The Optima Old Orchard Woods, a 656-unit, 1.6-million-sq.-ft. project in Skokie, consists of three, 20-story towers connected by bridges and pierced by a multistory open area that supports outdoor terraces.

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The three-phase project is adjacent to the Edens
Expressway and on the eastern edge of the Harms Woods forest preserve.

Additional features include a two-story spa/fitness center with a 75-ft.-long pool; two-story party room with kitchen; green roofs; mechanical penthouses; and indoor, heated parking.

The condos range in size from about 700 to more than 3,000 sq. ft. and range in cost from under $300,000 to more than $1 million. The budget for the design-build project was not released.

The project broke ground on October 2004, with first occupancy in March. Work will continue until spring 2008.

Constructed of reinforced concrete, the buildings feature skins of thermally insulated glass, providing floor-to-ceiling windows in the condos, with aluminum channels at the floor-slab edges. The aluminum channels step out slightly to provide a distinct shadow line on each floor of the exteriors.

Sequencing Key

Sequencing work has been one of the ongoing issues on the enormous project.

"We have concrete pours going on tower three while the cabinets are being installed in tower one," said Bill Duke, project director for Optima Inc. of Glencoe, the project's owner and architect.

He said that coordination has been essential in keeping the trades moving smoothly through the individual towers and flowing from one tower to the next.

"We have had a very structured sequence of weekly coordination meetings from Day One," he added. "This allows everyone to be as productive as possible."

One facet of the sequencing, the construction of towers two and three after parts of tower one were occupied, has meant light treading for West Chicago-based concrete and design-build contractor Concrete Structures of the Midwest Inc.

Frank Aiello, president of the firm, said that by completion, the project will have required more than 8,000 truckloads of concrete.

"That's more than went into the Soldier Field expansion," he added.

The quantity of concrete on the site is only the tip of the iceberg.

"The biggest challenge on the project, from a construction perspective, has been the multiple phases of construction," Aiello said. "There are three different residential towers that are going up one at a time."

Performing Construction Choreography

Buyers of units in tower one are already moving into their new homes while work continues on towers two and three.

"Optima has taken great pains to maintain a safe working environment," Aiello said.

"This has meant a separation of church and state as far as keeping the construction and homeowner interaction to an absolute, bare minimum."
Safety concerns, as well as buyer comfort, have required some careful choreography from Aiello's crews.

"We are actually building the second and third buildings from one side only," he said.

"Construction on tower two is taking place from the back side of the building, between the Edens and the buildings. Construction on tower three is going on between the building and the commercial property to the north."

That means construction traffic, including trucks loaded with steel or ready-mix, are tiptoeing around the backsides of the buildings and steering clear of the residents.

Duke said ensuring worker safety, through the presence of an onsite safety director and the implementation a comprehensive safety program, has helped productivity and work flow.

"We can get up to 400 guys out there on pour days," he added. "The simplest thing, like a tripping hazard, can make a difference.

Midwest Quake Considered

Peter Danos, executive vice president of CS Associates Inc. of Oak Lawn, the project's structural engineering firm, said the multistory, open "hole" in one of the buildings presented structural hurdles.

"That open space required that the architect work with us in allowing certain column sizes," Danos said. "The challenge was designing five-story, unbraced columns, which was primarily an issue of getting a minimum size that would work for that unbraced length."

Working with Concrete Structures, CS Associates was able to come up with a size that pleased the architect. The result is graceful, slender columns that provide support as well as visual interest to the structures.

Because of the unusual shape of the buildings, a wind-tunnel study was done.

Although the original concept for the buildings was that of towers separated by expansion joints, which is common, the wind study showed the buildings moving in opposite directions.

In addition, the buildings had to comply with the International Building Code 2003 requirements, which include consideration for seismic events.

"Studies indicate that if the San Madrid fault near St. Louis goes full tilt, we will definitely feel it up here," Danos said. Predictions for such an event see some buildings in Chicago coming down.

As a result of wind forces, discontinuous floors in some areas and possible seismic forces, the decision was made to transfer horizontal forces to the structures through the diaphragm of the floor slabs of bridges that connect the structures.

Danos said that a sound-deadening berm between the buildings and the Edens Expressway created unbalanced earth loads on the buildings' foundations. The result was an increase in caisson size in some areas of the development.

The buildings feature high-end finishes, including two-story lobby spaces sporting sandblasted white marble set off by terrazzo floors.

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