Reaching Water

Sandia National Laboratories' Mixed Waste Landfill (MWL), established during the Cold War in 1959 and closed in 1988, has become one of the more controversial sites for discarded nuclear weapons research material in the state. It holds below its mere 15-25 feet of dirt more than 40 types of radioactive elements, as well as hazardous waste, solvents and volatile organic compounds (VOCs). Sitting on an unlined 2.6 acres, about 460 feet above the Albuquerque aquifer, it contains an estimated 73 cubic yards of transuranic waste (which is about 200-250 55-gallon drums worth), including plutonium, tritium and cobalt-60. Not all of the contents of the site are known.

Over the years, some groups have argued that the contents of the site should be removed and shipped to places better equipped to handle them, such as WIPP or Yucca Mountain. Others have rebutted, saying that moving the site and stirring its contents that have been sedentary for 17 years could be more dangerous than allowing them to remain.

A recent decision by New Mexico Environment Department (NMED) Secretary Ron Curry to cap the site with a biointrusion barrier and a mere three feet of dirt has garnered a mix of reactions from people in the community. As reported by the Alibi [Newscity, “Covering Our Tracks,” Oct. 20-26, 2005], Citizen Action New Mexico, a local government watchdog group spawned from ex-members of Sandia’s Citizen Advisory Board, has filed a lawsuit against NMED, appealing their decision to cap the site. A court date for the lawsuit has not yet been set.

Now, a recently released report by Sandia is stirring up more controversy, as it shows that at least one contaminant from the MWL could reach the Albuquerque aquifer as early as 2010.

Down and Dirty

Sandia's study, known as a “fate and transport model,” mainly looks at the probability of materials from the landfill reaching the aquifer. It does this by taking dirt samples from beneath the landfill, analyzing what materials have already escaped its boundaries and running a number of models to see if those materials will ever leach into the groundwater, and at what concentration.

Within the study, several materials were looked at, including various radionuclides, heavy metals and tritium, one of the more worrisome materials in the landfill because it is a radioactive element that binds with water, was found to have traveled more than 100 feet below the landfill 10 years ago and has been discovered in trace amounts in mice in the area. The study shows that none of the above will reach the aquifer within the next 1,000 years or so, and are therefore not a concern.

However, within the study there is a material that is predicted to reach water in the near future. Tetrachloroethane (also known as PCE) is a man-made VOC widely used as a metal degreaser that has been linked with liver and kidney damage as well as various cancers. PCE decays into TCE (trichloroethan), which degrades into DCE (dichloroethane), which degrades to VC (vinyl chloride), all of which have been found by the EPA to be “highly likely” to cause various cancers and disorders. And, according to Sandia's study, PCE could reach the aquifer in as early as four years.

But Dr. Cliff Ho, a scientist with Sandia and an author of the study, cautions the public to consider the results in context. He says that of the 100 models performed to see whether PCE would reach the aquifer, only one model showed that PCE would enter the groundwater in a concentration that exceeds the federal standard of 5 parts per billion (ppb). He says 70 percent of the models showed that PCE would only enter the groundwater in concentrations of 1 ppb or less, an amount that is undetectable. “The results show that the probability of [PCE in the water] posing a health risk is very small.”

Around the Watering Hole

But Sue Dayton, director of Citizen Action, is not reassured. Dayton is troubled not only with the results of the study, but also with the way the study was conducted, and cites several problems with it. Some of her concerns are that the study used samples from 1993 instead of taking new samples, it failed to look at the possible effects of materials mixing and it only modeled the movement of one out of many VOCs in the landfill. She adds that even though PCE was found to exceed the federal standard in only one model, that many models showed PCE entering the groundwater in concentrations that came very close to the maximum.

“[The study] only looked at one volatile organic—PCE,” she says. “It didn't look at the decay products, it didn't look at the rest of the chemicals, it didn't look at the entire sweep of radionuclides, it didn't look at what would happen when the drums would break and spill their contents into the surrounding soil, it left a lot of things out.”

Paul Robinson, research director for the Southwest Research and Information Center in Albuquerque who has been studying the MWL since the '70s, explains why VOCs are so troubling. “VOCs are a set of chemicals that move in a vapor phase,” he says. “Gasoline is an example—it's liquid, but there's a vapor that emanates off it. There is a pollution problem associated with these across the country; Superfund sites have VOCs. The soil in the Mixed Waste Landfill is sandy, and VOC vapor is heavier than air, and so it sinks. So then there's a vapor plume moving through the sand grains in and around the landfill; and there's no barrier around the landfill, no liner, the containment is very poor.”

Robinson also has issues with parts of the study, mainly with the fact that Sandia used old data and didn't look at any VOCs other than PCE.

“There is no idea of how much volatile organics are [in the landfill],” he says. “The estimate Sandia used is based on the amount that's already leaked, but the amount that's leaked hasn't been sampled since 1993. At that time, volatiles had already moved at least 30 feet from the trenches. But at that time they didn't go down to see how far it had really moved, and they still haven't done that. PCE is only one of 12 volatile organics found at the boundary of or below the landfill [13 years ago].

“Because Sandia doesn't know how much VOC is there, it has a poor idea of how much is leaking, they're just basing their estimates of what was detected in 1993. And the study doesn't address the pattern for the other [11 VOCs detected then]. They don't even know if more is leaking now.”

Ho defends the study, but admits there are possibly more scenarios that should be researched. He says the reason data was used from 1993 is because that's when the most extensive data collection was done for the site, adding that samples aren't taken very often because it can be dangerous to disrupt the site.

Ho says the reason PCE was the only volatile organic looked at is because it is the most mobile of the ones known to be in the landfill. “Rather than simulate all the VOCs,” he says, “we chose the most significant. Since we found it to be a threat, we're recommending triggers.”

Ho explains “triggers” as a prescribed set of concentration levels or values that can indicate a “problem.” For instance, in the case of PCE, Sandia will continue to monitor the groundwater beneath the landfill to check for levels of PCE. If PCE concentrations reach 2.5 ppb, half of the federal standard, then action will be taken to correct the problem. What kind of action has not yet been determined.

However, Ho says the study is only the first step in making recommendations for how the site should be monitored. “Citizen Action and others have raised some valid comments about scenarios not in the model. One of their comments was that Sandia should test soil samples [above the aquifer, to know if PCE is there before it reaches water]. I think that's a good idea. If it's an oversight, it should be looked at.”

Wrap Up

Adam Rankin, spokesperson for NMED, says he cannot comment at this time on NMED's opinion of the study, as they are not finished reviewing it. He estimates that the review will be complete around July.

In the meantime, the NMED is working to create a technical discussion group, which would include members from NMED, Sandia, Citizen Action and other groups. According to Rankin, the first meeting will likely take place sometime in May.

There have been four other sites at Sandia where VOCs have reached the groundwater and exceeded federal standards, including the Chemical Waste Landfill, which was excavated a few years ago. Like the MWL, none of the sites were proposed for excavation before contamination was found. All of the sites have now been excavated, and the water has been pumped and treated.

Still, for Dayton, the MWL is a hazard to Albuquerque's groundwater supply that should be removed before it has a chance to do any real damage.

“Once contamination occurs, the water will never be the same—they can clean it, but it will never again be in its virgin state. It's unfortunate that we rationalize poisoning our groundwater, but it is a reality.”