Neighbors included the U.S. Mint and other sensitive federal buildings. To protect them, the GC had to shorten crane booms to reduce overswings. That meant seven tower cranes instead of six.

Aside from the office bridges, the second most complicated part of the project was the system of 60-ft-long, 6-ft-deep steel-plate box girders in the upper-basement-level ceiling—designed by the local office of structural engineer Thornton Tomasetti—that transfer loads from building-column grids to basement grids. The biggest crane available, set outside the site's perimeter, could not lift the heavy girders, which have 5-in.-thick plates, in one piece. Therefore, the box girders were fabricated in two sections. After installation, ironworkers created full-penetration welds to connect the sections, says Haas.

Though the concurrent construction has been much like a three-ring circus because of the different uses, "generally, it's been a smooth project," says Haas.

Win-Win Partnership

With the end of phase one in sight and the hotel moving forward, Hines' Riker is upbeat about the project, especially about the terms of the partnership Hines crafted with the city. According to the agreement, land associated with office, rental apartment and retail uses is controlled by the developer through 99-year ground leases. Land associated with the condos, initially, is owned by the developer, then by condo owners.

Under each ground lease, the developer pays the district a fixed annual ground rent of $500,000. In addition, the district is entitled to receive 25% of cash flow available after the developer receives a return on its investment.

The district also shares in added value created upon a sale or refinancing after the developer has realized a threshold internal rate of return. The venture structure is unique because any realized upside will be shared with the city, says Riker.

"The nature of the relationship could serve as a case study for other cities to emulate," he adds. "We created mutual objectives and win-wins."