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t ..i Starttec PHASE II ENVIRONMENTAL SITE ASSESSMENT REPORT Field Activities March 31,2011 Stopcock connections were placed at the ends of the tubing to seal the tubing above the ground surface and maintain the integrity of the vapor point. Traffic cones were placed around the soil vapor wells for safety. The soil vapor wells were allowed to equilibrate for 3-days prior to collecting the soil vapor samples. 2.2.1.3 Investigation Derived Waste Soil cuttings and decontamination fluids generated during the field activities were placed into Department of Transportation (DOT)-approved 55-gallon drums, segregated by matrix (solid/ liquid), and labeled as non-hazardous waste for disposal. The drums were located along the southern property line and were secured inside the perimeter fence awaiting disposal by a licensed waste disposal contractor. Disposal of the drums will be based on the analytical results. A letter summarizing the disposal of the investigation derived waste will be addressed under a separate cover. The waste manifest documentation will be forwarded to Calpine upon receipt. 2.2.2 Soil Vapor Sampling The soil vapor investigation was conducted in accordance with the Interim Final — Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air, (Department of Toxic Substances Control [DTSC], 2005) and the Advisory — Active Soil Gas Investigations (DTSC, 2010). The soil vapor probes were installed on March 8, 2011. No rainfall was recorded at the Lodi weather station between the soil vapor probe installation date and the sample collection date. On March 11, 2011, Stantec personnel purged and collected the soil vapor samples from the Site. All field work was conducted under the supervision of a California Professional Geologist. 2.2.2.1 Shut-In Test Prior to purging and sampling the soil vapor wells, shut-in tests were conducted on each soil vapor sampling point. The shut-in test checked for leaks in the above ground fittings. The shut-in test consisted of assembling the above-ground apparatus (e.g., valves, lines and fittings), and evacuating the lines to see if there is any observable loss of vacuum. The fittings were adjusted as needed until the vacuum in the above-ground portion of the sample train did not noticeably dissipate. 2.2.2.2 Purge Volume Testing The purge volume test ensures that stagnant and/or ambient air is removed from the sampling equipment and that subsequent samples are representative of the native subsurface conditions. The actual purge volume removed was based on the total of the sample probe, the internal volume of the sample tubing, the annular space around the soil vapor probe tip, and the dry bentonite in the annular space. Three purge volumes was selected as the default volume for the soil vapor probes since SUMMA® canisters were used for the collection of the soil vapor i:\projects\calpine\lodi\reportVodi.svrpt.docx 2.3