As time marches on and communities grow, new parcels of land are developed for commercial, civic, residential, and public use. Ultimately, infrastructure must link it all together. Whether driving through a residential neighborhood or over a federal highway at more than 70 mph, most people can't imagine the effort and expense that go into creating safe streets, roads, and bridges. For those who manage the projects, though, the complexities are inevitable and ever-changing.
Savvy public works managers know the most cost-effective solutions are reached by collaborating with the design and construction professionals they selected to complete the work. Betty Purdie, PE, of Ralph L. Wadsworth Construction in Salt Lake City, has been on both sides for more than three decades, completing road, bridge, and highway projects of every scope and scale.
“I’ve seen a lot of innovations in engineering,” says Purdie, who spent more than 25 years working for Utah DOT (UDOT) before joining Wadsworth Construction in 2010. Today, as a construction project manager, she enjoys working with designers and public works professionals to find new ways to solve old problems. An overpass on the edge of Brigham City, about an hour north of Salt Lake City, offered such an opportunity.
“The scope called for widening the interchange overpass at I-15 and US 91 and the natural geological conditions surrounding the bridge were unstable,” says Purdie. The design called for simply adding a second structure adjacent to the first. However, settlement and global stability calculations indicated that the weight of the soil embankments for the second bridge would impact the existing bridge and the plan had to be reworked.
The lead engineering firm, Michael Baker International, suggested geofoam as an alternative to soil. Lightweight and versatile, geofoam is made from expanded polystyrene, a closed-cell material with high compressive strength. It's more expensive than soil but often doesn't increase overall cost because it solves various construction and scheduling challenges.
“Using geofoam blocks to support the embankments was a first for me,” says Purdie. Her team worked with geofoam design and testing expert Marv Cook, of Oracle Construction, to develop a block configuration capable of supporting the new road and live traffic loads that also fit within the project's budget.
“Working with Cook and the geofoam supplier, the scope became more like a design-build project,” says Purdie. ACH Foam Technologies did some initial testing, which Oracle validated while fine-tuning the block placement patterns. Using two densities (EPS22 and EPS29), Purdie and ACH Foam Technologies calculated the project’s precise material requirements and delivery schedule to ensure the products arrived onsite ahead of installation.
Purdie was also surprised at how easy the embankments were to build with manual labor over a period of just a few weeks, requiring no specialized or heavy equipment. When the geofoam embankments were built, they were covered with a reinforced concrete slab and then the road surface.
“Using ACH Foam’s geofoam, we completed two phases of bridge construction over I-15 without having to shut the interstate down,” says Purdie. Though traffic did have to be diverted around the construction site, the project kept people moving, a primary goal in public works projects of any size.
A smaller-scale road improvement project in the Chicago suburb of Willowbrook faced similar soil settlement challenges coupled with the need to keep this important community thoroughfare moving as efficiently as possible despite the road reconstruction.
“It’s always important to keep people affected by the construction happy, and moving is happy,” says Anselmo Presisto, PE. As Greco Construction’s project manager on the rehabilitation project, Presisto was charged with replacing a box culvert crossing used to move water runoff from a golf course adjacent to State Highway 83 to a small pond on the other side of the road.
“With water draining from the golf course to the pond, the soil along the southeast side of 63rd street had been settling for a long time,” he says. The result: a swampy area dividing the road from the pond and the need for a lightweight fill to support the road that wouldn’t settle. During procurement, Presisto was surprised to see a product he’d never worked with before.
“I admit I was skeptical of putting a highway on top of foam blocks,” he says. Like many first-time users, Presisto was amazed by its compressive strength. At about 1% the weight of traditional earth materials, ACH Foam Technologies’ geofoam has a compressive resistance of up to 18.6 psi at 1% deformation, making it an ideal in-fill solution where settlement is a problem. After evaluating several products and project logistics, Presisto selected Foam-Control geofoam EPS19.
“ACH Foam Technologies had a better lead times and more product availability to meet our schedule,” says Presisto of needing to avert material shortage delays while working on a tight 60-day delivery. As a first-time user, it was the company's technical assistance during product selection and installation that made him most comfortable with his decision.
“Building with geofoam was very easy,” says Presisto. “We excavated the area, put in the subbase, and laid the blocks by hand.” His team laid 600 cubic yards in a few hours, using a hot wire cutter to trim pieces to fit when needed.
Designs called for a lightweight concrete fill around the box culvert being placed for the drainage channel. Additional water table issues discovered while excavating meant that concrete curing was going to require at least seven days, greatly disrupting the schedule and increasing public frustration. Presisto suggested using the geofoam instead of concrete because it would allow construction to proceed unimpeded.
Since the ACH Foam Technologies’ representative was available when the challenge was discovered, understanding the technical specifications of the various types of geofoam was simple. New material was quickly delivered. The hot wire cutter was used to precisely shape the block as needed. A rebar lattice was assembled over the blocks and a much thinner concrete profile was poured without water table impacts.
“It was a great first experience with a very useful product,” says Presisto, who is sure public works professionals, designers, and builders alike will benefit from considering geofoam as a possible solution to a wide range of civil infrastructure challenges.
