Dry stack tailings continue to shape as a waste storage option for Lumina Gold Corp at its proposed US$925 million, 371,000 ounces-a-year gold mine at Cangrejos in Ecuador, with Lumina’s delivery of a prefeasibility study this week paving the way for it to start construction permitting.
“Similar to the 2020 PEA, a siting and tailings storage study was performed for the PFS with the goal of balancing capital costs, operating costs and non-monetary considerations such as environmental and social impacts,” the company said.
“The dry stack tailings facility [DSTF] approach has a smaller footprint, positive environmental and social benefits, as well as reduced overall costs when compared to conventional tailings dam storage facility options.”
Lumina is looking at a site several kilometres from the proposed circa-11 million tonnes per annum process plant (expanding to around 30Mtpa after six years) for a DSTF, with tailings to be pumped via slurry pipeline to a filter plant next to the facility. Filtered tailings would then be taken by overland conveyor to a stacker at the DSTF, which could hold at least 659Mt of tailings.
Waste and saprolite storage catering for about 843Mt of material would be established at a different location.
Lumina said it was seeking to reduce environmental impacts with its project design.
Most of its electrical power would come from hydroelectric sources while a dry stack tailings filtration plant would enable a substantial portion of tailings water to be recycled for reuse in the processing plant.
“Dry stack tailings deposition virtually eliminates carbon emissions associated with conventional tailings design,” it said.
“Geochemistry work to date indicates that both the DSTF and WRSF are non-acid generating based on results of acid-based accounting tests, as well as onsite kinetic barrel leaching tests and humidity cells of up to three years duration.
“The tailings and waste rock contain low sulphide concentrations and naturally occurring neutralising minerals which prevent acid rock drainage.”