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

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34 Conclusions Based on this study, it appears that DOTs are continuing to advance project-level air quality analyses and working on related issues. In fact, except for a handful of DOTs, air quality, at least at the project level, is no longer a priority environmental issue. These conclusions are based on the following findings and observations from the study: • The cognizant federal agencies, particularly U.S. EPA and FHWA, have provided guidance on addressing a number of pollutants that are of concern at a transportation project level. Although U.S. EPA’s guidance is directed toward requirements to meet the transportation conformity regulation, DOTs have adopted the technical aspects of the analyses and applied them to all analyses they may do for any project, including NEPA analyses, if any. • As the literature review has revealed, other studies and documents exist that provide guidance to DOTs on applying the federal guidance or ancillary topics that occur at project-level air quality analyses. The NCHRP 25-25 series is a detailed source of supplemental project-level guidance and information, although some of the early work has become dated as conditions (models, air quality standards, or policies) have changed. • Within the last 5 years, the survey revealed that no DOT has performed an air quality analysis for a transportation project that caused an exceedance of an applicable air quality standard, and that no DOT has had to apply air quality mitigation measures in order to have a project not cause an exceedance of a standard and have an unacceptable air quality impact. Only one DOT reported being involved in litigation related to air quality on a transportation project. That case involved GHG issues, not criteria air pollutant concerns. • Some DOTs have detailed, written project-level air quality analysis procedures. On the other hand, other DOTs do not have any written project-level air quality analysis procedures. Those DOTs do not seem to have been adversely affected by not having written air quality procedures. • Of the DOTs that do have written air quality analysis procedures, there is a wide disparity in the issues and depth of information contained in the written procedures. Some procedures cover all pollutants; others only cover pollutants of concern in their state/district. Some cover modeling and documentation in detail, others less so. The survey attempted to query all issues of relevance concerning project-level air quality analysis. The responses, by examining which questions were answered in the negative or were not answered, demonstrated the substantial range of coverage of issues by the DOTs. What one DOT feels is necessary may not apply to other DOTs, depending on their circumstances. • Transportation conformity appears to be the best predictor of DOT involvement and practice with respect to overall transportation air quality issues and to project-level air quality issues. Of the agencies that responded to the survey, none of the states with no nonattainment or main- tenance areas have written air quality analysis procedures. Of the states where transportation C H A P T E R 5 Conclusions and Suggested Further Research

Conclusions and Suggested Further Research 35   conformity was becoming less of a concern (i.e., where the maintenance period for CO has come, or is coming, to a close), there is an expectation that air quality analyses will become more infrequent. • Performing a project-level air quality analysis primarily for NEPA purposes is not occurring very frequently and will likely become less frequent in the future. Some DOTs have agreements with their respective air quality agency or interagency consultation partners that transporta- tion project-level hot-spot CO air quality analyses for NEPA or state environmental require- ments are no longer necessary. Indeed, some recent research proposals have suggested an examination of the need for continuing CO project-level hot-spot analyses. • Several factors are contributing to the downward trend in project-level air quality analyses. New vehicles are much cleaner (less emitting) than in the past, the traffic volume thresholds that trigger an air quality analysis in the federal guidance (e.g., MSATs, projects of air quality concern) are relatively high, and there are relatively few projects on DOT programs that substantially increase highway capacity. • DOT air quality specialists want to improve and maintain their skills. The relevant emission and dispersion models are complex and training is infrequent or unavailable to them. Some are also asked to develop skills and knowledge in other environmental fields and, in some states, the air quality function is divided between functional units that deal with regional air quality issues and those that deal with local or project-level issues. Suggested Further Research From the literature review, survey results, case examples, and email and telephone discussions with selected DOTs, several topics emerged for possible follow-up and research. These include the following: • Although the lack of written project-level air quality guidelines or varying stages of development of written guidance does not seem to be hindrance to DOTs in completing environmental studies for their projects, having written procedures is good practice. With a DOT’s having written guid- ance, staff (especially new staff) will know how to proceed etc. with an analysis, and to what depth of analysis, when and if a need should arise for a project-level analysis. A template could be developed that DOTs could use “as is,” or portions thereof, that suits their needs. The template could cover all aspects and all pollutants that can occur in a project-level air quality review and in sufficient detail that little or no additional research would be needed by the DOT. DOTs could adopt as much of the template as meets their policies and conditions. Common modeling inputs could also be explored. The template would need to be maintained and updated into the future as models, air quality standards, federal policies, or other analytical or regulatory aspects change. • One DOT discussed the need for NO2 guidance at the project level. Despite the analysis from the ongoing U.S. EPA near-road monitoring that NO2 exceedances of the short-term ambient air quality standard are not occurring, no study has examined the potential of exceedances of the standard under conditions that are typically modeled for transportation projects. A modeling study could be performed that looks at project types and conditions that are typically encoun- tered by DOTs. This would include congested intersections and other facility types with near-by sidewalk receptors. • One DOT discussed the need for additional information on PM mitigation measures. With PM background levels at or near the appropriate PM ambient air quality standard, a project- level analysis could result in PM concentrations at or above the standard, in which case the DOT would have to consider implementation of one or more mitigation measures. Although some DOTs have information and lists of PM mitigation measures, more information would be useful to the DOTs. This additional information could include range of effectiveness, costs

36 Practices for Project-Level Analyses for Air Quality and practical issues of implementation, and speciation and other sources contributing to back- ground levels. • Since the rescission by CEQ on project-level analysis requirements under NEPA, some DOTs are unsure of how to proceed on project-level GHG analysis. Areas of uncertainty include criteria for analysis, frequency of analysis, factors that influence differences in GHG emis- sions among alternatives (such as scale and scope of the project), among others. Depending on a state’s/district’s executive order, legislation, or climate action plan for GHG emission targets, this guidance or template could also research methods to foster consistency among GHG emission targets with project alternatives and transportation improvement programs and long-range plans.