Laserfiche WebLink
Extended Site Characterization Report: 7500 West Eleventh Street, Tracy, C4, Page 33 <br /> t The tanks removed from Tank Pit No. 2, which had characteristics indicating that they <br /> 0% were probably made circa 1930, were in very poor condition, with large holes that had <br /> developed due to rusting (The San Joaquin Company Inc. 1999). However, the samples <br /> recovered from the bottom of that pit contained only zero- to-moderate concentrations of <br /> ' diesel and, significantly, no concentrations of gasoline. Thus, it is apparent that those <br /> tanks could not have been a source of the gasoline-containing floating product that had <br /> been seen flowing through the west wall of Tank Pit No. 1. <br /> _.� 7.3.1.3 Dispenser Pit <br /> When Dietz Irrigation removed the concrete islands on which fuel dispenser pumps had <br /> -. been located and began excavating to remove piping, the soil in that area was discolored <br /> and emitted strong olfactory indicators of the presence of fuel hydrocarbons. <br /> Because complete removal of the complex and congested array of piping involved the <br /> excavation of what appeared to be the remnants of at least three levels of historic service <br /> station infrastructure, Dietz Irrigation's excavation in this area of the site was extensive <br /> and, for purposes of identification, it was designated as the "Dispenser Pit." <br /> To remove soil that was obviously affected by high concentrations of fuel hydrocarbons, <br /> Dietz Irrigation over-excavated the Dispenser Pit to remove as much affected soil as was <br /> practicable without penetrating below the groundwater table. The excavated soil <br /> contained moderate- to-high concentrations of both diesel and gasoline. <br /> As can be seen in Table 3, samples recovered from the bottom of the Dispenser Pit, at the <br /> locations shown on Figure 5, contained diesel at concentrations ranging from 150 to <br /> 1,800 mg/Kg and gasoline at concentrations ranging from 140 to 1,400 mg/Kg, together <br /> with Iow concentrations of the BTEX compounds. MTBE, at a concentration of 4.4 <br /> mg/Kg, was detected in one of the three samples recovered from the floor of that pit. <br /> The high concentrations of gasoline, as well as diesel, present in the Dispenser Pit area <br /> prior to its removal by over-excavation strongly indicate that leaks from the massive <br /> array of piping found under the dispenser islands was the source of the floating product <br /> that was extracted from Tank Pit No. 1 by vacuum.trucks. <br /> _j 7.3.1.4 Pipe Trenches <br /> Because of the maze of pipelines found in the area beneath the former pump islands, the <br /> ' normal procedure by which soil samples are recovered at intervals along the length of the <br /> trench from which a pipe has been removed could not be applied at this site. <br /> The complex array of piping found beneath the area of the former pump islands was <br /> removed in bulk and, as was noted above, the area was over-excavated to remove soil <br /> affected by fuel hydrocarbons. However, there were two pipelines, the routes of which <br /> could be distinctly identified, and it was clear that, when installed, they had been used to <br /> =j <br /> connect one area of the site with another. Those pipelines were removed and trenches <br /> -- sic <br /> i <br />