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I t) �� lIfl1H1�X�[f HNfA Mr Bill Vizza 1 June 1994 Page 3 Soil samples were visually inspected for the presence of soil staining and screened for petroleum hydrocarbon vapor using an organic vapor analyzer equipped with a flame ionization detector Prior to beginning sampling activities, the organic vapor analyzer was calibrated using zero gas and methane gas standards Following standardization, a background reading for ambient air of 2 8 part per million was obtained Due to drilling refusal, three attempts were required before the desired soil sample could be collected (Refer to Figure 1) The initial soil boring location, B-1, was two feet east of the concrete slab constructed over the former tank location The second location, B-IA, was five feet east of the concrete slab and the third location, B-1 B, was ten feet east of the concrete slab Drilling location B-1 was refused at a depth of 8 feet below ground surface by broken concrete debris Unverified construction plans suggested that a concrete slab may have been present beneath the former tank However, such a slab was not noted to be present at the time of the tank removal The nature of the drilling refusal and visual inspection of the drilling bit following removal from the boring indicated that drilling was refused by broken concrete rubble and not a flat concrete surface Visual inspection of soil collected from the depth of refusal indicated the presence of broken concrete fragments not resultant from drilling Field screening of thus soil using an organic vapor analyzer (OVA) equipped with a flame ionization detector revealed readings which were less than 5 ppm, less than 3 ppm over ambient aur, and not considered to be significantly elevated Following refusal at location B-1, drilling of B-1A was attempted at a location three feet further to the east of B-1 Drilling at location B-I A was again refused at a depth of eight feet below ground surface by broken concrete debris A third attempt, drilling of B-1 B, was made at a location five feet further east of location B-IA On the basis of information provided by the City of Tracy, it is believed that this location lies at the eastern end of the former underground storage tank Drilling at location B-IB was not refused by concrete debris and reached a depth of 10 feet below ground surface where a soil sample was collected RESULTS OF LABORATORY ANALYSES Groundwater Results Each groundwater sample submitted was analyzed for total petroleum hydrocarbons as diesel (TPH-D) using EPA Method 8015 modified and benzene, toluene, ethylbenzene and total xylenes (BTEX) using EPA Method 8020 Laboratory results for April 1994 groundwater samples are summarized in Table 2 and verify the initial results indicating that petroleum hydrocarbons as diesel and benzene, toluene, ethylbenzene and total xylenes are not present in shallow groundwater at concentrations greater than their method detection limits