OceanaGold Waihi North Project Vibration Performance Assessment Page 22 of 41 Project Number: HP2006-2 Heilig & Partners Save Date: 21/06/2022 5:55:00 PM ABN 56 082 976 714 File Name: WAI-985-000-REP-LC-0018_Rev 0 is approximately 6.5 kilometres. The tunnel dimensions are approximately 6.5 metres in height with a 5 metre width. The location of the tunnel is as per the description in Figure 3. The possible effects in terms of vibration from blasting have been assessed for blasting with a 6 kilogram explosive weight. This corresponds to a 51mm diameter blasthole drilled over 3.6 metres and loaded with an explosive density of 0.95g/cm3. The separation between the decline and the existing surface level varies because of the terrain. Around the midpoint of the decline, the existing surface level is higher than RL440 which leads to a separation distance to the crown of the decline of more than 250 metres. Aside from near the portal, the minimum separation distance is around 140 metres. The modelling indicates there is a small section above the tunnel portal where vibration levels increase to 5mm/s. Other areas of the decline are modelled to induce low vibration, less than 2mm/s. There is a small section of development higher within the orebody where levels exceed 5mm/s because of higher elevations and reduced separation to surface. The modelling results are presented in Appendix B. There are no areas of the decline where drilling and blasting will produce levels of vibration at the nearest properties that would be perceptible to the residents. The separation distance reduces vibration from the decline blasting to immeasurable levels at these properties. No areas of the decline north of the Willows Road farm will produce levels of vibration above 1mm/s. 11.3. WUG Access Tunnel The transportation of ore from WUG includes the WUG Access Tunnel running from the existing Processing Plant at Baxter Road to join with the dual tunnel and willows access tunnel. The engineering assessment has considered several alignments for the tunnel. The results are shown in the attached plate in Appendix C with the vibration contours representing the expected maximum level of vibration for the planned tunnel alignment. The assessment indicates: The depth of the tunnel below the surface in the area around the eastern end of Mataura Road that are around 870 metres from the Processing Plant tunnel portal is approximately 120 metres When coupled with the horizontal offset to the properties to the west of the tunnel alignment, the separation distances increase to around 140 metres. The level of vibration from development blasting will be perceptible to residents at the eastern end of Mataura Road for blasting potentially 350 metres either side of the point of blasting closest to these Mataura Road properties Blasting with a 51mm diameter blasthole drilled over 3.6 metres is modelled to be borderline compliant with the 5mm/s criterion at these same properties There are other properties above the alignment where adjustments to blasting practices will also be required Blasting is expected to progress with two rounds per day producing an advance rate of around 50 metres per week. The vibration levels will increase as the tunnel approaches a property, reach a maximum value when the development is at the closest point and the decrease as the tunnel moves away from the property. The maximum duration of perceptible vibration may exist for around 7 weeks before and 7 weeks after the closest point to the property. This occurs for those properties directly above the tunnel alignment. For properties that are offset horizontally from the tunnel alignment. The duration will reduce from these values. 11.4. Wharekirauponga Underground Mine The WUG operation is planned to include production blasting over a range of depths, including both cut and fill mining and conventional stoping in the deeper sections. The variable mining methods are
RkJQdWJsaXNoZXIy MjE2NDg3