| Environmental Setting | WNP Wharekirauponga Underground Mine - Assessment of Effects of Discharges to Air | 4397169-66885702-23 | | 23 The Ministry for the Environment (MfE) Good Practice Guide for Assessing and Managing Dust (GPG Dust)7 describes typical background concentrations of deposited dust for different environments. These are usually less than 1 g/m2/30 days for rural areas such as Willows Road. There is only a limited amount of data available relating to ambient concentrations of total suspended particulate (TSP) levels in New Zealand. The GPG Dust notes that background TSP levels in clean environments are about 10-20 µg/m3. TSP concentrations in the area of the Willows Road site are expected to be of this order as there are no large sources of particulate in the area such as industries or urban developments. OGNZL does not currently monitor air quality in the vicinity of the Willows Road site. However, OGNZL and predecessors have been monitoring deposited dust in the vicinity of the Waihi Gold Mine since 1982 and total suspended particulate (TSP) since 2005. A summary of the results of air quality monitoring carried out at the Waihi Mine monitoring sites is included in Section 6. 3.5 Meteorological Data OGNZL measures meteorological parameters at a climate station located at Barry Road (Site 6.63 Met Station). This climate station lies approximately 3 km to the south of the Willows Road site and 140 m to the east of Martha Pit. The local topography at the project site is complex and is likely to influence local wind conditions. The site may be sheltered to some extent from the prevailing westerly winds, but these may also be channelled in a more north-westerly direction down the gully between the two steep hills on the southern and northern sides of the site. Overall, however, there are no topographic features between the Barry Road station and the project site that would result in significant differences in the meteorological characteristics of these two sites. On this basis, the data measured at the Barry Road climate station can also be considered to be relevant to the project site. A windrose showing hourly average windspeed and directions for years 2013 to 2019, at the Barry Road climate station, is provided in Figure 3-3 (data supplied by OGNZL). The prevailing and strongest winds come from the west and south-westerly directions. Secondary winds come from the northeast and occur for approximately 10% of the time, while winds from other directions are rare. The average wind speed measured in the 2013 – 2019 period was 3.43 m/s and calm conditions (i.e wind speeds <0.5m/s) occurred for 10.8% of the time. Winds that exceed 5 m/s, which is the critical wind speed for the lifting of dust from unconsolidated surfaces, occurred for approximately 26.3% of the time. 7 Ministry for the Environment (November 2016) “Good Practice Guide for Assessing and Managing Dust”
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