7.5.1 Cut/fill volumes
A high-level estimate of cut and fill volumes required for the embankment construction is summarised in Table 7.1.
Table 7.1
Summary of estimated cut and fill volumes
Stage crest
Cut
Stage fill
Total fill
Stage
m 3
m 3
m 3
RL m
1
360
320
443,000
2,280,000
2
390
-
1,837,000
7.6 Seepage management
A high-level seepage assessment was previously completed for Sandstone Gully TSF as part of the Definitive Feasibility Study [9]. The assessment concluded that “seepage flows are expected to continue towards Mundic Creek in accordance with historical observations and as such seepage interception and management systems in place will need to be maintained” . Seepage from the Upper Mundic Gully TSF would also be expected to occur through the embankment and foundation, as indicated in the conceptual hydrogeological model presented in Figure 7.1.
The proposed seepage management strategies include:
— Installation of a lining system on the embankment (Section 7.6.1) — Management of the decant pond to limit volume and maintain position away from the embankment — Installation of instrumentation to monitor seepage impacts to groundwater (Section 7.6.2). Limited geotechnical information is available for the floor of Upper Mundic Gully and as such geotechnical investigations (Section 7.8) are needed to assess potential seepage impacts.
Airfield dump
Figure 7.1
Upper Mundic Gully conceptual hydrogeological model (Source: Heritage Minerals)
Project No PS213278 Upper Mundic Gully TSF Concept Design to RL 390 m Mount Morgan Project Heritage Minerals
WSP October 2025 Page 14
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