On site vehicle traffic can produce a significant amount of particulate emissions for some industries. Sections 13.2.1 (10/97) and 13.2.2 (1/95) of AP-42 provide empirical procedures for estimating overall haul road particulate releases from both paved and unpaved surfaces. In general, the particulate emissions are proportional to the number of vehicle miles traveled, road surface silt conditions, vehicle speed, and vehicle weight. Haul road dust that is generated will contain several trace metals at PPMW levels. Default trace metal concentrations for San Diego County have been developed by analyzing multiple haul road silt samples taken from several mineral products industry sites.