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EPS geofoam fills void for Chicago metro airport and train station
Expanded polystyrene (EPS) geofoam has been used in several recent Windy City construction projects, among them, Millennium Park, Soldier’s Field and, most recently, the Gary Chicago International Airport roadway expansion and the Metra 35th Street train station adjacent to the White Sox U.S. Cellular Field.
As part of the airport’s roadway expansion, a two-span steel bridge was built over the EJ&E railroad tracks that bisect Airport Road near Chicago Avenue. This was project number 6 of 18 work segments included in the comprehensive Gary Chicago International Airport expansion that is scheduled for completion by mid-September of 2014.
Pete Keilman, project superintendent for the roadway expansion bridge, said that the bridge had to be built over two existing rails as well as two future rails. There was a potential problem with the quality of the soil where the new bridge was planned and also an embankment that might have required purchasing additional right-of-way.
Keilman explained: “The soil where the bridge would be built was questionable. The engineers at Oracle found soil about 12 feet down that contained a large percentage of peat, which would settle over time. They determined that geofoam would distribute the load and prevent future settling.”
Keilman’s crew of 5-7 men was able to cut a trench through the geofoam, which would carry a stormsewer pipe for 400 feet on each side of the bridge approach.
“We hadn’t done this before,” he explained. “Engineers provided detailed drawings we followed on the jobsite, and [we had] a hotwire that easily cut through the foam. We also used a chain saw and a smaller saw in various sections.
“Once we had the foam down and the sewer pipe in, we laid a single mat of rebar, then poured 6 inches of concrete on top of that, “ Keilman continued. “Two feet of stone topped the concrete and that stone was surfaced with a foot of asphalt. The bulk of the geofoam embankment was installed in the fall of 2012; more geofoam was installed this spring [2013] for a total of 43,000 cubic yards of geofoam.”
The property line of a trucking company to the east was too close to the bridge embankment to allow for a slope built with conventional soil fill. But vertical geofoam embankments made purchase of additional right-of-way unnecessary.
Marv Cook, an EPS design engineer, called the geofoam installation “a cakewalk. … We put utilities in EPS all the time. For the roadway we ran the sewer pipe right through the geofoam. The easy way to cut a trench is to use hotwire on the jobsite. Using geofoam as an alternative fill lessened the load against the bridge structures as well as adjacent roadways,” Cook said.
When asked about settlement issues on the Gary Chicago roadway, Cook estimated that stage one settlement of the soil would have taken from 6 to 12 months. “Then you’d build the bridge and wait some more [up to two years].”
Using geofoam eliminated that settlement time, so the road closure only lasted about two months before the airport road was reopened in November 2012.
ACH’s Frank Kiesecker said that geofoam is being used in transportation projects with greater frequency. “Once it becomes common knowledge that geofoam weighs about 1/100th the weight of soil, and saves money and time for installation, as well as road closures,” Kiesecker explained, “the `a www.fhwa.dot.govFederal Highway Administration (FHWA) began to require that DOTs compare cost and time savings using geofoam vs. soil and other alternatives.”
The Chicago White Sox baseball stadium, U.S. Cellular Field, is now directly accessed from the new Metra station platform on 35th Street.
During the 2010 design phase for the station platform, architects had safety concerns about the elevation of the American with Disabilities (ADA)-compliant concrete. In addition, the aggressive construction schedule wouldn’t allow for the settlement time that conventional soil fill would require.
Architects turned to EPS Type 12 geofoam to solve their design challenges and shorten the construction time. According to Dan Orlich, Metra’s construction manager: “A great amount of time and labor was saved by not having to compact the lifts of traditional fill. Compensating for the drains within the ramp cells was a snap because on-site cutting of the geofoam was so easy.”
More than 31,000 cubic feet of termite-resistant geofoam was installed as stairway and ramp fill for the Metra’s 35th Street station platform.