UVU Bridge snow-melt project clears safe path over interstate highway

Contractor Aron Frailey estimates he has installed as many as one thousand radiant snow-melt projects since entering the business right out of college nearly 20 years ago. The jobs have been many and varied — from high-end residential to large commercial. He even spent three weeks in Moscow in 2017 at the behest of the U.S. State Department, building a snow-melt system for the U.S. Embassy there — “Although I couldn’t speak a lick of Russian,” he notes.

But, Frailey’s most unusual job to date is one of his most recent: The UVU Pedestrian Bridge on the Orem campus of Utah Valley University, the largest public university in the state. “It’s the first bridge I have ever done,” says Frailey, who founded Thermal Engineering in Salt Lake City in 2008. After nearly two decades working on some of the largest snow-melt jobs in the world for his own firm and a previous employer, he does not hesitate to label the UVU Bridge “as definitely a learning experience.” By that, he doesn’t mean an easy one.

UVU is a “landlocked” campus, with all student housing located west of the super-busy U.S. Interstate 15. The school itself sits on the opposite side to the east. In the fall of 2019, the Utah Department of Transportation (UDOT), the Utah Transit Authority (UTA), general contractor Kraemer North America (Plain, Wisconsin), and UVU broke ground on the pedestrian walkway that will provide safe egress from one side to the other.

Suspended 22 to 35 feet above ground, the 17-foot-wide bridge spans almost 305 feet across I-15, providing access for up to 6,000 students a day, according to Josh Sletten, project manager for the engineering firm WSP USA. The structure includes bicycle access and elevators to make it ADA-compliant, a covered roof with perforated sides for comfort, and a radiant-heated deck.

Obviously, the project will make transit from one side of the highway to the other far more appealing to university students, staff and visitors. (Not only does the new bridge overarch I-15, but also railroad tracks owned by Union Pacific and the UTA Frontrunner Commuter Rail.) The ability to snow melt the upper landings and the walkway is another critical ingredient to safety, to both walkers and the fast-moving vehicles below. Orem receives, on average, more than 40 inches of snow annually.

“There were concerns about how to incorporate snow melt in a project of this scale,” says Frailey. “But UVU and UDOT saw the liability issue as ample justification for the extra cost.” After all, the logistics of manual snow removal from such a large pathway that high in the air were beyond daunting.

As Frailey notes: “How would you get a piece of equipment up there to plow it? If you did, where would all the snow go?”

With snow melt, the bridge’s curving contours will efficiently direct runoff to both sides of the bridge, safely disposing whatever liquid remains from the melting process. As Frailey explains: “The system generates quite a bit of evaporation to help remove the snow.”

PP-RCT + PEX

Frailey’s “learning experience” goes beyond never having put snow melt on a bridge before. The UVU project also represents his largest use of a polymer plastic pipe known as PP-RCT — shorthand for “polypropylene, random copolymer, with modified crystallinity and temperature resistance.” Having used the pipe on two smaller commercial projects in Boston and Cleveland, the Thermal Engineering team was “not unfamiliar with it,” says Frailey. “But we had never used the material on a project this large and this different.”

The UVU Bridge also represents another major first: The first full-scale use of Uponor North America’s PP-RCT pipe and fittings offering, made exclusively for the company through a partnership with Pestan North America. The two companies announced their partnership in September 2019, with a phased rollout throughout 2020, beginning mainly in the Far West. Shipping diameters from 1/2-inch to 12 inches from stock (up to 24 inches for special orders), Uponor is targeting a wide array of commercial hydronic distribution applications in the U.S. and Canada.

The UVU Bridge is actually a “hybrid” snow-melt installation involving both PP-RCT and the type of polymer plastic pipe Uponor is best-known for: Crosslinked polyethylene, or PEX-a. Thirty-six thousand linear feet of 5/8-inch PEX has been installed in a snow-melt grid along the bridge’s pedestrian walkway and landings. In addition, 1,900 linear feet of PP-RCT, ranging in diameter from 2 1/2 inches to 4 inches, performs a supply-and-return function, transporting a warm glycol solution from a boiler in a mechanical room in a tower on the east side of the bridge to the PEX-a snow-melt grid.

Frailey recalls the day he first heard about the project. “My salesperson walked into my office — ‘How do you feel about quoting a snow-melt job for a thousand-foot bridge?’ Wow, I thought: A bridge? Can that even be done?”

Thermal Engineering began communicating with WSP and Kraemer, submitting load calculations based on the engineer’s initial design concepts. But it took some time for the project to gain traction. When it did, Frailey remained unsure.

