Collection and Integration of Geoscience Information to Revise the Wipp Hydrology

The Waste Isolation Pilot Plant (WIPP) is the U.S. Department of Energy (DOE) deep geologic repository for transuranic (TRU) and mixed waste. The repository was constructed 655 m below ground surface in bedded halite of the Permian Salado Formation in southeastern New Mexico (Figure 1). Site-characterisation activities began in 1974, and WIPP became a licensed, operating repository in March 1999. The Culebra Dolomite Member of the Rustler Formation (Figure 2) is the most transmissive fully saturated unit above the WIPP repository horizon and the most likely groundwater pathway for radionuclides released from the repository by potential inadvertent human intrusion. Consequently, the Culebra is the focus of groundwater monitoring at WIPP. On-going monitoring has shown that Culebra heads are rising and that they respond to discrete, present-day events, an apparent contradiction of the original conceptual model for the Culebra which envisaged steady-state, or slowly declining, heads. Accordingly, the WIPP regulator, the Environmental Protection Agency (EPA), has requested that the DOE undertake additional studies of the Culebra and develop a revised conceptual model consistent with recent observations.