(a) Revisions to the Colorado State Implementation Plan, Carbon Monoxide Redesignation Request and Maintenance Plan for Greeley, as adopted by the Colorado Air Quality Control Commission on September 19, 1996, State effective November 30, 1996, and submitted by the Governor on September 16, 1997.

(b) On June 25, 1996, the Governor of Colorado submitted a revision to the Colorado Springs element of the carbon monoxide (CO) portion of the Colorado State Implementation Plan (SIP). The revision to the Colorado Springs element was submitted to satisfy certain requirements of part D and section 110 of the Clean Air Act (CAA) as amended 1990. The revision substitutes Colorado's oxygenated gasoline program for the Colorado Springs bus purchase program as a source of emissions reductions credits in the Colorado Springs CO element of the SIP. This revision removes the bus purchase program from the EPA-approved SIP. EPA originally approved the bus purchase program as part of the Colorado Springs CO element of the SIP on December 12, 1983 (48 FR 55284).

(c) Revisions to the Colorado State Implementation Plan, Carbon Monoxide Redesignation Request and Maintenance Plan for Colorado Springs, as adopted by the Colorado Air Quality Control Commission on January 15, 1998, State effective March 30, 1998, and submitted by the Governor on August 19, 1998. The Maintenance Plan removes the Clean Air Campaign from the SIP. The Clean Air Campaign was approved into the SIP at 40 CFR 52.320(c)(43)(i)(A).

(d) Revisions to the Colorado State Implementation Plan, Carbon Monoxide Redesignation Request and Maintenance Plan for Longmont, as adopted by the Colorado Air Quality Control Commission on December 18, 1997, State effective March 2, 1998, and submitted by the Governor on August 19, 1998.

(e) Revisions to the Colorado State Implementation Plan, Carbon Monoxide Revised Maintenance Plan for Colorado Springs, as adopted by the Colorado Air Quality Control Commission on February 17, 2000, State effective April 30, 2000, and submitted by the Governor on May 10, 2000.

(f) Determination. EPA has determined that the Denver carbon monoxide “serious” nonattainment area attained the carbon monoxide national ambient air quality standard by December 31, 2000. This determination is based on air quality monitoring data from 1998, 1999, and 2000.

(g) Revisions to the Colorado State Implementation Plan, carbon monoxide NAAQS Redesignation Request and Maintenance Plan for Denver entitled “Carbon Monoxide Redesignation Request and Maintenance Plan for the Denver Metropolitan Area, “excluding Chapter 1, Chapter 2, and Appendix C, as adopted by the Colorado Air Quality Control Commission on January 10, 2000, State effective March 1, 2000, and submitted by the Governor on May 10, 2000.

(h) Revisions to the Colorado State Implementation Plan, carbon monoxide NAAQS Redesignation Request and Maintenance Plan for Fort Collins entitled “Carbon Monoxide Redesignation Request and Maintenance Plan for the Fort Collins Area,” excluding Part I - Chapter 1 and Part I - Chapter 2, as adopted by the Colorado Air Quality Control Commission on July 18, 2002, State effective September 30, 2002, and submitted by the Governor on August 9, 2002.

(i) Revisions to the Colorado State Implementation Plan, revised Carbon Monoxide Maintenance Plan for Denver, as adopted by the Colorado Air Quality Control Commission on June 19, 2003, State effective on August 30, 2003, and submitted by the Governor on October 15, 2003.

(j) Revisions to the Colorado State Implementation Plan, carbon monoxide NAAQS, revised maintenance plan for Colorado Springs entitled “Revised Carbon Monoxide Maintenance Plan for the Colorado Springs Attainment/Maintenance Area”, as adopted by the Colorado Air Quality Control Commission on December 18, 2003, State effective March 1, 2004, and submitted by the Governor on April 12, 2004.

(k) Revisions to the Colorado State Implementation Plan, carbon monoxide NAAQS, revised maintenance plan for Longmont entitled “Revised Carbon Monoxide Maintenance Plan for the Longmont Attainment/Maintenance Area”, as adopted by the Colorado Air Quality Control Commission on December 18, 2003, State effective March 1, 2004, and submitted by the Governor on April 12, 2004.

(l) Revisions to the Colorado State Implementation Plan entitled “Revised Carbon Monoxide Maintenance Plan for the Greeley Attainment/Maintenance Area,” as adopted by the Colorado Air Quality Control Commission on December 19, 2002, and submitted by the Governor on June 20, 2003.

(m) Revisions to the Colorado State Implementation Plan, revised Carbon Monoxide Maintenance Plan for Denver, as adopted by the Colorado Air Quality Control Commission on December 15, 2005, State effective on March 2, 2006, and submitted by the Governor's designee on September 25, 2006.

(n) Revisions to the Colorado State Implementation Plan, revised Carbon Monoxide Maintenance Plan for Longmont, as adopted by the Colorado Air Quality Control Commission on December 15, 2005, State effective on March 2, 2006, and submitted by the Governor's designee on September 25, 2006.

(o) Revisions to the Colorado State Implementation Plan, revised Carbon Monoxide Maintenance Plan for Colorado Springs, as adopted by the Colorado Air Quality Control Commission on December 17, 2009 and submitted by the Governor's designee on March 31, 2010.

(p) Revisions to the Colorado State Implementation Plan, revised Carbon Monoxide Maintenance Plan for Greeley, as adopted by the Colorado Air Quality Control Commission on December 17, 2009 and submitted by the Governor's designee on March 31, 2010.

(q) Revisions to the Colorado State Implementation Plan, revised Carbon Monoxide Maintenance Plan for Fort Collins, as adopted by the Colorado Air Quality Control Commission on December 16, 2010 and submitted by the Governor's designee on May 25, 2011.