Strong as an Ox
Brigham Young made the streets in Salt Lake City big enough so an ox cart could turn around with little difficulty. At the end of this month, Doug Brannon’s "animal" will change direction, but it hasn’t been all that easy.
Brannon is one of the paving leaders for Wasatch Constructors, a joint venture between Peter Kiewit Sons’ Inc., Morrison Knudsen Corp. and Granite Construction Co., and keeps a cool demeanor as he leans back in his office chair and talks about a beastly reconstruction project on I-15. The 22-mile job, the largest design-build in the country, will be taking a monumental turn by the end of the month, when traffic is switched onto new pavement and the rebuilding of existing pavement begins.
"As far as big projects go, the complexity of it . . . sometimes I like to call it an animal," Brannon told ROADS & BRIDGES. "You need to stay on top of it, and it requires a lot of coordination and a huge team effort project-wide on everybody’s part."
The first concrete pour started back in June of 1998, when approximately 120,000 yd of pavement was placed that year. This year, Wasatch is right around the 230,000 yard mark and expects to get another 90,000 done before winter to reach 43%completion.
"I think this has been a learning process, but it’s probably been a positive process," said Brannon. "This is the largest design-build project in the country, so I think we’re under the microscope. A lot of people are watching this to see how it turns out."
Turning out a product
If Wasatch was going to melt a 10-year construction time table down to just over four, every possible way to save time was looked at and analyzed. An immediate concern was the soft lake bed sediment foundation in some spots. To reduce the surcharge time before pavement could begin, geofoam was used for fill. Produced by Advanced Foam Plastic Inc. in Salt Lake City, the high-quality styrofoam, used on five sections of the project, 300 North, 800 and 900 South, I-80 and State Street, alleviated some of the settlement problems, especially in areas where Wasatch wanted to put a sliver fill along existing embankments.
Nilex wick drains also have been used on embankments extensively to accelerate settlement times in the soil. The whole idea behind the wick drain is to provide a path for water to move out. Once the water is pulled the soil is free to compress.
"They had some big challenges with differential settlements where the new embankment would want to settle, but the existing embankment in place wasn’t going to settle," said David Nazare, technical support manager for the Utah Department of Transportation (UDOT). "The geofoam takes away the differential settlement problem."
Deciding on a concrete mix didn’t demand as much thought. Wasatch is using a standard 4,000-psi mix with 1-1/2 in. coarse aggregate. The concrete contains a 40/60 split with sand, 255fly ash, Ash Grove Cement and air entrainment and water reducer admixtures from Master Builders.
Three concrete plants have been erected along the I-15 corridor: A Rex Model S plant, which comes with a shrink drum, located at 600 South, a Ross USA twin drum plant set at 2100 South and a Con-Eco twin drum plant on 9000 South, which will be dismantled at the end of the construction season. Each facility is capable of producing 500-600 yd of mix an hour. Combined, the three could reach 1,800 yd an hour.
A fleet of Gomaco pavers have turned the mix into an actual surface. Three Gomaco 4000 pavers have been in use. Two are set at 7.2 meters and have a dowel bar system, while the other, what Wasatch calls its "three-lane paver", is set at 10.8 meters and also has a dowel bar inserter system. A Gomaco 3500 machine, which paves from 7 meters down to 6.2 meters, is handling middle of the road type projects, while a Commander III and Gomaco 2000 work with shoulder pours. Gomaco TC 600 cure/tining machines follow the pavers during the roadbuilding process, while a group of Freightliner ready-mix trucks pour the concrete.
Most of the mainline paving is 330 mm thick. Other areas measure out to 280 and 250 mm, depending on the ramp and section.
Smoothness testing is being conducted on-the-go using a profilograph. UDOT is requiring a profile index of 5, and so far test results are coming in under that number, according to UDOT Engineering Support Supervisor K.N. Gunalan.
Bend over backward
Sept. 9 was opening night for the Brigham Young University football team, which meant no evening closures for the I-15 project. Nighttime paving was set back almost two hours to avoid traffic congestion.
From day one, maintaining some kind of traffic flow has been a top objective, even if it means moving bulky equipment from site to site.
During the early stages, paving was almost done exclusively during off-peak hours. Three separate setup crews would go out during the day to conduct dowel bar and cure work and set or strip any forms, then the concrete would roll in between 10:30 p.m. and 6 a.m. The big pavers—the Gomaco 3500 and 4000—had to be moved at night under full freeway closures, while smaller pavers were relocated in the morning or afternoon.
"From a concrete standpoint, I would say the most difficult part has been having such a small window when you can actually do the paving with the traffic constraints and the time limitations," said Brannon. "It’s a pretty tough task to get done."
"They have to move the pavers back and forth, make sure bits and pieces of the pavement all get filled and plugged in, make sure they meet the specifications and requirements of having the seven-day cure of the paving surface and also make sure the proper strengths have been obtained before they can put traffic on," said Gunalan. "It’s a pretty tough juggling act that Wasatch has to go through to make sure all the requirements are met, and at the same time accomodate the public."
Since the start of this season some hand placements and small machine pavement placements have taken place during the day, but most of the work is still done at night.
Work also had to be done to relieve a couple of bottlenecks at the I-215 to
I-15 southbound connection and the I-15 northbound transition into I-215. In both instances, one lane was widened to two by using existing shoulders.
What else is being done?
Along with the switching of traffic onto a new two lane, several overpasses and one important viaduct are ready for traffic.
The 600 North overpass was completed last year, and the ones located at 10600 South, 3900 South, 2700 South and Vine Street were expected to be completed by the end of October.
Commuters also will have another avenue to take in and out of Salt Lake City. The 400 South viaduct was scheduled to be complete in late September and motorists will be able to use the route to drive into the downtown area from I-15 or enter the expressway from 400 South. Prior to the project, 600 South led drivers to the city and 500 South was the way to hook into I-15. Both will still be options once 400 South is open.
"This is really an exhilirating experience because you’re on the cutting edge of technology here in a lot of aspects," said Gunalan. "Overall, the design-build has been a good experience for everybody, and it’s probably as good from a public perspective. This whole project is hair raising and exciting."