EGL Ref: 8983 23 June 2022 Page 36 WAI-985-000-REP-LC-0004_Rev0.docx This report shall only be read in its entirety. is likely to be low or medium. Design criteria will then be set from this assessment. A design report will need to be prepared for each Collection Pond and submitted for building consent. 13.10. Embankment surface water drainage sizing The embankment surface water system will be sized in accordance with the design criteria in section 10.4. The design concepts will be the same as for the existing TSFs with a combination of benches that divert runoff to sumps and buried pipes that discharge runoff down the slope into the perimeter drain. In very large rainfall events runoff overflows the benches and flows as sheet flow down the embankment. The embankment will be mostly pasture and it is resistant to erosion from short duration flows. 13.11. Paleo Gully Undercut Settlement Effects on Storage 1A The potential settlement effects on Storage 1A and Collection Pond S5 as a result of the Paleo Gully excavation dewatering have been considered. GHD (Ref. 22) has undertaken a preliminary groundwater drawdown assessment on a section extending beneath Collection Pond S5 and the Storage 1A embankment. The preliminary predicted groundwater drawdown beneath Collection Pond S5 is approximately 5 m, beneath the toe of Storage 1A the prediction is 4 m, and below the crest of Storage 1A it is 1 m. EGL settlement calculations indicate up to 20 mm of settlement. Settlement of this order would have no noticeable effect on Collection Pond S5 or Storage 1A. Even if greater settlements did result, they would not have a material effect unless they affected the impoundment freeboard. To have a material effect settlement would need to be greater than 100 mm. Even then this could be managed by topping up the embankment crest with construction plant on site. Settlements in the range calculated will not affect the Zone A liner or Zone G capping. 14.0 DRAWINGS The following Drawings have been prepared Storage 3 to RL155 for this technical report. Drawing No. Drawing Title WAI-983-080-DWG-CI-0500 Locality Plan and Index - Storage 3 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0101 Site Plan - Waste Disposal Area - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0511 Layout Plan - Storage 3 RL135 Embankment - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0512 Layout Plan - Storage 3 RL145 Embankment - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0513 Layout Plan - Storage 3 RL155 Embankment - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0516 Sections - Storage 3 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0517 Sections - Storage 3 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0518 Sections - Storage 3 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0519 Sections - Storage 3 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0520 Sections - Storage 3 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0541 Sections - Storage 3 - Uphill Diversion - Tails / Waste Rock 080
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