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

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 expected to be completed in 2022.

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

Construction on the I-25 South Gap began in September 2018 in this 5-mile section. This section is expected to be complete in fall 2020. It will open with wider shoulders. The Express Lane will open with the rest of the 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: Similar to work on the northern end of the project, construction in this area began in the median, with traffic shifted to the outside shoulders. Then, the configuration will switch. 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: Work in this area began on the outside shoulders, so traffic was shifted to the middle. 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 2021. View illustration.

Greenland Road Crossover: The Greenland Road interchange will be completely rebuilt and include a new wildlife crossing. For crews to safely work, a major traffic shift is necessary. Northbound and southbound I-25 traffic will ride on southbound I-25, separated by a temporary concrete barrier. Then, both driving directions will switch to the northbound side. View illustration.

Monument Hill Frontage Road: To build a new wildlife crossing, crews will need to close Monument Hill Road for up to seven months, starting in summer 2020.

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.

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