GHD | Oceana Gold New Zealand Ltd. | 12552081 | Waihi North Project E-13 • WRS uncaptured seepage • NRS uncaptured seepage • TSF3 uncaptured seepage • Gladstone uncaptured seepage • Baseline uncaptured seepage Contaminant mass load coming from the WTP discharge was calculated using daily discharge concentration and flow. Baseline Ohinemuri River and Ruahorehore Stream mass loads were calculated using an assumed median concentration and daily AWBM flow rates. Relative calibration of the cumulative component of the model has been achieved by comparing a realisation within the model that had a similar annual rainfall to that recorded in 2019 – in which the uncaptured background contaminant loads have been calculated. Annual average key contaminant concentrations were generally modelled in line with or above the average 2019 monitoring data. Differences observed were attributable to samples being recorded below the method detection limit and the simplification of the water quality data to median values. However for the purposes of the cumulative assessment and assessment of additional loading through the Waihi North Project, the calibration is deemed adequate.
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