SRS cleanup

Savannah River Nuclear Solutions employees Terry Killeen, left, and Jimmie Lee take groundwater samples prior to the start of a cleanup project that will inject a 36,000-gallon mixture of emulsified oil, microorganisms, water and other ingredients into the aquifer beneath the Savannah River Site.

Environmental Management and the management and operations contractor at the Savannah River Site are relying on a low-cost strategy using microorganisms found in nature to safely remove chemicals from a narrow groundwater plume.

"Finishing this phase will aid in the cleanup of another environmental restoration project at SRS, an important step towards returning the site to its natural state," said Karen Adams, DOE-Savannah River federal project director.

Workers will inject 36,000 gallons of a mixture that includes microbes known as dehalococcoides, vegetable oil, water and vitamins B-12 and C through 15 pipes into the groundwater aquifer to get rid of contaminants such as trichloroethylene (TCE).

"Whenever possible, we believe it is best to harness and use nature for our environmental cleanup projects," said Terry Killeen, an environmental geologist with Savannah River Nuclear Solutions. "Through extensive study and testing, it has been proven that this microbe, native to this area, actively eats TCE. We provide the oil and microbes and Mother Nature does the rest.”

Killeen said the oil and microbes thoroughly mix with the groundwater and coat particles of sand and clay in the subsurface. The TCE flowing through the area sticks to the oil, where both are ingested by the microbes, resulting in harmless substances consisting of ethene and chloride.

An advantage of this treatment is that it involves a one-time injection of a relatively small amount of oil to treat a large quantity of water over three to five years, Killeen noted. Conservative estimates indicate more than 1 million gallons of groundwater per year will be treated.

Remediating the groundwater using microbes and oil costs 30 to 60 percent less than many traditional types of TCE remediation at SRS, according to Killeen.

During the Cold War, workers often used chemicals such as TCE to remove grease from nuclear components manufactured throughout the DOE complex. Disposal of those chemicals often resulted in groundwater contamination including at the former C Reactor facility at SRS.

Nearly all degreasing chemicals found in the groundwater at or near the C Reactor were removed in a cleanup in 2006. Crews used high voltage electricity to heat the subsurface, vaporizing the TCE, which was then extracted from the groundwater. However, TCE still exists in the estimated mile-long groundwater plume between C Reactor and Castor Creek that will be nearly eliminated through this project.