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. The main purpose of this update is to reflect the recent establishment of vapor intrusion screening levels as official remediation standards. In addition to this, several other updates and clarifications are also proposed to the guidance document. While most of these changes are minor, there is one significant change: the number of sub-slab soil gas samples required in larger buildings.
The current document 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 document does not change this frequency for indoor air sampling; however, there are proposed changes to the sub-slab soil gas sampling frequency. A table summarizing current sampling frequency and the proposed frequency is outlined below.
As indicated above, the number of samples required for larger buildings has increased significantly. For example, a 500,000–square foot building currently requires 10 sub-slab soil gas samples to evaluate the vapor intrusion pathway. Under the proposed new guidance this building would require somewhere between 160 to 600 samples. Therefore, this change will significantly impact the cost of conducting vapor intrusion investigations in larger buildings. This proposed document is still draft, and therefore these proposed sampling quantities could change. JMS will continue to track the updated VI guidance and will provide updates as they are available.
Project Manager, JM Sorge, Inc.