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,aa Underground Storage Tank Excavation and Soil Sampling Report PG&E's Stockton Service Center, 4040 West Lane, Stockton, CA Page 2 Phase H Sampling - January 27, 1993 On January 27, 1993 additional excavation was conducted in the areas noted above Samples collected subsequent to re-excavation of the impacted areas were analyzed for TPH as transformer oil, TOG, and PCB's by the previously mentioned EPA methodology No noticeable odor or discoloration was noted during excavation and a layer of hard silt material was encountered in the line areas Analysis of the samples indicated that significant levels of TPH as transformer oil (1800 parts per million, ppm) and oil and grease (1300 ppm) were present in the former sump area Phase III Sampling - February 10, 1993 To estimate the extent of further excavation needed in the former sump area a shovel was used to remove two feet of soil in the impacted area A sample was then collected for analysis for TPH as transformer oil, and PCB's by the previously mentioned EPA methodology TPH as transformer oil (870 ppm) and PCBs (1 1 ppm) were present above method detection limits Phase IV On March 10 the final round of excavation and sampling was conducted in the former sump area The collected sample was analyzed for TPH as transformer oil, and PCB's Analysis of the sample indicated only low levels of TPH as transformer oil (29 ppm) was present in the sump area (PCBs were not present above method detection limits) Analytical data is summarized in Table 1 and laboratory data sheets and chain-of-custody documentation are included in Attachment 1 Excavated Sail Approximately 435 cubic yards of soils were stockpiled on site, placed on and covered with visqueen As excavation was conducted apparent "clean" overburden soils were segregated from suspected petroleum contaminated soil Clean soils were stockpiled in soil piles SPI, SP3, and SPS Dirty soils were stockpiled in soil piles SP2, SP4 and SP6 Upon request from the client stockpiled soils were sampled for hazardous characterization for disposal purposes Samples collected from the stockpiled soil were analyzed for BTEX, TPHD with a fuel fingerprint, and PCBs Additionally one composite sample was analyzed for toxicity by 96 hour Fish Bioassay under Title 22 parameters Stockpiled soil characterized as "clean" have been disposed of at Gibson Oil by PG&E "Dirty" soils are on site pending preparation of a disposal plan UPORTSISSR-0393 FNL i I