| Existing Air Quality Effects | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 48 Figure 6-6. 7-day average TSP concentrations (µg/m3) (March 2005 – December 2020) The results of monitoring show that TSP concentrations are generally below the OGNZL trigger limit of 45 µg/m3 (7-day average), except for 10 exceedances that have been recorded during the monitoring period. Six of these exceedances occurred at Site 6.63 (Met Station), three at Site 6.64 (Courthouse), and one at the Site 6.78 (Slevin St). Only one exceedance of the trigger level has occurred since July 2010 (at Site 6.78 (Slevin St)). A statistical analysis of the 7-day average TSP concentrations recorded at each of the sites was conducted using a pairwise Wilcox Rank Sum test. The test compares the 7-day average TSP concentration recorded at each monitoring site against all the other sites in a pair-wise manner. The test was used to assess whether there was a statistical difference between the TSP concentrations recorded at any of the sites. The methodology and results for this analysis are provided in Appendix D. Sites 6.65 (Old House) and 6.66 (College) TSP concentrations are on average lowest at Site 6.66 (College) site. The College site is located 630 m west of the Martha Pit and upwind of the mine in prevailing wind conditions. The College is located on the edge of Waihi with rural land to the west, north and northeast. There are residential properties to the east and south of the site. The concentrations recorded at the site are considered to be representative of background levels in the rural residential areas surrounding Waihi. The results of the Wilcox Rank Sum test indicate that there is no statistically significant difference between the distribution of TSP concentrations measured at the Site 6.65 (Old House) and those measured at the Site 6.66 (College) site. Site 6.65 (Old House) is located relatively close to the mine (i.e. 75 m to the southwest) and downwind in secondary wind conditions. However, the statistical test results indicate that mining activities do not appear to make a significant contribution to TSP concentrations at this location. The results also indicate that there is no strong significant statistical difference between the distribution of TSP concentrations measured at 6.65 (Old House) and at Site 6.78 (Slevin St) (p-values of 0.086). 0 10 20 30 40 50 60 70 80 90 7 Day Average TSP Concentration (µg/m3) 6.61 (Grey Street) 6.63 (Met Station) 6.64 (Courthouse) 6.65 (Old House) 6.66 (College) 6.78 (Slevin St) North Wall Collaspe Trigger Level (45 µg/m3)
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