US-287 at Springfield, CO

Project Focus
This $16.6 million project, an 11.2 mile section of US-287 north of Springfield, is a portion of the NAFTA ports to plains freight corridor from Mexico to I-70 at Limon. This project continues the heavy-duty whitetopping strategy that CDOT has employed over the last several years. This involves upgrading the roadway for the long-term to carry the massive truck volume that is forecasted at 72% of the 3073 vehicles per day in year 2033. In addition to the 285,000 square yards of PCCP, the project scope included widening and building new approaches at 14 county road intersections; rehabilitation of four bridges; box culverts and pipe extensions; and over fifty runs of new RCP drainage pipe up to a 106” diameter.

Project Details
Schedule & Complexity
Since a detour around the construction was not available, the existing 44-foot, two-lane roadway with shoulders, was overlaid with a new 12” PCCP doweled "whitetopping”. The traffic was carried through the work zone using flagging stations and 24-hour pilot car operations. Any incident of a delay over 30 minutes would have been charged to the contractor at $1200 each after four incidents, adding up to a significant potential daily penalty if the queue-waits were not well controlled. In order to meet this requirement, the project was split in half and built in two phases thus limiting the pilot operation to leading a traffic stream down and back for a total of 11 rather than 22 miles. The project never exceeded the specified 30-minute queue-delay. The contractor constructed the entire project in 387 calendar days, shortening the contract by 25 days and earning the maximum lane-rental incentive of $75,000, (30 days at $2500 each) by limiting the overall 24-hour pilot car operations to 145 days - 30 fewer than allowed.

Safety
Workzone safety was outstanding with only four minor fender-bender accidents and no injuries during the 24-hour pilot car operation. Rumble strips were used in advance of the waiting area while portable speed monitors and vertical panels were also used to slow traffic. A public address system was setup to allow the radio flagger to inform the waiting vehicles of the status of pilot operations. A special grant received by the Colorado state patrol provided additional resources to more closely monitor the traffic. The project team received a CDOT statewide safety award.

Construction & Innovation
Concrete was mixed on-site in a central mix plant, hauled in end-dump trucks and placed with a Guntert Zimmerman 850 paver with an automatic dowel-bar inserter. The PCCP was paid by the square yard with surface preparation prior to paving incidental to the pavement cost. This method allowed the contractor to choose the most cost-effective method of surface preparation to meet the contract requirements. The Contractor chose careful surveying of the existing profile and selective milling as the most suitable and cost effective method for its operations over other options such as leveling with asphalt concrete or thickened PCCP. The dirt shouldering was also incidental to the PCCP cost. The millings were used to improve the track line for the slipform paver, leveling remaining ruts and low spots prior to overlay and improving the final smoothness.

Quality
The contractor earned 88%, or $192,000, of the available ride incentive for achieving an average of 6.31”/mile smoothness on a 0.1” blanking band specification. The contractor elected to use the optional flexural strength specification and earned an additional 92%, or $292,000, of the available strength quality incentive, with control processes that achieved an average 28-day flexural strength of 703 psi and a standard deviation of 51 psi.