1. FRC Area 3 Site Bioremediation (August 24, 2003 – August 7, 2005) Tests were performed in two phases: (1) a clean water flush to remove bulk nitrate, Al, and Ca (days 9-137). (2) biostimulation by repeated ethanol injection (days 138-present). Uranium is immobilized in the sediments at 700-2000 mg/kg Uranium concentration in the groundwater has dropped below US EPA drinking water maximum limit (0.03 mg/l) in the monitoring wells. An active remediation zone has been established with high microbial activity for denitrification, Fe(III) reduction, sulfate reduction and U(VI) reduction.

2. Well System for Field-scale Test for in situ Bioremediation of Uranium Contaminated site, FRC Area 3

3. Injection of Electron Donor (ethanol) for Bioremediation (day 137-710) Started ethanol injection on day 137

4. Nitrate Concentration Changes during Remediation Clean water flush (day 9-137) Bioremediation (day 138-670) To avoid production of nitrogen gas bubbles in subsurface and inhibition, nitrate should be reduced below 1 mM

5. U(VI) Concentrations in inner loop wells and MLS wells The maximum concentration of uranium in drinking water is 0.03 mg/l (US EPA). Injection and extraction wells Monitoring wells

6. Before bioremediation the uranium content in core samples from FW104 ranged from 0.03 to 0.8 g/kg Day 247 Day 409 Day 535Day 622Day 670 Variability in the content of U in the injection well sediment is likely due to variability in the removal of U during the surging operation. injection well monitoring well extraction well Uranium Content in Sediments from Injection, Monitoring and Extraction Wells during Bioremediation

7. Uranium Redox State – Day 535

8. The sediment changes color as microbial reduction progresses injection wellmonitoring well Day 333 Day 670 extraction well monitoring well injection well extraction well sample from day 670 incubated 3 days with no added ethanol extraction well sample from day 670 incubated 3 days after adding 100 mg/L ethanol Now black brown