B-7 – Area 7 - Assessment of Environmental Effects 32 The average wind speed recorded since 2013 is 3.43 m/s. Calms occur for 10.82% of the time. Wind speeds > 5 m/s - which lifts dust from unconsolidated surfaces – occurred approximately 26% of the time. Wind speeds are highest in spring and lowest in autumn. NIWA data indicates that Waihi’s long-term average annual rainfall is approximately 2,110 mm. The lowest annual rainfall recorded was 1,265 mm, in 1919. The highest annual rainfall was 3,235 mm, recorded in 1928. The months of January to March, and October are the driest with average monthly rainfall of approximately 60 mm to 95 mm. The months of January to March also have the lowest average number of rainy days, at between six and eight days per month. Rainfall during the rest of the year averages from approximately 110 mm in May to almost 250 mm in June. All other months have between 10 (April, November, December) and 18 (August) rainy days on average. Area 7 is in the airshed that covers rural land in the Waikato region. Beca (2022a) expect that air quality in the rural airshed is typical of other rural areas in New Zealand and within the NES Air criteria. The Waihi Airshed is not a “polluted” airshed and therefore, resource consent applications involving discharges of PM10 are not required to be declined in accordance with Regulation 17 the NES Air. OGNZL monitors dust deposition rates and Total Suspended Particulate concentrations in accordance with an Air Quality Management Plan required by resource consent conditions. The Air Discharge Assessment reviewed dust monitoring results from nine permanent monitoring sites around the Martha Pit, TSFs and north of the Water Treatment Plant (“WTP”). The review indicated that dust deposition rates are relatively low at all monitoring sites and are generally comparable to background levels. Slightly higher dust levels than the monitored average were recorded at three sites, but remained within an acceptable range. Since January 2000, dust deposition rates have exceeded the consented levels four times, over three locations. However, no exceedances have been recorded since November 2012. Six sites around the Martha Pit monitor and record Total Suspended Particulate levels. Between 2005 and 2020, Total Suspended Particulate concentrations were generally below the consented limit of 45 μg/m³ (7-day average). Ten exceedances were recorded during this 15-year period at the three monitoring sites nearest the Martha Open Pit. However, only one exceedance was recorded after July 2010.
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