| Potential Effects on the Environment of WNP | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 57 7 Potential Effects on the Environment of WNP 7.1 Approach to Assessment of Dust Nuisance Effects For the WNP, the effects of the existing Waihi Gold Mine activity have been assessed by analysing the last 20 years of available environmental monitoring data (as discussed in Section 6), guidance published by the MfE and IAQM, the proposed mitigation, and Beca’s experience with comparable mining and quarrying operations. For applications such as this, assessment methods which involve the calculation of emission rates from fugitive sources and the likely downwind concentrations of contaminants using dispersion modelling are impractical as it is very difficult to estimate emission rates and model the effects of the emissions, as the scale and locations of the sources change frequently, as well as the local topography. Consequently, where these constraints are present, qualitative methods should be used. The likelihood of the discharges to air from WNP resulting in adverse effects on sensitive receptors are estimated based on the historic and existing effects of mining at Waihi and the likely changes to the scale and location of the emissions. The likelihood of each of the project features resulting in adverse effects on the nearest sensitive receptors has been assessed taking into account the location of the sensitive receptor in relation to the potential sources of dust, the likely frequency of potential impacts and the likely severity (i.e. intensity and duration) of any potential impact (consistent with the FIDOL factors). Where an elevated risk of adverse effects occurring has been identified, additional dust control and monitoring methods are recommended to mitigate the risk. The risk factors assigned to each sensitive receptor group are in accordance with the factors shown in Table 7-144. Table 7-1 Risk factors assigned to each sensitive receptor group Risk Factors Less than 50m from works Between 50m and 100m from works Between 100m and 200m of works Further than 200m from works Downwind of works in prevailing wind conditions Very high High Moderate Moderate Downwind of works in secondary wind conditions High Moderate Moderate Low Infrequently downwind Moderate Low Low Low 7.2 Effect of Separation Distances on Dust Concentrations The dust and fine particulates (PM10 and PM2.5) which will be emitted from the proposed WNP will disperse and dilute as they are transported downwind. Ambient air contaminant concentrations and deposition rates will decrease rapidly with distance downwind in an approximately exponentially manner. The risk of adverse air quality effects is greatest for receptors located in close proximity to an emission source, and generally highest for receptors located within 100 – 200 m of an emission source. 44 The risk matrix is based on the risk assessment procedure recommended in “Guidance on the Assessment of Mineral Dust Impacts for Planning” published by the Institute of Air Quality Management in May 2016.
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