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10 <br /> during the removal of the tanks; one sample from beneath the north and south ends of each of <br /> the two tanks Although the exact depths of the samples are not listed, the PHS/EHD <br /> inspection report states the samples were collected "approximately 2 feet below the bottom <br /> of the tanks," which would place them about 13 feet bgs No groundwater was encountered <br /> during excavation or sampling Gray soil discoloration and strong petroleum product odor <br /> were noted at the southern end of both tanks. Minor product odor was noted at the north end <br /> of Tank //1, while no odor was noted at the north end of Tank #4. <br /> Four additional soil samples were collected by SSSE on March 15, 1988 These samples were <br /> collected from the same locations as during the tank pulls, but from a depth of 16 feet bgs <br /> A PHS/EHD inspection report indicates "grey soil observed on all samples with petroleum-like <br /> odor." The report also notes that no groundwater was encountered to a depth of 16 feet bgs <br /> Subsequent to the removal of the tank, the area over the former tanks and excavation has been <br />' paved with concrete <br />' 2.2 SUMMARY OF PREVIOUS SITE CHARACTERIZATION WORK <br /> Soil samples collected from beneath the tanks were submitted to California Water Laboratories <br /> for analysis All soil samples were analyzed for total petroleum hydrocarbons as gasoline <br /> (TPHg) and total petroleum hydrocarbons as diesel (TPHd) by EPA method 8020, and <br /> benzene, toluene, and total xylenes (BTX) by EPA method 8020. Selected samples were <br /> analyzed for ethylene dibromide(EDB) by EPA method 8010, and total lead (analytical method <br />' for lead not specified on laboratory reports, see Appendix A). Analytical results (Table 1) <br /> indicated low levels of PHCs detected in the initial soil samples, primarily in the samples <br /> collected at the south ends of the tanks where petroleum product odor was noted. However, <br /> ' PHCs in the follow up samples collected approximately 5 feet below the initial samples, were <br /> significantly attenuated relative to the initial samples (Table 1). No EDB was detected in any <br /> ' of the samples. Lead was detected at 6 to 12.4 mg/kg in the i utial samples from the north <br /> ends of both tanks, but was not detected in the follow up samples at 16 feet bgs (Table 1). <br /> ' <br /> 2.3 GEOLOGIC AND HYDROLOGIC CHARACTERISTICS <br /> The subject site is located on the delta of the San Joaquin River, approximately 2 miles east <br /> of the confluence of the San Joaquin and Calaveras Rivers The subsurface geology consists <br /> of a thick sequence of alluvial deposits of late Tertiary to Holocene Age, overlying sedimentary <br /> rocks of Cretaceous to Tertiary age, which in turn overlie crystalline basement rocks (Bartow <br /> ' 3 sa1i7+s23usrav wmv <br /> BOYAJIAN & ROSS, INC <br /> Environmental Scientists & Engineer% <br />