With hurricane season facing U.S. businesses, AT&T completed its latest in a series of regular tests of the carrier’s ability to respond quickly to natural disasters and major outages.

AT&T ran a network disaster recovery exercise outside Washington D.C. on June 7 and 8. AT&T conducts these exercises four times per year in different cities around the country.

In these exercises, AT&T simulates large-scale disasters and network service disruptions, and then the carrier’s employees work to restore communications to customers as quickly as possible.

The Washington, D.C. area exercise featured 24 trailers, which house network equipment that mimics the technology in a central office switch. Forty AT&T employees participated in the exercise.

"We can duplicate any of our central offices in the trailers," says Ken Smith, director of operations for AT&T’s network disaster recovery team. "We keep off-site copies of all software configurations as well as the engineering piece in centralized repositories."

AT&T officials wouldn’t say how much the Washington D.C. exercise cost. However, AT&T says it has invested $300 million in its network disaster recovery program during the last 10 years. The program includes specially trained managers, engineers and technicians from across the United States as well as a fleet of more than 150 equipment trailers and support vehicles that can support voice and data communications.

AT&T says its network disaster recovery team has been activated 21 times since 1990, including responding to the September 11, 2001 terrorist attacks in New York as well as last year’s Hurricane Katrina in Louisiana and Mississippi.

AT&T officials said they have refined their disaster response efforts after each incident. For example, the September 11 terrorist attacks were the first time that AT&T’s network disaster recovery team was unable to fly into the region involved in the disaster.

"Until 9/11, we made the assumption that whatever disaster we faced we could fly people in from all over the U.S.," Smith says. ``Another thing that’s changed for us since 9/11 is that we learned an environment with a destroyed central office will not necessarily be a clean office. It could have anthrax in there. So now we have a fully functional hazmat team. We fill our own air tanks. We don’t clean up the office, but we can go into a condition and do telephone-level work."