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Oregon Department of Environmental Quality

Land Quality 


Environmental Cleanup
Hazardous Waste
Solid Waste

Risk-Based Decision Making for the Remediation of Petroleum-Contaminated Sites

Last Updated: June 2012


DEQ originally developed the guidance document, “Risk-Based Decision Making for the Remediation of Petroleum-Contaminated Sites,” in September 1999 and has updated it periodically. Significant updates expanded the original guidance document in 2003 to cover hazardous substance cleanups as well as petroleum-contaminated sites. In 2006 and 2007 DEQ expanded the spreadsheets associated with the guidance document to include generic risk-based concentrations for most hazardous substances of interest to DEQ. DEQ made additional updates to the spreadsheets in 2007, 2008, 2009, 2011 and most recently in June 2012. These updates included changes to some exposure factors to account for early-life exposure to certain carcinogenic hazardous substances, including some petroleum constituents, a 2009 update to the inhalation assessment methodology, and a 2011 update to account for infant exposure to bioaccumulative contaminants. Each update also included current toxicity value revisions.

The 2003 guidance document and the subsequent revised spreadsheets can be used for both: a) cleanup of petroleum releases from regulated underground storage tanks under Oregon cleanup rules for Leaking Petroleum Underground Storage Tank Systems (OAR 340-122-0205 through 340-122-0260); and b) releases of hazardous substances including petroleum under the state’s hazardous substance remedial action rules (OAR 340-122-0100 through 340-122-0115).

This guidance provides a consistent, streamlined decision-making process for evaluating risk posed to human health and the environment. Use of the guidance is optional. Responsible parties and DEQ may use other models or approaches to evaluate site risk ; these options may be more appropriate for individual sites. Alternative approaches must also meet risk-based cleanup standards specified in Oregon statute 465.315.

DEQ continues to update and revise this and related guidance and associated spreadsheets. In 2010 DEQ released two related guidance documents: 1) “Guidance for Assessing and Remediating Vapor Intrusion in Buildings” (March 2010) and 2) Human Health Risk Assessment Guidance (October 2010). Both documents contain elements that supersede the risk-based decision making guidance for evaluation of vapor intrusion problems or assessment of risk from bioaccumulative contaminants to infants. In 2009, DEQ amended equations in Appendix B of the document. Accordingly, Appendix B of the document is now outdated and does not represent current methodology as described by the U.S. Environmental Protection Agency in 2009, and as implemented in the most recent version of DEQs spreadsheets. DEQ will update Appendix B as part of the next revision of this guidance. Updated equations used in the 2011 version of DEQs spreadsheet are in Appendix C of DEQ’s Human Health Risk Assessment Guidance, available at:

Comparable equations to those used by DEQ are used by EPA for residential scenarios and are available at:

Guidance Document and Spreadsheets

In addition to the written guidance document, DEQ's environmental cleanup and tanks section periodically updates two spreadsheets used to calculate generic risked-based concentrations. These spreadsheets are provided to interested parties primarily as reference documents that contain:

  • Environmental cleanup and tanks section generic risk-based concentrations; and
  • Default exposure factors, chemical data and toxicological data used to calculate generic risk-based concentrations.

The default exposure factors, chemical data and toxicological data in these spreadsheets can be modified, where appropriate, to calculate site-specific risk-based cleanup levels.

For more complete information about the derivation of the RBCs, please refer to Appendix C of:

Copies of the Risk-Based Decision Making guidance document and spreadsheets can be obtained by downloading them from the links below. DEQ offers these spreadsheets for informational and calculation use and without official authorization or support.

[print version]


For more information about DEQ's Land Quality programs, visit the DEQ contact page.

Oregon Department of Environmental Quality
Headquarters: 811 SW Sixth Ave., Portland, OR 97204-1390
Phone: 503-229-5696 or toll free in Oregon 1-800-452-4011
Oregon Telecommunications Relay Service: 1-800-735-2900  FAX: 503-229-6124

The Oregon Department of Environmental Quality is a regulatory agency authorized to protect Oregon's environment by
the State of Oregon and the Environmental Protection Agency.

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