94 16.4 Effects Management for construction of GOP The loss of the intermittent headwater gully is unavoidable and therefore there is a residual effect of loss of some 70 m length (approximately 70 m2 of surface area) of intermittent watercourse. This residual effect of loss of stream area will be offset with stream enhancement (including riparian enhancement). Details of the stream offset is provided in section 22 of our report. Figure 23: Conceptual hydrology of Gladstone Wetland (from GWS 2021). 16.5 Effects of GOP TSF on aquatic ecological values As outlined above, once the base layer is formed within the pit, the layer will be then covered with a geomembrane liner and tailings from the processing plant will be deposited within the pit. Post settlement, the tailings pond will be emptied, and a 1 m layer of NAF rock will be placed over the tailings surface for closure. GHD (2022A) report that there have been no overflows from the currently active TSFs since the mine has been in operation. Decant water is pumped to the processing plant for re-use or to the WTP. As part of the WTP operation, the storage available in the active TSF is monitored and if necessary, decant water treatment is prioritised to ensure freeboard is maintained. We expect the same management regime to occur at the GOP TSF. We understand that a surface drain carrying surface runoff waters from the GOP TSF closure landform will discharge to the western GOP watercourse. We expect this discharge to comprise only surface rainwater. We have classified the western GOP watercourse as intermittent, and we would expect the additional runoff to contribute to the intermittent nature of the watercourse.
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