Interstate 25 South Gap Project Underway in Colorado
Mind the Gap: Colorado DOT Initiative Aims to Improve Safety and Accommodate Increasing Traffic Between Denver and Colorado Springs
The Gap is an 18-mile stretch of Interstate 25 in Colorado, running 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. On average, nearly 80,000 vehicles travel the I-25 South Gap corridor daily; by 2040, this number is predicted to increase to more than 120,000 vehicles per day.
Over the years, congestion, crashes and delays have increased due to population growth and more people using the roadway. Safety along this stretch has been a concern as volume has increased, reports Tamara Rollison, Colorado Department of Transportation (CDOT) Communications Manager (Region 1 and Headquarters).
“Two State Troopers were killed in the line of duty over the course of just one year, responding to incidents in this corridor,” she relates. “In addition, travel delays and trip unreliability are a source of frustration for travelers now and will only get worse as Colorado’s population grows from 5 million to more than 8 million in the next 20 years.”
To address these issues, a major CDOT construction initiative – the I-25 South Gap project – is now underway. According to Rollison, “This project will deliver many benefits to drivers, decreasing congestion and increasing safety, and will feature a new Express Lane in each direction, wider shoulders, wildlife underpasses, new pavement and advanced technology.”
Construction on the $350 million project, which is currently the longest construction zone in the state, began in the fall of 2018; project completion is scheduled for 2022. Funding includes contributions from Douglas and El Paso counties, the Pikes Peak Rural Transportation Authority, and a federal INFRA grant. Contractor on the project is Kraemer North America, a privately-held general contractor with its headquarters in Plain, Wisconsin, and a Colorado regional office in Castle Rock.
Among the planned primary benefits of the project:
- Safety: Shoulders outside and inside the travel lanes will be widened for vehicle pull-off and emergency response, an improvement that will also help with drainage.
- Driver Choice: With the addition of 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 will be able to ride the Express Lanes for free.
- Wildlife Safety: Crews will construct four new wildlife crossings and install deer fencing.
- Improved Pavement: A new overlay will be added to the existing pavement for a smoother ride.
- Improved Infrastructure: Crews will reconstruct four bridges and extend ramps.
- Improved Truck Access: Truck climbing lanes will be added near Monument Hill and the Greenland exit.
- Advanced Technology: Communications and power along the corridor will be modernized to enable advanced technology.
Splitting Project Into Three Sections Accelerates Construction
As Rollison points out, from initial study to groundbreaking, this is the fastest delivery of a project of this size in CDOT history. The South Gap project is split into three geographic sections – North (Castle Rock to Tomah Road); South (Greenland Road to Monument); Middle (Tomah Road to Greenland Road). “Splitting up the project allowed construction to begin on one section, while design was finalized on another,” she comments. “This means construction could begin much sooner than anticipated.
“Breaking the project into three different ‘packages’ or ‘segments’ – basically work contracts – allows for construction to begin in one of segments while design is being completed in another segment. This helps to accelerate the overall schedule. In the construction world, this approach is known as a CMGC, or Construction Manager/General Contractor.
“Construction crews started in September 2018 on the northern area of the project, between Plum Creek Parkway and Sky View Lane (Tomah Road). While the project is being completed in phases, all three phases will open to traffic together.”
