Newton

A former manufactured gas plant (MGP) site was redeveloped into a multi-unit commercial plaza, and an assessment of the potential for subsurface vapor intrusion to indoor air was required to comply with new Guidance from the New Jersey Department of Environmental Protection (NJDEP). The various businesses located with the commercial plaza included a hardware store, restaurant, and beauty salon, all of which were expected to have interior sources of various chemical vapors. In addition, outdoor air in parts of New Jersey occasionally exceeds the target concentrations for benzene, which is an expected constituent of MGP wastes. In order to comply with the NJDEP Guidance, without erroneously attributing background contributions to subsurface vapor sources, Geosyntec designed an investigative program and conducted forensic analysis of the data to distinguish the relative contributions of subsurface, interior and outdoor sources to indoor air vapor concentrations.