Emergency management agencies from Washington to Bel Air plan to spend millions of dollars over the next two years to prepare for a mustard agent accident at Aberdeen Proving Ground that has been given a one in 100 million chance of occurring.
Planners say a major release from the proving ground's 40-year-old mustard agent stockpile could occur only if a plane crashed into the three-acre mustard agent storage yard on the Bush River and caused a fire that burned for at least 30 minutes.
Only during a major fire would the deadly chemical warfare agent become hot enough to vaporize.
Although an accident is highly unlikely, authorities are worried that the emergency planning itself could stir up panic and confusion.
The planners acknowledge that it will raise concerns about property values within the 10-kilometer (6.2 mile) "Immediate Response Zone" around the stockpile.
"It's such an emotional issue," says James Terrell, chief of Harford County's Department of Emergency Operations.
Planners will concentrate most of their efforts in the 10-kilometer zone, under the assumption that the mustard agent probably would not travel much farther.
Of the eight chemical agent stockpile sites in the United States ++ for which similar emergency plans are being developed, Aberdeen has the greatest population living and working nearby -- about 50,000.
Terrell's agency is working with the Army, Baltimore and Kent counties, and state and federal emergency planners on the Chemical Stockpile Emergency Preparedness Program. He says planners must find a way to protect residents around the stockpile without panicking them.
Among the efforts planned or considered so far:
* "Over-pressurizing" at least four public school buildings near the stockpile. That means permanently raising the air pressure in Deerfield and Edgewood elementary schools, Edgewood Middle School and Edgewood High School so airborne mustard agent could not enter the buildings.
Filter systems also would be installed in the schools. Terrell and other officials say the change in the air pressure will not be noticeable or harmful.
The pressurized schools could also shelter residents living along Willoughby Beach Road -- an area that officials say would be too hard to evacuate in the event of an accident.
* Teaching residents near the proving ground how to seal a portion of their houses with plastic and other materials. During the Iraqi Scud missile attacks on Israel during the Persian Gulf War, many Israeli families sealed rooms to protect against a chemical attack, which never materialized.
* Installing warning sirens around the stockpile similar to those around nuclear power plants, as well as computer dialing systems to alert many residents by telephone.
* In-home alert devices for blind or deaf residents.
* A plan to alert boaters on Chesapeake Bay and its tributaries.
In addition, representatives of the Army and the emergency agencies are developing a public affairs plan to explain the nature of the mustard agent and why the preparedness effort is necessary.
"I want to demystify mustard," says Gary Holloway, chief of public affairs at the proving ground. "It's not the monster that everyone thinks it is."
Many people mistakenly refer to mustard agent as a gas, thinking any release would cause the chemical to waft into neighboring communities. But most chemical warfare agents, including mustard and nerve agents, are liquids under normal conditions. When a chemical shell or bomb explodes over a battlefield, it spreads the agent in a fine, poisonous mist.
Mustard agent is a syrupy liquid that freezes when the temperature is under 58 degrees. It blisters the skin and eyes and burns the respiratory system. Unlike newer chemical agents, mustard is persistent and can linger in an area for months without breaking down chemically.
In summing up the consequences of a major accident, a 1988 Army report says the "social disruption to the community would be extensive and enduring." Many people would need to be relocated during a cleanup operation, the report says.
Wind and other weather factors would determine where a chemical plume traveled -- either northward into the highly populated Edgewood communities, southward over Chesapeake Bay and the shoreline communities of Kent County, or elsewhere.
Terrell says the emergency plan could cost several million dollars in Harford alone. More money will be spent in neighboring counties, but officials are not yet sure of the total cost.
An Army estimate several years ago put the bill at $11 million. All the money will come from the Army's budget.
Harford County already has received nearly $200,000 in federal funds from the preparedness program to upgrade its emergency communications system and buy cellular phones for all its medic units.
The proving ground's mustard agent stockpile is contained in large steel cylinders stacked in a field several hundred yards from the Bush River.