 The Federal Clean Air Act (CAA) requires states with areas that fail to meet the National Ambient Air Quality Standards (NAAQS) prescribed for criteria pollutants to develop a State Implementation Plan (SIP). The SIP describes how the state will reduce and maintain air pollution emissions in order to comply with the federal standards. Important components of a SIP include emission inventories, motor vehicle emission budgets, control strategies, and attainment demonstration.
The Texas Commission on Environmental Quality develops the Texas SIP for submittal to the US Environmental Protection Agency (EPA). The original document for Texas was approved in May 1972. One SIP is created for each state, but portions of the plan are specifically written to address each of the nonattainment areas (e.g. a “Dallas-Fort Worth SIP”).
As changes are needed, the SIP is revised rather than rewritten in its entirety. Revisions are often prompted by new federal or state regulations, new modeling techniques, or a change in an area’s attainment status. Most recently, the change in the federal ozone standard from a one-hour NAAQS to an eight-hour NAAQS required nonattainment areas to update the SIP to address the eight-hour standard. The eight-hour SIP revisions supersede the one-hour documents. However, in order to ensure that progress toward cleaner air continues, anti-backsliding laws require all nonattainment areas to fulfill the requirements, programs, and goals of the pre-existing one-hour SIP revisions.
Use the following links to explore various aspects of the SIP.
8-Hour SIP Revisions
1-Hour Attainment SIP Revisions
2009 Transportation Control Measures Substitutions
1-Hour Substitution List
8-Hour Substitution List
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