EGL Ref: 9215 23 June 2022 Page 25 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. FIGURE 18: STORAGE 2 SUBSURFACE AND LEACHATE DRAINAGE NETWORK Underdrains are located beneath the tailings and intercept seepage through the tailings. Upstream cutoff drains are located along the upstream toe of Storage 2 embankment and intercept seepage from the tailings. The upstream cutoff drain connects with the tailing underdrains and the combined discharge flows in pipes located beneath the embankment to locations at the downstream toe. There are four outlets U1-U4 which are shown in red in Figure 18. The initial toe drain is located along the downstream toe of the initial embankment. This functions to intercept tailings seepage beneath the embankment and to limit saturation of the downstream shoulder of the initial embankment. There are two separate outlets IT1 and IT2 which are shown in green in Figure 18. The final embankment toe drains are located along the downstream toe of the final footprint of Storage 2 to intercept seepage from either the tailings or from the embankment itself. Seepage flow is collected at 14 sumps along the toe drain T1 – T14 which are shown in navy blue in Figure 18.
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