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Summary of Central Puget Sound Area 2nd 10-Year Carbon Monoxide (CO) Maintenance Plan


The Central Puget Sound Area was designated nonattainment for carbon monoxide (CO) and classified as moderate upon enactment of the Clean Air Act Amendments in 1990.

Washington submitted a CO maintenance plan on February 29, 1996, and EPA announced its proposed approval of the plan on June 11, 1996 (61 FR 29515 (PDF)(4 pp, 127 K, About PDF)).

On October 11, 1996, EPA approved the Central Puget Sound Area CO maintenance plan (61 FR 53323 (PDF)(6 pp, 140 K)).

Washington submitted a second 10-year CO/ozone maintenance plan on December 17, 2003, and EPA announced its proposed approval of the plan on June 1, 2004 (69 FR 30847 (PDF)(6 pp, 164 K)).

On August 5, 2004, EPA approved the Central Puget Sound Area 2nd 10-year CO/ozone maintenance plan (69 FR 47365 (PDF)(2 pp, 143 K). 


The plan relies on control strategies needed to assure attainment of the National Ambient Air Quality Standards (NAAQS) for CO. The strategy relies on the existence of an approved vehicle Inspection and Maintenance program.


  • WAC 173-422, Motor Vehicle Emission Inspection

Contingency Measures

  • PSCAA Regulation I, Section 8.06, Outdoor Burning Ozone Contingency Measure
  • PSCAA Regulation II, Section 2.09, Oxygenated Gasoline Contingency Measure & Fee Schedule
  • PSCAA Regulation II, Section 2.10, Gasoline Station Ozone Contingency Measure

EPA Effective Date

September 7, 2004