Resistivity Changes Over Time Related To Modeled Fluid Fl,Ow In Room-Q Of The Waste Isolation Pilot Plant

The Waste Isolation Pilot Plant (WIPP Site) is located in southeastern New Mexico about<br>35 miles east of the town of Carlsbad. The purpose of the WIPP Site is to evaluate the<br>storage of transuranic waste in mine excavations within the layered Salado salt formation.<br>Consequently it is important to understand the potential for fluid inflow into the<br>underground facility. Room-Q is a horizontal cylindrical room that was excavated and sealed<br>to measure brine influx. The Colorado School of Mines installed a stationary, permanent<br>DC resistivity grid in Room-Q in late 1989 and following electrode stabilization, the grid has<br>been read periodically since then.<br>A fluid flow model of Room-Q was constructed using the MODFLOW modeling<br>program. The profile-oriented model incorporated geologic information from underground<br>mapping and hydraulic parameters available from limited borehole permeability testing in<br>Room-Q. Electrical geophysical data gathered in the room from January to March, 1990,<br>were correlated with modeled fluid flow for the same length of time and a similar overall<br>trend was observed. The introduction of minor geological heterogeneities produced an<br>improved fit. A correlation was found to exist between the change in resistance over time<br>and the change in fluid content within the unsaturated fracture porosity zone surrounding<br>the room.