I-70 West Vail Pass Auxiliary Lanes | Planning Phase

Environmental Assessment & Section 4(f) Evaluation Public Review Presentation

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Public Review Presentation in English   Presentación de revisión pública en español

Environmental Assessment   Finding of No Significant Impact

About the Study

CDOT conducted an environmental assessment and conceptual design for safety improvements on West Vail Pass. The study concluded in January 2021 with a Finding of No Significant Impact. The Proposed Action is a package of improvements including an eastbound and westbound auxiliary lane on I-70 on the west side of Vail Pass in Eagle County, from the East Vail exit (Mile Point 180) to the Vail Pass Rest Area (Mile Point 190). Other improvements include a widened inside shoulder, reconstruction of tight curves, wildlife underpasses and fencing, water quality improvements, truck ramp and parking enhancements, median glare screens and relocation of two miles of the recreation path that is currently next to I-70. The latest technology will be used to add variable speed limit and message signs and a way to close the pass immediately through a remote system when necessary.

Study Facts

  • What: Study improvements to I-70 on the west side of Vail Pass, including auxiliary lanes in both directions
  • Why: Make it safer to travel this steep terrain
  • Location: On the west side of Vail Pass on I-70, from mile points 180 to 190

A detailed description and evaluation of the proposed action has been documented in the environmental assessment (EA) and Section 4(f) evaluation, which considers benefits, impacts, and proposed mitigation for numerous environmental and community resources. View the EA online here. Project elements included:

  • implementing the I‐70 Mountain Corridor Context Sensitive Solutions (CSS) process.
  • providing public and stakeholder involvement opportunities.
  • analyzing traffic and safety data and evaluating the impacts of proposed safety improvements.
  • collecting data and updating reports for potentially impacted environmental resources along the corridor.
  • conducting analysis to determine the most practical and least impactful solutions to add auxiliary lanes on West Vail Pass.
  • completing an environmental assessment (EA).


I-70 through Vail Pass serves as a major transportation route across Colorado's Rocky Mountains, providing a critical interstate link for the country. The steep grades, roadside terrain, and extreme weather events make I-70 over Vail Pass a challenging mountain pass to travel and maintain.

When originally constructed in the 1970s, Vail Pass was at the forefront of modern highway design. The existing roadway was purposely constructed to minimally impact the unique natural environment of Vail Pass.

I-70 PEIS & ROD: 2011
Improvements in this project study area were included as a part of the preferred alternative CDOT selected in the I-70 Mountain Corridor Programmatic Environmental Impact Statement (I-70 PEIS, a tier 1 National Environmental Policy Act (NEPA) process).

In 2011, FHWA signed a Record of Decision (ROD), which included a decision about capacity, mode and location for future transportation improvements. The PEIS recommended to add auxiliary lanes up and down the west side of Vail Pass from mile point 180 to mile point 190.

West Vail Pass Environmental Assessment: 2006/2007
An environmental assessment was initiated in 2006 to identify the transportation needs on West Vail Pass and evaluate alternatives to address the needs. The project was halted due to the ongoing PEIS study and a lack of funding.