The value of geochemistry for tailings facility design
I had the opportunity recently to work with a diverse group of professionals on a feasibility study for a tailings reprocessing project. In short, the project involved remining an old tailings dam, processing the tailings to remove economic metals, and placing the tailings on a new facility - the "Residue Disposal Facility". My task was to develop a source term for the RDF - the contaminant mass emitted from the RDF footprint over time.
A rather important question in tailings facility design is the need for, and cost, of a liner. Geochemistry can assist decision-makers by evaluating the source term for different facility designs. In this case, the proposed RDF design would result in a wedge of tailings, and possibly, a pool closer to the starter wall. I provided estimates of seepage from the "no liner" and "liner" scenarios. Not surprisingly, the "no liner" scenario showed seepage volumes orders of magnitude higher than the "liner" scenario.
However, in discussions, I pointed out how the facility configuration could possibly allow for a partially-lined scenario (green lines in the figure) and still reduce seepage volume to the underlying groundwater.
With liner installation costs in the millions, I could practically hear the gears in my audience's heads churning...