OceanaGold | Waihi North Project | Recreation and tourism assessment 41 5.2 Effects of the treated water discharge on recreation The scale of the discharge of the treated water into the Ohinemuri – which ranges between 10% and 60% of its flow at the discharge point – has been previously consented and is not considered in this assessment. No changes to the conditions of the WTP Discharge Consents are required to accommodate the Waihi North Project. This means that the existing instream water quality criteria are proposed to be retained. Boffa Miskell (2022a) reports on the effects of the treated water discharge on the ecology of the Ohinemuri River and notes that the River is an important rainbow trout fishery, with spawning grounds in its tributaries, and is classified as a significant trout fishery. They find that the condition of the Ohinemuri River, as measured by macroinvertebrate indicators, is poor to fair. This condition occurs throughout the reach of the River in the vicinity of the OGNZL operations and has essentially remained consistent over the period of monitoring from 2009 to 2017. Periphyton levels were found to be within the parameters required to protect recreation and trout habitat and angling. Boffa Miskell (2022a) also considers the ecological effects of all components of the Waihi North Project on tributaries of the Ohinemuri River and proposes a mitigation programme to sustain and improve freshwater ecology values in the catchment. This is a separate assessment to that of the WTP discharge and is reviewed in full in that report. In summary, Boffa Miskell (2022a) finds that there is no evidence that the water quality of the Ohinemuri River has caused any detrimental effects to the ecological values of the River, and the ecological values have been upheld as anticipated by the criteria as set out in OGNZL’s consent conditions. Also, that the required receiving water quality standards are achieving the desired outcome for the River and the requirements of the National Policy Statement for Freshwater Management. Accordingly, re-consenting the WTP with the same receiving water quality standards will not result in detrimental effects on the ecological values of the Ohinemuri River. Figure 27 shows the locations of the two diffusers in Ohinemuri River on a Strava heatmap for all activities (12 months of data to June 2022), and Figure 28 shows diffuser 2 in the bed of the River. It is proposed to duplicate these structures adjacent to the current diffusers. Diffuser 1 is located away from any areas of public access and has no effect on recreation amenity. Diffuser 2 is located adjacent to the walkway beside the Ohinemuri River, which Figure 27 shows to be well used by pedestrians and cyclists. A short path leads from the walkway to the diffuser which has been constructed to allow access to it for testing and maintenance. The short path is not a recreation route. Figure 29 shows the visual effect of operation of diffuser 2 within the River, with bubbles spreading on the water’s surface. The effect of diffuser 2 on recreation amenity is considered minor due to the low level of recreational use of the site and the low scale of effect, and this scale of effect is likely to remain with the additional diffuser installed adjacent. It is therefore taken that the recreation values of the Ohinemuri River – considering its trout angling, contact recreation and terrestrial recreation values – will be sustained within the current consented operating regime for the discharge, particularly considering that the majority of water contact recreational and angling use of the Ohinemuri River occurs well downstream of the discharge – 13 km approximately for the upstream end of the Karangahake Gorge, for example – and in the case of dry fly angling, upstream of the discharge.
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