In Situ Stabilization of Inactive Low Level Waste Pipelines in the Melton Valley Watershed at Oak Ridge National Laboratory

The Melton Valley watershed at Oak Ridge National Laboratory (ORNL) contained an inactive waste pipeline system consisting of approximately 12 kilometers of buried waste pipelines and over 142 m3 in surface/subsurface appurtenances (e.g., vents, valve pits, pump vaults, etc.). Historically, the system was used to transport liquid low level and process waste between generator facilities in Melton Valley, storage and disposal sites in Melton Valley, and storage/treatment facilities in Bethel Valley. The selected remedy in the Melton Valley Record of Decision (ROD) for inactive pipelines was isolation, removal, or stabilization. Pipeline remediation activities began in the summer of 2005 and were completed in the spring of 2006. The task entailed an iterative process of selecting pipeline access points, excavating and exposing pipelines, performing tapping, draining and cutting activities, either installing fittings for grouting or plugging and capping the lines. Grouting was accomplished using paired access points, with one location serving as the grout injection point and the other as vent/drain and grout confirmation point. Grouting was conducted by pumping a cement-bentonite grout into the specially installed fittings and typically proceeded from a low point to a high point to ensure complete filling of the pipeline (i.e., no void space). The project successfully grouted a total of 8,454 meters (linear distance) of pipeline; another 3,573 meters of pipeline was stabilized through isolation. (authors)