Ohio EPA Issues Guidance for Response Action Levels and
Timeframes at Vapor Intrusion Sites
In August 2016, Ohio EPA’s Division of Environmental Response and Revitalization (DERR) released guidance
specifically for sites with a potentially complete pathway for trichloroethene (TCE) concentrations in the
groundwater or sub-slab vapors to migrate to indoor air and where sensitive receptors (i.e., women of childbearing
age) may be exposed.
Background
June 2015, the U.S. EPA’s Office of Solid Waste and Emergency Response (OSWER) issued final guidance for the
evaluation of vapor intrusion (VI) to indoor air (U.S. EPA VI guidance).
The U.S. EPA VI guidance is similar to Ohio’s 2010 VI guidance1 with emphasis on multiple-lines of evidence to
evaluate whether the VI pathway is complete. However, while Ohio’s 2010 VI guidance includes use of
mathematical models for evaluating the VI pathway (e.g., J&E models), while U.S. EPA refers to the Vapor
Intrusion Screening Level Calculator (VISL) as a primary screening method. If concentrations exceed screening
levels, further action (sampling or mitigation) is emphasized.
In May 24, 2016, Ohio’s Division of Environmental Response and Revitalization (DERR) rescinded parts of its
2010 VI guidance and currently recommends the use of the VISL when evaluating sites in Ohio. DERR further
evaluated the VI pathway leading to the recent release of the August 2016 updated guidance.
Guidance Details
The August 2016 Ohio EPA Guidance (“Guidance Document for Common Contaminants of Concern at Vapor
Intrusion Sites in Ohio”) establishes action levels (ALs) for concentrations of common chemicals encountered
during VI investigations, emphasizes the need for expedited timeframes for assessing VI risks, and outlines
updated investigation and response actions for the VI pathway. DERR indicated that ALs and expedited time
frames for TCE are particularly aggressive due to the potential for cardiac malformations in developing fetuses as
a result of short term exposures.
The response times and ALs established for TCE concentrations in indoor air, sub-slab soil gas, or groundwater as
listed below.
1
Sample Collection and Evaluation of Vapor Intrusion to Indoor Air for Remedial Response and Voluntary Action Programs”
(May 2010)
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Accelerated
Response AL
Urgent
Response AL
Imminent Hazard
Response AL
Indoor Air (ug/m3)
Residential
Commercial
> 2.1
> 8.8
> 6.3
> 26
> 20
> 60
Subslab/Soil Gas (ug/m3)
Residential
Commercial
> 70
> 290
Residential
> 11 to > 21
Commercial
> 44 to > 89
> 210
> 880
Groundwater (ug/L)
> 32 to > 63
> 130 to > 270
na
na
na
na
Response actions may include sampling, mitigation, or receptor relocation. In all cases, the appropriate state,
local, and health authorities should be notified. The accelerated timeframe for required action ranges from
immediate to within a few weeks.

Accelerated Response Action Level: Early or interim response measures evaluated and implemented
within a few weeks.

Urgent Response Action Level: Early or interim response measures evaluated and implemented within a
few days.

Imminent Hazard Response Action Level: Relocate receptors until post-remedy indoor air are
demonstrated below the accelerated response action levels.
For other chemicals of concern, action within days or weeks may not be warranted for concentrations exceeding
chronic response action levels. However, response actions may be accelerated beyond typical remedial action.
Next Steps
Although this guidance does not have the force of law, Ohio EPA recommends its use to stakeholders, including
the Voluntary Action Program (VAP), in evaluating the concentrations of volatile compounds in ground water,
soil gas, or indoor air for residential and commercial scenarios. As a result of this revised guidance, projects
should re-evaluate the vapor intrusion pathway to ensure on and off-property receptors are not at risk from the
vapor intrusion pathway. Projects currently under review may be re-evaluated against these changes in
guidance and closed TCE sites that used modeling only are being re-opened.
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How Can TRC Help?
TRC’s professionals have been assessing issues related to vapor intrusion into indoor air since the early 1980s.
TRC’s experience includes the following:
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Developing a conceptual site model (source identification and exposure pathway evaluations)
Site screening and modeling
Soil vapor, sub-slab, and indoor air testing
Vapor intrusion risk assessment
Vapor intrusion mitigation design
Remedy implementation
Coordination with USEPA and Ohio EPA
TRC utilizes its expertise from decades of contamination investigation and remediation experience, along with
our knowledge of industrial sites and processes, to identify and characterize the sources, investigate exposure
potential pathways (including preferential pathways) to the constituents of concern (COCs), and develop riskbased VI mitigation and remediation solutions.
Contact Us
For more information, please contact:
Kathleen Teuscher
Senior Project Manager/Risk Assessor
216-505-8189
[email protected]
Don Fay, PG
Vice President, Ohio VAP Certified Professional
513-489-2255
[email protected]
Dave Kreeger, PG
Project Manager, Ohio VAP Certified Professional
614- 423.6359
[email protected]
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