5.9 Seepage Management A Seepage Management Plan (SMP) has been developed based on the current conceptual understanding of the hydrogeological and geological conditions at the site, including the interpreted groundwater flow regime, stratigraphic framework, and potential seepage pathways associated with the proposed UMG TSF. The SMP is provided in Appendix H. This SMP presents an initial characterisation of potential seepage behaviour during operations and in the period following completion, recognising the current level of site understanding. In this context, the SMP identifies key stages of Project development during which the understanding of potential seepage is progressively advanced through future numerical assessments, including the development and refinement of seepage modelling and, where required, the evaluation and incorporation of mitigation measures into the TSF design. At this stage of the Project, the SMP serves as a guiding framework to inform targeted investigations and assessments required to address current knowledge gaps and to test and refine the current understanding of seepage processes. The SMP defines the information requirements, monitoring activities, and further studies necessary to improve confidence in seepage risk characterisation and to support the progressive refinement of seepage assessments as additional data are collected and the Project advances. Each stage builds on the outcomes of the previous stage, increasing confidence in seepage prediction and supporting informed decision making regarding TSF design, monitoring requirements, and, where required, the evaluation and incorporation of mitigation measures. This adaptive staged approach provides a framework to reduced uncertainties and evaluate seepage risk over time, ultimately supporting appropriate design and management responses consistently with the evolving level of site knowledge. An overview of the proposed staged approach is in presented in, below:
Figure 29. Proposed seepage management approach The SMP identifies the following key stages of Project development as: ∕ Stage 1 – Initial Conceptualisation, Data Gap Identification and Field Investigation Scoping – Establish a preliminary understanding of the hydrogeological and geological setting, including groundwater flow, stratigraphy, and potential seepage pathways, and identify key data gaps, uncertainties, and limitations that influence confidence in this understanding, and scoping field investigation requirements to address these gaps and improve the reliability of the conceptual model. ∕ Stage 2 – Field Campaigns, Numerical Seepage Modelling and Risk Characterisation – Address data gaps undertaking those field investigations identified in stage 1, develop and apply numerical assessments to evaluate potential seepage behaviour, including groundwater responses and migration pathways, and to define the level of seepage risk under the updated conceptual understanding. ∕ Stage 3 – Impact Assessment, Consequence Evaluation and Mitigation Assessment
Project number: 25B061
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