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Site Characterization Report: 7500 West Eleventh Street, Tracy, CA. Page 13 5.2 Tank Pit No. 2 The locations from which soil samples were recovered in the bottom of the tank pit from which the four abandoned and antiquated tanks that had been discovered during Dietz ' Irrigation's tank removal operations are shown on Figure 6 and the results of the sample analyses are included in Table 1, No MTBE was detected in any of the samples of soil recovered from Tank Pit No. 2. 7 The tanks removed from Tank Pit No. 2, which had characteristics indicating that they were probably made circa 1930, were in very poor condition, with large holes that had developed due to rusting. (The San Joaquin Company Inc. 1999.) However, the samples recovered from the bottom of that pit contained only zero- to-moderate concentrations of diesel and, significantly, no concentrations of gasoline. Thus, it is apparent that those I'A tanks could not have been a source of the gasoline-containing floating product that had been seen flowing through the west wall of Tank Pit No. 1. 5.3 Dispenser Pit r ' As noted in Section 2.5, when Dietz Irrigation removed the concrete islands on which dispenser pumps were located when the fueling station was in operation, and began excavating to remove piping, it was found that the soil in that area was discolored and emitted strong olfactory indicators of the presence of fuel hydrocarbons. Because complete removal of the complex and congested array of piping involved the j excavation of what appeared to be the remnants of at least three levels of historic service station infrastructure, Dietz Irrigation's excavation in this area of the site was extensive and, for purposes of identification, it was designated as the "Dispenser Pit." As was also noted in Section 2.5, to remove soil that was obviously affected by high concentrations of fuel hydrocarbons, Dietz Irrigation over-excavated the Dispenser Pit to f remove as much affected soil as was practicable without penetrating below the J groundwater table. The excavated soil contained moderate- to-high concentrations of both diesel and gasoline. As can be seen in Table 1, samples recovered from the bottom of the Dispenser Pit, at the locations shown on Figure 5, contained diesel at concentrations ranging from 150 to 1,800 mg/Kg and gasoline at concentrations ranging from 140 to 1,400 mg/Kg, together with low concentrations of the BTEX compounds. MTBE, at a concentration of 4.4 mg/Kg, was detected in one of the three samples recovered from the floor of that pit. The high concentrations of gasoline, as well as diesel, present in the Dispenser Pit area prior to its removal by over-excavation strongly indicates that leaks from the massive array of piping found under the dispenser islands was the source of the floating product that was removed from beneath the site when it was extracted from Tank Pit No. 1 by vacuum trucks. sic