The I-15 Corridor Expansion Project (I-15 CORE) is the largest construction project that the state of Utah has ever built. The $1.2 billion project included 24 miles of removal and replacement of Interstate 15 between Lehi and Spanish Fork. The existing I-15 was widened by two lanes and the remaining lanes were replaced, for a total of six lanes—and it was all completed in 35 months.
The new 364 lane miles of concrete roadway were slipformed 12 or 12.5 inches thick for a total of 2.67 million square yards of concrete pavement. The Utah Department of Transportation used a fixed price/best design delivery method for the project. “Essentially, we said, ‘Contractors, here’s the contract amount. You propose to us what you can build for the contract amount of $1.2 billion,’” says Robert Stewart, UDOT’s deputy project director for the CORE project.
UDOT created a list of “must-have” requirements for the project, as well as an additional list of “wants” for the bidding consortiums. “It’s the first time we’ve done this in Utah…the concept of just putting out a price and having proposers come back to us and tell us the scope,” Stewart says. “We asked for a completion date of December 2014. And we specified a 30-year design, and we required the proposers to submit a life cycle cost analysis. We emphasized that we preferred concrete. We didn’t require it, but we preferred it.”
Three consortiums were the final bidders on the project. The winner was Provo River Constructors (PRC) with team members Ames Construction, Fluor Corp., Ralph L. Wadsworth Construction Co., and Wadsworth Brothers Construction. “There are myriad components that won PRC the project,” Stewart says. “First was their Maintenance of Traffic strategy. PRC kept all existing lanes of traffic open during construction. A second item was the pavement design. PRC proposed a 40-year pavement design, placing concrete on top of an asphalt base. Our estimate showed that we could get 16 miles of pavement from Lehi Main Street to Provo Center Street. PRC stretched that by eight miles to the south, with 40-year pavement, extending the scope of our project.
“The most important aspect of their proposal was their completion date of December 2012,” says Stewart. “PRC delivered 24 miles of urban reconstruction in just slightly less than three years. This is the fastest project of this magnitude ever delivered in transportation.”
PRC’s paving partners, Ralph L. Wadsworth Construction Co. and Wadsworth Brothers Construction, brought their concrete paving experts and Gomaco equipment to the project. The entire list of paving equipment included eight Gomaco pavers. Three four-track Gomaco pavers had internal dowel bar inserters (IDBIs). PRC also used one GHP-2800 two-track paver and four Commander III four-track pavers. Four Leica 3D stringless paving systems were used to control the pavers.
“I was in charge of putting together the paving plan and actually had stringline laid out for the entire project,” said Tracy Trane, Paving Engineer. “Stringline just wasn’t going to work on the project for a variety of reasons, and time constraint was one of the biggest reasons.
The concrete is slipformed on top of a 3-inch asphalt base. Holes for the stringline stakes would have had to be predrilled into the asphalt base, the stakes pounded in, and the stringline set and fine-tuned. It’s a time consuming process on a project where time is precious.
“Our maintenance of traffic plan and schedule drives the project,” said Kelly Steeves, concrete paving manager. “Using the Leica 3D system, we were able to move our paving spreads in on the heels of the asphalt pavers and start paving concrete with minimal setup time. The Leica system makes the paving operation much safer to work around than stringline. We do not have to contend with people tripping over or driving through the stringline. With the dynamics of the project, the large amount of foot and vehicular traffic, the Leica 3D system is one of the reasons we ran ahead of schedule.”
Most of PRC’s new crews had never paved with a 3D system. Learning to pave stringless while establishing trust among the paving superintendents on the seven different paving spreads was a challenge at times. Mike Sink, paving superintendent on the Gomaco GP-4000 paving spread, was new to 3D paving but quickly came to realized its value. “It’s definitely a benefit,” Sink says. “It decreases the margin of error and increases productivity. It makes it easier to jump from pave to pave without having to stop to double-check stringline. Even for setting up the paver, we used total stations to make sure our pans were set up straight and square with each other. Shoot the pan, shoot the stainless, and you can calibrate the paver a lot more effectively than you ever could using stringline and a level.”
PI for Smoothness
UDOT uses a profile index (PI) to measure smoothness on its projects. It’s a measure of the deviation of the ride surface from the true surface with characteristic dimensions that affect the vehicle’s dynamics and ride quality. The PI is calculated by taking a 528-foot section and summarizing the count and size of all the deviations from both wheel tracks in each lane. Then the two wheel tracks are averaged and extended out to equal a count for a full mile. The I-15 project requires a PI of less than 5 inches per 528-foot section.
PRC’s corridor-wide PI average is only 2.7 inches, compared to the 5-inch standard. “When we started paving, my goal was a PI of 3.8 inches paving with the IDBI’s, so I’m very happy,” Steeves says. “Rideability starts at the batch plant with consistent concrete coming to the grade. The paver has to be fed properly, too, with a good consistent head of concrete out in front.”
One Gomaco four-track GP-4000 with IDBI attachment and its crew was responsible for slipforming the project’s long mainline runs. The paver has been used at various paving widths—at 36 and 39 feet on the southern portion of the project, and 24 and 26 feet on the northern portion. UDOT requires a transverse joint every 15 feet. The IDBI attachment inserts 10 dowel bars, each 1.5 inches in diameter and 18 inches long, into each lane of travel.
Paving production for the GP-4000 with IDBI attachment averaged 3,500 cubic yards in a 14-hour paving day. The PI averaged around 2 inches on the project for the GP-4000 with IDBI. “Our best production day with the paver, and the record for the project, was 6,450 cubic yards in a 14-hour period,” Sink said. “We had 36 trucks feeding us out of two of the batch plants. It was an impressive day.”