A renewed approach to surface mining cost estimating

Sherpa for Surface Mines has been reinvented as Costmine’s Sherpa Surface, an improved, cloud-based mining-cost-estimating application. The transition of this unique application to the web gives anyone with an internet connection, and a need to estimate the capital and operating cost associated with surface mining, instant access to a powerful engineering-based tool with a new easy-to-use interface.

The original Sherpa for Surface Mines was created to allow mining cost estimators to use advanced cost engineering procedures at the pre-feasibility level and earlier. The program was designed to be both highly flexible, so experienced engineers could fully utilize their expertise, and easy to use, so that those not fully versed in cost engineering techniques could produce reliable estimates. These design principles have endured the application’s transformation into the new Sherpa Surface.

Rather than relying on obscure statistical relationships, Sherpa Surface takes a cost engineering approach. As it was with Sherpa, this updated application uses established engineering procedures and algorithms to calculate all the engineering parameters necessary to estimate the costs associated with surface mining and development. Haul cycle times, excavator productivity, explosive consumption rates, pumping requirements, and a host of other engineering parameters are determined using accepted mathematical procedures. Finally, these engineering parameters are coupled with up-to-date itemized cost data, provided by Costmine’s Mining Cost Service and a variety of other sources, to arrive at complete surface mining capital and operating cost estimates.

Sherpa Surface can accomplish all of this (including data entry, determination of engineering parameters, application of itemized costs, and detailed reporting) in a matter of seconds. However, when site-specific data is available and/or the user is experienced, the application encourages you to overwrite any and all intermediate calculations, estimates, and costs that it provides. This allows the user to tune his or her cost estimate to their project’s specific characteristics, bolstering the reliability of their cost estimate; and making the Sherpa Surface capable of estimating the costs of projects located around the globe.

Equipment selection

Figure 1 shows us the minimum amount of data entry required to estimate the capital and operating costs associated with a surface mining project, covering basic project, production and deposit data. After the minimum data entry has been saved, the Sherpa Surface begins the process of selecting the primary equipment fleet. You can request that the application specify the fleet for you, or you can specify your own fleet if more appropriate for your project.

If you choose to let the Sherpa Surface determine your fleet, standard engineering techniques are used to select the types and determine the sizes of the excavators and haulers. The application then goes through an optimization process to determine the most economically attractive excavator-hauler combination. Equipment availability, bucket fill factors, material densities and swell, fixed cycle times, and travel speeds (adjusted for load and gradient) are all considered when determining productivity.

Once excavators and haulers have been selected, the Sherpa Surface examines the specified powder factors, bench heights, and production requirements to select the type and determine the size of the blasthole drills. Requirements for ancillary equipment, including graders, pumps, dozers, lighting plants, water tankers, pick-up trucks, maintenance trucks, and explosives loaders are also provided. A summary of the primary and ancillary equipment fleets is displayed on the Settings Summary page of the application, shown in Figure 2. As with all fields in the application, you may alter any or all of the fleet related parameters, or even specify new equipment, by simply overwriting the values suggested by the application.

With the equipment fleet specified, the Sherpa Surface begins the task of determining the requirements for all other aspects of the operation. The numbers of hourly and salaried workers required to meet the specified production rate are estimated. Consumption rates for all pertinent supplies are calculated. The sizes of the shop, mine office, change house, and warehouse are provided, as are requirements for explosives storage facilities and the electrical distribution system. The Sherpa Surface also estimates pre-production development and haul road requirements, as well as working capital, engineering, and management parameters.

Once all necessary engineering parameters have been determined, they are used in conjunction with the information contained in the itemized cost database to calculate all relevant capital and operating costs. Overall costs are displayed in an easy-to-read Executive Summary. Detailed costs are displayed in four menus, including a Total Project Cost Summary (see Figure 3) displaying annual average operating costs by category and a schedule of annual capital costs incurred. All the reports and the Executive Summary are downloadable as a PDF with one click. Finally, the data can also be transferred to other applications, such as your favourite spreadsheet application, for further analysis.

A unique approach to mining cost estimating

The cost estimating techniques used by the Sherpa Surface rely on numerous project-specific engineering parameters, along with user entered resource data and ore and waste production rates, provide the foundation upon which the cost estimate is based.

Sherpa Surface will suggest entries that allow you to complete reasonable estimates with a minimal amount of information in a small amount of time. The only items that absolutely must be specified are daily production rates, shift schedules, and the total resource size. CMJ

Sam Blakely is a mining engineer and cost analyst at Costmine (www.costmine.com).

---