— The final soil surface is to be revegetated to limit erosion.
5.3 Tailings beach The final tailings beach will need to be formed to provide a shedding cover, which may be achieved using tailings deposition to reduce required earthworks. A short-term deposition plan should be prepared near completion of filling to provide specific requirements for spigot operation to form the tailings beach, reduce the pond size, and position the pond at the closure spillway.
5.4 Closure spillway
A closure spillway, capable of conveying the PMF flow, will be installed during the construction of the Stage 2 raise of the embankment.
5.5 Closure maintenance and monitoring plan A maintenance and monitoring plan will be required so that post-closure performance can be assessed against pre- planned objectives. This will entail proactive monitoring (in earlier closure years) and reactive monitoring (in later closure years), prior to relinquishment. Proactive monitoring consists of routine-based monitoring at a reduced frequency than would typically be undertaken during operations. The transition to reactive monitoring will only occur upon demonstration of acceptable environmental performance. The reactive program is characterised by monitoring and maintenance in response to a particular event rather than a schedule basis. The following monitoring should be undertaken during post-closure: — Surface water monitoring – observations from site inspections and review of borehole and piezometer data — Groundwater quality monitoring – water quality testing from borehole data — Erosion monitoring and maintenance – observations from site inspections — Settlement monitoring – review of fixed survey prisms, LiDAR or satellite based InSAR data. — Topsoil and subsoil quality – soil sample testing prior to and during revegetation, until it is adequately established — Cover design performance and effectiveness: — Observations from site inspections — Cover material geochemical laboratory testing.
Project No PS213278 Upper Mundic Gully - Tailings Management Plan Mount Morgan Gold Mine Heritage Minerals
WSP March 2026 Page 9
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