EGL Ref: 9215 23 June 2022 Page 35 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. redistribution of stress with raising of the embankment. Generally, for Storage 2 the vectors show small displacement, and the direction of movement is downslope. For Storage 1A most of the vectors are within the accuracy of the survey (15 mm) and show little movement. FIGURE 29: DEFORMATION MONITORING VECTOR PLOTS. LESS THAN 15MM IS SHOWN AS ZERO (AS THIS IS THE ACCURACY OF THE SURVEY) 4.9.5. Surface water diversion and collection ponds Surface water from above Storage 2 and Storage 1A is diverted away by uphill diversion drains. The Northern Uphill Diversion Drain diverts water from above Storage 2 and part of Storage 1A to the north. The Southern Uphill Diversion Drain diverts water from the other part above Storage 1A to the east. These drains are shown in Figure 30. Surface water which lands on the embankments is collected by perimeter drains, which discharge to three collection ponds around Storage 2 (Northern, West Silt Pond and S1), and three ponds around Storage 1A (S3, S4, and S5). The locations of the perimeter drains and collection ponds are shown in Figure 30. The perimeter drains and collection ponds are constructed from low permeability fill with HDPE geomembrane liners up to a certain level to prevent seepage losses to the ground water. Water collected in the collection ponds is monitored and either pumped to the Process Plant for reuse, to the Waste Water Treatment Plant to be treated and discharged to the Ohinemuri River, or discharged directly from the collection ponds to the Ohinemuri River or Ruahorehore Stream if it meets acceptable water quality standards.
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