A gold–silver mine in Latin America that has been operational for over 20 years with a single tailing storage facility (TSF) has recently expanded its life of mine (LOM) above the current TSF storage capacity. With the objective of guaranteeing continuous tailing deposition, a storage alternative assessment was conducted to determine the preferred alternative to store the additional tailings during the LOM once the current TSF capacity is achieved.
- The following options were assessed:
- Downstream, centreline or upstream raise of the current TSF.
- Central thickened disposal (CTD) in the current TSF.
- Construction of a new TSF.
- In-pit tailings deposition.
To determine the preferred alternative, a series of workshops with the mine and corporate personnel were held. A pre-screening assessment was conducted and conceptual-level designs for the pre-selected alternatives were developed.
A comparative analysis was finally conducted, in which the upstream raise of the current TSF was identified as the preferred alternative for the following reasons:
- Site-specific and facility conditions are adequate for the implementation of an upstream raise. The RoR is ~0.7 m. per annum, and current TSF conditions allow for a controlled beach and prevent water ponding against the embankment. Evaporation is considerably higher than precipitation throughout the year, and the site is in a stable seismic area.
- Upstream raising complies with tailings and water storage requirements throughout the LOM.
- Only one additional pump is needed, preventing the need to move ancillary infrastructure located at the toe of the current embankment.
- Total cost per tonnage of tailings is lower than the other alternatives, except the in-pit TSF.
- Closure of only one facility is needed.
The CTD alternative was ruled out for not complying with tailings and water storage requirements. However, creating the tailings land-forming near the end of the LOM was identified as an option, minimizing earthworks and preventing water ponding through the embankment.
The in-pit TSF alternative might be a competitive alternative, since it minimizes risks associated with dam failure and capital and operational expenditure requirements (particularly if no lining or sealing is required). However, for the relatively short LOM, the benefit could not be fully realized. Should LOM be expanded, an integration between operation and closure should be studied, leading to minimizing the closure of earthworks and reducing environmental passives. Eventually, a reduction in environmental passives, in comparison with the closure of the pit itself, could be achieved (though this requires further study).
