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Environmental <br /> Mr Harlin Knoll Resources <br /> 27 January 2000 Management <br /> Page 5 <br /> Evaluation of Results - UST 2 <br /> At MW-2, the concentrations of chemicals decreased during the June, <br /> September, and October 1999 sampling events During the last two <br /> sampling events (October 1999 and January 2000), TPH-g and BTEX have <br /> not been detected in samples collected at MW-2 Therefore, it appears <br /> that as a result of ORC injection, enhanced bioremediation has reduced <br /> the concentration of chemicals at this location to non-detectable levels <br /> Figure 5 presents the historical chemical concentrations detected at <br /> MW-2 <br /> At MW-6, the concentration of TPH-g has decreased 50 percent since <br /> ORC injection was performed Prior to ORC injection, TPH-g was <br /> ' detected at a concentration of 98 milligrams per kilogram (mg/kg) <br /> During the current sampling event, TPH-g was detected at a <br /> concentration of 49 mg/kg Similarly, the concentration of benzene has <br /> decreased by over 50 percent since ORC injection at MW-6 The <br /> concentration of benzene detected at MW-6 during the current sampling <br /> event was 14 mg/kg, compared to 3 4 mg/kg detected prior to ORC <br /> injection All other compounds detected at MW-6 have shown similar <br /> reductions since ORC injection was completed Figure 6 presents the <br /> historical chemical concentrations detected at MW-6 <br /> RECOMMENDATIONS <br /> ' Based on the results of groundwater samples collected in monitoring <br /> wells at the site prior to, and since ORC injection, the overall detection of <br /> petroleum based compounds in groundwater downgradient of each <br /> ' former UST location depicts a decreasing trend In addition, several <br /> parameters are stable and have shown no significant increase or <br /> decrease Specifically, at UST 1, the concentrations of TPH-g and BTEX at <br /> ' MW-4 have decreased since ORC injection was performed Further <br /> downgradient at MW-1, the concentration of TPH-g and BTEX <br /> compounds have remained stable since ORC injection At the UST 2 site, <br /> the concentrations of TPH-g and BTEX at MW-6 (immediately <br /> downgradient) have decreased by 50 percent since ORC injection <br /> Further downgradient at 1\4W-2, TPH-g and BTEX have been reduced to <br /> non-detectable concentrations since ORC injection <br />