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Ground water analytical data from recent monitoring events was <br /> reviewed to establish expected VOC concentrations in ground water <br /> extracted at the plume margin, and corresponding design parameters for <br /> the Treatment System. Influent ground water concentrations are <br /> tabulated in Table 4-2. <br /> TABLE 4-2 <br /> Influent VOC Concentrations from Plume Margin Extraction Wells <br /> Constituent Treatment System Influent Ground Water <br /> Concentration <br /> (Plume Margin Extraction Well Contribution) <br /> u /L <br /> cis 1,2-Dichloroethene 8.3 <br /> 1,1-Dichloroethane 16.0 <br /> Vinyl Chloride 2.3 <br /> Benzene 0 <br /> Total HVOCs 39.1 <br /> Total AVOCs 0 <br /> Ground Water Plume Containment <br /> The dual phase extraction wells shown in Drawing C-2 will be used for <br /> both soil vapor extraction and ground water extraction. Therefore, each <br /> dual phase well is screened to 5 feet below the static water table. <br /> Study of A-zone aquifer pump test data and pilot test results indicate that <br /> the maximum sustainable ground water extraction rate at the site is <br /> approximately 4 gpm. Therefore, each dual phase extraction well is <br /> designed for an extraction rate of 4 gpm. It is anticipated that 4 to 5 dual <br /> phase extraction wells will be operated simultaneously, such that the total <br /> extraction rate from dual phase extraction wells will be 16 to 20 gpm. The <br /> total extraction rate from plume margin wells is 10 gpm. Therefore, the <br /> total ground water flow capacity of the Treatment System is 30 gpm. <br /> Each dual phase extraction well will initially be operated such that 4 gpm <br /> will be extracted from each well. The extraction tube will be adjusted to <br /> the correct distance above the water table such that this extraction rate is <br /> achieved. At an extraction rate of 4 gpm per well, the corresponding <br /> 4-6 <br />