Contractor detects possible increases in mercury at well sites

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By Tris DeRoma

N3B, the contractor in charge of legacy waste cleanup at the Los Alamos National Laboratory reported to the Department of Energy Aug. 21 that there were slight increases in mercury at one monitoring well site and perchlorate at a separate well site. 

The wells are used to sample groundwater tables. The samples were taken in June. 

N3B officials noted a sample taken from well R-3 showed a .01 micrograms increase above the 2 micrograms per liter maximum contaminant level allowed by the Environmental Protection Agency, making the sample taken 2.01 micrograms per liter.

Mercury is often used in scientific research applications and is also a naturally occurring element found in rock, according to the Environmental Protection Agency. Perchlorate is a chemical found in rocket fuel and munitions, but is also naturally found in high amounts in the southwestern United States, according to the U.S. Department of Health and Human Services. 

At the well monitoring site, the spread of a chromium plume in Mortandad Canyon, well samples recorded perchlorate levels at 15 micrograms per liter, 1.2 micrograms over the allowed New Mexico Water Quality Control Commission standard. 

Officials from N3B said the mercury reading is likely an anomaly, and more samples have to be taken to make sure.

“The mercury value that is presented in the letter report is from samples collected in a well that is unrelated to the chromium plume. Multiple other samples were analyzed for mercury at the well, R-3, from the same sampling event and all were undetected for mercury,” N3B officials said, in response to a written inquiry from The Los Alamos Monitor. “It’s likely an erroneous value which sometimes occurs related to sample processing at the analytical laboratory.”

N3B officials also noted, however, they are monitoring the situation.

“When this occurs, we pay special attention to subsequent samples collected from the same location to see if the result is repeatable which can be a sign that the initial result was a real detection of a given contaminant,” a written statement from N3B said.

As for the increase in perchlorate, N3B officials said they’ve detected a gradual increase at Well R-61 since monitoring of the chromium plume began about 13 years ago. The reading marks the first time perchlorate levels have exceeded limits set by the New Mexico Environment Department. 

“We have been monitoring the variable results (concentrations go up and down slightly), but overall slowly increasing perchlorate concentrations have been observed at well R-61 for several years and the value of 15 ppb from the most recent sampling even is the first detection above the standard of 13.8 ppb (parts per billion.)”

Because of the noted increase, N3B officials said they are monitoring the well for further evaluation.

“Additional monitoring is conducted to see if the trend persists,” N3B officials said. “For the specific issue of perchlorate within the chromium plume, the remediation strategy for chromium will include any collocated contaminant that may be present above a standard in the plume. 

Los Alamos National Security, which managed legacy cleanup operations before the Department of Energy selected N3B in December for the task, installed a network of wells around the perimeter of the chromium plume to monitor its spread and ground penetration. LANS, and now N3B have been stopping and slowing the plume using a network of clean water injection and extraction wells strategically placed around the plume’s perimeter. The plume is about one mile long, a half a mile wide and is located within the top 100 feet of an aquifer that is 900 to 1,000 feet below ground under Mortandad Canyon. The well network is an interim measure. The Department of Energy is currently considering permanent options to get rid of the chromium plume. LANL officials said the chromium plume originated from lab activities occurring in Mortandad Canyon from the 1950s through the 1970s. The plume was discovered in 2005.

Since testing began, no chromium associated with the plume has been found in Los Alamos County’s drinking water.

In December, the DOE awarded N3B a 1.39 billion contract to clean up waste generated by National Laboratory from the 1940s through 1999. 

N3B is the Los Alamos National Laboratory’s first contractor hired to focus solely on cleaning up toxic waste generated by lab. The Department of Energy decided to separate the legacy cleanup work from the lab’s management and operations contract so the lab’s new contractor, Triad Nuclear Security, can focus on helping Los Alamos National Laboratory with its core mission of maintaining the nation’s nuclear stockpile.