Item
Description
Information Requested
Response
Corresponding Sections
Groundwater It is stated the UGM TSF is determined to be of negligible risk to all environmental values (WTS, 2025). There is no understanding of groundwater environmental values within the UGM TSF footprint or close proximity. To support the assertion made, groundwater environmental values must be investigated. This information cannot be delayed via proposed conditioning and must be provided to support the application to understand the baseline conditions, the predicted and potential impacts and risks to groundwater to appropriately inform the mitigation and management measures. The application material, although related to the Mundic Creek Catchment and not the UGM TSF, identifies seepage may occur through the shallow bedrock. It is also stated groundwater flow and influence is not understood and the influence of the OCP and western dump on the UGM TSF is unknown. A comprehensive understanding on all seepage flows and pathways from the UGM TSF must be provided. Further, the high liquid content of the tailing’s slurry, coupled with the intention to store water on the facility under extreme climatic events increases the potential for seepage and groundwater contamination, necessitating a comprehensive groundwater assessment.
Provide all relevant information in accordance with the Guideline Application requirements for activities with impacts to water (DETSI, 2026)[6]. The revised application must also include: a) Investigate, nominate and implement groundwater monitoring bores within and surrounding the proposed UGM TSF at appropriate and representative locations. The bores must be located in areas to effectively capture baseline conditions and detect potential impacts from the proposed activity. b) Undertake and submit detailed groundwater monitoring information including:i. Background quality and characteristics. ii. Groundwater level and depth. iii. Hydraulically conductivity, transmissivity and flow rate. iv. Seasonal variations and influences.As per DES (2021) , a minimum of 18 samples over at least 12 and preferably 24 months is required to calculate limits. Alternatively, if there is urgency in the application, the department may consider a minimum of 8 monthly datapoints, if the concentrations are relatively stable and consistent. c) Provide further detail on the composition of tailings material including:i. Identification of potential contaminants of concerns.ii. Describe the results of leachate testing to determine the potential for contaminants to leach into groundwater.iii. Potential impacts on ecological systems and groundwater environmental values. d) Identify and describe all seepage pathways and flows from the UGM TSF including the receiving receptors. e) Provide a seepage management plan which includes: i. Design specifications to mitigate or manage potential flows through the facility, including evidence of the liner's ability to withstand the hydraulic pressure from the high liquid content and storage of water under extreme climatic events, and prevent seepage.ii. Proposed measures to minimise seepage, including monitoring and maintenance strategies.iii. Contingency measures in the event of seepage detection. f) Describe in detail the potential impacts due to the proposed activity and all associated risks to the groundwater environmental values in consideration of the above requested information. Consideration must be given on whether the identified impact on receiving waters supports the management intent for those waters, to the extent practicable. g) Describe in detail the strategies to mitigate and manage the identified risks to groundwater environmental values. For example: i. The locations, depths and purpose of the monitoring bores. ii. Frequency and parameters for groundwater quality and level monitoring. h) Submit a long-term groundwater monitoring plan for the UGM TSF, including post- closure monitoring requirements and measures to ensure the long-term stability of the facility and the prevention of groundwater contamination after closure from the facility. The information requested above must demonstrate the UGM TSF will not further impact waters environmental values of the receiving environment of the Mount Morgan Mine. Consideration can be given to the approved activities as a whole, however, reduction of the contaminant load to the receiving environment as a result of the approved activities must be demonstrated via modelling or other supporting evidence.
Since lodgement of the initial EA amendment application, three groundwater monitoring bores have been installed within the Upper Mundic Gully catchment. The application has been updated to include the information obtained from the drilling and subsequent groundwater sampling to inform potential risks to environmental values a) Three groundwater bores were installed within the UMG TSF footprint and surrounds during December 2025 and the application has been updated to include this information. The forward works plan commits to the installation of further groundwater monitoring bores to address data gaps. b) Whilst there are long term existing groundwater records from across the mining lease, there is only a limited dataset of groundwater information from UMG TSF. The Forward works plan commits to the installation of additional groundwater monitoring bores to be sampled at a monthly frequency. Updates to existing table W1 in the EA are proposed whereby the locations of the monitoring bores to be installed are conditioned. c) i. A tailings geochemical characterisation assessment was undertaken with information summarised in Section 5.14.1 of the supporting information report and the complete report provided in Appendix G. Bench testing indicates that Heritage Minerals processing activities will reduce metals in solids as they become leached by the cyanide. Although these metals were leached from the solids, they were absorbed onto the resin to be subsequently recovered, resulting in a lower final solution of metals. The potential residual contaminants of concern in the tailings include residual salts expressed as electrical conductivity. ii. Geochemical characterisation of the processed tailings to be discharged has been extensively studied by Hydrobiology in the report titled “Mt Morgan Open Cut Pit Water Quality Modelling Stage 2 (March 2025)”, provided in Appendix G. The Hydrobiology report provides a predicted water quality of the new tailings assuming a range of OCP water qualities based on extensive leach testing iii. The results of the geochemical modelling indicate that the final tailings solution analytes do no exceed any of the HILs and it is concluded that any leaching from the tailings material is benign to human health. Potential impacts on ecological systems and groundwater environmental values are proposed to be further understood through completion of additional groundwater installation programs and updates to the site wide groundwater model. d) Identification of potential seepage pathways has been provided in the seepage management plan. The seepage management plan has been developed based on the current conceptual understanding of the hydrogeologic and geological conditions at the site including the interpreted groundwater flow regime, stratigraphic framework and potential seepage pathways associated with the proposed UMG TSF. 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. e) A seepage management plan has been provided in the updated application. f) The existing risk assessment provided in Section 7 of the supporting information report has been updated (g) The existing risk assessment provided in Section 7 of the supporting information report has been updated. h) development of a long term groundwater plan has been included in the forward works plan As stated in Section 6.6.7 of the current supporting information report, a groundwater model exists for the site. This is a validated and calibrated groundwater model developed in FEFLOW that provides explanation on mechanisms by which contaminants can migrate through groundwater and impact receptors. The groundwater model mesh grid covers an area of 7.7km 2 . The model calculates contaminant load from each catchment and was relied upon by the State to inform rehabilitation strategies. This model provides a characterisation of all catchments that occur within the mine lease boundaries. The application has been updated to commit to further updates to the groundwater model to incorporate site specific data obtained from the UMG TSF footprint and surrounds.
a) Section 6.6.1 and Section 9 b) Section 6.6.8 and Section 9, c) Section 5.15.1 and Appendix G d) Section 5.10 and Appendix H e) Section 5.10 and Appendix H
f) Section 7 g) Section 7 h) Section 9
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Groundwater modelling In the absence of a groundwater model, it is significantly challenging to assess impacts to groundwater from the proposed UGM TSF. A numerical groundwater model must be developed to assess the risks and potential impacts with the resulting report to be provided.
Complete numerical groundwater modelling for the UGM TSF. The groundwater model report to be submitted must include: a) A hydrogeological model of the UGM TSF and its receptors, including: i. Geological cross sections. ii. Aquifer connectivity and flow dynamics. iii. Recharge and discharge zones. iv. The potential interactions between surface water groundwater. This model must be based on field verified data and information within the UGM TSF area and proximity. b) The basis for the numerical groundwater model parameters, assumptions and model design. It must be demonstrated the model domain extent is sufficient to the extent necessary to understand potential impacts from the UGM TSF.
a) – i) Section 6.6.9 and Section 9
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ISO 9001 • ISO 14001 • ISO 45001
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