Early Days at the Disaster
What I saw next was also shocking: a large front-end loader and 100 firemen were removing debris from the sidewalk between the plaza staircase and Church Street. I knew that directly below were a subway station, a shopping concourse, escalators to commuter rail stations, and a five-level garage.
Because of concerns about the integrity of the structural steel that supported the plaza level, I suggested to the captain in charge that he remove all his personnel immediately. Apparently none of them was aware of the habitable space below.
As if to underscore my point, the front-end loader made a pass in our direction, and we felt a noticeable jolt of the plaza floor. I had been up and down that staircase many times without feeling any vibrations so I was concerned for everyone's safety.
Sketching the Underground
I suggested to the contractor that portions of the sidewalk be chopped out in order to evacuate anyone below. I drew for him a sectional view of the area, indicating the staircase and plaza above.
From vivid childhood memories, I remembered a foundation wall that extended from grade level down to bedrock. But I wasn't sure of the horizontal distance between it and the towers. A call to my father assured me that it was closer to the center of the Plaza than to Church Street.
Based on my sketch, three holes, each about 8 feet (2.5 meters) square, were dug that night directly above the main corridors below, giving access for rescue workers.
Thursday, September 13
Next morning, on arriving at the corner of Church and Vesey Streets, I saw three pieces of equipment removing the sidewalk from the plaza area near the staircase. Two "spiders," or single-person, cable-mounted hoists, were on the plaza, having been used the night before to lower rescue workers into the concourse and shopping levels.
I walked onto West Street and was enlisted in a line of people moving rubble piece by piece. At times like this, there's no choice but to get your hands dirty and do whatever you can. On this day, I saw seven people rescued from the rubble.
Late that afternoon, I was interviewed by the Secret Service in anticipation of the president's visit the following day. I explained to them my opinion that the Port Authority did nothing wrong in the design or construction of the World Trade Center. Building codes only give us a maximum load to design for. No one ever knows the size of the next bomb that may be dropped on us.
Also on Thursday, federal agencies began to establish a presence on the site. They erected white tents on Church Street directly across from the entrance to the World Trade Center plaza. Their visible presence made communications flow more efficiently.
Friday, September 14
On Friday I continued a review I had begun the day before of adjacent buildings damaged by the intense heat. Starting at the northeast corner of the site is the Post Office Building. Fifteen years ago, while working for Horst Berger Partners Consulting Engineers, I had analyzed this building and determined that it could support a ten-story addition.
This fact, coupled with the structural framing type of the building, assured me that it was not dangerously affected by heat. In the 1920s, federal office buildings were typically built with steel frames encased in terra cotta, mortar, concrete, and/or granite.
These materials gave the desired appearance of an imposing stone building. An added benefit of this structural system was that the stone or concrete added fire protection to the columns and beams.
I was also familiar with a few of the other perimeter buildings and relayed my opinions to the Federal Search and Rescue team. I was able to assure them, for example, that the tall, slender 52-story Millennium Hotel was of reinforced concrete and therefore more fire resistant than buildings of structural steel. I saw no immediate danger of failure but recommended that the building's owner arrange for an independent assessment.
Several perimeter buildings sustained incidental damage. In the World Financial Center directly across from the south tower, every window was broken. Although extensive repairs will be required before tenants reoccupy the building, it appears to be structurally sound.
I was only one of hundreds of people who went to the site to offer help. In those first hours, no one told us where to go, what to do, or how to do it. One useful role I discovered was that of rumor control. It was common to hear rumors that a certain building would be the next to fall.
I learned a technique to persuade other people on this matter. Once, when my engineering experience told me a building was safe despite the rumors, I walked up 29 flights to the roof to photograph a sunset. To me, the photo symbolizes our resilience.
Patrick J. McNierney has been a consulting engineer with Horst Berger Partners and Deputy Director of the New York City Bureau of Bridges. He holds degrees in engineering from Bucknell and Columbia Universities and is a member of the Columbia University Faculty House.