Storage volume Note (1)
Basis value
Description
Criteria
Mm 3
m
Minimum Pond depth
-
No allowance at this stage
-
(1) Calculated based on catchment area of UMG TSF equal to 50.2 Ha.
The PMF storage allowance will provide adequate capacity to meet the DETSI [2] and ANCOLD [16] Design Storage Allowance (DSA) and Emergency Storm Storage (ESS) requirements.
4.5 Spillway The TSF has been designed with sufficient storage to contain a PMF event and a spillway will not be required during operation. A spillway with capacity to pass the PMF will be required for the closure of the UMG TSF, to limit water storage in the longer term. Construction of this spillway for the 2 nd and final stage of the TSF would allow for additional tailings storage within the UMG TSF. 4.6 Tailings and water storage capacity The estimated tailings and water storage capacity for UMG TSF is summarised in Table 4.3, Figure 4.3 and Figure 4.4The estimated tailings and water storage capacity for UMG TSF is summarised in Table 4.3, Figure 4.3 and Figure 4.4..
Table 4.3
Estimated tailings storage capacity
Stage
Crest elevation (m RL)
Tailings beach (m RL)
Tailings storage (Mm³) Note1
Tailings storage (Mt)
Maximum water elevation (RL m)
Water storage (Mm³) Note1
1
360
350.3
1.15
1.26
359.0
1.32
2
390
386.8
8.09
8.90
389.0
1.32
Total
-
-
9.24
10.16
-
1.32
(1) Required PMP storage – does not include operational pond volumes.
Project No PS213278 Upper Mundic Gully - Tailings Management Plan Mount Morgan Gold Mine Heritage Minerals
WSP March 2026 Page 3
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