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), Proceedings of the Ninth International Seminar on Paste and Thickened Tailings
, Australian Centre for Geomechanics, Perth, pp. 131-145.
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.
Jurjovec, J., Ptacek, C.J. and Blowes, D.W. (2002) Acid Neutralization Mechanisms and Metal Release in Mine Tailings: A
Laboratory Column Experiment. Geochimica Cosmochimica Acta, Vol. 66, No. 9, pp. 1511-1523.
Mayer, K.U., Frind, E.O. and Blowes, D.W. (2002) Multicomponent Reactive Transport Modeling in Variably Saturated Porous
Media using a Generalized Formulation for Kinetically Controlled Reactions. Water Resources Research, Vol. 38, No. 9.
Molson, J.W., Aubertin, M., Bussière, B. and Joanes, A-M. (2004) Simulating Acid Mine Drainage through Mine Wastes
Constructed with Capillary Barrier Covers. Proceedings 57th Canadian Geotechnical Conference, Quebec.
Newman, P.D., Verburg, R. and Fordham, M. (2004) Field Cell Testing of Sub-Aerial Paste Disposal of Pyritic Tailings. Paste 2004,
March, 2004. Cape Town, South Africa.
Parkhurst, D.L. and Appelo, C.A.J. (1999) User’s Guide to PHREEQC (Version 2) - A Computer Program for Speciation, Batch-
Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations, U.S. Geol Survey Water-Resources
Investigations Report 99-4259, Denver, CO.
Verburg, R., Johnson, B., Fordham, M and Logsdon, M. (2003) A Rapid and Cost-Effective Method for Bench Screening of
Geochemical Performance and Disposal Options for High-Sulphide Tailings. Proceedings from the Sixth International
Conference on Acid Rock Drainage. Cairns, QLD, July 12-18.
Verburg, R., Newman, P.D. and Fordham, M. (2006) Surface Paste Disposal of High-Sulfide Tailings – Field Cell Monitoring and
Pilot Plant Testing. 7th ICARD, March 26-30, 2006, St. Louis MO. Published by ASMR, 3134 Montavesta Rd., Lexington, KY
40502 (In publication).