Authors: Verburg, R; Ross, C; Dillon, M; Newman, P; Fordham, M

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Verburg, R, Ross, C, Dillon, M, Newman, P & Fordham, M 2006, 'Surface Paste Disposal of High-Sulfide Tailings – Geochemical and Geotechnical Testing', in R Jewell, S Lawson & P Newman (eds), Paste 2006: Proceedings of the Ninth International Seminar on Paste and Thickened Tailings, Australian Centre for Geomechanics, Perth, pp. 131-145,

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The disposal on surface of acid generating waste is a common problem for base metal mines around the world. Sociedade Mineira de Neves-Corvo, S.A (Somincor), who own the Neves Corvo Mine and associated tailings facility near Castro Verde in southern Portugal, have been investigating surface paste applications for five years since a feasibility study indicated life-of-mine savings. Given the long remaining mine life (reserves suggest 2029), the existing sub-aqueous disposal method will require substantial dam raises. In addition, the presence of a water cover in perpetuity as a closure option is a considerable challenge in the very arid and net evaporative climate of southern Portugal. Understanding the geochemical behaviour of the sulphide-rich tailings was paramount as conventional sub- aerial disposal methods can facilitate and promote significant generation of acid rock drainage (ARD) and metal leaching (ML). The first phase of geochemical characterization of the tailings was conducted in the Somincor laboratory in 2001 and involved a screening-level assessment of different sub-aerial placement options including wet paste (250-mm slump), stiff paste (150-mm slump) and filter cake, both with and without amendments (cement, lime, bactericide). This investigation and its findings are described in detail in Verburg et al., 2003. The study expanded to the field in 2002 with the construction of six field cells to monitor the performance of the sub-aerial placement option. Wet paste was selected for the field cell trials based on the results of the laboratory testing. Since their construction in September 2002, the cells have been monitored with weekly collection of seepage and runoff. Significant quantities of data have been generated, and the results of the first year of field cell testing are described in Newman et al., 2004. In 2004 the study progressed to a pilot paste program, which included the construction of an 8 m DCT which has been used to produce some 30,000 m3 of paste. This paper presents the results from the second year of field cell monitoring and describes the initial results from the pilot paste trial. Geochemical results from the field cells are discussed and compared with the results from the oxidation modelling. The geotechnical characterisation of the placed paste is described and preliminary results presented. Paste2006–R.J.Jewell,S.Lawson,P.Newman(eds) ©2006AustralianCentreforGeomechanics,Perth,ISBN0-9756756-5-6 Paste2006,Limerick,Ireland 131

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Paste2006,Limerick,Ireland 145
surfAce disPosAl

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