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Proposal for of Site Cleanup Confirmation May 5, 1992 <br /> Southland, 7-Eleven No 20680, 9110 Thornton Road, Stockton, CA 2 <br />' the site for evidence of petroleum hydrocarbons The following summanzes site assessment and <br /> remediation activities performed by Groundwater Technology from Apnl 1986 to date <br />' ■ Site work was initiated in 1986 Between 1986 and 1990, a total of 17 monitoring <br /> wells were installed to acquire data relevant to the lateral and vertical extent of <br /> groundwater impacted by petroleum hydrocarbons (See Figure 2 for well locations <br /> MW-1 through MW-17) Monitoring and sampling of monitoring wells confirmed the <br /> presence of separate-phase gasoline and dissolved hydrocarbons The greatest <br /> gasoline thicknesses were found in August 1986, with up to 4 55 feet detected in <br /> well MW-4 <br /> ■ Gasoline recovery and groundwater extraction was Initiated in 1986 A total of <br /> I approximately 760 gallons of gasoline were removed by the separate-phase <br /> hydrocarbon recovery system, and a total of approximately 1 6 million gallons of <br /> water has been pumped and treated by the groundwater treatment system <br />' ■ The groundwater monitoring wells have been monitored and sampled routinely since <br /> the project started Sampling of domestic wells adjacent to the site has also been <br /> conducted on a routine basis (See Figure 3 for domestic well locations) <br /> ■ Soli sampling activities conducted at the site confirmed the presence of gasoline <br /> constituents in the vadose zone soils on site In situ soli venting was initiated in <br /> 1987 A total of approximately 576 gallons of gasoline was removed via the soil vent <br /> system <br /> A review of historic data collected through October 1990 was presented in the March 1991 report <br /> I Site Closure Work Plan, Southland Coloration, 7-Eleven Property #20680, 9110 Thornton Road <br /> Stockton California prepared by Groundwater Technology The report presented a summary of the <br /> site assessment and remediation activities conducted, an overview of the well monitoring and <br /> sampling results, an overview of the soil sampling and results, and recommendations to move the <br /> site toward closure <br /> I Inv h <br /> March 1991, Groundwater Technology proposed specific work steps to move the it t site toward <br /> and <br /> closure The following work steps were approved by the SJPH and implemented <br /> 1) Removal of three underground tanks and associated piping at the site in September <br /> 1991 <br /> 2) Installation of three monitoring wells to confirm water quality, one on site and two <br /> hydraulically upgradient of the site (See Figure 2 for locations of wells MW-18, <br /> MW-19, and MW-20) <br /> GROUNDWATER <br /> TECHNOLOGY INC <br /> I <br />