As of this writing, the following work is underway, Rollison reports:
- North Section: Building the permanent concrete barrier wall to separate northbound and southbound I-25; constructing foundations for overhead signs; constructing permanent roadway, including embankment and asphalt
- South Section: Repaving, restriping and setting concrete barrier to create a 7-mile work zone; excavating, paving and installing drainage; installing detour pavement for traffic shifts; constructing wildlife crossings just north of County Line Road and near the Greenland Road exit; re-striping the truck climbing lane to merge earlier or force exit at County Line Road; shifting traffic at the southbound I-25 Weigh Station for pavement construction
- Middle Section: Setting concrete barrier to create a 6-mile work zone; reducing the speed limit
Tight Construction Environment and Weather Among Project Challenges
Rollison says that the middle section of the project, Sky View Lane (Tomah Road) to Greenland Road, is considered the most complex section of the project. As she explains, “This section of roadway has some of the largest grade separations between northbound and southbound I-25 and the most structures to rebuild. Along with some of the larger concrete box culverts for drainage, this stretch will also see the addition of a wildlife crossing near the old rest areas. The Spruce Mountain Road on-ramp to northbound I-25, I-25 over Plum Creek, and Upper Lake Gulch Structures will be replaced, and I-25 over the Union Pacific Railroad will see improvements to the bridge rail and surfacing. These structures all exist in less than a one-mile stretch that will have to be phased together for construction.
“This corridor is a tight construction environment. Crews have worked to balance commuter access by maintaining two travel lanes in each direction during daytime peak hours while still giving crews room to work safely. We’re using every inch of pavement and construction space. Speeding drivers make it especially dangerous for our team on the job site.
“In addition, weather is always a factor for construction in Colorado. In some cases, wet weather can delay paving, or low visibility can halt work for a day due to safety concerns. However, the Kraemer North America team is made up of people who are experts at anticipating these challenges, so we remain on schedule.”
Technology Plays a Major Role in Enhancing Driver Safety
CDOT has worked to improve safety along frontage roads during construction of the I-25 South Gap project. Early this year, crews installed a vehicle headlight glare mitigation system, with the goal of shading vehicle headlight glare from motorists on local roads which face the highway.
Technology is playing a role on this project in other ways as well, Rollison reports. “On this project, we have an onsite Traffic Operations Center (TOC) to monitor current roadway conditions and possibly reduce congestion by suggesting alternate routes to drivers when incidents occur. Typically, construction projects feed into the larger TOCs across the state, but this project is the first ever to have its own onsite TOC, which benefits both motorists and the project team because they can gather and provide real-time information.
“In addition, CDOT and Kraemer North America have deployed smart work zone technology to warn drivers about trucks entering/exiting the highway and to distribute real-time traffic information. A sensor is attached to the concrete barrier in the work zone. When a truck passes the sensor, a VMS board farther back in the corridor is triggered and will light up a sign to warn motorists in time to yield to the truck. With the queue warning system, sensors detect speeds upstream and update VMS signs to let motorists know about slow or stopped traffic ahead.”
Abundance of Wildlife in Corridor Addressed
One of the unique and historic characteristics about this corridor is the variety and quantity of wildlife. While viewing wildlife along the corridor is enjoyable and unique to Colorado, wildlife has contributed to serious crashes in the I-25 corridor.
CDOT worked with Colorado Parks and Wildlife (CPW) to study, gather data and develop solutions. As part of that work, 12 trail cameras were deployed along I-25 to determine the diversity of wildlife present and capture travel patterns. CDOT and CPW analyzed locations along the corridor where wildlife collisions were highest, areas of expected wildlife movements, existing game trails, culverts, drainages and existing bridges. Data collection is expected to continue through the end of the year.
CDOT will install four new wildlife crossings and more than 30 miles of deer fence as part of the I-25 South Gap project.
Enhanced Safety and Traffic Efficiency at Project’s Completion
The completion of this expansive project will result in major improvements in safety and traffic efficiency along a major Colorado highway which will see rapidly increasing traffic in coming years. As Rollison comments, “With one crash per day on average along this corridor, this project is critical to the safety of motorists and first responders traveling and working along I-25 between Castle Rock and Monument.
“CDOT’s Whole System, Whole Safety initiative focuses on improving the safety of Colorado’s transportation network by reducing the rate and severity of crashes and improving safety conditions for those traveling by all transportation modes, which is the number one goal of the South Gap Project. By enhancing safety along this 18-mile stretch, our mission is to get everyone home safely.”