DOE EM-LA Engages With Public On What To Do With Material Disposal Area H At Los Alamos National Laboratory

Listening to comments from the audience at a recent DOE EM-LA forum on Material Disposal Area H are, from left, Sarah (Ellie) Gilbertson, EM-LA Deputy Manager, Brad Smith, President of N3B-Los Alamos and David Diehl, N3B’s Program Manager for MDA closure. Photo by Maire O’Neill/


What is MDA H at Los Alamos National Laboratory and why it in the news again? Material Disposal Areas (MDAs) at Los Alamos National Laboratory are typically disposal areas for solid or sometimes liquid waste from the Manhattan Project through the Cold War – 1945-1990 and there are 26 of them scattered around the Lab that need to be cleaned up by the Department of Energy Environmental Management  Los Alamos Field Office (EM-LA). Some of the MDAs have solvent organic compounds and others have radioactive materials. They are located all the way from DP Mesa to the far end of the Laboratory.

David Diehl, N3B’s Program Manager for the Material Disposal Areas closure, recently spoke at a public information forum hosted by EM-LA at Fuller Lodge where he discussed and answered questions particularly about MDA H, which he called “a mixed bag”. The New Mexico Environment Department (NMED) has authority over the hazardous wastes that are in these pits and the Department of Energy has regulatory authority over radioactive waste. The Big Seven MDAs that have to be cleaned up are MDAs A, T, C, H, L, G and AB.

“They are all located within the LANL boundaries so we don’t have any of these disposal sites that are out in any of the canyons to the north of here or in town. They’re all secured with fencing and placarding as appropriate, mostly radioactive, and they’re protected from the public. The public can’t get into these because they’re secured,” Diehl said. “They’re all secured from solid contaminant transport through the use of covers. These pits and shafts and other disposal facilities all have covers on them so none of this waste is exposed to nature. It can’t be picked up by animals or anything like that and it can’t be picked up by humans just walking by.”

Diehl said the MDAs are regularly monitored to make sure contamination isn’t moving toward groundwater and that the tops of the protective covers have not somehow gone away.

“Most of them are inspected monthly and some of them are on a quarterly cycle because they don’t pose as much of a concern. We also go in and clear the vegetation often because we don’t want any plants tap-rooting down and potentially bringing stuff to the surface. So when we go out and inspect them, if we realize that there’s vegetation that we’re concerned about, it all gets chopped down and taken away. And they’re repaired. If we start developing any sort of erosion or gulleys or anything like that, we fix those so we don’t have the potential of exposing waste,” Diehl said.

MDA H is pretty small. It’s .3 acres and it’s an inactive site out on Mesita del Buey in the Pajarito Corridor about half-way up the hill from White Rock.  The site is 70 feet by 200 feet and there are nine disposal shafts there that are six-feet in diameter and they were drilled into the ground 60 feet deep, the soil was removed and the waste was put in them.

“The waste was classified, non-hazardous waste with radionuclide contaminated materials. It also includes explosives. The status of it right now is we’re working on a Corrective Measures Evaluation (CME). As part of our regulatory process we’ve investigated the site. We know where the waste is, where it’s not, and we’re working toward an evaluation of what the remedy may be for this site for the future,” Diehl said.

MDA H was active from 1960 to 1986.

“The waste was classified, in solid waste form. No drums and no large containers of stuff that can migrate readily. It was restricted to classified items that were determined to be no longer required for their intended use. Liquids were prohibited. They also kept a waste inventory of what was put in the shafts over the years,” Diehl said. “The waste is located six feet below ground – with three feet of concrete and then three feet of crushed tuff to keep biointrusion etc. out. Your burrowers, your animals that like to dig around, your ants and your other tap-rooting stuff are kept from burrowing down into this waste.”

Twenty four percent of the waste that was inventoried is depleted uranium. Another 33 percent is metals other than plutonium.

“This was all stuff that was classified as part of the weapons research of whatever they were doing and put in the shafts. It’s mostly metals, and we have graphite, plastics mostly high speed film taking a look at stuff they were doing it as far as their research explosives and all that stuff that they didn’t want getting into someone else’s hands. There are radioactive materials – mostly waste stuff, no liquids and then kind of the kicker is part of the top is less than 1 percent paper. There is less than one percent of high explosives but enough that it’s of concern – and then there are lithium compounds,” Diehl said.

Over time, the site has been investigated in various phases.

“We collected subsurface samples of soil to figure out where the contamination is and bound it so that we know that it has not run off down the hill to the left or to the right, away from us or behind us. We also have some vapor phase contaminant monitoring out there, also known as volatile organic compounds and vapor tritium. We also monitor the ground that’s down below the site to 1,000 feet.” Diehl said. “We look at these sites because historically there were drums like MDA C and MDA L where we did have release of solvents that vaporized and created vapor plumes that are below the site that we continuously monitor. We do the same thing here. We have four vapor monitoring wells. There are 28 sampling ports ranging in depth from 6.5 feet below ground to almost 300 feet below ground.  We’re taking a pretty comprehensive snapshot of these vapors and where they may be.”

