Asphalt plants frequently asked questions

Division of Air Quality r к r inrt- ? a - 'JU What is asphalt and how is it made? Asphalt is a paving material made from crushed rock and asphalt cement, which is a mixture of petroleum compounds pro¬ duced by oil refineries. Asphalt plants heat the asphalt cement in enclosed tanks then combine it with crushed rock. The asphalt is then conveyed to storage silos, where it is loaded onto trucks for delivery to construc¬ tion sites for highways, parking lots and residential areas. Asphalt Plants: Frequently Asked Questions The N.C. Department of Environment and Natural Resources (DENR) receives many calls and letters about asphalt plants, generally when companies apply for permits to build new facilities. North Carolina has about 150 asphalt plants, and about five new facilities are permitted each year. Many asphalt plants are portable, so they can be moved to different locations based on needs for new highways and other construc- projects. Before a company can build operate an asphalt plant, it must obtain air quality permit and in some cases need water quality permits. In DENR, Division of Air Quality handles air .permits for asphalt plants, and the Division of Water Quality handles water permits (if applicable). How do asphalt plants affect air quality? Air emissions are created at several stages during asphalt production. Most of the emissions come from an asphalt plant’s main stack. Fumes from asphalt storage and loading areas account for the remaining air emissions, collectively referred to as fugitive emissions. Asphalt production, like any process in which materials are heated or burned, can produce a range of air emissions. Many of these same compounds are emitted by cars and trucks, fireplaces and wood stoves, wildfires, and other industries. While some of these emissions potentially can be un¬ healthy to breathe, such problems can be prevented by requiring asphalt plants to install controls or take other measures that reduce their emissions of harmful air pol¬ lutants. That is the guiding principle behind state air quality rules, which set stringent hmits for a range of pollutants based on their known health effects. In addition, the Division of Air Quality (DAQ) plans to re-examine its permitting proce¬ dures pending the results of a nationwide study of asphalt plant emissions being conducted by the U.S. Environmental Protection Agency (EPA). If changes are warranted based on the EPA study, the DAQ can reopen asphalt plant permits issued since April 1998. How does the Division of Air Quality control asphalt plants? All asphalt plants must obtain an air permit from the Division of Air Quality. The DAQ reviews all air permit applications for comphance with state and federal air quality regulations. All asphalt plants must meet air quality hmits for particulates, which include dust and soot. In addition, all new, modified or relocated asphalt plants must comply with the state air toxics rules, including emissions from stacks and fugi¬ tive sources. To meet air quahty hmits, all asphalt plants have emissions control equipment such as bagfilters or scrubbers. Other options for curbing their emissions include: • Limiting production rates or hours of operation. • Constructing taller emissions stacks. • Increasing the distance between facilities and property hnes. • Using higher grades of fuel for asphalt heaters. In reviewing permit apphcations, the DAQ uses computer models to determine whether emissions will exceed state or federal air quahty standards. These computer models, which are approved by the EPA, factor in such information as plant emissions rates, production levels, property lines, local terrain, winds and temperatures. The models assume worst- case meteorological conditions - that is, weather conditions that are most likely to cause air pollution problems.