4.4 Dam 8 Description and Environmental Values Dam 8 is located off the mining tenure and is not included as a mine feature in the EA. The State Government, through the DNRMMRRD, conducted engineering works to seal the Dam 8 upstream wall as a means of reducing seepage into the OCP as it was historically observed that during high flow events, water was evidently seeping into the OCP. Similarly to the Upper Mundic Gully catchment, the Dam 8 catchment appears heavily modified associated with historical mining operations, primarily associated with the placement of the western dump. Dam 8 is in a separate catchment to Upper Mundic Gully catchment. Water in Dam 8 is used by Heritage Minerals as a source of construction and processing water. During high flow events, water from the ephemeral dam can migrate from to Dam 8 via the tunnel. Water quality sampling of the ephemeral dam occurred on 3 November 2025 with results summarised in Table 19. These results have been compared to Australian and New Zealand Guidelines for Fresh Water Quality (ANZECC & ARMCANZ, 2000) default trigger values for toxicants for the 80% protection of aquatic ecosystems with exceedances highlighted in bold. Table 19 Dam 8 Water Quality
Analyte
Unit
Value
Guideline Value
pH
pH unit
8.35
6.5-8
EC
µS/cm
665
30-350
TDS
mg/L
432
-
Sulfate as SO4
mg/L
179
-
Aluminium (total) (ph < 6.5)
mg/L
<0.01
-
Arsenic (AsV) (total)
mg/L
0.001
0.140
Cadmium (total)
mg/L
<0.0001
0.0008
Chromium (total)
mg/L
<0.001
0.040
Copper (total)
mg/L
0.003
0.0025
Cobalt (total)
mg/L
<0.001
-
Nickel (total)
mg/L
<0.001
0.017
Lead(total)
mg/L
<0.001
0.0094
Zinc (total)
mg/L
<0.001
0.031
Manganese (total)
mg/L
0.031
3.6
Selenium (total)
mg/L
<0.010
0.034
Boron (total)
mg/L
<0.05
1.3
Iron (total)
mg/L
0.19
-
Mercury
mg/L
<0.0001
0.0054
Project number: 25B061
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