Notice
Information request
g) Demonstrate how the updated water balance model accounts for water inputs, outputs and storages across the site, and detail how this aligns with the approved and proposed activities.
8
Water balance model report
Provide revised application material which:
The WBM Memo is a technical memorandum and not a comprehensive water balance model report. The referenced report Water Balance Modelling Report – Heritage Minerals EA Amendment Application, Revision 3 (GHD, 2022) was not provided in support of this application. It is understood the UGM TSF is intended to provide a more resilient tailings and water management strategy which can better accommodate more extreme climatic conditions and further reduce water balance risks (Wulguru, 2025). Despite this, the transfer of water under extreme climatic conditions nor climate change impacts have been modelled. It is assumed based on the WBM Memo, the UGM TSF construction and status prior to it receiving reprocessed tailings will potentially be fifty-two (52) months. During that time, it is acknowledged the UGM TSF area will naturally retain water from the contributing catchment runoff, however, this has not been simulated in the model. An understanding of why this was not included in the model, and the destination of this water is required. Consideration must also be applied detailing if this water is likely to be contaminated given the western dump surface area. Further, it is acknowledged a sump and pump system will be required for the UGM TSF, however, no further information is provided.
a) Provide the comprehensive water balance model report prepared by GHD (2022) referenced in the adjacent column. b) Update the water balance model report to incorporate scenarios of the extreme climatic conditions which control the transfer of water to the UGM TSF, and climate change impacts. Present the findings clearly and ensure the updated comprehensive water balance model report is provided. c) Clarify why the clean water entering the system from the contributing catchment was not simulated and demonstrate this is suitable to not include in the model. Provide further information on the proposed sump and pump system, including the expected quantity and quality, the destination of the water pumped through this infrastructure and if this is suitable and aligns with the sites approved activities. d) Clarify who operates the DNRMMRRD water treatment plant and confirm the assumption applied is appropriate. e) Clarify who operates and maintains the evaporators and detail the reliability and efficiency of the evaporators. Provide the site data which supports the evaporators throughput capacity applied in the model. Apply a sensitivity scenario which removes the evaporators from the model and present the findings. f) Clarify the transfer of water from UGM TSF to plant (7.8 ML/d), what this is attributed to how this has been calculated. g) Clarify the transfer of water from OCP to UGM TSF (0.5 ML/d), why this is required and how this has been calculated. Confirm this
Notwithstanding information request item 7 , the following assumptions within the WBM Memo require clarification:
a) The DNRMMRRD water treatment plant is assumed to be actively pumping throughout the entire simulation period (4.8 ML/d). It is unclear who operates and maintains the
Page 7 of 20 • ESR/2016/3447 • Version 4.02 • Last reviewed: 29 OCT 2025
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