Original EA Amendment

Table 10. Proposed Table H2 Replacement

Consequence Category

Maximum Surface area (ha)

Maximum volume (m 3 )

Purpose of Regulated Structure

Name of Regulated Structure

Sandstone Gully Tailings Storage Facility Upper Mundic Gully Tailings Storage Facility

High

49.2

11,532,416

Storage of Cyanide Tailings

Significant

43.4

9,240,000

Storage of Tailings

Justification for changes described in Table 10 are as follows:

• The existing values in Table H3 relating to spillway, DSA and MRL do not reflect the ‘High’

consequence category for Dam Break (and ‘Low’ for Overtopping and Seepage);

• Changes to Spillway are derived from Table 6 from the DETSI Manual for assessing

consequence categories and hydraulic performance of structures;

• Changes to DSA are derived from Table 3 of ANCOLD requirements; and

• Changes to mandatory reporting level are derived from Table 5 from the DETSI Manual for

assessing consequence categories and hydraulic performance of structures.

Table 11. Proposed Table H3 Replacement

Name of Regulated Structure

Spillway

Design Storage Allowance

Mandatory Reporting Level

Sandstone Gully Tailings Storage Facility

1:20 AEP

Peak discharge from a 0.001 AEP storm of critical time of concentration on the total

1:10 AEP 72-hour ESS

1:100,000 AEP + Wave run-up allowance for 1:10 AEP wind

1:100 AEP 72-hour duration ESS

natural catchment with diversions inoperable

1:5 AEP Wet Season Water Storage DSA

2.3.3. Figures within the EA

Justification for amendments to Schedule I, Figure 1 include:

• Inclusion of the Upper Mundic Gully TSF to ensure consistency with Table A1; and

• Inclusion of the pipe corridor to ensure consistency with Table A1.

The proposed replacement Schedule 1, Figure 1 is provided in Figure 9.

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