I-25 Between 5th Street and Meadows Parkway - Castle Rock, CO
Project Focus
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Project Details
Schedule & Complexity
The original design called for a three-phase, multiple traffic switch project with a completion date of May, 2008. CDOT approved a contractor initiated Value Engineering Proposal to change to two construction phases allowing the contract to be completed 7 months early in October, 2007. This change created significant quantity reductions for detour paving and traffic control with a resulting cost savings of nearly $2.1 million, shared equally between CDOT and the Contractor. One facet of the change was to construct the northbound side first, preventing the potential 8-month delay predicted by IREA to relocate major utilities near a new railroad bridge. A portion of the south end of the project, running through the older part of Castle Rock adjacent to Plum Creek, and a designated habitat for the endangered Preble’s Jumping Mouse, was restricted for dirt operations between October through March to protect the mouse. The Contractor proposed phasing, special slope protection and erosion control measures to ensure no encroachment of construction activities into the mouse habitat. Ultimately, 53 change orders were issued with 100% of the change order work completed concurrently with other work, requiring no additional time.
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Construction & Innovation
The escalating prices of asphalt resulted in a unique innovation: the contractor used “temporary” concrete pavement in lieu the “usual” bituminous for detour paving, at no additional cost to CDOT. The Contractor used a slipform paver to place the detours in the Fall of 2006, also an advantage, because the concrete could be placed and protected in cold-weather. A second breakthrough followed as the Contractor brought in a crusher, and recycled the Phase I detours and the removed concrete from the old pavement, providing over 60,000 tons concrete coarse aggregate and base for the second phase of construction. An important side benefit was the significant reduction of environmental impacts by decreasing haul into the project for virgin aggregates and out of the project for disposal of the detour and existing pavement.
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Quality
A rigorous quality control program of onsite testing and constant exchange of data between the plant and paving crews was key to the successful product result, with the Contractor receiving nearly $380,000 in quality incentives for strength and ride. The Contractor led with testing for QC, while the Owner held responsibility for Assurance. The QC/QA representatives formed a program of superior cooperation. Test results were shared between all involved parties so immediate adjustments could be made as necessary. The Contractor achieved an average flexural strength of 792 psi with a standard deviation of 40 psi on the contractor selected option of a compressive strength mix requiring more cement. A smooth, safe, quiet riding surface was achieved with careful attention to the uniformity of the burlap drag and longitudinal tining operation.
Public Relations
I-25 traffic was never shut down nor subjected to delay during the course of this project, even though over 78,000 vehicles on average pass through this area daily. Continuous communication with media representatives, Douglas County and the Town of Castle Rock set the foundation for information distribution. This communication stream was assisted by CDOT-held public meetings and flyer distribution. The changed phasing reduced the number of traffic switches and detour duration on the job, providing the public with a much safer construction site.