60 Boffa Miskell Ltd | Waihi North Project | Terrestrial Ecology Values and Effects of the WUG | 22 June 2022 6.4.4 Continuous Noise from Ventilation Raise - Effects on Fauna Noise associated with the operation of the ventilation raises is described in the Noise Assessment (Marshall Day, 2021). The source of noise from the ventilation raises are the fans located at the base of the raise within the underground mine. Predictions of fan noise were found to be only above ambient noise levels (around 40 – 45 dB LAeq (15 min)) in very close proximity to the vent raise at the orebody (Figure 11). We understand that the calculated sound power levels were based on measurements of sound from existing underground mine vent shafts at Union Hill, adjusted for location, changes in duty and vent raise geometry. We rely on the Marshall Day Noise Assessment (2021) in our discussion below. Natural noise sources in the forest include high winds, swaying trees, heavy rainfall, and thunderstorms, and as such, animals within the forest are adapted to episodically high noise levels. However, noise from the fans would be continuous and as a worst-case scenario could result in heightened stress, avoidance behaviours, reduced/failed reproductivity for fauna species, and masking vocal communications and other sounds of interest (e.g. predator noise). The ability to move away from these stressors varies between species and factors like mobility, habitat requirements, exposure to predators and reproductive state may impact their ability to move. Literature examining the impact of human-induced noise on New Zealand fauna is very limited, and where available, is described in Section 6.2. Any potential effects on fauna are most likely frequency37 and amplitude38 dependent, and species specific39. The predicted noise levels of 40 – 45 dB LAeq (15 min) are consistent with moderate rainfall levels (i.e. ~50 dBL). At the predicted levels, the noise profile would likely dissipate rapidly across the environmental landscape (i.e. the primary impact area would be very localised). Invertebrate Populations The magnitude of effect of noise generated by ventilation fans on invertebrates within the Project site and surrounding area is Low. This assessment takes into account that the change from baseline noise levels is potentially a minor increase in a small area around the vent shaft. Although many species communicate by sound, they are likely to have a behavioural response to either avoid or compensate for increased, continuous, background noise. The ecological value of the invertebrate communities is High and the level of effect of noise is Low. Frog Populations The magnitude of effect of noise associated with ventilation fans on frogs within the Project site and surrounding area is Negligible given the low sensitivity of frogs to noise, and the small change expected to the existing noise environment. The ecological value of the frog communities is High and the level of effect of noise is Low. Lizard Populations The magnitude of effect of noise associated with ventilation fans on lizards is Low given the apparently very low density of lizards in the Project Area and the ability of lizards to move away from disturbance. As noted in Section 6.2.4 and 6.4.3 lizards may acclimatise to continuous 37 The frequency of a sound wave is perceived as its pitch or tone. 38 Amplitude is the height of the sound wave from peak to valley. Amplitude determines the loudness or intensity of the sound. 39 Factors that may impact an animals’ response to noise include the threat-response characteristics of the species (e.g. ‘freeze’ behaviour), previous exposure of the individual, life cycle stage and habitat features (Harbrow et. al. 2011).
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