by Luke Ramseth, originally posted on August 18, 2016

A hazardous chemical continues to show up in groundwater tests at a well located on the U.S. Department of Energy’s desert site, but officials say it doesn’t mean the aquifer is contaminated.

Recent testing of well No. 2051 by the U.S. Geological Survey, the Idaho Department of Environmental Quality and cleanup contractor Fluor Idaho detected tetrachloroethylene at “well above safe drinking water levels,” according to a USGS report. The clear liquid is commonly used for dry cleaning and as a metal degreaser.

But officials said Thursday they think the chemical, commonly known as PCE, is most likely coming from inside the 1,100-foot-deep well itself. They said it does not pose a threat to the surrounding East Snake Plain Aquifer or nearby drinking water sources.

“We’re convinced it’s a well problem rather than an aquifer problem,” said Marc Jewett, director of environmental restoration for Fluor.

Officials grew concerned when traces of PCE first showed up in routine tests late last year. Dozens of similar monitoring wells are positioned around the DOE site, ensuring nuclear cleanup and research activities aren’t polluting the region’s most abundant water source. Officials were stumped on how this unusual chemical may have reached the aquifer, and why it had only been detected in a single well.

“It certainly gave us a mystery to kind of work through,” said Roy Bartholomay, a USGS hydrologist who leads the agency’s Idaho National Laboratory office.

Another round of testing by the contractor in March found low levels of PCE. In June, Fluor and the two government agencies met at the well site to take samples, before testing them at separate laboratories. Last month, they also sent a camera to the bottom of the well to investigate.

Results from all three tests have once again showed PCE — this time at levels far above standards safe for drinking. One test showed 824 micrograms of PCE per liter of water in the well. The federal safe water drinking standard is 5 micrograms.

But officials said the off-the-charts PCE sample most likely was accidentally taken from the water that resides inside the sealed-off well hole, not from the surrounding aquifer. Other samples may have collected aquifer water, then become contaminated with PCE as they were transported back to the surface.

Monitoring wells are sealed with plastic piping; steel water bottles are lowered to withdraw the samples from the aquifer at various depths. It appears water sealed inside the pipe — added when the well was built in 2005 — has been contaminated with PCE, which in turn polluted the water samples taken from the aquifer, Bartholomay said.

“We put it in clean,” Jewett said of the water inside the well, which keeps the pipe from collapsing due to the pressure of the aquifer. “But somewhere along the way it got contaminated.”

Officials still don’t know how the well water was contaminated, however. Maybe the cable that runs inside the pipe had PCE on it, or pipe seals inside the well are breaking down, releasing the chemical, officials speculated. More investigation is planned.

Additional tests are set to be conducted on wells around the site, to ensure they don’t have the same PCE issue, Jewett said. Fluor and DOE officials also are looking at ways to clean the chemical out of the well.

Tests for PCE at the nearby Big Lost River Rest Area drinking water well came back negative, Bartholomay said. There are no other drinking water wells nearby, he said.

So the PCE mystery continues: “We really don’t know how it got there,” Jewett said.