Boffa Miskell Ltd | Waihi North Project | Terrestrial Ecology Values and Effects of the WUG | 22 June 2022 67 the surface and potential disturbance to fauna within Coromandel Forest Park. Blast designs were modelled using different explosive weights and packing options based on location. To aid in interpreting the vibration modelling, Helig & Partners have generated a series of vibration contours to demonstrate what level of vibration will be experienced on the surface (Figure 12). The contours indicate the maximum level of vibration that could be expected within each year, irrespective of the source of blasting (i.e. not all of the area within each contour will experience blast vibrations at that level each time there is a blast). Histograms are also provided, indicating the expected number of blast events per year within each of the contours. Key vibration parameters include: • Amplitude varies with distance from the blast and with size of explosive weight. • Frequency of vibration refers to the number of cycles per second. For the WUG, frequency varies with distance from the blast, but frequencies between 30 -60 Hz are expected. • Duration of the production blast events is expected to be approximately 5 seconds. To generate the total duration of blasts within each year, the number of blast events is multiplied by 5 seconds (e.g. in Year 5, total blast duration generating vibrations of >2 mm/s is less than 39 minutes). • Frequency of occurrence unlikely to exceed 3 or 4 times per day, or 10 – 15 times per week. This analysis was used to inform our assessment. We consider that vibrations are likely to be felt more strongly by ground-dwelling species, particularly those that burrow into root crevices and refuges like Archey’s frogs (and to a lesser extent, Hochstetter’s frogs44), invertebrates and lizards. Measurable vibrations may be expressed on the surface over an area of approximately 314 ha. Vibration greater than >2 mm/s (above which there is a low, but unknown likelihood of impacts on native frogs) will be experienced at some time during the life of the mine, as it is currently designed, over an area of 314 ha. 44 Hochstetter’s frogs in WKP have only been recorded around stream margins, although it is possible that they are present in the forest itself in the same areas as Archey’s frogs. Therefore, our assessment of the level of effect on Archey’s frogs also applies to Hochstetter’s frogs.
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