The Federal Emergency Management Agency (FEMA) assembled the BPAT, which was composed of American Society of Civil Engineers (ASCE) and Federal Government engineers. Forensic engineering techniques allowed the BPAT to determine the condition of the building before the blast, the blast size, and the mechanism of failure. These findings provided a means for assessing potential mitigation techniques. The team concluded that the building was designed as an ordinary reinforced-concrete-frame structure in accordance with Federal specifications. Records indicate that the building was extremely well detailed. When the building was designed, Oklahoma City codes did not require consideration for earthquake, blast, or other extreme loadings. The large explosion (equivalent to 4,000 pounds of TNT) was centered approximately 15.6 feet from column G20, which was immediately removed with a shattering effect. Loss of this column removed support for the transfer girder on the third floor between columns G16 and G24. The team found that the loss of columns G24, G20, and G16, along with significant portions of the floors above, was only partially attributable to the effect of the blast. The progressive collapse that followed was the direct cause of the majority of the damage and up to 90 percent of the fatalities. Columns G16 and G24 probably would have survived if detailed with more tie reinforcement. Increased concrete strength could also have increased the lateral load capacity of columns G16 and G24. If all techniques, including higher concrete strength, more continuity of reinforcement, and greater standoff distances were used, progressive collapse could have been reduced by 95 percent or more. 3 references