Ozone management in Colorado: Why aren’t we there yet?

Since 2004, the state of Colorado in the United States of America has created multiple nonattainment State Implementation Plans (SIPs) that are supposed to comprise air pollution mitigation actions, that have so far been unsuccessful at ensuring Front Range Communities have reduced ozone levels to below the United States Environmental Protection Agency (EPA) standards. By interviewing eight stakeholders and decision-makers involved in ozone SIP rulemaking and drawing on secondary literature, this paper examines shortcomings in the SIP process in Colorado. We found that ozone precursor measurement and the modeling of attainment could be improved by better factoring in uncertainties in emissions inventories and conducting appropriate sensitivity analyses that would require more investment of state staff time and resources. Structural issues with the way the process is organized in Colorado limit optimum overlap between state: Air Pollution Control Division (APCD) and quasi-state: Regional Air Quality Council (RAQC) agencies during the SIP process. Specifically, although the RAQC is currently charged with developing and submitting SIPs to the State for approval, it does not have the power to implement control strategies for several key sources and therefore does not have the authority to propose key policies to be included in the SIP. In recent years, Colorado SIPs have largely focused on the bare minimum emissions controls to demonstrate attainment via modeling. Interviewees recommend that state political leaders take more of a leadership role to lower ground-level ozone levels and bring the Denver Metropolitan Area/North Front Range back into attainment with EPA standards.<i>Implications</i>: We evaluate why the State Implementation Plan (SIP) process has failed to achieve the attainment of the ozone standards in the Denver Metropolitan and North Front Range Area. Specifically, through interviewing several experts we identified several problems, namely: 1) errors in emissions inventories and modeling of ozone levels that have resulted in incorrect determinations that the ozone standards would be met with proposed emissions controls, and 2) structural problems in the way the SIP process is organized in Colorado, and the lack of political leadership.