The new BRAC federal office building overlooking I-395 in Alexandria. An internal Pentagon study says the building is highly vulnerable to the type of truck bombs used by terrorists against other U.S. government buildings. (Tom Jackman/The Washington Post)

And the results are quite horrifying.

Time magazine obtained the Pentagon’s internal blast study, which used blast sizes from other terrorist attacks, such as Oklahoma City in 1995, Beirut in 1983 and Khobar Towers in Saudi Arabia in 1996. “Several of the studies show the Mark Center would essentially be wiped out,” reporter Mark Benjamin wrote. “Some scenarios show almost the entire 6,400-worker facility bathed in red, indicating areas with: ‘Many serious injuries and many fatalities in outer offices.’”

Those 6,400 federal employees began gradually moving last month into the site at Seminary Road and I-395 as part of the Pentagon’s Base Realignment and Closure (BRAC) moves.

An antiterrorism official apparently leaked the report to Time after the Pentagon made no response to the warnings. Some Defense Department officials question why the BRAC building was built there and why it has so little security, Benjamin reports.

He also says the Project on Government Oversight warned then-Defense Secretary Robert Gates in April that a truck bomb “could easily be detonated in close proximity to the proposed new building,” but the Pentagon didn’t answer. The Pentagon also didn’t respond to Time’s recent inquiries. It’s not clear if this is the same report that was accidentally posted briefly on the Internet by the Army Corps of Engineers in April, but Benjamin’s story has far more scary details.

Peter Stockton of the Project on Government Oversight told Benjamin, ”Depending on the size of the bomb and the location of the detonation, the whole building could be brought down.”

Sit down before you read the rest of the story here.