Vapor intrusion

OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance) (USEPA 2002)... 

Published by the EPA Office of Sohd Waste and Emergency Response (OSWER), this document provides guidance for the evaluation of the vapor intrusion exposure pathway. 

Mills, W. B., Liu, S., Rigby, M. C., and Brenner, D. (2007). Time-variable simulation of soil vapor intrusion into a building with a combined crawl space and basement. Environ Sci Technol 41(14), 4993-5001. 

Olson, D. A., and Corsi, R. L. (2001). Characterizing exposure to chemicals from soil vapor intrusion using a two-compartment model. Atmos Environ 35, 4201-4209. 

I maintain a minimum design horizontal velocity (called the escape velocity) of about 1 to lid ft per second below the bottom edge of the downcomer to prevent vapor intrusion into the downcomer (See V, Fig. 5.4). 

Work is continuing in the area of vapor intrusion, and hopefully the level of precision in modeling will increase as we learn more about how specific vapors move through the subsurface environment and foundation cracks and wall seams. Given that several volatile chemicals are more toxic when inhaled than ingested (e.g., chloroform, toluene, methylene chloride, hexane, hydrogen cyanide, chlorine, methyl isobutyl ketone, naphthalene), rigorous and accurate evaluation of this potential exposure pathway is critical to adequately protect human health. 

This second edition is organized into twelve chapters. This edition updates information presented in the first edition, and adds two new chapters that discuss emerging issues that require more research but will likely play a larger role in our everyday lives in the near future (e.g., endocrine disrupters, nanotechnology, vapor intrusion see chapters 10 and 11), and the stringent regulatory process for approving new chemicals (see chapter 12). 

FIGURE 8.10 (a) Time series of subslab and surface moisture content measured using time-domain reflectometry and (b) 5 min rainfall totals at USEPA vapor intrusion research building in Athens, Georgia. 

In this case study, we can use data generated at the test site to evaluate the influence of variability in soil moisture content and the predictive relationship used on the estimates of effective diffusion coefficients for trichloroethylene. The effective diffusion coefficient is necessary to predict TCE fluxes that could enter a stmcture due to vapor intrusion. Figure 8.10 presents data showing the observed rainfall measured at the site as well as the moisture contents observed at three locations at a consistent depth ( 0.6 m) beneath the concrete slab under the EPA facility in Athens, GA. 

Tillman, R D. and J. W. Weaver. 2005. Review of Recent Research on Vapor Intrusion. U.S. Environmental Protection Agency, Athens, GA. Publication No. EPA/600/R-05/106, 47pp. 

TUhnan, E. D. and J. W. Weaver. 2006. Subsurface soil conditions beneath and near buildings and the potential effects on soil vapor intrusion USEPA Office of Underground Storage Tanks 18th Annual National Tanks Conference, Memphis, Tennessee, March 19-22, 2006. 

Fitzpatrick, N. and J. J. Fitzgerald. 2002. An evaluation of vapor intrusion into buildings through a study of field data. Soil and Sediment Contamination 11, 603-623. 

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