5 Closure and rehabilitation A closure plan has been prepared by Heritage for the Mount Morgan TSFs and is presented in Appendix A. The rehabilitation strategy for the Mount Morgan TSFs is based on achieving a landform that is safe, stable, non-polluting, and capable of supporting a non-use management area (NUMA) consistent with the Progressive Rehabilitation and Closure Plan (PRCP). As of 26 May 2025, Environmental Authority (EA) [4] authorises SSG TSF as a mining activity, however, UMG TSF is not yet authorised. An amendment application was lodged to DETSI in October 2025 with anticipated approval in the second half of 2026. The SSG TSF rehabilitation requirements from the EA are replicated in Table 5.1 below.
Table 5.1
Rehabilitation requirement from EA
Land suitability objective
Mine Feature
Rehabilitation
Final land use
Sandstone Gully TSF
— Completely backfilled. PAF waste rock and tailings transferred from stockpiles to void. — Water removed.
Land management monitoring and maintenance of rehabilitated areas
Class 4
— Dry cover – store and release. — Drainage system constructed.
In general, the closure plan for UMG TSF will need to include the following aspects: — Seepage management — A cover over the tailings to prevent tailings erosion and generate vegetation growth — Shaping of the final surface to provide a direct flow path to the spillway and minimise ponding of water — Runoff management systems on the embankment crest and slopes — A spillway capable of conveying runoff generated by the probable maximum precipitation (PMP), also known as the probable maximum flood (PMP) event.
5.1 Embankment runoff management systems
The final stage of the embankment will require design for closure and incorporation of the following elements: — Drains on the benches to direct runoff water to the down-drains located on the abutments — Runoff down-drains down the confluence of the embankment and the abutments. — These elements would be constructed at the time that the final raise is constructed.
5.2 Cover system
A shedding cover is to be placed over the final tailings beach after closure, so that no water is stored in the TSF after closure, which will likely consist of the following layers: — An initial layer of waste rock selected from the dumps on site to provide an access platform for mobile equipment — A topsoil layer to provide growth medium for vegetation. — Cover placement may be a slow process, as access is developed across the soft tailings in the TSF.
Project No PS213278 Upper Mundic Gully - Tailings Management Plan Mount Morgan Gold Mine Heritage Minerals
WSP March 2026 Page 8
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