The Nevada Department of Transportation (NDOT) needed to widen and revamp ramps along a 3.7-mile stretch of Interstate-15, between U.S. Route 95 and Sahara Ave. Known as Project NEON, it has proven to be the largest infrastructure project in Nevada’s history and has earned the American Concrete Pipe Association’s 2019 Project Achievement Award, ACPA’s annual award to recognize innovative projects utilizing precast concrete pipe or boxes. Although it took nearly two decades to plan Project NEON, the use of precast concrete culverts allowed for a speedy completion once construction began.
Las Vegas is growing at an exponential rate with new construction and a population boom. In 2016, NDOT began construction on this long-planned project to improve mobility and safety for the public travelling on the busiest stretch of highway in Nevada, which saw 300,000 vehicles daily and 25,000 lane changes an hour. Traffic through the corridor is expected to double by 2035.
NDOT teamed up with Atkins Engineering and Kiewit Infrastructure West to oversee the design-build of the project and Rinker Materials in Las Vegas to produce the precast concrete culverts that helped accelerate the project timeline. Project NEON was bid in 2016, and all reinforced concrete boxes were shipped and installed in 2017, ahead of schedule.
“It took a lot of coordination and teamwork in working with the consultant and contractors to make sure things went seamlessly,” said Steve Nilforoushan, regional civil engineer, Rinker Materials.
The team opted to use precast concrete culverts because they were locally available from Rinker’s Las Vegas Pipe Plant, which led to a faster completion. The pace of construction did not allow for time to sit and wait for the concrete to cure.
“The turnaround is a lot quicker with precast, which helps construction crews significantly minimize road closures affected by box culvert installation,” Nilforourshan said.
A variety of reinforced concrete pipe and box designs were specified for this project, including nearly 7,200 linear feet of mega reinforced concrete boxes, from 12 by 6 foot through 22 by 6 foot, and 47,580 linear feet of 18-inch through 72-inch reinforced concrete pipe. More than 1 mile of reinforced concrete box culvert was placed for flood control, and 46 girders were set, including the longest precast girders in the state, measuring 168 feet long.
Installation was straightforward. The box culverts were lowered with a crane and pushed into place. A mastic joint sealant created a sound joint. Construction crews were able to drive the crane over the concrete box culverts as soon as they were set in place. Additionally, the crew was able to achieve curved alignments, accomplished with beveled joints to an extreme degree, with ease whenever necessary.
“Box culverts move a lot of water to help alleviate flooding,” Nilforourshan said. “Las Vegas is like a large bowl, with rocky soils that create such high runoff that flash floods are frequent. The mega box culverts create huge underwater tunnels to help address the problem.”
After three years, Project NEON was completed in August of 2019 with a price tag of $1 billion. The citizens, as well as the visitors of Las Vegas are enjoying an 81-foot-tall, 2,606-foot-long High Occupancy Vehicle (HOV) flyover bridge, as well as a general purpose and HOV lane. These improvements allow for easier access to downtown, while reducing merge and traffic weaving on I-15. The bottom line, the reduced travel time is expected to yield $110 million in annual savings through increased productivity. Drivers are saving time, and everyone is benefiting from the improved air quality.
Project Neon Team
Owner: Nevada Department of Transportation
Engineer: Atkins Engineering
Contractor: Kiewit Infrastructure West
Supplier: Rinker Materials