The Clean Air Act section 176(c) requires that federally supported highway and transit project activities are consistent with state air quality goals, found in the state implementation plan (SIP). The process to ensure this consistency is called Transportation Conformity. Conformity to the SIP means that transportation activities will not cause new violations of the National Ambient Air Quality Standards (NAAQS or "standards"), worsen existing violations of the standard, or delay timely attainment of the relevant standard.
Transportation conformity is required for federal supported transportation projects in areas that have been designated by the U.S. Environmental Protection Agency (EPA) as not meeting a NAAQS. These areas are called nonattainment areas if they currently do not meet air quality standards or maintenance areas if they have previously violated air quality standards, but currently meet them and have an approved Clean Air Act section 175A maintenance plan. On January 5, 2005, the EPA designated the Baltimore, MD area as nonattainment for fine particulate matter, called PM2.5. This designation became effective on April 5, 2005, 90 days after EPA's published action in the Federal Register. Transportation conformity for the PM2.5 standards applied on April 5, 2006, after the one-year grace period provided by the Clean Air Act.
The I-695 corridor project, located in Baltimore County, Maryland, is within the Baltimore, MD PM2.5 nonattainment area; and therefore the project is required to meet Transportation Conformity requirements found in 40 CFR Part 93 as amended. Therefore, the project must be included in a transportation plan and transportation improvement program (TIP) that conforms. For PM2.5, project-level conformity also requires an assessment of localized emissions impacts for certain projects. This localized assessment is called a hotspot analysis.
EPA amended the Transportation Conformity rule on March 10, 20061, requiring a hotspot analysis as part of project-level conformity in PM2.5 nonattainment areas for certain projects. This requirement began for all federally-supported projects requiring approval on or after April 5, 2006. Since the Finding of No Significant Impact (FONSI) for the I-695 corridor project was approved on November 15, 1991, the PM2.5 hotspot analysis was not included in the FONSI. Therefore, public review and comment for this PM2.5 hotspot analysis is being undertaken separately from that of the I-695 corridor FONSI.