Evolution of a conceptual model : Tritium concentration vs discharge in first-order tributaries draining Oak Ridge National Laboratory

The concentrations of tritium in surface water on the Oak Ridge National Laboratory (ORNL) are well above the Environmental Protection Agency (EPA) drinking water standard of 20,000 pCi/L. Past ORNL studies suggest that a relationship exists between streamwater discharge (Q) and contaminant concentration (C). This study attempts to test the C - Q model in first-order tributaries draining a low-level radioactive waste burial ground in Waste Area Group (WAG) 6 at ORNL.

The model was intended as an analytical tool to evaluate the effectiveness of remediation activities. Data collected for this study were input to the model and used to evaluate the Interim Corrective Measure (ICM) remediation by comparison to the historical data. Continuous stage measurements were collected on four first-order tributaries and converted into discharge. Samples were collected during storm events and baseflow conditions and analyzed for tritium concentration.

This study determined that tritium concentration is independent of streamwater discharge during baseflow conditions but during storm events, the C - Q model can be used to evaluate remediation within limits imposed by seasonal and annual variables.