Item
Description
Information Requested
Response
Corresponding Sections
Basal Seepage
Provide revised application material which:
a) Three monitoring bores named WGMB01, WGMB02 and WGMB03 were installed within the proposed TSF area during December 2025. Review of the geological bore logs indicates that the subsurface is generally characterised by a thin layer of residual soil or highly fractured bedrock, which transitions into competent volcanic units of Palaeozoic age at shallow depths (i.e. less than 2 m from surface). The hydraulic aquifer properties indicate a hydraulic conductivity of 8.6x10 -2 to 8.6 x 10 -3 for the saprolite and fractured Palaeozoic bedrock and a hydraulic conductivity of 8.6x10 -3 for the competent Palaeozoic bedrock b) As outlined in the response to item #13, the updated groundwater model will include site specific data to be collected from the base of UMG TSF A spillway with capacity to pass the PMF will be required for UMG TSF closure to limit water storage in the longer term. The closure spillway concept design has been provided in the updated CCA and shows a direction towards the west away from the OCP. During detailed design the final closure spillway option will be further developed and other technical studies including PMF assessments will be undertaken. Typically, spillway designs are updated following cessation of tailings deposition, once final tailings surface levels, settlement, and surrounding infrastructure are known. Updated DBA/CCA and PMF modelling incorporating the closure spillway will be undertaken at least 6 months prior to cessation of tailings deposition. Existing condition H24 requires submission of a decommissioning plan to the administering authority at least one (1) year prior, to decommissioning any regulated structure specified in the EA. It is appropriate that the submission of this decommissioning plan must include relevant and contemporary technical studies, including PMF assessments. a) The proposed condition “PAF waste rock and tailings transferred from stockpiles to void” has been removed from the application. There is no requirement to dispose of any material into any void. b) The design intent is for the embankment to be keyed into the existing western dump. This is portrayed on the Longitudinal section in existing Figure 20. The application has been updated to include better description of the embankment design
a) Section 6.2 and Section 6.6.2 b) Section 9
The application material states the underlying geology provides for limited connectivity between the proposed TSF and underlying aquifers. No site testing has taken place within the TSF footprint to verify this.
a) Provides evidence to confirm the hydraulic permeability of the base of UGM TSF to support the adjacent statement identified in the application material. b) Confirms the permeability of the base of UGM TSF is accurately represented in the groundwater model.
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PMF Assessment PMF modelling has not been conducted for the proposed UGM TSF facility. A detailed PMF assessment is required and must quantify the total flood volume and peak flood level, and must evaluate the spillway positioning and requirements.
Provide a PMF assessment of the proposed UGM TSF including consideration of the hydraulically connected features and present the findings.
Section 5.15.
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Rehabilitation
Provide revised application material which:
a) Section 2.3.2 b) Section 4.5.8
The application materials states rehabilitation for the proposed UGM TSF structure will involve the transfer of potentially acid forming (PAF) waste rock exposed during construction transferred to a void. Based on the EA definition of ‘void’, there is no clear understanding on the disposal location of PAF waste rock. The only available information on the rehabilitation of the embankment is ‘runoff management systems installed on the embankment’. There is limited understanding on what this entails and more importantly how the embankment will achieve the proposed post mining land use.
a) Clarify what ‘void’ is intended to be used as the disposal location for PAF waste rock and demonstrate this aligns with Heritage Minerals Pty Ltd activities. b) Provide information on the rehabilitation of the embankment including details on the runoff systems proposed and how the feature will achieve the proposed post mining land use.
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Laboratory waste disposal
Provide justification for the proposed amendment to EA condition E7. In providing a response, detail:
Amending condition E7 is no longer part of the project description and reference to the proposed change in wording of the condition has been removed from the application
NA
It is proposed to amend existing EA condition E7 to dispose mineral waste from the laboratory into the UGM TSF. Further justification is required on this proposed amendment including what constitutes laboratory waste and why this cannot be accounted for under the existing approval.
a) What constitutes laboratory waste. b) The expected quantity of laboratory waste to be disposed of in the UGM TSF, including why this cannot be accounted for under the existing approval and disposal locations. c) Demonstrate the expected quantity has been accounted for in the UGM TSF capacity and does not impact the storage volume determined.
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ISO 9001 • ISO 14001 • ISO 45001
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