EGL Ref: 8983 23 June 2022 Page 34 WAI-985-000-REP-LC-0004_Rev0.docx This report shall only be read in its entirety. Table 9: SUMMARY OF EMBANKMENT FREEBOARD SCENARIOS Parameters Freeboard Scenarios* Operation Closure Normal Conditions Inflow Design Flood during operation Post SEE Earthquake during operation Inflow Design Flood after closure# Post SEE Earthquake after closure Embankment as-built crest level (RL) 155 155 155 155 155 Approximate tailings level against embankment 152.5 152.5 152.5 152.5 152.5 Reservoir/Pond water level (RL) 151.5 154 151.5 153.7* 151.8& (estimated closure outlet channel invert) Static embankment fill settlement (m) 0m 0m 0m 0.7% x 46m = 0.32m 0.7% x 46m = 0.32m SEE slope displacement related crest settlements affecting freeboard - - 0.19m - 0.19m SEE fill shakedown related crest settlements - - 0.2% x 46m = 0.09m - 0.2% x 46m = 0.09m Freeboard without wind, wave or settlement (m) 3.5 m^ 1.0 m 3.22 m 1.08m 2.6m Wind design event 1 in 100 AEP 1 in 10 AEP 1 in 10 AEP 1 in 10 AEP 1 in 10 AEP Wave run-up (m) 0.34 m 0.30m 0.30m 0.30m 0.30m Freeboard allowing for wave run-up (m) 3.16 m 0.7m 2.92m 0.78m 2.3m *Levels reported for the freeboard scenarios are based on operating experience and expect catchments for Storage 3. Level will vary during operation depending on the tailings surface profile and specific calculations are required to confirm sufficient freeboard is maintained at regular intervals by operational staff. This table is indicative of the likely scenarios. ^Normal operation freeboard is targeted to allow sufficient volume to hold the IDF with 1.0m freeboard remaining, without including wave runup. # Closure scenario assumes an outlet channel at normal water levels which spills clean water to receiving catchment. Outlet channel will need to be sized to pass sufficient volume to limit maximum water level under IDF (72 hour PMP) to approximately RL153.7. To be confirmed at closure. & Outlet channel invert level will need to consider tailings coverage with pond water where there is no dry capping. Level estimated. To be confirmed in closure.
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