Monitoring bores will be constructed using:
— Boreholes for monitoring bores should be drilled using any viable method at diameters of 125 mm or more, and the monitoring bores constructed using the following materials.
— 60 mm external diameter (50 mm internal diameter, 5 mm wall thickness) Class 18 uPVC screw-threaded casing.
— 60 mm external diameter (50 mm internal diameter, 5 mm wall thickness) Class 18 uPVC screw-threaded and 0.4 mm aperture machine-slotted screen.
— 60 mm external diameter (50 mm internal diameter) Class 18 end caps.
— 1 to 2 mm graded and washed quartzose sand filter pack.
— ¼-inch sodium-coated Pel-Plug TR30 bentonite pellets for annular seals.
— A cement-bentonite (powder) mix grout, typically with a mass ratio of about 30 litres of water, 20 kg of cement, and 1 kg of bentonite. — Bores will be completed at the surface with lockable caps, protective casing, and concrete plinths or equivalent protection to ensure long‑term integrity and safe access. 5.3 Groundwater monitoring activities Groundwater monitoring forms a key component of the SMP by providing the data required to verify conceptual assumptions, assess future groundwater response to TSF development, and support adaptive seepage management. Monitoring at existing bores WGMB01, WGMB02, and WGMB03 is currently focused on establishing baseline groundwater levels and quality and detecting early changes in groundwater conditions. The additional downgradient monitoring bores proposed under this SMP will be incorporated into the same monitoring framework.
5.3.1
Purpose and relevant standards
Groundwater monitoring comprises routine groundwater level measurement and groundwater quality sampling to support verification of future modelling inputs and assumptions. Monitoring is undertaken to further characterise baseline groundwater conditions outside the TSF area, including spatial variability and seasonal responses across wet and dry periods, and to confirm the current hydrogeological conceptualisation. Data collected from the groundwater sampling will be used to assess groundwater levels, gradients, vertical connectivity, and groundwater quality trends over time, and to evaluate consistency between observed groundwater behaviour and model predictions. All groundwater level measurements, sampling, field procedures, and data management will be undertaken by a Suitably Qualified Person and in accordance with recognised Australian and Queensland standards and guidance, including AS/NZS 5667.11:1998 – Water quality – Sampling – Guidance on sampling of groundwaters .
5.3.2
Monitoring location, frequency and duration
Groundwater monitoring will be undertaken at the existing monitoring bores WGMB01, WGMB02, and WGMB03, together with the additional downgradient monitoring bores specified in Table 5.1 once they are installed. Groundwater level monitoring and groundwater quality sampling will be conducted on a quarterly basis at all monitoring locations. Monitoring will continue for a minimum period of two years, capturing seasonal variability across wet and dry conditions and providing sufficient data to evaluate trends, verify seepage modelling inputs and assumptions, and support adaptive seepage management. Monitoring frequency and duration may be reviewed and refined as additional site data become available and as the Project progresses.
Project No PS213278 Mount Morgan Mine - Upper Mundic Gully TSF Seepage Management Plan Heritage Minerals
WSP May 2026 Page 24
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