EGL Ref: 9215 23 June 2022 Page 36 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. FIGURE 30: SURFACE WATER DRAINS, COLLECTION PONDS AND SILT PONDS 5.0 FAILURE OF TAILINGS STORAGE FACILITIES COMPARED TO WAIHI TSFS It is estimated that there are at least 18,000 TSFs globally. The NZDSG include recommendations for tailings dams and cover design, construction, and operation. The NZDSG include governance, dam safety of operating dams and requirements for independent review of design and ongoing operations. The NZDSG are rigorous and represent current best international practice. Unfortunately, some TSFs in other countries have failed due to the nature of their design, construction, and poor governance and dam safety practices during operation. Many of the failures are related to large tailings dams constructed by the upstream construction method which often involves the dams being constructed of actual tailings. Upstream construction is not used at the Waihi Operation and the downstream constructed embankments are constructed of earth and rockfill from Martha Open Pit. The upstream construction method is often chosen as it is efficient economically or there is no readily available source of earth or rockfill (e.g., underground mining operations that do not have large quantities of overburden that are associated with open pits). Most upstream West Silt Pond S1 Silt Pond
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