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Site Characterization Report: 7500 West Eleventh Street. Tracy, CA. Page 4 ' at successive times since a fueling station was first operated on the property, older fueling stations were demolished and overlain by the infrastructure and appurtenances of new facilities. 2.3 Removal of Unregistered Tanks r= As the complex piping system was removed from the subsurface, two lines, having distinct linear routes, were found and removed by trenching. The locations of the trenches, designated Pipe Trench No. 1 and No. 2, are shown on Figure 2. After the pipes had been removed, Dietz Irrigation began to recover soil samples from along their lengths. However, during the course of that work, another underground storage tank was detected just beneath the floor of Trench Pit No. 1, at sampling location PL-3 that is shown on Figure 5. Excavation around the area of that discovery revealed that there were, in fact, four 1,000-gal, underground fuel storage tanks in that vicinity, the presence of which was previously unknown. These very old (circa 1930) tanks were badly deteriorated; thus, it was impractical to inert them prior to removal from the ground. Consequently, under the oversight of a representative of the SJCPHS they were lifted r` from the ground, cut up and shipped off-site for disposal. Following the unexpected discovery of the four old tanks described above, a search was performed by excavating near the ends of all the pipe trenches and at other suspect locations on the property, but no additional tanks or fuel-dispensing infrastructure were found. 2.4 Soil Sampling in Tank Pits and Pipeline Trenches Following removal of the underground storage tanks and pipelines from the site, Dietz Irrigation recovered samples of soil from the tank pit bottoms and from locations along the trenches from which the piping had been removed, as directed by the SJCPHS }:= representative who oversaw the tank removal. Analyses were made for Total Petroleum Hydrocarbons quantified as diesel (TPHd), Total Petroleum Hydrocarbons quantified as gasoline (TPHg), Benzene, Toluene, Ethel benzene, Total Xylene Polymers (the BTEX compounds), Methyl tertiary-butyl ether (MTBE) and Total Lead. The results of those analyses are included in Table 1. These data are discussed in Section 5.0 of this report. 2.5 Over-excavation of Dispenser Pit Excavation of the piping from the area around the former pump islands revealed that soil in that vicinity was heavily affected by fuel hydrocarbons to a depth at least equal to that of the groundwater table. To remove that heavily-affected soil, Dietz Irrigation over- j excavated that area and formed a temporary stockpile of that material. For convenience of reference, the area from which that soil was excavated was designated the "Dispenser Pit." See Figure 3 for location. Analyses of representative samples of the stockpiled soil contained TPHd in the range 73 - 4,100 mg/Kg, TPHg from less than detectable concentrations to 760 mg/Kg, together sic