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ERI 205505 R02 Tosco Service station 5886, Stockton Califortna September 25,2001 <br /> • The projected initial removal rates for SVE was less than 0 03 pounds per day TPHg, and 0 06 <br /> pounds per day MTBE <br /> • Based on data collected during the feasibility testing, SVE with AS appears to be technically <br /> Ifeasible <br /> 4.0 REMEDIATION ALTERNATIVES <br /> ERI evaluated four remedial alternatives for this CAP, 1) natural attenuation, 2) AS/SVE, 3) periodic <br /> purging from the UST cavity well and well MW3, and, 4) ozone microsparging Cumulative <br /> assessment data indicate that residual hydrocarbons in vadose soil are not acting as a secondary source <br /> to groundwater Therefore, remediation by excavation and removal of soil was not considered because <br /> it fails to address the current dissolved hydrocarbon and MTBE mass <br /> 41 Natural Attenuation <br /> Natural attenuation is the degradation of petroleum hydrocarbons by naturally occurring biological <br /> processes and hydrodynamic dispersion ERI does not consider natural attenuation an effective <br /> remedial alternative at this site based on the concentrations of MTBE in groundwater Natural <br /> attenuation was not selected because it appears that remediation goals could be reached in a timelier <br /> manner using a more aggressive remediation technology <br /> 42 AS/SVE <br /> AS is a remedial alternative capable of volatilizing dissolved petroleum hydrocarbons in groundwater <br /> and enhances intrinsic biodegradation SVE is utilized to extract hydrocarbons from the infected air <br /> stream as well as extract residual hydrocarbons from the vadose zone However, while AS/SVE is <br /> feasible at the site, based upon soil vapor concentrations and removal rates, it is not economical to <br /> implement AS/SVE as a remediation alternative at this site <br /> 6 <br />