The 1993 Construction Collapse at Chicago’s Main Post Office: What Happened and What We Learned

Chicago’s main post office is a historic landmark that spans three city blocks along the Chicago River. The original building was completed in 1921 and expanded in 1932 to meet the growing demand for postal services. The building was designed by the renowned architectural firm Graham, Anderson, Probst & White in the Art Deco style, featuring a limestone facade, ornamental details, and a massive lobby with marble floors and walls.

The building served as the main post office for Chicago until 1996, when it was replaced by a new facility nearby. The old post office was then left vacant for more than two decades, until a New York-based developer, 601W Companies, acquired it in 2016 and embarked on an ambitious $800 million renovation project to transform it into a modern office complex with retail, fitness, and entertainment amenities.

However, the old post office also has a tragic history of a construction collapse that occurred in 1993, when a new nine-story building was being built across the street from the original structure. The collapse killed two workers and injured six others, and led to criminal charges and lawsuits against the contractor and subcontractor involved.

The Project Background

The new post office building was part of a $316 million project that started in 1991 and was expected to be completed by 1995. The project was overseen by the U.S. Postal Service and contracted to Morse Diesel International Inc., a New York-based construction management firm. Morse Diesel hired Pitt-Des Moines Inc., a Pittsburgh-based company, as the subcontractor responsible for erecting the structural steel frame of the building.

The new building covered half a city block and had a steel frame consisting of columns, beams, girders, and braces that were connected by bolts or welds. The steel frame was designed to support the concrete floors and exterior walls of the building. The steel frame was erected in sections, starting from the ground level and moving up to the ninth floor.

The Collapse and Its Causes

On November 3, 1993, while the structural steel frame of the building was being constructed, a 30 m (100 ft) by 32 m (106 ft) by five story tall section of the frame collapsed, injuring several workers, some fatally¹. The collapse occurred around 10:30 a.m., when about 50 workers were on site. The section that collapsed was located on the south side of the building, near Van Buren Street.

The collapse was triggered by the failure of a single connection between a beam and a girder on the fifth floor of the frame². According to an investigation by the Occupational Safety and Health Administration (OSHA), the connection was not properly secured with two bolts as required by the design specifications. Instead, only one bolt was partially inserted and not tightened³. This caused the connection to break under the weight of the steel above it, resulting in a domino effect that brought down the entire section of the frame.

The investigation also found that Pitt-Des Moines had violated OSHA regulations by failing to train workers to recognize and avoid unsafe conditions³. Furthermore, Pitt-Des Moines had ignored warnings from its own quality control inspector about the improper bolting of connections⁴.

The Aftermath and Lessons Learned

The collapse of the post office building was one of the worst construction accidents in Chicago’s history. It claimed the lives of two Pitt-Des Moines employees: Patrick Newsome, 25, of Thornton, and Larry Thormeyer, 47, of South Holland². Five other workers were seriously injured and hospitalized. The collapse also caused extensive damage to nearby buildings and vehicles.

The collapse sparked public outrage and scrutiny over the safety practices and accountability of construction companies. In 1996, Pitt-Des Moines was indicted on criminal charges of willfully violating OSHA regulations². In 1997, Pitt-Des Moines was convicted and fined $500,00⁰⁴. Morse Diesel also faced civil lawsuits from the victims’ families and settled for undisclosed amounts⁴.

The collapse also exposed the need for better oversight and enforcement of construction standards and codes. OSHA admitted that it had not conducted any inspections at the site before the accident². The city of Chicago also acknowledged that it had no authority or responsibility to inspect federal projects like the post office building².

The collapse also highlighted the importance of proper design, installation, inspection, and maintenance of structural connections in steel buildings. Connections are critical components that transfer loads and forces between members of a structure. If connections fail, they can compromise the stability and integrity of the entire structure. Therefore, connections must be designed and installed according to the specifications and codes, and inspected and maintained regularly to ensure their performance and safety.

The collapse also demonstrated the potential of human error and negligence in construction projects. Construction workers must be trained and qualified to perform their tasks, and follow the procedures and instructions provided by the engineers and managers. Construction managers must also supervise and monitor the work of their subcontractors and employees, and ensure that they comply with the regulations and standards. Construction companies must also foster a culture of safety and quality, and not compromise them for the sake of speed or profit.

Conclusion

The 1993 construction collapse at Chicago’s main post office was a tragic event that resulted from a combination of factors, including a faulty connection, a lack of training, a disregard for warnings, and a failure of oversight. The collapse caused death, injury, damage, and litigation, and tarnished the reputation of the construction industry. The collapse also taught valuable lessons about the importance of structural connections, safety regulations, worker education, quality control, and accountability in construction projects.

Learn More

• [Investigation of Construction Collapse of Steel Structure of The Post Office Building in Chicago](https://ascelibrary.org/doi/abs/10.1061/40482%28280%2968)
• [U.S. INDICTS COMPANY IN POST OFFICE COLLAPSE](https://www.chicagotribune.com/news/ct-xpm-1996-08-23-9608230041-story.html)
• [FIRM FOUND GUILTY IN OFFICE COLLAPSE](https://www.chicagotribune.com/news/ct-xpm-1997-08-01-9708010153-story.html)

(1) Investigation of Construction Collapse of Steel Structure of The Post …. https://ascelibrary.org/doi/abs/10.1061/40482%28280%2968.
(2) 1 Worker Dies, 6 Hurt in Chicago Building Collapse. https://www.latimes.com/archives/la-xpm-1993-11-04-mn-53278-story.html.
(3) U.S. INDICTS COMPANY IN POST OFFICE COLLAPSE — Chicago Tribune. https://www.chicagotribune.com/news/ct-xpm-1996-08-23-9608230041-story.html.
(4) FIRM FOUND GUILTY IN OFFICE COLLAPSE — Chicago Tribune. https://www.chicagotribune.com/news/ct-xpm-1997-08-01-9708010153-story.html.
(5) Developers Unveil $800M Makeover of Chicago’s Old Post Office in ‘Grand …. https://www.nbcchicago.com/news/local/new-old-chicago-post-office-makeover/1970301/.
(6) A detailed look at the redevelopment of the Old Chicago Post Office …. https://chicago.curbed.com/2017/9/18/16327244/old-post-office-renderings.
(7) Vitro Case Study — VitroGlazings.com. https://projects.vitroglazings.com/project-assets/files/967/VIT_Case_Study_ChicagoPostOffice.pdf.
(8) Chicago’s Old Post Office get new zip with massive … — Construction. https://www.bdcnetwork.com/chicagos-old-post-office-get-new-zip-massive-900-million-renovation.
(9) Chicago Post Office · Sites · Open House Chicago. https://openhousechicago.org/sites/site/chicago-post-office/.