More than 60 years after scientists assembled the nuclear bombs dropped on Hiroshima and Nagasaki, lethal waste is seeping from mountain burial sites and moving toward aquifers, springs and streams that provide water to 250,000 residents of northern New Mexico.
Isolated on a high plateau, the Los Alamos National Laboratory seemed an ideal place to store a bomb factory's deadly debris. But the heavily fractured mountains haven't contained the waste, some of which has trickled down hundreds of feet to the edge of the Rio Grande, one of the most important water sources in the Southwest.
So far, the level of contamination in the Rio Grande has not been high enough to raise health concerns. But the monitoring of runoff in canyons that drain into the river has found unsafe concentrations of organic compounds such as perchlorate, an ingredient in rocket propellent, and various radioactive byproducts of nuclear fission.
Laboratory officials insist that the waste doesn't jeopardize people's health because even when storm water rushing down a canyon stirs up highly contaminated sediment, it is soon diluted or trapped in canyon bottoms, where it can be excavated and hauled away.
"We are seeing no human or ecological risk," said Danny Katzman, director of the lab's water stewardship program. "We won't be surprised on occasion to see a higher than normal reading. But those higher values last for 40 minutes during a flood, and maybe two hours out of a year."
Much surface contamination, however, becomes embedded in sediment or moves down into groundwater. That subterranean migration poses the greatest long-term danger to drinking-water wells and ultimately the Rio Grande.
"When you see a child's footprints and Tonka toys in canyons where there is plutonium, there is reason to believe that a lot more work needs to be done to make the environment safe," said Ron Curry, secretary of the New Mexico Environment Department.
In 2002, the department issued an extensive cleanup order stating that waste at Los Alamos may pose "an imminent and substantial endangerment to human health and the environment." Laboratory officials accused the department of exaggerating the threat and resisted the order for several years before agreeing to a revised plan to scrub about 2,000 dirty sites by 2015.
As part of that effort, about 300 monitoring wells and gauges have been installed. Contaminated soil is being removed from canyon bottoms. Wetlands are being planted and small dams built to arrest the flow of polluted storm water. In the summer, the lab began loading some of its hottest radioactive waste into sealed containers by remote control and trucking it to a federal underground storage facility in Carlsbad, N.M.
Ambitious as it is, the plan deals with surface sites, not tainted aquifers. About 18 million cubic feet of waste is sequestered at Los Alamos. No one knows how it is slipping through scrambled layers of rock described by Katzman as "unbelievably complex geology."
Moreover, scientists at Los Alamos say they haven't determined where all of the waste was buried across the laboratory's 40-square-mile property. And they acknowledge that some of the monitoring wells used to measure contamination in deep groundwater may have failed to detect certain radioactive isotopes.
Adding to the uncertainty, a draft report released last summer by the Centers for Disease Control and Prevention said that the lab may have substantially underreported the extent of plutonium and tritium released into the environment since the 1940s.
More recently, the state Environment Department reported finding DEHP, an organic compound used in plastics and explosives, at 12 times the safe exposure level in an aquifer that supplies drinking water to Los Alamos and the nearby community of White Rock. The U.S. Environmental Protection Agency classifies DEHP as a probable human carcinogen also capable of harming reproductive systems.
In another surprise, water from a broken main flushed out buried waste near an old plutonium processing plant last year and pushed it beyond the largest dam built to stop the spread of contamination. Analysis of sediment by the U.S. Department of Energy's Oversight Bureau revealed "the highest concentrations [of plutonium] the bureau has ever recorded for this medium."
One of the canyons where radioactive waste has been found joins the Rio Grande just three miles above a diversion project the city of Santa Fe is building to capture nearly 3 billion gallons of water annually from the river. The $200-million project, scheduled to start operating in two years, is being designed to screen out and treat contaminated water. But not all radioactive isotopes are easily treatable. Tritium, which has been detected near the Rio Grande, bonds with water.
The directors of the diversion project -- while publicly expressing their confidence in the treatment system -- have been quietly urging the laboratory to do more to stop waste from moving toward the river.
George Rael, assistant manager of environmental operations at the lab, said it would cost as much as $13 billion to remove all accessible contamination. Even if there were enough money available, exhuming the waste could put more people at risk than leaving it alone -- at least in the short run.
"Some of the waste offers quite a challenge," said David McInroy, director of the lab's corrective action program. Digging it up, he said, could expose workers and others to a toxic cloud of debris. If left in place, it might turn up years later in groundwater.
With a population of more than 12,000, Los Alamos today is a far different place than it was in 1943 when the secret weapons complex was known as "Site Y."
The lab conducts climate-change research, screens AIDS vaccines, evaluates new tests for breast cancer and analyzes biological pathogens. Yet most of its budget still goes toward national defense. Los Alamos is the nation's sole manufacturer of plutonium pits, the triggers for nuclear weapons, and it continues to produce toxic waste.
Many residents of Los Alamos have become inured to the hazards of their environment. They hike and picnic in canyons dotted with toxic hot spots.
Just north of Los Alamos, the Santa Clara Pueblo recently installed air monitors that confirmed fears that the wind carries radioactive dust.
Joseph Chavarria, head of Santa Clara's environmental affairs department, said dust settles on the ground after it rains and contaminants are absorbed by edible plants. He said even potters are at risk: "When we make pottery, we test the texture of the clay by putting it in our mouths."
Pueblo officials would not reveal the levels of contamination detected by the air monitors. "I can say they were high enough to raise concerns about the future," said Santa Clara Gov. Walter Dasheno. "It made me think it might not always be safe to live here."