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Air Quality

Air pollution is derived from numerous sources. These include: stationary sources such as power plants, large industrial sources, metals, and chemical processing as well as small businesses such as print shops, gas stations, and dry cleaning shops; mobile sources including cars, trucks, buses, planes, trains, as well as construction and lawn equipment; natural sources such as dust, volcanoes or fires including forest and wild fires, controlled burns such as prairies; and finally, other combustion sources including furnaces in our homes, plants, and fires from wood-burning fire places, etc. All these sources contribute to and release different pollutants and incomplete combustion emissions into the atmosphere. The chart below depicts the air pollutants by emission category.

Source: U.S. EPA, Our Nation’s Air Status and Trends Through 2008, February 2010.
*(Particulate Matter (PM); Ammonia (NH 3); Sulfur Dioxide (SO 2); Nitrogen Oxides (NO x); Volatile Organic Compounds (VOC); Carbon Monoxide (CO)) 

Air emissions from these source categories are regulated by the U.S. Environmental Protection Agency (U.S. EPA) and state and local air agencies. U.S. EPA has developed health-based air standards which are known as the National Ambient Air Quality Standards (NAAQS) for six criteria pollutants. These include: carbon monoxide, lead, nitrogen dioxide, particulate matter (PM2.5 and PM10), ozone, and sulfur oxide.

According to the Federal Highway Administration (FHWA), “Transportation contributes to four of the six criteria pollutants: ozone, carbon monoxide, particulate matter, and nitrogen dioxide.” Currently in Illinois, two areas of the State do not achieve the NAAQS for the 8-Hour ozone standard and PM2.5 annual standard: the Chicago Metropolitan Area and the Metro East St. Louis area. The exhibits below depict Illinois’ PM2.5 and ozone 8-hour non-attainment areas. The Illinois EPA Annual Air Quality Report includes additional information.

To fulfill specific air quality requirements under the Clean Air Act (CAA), IDOT partners and works closely with the U.S. Department of Transportation, U.S. and Illinois Environmental Protection Agency (EPA), and Metropolitan Planning Organizations (MPO), to deal with regional as well as micro-scale air quality issues. To help achieve transportation air quality planning goals and to attain the NAAQS, IDOT works through the inter-agency consultation process to ensure that the Long Range Plans and Transportation Improvement Programs, developed by MPOs, conform with air quality improvement plans.

IDOT also evaluates and documents various micro-scale air quality issues such as carbon monoxide and particulate matter hot-spot analyses, in our environmental documents to fulfill National Environmental Policy Act (NEPA), CAA, and other air quality requirements. Chapters 24 to 26 of the Bureau of Design and Environment (BDE) Manual outlines various highway-related air quality issues that are documented in IDOT NEPA documents. 

In addition, air quality emissions from construction-related activities are also addressed. To address potential dust concerns, Dust Control requirements are outlined in IDOT’s Standard Specifications for Road and Bridge Construction.

IDOT has developed additional construction-related specifications and contract special provisions dealing with the use of cleaner diesel fuel, idling reduction requirements for construction equipment, and the installation of emission control devices on contractor vehicles. Construction air quality specifications (cleaner diesel fuel and idling reduction requirements) are contained in Article 107.41 of the Standard Specifications for Road and Bridge Construction.

IDOT has also included a special provision for the installation of emission control devices on contractor vehicles.

IDOT has also sponsored various Air Quality meetings and Peer Exchanges to discuss emerging air quality issues and state-of-the-art air quality practices. Representatives from state DOT’s, FHWA, MPOs, U.S. and Illinois EPA have attended and participated in these meetings. Proceedings from these meetings are provided below: