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w <br /> a� <br /> r <br /> f's <br /> June 25, 1991 <br /> ARCO Service Station 760, Lodi, California <br /> i Initial estimates of the effective radius of influence of 22 feet from each vaporextraction <br /> well were`mada wing a vacuum of 30 inches of water column, a flaw rate r..f 50 cmf, an <br /> initial TPTg concentration of 10,000 mg/m3, and the duration of operation of-a vapor <br /> extraction aratem of 12 months. This estimate of the radius of influence can be further <br /> refined as the subsurface environmental investigation progresses. The location and screened : <br /> interval of subsequent vaporextraction wells will be based on this refined data. <br /> Conclusions <br /> Low levels of residual hydrocarbons were detected in the proposed tank cavity. Results of <br /> f vapor extraction at this site is a practical and <br /> the vaporextraction test indicate the use o <br /> efficient choice as a soil remediation alternative. <br /> At the request of ARCO, we will observe <br /> the installation of six conductor casings in the <br /> locations shown on Plate 2 before the tanks are installed. These conductor casings will <br /> allow soil borings to be drilled between the new tanks at a later dale to delineate the <br /> residual hydrocarbons. After the residual hydrocarbons are delineated vertically and <br /> laterally, vaporextraction wells can be installed between the proposed tanks to <br /> remediate the soil if warranted. <br /> .ARCO'li.requesting,authorization to install the new tanks in the proposed tank 81)ity as <br /> planned No;remediation will be conducted until we submit a Remedial flan to your agency i <br /> and:the plan is ciriated`for a 30-day public review. ; <br /> N..'. <br /> 0624ctm 4 <br /> r' <br />