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r a Soil and groundwater samples were placed in an ice-cooled chest and submitted under chain-of- custody procedures to BSK Analytical Laboratories (BSK), a California DHS-certified laboratory for PHC analyses. Samples were analyzed for BTEX, TPHg, and methyl tertiary- butyl ether (MTBE) using EPA Methods 802018015. The Work Plan stated that EPA Method — 200.8 would be used for analysis of lead in soil and water samples. This method uses inductively coupled plasma and mass spectrometry (ICP/MS) as the analytical technique and is typically used on low turbidity drinking water samples. However, due to the high turbidity in water samples collected during this investigation, BSK.performed lead analyses for water samples using EPA Method 200.7. Soil samples were analyzed using EPA Method 6010. Both these methods use ICP as the analytical technique. According to BSK, these ICP methods provide the same detection limits as the ICPIMS method while offering the advantage of being able.to accommodate analysis of turbid water samples. This change in analytical method for analysis of lead was conveyed to Carol Oz. 4.0 DiVESTIGATION FINDINGS Findings of the investigation, including geologic and.hydrologic characteristics, and analytical results of the soil and groundwater samples, are discussed in the following sections. 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 within 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 B1-;1 (Appendix A) indicate predominantly fine- to very fine-grained sediments to a depth of 20 feet bgs, the maximum depth explored at the site. Soils encountered at the site comprise mostly clay, silt, and silty sand. 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 ' I groundwater was encountered during excavation of the tank or soil resampling to a depth of as much as 16 feat bgs. Water levels in this area have risen as much as 8 feet since 1994, 2 4 48117UNVRPT M USTIN V APT