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----------------- Site Chap-ac•terization and So mediation Plan: 7-500 West Eleventh Street, Tracy,' Page 5 �., HYDROCARBONS IN SOIL AND GROUNDWATER - J As directed by the SJCPHS representative who oversaw the tank removal, Dietz Irrigation recovered and analyzed soil samples from the tank pits, the pipeline trenches, and the excavation in the Dispenser Pit_ The results of those . -� analyses are summarized in Table 1 and discussed below. ; I Tank Pit No. 1 Four soil samples were recovered from the walls of Tank Pit No. 1 (where the four registered, recently-used tanks had been located) at the depth of the surface of-the groundwater that flowed into the pit when it was excavated to 1 remove the tanks. These sampling locations are shown on Figure 4. f None of the samples taken from the walls of Tank Pit No. 1 contained any detectable concentrations of gasoline, although low concentrations of one or more of the following: benzene, toluene, ethyl benzene and xylene isomers (the BTEX compounds) were present in three out of four of the samples. Methyl tertiary butyl ether (MTBE) was present at very low concentrations)in all four._of the samples. Diesel was detected at the moderate concentration of 2,200 Mg/Kg in the sample from the wall at groundwater level (approximately 9 ft 1 below the ground surface) in the southwest corner of the pit. However, no diesel was detected in the sample from the northeast wall, and it was found at the low concentrations of Ib mg/Kg and 270 mg/Kg, respectively, in samples _:'' from the northwest and southeastern walls of the pit. `i Only one of the samples recovered from Tank Pit No. 1 — sample TP-SE from the southeastern corner - contained any detectable concentration of lead. That concentration, at 5.3 mg/Kg, is well within the range of concentrations that . occurs naturally in soil. Similar non-detectable or very low concentrations of = 1 ead were found in other samples recovered •as part of the soil sampling program performed at the time the tanks and piping were removed from the 1 site When Tank Pit No 1 was excavated, it was necessary to penetrate below the groundwater table to effect the tank removal. When the water in the pit bottom came to a state of quiescence, floating scum of aged fuel hydrocarbons covered the water surface_ That floating product was skimmed from the water surface i._I using a vacuum truck and shipped in that truck under a hazardous waste manifest for disposal at a permitted facility. This procedure cleared the groundwater in the tank pit, and it remained free, for a time, of any obvious presence of fuel hydrocarbons. However, over the next several hours, additional floating product seeped into the groundwater from the southeaster-a corner of the pit. This floating product was also removed from the subsurface by drawing it into a vacuum truck for off-site disposal. A total of some 2,000 ( 1 gal. of floating product and affected groundwater was removed from the sic