B-6 – Area 6 – Assessment of Environmental Effects 84 The effects management hierarchy has been applied to the design of the NRS to minimise the effects on river extent and values, by: occupying the smallest footprint practicable during construction of the NRS; protecting instream native fish species and trout, including those associated with potential mahinga kai, but undertaking native fish and koura relocation within TB1 prior to works commencing; and minimising the potential for groundwater and surface water contamination from seepage by installing seepage drains to capture contact water before being diverted to the WTP for treatment prior to discharge into the Ohinemuri River. The diversion of groundwater and surface runoff in this manner will ensure there is no net loss of water of surface water and that groundwater remains within the catchment of origin. Despite the above measures, it is not practicable for the design of the NRS to minimise all adverse effects associated with loss of river extent and values. Residual effects on natural character and amenity are therefore remedied by providing riparian enhancements along the length of the modified watercourse and along the margins of the Ohinemuri River. With the above measures in place, more than minor residual effects remain that cannot practicably be avoided, minimised or remedied. In this instance, an extensive aquatic offsetting programme is proposed, including: the establishment of a diversion channel located between the NRS and northern fragment of SNA 166. The diversion channel will replicate aquatic habitat attributes with a range of suitable stable microhabitats for fish and invertebrates, including the creation of stable pool habitats, the inclusion of gravel and cobble riffle habitats and provide for the passage of climbing fish, especially eels; and the establishment of at least 10 m of riparian vegetation planting along both sides of the diversion channel, including low ground species which overhang the channel to improve habitat quality. As described by Boffa Miskell (2022a), development of the NRS will have a “Very Low” adverse effect on freshwater ecological values, when effects management measures are applied. Boffa Miskell (2022a) characterise residual adverse effects on freshwater ecology as “Minimal/None”. Consequently, following application of the NPSFM effects management hierarchy to the NRS, avoidance of the activity is not required. Notwithstanding the above, enhancement works are proposed as part of the wider WNP which are not required as part of any offsetting measures. These are detailed by Boffa Miskell (2022a). With these measures in place, a substantial net gain is anticipated across the wider project area.
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