Pentagon Renovation: Making the Biggest Better
By Tom Inglesby
The Pentagon Renovation Program ? PenRen ? is designed to make the building up-to-date in every way. Masonry Arts had the responsibility of adding security measures to make it better able to withstand blasts. September 11 proved the process worked.
In 1993, the Pentagon began undergoing a renovation project that would modernize the largest office building in the nation. The first phase, in Wedge 1, was five days from completion sign off and turnover to the government when Flight 77 hit. MCAA member Masonry Arts, Bessemer, Ala. was the contractor installing the blast wall system reinforcement and blast resistant window in Wedge 1.
The Pentagon is divided into five "wedges" centered on each of its five corners. Each wedge encompasses approximately one million square feet of office, storage and corridor space. Wedge 1's structural demolition (interior) and abatement of hazardous material began in 1998. This was a major undertaking, not the least because the Pentagon workforce in this area was relocated so that operations would not be negatively impacted, requiring temporary office space, called "swing space," in scattered areas of Washington and Virginia.
According to the PenRen program office, "In order to begin demolition and abatement work, it was necessary to isolate Wedge 1 from the rest of the building. To accomplish this task, mechanical, electrical, plumbing and communications systems had to be disconnected in Wedge 1 while ensuring that the rest of the building remained operational. Two sound attenuating barrier walls were constructed to separate Wedge 1 from the two adjacent wedges [2 & 5]. The barrier walls were mostly built in occupied spaces at night."
Demolition and abatement of asbestos and lead was a massive effort. Work began as soon as the various tenants vacated Wedge 1. Once the areas were cleared of nontoxic rubbish, they were enclosed to prevent the escape of asbestos fibers and abatement was carried out under strict safety precautions. In all, 2,000 tons of asbestos and 600,000 pounds of lead-contaminated debris was removed from the wedge. Items with salvage value were sold, with the proceeds reducing contract costs. Approximately 70 percent of the items demolished were recycled.
Then, before construction could begin, the entire wedge was brought down to its "barebones," as the PenRen office calls it. What remained were the concrete columns that support the building and concrete floor and ceiling slabs. Every wall, conduit and utility line was removed. In total, 83 million pounds of debris was removed from Wedge 1.
Masonry Arts came on the scene in 2000 to renovate the wall system in "E" ring, the outer section, and replace the 1942 windows with more modern, blast resistant units in "E" and "A" ? the innermost ? rings. The windows were specially constructed and had to match exactly the exterior look of the originals because the building is on the National Register of Historic Places.
Wedge 1 was the first to get a majority of the Pentagon's security upgrade attention. The PenRen office says, "The new windows on the "A" and "E"-rings are blast-resistant and permanently closed and fixed. This will not only increase the energy efficiency of the building but will also serve to protect the tenants against an external attack. Steel beams reinforce the walls around the new blast resistant units. Each window unit weighs approximately 1,600 pounds. The geo-technical material covering the wall between the steel beams acts as a giant 'catcher's mitt' in the event of an explosion, preventing debris from causing injury to the occupants of the room."
Rich Bartram, Masonry Arts' supervisor for the PenRen project adds, "We originally did the steel back up in the blast wall system and the blast windows for Wedge 1 where the September 11 impact occurred. Our blast wall, and the steel stacks from the first to the fifth floor, has everything connected with bolts through the slabs and with steel plates sandwiching the slabs. That blast steel allowed the fa?ade at floors three through five, to stand for 35 to 40 minutes after the plane initially came in, allowing several dozen people to get out of the building."
In other words, it worked the way it was supposed to.
Bartram talks about one of the things that happened that fateful day, "We have an e-mail from a general whose office was on the third floor directly above where the plane came in. His back was about one foot from the window. He got thrown through his office and then through another door. Immediately, the whole floor filled with smoke. He crawled out and saved five other people on the way down. He was able to go up to the fifth floor to see who he could find, and then he worked his way down and come right out the Corridor 4 door before that fa?ade collapsed."
