The potential for removing uranium from contaminated groundwater by stimulating the in situ activity of dissimilatory metal-reducing microorganisms was evaluated in a uranium-contaminated aquifer located in Rifle, Colo. Acetate (1 to 3 mM) was injected into the subsurface over a 3-month period via an injection gallery composed of 20 injection wells, which was installed upgradient from a series of 15 monitoring wells. U(VI) concentrations decreased in as little as 9 days after acetate injection was initiated, and within 50 days uranium had declined below the prescribed treatment level of 0.18 M in some of the monitoring wells. Analysis of 16S ribosomal DNA (rDNA) sequences and phospholipid fatty acid profiles demonstrated that the initial loss of uranium from the groundwater was associated with an enrichment of Geobacter species in the treatment zone. Fe(II) in the groundwater also increased during this period, suggesting that U(VI) reduction was coincident with Fe(III) reduction. As the acetate injection continued over 50 days there was a loss of sulfate from the groundwater and an accumulation of sulfide and the composition of the microbial community changed. Organisms with 16S rDNA sequences most closely related to those of sulfate reducers became predominant, and Geobacter species became a minor component of the community. This apparent switch from Fe(III) reduction to sulfate reduction as the terminal electron accepting process for the oxidation of the injected acetate was associated with an increase in uranium concentration in the groundwater. These results demonstrate that in situ bioremediation of uranium-contaminated groundwater is feasible but suggest that the strategy should be optimized to better maintain long-term activity of Geobacter species.

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The UGTA QAPP implementation process had four steps: (1) identify gaps in compliance, (2) plan and schedule strategies to fill the gaps, (3) implement the strategies, and (4) evaluate the implementation. The first step was completed at the end of FY 2011. Step 2 finished in FY 2012. The final two steps began in FY 2012 and will continue through FY 2013. Assessments will continue throughout the UGTA Activity as part of normal operations. FY 2011 assessment corrective actions tracked in FY 2012 are summarized in Appendix A, Table A-1. FY 2012 assessments and corrective actions are described in Appendix A, Table A-2. 2.1 Gap Analysis Corrective Actions and QAPP Revision Corrective actions from the QAPP gap analysis continued in FY 2012 and served as the annual assessment requirement. The procedure matrix provided in Appendix B, Table B-1 closes the gap analysis corrective actions. Those procedures not finalized in FY 2012 (see Appendix B, Table B-1) will be identified as issues, tracked using the N-I Assessment and Condition Tracking System (ACTS), and statused in the FY 2013 Annual Report. The gap analysis identified three subject areas-Modeling and Software, Laboratory Analysis, and Data Management-where all participants needed to develop or improve implementing procedures. Committees were established with the following goals: • Share existing procedures • Standardize and streamline implementation • Recommend revisions to the QAPP The committees (see Table 5-4 for committee membership) developed forms and processes to fill the implementation gaps. These processes are not mandatory but give the participants options for QAPP compliance. The participants' processes and procedures for QAPP implementation are presented in Appendix B, Table B-1. The UGTA QAPP was revised to address implementation and clarification suggestions from the gap committees. The UGTA QAPP was also revised to require laboratories to be certified by the State of Nevada or approved by the Nevada Division of Environmental Protection (NDEP) Bureau of Federal

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