808 Columbus Avenue report of investigation February 15, 2008

In the evening on July 25, 2007, a 30-foot long segment of a sheeting system collapsed at the construction site of 808 Columbus Avenue, Manhattan. The sheeting had been installed to prevent soil movement and to protect the foundations of adjacent buildings. The building nearest the collapse was 784 Columbus Avenue, a 16-story, 287-unit apartment building. Following the assessment and immediate stabilization measures, the majority of the residents of 784 Columbus were permitted to reoccupy their apartments in the early morning hours of July 26, 2007. The Department of Building's Forensic Engineering Unit led this investigation to ascertain the cause of the sheeting failure. The Department was assisted by Stephen Young, P.E., and Dr. Chris Snee, C Eng, CPG, from Arup Engineering, an internationally renowned engineering firm. The Forensic Engineering Unit was represented by Dan Eschenasy, P.E. The investigation concluded that the segment of sheeting system that collapsed was erected on top of a highly weathered (fractured) weak rock formation, and not on the competent rock indicated on the design drawings.