Boffa Miskell Ltd | Waihi North Project | Landscape and Visual Effects | 17 A temporary Willows Rock Stack (WRS) of approximately 5 ha. and with a total capacity for storage of up to 900,000 m3 of rock is proposed. This rock stack will be constructed in 10 metre lifts, to a maximum height of 20 metres above natural ground. The rock stack has been located to integrate within the existing topography and minimise visibility from off-site locations. Implementation of the WRS is expected to occur in the first 5 years of operation associated with tunnelling. This is expected to be gradually returned until the completion of the project in approximately 15 years. At completion, all stockpiles will be removed and the underlying land rehabilitated. Collection Ponds A collection pond with a volume of 19,000m3 will be constructed to intercept run-off and seepage from the Willows Rock Stack. The collection pond will be formed as an earth dam located between unnamed tributaries 1 and 2. The run-off and seepage collected in the collection pond will be pumped in a dedicated pipeline offsite to the existing Waihi Water Treatment Plant for processing and discharge. Several other small retention ponds will be constructed across the site to intercept run-off water from sources other than the Willows Rock Stack to allow solids to settle prior to discharge to Mataura Stream. These ponds will be designed to accommodate silt removal as required. Silt from collection ponds will be periodically removed, allowed to dewater and placed on the Willows Rock Stack. Site Access Roads An internal access road off Willows Road into the Willows Road site will be constructed, with spur connections to main site infrastructure, including the first aid room/gatehouse, office/change house, workshop and private carpark. These roads will be sealed for the main trafficked section, with the balance constructed of gravel to provide a 6 m running width and provision for drainage. An 8-m wide haul road constructed of rock base with crushed rock surfacing will run from the portal to the rock storage pads, with a connection to the workshop and wash pad. The magazine will be accessed via upgrading an existing farm track to a width of 6 m. Power and Communications Three phase power will be brought to site via separate cables supplied from the new Waihi mine substation located near the existing Processing Plant. This line will be buried in a trench on OGNZL land and then on the SH25 and Willows Road corridors to reach the mine substation with no landscape or visual effects. A single overhead power and communications line will be installed at Willows Road to supply power and service security at the magazine site. A small ~80 kVa generator will be located on site to power vital communication and control infrastructure only in the event of power outages. No other back-up generation will be located on site. Water Supply Sources of water within the Willows Road site will include recycled tunnel ingress water and a water supply line from the existing Processing Plant. Explosives Magazines A series of explosives magazines which conform to New Zealand hazardous substances regulations will be located on the saddle to the south of the WRS. This will be accessed via an upgrade to an existing farm access which approaches this saddle from the south. Ventilation Fan Two 250 kW ventilation fans will be installed at the portal entrance in an insulated shipping container for noise mitigation. These fans will be relocated underground and integrated into the
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