The casualty toll at the Pentagon on 9/11 could have been much worse, but the damage was mitigated by reinforcement work that had begun on the building, which was built in 1941 and had marked its 60th anniversary that year:
In light of troubling world events like the first World Trade Center bombing in 1993 and the Oklahoma City bombing in 1995, officials believed it was time to retrofit the building in a five-phase renovation effort that prioritized safety and stability over aesthetics.
“The retrofit didn’t envision what happened,” Mlaker said. “It was more for something like a truck bomb going off.”
Nonetheless, the work included features like blast-resistant windows, ballistic materials and wall reinforcements. And the first phase of work, involving “Wedge 1” of the Pentagon building, divided up like a five-sided pie, had just been completed days before the plane hit the building.
The morning of September 11, Mlaker said, he’d had a conference call scheduled with the American Society of Civil Engineers to develop a standard for blast-resistant design. But of course, the test was coming sooner than anyone had anticipated.
On the west side of the building, according to ERDC officials, the impact of the plane destroyed the first and second floors, but the remaining three floors remained standing for another 35 minutes, allowing hundreds of people the chance to evacuate.
A side-by-side photo of two Pentagon window offices tells the story of the difference the retrofits made. One office just 17 meters north of impact that had received the new ERDC reinforcement technology looks untouched, its curtains still neatly framing its windows. Another non-reinforced office, 90 meters north of impact, is totally destroyed, its windows blown out and walls and ceiling burned and shredded.