Construction Overview

The longest construction zone in the state, the I-25 South Gap work zone, stretches 18 miles between Monument and Castle Rock.

The project is split into three geographic regions:

  • North: Castle Rock to Sky View Lane (Tomah Road)
  • Middle: Sky View Lane (Tomah Road) to Greenland Road
  • South: Greenland Road to Monument

Splitting up the project allowed construction to begin on one section, while design was finalized on another. Scroll down to learn about traffic impacts in each section. The project is on-time for completion in November 2022.

North: Castle Rock to Sky View Lane (Tomah Road)

This section is complete and will operate with two lanes and wider shoulders until the Express Lane can open with the entire project in 2022. 

South: Greenland Road to Monument

Here’s what to expect from construction between Monument and Greenland Road:

Monument to County Line Road: Construction includes widening, earthwork, asphalt paving, storm sewer pipes, a new wildlife crossing and new median barrier and retaining walls. View illustration.

County Line Road to Greenland Road: Construction includes a new wildlife crossing, widening, storm sewer pipes and median barrier and retaining walls. In 2019, CDOT added funding to replace the County Line bridge. Construction on that bridge is expected to start in spring 2021. View illustration.

Greenland Road: The Greenland Road interchange was complete rebuilt from a single-lane box culvert to a two-lane underpass. Construction in this area also included a new wildlife crossing and was mostly complete by December 2020.

Monument Hill Frontage Road: To build a new wildlife crossing, crews have closed a portion of this frontage road. It is expected to reopen in spring 2021.

County Line Road bridge: Crews will reconstruct the County Line Road bridge. It will double in size to accommodate one through-lane in each direction, a turn-lane in each direction and wider shoulders. Learn more

Temporary pavement will allow crews to maintain two driving lanes in each direction during peak travel times, though some extended ramp closures at Greenland and County Line roads will be necessary.

Middle: Tomah Road to Greenland Road

This 6-mile section is the most complex. Crews will build new Express Lanes, wider shoulders, a new wildlife underpass and bridge replacements at Upper Lake Gulch Road, Spruce Mountain Road and Plum Creek.

Overnight lane closures are ongoing along northbound and southbound I-25 to allow crews to safely perform construction activities. Like impacts occurring in the northern and southern sections, two lanes of traffic will be maintained in each direction during daytime peak travel hours.

Download project fact sheet.