It was the back yard that sold Christine Dieterich on the yellow brick Cape Cod on Glenbrook Road. She fell in love with the terraced gardens, pictured her children racing around outside and traversing the little bridge across a creek into the woods.

“It seemed idyllic,” Dieterich says.

She and her husband, Rogerio Zandamela, paid $1.5 million for the six-bedroom house in Spring Valley, an affluent neighborhood nestled in the far northwest corner of DC. They moved in in 2009.

Then one afternoon in late March 2010, Dieterich rounded the corner onto Glenbrook on her way home from work and found the street blocked by TV news trucks, cameras, and reporters. Army engineers excavating a yard across from hers had unearthed a rusty metal drum seven feet down that held a cache of glass bottles. Workers had noticed the ground smoking around the drum. White vapor was escaping from one of the bottles inside. They sealed off the site and tested the contents of the bottles.

“We found out the white vapor was arsenic trichloride,” Dieterich says. “That was our first piece of bad news.”

Arsenic-trichloride vapors can be lethal when inhaled. The Army Corps of Engineers, which was in charge of the dig, knew there might be toxic chemicals in the ground, but it wasn’t prepared for arsenic trichloride.

Neither was Christine Dieterich.

She knew that the campus of American University, just a block away, had been the site of chemical-weapons testing from 1917 to 1920. But the Army Corps had sent her a letter explaining the history and its current cleanup project. It said her property was safe.

What the Army failed to state explicitly was that Dieterich and her neighbors were living yards away from the first military Superfund site in a residential urban area, where the Army is actively searching for bombs and poisonous chemicals.

The 1918 picture showing Sergeant Charles Maurer at “the hole called Hades.” Photograph courtesy of the Army Corps of Engineers.

The Corps has been trying for years to pinpoint the location of a waste pit pictured in a grainy 1918 photograph. Sergeant Charles Maurer, shown standing over the pit, wrote on the back: “The most feared and respected place on the grounds. The bottles are full of mustard, to be destroyed here. In Death Valley. The hole called Hades.”

The Corps now believes that it has found “the hole called Hades”—directly across the street from Christine Dieterich’s home.

This past November, she watched from her kitchen as Army contractors tore down the three-story brick house at 4825 Glenbrook. The Corps will spend an estimated $12 million to excavate and restore the site. The dig could last into 2014.

“We are anticipating we will find additional lewisite in the soil under the house,” Army Corps project manager Brenda Barber says. Lewisite, made with arsenic, was perhaps the most toxic of the poisons tested on the AU campus. It was called “the dew of death” because a single drop could be lethal. Bombs with lewisite were on their way to Europe when World War I ended.

Dieterich has two children, ages five and one. She asked the Army to relocate her family until the digging was done, but her request was denied. “The Army assured us it would take care of my family if we were in harm’s way,” she says. “I should have asked more questions.”

The Corps has told Dieterich and her neighbors that its elaborate tenting system will protect them from any poisons. It plans to set up sensors that will trigger sirens if poison gases escape into the air.

“How can they expect me to have peace of mind and have my children play in the front yard while they are digging for chemical-warfare agents 20 feet away?” she asks. “I wake up at 3 am in a cold sweat. My children won’t be safe in their own home.”

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With its tall trees and stately homes—which sell for upward of $4 million—Spring Valley is one of DC’s most prestigious neighborhoods. Richard Nixon, Lyndon Johnson, and George H.W. Bush all lived there. Attorney General Eric Holder makes his home there now, as do TV anchor Jim Vance and attorney Brendan Sullivan.

But in 1918, when the US was fighting in the trenches of Europe, Spring Valley was fields and farms. American University, atop the hill at Ward Circle, was a small, struggling college. The military, facing chemical weapons for the first time, leased property from the university to establish labs and testing sites. It summoned more than 1,000 chemical-weapons researchers to mix poisons and test the substances’ killing potential at the American University Experimental Station. They lobbed mortars from the edge of AU down toward what’s now Dalecarlia Reservoir.

