In October 2011 The California Environmental Protection Agency’s Department of Toxic Substances Control (DTSC) released two documents related to Vapor Intrusion issues. The document titled “Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air” represents a revised document that incorporates public comments. This document, considered by the DTSC to be a final version outlining a stepwise approach to performing vapor intrusion evaluations, includes recommendations for field investigation techniques (i.e. soil gas, sub-slab, and air indoor sampling), screening of sampling results, and specific information relevant to California for use with the commonly applied Johnson and Ettinger vapor intrusion model. A description of changes to its prior guidance document is included.
The DTSC also released a final version of its Vapor Intrusion Mitigation Advisory document, which provides details on selection and design of vapor intrusion mitigation systems and operation and maintenance of mitigation systems.
Finally, the DTSC also noted that it plans to finalize its document titled “Advisory – Active Soil Gas Investigations” during the Fall of 2011. This document will provide greater detail on planning and designing field investigations related to soil gas characterization than other DTSC documents.