OceanaGold Waihi North Project Vibration Performance Assessment Page 32 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 Unlike the vibration data recorded from the monitoring of GOP or the access tunnel that is directly used in the process of assessing compliance against the permissible vibration criteria, the proposed approach for WUG is not to use the measured value from any of the three sensors for compliance but rather use these measured data for the purposes of calculating the vibration level at each of the 12 representative surface assessment locations. These latter values will be used to determine compliance with the permissible vibration criterion specified by the ecologists. Should the extents of the orebody be redefined based upon grade control specifics or other matters that may result in changes to the blasting locations, the representative assessment locations can be adjusted accordingly or supplemented with additional monitoring locations. It is proposed that these specifics be defined in the Vibration Management Plan. At regular intervals, defined as either annually or when the area of mining relocates to another area within the mine, it is proposed that several blasts are monitored on the surface to confirm the accuracy of the predictive algorithm and the reliability of the predicted vibration levels. Should there be any discrepancy that suggests the algorithm should be adjusted, these revised modelling parameters will be incorporated into the predictive model and the previous predictions at each of the assessment locations updated to reflect the adjusted modelling parameters. 16. SUMMARY OF EFFECTS Around 30 years of experience confirms that the vibration associated with blasting for WNP can be designed and managed to meet the 95% compliance limit of 5mm/s for most of the project, or of 15mm/s at WUG. The design and management of such a blasting program requires a high level of attention to all detail relating to the program. The previous 30 years of experience have also shown the proposed vibration limit provides for the mining activity while being largely protective of people’s amenity. The vibration impacts from blasting of the current Waihi orebodies are separated from the effects produced by the GOP or WUG mines because they are separated by more than 1-kilometre. While some of the blasting for the GOP will generate perceptible levels of vibration at a few properties along Heath Road, Boyd Road, and Moore and Clarke Streets, the extent and magnitude of perceptible vibration is similar to other consented underground and open pit Waihi mining. In broad terms, an assessment of WNP has identified: The current vibration environment around Waihi, including the CBD, will remain unchanged from the blasting at the GOP, except for some properties at the eastern end of town where perceptible vibration from some of the blasts will occur. The mining of the GOP changes the existing vibration environment for only a small isolated residential area around Heath Road, Boyd Road, and Moore and Clarke Streets. The location of the GOP virtually eliminates any combined effects from the underground blasting. The envelope of impact for the GOP is estimated as around 50 properties with most of these subjected to only low and marginally perceptible levels of vibration The access tunnel between WUG and the processing plant will result in perceptible levels of vibration for properties near to the alignment and generally around Mataura Road. The scale of blasting for the tunnel will be constrained to some extent by the properties around the Waihi East area. The advance rates for blasting of the tunnel will however ensure that the blasting progresses quickly with perceptible vibration expected to persist for not more than several months. The tunnel is expected to advance at 50 metres per week with potentially the tunnel advancing from both ends which would lead to a faster overall construction period. This could reduce the duration of perceptible impacts for some properties. The blasting for the WUG orebody will have no effect of the amenity of residents given the >5 kilometre separation distance, and will be limited to avoid adverse effects on Archey’s frogs The previous mining at Waihi has shown that compliance with the 5mm/s vibration criterion at the adjacent sensitive receivers requires strict control over the blasting process. Although the vibration effects for WUG are very minor, and for the GOP are controlled to similar or lesser values than from the
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