P-PRCP-100680336 · STANMORE SMC PTY LTD

Applicant repliedSection 3.1.2 of the PRC Plan describes baseline conditions of the Poitrel mine and the surrounding region as understood prior to first disturbance (2006) and more recently through ongoing technical assessments conducted for operational purposes using modern methodologies where relevant. Section 3.1.2.4 of the PRC Plan is a description of the of site hydrology (distribution of water) and regional fluvial networks (how the water is connected) as it relates to closure. The 2005 Environmental Impact Statement (EIS) has been used as a historical reference; however it is noted in section 3.1.2.4 of the PRC plan that the EIS did not include a comprehensive baseline water quality assessment of local water bodies. Instead, the EIS relied on one site-based sampling event and a summary of Queensland Department of Natural Resources and Mines (DNRM) Water Quality for surfaces waters (between 1997-2002) for comparison against the Australian and New Zealand Environment and Conservation Council (ANZECC) Guidelines as the regional baseline water quality assessment prior to first disturbance. A high-level discussion on this assessment of regional water quality prior to disturbance is included in Section 3.1.2.4, which is believed to be sufficient to address baseline water quality for the region. Section 3.1.2.4 further identifies that ongoing water quality sampling is conducted to meet the EA’s operational obligations of the Receiving Environment Monitoring Program (REMP). The associated water quality and other environmental data is not included as it is available in the associated REMP reports which provide a comprehensive analysis of the results based on the environmental and climatic conditions for that reporting year. It is not explicitly stated in the Statutory guideline - Progressive rehabilitation and closure plans ESR2019/4964 Version 3.01 (DETSI, 2024) (PRCP guideline) that background water quality data and CoCs are to be included in the description of baseline site hydrology and fluvial networks. CoC’s have been assessed through other operational obligations such as the Water Management Plan (WMP) and more recent updates to the water quality triggers identified in the EA. The outcome of these assessments have been included in relevant sections of the PRC Planning part to meet different information requirements. Table 53 in the Water Management Section (Section 3.6.1.7) provides a summary from a 2019 assessment of potential contamination sources that will be relevant to contaminated land investigations required by Rehabilitation Milestone (RM) 2, where CoC were investigated. As this is a summary table, the potential contaminants for each source where also summarised. Since Table 53 has been used as the basis for initial interpretation of potential CoC; the EA defined trigger contaminants for monitoring have been cross referenced with findings from Appendix 6 (Waste Characterisation) to confirm suitable water quality characteristics and limits for surface and groundwater suitable for inclusion in the PRCP schedule. The Water Quality and PRCP Information Sheet (Queensland Government, February 2025) was then used as a reference for reviewing available water quality data to determine if appropriate site-specific water quality triggers could be defined in the relevant PRCP schedule appendix for surface water. Available data (predominantly the annual REMP report) that meets the criteria for supporting site specific criteria was identified as being insufficient, varying from less than eight (8) samples at inadequate intervals to consider seasonal variation for surface water. Therefore, default Water Quality Objectives and Australian and New Zealand Guidelines for Fresh and Marine Water Quality (WQO/ANZG) values have been applied to the water quality schedules proposed in the revised PRC Plan Schedule Appendices 10 and 11 included with this IR response. Where applicable and data meet the criteria for supporting site specific triggers, it has been included in the PRC Plan Schedule with origin details against each trigger provided. In summary, the presented trigger limits for both surface water and ground water are a combined approach of site specific trigger levels and WQO/ANZG values. A review of the adopted default triggers will be conducted in future once sufficient data collection is achieved and change will be requested where appropriate. Section 3.8.4 of the PRC Plan has been updated with a full suite of water quality monitoring characteristics, which are a based on the current EA, Section 3.6.1.7.1 of the PRCP and Appendix 6 (Waste Characterisation). This has also been updated in the PRC Plan Schedule Milestone Criteria to reflect consistent rehabilitation methodologies.

Response, page 6

Applicant repliedIt is noted that the ERAs for Poitrel are listed in the second paragraph of Section 1 (Introduction) and elaborated in Table 1 (Environmentally Relevant Activities and Location Details at PTM) in Section 3.1.1.2 (Relevant Activities) of the original PRC planning part submission, where they remain in the revised version provided with this IR response. For completeness and to ensure consistency with the EA, Table 19 of the PRC Plan has been updated to clearly identify which mine domains include the following ERAs: - Chemical storage - Waste disposal - Resource recovery & Transfer Facility - Sewerage Treatment Facility. The PTM ERAs were considered in the development of the original PRC Plan and rehabilitation measures.

Response, page 7

Applicant repliedThe identified inconsistencies have been corrected by updating the following figures in the PRC Plan with the following comments: - Figure 23 (PTM Proposed NUMA) has been updated to provide more clarity on the extent and characteristics of the NUMA. - Figure 29 (Option 3: Partial Backfill During Operations (Chosen Option) Plan View) has been updated to provide more clarity on the extent and characteristics of the selected NUMA design with a defined boundary and pit lake and highwall sizes added. - Figure 25 (Option 1: Base Case No Filling of Void Plan View (Minserve)) and Figure 27 (Option 2: Partial Backfill Voids Plan View) have also been updated to match the level of information now included in the preferred option Figures 23 and 29. - Appendix 8 Figure 2.2 (formerly 2.4) (3D depiction of PTM residual void and indicative post- mining mean lake levels (Minserve, 2025) has been updated to align with the Figure 29 update. Appendix 3 Figures 1-3 and 7-5 have not been updated; as they are a visual representation of the void used within the PRCP groundwater model at a specific point in time to assist in the sink or source determination, which was an iterative process that informed the final NUMA characteristics. It is not to be relied on for defining the NUMA boundary rather the area of impact that has been considered in the groundwater model. The minor differences with the final NUMA boundary will not result in a material change in the groundwater assessment or modelling results.

