J.E. Dunn Construction is at work on the West Edge, an $88-million mixed-use project in the Country Club Plaza of Kansas City, Mo. The project, located literally on the west edge of the Plaza, is situated between Belleview Avenue and Roanoke Road at 48th Street. It includes a 10-story office building and a seven-story hotel on top of a six-level, underground parking facility that will accommodate more than 900 vehicles.
The office and hotel structures, with the office on the north side of the site and the hotel to the south, are concrete with pre-cast and glass skin. Among the project's signature features, the office building will include a 10-story atrium with a sky-lighted curtainwall system and terraced, "green" roofs with plantings and vegetation. The hotel includes a rooftop pool.
Construction began in January of 2006 and will be completed by mid-2008.
According to Project Superintendent Rusty Tuggle, the project has presented many interesting challenges for J.E. Dunn and its subcontractors to overcome, starting with the excavation of the site.
"Jim Kidwell Excavation took out about 200,000 cubic yards of earth and rock to as much as 85 feet deep and the rock was incredibly hard," Tuggle said. "They said it was the hardest rock they had ever encountered. The tower crane bases are 30 feet square by 7 feet deep and it took about three weeks to make each of those holes."
Traffic control is another constant challenge in the busy Plaza with Belleview a main thoroughfare for traffic from downtown to the south and Roanoke taking drivers into the downtown area. Getting materials in and out of the site with minimal disruption to the traffic flow is a priority, said Tuggle.
"Positioning the two tower cranes to reach the entire site without conflicting with each other was also a challenge," he said. To manage the conflicts, one tower crane is 300 feet tall and the other is at about 250 feet tall.
Because there is such a significant amount of pre-cast on the project with heavy weights and picks, J.E. Dunn acquired two new Comansa 21LC550 tower cranes for the project. "These are the largest capacity tower cranes the company owns and we initiated the wpurchase specifically for this job," Tuggle noted. Each crane's capacity is 40,000 pounds at the base and 18,000 pounds at the tip.
"We went through an exercise with Enterprise Precast to manage the weights of the pieces to try to fit within the crane specs," Tuggle said. "On the north elevation, we use a crawler crane to erect pre-cast to give us a little bit more range to the south."
It is somewhat unique and very beneficial to the job, he said, that the cranes are freestanding. "We imported three special mast sections so we could freestand the cranes so we don't have to have a jacking exercise or a tie-back operation to the structure of the building."
Freestanding provides benefits in time savings as well as weather protection. "The use of freestanding cranes means we don't have to leave miscellaneous skin off for temporary tie-backs," said Tuggle. "That saves a tremendous amount of time when you consider that it can take 30 days to remove the tie-backs and the crane and put the pre-cast on and the windows in. And because we don't have those 'holes' in the building we don't have to worry about rain getting in."
The capacity of the cranes is also proving to be a benefit for concrete pours by allowing the use of a 3-yard bucket. "Typically, a crane's capacity is around 6,000 pounds to reach out 180 feet," Tuggle explained. "That's a yard and a half of concrete. So we saw the potential here with a crane capacity of 18,000 pounds at the tip to go to a 3-yard bucket. With 12,000 pounds of concrete, plus the weight of the bucket, we still have a 5,000-pound cushion. With the 3-yard bucket we can move 3 yards of concrete in about the same time as moving 2 yards with the smaller bucket. That's a 33-percent increase but you have an increase in load time and discharge time, so it's really more like an 18-percent increase in placement of material. But that's a huge deal considering we pour concrete six hours out of eight generally, whether it's walls, columns, buttresses, or footings.
"On deck pours we go with pumps, but a lot of times, and especially as we get higher up on the office building, we'll have a 100-yard pour that's blocked off, so we'll use the bucket. And soon we'll be dealing with hot-weather concrete so we'll want the pour to be done in four to five hours. In that case, we may cut some of the pours down and use the bucket as opposed to renting a pump for the day."
Another challenge on the project is that the site is "super tight," Tuggle said, so deliveries are scheduled on an as-needed basis. "We have a little laydown for rebar and we try to schedule that so we can take it off the truck and put it in the work area but we can't do that with everything.
"We've got 15 feet on the north and about 30 feet on the other sides so there's no real staging area," he said. "We'll get a little relief, maybe 10 feet to 15 feet in some locations, when we get above ground and get the garage backfilled. Even after that, we'll have to continue to watch our delivery, staging and traffic control very closely."
J.E. Dunn is self-performing the bulk of project's construction, including rebar, concrete (except decks subcontracted to CECO) and carpentry. According to Tuggle, there are currently more than 100 workers on the site and that number will grow to about 500 as the project moves closer to completion.