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St. Louis, Missouri, Carbon Monoxide Maintenance Plan

Background of the Plan: An area within the Interstate 270 loop and the Mississippi River in the Missouri portion of the St. Louis area was designated nonattainment with respect to the ambient air quality standard for carbon monoxide (CO) in 1978. This designation was reaffirmed following passage of the Clean Air Act Amendments of 1990. The 1990 Amendments required that areas be classified based on current air quality data. Since the St. Louis area was already showing attainment of the CO standard at that time, it became an unclassified CO nonattainment area. As a result of this improvement in air quality, the state of Missouri submitted a request to redesignate the area to attainment in 1997 and prepared a plan to maintain the standard through 2008.

Summary of the Plan: The plan relies on an attainment level of emissions of CO to maintain the standard. The main emissions component which contributes to elevated levels of CO is from mobile sources. Consequently, the maintenance plan's level of emissions is primarily predicated on the Federal Motor Vehicle emission control program and the national emission standards for non-road engines. These two programs are expected to achieve sufficient emission reductions to offset any increases in vehicle travel. The plan was approved by EPA on January 26, 1999. (See 64 FR 3855.)

Emission Reductions: The following table shows the emissions projections through 2008.


Source  1993    1997    2001    2005    2008  
Non-road mobile  126127127126126

Stationary Source Regulations: No stationary source regulations were included as part of this plan. However, previous SIPs designed to bring the area into attainment included measures restricting open burning in the area. (See rule 10 CSR 10-5.070.)

Mobile Source Control Measures: As noted above, the St. Louis CO maintenance plan relies on the Federal motor vehicle emissions control program and EPA's emission standards for non-road vehicles. The plan also relies on continued implementation of the transportation conformity regulation (10 CSR 10-5.480), which is designed to ensure that transportation plans conform to air quality plans, and the general conformity rule (10 CSR 10-6.300) which is intended to ensure that Federal actions conform to air quality plans.

The plan also relies on continued implementation of a basic motor vehicle inspection and maintenance program which was part of a pre-1990 SIP designed to bring the area into attainment.

Other Features: As part of its redesignation request, the MDNR agreed to do the following:

Contingency Measures: The plan contains contingency measures in the event the "contingency action line" is exceeded. The contingency action line is defined as (1) one exceedance of the eight-hour CO standard at three or more CO monitors during the same 24-hour period, or (2) one exceedance of the eight-hour CO standard at two or more CO monitors during different non-overlapping episodes of a given calendar year.

The contingency measures, to be implemented in different combinations depending on the nature of the violation, include the following:

Date for Plan Revision: January 2007.

Additional Information: In April 2000 the state of Missouri implemented an enhanced vehicle inspection and maintenance program as part of the state's plan to attain the ozone standard in St. Louis. This program, originally identified as a contingency measure for the CO maintenance plan, will help ensure continued maintenance of the CO standard in St. Louis.

EPA Region 7 Contact: Wayne Kaiser, (913) 551-7603, kaiser.wayne@epa.gov

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