The recent completion of the design-build reconstruction of U.S. 36 between Boulder and Denver in Colorado offers unique multi-modal options for commuters, such as taking a bus or riding a bike, intended to provide greater capacity and relieve traffic congestion.
The two-phased project added express lanes for Bus Rapid Transit (BRT), High Occupancy Vehicles (HOV), and tolled Single Occupancy Vehicles (SOV). It also features a bikeway alongside the highway that ties into existing trail systems, and Intelligent Transportation Systems (IS) for tolling, traveler information and incident management. The Colorado Department of Transportation (CDOT) and the High Performance Transportation Enterprise (HPTE) (which operates as a government-owned, independent business within CDOT) sponsored the project.
Incorporating P3 and Design-Build
Phase 1 of the project began in April of 2012, and tolling has been fully operational since July of 2015. Phase 2, built as a public-private partnership project (P3), with concessionaire Plenary Roads Denver, started in October of 2013 and was completed in spring of 2016, with tolling beginning at the end of March. Plenary's concession on the road runs for 50 years.
With a total contract value of nearly $375 million, the two-phase design-build project was led by the joint venture partnership of Ames Construction and Granite Construction. HDR Engineering provided the design. Major subcontractors included Castle Rock Construction Company Of Colorado for concrete, Sturgeon Electric and W.L. Contractors for signals, lights and ITS, Brannan Sand & Gravel Company for paving. About 3 million man-hours went into the project.
Rebuilding the Corridor
Congestion had become an issue on the U.S. 36 corridor in recent years. The U.S. 36 between Denver and Boulder first opened as a toll road in 1951. Once toll road bonds were paid off, the tolling infrastructure was removed in 1968. When it was built, the road had only one interchange between Denver and Boulder. Reflecting population growth, there are now 10 interchanges along U.S. 36 between I-25 and Boulder. In December of 2009, the CDOT completed an Environmental Impact Statement, which called for one buffer-separated managed lane in each direction, Bus Rapid Transit (BRT) ramp stations, auxiliary lanes between most interchanges, and a bikeway.
Ernie Green, Project Manager for Ames, noted that everything in the corridor was rebuilt, including the total replacement of the interchanges. One of these, the McCaslin interchange, was replaced with a Diverging Diamond Interchange (DDI). Traffic crosses to the opposite side of the road so vehicles have unimpeded movement onto the freeway. Despite using fewer lanes, this innovative interchange can handle more traffic, reduce traffic signal delays, increase left-turn capacity and eliminate wrong-way entry to ramps. This is just the third DDI to be built in the State of Colorado.
Green said the DDI was advocated by officials in Superior and Louisville before the project had even begun, and the system has worked out well, despite the novelty. A design including raised islands between the lanes made it more natural for drivers.
The 16 miles of combined Phase 1 and 2 construction required installation of 1.3 million square yards of concrete paving. Ames maintained a crushing yard on site to reduce hauling and mobilization of materials, allowing all of the existing asphalt paving to be recycled and reused throughout the project.
Due to the geology of the area, extra work had to be done to the roadbed. "This whole corridor is known for the challenge of expansive clays," Green said, "To mitigate that we had to remove 2 feet of material and replace it with road stabilizers."
Coordinating All Groups Involved
Not surprisingly, it was a complex project, said Green, given the number of entities involved - including the municipalities, utility companies, RTD, CDOT and Plenary. Thankfully, everything came together relatively smoothly. The additional aspect of the public-private partnership did change the atmosphere of the project, Green said. In contrast to a simple contract with a transportation department, where adjustments to schedule might be handled as a matter of book-keeping, the P3 structure brought a stronger sense that everything depended on things happening on schedule. Contractors were aware that lenders and investors were counting on the revenue from tolling to begin.
Plenary Roads Denver is part of the Plenary Group, an international infrastructure business with 35 projects, valued at $24 billion, in Asia Pacific and the Americas.
Simon Spachnik, Project Manager for Plenary, worked previously for a Colorado engineering company. He said Plenary was involved in all aspects of the project, like a co-owner with HPTE.
"We reviewed plans with respect to the construction process and in light of our long term goals as the concessionaire over the next 50 years." Spachnik said. In addition to safety and quality of the work they paid special attention to aspects of the project that would have maintenance requirements. Plenary's maintenance provider, Broadspectrum consulted with them on those aspects of the project.
"The hard assets are ours to maintain," explained Spachnik. Plenary will plow the snow, fix the holes, and trim the trees. It also provides a courtesy patrol - a tow truck for breakdown assistance. Local police have responsibility for incident response. CDOT manages the Active Traffic Management System.
Spachnik said Plenary sees the United States as the next major market for P3. The U.S. 36 project was a major step for Plenary in entering the market. It is the third largest project but has the longest concession period. Also noteworthy that it is the first toll risk project for Plenary, which has usually done availability-based contracts. "It was a stretch, but so far it looks like it has worked out," said Spachnik.
Plenary has been operating the I-25 central lane toll since financial close on the deal in March 2014. "Initially it was not quite as planned, but with Phase 1 things started trending in a better direction and with Phase 2 we are now in line with the model," Spachnik said. The success has helped Plenary land further deals.
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