Response, page 7

Applicant repliedThe following amendments to Appendix 11 have been made to confirm the geotechnical risk has been adequately addressed in the model: - Section 3.4 (Statement of Model Uncertainty) has been updated to outline that the model uncertainty rating is not a reflection on the reliability of the geotechnical assessment process, rather a tool to guide selection of appropriate Design Acceptance Criteria, detailed in Section 5 of Appendix 11. This is in accordance with the ACARP Guidelines for Assessment of Geotechnically Safe and Stable Post-Mining Landforms (2024). - Section 5 (Design Acceptance Criteria) iterates that the stability assessment, the target values of FoS were adopted as Design Acceptance Criteria were dependent on both the model uncertainty and consequences of instability. Consideration of the geotechnical model as High Uncertainty was undertaken in conjunction with and the consequence level in accordance with the ACARP Guidelines for Assessment of Geotechnically Safe and Stable Post-Mining Landforms (2024). Therefore, the Geotechnical Stability Assessment has adequately assessed the geotechnical risks associated with the pit void landforms and no updates have been made in the PRC Plan (Part B).

Response, page 10

Applicant repliedThe most considerable impact to the high-wall geotechnical stability is expected to occur from slope failure. The lowest FoS has been determined within the unsaturated tertiary and weathered Permian materials. The lowest FoS still indicates a stable slope within this material. In relation to erosion along high walls resulting in gullies that could impact on the flood mitigation embankment, gullies will only erode down to competent material i.e. the fresh Permian and as the gully erodes, its catchment area reduces effectively cutting of the source of energy causing the erosion. For these reasons, monitoring of gully erosion along the high wall section where the embankment is in close proximity to the high wall is proposed with mitigation measures such as repair and armouring implemented as required. It should be noted that the NUMA section in the area of the flood mitigation embankment consists of the high wall only. The geotechnical section through the high-wall that has been assessed (section 4 in Appendix 8, Error! Reference source not found.) is through the steeper high-wall section. As the high-wall moves further south, the height of the high-wall decreases and the FoS is expected to increase. Furthermore, the distance between the high- wall crest and the toe of the embankment varies between 50 to 150 m. The area currently contains an operational access track, which will be adjusted post closure to establish the NUMA infrastructure and reduce the size of the operational track through rehabilitation activities including light ripping and seeding. This will result in the establishment of vegetative groundcover that will reduce the speed and amount of run off in this area. The revised Management Milestone (MM) criteria MM3 a)iii) and iv) in the PRCP schedule submitted with this response now require that the Achievement of sufficient improvement certification by an Appropriately Qualified Person (AQP) includes a review of rill or gully erosion and drainage measures to direct overland flow away from the highwall edge.

Response, page 11

Applicant repliedAppendix 11 – Geotechnical Stability Assessment Updates to Appendix 11 have been made to address the impact of a PMF flood scenario on the stability analysis. Section 3.3 now acknowledges that the PMF event was modelled for PTM (Appendix 10), however that it is applicable to dam design, specifically dams with major or catastrophic failure consequence (ANCOLD, 2000), and flood emergency management planning (Geoscience Australia, 2019). As the consequences of geotechnical instability of landforms at PTM range from negligible to medium (refer Section 4, Appendix 11), PMF is not an appropriate design standard to apply to the stability assessment. In summary, the effects of severe hydrological events appropriate to the consequences of void geotechnical instability have been addressed adequately through the establishment of multiple cross sections that included long term pit lake levels for a period of 300 years. Furthermore, the PRCP Guideline defines a floodplain at 1:1,000 AEP, not PMF and there is no legislation that requires designs are to be 'in perpetuity'. Appendix 10 – Flooding Assessment Appendix 10, Section 4.3 (Final Landform Erosion Risk) has been updated with further assessment of the flooding risk profile of the final landform to estimate the potential erosion risk during different AEP flood events using peak velocities along the northern and southern embankments. This assessment was based on the Soils Conservation in Queensland Guideline (2015) and it was determined that the average channel slope along the embankment (north and south sections combined) was approximately 1%. Conservative measures were applied with the assumption of erodible soils present in the embankment. Based on the identified risk of erosion, erosion risk of the embankment landform is expected to change over time. Appendix 10 (Table 4.2) provides periods for vegetation establishment on the embankment and a target groundcover for the embankment against RM6. This has been transferred into the PRC Plan (Section 3.6.1.2.3) and included in the Milestone Criteria. It is noted that Appendix 10 (Figure 4.2) has been updated to reflect a Cross-Section of the Northern Embankment at Chainage 1600 along the Final Landform Embankment and Figure 4.3 to reflect a Cross-Section at the Southern Embankment at chainage 4200 along the Final Landform embankment. Appendix 8 – Void Closure Plan Appendix 8, Section 4.2 has been slightly adjusted to include the requirement of monitoring landforms in areas where modelling indicated high flow velocities following rainfall events greater than 0.1% AEP. The statement has been repeated in the flooding section of Section 8 (Residual void management). Finally, it is noted that the impact of extreme weather events prior to final landform establishment has been considered in the PRC Plan, Section 3.7.3 (Risk identification) with controls and treatments suggested per the required PRCP guideline framework.

