Resolution Copper Mine — No. 9 Shaft Deepening Project

Developing one of the world's largest untapped copper deposits

Rio Tinto | Arizona, United States | 2016-2021

Deposit is nearly 1.3 miles below the earth’s surface

Deepest underground mine shafts in the U.S.

Anticipated production rate of 51,000 to 115,000 ore tpd

Potential to supply 25% of the U.S. copper demand


  • The Resolution copper deposit lies nearly 7,000 feet (or 1.3 miles) below the earth’s surface. It is one of the world's largest undeveloped copper deposits.
  • The most viable way to recover the resource is by going deep underground, and to do so, Resolution is using the block caving process—one of the most economical underground mining methods available for this type of large, deep deposit.
  • Originally constructed in 1971, the No. 9 mine shaft sat idle for nearly 20 years.
  • The No. 9 Shaft Deepening Project will rehabilitate the shaft, sink it to approximately 7,000 feet, and link it with the newer No. 10 shaft, which was completed in 2014.
  • The main challenge at Resolution is the high rock temperature and water inflows, which can escalate to 140 degrees Fahrenheit.


  • Following earlier study phases, Hatch was awarded the engineering, project and construction management (EPCM) contract to refurbish the existing No. 9 shaft and deepen it to the same level as the No. 10 shaft.
  • The No. 9 Shaft Deepening Project consists of the rehabilitation of the shaft from the surface to 4,823 ft. below surface and the deepening of the shaft by 2,022 ft., utilizing the blind sinking methodology.
  • It includes the excavation of five stations, three levels, and two pump stations.
  • The headframe and hoisting equipment have been reconfigured, strengthened, and upgraded.
  • The underground ventilation system has been reconfigured and upgraded to support new demands and the efficient operation of both personnel and equipment.
  • The mine dewatering system has been upgraded to meet the new demands.
  • New diesel generators have been installed for backup power.


  • Phase 2 of the project, the deepening works, will sink the shaft to a final depth of 6,845 feet below the collar.
  • The existing No. 10 Shaft at Resolution Mine is the deepest in the United States and the No. 9 Shaft will be at the same depth at completion.
  • Connecting the shafts will provide a second means of egress between the two shafts as well as improve ventilation.
  • Current life of mine studies are focusing on a production rate in the range of 51,000 to 115,000 ore tones per day at an anticipated ore grade of >1.5% copper.
  • Over 350,000 hours have been expended on this challenging work to-date without a Lost Time Injury (LTI).

Project numbers

  • Final depth of 6,845 feet below the collar
  • 4,750 feet of shaft rehabilitated
  • 1,284 cubic yards of concrete placed at fifteen (15) old mine level stations to permanently seal them and sections of shaft liner that required repairs
  • 450 shaft guide steel sets (950 tons) removed
  • 145 ring set liner plates removed at old level stations

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