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_ .. ...... Extended Site Characterization Report: 7500 West Eleventh Street, Tracy, CA. Page 34 excavated to expose the surrounding soil to permit observation and sampling of the soil IN, along their length. Those trenches were designated Pipe Trench No. 1 and Pipe Trench No. 2; their locations are shown on Figure 3. The results of analyses of soil samples recovered at intervals along the lengths of the two pipe trenches are presented in Table 3; the sampling locations are shown on Figures 5 and ' 7, respectively. 7.3.1.4.1 Pipe Trench No. I 1 Pipe Trench No. 1 connected the former dispenser area with Tank Pit No. 1, which had contained the four registered tanks in use at the time the Olympian Service Station ceased operation. Two samples were taken from the bottom of that trench. The samples contained 930 to 1,200 mg/Kg of diesel and 130 to 530 mg/Kg of gasoline. Each of the two samples contained very low concentrations of one or more of the BTEX compounds, . but no MTBE was detected in either sample. The routing of Pipe Trench No. 1 and the components of fuel hydrocarbons found to be affecting soil along its length are consistent with an arrangement whereby gasoline and diesel were pumped from the modern underground tanks that were located in Tank Pit No. 1 to the dispensing pumps located on the pump islands. Unfortunately, it is apparent that, although the underground tanks removed from Tank Pit No. 1 did not leak, there was significant leakage in the underground piping where it was routed to the individual f ieI dispensers. 7.3.1.4.2 Pipe Trench No. 2 A second distinctive pipeline route was found along a line beginning near the southwestern corner of the former truck service bay located at the rear of the Casa Mendoza restaurant and terminating at a point in the yard to the west of the restaurant building. As was the case for the pipe described in Section 7.3.1.4.1, a trench'(Pipe Trench No. 2) was opened along the length of that pipe and soil samples were recovered .: from it. Those sampling locations are shown on Figure 7 and the results of the analyses of ' the soil samples are presented in Table 3. No detectable concentrations of gasoline or MTBE were found in any of the samples ' J from Pipe Trench No. 2, althougli some of the samples contained very low concentrations of one or more of the BTEX compounds. Two of the five contained very low concentrations of diesel, ranging from 1.0 to 3.1 mg/Kg. At the time it was removed, the purpose of the pipeline in Pipe Trench No. 2 was not apparent. However, as can be seen in Figure 3, its alignment suggests that, at some time in the past, it may have continued in the direction of Tank Pit No. 1 or, possibly, Tank Pit _ No. 2. At the time it was removed, Dietz Irrigation's Field Superintendent also reported i that the ground around its southwestern end, near the former truck service bay, appeared to be disturbed, suggesting that a tank or some other structure, might have, at some time, sic