SECTION 6 Gladstone Open Pit and TSF C:\D Data\GWS C Drive\GWS\Client Files\1344 OGL - WKP\4 Deliverables\WUG Effects Summary\June 2022\WNP Groundwater Effects Summary_Final_Rev_0.docx 24 Figure 26 Gladstone Hill Dewatered Section (From GHD 2022) Excavation of the GOP will results in the physical loss of the subcatchment and groundwater recharge area. Predictions of baseflow loss to the wetland as a result indicates minimal effect (0.4 m3/d) with an imeasurable lowering of the water level likely. The loss of catchment will mean there is less interflow discharge into the wetland, meaning the recession flows following rainfall may be shorter. During GOP excavation and dewatering, loss of recharge and reduction in groundwater levels is predicted to result in a small reduction in groundwater flow to surface waters (10’s of m3/d) that would be immesurable in the River. Other Effects Related to the Take Given the limited drawdown effects associated with development of the open pit, no effects are expected on other groundwater users, plant growth, other aquifers or water quality. Land Discharge Effects Once mining of the GOP is complete it will be engineered to become a tailings storage facility. During its operational life and post closure the TSF will result in some discharge to groundwater and surface waters. Figure 26 shows a section of the Gladstone TSF during operation. The volume of the groundwater predicted to discharge from the facility is presented in Table 1. Table 2 Predicted Groundwater Discharge from Gladstone TSF (m3/d) Water Body Location Current Operational TSF Long Term TSF TSF Closure Gladstone Wetland / Ohinemuri Tributary TB4 1.0 2.5 0.5 – 2.0 2.5 – 5.0 3.0 Ohinemuri Tributary TB5 0 0 0 5.0 Ohinemuri River east of Gladstone Hill OH3 50 - 370 50 - 325 55 - 400 55 Ohinemuri River west of Gladstone Hill OH6 180 - 215 150 - 160 170 - 210 315
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