Improving Visibility in the United States
EM—October 2019: This issue of EM studies the federal regional haze program through the perspectives of key federal, state, and multi-jurisdictional stakeholders involved in implementing the program.
by John Kinsman and Gary Bramble
The statutory basis for the visibility protection and regional haze program in the United States is established in Section 169A of the U.S. Clean Air Act (CAA), which includes a goal to prevent future and remedy existing impairment of visibility from manmade air pollution in 156 Class I national parks and wilderness areas. Regional haze is visibility impairment caused by a variety of sources of air pollutants over a region-wide basis. Natural and anthropogenic emissions scatter/absorb light resulting in haze and can travel long distances, influencing areas far away. The major pollutants impairing visibility are elemental and organic carbon, oxides of sulfur and nitrogen, and dust (crustal materials). Owing to varying levels of anthropogenic and natural emissions, both domestic and international, and differing climate conditions, visibility varies from region to region. Generally, visibility is better in the Western United States than in the East, due to fewer anthropogenic emissions and lower humidity.
EPA's regulatory approach for reducing emissions in the 1980s and 1990s focused more on impacts of specific facilities, while also developing an understanding of the science around regional haze. In a 1999 rule, EPA clarified technical analysis expectations and established requirements for states to develop a first round of state implementation plans (SIPs) for regional haze in 2007, to address the need for reasonable progress in reducing regional haze for the period of 2008–2018. EPA established a national goal of attaining natural visibility conditions by 2064. EPA regulations require states to submit SIPs to implement the regional haze rule during 10-year planning or implementation periods. Planning for the second such period (2018–2028) is well underway, with SIPs due to EPA by July 31, 2021. SIPs include technical demonstrations showing reasonable progress toward EPA's goal of eliminating by 2064 domestic, anthropogenic visibility impairment in Class I areas.
In January 2017, EPA updated its regional haze regulation to further spell out specific requirements for states as they prepare and submit the second and later rounds of regional haze SIPs. The 2017 rule was supported by mid-2016 draft EPA guidance, which was replaced with final guidance in August 2019. EPA is expected to propose changes to the 2017 rule by early 2020. To assist states in their planning, EPA also has developed technical guidance in December 2018; implementation guidance in August 2019; and will release new technical modeling results in early Fall 2019. Most notable is EPA's August 2019 guidance, which came too late for the authors to address in this issue of EM. The August guidance assists states as they develop revised SIPs and replaces the agency's June 2016 draft guidance. It recognizes state discretion and potential flexibilities in developing regional haze SIPs, addressing key requirements and options for states, including selecting sources to analyze for potential control measures; how states analyze control cost, remaining useful life, and other considerations for individual sources; how to consider visibility benefits associated with control options; and how states might address previous controls installed to comply with other regulations.
The articles that follow in this issue address the regional haze program through the perspectives of key stakeholders.