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GEUSYNTEC CONSULTANTS <br /> Ms. Amy Terrell <br /> �;— 30 June 2004 <br /> Page 3 <br /> RESULTS OF MICROCOSM STUDY <br /> +' In the intrinsic control samples, nitrate decreased by 35% and ammonium <br /> decreased by 25% over the course of the evaluation. Nitrate in the molasses-amended <br /> microcosm was completely reduced to non-detectable (ND) levels within 14 to 28 days <br /> of incubation, while ammonium was reduced by 20%over the 90 day incubation period. <br /> In the samples treated with HRC-X, nitrate was completely reduced to ND levels within <br /> 7 to 14 days of incubation, and ammonium was reduced by 22% over the 90 day <br /> incubation period. These results indicate that the addition of an electron donor <br /> stimulated the microbial populations responsible for the denitrification of nitrate and <br /> �. nitrite to nitrogen gas,but not oxidation of ammonium. <br /> It appears the addition of molasses and HRC-X was successful in enhancing the <br /> rapid degradation of nitrate and nitrite present in the soil completely under anaerobic <br /> conditions. The degradation of ammonium in the enhanced microcosms, under both <br /> anaerobic and aerobic conditions, was similar to the degradation observed in the <br /> intrinsic control, indicating that the organisms responsible for ammonium degradation <br /> were either not present or not stimulated by the addition of HRC-X or molasses during <br /> �— the time frame (131 days) of the study <br /> ` RECOMMENDATIONS <br /> Based on the findings of the microcosm study, it appears the EISB would be <br /> ` effective in reducing the nitrate and nitrite concentrations in the soil in the vicinity of <br /> the former tank farm at the site. However, the results of the 131-day study also indicate <br /> that EISB would not be effective in rapidly reducing the ammonium concentrations in <br /> soil. As such, WFS does not propose to implement EISB at the site at this time. <br /> A field application of EISB .for soil at the WFS Merced site is currently underway. <br /> WFS will review these results when they are available to assess any potential relevance <br /> to the WFS Vernalis site. Alternatively, paving the former tank farm area at this site is <br /> L <br /> a viable alternative. <br /> P:\PR32003REM\WFS\VER\VERS-Treatability Study\Soil Plan 2003\Microcosm Report 6-2004.doe <br /> — (y rawm»oraw..e <br />