Ivanhoe Electric says its engineers are working on updates to a 2025 prefeasibility study on the proposed Santa Cruz copper project in Arizona, USA, after the company committed to spend about US$65 million on a tunnel boring machine it thinks can optimise 8km of decline development.
It expects to have the update finished in the third quarter this year.
Robert Friedland-chaired Ivanhoe Electric aims to have the TBM on site in Q1 next year and to start decline development in Q3.
Its 2025 PFS outlined a $1.2 billion project with underground mining of oxide ore feeding surface leach pads and a standard solvent extraction and electrowinning plant able to produce 72,000 tonnes of copper cathode per year at an average $1.32/lb cash cost for the first 15 years of operation. Ivanhoe Electric said the TBM spend replaced capital associated with roadheader decline development, silica gel grouting and a Railveyor material handling system included in the PFS. “The net impact to initial project capital of implementing the TBM system is projected to be less than $20 million,” the company said.
Its initial plan was to produce its first cathode copper in 2028. Now it says first ore is expected on heap leach pads in the fourth quarter of 2028 and initial cathode production is anticipated in Q2 of 2029. It says the TBM can excavate a 4km-long single decline in about 12 months.
The Robbins TBM acquired for Santa Cruz is ex-Australia where Anglo American engaged contractor Redpath to use it to complete nearly 1.8km of drift access development for Anglo’s Grosvenor coal mine in Queensland. The 8m-diameter machine reportedly spent about 1000 hours underground. Ivanhoe Electric said it became aware late last year of the potential availability of the Grosvenor TBM.
The company said its Santa Cruz geotechnical assessment indicated “mixed ground conditions” through the proposed decline development area. The TBM’s earth pressure balance capability “pressurises the cutterhead chamber against prevailing groundwater, controlling face stability and mitigating inflow through water-bearing zones and aquifer intersections”. A bi-directional cutterhead is used for excavation in softer tunnel conditions, mixed-face and hard rock geology, while a high-torque and high-speed cutterhead drive system is expected to deliver power needed to get through challenging geology and structures.
“The Robbins TBM can move through hard rock, wet and mixed-face ground within a single drive, eliminating cost, schedule and safety risks associated with machine swaps or re-mobilisation,” the new owner says.
Ivanhoe Electric says after Santa Cruz the machine could be used at Texaco, 2km to the northeast, which has a current inferred resource of 2.7Mt grading 0.8% copper.
“TBMs have been deployed globally for more than half a century in mining and countless civil engineering projects,” Friedland said.
“This specific crossover TBM is perfectly suited for accessing our high-grade orebodies at Santa Cruz and continues the derisking of our mine development with the best tunnelling technology America has to offer. Robbins is an American company that pioneered the modern TBM and remains at the forefront of tunnelling innovation.
“Owning the TBM gives our engineers the ability to pursue a future phased expansion of the project, including the high-grade Texaco deposit a mere 2km away.”
Ownership of 74-year-old The Robbins Company has passed through Swedish, Chinese, French and American hands in the past 30 years. It claims to have continued breaking TBM production records as its machines were deployed on high-profile projects such as the UK-France channel tunnel, the Niagara tunnel in Canada and the Dulles Airport train tunnel in Virginia.
Long-time Robbins CEO Lok Home owns the company today after buying it out of receivership in 2021.
“I believe the need for responsible, forward-thinking underground projects is as important now as it was 50 years ago,” Home says.
