Folks -

Many news reports have reported on the design and performance of the towers, with their remarkable pancaking collapse. My own involvement has been more below ground.

I am frequently down at "ground zero" as deputy chief engineer at the Transit Authority (a recent change from my previous career as a suspension bridge engineer). I have been in the subway tunnels that run under and adjacent to the WTC complex, have seen the destruction that was caused by the collapsed buildings, and have been amazed to see large areas of the basements that are OK. (See Friday's NY Times for a interesting story on subway damage at www.nytimes.com/2001/09/28/nyregion/28SUBW.html?searchpv=past7days) One of the things that amazed me to see was the steel columns from upper storeys of the WTC towers which speared down through the roadway and 10 feet of overburden to pierce through our tunnels. The N&R station on Church Street is a block away from the south tower. Steel columns from the 80th floor of that tower pierced down over 30 feet into the earth next to our subway box, and were sticking up out of the ground at least 50 feet. Removal of those spears is difficult to do without damaging our tunnel.

I am serving on a special committee advising on methods to secure the 70'high slurry basement wall which is now in danger of being breached. Collapse would let the Hudson River flow into the box. The wall was built with temporary tie-backs, or steel cables anchored in the outlying soil, but those were cut after the basement floors were in place (if not cut, they can snap over time and become missiles in the building). With the basement floors collapsed, the walls are being held in place by non-engineered rubble. Engineers (called "cave dwellers") are being lowered by cable through holes in the rubble to ascertain what parts of the basement flooring are intact and therefore presumably lending strength to the basement wall. A map is being developed for each basement level (7 levels in all) identifying good and bad areas. Removal of debris will take a long time just based on volume of material, but it will take even longer due to the need to protect the basement wall. For example, cranes cannot be placed within 30-50 feet of the wall for fear of adding to the outside pressure on it. This longer reach on the crane booms limits the load they can pick. Plans are underway to re-install the tie-backs so that the box can be emptied. Initially there were over 1000 tie-backs. Now they have to be installed hanging down on a cable from the top of the wall, a decidedly more difficult operation. Just to protect ourselves in case the wall is breached, we have installed concrete walls in the 1/9 tubes north and south of the WTC site to serve as plugs. The 1/9 tunnels are interconnected with other subway lines downtown. The Port Authority is doing the same thing in the Path train tubes over in New Jersey.

The change in the site over time has been amazing. Now it is much more of a construction site than a recovery site, although firefighters and FBI are still all over the place. Security requirements to get into the sight are changing every other day, as a new entity takes over which is confusing (Fire Dept, Police Dept, Mayor's Office of Emergency Management, FEMA). They are initiating a new pass system this weekend, this time with photos I understand, which means another wait in line. I am also involved in a private sector initiative by the NYC Partnership (a group of industry titans with political and financial pull) to come up with short- and long-term action plans to restore New York City to glory. I am part of a group pushing for a redistribution of NYC's financial district to a larger area. It doesn't make sense to have the financial might of the city (the country, the world?) in a single condensed neighborhood. I'm in favor of development along the lower west side of Manhattan, some of which is now a wasteland, along with improved transit in that area.

I feel very lucky that in the aftermath of the destruction that I was able to work productively, that I didn't feel helpless, as did many of my friends. I am also very much impressed by the efforts of the Transit Authority, where I have been employed only 4 months, to restore train service so quickly. The 2/3 tubes in the area were completely full of water on Thursday and Friday after the attack (the water main feeding collapsed 7 WTC was severed and pumped water into our subway, Con Ed cut off the power feeding our pump stations), yet they re-opened for service on Monday. To me, this is simply incredible.

Although our office is several blocks from the site, we did not loose anyone in the collapse. We did have a lot of people get close to the site who saw things that no one should have to see. Some employees lost loved ones. The emotional damage from this event touches just about everyone in some way.

Some lessons learned for disaster response:

- The as-built drawings for the WTC were closely held at the WTC by the Port Authority due to terrorist threats, and hence were destroyed in the attack. The only complete and accurate set that wasn't destroyed was in the office of Les Robertson, the original designer and a recent ENR Newsmaker of the Year. Unfortunately, his office was a couple blocks from Ground Zero, and couldn't be accessed for 2 days. Rescuers needed the drawings to identify potential pockets of survivers and means to get to them. We had similar experience trying to get a hold of drawings for other buildings in the area. A centralized, secure database for all buildings and infrastructure elements (water mains, etc.) is essential in times of disaster.

- Similarly, home and cell phone numbers for key people need to be readily available. This includes staff, consultants and contractors. We were displaced from our office, and it was difficult to locate and communicate with our own staff much less private sector folks, many of whom were also displaced. Thank goodness for my Palm Pilot, although I didn't have all the numbers I needed.

- Evacuation of people from lower Manhattan was accomplished mostly on foot, walking north on the perimeter highways. Tens of thousands walked over the Brooklyn Bridge, which was not a great idea considering it is a likely target. It took a long time to clear everyone out. A more secure means of quickly transporting lots of people needs to be considered.

- Our old subway tunnels were designed with a steel frame every 5 feet. An interesting byproduct is that the limits of destruction are abrupt and clearly defined. The tunnels are fine up to the first frame impacted, and then they are collapsed. Other types of construction would have had damage extend far beyond the zone of compression.

- The value of engineers has been greatly elevated during this disaster. No decisions, large or small, are made at Ground Zero without first consulting with an engineer. Engineers are quoted all over the NY Times and other newspapers and magazines. Engineers are even being referred to as "heros" which is not often heard.

Connie Crawford '78 *81