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' �..� Site Background Information Former Stefano's Gas Station Page 5 of 6 radius of influence is approximately 25 feet for both SVE1 and SVE2; at a vacuum pressure of 10.0 inches of water the radius of influence is less than 10 feet. TPH-g was detected in the soil vapor samples (vapor samples) at concentrations ranging from 7,500 gg/l to 13,000 µg/l. Toluene, ethylbenzene and total xylenes were detected in the vapor samples at concentrations as high as 550 µg11 toluene, 150 µg/l ethylbenzene and 1,100 µg11 total xylenes. Benzene and MTBE were not detected at or above laboratory reporting limits in the analyzed samples. No other analytes of concern were detected in any of the samples submitted for analysis. OZONE PILOT TESTING An ozone pilot test was initiated on 08 December 2004 at the site, and halted on 30 June 2005 by an EHD verbal directive. The pilot test was conducted using an HC-2.50 Ozone Generator, which could produce ozone at a rate of up to 2.5 pounds per day at a maximum pressure of 25 pounds per square inch(psi). The generated ozone was piped into three injection wells(OZ-1,OZ-2 and OZ-3) at a pressure of approximately 8 to 10 psi,and then injected into the hydrocarbon-impacted zone via a microsparge point in each well that was set at between 60.5 and 62.5 feet below surface grade (bsg); the ozone was supplied to each injection well on a two-hour on and two-hour off cycle. Based on system monitoring events,oxidation-reduction potential(ORP)measurements fluctuated between-202.93 millivolts(mV)in well MW-I and 150.5 mV in well MW-3.There were no distinct oxidation trends,although down-gradient well MW-1 and well MW-3 exhibited positive tendencies and up-gradient well MW-2 exhibited a negative tendency.Dissolved Oxygen(DO)measurements ranged from 0.57 mg/l in well MW-2 to 14.3 mg/l in well MW-3. DO readings were highest from well MW-3,which was the only well situated directly adjacent to a sparge well. Ground water samples were collected from monitoring wells during duration of the pilot test.MW-2 and MW-3 were the only impacted wells during the course of the ozone pilot study. TPH-g and all BTEX compounds were detected in MW-2 during each sampling event; TPH-g and the BTEX compounds toluene, ethylbenzene and xylene were detected in MW-3 only in the June sampling event.In addition,the fuel additives 1,2-DCA was detected in MW-2 and MW-3 during all sampling events and TAME was detected in MW-2 only in the May sampling event. The maximum contaminant concentrations in ground water during the 24-week ozone sparging test were 200,000 micrograms per liter(µg/l)TPH-g,3,000 gg/l benzene, 14,000 gg/l toluene,6,200µg11 ethylbenzene, 37,000 gg/l xylene, 38 µg11 TAME, and 84 µg11 1,2-DCA, all in samples from well MW-2. Enumeration of aerobic bacteria in the ground water sample collected from well MW-2 on 17 February 2005 determined that 4 x 103 colony-forming units per milliliter (cfu/ml) total heterotrophic bacteria,of which 2 x 103 cfu/ml were hydrocarbon-degrading bacteria,were present. t Advanced GeoEnvironmental,Inc.