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i t <br /> r <br /> i <br /> TECHNICAL DATA SUMMARY <br /> j THE SOUTHLAND CORPORATION <br /> 1 SOUTHLAND SITE NO. 20680 <br /> E 9110 THORNTON ROAD <br /> STOCKTON, CALIFORNIA <br /> Groundwater Technology, Inc. <br /> April 4, 1995 <br /> E <br /> t <br /> HISTORIC SUMMARY <br /> Please refer to the attached illustrated timeline (Figure 1). <br /> a <br /> 1. Assessment[Monitoring Tasks <br /> March 28, 1986 tank testing indicates failure of the unleaded fuel tank system. On April 2, 1986, the <br /> unleaded tank and the associated dispensing system were shut down. <br /> Assessment between 1986 and 1990 included 24 groundwater monitoring wells, 4 recovery wells, 1 soil <br /> boring, and 4 vapor recovery wells (Figure 2, Table 2). Groundwater monitoring confirmed the <br /> presence of separate-phase (SP) and dissolved hydrocarbons (Table 1). <br /> March 1988:Aquifer Test <br /> September 1991: two off-site and one on-site groundwater wells (MW-18, MW-19, and MW-20) <br /> installed (Figure 3). <br /> i' <br /> September 1992: USTs and product dispensing lines removed. <br /> 1986 to 1994:groundwater monitoring wells monitored. Initial high hydrocarbon concentrations and SP <br /> presence in some monitoring wells at the site has decreased to nondetectable levels of TPH-G and <br /> BTEX concentrations in groundwater samples collected from these wells (Figure 5). <br /> 1986 to 1993: off-site private domestic wells sampled monthly. Results of sampling indicated levels of <br /> hydrocarbon constituents have been at or below California action levels for drinking water since 1989. <br /> January 1994: latest groundwater monitoring sampling, coordinated with County: all samples contained <br /> nondetectable benzene, or 1 ppb. <br /> 2. Remediation Tasks <br /> extraction and treatment system was operated <br /> May 1986 to October 1990: a separate-phase hydrocarbon recovery system and groundwater <br /> . Approximately 760 gallons of hydrocarbons were <br /> recovered. Approximately 1.6 million gallons of groundwater were pumped and treated (Figures 6,7,8). <br /> i <br /> February 1987 to January 1991: soil vapor extraction system removed an equivalent of 576 gallons of <br /> hydrocarbons. <br /> r'--ID®GROUNDWATER <br /> L— TECHNOLOGY �, <br />