U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Soil Background and Risk Assessment (SBR)

Sponsored by: Interstate Technology and Regulatory Council

Archived: Thursday, June 23, 2022
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ITRC recognized that while some state and federal agencies and other entities have guidance documents regarding soil background, there is not one comprehensive and widely accepted guidance document that summarizes the state of the science on this topic. The Soil Background and Risk Assessment ITRC guidance document released December 2021 is intended to fill the gap by providing a comprehensive defensible framework for establishing and using soil background in risk assessments. It focuses on the process of establishing defensible background concentrations of naturally occurring or anthropogenic ambient chemicals that can be used when performing risk assessment at contaminated sites.

The target audience for the ITRC Soil Background and Risk Assessment Guidance Document (SBR-1) includes risk assessors, risk managers, and site investigators, which may include federal, state, tribal, and various local agency employees; contractors to these agencies; as well as potentially liable parties and their consultants.

For training purposes, the ITRC Soil Background and Risk Assessment team produced four videos:

  • Overview of the guidance document, introduction, and definitions
  • Sampling and analytical methods
  • Establishing and using soil background in risk assessment
  • Geochemical evaluations and environmental forensics

Once the four videos are released they will be able to be viewed on demand at ITRC's YouTube Channel.

This training course will include the viewing of two of the videos that the team produced and a panel of experts to answer questions. The two videos that will be shown are:

  • Overview of the guidance document, introduction, and definitions.
  • Establishing and using soil background in risk assessment.

Even though we are only viewing two of the videos during the training, our panel of experts will answer any questions related to the guidance document.

Accessibility, Recording, and Content Disclaimer

Rehabilitation Act Notice for Reasonable Accommodation

It is EPA's policy to make reasonable accommodation to persons with disabilities wishing to participate in the agency's programs and activities, pursuant to the Rehabilitation Act of 1973, 29 U.S.C. 791. Any request for accommodation should be made to ITRC Training Program at 202-266-4932 or, preferably one week or more in advance of the webinar, so that EPA will have sufficient time to process the request. EPA would welcome specific recommendations from requestors specifying the nature or type of accommodation needed. Please note that CLU-IN provides both alternate phone call-in options and closed captioning for all webinars, and requests for these specific accommodations are not necessary.

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Content Disclaimer

This webinar is intended solely to provide information to the public. The views and opinions expressed as part of this webinar do not necessarily state or reflect those of the U.S. Environmental Protection Agency. It is not intended, nor can it be relied upon, to create any rights enforceable by any party in litigation with the United States, or to endorse the use of products or services provided by specific vendors. With respect to this webinar, neither the United States Government nor any of their employees, makes any warranty, express or implied, including the warranties of merchantability and fitness for a particular purpose, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.


A photograph of Bonnie BrooksBonnie Brooks, Washington Department of Ecology (
Bonnie has over 11 and a half years of experience providing expertise in environmental toxicology and risk assessment for cleanup sites. Ten and a half years of that experience has been for state agencies in Washington and Minnesota. While working for the Minnesota Pollution Control Agency, Bonnie established the agencies first set of soil background threshold values. Bonnie also co-led the ITRC’s Soil Background & Risk Assessment team which released a comprehensive guidance and training videos on establishing and using soil background in risk assessment in 2022. Bonnie has a Bachelor of Science in Chemistry and Master of Science degree in Environmental Health/Toxicology.

A photograph of Charlie DeWolf, Ph.D., P.G.Charlie DeWolf, Ph.D., P.G., Trihydro Corporation (
Dr. DeWolf is a senior geochemist and risk assessor at Trihydro, with 30 years of experience in environmental and analytical chemistry, environmental geology, and risk assessment. As a human health and ecological risk assessment practitioner, he has focused on complex sites including current and former chemical processing facilities and hydrocarbon refineries. In this capacity, he has applied a range of environmental forensics techniques to distinguish between sources and/or ambient signatures and concentrations for a diverse array of chemicals in numerous distinct settings. Examples include distinguishing between polycyclic aromatic hydrocarbon (PAH) sources (including wildland fire), evaluating metals releases and background in soil and sediment, use of polychlorinated biphenyl (PCB) congener analysis to distinguish facility releases from regional anthropogenic background, and identifying various sources of volatiles to soil vapor and indoor air.

As adjunct faculty at the University of Wyoming, he has taught risk analysis and communication at the undergraduate and graduate level. He has been a contributor to Interstate Technology and Regulatory Council (ITRC) teams developing guidance for risk assessment of petroleum hydrocarbons (TPHRisk-1) and the use of soil background in risk assessment (SBR).

