I-25 South Gap Environmental Assessment: Monument to Castle Rock

The Gap

The Gap is an 18-mile stretch of I-25  from south of Castle Rock to Monument.  It is the only four lane section of I-25 from Denver to Colorado Springs.  Over the years, congestion, crashes and delays  have grown due to population growth and more people using the road.

Improving the GAP is a top statewide priority. The project is in the Environmental Assessment and design phase with construction scheduled to begin by end of 2018, pending funding. 

Project Map

The Project 

Over 100 alternatives were evaluated to improve the Gap, with three key needs identified: improve travel reliability, safety and mobility.  The proposed improvements are shown to best meet the project needs and will be evaluated further during the Environmental Assessment: 

  • Widen 18 miles of I-25 from south of Castle Rock to Monument by adding an Express Lane in each direction. Drivers would have the choice of using the Express Lane for a reliable trip in exchange for a variable toll or ride the two existing general purpose lanes for free. Carpoolers (vehicles with 3 or more people) could ride the Express Lane for free. This is likely the best option that offers motorists trip reliability over the long-term.
  • Widen shoulders outside and inside the travel lanes
  • Add new wildlife crossings
  • Add new overlay to existing pavement
  • Repair or replace bridges
  • Modernize highway with communications and power to enable advanced technology
  • Estimated project cost: $350 million
  • Construction scheduled to begin November 2018, pending funding

Highway will nearly double in width with proposed improvements

The Environmental Assessment

For more than a year, CDOT has undertaken a Planning and Environmental Linkages study to identify a long-term vision for the 34-mile stretch of I-25 from Monument to C-470. As a result of the study, CDOT identified the Gap as the most urgent priority.

To address that priority, CDOT is conducting an environmental assessment, with the goal of having this stretch of the highway ready for construction by November 2018.

While CDOT has found Express Lanes to be the best long-term solution for travel reliability on the state’s most highly traveled corridors, making the new lane in each direction an Express Lane or general-purpose lane will be evaluated for the I-25 South Gap.

Details of how the Express Lane would operate in the corridor are being worked out and will be described in the environmental assessment document. Public hearings are planned for April 2018, as well as ongoing public outreach and collaboration with public officials and localities along the corridor.  Final outcome will not be determined until the environmental assessment is approved in spring 2018.

Listening Sessions

  • 6:30-7:30 p.m.
    Tuesday, March 20
    Larkspur Firehouse
    9414 South Spruce Mountain Road

  • 12:30-1:30 p.m.
    Thursday, March 22
    Douglas County Library
    James H. LaRue Meeting Room
    100 South Wilcox St.
    Castle Rock

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