Guidance on Vapor Intrusion Risk-Based Concentrations Screening Levels - effective June 2023
The Oregon Department of Environmental Quality is updating how
vapor intrusion at cleanup sites is evaluated to align with the
U.S. Environmental Protection Agency's guidance and current screening levels. This is the first update since 2010.
DEQ is holding two virtual listening sessions on proposed revisions to vapor intrusion guidance.
- DEQ listening session: May 22, 2023
- DEQ listening session: June 22, 2023, 9 - 11 a.m.
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Join Zoom Meeting
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Meeting ID: 886 3409 0615 Passcode: 710352
- One tap mobile +12532158782,,88634090615# US (Tacoma) +13462487799,,88634090615# US (Houston)
For more information please contact the Vapor Intrusion Working Group at VIWorkGroup@deq.oregon.gov
Beginning in June 2023, DEQ will use risk-based concentrations, or RBCs, that match EPA's screening levels, including lowering the soil vapor and groundwater screening levels. Additionally, soil RBCs will be removed because soil has been shown to be an unreliable method for screening out vapor intrusion at a site. The updated
RBCs are available as an Excel spreadsheet and a PDF table on the
Risk Based Decision Making for the Remediation of Contaminated Sites web page.
DEQ recognizes that this may be a significant change for many of our sites. This change to vapor intrusion RBCs and the guidance will increase confidence that cleanup decisions are based on the latest science and more protective of human health and the environment.
Current guidance:
What the new RBCs will require?
- For all new screenings and risk assessments, updated RBC tables will be used unless an alternative approach is approved.
- For screenings and risk assessments underway, the updated RBCs and EPA regional screening values will apply on a case-by-case basis.
- For completed and approved evaluations, reassessment may be performed on a case-by-case basis.
- When updated RBCs are used, they should be used for all chemicals of interest at a facility.
For completed and approved evaluations, re-evaluation may be performed on a case-by-case basis. Typically, approved closures do not require reassessment unless a new decision is requested or required, and that decision needs the support of a current screening evaluation or risk assessment.
It is a significant change in these updated RBCs to not have soil screening values for this pathway. Soil data, though, has been shown to be unreliable for screening out this pathway due to its inherent heterogeneity and a variety of other reasons.
Groundwater, soil gas and indoor air are the more reliable and protective screening methods for this pathway.
- Under limited conditions, such as a soil matrix closure for Leaking Underground Storage Tank sites and a generic remedy for Heating Oil Tank sites, soil matrix values may be used to screen out this pathway and close out a site.
- These RBCs are default values to use for screening purposes. They are not rules. Project teams, with manager approval, may choose under certain site-specific circumstances to use soil data for screening out this pathway. An example may be a de minimis volume of soil contamination. However, overall, based on the latest scientific evidence, soil data is not recommended as a reliable way to screen out risk from vapor intrusion.
You can use EPA Vapor Intrusion Screening Levels at your site now. DEQ plans to publish a new RBC table at the end of May 2023. After the table is published, RBCs will be considered as follows:
- Use updated RBC tables for all new screenings and risk assessments, unless an alternative approach is approved.
- For screenings and risk assessments underway, the updated RBCs and EPA regional screening values will apply on a case-by-case basis.
- For completed and approved evaluations, reassessment may be performed on a case-by-case basis.
- When updated RBCs are used, they should be used for all chemicals of interest at a facility.
Contacts
Email VIWorkGroup@deq.oregon.gov for more information.