44-25 Exhibit B-Complete - VI Letter Report - DPW West Orange - April 2023.pdf

Bureau of Case Assignment &Initial Notice Re: Vapor Intrusion Investigation Report West Orange DPW 25 Lakeside Ave April 2023 Page 9 Based on the assessment of the results, these contaminants are found in the IA, but not the SSSG samples. These compounds are likely originating from background sources unrelated to VI and there is no completed VI exposure pathway. In this case, the Mitigation Decision Matrix directs the investigator to evaluate vadose zone (soil) contamination and preferential pathways as potential contributors to IA contamination, it is established that VI is not contributing to the IA contamination, no further action is necessary for this pathway. Concentrations of trichloroethene were reported above the Residential VI Exposure Pathway Remediation Standard Criteria in samples IA-1, IA-2 and IA-3 at concentrations that exceeded only Residential Indoor Air Remediation Standards (does not apply to the Site), however they were below the Rapid Action Levels (RAL). Trichloroethene was detected above the Non-Residential and Residential Soil-Gas Screening Levels in the sub-slab soil gas samples. Therefore, long -term monitoring (LTM), without system installation, may be the appropriate mitigative action. Table 1 presents the analytical results of the indoor air gas samples. Indoor Air at DPW Garage - Maintenance Area – Storage/Repair Garage : Indoor Air sampling was not conducted within the DPW Garage. In general, the investigator should not collect IA samples in a building (or portion of a building) where operations use, handle or store the same investigative Contaminant of Concern (COC) (e.g., dry cleaners, active gas service stations, maintenance facilities, various industrial operations). In these situations, it is difficult to determine whether air contaminants present in a building are from operational activities within the facility or from the subsurface (VI). “As recommended by the NJDEP Vapor Intrusion Technical Guidance, indoor air samples were not collected at (fill in name/address of specific building) due to operational use, handling or storage of the investigative COC within the building (insert alternative language if appropriate based on site-specific circumstances). Thus, the VI pathway at this building is “indeterminate.” Unless otherwise dictated by permit requirements, annual inspections of this building are necessary to

based on site-specific circumstances). Thus, the VI pathway at this building is “indeterminate.” Unless otherwise dictated by permit requirements, annual inspections of this building are necessary to identify any change in use. A change in use necessitates the prompt completion of the VI investigation consistent with N.J.A.C. 7:26E-1.15.” Sub-slab Soil Gas Sampling Results: Benzene was detected in one sub-slab soil gas sample (SSSG-4) located within the DPW garage area at a concentration 2.5 µg/m3 which is below the Non-Residential and Residential Soil-Gas Screening Levels. P:\I00 CME7\West Orange\DPW 25 Lakeside Ave\VI Investigation 2023\VI letter Report\VI Letter Report - DPW West Orange - April 2023.docx