In addition to overhead message boards, the Colorado Dept. of Transportation has a hotline, website and a text alert system that has some 20,000 subscribers, says Emily Wilfong, a CDOT spokesperson.

A 1,000-ft-long new viaduct is part of the realignment of I-70 through the Floyd Hill area.
Photo courtesy of Colorado Department of Transportation

Kraemer and designer AtkinsRéalis lead a construction manager-general contractor team that is literally moving mountains to widen, upgrade and realign the stretch of highway, including clearing a bottleneck on westbound I-70 at the top of Floyd Hill where three lanes of traffic coming from Denver narrow to two lanes by adding a tolled express lane in that section.

The $905-million project also includes rebuilding or constructing 10 bridges, adding a two-mile section of frontage road between the US 6 and Hidden Valley/Central City Parkway interchanges, moving the current left-merge US 6 on-ramp to westbound I-70, building an extended on-ramp from US 6 onto eastbound I-70, building a wildlife underpass and fencing, adding roundabouts at the intersections of US 40 and Homestead Road and US 40 and County Road 65 and paving the Clear Creek Greenway trail.

“We have up to 150 full-time employees on the Kraemer team and another 100 subcontractors,” says Matt Aguirre, AtkinsRéalis senior division manager. “They are fighting the elements of wind and snow and cold” while keeping an eye out for elk, deer, bears, bighorn sheep and mountain lions—as well as drivers, people fishing, rafters, cyclists and an active landslide.

The new alignment reduces hairpin curves and grades and adds capacity to the eight-mile section.
Photo courtesy of Colorado Department of Transportation

Past and Present

“The [I-70] Floyd Hill project has been in the works for a long time,” says Kurt Kionka, CDOT project director. It is a critical component of the I-70 Mountain Corridor Programmatic Environmental Impact Statement, a long-term multimodal plan established in 2011 to manage congestion and safety on the 144-mile corridor between Denver and Glenwood Springs.

Built in the 1960s, the Floyd Hill section “is ready for upgrades,” says Kionka. Design assessments around a decade ago determined that a tunnel would be too risky and expensive. Named after the founder of a wagon wheel company formed during the 1800s-era gold rush, the Floyd Hill stretch posed underground risks such as old mine shafts, he notes.

But realigning and widening the existing highway “has its own unique sets of challenges,” he says. “How do we fit a road through [the mountain]?” says Kionka. Crammed in by a canyon wall on one side and a creek on the other, the new alignment had to be elevated and shifted south in the central section, requiring a 1,000-ft-long, 115-ft-high concrete cast-in-place segmental viaduct that will carry westbound traffic.

Such design aspects were informed by public input. “We’d present concepts to stakeholders and work with them to establish whether they met the goals or not,” says Aguirre. Maintenance of traffic plans and a corridor aesthetic guideline including colors and patterns for noise walls were established.

The communication with stakeholders is ongoing. For example, “Idaho Springs is on the western limits of the project, and what can happen is sometimes it gets gridlocked” due to drivers entering it to wait out weekend traffic or rock blasting, notes Wilfong. “We meet quarterly with first responders to talk through concerns and about handling traffic. There is a plan in place if we see the queue building, and we can close the exit into the town.”

Average daily traffic at peak through the stretch reaches some 50,000, with Saturday mornings seeing drivers headed to ski resorts in the winter, says Kionka. “We’re designing this project for 2045 traffic volumes, where the average daily traffic will be up to 63,000.”

The goal is to avoid 90-minute delays on the stretch at peak travel times, he adds. “Right now we’re seeing 3,700 vehicles per hour maximum before it breaks down [into the major delays].”

Alleviating the sharp curves should reduce accidents by some 20%, and the new two-mile section of frontage road between the US 6 and Hidden Valley/Central City Parkway interchanges will improve resiliency and emergency response. The trail improvements will meet ADA standards, and the wildlife underpass and four miles of fencing will drastically reduce wildlife collisions.

The Floyd Hill section of I-70 carries thousands of commuters and tourists between the mountains and Denver foothills.
Photo courtesy of Colorado Department of Transportation

Dangerous Curves

The CMGC team began preconstruction in 2022, says Matt Hogan, Kraemer area manager. There are four construction packages. Package 1, for the first two miles of the project, recently reached substantial completion this month, he says. “That was at the far east end, and was the easiest to design,” he says. That included the four miles of deer fence and widening I-70 from five general purpose lines to seven lanes, including the express lane and new shoulders.

The section included four areas of rock excavation to move the highway to the south, totalling some 50,000 cu yd and entailing 70,000 soil nails.

Package 2 encompassed two miles of the west section, says Hogan, with 350,000 cu yd of rock cut adjacent to I-70. “We did a 220-ft-tall cut through drill and blast while keeping the highway open.” Crews are down to one or two blasts per week, he adds.

“We’re working to streamline blasting operations between 9 to 3” during the day, he says. “This corridor had 45 mph [capacity] curves. We’re upgrading it to 55 mph. We’re moving the mountain to flatten the curve. At the bottom of Floyd Hill is a sharp curve, [with capacity for] 35 mph, and a 7% grade.” The project section will lessen the grade to about 3-4% and is slated for completion in 2028.

“US 6 merges on the left into westbound I-70, and that’s tricky when navigating the curve,” Hogan adds. “That goes away too.” A frontage road is being extended by about a mile as well.

“The central section is the meat of the project,” says Hogan. It includes eight structures, including the viaduct over Clear Creek. “Just to build it, another contract was put out to build access and accelerate the schedule while the bridge was being designed,” he says. “Otherwise it would take nine months to start building the bridge.”

Across the section, bridge foundations range in depth from 30 ft to 80 ft, with drilled shafts ranging from 36 ft to 90 ft in diameter and one pier location requiring a cofferdam. The upgraded westbound I-70 is scheduled to open in 2027, with the eastbound lanes in 2028. “We’ll have one more year after that for restoration and landscaping and frontage work,” says Hogan. The project entails approximately 150,000 sq ft of soil nail walls, 30,000 sq ft of mechanically stabilized wire basket wall and some 1 million cu yd of excavation.

Crews must conduct periodic blasting and scaling operations to allow for the changed alignment.
Photo courtesy of Colorado Department of Transportation

“We try to process as much of the excavation into backfill and aggregate on site,” says Hogan. “If it’s good quality, it goes into crushing operations. Not all of it can be used, so we partner with landowners to develop some fill sites.” About 30% of the material is recyclable.

Subcontractor Arizona Drilling and Blasting, a division of Fisher Industries, will conduct some 150,000 cu yd of excavation through the spring in the west section and some 30,000 cu yd for the central section, says Hogan.

Aguirre notes that Kraemer was able to avoid realigning Clear Creek, which is a popular spot for rafters and anglers. At the 20% design stage, the plan was for three rock cuts in the western section and realigning the creek. “The contractor said that this rock on the northern face is much more solid than on the other side of the creek,” he notes. A larger cut avoided disturbing the creek.

“The CMGC delivery method was the only way to deliver this project in this location,” says Kionka. “It allowed the owner to take on risk where we saw it.”