Protocol for Tier 2 Evaluation of Vapor Intrusion at Corrective Action Sites

McHugh, Thomas E.; Beckley, Lila; Bailey, Danielle

doi:10.21236/ada571884

Cited by 4 publications

(6 citation statements)

References 4 publications

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“…Innovative site investigation techniques can be used to distinguish the background sources from VI (Table ). Portable GC-MS or GC has been successfully used for identifying potential indoor background sources or vapor entry points. ,,,, Another applicable method is building pressure cycling (BPC) which involves manipulation of indoor-outdoor pressure conditions to either induce or suppress VI. ,, Under positive indoor pressure, subsurface VI is minimized and indoor air sampling can be used to characterize the background sources of VI. , A combination of portable GC-MS and BPC has been successfully used to identify indoor background sources at several sites. ,, CSIA has been used to distinguish between background sources and VI. ,, Isotope signatures of VOCs may change over time due to fractionation effects associated with biodegradation or physical processes (e.g., diffusion, volatilization, sorption, and dissolution) . The differences in isotope signatures between subsurface sources and indoor-relevant products can be used to identify the origin of indoor VOCs. ,, CSIA analysis needs a relatively large amount of analyte (e.g., > 1 ng of C), but VOC concentrations in indoor air are relatively low (∼μg/m 3 ).…”

Section: Challenges In Vapor Intrusion Investigation and Decision Makingmentioning

confidence: 99%

Vapor Intrusion Investigations and Decision-Making: A Critical Review

McHugh

Beckley

et al. 2020

Environ. Sci. Technol.

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At sites impacted by volatile organic compounds (VOCs), vapor intrusion (VI) is the pathway with the greatest potential to result in actual human exposure. Since sites with VI were first widely publicized in late 1990s, the scientific understanding of VI has evolved considerably. The VI conceptual model has been extended beyond relatively simple scenarios to include nuances, such as biological and hydrogeological factors that may limit the potential for VI and alternative pathways, such as preferential pathways and direct building contact/infiltration that may enhance VI in some cases. Regulatory guidance documents typically recommend initial concentration-or distance-based screening to evaluate whether VI may be a concern, followed by a multiple-lines-of-evidence (MLE) investigation approach for sites that do not screen out. These recommendations for detailed evaluation of VI currently focus on monitoring of VOC concentrations in groundwater, soil gas, and indoor air and can be supplemented by other lines of evidence. In this Critical Review, we summarize key elements important to VI site characterization, provide the status and current understanding, and highlight data interpretation challenges, as well as innovative tools developed to help overcome the challenges. Although there have been significant advances in the understanding of VI in the past 20 years, limitations and knowledge gaps in screening, investigation methods, and modeling approaches still exist. Potential areas for further research include improved initial screening methods that account for the site-specific role of barriers, improved understanding of preferential pathways, and systematic study of buildings and infrastructure other than single-family residences.

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Section: Challenges In Vapor Intrusion Investigation and Decision Makingmentioning

confidence: 99%

Vapor Intrusion Investigations and Decision-Making: A Critical Review

McHugh

Beckley

et al. 2020

Environ. Sci. Technol.

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“…However, the method is not applicable to very large or leaky buildings, where the building pressure cannot be easily controlled (Hvidberg & Nielsen, 2015;McHugh et al, 2012).…”

Section: In Addition Literature References Indicate That the Buildinmentioning

confidence: 99%

“…It is well known that volatile organic compound (VOC) contamination in indoor air can be caused by evaporation from cleaning products, furniture, carpets, paint, wallpaper, and other interior sources. Benzene, toluene, ethylbenzene, and xylenes (BTEX) are the most common compounds found in indoor air (Johnson et al, 2016;McHugh, Beckley, & Bailey, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…With a blower door test (also known as a Building Pressure Control test, Building Pressure Cycling Methods, or Controlled Pressure Methods [CPM]), it is relatively easy to examine whether or not the presence of VOCs in indoor air is caused primary by subslab contamination or by interior sources. The Building Pressure Control test is described in several publications (Holton et al, 2017;Hvidberg & Nielsen, 2015;Johnson et al, 2016;McHugh et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Building pressure control test to examine if VOC contamination in indoor air is caused by an interior source or by a subslab source

Hvidberg

Nielsen

2017

Remediation

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When determining whether or not remediation of subslab contamination is warranted, it is often important to know if the presence of volatile organic compounds (VOCs) in indoor air is caused primarily by interior sources, or primarily by subslab contamination. With a Building Pressure Control test, the pressure differential across the building envelope and, thereby, also the pressure differential across the slab, can be controlled by a blower. By measuring the indoor air concentrations of VOCs under depressurization (upward pressure gradient over the slab) and under pressurization (downward pressure gradient over the slab), it can be determined if the subslab contamination contributes significantly to the VOC concentrations in indoor air. This technique has been applied at several sites in the Central Denmark Region, and the results show that a Building Pressure Control test is a quick and effective method to examine if VOC contamination in indoor air is caused primarily by interior sources or primarily by subslab sources. With numerous measurement points in the indoor air, at some sites this test method has identified the area where the subslab contamination is located. A pressure differential at ‒5/+5 Pa across the building envelope was sufficient at all the test sites to control the pressure gradient across the slab to be uniquely upward/downward.

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“…This research was supported by the U.S. Department of Defense, through Environmental Security Technology Certification Program (ESTCP) Project ER‐200707. See McHugh et al () for final project report. We thank Phil deBlanc with GSI Environmental for his assistance with the soil permeability model.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Influence of Shallow Geology on Volatile Organic Chemical Attenuation from Groundwater to Deep Soil Gas

McHugh

Beckley

Bailey

2013

Groundwater Monitoring Rem

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Vapor intrusion pathway evaluations commonly begin with a comparison of volatile organic chemical (VOC) concentrations in groundwater to generic, or Tier 1, screening levels. These screening levels are typically quite low reflecting both a desired level of conservatism in a generic risk screening process as well as limitations in understanding of physical and chemical processes that impact vapor migration in the subsurface. To study the latter issue, we have collected detailed soil gas and groundwater vertical concentration profiles and evaluated soil characteristics at seven different sites overlying chlorinated solvent contaminant plumes. The goal of the study was to evaluate soil characteristics and their impacts on VOC attenuation from groundwater to deep soil gas (i.e., soil gas in the unsaturated zone within 2 feet of the water table). The study results suggest that generic screening levels can be adjusted by a factor of 100× at sites with fine‐grained soils above the water table, as identified by visual observations or soil air permeability measurements. For these fine‐grained soil sites, the upward‐adjusted screening levels maintain a level of conservatism while potentially eliminating the need for vapor intrusion investigations at sites that may not meet generic screening criteria.

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Protocol for Tier 2 Evaluation of Vapor Intrusion at Corrective Action Sites

Cited by 4 publications

References 4 publications

Vapor Intrusion Investigations and Decision-Making: A Critical Review

Vapor Intrusion Investigations and Decision-Making: A Critical Review

Building pressure control test to examine if VOC contamination in indoor air is caused by an interior source or by a subslab source

Influence of Shallow Geology on Volatile Organic Chemical Attenuation from Groundwater to Deep Soil Gas

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