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Chevron Products Company 14 Former Chevron Service Station #9-5775, 301 West Kettleman Lane, Lodi, Calrfomra hrrre 5, 2001 To date, the SVE system has removed an estimated 3,769 5 pounds of TPHg, 85 1 pounds of ibenzene, and 440 3 pounds of MtBE (Table Q-3, Attachment Q) Plots of SVE system mass removal trends and influent soil vapor TPHg, benzene, and MtBE concentrations versus time are shown on Figures Q-4 and Q-5, respectively (Attachment Q) 52 1 SVE System Radius of Influence Soil vapor extraction (SVE) feasibility testing was conducted and reported by G -R on April 6, 13, 19, 27, and May 4, 2000 Based upon the results of the SVE feasibility testing G -R estimated an SVE radius of influence of 60 feet (G -R, July 14, 2000) The results are graphically presented as Figure Q-6 6.0 EVALUATION OF REMEDIAL ALTERNATIVES SECOR has evaluated several remedial approaches to reduce or eliminate hydrocarbon impact to the City of Lodi's drinking water supply and provide adequate plume containment. The remedial alternatives include over -excavation of impacted soils, removal of the sensitive receptor (Well 12), enhancement of the groundwater extraction system, dual phase extraction, enhanced biodegradation, maintaining operation of the existing SVE and GWE systems, natural attenuation or some combination of these These remedial alternatives are described in detail in the sections below and summarized in the table in the conclusion of this section • 6.1 Over -excavation • Over -excavation of impacted soils may result in a significant decrease in petroleum hydrocarbons in the source area Over -excavation activities would pnmanly be centered around the former UST pit, and would likely require the removal of over 5,000 cubic yards of material Because significant impact to soil has been identified to depths of 60 feet bgs in the source area, it is unlikely that conventional methods of over -excavation would be adequate to address significant portions of the impact While over -excavation of the source area may potentially result in the removal of sigmficant quantities of petroleum hydrocarbons from the subsurface, over -excavation does not address the off-site dissolved hydrocarbon plume Since over -excavation does not aid in plume containment, and because of the sigmficant costs associated with unconventional methods of excavation, over - excavation has not been chosen as a feasible remedial approach 6.2 Sensitive Receptor Removal City of Lodi municipal Well 12 is located approximately 350 feet downgradient of the source area Chevron has identified three methods of removing Well 12 as a sensitive receptor to the hydrocarbon plume, including the purchase and abandonment of the well, wellhead treatment, and removal of the well from active service ICChevron1957751ParFrpl9-5775PARFRP2 doc