Practices for Project-Level Analyses for Air Quality (2021)

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1   This study examined practices and procedures at departments of transportation (DOTs) for conducting project-level air quality analyses. DOTs are required to conduct these analyses to meet requirements of the National Environmental Policy Act (NEPA), the United States Environmental Protection Agency’s (U.S. EPA’s) transportation conformity regulation, or both. State and local requirements may also be a factor in the analysis. As the requirements, modeling, and guidance have become more complex and challenging, DOTs have adapted in different ways to meet the requirements, based on their environmental and administrative situations. This study found that these adaptations have resulted, except for some important common features, in a wide range of practices, expectations, staffing, and procedures, written as well as institutional. The study was accomplished with the use of the following three elements: 1. A literature review, 2. An electronic survey sent to 50 state DOTs and the District of Columbia, and 3. Case examples. The literature review concentrated on studies and reports that augmented and detailed federal guidance, rather than providing guidance itself. It was felt that this approach would be most helpful to the DOTs since the survey revealed that the vast majority had some or exten- sive knowledge of federal guidance. As a result, the literature review for this report comprises eight studies, six from the National Cooperative Highway Research Program (NCHRP), one from a state DOT, and one from the American Association of State Highway and Trans- portation Officials (AASHTO). A brief summary of each study is provided, highlighting the findings of the study. These studies consider elements of the analysis process, including traffic inputs and pollutants background data and modeling efforts, primarily for particulate matter (PM), carbon monoxide (CO) and mobile source air toxics (MSATs). The literature review concludes with an overview of the transportation project-level air quality analysis process. A survey was designed to capture all issues that DOTs are involved with when dealing with project-level air quality issues. It was sent electronically to 50 state DOTs and the District of Columbia. Forty DOTs responded to the survey, yielding a 78% response rate. The survey revealed both disparities and similarities among the DOTs in their approaches to project-level air quality analyses. The DOTs all use federally approved emission and disper- sion models; they all rely on federal guidance for addressing various pollutants (for those pollutants for which federal guidance exists); and when an analysis is performed, they all use similar approaches for documenting the analysis and its results. However, there is a wide range of practices among the DOTs, in having (or not having) written air quality analysis procedures, in the coverage and detail of those procedures when they are written, in their involvement in the interagency transportation conformity consultation process for those S U M M A R Y Practices for Project-Level Analyses for Air Quality

2 Practices for Project-Level Analyses for Air Quality states (and the District of Columbia) with nonattainment or maintenance areas, in consid- eration of pollutants, especially greenhouse gasses (GHGs), and in staffing and support within the DOT. Other significant findings from the survey include the following: • No DOT has performed an air quality analysis for a transportation project that resulted in a modeled exceedance of an applicable air quality standard. • No DOT has had to apply air quality mitigation measures in order to have a project not cause an exceedance of a standard and/or have an unacceptable air quality impact. • Transportation conformity appears to be the best predictor of DOT involvement and practice with respect to transportation air quality issues in general, as well as to project- level air quality issues. • Quantitative project-level air quality analyses primarily for NEPA purposes are not being performed very frequently and will likely become less frequent in the future. • DOT air quality specialists want to improve and maintain their skills. The case examples highlight this wide range of project-level air quality practice from five states (Colorado, Delaware, Illinois, Nevada, and Oregon) and the District of Columbia. The case examples were chosen to include areas • From coast to coast, • With DOTs having detailed written air quality procedures and where the air quality process at the project level is based on institutional knowledge and length of staff service, • With different experiences, longevity, and support for the air quality specialist(s) at the respective DOTs, and • Transitioning from maintenance status to attainment status and in which, therefore, project-level hot-spot analysis requirements may no longer apply. The report for the study includes a small number of recommendations for further research, primarily based on comments from the DOTs. Development of a template for written project- level air quality analysis procedures is suggested. The template could include a detailed set of guidelines covering all pollutants, which the states and the District of Columbia could adopt to meet their specific status and needs. Also suggested is a modeling study related to nitrogen dioxide (NO2) concentrations under transportation project scenarios, and additional infor- mation and guidance on PM mitigation measures and their effectiveness, and on addressing GHG emissions at the project level. Appendices of the survey questionnaire, the survey responses, links for state/district DOT air quality analysis procedures, and a matrix of nonattainment and maintenance areas by state/district are included in the report. Appendices A, C, and D print and post. Appendix B only posts.