U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting Charleston South Carolina March 8-12,1999--Volume 1 of 3--Contamination From Hard-Rock Mining, Water-Resources Investigation Report 99-4018A

Field Demonstration of Permeable Reactive Barriers to Control Radionuclide and Trace-Element Contamination in Ground Water from Abandoned Mine Lands

By D.L. Naftz, J.A. Davis, C.C. Fuller, S.J. Morrison, G.W. Freethey, E.M. Feltcorn, R. G. Wilhelm, M.J. Piana, J. Joye, and R.C. Rowland

This report is available in pdf format: Naftz.pdf 781KB

ABSTRACT

Pump-and-treat methods are costly and often ineffective in meeting long-term protection standards for contaminated ground water. Permeable reactive barriers (PRBs) may offer a cost-effective alternative to other ground-water remediation methods. A PRB functions as a passive in-situ treatment zone that degrades or immobilizes contaminants. A demonstration project is currently (1999) underway at an abandoned uranium upgrader operation site in southeastern Utah to evaluate the removal of uranium from ground water by using six different PRBs. Two methods of PRB deployment, the funnel and gate design and non-pumping well design, were installed to passively treat uranium-contaminated ground water. The six different PRBs have removed uranium from the ground water with various levels of efficiency. With respect to the PRBs installed using the funnel and gate design, the barrier containing zero-valent iron has consistently removed more than 99.9 percent of the input uranium concentration during the first year of operation. The percentage of uranium removed in the bone char phosphate and amorphous ferric oxyhyroxide PRBs was slightly less, averaging 94.0 and 88.1 percent, respectively. The three barrier deployment tubes in the non-pumping wells containing mixtures of bone-char phosphate and iron-oxide pellets removed less uranium than the PRBs deployed using the funnel and gate design. Numerous geochemical and hydrological factors that affect uranium removal efficiencies and processes in each of the PRBs are currently (1999) being evaluated.