In its recently filed National Instrument 43-101 Technical Report for its Marathon project feasibility study in north-western Ontario, Generation Mining says it is considering trolley assist for the haul truck fleet. The mine will produce an average 245,000 oz of palladium equivalent (PdEq) annually over a minimum 13-year mine life. Initial capital costs are estimated at C$665 million (US$520 million). Approximately 58% of the revenue will come from palladium, and a further 26% from copper. The proposed mine is approx 215 km east of Thunder Bay and the largest undeveloped palladium-copper Mineral Resource in North America.
The report states: “This project has the potential to benefit from the addition of a trolley system. A trolley system could be implemented in long stretches of consistent uphill climb, typically in sections of the mine that are in place for many years and receive significant traffic. A potential location would be on the west and east ramps of the North Pit as these sections are in production for seven or more years and will see a significant percentage of the mine traffic.”
The company outlined the pros and cons – on the plus side potential reduction in fuel consumption and costs, reduction in fuel burn (when the truck is operating on trolley) extending engine life, potential reduction in cycle time, GHG emissions reduction, delivering more power to the electric engines significantly increasing the uphill climbing speed plus potential reduction in haulage units required. Potential drawbacks are increased CAPEX of the trolley system and maintenance OPEX plus the additional trolley package having to be installed and maintained on all equipment that will use the haulage system as well as a potential decrease in the stripping ratio due to more waste having to be mined. Trolley systems typically include ramp widths capable of three lanes of traffic so mine designs would need to be updated to reflect this.
Trolley line at Boliden copper mine in Arctic Sweden
The concept of trolley assist was evaluated with Cat and Komatsu but was not included in the Base Case operating design. A dedicated study will be carried outto properly assess the implementation over the mine life. This study will include a updates mine designs, updated production schedule, updated waste balance, new haulage simulation and in–depth economic analysis to access the economic feasibility of the system over the entire mine life. This work is intended to be progressed in the detailed engineering phase.
In terms of the fleet currently planned, the report lists two hydraulic face shovels (29 m3 bucket size) and one large front–end wheel loader (30 m3 bucket size). The loading fleet is matched with a fleet of 13 x 216 t haulage trucks with the ramp designs in the report based on the Caterpillar 793F. A fleet of two 90 t excavators will be used to excavate the limited volume of overburden material and will also be allocated to mining of the narrow–thickness ore zones associated with the W–Horizon in the South Pit to mitigate additional dilution. Mining production at peak capacity is 40 Mt/y (110,000 t/d).
The project is split into the three separate pits: North Pit, Center Pit and South Pit. The North Pit contains three phases. The Center Pit and South Pit only have a single phase. Over the mine life, the project will produce 117.7 Mt of ore and 330.2 Mt of waste at an overall stripping ratio of 1 to 2.81 (ore to waste).
North America is becoming something of a new hotspot for potential trolley assist projects after Africa and more recently northern Europe. Copper Mountain Mining Corp is set to conduct a four truck trolley assist trial with Komatsu 830E trucks at its operation in southern British Columbia, while a trolley pilot has been proposed by Minnesota Power to its mining customers in the Iron Range. Other companies have mentioned the possibility of trolley, such as RNS Nickel in a DFS for the Dumont nickel-cobalt project in Quebec, though this asset has since changed ownership to Karora Resources and finally to private equity firm Waterton Global Resource Management.