9 Muriwai Downs: assessment of potential ecological effects Project 2042 Table 2. Potential adverse effects on ecological values and an assessment of level of ecological effect. Activity Potential adverse effect (unmanaged) Avoidance/ Mitigation proposed Magnitude of effect after management (Table 8 EIANZ) Level of effect (Table 10 EIANZ) Vibration (episodic) - caused by blasting associated with the construction and operation of the WUG Blasting may generate perceptible levels of vibration at the surface. Potential adverse effects include disruption of male Archey’s frogs during the breeding season (e.g. clutch abandonment), movement of individuals away from territories, and increased vulnerability to introduced predators. Potential loss of significant recruitment if effects persist or repeat over several years. Duration of potential effects may be up to 10 years over parts of the site (i.e. less than the expected reproductive lifespan for mature Archey’s frogs). Modelling of vibration at WKP site by OGNZL based on Golden Cross vibration effects on Hochstetter’s frogs and Archey’s frogs, and persistence of Archey’s frogs from roadside monitoring, indicates that surface vibration levels above those known from other locations where Archey’s frogs persist with anthropogenic vibration will affect around 315 ha of WUG. That area is estimated to support around 290,000 Archey’s frogs (between 0.53 % and 0.58 % of total estimated Coromandel population). The number and distribution of vibration events that are above the level measured at other Archey’s frog sites (i.e. above 2 mm / sec) comprises a mix of vibration levels spaced over time (for example in areas subject to the highest vibration years, blasts that generate a level of vibration above 2 mm /sec can comprise up to 78 % of the total blasts; however total number of such events would be around 3-4 events per day, each of around 10-12 seconds in duration, with a total time of such events around 30-50 seconds per day. 1. Reduce blast package size to smallest practicable level. 2. Undertake best practice pest control over 314 ha where any measurable vibration may be expressed on the surface, to a level designed to promote Archey’s frog population recovery. Low (or nil if pest control increases frog population over existing premine levels). Low (or netbenefit if pest control increases frog population over existing pre-mine level). Vent shaft – design Discharge vent stack x 4. Discharge vent stack design has a 10 m x 10 m footprint. 1. Install Animex exclusion fence around vent shafts. 2. Choose only sites with no recorded frogs. 3. Salvage/ relocate frogs if found during construction. Negligible Very Low
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