At the U.S. Department of Energy’s (DOE’s) Hanford Site, located in southeastern Washington State, iodine-129 (I 129) was produced as a byproduct of nuclear fission in the site’s nine Pu production reactors. Currently, there are large dilute I-129 groundwater plumes at Hanford, including a groundwater plume in the 200 UP 1 operable unit (OU), located within the Central Plateau. The interim Record of Decision (ROD) for the 200-UP-1 OU requires that DOE evaluate potential treatment options for I-129 before a final ROD is issued. A remedy evaluation plan was subsequently published and identified the approach for this effort.