Clean Air Act PM2.5 Hot-Spot Determination. The plaintiffs claimed that the Clean Air Act required FHWA to use a surrogate monitor located within the immediate vicinity of the project, rather than one located five miles outside the project area. After a detailed review of the conformity regulations (40 CFR Part 93), the court determined that “regulations do not decisively answer whether the CAA required qualitative hot-spot analysis within the immediate vicinity of the project area during the time period at issue.” Given the ambiguity in the regulations, the court then assessed the reasonableness of EPA and FHWA’s interpretation of those regulations, as expressed in a guidance document jointly issued by EPA and FHWA in 2006. The court noted that the 2006 guidance document “neither mentions a distance requirement nor requires installation of new air monitors; rather, it only requires project sponsors to use nearby air monitors at ‘locations similar to the proposed project.’” The court found that this interpretation was reasonable, and that the monitor location used in the analysis complied with the guidance. Therefore, the court upheld the qualitative hot-spot analysis: “Defendants’ Conformity Determination using this comparison method was a reasonable application of the EPA and DOT’s Conformity Guidance. … The Conformity Guidance makes clear that Defendants were permitted to use a surrogate air monitor, and this monitor’s distance from the Project—about one mile from the near end of the Project, and five miles from the far end—was well within the ranges approved in [previous cases]. In addition, Defendants used a second air monitor to verify that the North Long Beach station was representative of air quality in the project area, further bolstering the accuracy of their qualitative analysis.” NEPA Air Quality Impacts – New NAAQS. The plaintiffs claimed that the air quality impacts analysis in the EIS was inadequate because it failed to address whether the potential increase in PM 2.5 concentrations would violate new national ambient air quality standards (NAAQS) issued for PM2.5 in 2006. The new standards were not required to be used for the conformity determination, because the new standards did not go into effect until 2010, after the conformity determination had been completed. But the plaintiffs argued that the EIS should have included an analysis of the project’s potential to violate those standards. The court rejected this argument, finding that the EIS “was forthright in discussing the new standard.” Air Quality Impacts – Public Health. The plaintiffs also claimed that the EIS was flawed because it failed to disclose the project’s impacts on public health. The court found that the EIS adequately addressed public health impacts because it included a Health Impacts Assessment that took into account the effects of PM2.5 emissions and included the : “The EIS included a Health Risk Assessment that was subject to the public comment and review process. In the Health Risk Assessment, Defendants disclosed that the Project would lead to increased PM10 and PM2.5 concentrations in the immediate vicinity of the Project, and how those increased concentrations could have adverse health effects for local residents. The Health Risk Assessment also acknowledged that this type of transportation project usually leads to increased PM 2.5 concentrations in the area immediately adjacent to the project. “Defendants also conducted detailed studies based on 2006–2007 meteorological data, where they estimated cancer- and other health-risk increases at thousands of residences, schools, parks, and other areas in the immediate vicinity of the Project. Defendants explained the study results with color-coded diagrams illustrating the precise locations where adverse health effects would be the greatest. They also included statistical discussions and tables illustrating that roughly 97% of the adverse health effects would be due to diesel particulate matter concentrations. Additionally, Defendants determined that a heating, ventilation, and air conditioning retrofit program for residences within the vicinity of the significant impact zone would be a feasible mitigation measure.”