Air permitting for Colorado stationary sources in disproportionately impacted communities.

As the air permitting process evolves, so have environmental justice (EJ) considerations. Amidst several states' EJ-specificinitiatives, Colorado's Air Pollution Control Division (APCD) has become a national leader in addressing EJ concerns through the stationary source permitting process. Colorado began this process by publishing internal Division guidance that required longer public comment periods and other enhanced public outreach for certain stationary source permitting actions. Today, Colorado has enacted new laws and regulations, including the Environmental Justice Act and Air Quality Regulation Number 3 that aim to address harmful air quality disparities by requiring Environmental Justice Summaries, enhancedmodeling, and source-specific monitoring, among other measures. APCD has worked with several partners to establish a robust data set from which state permitting authorities can identify certain permit applications for facilities that are advised to conduct more extensive public engagement; a case study of enhanced engagement is included in this paper.Implications: Environmental Justice (EJ) in air permitting requires ongoing adaptation to regulatory frameworks, data availability, and community engagement. The Division has integrated EJ considerations into permitting through the implementation of EJ Summaries, enhanced modeling, and source-specific monitoring. However, significant challenges remain, including data limitations, the complexity of regulatory compliance, ensuring meaningful community participation, and addressing historic socioeconomic disparities. The Division is committed to refining its approach by improving data transparency, enhancing communication with affected communities, and integrating lessons learned from other state agencies. Revisions to Regulation 3 reflect a broader strategy to incorporate EJ principles into permitting decisions while maintaining regulatory clarity. The Division engages in local dialogue to ensure that impacted communities understand regulatory requirements and how to effectively participate in public comment opportunities. These conversations inform the Division's decision-making processes and help refine policies that mitigate health and environmental disparities.