Notice
Information request
an operational decant pond will be incorporated in the next stage of the design (WSP, 2025). It is acknowledged that a spillway with the capacity to pass the Probable Maximum Flood (PMF) event will be required for Stage 2 and closure of the UGM TSF (WSP, 2025). Despite this, a spillway for Stage 2 has not been nominated nor detailed, with advice suggesting further studies are required to assess suitable locations to discharge outflows.
operational practices required to maintain no operational pond level to ensure this operational objective can be met. c) Provide the designs, configuration and discharge outflows of the Stage 2 spillway for the UGM TSF and revise all necessary reports to include the spillway and present the findings.
10
Consequence category assessment (UGM TSF)
Demonstrate via field verified data and modelling the assumptions utilised for seepage and groundwater flows from the UGM TSF are appropriate. If required, revise the CCA with verified information regarding seepage and groundwater flow pathways.
Assumptions applied in the UGM TSF CCA Report (WSP, 2025a) for seepage suggest seepage is determined to be of ‘low’ consequence category rating with flows from UGM TSF directed towards the OCP with the preferential direction of groundwater flow from the OCP east towards Mundic Creek. This has not been demonstrated via field verified data or modelling.
11
Geotechnical investigations
As outlined in the UGM TSF Design Report, provide revised application material that demonstrates the implementation and finalisation of the identified recommendations, along with the associated findings. This must include an assessment on the geotechnical stability of the UGM TSF, considering the increased hydraulic pressure from the proposed storage of water under extreme climatic events and the liquid content of the tailings.
It is stated that geotechnical investigations are needed to assess potential seepage impacts (WSP, 2025). Sections 7.8 and 8 of the UGM TSF Design Report include several recommendations required, however, there is no forwards works plan provided to address the information gaps. In the absence of necessary geotechnical information to support the application, it is significantly challenging to assess the stability, safety, and suitability of the proposed tailings dam design, as well as its potential environmental, operational and closure risks.
Page 9 of 20 • ESR/2016/3447 • Version 4.02 • Last reviewed: 29 OCT 2025
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