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i r • 4.0 SITE GEOLOGY ' Sediments underlying the Site consist predominantly of a brown to tan-brown clayey silt with a localized lens of tan to grayish-tan sandy silt based on the lithologic logs of borings that were previously drilled at the Site rPrevious depth-to-groundwater measurements conducted at the Site indicated that groundwater is approximately 15 to 16 feet bgs ' Mapping and analysis of the groundwater elevation data suggested that the local groundwater gradient flowed in a northeasterly direction ' 5.0 SUPPLEMENTARY GROUNDWATER INVESTIGATION r Permits were obtained from SJC-EHD and the City of Stockton Public Works Department (Stockton-PWD) prior to the initiation of groundwater sampling activities Copies of the permits are included in Appendix B SJC-EHD and Stockton-PWD were also notified 48 hours prior to drilling and sample collection Site preparation included screening the boring locations using a magnetometer to assess the potential presence of underground utilities and saw cutting the sections of the sidewalk where the borings were located Underground Services Alert and Cruz Brothers of Milpitas, California were contacted to assist in utility clearance activities The drilling and sampling activities were conducted by West Hazmat Drilling Corporation of Rancho Cordova, California on November 17 , 2001 and observed and documented by ICES A total two grab groundwater samples were collected from two offsite boring locations Boring HP--1 was located within the ' sidewalk on the south side of West Sonora Street, approximately 25 feet west of the southwest corner of West Sonora and South Lincoln Streets Boring HP-2 was located within the sidewalk on ' the west side of South Lincoln Street approximately 18 feet south of the southwest corner of West Sonora and South Lincoln Streets . The approximate boring locations are shown in Figure 2 Grab groundwater samples were collected from HP-1 and HP-2 using a hydropunch from the borings Hollow diameter steel casing containing a perforated PVC screen at the bottom of the casing was advanced to approximately 3 feet below the first permeable zone The casing was retracted approximately 4 feet to allow infiltration of the groundwater. A groundwater sample was collected from each hydropunch by lowering a Teflon bailer through the hollow casing The samples were transferred into 40- ml VOA vials, 1-liter amber-colored glass bottles, and 500-m1 3 1