It's hard to miss the $300 million Heritage at Millennium Park condominium project in Chicago.

The structure involves two towers, and the highest one is the tallest under construction in the city, according to the Chicago Department of Planning and Development.

Jay Butler, senior project manager of Chicago-based Walsh Construction Co., the general contractor, said the tower's highest residential floor is at 57 stories, and there are three levels of mechanical space above that.

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The Heritage's location near Wabash and Randolph streets will make it a part of the panorama when observers from the east look at the Loop's landmarked Michigan Avenue street wall. Popular destinations nearby, such as the Chicago Cultural Center and Marshall Field's department store, make the high-rise part of the daily scene for thousands of passers-by.

And the Heritage's east facade commands a wide vista of Millennium Park, the recreational area east of Michigan Avenue with high-end art and architecture that is generating a lot of interest among residents and the press.

The park is expected to draw millions of visitors annually, according to projections from the Public Building Commission of Chicago, the city agency overseeing the park's development. The park includes the Frank Gehry-designed Jay Pritzker Pavilion and Thomas Beeby's Joan W. and Irving B. Harris Theater for Music and Dance.

The Heritage's design is intended to compliment the skyline and generate interest, said Andrew Warner, director of sales and marketing for Equity Marketing Services, the sales agent.

For instance, curves were incorporated in the facades and are intended to relate the structure to the Lake Michigan shoreline. Self-climbing formwork was custom made to accommodate the curves.

Colonnades integrated in the top of each structure and elsewhere on the building reflect those on the cultural center and Field's.

And, spandrel beams, which appear every three levels on the low tower and every six floors on the high tower, give the building horizontal interest.

Even fine architectural details were important, such as the precise placement of the 2- to 3-in.-thick horizontal reveal lines in the concrete facade, Butler said. They were to match the window lines precisely.

"The requirement was to create a very attractive building with very good floor plans," Warner added.

The 28-story low tower forms the development's southern part, and its 295-ft. height mirrors the stature of nearby structures to the south, Warner said. These include the 262-ft.-tall Garland Building and the 277-ft.-tall Pittsfield Building.

Likewise, the Heritage's high tower is compatible with structures to the north, such as the Stone-Smurfit Building and the Prudential Building, each of which is 41 floors.

Seven Out

Demolition began in July 2002 on the seven buildings that were previously on the site. Project completion is expected in June.

The Heritage will hold 356 condominiums and seven penthouses, and prices range between $315,000 and $2.8 million, Warner said. Units with one, two, three, four or five bedrooms are available.

The completed building will hold nearly 1.2 million sq. ft. of space, which includes the 18-ft.-deep basement. About 100,000 sq. ft. of retail will be located on three floors at the base.

Parking will be on levels three through eight, and there will be 599 spaces. Ten elevators will service the building.

Amenities include an exercise facility with pool and other elements, hospitality room, business center, sun decks and picnic area.

In mid-May, the Heritage was 95 percent sold, Warner said. Only 18 units were still available.

Old and New

The facades of four mid-rise structures previously on the site - the Burton, Couch, Peck and Porter buildings - were integrated into the Wabash frontage. The once-celebrated Blackhawk Lodge restaurant was located in the Couch.

The facades were deemed worth saving because each dates to immediately after the Great Chicago Fire of 1871 or the early 20th Century.

"The city encouraged us to keep the look and feel of Wabash," Warner added.

A steel frame was built around the facades for support, and the building structures behind the faces were removed, Butler said. Some steel members went through windows, and clamps secured the facade to the steel for lateral resistance.

"That's been done before, but not too often in Chicago," Butler added.

The old foundations for the support of the facades were cut, and the new caissons were attached to the facades. The frame has been removed because the facades were attached to the Heritage, but the restoration of the facades' masonry, terra cotta and brick has yet to be done.

Rather than their original look, the facades will be restored to reflect how they appeared in the 1920s because of their histories, Warner said.

The four building's main entrances were originally on the east, but the west facades became the main entryways in the 1920s when the former Chicago Public Library - now the cultural center - was erected on the east.

A Steady Structure

The structure's height and location resulted in several structural issues.

Transfer beams were incorporated into the ninth floor to shift loads from the towers' column grid to the parking garage's grid, said Boris Sverdlov, vice president of Chris P. Stefanos Associates, the structural engineer.

The post-tensioned beams are up to 15 ft. deep. Because of the beams' depth, more than 20 days were required to form that floor.

Smaller transfer beams are on the 27th and 58th floors.

Exterior exposed frames and shear walls were used to provide resistance to Chicago's winds, Sverdlov said. Four shear walls are in the parking and mid-rise tower and two in the high-rise.

"Huge" openings were cut in the parking garage's interior shear walls to ensure vehicles could get through them.

Below grade, an earth retention system was installed to avoid affecting other structures in the building-dense downtown neighborhood. The process involved multiple repeats of driving steel sheeting, partial excavation and installation of angled bracing.

The bracing conveys pressure to transfer beams, some of which have 7-ft. shaft diameters.

"There are quite a few around the perimeter of the building because the building is built near the lot line on the south side," Butler said.

A total of 222 caissons that reach 85 ft. deep absorb the building's pressure.

The project logistics were tricky because of the crowded site: The Garland Building to the south, Randolph Street to the north and the Chicago Transit Authority elevated tracks to the west.

As a result, deliveries entered only on Garland Court from the east. Night deliveries helped ease congestion, and truck access had to be shared with the cultural center.

The street canopy provided some room for staging, but a majority of materials were staged in the parking garage. The concrete was staged on the ninth floor, and about 58,000 cu. yds. form the building.