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20 YEARS OF
Scientists at SRS are using natural resources, including a
62-acre plantation of pine trees, to greatly limit radioactively contaminated PHYTOREMEDIATION
groundwater from reaching an on-site stream.
The trees effectively act like a forest of tall “hydraulic pumps,” each drawing
up irrigated water containing legacy tritium, pumped from a nearby holding
pond and harmlessly released into the atmosphere through photosynthesis.
“We knew that capturing and containing the contaminated groundwater
seeping to the surface and into a manmade pond would be of great benefit,”
said Jeff Thibault, SRNS Engineer, Area Closure Projects.
The extensive irrigation system uses piping and sprinkler heads to evenly
spread the tritiated water over the forest floor debris. Large-scale evaporation
takes place during this process as well, releasing additional tritium into the 1999
Earth’s vast atmosphere, where it is harmlessly diluted. Multi-organizational project team
United States Department of Agriculture (USDA) Forest Service-Savannah -- including DOE, Forest Service
River researchers, along with engineers from SRNS and DOE, began and Westinghouse Savannah River
designing this interim treatment in 1999. Company, formed to design and build
dam and photoremediation system
Since 2001, when this process began, approximately 190 million gallons of
water and nearly 7,000 curies of tritium that otherwise would have entered March 2001
the Savannah River have been safely sprayed throughout thousands of Phytoremediation system construction
loblolly pine trees. completed, irrigation of the original
“Traditional remediation costs associated with this level of tritium removal 21 acres begins
would cost close to $220 million over a 20-year period,” said USDA Forest
Service-Savannah River Civil Engineer Marsue Lloyd. “Our costs over that 2005 – 2006
same span of time for this project are approximately $12 million.” Irrigation pumping system upgraded
The costs associated with phytoremediation are low because only a few 2008
operators are needed, and the contaminated groundwater flows naturally to
the surface without a need for mechanized pumping. In addition, the process, Completed construction of the
which includes 51 irrigation zones, is largely computerized for optimal low permeability cap over the Old
Radioactive Waste Burial Ground
evaporation efficiency. “With this project, we learned a lot about harnessing (reduces the further migration of tritium
nature to continually move towards passive, low-energy, and sustainable from buried waste to the groundwater)
cleanup technology with minimal cost. And it’s accomplished effectively
without the generation of any waste,” explained Philip Prater, Senior Physical 2009
Scientist with DOE-Savannah River.
Completed eastern expansion, adding
Thorough sampling and testing, conducted annually by the Savannah River 24 more acres of irrigation
Ecology Laboratory, demonstrate that nearly 90% of the tritium within the
water applied to the pine plantation is evaporated. 2014
“Public concerns about managing contaminated water at SRS are Completed western expansion, adding
understandable,” said Thibault. “However, test results validate the level of 15 more acres of irrigation
tritium found within the plants and animals affected by this process are so TODAY
low as to be insignificant. The fact is that optimal water levels are being
maintained in the pond while the evaporated tritium becomes virtually Over the past 20 years, SRS remediated
immeasurable beyond the irrigated section of forest, much less at the 190 million gallons of contaminated
Site boundary. water using phytoremediation
“What we’ve achieved for 20 years now is the protection of nearby waterways,
and we’re doing so safely and cost-effectively. This project has been
extremely effective, and the data supporting this success has been verified
by South Carolina Department of Health and Environmental Control officials,”
said Thibault. “This project represents what can be accomplished through the
partnership of multiple organizations sharing the same vision, building on the
unique contribution each provides.”