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Tosco Corporation a subsidiary of Phillips Petroleum Company 4 Tosco staElOn#11192, 1403 Coun Club lane,Stockton,CA Februm 13,2002 . groundwater elevation FID readings collected from the vapor extracted from all wells were initially 350 ppmv and increased to 2,900 ppmv by the end of the test Applied vacuum, vapor extraction flow rates, groundwater extraction flow rates, and influent FID readings are presented in Table 1 LABORATORY ANALYTICAL DATA Laboratory analyses of soil vapor samples collected during the DPE tests are summarized in Table 2 and shown graphically on Figure 2 Groundwater samples were collected from wells MW-3 and MW-7 before and after DPE testing Below is a table showing the groundwater concentrations of TPHg, benzene, and MtBE in parts per billion (ppb) measured before and after the DPE event Refer to table 3 for a more complete list of all analytes The bolded values indicate reduced analyte concentrations ti-well A11ObInpb) M c'.w. .r 6rs, ? ''$ s✓R ., "`�»c '""y '$.°$X A r y.x'Qg6 Before DPE After DPE Before DPE After DPE Before DPE After DPE MW-3 c50 000 <50 <500 <0.56- 40,000 190 hM_7 <50,000 <50 <500 <0 50 —F98–,000 190 • DPE Mass Removal Rates The total mass of TPHg, benzene, and MTBE removed during the test were estimated using the influent air analytical results, an average well field flow rate, and the time duration of the test The calculated benzene and MtBE mass removed during the DPE test were approximately 0 01 pounds, and 7 49 pounds, respectively (Table 4 and Figure 3) Additionally, during the tests approximately 20,830 gallons of groundwater were extracted from the site Extracted groundwater was temporarily stored in a holding tank, prior to disposal at Tosco's Refinery in Rodeo, California Soil Vapor Radius of Influence The radius of influence was determined graphically by plotting the average lateral distance from the test well to the observation wells, versus the initial applied vacuum (in Hg)and the resulting induced vacuums (in of H2O), from Table 1 An induced vacuum of 0 1 inches H2O was used to represent the theoretical minimum induced vacuum defining "influence" from the applied vacuum The distance at which a "best fit" line formed by the data crosses 0 1 inches H2O is the estimated radius of vacuum influence for each test well Based upon this data, the estimated radius of influence for test well MW-7 was 36 feet (Figure 4) and for test well MW-3, the estimated radius of influence was 60 • feet(Figure 5)