Supporting Technical Assessments

WKP PFS – Geotechnical Section Approved by: Approval Date: TBA OceanaGold PEX-000-PLN-046-A Page 14 of 22 The stope designs for the PFS assumed that strike lengths would typically be restricted to 15m along strike. The floor-to-floor spacing of ore drives is 20m. Narrow stopes could be as high as 25m if the ore drive is included. Wider stopes would have “wing pillars” left below the upper ore drive, thus these stopes would only be 20m high. Stope widths would be restricted to about 12m wide. Wider ore bodies would be mined as separate longitudinal stopes, therefore the actual HR in the backs of would range from 1.9 in the narrow stopes, and up to 3.3 in the widest stopes if the “wing pillars” failed. Figure 11: Stope backs design chart Figure 11, the design chart for stope backs, shows the 1st quartile N’ plots in the “stable zone” for hydraulic radii up to 3, and then the N’ plots in the “transition zone” for hydraulic radii ranging from 3 to 5.5. The 2nd quartile (mean) N’ plots in the “stable zone for hydraulic radii up to 7.

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