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Extended Site Characterization Report: 7500 West Eleventh Street, Tracy, C4, Page 33 t The tanks removed from Tank Pit No. 2, which had characteristics indicating that they 0% 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 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. _.� 7.3.1.3 Dispenser Pit When Dietz Irrigation removed the concrete islands on which fuel dispenser pumps had -. been located and began excavating to remove piping, 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 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." To remove soil that was obviously affected by high concentrations of fuel hydrocarbons, Dietz Irrigation over-excavated the Dispenser Pit to remove as much affected soil as was practicable without penetrating below the groundwater table. The excavated soil contained moderate- to-high concentrations of both diesel and gasoline. As can be seen in Table 3, 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 Iow 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 indicate that leaks from the massive array of piping found under the dispenser islands was the source of the floating product that was extracted from Tank Pit No. 1 by vacuum.trucks. _j 7.3.1.4 Pipe Trenches Because of the maze of pipelines found in the area beneath the former pump islands, the ' normal procedure by which soil samples are recovered at intervals along the length of the trench from which a pipe has been removed could not be applied at this site. The complex array of piping found beneath the area of the former pump islands was removed in bulk and, as was noted above, the area was over-excavated to remove soil affected by fuel hydrocarbons. However, there were two pipelines, the routes of which could be distinctly identified, and it was clear that, when installed, they had been used to =j connect one area of the site with another. Those pipelines were removed and trenches -- sic i