Item
Description
Information Requested
Response
Corresponding Sections
Water balance model report 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. 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 DNRMMRRD water treatment plant, with the value applied requiring confirmation. b) The evaporators nominate a throughput capacity of 3.35 ML/d. No data is presented supporting this assumption. c) Table 3.1 of the WBM Memo suggests the UGM TSF return water to plant is 7.8 ML/d in Stages 3 and 4. However, clarity is required regarding the purpose of this water transfer and its source (i.e., decant water and/or runoff). d) Table 3.1 also suggests in Stages 3 and 4, the Open Cut Pit (OCP) to UGM TSF transfers is 0.5 ML/d. However, clarity is required regarding the purpose of this water transfer and the simulated rate. Further, this does not appear to align with the operational design aspects of the UGM TSF which states ‘no operational pond level’.
Provide revised application material which:
a) The application has been modified to reflect that water transfer between the OCP and UMG TSF will not occur. Reference to the GHD report (2022) has been removed from this application b) The application has been updated to remove references to the transfer of water to the UMG TSF c) As discussed throughout this application, the TSF design is at concept stage and the design of pumping infrastructure has not been undertaken. A forward works plan in Section 9 commits to undertaking the design of infrastructure during detailed design d) Heritage Minerals operate the water treatment plant on behalf of the DNRMMRRD e) DNRMMRRD operate and maintain the evaporators. Therefore the applicant does not maintain performance datasets. Assumptions that underpin the water model were based on previous reporting (Engeny, 2018). f) The Upper Mundic Gully TSF has been designed on the basis of no operational pond volume. Tailings deposition will be managed to minimise ponding, with systems to be installed to return any operational water to the process plant. The design includes sufficient freeboard to accommodate the PMP event without requiring any operational spillway. The estimated return volumes is calculated by considering the beach surface and tailings density. g) The application has been updated to remove references to the transfer of water to the UMG TSF
a) NA b) NA c) Section 9
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 aligns with the proposed operational design aspects of the UGM TSF and the overall best practice management of tailings dams.
d) NA e) NA f) NA g) NA
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ISO 9001 • ISO 14001 • ISO 45001
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