Ohio EPA Issues Final Vapor Intrusion Guidance
Published in the March 2020 Focus on the Environment Newsletter
Cox-Colvin & Associates personnel routinely provide vapor
intrusion (VI) training to regulators, attorneys, environmental professionals,
and the regulated community; and have helped in the development of VI guidance
within the US and throughout Latin America and Europe. As a result, we have had the opportunity to
review a large number of VI guidance documents over the years.
On March 10, 2020, Ohio EPA released a final version of its updated “Sample Collection and Evaluation of Vapor Intrusion to Indoor Air for Remedial Response and Voluntary Action Programs” (Ohio EPA VI Guidance or Guidance). In our opinion, Ohio EPA, with input from a variety of experienced stakeholders, have crafted a very comprehensive yet flexible approach to the assessment and mitigation of VI sites within Ohio. Even though the Guidance is by nature Ohio-centric, the approaches, processes, and documentation presented in the document could be helpful to anyone conducting VI assessments.
The Ohio EPA VI Guidance, initially released in 2010, was
developed for sites under the oversight of the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980 (CERCLA), the Resource
Conservation and Recovery Act (RCRA), and the Voluntary Action Program (VAP),
carried out under the supervision of Ohio EPA Division of Environmental
Response and Revitalization (DERR). The 2020 Version is the second
update. In May 2016, Ohio EPA rescinded Chapters 10 (data evaluation) and 11
(modeling the VI pathway using the Johnson and Ettinger [J&E] model). Ohio
EPA considered Chapters 10 and 11 out of date and no longer appropriate for
projects seeking cleanup under any of the DERR programs.
The 2020 Guidance has been significantly expanded and improved in
many ways. We can appreciate the difficulty and effort that went into the
rewrite, given the continued rapid evolution in the science of VI and in the
underlying human health toxicity factors for which there seems to be little
The general approach to sites is similar to other modern
guidance documents for VI: understand the history of volatile compound uses
and/or releases at your site, develop a robust conceptual site model (including
preferential pathway analysis), base decisions on multiple lines evidence
(sampling of various environmental media), compare results to applicable
standards and mitigate as necessary.
Provided below are some of the more significant changes to the
- The Guidance
incorporates Ohio EPA’s somewhat controversial imminent hazard indoor air
action levels published by Ohio EPA in the August 2016 as a standalone document
titled “Recommendations Regarding Response
Action Levels and Timeframes for Common Contaminants of Concern at Vapor
Intrusion Sites in Ohio.” In the 2016 document, Ohio EPA
established response actions and timeframes for common chemicals (TCE and
others) encountered during VI investigations when receptors are present. The response actions, tied to specific indoor
air and/or sub-slab soil gas concentrations, include removal of occupants until
a remedy can be put in place. If you are
a VI practitioner, you need to be aware of these limits and have a frank
discussion with your client about potential actions that may be advised
following the receipt of the analytical results.
environmental samples to support multiple lines of evidence is a common theme
in the guidance. The 202 guidance
incorporate a welcomed and fundamental shift in the significance of sub-slab
sampling, placing greater emphasis on the use of sub-slab data, and less
emphasis on groundwater, bulk soil, and exterior soil gas data. It is encouraging to see that Ohio EPA has included
significant warnings against using bulk soil samples. We have reviewed many assessments that have
incorrectly concluded that VI pathway was incomplete based on the results of
bulk soil samples. The most important
message we provide during VI training is that if you want to understand VI, you
must collect soil gas samples.
- The Guidance includes
a section devoted to VI from petroleum releases, based in part on the 2015 US EPA Technical Guide for
Addressing Vapor Intrusion at Leaking Underground Storage Tank Sites. Once released, petroleum hydrocarbons behave
differently in the environment and are generally less toxic and less mobile
than chlorinated solvents. Because of the effectiveness and speed of
aerobic biodegradation in biologically active soils, Ohio EPA recommends,
consistent with US EPA and ITRC Guidance, reduced lateral and vertical
investigation distances at relatively small petroleum releases compared to
chlorinated solvent sites.
