Dust is particulate matter (PM) consisting of very small liquid and solid particles. Fugitive dust is PM suspended in the air primarily from soil that has been disturbed by wind or human activities, such as earthmoving and vehicular/equipment traffic on unpaved surfaces. It is not emitted from vents, chimneys, or stacks.
Idaho's weather contributes to the fugitive dust problem. Unlike most other areas of the country, we have a wet season and a dry season. Long, hot summers allow the soil to dry out thoroughly and, if the surface is disturbed repeatedly, the soil may have months to blow away before normal rainfall can again saturate and hold it in place. Some areas are also prone to high winds, making matters worse.
Health Impacts of Particulate Matter
Due to the small size and weight of particulate matter (10 micrometers or less in diameter, compared to 70 micrometers for the average human hair), it can remain airborne for weeks. When inhaled, it can travel easily to deep parts of the lungs and may remain there, causing respiratory illness, lung damage, and even premature death in sensitive individuals.
Fugitive Dust Regulation in Idaho
DEQ is responsible for regulating fugitive dust emissions in Idaho. Authority is based on the Rules for the Control of Air Pollution in Idaho (IDAPA 58.01.01.651), which require that all "reasonable precautions" be taken to prevent particulate matter from becoming airborne. Reasonable precautions include using water or chemical, applying dust suppressants, using control equipment, covering trucks, paving, and removing materials.
When regulating fugitive dust, DEQ considers the proximity of dust-emitting operations to human habitations or activities and atmospheric conditions that might affect the movement of particulate matter. Failure to reasonably control fugitive emissions may result in enforcement action by DEQ with possible penalties assessed.
Fugitive Dust Control Measures
Keeping potential fugitive dust problems under control is an everyday job. Plan ahead by developing a dust prevention and control plan. Here are some specific suggestions for controlling fugitive dust:
First, think pollution prevention!
- Minimize the surface area disturbed. The less ground disturbed, the less dust raised while working, and the less cleanup when work is done.
- Limit dusty work on windy days. Apply dust suppression measures when needed. Monitor dust suppression efforts to ensure that dust emissions are adequately controlled. It may be necessary to adjust to fewer or more frequent application intervals depending on weather conditions.
- Clean up dusty spills immediately. Do not wait for the next scheduled housekeeping—the mess will just get bigger and cleanup will take longer.
Control dust in occasionally used areas.
- Grow vegetative ground cover. Growing grasses or legumes is the most effective, easiest and most economical control because these plants provide a dense, complete cover. Even when the vegetation dries up, the roots will help hold the soil in place. Do not leave open areas uncovered.
- Use wind erosion controls. Plant bushes or trees, construct wood or rock walls, or earthen banks as permanent windbreaks, or install porous wind or snow fences as more temporary measures. Reduced wind velocity allows larger particles to settle to the ground.
- Apply crust-forming chemicals. These chemicals may include mineral salts, petroleum resins, asphalt emulsion, acrylics, and adhesives. These treatments must be reapplied periodically to ensure continued effectiveness. Check with DEQ to ensure the material you want to apply is not harmful and may be used for this purpose.
Control dust in frequently used areas.
- Pave haul roads and storage areas. Heavy vehicles pulverize the surface material and create a constant source of dust. If wholesale paving is too costly, pave just the entrance and exit to minimize carryout. Gravel the remainder to reduce surface silt.
- Enclose storage and handling areas. If dusty materials are frequently loaded and unloaded in storage and handling areas, enclose the areas to reduce fugitive dust emissions. Use storage silos, three-sided bunkers, or open-ended buildings. If handling is less frequent, try wind fencing. Conveyor loading may require enclosure or the use of water or foam spray bars both above and below the belt surface to reduce emissions.
- Keep storage piles covered. When storage piles are not in use, apply a physical cover or a dust suppressant spray to help reduce fugitive dust emissions. Limit the working face of the pile to the downwind side. Most emissions come from loading the pile, loadout from the pile, and truck and loader traffic in the immediate area if the pile is batch loaded. Keep the drop height low to reduce dust and the ground at the base of the pile clear of spills.
- Water and/or sweep often. To ensure vehicle traffic is not picking up dust from wind action and carryout, water and sweep roadways often. Fewer treatments are necessary in cool, wet weather.
- Reduce speed limits. Reduce speed limits on unpaved surfaces to 10 to 15 miles per hour for well-traveled areas and heavy vehicles. Never exceed 25 miles per hour for any vehicle on any unpaved surface.
- Prevent transport of dusty material off site. Minimize transport of dusty material off site by rinsing vehicles before they leave the property and tightly covering loaded trucks.