Air Quality, Environment, and Health


The Air Quality, Environment and Health Branch is the Department’s lead advisor on air quality conformity policy questions for the Districts, and for the Divisions of Environmental Analysis (DEA), Local Assistance, and Programming. The Branch coordinates with DEA on Planning and Environment Linkages (PEL), to oversee use of Planning funds by environmental staff, and to promote consideration of environmental factors during transportation planning. The Branch also participates in the California Health in All Policies Task Force and coordinates with other units to promote consideration of public health in Caltrans’ activities.

What is Transportation Conformity?

"Conformity" is a requirement of the Federal Clean Air Act (§176(c)). All federal actions must further the purposes of the Clean Air Act, i.e. assist in attaining clean air standards. The process is called "SIP Conformity" because the programs in each state that are aimed at attaining and maintaining air quality standards are contained in the "State Implementation Plan" (SIP). Federal agencies are prohibited under the Clean Air Act from approving funding, projects, work or funding programs, and plans, that don't "conform" to the letter and purpose of the SIP. The Clean Air Act conformity requirement also extends to decisions made by federal funding recipients, as provided in EPA's conformity regulations, and for delegated federal actions (like NEPA authority assigned to Caltrans by FHWA).

Conformity Determinations related to highway and transit projects, programming, and plans are governed by US EPA's regulations at 40 CFR 93 Subpart A (Transportation Conformity). In areas that fail to attain (are "nonattainment" for) one or more of the National Ambient Air Quality Standards (NAAQS), or were previously nonattainment but have been re-designated to attainment status with a "maintenance" SIP, Regional Transportation Plans, Transportation Improvement Programs, and most project NEPA actions must have a conformity determination.

Conformity Determinations for other (non-highway/transit) federal actions are governed by the "General Conformity" regulations at 40 CFR 93 Subpart B. Caltrans seldom needs to deal with General Conformity requirements, because most Caltrans work is funded or approved using Title 23 (highways) or Title 49 (transit) procedures.

Where conformity requirements apply

Conformity applies only in areas that are designated nonattainment, or attainment with a "Maintenance SIP," for one or more federal criteria pollutants. The criteria pollutants that trigger conformity requirements are: ozone (O3), particulate matter (PM10 and PM2.5), carbon monoxide (CO), and nitrogen dioxide (NO2). Sulfur oxides (SOx), and lead (Pb) have air quality standards, but are primarily stationary source issues and don't affect transportation conformity. There are no nonattainment or maintenance areas in California for SOx, and the only lead nonattainment area is in Los Angeles County due to a specific industrial site. SOx can be considered as a precursor for some types of PM10 and PM2.5 in regional analysis, and Pb is also regulated as a hazardous air pollutant. As of October 2019, none of the counties in District 1 are subject to conformity requirements. Where conformity does not apply, project-level environmental documents should state that conformity requirements do not apply because the project area is designated "attainment/unclassified" for all federal criteria pollutant standards.

The conformity process - an executive summary

Plan and Program (regional) conformity is demonstrated by modeling the emissions of the transportation system with (sometimes several alternative) packages of projects, and evaluating the results using one of several tests defined in the EPA Transportation Conformity Rule. The standard test is comparison to "emission budgets" established in the SIP for the area. Modeling results, including adjustments for emission credits from various statewide and local emission control programs which are specified by the California Air Resources Board, US EPA, and/or local air districts, must be less than or equal to the emission budget. Where emission budgets are not available, a "build less than no build" or a "less than base year" test, or both in some cases, must be used.

The Metropolitan Planning Organization (MPO) is responsible for regional conformity analysis in most areas, in consultation with US EPA, US DOT (FHWA/FTA), Caltrans, ARB, the local air district, and other recipients of Federal Title 23 or 49 transportation funding in the area. Consultation may involve other parties, as well, if they approve or construct regionally significant transportation projects. Specific consultation requirements are defined in 40 CFR 93.105 and "Conformity SIP" submittals to US EPA. In rural, non-MPO areas that are not part of the same nonattainment area as an MPO, the State (Caltrans) is responsible for performing regional conformity analysis and is the primary contact for Interagency Consultation. The regional conformity analysis must also demonstrate "timely implementation" of any "transportation control measures" contained in an EPA-approved SIP.

In MPO areas subject to conformity requirements, regional conformity must be determined based on a full study when Regional Transportation Plan updates are done, or at least every 4 years. A regional conformity determination is also required for Federal Transportation Improvement Program approval (FTIP) at least every 4 years. Conformity must be demonstrated for amendments to both the Plan and TIP if regionally significant projects are added, deleted, or substantially modified, and when certain other triggering events occur (usually SIP-related or due to financial constraint issues).

Project-level conformity is usually demonstrated by showing that a project comes from a conforming Plan and Program, with substantially the same "design concept and scope" that was used for the regional conformity analysis, that it will not cause localized exceedances of CO, PM10, and/or PM2.5 standards in nonattainment or maintenance areas for those pollutants, and that a written commitment is made to implement mitigation or other control measures for hot spot pollutants that are specified in the SIP, project documents, or the regional conformity analysis. The project proponent is usually responsible for carrying out the studies required for this work, and a conformity analysis must be included in the NEPA document for the project.

In "isolated rural" nonattainment areas, the regional conformity analysis is done when a regionally significant project needs approval. There is no MPO in these areas to prepare a Federally-approved Regional Transportation Plan.

