EGL Ref: 9049 23 June 2022 Page 3 File: WAI-985-000-REP-LC-0050-Rev0.docx This report shall only be read in its entirety. 1.3. Consented ground settlement effects This report extends the assessment of potential ground settlement effects due to ground dewatering for the current as-built and Life of Mine Plan (LoMP) for the open pit and underground mines already consented, which includes: • Existing Martha Open Pit (MOP) (Ref. 2, 4, 10) • Favona Underground (Ref. 3, 11, 12) • Trio Underground (Ref. 5, 13, 14) • Correnso Underground (including Slevin Underground) (Ref. 6, 15, 16) • Martha Underground (MUG) (Ref. 7, 17, 18, 20) • Martha Open Pit – Phase 4 (MOP4) (Ref. 7, 17, 18 , 20) The last project consented was Project Martha (MUG and MOP4). The settlement prediction approaches applied in these past assessments have provided estimates which have been on a similar magnitude as the measured ground settlements effects. Where there has been a difference between predictions and measured ground settlement effects, this has been explained within this report (see Section 5.3). The elements and effects of the WNP interact with the existing as-built and consented projects. 1.4. Dewatering and settlement monitoring plan and annual reporting As a requirement of the existing consents, a dewatering and settlement monitoring plan has been prepared by OGNZL (Ref. 8). This outlines the monitoring of groundwater and settlement and process in the event of unusual ground movement. This plan is certified by Waikato Regional Council and Hauraki District Council. This plan will be updated for the WNP. As a requirement of the consent conditions, an annual dewatering and settlement report is prepared (Ref. 9). This reviews the six-monthly ground settlement survey data and the groundwater monitoring records. The monitored dewatering and settlement effects of the WNP will be included in this report annually. 1.5. Assessment limitations and management of risks This assessment considers ground settlement effects (settlement and tilt) caused by ground dewatering resulting in direct consolidation of soil and rock materials. Other causes of potential ground settlement from the WNP are assumed to be less than minor or to have been assessed by others. This assessment assumes that OGNZL undertakes best practice mining methods that minimises any other potential ground settlement effects. The extent of works covers a large area and the inferred ground conditions are based on a limited number of ground investigations. Unforeseen ground conditions can be expected. Uncertainty and risk around unforeseen ground conditions can be partially reduced by undertaking further ground investigations; however, risk will always remain and this risk will be managed by OGNZL.
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