Contact EPA Pacific Southwest Air Program
Pacific Southwest, Region 9
Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations
Air Actions, Arizona
Contact
Wienke Tax (tax.wienke@epa.gov)
Office of Air Planning
EPA Region 9
(415) 947-4192
Sulfur Dioxide Actions in Morenci, AZ
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December 2016: Approval of Arizona's Second Ten-Year Maintenance Plans for Sulfur Dioxide in the Ajo and Morenci Areas
On December 15, 2016, EPA signed a direct final approval of Arizona's maintenance plans to maintain attainment of the short-term (24-hour) and long-term (annual) primary National Ambient Air Quality Standards (NAAQS) for sulfur dioxide (SO2) in the Ajo and Morenci areas.
The Ajo and Morenci areas have not had a violation of either the annual or the 24-hour health-based standard since 1980 and 1984, respectively. The primary source of sulfur dioxide pollution in the Ajo was the Phelps Dodge Ajo Incorporated smelter, which ceased operation in 1985 and was dismantled in 1995 and 1996. The primary source of sulfur dioxide pollution in the Morenci area was the Phelps Dodge Morenci Incorporated smelter, which ceased operation in late 1984 and was dismantled in 1995 and 1996. There are currently no other SO2 sources of this magnitude in Ajo or Morenci.
- Federal Register Notice: Direct Final Rule (published January 9, 2017)
March 2004: Approval of Arizona's Plan to Meet the Sulfur Dioxide Air Quality Standards in the Morenci Area
EPA has approved Arizona's maintenance plan to maintain attainment of the short-term (24-hour) and long-term (annual) primary National Ambient Air Quality Standards (NAAQS) for sulfur dioxide (SO2) in the Morenci area, as well as Arizona’s request to redesignate this area from nonattainment to attainment for SO2.
The Morenci area has not had a violation of either the annual or the 24-hour health-based standard since 1984. The primary source of sulfur dioxide pollution in the Morenci area was the Phelps Dodge Morenci Incorporated smelter, which ceased operation in late 1984 and was dismantled in 1995 and 1996. There are currently no other SO2 sources of this magnitude in Morenci.
- Federal Register Notice: Direct Final Rule (April 26, 2004)
- Technical Support Document (PDF) (20 pp, 92K)