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SIPs and the Federal Clean Air Standard

The SIP is a set of air pollution regulations, control strategies, other means or techniques, and technical analyses developed by the state, to ensure that the state meets the National Ambient Air Quality Standards. The SIP is required by the Clean Air Act.

These SIPs can be extensive, containing state regulations or other enforceable documents and supporting information such as emissions inventories, monitoring networks, and modeling demonstrations. Each state must submit these regulations and control strategies to EPA for approval and incorporation into the federally enforceable SIP. Each federally approved SIP protects air quality primarily by addressing air pollution at its point of origin. SIP revisions are typically prepared for a specific nonattainment area, e.g., "Dallas-Fort Worth SIP."

The air quality standards are established by EPA as directed by the Clean Air Act. EPA has set standards for six principal outdoor air pollutants:

• ground-level ozone/smog (O3)
• particulate matter (PM)
• lead (Pb)
• nitrogen dioxide (NO2)
• carbon monoxide (CO)
• sulfur dioxide (SO2)

These "criteria pollutants" are commonly occurring air pollutants that can injure health, harm the environment and cause property damage. The air quality stanards present state and local governments with the minimum air quality level they must meet to comply with the Clean Air Act.

SIP revisions may become necessary when federal or state requirements that affect the SIP are enacted when standards are revised, when a specific area's attainment status changes, and when an area fails to meet an attainment date.

Background:
On July 18, 1997, EPA promulgated an 8-hour ozone standard of 0.08 per million (0.084 ppm when rounding is considered), which is more protective than the previous 1-hour ozone standard. Under EPA regulations, the 1997 8-hour ozone standard is attained when the 3-year average of the annual fourth highest daily maximum 8-hour average ambient ozone concentrations is less than 85 parts per billion.

EPA was litigated on the 1997 8-hour ozone standard and thereby delayed in publishing the ozone designations and classifications until April 30, 2004 (69 FR 23858). Subsequently, the DFW area was designated nonattainment, classified as “moderate,” and includes nine counties: Collin, Dallas, Denton, and Tarrant counties (these constitute the former 1-hour ozone nonattainment area, referred to as the “core counties”), and Ellis, Johnson, Kaufman, Parker and Rockwall counties. The effective date of designation for the 1997 8-hour ozone air quality standardswas June 15, 2004. The attainment demonstration for the DFW area was due by June 15, 2007 and was submitted on time.

The attainment date for the DFW area is June 15, 2010.

The December 17, 2008, action is finalizing conditional approval of the 1997 8-hour Ozone Attainment Demonstration SIP Revision. This is a significant milestone for EPA and DFW as it distinguishes North Texas as the first nonattainment area in the country to take action on the 1997 ozone standard.

Return to DFW Clean Air Plan page