California State Implementation Plan (SIP)
for Carbon Monoxide (CO)
in the South Coast Air Basin

This page updated September 19, 2006.

Following the 1990 amendments to the federal Clean Air Act, the California SIP for Carbon Monoxide (CO Plan) for the South Coast Air Basin was adopted by the South Coast Air Quality Management District (South Coast District) in 1992, revised in 1994, and subsequently approved by U.S. EPA in 1997.  The CO Plan was again revised in 1997 and the District's CO control strategy was approved by U.S. EPA in 1998.  Because improvements to California's Smog Check program were adopted after federal deadlines, U.S. EPA's approval for the Plan's attainment demonstration and rate of progress elements lapsed in 1998.  In 2002, California adopted a number of Smog Check program enhancements that addressed federal motor vehicle inspection and maintenance (I&M) requirements and significantly improved CO air quality.

As a result of State and local control strategies, the South Coast Air Basin has not exceeded the federal CO standard since 2002.  In March 2005, the South Coast AQMD adopted a CO Redesignation Request and Maintenance Plan that provides for maintenance of the federal CO air quality standard until at least 2015 and commits to revising the Plan in 2013 to ensure maintenance through 2025.  The AQMD also adopted a CO emissions budget that covers 2005 through 2015.

On February 24, 2006, ARB transmitted the Redesignation Request and Maintenance Plan (including the CO budgets) to U.S. EPA for approval.  In addition, on August 11, 2006, the ARB provided information to U.S. EPA that demonstrates the Smog Check program satisfies federal I&M requirements for CO and provides emission reductions necessary for continued improvement in CO air quality.


Request for Redesignation and Maintenance Plan for CO (March 2005)

Hearing Notice  (PDF-- 3.3 MB)

2005 Redesignation Request and Maintenance Plan  (PDF-- 1.3 MB)

Transmittal Letter to U.S. EPA  (PDF-- 31 KB)

ARB Executive Order G-125-332  (PDF-- 32 KB)

Inventories and Conformity Budgets Documentation  (link)

2005 Report to the Legislature on Smog Check Program  (link)

Documentation for 2003 South Coast SIP, including CO  (link)

Smog Check Program Cover Letter to U.S. EPA (PDF-- 16 KB)

Modeled Demonstration (PDF-- 53 KB)


If you would like to receive electronic notices from ARB about development of new SIP measures for these and other areas of the State, please go to