Even though Masonry Arts specializes in security work ? they have done work for U.S. embassies in countries such as Kenya and Russia ? they don't always have access to the details on how and why the government designs its facilities. As Bartram says, "We know the blast load the window will take. We fabricated and installed the steel at the direction of blast engineers who work for the government. We don't know the intent of this steel, whether it's intended to prevent progressive collapse or not. That's a top secret of the government. All we know is the force the window had to take in order to design the window and the transfer brackets."
The renovation project worked within the existing exterior walls. Once the interior walls were removed, Masonry Arts found the evidence of the rapid construction the building had undergone in 1942. The original windows had been secured in brick with a lot of grouting to even things up. Because the new work had to exist in the same space, with no visible difference on the outside of the limestone fa?ade, much of that old work had to be redone in the same manner.
Roy Swindal, Masonry Arts' president, says, "We grouted from the brick back up to the window, then to the steel reinforcement. We grouted everything solid to the wall. The blast-resistant windows are designed to take a certain intensity of blast and to minimize damage to people inside the building in much the same way."
Making the window to resist blast pressure was only part of the problem. The original ones were operable ? they could be opened for ventilation ? but blast windows are not or they would immediately lose their capability to withstand an explosion. They must have all the same features on the outside, complete with the pull handle, because those are all historic features. When Masonry Arts experts went around checking the original windows to replicate them, some things were recreated without even knowing why the original feature existed.
"If you look close, you'll see little tabs in the corners, on the upper lights," says Swindal. "Nobody knew what those were. One day, when we were taking the Capitol Architect around, he said, 'What do you think those are?' I said, 'I think they were tabs to hold the screens.' He replied, 'That's exactly what they are.'
"We didn't know what they were, we just knew they had to be on the window." Swindal admits.
Obviously, there were other changes made, but they are not obvious from the outside of the building. Swindal recalls, "When we started on Wedge 1, on the heliport side, if a helicopter landed, with all the original windows closed, you couldn't stand next to each other and talk, you couldn't hear. With the blast windows in place, people commented that the only way you know the helicopter is even out there is when you see the blades turning. You can't hear them at all."
The PenRen Program is a multi-year project, larger and more costly, not to mention more time consuming, than the original construction ? which only took 16 months. The work done so far shows the value of the project and where priorities can be placed. "If the aircraft had hit on the other side of the building, in a wedge that hadn't been renovated as Wedge 1 had been, it would have been a lot worse," Swindal cautions. "The experts say the plane might have come out the other side of "A" Ring, into the center courtyard."
Bartram notes, "The plane hit in an almost perfect spot to prevent even greater loss of life. What you saw collapse was an expansion joint that it hit. When it knocked out all the columns on the first floor, the rest of the building held for about 35 minutes and then it collapsed. We feel that if it hadn't hit that expansion joint, there would have been a hole in the first and second floor and that would have been it. The third, fourth and fifth floors would have stood."
Government engineers and Masonry Arts installers can take pride in accomplishing what they set out to do, making the building safer for its occupants in case of an attack. Unfortunately, the proof of concept of the PenRen project happened on September 11. The official report of the attack states:
"Three measures taken during the renovation of Wedge 1 to reinforce the inner and outer walls served to dramatically slow the plane as it entered the building, reduced the extent to which it penetrated the rings, and prevented the immediate collapse of the structure directly above the area of impact. Despite the tremendous impact of the plane and the fire that was fed by the plane's fuel, the 'web' created by the blast-resistant windows, steel columns, and geo-technical mesh, held the building together for 35 minutes, giving many Pentagon employees, some located directly above the area of impact, time to escape.
"The Pentagon Renovation Program received numerous accounts from personnel located in renovated areas directly above or adjacent to the area of penetration. Many of these personnel were standing directly in front of or close to the new blast-resistant windows. Most of the new units remained intact and prevented severe injuries and possible loss of life. However, old window units in Wedge 2, up to 200 feet away, blew out during the initial impact and explosion of jet fuel."
About the Author
Tom Inglesby is a San Diego-based freelance writer whose work has appeared in numerous online and print publications. He is the winner of the Construction Writers Association's 2002 Boger Award for Special Reports.