Response, page 11

Applicant repliedAppendix 7 (Landform Design) has been updated as a part of this IR response to capture the clarifications described below. To ensure consistencies across related technical studies developed by the same authors of Appendix 7, Appendices 4 (Material Characterisation Study), 9 (Cover Design), and 12 (Revegetation Plan) have also been updated to capture the additional recommendations and clarifications. 8.1 Technical clarifications Erosion assessment calibration Through discussion with the AQP and author of Appendix 7 (Landform Design), Section 6.2 has been updated to provide further detail on existing rehabilitation performance by including a discussion on a review conducted of the last three years of annual rehabilitation monitoring at PTM as summarized below. Terra Solutions (2024) undertook an erosion assessment of 6 rehabilitation areas at Poitrel (named Area 1–6). The assessment found that Areas 1, 2, and 3 exhibited only minor rill/gully erosion within the monitoring areas but noted a large gully outside of the monitoring area in Area 3. Areas 4, 5, and 6 were found to contain moderate rill/gully erosion. Tunnel erosion was also observed at Area 4. These erosion features are located in areas below currently unrehabilitated surfaces (angle of repose faces, roads, laydown areas) from which runoff has been allowed to discharge. These areas are not included in the modelled shape and as such have not been identified in the modelling. Increased erosion is to be expected in areas that are receiving significant volumes of concentrated flows from upslope areas. It is possible that these erosion features will stabilise over time once the upslope areas are rehabilitated. Terra Solutions (2024) note that many of the rill features are showing signs of stabilising. They also recommend verification and active monitoring of the eroding areas to identify potential ongoing erosion and the need for remediation. This would need to be performed as part of ongoing monitoring by an AQP. These recommendations have been transitioned into the milestone criteria in the form of additional/increased erosion monitoring (e.g. Erosion Classification Framework) and minimum vegetative cover. Performance of existing rehabilitation The model was not calibrated with existing rehabilitation performance; however it is likely that model outcomes would not have materially changed even when considering site specific data. The model output for the landform, including the existing rehabilitation (RA1) indicates that there is erosion, but that gully depths predicted are no more than 0.3m for grazing after 300 years. The RMs in RA1 have been adjusted in the revised PRCP schedule submitted with this IR response to account for areas that have not achieved the required criteria. Specifications and suitability of the rock mulch material The suitability of the rock mulch material as a growth medium is not to be considered in isolation of the proposed 0.1m depth; this layer is to be placed over a deep secondary growth medium layer. Section 3.4.1.1 of Appendix 7 (Landform Design) has been updated to provide further detail on the specifications of the rocky mulch as summarised below: Fresh Permian has similar pH and salinity to the soils. It is noted that the fresh Permian can be more sodic than the soils. However, the coarse nature of the Permian spoil will mitigate the risks posed by high sodicity because its coarse matrix will maintain the structural stability of the material. The Permian spoil is noted as being rocky, containing >30% rock by weight. However, that does mean that at least 30% of the Permian spoil is fine-grained. This means that the Permian spoil is a mixture of both coarse rock and fines. It will hold moisture (in the fines), and when mixed with soil will be able to store reasonable amounts of stored water. This will be accessible by woodland vegetation, especially deeper-rooted trees. When mixed this would create a layer of mixed soil and Permian spoil that is 0.3–0.4m thick. This soil/spoil mix layer would overlie a minimum 1.9m thick layer of non-acid forming fresh Permian waste Placement of the Permian spoil under the primary growth media layer will not likely constrain plant growth. Section 11.1 of Appendix 7 (Landform Report) provides detail on the cover profile to manage erosion risk and support vegetation growth in alignment with the criteria in the PRC Plan Schedule. Updated defined milestone criteria for ripping depth and specified growth medium (as taken from the technical assessments) ensures that adequate mixing of the growth medium layers to support sufficient vegetation performance. 8.2 Growth media milestone criteria The PRCP schedule has been updated to reflect consistency with Appendix 7 (Landform Design) and Appendix 12 (Revegetation Plan). RM4 now includes additional criteria that requires an assessment of growth media characteristics is to be completed by a AQP a minimum of six (6) months prior to progressive rehabilitation. This is to ensure the chemical and physical properties being applied as ameliorants are conducive to successful rehabilitation. 8.3 Cover design and vegetation cover milestone criteria Target vegetation cover levels for grazing and woodland PMLU is now defined in section 4.2.2 of Appendix 7 (Landform Design). This refinement details that target vegetation cover for grazing PMLU ≥80% and ≥50% for woodland PMLU. These targets have been transitioned into the milestone criteria for the PRC Plan Schedule, as below: • RM4 which provides criteria for all rehabilitation areas. This includes: - Minimum required topsoil depth per PMLU - Minimum required depth for growth medium - AQP assessment of growth media characteristics prior to progressive rehabilitation, to ensure the defined growth media quality targets are met - Updated growth medium suitability targets - Ripping depth along the contour for all slopes - Commencement of the surface and groundwater monitoring network • RM6 which provides detailed criteria for all rehabilitation areas. This includes: - Minimum vegetative cover and erosion control cover - Erosion monitoring criteria and acceptable limits per the Erosion Classification Framework 8.4 Landform construction milestone criteria Appendix 7 (Landform Design), Section 8.5 has been updated to provide further detail of the purpose/intent of bunding as part of the landform design. All landforms will be designed to be free draining and uncontrolled discharge of runoff from the flat top surfaces of the land will be minimised through the installation of crest bunds. These bunds are for intended use during the period that vegetation is establishing and has not reached the target groundcover levels. This has been transitioned into the milestone criteria as below: RM3 - Landforms are to be free draining - Where applicable, crests of rehabilitated landforms are to be bunded with designs informed by an AQP RM7 - Removal of any bunds used to initially control runoff from slopes, once target vegetation has been achieved and erosion levels are deemed acceptable by an AQP.

