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7-Eleven/Stockton 5 <br /> November 1989 <br /> Also, during October and November of 1986, three additional <br /> monitoring wells were installed off site (MW-10 through MW-7.2) 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's (TMG) domestic well. <br /> Initially, the groundwater recovered by pumping was treated <br /> by carbon adsorption prior to being discharged to the sanitary <br /> sewer system. In February 1987, the carbon filtration system was <br /> replaced by an air-stripping tower.. <br /> 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 hydrocarbon contamination detected in samples from <br /> domestic wells which are located upgradient of the siLp. Work in <br /> February 1987 also included the installation and activation of a <br /> soil-vent remediation system. The soil-vent system was installed <br /> to address the adsorbed and vapor phases of contamination in the <br /> vadose-zone soils. This system consists of four vapor-extraction <br /> points connected to a high-vacuum blower and manifolded to a <br /> vapor-phase, activated-carbon adsorption system. <br /> From late 1986 to early 1988, a prolonged decline in the <br /> regional water-table elevation was caused by abnormally arid <br /> conditions in the Stockton area. As a result the groundwater <br /> yield from the groundwater-pumping wells was reduced. To improve <br /> the recovery volume, a new recovery well (RW-1) was installed on <br /> February 1, 1988. At the same time, the remediation/abatement <br /> system's underground lines and electrical systems were upgraded. <br /> T1.iNuI1a10,)%L' <br />