U:\2021\BM210482_IBo_Waihi_North_Project\Documents\WNP_Freshwater_Report_May_2022\FINAL_Freshwater_Report_FOR DELIVERY_June 2022\FINAL DELIVERED 17 JUNE 2022\WAI-985-000-REP-LC-0007_Rev0_Freshwater_20220621_FINAL.docx • Surface water entering the headwaters of the unnamed tributary to the Ruahorehore stream should be diverted through a diversion channel located to the east of the TSF3 and discharging into the Ruahorehore Stream. • The diversion channel should convey clean surface water only (i.e., uncontaminated by mining activities) from within the forested catchment above TSF3 and surrounding pasture to the Ruahorehore Stream. • The stream gradient may make it difficult to maintain (upstream and downstream) fish passage for general fish species, so the design should allow the passage of migrating eels, and other native fish with climbing abilities, allowing them to access the remaining upstream habitat. • Riparian vegetation should extend to 10 m either side of the channel, where feasible, and must include low-growing species with overhanging cover. It is anticipated that the average riparian width for both sides combined will be 20 m. • It is anticipated that the gradient and engineering requirements of parts of the upper length of the diversion channel will have a low ecological functionality. • The lower reaches of the proposed diversion are anticipated to replicate a fully formed ecologically functional watercourse that is connected to the Ruahorehore Stream proper. • The long-term creation of a wetland to the east of the TSF3 is to be undertaken close in time to the completion of the TSF. This wetland is expected to be 1.2 ha in size and a portion of water within the diversion channel will be directed through the wetland to ensure it has ecological function. 17.4.2 Sediment Entering Waterways The movement of additional sediment from the construction of the TSF3 embankment and haul road could give rise to potential adverse effects on downstream habitats. Sediment can become suspended in stormwater and enter waterways, having the potential for a decline in water quality and the health of downstream aquatic ecosystems. Potential effects include: • Smothering and infilling of the streambed resulting in a loss of habitat for bottom dwelling organisms including periphyton, leading to the potential loss of food availability for fish. • Clogging and covering of the gills of invertebrates and fish reducing efficiency of oxygen uptake. • Modified fish feeding behaviour. • Cessation of interstitial flow which provides oxygenated water to fish eggs and larval fish. • Smothering of aquatic plants resulting in loss of habitat for algae and benthic fauna. • Reduced light penetration and visibility through the water column. Details of staging and sediment management for the TSF3 construction to avoid and otherwise minimise the above potential adverse effects are set out in OGNZL (2021) and accompanying SSESCP. 17.5 Effects of TSF3 on aquatic ecological values As outlined above, a spillway will be developed from the TSF3 to the Ruahorehore Stream as shown in Figure 25. As reported above for the GOP TSF, GHD (2022A) report that here have been no overflows from the currently active TSFs since the mine has been in operation. As
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