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CAMBRIA HYDROCARBON DISTRIBUTION IN GROUNDWATER TPHg and benzene were detected in groundwater from each boring at concentrations ranging from 688 to 439,000 parts per billion (ppb) and 1 52 to 13,200 ppb, respectively The highest concentrations for both TPHg and benzene were detected at 47 fbg in boring CPT-4 MTBE was detected by EPA Method 8260B only in boring CPT-] at 50 fbg at a concentration of 842 ppb and in boring CPT-4 at 47 fbg at a concentration of 29 4 ppb 1,2-DCA was detected only in borings CPT-3 and CPT-4 at concentrations ranging from 17 6 to 154 ppb TBA, ETBE, DIPE, TAME, and EDB were not detected in groundwater from any of the soil borings Groundwater chemical analytical data are summarized in Table 3 and presented on Figure 5 Laboratory analytical data are presented in Appendix C WELL SURVEY RESULTS Cambria reviewed the California Department of Water Resources Well Driller's Reports and identified two water production wells within a 2,000-foot radius of the site A municipal well owned by the City of Stockton is located at the intersection of Lincoln and Worth Streets at Columbus Park, approximately 2,000 feet north of the site A domestic well owned by Alegre Trucking of Lodi, California is located 1,900 feet northwest of the site Well specifications are summarized in Table 4 and the locations are plotted on Figure 6 SITE CROSS-SECTIONS Cambria reviewed cross-sections previously prepared by Delta and compared them with the data generated from this investigation Cambria prepared a new cross-section incorporating the logs from recent CPT borings (Figure 7) We included Delta's cross-sections in Appendix D for comparison purposes In general, the cross-section we prepared corresponds well with Delta's cross-sections The majority of the soil beneath the site is silt (silt, clayey silt, and sandy silt) However, we did note some differences between Delta's cross-sections and our cross-section Below approximately 30 fbg, Delta logged the soil as a clay (silty clay and sandy silty clay), whereas the CPT boring logs indicate the soil type at this depth is still predominantly silt Another notable difference was that Delta's cross-sections show a continuous silty sand layer extending across the site at depths ranging from 23 fbg to 32 fbg The CPT borings did not encounter this silty sand layer, which suggests it is not continuous across the site 0778 5