The basic project-level conformity determination remains effective as long as the project proceeds on a reasonable schedule (milestones are defined in the Transportation Conformity Rule at 40 CFR 93.104(d)) AND regional conformity is not lost (i.e. does not "lapse"). Meeting the project development milestones, and continued regional conformity, must be demonstrated whenever a subsequent Federal action (especially "PS&E" or "Full Funding" approval, which finally commits funds for construction) is given. If a nonattainment designation occurs for a new pollutant that wasn't included in the original conformity analysis, a new project-level conformity determination is needed even if "progress" can be shown when a Federal action after NEPA occurs.

Conformity Lapse

If for any reason conformity either cannot be demonstrated during the approval process for a Regional Transportation Plan or Transportation Improvement Program, or is lost for some other reason, a "Conformity Lapse" occurs. Conformity lapse can apply to a county, MPO, or air basin, depending on how the boundaries of the nonattainment area are set. Conformity applies only in specific areas that are nonattainment or maintenance for a Federal criteria air pollutant, so it may be possible for portions of an MPO to be unaffected when a lapse occurs if they are not subject to conformity, or the issue causing the conformity lapse affects only one of several nonattainment areas in the MPO.

A conformity "freeze" occurs when US EPA disapproves a required "Control Strategy" air quality plan (State Implementation Plan - SIP) submittal without a "protective finding" regarding transportation. A freeze prevents FHWA and FTA from making any regional conformity findings, positive or negative - simply, no action can be taken. Projects that are listed in the first 4 years of the conforming Transportation Improvement Program in force at the time of the freeze are not affected by the freeze, and if FHWA actions are required on such projects during the freeze (such as NEPA document approval) they normally can take place. However, if a required regional conformity action is needed during the freeze (such as a regular FSTIP approval, or a 4-year RTP action), that action cannot occur, and a conformity lapse will result.

A conformity "lockdown" occurs when something, usually a financial constraint or statewide "planning assumptions" issue, causes FHWA and FTA to stop accepting requests for new conformity determinations. It can also occur, de facto, when an area uses a previous conformity determination (usually for a Regional Plan) to apply to a TIP approval, and emission budgets or other reasons prevent the area from doing a new conformity determination. A lockdown has essentially the same effect as a freeze - no changes can be made to the RTP, FSTIP, or projects that would require a new regional conformity analysis. As with a freeze, a conformity lapse can occur if a mandatory, scheduled or triggered, conformity action cannot be taken due to a lockdown being in effect.

Some conformity lapses now begin as, in effect, a conformity lockdown due to the "grace period" added by SAFETEA-LU. If a lapse occurs as a result of missing a regular planning deadline, and a valid Federal Transportation Improvement Program (FTIP or FSTIP) continues to exist, full lapse consequences would be delayed for up to a year.

Statewide Conformity Working Group

The Statewide Conformity Working Group is a coordinating group for discussion and interagency agreement about transportation-related air quality and Federal Clean Air Act conformity issues in California. The public is welcome to participate, and there is a time on the agenda for public comment regarding issues not otherwise on the agenda. Actions taken by the group are not regulations; rather, they are informational in nature, or are agreements regarding procedures and interpretation of the transportation conformity regulations to be used by transportation agencies and project proponents.

Statewide Conformity Working Group meetings are generally held twice a year by teleconference. Teleconference access to the meeting is provided through regional call centers, usually located at offices of regional transportation planning agencies, air pollution control or air quality management districts, or Caltrans. Individual call-in access to the teleconference may also be provided; please contact the Working Group chair to arrange it.

The meeting and call center locations, with site contact information, are noted on the printable copy of the agenda for each meeting. Contact information for the call centers is also provided on the agenda.

Caltrans maintains an electronic mail list to forward announcements and other information to the working group. For network security reasons, the list archives are only available to list members. Go to the mailing list page to sign up.

2018 Meetings

2017 Meetings

Additional Resources

Planning and Environmental Linkages 

The Branch is a liaison between the Planning and Environmental Divisions on how to consider environmental issues in the planning process. The twofold goal of these activities is to streamline project delivery and to promote conservation. Staff works with DEA’s environmental specialists to help Planning staff incorporate environmental issues into planning documents. This can lead to new projects such as road undercrossings and culvert repairs that remove roadway barriers to the movement of fish and terrestrial wildlife. The Branch also represents Transportation Planning to assist Caltrans’ Advance Mitigation Program, which seeks to put biological mitigation in place prior to construction of transportation projects. This Program, which streamlines project delivery and conservation outcomes, is led by DEA. The Branch fosters coordination with District and Headquarters Planning staff to implement the Program’s activities.

Public Health and Transportation

The Branch represents Caltrans on the California Health in All Policies Task Force created by Executive Order S-04-10. This task force, with members from over twenty state agencies, seeks to undertake cross-functional activities to address a wide range of public health issues. The Branch contributes to the task force’s development and implementation of Action Plans related to health and transportation. The Branch also advises on public health perspectives in Transportation Planning documents and Caltrans’ strategic management activities. Additionally, the branch tracks the increased level of interest from the public health community in the transportation planning process at both the State and regional levels. Staff recently served on a research panel of the National Cooperative Highway Research Program, which oversaw the preparation of a national research roadmap to expand future research into diverse aspects of transportation and public health.