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Phase Q ESA —Work Plan 2222&2244 S.Airport Way, Stockton,California October 27,2017 Page 2 3.0 SUBSURFACE INVESTIGATION PLAN Condor will conduct a Phase II ESA to investigate the potential for past release of chlorinated solvents due to the reported presence of a former dry cleaning operation and for past releases of petroleum hydrocarbons from nearby former gas stations that could potentially impact the Site. This includes an evaluation of soil, soil gas and groundwater as close as possible to the location of potential contamination of the subsurface by chlorinated solvents and petroleum hydrocarbons. Four (4) soil borings and Four (4) temporary soil gas probes will be drilled and installed on Site and placed as follows: 1. One each along the norther property boundary to investigate potential vapor intrusion concerns related to the former gasoline stations located at 2141 and 2122/2156 S.Airport Way; 2. One each near the western property boundary, along the southern half of the Site, to investigate potential vapor intrusion concerns related to the former gasoline stations located at 2255 and 2305 S.Airport Way; 3. One each at the location of the former dry cleaner on Site to investigate potential vapor intrusion concerns related to the former dry cleaner; 4. One each along the eastern property boundary to investigate potential vapor intrusion concerns on the downgradient Site boundary. 4.0 FIELD PROCEDURES 4.1 SITE PREPARATION The proposed boring locations will be marked with white paint and Underground Service Alert (USA) will be notified at least 48 hours in advance of the fieldwork to locate and identify underground utilities in and near the work area. In addition, a private utility locator will be contracted to scan and identify potential subsurface piping and other anomalies, such as any remaining USTs. Prior to initiating fieldwork at the Site, all field personnel will familiarize themselves with the Site- Specific Health and Safety Plan (HASP) and a tailgate safety meeting will be held prior to commencement of fieldwork on location. The HASP pertains to field activities and includes information on potential hazards expected to be encountered at the Site,personal protective equipment, and directions to and telephone numbers for the nearest hospital.A copy of the HASP is included in Appendix B. 4.2 TEMPORARY SOIL BORINGS AND SOIL VAPOR TESTING The soil gas probes will be drilled and installed to a depth of approximately five feet bgs. Soil gas sampling will be conducted in general accordance with the DTSC's Advisory - Active Soil Gas Investigations, dated July 2015. The soil gas samples will be collected into laboratory-supplied summa canisters and shipped under chain-of-custody procedures to a California-certified analytical laboratory. After sampling is complete, each boring will be filled to the ground surface with neat cement grout. The proposed boring locations are shown on Figure 3,Appendix A. ;i1! C4ND0