Modeling of ground-water flow in subsurface Austin Chalk and Taylor marl in Ellis County, Texas, near the superconducting super collider site
- Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology
Numerical models are useful tools for developing an understanding of ground-water flow in sparsely characterized low-permeability aquifers. Finite-difference, cross-sectional models of Cretaceous chalk and marl formations near the Superconducting Super Collider (SSC) were constructed using MODFLOW to evaluate ground-water circulation paths and travel times. Weathered and fractured zones with enhanced permeability were included to assess the effect these features had on flow paths and times. Pump tests, slug tests, packer tests, core tests, and estimates were used to define hydraulic properties for model input. The model was calibrated with water-level data from monitor wells and from wire-line piezometers near a test shaft excavated by the SSC project. A ratio of vertical-to-horizontal permeability of 0.0085 was estimated through model calibration. A chalk-to-marl permeability ratio of 18 was needed to reproduce artesian head in a well completed in chalk beneath marl. Hydraulic head distributions and ground-water flow paths reflected local, intermediate, and regional flow systems with recharge beneath upland surface-water divides and discharge in valleys. Most of the flow (99%) occurred in the weathered zone, with average residence times of 5 to 10 years. Residence time in unweathered chalk bedrock was substantially longer, at an average of 1.7 Ma. As expected, the model demonstrated that deep and rapid ground-water circulation might occur in fracture zones. Particle paths calculated using MODPATH showed that ground-water travel times from recharge areas to the SSC subsurface facilities might be 20 to 60 years where flow is through fracture zones.
- OSTI ID:
- 5997843
- Report Number(s):
- CONF-9303212-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:1; Conference: 27. annual Geological Society of America (GSA) South-Central Section meeting, Fort Worth, TX (United States), 15-16 Mar 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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54 ENVIRONMENTAL SCIENCES
GROUND WATER
FLOW MODELS
SUPERCONDUCTING SUPER COLLIDER
SITE CHARACTERIZATION
AQUIFERS
COMPUTER CODES
FINITE DIFFERENCE METHOD
GEOLOGIC FORMATIONS
HYDROLOGY
LIMESTONE
MARLSTONE
PERMEABILITY
TEXAS
CALCULATION METHODS
CARBONATE ROCKS
DEVELOPED COUNTRIES
HYDROGEN COMPOUNDS
ITERATIVE METHODS
MATHEMATICAL MODELS
NORTH AMERICA
NUMERICAL SOLUTION
OXYGEN COMPOUNDS
ROCKS
SEDIMENTARY ROCKS
STORAGE RINGS
USA
WATER
580000* - Geosciences
540250 - Environment
Terrestrial- Site Resource & Use Studies- (1990-)