GRACast: Role of Heterogeneity in Vapor Intrusion Assessments

Presented by:

Roger Brewer, PhD

Hawaii Department of Health

 

Subsurface media (soil, groundwater, and soil vapor) are notoriously heterogeneous. Discrete samples can be misleading since they do not capture much of the heterogeneity, and may falsely identify cold spots and “hot spots” that are a function of limited sample locations rather than actual chemical distribution. Quite often, environmental practitioners chase down hot spots while missing the real problem areas. When only a few point sampling locations are selected, the results are random and not representative of actual conditions. Outdated regulatory guidance documents recommend limited point sampling on the assumption that chemical distribution in the subsurface is relatively homogeneous. We now know that this is not the case, so the practice of collecting limited discrete samples is flawed. Other industries that must conduct representative QA sampling (e.g., manufacturing) in heterogeneous media and employ different and often much more robust sampling methodologies than those typically used at environmental cleanup sites. There is value in first defining the “Decision Unit” which is the representative sampling volume, according to “sampling theory.” This volume is almost always much larger than the typical environmental datasets.

Dr. Brewer's presentation will provide insights on 1) The role of oftentimes unrecognized, small-scale heterogeneity in the reliability of indoor air and in particular soil vapor data, 2) Implications for USEPA’s default, subslab attenuation factors (SSAFs), 3) Use of estimated vapor entry rates and indoor air exchange rates to develop more reliable SSAFs for screening purposes, 4) Development of regional, climate-based, “Vapor Intrusion Risk” regions in the US and within individual states and 4) Use of “Large Volume Purge” and targeted “Decision Unit” volumes of subslab vapors to collect more useful subslab vapor data.

*Early Registration (January 20) is $75 for Members* and $100 for Non-Members*
*Registration after January 20 is $100 for Members* and $125 for Non-Members*


SPEAKER BIO:

Roger Brewer is senior scientist and environmental hazard assessment specialist with the Hawai’i Department of Health in Honolulu. Beginning his environmental career in 1993 he has expertise in regulatory compliance audits, field investigations, contaminant fate and transport modeling and human health and ecological risk assessments. He has been instrumental in the development and field implementation of the State’s Decision Unit and Incremental Sampling Methodology (ISM) guidance, initiated in 2004, and leads regular workshops on ISM investigations for consultants and regulators. Roger has also worked as an environmental consultant in the United States, Asia, and South America and as a senior geologist and environmental risk assessment specialist for the California Environmental Protection Agency. He joined the ITRC ISM team at the initiation of the project, with a focus on Decision Unit designation and field collection of ISM samples. Roger earned a bachelor’s degree in geology from Appalachian State University in Boone, North Carolina in 1984; a master’s degree in geology from the University of Tennessee in Knoxville, Tennessee in 1986; and a doctoral degree in geology from the University of Alabama in Tuscaloosa, Alabama in 1991. He was post-doctoral student in geology at the University of Nanjing in Nanjing, China from 1991 to 1993. Roger is a registered geologist in California.

 

MODERATOR BIO:

 

Peter Scaramella is an Associate Risk Assessor with Haley & Aldrich in Oakland, California. He has 10 years of experience with vapor intrusion, indoor air quality, and risk assessment. His primary area of experience involves evaluating potential human exposure to volatile organic compounds in indoor air via the vapor intrusion pathway. Mr. Scaramella has designed and implemented numerous subsurface and indoor air sampling programs to evaluate potential exposures in indoor air and validate fate and transport models. His work has resulted in regulatory closure at sites impacted with petroleum hydrocarbons or chlorinated solvents. Mr. Scaramella holds a B.S. in chemistry from the University of California, Berkeley and a M.S. in Civil Engineering from the University of Colorado at Boulder.

 

When?

Wed, Jan. 25, 2017
12:00 p.m. - 1:00 p.m.

Event has ended

Where?

This GRACast will use a conference call for audio and WebEx to display the presentation slides. Each registration is allowed access via one phone line and one log in to the WebEx module. More than one person may participate per registration by using a shared computer screen and speaker phone. ...

This GRACast will use a conference call for audio and WebEx to display the presentation slides. Each registration is allowed access via one phone line and one log in to the WebEx module. More than one person may participate per registration by using a shared computer screen and speaker phone. GRA reserves the right to invoice those individuals and/or organizations that are logged in or connected from telephone numbers that don't correspond to a paid registration.

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