Client: Real Estate Management Company
Project: Vapor Intrusion Pathway Investigation and Mitigation
Location: New Jersey
Description: EWMA performed a vapor intrusion pathway investigation and designed and installed a vapor intrusion mitigation system for an office complex based on the guidelines provided in the New Jersey Department of Environmental Protection (NJDEP) Vapor Intrusion Guidance Document (VIG), issued in October 2005. The vapor intrusion investigation and mitigation was undertaken due to the presence of a large chlorinated volatile organic compounds (VOCs) contaminant plume in the ground water beneath the subject property that originated from an upgradient historic source.
Initially, indoor air and outdoor background air samples were collected at the office complex and analyzed for VOCs using United States Environmental Protection Agency (USEPA) Method TO-15. Upon confirmation that VOCs were present in the office complex above the applicable health-based regulatory screening levels, EWMA implemented sub-slab vapor sampling investigation at locations in close proximity to the indoor air sampling locations. The sub-slab vapor intrusion air samples were also analyzed for VOCs using USEPA Method TO-15. The results of the sub-slab air sampling were evaluated and compared to the applicable regulatory screening levels to determine if they represented a potential source of vapor intrusion.
Once it was determined that the sub-slab beneath the office complex represented a potential source of vapor intrusion from the contaminated ground water, EWMA performed field activities to aid in the design and installation of an appropriate Sub-Slab Depressurization System (SSDS), which was designed to eliminate sub-slab vapor intrusion pathways and reduce VOCs inside the office complex below regulatory permissible levels. The field activities included a field inspection of the building foundation/slab to identify any potential routes for vapor intrusion and a diagnostic field vacuum test.
EWMA used the results of the field inspection and diagnostic field vacuum test to determine the number and locations of depressurization points required, the type of SSDS most appropriate for the subject building, and to prepare a SSDS design and operational strategy, which was submitted to the client for their review and approval. In addition, an Air Permit was obtained from the NJDEP Air Quality Permitting Program (AQPP) for the installation and operation of the proposed equipment. Since the SSDS was designed to create sub-slab depressurization, and not create active soil venting, the air permit was obtained for only “de-minimis” emissions without the need for any control apparatus and/or emissions management.
Upon approval, EWMA installed the SSDS to prevent VOCs vapors from entering the interior of the subject building at the office complex. Upon completion of the SSDS installation, the sampling ports and system piping were covered with flooring and carpeting materials, and as a result were unnoticeable to building occupants. The mechanical components of the SSDS were installed in a shed outside the subject building. Following the start-up of the SSDS, to ensure that the SSDS was preventing the intrusion of VOCs vapors, and as part of the Air Permit requirements under the NJDEP AQPP, mandatory indoor air monitoring and air sampling was performed frequently during the initial two (2) years of operation and annually thereafter. The indoor air monitoring and air sampling confirmed that the SSDS was successful in reducing indoor air concentrations of the target VOCs to either non-detect (ND) levels or below the applicable NJDEP screening levels in the subject building at the office complex.