Air Quality Conformity and Trends

Progress and Ongoing Challenges

Air quality along the Wasatch Front has improved markedly over the past two decades. Salt Lake City was recently designated by the Environmental Protection Agency (EPA) to be free of carbon monoxide (CO) pollution after being designated as a CO non-attainment area 42 years ago in 1978. This improvement is largely due to cleaner vehicle technology and growing options to walk, bike, or use transit. Even with this progress, improving air quality remains an ongoing challenge.

Portions of the WFRC region are still designated as non-attainment areas for fine particulate matter (PM2.5) and ozone, and Salt Lake County and Ogden City are also designated non-attainment for coarse particulate matter (PM10). Emissions from transportation sources are projected to decline by 52% from 2019 to 2050 due to cleaner vehicles, increased transit use, and other travel choices. Despite these gains, more work remains.

How Transportation Planning Supports Cleaner Air

Air quality is central to WFRC’s work. We consider air quality impacts when developing the Wasatch Choice Vision and the Regional Transportation Plan (RTP). The RTP must meet the air quality standards set in the Utah State Implementation Plan (SIP), ensuring that emissions from proposed transportation projects stay within federally approved limits.

As we expand transportation choices and plan communities around the principles of the Wasatch Choice Vision, air quality benefits follow: cleaner vehicles, more transit options, shorter trips, reduced congestion, and fewer auto emissions.

What is air quality conformity?

Air quality conformity is a federal requirement in the context of transportation plans and air quality goals. Emissions from vehicles may not exceed limits defined in the SIP, a plan for reducing and controlling emissions in the state to meet National Ambient Air Quality Standards (NAAQS). The RTP and the Transportation Improvement Program (TIP) developed by WFRC must meet this air quality conformity requirement for all of the years defined in these plans. This means that vehicle emissions estimated for the last year of the RTP may not exceed the budget identified in the SIP. Failure to meet conformity requirements restricts spending of federal and local transportation funds to safety, maintenance, or projects on minor roads only. If conformity requirements are not met, transportation funds may not be used to add capacity to principal arterials and freeways or to expand fixed guideway transit facilities.

All current transportation plans and programs for the Wasatch Front region conform to the established SIP and its various sections. Changes will likely continue to be made to federal air quality standards, which will require corresponding changes to the SIP.

What is a State Implementation Plan (SIP)?

There is a separate section in the State Implementation Plan (SIP) for air quality for each regulated pollutant and each designated area of air quality non-attainment or maintenance. Within the Wasatch Front region, there are five areas that are addressed in separate sections of the SIP: Salt Lake County and Ogden City (PM₁₀ or coarse particulate matter), Ogden City (carbon monoxide or CO), Northern Wasatch Front ozone non-attainment area (including Salt Lake and Davis Counties, as well as portions of Weber and Tooele Counties), and the Salt Lake PM_2.5non-attainment area (fine particulate matter pollution control area including Salt Lake and Davis counties, as well as portions of Weber, Box Elder, and Tooele counties).

Wasatch Front Region Non-Attainment Designations

Area	Designation	Pollutant
Northern Wasatch Front (including Salt Lake and Davis Counties, as well as portions of Weber and Tooele Counties)	Marginal Non-Attainment Area	Ozone
Ogden City	Maintenance Area	Carbon Monoxide (CO)
Ogden City	Moderate Non-Attainment Area	Particulate Matter (PM10)
Salt Lake County	Maintenance Area	Particulate Matter (PM10)