Page 7 - SRNS_Today_August_2021
P. 7

T
                                                                                          UGUST 2021    |   SRNS
                                                                                                            ODA
                                                                                                               Y   |   7
                                                                                         A
                                                                                            AUGUST 2021    |   SRNS TODAY   |   7
                                                                                  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.”
   2   3   4   5   6   7   8   9   10   11   12