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Interstate 11 Corridor Tier 1 Environmental Impact Statement, Nogales to Wickenburg
Interstate 11 Corridor Tier 1 Environmental Impact Statement, Nogales to Wickenburg

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Current Status

Record of Decision and Final Preliminary Section 4(f) Evaluation

The Record of Decision and Final Preliminary Section 4(f) Evaluation was published on Nov. 16, 2021 and can be found on the Documents page. This decision document identifies the Selected Corridor Alternative, which is a Build Alternative.

The Selected Corridor Alternative is the same as the Preferred Corridor Alternative outlined in the Final Tier 1 Environmental Impact Statement published on July 16, 2021. The Selected Corridor Alternative is a 2,000-foot-wide starting point within which the proposed I-11 facility could be built.

Interactive Map – Zoom in on a satellite view of the Selected Alternative.

Final Tier 1 Environmental Impact Statement and Preliminary Section 4(f) Evaluation

The Interstate 11 Final Tier 1 EIS and Preliminary Section 4(f) Evaluation (Final Tier 1 EIS document) was completed and made available for a public 30-day review July 16 through August 16, 2021. As a final document, the Final Tier 1 EIS will be available for review indefinitely and is not anticipated to change.

In addition to the PDF version of the Final Tier 1 EIS document, an interactive Final Tier 1 EIS is also available and can be accessed by visiting the following website:

Throughout the more than five-year environmental study process for the proposed I-11 facility from Nogales to Wickenburg, study team members from the Arizona Department of Transportation and the Federal Highway Administration have listened to and heard the public during formal comment periods, public meetings and public hearings that were held throughout the 280-mile study corridor. All comments during this Tier 1 study have been documented as part of the study record.

Pursuant to NEPA, a formal public comment period was part of the I-11 Draft Tier 1 Environmental Impact Statement, which was published on April 5, 2019. This process included six public hearings throughout the 280-mile study corridor and a 90-day public comment period. Extensive public comment submissions during this period resulted in revisions to the corridor, which are reflected in the Final Tier 1 EIS that was published on July 16, 2021. All public comments and questions received during the Draft Tier 1 EIS comment period were addressed in the Final Tier 1 EIS and can be viewed in Appendix H5.

It is important to note that the I-11 Final Tier 1 EIS, as a planning-level decision document, focuses only on potential corridor locations for the 280 miles from Nogales to Wickenburg. For I-11 to advance as a construction project, several additional steps would be required. These steps would include NEPA approval, identifying funding, and conducting specific project-level Tier 2 NEPA studies of priority corridor segments. Based on need and purpose, these segments will focus on smaller and shorter sections of I-11 and not the entire corridor. At this time, no funding has been identified to plan, design or construct any part of I-11, including any Tier 2 analysis. If funding becomes available for a Tier 2 study, that process also would include an extensive public comment period in accordance with NEPA. As such, opportunities for additional public involvement would be provided.

Study Overview

Study Map


In December 2015, the U.S. Congress approved the Fixing America’s Surface Transportation (FAST) Act, which is legislation to improve the nation’s surface transportation infrastructure during a five-year period. The FAST Act formally designated I-11 as a proposed transportation route in Arizona. It stated that the I-11 corridor will generally follow State Route 189 and Interstate 19 from Nogales to Tucson, Interstate 10 from Tucson to Phoenix, and US 93 from Wickenburg to the Nevada state line.

The designation doesn’t include funding but identifies I-11 as a high-priority corridor eligible for federal funding. ADOT continues to work with its federal, state and local partners to identify funding for I-11, which, if constructed, is expected to include a combination of new and existing roadways.

Tier 1 EIS Environmental Review Process

ADOT is currently funding and conducting the first step in a tiered environmental study to identify a potential corridor for I-11 between Nogales and Wickenburg. The Tier 1 EIS environmental review process will consider both Build Corridor Alternatives and the No Build (do nothing) Alternative.

Navigating NEPA

For more information on the environmental review process, visit the Environmental Process page.

Tier 1 EIS

The Tier 1 EIS, required by the National Environmental Policy Act, is expected to be complete in 2021. The Federal Highway Administration will issue a Record of Decision that will present either a Selected Corridor Alternative or the No Build Alternative. If a Build Corridor Alternative is selected, Tier 2 environmental studies would then be required to determine the alignment (the specific route) and design details, such as the width of the median, frontage roads, traffic interchange locations, and other roadway features.

The Difference Between a Corridor and an Alignment For planning purposes, the Build Corridor Alternatives in the Tier 1 EIS are identified as 2,000-foot-wide corridors. The potential I-11 facility (also referred to as an alignment) would generally be 400 feet wide, which includes travel lanes, shoulders, median, and other possible features like frontage roads. The 2,000-foot wide Build Corridor Alternatives for the Tier 1 EIS lay the groundwork for where I-11 could be located. If a Build Corridor Alternative is selected, future studies would be required to determine the specific alignment (or route) of I-11 within the 2,000-foot-wide corridor.
Wickenburg to Nevada

Currently all but 39 miles of the 200-mile drive from Wickenburg to the Nevada state line have been upgraded to a four-lane divided highway to improve traffic flow, support the movement of freight and enhance safety through this heavily traveled area. The entire northern segment of US 93 from Kingman to the Nevada state line (mileposts 1 to 68) is now a four-lane divided highway following the completion of a $71 million project in 2010.

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Study Purpose and Need

I-11 Purpose and need diagram.

History of the I-11 Corridor

The current ADOT-led Tier 1 EIS builds upon the prior I-11 and Intermountain West Corridor Study (IWCS) completed in 2014, which was a multimodal planning effort that involved ADOT, the Nevada Department of Transportation, Federal Highway Administration, Federal Railroad Administration, Maricopa Association of Governments, Regional Transportation Commission of Southern Nevada, and other key stakeholders.

Upon completion of the IWCS, FHWA and ADOT continued to advance the Tier 1 EIS Study in Arizona for the approximate 280-mile section between Nogales and Wickenburg, as shown on the corridor study area map. The FAST Act formally designates I-11 throughout Arizona, reinforcing ADOT's overall concept for the I-11 Corridor that emerged from the prior IWCS.

For additional information on the IWCS, please visit