420
410
400
390
380
370
360
350
340
330
320
0
5000
10000
15000
20000
25000
Volume (ML)
Figure 3.2
UMG Stage Storage Curve
3.3
Pumping rates
3.3.1 DOR WTP The DOR Water Treatment Plant (WTP) processes water from the OCP to manage and reduce on-site water levels. Following other updates as part of this study, the pumping rate was adjusted to achieve a 1% Annual Exceedance Probability (AEP) volume buffer below 263 m Australian Height Datum (AHD), at 259.3m AHD, which corresponds to the Relative Level (RL) of the coffer dam in the SSG. The WTP was assumed to be actively pumping throughout the entire simulation period (from Phase 1 to 4) to continuously transfer water from the OCP to the WTP, maintaining the OCP as empty as possible. The net throughput (i.e. net loss from the OCP) through the WTP was set to 4.8 ML/d (55.56 litres per second; ℓ/s). Evaporators From Phase 1 (construction) to Phase 4 blowing takes place on the OCP, only. The throughput capacity was assumed at 38.77 ℓ/s (3.35 ML/d). For details on the Evaporator throughput and efficiency, please refer to the GHD (2022a) Report. 3.3.2 3.3.3 Seepage pump-back to OCP All previously modelled seepage pump-backs from the surrounding sumps to the OCP have been reinstated, from the May 2024 report, to replicate the original GHD (2022a) Report inputs.
3.3.4
Other pumping rates
All relevant changes in pumping rates in comparison with the GHD (2022a) water balance model are presented in Table 3.1.
12624987 | Heritage Minerals EA Amendment Application – Updates to Water Balance Model July 2025 (Final) 5
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