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DETSI Comment
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As such clean water diversion drains have not been designed for or simulated in the water balance. For the Upper Mundic Gully TSF, the contributing catchment is very steep and small relative to the size of the TSF. Further, this system would function as a sink, requiring a sump and pump system to remove the clean water. As such, there is no significant benefit in including clean water diversions upstream of the TSF, especially given the complexities that constructing on steep slopes would add. However, for the OCP, a coffer dam wall has been constructed between Sandstone Gully and the OCP. As such, this will effectively keep the mine impacted stormwater runoff generated upstream of this coffer dam out of the OCP, acting as a form of catchment segregation and aiding in water management. The Sandstone Gully has no outlet from the mine site, other than through evaporative losses. Clean water is not captured as the contributing catchment is very steep and small relative to the size of the TSF. Any clean water entering the TSF has been accounted for in the water balance model. (refer to Figure 27) Characterisation of groundwater across a majority of the site is well appreciated, as documented extensively in Sections 5.6 and 6.3. Installation of groundwater monitoring bores on the periphery of the Upper Mundic Gully TSF is proposed through inclusion of new conditions (Schedule W). Groundwater properties specifically within the Upper Mundic Gully TSF area have not been previously investigated, however groundwater properties of the Mundic Creek have. Accounting for some natural variability and acknowledge the modified landform through previous mining
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If clean water is captured (potentially now MAW), how is this managed? Does water within the TSF get pumped to another structure to maintain ‘no operational pond level’. If so, how much water is pumped to other site structures, and has this been included within the revised water balance modelling?
Figure 27
In terms of ground water management
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Address the gaps regarding groundwater quality, quantity, recharge abilities, hydraulic properties and potential flow pathways within the proposed TSF footprint or close proximity. This information is critical to satisfy properly made criteria (section 226A(1)(f) of the EP Act) and decision making criteria
Regarding the specific comment, •
Groundwater quality across the site is described in Section 5.6.1 Groundwater quantity and levels are described in Section 5.6 Groundwater recharge and discharge is described in Section 5.6.3
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