Thiess long-time joint venture Thiess Khishig Arvin (TKAJV) has secured a contract extension for the underground works at the Oyu Tolgoi copper complex in the southern Gobi Desert of Mongolia.

The engineering group said recently that the scope of work includes the construction of a 6.4-kilometre (3.97-mile) concrete conveyor decline road as well as a conveyor hanger and change house. All elements are part of the mine’s ongoing development program.

oyutolgoiTKAJV’s work will deliver the twin decline tunnel sand connect the C2S conveyor to the surface tunnel at the complex’s existing underground operations.

Thiess executive director of Mongolia Enkh-Amgalan Sengee said that the contract with the JV recognises its “ability to deliver excellence” for You Tolgoi, where Thiess has operated with Khishig Arvin Industrial since 2016.

“We are proud to build on our safe and successful record of underground delivery for our client at Oyu Tolgoi, and to contribute to the growth of this world-class copper operation,” Amgaa said.

“We’re focused on developing our experienced and award-winning Mongolia-based team and maintaining our valuable work in the community, delivering health and education programs and community building initiatives.”

You Tolgoi, an asset of Turquoise Hill Resources (66%), which is in turn owned by Rio Tinto, is one of the largest known copper and gold deposits in the world. In 2021, the mine produced 468,000 ounces of gold and 977,000 ounces of silver.