Table 1
GSDM and GTSMR PMP factors
Decay Adjustment Factor (DAF)
Topographic Adjustment Factor (TAF)
Moisture Adjustment Factor (MAF)
GSDM
Not applicable
Not applicable
0.88
GTSMR
1
1.16
0.76
2.2 Catchment This assessment utilised a catchment area 103 hectares as provided by Golder, and considered the final embankment stage at RL 330 mAHD. GHD initially estimated a larger area, however, it was noted that the position of the dam had moved upstream, reducing the catchment area and the exact outlet point was not known to GHD. Out of the 103 ha, 46.2 ha was estimated to be the water impoundment area at 330 mAHD and thus considered to 100% impervious. The remaining 56.8 ha was the contributing catchment to SSG and considered fully pervious. The catchment area is illustrated in Figure 1, with the key parameters used in the RAFTS model presented in Table 2.
56.8 ha
46.2 ha
Figure 1
SSG catchment area considering final embankment stage at RL 330 mAHD
Table 2
SSG sub-catchment parameters
SSG
Area
Vectored Slope (%)
PERN Manning’s n
Impervious %
Dam impoundment
46.2
0.83
0.06
100
Contributing catchment
56.8
11
0.015
0
12624987 | Hydrological assessment of PMF for the Sandstone Gully Tailings Storage Facility 2
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