Under CDI direction, Homrich/NASDI’s 21 man crew needed three months to investigate the complex and four months to complete preparations for CDI’s implosion design. During that period, the lower two basements of the structure were filled with engineered fill and the perimeter basement walls bermed to 1st basement level with soil to support perimeter walls which would surely have failed under soil and hydrostatic loads once the horizontal support of the Hudson’s internal structure was removed by the implosion.
Double column rows installed in the structure between vertical construction phases, internal brick shear walls, x-bracing, 70 elevators and 10 stairwells created an extremely stiff frame. Columns weighing over 500 lb/ft, having up to 7.25 inch thick laminated steel flanges and 6 inch thick webs, defied commercially available shaped charge technology. CDI analyzed each column, determined the actual load it carried and then used cutting torches to scarf-off steel plates in order to use smaller shaped charges to cut the remaining steel. CDI wanted to keep the charges as small as possible to reduce air over pressure that could break windows in adjacent properties.
CDI’s 12 person loading crew took twenty four days to place 4,118 separate charges in 1,100 locations on columns on nine levels of the complex. Over 36,000 ft of detonating cord and 4,512 non-electric delay elements were installed in CDI’s implosion initiation system, some to create the 36 primary implosion sequence and another 216 micro-delays to keep down the detonation overpressure from the 2,728 lb of explosives which would be detonated during the demolition.
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