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Miami | Sulfur Dioxide (SO2) Nonattainment Area

County Affected:

Parts of Gila County  | View on a Map >

Nonattainment Area Designation Date:

Aug. 5, 2013
(78 FR 47191)

Pollutant of Concern:

Sulfur Dioxide (2010 standard)


The concentration of SO2 in the air in Miami has been above federal standards for several years.  ADEQ submitted a nonattainment State Implementation Plan (SIP) to the EPA in March 2017. Freeport McMoRan made numerous improvements to the Miami Operations in 2017 as a part of $250 million expansion project to substantially reduce SO2 emissions. In 2019 EPA took final action to approve Arizona’s SIP revision for attaining the 2010 1-hour sulfur dioxide primary national ambient air quality standard for the Miami, Arizona sulfur dioxide nonattainment area, effective April 11, 2019.

Some of the controls implemented at the smelter to reduce SO2 emissions include:• Capture of fugitive emissions from converters and anode furnaces rooflines, and routing of these to new caustic aisle scrubber

• Routing of emissions from the anode furnace baghouse to aisle scrubber
• Upgrade of the vent fume scrubber, and acid plant tail gas scrubber to caustic use.
• Improvements in capture of fugitive emissions from IsaSmelt furnace feed port and matte taping
• Stringent SO2 emission limits established to meet federal standards

Source of Pollutant:

  • Smelting Metal

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