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The Boston Globe

Metro

NStar report cannot find a blackout cause

But human error absolved

An independent forensic engineering firm hired by NStar could not determine the under­lying cause of a catastrophic power failure in March that plunged the Back Bay and other Boston neighborhoods into darkness, according to a 220-page report commissioned by the electric utility.

The report by RTI Group detailed an investigation of a massive fire at the Scotia Street substation that ultimately cut electricity to 21,790 NStar customers. To help compile the report, engineers examined tons of twisted metal and melted wire removed from the site of the blaze in 17 red dumpsters and hauled to an industrial area in South Boston.

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