HR: 1340h
AN: H33H-1721    [Abstracts]
TI: Characterization of Preferential Flowpaths at the T-Tunnel Complex, Rainier Mesa, Nevada
AU: * Reeves, D M
EM: mreeves@dri.edu
AF: Desert Research Institute, Division of Hydrologic Sciences/Graduate Program of Hydrologic Sciences, 2215 Raggio Parkway, Reno, NV 89512, United States
AU: Schultz, R
EM: schultz@mines.unr.edu
AF: University of Nevada, Reno, Department of Geological Sciences and Engineering, 1664 N. Virginia, Reno, NV 89557, United States
AU: Bingham, C
EM: kb@umn.edu
AF: University of Minnesota, School of Statistics, 224 Church SE, Minneapolis, NV 55455, United States
AU: Pohlmann, K
EM: Karl.Pohlmann@dri.edu
AF: Desert Research Institute, Division of Hydrologic Sciences, 755 E. Flamingo, Las Vegas, NV 89119, United States
AU: Russell, C
EM: Chuck.Russell@dri.edu
AF: Desert Research Institute, Division of Hydrologic Sciences, 755 E. Flamingo, Las Vegas, NV 89119, United States
AU: Chapman, J
EM: jenny.chapman@dri.edu
AF: Desert Research Institute, Division of Hydrologic Sciences, 755 E. Flamingo, Las Vegas, NV 89119, United States
AB: Rainier Mesa (RM), a tuffaceous plateau on the Nevada Test Site, has been the location of numerous subsurface nuclear tests. The tests were conducted in a series of tunnel complexes located approximately 450 m below the top of the mesa and 1000 m above the regional ground water flow system. The tunnels were constructed near the middle of a 690 m sequence of low-permeability bedded and non-welded vitric and zeolitized tuff units. Though these tuff units are nearly saturated, active ground water flow is restricted to perched lenses occurring within poorly connected normal faults linked to recharge pathways. The perched systems vary from 100 to 150 m above the tunnel complexes which suggests that the now-sealed tunnels could enhance connectivity between otherwise isolated preferential flow pathways. This work represents the first stage of radionuclide transport investigations for the T-tunnel complex at RM: the characterization and stochastic generation of preferential pathways based on fault and joint data collected along tunnel transects. Analysis of fault and joint orientations demonstrate that fractures at RM are steeply-dipping and trend approximately NE-SW. A higher degree of spread about the mean strike relative to the mean dip direction results in an elliptical distribution of fracture orientation. A novel method based on a bivariate normal is used as an alternative to the Fisher distribution to generate fracture orientations. The spatial distribution of fractures along transects indicates fractal clustering (D=0.3) with a power-law distribution of fracture spacing (α=1.1). Fault displacement data are used in conjunction with mechanical models of fault growth to infer both the length and vertical extent of large faults. Major faults are deterministic features in the model domain, while a cascade process is used to govern the spatial distribution of background fractures. Assessment of methods for assigning hydraulic conductivity values to the joints and faults are underway.
DE: 1847 Modeling
DE: 1869 Stochastic hydrology
DE: 1875 Vadose zone
DE: 3265 Stochastic processes (3235, 4468, 4475, 7857)
DE: 5104 Fracture and flow
SC: Hydrology [H]
MN: 2007 Fall Meeting