EGL Ref: 9215 23 June 2022 Page 26 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. Leachate drains are located within the embankment, generally near the downstream shoulder, to collect seepage from within the embankment. There are 16 leachate drains L1 – L16 which are shown in light blue on Figure 18. They discharge into the perimeter manholes that are pumped back to the Water Treatment Plant. Cutoff drains located west of the perimeter drain function to intercept shallow potentially contaminated seepage from the perimeter drain. There are 5 cutoff drains K1 – K5 which are also shown in navy blue in Figure 18. All drains discharge to the collector manhole sumps and are pumped back to the Water Treatment Plant. Collection sumps are located around the perimeter of the embankment and the collected leachate is pumped to the Process Plant or Water Treatment Plant. In addition to the subsurface under drains and leachate drains, Storage 2 has an uphill diversion drain, which diverts clean water from the hills above, north to the Ohinemuri River. FIGURE 19: CLEAN WATER UPHILL DIVERSION DRAIN - NORTH Surface water which lands on the embankments is collected by perimeter drains, which discharge to two collection ponds (West Silt Pond and S1). Water collected in the ponds is monitored and either pumped to the Process Plant or Waste Water Treatment Plant to be treated or discharged clean to the Ohinemuri River or Ruahorehore Stream.
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