This report describes a study of atmospheric emissions from the transport of sand and gravel on unpaved roads. The potential environmental effect of this emission source was evaluated using source severity, defined as the ratio of the time-averaged maximum ground level concentration of a pollutant at a representative plant boundary to a hazard factor. The hazard factor is the ambient air quality standard for criteria pollutants and an adjusted threshold limit value for noncriteria pollutants. A representative sand and gravel plant processes 274 metric tons/hr, with vehicular traffic of 22 vehicles/hr. The average unpaved road length of sand and gravel plants is 2.2 kilometers, and each truck carries an average of 21 metric tons. The uncontrolled particulate emission factor for the industry due to vehicular movement is 87 g/metric ton. The source severities for particulates and free silica-containing particulates are 0.02 and 2.9, respectively. Some plants have effectively used certain control measures, such as application of oil and chemical solutions into the road surface. Future control techniques would consider the emission-influencing factors of vehicle speed, vehicle size, number of wheels, tire width, particle size distribution, and road moisture content.

EPA Contract No. Contract Number: 68-02-1874 "October 1978." Includes bibliographical references (pages 22-24).