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4.0 FIELD INVESTIGATION ACTIVITIES <br /> APTIM will conduct the following activities as part of the Site investigation: <br /> • Utility location and sanitary sewer video inspection <br /> • Passive soil gas probe installation and sampling <br /> • Limited grab groundwater sampling <br /> • Photoionization detector screening and conditional soil sampling <br /> • Conditional sub-slab soil gas, indoor air, and outdoor air sampling <br /> • Waste sampling <br /> The following subsections describe each activity. Additional subsections also provide information <br /> regarding field observation documentation, field quality control sampling, sample packaging and <br /> shipment, and sample container preservation and storage. Table 2 provides a sampling summary for <br /> planned and conditional soil gas, groundwater, conditional soil, and investigation derived waste (IDW) <br /> sampling. Quality assurance requirements are discussed in Appendix B. Relevant Standard Operating <br /> Procedures for the below discussed activities are provided in Appendix C. <br /> 4.1 Utility Location and Video Inspection <br /> The Utility Location and Video Inspection task will involve a professional utility location contractor to <br /> identify subsurface utilities within the planned investigation areas and to trace the subsurface <br /> sanitary sewer line from the Site. This task will also involve a sanitary sewer line video inspection to <br /> assess the condition of the sanitary sewer line and identify potential locations where liquid may have <br /> historically leaked to the subsurface. APTIM will oversee the utility location contractor and video <br /> inspection. APTIM will document locations of suspected subsurface pipelines and provide the <br /> information on figures for discussion with the RWQCB. <br /> 4.2 Passive Soil Gas Probe Installation and Sampling <br /> The primary objective of the soil gas sampling task is to assess whether PCE has been released at the Site <br /> and whether the PCE concentrations are sufficiently high to pose an unacceptable risk to human health <br /> through the vapor intrusion pathway in nearby buildings. An additional objective is to confirm if PCE <br /> concentrations are present in soil gas at up to three nearby residences where the RWQCB collected indoor <br /> air samples that reported PCE. Passive soil gas results will be used to evaluate potential vapor intrusion <br /> and characterize potential sub-surface contamination. <br /> FINAL RIPON PCE INVESTIGATION WORK PLAN.DOCX 4-1 PROJECT NO.631021512 <br />