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Final Remediation Plan Page 8 Ranch Market 23569 South Santa Fe Road Riverbank,CA February 28 2001 3.2 SVE Mass Removal Rates The total mass of TPHg and benzene removed during the test were calculated using the Influent air sample analytical results and average vapor extraction flow rates The calculated TPHg and benzene mass removed during the SVE and air sparge tests was approximately 102 pounds and 1 9 pounds, respectively (Table 8) Assuming an average extraction rate of 250 scfm and an average TPHg concentration of 1,000 ppmv, the dally extraction rate would be 100 pounds of TPHg and 16 pounds of benzene from the six extraction wells 3.3 Vapor Extraction Radius of Influence Refernng to SVE Test#2 results present Table 6, an applied vacuum to well V-i resulted in 0 20 to 0 32 in H2O of Induced vacuum in well V-3 located 38 feet away Referring to SVE Test#3 results present Table 6, an applied vacuum to well V-5 resulted in 0 26 to 0 43 in H2O induced vacuum in well V-3 located 36 feet away An increase in applied vacuum resulted in an increase in the induced vacuum Based on the induced vacuum responses and the slight rise in groundwater levels observed dunng the tests the estimated soil vapor extraction radius of influence is approximately 40 feet The estimated radius of influence assumes an induced vacuum of 0 2 in H2O will be present at 40 feet away from the extraction well 3.4 Air Sparge Radius of Influence Refemng to the SVE/AS test results present Table 5, air sparging resulted in an increase in the dissolved oxygen concentrations in well MW-1 and well V-1, located 7 and 21 feet from AS-1 respectively Referring to the SVE/AS Test#5 results present Table 6, air sparging resulted in positive pressure readings in wells MW-1, MW-2, and MW-4 that are located 7 feet, 34 feet, and 35 feet away from AS-1 respectively Although the air sparging did not result in an immediate increase in TPHg vapor concentration, the Increase in dissolved oxygen concentration and slight nse in the water table in offsetting wells indicates a radius of influence of approximately 30 feet Referring to Table 3, a significant decline in the concentration of benzene, TPHg, and MtBE was observed in wells MW-1, MW-2, MW-3, and MW-4 that are centered about the former tank pit Conversely, the concentration of benzene, TPHg, and MtBE increased in three perimeter wells MW--6 located upgradient of the former UST, MW-8 located cross gradient of the former UST, and MW-9 located downgradient of the former UST The variations observed in the analytical results of the water samples in Fourth Quarter 2000 are possibly caused by the 5-hour soil vapor extraction/air sparging test conducted October 3, 2000 File FRP-report doc SECOR International Incorporated