| Existing Effects of Waihi Operations on the Environment | WNP Wharekirauponga Underground Mine - Assessment of Effects of Discharges to Air | 4397169-66885702-23 | | 34 6 Existing Effects of Waihi Operations on the Environment 6.1 Potential for Dust to Cause Adverse Effects 6.1.1 FIDOL factors Dust deposition is the settling of dust onto surfaces. The effects of dust can be subjective and are dependent on the sensitivity of the receiving environment. Some people will find dust a nuisance, others will be less concerned. For example, dust fallout on a gravel road or rural farmland may not be a nuisance to some neighbours even at relatively high deposition rates. However, others may find the dust objectionable or offensive. Typically, the most common areas of concern from dust deposition arise at residential properties (or similar sensitive locations such as schools or retail premises). Concerns typically relate to the visual soiling of clean surfaces such as cars, window ledges, washing on lines and deposits on vegetation. The GPG Dust18 notes that potential for a dust discharge to cause an objectionable or offensive effect depends on the characteristics of the dust fallout. These characteristics are known collectively as the FIDOL factors and are also used to consider whether an air discharge has caused an offensive or objectionable effect. The FIDOL factors are ● The frequency of dust nuisance events ● The intensity of events, as indicated by dust quantity and the degree of nuisance ● The duration of each dust nuisance event ● The offensiveness of the discharge having regard to the nature of the dust ● The location of the dust nuisance, having regard to the sensitivity of the receiving environment. 6.1.2 Dust deposition measurement and TSP monitoring Dust deposition is typically measured over a period of about 30 days using a dust gauge. However, this does not mean that dust deposition occurs gradually and evenly over that 30-day period. Dust concentrations in the ambient air downwind of a dust discharge vary with the rate of dust emission and the wind conditions. Therefore, the rate of dust deposition varies as well. It is possible that the majority of the dust deposition measured in a 30-day period by a dust gauge occurs during a small number of short, relatively high-rate deposition events, or it may occur at a relatively constant rate throughout the month. Short term events of relatively high-rate dust fallout are more likely to be noticed by residents as deposits on surfaces, cars and washing. Total suspended particulate (TSP) monitoring measures particles that are suspended in the air. Most monitoring equipment collects particles that vary in size between 0.1µm and about 100µm. The finer fractions can travel large distances downwind before they reach ground level. The larger fractions of TSP can have nuisance effects but the perception of potential for TSP to cause health effects is usually the cause of most concern for nearby residents. 18 Ministry for the Environment (2016) Good Practice Guide for Assessing and Managing Dust
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