Those same events began a 24-hour-per-day, 7-day-per-week effort by structural engineers to investigate the condition of the buildings remaining at the World Trade Center site, to work with the rescue and clean-up crews in evaluating the safety of the towering piles of rubble, and to try to explain what happened to the buildings as they collapsed. After 9-11 describes one engineer's experiences on site and off as part of that effort.
The government agencies responsible for the physical site after the building collapses - the New York City Department of Design and Construction and the Port Authority of New York and New Jersey - began planning the work assisting the emergency service crews and cleaning the site on September 11. Friedman, as part of the first effort, was on site beginning September 12 and continuing through the fall. His account includes descriptions of the damage to the buildings near the site, the methods used by engineers to assist the rescue and recovery work, and what it was like to be part of the civilian response to the disaster.