Chemical, Biological Threats Pose New Design Challenges
March 25, 2002
Appeared in Engineering News-Record
Simple measures that can protect the inhabitants of a building or users of critical infrastructure from chemical and biological attack are becoming routine since the Sept. 11 terrorist attacks and the subsequent anthrax outbreaks. Many building owners and developers are demanding that design criteria for their projects include security master plans. And those in charge of protecting infrastructure are working out protocols to protect water, wastewater and other systems. These include risk assessments to determine how much security is truly needed.
Threat and vulnerability assessments analyze everything as a system, not just "what can be done to protect," contends Keith Henson, director of security services for Lockwood Greene, Spartanburg, S.C. "We start at the basics to determine what the asset is and what the threat is." An office building is a higher risk, for example, if corporate officers are there regularly.
The U.S. Army Corps of Engineers is charged with protecting the armed forces, including civilian employees, from chemical, biological and nuclear attacks in military buildings. Each military installation is responsible for designing its own buildings.
The Corps' Construction and Engineering Research Laboratory in Champaign, Ill., is developing a software tool to ensure that architects can understand the threats and design buildings to a certain threshold of protection. "The software will include ‘wizards' that will allow users to evaluate such complicated issues as computational fluid dynamics without knowing what that is," says Jim Miller, a mechanical engineer at the lab.
The Corps expects the software to familiarize designers with various materials as well. Some building materials are almost impossible to clean, for example, while others only need to be wiped down. Other high-tech materials, such as carpet that can neutralize contaminants, are under investigation.
The laboratory is participating in a program run by the Defense Advance Research Program Agency to develop buildings that are immune to chemical, biological and radiological attacks. "The thrust is to develop and demonstrate technologies that actively resist attacks," says Miller. They will test various response modes such as filtration and neutralization.
The Corps is also looking at how best to protect water treatment infrastructure. Plans include development of dynamic models of distribution systems that could tell officials how long they have before a biolgical agent reaches a critical facility.
More importantly, the model helps officials identify all access points to the system, says Vincent Hock, the Corps' project leader for infrastructure. Water towers, well heads, manholes and fire hydrants are not typically secure, and are considered the most vulnerable points of a water system. "Preventing physical access is most important," he says.
Many public utilities are not waiting for government directives. In February, the Metropolitan Water District of Southern California (MWD) authorized $5.5 million for additional protection of its facilities and drinking water supplies. The district will upgrade its automated, remote water-quality sampling and analytical capabilities, as well as purchase additional contaminant monitoring equipment and instrumentation and beef up physical security at water filtration plants.
"We asked the board to authorize this expenditure now, rather than wait for the passage of one of several federal and state bills on security measures that may provide funding for increased security costs for water agencies," says Ronald R. Gastelum, MWD's CEO. "While we hope for eventual reimbursement, we spend this money on critical security programs with no regrets."
One advantage of U.S. systems is that they still chlorinate water to disinfect it. "It is one of the single most effective killers of bioactivity," says Hock. Super chlorinating is a low-tech way and easy way to kill biological agents.
Dilution keeps chemical contamination from being much of a threat to water systems. "It's difficult to add enough of a chemical contaminant to be a threat," says Ed Wetzel, vice president of Montgomery Watson Harza, Pasadena, Calif. However, there is no way to guarantee that a water system is 100% safe, he says. As with buildings, the beginning point for protection is assessing the vulnerability of the system.
The U.S. Dept. of Energy's Sandia Laboratory in New Mexico has developed risk assessment methodology for dams, transmission systems and water systems. Company executives are trained and certified by the lab. "We think it gives us a leg up," says Wetzel, especially since Congress is considering requiring all public agencies to assess vulnerability using the Sandia methods.
The most fundamental method of reducing risk to water systems is deterrence, stresses Wetzel. "It's important to slow intruders down enough to give the response team time to catch them before they do something," he says.
MWH has formed an alliance with McLean, Va.-based research and engineering consultant Science Applications International Corp. to help its clients with such deterrents. "SAIC knows which systems to put in, and we know how to install them in water facilities," Wetzel says.
For buildings, Henson lists four basic methods of protecting assets: modifying daily routines of building facilities and maintenance personnel; changing the security force; installing physical barriers; and adding electronic surveillance systems. "The simplest protection from any threat is distance," he says.
