[en] A characterization study was conducted on the Old Hydrofracture Facility Pond, at Oak Ridge National Laboratory to provide information necessary for its proper disposition. This impoundment was constructed in 1963 to provide a containment basin for radioactive grout in the event of an emergency spill from the Hydrofracture Facility. The impoundment is rectangular and measures about 30 by 6 m at the bottom. Water in the impoundment overlies about 0.3 m of sediment waste. The pond sediment was sampled and analyzed to determine whether it would classify as a hazardous waste under regulatory definitions promulgated in accordance with the Resource Conservation and Recovery Act (RCRA). Chemical analyses indicate that the sediment/waste does not contain hazardous chemical constituents above levels permitted by RCRA regulations. The sediment was found to contain an estimated radioactivity inventory of about 260 Ci, consisting primarily of ¹³⁷Cs (60 Ci), ⁹⁰Sr (190 Ci), ⁶⁰Co (0.3 Ci), and ²³⁸U (0.3 Ci). The impoundment is excavated in clay soil and weathered sedimentary rock of the Conasauga Group. Four wells for monitoring the groundwater were constructed around the perimeter of the impoundment to depths ranging from 5.8 to 7.9 m. Sampling and analyses of the groundwater have been completed for the winter and spring seasons (1985) and will be continued for at least two more quarters to account for possible natural seasonal variation in groundwater quality. At the end of that time, a determination as to the effect of the impoundment on the groundwater quality will be made. Analyses from the first two quarters indicate that radioactivity (gross beta resulting from ⁹⁰Sr and tritium) of the groundwater exceeds limits allowed by RCRA regulations. Low levels (0.0001 mg/L) of polychlorinated biphenyls were also detected in the groundwater