- The Guidance includes
the following critical statements related to the evaluation of VI data in Ohio. “For Ohio EPA DERR RP (remedial program) sites, when considering
concentrations measured in sub-slab, soil gas, or ground water, the VISLs
should be applied corresponding to an excess lifetime cancer risk (ELCR) of
1E-5 and a hazard quotient (HQ) of 1. If the measured concentrations in
the sampled media are less than the appropriate VISLs set at an ELCR of 1E-05
and a HQ of 1 for the appropriate exposure scenario, Ohio EPA DERR considers
the pathway to be ‘incomplete’ and additional investigation or risk estimation
of this pathway is not warranted.” Although Ohio EPA
DERR has consistently utilized an ELCR of 1E-5 and a HQ of 1 in VI work, we believe
this is the first time this has been clearly stated in the guidance. A
similar comment is included for Ohio VAP sites which includes reference to the
VAP-required multiple chemical adjustment.
- The Guidance presents
Ohio EPA’s position on the Ohio EPA/OSHA jurisdiction issue when it comes to
indoor air contamination derived from vapor intrusion. You may or may not
agree with the position, but at least it’s out in the open.
- The Guidance includes
a section devoted to remedies (Section 13) organized largely around the concept
of risk level and time frame, including imminent, acute, chronic, and unknown. Included in Section 13 are discussions of
monitoring requirements for engineering controls (mapping of the
depressurization field and indoor air sampling) and post-mitigation sampling
(pressure and/or indoor air sampling to demonstrate system effectiveness
through seasonal variation).
- The Guidance covers,
as Section 14, the critically important topic of long-term management and exit
strategies at VI sites where mitigation measures are installed.
- Included as appendices
to the Guidance are special considerations for evaluating residential
properties, a VI conceptual site model checklist, Ohio EPA’s standard operating
procedures and field data collection forms, comparison of tubing type to vapor
absorption, and soil gas analytical methods and reporting limit ranges.
Although the Guidance is very comprehensive, we do suggest that
practitioners may want to keep a few things in mind going forward.
- The Guidance suggests
that you limit the COC for indoor air to those compounds detected in sub-slab
soil gas so that you can more easily eliminate the compounds associated with
indoor sources. We believe this is a bit
too conservative. Sanitary sewers are
probably the most important preferential pathway and as such, you should expand
the indoor COC list a bit to include compounds such as chloroform, carbon
disulfide, bromoform, and tetrahydrofuran.
If these compounds are detected in indoor air, the VI issue may be
related to poor plumbing connections, which can be easily and inexpensively
resolved. Without this data, you may end
up installing a more expensive sub-slab system and still have a VI issue.
- The Guidance is silent
to PFAS and PFOS. These compounds may
become risk drivers for indoor air in the future.
- US EPA is placing a
renewed emphasis on how to predict the most opportune time to collect an indoor
air sample. Expect new guidance on using
surrogates such as sub-slab differential pressure reading, indoor radon
concentration, outdoor temperature, and barometric pressure to predict timing
of air sampling.
- Continuous vapor
monitoring over a brief period (2 weeks or less) can help sort out the
complexities and temporal variability of COC concentrations in indoor air. The Guidance is silent on this as an
approach; however, we are confident if you proposed it for your site, Ohio EPA
would not resist its use.
Craig Cox is a principal and co-founder of Cox-Colvin & Associates, Inc., and holds degrees in geology and mineralogy from the Ohio State University and hydrogeology from the Colorado School of Mines. Mr. Cox has over 30 years of experience managing large environmental project implemented under CERCLA and state voluntary action programs. Mr. Cox is the inventor of the Vapor Pin® and has developed a variety of software products including Data Inspector, an internet-enabled environmental database application. Mr. Cox is a Certified Professional Geologist (CPG) with AIPG and is a Certified Professional (CP) under Ohio EPA's Voluntary Action Program.
Laurie Chilcote currently serves as Office Manager and Director of Sales & Marketing for Cox-Colvin & Associates, Inc, and is a Director and Vice President of Vapor Pin Enterprises, Inc. At Cox-Colvin, Ms. Chilcote is responsible for management and presentation of analytical data including the transfer of electronic analytical results from various resources. In addition, she is a managing Director and Vice President of Vapor Pin Enterprises and Vapor Pin Brazil, where she provides managerial and technical oversight on all marketing and sales for the Vapor Pin® both within the USA and Internationally. Laurie’s role includes educating the environmental community on Vapor Pin® technology, implementation, and quality control by making presentations to environmental firms, regulatory agencies and developers throughout the USA and Internationally.