EGL Ref: 9049 23 June 2022 Page 32 File: WAI-985-000-REP-LC-0050-Rev0.docx This report shall only be read in its entirety. o The additional settlements from the Wharekirauponga Access Tunnel east of Waihi East (Figure 2) are expected to be in the order of 10 to 100 mm, depending on the geological structures it passes through. The tunnel east of Waihi East is to be located at depth in andesite rock and the shallow water table in the younger volcanics is not expected to be materially affected. Therefore, any additional tilts in this area will be very small (see Section 6.1.4) and the residential dwellings in this area will not be damaged. Additional settlement and groundwater monitoring is required in this area to confirm settlement effects are as expected. o The settlements from the Willows Access Tunnel and Wharekirauponga Dual Tunnel (Figure 1) out to WUG are expected to be in the order of 10 to 100 mm depending on the geological structures. The tunnel is to be located at depth in andesite rock. There are no structures near to the Willows Access Tunnel and Wharekirauponga Dual Tunnel which could be affected (see Section 6.1.5). o Settlements around the ventilation shafts (Figure 1) are expected to be in the order of 50 to 300 mm. These settlements would have no adverse effects on the farmland (Willows Ventilation Shaft) and forest area (WUG Ventilation Shafts) in which they would be located (see Section 6.1.6). o Ground settlements at the WUG site (Figure 1) are expected to be unnoticeable as any change in level will occur gradually over hundreds of metres resulting in small tilts or change in grade. This is because the settlement will be caused by dewatering generally at notable depth below the ground surface. In the middle of the settlement area, the settlements are estimated to reach up to 300 mm to 1,000 mm depending on the ground profile. Due to the hilly terrain at the WUG site, surface settlements of this magnitude are not expected to have any material effects on stream flows as the change in grade is notably less than the steepness of the terrain. As the tilt of the ground will be small, no noticeable impact on the forest environment is expected (see Section 6.1.7). MUG Decline development mitigations and recommendations • The MUG Decline could potentially dewater the shallow younger volcanics (ignimbrites and tuffs) and cause settlement effects in Moore Street, Boyd Road and Barry Road. EGL recommends that OGNZL mitigate this risk through: o Detailed assessment of the MUG Decline alignment. ▪ Avoidance of the younger volcanics may be possible through refinement of the decline alignment and level so to stay completely within the andesite. ▪ Avoidance of historic workings may be possible. o Specific geotechnical and groundwater investigations to assist in determining the ground conditions and groundwater profile between the decline and closest properties. Such investigations can be undertaken on OGNZL property.
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