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I Mr. Soon Kim Page 11 December 19, 1995 measurable concentrations of petroleum hydrocarbons occur at 55 feet bgs (20.7 ppm). The concentration increases to 339 ppm at 65.feet bgs, coincident with the top of the aquifer.. Both boreholes were converted to SVE wells at the request of the PHS/EHD. The well construction and installation procedures for both SVE wells is identical. Groundwater at the site was measured at 64.70 feet bgs in MW-DIS-2. In accordance with the November 1, 1995 work plan, the screens were placed 10 feet above and 10 feet below groundwater. Each well was constructed with 20 feet of 0.020 machine slotted schedule 40 PVC screen from 55 to 75 f feet bgs. Blank schedule 40 PVC casing was used to construct the upper portion of the well.. The filter pack was constructed from 2/12 Lonestar sand. This sand was placed in the annular space around the well screens and brought up to 53 feet bgs. The filter pack was pre- developed by surge blocking for 20 to 30 minutes in an attempt to further settle filter pack around the screened interval. 'Following the pre-development procedures, a 2-feet thick intermediate bentonite seal was placed on top of the filter pack. The bentonite was hydrated with 10 gallons of water and allowed to hydrate for at least 1 hour. The remaining annular space was filled with neat cement. The neat consisted of four 90 pound concrete sacks per 30 gallons of water. i AS/SVE Progress Extracted soil-vapor, gasoline concentration dropped below 500 ppmv(measured at the engine intake), thereby triggering the replacement of the former internal combustion engine with granular activated carbon (GAC) vessels for off-gas treatment in late September.After replacement of the engine, it was realized that significant dilution air was required to sustain oxygen levels high enough to keep the engine running. Without the engine and this dilution air in the soil vapor stream, the end-of-pipe gasoline vapor concentration increased dramatically. GAC is presently used at a rate greater than 200 pounds per day. 'Conversion of the off-gas treatment system back to a thermal destruction system is being considered to save operating expense. AS/SVE Monitoring Soil and groundwater respiration measurements were not made this quarter, and the influence of applied vacuum was not measured because the monitoring wells were converted into vapor extraction wells. } Estimated Mass Removal by SVE Based on the assumption that gasoline has an average molecular weight of 120 grams/mole, the calculated AS/SVE system gasoline removal to date is 8,800 pounds, or approximately 1,400 gallons (specific gravity of gasoline is 0.74). Table 3 presents measured data, from the j system operations log, considered in the estimate of cumulative gasoline removal. Cumulative