Response, page 12

Applicant repliedTable 62 and 63 have been updated to be consistent with Section 3.6.1.8.9 and Appendix 6 of the PRC Plan Schedule. Table 62 heading has been updated to Representative RE Benchmark Criteria for Woodland Rehabilitation (<15% slope) for RA4 and RA5 Table 63 heading has been updated to Representative RE Benchmark Criteria for Woodland Rehabilitation (<15% slope) for RA7

Response, page 13

Applicant repliedRA3 has been removed from the PRCP Schedule. The area previously accounted for in RA3 is now included in RA2 with relevant RMs set for later years of rehabilitation. This is to allow the continued use of critical infrastructure, such as staging grounds and dams, during closure processes to maintain the health and safety requirements of rehabilitation operators. Additional milestone criteria has also been included in RM1 to ensure the intended use of this infrastructure is clarified.

Response, page 14

Applicant repliedSection 3.6.3.3 of the PRC Plan (Part A) states that the proposed residual void remains a groundwater sink as defined by the Void Closure Plan (Appendix 8). The geochemical assessment of the void lake in Section 7 of Appendix 8 further demonstrates that the PTM void lake presents favourable conditions for stratification due to steep sides, void depths and elevated Total Dissolved Solids (TDS). Therefore, water of higher density (cooler or more saline) has the potential to become isolated at depth. The determination of any seasonal or groundwater mixing processes require further hydrodynamic/limnological analysis which was not conducted as the residual void is considered a NUMA and modelled as a groundwater sink. As such, sampling of shallow water would potentially not present a full picture of the pit lake’s overall water quality. Furthermore, the Water Balance Model (Appendix 8) demonstrated that the void water levels remain below the residual void spill point (197m AHD) for the duration of the simulation. Therefore, the risk of the void overtopping is considered very low. This response maintains that there is not a requirement to monitor the void water quality as a milestone to successfully demonstrate that the proposed NUMA is not causing environmental harm; which is an approach consistent with approved PRC Plans. Monitoring of the groundwater as a means of validating that the NUMA is not causing environmental harm is considered more appropriate. Nevertheless, an additional milestone criteria has been added to the improvement area milestones of the PRC Plan Schedule to demonstrate the NUMA is non-polluting: MM3(h) - Certification from an AQP that water level in each residual void will not cause environmental harm to the surrounding environment, and the voids act as groundwater sinks to the receiving groundwater environment. As stated in the response to IR Item 1, surface water and ground water quality characteristics relevant to the receiving environment have been accounted for adequately across several sections of the PRC planning part which has since been consolidated into the PRC Plan Schedule as defined monitoring criteria (see Appendix 10 and 11). MM3 milestone criteria have been updated to include defined quality characteristics for groundwater monitoring and monitoring intervals (PRC Plan Schedule, Appendix 11) to demonstrate the pit lake/NUMA is not causing environmental harm beyond the designated footprint.

Response, page 14

Applicant repliedStanmore has removed RA3 from the PRC Plan and Schedule as it is no longer proposed to retain infrastructure for landholders post closure at PTM. As such, the Rehabilitation Planning Part has not been updated to include water storage monitoring. The PRC Plan and Schedule has been updated accordingly - RA3 (formerly 42ha) has been absorbed into RA2. All subsequent RAs have been updated with revised numbering.

Response, page 14

Applicant repliedAs defined in IR Item 1, the water quality characteristics for monitoring defined in the PRC Plan were reviewed and updates made to ensure consistency with potential CoC's, best practice for determining site specific criteria and default WQO/ANZG values at the appropriate rehabilitation milestones. Available water quality data for existing surface water monitoring locations predominately associated with the annual REMP were reviewed to determine if appropriate site-specific closure water quality triggers could be defined. Available data that meets the criteria for supporting site specific criteria was identified as being insufficient, varying from less than eight (8) samples to inadequate intervals to consider seasonal variation. Therefore, default WQO/ANZG values have been applied. Consistency between surface water and groundwater monitoring characteristics has also been reflected, capturing relevant CoC's. This has been reflected in Section 3.8.4 and the PRC Plan Schedule RM7, Appendix 10. The defined monitoring period has been updated to a minimum of five (5) years post- rehabilitation, which has been reflected in Section 3.8.4 and the PRC Plan Schedule RM7 (achievement of stable condition), Appendix 10. A review of the adopted default values will be conducted once sufficient data is achieved and water quality parameters requested to be updated if appropriate. Additional monitoring locations for surface water have not been proposed as the updates made to monitor quality characteristics and defined frequency are considered sufficient for demonstrating there is no environmental harm to the receiving environment post closure.