In 1920, two years after the armistice, the government closed down the project but didn’t clean up the land. Soldiers dug pits just beyond the edge of the campus and buried artillery shells and glass jugs full of lethal compounds. According to the Corps, they didn’t keep records of the disposals.

From the 1920s on, developers bought up the property, carved roads, and built homes. The Army and American University kept the neighborhood’s toxic past secret. It wasn’t until 1993—when workers digging a utility trench not far from Dieterich’s home struck bombs—that Spring Valley’s chemical-warfare history became public.

Since then, the Army Corps has spent $221 million to clean up what it calls the Spring Valley Formerly Used Defense Site. The project has been the subject of hearings before Congress and the DC Council. Having found arsenic in the ground, the Corps has carted away thousands of tons of soil, and it’s still testing for more toxic waste. The Corps has drilled 53 wells in Spring Valley and found arsenic as well as perchlorate, a component of rocket fuel, in the ground water.

• • •

Twenty years after the first bombs were found, what do we know?

It’s clear that contamination is not widespread over Spring Valley’s entire 660 acres. The majority of homes in the neighborhood haven’t been affected by the chemical testing, and the Army has removed contaminated soil at many others. Real-estate values have remained strong. Most residents would prefer that Spring Valley’s toxic past recede, but it remains immediate and relevant.

Using archival maps and satellite images, historical records, geophysical probes, and ground-penetrating radar, the Corps has identified specific waste pits, testing trenches, and pathways from the firing range. It has dug up more than 1,000 munitions, most empty, some still intact with toxic agents. It has destroyed hundreds of munitions in a detonation chamber on federal property between Sibley Hospital and Dalecarlia Reservoir.

Have the buried poisons made Spring Valley residents sick?

Two surveys of the entire neighborhood have found no elevated incidence of cancers. But because the contamination affected specific streets and groups of houses built over known trenches and dumps, many residents believe that surveys encompassing all of Spring Valley are too diffuse and not conclusive.

“We need an independent assessment by the National Academy of Sciences,” says Nan Wells, a biologist who represents Spring Valley on the Advisory Neighborhood Commission. “It’s important that we have experts review the studies.”

Johns Hopkins Bloomberg School of Public Health is close to finishing a survey, but it’s using entire Zip codes to compare the health of Spring Valley residents with that of Chevy Chase DC residents.

“We are not going to have any definitive information on actual cases,” says Mary Fox, the survey’s principal investigator. “We understand the frustration of the Spring Valley community. We are not going to be able to give them all the answers they are looking for.”

The best attempt at providing answers came from a 2004 survey of a 345-house “epicenter” of Spring Valley by Charles Bermpohl, a staff writer for the Northwest Current, a weekly paper that covers Spring Valley. Bermpohl found 160 cases of “chronic, often life-threatening and rare diseases.”

Bermpohl’s research found an alarming number of diseases, but experts have criticized the findings as anecdotal and unscientific. Bailus Walker, professor of environmental and occupational medicine and toxicology at Howard University, chaired a panel that studied Spring Valley for the District. “One of the most difficult things we faced was trying to determine if there were health effects, who was exposed, to what chemicals, how much, and for how long,” says Walker. “We were never able to get a handle on that. We did not see a cluster of cancers of the same organ system in the community.”

Kent Slowinski, an activist and Advisory Neighborhood Commissioner who worked with Bermpohl, says the research is “just the tip of the iceberg. It warrants further investigation.”

Two things have become clear in the 20 years of testing and turmoil: It’s nearly impossible to prove a direct connection between the toxic chemicals and a specific disease. And the laws are stacked against residents who attempt to use the legal system as a recourse, especially when the government is charged with creating the pollution.

Ask Camille Saum, who grew up on Sedgwick Street. She has been diagnosed with pernicious anemia—a rare and debilitating blood disorder—kidney disease, and lupus. She believes all of these conditions were triggered by an immune system weakened by toxic chemicals such as arsenic. She sued the Army to no avail.

“I don’t think the government treated me or anyone else well,” says Saum. “Look at all the people who died. I’m one of the lucky ones. At least I am alive.”