Award of Excellence: Historic Category
St. Charles Municipal Center River Wall and Plaza Restoration
St. Charles, Illinois
Submitted by Wiss, Janney, Elstner Associates, Inc.
City of St. Charles
St. Charles, Illinois
Wiss, Janney, Elstner Associates, Inc.
Bulley & Andrews, LLC
Cary Concrete Products, Inc.
The Municipal Center, situated along the eastern shore of the Fox River in St. Charles, IL, consists of the municipal building and an adjacent plaza. The plaza abuts the north, south, and west sides of the building and is generally located 12 ft (3.7 m) above the Fox River. The west edge of the plaza is defined by a 12 ft (3.7 m) tall Lannon limestone-clad river wall. After 60 years, the river wall had experienced extensive deterioration, which required repair. In addition, significant alterations to the original plaza had been performed in the 1970s and 1990s.
An investigation revealed significant deterioration of the original Lannon limestone cladding on the river wall due to weathering and of the Indiana limestone parapet wall due to corrosion of embedded steel bars and plates. Observed distress included spalls, incipient spalls, cracks, deteriorated mortar joints, exfoliating/scaling of the limestone surfaces, and displacement of the cladding. Investigative openings (cores) through the stone cladding revealed varying levels of distress of the concrete structure at the plaza and river wall, including spalls and delaminations. A laboratory study of concrete core samples indicated that the original concrete was not air-entrained.
Reconstruction of the original design of the plaza and river wall was performed from July 2009 through May 2010 at a cost of approximately $3.4 million. The intent of the project was to reestablish the design features of the plaza and river wall based on original available drawings, as well as an interpretation of the original designer’s intent.
The work site presented the contractor with many challenges, including a small site with difficult access, particularly for delivering, storing, and setting new materials; placing large volumes of concrete; maintaining egress for the functioning municipal building; and the need to perform extensive repairs from the Fox River. To accomplish the work from within the river, the contractor used a portable dam system, creating a semi-dry condition around the repair areas. The dam system was in place for approximately 4 months during the reconstruction.