Publications Details

Permeability and hydraulic diffusivity of Waste Isolation Pilot Plant repository salt inferred from small-scale brine inflow experiments

Mctigue, D.F.

Brine seepage to 17 boreholes in salt at the Waste Isolation Pilot Plant (WIPP) facility horizon has been monitored for several years. A simple model for one-dimensional, radial, darcy flow due to relaxation of ambient pore-water pressure is applied to analyze the field data. Fits of the model response to the data yield estimates of two parameters that characterize the magnitude of the flow and the time scale over which it evolves. With further assumptions, these parameters are related to the permeability and the hydraulic diffusivity of the salt. For those data that are consistent with the model prediction, estimated permeabilities are typically 10{sup {minus}22} to 10{sup {minus}21} m{sup 2}. The relatively small range of inferred permeabilities reflects the observation that the measured seepage fluxes are fairly consistent from hole to hole, of the order of 10{sup {minus}10} m/s. Estimated diffusivities are typically 10{sup {minus}10} to 10{sup {minus}8} m{sup 2}/s. The greater scatter in inferred hydraulic diffusivities is due to the difficulty of matching the idealized model history to the observed evolution of the flows. The data obtained from several of the monitored holes are not consistent with the simple model adopted here; material properties could not be inferred in these cases.