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URS Ms. Michelle Le San Joaquin County Environmental Health Department February 7,2006 Page 3 Over-Excavation Activities On December 29, 2005, approximately 35 cubic yards of soil were over-excavated from the southwest corner of the UST excavation in the area of UST sample location PB-3. The location could only be excavated to a depth of 21 feet bgs due to the limits of the excavator. Strong odors and stained soil were still observed at the 21-foot depth. No sample was collected at the bottom of the over-excavation of PB-3. The over-excavated soil was stockpiled on site. On January 3, 2006, over-excavation was conducted at dispenser sample locations DI-1 and DI-4; approximately 9 cubic yards and 13 cubic yards,respectively, were removed and stockpiled on site. The dispenser areas were over-excavated to an approximate depth of 13 feet bgs. A canopy limited backhoe access; subsequently, limiting the depth of the excavation. One soil sample was collected at approximately 13 feet bgs from the bottom of each dispenser over-excavation area (DI-1-13' and DI-4- 13'). Over-excavation soil sample locations are shown on Figure 3. Most of the soil encountered during excavation was green-gray in color and had a strong petroleum odor. Groundwater was not encountered during over-excavation activities. All over-excavation activities were conducted under the supervision of SJCEHD. The analytical results of soil samples collected from the limits of the dispenser over-excavations are summarized in Tables 1 and 2. Contamination increased with depth at sample location DI-1, with the following concentrations at 13 feet bgs: 1,000 mg/kg GRO; 6.9 mg/kg ethylbenzene; and 51 mg/kg xylenes. Contamination decreased with depth at DI-4, with the following concentrations at 13 feet bgs: 850 mg/kg GRO; 1.7 mg/kg toluene;5.8 mg/kg ethylbenzene; and 47 mg/kg xylenes. Stockpiled Soil Sampling and Disposition Soil excavated during initial UST removal activities and subsequent over-excavation activities was stockpiled on site. Samples of stockpiled soil were analyzed for GRO, BTEX, and fuel oxygenates/additives by EPA Method 826013; and for total lead by EPA Method 6010B. Stockpiled soil analytical data are presented in Tables 1 and 2. Laboratory analytical reports and chain-of-custody documentation are presented as Attachment D. The soil and pea gravel overburden excavated during initial UST removal was stockpiled on site, and six two-part composite samples were collected (SP-1-2 to SP-11-12). The analytical results indicated the material was not impacted with petroleum hydrocarbons,BTEX, oxygenates/additives,or lead (Tables 1 and 2). Therefore,the excavated material was used to backfill the tank pit. One two-part and two four-part composite soil samples were collected from approximately 57 cubic yards of soil generated by over-excavation of the UST pit and two dispenser areas (December 29, 2005, K:\Wprocess\J5 BP ARCO\00595\05 UST Removal\UST Removal Rpt.doc