1. 2010 Long-Term Surveillance and Maintenance Conference Old Rifle Title I Processing Site, Rifle, Colorado What Are They Doing on My Site? Richard Bush, Rifle Site Manager November 16, 2010

2. 2010 Long-Term Surveillance and Maintenance Conference 2 U.S. Vanadium Company Mill—1924

3. 2010 Long-Term Surveillance and Maintenance Conference 3 Union Carbide Mill—circa 1957

4. 2010 Long-Term Surveillance and Maintenance Conference 4 Old Rifle Site—1967 After Umetco Cleanup

5. 2010 Long-Term Surveillance and Maintenance Conference 5 Old Rifle Site—1999 Post-UMTRA Cleanup

6. 2010 Long-Term Surveillance and Maintenance Conference 6 Old Rifle Mill Site—Today

7. 2010 Long-Term Surveillance and Maintenance Conference 7 Site Conceptual Model Groundwater contamination from raffinate ponds and tailings Surface cleanup standard Ra-226; metals left Inflow of water from the north via seeps and drainage ditch contributes groundwater to site Colorado River contributes to flushing

8. 2010 Long-Term Surveillance and Maintenance Conference 8 Site Conceptual Model Diagram

9. 2010 Long-Term Surveillance and Maintenance Conference 9 Regulatory History 1996: Surface cleanup completed 1998: Licensed 1999: Final Site Observational Work Plan for the UMTRA Project Old Rifle Site 2002: Ground Water Compliance Action Plan for the Old Rifle, Colorado, UMTRA Project Site meets Nuclear Regulatory Commission approval Compliance Natural flushing for uranium, maximum contaminant level (MCL) 0.044 mg/L Alternate concentration limits for vanadium and selenium, higher than MCL based on background

10. 2010 Long-Term Surveillance and Maintenance Conference 10 Office of Science Investigations Two basic questions posed Can we immobilize uranium in the groundwater? How long will it last after amendments cease? Can we better predict uranium removal? Natural flushing relies on modeling Approach – to support compliance strategy Enhance microbial reduction of soluble uranium(VI) to precipitated or sorbed uranium(IV) Improved reactive transport simulations to predict removal of uranium from groundwater

11. 2010 Long-Term Surveillance and Maintenance Conference 11 Recent Developments, Plume Map

12. 2010 Long-Term Surveillance and Maintenance Conference 12 Recent Developments, T/C Plots

13. 2010 Long-Term Surveillance and Maintenance Conference 13 Groundwater Surface Map—Spring 2007

14. 2010 Long-Term Surveillance and Maintenance Conference 14 Conclusions Site not flushing as predicted Site more complex than expected Additional characterization/new modeling effort? Revisit compliance strategy in light of low risk U.S. Department of Science adding insights to uranium sequestration, cycling Integrated Field-Research Challenge provides an outdoor lab Leveraged funding for science and technology Future to expand to floodplain-wide analysis?