EGL Ref: 8983 23 June 2022 Page 9 WAI-985-000-REP-LC-0004_Rev0.docx This report shall only be read in its entirety. expansions. However, for this consent, the maximum crest level of this embankment is RL155. The Storage 3 embankment will be zoned with low permeability liners and capping to provide for secure containment of PAF rock from GOP or MOP. These liners and capping limit oxygen and water ingress, and along with the addition of lime into the material being placed, minimise any acid generation potential. This approach has been successful for Storage 1A and 2. For the material from GOP with a short lag time till acid generation, specific characterisation and placements controls will be applied. Figure 4.2 –TSF3 RL155 Layout Plan The RL155 crest height provides a total impoundment storage volume of approximately 7,000,000m3. Allowance will be made to safely manage surface water from extreme storm events on top of the tailings. The volume available for tailings storage is estimated at approximately 5,700,000m3. The tailings impoundment will be fully lined with an earth liner. Additionally, a 1.5mm HDPE geomembrane liner is proposed within the tailing’s impoundment and up to the initial embankment height (RL135) to further minimise tailings seepage over what was provided for Storage 1A and 2. Groundwater and leachate collected in the subsurface drains will be pumped back to the Water Treatment Plant via the perimeter ring main system around Storage 1A and 2, which will be extended to Storage 3. Power will be supplied by extending the existing power line at the Development Site. Tailings delivery pipelines, water return pipes and power for the decant return will be extended around the back of Storage 1A and Storage 3. The Storage 3 site is accessible from the Storage 1A site via the Baxter Road Security Gate and Southern Perimeter Road.
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