THUNDER BAY – MINING – Premier Gold has updated the Company’s 100% owned Hardrock Project. Recently completed work includes the completion of a geotechnical report on the proposed open pit at Hardrock for the purposes of assessing pit wall slopes.
The Company, in conjunction with Golder Associates Ltd. (“Golder”), has completed a study titled the Hardrock Mine Open Pit Feasibility Level Slope Design Recommendations. This technical document presents the results of the slope design investigations, slope design recommendations and the slope design risk management plans (design and monitoring) for the Premier Gold Mines, Hardrock Open Pit mine project.
The report concludes that the Hardrock Pit will be comprised of good to very good rock mass with gold mineralization within the saddles of tightly folded, upright, broadly sub-vertical axial planes that trend roughly east-west. The fold axes are shallowly west-plunging. Given its moderate overall slope height of 460m, rock mass failure is not a concern. The excellent rock mass quality is also demonstrated in the by longwall mining done previously.
RECOMMENDED MAXIMUM INTER-RAMP SLOPE ANGLES
Several structural domains have been assigned to the pit area. While there are localized differences in the orientations of the discontinuity populations, in general terms they do not appear to justify distinctly different slope designs. Given these favourable rock mass and structural fabric conditions, the feasibility level maximum inter-ramp slope design on all wall orientations is as follows:
Maximum Inter-ramp Angle (IRA): The maximum inter-ramp angle ranges from 60.1 degrees (Option 1) to 63.4 degrees (Option 2). Note that the inclusion of geotechnical benches at fixed vertical distance of 100m is key to Option 2. In Option 2, every 100m the final bench shall be widened to 16m to provide additional rock fall protection and to provide additional flexibility to the mine plan. Inclusion of the geotechnical bench reduces the overall slope angle every 100m to 60.8 degrees.
Final Wall Bench Height (H): 20m (double benching with vertical pre-split, no sub-grade drilling and excellent blasting practices)
Design Catch-berm Width (B): (Option 1) 11.5m with no fixed spacing for geotechnical benches comprised of 8.0m required catch-berm width to contain rock fall and 3.5m for backbreak.
(Option 2) 10m with fixed spacing for geotechnical benches comprised of 8.0m required catch-berm width to contain rock fall and 2.0m for backbreak, and 100m maximum bench stack height.
IRA – Inter-Ramp Angle. BFA – Bench Face Angle.
Single benches are 10 m high. The 20 m height is a double bench and assumes careful pre-split blasting, trim blasting and scaling with appropriate equipment.
The berm widths are designed to catch small failures and ravelling debris.
“The Golder work confirms the favourable rock conditions at Hardrock and the ability to steepen pit walls within the Hardrock pit shell” commented Eric Lamontange, Director of Project Development for Premier. “Rock competency of this nature will allow for the pit resource to be taken to greater depths and could result in a reduction in the overall strip-ratio”.
The geotechnical work completed by Golder, which will be incorporated into a new resource estimate for Hardrock, is part of ongoing work associated with the feasibility study being completed for the Hardrock Open Pit Mine Project. While the report recommends an overall pit slope in excess of 60 degrees, owing to pit ramps and geotechnical benches it is expected that a final pit slope closer to 55 degrees will be chosen.
The previous resource estimate (See Press Release dated October 29, 2013) used to prepare the Preliminary Economic Assessment (“PEA”) Study issued by Stantec – Mining in March 2014 utilized an overall pit slope angle of 50 degrees. This PEA study indicated the potential for a 15 year mine life and gold production in excess of three (3) million ounces.
The independent report entitled “Trans-Canada Property Hardrock and Brookbank Projects Preliminary Economic Assessment” was issued by Stantec – Mining in North Bay, Ontario on March 13, 2014. The Report provides detail to the disclosure contained in the Company’s news releases issued on January 28, 2014 and March 13, 2014. The Report may be found on the Company website or under the Company’s profile at www.sedar.com.
Stephen McGibbon, P. Geo., is the Qualified Person for the information contained in this press release and is a Qualified Person within the meaning of National Instrument 43-101.