Resolution Copper completed its multi-year, $200 million rehabilitation and deepening of the No. 9 shaft in Arizona, according to a Thursday statement.

Resolution Copper Mining is a limited liability company, in which a 55% stake is held by Resolution Copper, a unit of Rio Tinto Group (ASX:RIO), while BHP Group (ASX:BHP) unit BHP Copper holds a 45% interest.

The shaft was deepened to a final depth of 6,898 feet underground from 4,800 feet, and it measures 22 feet in diameter. The No. 9 shaft now connects to the No. 10 shaft, which will serve as ventilation and access for future underground development. The network of underground mine workings will be part of the project's next phase of underground development for copper production.

Ongoing litigation continues to stall development, but the firm is ready to advance the copper project, Resolution Copper's President, Vicky Peacey, said.