Allentown Corporate Plaza


The Beginning of the End:

The 7-story modern office building known as Corporate Plaza was built in downtown Allentown in 1986. Many local residents regarded it as a landmark achievement in Allentown's downtown revitalization efforts. But that all changed during the early morning hours of February 23, 1994.

The winter of 1993-1994 had been one of the region's worst in memorable history. It's an area that sees a few isolated winter storms each year. But that particular year saw ice storm after ice storm, followed by several heavy snowstorms. The runoff from all these storms finally took its toll in the form of a sinkhole in front of Corporate Plaza. The widening hole was discovered around 4:00 am by utility crews investigating a water main break. Fortunately, no one was in the office building at that early hour.

By 6:30 am the situation had worsened. The gaping hole had spread underneath one of the main support columns of the building. The column gave way, causing a V-shaped sag in the front facade. Because of the danger the building posed, a raze-or-repair order was issued to the building's owner.


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Despite the fact that area streets were closed to the public for safety reasons, the sinking building drew large crowds of local residents who wanted to check it out first hand. One of them, David Evans of Coopersburg, PA, provided these two photographs. This first one is looking south along 7th Street. You can see the sag in the northeast corner above the sinkhole. This photos shows the northwest corner, which gave way around noontime on February 23 as the sinkhole continued to grow underneath the building. David Evans took these photos just a few days after the sinkhole opened up. As you read this page, take note of how the building's condition continues to progressively worsen up until its implosion three weeks later.

Demolitions Crews Move In:

On February 27, the sinkhole was pumped full of concrete in an attempt to stabilize the building enough for salvage crews to save what they could inside, as well permit the demolition crews to begin preparing it for implosion.

Implosion was determined to be the quickest and safest method of bringing Corporate Plaza to the ground. With the building stabilized as well as it could be given the circumstances, Dykon, a reputable blasting firm from the midwest, was brought in to do the job. But working inside a progressively failing building, made it anything but a routine demolition.

Dave Hersey, Dykon's project manager, told Phillyblast that it was the scariest job he had ever worked on. "That building was in the process of sinking into the street while we were working. The stresses and loads inside the building were changing constantly. Some of the upper columns were twisting and some of them were failing under the pressure. We had to be so careful. We had people doing nothing but watching the cuts we made in the steel columns for movement."


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Taken on March 1, this photos shows another view of the northwest corner of the building, which sagged about 10 feet. A close up of the area reveals the extent of the growing sinkhole, which measured approximately 40 feet by 50 feet in area, and 15 feet in depth.

Please be patient while photo loads. A close-up shot of the northeast corner shows the extent of the damage along 7th street. The tilting column that the worker is standing by was the second column to give way along the front facade. In the background, now stripped of its brick cladding, is the first column that fell. Its failure caused the other front columns to deflect under the increasing load they were required to bear.

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Another shot of the front facade shows how the falling debris has littered the street below. Key support columns are sinking and twisting into the ground below, while cracks form in the brick, and glass windows bow out from their frames. If the views from the street aren't frightening enough, take a look from the inside of the building. This shot is looking towards the area where the first column fell along the front facade.

Conditions Worsen:

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The demolition process was slowed by continuing bad weather and the constant shifting of the building. Continual efforts were made to stablize it to prevent total collapse. Despite their best attempts, the northwest corner of the building eventually gave way, collapsing down to the fourth floor. Another frightening view from the interior shows just how warped and twised that corner had become. Luckily, noboby was hurt in the collapse.

The "Big Bang":

The city of Allentown decided to sell souvenir bricks and sweatshirts to help benefit the displaced tennants, and to help the local Red Cross. A raffle was also held to chose a local resident to push the plunger for the implosion to begin.

The building was successfully imploded on March 19, 1994, 3 1/2 weeks after the catastrophe had begun.


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As the dust cleared, the city of Allentown breathed a huge sigh of relief. The sinkhole had held the city block captive for 3 1/2 terrifying weeks. During that time, nobody was killed or injured as the building sunk into the ground. With Corporate Plaza reduced to rubble, the cleanup and rebuilding could now begin. Please be patient while photo loads.

The Aftermath:

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Today, the Corporate Plaza office building is just a bad memory for the city of Allentown and for those who helped bring it down. A parking lot now takes it's place, as it was determined that putting a new building on that plot of land was too risky.


Phillyblast would like to extend a big "thank you" to Dykon for providing the photos on this page (except where noted). Also, thank you to Dave Hersey for sharing his experiences in working on this project.


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Created: July 30, 2000 Last Updated: December 23, 2005