Vapor Intrusion Assessments

Are you looking for expert support for vapor intrusion assessments in California? Look no further than Path Forward. Our team of environmental engineers and geologists is equipped with the latest knowledge and experience to handle even the most complex projects.

We stay up-to-date with the latest requirements and guidance from key regulatory agencies, including the California Department of Toxic Substances Control (DTSC) and the California State Water Recourses Control Board (SWRCB).

Evolving Screening Levels

In California, the use of the attenuation factors for evaluating vapor intrusion has evolved over time. In 2018, California adopted the USEPA’s attenuation factor of 0.03 for evaluating vapor intrusion. In February 2023, the Cal/EPA released their Final Draft Supplemental Guidance for Screening and Evaluation Vapor Intrusion which memorialized the use of the generic 0.03 attenuation factor. Significant research has shown that this attenuation factor is not representative of conditions observed in California. For example, the June 2021 California Specific Attenuation Factor study presented by Lahvis et. al found that the use of a 0.03 attenuation factor resulted in over-predictions of vapor intrusion risk at many sites in California. Similarly, a study recently released by the California Department of Toxic Substances Control (DTSC) also found that the use of a 0.03 attenuation factor may not be appropriate in some cases and instead presented an empirical attenuation factor of 0.0009. Despite these findings, the Cal/EPA has decided to maintain the 0.03 attenuation factor as a conservative approach. This conservatism continues to create significant barriers for redevelopment and economic growth, as many properties are being flagged for potential vapor intrusion risks that are unlikely to exist.

Modeling and Lines of Evidence

The Johnson and Ettinger modeling approach is a numerical modeling method that takes into account various site-specific factors, such as soil type, building characteristics, and meteorological data, to determine a site-specific attenuation factor. This method can provide a more detailed assessment of the potential for vapor intrusion compared to the use of generic attenuation factors like the USEPA’s factor of 0.03 or the DTSC’s factor of 0.001.

In addition to the Johnson and Ettinger modeling approach, the DTSC and SWRCB also consider other site-specific factors, such as the land use, presence of a vapor intrusion mitigation system (VIMS), and the depth of the building’s foundation, when evaluating vapor intrusion.

Approach to Vapor Intrusion Assessments

Our team of experts will work with you to understand the scope of the issue and recommend the best approach to meet your specific needs. Whether you prefer a more conservative approach or a more cost-effective solution, we will ensure that you make the right choice for your specific needs.

At Path Forward, we use a combination of cutting-edge techniques, including traditional soil gas sampling, sub-slab soil gas sampling, indoor air sampling, and outdoor air sampling, as well as site-specific modeling, building design evaluation, and our regulatory relationships to provide comprehensive solutions for vapor intrusion assessments. Our team is committed to providing high-quality services and delivering real results that meet your specific needs.

So, if you’re looking for an experienced and reliable partner for vapor intrusion assessments in California, look no further than Path Forward. Contact us today to learn more about our services and how we can help you achieve your goals