| Air Quality Standards and Guidelines | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 29 Table 4-3 AQMP trigger values and limits Contaminant Trigger value/ License limit Value Averaging Period TSP Waihi trigger value 45 µg/m3 7 days Deposited particulate Waihi trigger value 4 g/m2/month One month * Note, the consent trigger limits do not refer to deposited dust concentrations above background levels and therefore include the contribution of background sources of dust, which will be variable and outside the control of OGNZL. The consent trigger limits are therefore more conservative than the trigger limits recommend by the GPG Dust. The 7-day OGNZL TSP trigger value of 45 µg/m3 is approximately equivalent to a 24-hour average concentration30 of 66 µg/m3, which is comparable to the MfE daily guideline trigger value for areas with a high sensitivity to dust of 60 µg/m3 (24-hour average). The consent conditions require that when trigger values are reached, OGNZL investigates the reasons for the high results and initiates any additional mitigation measures that are required. Overall, the current consent TSP and dust deposition trigger values are consistent with the recommendations of the MfE and with current good practice and it is recommended that they are adopted without change for the WNP. 30 To convert concentrations for different averaging periods the following power law equation Ct1 = Ct2 (t2/t1)0.2 is used. In this this instance, 66 µg/m3 = 45 µg/m3 * (7 days/1 day)0.2. Historically, the power law equation has beenused in dispersion modelling assessments to estimate pollutant concentrations for different average periods when there was insufficient meteorological data to do so.
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