Editor’s note: Alan Klimek, director of the N.C. Division of Air Quality, wrote the following article to address many of the issues concerning asphalt plants and their emissions.

Asphalt plants are like landfills - few people want to live near them. Although asphalt plants provide economic benefits to a community, some citizens have raised legitimate concerns about living near such facilities. Like many industrial plants, asphalt plants often are not the most attractive facilities to look at. They tend to generate more traffic from trucks picking up and delivering asphalt. They can be noisy at times, and they can generate odors similar to hot tar.

Such concerns, in part, have prompted North Carolina to strengthen substantially its permit review process for asphalt plants over the past three years. We apply stricter air pollution and analyses and limits for new and expanded plants. We also hold public hearings for many asphalt plant permits, even though such hearings aren't required under state or federal law. But despite additional oversight and controls, the permitting process for asphalt plants seems to have become more controversial - particularly in the mountains.

In North Carolina, asphalt plants must obtain air quality permits from the Division of Air Quality (DAQ). The DAQ’s job is to make sure that asphalt plants meet all state and federal regulations for air emissions. Our regulations for air toxics are more stringent than those required by the U.S. Environmental Protection Agency (EPA) and many states. I am not aware of any state in the Southeast, other than North Carolina, that requires new asphalt plants to meet guidelines for toxic air pollutants.
To obtain an air permit in North Carolina, businesses wanting to operate asphalt plants must demonstrate they can meet rules for controlling particulates (dust), sulfur dioxide, nitrogen oxides, and air toxics. These demonstrations include computer modeling of toxic emissions from the plant’s main stack as well as fugitive emissions, or fumes from asphalt storage and loading areas. Plants must show they can meet air quality guidelines at their property lines - meaning nearby residents should not be exposed to unhealthy levels of air pollutants, even if they live next door to a plant. These guidelines assume that nearby residents would be exposed to the air emissions 24 hours a day, 365 days a year, over a 70-year period - which is unlikely in most cases.

Modeling is done because toxic air emissions generally occur at levels too small to measure accurately. These computer models take into account the maximum projected emissions rates of a plant, the size and shape of its property, the characteristics of each emissions source (such as stack heights and gas temperatures), the elevation of the surrounding terrain, and other factors.

The models also assume “worst-case” meteorological conditions, whether they exist at a facility or not. Worst-case conditions include factors such as low wind speeds, temperature inversions, stagnant weather and temperatures most likely to prevent atmospheric mixing and concentrate air pollutants. As a result, if a plant can meet air quality guidelines under these worst-case conditions, we are confident that it would comply under the weather conditions that actually exist at the plant.

For example, an asphalt plant meeting North Carolina’s air toxics rules must show through modeling that its emissions would not increase levels of benzene in the air by more than 1.8 micrograms per day at the plant’s property lines. For comparison’s sake, a typical person would be exposed to about 200 micrograms of benzene in total per day through activities such as breathing second-hand cigarette smoke (20 micrograms/day), driving in traffic (38 micrograms/day), breathing indoor air (62 micrograms/day), and pumping gasoline (92 micrograms/occurrence). A person smoking 1.5 packs of cigarettes per day would be exposed to about 1,800 micrograms/day. These numbers show that living near an asphalt plant is actually much less risky, in terms of benzene exposure, than many everyday activities.

Despite these facts, the Division of Air Quality often is besieged by requests for us to deny permit applications for new asphalt plants - mainly because people do not want to live near them. The DAQ does not have the authority to deny a permit based on such concerns. If people want to stop an asphalt plant from being built in a particular location, they should contact their local planning officials. In North Carolina, local governments have the primary control over land use and zoning. Although few mountain communities have land-use controls, that lack of control does not give the DAQ the authority to assume it.

In other words, the DAQ cannot tell an asphalt company where to locate a plant. We cannot deny a permit because other asphalt plants already exist in a community, because it may lower nearby property values, or because a proposed plant would be near a stream, a subdivision or a school. If a plant demonstrates that it can meet air quality regulations, we are required by law to issue it a permit.

It's ironic, in a sense, that asphalt plants have become so controversial because we are all responsible for their prevalence. North Carolina has about 150 asphalt plants located across the state. One reason why there are so many asphalt plants is because there are so many cars and trucks as well as the highways to accommodate them. North Carolina has the second-largest state-maintained highway system in the nation, with about 78,000 miles of roads in total. The state’s rapid growth in recent years has created unprecedented demand for asphalt to pave or resurface highways, parking lots, subdivisions, driveways and other surfaces. Another factor contributing to the prevalence of asphalt plants is the nature of the material. Asphalt plants must be located fairly close to construction sites because delivery trucks can travel only limited distances and still maintain the temperatures needed for paving.

The Division of Air Quality is committed to ensuring that asphalt plants meet state and federal air regulations. However, local governments must exercise their authority over land-use matters if the public wants a say in where such facilities are located.

(This article was written in February 2001.)

 

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