Table 33. Tailings properties compared to Relevant Guidelines
Analyte
Unit
Processed/New Tailings Value
NEPM HILs Commercial/Industrial Setting (mg/kg)
pH
-
9.57
NA
Electrical conductivity
µS/cm
4000
NA
TDS
mg/L
30
NA
Magnesium as Mg
mg/L
100
NA
Sodium as NA
mg/L
70
NA
Sulfate
mg/L
2000
NA
Chlorine as Cl
mg/L
20
NA
Hardness as CaC0 3
mg/L
514
NA
Iron as Fe
mg/L
59
NA
Manganese as Mn
mg/L
10
40,000
Zinc as Zn
ppm
50
400,000
Calcium
%
2.4
NA
Magnesium as Mg
%
0.23
NA
Sodium as NA
%
0.17
NA
Aluminium as Al
%
1.5
NA
Arsenic as As
mg/L
102
3,000
Barium as Ba
mg/L
60
NA
Bismuth as Bi
mg/L
23
NA
Cobalt as Co
mg/L
62
4,000
Copper as Cu
mg/L
216
250,000
Molybdenum as Mo
mg/L
50
NA
Nickel as Ni
mg/L
7.83
4000
Selenium as Se
mg/L
26.09
10,000
Silver as Ag
mg/L
0.4
NA
5.15 Spillway design 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. A spillway with capacity to pass the PMF will be required for UMG TSF closure to limit water storage in the longer term. The closure spillway concept design has been provided in the updated CCA and shows a direction towards the west away from the OCP. During detailed design the final closure spillway option will be further developed and other technical studies including PMF assessments will be undertaken. Typically, spillway designs are updated following cessation of tailings deposition, once final tailings surface levels, settlement, and
Project number: 25B061
Page 97
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