Not all tailings deposition alternatives are created equal - and knowing which one is best for a project is not always straightforward given the multiple factors that need to be considered. Fluctuations in commodity prices, the need to reduce water consumption, and evolving regulatory requirements have prompted mining companies to develop adaptable tailings management alternatives. These may include new facilities, embankment raises or alternative technologies. Furthermore, the Global Industry Standard on Tailings Management publication in 2020 highlights the importance of conducting multi-criteria alternatives analyses to minimise risks to people and the environment for a facility’s entire lifecycle.
To address this need holistically, the authors applied a Multiple Accounts Analysis (MAA) tool, which integrates technical, environmental, economic, and socio-economic considerations. This approach enables technical specialists to communicate key engineering factors while allowing stakeholders to provide input to the decision-making process based on their values and priorities.
An MAA involves developing a multiple accounts ledger that explicitly identifies the technical, environmental, economic and socio-economic elements that differentiate alternatives. This ledger consists of sub-accounts (evaluation criteria) and indicators (measurement criteria), which are scored and weighted to complete the evaluation. Sensitivity analyses are also conducted to evaluate the robustness of the preferred alternative. This involves considering a range of weightings that are representative of the disparity perceived by stakeholders throughout the evaluation process.
In the authors’ experience, the MAA has been successfully applied across different regions, site conditions, commodities, and project stages. A structured series of workshops helps facilitators, mining personnel, and stakeholders to establish a shared understanding of each factor’s relevance and provides a valuable opportunity to build consensus around the preferred tailings deposition alternative. Effective workshop facilitation can make the difference between a good and a great MAA outcome. Considering all stakeholders enables the nuances of each alternative to be truly exposed and evaluated.
The following cases illustrate the method’s relevance, adaptability, and complexity:
Case A: For a lithium project in northern Argentina under extreme arid conditions, the MAA was used to select the preferred location for a ~25 km2 spent brine evaporation pond and determine the optimal sequencing to accommodate forecasted production. Due to the large size of the facility, modular construction using crystallized halite extracted from the impoundment area was identified as the preferred solution. This modular construction enables subsequent cell designs to be optimized, taking advantage of increasing knowledge of the facility’s performance (especially the amount of infiltration and spent brine evaporation) and the availability of crystallized halite for constructing the embankments.
Case B: At an operating gold mine in Nicaragua under water-surplus conditions, the MAA guided the selection of the preferred alternative for expanding tailings storage capacity. Options included different technologies, raising the existing dam, constructing a new dam, or using multiple in-pit facilities. Slurry deposition in a new in-pit facility emerged as the preferred solution due to the short time required for permitting, constructing and commissioning the facility, the reduced risk of tailings release due to the absence of dams, the low CAPEX and OPEX costs, the flexibility for future expansions, and the opportunity for integration with closure planning.
Case C: At a gold-silver mine in southern Argentina, the MAA was used to determine the preferred alternative for tailings storage expansion. Alternatives included raising the existing TSF, constructing a new dam, implementing a central thickened deposition (CTD) strategy at the existing TSF, and in-pit deposition. Upstream raising of the existing TSF was picked as the preferred option, with CTD and in-pit deposition identified as opportunities for integration with future Life of Mine (LOM) expansions and closure planning.
The MAA enabled the identification of preferred solutions by balancing cost-benefit considerations with overall project risks and uncertainties, while providing the operational flexibility required to increase tailings storage capacity, in line with future LOM expansion and closure planning.
