The events of Sept. 11, 2001, were a sobering reminder to the world's last standing military superpower that even the United States was not invulnerable to outside attack.

After the twin towers fell, and a chunk of the Pentagon lay in smoldering ruins, government-run institutions across the country tightened and re-evaluated security in light of the threat of terrorism -- including some in the Mid-Columbia.

Because of the 9/11 attacks, public tours ceased at places such as Hanford and the Umatilla Chemical Depot, and the cars no longer were allowed to use the region's dams as crossing points over the Snake and Columbia rivers.

Some of those restrictions have been eased, but those in charge of making sure terrorists don't gain access to hazardous materials or vital infrastructure remain vigilant.

Tri-Cities Airport

Travelers who flew in the months following the attacks walked into airports -- including the Tri-Cities Airport in Pasco -- and saw armed National Guard troops protecting airports until the Transportation Security Administration was created and took over airport security in 2002.

Passengers have been subjected to tighter and tighter rules during the past decade, from more strict baggage screening and rules for what can be carried on to a plane, to the controversial full-body scanners now being used across the country. Travelers flying out of Pasco paid higher parking fees to offset the cost of security measures, Herald archives show.

Despite the restrictions and many Americans' anxiety about air travel, the Pasco airport saw a then-record number of boardings in 2002. The number of passengers has continued to grow.

The airport also underwent a nearly $1 million lobby expansion in 2003-2004 to accommodate machines that could screen for explosives behind ticket counters. The screening area is set to be expanded again in 2013 to make room for the growing number of passengers using the airport -- and the increased number of TSA screeners who must be hired.

Dams

The Army Corps of Engineers immediately stopped allowing public crossings via the Lower Snake River dams because of 9/11.

"These closures were in response to the tragic events of Sept. 11, 2001, and those threats to our national security," said Corps spokesman Bruce Henrickson. "Later, as we gained more situational awareness and as part of our service to the public, we were able to reopen dam crossings to the public on a limited basis under tighter security restrictions."

The first dam to re-open was the Lower Granite Dam in December 2004, later followed by Little Goose Dam in August 2005 and Lower Monumental Dam in June 2006.

Significant security measures were added to all the dams. Some never re-opened because they weren't necessary for river crossings, Henrickson said.

The Corps only recently re-opened the Washington Fish View Room at McNary Lock and Dam for public viewing.

Public access to the north shore fish viewing room and navigation lock has been limited since 9/11, other than occasional educational tours led by park rangers.

Umatilla depot

Monthly public bus tours of the Umatilla Chemical Depot stopped after 9/11 and have not resumed.

Depot spokesman Jim Hackett said bus tours had been part of a strategy to help ease people's minds about the activities at the depot and that chemical weapons were being stored and disposed of safely.

The depot also staged an Armed Forces Day celebration each May. Hackett said it was a popular community event, but it also was discontinued after 9/11.

"That's one thing the community probably misses more than anything else," he said.

The depot does hold occasional public events -- such as ceremonies for a change in command -- but nothing like what was offered before 9/11, Hackett said.

Hanford

Public bus tours of Hanford also stopped from 2001 until 2004, but when they resumed they went gangbusters.

Department of Energy spokesman Geoff Tyree told the Herald demand has grown for tours of the nuclear site, and tours were added each year from 2004 -- when just four tours were offered -- through 2009, when 60 tours were available.

Tours often fill up within minutes of reservations opening.

Tyree noted the increase in tours does not represent a change in security posture. It's as tight as ever, he said.

"We've grown the tour program in order to provide more people with a look at what we're doing, and we're responding to a continued and growing demand for tours," Tyree said.

PNNL

The Pacific Northwest National Laboratory in Richland has made changes to enhance security during the decade since 9/11.

"Our lab is different (from other national labs) in that it doesn't have fences and guard shacks," said PNNL spokesperson Geoff Harvey. "But heightened security since 9/11 has us enabled to do things to improve our security here."

Existing call stations, or poles, placed around the campus so people can quickly summon help now have security cameras on them.

"So the campus is wired for visual surveillance," Harvey said.

And PNNL now has an emergency notification system that makes it possible to have a campus-wide lockdown, if needed.

Harvey said less obvious security upgrades include having all the security people trained as first responders, putting automatic electronic defibrillators in all the vehicles, and placing security signs with phone numbers on PNNL security vehicles.

"Security is much more visible now, and people seem to feel more secure with a visible police presence. It is more welcomed and accepted," Harvey said.

Part of the additional security effort is related to 9/11, but some could be attributed to shooting violence at Virgina Tech and similar outbreaks of violence in the past decade, Harvey said.

Columbia Generating Station

Energy Northwest spokeswoman Rochelle Olson said security always was important for nuclear power plants, but the company did add some measures at the Columbia Generating Station in Richland post-9/11.

"The U.S. Nuclear Regulatory Commission holds nuclear power plants to the highest security standards of any American industry, and we exceed those standards," Olson said. "Nuclear plants are widely acknowledged to be the best-defended facilities among the nation's critical infrastructure."

In the past decade, Energy Northwest has increased security staffing at the power plant, extended and fortified security perimeters, increased patrols within security zones, installed barriers to protect against unauthorized vehicle access, installed high-tech surveillance and detection equipment, and enhanced local and federal law enforcement agreements and interfaces, Olson said.