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i 1444 MARIPOSA ROAD WKA No 293 8 05 August 26, 1999 ' Page 3 depth of approximately 5 feet underlain by clayey silts with lens of silty sands to the bottom of the borings The site lies within the San Joaquin Valley Ground Water Basin(California Department of Water Resources, 1986) The upper ground water table is unconfined and approximately 40 to 50 feet bsg,based on the Fall, 1997 Ground Water Elevation Contour Map published by San Joaquin Flood Control and Water Conservation District The regional ground water flow direction is reported to be southeasterly, ground water depths have been observed to fluctuate from 111, 67 feet below grade Site History Soil Excavation On October 29 and November 2, 1992 our firm observed the excavation of approximately 1500 cubic yards of soil from the vicinity of the former underground storage tanks Ten soil samples were obtained from the sidewalls and bottom of the excavation The location of the sidewall samples is presented in Appendix B, exhibit 1 Laboratory test results for the sidewall samples, obtained from a depth of approximately 22 feet,revealed non-detectable concentrations of Total Petroleum Hydrocarbons (TPH) as gasoline, diesel, and motor oil and non-detectable concentrations of Benzene, Toluene, Ethylbenzene, and Total Xylenes(BTEX) Results for the bottom samples, obtained from depths of 27 to 30 feet,revealed TPH as gasoline (TPHg) concentrations ranging from non-detectable to 25,000 mg/kg Based on these results, the excavation was deepened to approximately 36 feet below grade on November 9, 1992 A summary of analytical results of soil samples obtained from the bottom and sidewalls of the former UST excavation are included in Appendix A, Exhibit 1 At approximately 36 feet below surface grade,petroleum hydrocarbon odors were still noticeable in the soils, so an exploratory trench was constructed in the center of the excavation to a depth of approximately 44 feet below surface grade Soil sample EX11-44' was obtained at the bottom of the exploratory trench Results of laboratory analysis revealed detectable concentrations of TPH I 0 ' WALLACE KUHL Recycled paper &ASSOCIATES INC.