Original EA Amendment

12 February 2020

20137096-009 Rev A

Parameter

Design Input

Reference

Acceptable Embankment Factors of Safety

Table 2

Drained Undrained Post-seismic

1.5 1.5 (Global) and 1.3 (Local) 1.0 – 1.1

ANCOLD 2012

Water Management

Catchment area to RL 335 m

114 Ha

APPENDIX A

Size of normal operating pond

10% of operating area

Practice

Minimum operational (tailings) freeboard

1 m below crest level

Golder

To be determined as part of the design studies

Golder assessment

Design rainfall

Water Balance – Design Parameters

BOM station

Average annual rainfall

TBC

Surface Water Management

Consistent with other site infrastructure

Stormwater diversion drains

TBC

Seepage Management

Water retaining portion of TSF embankments lined with low permeability waste material or geomembrane liner

Liner requirement

Golder

Finger blanket underneath TSF embankment, and seepage collection trenches located along the outer embankment toe-line

Seepage drainage

Golder

Embankment zoning and provision of high seepage discharge chimney

Internal drainage

Golder

TBC and to be dependent on the water level from the PIT

Depth to original groundwater

Seepage Management

Water retaining portion of TSF embankments lined with low permeability waste material or geomembrane liner

Liner requirement

Golder

8

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