[en] This Explanation of Significant Differences (ESD) is being issued by the Department of Energy (DOE), the lead agency for the Savannah River Site (SRS), with concurrence by the Environmental Protection Agency-Region IV (EPA) and South Carolina Department of Health and Environmental Control (SCDHEC) to announce changes in the interim remediation strategy selected for the TNX Groundwater Operable Unit. The TNX Area is located adjacent to the Savannah River in the southwestern portion of SRS. The remedy selected in the Interim Record of Decision (IROD) to achieve the interim action goals was the Hybrid Groundwater Corrective Action (HGCA). The HGCA consisted of a recirculation well system and an air stripper with a series of groundwater extraction wells. The original remediation strategy needs to be modified because the recirculation well system was determined to be ineffective in this area due to geological factors and the nature of the contamination