County Affected:

Parts of Pinal County | View on a Map >

Nonattainment Area Designation Date:

May 31, 2012
(77 FR 32024)

Classification Level: 

Serious

Pollutant of Concern:

PM₁₀ (particulate matter 10 microns or less in diameter; 1987 standards)

Summary: 

The concentration of PM10 in the air in the West Pinal County PM10 nonattainment area (NAA) is frequently above federal standards. In a final rule published on 5/31/2012, the U.S. Environmental Protection Agency (EPA) redesignated this formerly unclassified area as a nonattainment area. This final rule required ADEQ to submit a nonattainment area plan by January 2, 2014 and to attain the 1987 PM₁₀ National Ambient Air Quality Standard (NAAQS) by December 31, 2018 | View Federal Register >

 ADEQ submitted a nonattainment state implementation plan (SIP) revision to EPA in December 2015. Controls in the plan revision include:

• Agricultural Best Management Practices (such as combining tractor operations or reducing tillage)
• Water/chemical dust suppressants on open areas/vacant lots
• Watering for dust-generating construction operations
• Vehicle speed limits
• Road dust trackout controls

In June 2016, the Governor of Arizona certified the Maricopa Association of Governments (MAG) as the lead planning organization for the West Pinal PM10 NAA. MAG will develop future air quality plans for these areas in cooperation with the Sun Corridor Metropolitan Planning Organization and ADEQ.

On June 24, 2020, EPA published a final rule to determine that the West Pinal County NAA has failed to meet the 1987 PM10 NAAQS by the Dec. 31, 2018, attainment date and reclassified the NAA from a Moderate to a Serious Area | View Federal Register >

The effective date was July 24, 2020. A Serious Area plan was due within 18 months of the reclassification date, which was Jan. 24, 2022.

On Jan. 8, 2021, EPA proposed to approve in part and to disapprove in part the SIP revision submitted by the State of Arizona to meet Clean Air Act requirements for the 1987 PM10 NAAQS in the West Pinal County PM10 NAA | View Federal Register >

EPA proposed to approve the base year 2008 emissions inventory for direct PM10 and to disapprove the remaining elements of the plan.

On May 31, 2022, ADEQ submitted a nonattainment area plan for the West Pinal PM10 NAA on behalf of MAG. EPA has not yet taken action on this plan.

On July 21, 2023, EPA found that the West Pinal PM₁₀ NAA had failed to attain the PM10 NAAQS by the Dec. 31, 2022 Serious area attainment date. As a result, Arizona is required to submit a SIP revision providing for reductions in PM₁₀ emissions of 5 % per year until the NAAQS is attained.

• Unpaved roads
• Paved roads
• Construction
• Windblown dust
• Agricultural activities

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