OceanaGold Waihi North Project Vibration Performance Assessment Page 12 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 6.3. Heritage Structures The proposed approach for structures that are identified as heritage is to assess the heritage elements that are near to the intended blast area and determine the condition of this infrastructure. Any infrastructure that is modelled to receive less than 2mm/s from the blasting will be ignored in the assessment as the additional stress resulting from vibration of 2mm/s would be inconsequential with respect to affecting the integrity of the structure. The induced stress from vibration that generates 2mm/s would be exceeded by naturally occurring mechanisms, like temperature, rainfall and humidity variations. Any condition assessment will identify whether the infrastructure is sound and in a generally good condition, or poor condition where small level of vibration could result in further damage to some of the elements. The condition assessment will subsequently determine whether there should be reduction to the base level specified in the British Standard BS7385 tables. The British Standard identifies that heritage elements should not be distinguished from other structures by applying a lower permissible level of vibration, but rather they should be assessed individually and an appropriate vibration level applied based upon their condition. Some heritage infrastructure is well constructed and not impacted by vibration. The equivalent vibration level for sound infrastructure is therefore the starting position for establishing the vibration level. This vibration level is subsequently adjusted according to the condition of the heritage elements. The British Standard BS7385-2:1993 indicates limits of vibration for prevention of minor damage as follows: Type of Building Peak component particle velocity in frequency range of predominant pulse 4Hz to 15Hz 15 Hz and above Reinforced or framed structures. Industrial and heavy commercial buildings 50mm/s at 4 Hz and above Un-reinforced or light framed structure. Residential or light commercial type buildings 15mm/s at 4 Hz increasing to 20mm/s at 15Hz 20mm/s at 15 Hz increasing to 50mm/s at 40 Hz and above Table 1 - Transient vibration guide values for cosmetic damage (reproduced from BS7385-2:1993) It is proposed that a baseline value of 25mm/s is applied as a screening vibration criterion for the adjacent heritage infrastructure. It should also be noted that vibration levels more than the 25mm/s criterion may be equally applicable providing the frequency content of the vibration pulse is higher. Whilst the above approach is appropriate for assessing building elements, like the Royal Standard Battery, other heritage places like water races, walking tracks, tramways, small dams or any other geological features would not be similarly assessed as they are not expected to require a vibration criterion for their protection. The condition of the 14 metre length tunnel that forms part of the Wharekirauponga walking track is unknown although the integrity of the tunnel as a whole is expected to be sound given it is understood that it is part of a publicly accessible walking trail. Whilst there could be some isolated sections of the tunnel that may have deteriorated and could continue to worsen over time and may require some mitigation plan, the results of the blasting model and a site investigation will confirm whether the vibration will impact upon the overall tunnel integrity. 7. TYPE AND SCALE OF BLASTING The blasting that is sought under this consent for WNP addresses the GOP and WUG production and development as well as the Willows and Plant Access Tunnels.
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