The Aug. 14th blackout, which was the worst in North American history, cost New York City’s economy as much as $1 billion, according to a recently released report by Mayor Michael Bloomberg.

The power outage, which left thousands of New Yorkers stranded in the heat, put a spotlight on serious problems with New York City’s emergency preparedness and showed the flaws of the 9-1-1 emergency call system, the report says.

The report faults Verizon Communications, Inc. for its role in problems with the 9-1-1 telephone system that New York City’s 8.4 million residents rely on to report fires, crimes, accidents, and other emergencies.

Many private companies and city agencies also lacked back-up generators, which led to problems evacuating workers. Tenants in high-rise apartment buildings had no drinkable water.

The city’s hospitals also suffered during the blackout, with a handful losing power in “certain functional areas,” the report says. Some hospitals were overwhelmed by people needing non-emergency prescriptions because drugstores were closed.