Hydraulic Characterization of Overpressured Tuffs in Central Yucca Flat, Nevada Test Site, Nye County, Nevada
A sequence of buried, bedded, air-fall tuffs has been used extensively as a host medium for underground nuclear tests detonated in the central part of Yucca Flat at the Nevada Test Site. Water levels within these bedded tuffs have been elevated hundreds of meters in areas where underground nuclear tests were detonated below the water table. Changes in the ground-water levels within these tuffs and changes in the rate and distribution of land-surface subsidence above these tuffs indicate that pore-fluid pressures have been slowly depressurizing since the cessation of nuclear testing in 1992. Declines in ground-water levels concurrent with regional land subsidence are explained by poroelastic deformation accompanying ground-water flow as fluids pressurized by underground nuclear detonations drain from the host tuffs into the overlying water table and underlying regional carbonate aquifer. A hydraulic conductivity of about 3 x 10-6 m/d and a specific storage of 9 x 10-6 m-1 are estimated using ground-water flow models. Cross-sectional and three-dimensional ground-water flow models were calibrated to measured water levels and to land-subsidence rates measured using Interferometric Synthetic Aperture Radar. Model results are consistent and indicate that about 2 million m3 of ground water flowed from the tuffs to the carbonate rock as a result of pressurization caused by underground nuclear testing. The annual rate of inflow into the carbonate rock averaged about 0.008 m/yr between 1962 and 2005, and declined from 0.005 m/yr in 2005 to 0.0005 m/yr by 2300.
- Research Organization:
- United States Geological Survey - Nevada, Henderson, NV
- Sponsoring Organization:
- USDOE - National Nuclear Security Administration (NNSA)
- DOE Contract Number:
- AI52-01NV13944
- OSTI ID:
- 859902
- Report Number(s):
- USGS SIR 05-5211; TRN: US200710%%124
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
CARBONATE ROCKS
CARBONATES
DEFORMATION
EXPLOSIONS
FLOW MODELS
GROUND WATER
HYDRAULIC CONDUCTIVITY
HYDRAULICS
NEVADA TEST SITE
PRESSURIZATION
RADAR
STORAGE
TESTING
WATER
WATER TABLES
hydraulic
overpressured tuffs
Nevada
Nevada Test Site
Central Yucca Flat
geology
hydrology