Transforming Ranger’s TSF to a process water storage facility

Authors: Paulka, SM; Staggs, D; Ralls, G; Sivarudrappa, K; Sigda, J Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2315_069

Cite As:
Paulka, SM, Staggs, D, Ralls, G, Sivarudrappa, K & Sigda, J 2023, 'Transforming Ranger’s TSF to a process water storage facility', in B Abbasi, J Parshley, A Fourie & M Tibbett (eds), Mine Closure 2023: Proceedings of the 16th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, https://doi.org/10.36487/ACG_repo/2315_069



Abstract:
The former Ranger uranium mine above-ground tailings storage facility (TSF) is a recent addition to an ancient Northern Australian landscape. The Ranger Project Area is surrounded by, but separate from, the dual World Heritage listed Kakadu National Park – recognised for its cultural and natural values. The responsible and safe closure of the TSF is essential with the recent cessation of uranium mining activities. As part of the Ranger Rehabilitation Project, Energy Resources of Australia (ERA) recently converted the TSF into a process water storage facility. The newly named Ranger Water Dam (RWD) will continue to store process water until treatment is completed, following which any residual contaminated material will be managed, and the facility will be deconstructed and revegetated. This paper reviews several of the geotechnical, hydrogeological, and other challenges associated with tailings removal from the TSF and its conversion to the RWD. ERA removed and transferred 27 Mt of uranium tailings to a nearby open pit for permanent storage. The transfer operation was unique and required specialist geotechnical input to plan and coordinate the tailings removal, including during dredging operations, final pump-out of contained process water, and mechanical removal of remnant tailings solids from the TSF. Methods employed by the mine’s consultant dam engineer included a weekly remote review of site monitoring data, frequent site visits at the height of a global pandemic, and office-based computational assessments described in the paper to support activities. All this work successfully met stringent stakeholder requirements and ongoing closure objectives. The original Ranger TSF design and construction was both a tailings and water storage facility; however, prior to conversion to the RWD a hydrogeological assessment was undertaken to quantify how the loading of groundwater solutes to creeks would change. The results showed that storage of process water would not impact the surrounding environment allowing stakeholders to approve the change in use of the facility.

Keywords: tailings storage facility, water storage facility, closure, geotechnical, hydrogeology

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