hydrogeological and geological conditions at the site. Based on the conceptualisation documented in the SMP, seepage from the TSF may migrate into surrounding formations. The assessment of impact to environmental values is therefore based on available information and current understanding of seepage and downgradient receptors. It is proposed that further analysis and modelling is completed to refine seepage understanding. Table 30 presents the “Failure to contain – Seepage” Consequence Category assessment according to DETSI for both proposed embankment stages of Upper Mundic Gully TSF. Table 30. Consequence Category Assessment– DETSI (Failure to contain – seepage)
Item
Stage 1
Stage 2
Low No loss of life is expected.
Same as Stage 1
Harm to humans
The contamination of water supply bores is expected to affect the health of fewer than 10 people Significant Based on the conceptualisation within the seepage management plan (Appendix H), a potential seepage pathway to the north-west of the TSF has been identified. This intersects the area identified as having mapped low to moderate potential for GDEs, with the impacted area expected to be at least 1km 2 . Field verification surveys within the TSF footprint did not indicate a clear connection between groundwater and vegetation 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 environmental harm
Same as Stage 1
General economic loss or property damage
Significant
Significant
Overall consequence classification
5.4 Tailings and Water Management The tailings and water management requirements have been estimated based on the consequence categories assessed in Section 5.2. Tailings and water storage requirements for the TSF have been assessed assuming the following: ∕ No operational pond volume; and ∕ Probable Maximum Precipitation (PMP) stored within the TSF results in no requirement for a spillway. The Upper Mundic Gully TSF has been designed on the basis of no operational pond volume. Tailings deposition will be managed to minimise ponding, with systems to be installed to return any operational water to the process plant. The design includes sufficient freeboard to accommodate the PMP event without requiring any operational 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
Project number: 25B061
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