Fonataba, O, Beaulavon, A, Singgir, Y & Nugraha, S 2024, 'Hydrological risks and water management in the transition of underground block cave mining: a case study of Deep Ore Zone–Deep Mill Level Zone transition', in P Andrieux & D Cumming-Potvin (eds), Deep Mining 2024: Proceedings of the 10th International Conference on Deep and High Stress Mining, pp. 1453-1466, https://doi.org/10.36487/ACG_repo/2465_95
(https://papers.acg.uwa.edu.au/p/2465_95_Ofonataba/)
Abstract: The East Ertsberg Skarn System (EESS) is located in the Ertsberg Mining District in Papua, Indonesia. It includes the historical Gunung Bijih Timur (GBT), Intermediate Ore Zone (IOZ) and Deep Ore Zone (DOZ) mines, while currently the operational focus is on the Deep Mill Level Zone (DMLZ) mine. This strategic shift aims to reach deeper ore reserves and optimise resource management within the EESS, although it also introduces significant hydrological challenges and risks associated with deep underground block cave mining. The transition phase is critical for helping ensure the sustainability of deep mining activities.
PT Freeport Indonesia’s (PTFI) operational area experiences very high rainfall, with certain weather stations recording over 5,000 mm of rainfall per year. This intense rainfall, coupled with the operational complexity of managing several inactive mines overlaying the DMLZ mine, such as the DOZ mine, creates unique challenges. These include managing regional groundwater inflows to prevent rainfall infiltration into the existing surface subsidence, and existing DOZ mine water from causing flooding or triggering wet muck spills into the DMLZ mine. Effective water management is therefore critical to mitigating operational risks and includes strategies such as surface water diversion, large-scale underground dewatering, caveline drilling and continuous monitoring of groundwater levels.
The practices and strategies implemented during the DOZ and DMLZ transition have valuable implications for deep mining operations globally, offering guidance for safe and efficient transitions in similar hydrological settings. 

Keywords: underground, block cave, transition, hydrology, hydrogeology, dewatering, hazard, management, drilling