| Existing Air Quality Effects | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 45 between the distributions of the site’s deposition rates39. The results indicate that deposition levels observed at these sites are similar to each other. No statistical difference was also found between the distribution and median values of deposited dust measured at Sites 6.66 (College), 6.72 (Baxters), 6.70 (Smith), and 6.00 (Bulltown) and the two background sites (i.e. sites 6.60 (Torrens Town End) and 6.59 (Torrens Alexandra)). The results suggest that the dust levels recorded at Sites 6.66 (College), 6.72 (Baxters), 6.70 (Smith) and 6.00 (Bulltown) are on average not significantly different from background levels. At these locations, site sources do not appear to have a measurable effect on the reported deposited dust levels. The highest long-term average dust deposition rates have been recorded at Sites 6.63 (Met Station), 6.71 (Morrison), and 6.61(Leaches). The dust deposition rates at these sites are on average all statistically higher than those recorded at the other monitoring stations, and the two background monitoring stations. Site 6.63 (Met Station) located approximately 140 m to the east of the Martha Pit, is downwind of the mine in the prevailing winds and would be expected to be the monitoring site most impacted by dust from the pit. Site 6.71 (Morrisons) is located approximately 270 m to the southeast of TSF1A and is only downwind of the TSF1A in northerly quarter winds, which are infrequent. It is possible that the higher than background concentrations of dust recorded by this gauge may be due to the application of lime to paddock-dumped rock and embankment construction activities carried out on the south-eastern side of the TSF1A. Site 6.61 (Leaches) is located approximately 550 m north-northeast of Martha Pit and is only downwind of the north-western edge of the pit in prevailing winds. The monitoring site is not downwind of the majority of Martha Pit in the prevailing wind direction, and it is beyond the distance at which deposited dust would normally be expected to be transported in the wind. Summary On average, deposition rates are highest at the Site 6.63 (Met Station). The median deposition rate at this site is approximately 0.35 g/m2/30-days higher than the median deposition rate observed at the background sites, or approximately 9% of the MfE guideline value of 4 g/m2/30 days. The median deposition rate at Sites 6.71 (Morrisons) and 6.61 (Leaches) are respectively 0.23 g/m2/30-days and 0.18 g/m2/30-days higher than the median deposition rate recorded at the background monitoring site, or less than 6% of the MfE guideline. Overall, the observed differences, while statistically significant, are comparatively small when compared to the trigger value. The monitoring results indicate that dust deposition rates are relatively low at all of the sites and are generally comparable to local background levels. Slightly higher average deposition rates are observed at Sites 6.63 (Met Station), 6.71 (Morrison) and 6.61(Leaches), which may be indicative of Sites 6.63 (Met Station) and 6.71 (Morrison) proximity to the site activities. The slightly higher than average deposition rates at Site 6.61 (Leaches) is within the range of typical background deposition rates. The MfE guideline and consent trigger values have only infrequently been exceeded at any of the sites during the previous 20-year monitoring period, which indicates that dust deposition in the vicinity of the site is considered to be within an acceptable level (refer to Table 6-3). 39 A test score p-value of <0.05 was used to determine whether a difference was statistically significant.
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