10 Memorandum : Vibration effects on amphibians (Leiopelmatid frogs) 64524 Vibration effects_memorandum (15 June 2022)_Final Rev 0 overlaid with Hochstetter’s frogs recorded during the operating life of the mines to determine influence of vibration on frog populations. At the frog location most affected by blast vibration (‘Location 1’), 41– 50 frogs were subjected to amplitude values of approximately 4–10 mm/s over the life of the mines. However, the vibration magnitude distribution curves indicated that while ‘Location 1’ may have experienced one blast that caused a vibration up to 10 mm/s, such magnitude of vibration was not typically generated. Indeed, most often (500 times), blasts generated vibration in the 1–1.5 mm/s range, with the vast majority of all blasts generating vibration no greater than about 4 mm/s (Heilig & Partners, 2020). Since Archey’s frog was known to occur in the vicinity of the mine and indeed, occurred within the modelled 2 mm/s vibration contour, it is safe to assume that Archey’s frog populations were subjected to amplitudes values of at least 2 mm/s during the life of the mines. Overall, the data from the long-term study on Hochstetter’s frog and the confirmed presence of both Hochstetter’s and Archey’s frog at the site (same locations) post-mine closure, suggests that both species of frogs did persist under the influence of these mining activities and did not appear to disperse away or perish from areas subject to mining vibration (2–4 mm/s) stimuli. Furthermore, the Hochstetter’s frog monitoring data provided no evidence for even temporal effects (e.g., local population declines, avoidance, or dispersal behaviours) on Hochstetter’s frog populations in the immediate vicinity of the mining operations. 2) Frog presence at sites subject to roadside vibration Due to the paucity of sites to accurately measure mining vibration effects against leiopelmatid frog presence/ abundance, surface vibrations at a selection of roadside sites where leiopelmatid frogs (either Archey’s frog or Hochstetter’s frog) are known to occur were explored. The objective of the investigation was to determine the level of surface vibration experienced by frogs due to road traffic, with road traffic vibration considered as a proxy for the potential impacts of mine-generated vibration stimuli. Heilig & Partners (2021) justified the direct comparison between road vibration and mining vibration by commenting that as long as there is consistency between vibration parameters (amplitude, frequency, duration, and frequency of occurrence) in studies comparing vibration data from various sources, then the vibration could be considered consistent and the impacts interchangeable (i.e., vibration from traffic sources could be like that from the proposed future mine blasting). A tri-axial geophone (vibration sensor) was installed at four roadside sites in the Coromandel Ranges (309 Road, Kopu-Hikuai, Tapu-Coroglen, and Kennedy Bay Roads) and one site in the Brynderwyn Ranges (SH1) in late September 2021 and early February 2022, respectively (Heilig & Partners, 2021; OceanaGold, 2022). At the Coromandel sites, geophones were placed between 1.8–5 m from the edge of the carriageway (i.e., the solid white line on the outer edge of the road) and maximum vibration amplitude values of 0.8–1.9 mm/s were recorded during daylight hours (Heilig & Partners, 2021). In the Brynderwyn Ranges, the geophones were placed between 0.5–5.6 m from the edge of the carriageway and maximum vibration amplitude values of 0.71–2.14 mm/s were recorded during daylight hours (OceanaGold, 2022). Archey’s frogs have historically been reported at 10 m or greater from the road edge (DOC Herpetofauna database, accessed April 2022), but more recent surveys of Coromandel sites recorded frogs at 4 m from the road edge (Boffa Miskell, unpub. data) and Hochstetter’s frogs were recorded 10 m from road edge
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