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Regional Haze

One form of air pollution, haze, degrades visibility in many American cities and scenic areas. Haze is caused when sunlight encounters tiny pollution particles in the air, which reduce the clarity and color of what we see. Section 169A of the federal Clean Air Act (CAA) includes as a national visibility goal, "the prevention of any future, and the remedying of any existing, impairment of visibility in 156 mandatory Federal Class I areas in which impairment results from manmade air pollution." Class I areas include national parks (over 6,000 acres), national wilderness areas, national memorial parks (over 5,000 acres), national monuments, and other areas of special national and cultural significance. A Class 1 area is one in which visibility is protected more rigorously than under (NAAQS). The NAAQS are regulations the United States Environmental Protection Agency (U.S. EPA) sets to limit common (criteria) pollutants in the outdoor air in order to protect human health and the environment. U.S. EPA provides and an overview of its program to monitor and address impairments.

U.S. EPA promulgated the federal Regional Haze Rule on July 1, 1999 requiring states to develop State Implementation Plans (SIPs) to mitigate their contribution to regional haze visibility impairment in Class I areas. A SIP is a formal plan describing how a state will work to meet federal air regulations. The federal Regional Haze Rule requires SIPs to include best available retrofit technology (BART) at certain large stationary sources determined to emit air pollutants that may reasonably be anticipated to cause or contribute to visibility impairment in a Class I area. Indiana does not have any Class I areas; however, Indiana sources were determined by U.S. EPA to impact visibility in Class I areas in other states.

Following are IDEM’s submittals to date for Indiana’s Regional Haze SIP. IDEM’s online archive contains additional historical information concerning the development of Indiana’s initial Regional Haze SIP and the BART rulemaking process.

  • Draft Indiana Regional Haze (RH) State Implementation Plan (SIP) for the Second Implementation Period (September 2021)
    • Indiana RH SIP 2021, Appendix A, Appendix B [ZIP]
    • Appendix C, Parts 1, 2, 3 [ZIP]
    • Appendix C, Parts 4, 5, 6 [ZIP]
    • Appendix C, Parts 7, 8 [ZIP]
    • Appendices D through H [ZIP]
    • Appendix I, Parts 1, 2, 3, 4 [ZIP]
    • Appendix I, Parts 5, 6, 7 [ZIP]
    • Appendices J through O [ZIP]
    • Appendices P through U [ZIP]
  • Indiana Regional Haze Five-Year Progress Report State Implementation Plan Revision (March 30, 2016) [ZIP]:
    • Federal Register Notice Concerning U.S. EPA Approval and Promulgation of Indiana’s Regional Haze Five-Year Progress Report State Implementation Plan Revision (February 2, 2018)
    • Transmittal Letter to the U.S. Environmental Protection Agency (March 30, 2016)
      • Indiana Regional Haze Five-Year Progress Report State Implementation Plan
        • Appendices A-E
  • Supplement to Indiana’s Regional Haze SIP Submittal (March 10, 2011 and January 14, 2011):
    • Documents – Part 1 [ZIP]:
      • Federal Register Notice Concerning U.S. EPA Limited Approval and Promulgation of Indiana’s Regional Haze State Implementation Plan (June 11, 2012)
      • Transmittal Letter (March 10, 2011), Transmittal Letter (January 14, 2011), and Indiana Regional Haze State Implementation Plan
        • Appendices 1 – 5
    • Documents - Part 2 [ZIP]:
      • Appendix 5a
      • Appendix 5b
      • Appendix 5c
    • Documents – Part 3 [ZIP]:
      • Appendix 5d
      • Appendices 6 – 9a
      • Appendix 9b
      • Appendices 9c – 10b
  • Initial Regional Haze SIP Submittal (September 29, 2008) [ZIP]:
    • Transmittal Letter and Indiana Regional Haze SIP Including Appendices 1 - 2
      • Appendix 3
      • Appendices 4 - 7