UPDATE: Power began coming back along Boylston Street and Commonwealth Avenue around 9 a.m.; BPD was maintaining officers in the area just in case.
The Back Bay and parts of the South End and Fenway went dark again overnight in its second major blackout in a little more than a year, when an underground cable feeding the Scotia Street substation failed around 3:15 a.m.
That's the same substation at which a transformer exploded last March. NStar Electric President Craig Hallstrom said one of the transformers was offline for repairs related to that explosion, leaving no back up when the supply to the second unit died, cutting power to 12,000 customers.
Hallstrom said residential areas could see power back on before noon thanks to underground connections to other parts of the NStar grid installed after the explosion. Commercial areas could come back online shortly after. But he warned of smaller scale outages throughout the day - and said the company will have to shut the entire area again for three to four hours tonight to make final repairs.
"By 5 in the morning, plus or minus, things will be back to normal," he said.
State Police shut the turnpike in both directions at the Pru around 8:30 a.m.
Kyle Katz reports the power went out in the Fenway at 3:15 a.m.
Saint Botolph power reliability is the sole reason I upgraded my UPC.