...or three, was the bear. “It’s the largest schedule we’ve ever had in our company,” says Mansell.

The primary path was the playing field, which had to be clear by June 2009 to allow the field to be completed by August, which also would allow the grass to grow before the cold season.

The subpaths were: 1) the 1,600 ft x 45-ft bridge over the railroad tracks; 2) the 99,000-sq-ft bridge over I-394; 3) the core building, including the station for the commuter-rail and light-rail extension near the west end of the Fifth Street side; 4) the Fifth Street bridge, which contains the light-rail line; 5) the interior finishes and 6) the structural-steel canopy.

The very first activity, started in July 2007, was relocating the rail line 75 ft farther west. Even so, during construction of the platform over the relocated tracks, Mortenson had to call as many as 14 “time-outs” in a day, each lasting 20 to 30 minutes. BNSF gave the CM two week’s notice about shutdown windows but “would only tell us the exact times the day before,” says Mansell. Several times, BNSF parked a train on the tracks for four hours, stopping work there altogether.

Virtual Aid

To master the schedule’s 14,000 activities, Mortenson used a construction BIM with partial 4D, adding schedule in critical areas so it could rehearse construction virtually. There was a full-time scheduler and three full-time modelers on the project.

Although the design BIMs were provided to the CM for reference and to use at its own risk, Mortenson elected to create or have the subcontractors themselves create construction BIMs from scratch, using the 2D documents. All the players agree that one of the potentials of BIM—inputting information once and reusing it again and again—was not realized on this project.

The complexity of the project made the structural engineer’s use of REVIT Structure, a BIM program, both helpful and problematic, says Slade. “Unfortunately, the structural engineer was the only design professional that fully utilized BIM, which tended to minimize benefits” during drawing coordination, he explains. He adds that changes to the BIM, late in the documentation process, “probably required more effort than a similar project in 3D AutoCAD.”

To boot, the structural BIM was so large that it slowed computer processing and documentation activities. WPM says a lesson learned, which it currently applies to complex projects, is to engage in detailed model planning—including modeling the structure in several submodels rather than a single large one. WPM currently creates predesign REVIT work plans, with input from the architect, contractor and owner.

From Mortenson’s point of view, a lesson learned is to apply even more resources in the preconstruction phase. There was an overlap of construction and design completion for a long while, says Wood. During that time, Mortenson’s team was focused mostly on construction activities, he adds.

If he had a second chance, Wood says he would have had two teams: One team would have been dedicated to supplying the expertise designers needed to make design decisions influenced by cost and schedule impacts; the other team would have focused on only construction.

“It was not a problem, but it was a handful for our project team to be gearing up for and dealing with the early demands of construction while also dealing with the design issues,” Wood says. “We probably should have had separate leadership for ongoing support of design activities and construction activities.”