Editor's Note: Click here to read an updated article about the completed Old Chicago Main Post Office.

Abandoned and in disrepair for the past two decades, the Old Chicago Main Post Office – once the largest building in the world – is getting a new lease on life.

For the past four months, demolition crews have been clearing away debris and old machinery inside the nine-story, 2.5 million square-foot building as part of a renovation plan that will convert it into a mixed-use facility. The developer, 601W, is hoping a combination of office and retail space will turn a blighted property into a centerpiece of the neighborhood along West Van Buren Street.

“It is going to help that part of the town to have its old post office building back,” said Greg Lakota, principal-in-charge for WSP USA, the structural engineer for the project.

The firm is working with Gensler, the architectural firm designing the building, to plan the renovation and improvement of the building, which was listed on the National Register of Historic Places in 2001.

This isn’t the first time that a developer has attempted to rescue the building since the United States Postal Service moved operations into a new postal facility in 1997. But after several unsuccessful attempts, the highly visible structure that spans the Eisenhower Expressway is finally seeing some significant progress.

Lakota’s involvement dates back to early attempts to revive the building in the late 1990s, when WSP was first tapped by Gensler as a structural engineer for the project.

“I remember walking inside that building for the first time thinking, ‘Wow, this is just one big machine,’” Lakota said. “The whole interior was very impressive, with conveyors that were installed to transport packages up and down the building, and 12-foot diameter spiral shoots that were used to move the mail. It was set up as one big sorting machine to handle huge amounts of mail on a daily basis.”

When it was first opened in 1921, the Postal Transportation System Building was a modest six-story structure along the river. In 1932, a significant addition created the Old Chicago Main Post Office that exists today, which held the distinction of being the largest building in the world. Its size was necessary as the hub for in-going and out-going mail and packages from two of the world’s largest catalog retail companies, Sears and Montgomery Ward.

Although most of the equipment is being removed and recycled, several pieces will remain in the building as a reminder of its role as an early 20th Century postal hub.

“A lot of the building’s features are being restored,” Lakota said. “They will be keeping some old mechanical scales, and the enclosed catwalks that were used as a surveillance system will be restored. Many of the ornate light fixtures and the marble flooring in the lobby on the north end of the building will be preserved. It will one day serve as the new public lobby, but in many ways it will feel like you’re stepping back in time.”

One of the challenges the developer faces is the renovation of a building that has active railroad tracks with passenger trains running directly underneath the building.

“As we determine which parts of the building to salvage and strengthen, and which to demolish and replace, we have to factor in the railroad running underneath,” Lakota said.

601W owns the building structure, but Amtrak owns the rails and passenger platforms directly below the building, as well as the airspace between the track and the building structure. The contractor is permitted to do work along the tracks only from 1 a.m. to 4 a.m. to avoid any disruption of the passenger rail service.

“Amtrak understandably doesn’t want us to interrupt its rail service, so that is proving to a big challenge; but some of the modifications will require some work around the tracks,” Lakota said. “We are working with Gensler and 601W to find the best ways that the structure can be repaired and modified with minimal disruption to Amtrak.”

One of the early tasks that the firm handled is the design of structural framing that will support the new fans that will disperse the diesel exhaust fumes generated by the trains.

“The track fan replacement is just beginning,” Lakota said. “It will be tricky construction work, as the existing old fans have to remain operational while the structure is strengthened for the installation of new fans. The new fans will ultimately handle the exhaust more effectively.”

The firm is also looking at whether it is better to strengthen or replace the existing structure to support the new ComEd transformers that will provide power for the building, modernization of the stairwells and elevators, support for new escalators, and the closure and infill of “hundreds of floor openings that were used for moving mail vertically.”

One of the biggest changes will be a replacement of the roof in order to create a proposed rooftop public space for tenants of the building.

“The current roof wasn’t built to handle those types of loads,” he said. “It will be one of the great new amenities that this building will be able to provide for the people who work there.” Lakota said another big selling point of the building will be the conversion of the large loading docks into a parking area.

Demolition is expected to continue for another four or five months, followed by construction of a few of the suites on the fourth level to begin showing prospective tenants what the building will be like when completed.

Lakota said public reaction has been enthusiastic.

“I was on a river cruise recently that was passing by the old post office, and the guide was speaking very enthusiastically about the work being done on the building,” Lakota said. “I don’t think he knew everything that was going on, but he was very excited that the building was going to be reused and restored.”

While maintaining the character of the old building, necessary renovations will bring it up to the standards of other contemporary commercial buildings – for example, the replacement of single-pane windows with modern insulated windows and the cleaning and restoration of the stone façade.

“It’s going to look a lot different from what it looks like right now,” Lakota said. “Once they start wiping away 100 years of grime from the façade, it’s going to be a very impressive building. It will bring a brand new life to it.”

He is also happy to still be involved with the project as things finally get rolling.

“I’ve been working on it for so long, it’s just so exciting that it’s finally now going to happen,” he said. “Since doing that structural investigation of the building back in 1996, there have been a lot of false starts. But we are finally seeing a scheme to reuse the building that is going to get implemented. It’s great to see this large, iconic building at a point where it is going to be used, not crumble away.”