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The Clean Air Act defines "conformity to an implementation plan" as eliminating or reducing the severity and number of violations of the national ambient air quality standards. In addition, federal activities may not cause or contribute to new violations of air quality standards, exacerbate existing violations, or interfere with timely attainment or required interim emission reductions towards attainment.
In North Carolina, the NC Department of Environment and Natural Resources, Division of Air Quality (DAQ) develops the State Implementation Plan (SIP). The SIP is the document that describes how North Carolina will keep the air clean enough so that the state does not violate the National Ambient Air Quality Standards (NAAQS). In the SIP, emissions from factories, power plants, dry cleaners, bakeries, construction equipment, lawn equipment, biogenics, vehicles and other sources are estimated. In order to assure that the standards are not violated, certain sources are limited in how much they can pollute.
Automobiles are the largest contributor to North Carolina's air pollution. Although automobile technology has greatly improved over the years, the total pollution from vehicles is rising. More people are driving, and traveling longer distances than ever. As a result, our air pollution worsens and roads become more congested.
The transportation conformity regulation, 40 CFR Parts 51 and 93, requires that the state Department of Transportation (DOT) or Metropolitan Planning Organization add up the vehicle emissions that an area will generate under its transportation plan. If the emissions exceed the limits established in the SIP, then federal money cannot be spent to fund projects.
In North Carolina, several areas must complete conformity analyses on their transportation plans because they lie within an air quality "maintenance" or "non-attainment" area. The following counties have been designated as non-attainment of the 2008 8-hour ozone standard: Gaston (partial), Mecklenburg, Cabarrus (partial), Iredell (partial), Lincoln (partial), Rowan (partial), and Union (partial). Catawba, Guilford, and Davidson are currently in maintenance of the PM2.5 standard. A new analysis is required whenever the transportation plan in one of these areas adds a project, deletes a project, significantly delays or accelerates a project, or changes the project scope. Wake, Durham, Forsyth, and Mecklenburg Counties are in maintenance for Carbon monoxide until 2015.
Congestion Mitigation and Air Quality Improvement Program (CMAQ)
The CMAQ Program was designed to expand substantially the focus and purpose of federal transportation funding assistance to include air quality improvement as a specific objective. These funds are to assist areas designated as nonattainment or maintenance to achieve healthful levels of air quality by funding transportation projects and programs that improve air quality.