Obvious measures, such as moving an air intake from ground level to the roof to make access more difficult or locating a "sensitive" building in the most secure area of a campus, are usually the least expensive.
But the most obvious measures are not always the best. The American Society of Heating, Refrigerating and Air-Conditioning Engineers Inc., Atlanta, concerned about opportunists pushing their wares, issued an eight-page "initial" directive in January that cautions against taking action without proper counsel (ENR 1/21 p. 12).
"We have to take time to figure out if [owners] need to do anything different to operate their buildings as safely as possible," said William J. Coad, ASHRAE president, at the organization's winter meeting in Atlantic City, N.J.
For existing buildings, ASHRAE recommends that owners first familiarize themselves with their buildings and building systems. They should then check that the building is performing as intended. Finally, they should not make any changes without understanding the consequences. The ASHRAE report counsels not to "close outdoor air intake dampers or otherwise block ventilation paths...change the designed airflow patterns or quantities; and...modify the fire protection and life safety systems without approval of the local fire marshal."
Mechanical engineers caution building owners that changing things in an existing building might solve one problem while creating another. For example, roof air intakes may be more difficult to reach than street-level intakes, but they are not intruder-proof either and must be guarded or secured against biohazards. Additionally, closing off air intakes can reduce a system's ability to purge contaminants.
Components and systems that should be studied go beyond the heating, ven-tilating and air conditioning, says ASHRAE. Areas of refuge, building shell and duct tightness, and fire protection and safety should also be considered. The organization also advises owners to develop a preparedness plan for "extraordinary incidents" against the building.
In advising that doing nothing may be the best course, ASHRAE is primarily addressing commercial building owners. For more specialized building types, such as laboratories that house chemical and biological agents, designers are adding more security than ever.
The 350,000-sq-ft emerging virus laboratory at the Centers for Disease Control and Prevention in Atlanta, likely to contain the most dangerous pathogens, will be protected by its location, says George Chandler, CDC's facilities planning officer. "We have a setback zone for certain buildings, away from pedestrian routes and roads," he says.
But the laboratory's campus master plan, developed long before Sept. 11, already had addressed security, Chandler says. "It didn't take the World Trade Center; Oklahoma City was enough," he says, referring to the 1995 bombing of the Alfred P. Murrah Federal Building. Besides setbacks, CDC looked at such protective measures as guard post and security camera placement and safety windows.
High-risk buildings require expensive protection from chemical or biological agents, such as duplicate security command posts and sophisticated heating, ventilation and air-conditioning systems with negative or positive pressure. But simpler measures can protect lower-risk buildings. Two examples are moving the mailroom off site or installing a stand-alone HVAC system. Taking security to the next level would mean adding a negatively pressurized duct system to suck harmful agents into a filtering system, say engineers.
Other vulnerable areas, such as building lobbies, also could be equipped with stand-alone HVAC systems that do not recirculate return air through the entire building. "The cost…becomes acceptable if it limits the disruption of the building," says Terry Gillick, vice president of technology, Syska Hennessy Group, New York City.
Most biological agents are between one and five microns in diameter. Anthrax, for example, is 2.5 microns. High-efficiency particle air (HEPA) filters in HVAC systems will filter out particles down to 0.3 microns. "That's very expensive, and the units must be oversized to get enough air flow," says Gillick.
Expense generally limits HEPA use to high-security federal facilities. Health- care facilities often install prefilters and use HEPA units as a final filtration system.
The U.S. State Dept.'s specifications mandate 100% filtration of the air in U.S. embassies overseas for chemical and biological agents. That added measure of security adds at least 5% to ventilation system costs, says Gillick. Ultraviolet-C emitters can destroy bacteria in ductwork, but the technology is not yet widely available. By and large, HVAC system protections are low-tech, "but the threat is complex," says Gillick. Most systems cannot give early warning of contamination. "It's a problem the military has grappled with," he says. There are systems, but they are large and cumbersome and hard to deploy.
Not everyone agrees that protecting buildings and infrastructure is worth the effort. "Terrorists are more likely to look at food or beverage distribution for raw casualties," says Eric Croddy, senior research associate at the Monterey Institute of International Studies, Monterey, Calif. Equipping hospitals with rapid diagnoses and detection will save more lives than building fortresses, he says. "Castles never held out anyone that wanted in badly enough," Croddy adds.