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Site Characterization and Son..emediation Plan: 7500 West Eleventh Street, Tracy, A. Page 6 r� subsurface by those operations. A sample of groundwater was taken from Tank Pit No i at a time when the pit was free of floating product. The sample was analyzed and the results are presented in Table 2. The groundwater was found to contain 210,000 µg/L (parts per billion) of diesel and 55,000 µg/L of gasoline, with commensurately . high concentrations of the BTEX compounds and 24,000 µg/L of MTBE. There were no holes in the tanks removed from Tank Pit No. 1 and there were no apparent locations from which fuel appeared to have spilled or leaked from them. It also appears from inspection of Tables 1 and 2 that the type and ` concentrations of components of fuel hydrocarbons found in the groundwater are inconsistent with those detected in soil from the walls of the pit. In addition, as noted above, fuel hydrocarbons flowed into the pit from itswestern wall after each occasion when floating product was removed from the surface of the water. f .l From the above observations, it appears that the principal source of fuel hydrocarbons in soil and groundwater is to the west of Tank Pit No. 1. (Although, given the presence of the recently introduced oxidizer MTBE in the soil samples taken from the walls of that pit, a secondary source of leakage in that immediate area cannot be excluded). It is probable that soil and groundwater in that area has been heavily affected by fuel hydrocarbons spreading from locations to its west most likely the area of the Dispenser Pit or ,;,.. Tank Pit No. 2, from which the four old, deteriorated tanks were removed (See Figure 3 for locations ) Dispenser Pit When the Dispenser Pit was excavated, the soil in that area was discolored and emitted strong olfactory indicators of the presence of fuel hydrocarbons. As directed by the SJCPHS representative, three samples were recovered from the bottom of the pit, at a depth of approximately 7 ft., which was a short distance above the groundwater table. The sample locations are shown on Figure 5; the concentrations of analytes of concern detected in those samples are presented at the bottom of Table 1 Diesel at a concentration of 1,800 mg/Kg was detected in sample D-2-7,,and at 270 mg/Kg and 150 mg/Kg, respectively, in samples D-3-7 and D-1-7. Gasoline, at concentrations ranging from 140 mg/Kg to 1,400 mg/Kg was also detected in the samples, together with low concentrations of the BTEX compounds and 4.4 mg/Kg of MTBE, which was found in sample D-3-7 No MTBE was detected in sample D-1-7 or D-2-7. As will be discussed later, the soil that was excavated from this pit also contained diesel, gasoline, BTEX and - MTBE at concentrations of generally similar magnitude to those detected in the samples recovered from the floor of the Dispenser Pit. sic