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GEoSYNCEC CONsuLTANrs <br /> r. <br /> Ms. Amy Terrell <br /> 30 June 2004 <br /> Page 2 <br /> The RAP identified enhanced in situ bioremediation (EISB) as the most viable <br /> corrective action for the nitrate and ammonium in soil at this site, and presented a plan <br /> to evaluate EISB to mitigate these fertilizer constituents in the vicinity of the former <br /> tank farm. EISB was selected because of the known effectiveness of denitrification for <br /> nitrate-nitrogen, the minimal disruption to site operations for implementing an in situ <br /> corrective action program, and the potentially lower overall costs. <br /> There is extensive literature indicating that nitrification (the two-step process in <br /> which ammonium is oxidized to nitrite, then to nitrate) plays a significant role in <br /> attenuating ammonium both in unsaturated soil and in groundwater [e.g. Buss, et al, <br /> �. 2003; Duthy, 1993]. However, anaerobic ammonium oxidation to nitrate and <br /> subsequent denitrification has not been well studied or documented. Consequently, the <br /> RAP included a proposal to perform a laboratory microcosm evaluation of the effects of <br /> L carbon source addition to site soil before moving to a field application of EISB. <br /> `, SiREM Laboratory in Guelph Ontario (SiREM) conducted the microcosm <br /> evaluation, using soil samples collected on 16 September 2003 from the former tank <br /> farm area at the site. Once the soil was received, SiREM prepared several microcosms <br /> to evaluate biodegradation under various intrinsic and enhanced conditions, and then <br /> sampled the microcosms at regular intervals to observe nitrate, nitrite, and ammonium <br /> concentrations with time. The intrinsic control microcosms were constructed to <br /> evaluate the ability of indigenous bacteria to degrade the nitrogen compounds,while the <br /> enhanced microcosms were amended with either molasses or a hydrogen releasing <br /> compound (HRC-X) to serve as an electron donor. All of the microcosms were <br /> prepared and sustained under anaerobic conditions for 91 days, then converted to <br /> aerobic conditions for an additional 40 days. Details of the microcosm evaluation, <br /> including information on the microcosm construction, laboratory analytical results for <br /> the amended site soil, and results of the study are included in the report from SiREM <br /> (Attachment A). Results of the microcosm study are summarized below. <br /> PAPRJ2003REM VrFS\VER\VERS-Treatability Study\Soil Plan 2003\Micmcosm Report 62004.doc <br /> r. p ,rcarn,.orccanaE � �� <br />