| Air Quality Standards and Guidelines | WNP Wharekirauponga Underground Mine - Assessment of Effects of Discharges to Air | 4397169-66885702-23 | | 28 In February 2020, the MfE released a consultation document on some proposed amendments to the NESAQ11 (MfE Consultation Document), including new standards for ambient air concentrations of PM2.5 and some new controls on mercury emissions (not relevant to the Willows Road project area as there will be no gold processing on this site). The proposed NESAQ standards for PM2.5 are 25 µg/m3 (24-hour average) and 10 µg/m3 (annual average). 4.2 Dust Guidelines There are no New Zealand environmental standards or guidelines for deposited dust or TSP. However, the GPG Dust recommends “trigger” levels which are intended to be used for proactive management of dust on a site. These trigger levels are not intended for enforcement because exceedance of these levels does not necessarily infer an adverse effect offsite12. The trigger levels are intended to apply beyond the site boundary. 4.2.1 Deposited Dust The recommended “trigger value” for deposited dust is 4g/m2/30 days above background concentrations. The GPG Dust notes that deposition rates of more than this value above background levels in some industrial and sparsely populated areas may not cause nuisance, but conversely in sensitive residential areas dust levels in the order of 2g/m2/30 days above background levels may cause nuisance. 4.2.2 TSP The GPG Dust recommends “trigger” levels for TSP for various time-averaging periods and sensitivities of the receiving environment. The “trigger” levels included in the GPG Dust for TSP are shown in Table 4-2. Table 4-2 GPG Dust TSP trigger levels Trigger Averaging Period Sensitivity of receiving environment High Moderate Low Short term 5 min 250µg/m3 n/a n/a Short term 1 hour 200 µg/m3 250 µg/m3 n/a Daily* 24 hours (rolling average) 60 µg/m3 80 µg/m3 100 µg/m3 * For managing chronic (ie, long term) dust only. The GPG Dust also provides guidance on the sensitivity of different receiving environments. For rural areas such as those surrounding the project site, the GPG Dust classifies the sensitivity to dust as low for rural activities but moderate to high for other activities such as industrial activities. Hence, in assessing the effects of dust it should be recognised that the residences near the Willows Road site will be more sensitive to such effects on the basis that they derive from a non-rural activity source. 11 Ministry for Environment (2020) Proposed Amendments to the National Environmental Standards for Air Quality, Particulate Matter and Mercury Emissions, February 2020 12 Ministry for the Environment (2016) Good Practice Guide for Assessing and Managing Dust
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