By Bryan Bender, Globe Staff
WASHINGTON -- Potomac River crossings will be closed for the first time since the Civil War. A state-of-the-art network of surveillance cameras and thermal imaging sensors will monitor the enormous crowds. Military units will be on standby to respond to a chemical or biological attack.
And in the event of an emergency, a specially-designed public address system will instruct the millions of expected participants -- as many as one person per three square feet -- how to evacuate.
These are just a few of the unprecedented security measures planned for the inauguration of President-elect Barack Obama on Tuesday, a series of events that are expected to draw the largest number of people ever to the National Mall and pose a litany of security nightmares for the US Secret Service, which has mustered an army of security agents, military personnel, police officers, and intelligence experts to ensure it all goes off without a hitch.
The preparations are designed to prevent a sophisticated strike by foreign or domestic terrorists or a clumsy attempt by a disturbed individual to disrupt the events or target Obama or other dignitaries. But the measures are also intended to mitigate what could be equally dangerous consequences from the more mundane, such as harsh weather conditions or chaos caused by some of the thousands of exuberant -- and possibly inebriated -- witnesses to history.
"This is a public safety Super Bowl," said James Carafano, a homeland security specialist at the Heritage Foundation and a retired Army officer. "Even if we didn't have 9/11 you would have to have a lot of security. The most innocent little problem could cause huge safety issues. A small fire could cause a stampede and people could get trampled. What if a person started firing a gun into the air? When you have a lot of people in a confined space it is difficult to control the flow of traffic."
(There is a history of disruptions at inaugurations.)
The precautions will extend well beyond the nation's capital. Obama plans to arrive in Washington by train Saturday from Philadelphia, making whistle stops along the way in Wilmington, Del. and Baltimore. The rail journey is reminiscent of Abraham Lincoln's inauguration and part of Obama's effort to make the historic occasion accessible to as many Americans as possible.
Yet it also poses its own unique challenges, including the need to monitor nearly 150 miles of track and thousands of onlookers and to protect critical infrastructure such as chemical plants along the route.
Mark Sullivan, chief of the Secret Service, said earlier this week there is no information suggesting the four days of official inaugural activities -- including concerts, balls, the swearing-in on the West front of the US Capitol, and a subsequent parade down Pennsylvania Avenue -- are being targeted for attack.
"We have no credible intelligence to suggest that there is a threat to any of the inaugural events," Sullivan told reporters. "Nevertheless, given its historic nature, its importance to our democratic process, and the large number of people expected to attend, collectively we have endeavored to make this inauguration as safe and secure as possible."
The range of possible threats is daunting for an event that will include most of the top officials -- both outgoing and incoming -- of the US government, celebrities, foreign leaders and diplomats, and as many as three million spectators.
Because the biggest fear is a large-scale terrorist attack, the Pentagon will have on hand specially trained troops to deal with the aftermath of a chemical or biological attack, or radioactive fallout from a so-called "dirty bomb."
As many as 10,000 National Guard members from eight states will help with crowd control and will provide snipers and medical personnel. A total of at least 11,500 military personnel will be participating in some support capacity, according to military officials.
"The military will be on high alert," said Lieutenant Commander Gary Ross, a spokesman for the US Northern Command in Colorado, which is responsible for defending American territory.
There is also the prospect, far more likely according to some authorities, that a home-grown extremist group or individual will try to disrupt the swearing-in of the first African-American president.
"We're also looking at the possibility of a lone wolf," Michael Chertoff, the secretary of homeland security, told reporters recently. "And that doesn't necessarily have to be a terrorist from al Qaeda. It can be a right-wing, crazy nut who decides that they because of racism or some other reason they want to carry out an attack."
And of course there is the Secret Service's primary responsibility of protecting Obama.
The agency announced on Wednesday that it plans to roll out a new armored limousine for Obama that is described as "the most technologically advanced protection vehicle in the world."
The Secret Service also plans to screen every single onlooker -- as many as 350,000 -- expected along the parade route from the US Capitol to the White House. The Coast Guard, meanwhile, will patrol the Potomac and the adjacent Anacostia River, while military aircraft patrol the skies.
In one of the most controversial security measures, the Secret Service has decided to close to traffic all the bridges into downtown Washington from neighboring Virginia -- although complaints forced the agency to backtrack and allow pedestrians to cross into the District of Columbia.
Another possible, if unintended, threat is posed by the hundreds of thousands of young people expected to descend on Washington this weekend to celebrate Obama's victory, which was made possible, in large part, by their dogged efforts.
In a controversial decision, the Washington, D.C., City Council voted to keep bars open until 4 a.m., a move intended to boost local business and contribute to the celebratory atmosphere, but one that means extra headaches for police. In addition to the city's 4,000-strong Metropolitan Police, 4,000 more officers from other jurisdictions are being brought in as back-up.
About Political Intelligence
Glen Johnson is Politics Editor at boston.com and lead blogger for "Political Intelligence." He moved to Massachusetts in the fourth grade, and has covered local, state, and national politics for over 25 years. E-mail him at email@example.com. Follow him on Twitter @globeglen.