A photograph of Brady JohnsonBrady Johnson, Idaho Department of Environmental Quality (
Brady Johnson is a hydrogeologist with the Idaho Department of Environmental Quality in Boise, Idaho. He received a B.S. in Geology from the University of Kansas and M.S. in Hydrologic Sciences from Boise State University. Brady has worked in the Technical Services Division of Idaho DEQ since 2011 with a focus on modeling and monitoring the fate and transport of chemicals in groundwater and soil and statistical methods for environmental monitoring and characterization. Brady served as a writing group co-lead for the ITRC Soil Background and Risk Team.

A photograph of Chrissy PetersonChrissy Peterson, EHS Support, LLC (
Chrissy Peterson is a Project Risk Assessor and Data Analyst for EHS Support with over 20 years of experience in environmental consulting. She graduated from the University of Virginia with a B.A. in Environmental Science and Economics and received her Certificate in Environmental Health Assessment from University of Pittsburgh – Graduate School of Public Health. Currently, her primary role is performing human health risk assessments in the US and internationally and acts as a liaison between clients and regulators to evaluate potential risks to receptors to support risk mitigation, remediation, and closure decisions. Chrissy assisted with development of the Interstate Technology and Regulatory Council (ITRC) Soil Background in Risk guidance and is actively participating in the development training modules for the guidance.

A photograph of Claudio SorrentinoClaudio Sorrentino, Department of Toxic Substances Control (California) (
Claudio Sorrentino is the Senior Toxicologist and Chief of the Northern California Unit of the Human and Ecological Risk Office, Department of Toxic Substances Control (DTSC), California Environmental Protection Agency in Sacramento. He joined DTSC in December 2007. His work includes providing scientific and technical advice to various programs within DTSC and to other agencies on risk assessment, exposure assessment, and toxicological issues. He also reviews and refines evaluations of complex sampling and analysis plans, risk assessments, and detailed biological effects studies, applying and integrating scientific, toxicologic and ecologic principles to site specific hazardous substance releases. He provides guidance in preparing more complex exposure assessments, risk assessments, and studies to evaluate the human health impacts of hazardous substance releases into the environment to determine what appropriate remedial alternatives or permit conditions are necessary. Claudio has been a member of the Environmental Molecular Diagnostic team since its formation. He graduated from the School of Pharmacy of the University of Rome (Italy) "La Sapienza" in 1989 and earned a Master in Pharmacology in 1995 from School of Medicine of the same university. He earned a Ph.D. in Environmental Health Sciences from the New York University in New York, NY in 2004 for his work on the molecular and organismic effect of co-exposure to metals and aromatic hydrocarbons in fish from the Hudson River, NY. From 2004 to 2007, he was a postdoctoral scholar performing research on the molecular mechanisms of dioxins and dioxin-like chemicals in M.S. Denison’s Lab at UC Davis. In 2006, he was the instructor in charge of teaching "Introduction to Environmental Toxicology" at UC Davis. Claudio is a full member of the Society of Toxicology and is a reviewer for the journal Chemico-Biological Interactions.

Karen Thorbjornsen, APTIM (
Karen Thorbjornsen is a Senior Geochemist with APTIM in Knoxville, Tennessee. She holds Bachelor of Science and Master of Science degrees in Geology; is a registered Professional Geologist licensed in Alabama, Georgia, South Carolina, and Tennessee; and has 25 years of environmental consulting experience. She performs background studies of metals and PAHs in environmental media and statistical analyses of environmental data. Her specialty is geochemical evaluation of metals data, to distinguish natural and ambient concentrations from site-related contamination. Ms. Thorbjornsen performs geochemical evaluations to delineate the extent of contamination, refine lists of chemicals of concern, optimize long-term monitoring programs, confirm the success of soil-removal actions, characterize background distributions, and examine statistical outliers. She has performed these evaluations at hundreds of sites across the U.S., authored several papers on the technique, taught over 30 short courses, and contributed to ITRC and ASTM guidance. Her papers have been published in Environmental Forensics Journal, Journal of Structural Geology, Remediation, and Soil & Sediment Contamination.


Nicole Henderson, ITRC Contractor (

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If you have a suggested topic or idea for a future CLU-IN internet seminar, please contact:

Jean Balent
Technology Integration and Information Branch

PH: 202-566-0832 | Email:
Michael Adam
Technology Integration and Information Branch

PH: 202-566-0875 | Email: