Item
Description
Information Requested
Response
Corresponding Sections
and interactions with nearby surface water receptors. As additional geological, hydrogeological, and monitoring data become available, the SMP will be reviewed and updated to reflect improved site knowledge and evolving project conditions. This iterative approach ensures seepage management remains evidence ‑ based, proportionate to risk, and aligned with regulatory expectations throughout the life of the Project. c) The design has been updated and no longer refers to mine spoil. The plug will be constructed of concrete A revised CCA for the SSG TSF has been completed and provided in the updated application. The UMG TSF will be the primary TSF and upon cessation of deposition into UMG TSF, tailings will then discharge into SSG TSF. The two TSFs will never be operating at the same time. The draft DBA and CCA prepared for UMG TSF results in a “High B” and “Significant” classification for the Stage 2 configuration, based on ANCOLD and DETSI respectively. The hydraulic design criteria for these consequence category classifications are provided in the application documentation. The design basis adopted for the UMG TSF aligns with the hydraulic design criteria for an ANCOLD “High B” classification, is consistent with industry practices and exceeds all DETSI requirements. The proposed construction of SSG TSF downstream of UMG TSF is identified in the draft CCA as a potential change. WSP is satisfied that the CCA reflects the current site configuration and any changes will trigger a review of the CCA at that time. As the concept design provides storage allowance to contain the PMF design flood, increasing the DETSI consequence classification would not result in any change to the adopted design criteria, while increasing the ANCOLD classification to Extreme would only impact the wet season and storm event storage which can be contained within current allowances. The concept design for UMG TSF currently includes allowances to store the design flood (PMF) however the closure spillway for the UMG TSF will discharge to the west to Turner Creek after placement of a suitable cover system. The UMG TSF draft CCA has been updated to reflect the above understanding of spillway configuration and potential direction of any overtopping events. a) The application has been updated to reflect that the SSG TSF will not be operational at the same time as the UMG TSF. Once the UMG TSF is approved, the SSG TSF will be reserved for Stage 2 of mine plan development, which is not yet authorised or planned. It would be misleading to include the SSG TSF in any WBM, because it will not exist during the life of the UMG TSF. b) The application material has been updated to reflect that there is no proposal to construct the SSG TSF during the life of the UMG TSF or during the life of mining activities that are currently approved under the EA. The presence of latent conditions in the Sandstone Gully TSF, whereby there is more latent tailings present than originally estimated, will result in a much slower excavation process. As such the timeframes to construct the Sandstone Gully TSF can not be surmised at this stage as dewatering and excavation timeframes can not be established until remining commences. c) The GHD report (2025) correctly identifies the "SSG area" as "an additional area within the mine site" (as opposed to an "additional mine area" as noted in the IR), rather than a TSF for the purposes of the WBM. There is no change to the classification of the SSG TSF under the EA. The EA amendment application to request new mine features does not relate to the SSG TSF. d) Nothing in the GHD report (2025) nor the EA amendment application should be taken as an application to amend the EA in a way that relates to the SSG TSF. The SSG TSF will continue to be approved in the EA. The applicant has confirmed that it does not propose to construct SSG TSF during stage 1 of their mine plan e) The area designated for the SSG TSF is intentionally not modelled as a TSF in the water balance model, so there would be no potential interactions or implications of 'removing' it from the model. f) and g) The application material has been updated to reiterate that the SSG TSF will remain as an approved structure, and will not be built during stage 1 of operations. To include a non- existent structure in a WBM would over-state the water storage potential of the site, thereby under-stating the over-topping risk of the OCP, and would be counter-productive and misleading.
Sandstone Gully Tailings Storage Facility (SSG TSF)
Provide a suitable CCA for the SSG TSF demonstrating the hydraulic performance criteria as proposed. Alternatively, revise and submit a CCA for the approved SSG TSF confirming the appropriate hydraulic performance criteria for the structure.
Section 2.3.2 and Appendix N
The hydraulic performance criteria for the SSG TSF is proposed to be amended. The application material, which includes the SSG TSF Report (Golder, 2020)[4], does not include information supporting the assertion that the consequence category assessment (CCA) for SSG TSF determined the consequence category as ‘high’ for dam break and ‘low’ for overtopping and seepage. As such, it cannot be determined if the proposed amendments are appropriate.
6
Water balance model (SSG TSF) The water balance technical memorandum confirms that SSG TSF is not considered a TSF in the assessment and instead ‘an additional area within the mine site’ (GHD, 2025). This change necessitates urgent clarification regarding the structures purpose, alignment with the sites approved activities and proposed water management strategies. Without incorporating the SSG TSF as a tailing’s dams into the water balance model or formally excluding it from the approved activities, the representation of water inputs, outputs, and storage cannot be considered accurate or reflective of the site's authorised operations. Consequently, the risks and findings presented in the report cannot be reliably validated.
Provide revised application material which: a) Provide a detailed explanation and clarify what is ‘an additional mine area’ and what its intended purpose is as it relates to the SSG TSF footprint. b) Confirm whether there is an intention to construct the SSG TSF. If so, provide a timeframe for the proposed construction which must consider the extreme failure events identified and the required revision of the dam break and consequence category assessments if both facilities are built (WSP, 2025a)[5]. c) Confirm and provide detail whether the reclassification of the SSG TSF as ‘an additional mine area’ aligns with the authorisation currently stated in the EA. d) If the SSG TSF is no longer intended to function as a tailing’s storage facility, confirm whether it will be decommissioned or repurposed. Provide an assessment against the environmental values, impacts and risks to environmental values and the management and monitoring measures, and rehabilitation information as a result of this change. If Heritage Minerals Pty Ltd plans to maintain the SSG TSF as ‘an additional mine area’, the SSG TSF should be removed as an authorised tailings storage facility from the EA as its purpose will no longer align with the current approved activities. e) If SSG TSF remains classified as ‘an additional mine area” in the model, provide an assessment that includes a risk evaluation of the potential interactions and implications of removing the SSG TSF as a tailing’s storage facility from the water balance model. Provide an evaluation of how this change impacts the water management risks associated with the site's approved activities. f) If SSG TSF is intended to be maintained as a tailing’s storage facility, update and include this approved activity into the water balance model and present the findings. 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.
a) Section 5.3 b) Section 5.3 c) NA d) NA e) NA f) and g) 5.14
7
ISO 9001 • ISO 14001 • ISO 45001
Page 4
Powered by FlippingBook