Reclamation of the Panna Maria tailings impoundment: A case history

Panna Maria Uranium Operations started reclamation of the Panna Maria uranium tailings impoundment (in southern Texas) following mill shutdown in 1992. The closure plan for the tailings impoundment was submitted for review and license amendment in April 1993, with details modified in 1994, 1995, and 1996. The closure plan included a multi-layered cover over the regraded tailings surface which was designed for long-term isolation of tailings, reduction of radon emanation to regulated levels, and reduction of infiltration for ground water protection considerations. The cover was constructed with on-site soils and off-site clay amendments. Reclaimed surfaces were designed to provide acceptable erosional stability. The cover was constructed with a slope of 0.5 percent, and regraded embankment slopes were constructed with a maximum slope of 20 percent. All reclaimed slopes were covered with topsoil and revegetated. A riprap-lined outlet channel was constructed to convey runoff from the reclaimed impoundment.