The Santo Antônio Tailings Management Facility (TMF) consist of an earth dam built for the purpose of forming a reservoir for the storage of tailings from the Kinross gold mining processing plant from the Morro do Ouro Mine located in the city of Paracatu, Minas Gerais, Brazil.
The dam area is about 950 hectares, the highest section reaches 105 meters in height, and the crest length is 5.2km. This TMF was constructed in 1987 and currently is the biggest tailings dam in operation in Brazil.
The Normative Resolution COPAM n.o 127/2008, applicable in Minas Gerais, establishes guidelines and procedures for environmental assessment during the mine closure phase and institutes the mandatory development of a closure plan. To satisfy the regulations Kinross started the development of the Santo Antônio Closure Plan with Pimenta de Ávila in 2013 and it was completed at a conceptual level in April 2014.
The main purpose of this Plan was to identify, evaluate and propose sustainable closure solutions to promote physical, chemical and biological stabilization of the whole site, making it appropriate for future uses considering acceptable risk levels. The main environmental issues at the site were found to be related to the potential acid drainage generation from the tailings, the geotechnical challenges considering the tailings and downstream slope, and the integration of the closure process with the mine operations.
The closure plan was segmented in two specific phases and the TMF was divided into separated components, and specific closure actions were developed for each one. In summary the closure solutions consist of reshaping the downstream slope, implementing a cover system, proposing a surface drainage system and revegetating the covered areas.
Finally the closure solution components were integrated to provide a consistent plan for the overall site, and a post-closure monitoring program was developed. The closure plan will be presented to the Brazilian environmental agencies as well as to the local communities.
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