The DOE Office of Legacy Management assumed responsibility for a tree in Study Area 4 of El Verde site (MED/AEC Legacy Site) in 2005. The tree, a Matayba domingensis, had been injected with 0.46 millicurie of cesium-137 in 1968 and required periodic monitoring and access controls. Radioactivity in the tree is concentrated at the base of the trunk and in the root system. The radiological surveys indicated that the cesium-137 in Study Area 4 is limited to a radius of about 10 feet around the injected tree. The radioactive half-life of cesium-137 is about 30 years, and currently more than half of the original cesium has decayed away. In 2008, the radioactive materials license for the tree in Study Area 4 was terminated. Termination was based on radiological conditions meeting criteria for protectiveness. The tree is no longer regulated and has been released for unrestricted use. The site requires records management and stakeholder support.
For more information about El Verde site, view the fact sheet.
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