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a 4.1 GEOLOGIC AND HYDROLOGIC CHARACTERISTICS The site is located on the delta of the San Joaquin River, approximately 2 miles east of the confluence of the San Joaquin and Calaveras Rivers.. The subsurface geology consists of a thick sequence of alluvial deposits of late Tertiary to Holocene Age, overlying sedimentary rocks of Cretaceous to Tertiary age, which in turn overlie crystalline basement rocks (Bartow and Nilsen, 1990). Data from nearby studies wifihin-the Port area indicate a soil profile to a depth of about 20 feet bgs comprised of interbedded sands and clays, mostly under reduced conditions (Sierra-Pacific Groundwater Consultants (SPGC], 1994). Lithologic data from boring B4-1 (Appendix A) indicate a predominance of very fine-grained sediments to a depth of 20 feet bgs, the maximum depth explored at the site. Soils encountered at the site comprise f mostly clay, clayey sand, and silty sand. An approximately 2-foot-thick bed of poorly-graded, fine-grained sand occurs at a depth of about 16 to 18 feet bgs (Appendix A). Data from nearby studies indicate that the current depth to groundwater in the vicinity ranges from about 5 to 10 feet bgs (SPGC, 1998, and EMCON, 1998). Seasonal fluctuations in the water table appear to range from about 3 to 5 feet, with some as much as 6 to 9 feet. Tank removal inspection records for this and other Port sites (dating back to`1987) indicate that no groundwater was encountered during excavation of the tank or soil resampling to a depth of as much as 16 feet bgs. Water levels in this area have risen as much as 8 feet since 1994, 2 to 3 feet of which appear to be attributable to the heavy and prolonged El Nino rainfalls of last winter. The water level measured in'boring B4-1 was 8.3 feet bgs on August 4, 1998. Groundwater flow directions in the vicinity of the site appear to be variable, ranging from west northwest to east southeast. Flow direction changes-may be due to tidal influences produced by the deep water channel to the north,and the San Joaquin River to the west and southwest of the Port area. 4.2 SOH. AND GROUNDWATER ANALYTICAL RESULTS Analytical results for soil and groundwater samples collected during this investigation are presented on Table 2. The laboratory data sheets and chain-of-custody record are included in Appendix B. No PHCs were detected in the soil or groundwater samples collected from the two borings. Additionally, no discolored soils or petroleum product-odors were noted and no f organic vapors were detected by the PID in either of the borings. 1� Table 2 indicates that total lead was detected in both soil samples from boring B4-1 and in the soil sample collected from 11.5 to 12.0 feet bgs in boring B4-2. Lead concentrations range 5 981MMVRT'r %MUSrMV.Rn BOYAJIAN & ROSS, INC. �, Environmental Scientists & Engineers