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Toxic legacy

A Cold War-era landfill may threaten Albuquerque's aquifer

 

ALBUQUERQUE, NEW MEXICO - Just south of Albuquerque on Kirtland Air Force Base lie 30 years' worth of canisters, boxes and even plastic bags, summarily dumped into unlined trenches by Sandia National Laboratories during nuclear weapons research. 

This mixed waste landfill, loaded with 100,000 cubic feet of "low-level" radioactive and hazardous waste, was once out in the middle of nowhere, but now the city of Albuquerque is growing rapidly in its direction. A new 90,000-resident development, Mesa del Sol, is going in west of the Air Force base. 

Even as the city creeps toward the dump, some of the toxic substances in the dump may be creeping toward the Albuquerque Aquifer, currently the city's sole source of drinking water. Sandia and the state regulatory agency have struggled to figure out a safe and legal way to keep that from happening. 

The area's burgeoning growth has depleted the aquifer, sinking it 180 feet. By next year a new water project, the San Juan-Chama diversion, should supply 90 percent of Albuquerque's water, but the aquifer will continue to be an important source for the growing city. 

The toxic wastes in the landfill, closed in 1988, include tritium, plutonium and other transuranics, volatile solvents, and some 270,000 gallons of nuclear reactor water. Tritium (radioactive hydrogen) has been detected less than 100 feet below the landfill; it's the most mobile form of waste, and Sandia officials believe the other contaminants have not gone as deep. 

Removing the containers of waste, many of which are broken and leaking, would cost about three-quarters of a billion dollars and endanger workers, according to the lab. And no approved "disposal pathway" exists for some of the waste. Sandia has proposed simply covering the dump with three feet of soil, seeded with shallow-rooted plants to take up rainfall and prevent leaching. But critics say that won't be enough to keep contaminants from reaching the groundwater, 460 feet below. 

"The landfill will be a whole lot safer with the cover than it is now," says David Miller, the Sandia engineer who manages the landfill. "But because of litigation from one citizens' group, we've had to put these plans on hold." 

FOR THE PAST DECADE, Citizen Action has demanded the excavation and removal of the wastes, and in 2005, it sued the New Mexico Environment Department and the U.S. Department of Energy over their approval of the soil cover. In turn, the environment department recently sued Citizen Action, trying to avoid making public a report on the risk of leaks at the dump. 

On such legacy waste sites, soil covers are inadequate, according to a 2003 report from the National Academy of Sciences: "... the hazards will persist for centuries ... millennia ... or essentially forever." Another NAS report, from 2000, notes that at such sites, subsurface contaminants often travel farther than expected and future risks cannot be accurately predicted. 

Even if the soil cover does its job, no one will be able to tell, according to geologist Robert H. Gilkeson, because the wells installed to monitor contamination don't work correctly. Gilkeson was lead consultant for a monitoring project at Los Alamos, but resigned when the state rejected his design in favor of a less expensive, quicker approach. Describing himself as a whistleblower, he now works independently - and for free - evaluating how the two New Mexico labs are affecting groundwater. 

"The installation of the wells started in the late 1980s with a belief - a belief - that the flow of water was to the north," Gilkeson says. By 1990, however, data clearly showed that the groundwater was moving southwest instead. Despite this, the wells were not moved. 

 

Gilkeson notes that the aquifer has two layers: a slow-moving sandy layer at the water table, and the actual drinking water source beneath. To accurately track wastes, both layers must be sampled. Only one monitoring well reaches the drinking water layer, but its screens cross both layers, mixing the waters. 

Some of the stainless steel well screens are also corroded and clogged. Sandia engineers say that corrosion is responsible for the chromium and nickel that have been found in water samples at higher levels than drinking-water standards allow. Gilkeson suspects that these levels are too high to be accounted for by corroded screens alone. Bentonite clay from the drilling process clogs many screens, "hiding the contaminants (the wells) are intended to detect, especially radionuclides," he says. The same drilling process was used in Los Alamos, and those wells failed to detect groundwater contamination. Now, plutonium is showing up in Santa Fe's drinking water. 

THE FINAL MONITORING plan now being reviewed by New Mexico's environmental department corrects some of these problems, but not all. Three new wells will be dug through the landfill cover, with plastic screens instead of stainless steel. They'll be located on the west side of the dump, closer to the potential contaminants. But there are still no wells on the landfill's south side, and none directly over the "hot spots" where tritium was dumped and where tetracholoroethane (PCE), a probable carcinogen, has been found.

"The landfill is being monitored by very competent staff at present," says Jerry Peace, a Sandia geophysical engineer, "and will continue to be monitored in the future." Sandia officials say the soils appear to slow the transport of wastes, and given the short half-life (12.5 years) of tritium, it may not reach groundwater until it has become relatively harmless. 

For the city's half-million residents, though, the implications are unsettling. Sandia and the Department of Energy appear to be taking a calculated risk, banking on the probability that contaminants will not reach groundwater. But in water-sparse New Mexico, Albuquerque's aquifer may well be priceless, and any risk too great. 

 

The author is a freelance writer who researches nuclear issues in Albuquerque.