PLATINUM GROUP METALS LTD

18.9 Dry Stack Tailings Storage Facility

Epoch was appointed in 2019 by DRA to complete the 2019 DFS design of a wet tailings upstream-deposited TSF and its associated infrastructure. These types of tailings facilities are associated with high water losses due to substantial evaporation and groundwater infiltration. They also carry high risk of potential collapse or liquefaction, which remains a worldwide concern for all wet deposited tailings facilities.

The Waterberg Project is in an area characterized by low rainfall and the viability of the operation has been tied to the continued supply of water from natural groundwater resources. Dry stack technologies provide mitigation to the combined risk of water supply and communities, the impacts on regional water supplies, environmental pollution risks and the serious safety concerns associated with wet deposited tails facilities. As such, this DFS Update has been amended to include this technology in lieu of the previously scoped wet deposition.

18.9.1 Introduction

Prime Resources (Pty) Ltd. (Prime Resources) was appointed to undertake the design of a filtered, Dry Stack TSF for the Waterberg Project, as part of the DFS Update. The work conducted by Prime Resources replaces the wet-deposited TSF design undertaken by Epoch during the 2019 DFS. However, it should be noted that the site selection, footprint, environmental and geotechnical studies as well as the geochemical and geotechnical test work (tailings characterization) undertaken on the TSF have been retained without amendment. Fraser McGill undertook the design of the bulk material handling and peripheral infrastructure to support the TSF. Fraser McGill was also responsible for the overall engineering integration.

18.9.1.1 Dry Stack TSF Design Criteria

The filtered residue for the Dry Stack TSF for surface disposal will in total produce 97.5 Mt over the 56-year LOM. The dewatered tailings will be conveyed to the perimeter of the TSF on an overland conveyor from where it will be deposited by a truck, spread and compaction fleet.

The key design criteria for the Dry Stack TSF are summarized in Table 18-7.

Waterberg Technical Report