4
Tailings and water management
The tailings and water management requirements are based on the ANCOLD and DETSI Consequence Categories presented in Table 2.2.
4.1.1 UMG TSF LOF deposition levels and tailings storage capacity
Tailings deposition into UMG TSF will be commenced after completion of deposition into OCP. The tailings deposition levels and tailings storage capacity for each stage are presented in .
Table 4.1
Upper Mundic Gully TSF – Deposition levels and tailings storage capacity
Stage crest level
Deposition level
Tailings deposited Tailings deposited
Stage
Mm 3
RL m
RL m
Mt
1
360
350.3
1.15
1.26
2
390
386.8
8.09
8.90
Total
-
-
9.24
10.16
4.2 Tailings slurry delivery and deposition Tailings slurry will be pumped to the TSF in a pipeline and discharged via a number of full-bore spigots spread along the embankment crest. The tailings deposition surfaces for both Stage 1 and Stage 2 are presented in Figure 4.1 and Figure 4.2 respectively. 4.3 Decant pond Deposition will be undertaken from the embankment crest so that tailings beaches away from the embankment and forms a decant pond against natural terrain of the valley at the western side of the impoundment. A nominal depth of 2 m has been assumed for the decant pond and a suitable return water pump system will be installed to maintain this depth to encourage desiccation of the exposed tailings.
4.4 Wet season and emergency storm storage
The water storage requirements for the UMG TSF will vary for Stages 1 and 2, as shown in Table 4.2
Table 4.2
Water storage requirements
Storage volume Note (1)
Basis value
Description
Criteria
Mm 3
m
Wet season water storage allowance
1:100 AEP 3-month wet season rainfall depth
1.260
0.633
Probable Maximum Precipitation
120 hr
2.620
1.32
1:1,000 AEP 72 hr storm
Extreme storm storage (ESS)
1.020
0.512
Minimum freeboard
-
1
-
Project No PS213278 Upper Mundic Gully - Tailings Management Plan Mount Morgan Gold Mine Heritage Minerals
WSP March 2026 Page 2
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