Response, page 15

Applicant repliedAs with the updated to surface water monitoring, the water quality characteristics for groundwater monitoring as defined in the PRC Plan have been reviewed and updated to ensure consistency with potential CoC's, best practice for determining site specific criteria and default WQO/ANZG values at the appropriate rehabilitation milestones. Available water quality data was reviewed to determine if appropriate site-specific water quality criteria for groundwater monitoring could be defined for all relevant CoC indicators. Available data that meets the criteria for supporting site specific criteria was identified as being insufficient for five groundwater bores drilled in March 2024 as there were less than eight (8) samples at inadequate intervals to consider seasonal variation. The last 3.5 years of groundwater quality monitoring results from the four long standing groundwater compliance bores (OBS1, OBS2, OBS5 and OBS10) have been reviewed to ascertain if site specific trigger values applicable to the closure scenario (95th percentile of background/baseline) could be applied. Where there was insufficient data for certain indicators, default WQO/ANZG values were applied. Where there was sufficient data to determine the site- specific limits for some indicators, those values were adopted. The groundwater quality limits table in the newly added PRC Plan schedule Appendix 11 identifies which indicator is site specific or a default value from the appropriate guideline. The data that has been used to inform site specific triggers for some indicators will be provided to the administering authority for verification separate to the IR response application package. The consistency between surface water and groundwater monitoring characteristics and indicators has also been reviewed to capture relevant CoC's. The defined monitoring period has been updated to a minimum of five (5) years post- rehabilitation, which has been reflected in Section 3.8.4 and the PRC Plan Schedule RM7 (achievement of stable condition), MM3 (Achievement of sufficient improvement), and Appendix 11. A review of the adopted default values will be conducted once sufficient data is achieved and water quality parameters requested to be updated if appropriate. Additional monitoring locations for groundwater have not been proposed as the updates made to monitor quality characteristics and defined frequency are considered sufficient for demonstrating there is no environmental harm to the receiving environment post closure.

Response, page 16

Applicant repliedAs RA3 has been removed from the revised schedule submitted with this IR response (see Item 10.1), the original RA5 (Waste Rock Dumps and Topsoil Dumps (PMLU Woodland)), is now RA4. RA4 has been adjusted to 568 ha in the revised PRCP schedule. RA5 will show as 568.01ha in the revised spatial data that will also be submitted with this IR response thereby removing any material discrepancy between the two data sets.

Response, page 17

Applicant repliedThe revised PRCP schedule submitted with this IR response includes revised MM and RM criteria in accordance with recommendations from Appendix 7 (Landform Design) as detailed below. The relevant Improvement Area MM’s have been updated to include detailed criteria on the overall stability and erosional stability of the landform. This includes: - Factor of Safety - Minimum and maximum heights of bunding, depths of voids - Minimum acceptable erosion to ensure stability is not impacted. RM3 now has criteria that includes: - Landforms are free draining - Where applicable, crests of rehabilitated landforms are to be bunded with designs informed by an AQP - Rock mulch application based on assessment. RM4 now has criteria that includes: - Topsoil and growth media depths - AQP assessments of growth media - Deep ripping along the contour and ripped depth RM6 has been added and provide detailed criteria for all rehabilitation areas. This includes: - Minimum vegetative cover and erosion control cover - Erosion monitoring criteria and acceptable limits per the Erosion Classification Framework - Factor of Safety for each landform

Response, page 17

Applicant repliedFurther detail regarding the recommended updated landform design for managing uncontrolled discharge of runoff from the flat top surfaces of the landform has been included in Appendix 7 (Landform Design) and transitioned into the milestone criteria. In the period that vegetation is establishing and has not yet reached the target groundcover levels, crest bunds may be installed on the outer edge of the flat top surfaces of landforms, as informed by an AQP. Removal of these bunds may be considered once target vegetation cover levels are achieved and levels of erosion are deemed acceptable by an AQP. The following milestone criteria has been added to RM3 of the revised PRCP Schedule submitted with this IR response: - d)"All landforms are to be free draining". - e) “Where applicable, crests of rehabilitate landforms are to be bunded with designs informed by an AQP” Additional criteria in RM7: h). “Removal of any bunds used to initially control runoff from slopes, once target vegetation has been achieved and erosion levels are deemed acceptable by an AQP”

Response, page 17

Applicant repliedThe following adjustment to the PRC Plan, Section 3.6.1.4.5 has been made to align with recommendations within Appendix 7: "Reshaped landforms will be ripped to a minimum depth of 500mm into soil and subsoil, to allow for adequate water and root penetration. This will occur in conjunction with the application of growth media and will be completed along the contour of the slopes". This updated has also been incorporated into RM4f (previously RM4d) for consistency.

Response, page 18

Applicant repliedRM6 has been updated to include the following criteria in the revised PRCP schedule submitted with this IR response: - Species used in revegetation remain present and show evidence of natural recruitment - Minimum 80% established and persistent vegetative groundcover for Grazing PMLU - Minimum 50% established and persistent vegetative groundcover for Woodland PMLU. - Presence of rocks, logs or other effective erosion control cover is limited to 30% of total vegetative groundcover. - Weed presence is less than 10% of total vegetative groundcover confirmed by an AQP in annual monitoring. The above updated criteria are supported by Appendix 7 (Landform Design), Section 4.2.2; which includes a review of grazing land management types in the vicinity of Poitrel, including rocky soil types (mapping by Department of Agriculture and Fisheries). The review concluded that vegetative cover levels ≥80% are achievable on rehabilitation carried out on topsoil at Poitrel. Erosion simulations considered vegetation groundcover levels 50—90% for soil covered surfaces. For surfaces that contain rock and lower fertility (spoil/soil mixtures), lower levels of cover can be expected to be maintained. Erosion simulations modelled vegetation groundcover levels for woodland PMLU of 50% however Water Erosion Prediction Project (WEPP) modelling showed that 30% vegetation cover levels would also achieve acceptable long term erosion rates. A conservative 50% has been applied into the milestone criteria for rehabilitation.

