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Updates to the NJDEP Vapor Intrusion Guidance document
The NJDEP has finalized the Vapor Intrusion Guidance (October 2005) document to provide assistance in the evaluation of contaminated sites. The document has been modified after consideration of the latest state of the science and comments received on the draft document after it was placed on the web site for external review in June 2005.
The document consists of a phased approach to investigate the vapor intrusion (VI) pathway that follows the basic provisions of the USEPA Draft Vapor Intrusion Guidance, while incorporating New Jersey specific factors/policies, when appropriate. The guidance includes a discussion of the VI pathway, VI screening levels to be used in the evaluation of a site, sampling and analytical requirements, site-specific screening options, remedial options, monitoring and maintenance requirements, community outreach, and a methodology to evaluate background air concentrations.
The following revisions to the draft (June 2005) document have been incorporated into the NJDEP Vapor Intrusion Guidance (October 2005).
- The attenuation factor used in the development of the Soil Gas Screening Levels (SGSL) has been decreased from 0.05 (20 times the health-based indoor air value) to 0.02 (50 times the health-based indoor air value) to reflect the latest science. (see Sections 4.4 and Appendix G)
- The Immediate Environmental Concern Indoor Air Action Levels (IECIAAL) have been renamed the Rapid Action Levels (RAL) and defined as trigger levels for the initiation of a prompt action at occupied buildings to investigate and/or remediate the VI pathway. The RAL are not applicable to nonresidential facilities currently handling VI related chemicals subject to OSHA regulations. (see Section 4.3.3)
- By policy, the RAL for trichloroethylene (TCE) has been changed to the TCE Health Department Notification Level noted below. (see Section 4.3.3)
- Health Department Notification Levels (HDNL) developed in cooperation with the NJDHSS has been included in the document for thirteen of the main VI contaminants of concern. (see Section 4.3.3)
- A Remedial Decision Matrix has been added to the Decision Flow Chart to better clarify the remedial action assessment in regard to the relationship between sub-slab soil gas and indoor air data. (see Sections 7.7 and Appendix A)
- The definition of a receptor has been clarified to include consideration of uninhabited structures due to the potential for future use. Open garages and limited access structures (small utility sheds) are considered case by case. (see Section 2.3)
- Several ground water sampling recommendations have been modified to provide greater clarity, more flexibility, and assist in site-specific decision making. (see Section 6.2.3)
- Descriptions of two additional “exit ramps” for completing a VI investigation have been added to the chapter on data evaluation based on analyses of ground water and/or soil gas data. (see Sections 7.2 and 7.4)
- The document has been modified to indicate that while the initial soil gas and indoor air sampling rounds are analyzed for the full suite of volatile chemicals, subsequent phases can employ a reduced list of parameters as part of an approved VI investigation work plan. (see Section 18.104.22.168 for soil gas)
Due to routine updates to the screening level tables, it is recommended that the user refer to the NJDEP Vapor Intrusion web site at http://www.nj.gov/dep/srp/guidance/vaporintrusion/ for the latest information. A notice will be placed on the web site to indicate future changes to this guidance.