EGL Ref: 9215 23 June 2022 Page 19 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. 4.2.5. Tailings impoundment lining and subsurface drains Storage 2 impoundment is earth lined against the embankment and is unlined on the base and against the hills. Storage 1A is earth lined against the embankment and is unlined on the base. Storage 1A is lined against the hills above approximately RL160. It is unlined below this level. Subsurface drains are installed beneath the tailings and provide some under drainage of the tailings and collection of seepage through the tailings profile. Storage 1A and 2 tailings densities achieved are shown in Figure 12 and Figure 13. The discharge rate of tailings into Storage 2 has varied from approximately 0.8 to 1.0 Mtpa (dry weight) up to 2001 when Storage 1A was commissioned. The discharge rate of tailings in Storage 1A has varied from approximately 1.1 to 1.5 Mtpa (dry weight) from 2002 to 2006. From 2006 to 2015 discharge varied between about 0.5 to 0.9 Mtpa. Since 2016 tailings discharge has been between about 0.4 to 0.45 Mtpa. For the Waihi North Project tailings production will start at 0.8 Mtpa and increase up to about 1.75 Mtpa. FIGURE 12: STORAGE 1A TAILINGS DENSITIES WITH TIME
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