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7-Eleven/Stockton 5 <br /> August 1989 <br /> Additionally, during October and November of 1986, three <br /> additional monitoring wells were installed (MW-10 through MW-12) <br /> off site to obtain further dissolved plume definition. Under- <br /> ground piping was connected to MW-12 allowing it to be used as a <br /> pumping well to intercept dissolved hydrocarbons that might <br /> impact the Tomato Growers' Association's (TMG) domestic well. <br /> Initially, the groundwater recovered by pumping was treated <br /> by carbon adsorption prior to discharge to the sanitary sewer <br /> system. In February 1967, the carbon filtration system was <br /> - replaced by an air-stripping tower. <br /> W„ Additional work conducted in February 1987 included the <br /> installation of two new monitoring wells (MW-13 and MW-14) . The <br /> monitoring well locations were selected to evaluate the origin of <br /> sporadic contamination observed in domestic wells which are <br /> located upgradient of the site. Work in February 1967 also <br /> included the installation and activation of a soil-ventilation <br /> system. The soil-ventilation system was installed to address the <br /> - adsorbed and vapor phases of contamination in the vadose-zone <br /> soils. This system consists of four vapor-extraction points con- <br /> nected to a high-vacuum blower and manifolded to a vapor-phase, <br /> activated-carbon adsorption system. <br /> From late 1986 to early 1988, a prolonged decline in the <br /> regional water-table elevation due to abnormally arid conditions <br /> in the Stockton area reduced the groundwater yield from the <br /> groundwater-pumping wells. To improve the recovery volume, a new <br /> recovery well (RW-1) was installed on February 1, 1988, and at <br /> the time, the remediation/abatement system's underground lines <br /> and electrical systems were upgraded. <br />