Utah DOT's I-15 Project Features Innovative, Time-Saving Conveyor Bridge
Many metropolitan areas deal with heavy traffic during rush hour. The same can be said for the greater Salt Lake City area. For the past several years, thousands of Utah County commuters have spent long hours driving to work and back on Interstate 15 in southern Salt Lake County.
"The Point Project" is designed to improve mobility and reduce congestion along a 7-mile stretch of I-15 between the south end of Salt Lake City and Provo. The Utah Department of Transportation (UDOT) is working in partnership with Utah County Constructors to widen and place new pavement between northern Utah County and Draper, specifically from S.R. 92 to 12300 South.
Major I-15 construction began in March 2015. The work will last two construction seasons, with projected completion scheduled for fall 2016. Construction phasing will include multiple major traffic shifts and lane splits.
Named for its location around Point of the Mountain, The Point Project will use $252 million of state funds to build the following improvements:
- Expand I-15 to six lanes in each direction, from S.R. 92 to 12300 South
- Replace the aged pavement with new, durable concrete pavement
- Reconstruct the 14600 South interchange in Bluffdale to improve safety and traffic flow
- Enhance the existing traffic management system by installing additional ramp meters, fiber optics and other infrastructure to improve mobility
- New signage and striping
The Conveyor Belt "˜Bridge'
A bridge of sorts crosses over I-15 at Point of the Mountain. While not for people or cars, this conveyor belt "bridge" is proving to be a shortcut for this major project, translating to less road time for the approximately 150,000 vehicles that travel its path on a daily basis.
Spanning about 100-feet-long by 20-feet-wide and a bit higher than the standard minimum 16-foot, 6-inch bridge elevation, the conveyor belt transports concrete from a nearby batch plant over the highway via a bridge and directly into the work zone, explained Tim Rose, Project Director for the UDOT.
While the bridge reduces truck trips to and from the work zone in the middle of the freeway, Rose said, it also enhances safety for drivers, reduces emissions and fuel consumption and improves efficiencies for crews overall. "Instead of taking 15 to 20 minutes to get a truck to the work site, we're getting there in just a few minutes. Overall, we're eliminating 15,000 trucks," Rose said. With the implementation of the conveyor belt bridge, crews can now work continuously without interrupting traffic. "We can work 24/7 if we choose to, which translates to an improved workflow" he noted.
While it is not the first time a conveyor bridge has been used on a UDOT road project, it is a first over a freeway in Utah. The major reason for using the conveyor bridge is to save the contractor money and time, Rose noted. Such innovations can prove useful in major construction projects. "It certainly makes it a more efficient operation," commented Rose.
GPS and 3-D Technologies Improve Precision
The I-15 Point Project utilizes wireless survey control on earth moving equipment, asphalt operations and concrete paving. All are controlled using two systems - a satellite-based Trimble GPS and the Leica PaveSmart 3-D System.
According to Travis Farr, Project Manager for Utah County Constructors and Wadsworth Brothers Construction, "In the old days, survey hubs (stakes) were placed in the ground to show the road grader operator where to level the dirt." Those would be placed every so often, at about 25, 50 or 100 feet. Today, he said, the three dimensional designs are uploaded to the equipment by the road engineers and surveyors. Through wireless control, bulldozer and road grader built-in receivers use messages from the survey equipment via Trimble GPS to tell the operator exactly where to place the blade. "Simply put, the operator is driving the grader and the computer is telling the grader's blade exactly where to go," noted Farr.
Trimble GPS and total stations are also utilized for the asphalt pavers while Leica PaveSmart is used for the concrete pavers. Replacing stringlines completely, Leica Geosystems total stations precisely track the machine´s position and elevation. PaveSmart 3-D calculates and compares to the design model´s grade and position. Steer and elevation corrections are then sent to the machine controller, regulating the hydraulics for precise paving results.
For the Point Project, survey control points are meticulously set with digital levels to ensure that all operations are on the same datum. "The total station is set up based on the control points that have been established right there in the ground," said Farr. Leica uses very accurate total stations to provide the tightest vertical tolerances available. "These systems have been instrumental to the success of this project thus far," commented Farr.
During winter 2016, UDOT crews will continue to work on ramps and the median throughout the project corridor and at the 14600 South interchange, weather permitting. Work also will continue on Pony Express Road and Minuteman Drive. By spring, crews will complete remaining items in this section and reconstruct and widen I-15 between Bangerter Highway and 12300 South. Of course, construction schedules are weather dependent.