Office of Environmental Management

Trees Help Clean Groundwater in SRS Project

November 16, 2016

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SRNS engineers George Blount and Jeff Thibault inspect equipment used to remove low-level groundwater contamination.

SRNS engineers George Blount and Jeff Thibault inspect equipment used to remove low-level groundwater contamination.

AIKEN, S.C.EM and contractor Savannah River Nuclear Solutions (SRNS) are using 60 acres of trees as a living, sustainable remediation system to remove low-level contamination from groundwater at the Savannah River Site (SRS). 

   Workers created a small pond in the path of the slow-moving groundwater contaminated with tritium. The groundwater continuously seeps into the pond, which serves as a short-term holding basin.

   An inexpensive irrigation system safely removes the water almost daily. More than 120 million gallons — about 10 million a year — have passed through it. The U.S. Forest Service-Savannah River designed and installed the system and continues to operate and maintain it in partnership with SRNS.

   This innovative process generates no waste, reduces remediation costs, and advances the site’s goal of conducting sustainable remediation protective of the environment and human health.

   “We use an extensive above-ground system of plastic pipes and sprinkler heads to irrigate the 60 acres with water pumped from the pond,” SRNS Geologist Gerald Blount said. “It’s man working with nature and, in this case, using thousands of trees to safely absorb the radioactively-tainted water, naturally evaporating it to the atmosphere.”

   Most of the water evaporates when it is sprayed into the air or as it lies on the forest’s ground cover, releasing the hydrogen-based contaminant into the air. The remaining water is used by the trees and plants, ensuring a healthy ecosystem without the potential for drought.

   “We know that the levels of tritium we’re seeing here do not represent an ecological issue. It does not biologically accumulate, and the energy associated with tritium is not going to create any kind of negative effects on the plants and animals in the area,” said Blount. “Multiple studies have confirmed this. In fact, the trees and animals receiving the irrigated water are flourishing.”

   While some radioactive particles last for hundreds of years, the half-life for tritium is 12.3 years. After a little more than 12 years, half of the nuclear activity is gone.

   “Photosynthesis and the fact that this particular nuclide quickly moves through the vegetation along with water means the trees can be harvested and sold for lumber after one or two years without irrigation,” Blount said.

   The small amount of tritium released into the air with each irrigation cycle is negligible considering it is dispersed into the enormous volume of air that makes up the earth’s atmosphere.

   Blount noted that the area’s tritium levels after irrigation are so low that SRNS workers can safely move about the irrigated area as needed without protective clothing.

   “This economic and highly effective system uses properties of nature to prevent this contaminated water from reaching SRS waterways,” said Phillip Prater, DOE manager, Infrastructure and Area Completion Division.

 

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