County Affected:

Parts of Santa Cruz County | View on a Map >

Nonattainment Area Designation Date:

Oct. 31, 1990

Learn more about the designation in the Federal Register (FR) (55 FR 45799, Page 5) | View >

Classification Level:

Moderate

Pollutant of Concern:

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

Summary: 

The concentration of PM₁₀ in the air in Nogales is occasionally above federal standards. ADEQ submitted a nonattainment State Implementation Plan (SIP) to the U.S. Environmental Protection Agency (EPA) in 2012. EPA approved the plan in 2012 (77 FR 58962). The plan demonstrates that the Nogales area would be attaining the PM10 standards, if not for emissions from across the border.

Regulatory Background:

EPA revised the particulate matter National Ambient Air Quality Standards (NAAQS) in 1987 (52 FR 24634; July 1, 1987). These primary and secondary standards apply to particulate matter 10 microns or less in diameter (PM₁₀) and superseded the previous total suspended particulate (TSP) standards. ADEQ began monitoring PM₁₀ in the Nogales Nonattainment Area in 1985.

With the Clean Air Act (CAA) Amendments of 1990, areas where previous violations of the PM₁₀ standard had been recorded prior to Jan. 1, 1989, were designated nonattainment for PM₁₀ by operation of law and classified as moderate. These areas included all former Group II PM₁₀ planning areas like the Nogales PM₁₀ Nonattainment Area (55 FR 45799; Oct. 31, 1990). On March 15, 1991, EPA published a list of the areas designated nonattainment for PM₁₀ upon enactment of the 1990 amendments, including the Nogales Nonattainment Area (56 FR 11101; March 15, 1991). Later, EPA codified the PM₁₀ nonattainment designations and moderate area classifications (56 FR 56694; Nov. 6, 1991).

As stipulated in the 1990 amendments, by Nov. 15, 1991, Arizona was required to submit a SIP for the Nogales Nonattainment Area demonstrating attainment of the PM₁₀ NAAQS by Dec. 31, 1994. Because Arizona did not submit a SIP for the Nogales Nonattainment Area by the Nov. 15, 1991, deadline, EPA made a finding of failure to submit a PM₁₀ SIP on Dec. 16, 1991. In response, on June 14, 1993, Arizona submitted the ‘‘Final State Implementation Plan for the Nogales PM₁₀ Nonattainment Area.” (1993 Nogales NA SIP) EPA found the plan to be complete by letter dated Nov. 30, 1993, but did not act on the plan.

In January 2011, EPA determined that the Nogales planning area attained the 1987 PM₁₀ NAAQS by the applicable attainment date. This determination was based on ambient air quality monitoring data from 1992 – 1994, retroactively affirming that the area had met the federal standard for the PM₁₀ NAAQS by the Dec. 31, 1994, deadline established by the 1990 amendments of the CAA (76 FR 1532; Jan. 11, 2011).

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