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Chevron Products Company 9 <br />Former Chevron Station 9-5775, 301 W Kettleman Lane, Lodi, CA July 24,2000 <br />• Analytical data from soil samples collected at the site indicate that typically, the maximum <br />concentration of hydrocarbons is found at approximately 15 feet bgs, and decrease <br />exponentially to below detection limits at 35 feet In order to conservatively estimate the mass <br />of hydrocarbons in soil, concentrations of petroleum hydrocarbons are assumed to be distributed <br />linearly with respect to depth <br />Based upon these assumptions and known densities of gasoline, benzene, and MtBE, the total <br />mass of each constituent has been calculated in the dissolved plume as follows <br />U <br />Constituent <br />Hydrocarbon Mass (lbs) <br />Gasoline Hydrocarbons <br />1450 <br />Benzene <br />370 <br />MtBE <br />67 <br />EVALUATION OF INTERIM REMEDIAL ALTERNATIVES <br />Remediation Feasibility Testing <br />Soil vapor extraction (SVE) feasibility testing was conducted and reported by G -R on April 6, <br />13, 19, 27, and May 4, 2000 Based upon the results of SVE feasibility testing G -R <br />estimated an SVE radius of influence of 60 feet (G -R, July 14, 2000) <br />Evaluation of Interim Remedial Alternatives <br />SECOR evaluated several technologies for remediating petroleum hydrocarbons in soil and <br />groundwater present at the site Only alternatives that would address both soil and groundwater <br />were evaluated The considered alternatives, estimated time line to closure, and respective costs <br />are summarized in Table 5 <br />Passive bioremediation (natural attenuation), enhanced bioremediation, and excavation were <br />determined not feasible for addressing the current subsurface petroleum hydrocarbon mass <br />Passive and enhanced bioremediation were determined not feasible at this point because of the <br />dissolved concentrations and potential for continued migration of the dissolved hydrocarbon <br />plume Excavation was determined to not be feasible based on the extent of adsorbed <br />hydrocarbons, impact to operations, and the associated cost <br />Soil vapor extraction (SVE) and groundwater extraction (GWE) were determined to be feasible <br />alternatives for mitigating subsurface impacts and protecting human health SVE has been <br />effective at remediating impacted soil at similar sites with radii of influence of up to 60 feet <br />GWE was determined to be feasible for limiting further migration of the current MtBE plume <br />and removing dissolved hydrocarbons through extraction <br />077 41991 043/9-5775PAR doc <br />