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Air Quality
The San Joaquin region is located within the federally designated San Joaquin Valley Air Basin. The basin is defined by the mountain and foothill ranges to the east and west, the San Joaquin County line to the north, and the Tehachapi and Sierra Nevada Mountains to the south. According to the San Joaquin Valley Air Pollution Control District, this geography creates a giant bowl, which is susceptible to air pollution creation and retention.
Federal air quality regulations require Metropolitan Planning Organizations (MPOs) to monitor air pollutants, including: ozone; particulate matter under 2.5 microns in diameter (PM 2.5); and particulate matter under 10 microns in diameter (PM-10).
The San Joaquin Valley is currently designated as nonattainment with respect to Federal air quality standards for ozone and PM 2.5; and has a maintenance plan for PM-10. As San Joaquin County's transportation planning agency, SJCOG is responsible for demonstrating that transportation plans and programs satisfy the requirements of the Clean Air Act.
NOTE: This webpage concerns Air Quality programs in the San Joaquin Valley.
The SJCOG Board adopted the Final 2025 FTIP [PDF] and Final 2024 Conformity Analysis [PDF] on August 22, 2024.
SJCOG has also updated its Air Quality Conformity Document in response to revised emissions budgets. This update includes no changes to the Regional Transportation Plan, the Federal Transportation Improvement Program, or any individual transportation projects of any kind. It is simply a technical correction to account for revised emissions budgets. The Final 2021 Conformity Analysis [PDF] was adopted by the SJCOG Board at its June 24, 2021 meeting.
The 2018 Air Quality Conformity Document outlines regulations concerning air quality and how those regulations affect the region's ability to deliver transportation projects. The final 2018 Air Quality Conformity [PDF] was adopted by the SJCOG Board on June 28, 2018.
PM Hot-spot Analysis
A hot-spot analysis, as defined in 40 CFR 93.101, is an estimation of likely future localized pollutant concentrations and a comparison of those concentrations to the relevant National Ambient Air Quality Standards (NAAQS). A hot-spot analysis assesses the air quality impacts associated with a specific transportation project. A PM Hot-Spot Analysis focuses on the project's impact on both PM2.5 (particulate matter 2.5 micrometers and smaller) and PM10 (particulate matter 10 micrometers and smaller). As part of the project-level National Environmental Policy Act (NEPA) process, PM hot-spot analyses are required for nonexempt, federal-aid transportation projects of local air quality concern, which include certain highway and transit projects that involve significant levels of diesel vehicle traffic.
For a nonexempt transportation project, the lead agency shall complete the project-level conformity analysis checklist and prepare a PM hot-spot analysis memo to determine if the project is not a Project of Air Quality Concern (POAQC). These will be posted on SJCOG's website for public review and comments.
City of Stockton Swain Road and Morgan Place Roundabout (Posted 2/24/26)
San Joaquin Council of Governments (SJCOG), on behalf of the City of Stockton, is providing a DRAFT PM2.5 and PM10 Hot-spot Conformity Assessment for interagency consultation for the Swain Road & Morgan Place Roundabout Project (5008(213)) located in the City of Stockton, San Joaquin County. The San Joaquin County is in non-attainment for PM2.5 and maintenance for PM10.
The proposed project consists of converting an existing four-way-stop-controlled intersection at Swain Road and Morgan Place to a roundabout.
As part of the environmental review, it is requested that the Interagency Consultation Partners concur that the project is not a "Project of Air Quality Concern" (POAQC) and will not result in new violations of Federal PM2.5 and PM10 air quality standards.
The NEPA document for this project is CE (23 USC 326); therefore, Caltrans and EPA concurrence is requested.
A project-level conformity group meeting, via Zoom, for this project was held on February 18, 2026, at 1 pm (PT). The group meeting agenda, project PM hot-spot checklist, and project presentation slides were provided prior to the meeting and were posted online. Public comments were accepted prior to (via email) and during the meeting. One public comment was received, and the City had responded.
