EGL Ref: 8983 23 June 2022 Page 23 WAI-985-000-REP-LC-0004_Rev0.docx This report shall only be read in its entirety. A Zone A earth liner a minimum of 0.75 m thick is proposed against the northern slopes above RL135, as shown in Section 6 in Drawing 520. Where the slopes are at more gentle grades the Zone A liner will be able to be constructed as a blanket 0.75 m thick. As the slopes steepen the thickness will need to increase to achieve a safe practical working width which is likely to be approximately 5 m to 7 m width. 11.12. Embankment Liner System The embankment is to be underlain by a 0.75 m thick Zone A earth liner. Previously the Zone A base liner was 1.5m thick beneath the embankment. However, this additional thickness has been shown to provide only minor benefit over 0.75 m thickness. Using a 0.75 m thickness reduces the demand on NAF material, saving it for more critical locations, like capping of the embankments and stockpiles. 11.13. Leachate Collector Drains Leachate collector drains are installed over the top of the Zone A base liner within the embankment. The drains are constructed from Type C Drainage Material which is a gravelly cobble. Drains are proposed at the downstream toe, extending over the downstream half of the Zone A blanket and up the eastern gully where leachate will collect at the upstream toe, as show in Drawing 626. Details of the drains are shown in Drawing 627. 11.14. Uphill Diversion Drain The uphill diversion drain is to be constructed before the foundations are stripped, establishing a clean water diversion to minimise the amount of water needing to be treated for sediment during early construction, and once PAF material is being placed, treatment for contaminants. Previous consents have required the uphill drains to be sized for a 1 in 10 year Average Recurrence Interval (ARI) Event. Preliminary drainage design has been sized for 1 in 50 year ARI Event. This minimises the water entering the impoundment to assist with water management at the Water Treatment Plant. 11.15. Haul Route B Behind Storage 1A The Haul Route B (also referred to as the Northern Haul Road) behind Storage 1A (refer Figure 3) will be the haul route for overburden material transported to Storage 3. The road will be extended down the East Stockpile. 11.16. Storage 3 Stockpiles Three proposed stockpiles are shown on Drawing 511. These are for stockpiling of topsoil and surplus soils from the strength stripping of the Storage 3 foundations. All
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