Vapor Intrusion Survey

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Most states are utilizing multiple lines of evidence in evaluating vapor intrusion. When assessing the vapor intrusion pathway, flux measurements were only used by less than one-third of the respondents, while all other media were used in vapor intrusion analysis at a rate of 80% or higher. The most popular medium to evaluate vapor intrusion is shallow soil gas or subslab gas. The second most frequent media to be evaluated is groundwater, followed by indoor air and deep soil gas. Direct soil analysis was used more than flux measurements at vapor intrusion sites.

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32-38. For which media does your agency evaluate the vapor intrusion pathway?

32. Soil
33. Soil gas vapor (depths greater than 10 feet)
34. Soil gas vapor (subslab or shallow depths)
35. Soil gas vapor (flux chambers)
36. Groundwater
37. Indoor air
38. Free product/Non-aqueous phase liquid

39-45. For the following media, identify by number the level of preference your agency has when reviewing the vapor intrusion pathway:

39. Soil
40. Soil gas vapor (depths greater than 10 feet)
41. Soil gas vapor (subslab or shallow depths)
42. Soil gas vapor (flux chambers)
43. Groundwater
44. Indoor air
45. Free product/Non-aqueous phase liquid

46. What best describes your agency’s procedure for estimating indoor air concentrations from subsurface data?
a. Modeling is preferred. The U.S. EPA spreadsheet version of the Johnson & Ettinger (J&E) model
is used.
b. Modeling is preferred. A different model or customized version of the J&E model is used.
c. Generic empirical attenuation factors, similar to U.S. EPA draft generic screening values, are
d. Site-specific indoor air measurements are preferred.
e. Unknown.

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