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12 2 Preliminary Investigation and Evaluation <br /> ' On Preliminary Investigation and Evaluation <br /> October 12, 1999, Ramage Environmental published ary <br /> Report, which documented the results of sod and groundwater-grab samples collected from five <br /> (5) Geoprobe®sod borings (Figure 2) One boring (SB-1) drilled through the northern end of the <br /> former UST excavation was continuously cored to a depth of 43 feet Groundwater levels <br /> measured in each of the soil borings ranged from 18 7 to 21 0 feet bgs <br /> The highest concentrations of diesel and gasoline hydrocarbons in soil and groundwater were <br /> detected in samples collected from SB-1, located within the former UST excavation Vertically, <br /> the extent of impacted soil beneath the former USTs appeared to be defined to a depth of <br /> ' between 35 and 43 feet bgs Laterally, the vertical extent of impacted soil appeared to be <br /> concentrated between 15 and 25 feet bgs, within the capillary fringe and zone of groundwater <br /> table fluctuation Concentrations of diesel and gasoline hydrocarbons were detected in the <br /> groundwater-grab samples collected at each of the five soil boring locations The soil sample <br /> analytical results are summarized in Table 1, and the groundwater analytical results are <br /> rsummarized in Table 2 <br /> 12 3 Installation of Three Monitorina Wells <br /> On March 23, 2001, Ramage Environmental published Monrtonng Well Installation Report, which <br /> documented the installation of three on-site groundwater table monitoring wells <br /> Sod and groundwater beneath the site were found to be impacted by diesel and gasoline <br /> hydrocarbons, in relatively equal proportion Concentrations of benzene were not present or <br /> significant in sod and were relatively low to groundwater Except for a couple of trace detectable <br /> concentrations, oxygenate compounds and 1,2-dichloroethane (1,2-DCA)were not present in soil <br /> or groundwater The soil sample analytical results are summarized in Table 1, and the <br /> groundwater analytical results are summarized in Table 2 <br /> 1 2 4 SensRtive Receptor Survey <br /> On June 5, 2001, Ramage Environmental published Sensitive Receptor Survey and Groundwater <br /> Mon►tonng Report, First Quarter 2001 For the site vicinity, three operating water supply wells <br /> were identified Two of these wells are operated by the city of Manteca for drinking water supply, <br /> and the other is operated by Manteca High School for all campus uses <br /> • 5 <br />