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

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3   Organization of the Report The organization of this report follows the approach to the study. It begins with background information on why project-level air quality analyses are required to be done by state DOTs and the District of Columbia, a discussion of the regulatory and procedural issues involved, and a brief narrative of the evolution of the practice. A literature review follows. The studies and reports cited in the literature review are selected to provide DOTs with information that builds upon and goes beyond federal guidance. It is intended that the sources will offer an opportunity to provide more information and insight on the air quality aspects, implications of the analyses of project alternatives, and selection of a preferred alternative. The survey design and results are then presented. There are 50 questions in the survey, so each individual question and its results are not discussed. Rather, many of the questions can be thought of as related to other questions, or in terms of themes. Thus, the report discusses and presents the results of themes based on the responses to the small number of related questions. Forty DOTs responded to the survey, equaling a 78% response rate. This chapter also discusses the limitations of the survey and its findings. The main section of the report concludes with a discussion of the findings and conclusions of the study and a brief inventory of issues that may benefit from follow-up research. There are four appendices: Appendices A, C, and D print and post. Appendix B only posts. Some clarifications of the following terms as used in this report would be helpful to the reader: • Transportation air quality – the general term covering regional and project-level transportation air quality matters. • Regional air quality – transportation air quality issues dealing with matters at a geographical scale larger than a transportation project area. These issues can be addressed in a quantitative or qualitative manner. Typical examples include a regional emissions analysis in support of a transportation conformity determination for a long-range plan or transportation improvement program (TIP), or a transportation sector GHG emission inventory in support of a state’s or municipality’s climate action plan. • Hot-spot analysis – a quantitative or qualitative assessment of potentially elevated concentra- tions of a pollutant, typically associated with vehicular emissions. • Project-level analysis – this includes a hot-spot analysis, if performed, and can also include determining a transportation project’s consistency with the long-range plan or TIP’s confor- mity determination, if needed, and qualitative or quantitative analysis for MSATs or GHGs, if needed. C H A P T E R 1 Introduction

4 Practices for Project-Level Analyses for Air Quality It should also be highlighted that observations and findings discussed in Chapter 3 – Survey of DOTs are current and correct based on the survey results. However, the requirements and situations of one DOT may not necessarily apply to others. Background Project-level air quality analyses for transportation projects are now approaching a half century of experience and accumulated knowledge. Over that time period, these analyses have under- gone a substantial change in complexity, and DOTs have had to understand and master those changes in order to move forward with important transportation projects across the nation. In the 1970s and early 1980s, the concerns associated with CO “hot spots” became apparent. The analysis issues moved away from highway segments to intersections with potentially elevated emissions associated with idling, deceleration, and acceleration. Based on guidance from U.S. EPA and FHWA (Federal Highway Administration), many analysts applied screening techniques using “worst-case” assumptions regarding meteorological and traffic conditions. Alternatively, analysts used one of several Gaussian line source dispersion models designed for near-roadway conditions with several receptors placed just outside the mixing zone, again, to simulate worst- case conditions. With the promulgation of National Ambient Air Quality Standards (NAAQS) for particulate matter less than 10 microns in diameter (PM10) and less than 2.5 microns in diameter (PM2.5), DOTs have had to master project-level analyses for these pollutants as well. Transportation project-level PM hot-spot analyses are challenging, both from a technical complexity standpoint and a resource-usage perspective. They are considerably more challenging than corresponding CO hot-spot analyses, because CO analyses can use various simplifying conditions that are not available for PM. With the newer emission and dispersion models, project-level quantitative analyses are becoming much more complex and challenging than the hot-spot analyses historically performed, with a potentially large drain on resources and an impact on project schedules, especially if the analysis indicates a potential exceedance of an ambient air quality standard. Recent developments in the field have also led to the emergence of analyses for MSATs and GHGs. When analyzed, these pollutants are only considered in terms of emissions, and concen- trations of these pollutants are not typically estimated. Nevertheless, these analyses add to the list of pollutants that DOTs may have to address at the project level. DOTs commonly perform project-level air quality analysis for a transportation project in order to address NEPA and to demonstrate compliance with the conformity provisions of the Clean Air Act Amendments of 1990 (quantitative hot-spot analyses or documenting consistency with regional conformity determinations). Many states and some smaller governmental entities have adopted laws and regulations that are intended to mirror NEPA and/or other environ- mental policies, which DOTs often must also comply with in order to successfully advance their projects. The nature of the transportation project-level air quality arena is evolving, and there are potentially significant impacts to project schedules and budgets should air quality issues arise with a project. For these reasons, this study examined the state of practice among DOTs with regard to their air quality practices and procedures and the degree to which those practices and procedures are sufficiently developed in order to meet the requirements in their respective states/district.

Introduction 5   Study Approach This study was accomplished in the following four stages: 1. Literature review, 2. Survey of DOT air quality practitioners, 3. Selected follow-up case examples, and 4. Conclusions and suggested further research. Stage 1 – Literature Review For this synthesis project, existing guidance documents, publications and online sources concerning transportation project-level air quality analysis were reviewed. The goal of the litera- ture review was to establish a background for this synthesis report and to gather information regarding current air quality analysis procedures and practices. The review identified federal guid- ance as well as research reports and studies related to practices addressing implementation of the federal guidance and aspects beyond the immediate scope of the federal guidance but intended to provide assistance to DOTs to address the air quality issue at hand. It is this latter aspect that the literature review discussion below focuses on. Stage 2 – State/District DOT Survey A survey was developed that queried all aspects of a DOT’s air quality practices and procedures. The survey was done electronically through Survey Monkey. The survey was distributed to the states and the District of Columbia in early January 2020. The survey was distributed to all 51 DOTs (50 states plus the District of Columbia). Along with the survey, a description of the information desired and background information about the study was provided to the DOTs. The target response rate for this synthesis effort was at least 40 entities. Responses were received from 40 DOTs (a 78% response rate), achieving the target. Stage 3 – Departments of Transportation Follow-up Case Examples Through the information gathered primarily from the survey responses, some DOTs were iden- tified for case examples of their air quality analysis procedures and practices. The goal behind conducting follow-ups was to get more detailed information from the selected DOTs regarding their survey responses, their written air quality analysis procedures, and their experiences and knowledge with transportation project issues related to air quality. Stage 4 – Conclusions and Suggested Further Research Finally, this study report concludes with a brief section of conclusions and suggested further research.