Item
Stage 1
Stage 2
moderate potential GDEs are located respectively west and north of the TSF, however, this is upgradient of the TSF and with the direction of seepage towards the south-east, no significant impacts are expected. Low No bores used for water supply have been identified in the vicinity of the TSF or in the direction of the groundwater flow. Therefore, loss of agriculture and/or stock is not expected.
Same as Stage 1
General economic loss or
property damage
Overall consequence
Low
Low
classification
4.3.3. Tailings and Water Management
The tailings and water management requirements have been estimated based on the consequence
categories assessed in Section 4.3.2. Tailings and water storage requirements for the TSF have been
assessed assuming the following:
No operational pond volume; and
•
• Probably Maximum Precipitation (PMP) stored within the TSF results in no requirement for a
spillway.
The PMP storage allowance will provide more than adequate capacity to meet the Queensland Design
Storage Allowance (DSA) and Emergency Storm Storage (ESS) requirements. As prescribed in the
Manual for Assessing Consequence Categories and Hydraulic Performance of Structures
(ESR/2016/1933), the DSA, ESS and mandatory reporting levels (MRL) requirements must be
addressed for those dams assessed as having a “significant’ or ‘high’ consequence for the “failure to
contain – overtopping’ scenario. If a dam was assessed in the low consequence category for the ‘failure
to contain – overtopping’ scenario, the determinations for a DSA, ESS and MRL are not required even
if the dam is otherwise a regulated structure. Based on results provided in Section 4.3.2, the Upper
Mundic Gully TSF does not require an operational spillway, DSA or ESS requirements in Table H3 of
the EA.
4.3.4. Water Balance
A revised site wide water balance that incorporates the Upper Mundic Gully TSF was undertaken by
GHD during October 2025. The report is provided in Appendix H and summarised below. The objective
of undertaking the water balance modelling was to understand the impact of the proposed construction
and mining activities on the water levels in the OCP and to confirm the level of spill risk from the OCP,
if any, based on the model configuration and assumptions used in its development.
The operational model has been updated into a phase approach as follows:
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Wulguru Technical Services Pty Ltd – Supporting Information to Amend an Environmental Authority
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