OceanaGold Waihi North Project Vibration Performance Assessment Page ii 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 EXECUTIVE SUMMARY In Waihi, the modern Martha Mine and underground operations have been operating for over 30 years. OceanaGold has been the owner since 2015. As a result of a major exploration campaign, OceanaGold has identified additional ore deposits that it is now proposing to mine through the proposed Waihi North Project (WNP). This report assesses the blasting-related effects associated with WNP, which encompasses: The Gladstone Open Pit (GOP), a new smaller pit to the west of the OceanaGold Waihi Processing Plant. The Wharekirauponga Underground Mine (WUG) A 6.5 kilometre decline from the mine Surface Facilities Area at Willows Road to the upper levels of the WUG mine A 5 kilometre tunnel linking the WUG to the existing Processing Plant (WUG Access Tunnel) The WNP will allow for mining over an approximate 13-year period, complementing the already consented mines and extending the life of mine of Waihi Site to 2036. The additional works associated with WNP involve developing a tunnel linking the WUG operation and the Processing Plant facility. Although the blasting from this tunnel is expected to produce measurable vibration at some properties near to the alignment, the duration will be short term and, for any affected resident, not expected to be more than several months. The potential effects of developing the WUG Access Tunnel are addressed in this report. The assessment for WNP is the seventh such detailed modelling exercise undertaken since 2002 (Favona, Trio, Correnso, SUPA (Slevin Underground Project Area) and MDDP (Martha Drill Drive Project), Project Martha all preceded the WNP) by Heilig & Partners. The Martha and Extended Martha projects were also mined prior to 2002. The assessments for each of the previous projects were subjected to a detailed review and were found to appropriately predict the vibration effects with enough detail and accuracy to allow grant of consents for those projects. The WNP vibration modelling process and the reliability of the results it produces is fully expected to remain unchanged from those of the previous projects. The recommendations and conclusions for WNP are based upon around 30 years of operational experience of the effects and responses to blast vibration since the start of modern mining in the Martha Open Pit. The proposed consent conditions are intended to ensure that the effects of blasting activities associated with mining remain appropriate. The controls on vibration from blasting at the Waihi mines remain amongst the most rigorous applied to blasting activities internationally. Their basis of protecting amenity necessarily ensures that they are also protective of building integrity which is known to occur at values more than those assigned to personal amenity protection. The proposed conditions for WNP are generally based around the permitted standards in the Operative Hauraki District Plan and the conditions of the existing mines’ resource consents. Because of the location of the underground mine, the additional conditions relating to blasting, such as the averaging, duration and differentiation of blast types that formed the, Favona, Trio, Correnso, SUPA and MDDP consent conditions, are not necessary. In this respect, the proposed vibration conditions will be well aligned with the Hauraki District Council plan objectives of maintaining amenity. The proposed WNP conditions will include: For the GOP, limits measured at the boundary of the nearest non-company owned property or notional boundary of a dwelling on rural land of: Vibration between the hours of 0700 and 1800, Monday to Saturday (excluding public holidays) - 95% of blast events no greater than 5mm/s; Vibration at all other times - 95% of blast events no greater than 1mm/s; and Overpressure - a maximum of 120dBL. For the Wharekirauponga Underground Mine tunnels between the northern boundary of Willows Road Farm and the Processing Plant, vibration limits measured at the nearest non-company owned property of: 95% no greater than 5mm/s between the hours of 0700 and 2000, Monday to Saturday (excluding public holidays); and 95% no greater than 1mm/s at all other times.
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