“Looking at the project in its initial stages on paper, it was difficult to see how we would do it,” he says. “Even with 3D models, we struggled to understand how we would thread roughly 2,000 feet of pipe through all the girders of this bridge structure. There is a whole steel truss we had to work around and through, and I feared it could be a disaster from the standpoint of safety.”

Change the pipe spec

Part of the challenge was the structure’s height. Then there was the original specification, calling for the hydronic-distribution part of the project to be built with the conventional choice for this application type: Four-inch steel pipe. A standard length in that diameter weighs in at more than a ton. Numerous installers would need to be involved, and the work would involve welding. Frailey wanted no part of welding — “We don’t have those capabilities,” — and he wasn’t excited about grooved pipe, either.

So Thermal Engineering began investigating — and eventually recommended — PP-RCT as a worthy alternative. A non-corrosive plastic polymer would be better able to withstand the salt and magnesium chloride Utah uses for snow and ice melting on its highways. Even with the bridge 30 feet in the air, this was a major concern, because the hydronic piping would be installed in the structure’s underside, facing fast-moving traffic below.

Moreover, PP-RCT would be far easier to handle and therefore less labor-intensive than steel. Shipped in 19-foot lengths, a stick of 4-inch PP-RCT weighs a mere 63 pounds — a tiny fraction of its steel counterpart. Under normal circumstances, a single fitter can handle the pipe connections, using the special heat-fusion machinery and tools required by PP-RCT. (Of course, “circumstances” at the UVU Bridge were anything but normal, requiring a three-man installation crew: More on that in a bit.)

PP-RCT offered one other critical advantage over steel: The ability to move in unison with the bridge. “The structure is intended to move as much as 18 inches and in every direction all the time: Left to right, backwards and forwards, up and down,” says Frailey. “I was concerned about the joint integrity of a steel piping system with all that movement, and I really liked the flexibility of PP-RCT to handle it.”

For all these reasons, Thermal Engineering formally asked the engineer to change the specification to PP-RCT. After due consideration, the change was made.

“The engineer understandably had lots of questions,” says Frailey, who came to appreciate the “high level of trust” that flourished among his firm and Kraemer North America, WSP and the rest of the build team on this unusual and highly challenging project.

“We sent samples and demonstrated how to make a heat-fusion pipe connection. We also cut some joints apart, so the engineer could confirm how completely the materials bonded. When we began reviewing the flow and weight characteristics, as well as the integrity of the joints and the ability to flex with the bridge, PP-RCT won the day.”

On-the-job learning

So how did the Thermal Engineering crew finally master the art and science of running a hydronic distribution pipeline across a 970-foot-long bridge that spanned a busy interstate highway? By doing the work, says Frailey.

“I never really understood how we were going to do it until Kraemer North America began prefabricating sections of the bridge offsite before reassembling them over the freeway,” he says.

As it turned out, Frailey’s crew threaded the majority of the PP-RCT through the bridgeworks while it sat on the ground in the prefab steelyard, located roughly a mile and a half from the job site. Using a lift truck fitted with a winch for moving the pipe laterally, the team created a workstation for the McElroy Acrobat heat-fusion machine to connect the 19-foot lengths of PP-RCT.

Although the heat-fusion process normally requires only two fitters, according to Frailey, “We needed a three-man team for this job,” to reach the underside of the bridge. The first pipefitter’s task was to maneuver the 19-foot piece of PP-RCT off the ground and up into the bridge’s girder diaphragms. Project superintendent Scot Layland situated himself in the airborne workstation, hooking each length of pipe to the fusion machine and butt-fusing it to another length ahead of it in the line. Meanwhile, a third person manned the boom truck and the winch, pulling the steadily lengthening, fused-pipe assembly through the bridge.

Frailey estimates that each “lift-fuse-pull” cycle spanned 45 minutes, including the cooling time each connection required before it could be eased along and the process begun anew.

The entire UVU Bridge is constructed on two girders. Some sections could be picked up and trucked to the job site with the girders intact, including the butt-fused PP-RCT. But several were too heavy to be transported as pairs. They had to be disassembled, moved and reconnected on the bridge site, where Frailey’s PP-RCT team performed their “lift-fuse-pull” routine as well, sometimes working at night by the interstate highway.

“Our men ran a rope through the girders and attached it to the pipe, pulling it through the girders while working on opposite ends of the bridge, rather than right over the highway,” says Frailey. Because of the PP-RCT’s weight, “the crane pulled the pipe easily — no big deal.”