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T & T EARTH SERVICES y Tom Hunt Tim Smith P.O. Box 1121 P.O. Box 1618 Jackson, CA 95642 Sutter Creek, CA 95685 WAM T $ T (209) 223-281109 ►� E�AtH SERY��S (209) 267-0903 sF�r *`J'a August , lip 1992 ' LES CALKINS TRUCK YARD UST SAMPLING RESULTS AND RECOMMENDATIONS FOR FURTHER ACTION INVESTIGATION RESULTS ' SUMMARY Soil boring and sampling of the existing spoils pile was completed on the Les Calkins Truck Yard site on 7-7 and 7-8-92. ' The work was completed in the presence of Michael Collins of San Joaquin County Environmental Health Department and under the California Luft Manual guidelines. Four soil borings and 4 spoils ' pile samples were completed . Sampling showed a halo of diesel contamination around the tank excavation pit . The contamination appears to be dispersed M out from the tank area and diminishes to low levels at about 15 feet below surface elevation at the perimeter of the pit and at about 20 feet in the middle of the pit . Considering the geology and hydrologic conductivity of the units encountered the sampling results fit closely a conceptual model which seems appropriate for the site. The surface units down to about 20 feet had been tentatively ' characterized as sands. These units upon closer examination should more properly be characterized as clays with a high sand component . Hydrologic conductivities within these units should be in the range of .002 to . 1 meter per day. The clean sand unit ' from 20 to 25 feet should have a hydrologic conductivity of . 1 to 2.5 meters per day. Sampling shows the diesel hydrocarbons did not disperse to ' the clean sand except for a minor amount in drill hole SB-4 at 22.5 to 24 feet. The bulk of the hydrocarbons from the repeated spills at the tank fill and pump area appear to have been heavily ' sorbed to the clay particles in the upper clay zone. This would be expected in the vadose zone of a system such as this . The entire sampled area is underlain by a tight clay unit at 34 to 35 feet . The bottom of this clay layer was not encountered ' but it was at least 1 .5 feet thick in hole ##2. No contamination was evidenced at this sand/clay interface indicating no exposure to hydrocarbons at this depth . No ground water was encountered in any of the holes nor was evidence of seasonal saturation encountered . Investigation into the probable depth to ground water indicate seasonal fluctuations from about 45 to 60 feet below ground surface in the area . Table 1 shows the sample results of the sampling completed .