SANTA FE – A well located outside what was believed to be the boundaries of a chromium plume in the Los Alamos area’s regional aquifer has been found to have chromium levels at five times the state groundwater standard.
The finding could be an indication that the plume, which has been defined as about a mile long and a half-mile wide, is growing or is bigger than previously mapped. In any case, the New Mexico Environment Department says more testing will be required before Los Alamos National Laboratory can use the well as part of plan to contain the contamination plume.
Chromium is naturally occurring at low levels but at higher concentrations is a suspected carcinogen and can damage DNA, the liver and kidneys.
The plume at Los Alamos, first confirmed about 12 years ago, is 900 feet below the surface but 800 to 1,200 feet above the aquifer level from which the area’s water supply wells draw. Officials have said the chromium levels at the water supply wells are tiny. Chromium was used as a corrosion inhibitor at LANL’s power plant at the head of Sandia Canyon from 1956 to 1972 and was released into the canyon in cooling-tower water.
In an interim plan approved over the past two years – to keep the plume from spreading onto adjacent San Ildefonso Pueblo – water is to be extracted from the plume, treated and then injected back underground as a clean-water barrier to control the plume’s migration. Six injection wells were built.
The state groundwater standard for hexavalent chromium is 50 parts per billion and the Environmental Protection Agency’s drinking water limit is 100 ppb. At five of the six injection wells, chromium was found at roughly the expected levels for the plume’s edge – 50 to 100 pbb (the plume’s center, officials said in 2015, had been measured at 1,000 pbb).
But at one well, just outside the plume boundary, samples taken July 17 showed about 250 ppb, five times the state groundwater standard and more than twice the EPA drinking water standard.
The state Environment Department said in a statement Monday that the lab will be required to “address” the sampling results “before full-scale injection can proceed.” There is potential that injections at the well in question and at a second one “might accelerate migration of chromium” and violate LANL’s state permit that is “protective of New Mexico’s groundwater,” said NMED.
The readings were first made public by Nuclear Watch New Mexico, which said in a news release, “The new data suggest there will have to be a complete rethinking of chromium groundwater treatment” and that cleanup will take longer and cost more. The injection wells cost $3.5 million each and $50 million was spent on the project over the past two years. A “final remedy” for removing or treating the plume will be proposed for what’s expected to be an eight-year cleanup period.
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