Pursuant to sections 169A and 169B of the Clean Air Act, the US Environmental Protection Agency (EPA) requires states to submit regional haze State Implementation Plans (SIPs) that describe the states’ measures for meeting the national goal of a return to natural visibility conditions at Class I areas by 2064.

States with Class I areas must set reasonable progress goals for achieving and maintaining natural visibility conditions in their SIPs. States with emission sources affecting visibility in Class I areas must submit SIPs detailing anticipated actions to be taken to improve visibility in those areas. States must show how their actions will help Class I areas meet reasonable progress goals, as well as explaining the long-term strategy for improving visibility, including enforceable emissions limitations, compliance schedules, and other measures for meeting reasonable progress goals.

Regional haze SIPs are also required to include calculations of baseline and natural visibility conditions as well as monitoring strategies for tracking reasonable progress. Finally, regional haze SIPs must include a determination of Best Available Retrofit Technology (BART) for sources of a certain size or emissions profile that began operating during a specific time frame.

In the future, states must submit revisions to the regional haze SIP every 5 years evaluating progress toward meeting reasonable progress goals and also updating the long-term strategy in 2018 as well as every 10 years thereafter.

The following resources provide more information that pertains to the regional haze SIPs due in 2008.