Significant reports on MDA H have been generated during the last 22 years and to the lay reader, little has changed in the findings. People who have lived in the area for a long time will probably remember some of the extensive outreach to stakeholders seeking input on the best approach for cleanup at MDA H, including mailers and meetings.

“There was a Corrective Measures Evaluation that was performed in 2011 that went to the state. Some priorities changed within the program and that document was withdrawn from the state,” Diehl said. “A lot of material was borrowed out of that as a preface to what would be included in the next one.  In the 2011 CME it was determined tritium was the primary constituent in the subsurface. Volatile organic compounds (VOCs) were present in low concentrations. It concluded that the VOCs measured at MDA H pose no potential threat to groundwater because it was high up and in very low concentrations.”

Diehl said part of what’s being done now is refreshing all the data in the 2011 Corrective Measures Evaluation in an effort to have the information as current as possible when the newest CME is turned in to NMED.

“In January we collected a whole new series of samples and vapor just to see what’s going on and if anything has changed. What we found is that nothing has changed essentially. We saw tritium in the same place, similar types of concentrations of solvent VOCs in the same place, so nothing has really changed,” he said.

The groundwater is also monitored with 16 regional wells in the area and data is collected quarterly or semi-annually based on what is required by the Interim Facility-Wide Groundwater Monitoring Program. When EM-LA begins cleanup work on a site like MDA H maps and models are created of how contamination can get moved, where it’s located and the potential for downward or lateral movement. In previous MDA H reports there were concerns about releases of tritium releases. Although tritium is not RCRA-related, it is radioactive. There was also concern about the potential for human intrusion and erosion as well as the need for more extensive characterization of the waste in the nine shafts.

Diehl pointed out that there had been an extensive search through historical documents related to the MDA.

“One of the key findings was that there is 1,275 lbs. of RDX high explosive that is mixed into the matrix of the waste that’s down below. So at the time uranium and high explosive were involved presumably with the weapons program and presumably know how this works and what makes it unhappy,” Diehl said.

Appendix C was included in the CME and it makes some interesting reading. It lists the known inventory of the shafts.

“I tried to pick out some of the key points that really caught my attention. We have this waste and they state mechanisms that may cause unwanted reactions in explosives – including spark, friction, heat, impact and pinch. Don’t bang on it. Don’t cause sparks don’t heat it. That precludes a lot of our methods for getting rid of stuff. Further in the Appendix C, were explosives, which while undisturbed in the shafts were expected to remain stable and only subject to slow, natural degradation and decomposition,” Diehl said.  “Once ignited, massive metal burns very slowly. Unless covered with oil, massive metal burns with virtually no flame so once it ignites you won’t be able to see it.”

In situ vitrification, thermal treatment or excavation and other options for remedial action pose potential hazardous reactions that could be hazardous to workers and the environment. The waste includes pyrophoric materials what when combined with water can spontaneously combust.

“When I think of the high explosives I would be concerned about fire. I don’t want them to pull the high explosives out – you can tell where I’m coming from. I don’t want to touch the stuff,” Diehl said.

The CME will be submitted in accordance with the 2016 Consent Order, which is the regulatory agreement between DOE and NMED.  

“The CME will have our logic of why we either include or dismiss different types of remedies. The Consent Order requires that the options proposed be examined to see whether or not they are doable,” Diehl said. “Threshold criteria are: protect human health and the environment, attain acceptable cleanup standards, control the sources of release, apply required standards for management of the waste.”

A 2020 presentation to the Northern New Mexico Citizens Advisory Board on the interpretation of “risk” for LANL legacy waste cleanup given by Erich Evered, then director of enhanced stakeholder engagement at N3B, included how the above standards are addressed. See

While Diehl admitted that not touching the MDA H waste seems like a good idea to him, EM-LA will still look at what it would take to get the waste out of the shafts. EM-LA doesn’t have the final say – the preferred alternative will ultimately be recommended to NMED who will eventually pick the remedy after working though the public hearing and comment period.

While some individuals and entities are pushing for the return of MDA-H to its “pristine” state, others particularly in Los Alamos County do not want to see trucks of material going from LANL’s Pajarito Road through White Rock to disposal sites and back putting even more stress on the roadway system and adding the risk of introducing contaminants into the air.  One of the proposals is an optimized evapotranspiration cover which is more defensible and more time effective.

“We want input and recommendations. At a couple of Technical Working Groups recently, we had some really good technical questions about stuff we hadn’t even thought about or elaborating on things that are not covered as well as we could have. Your input is vital to what we’re doing. We want to get the right answer. We want to hear from you and understand your values and priorities, what you believe should be in these documents. There are political questions with all of these. I’m a technical guy. I look at what can we do. People have views on things that aren’t necessarily technical,” Diehl said.

For more information or to submit comments on the MDA-cleanup, email