Areas that fail to meet the national ambient air quality standards (NAAQS) for a criteria pollutant are required to develop a state implementation plan (SIP). SIPs include emission inventories, air quality projections, and control measures designed to reduce emissions. They demonstrate how an area will attain a standard by a future date.
Emission Inventories and Analysis – Emission inventories are compilations of estimated emissions from various sources. Estimates are typically calculated using data on source activity and historical emission rates per pollutant. Emission inventories are combined with meteorological and other technical data using computer models to forecast pollutant levels in future years. Numerous agencies and organizations throughout the region partner with the District to develop SIPs that include emission inventories, modeling, and related analyses.
State Implementation Plans – The District is in nonattainment of the ozone NAAQS. The District is in attainment of the PM2.5 and carbon monoxide (CO) NAAQS but was previously in nonattainment of both standards. The following SIPs for ozone, PM2.5, and CO were approved by the U.S. Environmental Protection Agency because they adequately demonstrate how the District plans to attain or maintain each NAAQS:
- 1997 8-Hour Ozone SIP
- 1997 Fine Particulate Matter (PM2.5) Maintenance Plan
- 1994 Carbon Monoxide (CO) Maintenance Plan – effective through March 2016
The District also develops an infrastructure SIP (“i-SIP”) for each NAAQS, regardless of attainment status, to demonstrate its authority to implement, maintain, and enforce compliance with the NAAQS. I-SIPs are available upon request.
Emission Control Programs – The following emission control program plans are included in the District’s SIP to meet Clean Air Act requirements:
• Regional Haze Plan (PDF attached below)
• Vehicle Inspections & Maintenance Plan
• Emergency Episode Plan (PDF attached below)
The District’s air quality regulations also contain limits that sources in the District must meet.
When a SIP is approved by the EPA, control measures in the SIP become federally enforceable. A record of the history of changes to the District’s federally-approved SIP can be found in Title 40, Part 52, Subpart J of the Code of Federal Regulations.