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What is the Regional Haze Plan?

In 1999, EPA finalized the Regional Haze Rule, which aims to reduce emissions that contribute to haze in Federal Class I areas, or designated wilderness areas, national parks, and monuments.

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.  

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 weaken visibility. Arizona currently has several stationary sources subject to control requirements under BART:

  • Arizona Electric Power Cooperative (AEPCO), Apache Generating Station
  • Arizona Public service (APS), Cholla Generating Station
  • Salt River Project (SRP), Coronado Generating Station
  • Freeport-McMoRan, Miami Smelter
  • ASARCO Inc., Hayden Smelter
  • Tucson Electric Power (TEP), Sundt Generating Station
  • Nelson Lime Plant

In addition to the sources listed above, there are two sources deemed not subject to BART that EPA determined required control measures under the Regional Haze Program:

  • Phoenix Cement Co., Clarkdale (Kiln 4)
  • CalPortland Cement, Rillito (Kiln 4)

Reasonable Progress Goals

Each area is given a reasonable progress goal (RPG) for the 20 percent best and 20 percent worst days, which is reevaluated during each SIP revision. The RPGs incrementally 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, or a measurement based on perceptible change to the human eye. Below is a table listing the Federal Class I areas in Arizona and their associated visibility values in deciviews (dv). 

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