Table 12. Environmental Values Risk Assessment Summary
Aspect
Environmental Value
Description of Risk
Magnitude of Impact
The Dee River is classified as highly disturbed from the Mount Morgan Mine to the confluence of the Don River. ARD is the key environmental concern at the mine site, posing a significant adverse risk to downstream catchments
Embankment overtopping was deemed as non-credible for the proposed Upper Mundic Gully TSF as the storage design that allows containment of a 120-hr PMP storm volume. A flood potential impact study was undertaken to determine impacts that might occur in the event of a catastrophic failure of the proposed Upper Mundic Gully TSF as a result of a piping failure. The geochemical properties of the processed tailings do no exceed any of the HILs and it is concluded that leaching from the tailings material is benign to human health.
• It is anticipated that there will be no impact on surface water quality environmental values as a result of the proposed activity. • Given that the TSF will be located in a valley, it is expected that any release events caused from a
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piping failure scenario spills would be largely attenuated by the OCP and contained in the downstream drainage infrastructure
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• The results of flood simulation testing indicated that the OCP is the primary receptor of breach outflows in all scenarios with these being heavily attenuated and controlled by its spillway discharge. For the Stage 2 Scenario a dam break would primarily impact the site infrastructure immediately downstream of the OCP. The maximum depths and velocities were observed immediately downstream of the OCP and natural flow paths towards the Dee River • When tailings are appropriately managed in a TSF, the geochemical properties of the treated tailings are not expected to cause harm to the receiving environment • It is anticipated that there will be no impact on groundwater environmental values as a result of the proposed activity as the TSF has been designed in accordance with relevant guidelines and best practice
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Surface Water
ARD has severely affected the groundwater at the Mount Morgan Mine, with high levels of dissolved metals including sulfate, aluminium, iron, magnesium, calcium, copper and zinc
Highly unlikely that the proposed activity cause further impacts to groundwater, as the geochemical properties or the tailings are considered benign to human and ecological health, the embankment will be constructed with an engineered liner and there the underlying geology provides for limited connectivity between the proposed TSF and underlying aquifers
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Groundwater
The seepage interception system and Water Treatment Plant will continue to be operated by the State. The groundwater condition within the Upper Mundic area is unknown as monitoring bores have not been installed. As part of this amendment, it is
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Wulguru Technical Services Pty Ltd – Supporting Information Report
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