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2 July 13,2011 Cardno ERI 279603.W01 City of Stockton Right-of-Way,Stockton,California PREVIOUS WORK The following description of the transformer oil releases, response, and assessment is based on information provided in the Notice and associated documents (Appendix A) Transformer Oil Release On February 21, 2011, one of the two pole-mounted electrical transformers released approximately 1 to 5 gallons of mineral oil containing PCBs. The EHD was notified on February 22, 2011, by PG&E personnel. Clean Up and Assessment Activities On February 21, 2011, PG&E personnel removed the released transformer oil from the asphalt and soil beneath the pole-mounted transformers. A sample of the released oil was collected and analyzed; PCB (Arochlor 1254 exclusively)was reported at a concentration of 268 parts per million(ppm). On February 22, 2011, Phillips Transportation Services (Phillips), under contract to PG&E, removed additional I soil from the area underneath the transformers and cleaned the asphalt pavement with Penetone solution. Phillips removed approximately six 55-gallon drums of soil from the spill area. The removed soil was transported to a secure PG&E facility on West Lane in Stockton pending characterization and disposal. I I On February 23, 2011, personnel of Applied Technology Services (ATS), under contract to PG&E, collected post clean-up samples. Twelve wipe samples were collected off the asphalt pavement surface, and nine soil i samples were collected. Approximate sample locations are shown on Plate 3. Analytical results are summarized on Plate 3 and Table 1. Residual PCB concentrations (Arochlor 1254 exclusively) in soil samples ranged from 0.09 mg/kg to 2.9 mg/kg. The maximum concentration of PCB was in sample NE-21, collected along the fence line of the adjacent property owned by Teichert. PROPOSED WORK ! In the Notice issued on April 14, 2011, the EHD requested additional investigation of the release. Cardno ERI, under contract to PG&E, has developed a scope of work to address the EDH's Notice. The proposed work consists of collecting surface and shallow subsurface soil samples at ten locations in the vicinity of release. Four sample locations are proposed in exposed soil west and southwest of the pole-mounted electrical transformer location;four additional sample locations are proposed in exposed soil in the northeast comer of the I adjacent Teichert property; and two additional sample locations are proposed within the area of the release (Plate 3). At each of the eight sample locations outside the identified spill area, two soil samples will be collected: one from just below ground surface (bgs) and the second from a depth of approximately 12 inches bgs. At each of the two sample locations inside the identified spill area, one soil sample will be collected from a i i i