This project was part of the Colorado Department of Transportation's ongoing widening of I-225 between I-25 and I-70. The 2 mile reconstruction widened the existing highway to 3-lanes in each direction with an additional auxiliary lane. The project scope included removal of the existing pavement, earthwork, placement of median barrier, sound walls, MSE walls, soil nail walls, storm sewer and drainage improvements, electrical and signage upgrades, sub-grade improvements, and repaving with over 135,000 SY of 13" thick PCCP.
Schedule and Complexity
The project started in June, 2010 with time allowed for 385 calendar days. The project hit the first hurdle right away when the City of Aurora refused to issue permits for the batch plant. CDOT and the contractor solved the problem by placing the plant in CDOT's right-of-way, literally next to I-225. It quickly became the subject of media reports and travelling public comments. As removal efforts commenced, many unmapped utility surprises were uncovered, and existing conditions forced the redesign of one sound wall. In light of these discoveries, CDOT added 15 days to the schedule.
Construction and Innovation
As removals progressed, the existing 8" concrete pavement with 4" of asphalt overlay was recycled. The asphalt was hauled to an off-site recycling center, and the concrete was crushed on-site to produce coarse concrete aggregate and Class II backfill. The original design specified 12" asphalt construction of the temporary detours, but the Project Team changed the designed to 7" PCCP. This temporary pavement was ultimately recycled and used on-site, as well. The 10" thick ramp concrete and 13" PCC for the mainline was batched in the on-site Portable REX plant. The concrete was placed over 12" of lime treated subgrade and finished with a Guntert-Zimmerman model S850 paver.
The project-specific Quality Control plan was administered by the full-time on-site Quality Control Manager. The team of ACI certified craftsmen stationed at the plant and paver continuously monitored quality and uniformity using tests and reporting procedures outlined in the QC plan. Mixer efficiency, slump, unit weight, air content, flexural strength, aggregate gradations and stockpile moisture were all closely scrutinized. Stockpiles were kept small to minimize segregation. Loaders blended incoming materials into the existing piles to ensure a consistent product. All efforts resulted in a product deserving of 100% of thickness, 104% of strength and 74% of overall project available incentives.
Safety of the traveling public and the construction site was of primary importance on this extremely busy, very tight project. Temporary barrier separated the head-to-head travel lanes, as well as separating the construction area from the travel lanes. Temporary signs were placed throughout the construction limits, with flaggers, drums and cones at all intersections. Up to 8 variable message boards were in use at times to keep travelers apprised of approaching conditions. A 24 hour public information hotline was set up, and CDOT updated media outlets with weekly lane closure schedules.