Boffa Miskell Ltd | Waihi North Project | Terrestrial Ecology Values and Effects of the WUG | 22 June 2022 5 2.3 Wharekirauponga Project Activities The WUG Project Area has two components: the portal entrance and associated surface infrastructure located on the OGNZL landholding currently in use as a farm (Willows Road Farm); and up to four discrete sites within the Wharekirauponga Stream catchment within CFP where the vent raises and egress shaft will be located. Willows Road Farm to WUG Portal Background The Willows Road Farm comprises 197 ha of primarily pastoral land located approximately 5 kilometres north of the Waihi township. The Project Area is accessed from SH25 at the foothills of the Coromandel Ranges. Surface infrastructure will include workshops, administrative buildings and materials / chemicals storage areas, private roads, a helipad, an explosives magazine, sumps / ponds for general surface water and mine water collection, carparking, a tunnel portal and ventilation raise, a rock storage pad (approximately 5 ha), topsoil stockpiles (2 – 3 ha) and holding ponds1 (Figure 2). The surface infrastructure footprint comprises approximately 18 ha of farmland (approximately 9.1 % of total). Once mining is complete, all surface infrastructure will be removed, and footprint areas will be rehabilitated with stored topsoil. The land will be returned to arable farming land. Rock Stack The design of the rock stack incorporates dish drains around the stockpile which separate catchment water from rock stack contact water. Springs within the catchment of Tributary 2 will be capped and the water piped beneath the rock stack and delivered to Tributary 1 below the rock stack. . Catchment water will be directed back to the Mataura Stream. During the mining operation all rock stored on the rock stack will be returned underground as backfill. Once this occurs, the overburden will be removed and Tributary 2 will be rehabilitated and returned largely to its original configuration, with improved riparian areas and stock exclusion fencing to protect the waterway. Services Trench A buried Services Trench connecting the Willows Road Farm to the existing Processing Plant will carry electricity, fibre optic cables and treated / potable and recycled water. A materials handling portal will be located near the Processing Plant in Waihi (the WUG Portal) which will be used to transport ore out of the mine and rock back to the mine for stope backfilling. Services Trench construction will be standard cut and cover trenching by a small excavator. Some drilling may be required beneath SH25 but it is that this can be completed through standard trenching methods. Tunnel development The method of tunnel development for the Willows Access Tunnel, the Dual Access Tunnel and the Wharekirauponga Access Tunnel is by drill and blast, which has practical advantages for the project. The impacts of drilling and blasting and their associated dust, noise and vibrations for the Dual Access Tunnel and Willows Access Tunnel are assessed in this report. Tunnelling speed will be approximately 10 meters per day. The Wharekirauponga Access Tunnel is a single decline tunnel that connects Willows Road Farm to the Processing Plant in Waihi and is not discussed here. 1 The pads will be lined with a low-permeable base and include provision for drainage and collection of runoff water into sediment (or collection) ponds. The holding ponds for each rock stack will have a capacity of approximately 9000m³, designed to contain a 1 in 100 storm event and include a sump and pumping station. Contact water collected in the pond will be pumped to the existing Waihi Processing Plant for treatment and disposal.
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