On February 18, 2026, Caltrans and EPA have concurred that this project is not a POAQC.
City of Tracy Interstate 580 (I-580)/Corral Hollow Road Interchange Bridge Improvement (Posted 2/24/26)
San Joaquin Council of Governments (SJCOG), on behalf of the City of Tracy, is providing a DRAFT PM2.5 and PM10 Hot-spot Conformity Assessment for interagency consultation for the I-580/Corral Hollow Road Interchange Bridge Improvement Project (EA 10-1Q550) located in the City of Tracy, San Joaquin County. The San Joaquin County is in non-attainment for PM2.5 and maintenance for PM10.
The proposed project consists of converting the existing Tight Diamond interchange into a Diverging Diamond Interchange, including widening the Corral Hollow Road Overpass (Bridge No. 29-0080) to 4 lanes and adding a center-running bike/pedestrian path, reconfiguring the eastbound and westbound I-580 ramp termini with a two-phase signal, and installing new traffic signals and crosswalks at the ramp termini.
As part of the environmental review, it is requested that the Interagency Consultation Partners concur that the project is not a "Project of Air Quality Concern" (POAQC) and will not result in new violations of Federal PM2.5 and PM10 air quality standards.
The NEPA document for this project is CE (23 USC 326); therefore, Caltrans and EPA concurrence is requested.
A project-level conformity group meeting, via Zoom, for this project was held on February 18, 2026, at 1 pm (PT). The group meeting agenda, project PM hot-spot checklist, and project presentation slides were provided prior to the meeting and were posted online. Public comments were accepted prior to (via email) and during the meeting. There were no public comments.
On February 18, 2026, Caltrans and EPA have concurred that this project is not a POAQC.
City of Lathrop Interstate 5 (I-5)/Louise Avenue Interchange Improvement (Posted 10/23/25)
San Joaquin Council of Governments (SJCOG), on behalf of the California Department of Transportation (Caltrans) and the City of Lathrop, is providing a DRAFT PM2.5 and PM10 Hot-spot Conformity Assessment for interagency consultation. The project is the Interstate 5/Louise Avenue Interchange Improvement Project (FTIP ID SJ07-2005) and is located in San Joaquin County. The San Joaquin Valley Air Basin is in non-attainment for PM2.5 and maintenance for PM10.
This interagency consultation (IAC) meeting is a follow-up to address comments from the August 14, 2024, meeting.
The proposed project consists of improving the local and regional circulation and reducing existing and future congestion by improving the Interstate 5 (I-5)/Louise Avenue Interchange. The interchange improvements are needed to enhance traffic operations and mobility, which will accommodate future traffic demands as a result of the growth planned for in the City of Lathrop's General Plan. The proposed project would improve the existing compact diamond (Type L-1) interchange at I-5/Louise Avenue by constructing a diverging diamond interchange (DDI) to accommodate the traffic associated with the growth planned in the City of Lathrop's General Plan. Additionally, the project would include the following major project elements, widen the existing I-5 on- and off-ramps, reconstruct the undercrossing underneath the existing freeway bridge, construct I-5 ramp metering, construct two new auxiliary lanes (less than one mile in length), provide new traffic signals, construct Class II bicycle lanes along Louise Avenue and new sidewalks along Louise Avenue.
As part of the environmental review, it is requested that the Interagency Consultation Partners concur that the project is not a "Project of Air Quality Concern" (POAQC) and will not result in new violations of Federal PM2.5 and PM10 air quality standards.
The NEPA document for this project is CE (23 USC 326); therefore, Caltrans and EPA concurrences are requested.
A project-level conformity group meeting, via Zoom, for this project was held on October 13, 2025 at 1 pm. The group meeting agenda, project PM hot-spot checklist, and project presentation slides were provided prior to the meeting and were posted online. Public comments were accepted prior to (via email) and during the meeting. There were no public comments.
On October 13, 2025, Caltrans and EPA concurred that the I-5/Louise Avenue Interchange Improvement Project was NOT a POAQC.
