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Questions & Answers
Q. What is asphalt?
A. What most people mean when they say "asphalt" — also known as blacktop, macadam or tarmac — is actually a particular product known as asphalt pavement, or sometimes as hot mix asphalt (HMA) pavement. Asphalt pavement is a high-quality, thoroughly controlled, engineered material.
There are two basic ingredients in hot mix asphalt. The first is aggregates (stone, gravel and sand). The aggregates used are almost always locally available stone. About 95 percent of the total weight of an asphalt pavement consists of aggregates.
The remaining 5 percent is asphalt cement, a derivative of crude oil refining that is the binder or "glue" in the asphalt pavement mixture. Asphalt cement is one of the heaviest, most viscous parts of petroleum. Mix the two ingredients together, and you get hot mix asphalt.
Q. What happens at an asphalt facility?
A. Basically, the paving aggregates are dried and heated, then mixed and coated with asphalt cement. The hot mix asphalt is taken by truck immediately to the paving site or put in silos for short-term storage.
Q. Why do we need an asphalt facility in my community?
A. Hot mix asphalt is usually mixed at temperatures between 300 and 325 degrees. It has to be placed while hot. Getting asphalt from the facility to the paving site is like delivering a pizza. The farther you have to carry it, the cooler it gets. If it gets too cool, it is no longer useful for paving. So asphalt facilities must be located close to work sites.
Q. Are there any health risks?
A. To the community, none. For those who work at an HMA facility, the greatest risk is getting burned. If you visit an HMA facility, you’ll see that the people working there wear typical construction clothes such as hard hats, gloves, and long-sleeved shirts. There is no scientific evidence that the very low levels of emissions from an asphalt facility pose health risks to humans.
Q. Does an asphalt facility keep hazardous chemicals on site?
A. Liquids that must be handled with care at an asphalt facility are:
- fuel oil for the burner, the same kind of fuel oil you may be using to heat your home;
- fuel for vehicles, the same product you buy at the gas station; and
- at some facilities, a small amount of solvents for the quality control lab. These solvents are used in small quantities with great care, and new lab procedures are quickly making solvents obsolete.
By federal law, a hot mix asphalt facility must keep these products, including the fuel oil, either in underground tanks that meet strict EPA standards or in aboveground tanks surrounded by berms that would hold all the contents in the event of a spill.
Q. What happens if there is an asphalt spill?
A. Asphalt cement starts to harden the moment it cools. Unless it’s 250 degrees Fahrenheit outside, it simply cannot travel over the ground more than a few feet. It will not penetrate the soil more than an inch or two before solidifying. Asphalt cement does not mix with, or become soluble in, water.
Q. What effect does asphalt production have on the environment?
A. Years ago, asphalt facilities often generated noticeable levels of dust, smoke, odors and noise. But two things have brought big changes. One was the EPA’s New Source Performance Standards, which went into effect in 1973. These required HMA producers to pass strict emission standards and install control systems to prevent the release of dust and smoke into the air. While annual production of asphalt paving material has increased by more than 250 percent over the past 40 years, total emissions from asphalt plants have dropped by 97 percent or more. In 2002, the United States Environmental Protection Agency acknowledged in two separate actions that asphalt facilities are not a major source of hazardous air pollutants.
An even stronger incentive for clean operation is economic. It’s in the facility owner’s best interest to ensure that all the equipment is operating at peak efficiency — which means producing very few emissions.
Asphalt pavements offer environmental benefits, too. Asphalt is the only pavement material that is 100 percent recyclable. In fact, asphalt pavement is the number one recycled material in America. Some asphalt pavements also reduce noise pollution and offer other environmental benefits.
Q. What if I have a concern about the asphalt plant in my community?
A. Just pick up the phone! Many asphalt facilities have dedicated helplines to answer questions and address concerns from people in their communities. They want to be available should you ever have a problem or question about plant operations or policies.
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