Unconventional decommissioning of geotechnical structures of Corrego do Meio Mine

Abstract

Corrego do Meio is an old iron mine whose activities closed in 2005. Its main geotechnical structures are the open pit, the Galego tailings dam and two waste dumps. For the waste dump decommissioning, slope stability analyses were conducted for adequacy to Brazilian standard for mining waste dump (NBR-13029). Cut-and-fill reconformation works were conceptually designed, as low factors of safety were estimated. The Galego Dam is a conventional downstream earthfill with 35 m height. The conceptual decommissioning design of this dam provided a reconformation of the dam to an overtopping rockfill dam, decreasing 10 m of its height and flattening the downstream slope to 14°. The remaining reservoir will be transformed into a wetland by planting macrophytes species. The solution of constructed wetlands and overtopping structures presents an attractive alternative for decommissioning small tailings dams to the classic solution of decommissioning by construction/enlargement and operation/maintenance of spillways designed for the probable maximum discharge usually required.