EGL Ref: 9049 23 June 2022 Page 18 File: WAI-985-000-REP-LC-0050-Rev0.docx This report shall only be read in its entirety. 4.5.6. Ventilation shafts GWS (Ref. 41) assessed the potential for groundwater drawdown with distance from the ventilation shafts (at Willows Road and WUG) for the purposed of making a general assessment of ground settlement. The assessment assumes drawdown for 40 days until the ventilation shafts can be lined (with sprayed concrete). Estimated drawdown of the groundwater at the vent shafts ranged from 40 to 70 mbgl. 5.0 GROUND SETTLEMENT MEASUREMENTS AND PREDICTIONS 5.1. Settlement effects 1989 to 2021 Ground settlement measurements have been made around the Martha Open Pit and throughout Waihi since 1989. Six monthly surveys have been undertaken as required by condition 11 of the Mining Licence, condition 9 of Water Permit 971286 and conditions 5 to 7 of resource consent 124860. The locations of the settlement markers where settlement measurements are made are shown in Figure 47 to Figure 50. Land Use Consent (No.97/98-015, Condition 3.30g) granted in 1999 refers to Figure 8 of the evidence presented by Dr R. Semple to the Environment Court in 1998 (Ref. 2). Seven zones (Zones 1 to 7) are identified in Figure 8 of this evidence and a copy of this figure is attached (refer to Figure 50 in this report). The seven zones are intended to represent areas of different magnitude of settlement. The zone boundaries were based on settlement monitoring up to 1997, site geology and distance from the pit. Generally, settlements within the different zones have been relatively consistent. However, there are some settlement markers that do not fit with the zones they are currently associated with. In 2018, EGL reviewed and updated the zonation for Project Martha taking into consideration of the monitoring data since 1997. This is shown in Figure 51. The monitoring data show that some of the settlement markers indicate greater settlements than their zone category. These are noted in the annual dewatering and settlement report. The latest figure noting these locations is included in this report in Figure 52. The results of settlement monitoring for Zones 1 to 7 are presented in Figure 53 to Figure 61. The settlement data indicate general trends, either showing gradual slow settlement over time or more notable response to specific stages of groundwater drawdown. Figure 47 to Figure 49 show that generally, settlements decrease with distance from Martha Pit, except for the area of Favona Underground. Settlements are greatest near the perimeter of the pit on its east side where the younger volcanic are deeper. Settlements in this area (Zone 7) are currently up to approximately 300 mm (Figure 61). Settlement reduces away from the pit, however there is still recorded settlement greater than 20 mm up to 2.9 km from the pit indicating the depressurisation has some slight influence in the deep andesite for a notable distance. This slight depressurisation at depth is of no material effect. Comparison of settlements with groundwater levels indicates that with ongoing dewatering, settlement has continued. The settlement typically follows a general trend
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