[CPEO-BIF] San Diego vapor intrusion workshop

[Lenny Siegel <lsiegel@cpeo.org>]

On March 16, 2006 I attended U.S. EPA's vapor intrusion workshop in San 
Diego, "Development, Review, and Use of the U.S. EPA's updated J & E 
[Johnson and Ettinger] Model Spreadsheet."

Some of the best minds in the field presented their recent research, and 
EPA's national vapor intrusion team presented a revised model that would 
allow investigators to walk away from a contaminated site without going 
indoors to conduct indoor air and subslab sampling, by using so-called 
"conservative" assumptions in a "Tier Three" screening. The model 
suggests using external soil gas sampling and groundwater concentrations 
to screen sites. EPA also mentioned a plan to develop a method of 
modeling based upon bulk soil sampling, but that wasn't presented.

In the evening, however, Dominic DiGiulio of EPA's Office of Research 
and Development, who applied the model to the Raymark site in Stratford, 
 Connecticut site and two New York representatives (Bill Wertz of the 
Department of Environmental Conservation and Krista Anders of the 
Department of Health) presented convincing data that the model, even 
with recent improvements, often under-predicts indoor exposures.

The modelers were shocked by the real-world data, and they were hesitant 
to believe it. The evening presenters explained that spatial variability 
often leads to low soil-gas readings, and that's what causes 
under-prediction. To some, this means taking more and deeper external 
soil-gas sampling.

To the New York agencies, it means that vapor intrusion investigations 
have to go indoors - for the collection of subslab and indoor air vapor 
samples. (Obviously, this can apply only to properties with existing 
structures.) Subslab vapor sampling complements air testing, because it 
can determine potential vapor intrusion and help determine if indoor 
readings are the result of sources other than the subsurface.

From the floor, I agreed with the New York speakers, stating that one 
can't expect people who live above subsurface contamination to be 
re-assured that their air is safe without testing that air. I also urged 
EPA to spend some energy developing  or demonstrating less expensive 
methods of real-time and near-real-time sampling for indoor air.

The predictive model still has value, particularly at redevelopment 
sites where there are no structures to sample inside or under. But it 
must be used carefully.

Lenny

Note: DiGiulio has just (March 2006) published a detailed description of 
the Raymark investigation. It can be downloaded from 
http://www.epa.gov/ada/pubs/reports.html.
However, as far as I can tell from a quick scan of the document, it 
doesn't include the comparison that he presented in San Diego.



--
Lenny Siegel
Director, Center for Public Environmental Oversight
c/o PSC, 278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918
http://www.cpeo.org
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