B-3 – Area 3 - Assessment of Environmental Effects 28 As is the case for its existing activities OGNZL also propose a consent condition be included which requires it to make an alternative water supply available within 12 hours where the Waikato Regional Council considers the proposed activities are having an adverse effect on any existing stock, domestic or other water supply. 5.5 SETTLEMENT EFFECTS An assessment of potential ground settlement effects from dewatering associated with the Waihi North Project has been prepared by EGL (2022), a copy of which is provided in Part H of these application documents. Managing the settlement effects from mine related dewatering has been undertaken successfully for many years at Waihi where OGNZL operates an extensive network of underground mines. This is achieved by differentiating Waihi into several different settlement zones, each containing an area in which settlements are expected to be similar, and managing dewatering in accordance with a Council certified Dewatering and Settlement Monitoring Plan to ensure differential settlement, or tilt, is within acceptable parameters. For the most part, EGL identifies that in locations north of Waihi East settlement is expected to be in the order of 10 to 100 mm. Depending on the length of the tunnel and the geological structures it passes through, and provided the shallow water table is not affected, additional tilts will be very small. However, EGL (2022) have identified the potential for the Wharekirauponga Access Tunnel decline to potentially dewater the shallow younger volcanics (ignimbrites and tuffs) and cause settlement effects at Boyd Road and eastern end of Barry Road in a manner which could affect dwellings in that area. EGL (2022) identifies several available options for managing this potential effect, including designing the tunnel to avoid the younger volcanics and stay completely within the andesite, or mitigation of groundwater inflows into the tunnel during construction with grouting. The preferred option for managing this effect will be chosen at the detailed design stage and, as it does currently for its Waihi operations, OGNZL will manage this potential effect through its Dewatering and Settlement Monitoring Plan. While no property damage effects are expected OGNZL also proposes conditions of consent which require it to remedy any damage at its cost as soon as practicable and to the reasonable satisfaction of the property owner. 5.6 NOISE EFFECTS An assessment of the actual and potential noise effects as a result of the Waihi North Project is provided in Marshall Day (2022), a copy of which is provided in Part H of these application documents.
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