IDAHO FALLS, Idaho – EM and cleanup contractor Fluor Idaho will assist the U.S. Geological Survey in drilling a well at the north end of the 890-square-mile Idaho National Laboratory (INL) Site early next year to enhance the effectiveness of a groundwater treatment system that removes hazardous waste from the underlying aquifer.
For nearly two decades, crews have employed a pump-and-treat technology to reduce concentrations of trichloroethylene (TCE) and other hazardous organic compounds from beneath the former Test Area North (TAN) facility.
The program also uses a simple, effective method called bioremediation to inject a sodium-lactate and fatty-acid solution directly into the aquifer to encourage naturally occurring microorganisms to consume the common industrial solvent TCE.
Fluor Idaho Environmental Restoration Program Director Rich Abitz said a new well is needed to target a residual TCE source zone in the aquifer that is inaccessible using current bioremediation injection wells.
“The new well will allow us to target an area of the aquifer that shows a weak response to the bioremediation efforts that have been successful in shrinking the source zone of the contaminant plume,” he said.
The aquifer depth at the north end of the INL Site is about 225 feet below the ground surface. The area of the aquifer near the TAN facility is not used as a source for drinking water.
TAN was established in the early 1950s to build and test nuclear-powered jet aircraft engines for an aircraft nuclear propulsion program that ended in 1961. The facility was later used to study the effects of the loss of coolant from commercial reactors.
Abitz said it will take some time to determine the effectiveness of lactate injections at the new well to reduce TCE in the suspected source zone, but he’s optimistic.
“Going at this problem using several locations for lactate injections is the best solution,” he said. “We have to deal with a complex subsurface flow regime controlled by fractured basalt, which requires multiple injection points to deliver the lactate over the entire TCE source zone.”
DOE, the Environmental Protection Agency, and state of Idaho agreed to implement the pump-and-treat and bioremediation systems in a record of decision signed about 20 years ago.
“Once we treat the TCE source zone, we can begin the final rebound test to determine if the remedy met the conditions of the record of decision,” Abitz said. “After those conditions are met, we can shut off the treatment systems permanently.”