Perched aquifers - their potential impact on contaminant transport in the southern High Plains, Texas
- Univ. of Texas, Austin, TX (United States)
Understanding the hydrogeology and hydrochemistry of perched aquifers at potential and known contaminated waste sites has become increasingly important because of the impact these aquifers may have on contaminant transport independent of regional aquifer processes. Investigations of a perched aquifer above the Ogallala aquifer are being conducted in the region of the U.S. Department of Energy's Pantex Plant, a proposed Superfund site, located approximately 20 mi northeast of Amarillo, Texas. Since the early 1950s, a small playa basin located on the Pantex Plant has been used as a waste-water discharge pond with daily discharge rates ranging from 400,000 to 1 million gal. The focus of this investigation is an unconfined, perched aquifer that overlies a thick silty clay sequence within the upper, mostly unsaturated part of the Ogallala Formation (Neogene). In the area of the Pantex Plant, measured depths to the perched aquifer range from 200 to 300 ft below land surface, whereas depth to the regional Ogallala aquifer ranges from 375 to 500 ft. The potentiometric surface of the perched aquifer typically represents groundwater mounds proximal to the playas and thins into trough in the interplaya areas. Hydrologic gradients of the primary mound under investigation are relatively high, ranging from 28 to 45 ft/mi. Calculated transmissivities have a geometric mean of 54 ft[sup 2]/day, with saturated thicknesses ranging from 4 to 1000 ft. Modeling of the perched aquifer was designed to determine how much, if any, discharge to the small playa basin has enhanced recharge to the perched aquifers and increased the vertical and lateral extent of the perched aquifer. Preliminary results indicate that measurements of vertical conductance through the perching silty-clay sequence and recharge rates through playas are critical for calibrating the model. Accurate delineation of rates and flow directions in the perched aquifer is critical to any successful remediation effort.
- OSTI ID:
- 7131899
- Report Number(s):
- CONF-9310237-; CODEN: AABUD2
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 77:9; Conference: American Association of Petroleum Geologists (AAPG) mid-continent section meeting, Amarillo, TX (United States), 10-12 Oct 1993; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
Similar Records
Geochemical characterization of groundwater in the vicinity of the Pantex Plant near Amarillo, Texas
Investigation of groundwater recirculation for the removal of RDX from the Pantex Plant perched aquifer
Related Subjects
54 ENVIRONMENTAL SCIENCES
AQUIFERS
RADIOACTIVITY TRANSPORT
GROUND WATER
RECHARGE
PANTEX PLANT
WASTE DISPOSAL
GEOLOGIC MODELS
RADIOACTIVE WASTES
TEXAS
WASTE WATER
DEVELOPED COUNTRIES
HYDROGEN COMPOUNDS
LIQUID WASTES
MANAGEMENT
MATERIALS
NATIONAL ORGANIZATIONS
NORTH AMERICA
OXYGEN COMPOUNDS
RADIOACTIVE MATERIALS
US DOE
US ERDA
US ORGANIZATIONS
USA
WASTE MANAGEMENT
WASTES
WATER
053002* - Nuclear Fuels- Environmental Aspects- Radioactive Effluents- (1992-)
540350 - Environment
Aquatic- Site Resource & Use Studies- (1990-)