They are bolted to angle irons that are fastened to the enclosure's walls. Investigators determined that the work plan for dismantling the enclosures required that the construction workers unbolt and remove each roof panel individually. The workers followed this work plan without incident when the first enclosure was dismantled, and they had already removed 7 of the 12 panels from the second enclosure. When the construction workers simultaneously unbolted the remaining five roof panels on the second enclosure, the enclosure's walls flexed and spread, which allowed the roof panels to fall onto the worker inside the enclosure. NFS has reported failures to follow or implement work control programs in several Weekly Summaries.
Some examples follow.
Weekly Summary 99-04 reported that environmental services subcontractor personnel at the Idaho National Engineering Environmental Laboratory removed a caustic storage tank flange and took a sample from the tank without obtaining authorization for the work. The subcontractors were authorized only to erect scaffolding and there were no plans to open the tank or sample its contents. The facility manager directed that facility construction work be placed on hold until facility personnel could verify if there were additional construction work control issues. Investigators determined that because the Broomfield warehouse is off-site and is not a DOE facility, no one implemented the necessary work control programs or safety measures. A Type A Accident Investigation Board Report identified two root causes for the accident.