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Proposed Updates to NJDEP’S Vapor Intrusion Technical Guidance

The New Jersey Department of Environmental Protection (NJDEP), in coordination with stakeholders, is currently in the process of revising and updating the January 2018 Vapor Intrusion Technical Guidance document which outlines requirements for conducting vapor intrusion investigations in the state of New Jersey.  

Vapor Intrusion Technical Guidance version 5.0 is being issued primarily to reflect the recent incorporation of vapor intrusion screening levels as the NJDEP’s official Indoor Air Remediation Standards.  However, other significant changes are proposed. Arguably the most significant proposed change is the increased frequency and number of sub-slab soil gas samples that will be required based upon the size of the building footprint.   

The current document (NJDEP, 2018 Version 4.1) provides guidelines on the number of indoor air and sub-slab soil gas samples required to evaluate vapor intrusion in a building, based on the building’s size.  The proposed new version does not alter the indoor air sampling; however, proposes significant changes to the sub-slab soil gas sampling frequency as shown in the table below. 

The result of changes in the guidance will have little impact on facilities 10,000 ft2 or smaller.  Larger facilities such as warehouses, will see the number of samples  increase by an order of magnitude or greater.  For instance, a 250,000 ft2 building could require as many as 160 sub-slab vapor samples instead of the current 8 samples.  

If the proposed amendments are incorporated as currently written, the increase in the number of required sub-slab samples, especially in larger buildings, will create staggering ncreases to the complexity and cost of vapor intrusion investigations 

NJDEP, vapor intrusion