In 1999, EPA finalized the Regional Haze Rule under the Clean Air Act, which aims to reduce emissions that contribute to haze in Federal Class I areas, or designated wilderness areas, national parks, and monuments | View Rule >

EPA defines “regional haze” as visibility impairment produced by sources and activities that emit fine particles and their precursor emissions across a broad geographic area, which can interfere with the scenic vistas integral to our national parks, forests, and wilderness areas.  

For each ten year planning period, states are required to develop plans to analyze emissions of pollutants that reduce visibility at Class I areas and develop control strategies to reduce those emissions and improve visibility.

Arizona has 11 Class I areas:

• Chiricahua National Monument and Wilderness Area
• Galiuro Wilderness Area
• Grand Canyon National Park
• Mazatzal Wilderness Area
• Mount Baldy Wilderness Area
• Petrified Forest National Park
• Pine Mountain Wilderness Area
• Saguaro National Park and Wilderness Area
• Sierra Ancha Wilderness Area
• Superstition Wilderness Area, and
• Sycamore Canyon Wilderness Area

View on Map | View >

BART Determinations

The Regional Haze Rule requires state agencies to make Best Available Retroactive Technology (BART) determinations for stationary sources located near Class I areas. The BART determinations dictate whether a source must comply with emission limits or implement technology-based control measures to reduce pollutants that impact visibility. Arizona currently has several stationary sources subject to control requirements under BART as well as additional sources, not subject to BART, but subject to control measures to advance visibility progress under the Regional Haze Program.

Reasonable Progress Goals

Each area is given a reasonable progress goal (RPG) for the 20 percent clearest and 20 percent haziest days, which is reevaluated during each state implementation plan revision. The RPGs gradually reduce the amount of pollutants in an effort to ultimately reach a physical state termed “natural conditions” by 2064. Visibility values are expressed in deciviews (dv), or a measurement based on noticeable change to the human eye.

Learn more about and view ADEQ’s various plans, rules, reports, and actions to fulfill the Regional Haze rule and enhance visibility at Arizona Class I areas | View >

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