The ore bodies of the North and South Hugo zones and the Heruga deposit are planned to be mined using panel caving methods. Initially, the North Hugo zone is planned to be divided into two mining lifts for extraction.
Development and lateral excavation work for the first lift of the North Hugo zone resumed in July 2016. The first ore pass blasting began in May 2022, and ore production started stabilizing from January 2023.
From the ore passes, the ore is loaded by load-haul-dump (LHD) machines and dumped into central ore passes. From there, the ore drops to the haulage level where it is loaded onto haulage trucks, which transport it to one of two surface cone crushers located outside the mining area. Between 2022 and 2024, during the ramp-up period to increase mining capacity to 30,000 tonnes/day, the crushed material will be conveyed to the Shaft 2 ore storage bin and then hoisted to the surface. Starting in 2024, after commissioning the surface ore conveyor, crushed ore will be transported from the crusher to a surface (tactical) ore stockpile via an inclined conveyor. During maintenance of the surface conveyor system, the hoist at Shaft 2 will serve as a backup transportation system.
The Primary Crusher and the conveyor connecting it to Shaft 2 have been successfully installed. Additionally, 79% of the construction work for the inclined ore haulage tunnel from the underground mine to the surface has been completed.
According to the updated underground project estimate, the first ore pass blasting occurred in May 2022, and stable production levels were reached in January 2023.
The Oyu Tolgoi underground project has faced schedule and capital cost impacts due to the effects of the COVID-19 pandemic and the geotechnical conditions of the first lift of the North Hugo deposit. Consequently, "Erdenes Oyu Tolgoi" LLC and the Government of Mongolia are working to improve project operations, financing, and contractual negotiations.