I-25 South Gap: Monument to Castle Rock

I-25 South Gap Logo

About the Project

Construction on the 18-mile South Gap project to improve safety and travel reliability began in September 2018. The I-25 South Gap is Colorado's longest construction zone. 

Project Facts

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

Efforts to improve these conditions are underway.

  • Cost: $419 million, with contributions from Douglas and El Paso counties, Pikes Peak Rural Transportation Authority and a federal INFRA grant (scroll down for details)
  • Contractor: Kraemer North America
  • Timeline:  Project completion is slated for November 2022
  • Location: 18 miles in both directions of I-25, south of Castle Rock to Monument, in Douglas and El Paso counties

Construction Underway 

Crews are actively improving an 18-mile stretch of Interstate 25 known as "The Gap," which starts south of Castle Rock and continues to Monument. 

Project benefits

 Safety: Crews will widen shoulders outside and inside the travel lanes for vehicle pull-off and emergency response. This improvement will also help with drainage.

 Driver choice: After crews add an Express Lane in each direction of I-25, drivers will have the choice to use the Express Lane for a reliable trip in exchange for a toll, or to use one of the two general-purpose lanes for free. Carpoolers (vehicles with three or more people) and motorcyclists can ride the Express Lanes for free.

 Wildlife safety: Crews will construct four new wildlife crossings and install 28 miles of deer fencing.

 Improved pavement: Crews will add a new overlay to the existing pavement for a smoother ride.

 Improved infrastructure: Crews will reconstruct five bridges and extend ramps.

 Improved truck access: Crews will add truck climbing lanes near Monument Hill and the Greenland exit.

 Advanced technology: Crews will modernize communications and power along the corridor to enable advanced technology.

Additional Funding Provides for Additional Improvements

The original project cost was $350 million. Additional funding was needed to cover the construction of the County Line Road bridge, southbound I-25 Monument Hill truck climbing lane, southbound I-25 truck chain-up station, and to address the issue of unsuitable soil found following the start of construction. In 2019 and 2020, funding became available for these improvements. The current total budget is $419 million. The project remains on budget, but the overall project cost increased when additional benefits were included.

Gap Map Horizontal view of Stretch.

Driver Impacts

Construction, by nature, will always impact those who use the road. Two lanes of traffic will be maintained in each direction of I-25 during the day.

Still, drivers should expect slower speed limits, narrower lanes, increased volume, nighttime lane closures, and construction trucks entering and exiting the interstate throughout the corridor.

Construction crews will be working around-the-clock and on weekends to deliver these improvements on-time, on-budget and with as little impact as possible.