Response, page 18

Applicant repliedRM6 has been updated, to include the following criteria in the revised PRCP schedule submitted with this IR response: 'Weed presence is less than 10% of total vegetative groundcover confirmed by an AQP in annual monitoring'.

Response, page 18

Applicant repliedRM7 has been updated to include additional references/controls to erosion management by including the following criteria in the revised PRCP schedule submitted with this IR response: - “No evidence of erosion classified as moderate or severe as defined by Erosion Classification framework” RM10 (Achievement of Watercourse PMLU) includes reference to the IDC method providing quantitative assessment of erosional stability for the diversion and watercourse RAs. The IDC method is an industry standard monitoring method, built into the diversion water licence, that monitors the geomorphic stability of diversions. The IDC method is intended to be used to justify the stability and relinquishment of diversions. Stanmore considers this adequate for application as a suitable milestone criteria. The Erosion Classification Framework is taken from the Australian Soil and Land Survey Field Handbook, published by CSIRO, is a widely used tool within Australia as well as being guided by the National Committee on Soil and Terrain. The Erosion Classification Framework is applied to all RAs. The current milestone criteria is based on the Erosion Classification framework which has been used as an acceptable monitoring framework for erosion across approved PRCPs. The criteria states that no evidence of erosion under the moderate or severe categories of the framework is to be used as the baseline of acceptance for erosion monitoring. The Framework (provided as Appendix 7 to the PRCP Schedule) defines rill and gully erosion and how they are to be identified in the landform. Finally, it is noted that achieving the prescribed percentage of groundcover in later RMs will be a primary methodology in the prevention and mitigation of erosion as studied in the Landform Evolution Modelling (LEM).

Response, page 19

Applicant repliedThe PRCP Schedule has been updated to include more clarity on water quality and monitoring as discussed in the responses to Items 1, 13 and 14. Appendix 10 and 11 have been added to the PRCP schedule submitted with this IR response. These additional appendices include quality characteristic for monitoring of surface water and groundwater that are consistent with CoC's and WQO/ANZG values. Frequency of monitoring has been updated in the relevant RMs and MMs to reflect a minimum of five (5) years of monitoring post rehabilitation to support the objective of achieving a stable landform and quarterly monitoring annually.

Response, page 19

Applicant repliedRM8 (Achievement of cattle grazing PMLU) states that the area must be certified by an AQP that pasture meets pasture condition rating ≤3, based on the Pasture Condition Assessment Table as per “Stocktake: Balancing Supply and Demand” (Developed by FutureBeef – futurebeef.com.au), as provided in Appendix 5: Pasture condition assessment. Appendix 5 includes the relevant SMART criteria to confirm this classification has been met. This approach has been transitioned from Table E1 of EPML00963013 with modifications to ensure productive and sustainable land use. The growth medium criteria in RM4 further supports the ability to achieve a PMLU of grazing for nominated RAs. Appendix 7 (Landform Design) provides details on the specific assessment of the soil types and then further discusses the suitability of grazing as a PMLU. The limitations identified during the land suitability assessment were considered during the landform design assessment, and adequate controls were discussed. Controls include; amelioration, maximum slope design, assessment by an AQP for sufficient FoS, minimum vegetative groundcover milestone criteria and erosion controls have been included in the rehabilitation process. These controls have been developed by an AQP and are considered appropriate for the landform to achieve the proposed PMLU. Further the controls identified in Appendix 7 have been included in the criteria updates to RM4 in the revised PRCP schedule included with this IR response. The assessment in Appendix 7 (Landform Design) has been use as a basis for the rehabilitation methodology developed for PTM to ensure that the landform is able to sustain a grazing PMLU.

Response, page 20

Applicant repliedThe revised PRCP schedule provided with this IR response now includes water quality criteria for surface and groundwater in RM7. Groundwater monitoring requirements have also been added to Improvement Area MM3 to align with SMART principals. MM3 has been further expanded to include the below criteria: "Certification from an AQP that evidence, based on up-to-date groundwater modelling, that the final void lake will not overflow nor potentially contaminate any other surface water bodies". As discussed in the response to Item 11, the NUMA has been determined as a groundwater sink with a pit lake that will not overflow into the receiving environment. As such there are no relevant water quality characteristics that can be applied to the pit lake to demonstrate the lack of environmental harm. The monitoring focus of the revised PRCP schedule included with this IR response assesses relevant aspects of the receiving environment. The updated monitoring characteristics and frequency will demonstrate that the proposed NUMA is not causing environmental harm to the receiving environment as part of the rehabilitation methodology.

