Chemical find halts Army dig at munitions site

The U.S. Army Corps of Engineers has suspended its search for World War I-era chemical weapons in an affluent Northwest Washington neighborhood after workers discovered an open glass flask containing traces of the chemical agent mustard.

Officials said Wednesday they were halting the excavation while they reviewed safety measures at the site.

The discovery was made last week at a vacant home behind American University’s campus. The school was used as an Army experiment station to develop and test chemical weapons during World War I. Workers disposed of munitions and laboratory glassware by burying them behind the campus.

Corps officials leading a cleanup of the site thought they had cleared the area known as “Pit 3” and in March removed an airtight protective structure from the property, said project manager Dan Noble.

The mustard agent was uncovered just 2 feet below ground level in a test pit workers dug in the backyard of the home, he said. The find was somewhat unexpected.

“We had judged the likelihood of making a discovery like this was low probability, but not zero probability,” Mr. Noble said. “We have a high level of confidence that there was absolutely no public exposure here.”

Air monitors in the area didn’t detect any traces of the mustard agent, he said.

During World War I, mustard gas was used as a weapon to cause blisters, temporary blindness, breathing problems and vomiting. It could be fatal in high enough doses. Depending on the temperature and other factors, mustard can be a liquid, solid or gas, said Todd Beckwith, a Corps project manager.

“The intent during World War I,” Mr. Beckwith said, was that “they were looking at causing casualties, not necessarily deaths.”

Eight workers who were near the substance underwent precautionary medical tests but showed no symptoms or complaints. Mr. Noble said all appear healthy, though additional blood testing is being conducted.

The flask with the mustard agent was taken to Edgewood Arsenal in Maryland.

This is the fourth major dig for munitions and toxic agents over the past 15 years since the burial pits were discovered in Spring Valley, a neighborhood of multimillion-dollar homes. The current excavation began in 2007 at a house between the South Korean ambassador’s residence and the former university president’s home.

Previously, the Corps of Engineers announced it had removed a munition configured to explode that contained the volatile gas arsine, as well as a sealed glass test tube containing a military vomiting agent known as DA. The Corps has not released a full inventory of chemicals removed from the site because of security regulations, Mr. Noble said.

Safety procedures will be reviewed before the excavation continues, he said, and soil in the area must be examined for traces of chemicals. Officials will determine whether a containment structure should be rebuilt at the site.

The Corps also continues to investigate more than 60 pounds of debris and laboratory glassware found behind a building on campus, according to a university memo. Workers plan to drill beneath that building as well.

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