EGL Ref: 9215 23 June 2022 Page 27 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. FIGURE 20: PERIMETER DRAIN BESIDE PERIMETER ROAD SOUTHEAST SIDE OF STORAGE 2. Construction to RL152 was mostly undertaken by DML Resources. Construction to RL156 was undertaken by McMahon Contractors Ltd. Earthworks QA/QC was initially undertaken by Waihi Gold staff. Since November 1998 it has been undertaken by an independent testing agency (Geotechnics). During construction EGL undertakes regular site visits and provides technical assistance to mine staff who are responsible for supervising construction. Storage 2 is consented to be raised to RL160.7 with a modified centreline lift of 4.7m. 4.5. Storage 1A design and construction Storage 1A was design by EGL and it was commissioned in May 2001. Since then, virtually all tailings associated with the Martha Mine have been deposited into Storage 1A and it was raised progressively to RL172 by April 2016.Raising of the crest stopped from 2017 to 2020. In 2021 and 2022 it was progressively raised to RL174.8 . Storage 1A is designed using the same zoned embankment design philosophy as Storage 2 and is approximately 78m high. A typical cross-sectional profile is shown in Figure 21. Storage 1A bulk fill is predominantly to Zone D2 specification and only has small proportions of the weaker Zone D3 bulk fill material compared to Storage 2. Storage 1A was initially designed with a crest at RL166, however, over time, with changes in the mining schedule, the profile has been adjusted, to reduce the fill profile and then finally to maximise storage capacity. Storage capacity has been increased by steepening the upstream and downstream slopes. The current consented design has the crest at RL177.25. The upstream shoulders vary from 1V:2H to 1V:1.5H. The downstream shoulder inter-berm slopes vary from about 1V:4H below RL120 to 1V:2.78H above RL140.
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