| Existing Air Quality Effects | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 42 TSP OGNZL measures TSP using High Volume samplers (HiVols). HiVols measure TSP concentrations by drawing a measured volume of air through a filter for a known period of time and then weighing the dust collected on the filter. The most common measurement period is 24 hours, however, OGNZL exposes each filter for a period of 7 days which was the approved technique when TSP monitoring began at the site. 6.2.3 Summary of monitoring results The following sections summarise the results of the ambient air monitoring programme for the period January 2000 to December 2020. More detailed data is included in Appendix B. It is noted that following the North Wall collapse in 2015 most activity within Martha Pit ceased. Deposited dust Table 6-2 summarises the long-term average, maximum, minimum and median values for deposited dust for each of the current monitoring sites between 2000 and 2020. The distribution of the monthly deposition rates at each monitoring site is illustrated in Figure 6-2 by box and whisker plots. The “boxes” in the figure show the median, upper quartile and lower quartile monthly deposition rates (i.e. the 50th, 75th and 25th percentiles) recorded at the monitoring sites. The ‘whiskers’ show the highest and lowest deposition rates observed during the monitoring, excluding outlier values. The outliers are shown in the figure as circles35. The maximum deposition rate of 11.66 g/m2/30-days recorded at the Site 6.70 (Smith) in November 2000 is not included in the figure for the reasons explained further below. The variations in monthly deposition rates over the monitoring period are shown in Table 6-2 . Table 6-2. Distribution of the monthly average deposited dust (g/m2/30-days), January 2000 - December 2020 Monitoring Locations Average Maximum Minimum Median 6.59 (Torrens Alexander) 0.84 3.08 0.00 0.74 6.60 (Torrens Town End) 0.87 2.76 0.14 0.78 6.61 Leaches (Grey Street) 1.05 3.30 0.02 0.92 6.63 (Met Station) 1.17 4.73 0.16 1.09 6.66 (College) 0.77 2.16 0.05 0.70 6.70 (Smith) 0.96 11.66*** 0.19 0.78 6.71 (Morrison) 1.13 5.23 0.06 0.97 6.72 (Baxters Road) 0.79 3.14 0.07 0.66 6.75 (TSF-East)** 0.72 1.70 0.13 0.65 6.00 (Bulltown Rd)* 0.74 2.32 0.11 0.61 *Monitoring data from January 2017 in this location. ** Monitoring data from February 2017. *** spurious results 35 Outliers are defined as values which are higher than the upper quartile plus 1.5 x the interquartile range (or the highest value in the data set – whichever is lowest), or lower than the lower quartile minus 1.5 x the interquartile range (or the lowest value in the data set, whichever is highest)
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