Response, page 20

Applicant repliedAs demonstrated in the final landform modelling (Appendix 10), flood interaction within the NUMA footprint is only modelled to occur in extreme weather events (PMF). Based on this information, Appendix 8 section 8 has been updated to recommend that monitoring of the landform in areas with modelled high velocities be conducted following rainfall events greater than 0.1% AEP. Subsequent mitigation measures will be identified and implemented for appropriate protection works such as rock armouring in areas where floodwaters from watercourses have interacted with the final mine closure landforms at elevated velocities. The risk of final landforms being compromised by extreme weather events is captured in Section 3.7 (Risk Assessment) of the PRC Planning Part, which will remain a living document. In addition to the above improvements to ensure the stability of the proposed NUMA in the face of potential flooding, the following MM criteria has been added to the revised PRCP Schedule submitted with this information request: MM1 - Inclusion of certification by an AQP, that final voids are stable, including design specifications for the void highwall and end wall. This also includes a criteria that the void is to be considered geotechnically stable for the foreseeable future. MM2 - Bunding confirmed to be geotechnically stable by an AQP. MM3 - Detailed criteria for assessment of the stability of the final void, to be completed by a AQP. - Criteria for erosional management, including additional monitoring following rainfall events greater than 0.1% AEP - Final design criteria for the final void - Reference to assessed risks as ALARP in accordance with AS/NZS ISO 31000:2009 and certified by an AQP.

Response, page 20

Applicant repliedBefore responding to the request to report on the full extent of environmental impacts of a NUMA option that is not the basis of the original PRCP submission through new analysis in five separate technical studies; a summary on the robustness of the original NUMA options assessment is warranted. PTM and its associated EA meet the transitional provisions for PRC Plans due to the EA being granted in 2006 prior to the assent of the progressive rehabilitation and closure plan amendments to the EP Act. Nevertheless, Stanmore understands obligations that are still applicable under the EP Act to minimise the NUMA area through an assessment of the options to select one that ensures geotechnical stability, safe borders and no harm to the receiving environment. This understanding has been one of the primary drivers in the determination of the NUMA area since preparation for the PRC Plan began in 2023. Preparation involved iterative mining planning informed by preliminary studies that considered key indicators of environmental protection in the selection of the final landform presented in the original submission of the PRCP. At the same time, the mine planning that led to the final landform design had to consider the EA approved life of mine plan, economic feasibility of final landform implementation and the potential change to long term closure liability. Option 3 was put forward for full assessment in the technical studies that supported the development of the PRCP (Part C) on the basis it represented the latest mine plan and presented the best compromise across the diverse list of considerations, including the minimisation of the NUMA area and environmental harm. The results of technical studies have been considered in the risk assessment process and used to inform treatment, monitoring and management of the final landforms as milestone criteria in the PRC Plan Schedule. In response to the remaining items of this IR, the PRC Plan Schedule milestone criteria have been improved further to address any remaining concerns on the selected NUMA Option 3 design. Stanmore continues to assert that the selection of Option 3 has met the requirements of PRCP guideline as it relates to minimising environmental harm while also being economically achievable with a manageable amount of liability in the event of planned or unplanned closure. Option 2 was revisited to adequately respond to this Item by confirming if it warrants full assessment in revised or new technical studies (Part C) and subsequently a revised PRC Plan (Parts A and B) to account for this significant change. It is important to note that the area for Option 2 reassessed in response to this Item request has changed slightly from the original PRC Plan submission. The revised Option 2 area reinstated the entire pre-mining flood plain to the pre mining topography rather than backfilling the southern void to an arbitrary location as was the case for the original Option 2 assessment. The first step was re-running the mine schedule against the latest life of mine plan that included the following assumptions: - The same coal extraction rate as present operations. - Minimise post last-coal rehandle of waste rock to achieve the final landform. - Full removal of the currently vegetated landform embankment. - R50 reject placement area would be open until end of mine life (2033) which would require ~7 million cubic metres (Mm³) of rehandle from adjacent partially rehabilitated spoil dumps for capping to the final landform topography in closure. The resultant Option 2 NUMA would significantly larger than Option 3, being 428 ha including the low wall to be pushed to 25%, pit lake at RL 150.5m (WSP, 2025) and 6.2 kilometers (km) highwall with FoS setback, safety bund and fence. As this mine scheduling sequence is substantially different from present day scheduling, further short- and long-term planning assessments to inform feasibility studies would be required to understand the full implications implementing this mine plan. Preliminary results of this rescheduling indicated the following: - A decrease in PMLU of 24ha. - A substantial increase in the volumes of backfilled material at later stages of mine life. - Significant reduction in potential for progressive rehabilitation until dumping is completed in southern half of mine. - Disturbance of existing rehabilitation will be required that will not be revegetated until backfilling is completed. - Any closure planned (or unplanned) before 2033, will result in a significant quantity of backfill rehandle to achieve the post mining landform, increasing the size of the void, potentially beyond an authorized maximum size. - Opportunistic dumping of such large volumes of material (~67 Mm³) to achieve a backfilled void will result in backfill material that is not uniform. As a result, the final landform will contain layers of varied material including extremely weathered spoil, waste rock and rejects. These layers respond differently to the mechanical stresses of cyclical periods of saturation and drying with the long-term stability of this landform option uncertain and extremely difficult to assess. - The resultant landform would continue to be subject to flood inundation. Coupled with the uncertain long-term stability of the landform, flooding risk on stability is also unknown. To assess flooding risk and potential impacts would require knowledge of how the landform would settle (which is not able to be determined through modelling) and therefore the monitoring and maintenance period would extend indefinitely until a PMF event is experienced, delaying milestone achievement (potentially indefinitely). - The southern void section backfill option also resulted in a final (extended) residual void area of 428 hectares (ha), larger than the proposed NUMA area (Option 3). Re- handling of large amounts of waste material (~7 Mm³) would be required to achieve the final landform following closure. - Additional mining machinery fleet movements will contribute to a material increase in greenhouse gas (GHG) emissions from the implementation of Option 2 as the mining fleets required for this type of activity contribute >50% of the mine’s total scope 1 emissions. To backfill the southern void to approximate original contour will require an additional one year of planning and operations for an 800-tonne fleet to rehandle 7 Mm³ of waste, using >6,000,000 litres of diesel leading to approximately 15,000 additional tonnes of scope 1 greenhouse gas emissions during a period of projected (and required) decrease in GHG emissions. - Option 2 would increase PTM’s current instantaneous closure (Estimated Rehabilitation Cost) liability by approximately $330m. Preliminary assessments were conducted on the revised Option 2 final landform in the geotechnical stability assessment and final void water balance model (WBM). The results of these preliminary assessments included the following: - The WBM indicated very low risk of the void lake overtopping and remains a groundwater sink. - The WBM assumes the backfilled southern landform drains to areas outside of the residual void. Flooding impacts to the landform may result in re-direction of additional catchment towards the residual void and increasing the risk of the void overtopping and interacting with groundwater. - The outcome of the geotechnical stability assessment is not significantly different as it meets the same design acceptance criteria applicable to the land uses as Option 3 (preferred). Appendix 8 (Void Closure Plan) and Appendix 11 (Geotechnical Stability Assessment) have been updated with this new understanding of Option 2. Section 3.4.2 and 3.4.3 of the PRC Plan (Part A) have been updated to reflect the adjustments to Appendix 8 and Appendix 11 and removed any previous assumptions on Option 2 that are no longer valid. The options assessment process has been elaborated further in section 3.4.3 of the PRC Plan to reiterate the depth of the considerations made across the three options and strengthen the argument that Option 3 promotes the most balanced approach to the NUMA design. The original EIS mine plan, and each subsequent refinement to these plans, are based on two decades of exploration and geological model refinements which have optimised the removal of waste and extraction of coal targeting a final void size and location that is permissible in the current approved EA. With 80% of the overburden already removed, considering alternatives in locating and re-locating waste by rehandle would have a significant impact on the sustainability of mining at Poitrel. Furthermore, the resulting significant increase in closure liability and scope 1 GHG emissions pose additional risk to the environment while not minimising the NUMA area, which confirms Option 2 is not without risk to the environment. Stanmore continues to maintain that Option 3 demonstrates that environmental harm has been minimised and has strengthened this commitment further through the response to the remaining items of this IR. Appendix 3 (Hydrogeology Assessment) was not updated as the WBM determined the source/sink designation for Option 2, which will not be realised. Appendix 5 (Voids in Floodplain Assessment) was not updated as the results will not materially change for any of the options considered. Appendix 10 (Flooding Assessment) was not updated as Option 2 will not be realised.

