June 2022 G-01483.84-017-R-Rev0 Because the 50 8.0 WRS ALTERNATIVES AND FUNCTIONAL NEED ASSESSMENT The proposed WRS design and layout was selected following a comprehensive assessment of options. Key considerations were: ▪ Minimize disturbance footprint. ▪ Geotechnical stability and constructability. ▪ Avoid sensitive areas of significant indigenous biodiversity, waterbodies (including wetlands, rivers and streams) and the margins of any waterbody. ▪ Avoid all other areas of indigenous biodiversity, waterbodies and their margins as far as reasonably practicable. ▪ An ability to reinstate the healthy functioning of the site when the WRS is deconstructed and to improve its overall condition ▪ An ability to offset the unavoidable effects on the tributary caused for the time the WRS is in situ ▪ Reduce noise and visibility to public. ▪ Water management, efficient collection of stormwater and seepage for treatment to contain potential acid generation from the tunnel spoil rock. ▪ Adequate capacity to meet development schedule, originally 1,000,000 lcm (later reduced to 850,000 lcm by relocation of spoil with inclusion of 2nd tunnel to Waihi operations). ▪ Tunnel portal location, near the WRS to reduce haulage distance for the placement and rehandle back to underground, cost and carbon reduction. ▪ Land access and ownership. Over ten design versions of the WRS options including dual and single sites, four different portal locations with access, and various water collection pond scenarios were developed and assessed during the study. While these designs attempted to avoid locating in areas that would affect any wetlands, stream margins or habitats of indigenous biodiversity, due to the functional and locational requirements of the WRS (i.e., its overall size and need to be located within close proximity to the mine), it was not practicable to avoid these areas in their entirety. The proposed WRS is sited in a narrow gully (referred by others as Tributary 2 (GHD 2022) approximately 200 m upstream from the confluence with Mataura Stream. Key factors that led to the choice of site include: ▪ Close proximity to the WUG portal. ▪ Location furthest from the public roads and properties, with the WRS sited in a natural depression that would lead to least visual amenity and landscape effects. ▪ The low value of the tributary; the WRS was located above an existing farm access track, in an active grazing area, avoiding the higher ecological value of the lower reach and Mataura Stream. ▪ Gradient and shape of the natural depression that allows effects to be effectively and efficiently managed. ▪ Avoids surveyed wetland areas and areas of high value flora and fauna.
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