of time (EPA, 2015 and EPA Region 5, 2020). ↩

  7. Perfluorocarbons (PFCs): Perfluorocarbons (PFCs) are compounds found at low levels in the atmosphere and present no identified danger to humans if inhaled or ingested. They are chemically inactive, nontoxic and nonflammable (Brookhaven National Laboratory). ↩

  8. Perfluorocarbons (PFCs): Perfluorocarbons (PFCs) are compounds found at low levels in the atmosphere and present no identified danger to humans if inhaled or ingested. They are chemically inactive, nontoxic and nonflammable (Brookhaven National Laboratory). ↩