Response, page 7

Applicant repliedBased on the assessment outcomes, the analysed sections achieved a high-wall FoS of greater than (>) 1.25 and therefore met the nominated design acceptance criterion for instability contained within a NUMA. However, to achieve the nominated design acceptance criterion for instability extending into a grazing PMLU (FoS ≥1.5), additional set-back distances of between 15 and 40 metres are required. These set-back distances have informed the NUMA boundary, which includes the positioning of exclusion bunding and fencing outside of these FoS set-back distances. Whilst vegetation may establish within the set-back distances and along the bund, active revegetation and access for maintenance and management will be restricted in this zone and therefore have been included in the NUMA boundary. Section 3.4.3.1.3 and Figure 23 in the PRC Plan shows the NUMA/PMLU boundary for the preferred NUMA option. Section 3.6.3.1.3 in the PRC Plan has been updated to reflect the clarity provided in the revised Appendix 11 (Section 6) in response to this item. Figure 79 (Representative Highwall setback distances) has been added to show variation between the PMLU/NUMA boundary cross sections in the central (with pit lake) and southern highwall (no pit lake). Figure 80 (Cross- section locations for the PTM residual void high-wall geotechnical assessment) has been updated to align with the boundary clarity provided to the NUMA figures mentioned in the response to Item 3. A strip of narrow woodland PMLU that will contain NUMA infrastructure (bund and fencing where required) along the entire western NUMA boundary is not considered a practical and achievable outcome for the area just outside the required geotechnical setback, therefore the total NUMA area has not been changed from the original request.

Response, page 10

Applicant repliedB. Neilson holds the majority of land within the designated surface disturbance zone as described in Section 3.1.2.11 of the PRC Plan (Part A). Figure 20 (Land Ownership Surrounding PTM) is considered appropriate to address this information requirement.

Response, page 14

Applicant repliedThe PRC Plan and Schedule submitted with this IR response has been updated to include the additional RM 6 (achievement of surface requirements). The milestone criteria includes: - Acceptable Factor of Safety (FoS) for slopes - Minimum criteria for groundcover - Weed monitoring and criteria - Acceptable erosion rates per the industry accepted Erosion Classification Framework. - Surface water quality monitoring parameters and monitoring schedule performance. These updated criteria are informed by the latest versions of Appendix 7 (Landform Design) and 9(Cover Design).

Response, page 16