Technical Report and Preliminary Feasibility Study for the DeLamar and Florida Mountain Gold-Silver Project
Integra Resources Corp. (“Integra”) is a development stage gold mining company focused on exploration and de-risking the previously mined DeLamar Project in Idaho. Integra contracted with MDA, the Reno office of RESPEC (“RESPEC”) and other consultants to conduct the DeLamar Project Prefeasibility Study in late 2020 through early 2022 on two deposits in the study area: DeLamar; and Florida Mountain. The prefeasibility was compiled with RESPEC as the lead consultant and provided definition and signature of Mineral Resources and Mineral Reserves following Canadian Institute of Mining (“CIM”) definition standards. The results of the study were published in a Canadian NI 43-101 Technical Report: “Technical Report and Preliminary Feasibility Study for the DeLamar and Florida Mountain Gold- Silver Project, Owyhee County, Idaho, USA”.
Michael Gustin was the primary author for resource statement. Drilling data was statistically and spatially analyzed for mineral populations. Then mineral domains were created along set intervals for low, medium, and high grades. The block model was coded for each of the two main deposit areas using the domain polygons. This model was then geostatistically analyzed to establish estimation and classification parameters. Gold and silver grades were interpolated using inverse distance methods in the previously created block model.
Reporting Mineral Reserves requires collaboration with other engineers and consultants to identify modifying factors that are applied to the resources. These modifying factors include consideration of land and legal issues, permitting requirements, metallurgical and processing requirements, geotechnical design requirements, pit and waste rock storage facility design, road design, equipment, and many other factors. The determination of reserves is an iterative process, requiring pit optimizations, pit design, waste dump design, and road design. These were done for each deposit from which a combined production schedule was created for the project.
The pit optimization was based on geometrical, metallurgical, and economic parameters using Whittle. The geometric parameters included land boundaries and slope parameters which defined the angles to be used for the pit walls. Metallurgical parameters included oxidation state, process method, and process recovery. Pit optimization started with assumed walls based on input from geotechnical engineers. The RESPEC Rapid City office completed the geotechnical studies for the DeLamar prefeasibility study and the pits were designed based on the slope parameters provided. Due to the placement of haulage ramps, the final pit is bit flatter than the original parameters used. All pit and dump designs were completed using Surpac software.
A total of five mining phases for the Delamar deposit and three for the Florida Mountain deposit were used. These phases were designed around smaller optimized pit shells that allow more valuable material to be mined earlier in the schedule and consequently lowering the strip ratio for early mining. The tonnes and grades of measured and indicated resources were tabulated inside of the design and reported as proven and probable reserves. The resulting waste volumes were also tabulated and used as targets for the waste rock storage facility (WRSF) design. These dump designs were also sequenced to provide a logical order in how they would be constructed. This also includes prioritizing pit backfill where available. This reduces the costs as backfill typically allows for shorter haulage routes.
MineSched was used to create the production schedule using the pit and dump designs as mining and fill locations. Material types were created to differentiate where material was to be sent and report the timing of ore placed on the run-of-mine pad as well as sent to the crusher. The haulage profiles were developed in MineSched to calculate the haulage hours required for the schedule.
Equipment and personnel requirements were developed to estimate the mining costs. These costs were detailed into drill, blast, load, haul, support equipment, mine maintenance and mine general. These costs were developed from first principles, meaning that the hours for the equipment were estimated, then costs per hour for the equipment were used to estimate the overall costs. Estimation of equipment hours considered standby, delay, and efficiency assumptions.
Personnel requirements were simply an estimate of the personnel, operating, supporting, and supervisory, required to operate the mine.
The mine capital estimate included the equipment costs based on vendor quotations along with other items required for the mining operations including roads, explosive silos, explosive magazines, radios, office equipment, survey equipment etc. The goal on the prefeasibility study was to provide costs estimated with an accuracy of -15% to +20%.
RESPEC created the economic model which was used to estimate the revenues and consolidate the operating and capital costs. Tax considerations were provided by the client and the after-tax net present value and internal rate of return was reported by RESPEC out of the Reno office.
The culmination of this work is documented on Sedar.com for those interested in further details.
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