LOS ALAMOS, N.M. — 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.