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MA,R - 9 - S9 THU 1 V9 P 0 4 KLEINFELDER from the backhoe bucket. Soil samples were obtained by scraping away about 4 inches of the soil in the backboe bucket with a hand trowel, then driving a clean brass tube into the native soil. Sample tubes were decontaminated prior to sampling by washing in a solution of trisodium phosphate (TSP), followed by a distilled water rinse. Each tube was retracted, capped with Teflon sheeting and tightly fitting plastic end caps. Samples were labeled, logged on a chain-of-custody, and stored on ice until delivery to California Analytical Laboratories/Enseco in West Sacramento, California. A representative from the San Joaquin Health District (SJLHD), Ms. Kasey Foley,was present throughou- the sampling process. Sample 31034 was taken from the west end of the excavation, and sample 31035 was obtained from the east end (Plate 3). Both samples were taken at approximately 8.5 feet below ground surface. The soil consisted of a medium brown, moist, silty clay. A photoionization detector (PID) used in the field to screen the soil for volatile organic constituents, Neither of the two soil samples showed PID readings above ambient background levels. The samples were analyzed for total petroleum hydrocarbons extractable (Method 3550) by GC-FID; and benzene, toluene, ethylbenzene, and xylene by EPA Method 8020. The samples were analyzed on a one-week, rush, turnaround schedule. Of the analyses requested by the SJLHD, only one constituent was present above the laboratory reporting limit. Sample 31035 (east end of the tank) had 110 mg/kg total petroleum hydrocarbons as diesel (Plate 3), 4. Depth to ground water has been measured at a depth of approximately 30 feet by Kleinfelder geotechnical personnel during a soils engineering study of the site in 1988. Soil staining was not visible in the area where Sample 31035 was collected. Based on the lack of visible soil staining and the low concentration of total petroleum hydrocarbon (TPH) deqtected, i,t is estimated that the re-excavation should not extend more than sev@rraI feet beyond the location where Sample 31035 was collected. The sample points to verify completion of the re-excavation will be selected using SJLHD guidelines for assessing lateral and vertical extent of soil contamination (Guidelines for Re-excavation Work Plan for UGST Soil 171-89-412