DAVE PERAZA: On September 12th and 13th, as rescue workers were scouring Ground Zero for signs of life, seven teams of engineers, police and firefighters conducted emergency assessments of the surrounding buildings. Working from the street, and gaining entry where possible, we looked for structural as well as superficial damage that might be hazardous to the workers. Structural engineers systematically assessed about 400 buildings in late September, then repeated the job in October. About 30 buildings, having suffered structural damage or extensive damage to their facades, underwent more detailed inspections. Engineers went floor by floor, examining structural systems, fire alarms, sprinklers, and other life-safety systems. Remarkably, while all seven World Trade Center buildings and the St. Nicholas Church behind the South Tower were a total loss, no other buildings were beyond repair.
Click on the map above for what the engineers saw. To see their complete buildings assessment, visit the Structural Engineers of New York Web site.
Video: The Surviving Structures
Engineers assess the buildings still standing
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