OceanaGold Waihi North Project Vibration Performance Assessment Page 20 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 9, including the variable geology, water saturation, and structural features. Table 5 lists the vibration relationships that were applied for each of the projects during the assessment and hearing phase of the project. The third column in the same table shows the relationship which has been subsequently derived from the measured data and the fourth column shows the difference between the predicted and measured results. Project Predicted 95 percentile equation Calculated 95 percentile equation from recorded data Difference Martha Open Pit = 2720� √ �−1.49 = 3130� √ �−1.49 15% greater Favona Underground = 3500� √ �−1.49 = 4540� √ �−1.49 29% greater Trio Underground = 2230� √ �−1.49 = 2160� √ �−1.49 3% less Correnso Underground = 2230� √ �−1.49 = 1920� √ �−1.49 13% less Table 5 - Comparison between predicted and actual vibration results from Waihi projects A comparison of the predicted and expected relationships show good agreement, typically within 15%. The results showing increased variability are typically associated with unfavourable rock mass conditions. Improved practices, better accuracy in terms of the delivery of explosive quantities and an improved understanding by the underground workers of the critical nature of blasting compliance has contributed to the reduced variability in the vibration levels from the Correnso operation when compared to the initial stages of mining the Favona orebody. It is expected that the accuracy of the predictions for WNP will be like the recently completed projects, that is, within 5 to 15%. 10. ASSESSMENT APPROACH The impacts of blasting in each of the two mines and two accesses have been assessed. This includes determining the maximum extents of the vibration by showing a series of vibration contours of varying levels between 2 and 20mm/s increments. These contours consider the maximum permissible scale of the blasting and the rate of vibration attenuation specific to the particular blast area. The contours present the maximum extent of vibration over the full mine life. Importantly, properties will not receive the same level of vibration designated by the contour level for each and every blast. As an example, when blasting in the southern section of the GOP, residents along Boyd Road and Moore Street are not expected to receive perceptible vibration. The vibration contours also represent the maximum extent of vibration, but not the most frequently experienced or average level of vibration. The expected vibration levels are based upon the maximum explosive weight. There are likely to be situations where OGNZL chooses to use alternative mining designs which result in a lower explosive weight, such as a reduced bench height or smaller sub-level interval. 11. RESULTS OF THE VIBRATION ASSESSMENT Modelling results are given as a series of vibration contours for each of the different mining areas. The plates in Appendix A to D show the expected vibration contours for the planned GOP and WUG operations respectively. The contours are shown based upon the complete mining schedule and the relevance may vary according to the planned mining areas within the year, including the depth of the operation.
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