Project Description


In accordance with the Federal Highway Administration (FHWA), the Colorado Department of Transportation (CDOT), through its consultant team of Wilson & Company and PBS&J, initiated the C-470 Corridor Project.The project consisted of an Environmental Assessment (EA) along the southern reach of the Corridor and an Express Lanes Feasibility Study (ELFS) from South I-25 to West I-70. The completed EA identifies the future needs, then examines improvements that meet those needs, including the number of travel lanes, interchange modifications and other major capacity improvements, as well as alternative modes of transportation. The EA has taken approximately three years to complete. See Schedule

The Express Lanes Feasibility Study (ELFS) examined the feasibility of tolled express lanes to address congestion along the corridor from South I-25 to West I-70. The study results were incorporated into the EA as one of the examined alternatives.

The Corridor is bordered by three counties (Arapahoe, Douglas, and Jefferson) and seven cities (Centennial, Greenwood Village, Golden, Lakewood, Littleton, Lone Tree and Morrison.)

Public input is a critical component of the project. Please contact us with your issues or concerns.

First Steps

The first step in the C-470 Corridor Project was an Environmental Assessment. The Environmental Assessment is a study that:

  • Determined purpose and need for the project. The project team looked at current conditions on C-470 using multiple tools such as future land use, existing traffic counts, travel demand modeling and what the traffic conditions or operations on the roadway look like in 20 years. Purpose and need also further defined the actual project limits for the environmental assessment.
  • Examined numerous solutions that address the needs defined in the purpose and need statement. Those alternatives consist of a wide array of solutions, such as highway improvement, mass transit, or incorporating tolled express lanes into the alternatives. The potential solution(s) were then rigorously examined in the next steps.
  • Identified the potential environmental impacts of possible transportation improvements needed to best serve the users and the communities along the C-470 Corridor.

The Express Lanes Feasibility Study is a concurrent study that:

  • Helped CDOT understand this innovative alternative in the context of the community and the needs of the users.
  • Assessed the effectiveness of this alternative in meeting the purpose and need.
  • Recommended inclusion or exclusion as an alternative selected for further study in the EA.

Why we needed an Environmental Assessment

Under federal regulations and state policy, major transportation improvements are approved for funding only after it has been determined that the environmental impacts on the surrounding area are within acceptable limits. This determination is made by the Federal Highway Administration (FHWA) based on the findings of the EA.

The EA was conducted with the careful supervision of the FHWA. The FHWA oversaw the process and ensured that all federal guidelines and requirements were met.

The National Environmental Policy Act of 1969 (NEPA) is the main federal policy that governs projects like the study of C-470. NEPA requires that all federally funded highway projects be evaluated to determine their social, economic and environmental effects on the community.

Once the draft EA was prepared, the document was reviewed by appropriate federal and state agencies such as the US Environmental Protection Agency, the State Historic Preservation Office, the US Fish and Wildlife Service, the U.S. Army Corps of Engineers, and the Denver Regional Council of Governments. The document was also available for public review and was the subject of a Public Hearing.

If the impacts are not significant, a Finding of No Significant Impact (FONSI) will be issued by the FHWA. If the impacts are significant, a more formal Environmental Impact Statement (EIS) will be prepared to document these impacts and obtain a Record of Decision (ROD) from FHWA.

What We Investigated

Below is a list of the environmental resources CDOT has examined in order to understand the environmental impacts of various alternatives, including doing nothing.


  • Neighborhoods
  • Recreational resources
  • Relocations
  • Social services
  • Pedestrian trails
  • Low-income or minority
  • Visual character
  • Noise
  • Bikeways


  • Land Use
  • Economy
  • Jobs
  • Transportation


  • Air quality
  • Water quality
  • Floodplains
  • Ecology
  • Wetlands
  • Wildlife habitat
  • Geology
  • Threatened and
    endangered species
  • Historical resources
  • Archaeology
  • Paleontology
  • Prime and unique
  • Hazardous waste