Approval and Promulgation of Implementation Plans; California; San Joaquin Valley; Revisions to Motor Vehicle Emissions Budgets for Ozone
Key claim: The EPA proposes to approve updated motor vehicle emissions budgets for NOx and VOCs in California’s San Joaquin Valley for 2026, 2029, and 2031 under the 2008 8-hour ozone NAAQS, replacing budgets based on an earlier emissions model.
Abstract
(Proposed Rule · Environmental Protection Agency) The Environmental Protection Agency (EPA) is proposing to approve revisions to the State of California’s State Implementation Plan (SIP) for the San Joaquin Valley (SJV) area. The revisions consist of an update to the SJV area’s motor vehicle emissions budgets (“budgets”) for nitrogen oxides (NOX) and volatile organic compounds (VOC) for the 2008 8-hour ozone national ambient air quality standard (NAAQS or “standard”). These updated budgets for 2026, 2029, and 2031 were developed with the latest modeling method approved for California. These updated budgets apply to all subareas within SJV. If the EPA approves these budgets, they would supersede the existing approved SJV subarea budgets for the 2008 ozone NAAQS that were based on an earlier emissions model. The EPA is proposing to approve the updated SJV ozone budgets in accordance with the requirements of the Clean Air Act (CAA or “Act”) and the EPA’s regulations.
Why this matters
Motor vehicle emissions budgets set the ceiling for on-road NOx and VOC emissions that transportation plans and projects in the San Joaquin Valley must conform to, so revisions using an updated emissions model directly affect which highway and transit projects can proceed under transportation conformity. Adequate, EPA-approved budgets also anchor the region’s attainment demonstration for the 2008 8-hour ozone NAAQS, a persistent nonattainment area with significant public-health stakes.