Nearly 70 years after its creation, the iconic City Municipal Center along the Fox River in St. Charles, Illinois had lost much of its original lustre.

Key elements of the striking Art Moderne structure, designed in the 1940s by noted architect R. Harold Zook, had begun to crumble. The north end of the limestone clad river wall was deteriorating badly, while parts of the river-level fishing platform had been closed due to safety hazards. Below the 84-foot white marble tower, the building’s dramatic, 3-sided plaza had suffered a series of poorly planned repairs.

Rescuing a fading beauty

City officials tapped the engineering/design firm of Wiss, Janney, Elstner Associates to spearhead a $4 million rehabilitation of the treasured landmark. Inspired by Zook’s original design, the team envisioned a new plaza featuring decorative elements from the building’s star-studded interior floor.

Materials for the renovation needed to harmonize with the building’s Art Moderne spirit while standing up to the local climate. Prairie Pure Color from Prairie Material was chosen to deliver the beauty and durability required.

General contractor Bulley & Andrews called on Baumgartner Construction to handle placement of the integrally colored, air-entrained mix which was reinforced with epoxy-covered steel.

Intricate lines, vintage colors

From the start, the plaza presented unique challenges, says project manager Rich Baumgartner. “We had to match the colors and intricate patterns of the inlaid floor while working with concrete,” he explains. “Our formwork had to be incredibly precise.”

Designs for the 6-inch-deep plaza featured cast-in-place planters and a triple-star and chevron motif. Each design element used up to 4 unique colors, while black was specified for the pavement and planters.

“The black mix posed a real challenge,” notes Gary Hall of Prairie Material’s Technical Services team. “To compensate for the carbon in the formula, we boosted air entrainment significantly. We did multiple tests of all colors and followed a strict quality control process to achieve consistent results.”

Waiting for ideal conditions​

Weather and tricky site conditions added to the demands of the job, says Baumgartner. “We waited until April to start on the plaza, and limited pours to days within a certain temperature and humidity range. Narrow access points to the site forced us to place the star patterns on the south, west and north sides on different days, working with as little as 4-yard batches of each colored mix.”

The plaza alone took a month to place, Baumgartner notes. “Prairie was flexible in providing us with the amounts we needed right when we needed them, and the batch-to-batch consistency was definitely there.”​

Fresh look captures awards

The brilliant greens, yellows and whites of the plaza’s finished design dazzle the eye, boldly set off by the deep tones of black that surround them. Nearly 2 years after placement, colors remain vibrant with no fading or cracking.

The finished restoration garnered the prestigious Richard H. Driehaus Foundation Preservation Award from Landmarks Illinois, along with awards from the American Public Works Association and the Illinois Concrete Repair Institute.