Norfolk, Va. - The Norfolk Fire Marshal Office has released its final report on the explosion that rocked the Selden Arcade on April 17th, 2015.
The blast occurred at 7:58pm and heavily damaged the building.
Investigators found that the origin of the explosion came from outside the building in the main 208 volt power feed to the building's electrical power switch room.
A contractor had struck that line at 10:14am that morning.
According to the report, the contractor strike damaged the line, starting a chain of events that led to the catastrophic failure of the electrical system, which caused severe arching and an explosion, also referred to as an arc blast.
The gasses produced by the failing and overheating electrical system traveled into the building's switch room and built up to explosive levels. 9 1/2 hours later at 7:55pm the cables in the conduit failed completely, creating temperatures in the conduit over 2,000 degrees Farenheit. This melted the copper in the wires and pushed superheated gas into the switch room where it ignited the gases that had been building up.
The fire in the room lasted only a few seconds and did not trigger the sprinklers in the area, the report says.