Our editor sat down with Fulton Hogan Principal Air Quality Scientist and asked him some pertinent questions.
Can you tell us the difference between dust impacts to show the affected areas vs. wind direction?
We took measurements that zoomed in on the Roydon quarry site and have a windrose overlaid in the centre of the site. Again, it is formatted to show the direction that the winds will blow towards. This wind rose, however, is simplified to only show the winds that occur on dry days and when the wind speed is above 7 m/s (25 km/hr) – these are typically the worst case conditions for dust emissions.
Notwithstanding this, light winds can be worst case in terms of poor dispersion of dust that is generated, but these conditions are the easiest to mitigate and for this reason we focus on the strong wind conditions. This figure can be used to infer the downwind locations from the site that are likely to be most exposed to potential dust impacts from the quarry site – in this case the most exposed locations will be those to the southwest of quarry operations (i.e., under north-easterly winds). In other words blowing in the direction of Rolleston as opposed to Yaldhurst or Templeton.
Is there any micro-climate impact in the proposed quarry location?
With regards as to whether the effects of micro-climate on dust generation and suppression would be significant. In particular, does extraction and processing below ground level in the quarry pit (and the micro-climatic effects of this pit) significantly effect dust generation and/or suppression. Our position is that there may be some small degree of beneficial reduction in wind speed within the pit, which could minimise dust emissions – we would not expect it to exacerbate dust emission. However, this ‘sheltering’ effect is only usually significant in cases of very deep quarries or mines. As such our assessment will not seek to quantify this micro-climatic effect other than to discuss it in a qualitative manner as having a minor beneficial effect.