Stockton Channel Viaduct Bridge Replacement Project 10-0X460 (Posted 11/26/24)
San Joaquin Council of Governments (SJCOG), on behalf of the California Department of Transportation (Caltrans) and the City of Stockton, is providing a DRAFT PM2.5 and PM10 Hot-spot Conformity Assessment for interagency consultation. The project is the Stockton Channel Viaduct Bridge Replacement in the City of Stockton, San Joaquin County. The San Joaquin County is in non-attainment for PM2.5 and maintenance for PM10.
The proposed project consists of replacing the northbound and southbound (NB, SB) bridges (No. 29-176L/R) of the Stockton Channel Viaduct bridge with a modified I-5 mainline alignment. Additionally, a two-lane roundabout will be constructed at the intersection of Pershing Avenue and Park Street at the termini of the I-5 northbound on- and offramps.
As part of the environmental review, it is requested that the Interagency Consultation Partners concur that the project is not a "Project of Air Quality Concern" (POAQC) and will not result in new violations of Federal PM2.5 and PM10 air quality standards.
The NEPA document for this project is CE (23 USC 327); therefore, FHWA and EPA concurrence are requested.
A project-level conformity group meeting, via Zoom, for this project was held on December 16, 2024 at 10:30 am. The group meeting agenda, project PM hot-spot checklist, and project presentation slides were provided prior to the meeting and were posted online. Public comments were accepted prior to (via email) and during the meeting. There were no public comments.
On December 16, 2024, FHWA and EPA have concurred that this project was NOT a POAQC.
Caltrans State Route (SR) 120 Intersection Control Improvement 10-1Q010 (Determination 8/28/24)
San Joaquin Council of Governments (SJCOG), on behalf of the California Department of Transportation (Caltrans), is providing a DRAFT PM2.5 and PM10 Hot-spot Conformity Assessment for interagency consultation. The project is the SR 120 Intersection Control Improvement 10-1Q010 and is located in San Joaquin County. The San Joaquin Valley Air Basin is in non-attainment for PM2.5 and maintenance for PM10.
The proposed project consists of replacing the existing unsignalized four-legged intersection at State Route (SR) 120 and Murphy Road with a single-lane roundabout. The purpose of the project is to reduce the number and severity of broadside collisions at this location due to motorists' failure to yield.
As part of the environmental review, it is requested that the Interagency Consultation Partners concur that the project is not a "Project of Air Quality Concern" (POAQC) and will not result in new violations of Federal PM2.5 and PM10 air quality standards.
The NEPA document for this project is CE (23 USC 326); therefore, Caltrans and EPA concurrences are requested.
A project-level conformity group meeting, via Zoom, for this project was held on August 28, 2024 at 1 pm. The group meeting agenda, project PM hot-spot checklist, and project presentation slides were provided prior to the meeting and were posted online. Public comments were accepted prior to (via email) and during the meeting. There were no public comments.
On August 28, 2024, Caltrans and EPA concurred that the SR 120 Intersection Control Improvement Project was NOT a POAQC.
City of Stockton Alpine Avenue and Alvarado Avenue 3-Way Traffic Signal (Posted 5/21/24)
A project-level conformity group meeting, via Zoom, for this project was held on June 5, 2024 at 1 pm. The group meeting agenda, project PM hot-spot checklist, and project presentation slides were provided prior to the meeting and were posted online. Public comments were accepted prior to (via email) and during the meeting. There were no public comments.
The following materials are the final materials:
- Project-level conformity group meeting agenda [DOCX]
- June 5 project-level conformity group meeting minutes [PDF]
- Final Alpine Avenue and Alvarado Avenue 3-Way Signal Hot-Spot Checklist, with the IAC and public participation updated [PDF]
- Alpine Avenue and Alvarado Avenue 3-Way Signal Presentation Slides [PPTX]
On June 5, 2024, Caltrans and EPA concurred that City of Stockton Alpine Avenue and Alvarado Avenue Three-Way Traffic Signal is NOT a POAQC.