6 Tonkin & Taylor Ltd Assessment of mine vent air quality impacts to inform an assessment of ecological effects on Archey’s frog Oceana Gold (NZ) Limited June 2022 Job No: 1017908 5 Comparison with air quality near unpaved public roads Bluett el al (2017) examined the impacts of exposure to dust from unsealed roads, which included monitoring PM10 adjacent to an unsealed road in Northland. The monitoring programme was undertaken in 2015. 7-day average vehicle counts were in the order of 250 vehicles per day, comprising approximately 30% heavy commercial vehicles (HCVs). Weekend average vehicle counts were in the order of 150 vehicles per day comprising approximately 16% HCV. Figure 5.1 reproduces Figure 4.9 from Bluett et al, summarising measured PM10 concentrations, highlighting the weekend days (to illustrate the difference in air quality effects on days with lower traffic volumes). This plot shows measured 24-hour average concentrations at two locations; 5 m and 30 m set back from the roadside. Although lower than on weekdays, weekend traffic conditions gave rise to elevated PM10 concentrations that approached or exceeded the 50 µg/m³ (24-hour average) at 5 m from the roadside on two days over the eight weekends monitored. Concentrations were typically about 50% lower at 30 m from the roadside and were approximately 25 µg/m³ on four days. The air quality measured in Bluett el al can be compared to likely air quality adjacent to unsealed roads with known populations of Archey’s frogs to give an indication of their tolerance to dust and fine particles. Traffic monitoring was carried out in June 2021 on two unpaved roads in the Coromandel where ecological monitoring for Archey’s frogs has been undertaken: • ‘309 Road’ near to Waiau Falls Scenic Reserve. The 7-day vehicle count in June 2021 was 174 vehicles per day, comprising on average 10.5% heavy commercial vehicles. • ‘Kennedy Bay Road’ The 7-day vehicle count in June 2021 was 370 vehicles per day, comprising on average 8.2% heavy commercial vehicles. Traffic flows on these unpaved roads in the Coromandel were broadly similar to the weekend traffic conditions in the Northland study of air quality impacts. Therefore, although there may be some difference in road conditions affecting dust emissions (road surface fines content and moisture), the measured concentrations adjacent to 309 Road (Coromandel) are likely to be similar to the weekend PM10 concentrations discussed above. That is, PM10 concentrations are likely to be greater than 25 µg/m³ (24-hour average) within 30 m from the road. The modelled worst case cumulative PM10 concentrations as a result of emissions from the vents are less than 25 µg/m³ (24-hour average) (see Section 4.1). This indicates that PM10 concentrations in the vicinity of the vents are likely to be lower than at locations within 30 m of 309 Road, Coromandel, where populations of Archey’s frogs are known to occur.
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