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FARMINGTON — It's difficult to miss all the construction tied to the new West Davis Highway when traveling along Interstate 15 in Davis County.
One component of all that work seems to stick out the most. Construction workers have stacked thousands of large plastic foam blocks to form a new bridge that will eventually connect the new highway and I-15 by crossing over three railroad lines and Legacy Parkway in Farmington.
These massive blocks — each about 9 feet long, 5 feet wide, 4 feet thick and 200 pounds in weight — are called Geofoam, and about 3,000 of these blocks are being used to form the base of a new on-ramp from the West Davis Highway to southbound I-15, according to the Utah Department of Transportation.
The blocks are either stacked on top of each other or trimmed to form the ramp. Once complete, crews will pour concrete over the blocks.
Rex Harris, UDOT's West Davis Highway project director, said it's a practical solution that allows for construction in a narrow space between the railroad tracks and the freeway. While crews use dirt for many projects, the weight of dirt typically causes the underneath ground to settle a few inches to a few feet — space that just doesn't exist without potential impacts to the freeway or railroad tracks.
"The reason why we're using it is because earth, concrete (and) asphalt are really heavy. And this polystyrene is about 100 times lighter than those materials," he said Wednesday.
While lightweight, the blocks are also sturdy. Harris adds that 1 square foot of the plastic foam blocks can absorb more than 4 tons of equally distributed weight.
Geofoam, developed in the 1950s, was first used for road projects in 1965, when engineers used it for a road insulation project in Norway, a report compiled by Softoria in 2006 points out. In 1972, Norwegian engineers turned to the foam again, for a road embankment project, helping build a bridge in Oslo.
Since then, it's been used in some projects across the globe, including in Utah. UDOT officials point out that the state has "extensive experience" using Geofoam, first using it as a part of its I-15 reconstruction in Salt Lake County ahead of the 2002 Winter Olympics, as well as other parts of the state. Utah Transit Authority engineers also relied on it as they constructed parts of the TRAX green line route over a decade ago.
The Softoria report points out the unique product is often used in situations where engineers are looking to avoid settlement problems, such as the case in Farmington. Harris adds that most people don't know even know they're driving over fills with Geofoam inside when they're traveling.
"Sometimes there are unique challenges on our projects, and they require innovative solutions," he said. "Geofoam is another tool in our toolbox to efficiently build the roads, trails and bridges we all need to get where we want to go."
The West Davis Highway project, which began in 2021, reached the 70% completion mark earlier this year. The 16-mile highway is still expected to open in 2024, UDOT officials say.
Contributing: Karah Brackin
