Department of Health Seal

TGM for the Implementation of the Hawai'i State Contingency Plan
Section 7.3
DEVELOPMENT OF VAPOR INTRUSION SCREENING TOOLS

7.3 DEVELOPMENT OF VAPOR INTRUSION SCREENING TOOLS

Assumptions regarding the local nature of vapor intrusion and building ventilation can be used to develop environmental action levels for rapid screening of suspect sites. Development of the HDOH soil, groundwater and soil gas (“vapor”) action levels for vapor intrusion is discussed in the HDOH EHE guidance document (HDOH 2016; see also HDOH, 2016b.). A detailed discussion of indoor air:subslab soil gas attenuation factors selected for use in Hawai‘i is provide in Section 13 and serves as a supplement to the EHE guidance.

Application of the guidance and screening tools at petroleum-contaminated sites was evaluated in the HDOH study entitled Field Investigation of the Chemistry and Toxicity of TPH in Petroleum Vapors: Implications for Potential Vapor Intrusion Hazards (HDOH, 2012). The results of this study were incorporated into the petroleum section of the HDOH EHE guidance (HDOH 2016). A Question and Answer fact sheet on this document provides additional clarification on the application of the guidance and screening tools at petroleum-contaminated sites (HDOH, 2012c).

As discussed in Section 13 and the EHE guidance, the selected attenuation factors and associated HDOH action levels for vapor intrusion may not be adequately conservative for use in colder regions on the US mainland and elsewhere. Adjustment of the action levels to assumptions regarding vapor flux and building ventilation is required and should be discussed with the overseeing regulatory agency.