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CLEARWATER <br /> do <br />' 1.0 INTRODUCTION <br /> This report presents the results of third quarter 1995 field activities performed by <br />' Clearwater Group, Inc (Clearwater) at 1702 Jackson Street in Escalon, California <br /> (Figure 1) The tasks performed during this phase of work included groundwater <br /> gauging, groundwater sample collection, and vapor extraction system monitoring <br />' 2.0 BACKGROUND <br /> The subject site is located in a mixed commercial and residential neighborhood of <br />' central Escalon, a small town lying in the northern San Joaquin Valley of California <br /> The site was formerly a retail fuel facility, the service station building is the only <br /> structure that remains on site (Figure 2). <br />' Results of a subsurface investigation conducted at the site indicates that the shallow <br /> subsurface consists predominantly of unconsolidated sand and silt In general, <br />' subsurface materials contain greater clay content below depths of 55 to 65 feet below <br /> ground surface (bgs) Depth to groundwater varies seasonally from approximately <br /> 67 to 70 feet bgs. <br /> Results of analysis of soil samples collected during underground storage tank (UST) <br /> removal indicated the presence of moderate to low concentrations of fuel <br /> hydrocarbons Details of UST removal, soil sampling and preliminary site <br /> evaluation have been presented by RESNA in reports entitled Preliminary Report, <br /> Assessment of Soil Contamination (July 30, 1991) and Problem Assessment Report, <br />' Soil Contamination (December 23, 1991) <br /> A second phase of site characterization was implemented by RESNA following <br />' completion of the preliminary evaluation Four groundwater monitoring wells and <br /> several soil borings were drilled during this evaluation Results of this phase of <br /> activity indicated the presence of fuel hydrocarbons in the vicinity of the former <br />' diesel tank, the former gasoline tanks, and the gasoline dispenser island. RESNA <br /> proposed and implemented a plan for the excavation of soil containing diesel <br />' components following completion of the comprehensive site characterization <br /> RESNA also recommended the implementation of a vapor extraction program to <br /> address residual hydrocarbons beneath the former gasoline UST's <br />' A workplan for the implementation of RESNA's recommendations was prepared by <br /> Clearwater and approved by the San Joaquin County Public Health Services/ <br /> Environmental Health Division (PHS/EHD) A modification of the original plan <br /> was recommended in this workplan, the modification consisted of the installation <br /> of two additional vapor extraction wells in the vicinity of the former gasoline <br />' D-102 3Q95 1 October 23, 1995 <br /> 1 <br />