At the recent LANL Hazardous Waste Permit Hearings, the public was presented with two cross-sections of the current understanding of the geology under the Lab’s largest nuclear waste disposal area, Tech Area 54. These cross sections are important because the NM Environment Department, with public input, will soon have to decide the final disposition of the over 800,000 cubic yards of radioactive and hazardous waste buried there. The options range from leaving the waste in place with some sort of cover to exhuming the waste.
The geology under the site is very complicated and includes layers of lava flows, ash falls, and old stream beds. The waste is buried in unlined pits, shafts and trenches and is perched 800 – 1000 feet above our sole-source aquifer. Some of the more soluble contaminants, such as tritium, perchlorate, explosives, and chromium have already made their way to the aquifer from other parts of the Lab. The cross-sections are needed to understand the contaminant pathways from the dumps to the aquifer.
First, the Lab’s version – (click on image for larger picture)
The MDAs, or Material Disposal Areas or dumps, are across the top. MDA G is the largest by far. The PM-#s are wells where drinking water is drawn. The R-#s are characterization and contaminant sampling wells. The elevation is on each side. The top of the regional aquifer is the horizontal blue line near 5800′. There are some perched aquifers shown, too. The one question is a new structure that the Lab is calling a “dike” discovered by well R-22.
The NM Environment Department’s Version – (click on image for larger picture)
The Environment Department’s version gives a different interpretation of the fractures that could be pathways to the aquifer. It has many question marks, including the “vent” and the perched aquifers.
We appreciate the two versions. With so many unknowns, with so much waste, and with such a potential negative impact to our aquifer, the most protective course would be to remove the waste.