The Colorado Department of Transportation (CDOT) and Concrete Works of Colorado, Brighton, teamed up to build the second and third phases of a new urban interchange at Santa Fe Drive (U.S. Highway 85) and Belleview Avenue (State Highway 88) in Littleton.
"It was a very complex urban project involving numerous businesses and residences and relocating a massive amount of utilities," said Ron Buck, CDOT Region 6 resident engineer. Complicating the project was limited construction space, six intersections, heavy work-zone traffic, limited working hours and intricate phasing. The $10 million second phase of this three-phase project won an American Concrete Pavement Association "Excellence in Concrete Pavements" award in the best urban arterial project category.
Working closely together, CDOT and Concrete Works developed a creative game plan that resulted in a high-quality pavement with minimal disruption to businesses and motorists.
Concrete handles traffic
Phase two of this challenging project involved removing the old road and building the new road next to it. The existing road, historic Santa Fe Drive, was constructed with concrete in 1917 as the first federal aid project for the state of Colorado. According to Buck, heavy traffic volumes (55,000 average daily traffic on Santa Fe Drive and 35,000 on Belleview) dictated that the whole interchange be reconfigured, including an overpass (phase one of the project). In fact, the entire Santa Fe corridor into downtown Denver is being reconstructed with concrete, section by section.
"Concrete was the obvious choice to accommodate the large percentage of trucks and the high traffic volumes on this light industry corridor," said Buck.
Concrete Works completed all earthwork, utility and structural work. "They did the majority of the work," said Buck. "By not using a lot of subcontractors, they made it easier to manage the schedule."
The pre-paving part of the project included 52,000 cu yd of earthwork, 8,200 ft of concrete pipe storm sewer, 2,200 ft of waterline and a 620-ft-long concrete box culvert.
For Marc Lenart, owner of Concrete Works, the construction of the box culvert was the most challenging part of the project.
"Sewage lines from South Denver to the sewage plant ran through the project," he said. "We had to suspend old concrete sewage pipes across the 30-ft-wide excavation, and we were worried they would break or start leaking. If one had collapsed it would have filled the river with sewage." The project runs next to the Platte River, about 50 ft away.
It also was a challenge to achieve a solid and workable subgrade with soils that varied from alluvial river sands to clay. The fact that concrete trucks used the prepared subgrade for deliveries proved that the contractor achieved this goal.
The pavement is unusually thick for a city arterial–12.5 in.
"The thickness of the pavement reflected the weak natural subgrade and the heavy truck traffic," said Buck.
The reinforced concrete pavement featured 14.8-ft joint spacing, dowels at all construction joints and longitudinal contraction joints, and tied concrete shoulders with curb and gutter.
Easy on the shocks
The contractor achieved a quality pavement, with minimal random cracks and little corrective grinding. According to the contractor, this was accomplished through a combination of careful subgrade preparation, quality control, high concrete strength and timely joint sawing.
The pavement also was very smooth. The specification called for 12.04 in./mile maximum mainline profile index. The average profile index after limited corrective grinding was 4.24 in./mile on a 0.2-in. blanking band.
"The biggest challenge of this project," said Buck, "was keeping traffic moving." The businesses along the route were dreading construction at the intersection.
"They were convinced it would ruin their business," said Buck. "So the DOT made every effort to maintain access, kept routes well marked, got in and out quickly, worked at night and used fast track mixes."
The DOT did not allow lane closures during weekdays between 5:30 a.m. and 7 p.m. on Santa Fe Drive and suggested using weekend closures to shorten the length of the project, minimizing overall disruption to traffic. The contractor used high early strength concrete at intersections and on and off ramps to shorten closure times.
"The use of the fast-track concrete allowed us to open some pavement to traffic within six hours," said Buck. "In most cases, we waited 12 hours."
Even with all the project complexities, the job was completed ahead of schedule.
The word on the street
The contract required the contractor to provide public information services for the project, including newsletters and notices, a phone information line and media relations. According to Buck, CDOT has been including the public relations specification in its Denver metro area paving contracts for the past five years.
He attributed the quality, innovation and timeliness of the project to the expertise and commitment of the contractor.
"The success of this project is due to the contractor’s conscientiousness and diligence," said Buck. "Concrete Works put safety first, and totally embraced the teamwork concept. They made the PR spec even better, taking careful steps to make sure everyone had up-to-date schedules, and the motorists and businesses knew what to expect."