PLATINUM GROUP METALS LTD

Note: Approximated scale

There will be a box cut and portal at the Central Complex that will also be used to access the South Complex and a separate box cut and portal to access the North Complex. Each Complex will be accessed via twin declines (service decline and conveyor decline) that will service the complex for the LOM.

1.12.1 Geomechanical

Geomechanics core logging and laboratory test data from the PFS and additional data collected during the 2019 DFS were combined in a database and used to develop a geomechanical model and for use in rock mass classifications systems to develop rock mechanics parameters for the mine design. The analysis utilized several common empirical models and was validated with numerical modeling in several instances.

Waterberg Technical Report

A thrust fault located in the footwall of the T-Zone mineralization was identified during the DFS Update. The thrust fault and surrounding zone of influence is characterized as very poor to extremely poor ground and impacted the positioning of the declines and footwall development. A reduced development advance rate and additional ground support in the thrust fault zone of influence have been accounted for in the mine design, schedule, and costs.

Support requirements for development headings were developed and are in line with both empirical calculation methods and common support types. Generally, primary ground support will consist of patterned rock bolts and screen, with application of shotcrete in areas deeper in the mine.

An updated numerical modeling exercise for the Central Complex and South Complex was undertaken during the DFS Update to further evaluate the evolution of rock mass damage and paste backfill performance as mining progresses. The modeling was completed in five-year excavation steps based on the mining schedule. Modeling steps incorporated stope excavation and then immediate backfill before starting the next excavation step. The principal findings of the modeling exercise are listed below.

• Beyond the end of LOM with complete backfilling of mined stopes, vertical deflection at the ground surface is not expected to exceed 11 cm at the Central Complex, and no measurable surface deflection is expected at the South Complex.

• Surface strain is within tolerance at both the Central Complex and South Complex and will not impact any category of present or future surface development or infrastructure, including buildings, roads, and pipelines.

• The mine design should account for ore loss at the lowest elevation mine workings at the Central Complex, due to stress conditions exceeding rock strength thresholds. Ore loss may be due to sterilizing stopes or modifying stope designs, where critical stress conditions may lead to active fracturing of the rock mass.

• To mitigate this risk, all stopes in the mine plan have a 5% geological losses factor applied as well as a 90% mining recovery factor. To further account for ore losses due to stress conditions in the Central Complex, a second 90% mining recovery factor has been applied to all secondary stopes with an average true width of 25 m or greater. This second recovery factor represents 5.3 Mt of ore. The risk of rock mass damage and impact to operations can be reduced by optimizing the mining sequence, which should be undertaken during execution.

• Paste backfill dilution in wider parts of the ore body is expected, principally affecting secondary transverse stopes. In general, paste backfill dilution is anticipated to increase with depth and towards completion of the mining level and has been reflected in the dilution estimates.

Backfill stability was assessed primarily using empirical-analytical methods with developed backfill strength requirements validated by benchmarking and limited 3D finite element modeling.

Waterberg Technical Report

1.12.2 Mine Development

All decline and lateral excavations will be developed using drill and blast methods and mechanized diesel-powered mobile equipment. A summary of the development totals by Complex is included in Table 1-7 and the development profile is shown in Figure 1-5.