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Summary of Portland Carbon Monoxide (CO) Maintenance Plan


The Portland, Oregon, nonattainment area was designated nonattainment for carbon monoxide (CO) and classified as moderate upon enactment of the Clean Air Act Amendments in 1990.

Oregon submitted a CO maintenance plan on August 30, 1996, and EPA announced its proposed approval of the plan (62 FR 31398 (PDF)(8 pp, 155 K, About PDF)).

On September 2, 1997, EPA approved the Portland CO Maintenance Plan (62 FR 46208 (PDF)(4 pp, 126 K)).

On November 5, 1999, Oregon submitted a complete rule renumbering and relabeling package to EPA for approval in the SIP. On January 22, 2003, EPA approved the recodified version of Oregon's rules to remove and replace the outdated numbering system (68 FR 2891 (PDF)(19 pp, 205 K)). The following list refers to the currently approved SIP rules.


The plan relies on control strategies needed to maintain the National Ambient Air Quality Standards (NAAQS) for carbon monoxide. The strategy focuses on an enhanced I/M program, continuation of wintertime oxygenated fuel program, Federal Motor Vehicle Emission Control Program, and Central City Transportation Management Plan (CCTMP).


  • OAR 340-024-0100 to 0360 - Enhanced I/M Program 
  • OAR 340-204-0090 - Wintertime Oxygenated Fuel Program
  •  40 CFR Part 86 - Federal Motor Vehicle Emission Control Program 
  • OAR 340-224-0060 - Requirements for Sources in Maintenance Areas
  • CCTMP adopted December 6, 1995

Contingency Measures

Downtown Portland Parking Local Improvement District (LID):

  • Increased parking pricing in the Central City.
  • Increased funding for transit.
  • Congestion pricing on major regional transportation corridors.
  • A trip reduction program.
  • Regional mandatory parking ratios.
  • Accelerated implementation of bicycle and pedestrian networks.

Best Available Control Technology will be replaced with requirement to install Lowest Achievable Emission Rate technology.

EPA Effective Date

October 2, 1997