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Stantec PHASE II ENVIRONMENTAL SITE ASSESSMENT REPORT Conclusions and Recommendations March 31,2011 general background concentrations in California. Stantec recommends no further action. • Soil cuttings and decontamination fluids generated during the field activities were placed into DOT-approved 55-gallon drums, segregated by matrix (solid/liquid), and labeled for disposal. Waste disposal services will be subcontracted to Advanced Chemical Transport. The analytical results for the investigation-derived waste have been submitted to Advanced Chemical Transport and are pending pickup and disposal. Upon transportation and disposal of the drums a letter summarizing the disposal will be prepared under a separate cover. Disposal of the drums will be based on the analytical results; it is assumed that the waste will be classified as non-hazardous. 4.2 RECOMMENDATIONS Stantec recommends the following: • The soil vapor sample SS-2 reported PCE in the vapor phase of the soil. The practice of using PCE as a cleaning agent is no longer used by Calpine. The associated soil sample had no detections for VOCs including PCE; therefore the source of the PCE is unknown. It does not appear that a generally reportable quantity of PCE (10 pounds) has been released to the environment at this location. Due to the limited source and size of the PCE vapor concentrations and the depth to groundwater(approximately 45 to 50 feet bgs) no media other than limited soil vapor appears affected. The northern warehouse is constructed with a concrete slab-on-grade foundation and floor, a wood truss roof, and corrugated metal walls with no insulation. The building is well ventilated and has a high roof, approximately 20 feet. Soil vapor, should it penetrate the concrete floor, would rise in the building towards the roof and would not be within the breathing zone of the workers. The ventilation in the warehouse and lack of insulation would preclude the accumulation of soil vapors in the warehouse. The immediate area around the SV-2 is used for storage of boxes and cardboard. Personnel exposure would be very limited. Additionally, since the location of the sample is within the building, the potential for utility worker exposure is also limited. Due to the location of the soil vapor contamination and limited exposure, as well as an apparent limited vertical and lateral extent of PCE, vapor intrusion into buildings and long term dermal exposure and inhalation to the workers are not considered a threat to human health and therefore, Stantec recommends no further Site investigation or remediation. • Based on the soil and soil vapor samples collected as part of the Phase II ESA, no additional Site investigation is recommended. • 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 and Union Bank of California upon receipt. • Decommissioning of the soil vapors boreholes upon approval of this report and the proper permitting by the San Joaquin County Environmental Health Department is recommended as soon as possible.. is\projects\calpine\lodi\report\lodi.svrpt.docx 4.3