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 Ecological Compensation Ratio (ECR) of 2.9 to the loss of 390 m of stream length (150 m2 of stream surface area) providing for just under 1,150 length (600 m2 of stream surface area). We have recommended that this offset be applied to tributary 3 (Figure 21). Lower catchment flows within tributary 2 will be maintained from surface water collection and discharge downstream. Prior to any offset occurring, the effects on stream ecological values of the unnamed tributary are Low. With the maintenance of flows downstream and appropriate extent of stream offset we consider that the effects of loss of 390 m of stream length are Very Low. We emphasise that the rehabilitation of tributary 2 following the removal of the rock stack will result in a net gain benefit. 14.4.3 Effects on Mataura Wetland Ecology 14.4.3.1 Effects The Mataura Wetland containing the swamp maire will be retained and a minimum 10 m planted buffer (with fencing) is proposed around this wetland. The proposed construction works will avoid the full extent of the wetland feature. A desktop assessment of effects on the Mataura Wetland (in terms of hydraulic load) has been carried out by GHD (2022A). Based on the topography of the site (characterised as a steep relatively incised valley), GHD (2022A) inferred that the water source for the wetland is a combination of surface water via runoff and direct rainfall, interflow from infiltrating rainfall within the catchment, and groundwater baseflow. During mining the catchment supporting the wetland is expected to decrease by up to 19% (as a worst-case scenario)24. GHD (2022A) go on to suggest that the water source for the Mataura wetland is therefore estimated to decrease by a similar proportion (and by the same proportion for groundwater recharge). GHD (2022A) concluded that during wetter winter periods, reduction in recharge is unlikely to result in any impact to the wetland but during drier summer periods, the reduction in peak flows may result in an extended period of lower groundwater levels/dry conditions within the wetland. They go on to conclude that is not likely to be discernible from natural variability between summer conditions and the effect is considered to be at most minor. 14.4.3.2 Effects management The Mataura wetland has recognised albeit currently low ecological values. Our assessment suggests that effects on the Mataura wetland are likely to be indiscernible. However, we recognise the potential for improvement to the ecological values and recommend enhancement of the Mataura wetland. Accordingly, we recommend that the preparation of a Mataura Wetland Restoration Management Plan is a required condition of consent that includes as a minimum: • Stock exclusion fencing around the wetland. • A programme of weed and pest management is implemented and maintained. • As much as possible nurture the natural regrowth of wetland plants available in the local seed bank. • Staged planting of wetland plants within the wetland area. 24 This reduction assumes no leakage will occur from the collection pond, which will be dependent on liner design and construction.
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