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I-10 Corridor History

A Critical Corridor

Interstate 10 (I-10) between Phoenix and Tucson is critical for Arizona’s economy, as it links the state’s two largest metropolitan areas while also providing a key link for the national and international movement of freight. Arizonans use this route to commute to and from the cities daily from rural communities. This route also serves the Gila River Indian Community by providing key connections to employment, medical, educational, and other necessary services both within and outside of the Community.

Since about 2005, Arizona Department of Transportation (ADOT) had been expanding the capacity of I-10 between Phoenix and Tucson in segments. By 2019, I-10 consisted of three lanes in each direction between SR 387 near Casa Grande and Tucson. That left the 26 miles of I-10 across the Gila River Indian Community as the only remaining stretch with two lanes in each direction.

Corridor Planning & Development

In the summer of 2019, ADOT and partner agencies took the essential first step toward studying ways to increase the capacity of a 26‑mile section of I-10 south of the Phoenix metropolitan area.

A map of the I-10 Wild Horse Pass corridor showing the proposed locations of crossroads and interchange improvements as well as bridge replacements

The study focused on the 26-mile section of I-10 between the Loop 202 interchange south of Phoenix to just south of the State Route (SR) 387 interchange near Casa Grande. This section of I-10 was labeled the Wild Horse Pass Corridor. It was the last remaining segment of I-10 between Phoenix and Tucson that had only two lanes in each direction.

The I-10 bridges over the Gila River were part of a separate ADOT project that was excluded from the overall corridor study but closely coordinated with the Community.

In collaboration with the Gila River Indian Community, the Bureau of Indian Affairs (BIA), the Federal Highway Administration (FHWA) and Maricopa Association of Governments (MAG), ADOT prepared an environmental study under the National Environmental Policy Act (NEPA) and an engineering study to evaluate improvements to I-10. This study was important because I-10 supports significant commercial and economic growth for the region, state and nation, and is considered a Key Commerce Corridor.

The study process produced a NEPA-compliant environmental report (an Environmental Assessment [EA]) and an engineering report called a Design Concept Report (DCR) that:

  • Developed a range of alternatives and options, including the no-build alternative.
  • Evaluated the alternatives’ and options’ costs, right-of-way implications, engineering factors and environmental considerations.
  • Documents the mitigations necessary to offset identified impacts associated with the preferred alternative.
  • Selected a preferred alternative based on technical analysis and the agency and public feedback received.

In 2022, the Final Project Assessment for the Gila River Bridge replacement was completed, and then in 2023, the Final Categorical Exclusion environmental document for that project was also completed. These documents can be found below in the Corridor Documentation section.

In early 2024, the Final Environmental Assessment, the Finding of No Significant Impacts (FONSI), and the Final Design Concept Report were completed for the I-10 Wild Horse Pass Corridor study. These documents, along with other related corridor documents and resources, are posted in the Corridor Documentation section below.

Corridor Development Timeline

The timeline below depicts the corridor planning process steps that were followed by ADOT and the project stakeholders.

From 2019 to 2024, the project was Scoping, Developing and Evaluating Alternatives, Publishing Studies and Reports and Finalizing a Route and Concept.  In the future, the project will begin Design, Right-of-Way and Construction.

View Study Documents

Highlights of the I-10 Corridor Improvements

  • Adding a new general-purpose lane in the median in both the east- and westbound directions for the entire 26-mile corridor, providing three continuous lanes in each direction between Phoenix and Tucson once constructed.
  • Extending the High Occupancy Vehicle (HOV) lane in each direction on I-10 from Loop 202 to Riggs Road.
  • Improving interchanges and crossroads for enhanced capacity and safety, and multimodal (bike and pedestrian) crossings, as well as addressing age/condition issues.
  • Removal of Dirk Lay Road crossing over I-10 and the return of the associated easement/right-of-way back to the Gila River Indian Community.
  • Replacing the aging and narrow Gila River Bridges as a part of a separate project.
  • Installing a fiber optic backbone to install freeway management technology to allow for the installation of sensors, cameras, variable message signs and other highway operations and safety-related technology.

Planning & Development Documents

Final Studies & Project Documents

  • Final EA (Report PDF Only) Coming soon
  • Final EA (Appendices PDF Only) Coming soon
  • Finding of No Significant Impact (FONSI PDF) Coming soon
  • Finding of No Significant Impact (FONSI PDF — Bureau of Indian Affairs) Coming soon
  • Final Public Hearing Report PDF (Sept 2022) Coming soon
  • I-10 Gila River Bridge Final Categorical Exclusion

Previous Studies & Documents

Study Documentation

General Meeting Information
Level 1 Basic Information Overview
Level 2 Detailed Alternative/Options and Evaluations
Level 3 Technical Alternatives/Options and Evaluations