Waste Rock Pile Remediation

Moving mountains

The remediation concept developed for the Ronneburg site proposes to relocate all waste rock piles located south of the A4 (with the exception of waste rock pile 381) into the Lichtenberg worked-out open pit. Reasons why the former open pit uranium mine required backfilling included unstable pit walls and radiological exposure for nearby population centres. The sequence of placing waste rock material into the open pit is determined by the contaminant inventory. In a large-scale field and laboratory investigation programme, the waste rock materials were classified according to their acid generating potential.

To ensure long-term ground water protection, the material has to be placed into different zones. Material with the highest acid generating potential will be placed into the bottom – Zone A, below the final ground water level. Low acid-generating materials will be placed in the overlying oxygen depleted Zone B, while Zone C will be filled with acid-consuming waste rock materials.

Excavation and moving of the first mine dump began in 1991. The Gessenhalde waste pile was the first to be moved. It took four years to complete relocation of the waste rock material with the highest hazard potential of the Ronneburg mining district into the open pit.All other mine dumps followed suit, with the relocation sequence taking their acid generating potential into account. When the Absetzer and Nordhalde dumps had been removed, the landmarks of the East Thuringia uranium mining district, the twin terraconic waste piles from the Reust and Paitzdorf sites, were relocated into the Lichtenberg open pit.

The Schutzdamm Ronneburg mine dump excavated during the spring of 2008 was the last of a total of twelve dumps relocated at the Ronneburg site since 1991. More than 125 million m³ of waste rock material were excavated and relocated into the Ronneburg open pit.

In the Ronneburg district north of the A 4 motorway, the Drosen and Korbußen waste rock piles were excavated and hauled to the Beerwalde complex where they were banked against the Beerwalde mine dump. This move was designed to concentrate the contaminant inventory in a single place. A cover of 1.9 metre thickness was placed on top of the Beerwalde mine dump. Holding 9 million cubic metres of waste rock, the newly constructed landscape feature was capped with a 2 m thick cover which supports initial vegetation growth.

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