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Phase II ESA—Work Plan Yosemite Senior Housing Project Manteca,California Page 2 Condor therefore proposes to conduct a groundwater and soil-gas investigation at the Site to evaluate if a vapor encroachment concern (VEC) exists at the Site and to evaluate whether PCE is present in groundwater. Groundwater at the Site is anticipated to be encountered at 20 feet below ground surface (bgs). All work will be performed by a State-licensed (C-57 drilling license) drilling contractor under supervision of a Condor geologist. 2.0 SITE PREPARATION Condor will obtain the necessary drilling permits from San Joaquin County Environmental Health Department(EHD)prior to scheduling field activities with the sub-contractors and notifying Underground Services Alert(USA). The proposed boring locations will be marked with white paint and 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. Condor will utilize a State-licensed (C-57 drilling license) drilling contractor to conduct the drilling. We anticipate using a drilling rig equipped with direct push capability, which will minimize soil cuttings generated during the investigation. Any soil cuttings generated during the investigation will be placed in a 55-gallon drum or lidded plastic bucket, sealed, labeled, and left on-site pending laboratory analyses for disposal characterization. All borings will be backfilled with neat cement grout pursuant to EHD guidelines. 3.0 PROPOSED FIELD ACTIVITIES 3.1 SOIL GAS SAMPLING A total of three(3)multi-depth soil gas sampling probes will be installed at the Site. The temporary soil gas sampling points will be installed in general accordance with the Department of Toxic Substances Control (DTSC) and Regional Water Quality Control Board's (RWQCB) guidelines set forth in the California Environmental Protection Agency's Advisory—Active Soil Gas Investigations,dated 2015. At each of the three locations, a C-57 licensed driller will advance direct push sample rods to depths of 15 feet bgs. Double-nested temporary soil gas wells in the borings will be constructed with Nylaflow tubing and nylon screen. The screens will be placed at depths of approximately 5 and 15 feet in the middle of a one-foot-thick sand filter pack. The filter pack will be overlain with six inches to one-foot of bentonite chips followed by hydrated bentonite to the base of the next sandpack interval or to the ground surface. Prior to purging and sampling,the wells will be allowed to sit for at least two hours to equilibrate. Shut-in tests will be performed to ensure that no leaks are present in the sample train. The wells will then be purged of three void volumes (tubing and sandpack)and sampled using 400 milliliter Summa Canisters at a flow rate less than and up to 200 milliliters per minute(ml/minute).