IE. the pulverized concrete and glass, light steel and other building contents (including the thousand + that were vaporized) was sent to Fresh Kills landfill and sifted through. The heavy core columns and lighter perimeter columns were removed, with virtually no inspection, put on barges and shipped overseas or directly to local recyclers (IE "friends" of Guiliani.)
Statements from the House Committee on Science
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"According to reports that we have heard since, there has been no comprehensive investigation. One expert in fire engineering concluded that there was virtually a nonexistent investigation. We haven't examined any aspects of the collapse that might have impacted rescue worker procedures even in this last month.
Second, reports have emerged that crucial evidence has been mishandled. Over 80 percent of the steel from the World Trade Center site has already been sold for recycling, much of it, if not all of it, before investigators and scientists could analyze the information."
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"I am concerned that no clear protocol was in place for building investigators who were attempting to understand how the two buildings collapsed. While I understand that Ground Zero is first and foremost a crime scene and rescue area, we must also allow investigators the ability to fully examine evidence that will give us a greater understanding of why the buildings collapsed. I was disappointed to learn that investigators were unable to examine recovered pieces of steel from the Twin Towers before they were recycled."
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"The FEMA BPAT encountered numerous obstacles during its investigation, including an inability to examine the steel, either removed from the site during the early search and rescue work or shipped to recycling plants, and the denial of access to building design, construction, and maintenance documents."
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"The American Society of Civil Engineers team, whose report is due in April, admits they may have lost data due to the decision to recycle the structural steel."
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"In the month that lapsed between the terrorist attacks and the deployment of the BPAT team, a significant amount of steel debris—including most of the steel from the upper floors—was removed from the rubble pile, cut into smaller sections, and either melted at the recycling plant or shipped out of the U.S. Some of the critical pieces of steel—including the suspension trusses from the top of the towers and the internal support columns—were gone before the first BPAT team member ever reached the site"
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"The efforts of NSF-funded researchers were impeded by the same obstacles the BPAT team encountered: an inability to examine the steel, either removed from the site during the early search and rescue work or shipped to recycling plants"
http://commdocs.house.gov/committees/science/hsy77747.000/hsy77747_0.htm#0