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I , a. Al9ni 28, 1995 95-1104802 80 Hinaman Trust Attention Mr David ChYnchen Subject REPORT - Preliminary Subsurface Investigation 2409 East Main Street Stockton, California Page 4 for the presence of total petroleum hydrocarbons as oil and grease Oil and grease were not detected by the laboratory in the soil samples from these locations Samples from the UST area, the pump island area, and the transfer pipeline area were analyzed for TPH-G and BTEX TPH-G [170 milligrams per kilogram (mg/kg)], benzene (0 051 mg/kg), toluene (0 15 mg/kg), ethylbenzene (0 30 mg/kg), and xylenes (1 0 mg/kg) were detected in soil sample B-2 TPH-G and BTEX were not detected in the soil samples from the pump island, transfer pipeline areas, and the boring adjacent to the UST's Conclusions Some relict petroleum hydrocarbons as gasoline were identified in the shallow fill material at the southern end of the former UST area No other petroleum hydrocarbons as gasoline, oil, or grease were identified in the soil samples collected from the other areas of concern at the site MARK was not able to obtain samples from directly beneath the former USTs due to till m the former UST locations One sample he presence of concrete rubble backf (B1-G) from a depth of 13 feet bgs was collected to evaluate the soil quality adjacent to the former USTs, however, due to the rubble in the UST area, this sample was collected outside the footprint of the former USTs Although this sample did not contain detectable amounts of TPH-G or BTEX, it was collected outside of the former UST footprint area Hence, the subsurface beneath the UST area remains unexplored In our conversations with Mr Ron Rowe, SJCHA, we were told that there are no records in their files of the removal of the USTs at the site Chevron USA Products Company (Chevron) has provided MARK with some limited information on the removal of the USTs, which included a copy of an engineers abandonment checklist and a ground and piping plan of the former service station The information indicates that the gasoline USTs were removed from the site in 1975 or 1976 Some of the pipelines associated with the USTs may have been left in place at the site There was no information provided on sampling or testing of the subsurface beneath the former UST area as required by present state and local UST regulations Furthermore, in MARK's discussions with Chevron, it is out understanding there are no other Chevron records to indicate that soil samples were collected during the UST removal Hence, additional sampling and analysis beneath the UST area is required Because of the concrete rubble in the backfill, a backhoe will be required to excavate the backfill in selected areas so that samples of the native soils can be collected and tested