Tuesday, 11 July 2006

Rehabilitation of Uranium Mining Sites of WISMUT: Lysimeter Measurement.

Manfred Seyfarth1, Uwe Hoepfner2, and Gert Neubert2. (1) UGT Environmental Measuring Techniques Ltd., Eberswalder Strasse 58, Muencheberg, 15374, Germany, (2) WISMUT GmbH, Ronneburg Operation Office, Abt. T 1.2 Engineering, NL Ronneburg, BT Paitzdorf, PO box 41, Ronneburg, 07576, Germany

The rehabilitation of WISMUT's former uranium mining sites involves backfilling of the Lichtenberg open pit with waste rock, which has to be covered to control water infiltration and gas diffusion. The preferred rehabilitation option for tailings impoundments includes the construction of soil covers on top of the dewatered and recontoured tailings surface to ensure the long term limitation of infiltration and gas diffusion into the tailings. An intensive testing program concerning the vadose zone of soil covers has therefore been started in 2000. To test soil cover design, WISMUT built test plots with different cover constructions. Soil water content and soil suction are monitored within and below the cover. Interflow above sealing layers and waste rock is measured with drains. For measuring deep percolation into the waste rock and tailings, we used lysimetric methods (zero tension lysimeters). Additionally, suction controlled pressure-plate lysimeters measure flow in the recultivation layer of cover soils. We will present an overview of the test design, including lysimeter methodology, and the results of the vadose zone measurements. Concluding remarks about the cover design of the waste rock site and the tailings impoundments will be given.

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