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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

The Interstate 11 (I-11) Final Tier 1 Environmental Impact Statement and Preliminary Section 4(f) Evaluation (Final Tier 1 EIS) is now available for public review on the Documents page.

In addition to the traditional Final Tier 1 EIS document, an interactive Final Tier 1 EIS is also available and can be accessd by visiting the following website:

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

The public review period for the Final Tier 1 EIS is 30 days and will run from July 16 through August 16, 2021.

In 2019, the I-11 Draft Tier 1 Environmental Impact Statement and Preliminary Section 4(f) Evaluation (Draft Tier 1 EIS) was completed and made available for public review and comment from April 5, 2019 through July 8, 2019. The study team considered all comments received on the Draft Tier 1 EIS, conducted additional analysis, and coordinated with stakeholders to prepare the Final Tier 1 EIS, which identifies a Preferred Corridor Alternative for I-11. The range of alternatives considered in the Draft Tier 1 EIS and Final Tier 1 EIS include the No Build Alternative.

All public comments and questions received during the Draft Tier 1 EIS comment period are addressed in the Final Tier 1 EIS and can be viewed in Appendix H5.

If you would like to leave a comment on the Final Tier 1 EIS, visit the Contact Us page.

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