1. Passive Enclosures for Dust Control ©2002 Dr. B. C. Paul

2. Overview of Dust Sources  Dust sources are Fugitive or Process  Fugitive sources tend to be more dispersed in field Drilling and Blasting Rock Loading and Dumping Rock Vehicle Traffic on Roads Stockpile Areas  Process from discrete areas Crushing, Screening, Conveyor Drop Points

3. Techniques for Controlling  Four Major Control Techniques Passive Enclosure Wet Suppression Surfacing and Cleaning Dry Collection

4. Passive Enclosure  Technique works by limiting the ability of wind currents to pick up fine material Objective is not to capture - captured dust could become a RCRA or CERCLA issue If emissions escape at a point - it could turn source into point source and trigger opacity limits –opacity is how clear the air is to see through Sometimes eddy currents in an enclosure can cause some dust to drop out in enclosure

5. Passive Enclosure Examples  Cover Transfer Points on Conveyor  Cover the Entire Conveyor  Unloading coal to a stockpile using a stacking tube is falling out of favor  Store Aggregate in Bins instead of open stockpiles  Spray latex coatings over open stockpiles

6. More Examples  Install Wind fences or Screens  Natural Wind fence is a line of trees Used by farms to break up dust bowl of 30s Low maintenance Generally make natural vista that reduces public visibility and looks environmentally friendly  Can also build about 10 foot high wood lathe fence to get a wind shadow