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IM A <br /> 7-Eleven/stockton 5 <br /> August 1990 <br /> It (PW-2) has never been used as a pumping well. A deeper, <br /> 12-inch-diameter recovery well (PW-3) was installed on site to <br /> replace the 4-inch-diameter monitoring well, MW-4, which had been <br /> used as an interim on-site recovery well. <br /> Also, during October and November of 1986, three additional <br /> monitoring wells, MW-10 through MW-12, were installed off site to <br /> obtain further dissolved-plume definition. Underground piping <br /> was connected to MW-12 in order to allow it to be used as a <br /> pumping well to intercept dissolved hydrocarbons in the event <br /> that migration was detected approaching the Tomato Growers <br /> Association (TMG) domestic well at 9036 Thornton Road. <br /> Monitoring well MW-12 has not ben used as a pumping well to date. <br /> . Initially, the groundwater recovered by pumping was treated <br /> by carbon adsorption prior to being discharged to the City of <br /> Stockton sanitary sewer system. In February 1987, the carbon <br /> filtration system was replaced by an air-stripping tower. <br /> Additional work conducted in February 1987 included the <br /> r' installation of two additional monitoring wells, MW-13 and Md-14. <br /> The monitoring well locations were selected to evaluate the <br /> origin of hydrocarbon concentrations which had been occasionally <br /> detected in samples from domestic wells which are located <br /> upgradient of the site. Work performed in February, 1987, also <br /> _ included the installation and activation of a soil-vent <br /> remediation system. The soil-vent system was installed to <br /> address the adsorbed and vapor phases of contamination in the <br /> vadose-zone soils. This system consisted of four vapor- <br /> extraction points connected to a high-vacuum blower and <br /> - manifolded to a vapor-phase, activated-carbon adsorption system. <br />