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' shows the groundwater gradient is relatively flat at approximately 8.5 x 10-4 feet per foot and the flow direction is generally toward the east southeast The flow direction appears to be consistent with the previous (third) quarter and may be locally affected by the recent operation of a groundwater extraction system approximately one quarter mile east southeast of the site 3.0 REMEDIAL PROGRAM STATUS All work conducted is focused on the goal of eventually obtaining closure for the tank area excavation and any other remedial excavation work which may be required onsite. The following is a summary of the work completed on tasks associated with soils remediation during November and December 1992. 3.1 Fourth Quarter 1992 Activities During the fourth quarter, remedial program work focused on preparation for conducting the additional excavation of the former underground tank area This work involved additional sampling of the soil stockpile onsite, evaluation of the potential effects on the buildings onsite and offsite of deepening the excavation, defining soil disposal options, and assisting the County with advising nearby residents of the current remedial plan and schedule. ' 3.1.1 Stockpile Core Sampling The soil stockpile located on the southeast corner of the site was resampled on November 3, 1992 The outside surface of this stockpile had been sampled previously but additional data was needed on the possible presence of hydrocarbon residues within the interior of the stockpile The soil stockpile is approximately 150 cubic yards in volume Four soil samples, designated S-1, S-2, S-3, and S-4 were collected from the stockpile. Refer to Figure 4 for the approximate sample locations Each sample was collected by first boring 4 to 6 feet into the stockpile with a hand auger then sampling with a drive sampler fitted with a clean stainless steel sample tube The drive sample method insures that the soil sample is undisturbed and that volatile hydrocarbon compounds, which may be present in the soil, are retained to the extent possible The drive sampler was driven into the soil in the auger borings and the sample tubes were retrieved, sealed and stored in a cooler pending shipment to the laboratory. A duplicate sample (designated S-5) was collected from the same boring as S-2 as a check on laboratory repeatability The samples were submitted under chain of custody to the Quality Assurance Laboratory in Sacramento, California for analysis of total petroleum hydrocarbons as gasoline (TPH-G) by DHS Method 3550 and for benzene, toluene, ethylbenzene and xylene (BTEX) by EPA Method 8020 The laboratory is certified by the State of California for the required analyses The analytical reports are presented in Appendix C and the results are summarized in Table 3. SCKCIRPTSI. R 4QTR WP 7 01!1N9J