A February federal court rulling may force a “re-examination” of air quality models used by transportation agencies in 82 areas around the country, including several major cities such as Boston, Charlotte, and Las Vegas.

In a lawsuit brought by the South Coast Air Quality Management District against the U.S. Environmental Protection Agency, the D.C. Circuit Court ruled that the EPA exceeded its authority in 2015 when it issued a rule making 2008 National Ambient Air Quality Standards or “NAAQS” the sole set of air quality rules transportation projects were required to meet – unilaterally superseding existing 1997 standards.

As a result of the court’s verdict, 82 areas in 24 states that were previously nonattainment or maintenance areas for the 1997 ozone standard but are in attainment under the 2008 ozone standard must “re-do” their air quality models to ensure they are in compliance with the 1997 standards as well.

According to an AASHTO analysis, it is “highly likely” projects in those 82 areas will be able to re-comply with the 1997 standards because the 2008 standards they already meet are far stricter in nature. Yet that re-compliance process could take a significant amount of time. The Texas Department of Transportation, for one, estimates that this re-examination of air quality models could take it anywhere from six to 24 months complete.

The Federal Highway Administration and Federal Transit Administration sent out “guidance” to their division administrators and air quality staff in light of the court’s decision. That guidance breaks down as follows:

• Except for the 82 affected areas, all routine planning and project development actions may proceed throughout the country.
• Actions within the 82 identified areas that should be considered “on-hold” for now.
• FHWA metropolitan plans and FTA transportation improvement program (TIP) updates and amendments that involve “non-exempt” projects may not proceed. However, those plan/TIP actions that involve administrative modifications or amendments that add or delete exempt projects may proceed because those actions do not require a conformity determination.
• Statewide transportation improvement programs or “STIPs” approvals that include TIPs from the 82 identified areas may not proceed, unless they conform with the 1997 ozone NAAQS or are limited to projects that are exempt from transportation conformity. Again, though, FHWA and FTA said STIPs may proceed if they are outside one of the 82 areas.
• Projects with National Environmental Policy Act or “NEPA” approvals may not proceed unless the project is included in a metropolitan plan and TIP.  Yet projects with completed NEPA approvals may proceed, the agencies noted.