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SELECTED REMEDIAL METHOD Soil vapor extraction is anticipated to be the most cost-effective method for remediation of vadose zone soils and mitigation of vapor intrusion risk at the Site. Soil vapor extraction pilot testing will be required to assess vapor extraction flow rates, radius of influence and mass removal rates. At this juncture, the selection of vapor extraction remediation at the Site is based primarily on the objective of mitigating potential vapor intrusion risk to the Site building. Should it be found that groundwater remediation, and/or remediation of the silty clay layer at and below depths of 15 feet bgs is required to further address the vapor intrusion issue, and/or to meet LTCP groundwater criteria, then additional remedial pilot testing of other remedial methods may be warranted. The following section presents a work plan for conducting soil vapor extraction pilot testing at the Site. WORK PLAN FOR SOIL VAPOR EXTRACTION PILOT TESTING The following scope of work is proposed to conduct vapor extraction pilot testing at the Site using an existing soil vapor extraction well, existing and proposed soil vapor probes (6 feet bgs), and proposed sub-slab soil vapor probes. The vapor extraction pilot testing will assess vapor extraction parameters for designing a vapor extraction system for reducing concentrations of petroleum hydrocarbons in soil and soil vapor beneath the Site to mitigate vapor intrusion risk. PRE-FIELD ACTIVITIES • Apply for and obtain a permit to install the soil vapor probes from the San Joaquin County Environmental Health Department (SJCEHD) to install soil vapor probes at the Site. • Apply for and obtain a required encroachment permit from the City of Stockton Public Works Department (SPWD) to close the sidewalk in front of the Site building for installing soil vapor probes, and for conducting soil vapor extraction pilot testing. • Mark each proposed drilling location with white paint for Underground Services Alert (USA) notification. Please note that proposed drilling locations were previously-cleared either by visual observation during previous public right-of-way improvement work conducted by the City of Stockton, or by a previous geophysical survey conducted by a licensed utility location contractor. • Provide required notifications to USA, SPWD, SJCEHD, the RWQCB, and on- and off- Site property owners as warranted prior to the conduct of field activities. FREY Environmental, Inc. 5 1092-01